CR and brain disease

[Guest guest]

Hi All,

It has been wondered by some whether CR is bad for brains. The below

suggests this is not true, as some reports have indicated.

Alzheimer's disease is found to be less of a risk with CR it seems.

1: FASEB J. 2005 Jan 13; [Epub ahead of print]

Caloric restriction attenuates beta-amyloid neuropathology in a mouse

model of

Alzheimer's disease.

Wang J, Ho L, Qin W, Rocher AB, Seror I, Humala N, Maniar K, Dolios

G, Wang R,

Hof PR, Pasinetti GM.

This study was designed to explore the possibility that caloric

restriction (CR)

may benefit Alzheimer's disease (AD) by preventing beta-amyloid

(Abeta)

neuropathology pivotal to the initiation and progression of the

disease. We

report that a CR dietary regimen prevents Abeta peptides generation

and neuritic

plaque deposition in the brain of a mouse model of AD neuropathology

through

mechanisms associated with promotion of anti-amyloidogenic alpha-

secretase

activity. Study findings support existing epidemiological evidence

indicating

that caloric intake may influence risk for AD and raises the

possibility that CR

may be used in preventative measures aimed at delaying the onset of

AD amyloid

neuropathology.

PMID: 15650008 [PubMed - as supplied by publisher]

Recent prospective studies indicate that increased caloric intake

is a risk factor for

Alzheimer's disease (AD) (1–3). Although there is evidence supporting

a potential

neuroprotective role of caloric restriction (CR) in the brain (3),

there is no information

whether a CR regimen may influence AD. A fundamental problem in AD is

the aberrant

generation of amyloidogenic â -amyloid peptides in the brain leading

to abnormal deposition of

neuritic plaques, which is a neuropathological landmark in AD (4).

Based on this consideration,

in this study using a mouse model of AD-type amyloidosis (5), we

tested the hypothesis that CR

may beneficially influence AD through mechanisms that prevent A â

generation and eventually

neuritic plaque deposition in the brain.

...

RESULTS

To test the hypothesis that CR can modulate amyloidosis, 3-month-old

Tg2576 mice, which

develop AD-type amyloid neuropathology by 8-10 months of age (5, 12),

were maintained for 9

months with a daily low carbohydrate diet resulting in a 30% lower

caloric intake compared with

that consumed by age- and gender-matched control Tg2576 mice fed AL

with a standard

laboratory rodent diet. Nutrient composition in the CR diet was

adjusted so that CR was achieved

by selectively reducing the carbohydrate content of the diet while

consumption of protein, fat,

cholesterol, vitamins, and minerals was identical to that of AL-fed

Tg2576 mice (Table 1). This

dietary regimen resulted in body weight stabilization over the 9

month study period among CR

Nutrient composition in ad libitum (AL) and caloric restriction

(CR) diets

Ad-libitum diet Caloric restriction diet

Nutrient composition (per 1 g diet) Nutrient composition (per 0.71 g

diet)

Total calories 3.8 Total calories 2.7 (30% caloric restriction)

Protein (g) 0.19 Protein (g) 0.20

Carbohydrate (g) 0.67 Carbohydrate (g) 0.39

Fat (g) 0.04 Fat (g) 0.04

Vitamin mix (mg) 9.48 Vitamin mix (mg) 9.48

Mineral mix (mg) 9.48 Mineral mix (mg) 9.48

Cholesterol (mg) 0.20 Cholesterol (mg) 0.20

Cellulose (mg) 47.38 Cellulose (mg) 47.38

Dicalcium phosphate (mg) 12.32 Dicalcium phosphate (mg) 12.32

Calcium carbonate (mg) 5.21 Calcium carbonate (mg) 5.21

Potassium citrate (mg) 15.64 Potassium citrate (mg) 15.64

Choline bitarttrate (mg) 1.90 Choline bitarttrate (mg) 1.90

Animals on CR diet consumed amounts of proteins, fat, cholesterol,

and micronutrients identical to those consumed by those on AL diet.

CR animals consumed 42% less carbohydrates, however, accounting

for a 30% decrease in total caloric intake.

Tg2576 mice relative to the AL-fed group (Fig. 1A) and coincided

with ~3-fold lower ependymal

fat pad weight (Fig. 1B) and improved glucose tolerance response as

determined by an

intraperitoneal glucose tolerance test (IGTT) (Fig. 1C). These

physiological adaptations in the

CR Tg2576 mice relative to AL-fed controls are consistent with

clinical evidence that low

carbohydrate CR considerably improves abnormal glucose control and

obesity (13–15), which

are risk factors not only for diabetes but also for AD (16–19).

We compared baseline glucose utilization in Tg2576 and wild-type (WT)

control mice to

exclude the possibility that inherent aberrant glucose metabolism in

12-month old female

Tg2576 mice may influence the anti-amyloidogenic mechanism in caloric

restricted Tg2576

mice. We found no detectable differences in baseline glucose

utilization by IGTT assay between

12 month old Tg2576 mice and strain-, age-, and gender-matched WT

mice fed AL with a

standard rodent laboratory diet (two-way ANOVA; P<0.0001, F4,55=15.0

for glycemic content

over time; P=0.623, F1,55=0.245 for genotype; P=0.793, F4,55=0.4199

for interaction). Based on

the evidence that AL-fed female Tg2576 mice on a standard laboratory

diet presented normal

baseline glucose metabolism, we continued to explore the relationship

between CR and AD-type

amyloidosis in the brain of Tg2576 mice.

When Tg2576 mice were examined for AD-type neuropathology at 12

months of age, we found

that 9 month CR treatment almost completely prevented cortical and

hippocampal AD-type

amyloid plaque development (Fig. 2A and relative to animals in the

AL-fed group. Consistent

with this evidence, we noted commensurately lower concentrations of

amyloidogenic A â 1-40

and A â 1-42 peptides in the neocortex and hippocampus as evaluated

by ELISA assay, relative to

AL-fed controls (Fig. 2C). No detectable change in total full-length

APP level was noted in

either brain region of CR vs. AL-fed Tg2576 mice (Fig. 3A).

To further evaluate the anti-amyloidogenic role of CR in the brain of

Tg2576 mice, we continued

to explore APP processing and A â peptide generation using IP-MS

(11). Consistent with the

aforementioned ELISA evidence, using 4G8 antibody for A â IP, we

confirmed decreased levels

of A â 1-40 and A â 1-42 in the same neocortical samples we used for

the A â ELISA assay (Fig.

2D). In addition, a relative proportional reduction in A â 1-37, A â

1-38, and A â 1-39 peptide

content was also observed in the neocortex of the CR group compared

with the AL-fed control

group (Fig. 2D). This evidence, together with our observation that

the concentration of the ~7

kDa carboxy terminal fragment (CTF)-ã cleavage product of APP, an

index of ã -secretase

activity, was unchanged in the neocortex of the CR group relative to

AL-fed controls (Fig. 3B),

is consistent with the possibility that ã -secretase activity was not

involved in the CR-associated

anti-amyloidogenic activity.

To further identify A â carboxy-termini peptide fragments that would

have been otherwise

undetected in the 4G8 IP-MS studies, we used 6E10 antibody in

additional A â IP-MS studies.

Consistent with the 4G8 IP-MS spectra, we noted decreased levels of A

â 1-40 and A â 1-42 as

well as A â 1-37, A â 1-38, and A â 1-39 peptide in the CR group

relative to AL-fed control animals

(Fig. 2E). In addition, we found a major elevation in A â 1-16

peptide fragment concentration in

the neocortex of the CR group that was not detected in the AL-fed

controls (Fig. 2D). Because á -secretase

can cleave APP eventually resulting in the generation of A â C-

termini fragments

ending at the AA residue leucine16 of A â (20–22), we continued to

explore the role of CR in á -secretase

activity in the brain.

Cleavage of APP by á -secretase releases the amino-terminal

extracellular domain known as

soluble á -secretase amyloid precursor protein (sAPP)á domain

coincidental with elevation in

membrane-bound á -secretase-cleaved APP carboxy-terminal fragment

(CTF)-á (11). We

therefore explored the regulation of sAPP á and CTF-á cleavage

products of APP in the brain as

indices of á -secretase activity in response to CR. Interestingly, we

found that CR in Tg2576

mice resulted in a >2-fold elevation in concentration of neocortical

sAPP á (Fig. 4A) and

membrane-associated CTF-á (Fig. 4B) relative to AL-fed control Tg2576

mice. The increase in

CTF-á was somewhat less, ~1.6-fold, presumably because of further

cleavage of CTF-á by ã -secretase.

Compared with the CTF-á fragment, the abundance of CTF-â signal was

at the limit

of detection in the neocortex of both CR and AL-fed Tg2576 mice,

preventing reliable

quantification (Fig. 4B).

In light of recent evidence indicating that the proteinase ADAM10 (a

disintegrin and

metalloproteinase) may act as an á -secretase (23), we continued to

explore the regulation of

ADAM10 expression in the brains of Tg2576 mice in response to CR,

relative to AL-fed

controls. Both mature (62 kDa) and proform (90 kDa) ADAM10 species

were detected in the

neocortex of the AL-fed control animals, confirming previous evidence

(23) (Fig. 4C). The 62

kDa mature ADAM10 protein species is known to act as an á -secretase

in vitro and to cleave

A â -derived peptides at leucine16 (20). Excitingly, we found that

the CR diet regimen resulted in

a 30% elevation of neocortical mature ADAM10 species concentration

(Fig. 4C), coinciding

with a commensurate elevation in neocortical á -secretase activity

(assessed fluorometrically; ref

24) (Fig. 4D), compared with AL-fed control mice. No detectable

change in proform ADAM10

species concentration was noted in the neocortex of the CR group

relative to the AL-fed control

group (Fig. 4C). In addition to ADAM10, two other members of the ADAM

proteinase family,

namely ADAM17 (TACE) and ADAM9, can act as á -secretase in various

cell lines (20, 25–27).

In parallel studies, we found that the CR regimen in Tg2576 mice did

not change the

concentration of the proform or the mature form of either the ADAM17

(Fig. 5A) or the ADAM9

(Fig. 5B) species, relative to AL-fed control Tg2576 mice. Similarly,

there was no detectable

change in the neocortical concentration of the BACE1 species or of â -

secretase activity in

response to CR relative to the AL-fed control group (Fig. 5C).

IDE was originally recognized for its role in degrading insulin, but

recent evidence indicates it is

also an " amyloidase " integral to the clearance of A â from the brain

(28–32). Thus, we explored

the hypothesis that CR may influence IDE expression in the brain of

Tg2576 mice. Interestingly,

we found that CR resulted in a significant ~1.3 increased expression

of IDE protein content in

the neocortex of CR mice as compared with AL-fed mice (AL-fed Tg2576

mice, 100±11.9% vs.

CR Tg2576 mice 123±20%; 2-tail t test, P<0.05). Thus, although CR

attenuated the A â synthetic

pathway through promotion of anti-amyloidogenic á -secretase activity

in the brain, CR may also

influence A â peptide degradation via promoting IDE expression in the

brain.

DISCUSSION

Our studies support the hypothesis that low carbohydrate CR may

prevent AD-type amyloid

neuropathology through mechanisms that influence á -secretase

activity in the brain, possibly by

promoting the generation of mature, catalytically active ADAM10

species. Since á -secretase

proteolysis of the APP sequence within the A â peptide would preclude

the generation of

amyloidogenic A â peptides, our studies suggest that CR may provide

an attractive anti-amyloidogenic

strategy by promoting á -secretase activity in the brain. Moreover,

because AD-type

amyloid neuropathology is undetectable in the brain of 3-month-old

Tg2576 mice (12), the

age when our mice were initially exposed to the CR dietary regimen,

our studies support the

possibility that CR, by promoting á -secretase activity preventively,

possibly through

mechanisms involving ADAM10 maturation, may result in reduced AD-type

amyloid

neuropathology. This possibility is supported by recent evidence

showing that decreased á -secretase

activity in the brain of dominant negative ADAM10-APP(v717) double

transgenic

mice develop more amyloid neuropathology than controls (23).

Among the three ADAM family members exhibiting á -secretase activity,

ADAM10 has many

properties of a physiologically relevant á -secretase: it cleaves APP-

derived peptides at the main

á -secretase cleavage site between position 16 and 17 of the A â

region and exhibits á -secretase

activity in cultured cells (20). Moreover, the mature ADAM10 species

may also act as an

efficient á -secretase in the brain of ADAM10-APP(v717) double

transgenic mice (23). Our

evidence showing increased levels of mature (62 kDa) catalytically-

active ADAM10 species (but

not ADAM17 or ADAM 9 proform or mature species) coincident with

increased levels of

sAPP á and CTF-á and increased á -secretase activity in response to

CR relative to AL-fed group

is also consistent with an á -secretase activity role of ADAM10 in

the brain.

In addition to promoting á -secretase activity, we found that CR led

to a small but significant

elevation of IDE content in the brain of Tg2576 mice. A role for IDE

in A â degradation was

demonstrated by recent studies showing that mice deficient for IDE

exhibit increased cerebral

accumulation of endogenous A â peptides (33–34). Thus it is possible

that the attenuation of A burden in the brain of CR Tg2576 mice might

also derive from enhanced IDE-mediated

clearance of A â peptides in addition to the promotion of the

nonamyloidogenic á -secretase

cleavage of APP.

In control studies, we further explored features in glucose

utilization in female Tg2576 mice

relative to WT control mice fed AL with a normal rodent laboratory

diet. We found no intrinsic

alterations in baseline glucose utilization in female Tg2576 mice

relative to strain-, age-, and

gender-matched WT controls as assessed by IGTT at 12 months of age,

consistent with previous

evidence at 9 month of age (7). Collectively, this finding suggests

that 1) conditions of altered

glucose metabolism in AL-fed female Tg2576 do not underlie A â

neuropathology, and 2) it likely that the physiological conditions

associated with improved glucose utilization resultant

from CR may be involved in the observed attenuation of amyloid

neuropathology in female

Tg2576 mice.

However, we also note that a recent study suggests that male Tg2576

mice have impaired

glucose utilization in response to insulin challenge relative to age-

and gender- matched Tg2576

mice (35). This apparent inconsistency with respect to

glucoregulation in Tg2576 mice in our

study and that from by Pedersen and Flynn (35) may be a reflection of

1) potential different

assay systems used in the assessment of glucoregulation (IGTT vs.

insulin-stimulated glucose

uptake) and/or 2) gender-related glucoregulation features. Male

Tg2576 mice were used in the

Pedersen and Flynn study and female Tg2576 mice were used in the

current study. This apparent

inconsistency is of high interest especially because male Tg2576 mice

are known to have a

higher mortality rate in response to stress (G. Pasinetti,

unpublished observation; W. Pedersen,

personal communication) and milder AD-type amyloid neuropathology

relative to female

Tg2576 mice (5).

Current strategies to treat AD are aimed at preventing formation of

amyloidogenic A â peptides.

Therefore, â - and ã -secretases that generate A â peptides by

sequential cleavage of the APP or

proteases responsible for degrading released A â peptides are obvious

and central targets for

development of therapeutic reagents (4). It has, however, been

difficult to find safe, selective â -

and ã -secretase inhibitors, mainly because of the influence of these

inhibitors on other cellular

substrates (4). Thus, our evidence showing that CR may positively

influence á -secretase,

possibly through mechanisms that may involve the generation of

mature, catalytically active

ADAM10 species in the brain, might prove in the future the basis of

potential novel preventative

measure aimed at delaying the onset of AD neuropathology. In

addition, since á -secretase

cleavage of APP releases sAPP á , which is well known for its

neuroprotective properties (21),

our study tentatively suggests that promoting low carbohydrate CR

dietary regimen may also

result in increased brain repair activities as a consequence of sAPP

á neurotrophic function. We

cannot, however, exclude the possibility that CR might also influence

other mechanisms,

eventually resulting in decreased amyloid deposition in the brain by

promoting á -site cleavage of

APP or degradation of released A â by other proteases such as plasmin

(36) and neprilysin (37),

respectively.

In conclusion, consistent with the evidence that caloric intake may

be a risk factor for AD (1–3,

38), this study offers a rational basis for a potential future

preventative measure aimed at

delaying the onset of AD amyloid neuropathology via control of

dietary intake.

Cheers, Al Pater.

[Guest guest]

The referenced paper implemented CR *and* a LOW CARBOHYDRATE

macronutrient ratio. Amyloid plaques consist of proteins combined

with polysaccharides (a glycation product). A diet that reduces

protein would lead to kwashiorkor, whereas a diet that reduces

carbohydrates does not eliminate any *essential* nutrients, but limits

one of the components necessary for glycation. It is known that CR

reduces glycation even with diets with standard macronutrient ratios

(e.g., PMID: 7583789, below). The combination of CR and low carb

appears to be particularly effective for reducing glycation products.

The discussions about CR being bad for brains have focused on the

problems that arise when the percent of body fat is less than 6% (The

" Gray Zone " , etc). This experiment did not reduce dietary fat.

Tony

===

http://www.ghr.nlm.nih.gov/ghr/glossary/amyloidplaque

===

J Gerontol A Biol Sci Med Sci. 1995 Nov;50(6):B337-41.

Caloric restriction decreases age-dependent accumulation of the

glycoxidation products, N epsilon-(carboxymethyl)lysine and

pentosidine, in rat skin collagen.

Cefalu WT, Bell-Farrow AD, Wang ZQ, Sonntag WE, Fu MX, Baynes JW,

Thorpe SR.

Department of Internal Medicine, Bowman Gray School of Medicine,

Winston-Salem, North Carolina, USA.

Nonenzymatic glycation of body proteins and subsequent advanced

glycation reactions have been implicated in the aging process, while

caloric restriction (CR) in rodents results in an increase in both

mean and maximum life span. We have evaluated the effect of chronic

(25 months) CR on glycation of blood proteins and accumulation of

advanced glycation and oxidation (glycoxidation) products, N

epsilon-(carboxymethyl)lysine (CML), and pentosidine, in skin

collagen. Brown-Norway rats, fed ad libitum (AL) from birth, were

divided into two equal groups at 4 months of age and placed on AL or

CR diets (CR = 60% of AL diet). Cohorts of animals were sacrificed at

7, 13, and 25 months after the initiation of CR. At necropsy glycated

hemoglobin was measured by affinity HPLC and glycated plasma protein

by the fructosamine assay; extracts of skin collagen were analyzed by

gas chromatography-mass spectrometry for CML and by reversed-phase

HPLC for pentosidine. Glycation of hemoglobin, plasma proteins, and

skin collagen was decreased significantly (18-33%) by CR.

Concentrations of CML and pentosidine increased significantly with age

in skin collagen in both AL and CR animals; however, CR significantly

reduced levels of CML (25%), pentosidine (50%), and fluorescence (15%)

in collagen in the oldest rats. We conclude that CR reduces the extent

of glycation of blood and tissue proteins and the age-related

accumulation of glycoxidation products in skin collagen.

PMID: 7583789

>>>

From: " old542000 " <apater@m...>

Date: Sat Jan 15, 2005 5:15 pm

Subject: CR and brain disease

It has been wondered by some whether CR is bad for brains. The below

suggests this is not true, as some reports have indicated.

Alzheimer's disease is found to be less of a risk with CR it seems.

1: FASEB J. 2005 Jan 13;

Caloric restriction attenuates beta-amyloid neuropathology in a mouse

model of Alzheimer's disease.

[snip]

RESULTS

To test the hypothesis that CR can modulate amyloidosis, 3-month-old

Tg2576 mice, which develop AD-type amyloid neuropathology by 8-10

months of age (5, 12), were maintained for 9 months with a daily low

carbohydrate diet resulting in a 30% lower caloric intake compared

with that consumed by age- and gender-matched control Tg2576 mice fed

AL with a standard laboratory rodent diet.

>>>