One of the diseases more related to the continuous aging of the population is Alzheimer's disease, which is a type of dementia currently without either effective diagnosis biomarkers or treatments. Its higher prevalence in women makes it necessary to study pathways/systems that could participate and/or be involved in its development, as well as those that could be affected by hormonal factors, which, in this case, are estradiol levels. In this sense, one of the systems under study that is gaining special relevance in the scientific community is the brain renin-angiotensin system and its regulatory proteolytic enzymes. This system is strongly modulated by estrogens, and it is also connected with the cerebral glucose metabolism through the angiotensin IV receptor, also recognized as the insulin-regulated aminopeptidase (IRAP). Due to the fact that the cerebral glucose metabolism is highly compromised in patients with Alzheimer's disease, it is necessary to know the elements of the systems and their functions in this process, namely, the cerebral renin-angiotensin system, estradiol and IRAP, an enzyme and receptor co-localized in brain tissue with the insulin-dependent glucose transporter 4 (GLUT4). Knowledge of the connection between them could shed light on the molecular mechanisms of this disease and also provide new diagnostic and therapeutic targets.
Citation: María Pilar Carrera-González, María Jesús Ramírez-Expósito, Carmen Guerrero-González, José Manuel Martínez-Martos. Alzheimer's disease: Is there a relationship between brain renin-angiotensin system, estradiol and glucose transporter-4 (GLUT-4)?[J]. AIMS Molecular Science, 2023, 10(1): 37-51. doi: 10.3934/molsci.2023004
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One of the diseases more related to the continuous aging of the population is Alzheimer's disease, which is a type of dementia currently without either effective diagnosis biomarkers or treatments. Its higher prevalence in women makes it necessary to study pathways/systems that could participate and/or be involved in its development, as well as those that could be affected by hormonal factors, which, in this case, are estradiol levels. In this sense, one of the systems under study that is gaining special relevance in the scientific community is the brain renin-angiotensin system and its regulatory proteolytic enzymes. This system is strongly modulated by estrogens, and it is also connected with the cerebral glucose metabolism through the angiotensin IV receptor, also recognized as the insulin-regulated aminopeptidase (IRAP). Due to the fact that the cerebral glucose metabolism is highly compromised in patients with Alzheimer's disease, it is necessary to know the elements of the systems and their functions in this process, namely, the cerebral renin-angiotensin system, estradiol and IRAP, an enzyme and receptor co-localized in brain tissue with the insulin-dependent glucose transporter 4 (GLUT4). Knowledge of the connection between them could shed light on the molecular mechanisms of this disease and also provide new diagnostic and therapeutic targets.
Tanti auguri caro amico Sandro! Con molta stima, Italo.
The purpose of this paper is to provide a review of a few classical and some quite recent results about the validity of the weak Maximum Principle in a rather general setting involving non smooth functions satisfying fully nonlinear degenerate elliptic partial differential inequalities in the viscosity sense in an unbounded domain Ω. Since no regularity assumption will be made on ∂Ω the classical methods based on the construction of suitable distance-like barrier functions are not viable in our framework.
Consider the set USC(¯Ω) of upper semicontinuous functions on ¯Ω and a mapping
F:Ω×R×Rn×Sn→R |
where Sn is the space of n×n symmetric matrices and F is degenerate elliptic, that is
F(x,s,p,Y)≥F(x,s,p,X) if Y−X is non-negative definite | (1.1) |
In this context, the weak Maximum Principle for (F,Ω) is the validity of the following sign propagation property:
u∈USC(Ω):F(x,u,Du,D2u)≥0in Ω,u≤0on ∂Ω |
implies
u≤0inΩ |
The partial differential inequality above involving in a nonlinear way the gradient and the Hessian matrix of u will be always understood in the Crandall-Ishii-Lions viscosity sense, see [15]. The motivation for considering non-smooth functions is of course a strong one when dealing with fully nonlinear partial differential inequalities or equations but is also a relevant one in the linear case, as pointed out by E. Calabi in his 1958 paper [10] on entire solutions of some elliptic partial differential inequalities. In that paper, brought to my attention by N. Garofalo, some version of the Hopf Maximum Principle is indeed proved to hold for upper semicontinuous functions u satisfying the linear partial differential inequality
Tr(A(x)D2u)+b(x)⋅Du+c(x)u≥0, |
in an appropriately defined weak sense.
It is worth to note from an historical point of view that the weak notion introduced by Calabi is in fact similar although somehow stronger than the Crandall-Lions viscosity notion, see [17] for comments in this respect.
In Section 2 I recall a few results concerning Alexandrov-Bakelman-Pucci estimate, in short (ABP), and as a by-product the weak Maximum Principle in the uniformly elliptic case for possibly unbounded domains satisfying a measure-type condition. Section 3 reviews more recent results concerning a class of directionally degenerate elliptic operators in domains satisfying geometric conditions related to the directions of ellipticity. Section 4 is the announcement of a recently obtained result in collaboration with A. Vitolo concerning the weak Maximum Principle in the case of cooperative systems.
Due to the expository character of the paper the proofs of the reviewed results are just sketched; for full details we refer the interested reader to the original papers [11,12,13,14].
It is well-known that the weak Maximum Principle may not hold in unbounded domains: just observe that
u(x)=1−1|x|n−2 |
with n≥3 satisfies Δu=0 in the exterior domain Ω=Rn∖¯B1(0), u≡0 on ∂Ω but u>0 in Ω.
Some remarkable results concerning the validity of (ABP) estimates and the weak Maximum Principle for linear uniformly elliptic operators in unbounded domains are due to X. Cabré [7]. He considered domains satisfying the following measure-geometric condition:
(G) for fixed numbers σ,τ∈(0,1), there exists a positive real number R(Ω) such that for any y∈Ω there exists an n-dimensional ball BRy of radius Ry≤R(Ω) satisfying
y∈BRy,|BRy∖Ωy,τ|≥σ|BRy| |
where Ωy,τ is the connected component of Ω∩BRy/τ containing y.
The above measure-type condition introduced in [3] requires, roughly speaking, that there is enough boundary near every point in Ω allowing, so to speak, to carry over the information on the sign of u from the boundary to the interior of the domain.
Note that (G) holds in particular in the following cases:
● Ω is bounded: R(Ω)=C(n)diam(Ω)
● Ω is unbounded with finite Lebesgue measure: R(Ω)=C(n)|Ω|1n
● Ω is a cylinder with diam(Ω)=|Ω|=+∞ such as {x=(x1,x′):a<x1<b} : R(Ω)=b−a
Since (G) implies the metric condition supΩdist(y,∂Ω)<+∞, (G) does not hold on cones. Note also that the periodically perforated plane
R2per=R2∖⋃(i,j)∈Z2¯Br(i,j) |
as well as its n−dimensional analogues or variants are (G) domains while of course this is not the case for exterior domains such as Rn∖¯Br(0).
For domains satisfying condition (G), X.Cabré [7] proved an Alexandrov-Bakelman-Pucci estimate for strong solutions:
Theorem 2.1. Let Ω satisfy (G), f∈Ln(Ω) and c≤0. If u∈W2,n(Ω) satisfies almost everywhere the uniformly elliptic partial differential inequality
Tr(A(x)D2u)+b(x)⋅Du+c(x)u≥f(x)inΩ |
with
A(x)ξ⋅ξ≥λ|ξ|2,λ>0, |
then
(ABP)supΩu≤sup∂Ωu++CR(Ω)||f||Ln(Ω) | (2.1) |
If f≡0 and u≤0 on ∂Ω, the validity of weak Maximum Principle follows from (2.1) in the case of linear uniformly elliptic operators. Observe also that (2.1) extends to the case of (G) domains the classical (ABP) estimate for bounded domains, see [16].
Some of the results of [7] have been later generalised in two directions in the paper [11]:
● viscosity solutions of fully nonlinear uniformly elliptic inequalities
● more general domains satisfying a weaker form of (G)
The above mentioned condition, which differs from (G) since does not require a priori the boundedness of the radii Ry reads as
(wG) there exist constants σ,τ∈(0,1) such that for all y∈Ω there is a ball BRy of radius Ry containing y such that
|BRy∖Ωy,τ|≥σ|BRy| |
where Ωy,τ is the connected component of Ω∩BRy/τ containing y.
If supy∈ΩRy<+∞, then (wG) boils down to condition (G). Relevant examples of unbounded domains satisfying condition (wG) but not (G) are cones of Rn and their unbounded subsets. Indeed, condition (wG) is satisfied in this case of cones with Ry=O(|y|) as |y|→∞.
A less standard example which shows that there is no a priori restriction on the growth at infinity of Ry is the plane domain described in polar coordinates as
Ω=R2∖{ϱ=eθ, θ≥0} |
Here (wG) holds with Ry=O(e|y|) as |y|→∞.
In order to state the main result in [11] concerning a nonlinear version of the Alexandrov-Bakelman-Pucci we assume that the structure conditions (SC) hold:
● F is continuous with respect to all variables x,t,p,X
● uniform ellipticity: λTr(Q)≤F(x,t,p,X+Q)−F(x,t,p,X)≤ΛTr(Q)
for all Q positive semidefinite and some 0<λ≤Λ
● properness: t↦F(x,t,p,X) is nonincreasing
● linear growth with respect to the gradient F(x,0,p,O)≤β(x)|p| for some bounded β
Under the assumptions above we proved the following form of the (ABP) estimate for bounded above viscosity subsolutions:
Theorem 2.2. Let u∈USC(¯Ω) with supΩu<+∞ satisfy in the viscosity sense
F(x,u,Du,D2u)≥f(x),x∈Ω |
where f∈C(Ω)∩L∞(Ω). If Ω satisfies (wG) for some σ,τ∈(0,1), F satisfies (SC) and, moreover,
(C)supy∈ΩRy‖β‖L∞(Ωy,τ)<∞ |
then
supΩu≤sup∂Ωu++Csupy∈ΩRy‖f−‖Ln(Ωy,τ) |
for some positive constant C depending on n, λ, Λ,σ,τ and supy∈ΩRy‖β‖L∞(Ωy,τ).
For u≤0 on ∂Ω and f≥0 the above yields the weak Maximum Principle.
To obtain the (ABP) estimate in this more general case we will assume, besides condition (wG) on the domain, the extra condition (C) which can be seen as a control of the interplay between the geometrical size of the domain (the opening, in the case of cones) and the growth of the first order transport term.
This condition is trivially satisfied if supy∈ΩRy≤R0<+∞ in (wG), i.e., if Ω satisfies (G) or, for example, when b≡0, namely when F does not depend on the first order transport term. Let us observe also that condition (C) is unavoidable in general, as shown by by the next
Example 2.3. The function u(x)=u(x1,x2)=(1−e1−xα1)(1−e1−xα2), with 0<α<1, is bounded and strictly positive in the cone Ω={x=(x1,x2)∈R2: x1>1, x2>1} and satisfies
u≡0 on∂Ω,Δu+b(x)⋅Du=0inΩ |
where the vectorfield b is given by b(x,y)=(αx1−α1+1−αx1,αx1−α2+1−αx2).
As observed above, Ω satisfies (wG) with Rz=O(|z|) as |z|→∞. Since ||b||L∞(Ωz,τ)=1 the interplay condition (C) fails in this example.
Some non trivial cases in which condition (C) is fulfilled are:
(a) the cylinder Ω={x=(x′,xn)∈Rn−1×R:|x′|<1, xn>0} is a (G) domain and therefore condition (C) is obviously satisfied,
(b) Ω={(x′,xn)∈Rn−1×R:xn>|x′|q} with q>1, This non convex conical set is a genuine (wG) domain with radii Ry=O(|y|1/q) as |y|→∞.
In this case, (C) imposes to the function β a rate of decay β(y)=O(1/|y|1/q) as |y|→∞.
(c) Ω is the strictly convex cone {x∈Rn∖{0}:x/|x|∈Γ} where Γ is a proper subset of the unit half-sphere Sn−1+={x=(x′,xN)∈Rn−1×R:|x|=1, xn>0}.
In this case (wG) is satisfied with Ry=O(|y|) for |y|→∞ and condition (C) requires the rate of decay β(y)=O(1/|y|) as |y|→∞.
Note that cases (a) and (c) can be seen as limiting cases of situation (b) when, respectively, q→+∞ and q=1.
The proof of Theorem 2.2 is based on several viscosity calculus tools but not on the Comparison Principle for viscosity sub and supersolutions. It relies indeed on rescaled versions of the weak Harnack and of the boundary weak Harnack inequality for operators including first order terms, see [11] and [8] for the case of Pucci operators.
Let us briefly sketch the main steps of the proof with the aid of the following three lemmas. The minimal Pucci operator with parameters 0<λ≤Λ is defined by
P−λ,Λ(X)=λTr(X+)−ΛTr(X−) |
where X+ and X− are nonnegative definite matrices such that X=X+−X− and X+X−=O. Under our assumption the following holds:
Lemma 2.4. If w∈USC(Ω) satisfies
F(x,w(x),Dw(x),D2w(x))≥0,x∈Ω |
in the viscosity sense, then for each M∈R the function u=M−w+∈LSC(Ω) satisfies
P−λ,Λ(D2u)−β(x)|Du|≤f−(x),x∈Ω |
The proof is a direct application of the viscosity notions.
Lemma 2.5 (the rescaled weak Harnack inequality). Let R>0, τ∈(0,1) and f∈C(BR/τ)∩L∞(BR/τ). If u∈LSC(¯BR/τ),u≥0 is a viscosity solution of
P−λ,Λ(D2u)−β(x)|Du|≤f−(x),x∈BR/τ |
then
(1|BR|∫BRup)1/p≤C∗(infBRu+R‖f−‖LN(BR/τ)) | (2.2) |
where p and C∗ are positive constants depending on λ,Λ,n,τ and on the product R‖β‖L∞(BR/τ).
Inequality (2.2) is a consequence of the weak Harnack inequality for nonnegative viscosity solutions in a cube Q1 with side-length 1
‖u‖Lˆp(Q1/4)≤ˆC(infQ1/2u+‖f−‖LN(Q1)), |
where ˆp and ˆC depend on λ, Λ, N as well as on ‖β‖L∞(Q1), see [8]. Inequality (2.2) is indeed obtained from the above by rescaling and using the positive homogeneity of the operator P−λ,Λ and a standard covering argument.
Let A be a bounded domain in Rn and BR,BR/τ be concentric balls such that
A∩BR≠∅,BR/τ∖A≠∅. |
For u∈LSC(ˉA), u≥0, consider the following lower semicontinuous extension u−m of function u
u−m(x)={min(u(x);m)ifx∈Amifx∉A |
where m=infx∈∂A∩BR/τu(x).
Lemma 2.6. With the above notations, if g∈C(A)∩L∞(A) and u∈LSC(ˉA) satisfy
u≥0,P−λ,Λ(D2u)−b(x)|Du|≤g(x)inA |
in the viscosity sense, then
(1|BR|∫BR(u−m)p)1/p≤C∗(infA∩BRu+R‖g+‖Ln(A∩BR/τ)) |
where p and C∗ are positive constants depending on λ,Λ,n,τ and on the product R‖β‖L∞(BR/τ).
It is not hard to check, see [8] for the case b≡0, that u−m is a viscosity solution of
u−m≥0,P−(D2u−m)−χA(x)b(x)|Du−m|≤χA(x)g+(x)inBR/τ |
where χA is the characteristic function of A. The statement follows then by applying the weak Harnack inequality (2.2) to u−m, observing that infBRu−m≤infA∩BRu and that χAg+≡0 outside A.
The role of Lemma 2.6 in the proof of Theorem 2.2 is a crucial one, in connection with the (wG) condition, in establishing a localized form of the (ABP) estimate. Indeed, if w∈USC(Ω) satisfies F(x,w,Dw,D2w)≥f then, as we have seen above, for u(x)=supΩw+−w(x)≥0 we have
P−λ,Λ(D2u)−β(x)|Du|≤f−(x),x∈Ω |
Apply now Lemma 2.6 with A=Ωy,τ and g=f− to obtain
(1|BRy|∫BRy(u−m)p)1/p≤C∗y(infΩy,τ∩BRyu+Ry‖f−‖LN(Ωy,τ)) |
for positive constants p and C∗y depending on N, λ, Λ, τ and Ry‖b‖L∞(Ωy,τ).
The left-hand side of the above inequality can be of course estimated from below as follows
(1|BRy|∫BRy(u−m)p)1/p≥(1|BRy|∫BRy∖Ωy,τ(u−m)p)1/p=m(|BRy∖Ωy,τ||BRy|)1/p |
where m=infx∈∂Ωy,τ∩BR/τu(x). Hence, using condition (wG),
(1|BRy|∫BRy(u−m)p)1/p≥mσ1/p |
At this point a few technicalities lead to estimate the value of w+ at any y∈Ω as follows:
w+(y)≤(1−θy)supΩw++θysup∂Ωw++Ry‖f−‖LN(Ωy,τ) | (2.3) |
for suitable choice of θy∈(0,1) depending on n, λ, Λ, σ, τ and on y through the quantity Ry‖b‖L∞(Ωy,τ) which appears in the statement of Theorem 2.2. The proof of the theorem is easily deduced from (2.3) through the use of condition (C).
This section is about the validity of the weak Maximum Principle for degenerate elliptic operators F which are strictly elliptic on unbounded domains Ω of Rn whose geometry is related to the direction of ellipticity. Some results of that kind for one-directional elliptic operators in bounded domains have been previously established, among other qualitative properties, by Caffarelli-Li-Nirenberg [9].
We assume:
Fiscontinuouswithrespectto(x,t,p,X) | (3.1) |
the following standard monotonicity conditions on F
F(x,s,p,Y)≥F(x,s,p,X) if Y≥X | (3.2) |
F(x,s,p,X)≤F(x,r,p,X) if s>r | (3.3) |
and, just for simplicity,
F(x,0,0,O)=0∀x∈Ω | (3.4) |
where O is the null matrix. Our last requirement is on a Lipschitz behavior of F with respect to the gradient variable,
there existsγ>0:|F(x,0,p,X)−F(x,0,0,X)|≤γ|p|for allp∈Rn | (3.5) |
The class of domains that will be considered in this section is conveniently described by decomposing Rn as Rn=U⨁U⊥, where U is a k-dimensional subspace and U⊥ is its orthogonal complement and denoting by P and P⊥ the projection matrices on U and U⊥, respectively.
We will consider the open domains Ω which are contained in unbounded slabs whose k-dimensional sections are cube of edge d, namely
Ω⊂{x∈Rn:a≤x⋅νh≤a+dh,h=1,…,k}:=Cfor somea∈R,dh>0, | (3.6) |
where {ν1,…,νk} is an orthonormal system for the subspace U. We will refer to vectors in U⊥ as unbounded directions.
Such domains may of course be unbounded and of infinite Lebesgue measure but they do satisfy the measure-geometric (wG) condition of the previous section. Note once more that no regularity requirement is made on ∂Ω.
The next assumptions are crucial ones in establishing our results on the weak maximum and on Phragmèn-Lindelöf principles
there existν∈U andλ>0:F(x,0,p,X+tν⊗ν)−F(x,0,p,X)≥λt | (3.7) |
for all t>0.
Observe that the matrix ν⊗ν is the orthogonal projection over the one dimensional subspace generated by ν: the strict directional ellipticity condition (3.7) related to the geometry of Ω will play a crucial role in our results.
there existsΛ>0:F(x,0,0,X+tP⊥)−F(x,0,0,X)≤Λt|x| | (3.8) |
for all t>0, as |x|→∞.
The above one-sided Lipschitz condition is satisfied in the linear case if the coefficients corresponding to second derivatives in the unbounded directions (i.e., belonging to U⊥) have at most linear growth with respect to x. It is worth to observe that ν⊗ν and P⊥ are symmetric and positive semidefinite matrices and that (3.7), (3.8) form a much weaker condition than uniform ellipticity. Indeed, they comprise a control from below only with respect to a single direction ν∈U together with control from above in the directions of U⊥, a much weaker condition on F than uniform ellipticity which would indeed require a uniform control of the difference quotients both from below and from above with respect to all possible increments with positive semidefinite matrices.
We will refer collectively to conditions (3.1) to (3.8) above as (SC).
The following very basic two dimensional example is useful to clarify our structural assumptions. Let U={x=(x1,x2):x2=0} and consider the linear operator
F(x,u,Du,D2u)=∂2u∂x21+H(x,Du)+c(x)u |
where H, c are continuous and bounded with respect to x. Obviously, F satisfies (3.1), (3.2), (3.4) and (3.3) if c(x)≤0 and H(x,0)=0. The strict ellipticity condition (3.7) is trivially satisfied by ν=(1,0) and λ=1. Condition (3.7) is fulfilled with Λ=1 since
F(x,0,0,X+tP⊥)−F(x,0,0,X)=tTr(P⊥) |
and P⊥ is the matrix
(0001) |
Condition (3.5) is trivially satisfied if H is Lipschitz continuous.
Operators of this kind arise in the dynamic programming approach to the optimal control of a deterministic system in Rn which is perturbed by a lower dimensional Brownian motion. A more general example is
F(x,u,Du,D2u)=Tr(AD2u)+H(x,Du)+c(x)u |
with
A=(Ik00φ(x)In−k) |
The structure condition (3.7) requires in this case a sublinear growth of the coefficient φ in the unbounded directions of the domain.
The Bellman-Isaacs operators are an important class of fully nonlinear operators arising in the theory of differential games. They have the following form
F(x,u,Du,D2u)=supαinfβ[Tr(AαβD2u)+bαβ(x)Du)+cαβu(x)] |
with constant coefficients depending α and β running in some sets of indexes A, B.
It is not hard to check that condition (SC) is satisfied in any domain Ω contained in a (n−k)-infinite slab as in (3.6) if all matrices Aαβ, whose entries are denoted by aαβij(x), are positive semidefinite and
Aαβνh⋅νh≥λ>0h=1,…,k,n∑i,j=1aαβijνhiνhjaαβijνhiνhj≤Λ|x|,h=k+1,…,n|bαβ(x)|≤γ,cαβ(x)≤0, |
where λ,Λ,γ are independent on α,β and {ν1,…,νk} is an orthonormal basis of U.
The main results concerning the validity of (wMP) are stated in the following theorems:
Theorem 3.1. Let Ω be a domain of Rn satisfying condition (3.6):
Ω⊂{x∈Rn:a≤x⋅νh≤a+dh,h=1,…,k}for somea∈R,dh>0, |
and assume that F satisfies the structure condition (SC).
Then (wMP) holds for any u∈USC(¯Ω) such that u+(x)=o(|x|) as |x|→∞.
Note that some restriction on the behaviour of u at infinity is unavoidable. Observe indeed that u(x1,x2,x3)=ex1sinx2sinx3 solves the degenerate Dirichlet problem
∂2u∂x21+∂2u∂x22=0 in Ω, u(x1,x2,x3)=0on∂Ω |
in the 1-infinite cylinder Ω=R×(0,π)2⊂R3 and u(x1,x2,x3)>0 in Ω so (wMP) fails in this case.
As a consequence of the previous Theorem a quantitative estimate can be obtained:
Theorem 3.2. Let Ω be a domain of Rn satisfying condition (3.6) and assume that F satisfies the structure condition (SC).
If
F(x,u,Du,D2u)≥f(x) inΩ |
where f is continuous and bounded from below and u+(x)=o(|x|) as |x|→∞, then
sup¯Ωu≤sup∂Ωu++esupf−(x)λd2 |
where d=minhdh and f−(x)=−min(f(x),0).
The method of proof of the above theorems is considerably different from that of the analogous results in Section 2 since tools as Harnack inequalities are not available in the present degenerate elliptic setting.
In order to simplify the notations a sketch of the proof of Theorem 3.1 is given below for the case F=F(x,∇2u)+c(x)u where c≤0 and Ω={x∈R2:−d/2<x1<d/2}. So we take ν=(1,0) and the projection matrix on U is
ν⊗ν=P=(1000) |
Arguing by contradiction we suppose that u(x0)=k>0 at some x0∈Ω.
Let us consider then, for ε>0, the function uε(x)=u(x)−εϕ(x) where ϕ(x)=√x22+1 is smooth function penalising the unbounded variable x2. The prescribed behavior of u at infinity implies then that there exists a bounded domain Ωε⊂Ω such that uε≤0 outside Ωε. Hence, for ε<k2ϕ(x0),
supΩuε=max¯Ωεuε=uε(xε)≥k/2 |
Since ϕ is smooth it is easy to check that
F(x,∇2uε(x)+ε∇2ϕ(x))+c(x)(uε(x)+εϕ(x))≥0 | (3.9) |
in the viscosity sense. The next step is to construct a smooth function hε, depending on a positive parameter α to be chosen later, to be used as a test function replacing uε in 3.9. At this purpose, set
hε(x)=kε(1+e−αd)−kεeα(x1−xε1)−αd |
where kε=uε(xε). We have
hε(xε)=uε(xε)andhε≥k2e−2αdon¯Ω |
Modulo a translation by a nonnegative constant δε we can find some point ¯xε such that hε+δε+εϕ touches uε from above at ¯xε. So, by definition of viscosity subsolution and using the assumption that the zero-order coefficient c is ≤0 and that hε, δε and εϕ are positive,
F(¯xε,∇2hε+ε∇2ϕ)≥0at¯xε. | (3.10) |
Observe now that ∇2hε(¯xε)=−α2kεeα(¯xε1−xε1)−αdν⊗ν and apply the directional ellipticity assumption (3.7) with X=∇2hε(¯xε)+ε∇2ϕ(¯xε) and t=k2e−2αd to obtain, taking (3.10) into account,
0≤F(¯xε,∇2hε(¯xε)+ε∇2ϕ(¯xε))≤F(¯xε,ε∇2ϕ(¯xε))−λα2k2e−2αd | (3.11) |
In order to let ε→0 in the above let us consider first the case where ¯xε is bounded and therefore, at least for a subsequence ¯xε→¯x as ε→0+.
By continuity of F and ∇2ϕ we obtain thanks to (3.4) the contradiction
0<λα2k2e−2αd≤F(¯x,O)=0 |
and the Theorem is proved in this case.
Suppose now that ¯xε is unbounded and observe that 1ϕ(x)P⊥≥∇2ϕ(x) in the matrix ordering as in (3.2) where
P⊥=(0001) |
Hence, by degenerate ellipticity and (3.11),
λα2k2e−2αd≤F(¯xε,ε∇2ϕ(¯xε))≤F(¯xε,ε1ϕ(¯xε)P⊥) |
Using condition (3.8) with t=εϕ(¯xε) and X=O we have
F(¯xε,ε1ϕ(¯xε)P⊥)=F(¯xε,ε1ϕ(¯xε)P⊥)−F(¯xε,O)≤Λεϕ(¯xε)|¯xε| |
Since |¯xε|ϕ(¯xε) remains bounded as ε→0, using the above estimate we derive the contradiction
0<λα2k2e−2αd≤lim infε→0F(¯xε,ε1ϕ(¯xε)P⊥)=0. |
Let us now sketch the proof of Theorem 3.2 in the setting adopted for the proof of Theorem 3.1 and assume as a further simplification that Ω is the strip (0,1)×R. The first step is to show by simple viscosity calculus that if u satisfies F(x,D2u)+c(x)u≥f(x) in Ω with c≤0, then u+=max(u,0) satisfies
F(x,D2u+)≥−f−(x). | (3.12) |
Consider the auxiliary function
w(x)=u+(x)−sup∂Ωu++C(ex1−e) |
where C is a positive constant to be chosen in the sequel.
The structure condition (SC) yields
F(x,∇2w)≥F(x,∇2u+)+λCex1≥−f−(x)+λC inΩ |
Choosing C=supΩf−λ we obtain
F(x,∇2w)≥0 in Ω, w≤0on∂Ω |
By Theorem 3.1 we conclude that w≤0 in Ω, yielding
u(x)≤u+(x)≤sup∂Ωu++esupΩf−λ |
which proves the statement in this slightly simplified case. The case d≠1 can be dealt by working with the rescaled variable y=xd since the function v(x)=u(dy) satisfies the inequality
G(y,∇2v(y)≥d2f(dy) |
for y∈d−1Ω⊂(0,1)×R where G(y,X)=d2F(dx,d−2X).
It is well-known that the weak Maximum Principle for linear uniformly elliptic operators
Tr(A(x)D2u)+b(x)⋅Du+c(x)uinΩ |
in bounded domains may hold by replacing the standard assumption c≤0 by suitable alternative conditions, see for example [3,18].
The next result which easily follow from the previous Theorem go in this direction.
Theorem 3.3. Let Ω satisfy (3.6) and assume that F satisfies (SC) with (3.3) replaced by the weaker condition
F(x,s,p,M)−F(x,r,p,M)≤c(x)(s−r) | (3.13) |
for some continuous bounded function c(x)>0 and for all s>r.
Then (wMP) holds for u∈USC(¯Ω), u bounded above, provided 1λmind2hsupΩc(x) is small enough.
As already observed F(x,u,Du,D2u)≥0 implies F(x,u+,Du+,D2u+)≥0 and so, by (3.13) with r=0,s=u+,
F(x,0,Du+,D2u+)≥F(x,u+,Du+,D2u+)−cu+≥−cu+. |
Since u+=0 on ∂Ω, Theorem (3.2) applies with f=−cu+ leading to
sup¯Ωu+≤ed2C λsup¯Ωu+ |
where C≥c(x). From this estimate the statement follows if K=ed2C λ<1.
For fixed C>0 this results applies to narrow domains, that is those whose thickness d is sufficiently small. Conversely, for fixed d>0 (wMP) holds provided C is a sufficiently small positive number. The estimate above shows also that (wMP) holds if the directional ellipticity constant λ is large.
In a work in progress with A.Vitolo [14] we consider systems of elliptic partial differential inequalities of the form
F[u]+C(x)u≥0 | (4.1) |
in a bounded domain Ω⊂Rn. Here u=(u1,...,uN) is a vector function u:Rn→RN, C(x)=(cij(x)) is a N×N matrix and F=(F1,...,FN) are second order operators acting on u of the form
Fi[u]=Fi(x,∇ui,∇2ui)(i=1,...,N) |
It is well-known that the validity of the weak Maximum Principle, namely the sign propagation property
ui≤0in∂Ωimpliesui≤0inΩ(i=1,...,N) |
may fail for general matrices C. Several papers, see for example [1,5,19] for linear Fi and [6] for fully nonlinear differential operators, considered such systems in the case C(x) is a cooperative matrix, often called essentially positive, see [4], that is
cij(x)≥0for alli≠j,N∑j=1cij(x)≤0 | (4.2) |
in order to establish the validity of the weak Maximum Principle. The results obtained in those papers require uniform ellipticity of the operators Fi.
In our work in progress we select a sufficient condition guaranteing the validity of a vector form of the weak Maximum Principle for upper semicontinuous viscosity solutions of systems (4.1), where the interaction matrix satisfies (4.2), in the more general context of operators Fi which are just degenerate elliptic, namely
0≤Fi(x,p,X+Q)−Fi(x,p,X)(i=1,...,N) |
for all matrix Q≥O. A basic example of such operators are Bellman operators
Fi(x,∇2ui)=supγ∈ΓTr(Aγi(x)∇2ui)+bγi(x)⋅∇ui+cγi(x)ui |
where Aγi(x) are symmetric positive semidefinite and γ is a parameter running in an arbitrary set Γ.
For the proof of that result, which seems to be new even in the linear case
Fi(x,∇ui,∇2ui)=Tr(Ai(x)∇2ui)+bi(x)⋅∇ui+ci(x)ui |
where Ai(x) are symmetric positive semidefinite matrices, the reader is referred to [14].
It relies on a suitable combination of results in [2] concerning the validity of the weak Maximum Principle for scalar degenerate elliptic operators with ideas in [6] and some viscosity calculus to exploit conveniently the cooperativity assumption.
The author declares no conflict of interest.
[1] |
Harada CN, Natelson Love MC, Triebel KL (2013) Normal cognitive aging. Clin Geriatr Med 29: 737-752. https://doi.org/10.1016/j.cger.2013.07.002 ![]() |
[2] |
Lin KA, Choudhury KR, Rathakrishnan BG, et al. (2015) Marked gender differences in progression of mild cognitive impairment over 8 years. Alzheimers Dement (N Y) 1: 103-110. https://doi.org/10.1016/j.trci.2015.07.001 ![]() |
[3] |
Corder EH, Ghebremedhin E, Taylor MG, et al. (2004) The biphasic relationship between regional brain senile plaque and neurofibrillary tangle distributions: modification by age, sex, and APOE polymorphism. Ann N Y Acad Sci 1019: 24-28. https://doi.org/10.1196/annals.1297.005 ![]() |
[4] |
Barnes LL, Wilson RS, Bienias JL, et al. (2005) Sex differences in the clinical manifestations of Alzheimer disease pathology. Arch Gen Psychiatry 62: 685-691. https://doi.org/10.1001/archpsyc.62.6.685 ![]() |
[5] | Scheyer O, Rahman A, Hristov H, et al. (2018) Female Sex and Alzheimer's Risk: The Menopause Connection. J Prev Alzheimers Dis 5: 225-230. https://doi.org/10.14283/jpad.2018.34 |
[6] |
Ganten D, Boucher R, Genest J (1971) Renin activity in brain tissue of puppies and adult dogs. Brain Res 33: 557-559. https://doi.org/10.1016/0006-8993(71)90137-5 ![]() |
[7] |
Dzau VJ, Ingelfinger J, Pratt RE, et al. (1986) Identification of renin and angiotensinogen messenger RNA sequences in mouse and rat brains. Hypertension 8: 544-548. https://doi.org/10.1161/01.HYP.8.6.544 ![]() |
[8] |
Harding JW, Sullivan MJ, Hanesworth JM, et al. (1988) Inability of [125I] Sar1, Ile8-angiotensin II to move between the blood and cerebrospinal fluid compartments. J Neurochem 50: 554-557. https://doi.org/10.1111/j.1471-4159.1988.tb02946.x ![]() |
[9] |
Deschepper CF, Bouhnik J, Ganong WF (1986) Colocalization of angiotensinogen and glial fibrillary acidic protein in astrocytes in rat brain. Brain Res 374: 195-198. https://doi.org/10.1016/0006-8993(86)90411-7 ![]() |
[10] |
Lavoie JL, Cassell MD, Gross KW, et al. (2004) Adjacent expression of renin and angiotensinogen in the rostral ventrolateral medulla using a dual-reporter transgenic model. Hypertension 43: 1116-1119. https://doi.org/10.1161/01.HYP.0000125143.73301.94 ![]() |
[11] |
Labandeira-Garcia JL, Rodriguez-Perez AI, Garrido-Gil P, et al. (2017) Brain Renin-Angiotensin System and Microglial Polarization: Implications for Aging and Neurodegeneration. Front Aging Neurosci 9: 129. https://doi.org/10.3389/fnagi.2017.00129 ![]() |
[12] |
Milsted A, Barna BP, Ransohoff RM, et al. (1990) Astrocyte cultures derived from human brain tissue express angiotensinogen mRNA. Proc Natl Acad Sci USA 87: 5720-5723. https://doi.org/10.1073/pnas.87.15.5720 ![]() |
[13] | Ciobica A, Bild W, Hritcu L, et al. (2009) Brain renin-angiotensin system in cognitive function: pre-clinical findings and implications for prevention and treatment of dementia. Acta Neurol Belg 109: 171-180. |
[14] |
Haron S, Kilmister EJ, Davis PF, et al. (2021) The renin-angiotensin system in central nervous system tumors and degenerative diseases. Front Biosci (Landmark Ed) 26: 628-642. https://doi.org/10.52586/4972 ![]() |
[15] |
Puertas Mdel C, Martinez-Martos JM, Cobo M, et al. (2013) Plasma renin-angiotensin system-regulating aminopeptidase activities are modified in early stage Alzheimer's disease and show gender differences but are not related to apolipoprotein E genotype. Exp Gerontol 48: 557-564. https://doi.org/10.1016/j.exger.2013.03.002 ![]() |
[16] |
Ramirez-Exposito MJ, Martinez-Martos JM (2018) Anti-Inflammatory and Antitumor Effects of Hydroxytyrosol but Not Oleuropein on Experimental Glioma In Vivo. A Putative Role for the Renin-Angiotensin System. Biomedicines 6. https://doi.org/10.3390/biomedicines6010011 ![]() |
[17] |
Martinez-Martos JM, Correa-Rodriguez M, Rus A, et al. (2019) Altered Serum Oxytocinase and Enkephalin-Degrading Aminopeptidase Activities in Patients With Fibromyalgia. Biol Res Nurs 21: 431-439. https://doi.org/10.1177/1099800419854207 ![]() |
[18] |
Ramirez-Exposito MJ, Duenas-Rodriguez B, Martinez-Martos JM (2019) Circulating renin-angiotensin system-regulating specific aminopeptidase activities in pre- and post-menopausal women with breast cancer treated or not with neoadyuvant chemotherapy. A two years follow up study. Breast 43: 28-30. https://doi.org/10.1016/j.breast.2018.10.010 ![]() |
[19] |
Ramirez-Exposito MJ, Martinez-Martos JM (2019) Differential Effects of Doxazosin on Renin-Angiotensin-System-Regulating Aminopeptidase Activities in Neuroblastoma and Glioma Tumoral Cells. CNS Neurol Disord Drug Targets 18: 29-36. https://doi.org/10.2174/1871527317666181029111739 ![]() |
[20] |
Ramirez-Exposito MJ, Carrera-Gonzalez MP, Martinez-Martos JM (2021) Sex differences exist in brain renin-angiotensin system-regulating aminopeptidase activities in transplacental ethyl-nitrosourea-induced gliomas. Brain Res Bull 168: 1-7. https://doi.org/10.1016/j.brainresbull.2020.12.008 ![]() |
[21] |
Marc Y, Llorens-Cortes C (2011) The role of the brain renin-angiotensin system in hypertension: implications for new treatment. Prog Neurobiol 95: 89-103. https://doi.org/10.1016/j.pneurobio.2011.06.006 ![]() |
[22] |
Le Noble FA, Hekking JW, Van Straaten HW, et al. (1991) Angiotensin II stimulates angiogenesis in the chorio-allantoic membrane of the chick embryo. Eur J Pharmacol 195: 305-306. https://doi.org/10.1016/0014-2999(91)90552-2 ![]() |
[23] |
Ardaillou R, Chansel D (1997) Synthesis and effects of active fragments of angiotensin II. Kidney Int 52: 1458-1468. https://doi.org/10.1038/ki.1997.476 ![]() |
[24] |
Albiston AL, McDowall SG, Matsacos D, et al. (2001) Evidence that the angiotensin IV (AT(4)) receptor is the enzyme insulin-regulated aminopeptidase. J Biol Chem 276: 48623-48626. https://doi.org/10.1074/jbc.C100512200 ![]() |
[25] |
Chai SY, Yeatman HR, Parker MW, et al. (2008) Development of cognitive enhancers based on inhibition of insulin-regulated aminopeptidase. BMC Neurosci 9: S14. https://doi.org/10.1186/1471-2202-9-S2-S14 ![]() |
[26] |
Rodriguez-Pallares J, Rey P, Parga JA, et al. (2008) Brain angiotensin enhances dopaminergic cell death via microglial activation and NADPH-derived ROS. Neurobiol Dis 31: 58-73. https://doi.org/10.1016/j.nbd.2008.03.003 ![]() |
[27] |
Abadir PM, Walston JD, Carey RM, et al. (2011) Angiotensin II Type-2 receptors modulate inflammation through signal transducer and activator of transcription proteins 3 phosphorylation and TNFalpha production. J Interferon Cytokine Res 31: 471-474. https://doi.org/10.1089/jir.2010.0043 ![]() |
[28] | De Silva TM, Faraci FM (2012) Effects of angiotensin II on the cerebral circulation: role of oxidative stress. Front Physiol 3: 484. https://doi.org/10.3389/fphys.2012.00484 |
[29] |
Wright JW, Harding JW (2013) The brain renin-angiotensin system: a diversity of functions and implications for CNS diseases. Pflugers Arch 465: 133-151. https://doi.org/10.1007/s00424-012-1102-2 ![]() |
[30] |
Forrester SJ, Booz GW, Sigmund CD, et al. (2018) Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology. Physiol Rev 98: 1627-1738. https://doi.org/10.1152/physrev.00038.2017 ![]() |
[31] |
von Bohlen und Halbach O, Albrecht D (2006) The CNS renin-angiotensin system. Cell Tissue Res 326: 599-616. https://doi.org/10.1007/s00441-006-0190-8 ![]() |
[32] |
Chai SY, Fernando R, Peck G, et al. (2004) The angiotensin IV/AT4 receptor. Cell Mol Life Sci 61: 2728-2737. https://doi.org/10.1007/s00018-004-4246-1 ![]() |
[33] |
Kramar EA, Harding JW, Wright JW (1997) Angiotensin II- and IV-induced changes in cerebral blood flow. Roles of AT1, AT2, and AT4 receptor subtypes. Regul Pept 68: 131-138. https://doi.org/10.1016/S0167-0115(96)02116-7 ![]() |
[34] |
Naveri L, Stromberg C, Saavedra JM (1994) Angiotensin IV reverses the acute cerebral blood flow reduction after experimental subarachnoid hemorrhage in the rat. J Cereb Blood Flow Metab 14: 1096-1099. https://doi.org/10.1038/jcbfm.1994.143 ![]() |
[35] |
Dalmay F, Mazouz H, Allard J, et al. (2001) Non-AT(1)-receptor-mediated protective effect of angiotensin against acute ischaemic stroke in the gerbil. J Renin Angiotensin Aldosterone Syst 2: 103-106. https://doi.org/10.3317/jraas.2001.009 ![]() |
[36] |
Ismail MA, Mateos L, Maioli S, et al. (2017) 27-Hydroxycholesterol impairs neuronal glucose uptake through an IRAP/GLUT4 system dysregulation. J Exp Med 214: 699-717. https://doi.org/10.1084/jem.20160534 ![]() |
[37] |
Ascher DB, Cromer BA, Morton CJ, et al. (2011) Regulation of insulin-regulated membrane aminopeptidase activity by its C-terminal domain. Biochemistry 50: 2611-2622. https://doi.org/10.1021/bi101893w ![]() |
[38] |
Wright JW, Harding JW (2008) The angiotensin AT4 receptor subtype as a target for the treatment of memory dysfunction associated with Alzheimer's disease. J Renin Angiotensin Aldosterone Syst 9: 226-237. https://doi.org/10.1177/1470320308099084 ![]() |
[39] |
Mpakali A, Saridakis E, Giastas P, et al. (2020) Structural Basis of Inhibition of Insulin-Regulated Aminopeptidase by a Macrocyclic Peptidic Inhibitor. ACS Med Chem Lett 11: 1429-1434. https://doi.org/10.1021/acsmedchemlett.0c00172 ![]() |
[40] |
Brant AM, Jess TJ, Milligan G, et al. (1993) Immunological analysis of glucose transporters expressed in different regions of the rat brain and central nervous system. Biochem Biophys Res Commun 192: 1297-1302. https://doi.org/10.1006/bbrc.1993.1557 ![]() |
[41] |
Leloup C, Arluison M, Kassis N, et al. (1996) Discrete brain areas express the insulin-responsive glucose transporter GLUT4. Brain Res Mol Brain Res 38: 45-53. https://doi.org/10.1016/0169-328X(95)00306-D ![]() |
[42] |
Vannucci SJ, Koehler-Stec EM, Li K, et al. (1998) GLUT4 glucose transporter expression in rodent brain: effect of diabetes. Brain Res 797: 1-11. https://doi.org/10.1016/S0006-8993(98)00103-6 ![]() |
[43] |
El Messari S, Leloup C, Quignon M, et al. (1998) Immunocytochemical localization of the insulin-responsive glucose transporter 4 (Glut4) in the rat central nervous system. J Comp Neurol 399: 492-512. https://doi.org/10.1002/(SICI)1096-9861(19981005)399:4<492::AID-CNE4>3.0.CO;2-X ![]() |
[44] |
Apelt J, Mehlhorn G, Schliebs R (1999) Insulin-sensitive GLUT4 glucose transporters are colocalized with GLUT3-expressing cells and demonstrate a chemically distinct neuron-specific localization in rat brain. J Neurosci Res 57: 693-705. https://doi.org/10.1002/(SICI)1097-4547(19990901)57:5<693::AID-JNR11>3.0.CO;2-X ![]() |
[45] |
El Messari S, Ait-Ikhlef A, Ambroise DH, et al. (2002) Expression of insulin-responsive glucose transporter GLUT4 mRNA in the rat brain and spinal cord: an in situ hybridization study. J Chem Neuroanat 24: 225-242. https://doi.org/10.1016/S0891-0618(02)00058-3 ![]() |
[46] |
Fernando RN, Albiston AL, Chai SY (2008) The insulin-regulated aminopeptidase IRAP is colocalised with GLUT4 in the mouse hippocampus--potential role in modulation of glucose uptake in neurones?. Eur J Neurosci 28: 588-598. https://doi.org/10.1111/j.1460-9568.2008.06347.x ![]() |
[47] |
Ramirez-Exposito MJ, Martinez-Martos JM, Canton-Habas V, et al. (2021) Putative Involvement of Endocrine Disruptors in the Alzheimer's Disease Via the Insulin-Regulated Aminopeptidase/GLUT4 Pathway. Curr Neuropharmacol 19: 939-956. https://doi.org/10.2174/1570159X18666201111103024 ![]() |
[48] |
Funaki M, Randhawa P, Janmey PA (2004) Separation of insulin signaling into distinct GLUT4 translocation and activation steps. Mol Cell Biol 24: 7567-7577. https://doi.org/10.1128/MCB.24.17.7567-7577.2004 ![]() |
[49] |
Leto D, Saltiel AR (2012) Regulation of glucose transport by insulin: traffic control of GLUT4. Nat Rev Mol Cell Biol 13: 383-396. https://doi.org/10.1038/nrm3351 ![]() |
[50] |
McNay EC, Gold PE (2001) Age-related differences in hippocampal extracellular fluid glucose concentration during behavioral testing and following systemic glucose administration. J Gerontol A Biol Sci Med Sci 56: B66-B71. https://doi.org/10.1093/gerona/56.2.B66 ![]() |
[51] |
McEwen BS, Reagan LP (2004) Glucose transporter expression in the central nervous system: relationship to synaptic function. Eur J Pharmacol 490: 13-24. https://doi.org/10.1016/j.ejphar.2004.02.041 ![]() |
[52] |
Singh Y, Gupta G, Shrivastava B, et al. (2017) Calcitonin gene-related peptide (CGRP): A novel target for Alzheimer's disease. CNS Neurosci Ther 23: 457-461. https://doi.org/10.1111/cns.12696 ![]() |
[53] |
Moss SJ, Harkness PC, Mason IJ, et al. (1991) Evidence that CGRP and cAMP increase transcription of AChR alpha-subunit gene, but not of other subunit genes. J Mol Neurosci 3: 101-108. https://doi.org/10.1007/BF02885531 ![]() |
[54] |
Koth CM, Abdul-Manan N, Lepre CA, et al. (2010) Refolding and characterization of a soluble ectodomain complex of the calcitonin gene-related peptide receptor. Biochemistry 49: 1862-1872. https://doi.org/10.1021/bi901848m ![]() |
[55] |
Tian M, Zhu D, Xie W, et al. (2012) Central angiotensin II-induced Alzheimer-like tau phosphorylation in normal rat brains. FEBS Lett 586: 3737-3745. https://doi.org/10.1016/j.febslet.2012.09.004 ![]() |
[56] |
Chen JL, Zhang DL, Sun Y, et al. (2017) Angiotensin-(1-7) administration attenuates Alzheimer's disease-like neuropathology in rats with streptozotocin-induced diabetes via Mas receptor activation. Neuroscience 346: 267-277. https://doi.org/10.1016/j.neuroscience.2017.01.027 ![]() |
[57] |
Bailey ME, Wang AC, Hao J, et al. (2011) Interactive effects of age and estrogen on cortical neurons: implications for cognitive aging. Neuroscience 191: 148-158. https://doi.org/10.1016/j.neuroscience.2011.05.045 ![]() |
[58] |
Brinton RD, Yao J, Yin F, et al. (2015) Perimenopause as a neurological transition state. Nat Rev Endocrinol 11: 393-405. https://doi.org/10.1038/nrendo.2015.82 ![]() |
[59] |
Brinton RD (2009) Estrogen-induced plasticity from cells to circuits: predictions for cognitive function. Trends Pharmacol Sci 30: 212-222. https://doi.org/10.1016/j.tips.2008.12.006 ![]() |
[60] |
Nilsson S, Koehler KF, Gustafsson JA (2011) Development of subtype-selective oestrogen receptor-based therapeutics. Nat Rev Drug Discov 10: 778-792. https://doi.org/10.1038/nrd3551 ![]() |
[61] |
McEwen BS, Akama KT, Spencer-Segal JL, et al. (2012) Estrogen effects on the brain: actions beyond the hypothalamus via novel mechanisms. Behav Neurosci 126: 4-16. https://doi.org/10.1037/a0026708 ![]() |
[62] |
Morrison MF, Kallan MJ, Ten Have T, et al. (2004) Lack of efficacy of estradiol for depression in postmenopausal women: a randomized, controlled trial. Biol Psychiatry 55: 406-412. https://doi.org/10.1016/j.biopsych.2003.08.011 ![]() |
[63] |
Schmidt PJ, Nieman L, Danaceau MA, et al. (2000) Estrogen replacement in perimenopause-related depression: a preliminary report. Am J Obstet Gynecol 183: 414-420. https://doi.org/10.1067/mob.2000.106004 ![]() |
[64] |
Soares CN, Almeida OP, Joffe H, et al. (2001) Efficacy of estradiol for the treatment of depressive disorders in perimenopausal women: a double-blind, randomized, placebo-controlled trial. Arch Gen Psychiatry 58: 529-534. https://doi.org/10.1001/archpsyc.58.6.529 ![]() |
[65] |
Dwyer JB, Aftab A, Radhakrishnan R, et al. (2020) Hormonal Treatments for Major Depressive Disorder: State of the Art. Am J Psychiatry 177: 686-705. https://doi.org/10.1176/appi.ajp.2020.19080848 ![]() |
[66] |
Ishunina TA, Swaab DF (2001) Increased expression of estrogen receptor alpha and beta in the nucleus basalis of Meynert in Alzheimer's disease. Neurobiol Aging 22: 417-426. https://doi.org/10.1016/S0197-4580(00)00255-4 ![]() |
[67] |
Ishunina TA, Kamphorst W, Swaab DF (2003) Changes in metabolic activity and estrogen receptors in the human medial mamillary nucleus: relation to sex, aging and Alzheimer's disease. Neurobiol Aging 24: 817-828. https://doi.org/10.1016/S0197-4580(03)00009-5 ![]() |
[68] |
Ishunina TA, Swaab DF (2003) Increased neuronal metabolic activity and estrogen receptors in the vertical limb of the diagonal band of Broca in Alzheimer's disease: relation to sex and aging. Exp Neurol 183: 159-172. https://doi.org/10.1016/S0014-4886(03)00138-9 ![]() |
[69] |
Hestiantoro A, Swaab DF (2004) Changes in estrogen receptor-alpha and -beta in the infundibular nucleus of the human hypothalamus are related to the occurrence of Alzheimer's disease neuropathology. J Clin Endocrinol Metab 89: 1912-1925. https://doi.org/10.1210/jc.2003-030862 ![]() |
[70] |
Hu XY, Qin S, Lu YP, et al. (2003) Decreased estrogen receptor-alpha expression in hippocampal neurons in relation to hyperphosphorylated tau in Alzheimer patients. Acta Neuropathol 106: 213-220. https://doi.org/10.1007/s00401-003-0720-3 ![]() |
[71] |
Wang C, Zhang F, Jiang S, et al. (2016) Estrogen receptor-alpha is localized to neurofibrillary tangles in Alzheimer's disease. Sci Rep 6: 20352. https://doi.org/10.1038/srep20352 ![]() |
[72] |
Yaffe K, Lui LY, Grady D, et al. (2002) Estrogen receptor 1 polymorphisms and risk of cognitive impairment in older women. Biol Psychiatry 51: 677-682. https://doi.org/10.1016/S0006-3223(01)01289-6 ![]() |
[73] |
Olsen L, Rasmussen HB, Hansen T, et al. (2006) Estrogen receptor alpha and risk for cognitive impairment in postmenopausal women. Psychiatr Genet 16: 85-88. https://doi.org/10.1097/01.ypg.0000194445.27555.71 ![]() |
[74] |
Ji Y, Urakami K, Wada-Isoe K, et al. (2000) Estrogen receptor gene polymorphisms in patients with Alzheimer's disease, vascular dementia and alcohol-associated dementia. Dement Geriatr Cogn Disord 11: 119-122. https://doi.org/10.1159/000017224 ![]() |
[75] |
Cheng D, Liang B, Hao Y, et al. (2014) Estrogen receptor alpha gene polymorphisms and risk of Alzheimer's disease: evidence from a meta-analysis. Clin Interv Aging 9: 1031-1038. https://doi.org/10.2147/CIA.S65921 ![]() |
[76] |
Maioli S, Leander K, Nilsson P, et al. (2021) Estrogen receptors and the aging brain. Essays Biochem 65: 913-925. https://doi.org/10.1042/EBC20200162 ![]() |
[77] |
Uddin MS, Rahman MM, Jakaria M, et al. (2020) Estrogen Signaling in Alzheimer's Disease: Molecular Insights and Therapeutic Targets for Alzheimer's Dementia. Molecular Neurobiology 57: 2654-2670. https://doi.org/10.1007/s12035-020-01911-8 ![]() |
[78] |
Brinton RD (2008) Estrogen regulation of glucose metabolism and mitochondrial function: therapeutic implications for prevention of Alzheimer's disease. Adv Drug Deliv Rev 60: 1504-1511. https://doi.org/10.1016/j.addr.2008.06.003 ![]() |
[79] |
Brinton RD (2008) The healthy cell bias of estrogen action: mitochondrial bioenergetics and neurological implications. Trends Neurosci 31: 529-537. https://doi.org/10.1016/j.tins.2008.07.003 ![]() |
[80] |
Yao J, Brinton RD (2012) Estrogen regulation of mitochondrial bioenergetics: implications for prevention of Alzheimer's disease. Adv Pharmacol 64: 327-371. https://doi.org/10.1016/B978-0-12-394816-8.00010-6 ![]() |
[81] |
Liu F, Day M, Muniz LC, et al. (2008) Activation of estrogen receptor-beta regulates hippocampal synaptic plasticity and improves memory. Nat Neurosci 11: 334-343. https://doi.org/10.1038/nn2057 ![]() |
[82] |
Yao J, Irwin R, Chen S, et al. (2012) Ovarian hormone loss induces bioenergetic deficits and mitochondrial beta-amyloid. Neurobiol Aging 33: 1507-1521. https://doi.org/10.1016/j.neurobiolaging.2011.03.001 ![]() |
[83] |
Ding F, Yao J, Rettberg JR, et al. (2013) Early decline in glucose transport and metabolism precedes shift to ketogenic system in female aging and Alzheimer's mouse brain: implication for bioenergetic intervention. PLoS One 8: e79977. https://doi.org/10.1371/journal.pone.0079977 ![]() |
[84] |
Rettberg JR, Dang H, Hodis HN, et al. (2016) Identifying postmenopausal women at risk for cognitive decline within a healthy cohort using a panel of clinical metabolic indicators: potential for detecting an at-Alzheimer's risk metabolic phenotype. Neurobiol Aging 40: 155-163. https://doi.org/10.1016/j.neurobiolaging.2016.01.011 ![]() |
[85] |
Mattson MP, Magnus T (2006) Ageing and neuronal vulnerability. Nat Rev Neurosci 7: 278-294. https://doi.org/10.1038/nrn1886 ![]() |
[86] |
Mielke MM, Vemuri P, Rocca WA (2014) Clinical epidemiology of Alzheimer's disease: assessing sex and gender differences. Clin Epidemiol 6: 37-48. https://doi.org/10.2147/CLEP.S37929 ![]() |
[87] |
Seshadri S, Wolf PA, Beiser A, et al. (1997) Lifetime risk of dementia and Alzheimer's disease. The impact of mortality on risk estimates in the Framingham Study. Neurology 49: 1498-1504. https://doi.org/10.1212/WNL.49.6.1498 ![]() |
[88] |
Zhao L, Mao Z, Woody SK, et al. (2016) Sex differences in metabolic aging of the brain: insights into female susceptibility to Alzheimer's disease. Neurobiol Aging 42: 69-79. https://doi.org/10.1016/j.neurobiolaging.2016.02.011 ![]() |
[89] |
Mosconi L, Berti V, Quinn C, et al. (2017) Perimenopause and emergence of an Alzheimer's bioenergetic phenotype in brain and periphery. PLoS One 12: e0185926. https://doi.org/10.1371/journal.pone.0185926 ![]() |
[90] |
Rasgon NL, Geist CL, Kenna HA, et al. (2014) Prospective randomized trial to assess effects of continuing hormone therapy on cerebral function in postmenopausal women at risk for dementia. PLoS One 9: e89095. https://doi.org/10.1371/journal.pone.0089095 ![]() |
[91] |
Yin JX, Maalouf M, Han P, et al. (2016) Ketones block amyloid entry and improve cognition in an Alzheimer's model. Neurobiol Aging 39: 25-37. https://doi.org/10.1016/j.neurobiolaging.2015.11.018 ![]() |
[92] |
Rettberg JR, Yao J, Brinton RD (2014) Estrogen: a master regulator of bioenergetic systems in the brain and body. Front Neuroendocrinol 35: 8-30. https://doi.org/10.1016/j.yfrne.2013.08.001 ![]() |
[93] |
de la Monte SM, Wands JR (2008) Alzheimer's disease is type 3 diabetes-evidence reviewed. J Diabetes Sci Technol 2: 1101-1113. https://doi.org/10.1177/193229680800200619 ![]() |
[94] |
Henderson VW, St John JA, Hodis HN, et al. (2016) Cognitive effects of estradiol after menopause: A randomized trial of the timing hypothesis. Neurology 87: 699-708. https://doi.org/10.1212/WNL.0000000000002980 ![]() |
[95] |
Foy MR, Baudry M, Foy JG, et al. (2008) 17beta-estradiol modifies stress-induced and age-related changes in hippocampal synaptic plasticity. Behav Neurosci 122: 301-309. https://doi.org/10.1037/0735-7044.122.2.301 ![]() |
[96] |
Foy MR, Baudry M, Diaz Brinton R, et al. (2008) Estrogen and hippocampal plasticity in rodent models. J Alzheimers Dis 15: 589-603. https://doi.org/10.3233/JAD-2008-15406 ![]() |
[97] |
Foy MR (2011) Ovarian hormones, aging and stress on hippocampal synaptic plasticity. Neurobiol Learn Mem 95: 134-144. https://doi.org/10.1016/j.nlm.2010.11.003 ![]() |
[98] | Depypere H, Vergallo A, Lemercier P, et al. (2022) Menopause hormone therapy significantly alters pathophysiological biomarkers of Alzheimer's disease. Alzheimers Dement . https://doi.org/10.1002/alz.12759 |
[99] |
Kedia N, Almisry M, Bieschke J (2017) Glucose directs amyloid-beta into membrane-active oligomers. Phys Chem Chem Phys 19: 18036-18046. https://doi.org/10.1039/C7CP02849K ![]() |
[100] |
Wang F, Song YF, Yin J, et al. (2014) Spatial memory impairment is associated with hippocampal insulin signals in ovariectomized rats. PLoS One 9: e104450. https://doi.org/10.1371/journal.pone.0104450 ![]() |
[101] |
Grillo CA, Piroli GG, Hendry RM, et al. (2009) Insulin-stimulated translocation of GLUT4 to the plasma membrane in rat hippocampus is PI3-kinase dependent. Brain Res 1296: 35-45. https://doi.org/10.1016/j.brainres.2009.08.005 ![]() |
[102] |
Emmanuel Y, Cochlin LE, Tyler DJ, et al. (2013) Human hippocampal energy metabolism is impaired during cognitive activity in a lipid infusion model of insulin resistance. Brain Behav 3: 134-144. https://doi.org/10.1002/brb3.124 ![]() |
[103] |
Meng Y, Wang R, Yang F, et al. (2010) Amyloid precursor protein 17-mer peptide ameliorates hippocampal neurodegeneration in ovariectomized rats. Neurosci Lett 468: 173-177. https://doi.org/10.1016/j.neulet.2009.07.058 ![]() |
[104] |
Yonguc GN, Dodurga Y, Adiguzel E, et al. (2015) Grape seed extract has superior beneficial effects than vitamin E on oxidative stress and apoptosis in the hippocampus of streptozotocin induced diabetic rats. Gene 555: 119-126. https://doi.org/10.1016/j.gene.2014.10.052 ![]() |
[105] |
Albiston AL, Mustafa T, McDowall SG, et al. (2003) AT4 receptor is insulin-regulated membrane aminopeptidase: potential mechanisms of memory enhancement. Trends Endocrinol Metab 14: 72-77. https://doi.org/10.1016/S1043-2760(02)00037-1 ![]() |
[106] |
Lew RA, Mustafa T, Ye S, et al. (2003) Angiotensin AT4 ligands are potent, competitive inhibitors of insulin regulated aminopeptidase (IRAP). J Neurochem 86: 344-350. https://doi.org/10.1046/j.1471-4159.2003.01852.x ![]() |
[107] |
Fernando RN, Larm J, Albiston AL, et al. (2005) Distribution and cellular localization of insulin-regulated aminopeptidase in the rat central nervous system. J Comp Neurol 487: 372-390. https://doi.org/10.1002/cne.20585 ![]() |
[108] |
Demaegdt H, Lukaszuk A, De Buyser E, et al. (2009) Selective labeling of IRAP by the tritiated AT(4) receptor ligand [3H]Angiotensin IV and its stable analog [3H]AL-11. Mol Cell Endocrinol 311: 77-86. https://doi.org/10.1016/j.mce.2009.07.020 ![]() |