Calorie-restricted Rats Research Articles

Caloric restriction delays cardiac ageing in rats: role of mitochondria

We tested whether long-term caloric restriction (CR) corrects pre-existing manifestations of cardiac ageing in rats. The age-specific effects of CR (-40%, 6 months) on mortality, left ventricular (LV) function, mitochondrial function, oxidative damage, and apoptosis were analysed in young (6 + 6 months) and senescent rats (24 + 6 months). CR in senescent rats significantly reduced mortality. LV and cardiomyocyte hypertrophy were reduced together with the mRNA expression and plasma concentrations of overload indicators BNP/ANP. Mitochondrial function was improved, resulting in lower oxidative damage and apoptotic activation. In particular, the pro-apoptotic Bcl-xS/Bcl-xL isoform pattern, mitochondrial translocation of Bax, release of cytochrome C into cytosol, and caspase-9 activation were reduced in comparison to age-matched rats on the control diet. However, CR resulted only in minor changes in young rats. Serum obtained from old control or CR rats was used for in vitro experiments. H9C2 cardiomyoblasts and adult rat ventricular cardiomyocytes preconditioned with CR serum demonstrated a low Bcl-xS/Bcl-xL ratio. H9C2 cells were resistant against H(2)O(2)-mediated loss of mitochondrial membrane potential, apoptosis activation, and reduced cell viability. Thus, beneficial effects of CR are mediated through circulating factors and can be mimicked with CR serum. However, this protection critically depended on a high Bcl-xL protein expression as seen after siRNA-mediated Bcl-xL knockdown. CR is cardioprotective in senescent myocardium by correcting pre-existing mitochondrial dysfunction and apoptotic activation and by preventing deterioration in LV function. Therefore, interventions that mimic these effects of CR may represent an additional therapeutic option for the aged or failing heart.

Calorie restriction: A new therapeutic intervention for age-related dry eye disease in rats

A decrease in lacrimal gland secretory function is closely related to aging and leads to an increased prevalence of dry eye syndrome. Since calorie restriction (CR) is considered to prevent functional decline of various organs due to aging, we hypothesized that CR could prevent age-related lacrimal dysfunction. Six-month-old male Fischer 344 rats were randomly divided into ad libitum (AL) and CR (−35%) groups. After 6 months of CR, tear function was examined under conscious state. After euthanasia, lacrimal glands were subjected to histological examination, tear protein secretion stimulation test with Carbachol, and assessment of oxidative stress with 8-hydroxy-2 deoxyguanosine (8-OHdG) and 4-hydroxynonenal (HNE) antibodies. CR significantly improved tear volume and tended to increase tear protein secretion volume after stimulation with Carbachol compared to AL. The acinar unit density was significantly higher in the CR rats compared to AL rats. Lacrimal glands in the CR rats showed a lesser degree of interstitial fibrosis. CR reduced the concentration of 8-OHdG and the extent of staining with HNE in the lacrimal gland, compared to AL. Furthermore, our electron microscopic observations showed that mitochondrial structure of the lacrimal gland obtained from the middle-aged CR rats was preserved in comparison to the AL rats. Collectively, these results demonstrate for the first time that CR may attenuate oxidative stress related damage in the lacrimal gland with preservation of lacrimal gland functions. Although molecular mechanism(s) by which CR maintains lacrimal gland function remains to be resolved, CR might provide a novel therapeutic strategy for treating dry eye syndrome.

Validated biomarkers of caloric restriction in rats: Markers of disease risk in humans?

Caloric restriction (CR) robustly increases longevity/reduces morbidity in mammals, eg., breast cancer risk is generally decreased >90% in CR rodents. CR is usually dominant to other risk factors and are directly analogous to human data linking obesity with poor health outcomes, including cancer. We tested if biomarkers of diet in rats predicts future disease in humans.MethodsMetabolomics measurements in sera/plasma were conducted w/HPLC/Coularray detectors (N~600 rats, ~1700 humans). Classification/predictive power were tested, optimized, and validated using a series of megavariate data analysis approaches in sequential blinded cohorts.ResultsModels distinguish diet groups with >95% accuracy. Diets varying in extent/duration of CR were used to develop models for intermediate caloric intakes. Markers were adapted for human study, analytically validated at instrumentation (N=30; 100% blinded split accuracy) and sample collection levels (N=34; most stable under worst case conditions), then biologically validated (N~70 in triplicate, metabolites/profiles had intraclass correlation coefficients ~0.65–0.85). Marker profile scores reflects energy intake/risk of future breast cancer in 210 case/control pairs nested within the Nurses’ Health Study.ConclusionMetabolomics profiles offer a potential biochemical approach to validate nutritive status and contribute to risk analysis. NIH

Effects of long-term dietary interventions on pituitary growth hormone-releasing hormone receptor in aging rats and potential mechanisms of action

Long-term moderate caloric restriction (LTMCR) is a powerful intervention to delay age-related health deterioration. In this study, the effects of 40% caloric restriction (CR), implemented at 8 months with or without protein restriction, and 40% dietary protein restriction alone, implemented at 2 months, were examined on pituitary growth hormone-releasing hormone receptor (GHRH-R) and GHRH sensitivity in 12–20-month-old male Sprague Dawley rats. An increase of the 4-kb GHRH-R mRNA transcript and 4 kb/2.5 kb ratio, the blunting of high affinity GHRH binding sites and a decrease in GHRH-induced cAMP production were observed in old rats. Only 40% CR maintained youthful levels of GHRH-R transcripts and GHRH binding parameters as well as maximal GHRH-induced cAMP production. Moreover, the GHRH-induced capacity of somatotrophs to synthesize/repair DNA in vitro, in the presence of moderate glucotoxic stress (12 mM d-glucose), was maintained in old CR rats. Among the hormonal and metabolic regulators of GHRH-R that were modified by LTMCR, glucose, free fatty acids and glucocorticoids represent promising candidates for future investigation. A better understanding of the molecular and cellular mechanisms by which they regulate the pituitary GHRH-R should help define strategies to mimic the beneficial effects of LTMCR by less demanding interventions.

Effect of caloric restriction on base-excision repair (BER) in the aging rat brain

Apyrimidinic/apurinic endonuclease (APE) is a key protein involved in the base-excision DNA repair (BER) pathway of oxidative DNA lesions. Using a novel oligonucleotide substrate, we demonstrate that APE activity in the frontal/parietal cortex (F/PCTX), cerebellum, brainstem, midbrain and hypothalamus declined with age in rats on an ad libitum (AL) diet. In contrast, APE activity for these brain regions was ∼1.5–3 times higher in young, caloric restricted (CR) rats. Despite continuous CR treatment in all animals since six weeks of age, APE activity in the CR group started to decline by middle-age and continued into old age. However, CR maintained APE activity at a level that was significantly higher than that in AL rats across age and in the brain regions examined. Because Western analysis of APE, DNA polymerase β and DNA ligase III levels in the F/PCTX of both CR and AL rats remained unchanged with age, this suggests that the increased APE activity in CR rats is the result of differential post-translational modification of APE.

Inaccessible food cues affect stress and weight gain in calorically-restricted and ad lib fed rats

Research suggests that caloric restriction (CR) is beneficial; however, the effects of CR in the context of food cues are unclear. A 2 (food cue vs. no cue) × 2 (CR vs. ad lib) between-subjects design was employed to test these effects in 40 rats. It was predicted that cue exposure and CR would induce stress, and that these factors might interact synergistically. The results demonstrated that cue-exposed CR rats weighed less than did non-exposed CR rats. A blunted stress response was evident in CR rats relative to ad lib rats. Finally, cue-exposed rats had higher corticosterone levels and body weight during ad lib feeding than did non-cued rats. These results suggest that both CR and chronic food-cue exposure can be stressful, and the implications of this research are discussed in the context of humans’ ‘obesigenic’ environment.

Skeletal muscle autophagy and apoptosis during aging: Effects of calorie restriction and life-long exercise

Sarcopenia, loss of muscle mass and function, is a common feature of aging. Oxidative damage and apoptosis are likely underlying factors. Autophagy, a process for the degradation of cellular constituents, may be a mechanism to combat cell damage and death. We investigated the effect of age on autophagy and apoptosis in plantaris muscle of male Fischer 344 rats that were either fed ad libitum, or mild, life-long calorie restricted (CR) alone or combined with life-long voluntary exercise. Upstream autophagy-regulatory proteins were either upregulated with age (Beclin-1) or unchanged (Atg7 and 9). LC3 gene and protein expression pattern as well as LAMP-2 gene expression, both downstream regulators of autophagy, however, suggested an age-related decline in autophagic degradation. Atg protein expression and LC3 and LAMP-2 gene expression were improved in CR rats with or without exercise. The age-related increase in oxidative damage and apoptosis were attenuated by the treatments. Both, oxidative damage and apoptosis correlated negatively with autophagy. We conclude that mild CR attenuates the age-related impairment of autophagy in rodent skeletal muscle, which might be one of the mechanisms by which CR attenuates age-related cellular damage and cell death in skeletal muscle in vivo.

Anorexic Vs. Metabolic Effects of Central Leptin Infusion in Rats of Various Ages and Nutritional States

Age-related obesity is known to be adjoined by leptin resistance. It has not been clarified whether the resistance is cause or result of obesity. In the present experiments, the anorexic (suppressing food intake and body weight) and hypermetabolic (increasing body temperature (Tc), activity, and heart rate (HR), indicating metabolic rate) responses to 7-day-long intracerebroventricular leptin infusion were compared in 2- and 6-month-old normally fed (NF2 and NF6 groups), 6-month-old high-fat-diet-induced obese (HF6), and 6-month-old calorie-restricted (CR6) rats. The anorexic effects were inversely related to fat content: They were most pronounced in NF2, less in NF6, non-significant in HF6 rats, but also absent in CR6 animals of the lowest fat content. This virtual leptin resistance in CR6 rats was due to their high orexigenic activity (enhanced feeding response to NPY). In contrast, CR6 rats were hypersensitive to the metabolic effects of leptin infusion (rise in Tc and HR; biotelemetric measurements), NF2 were still sensitive, while NF6 and HF6 rats exhibited moderate or low sensitivity. In conclusion, leptin resistance depends on body fat content rather than on age itself, although with age the proportion of fat tissue increases and contributes to self-perpetuating rise in body weight.

Beta-Catenin Activation Promotes Liver Regeneration after Acetaminophen-Induced Injury

Acute liver failure (ALF) remains a disease with poor patient outcome. Improved prognosis is associated with spontaneous liver regeneration, which supports the relevance of exploring 'regenerative' therapies. Therefore, the role of the Wnt/beta-catenin pathway in liver regeneration following ALF was investigated. ALF was induced in mice by acetaminophen overdose, which is also a leading cause of liver failure in patients. beta-catenin distribution was also studied in liver sections from acetaminophen-induced ALF patients. A nonlethal dose of acetaminophen, which induces liver regeneration, led to stabilization and activation of beta-catenin for 1 to 12 hours. These data were also verified by increased expression of the beta-catenin surrogate target glutamine synthetase. Beta-catenin activation occurred secondary to the inactivation of glycogen synthase kinase-3beta and an increase in levels of casein kinase 2alpha, and led to increased cyclin-D1, another known beta-catenin target. These observations were next substantiated in beta-catenin conditional-null mice (beta-catenin-null), which show dampened regeneration after acetaminophen injury following induction of CYP2e1/1a2 expression. In light of decreased acetaminophen injury in beta-catenin-null mice despite CYP induction, equitoxic studies in control mice were performed. Significant differences in regeneration persisted following comparable injury in beta-catenin-null and control animals. Retrospective analysis of liver samples from acetaminophen-overdose patients demonstrated a positive correlation between nuclear beta-catenin, proliferation, and spontaneous liver regeneration. Thus, our studies demonstrate early activation of beta-catenin signaling during acetaminophen-induced injury, which contributes to hepatic regeneration.

Divergent regulation of adipose tissue metabolism by calorie restriction and inhibition of growth hormone signaling

Calorie restriction (CR) and a reduced growth hormone (GH) signal affect insulin sensitivity and lifespan in mammals in a similar manner. We investigated the effects of CR and moderate inhibition of GH on glucose-stimulated activation of insulin signaling and the expression of genes related to fat metabolism in white adipose tissue (WAT) in rats. We used 10-month-old male, wild-type (W) Wistar rats, fed ad libitum (AL) or a 30% CR diet from 6 weeks of age, and transgenic (Tg) rats with moderately suppressed GH signaling. Rats were killed 15 min after an intraperitoneal injection of glucose or saline. In control W–AL rats, the levels of serum insulin, phosphorylated (p) insulin receptor (pY-IR), p-Akt, and the expression of glucose transporter (Glut) 4 in the membrane fraction were greater in the glucose-injected group than in the saline-injected group, indicating significant activation of insulin signaling in response to glucose loading. In the W–CR and Tg–AL rats, the serum insulin and pY-IR levels were lower than those in the W–AL rats. The Akt–Glut pathway was up-regulated even after saline-injection. Expression levels of adipogenic and lipogenic genes including PPARγ, adiponectin, and its receptors, were higher in the W–CR rats than in the W–AL and Tg–AL rats. The present findings indicate adipose tissue metabolic profiles specific to CR.

Influence of Calorie Restriction on Measures of Age-Related Cognitive Decline: Role of Increased Physical Activity

Controversy exists as to whether lifelong 40% calorie restriction (CR) enhances, has no effect on, or disrupts cognitive function during aging. Here, we report the effects of CR versus ad-lib feeding on cognitive function in male Brown Norway x Fisher344 rats across a range of ages (8-38 months), using two tasks that are differentially sensitive to age-related cognitive decline: object recognition and Morris water maze (MWM). All ages performed equally in object recognition, whereas, as a group, CR rats were impaired. In contrast, there was an age-related impairment in the MWM that was attenuated by CR as measured by time in proximity with and latency to reach the platform. Distance to the platform, a more sensitive measure, was not affected by CR. Finally, CR resulted in an overall increase in physical activity, one of several behavioral confounders to consider in the interpretation of cognitive outcomes in both tasks.

Highlights From The Literature

Highlights From The Literature

Stability of local brain levels of insulin-like growth factor-I in two well-characterized models of decreased plasma IGF-I

Insulin-like growth factor-I (IGF-I), a functionally important neurotrophic factor, impacts tissues throughout the body including the central nervous system. In addition to the significant proportion of IGF-I that is synthesized in the liver and released into the plasma, IGF-I is expressed locally in tissues. The present study investigated the relationship between plasma and local brain levels of IGF-I in two well-characterized models of decreased IGF-I. The first is an adult-onset growth hormone deficiency (AOGHD) model, and the second is a caloric restriction (CR) model. In the first cohort of animals from both models, the hippocampus was removed from the brain immediately following decapitation, and in the second cohort, the animals were perfused transcardially with phosphate buffered saline to remove cerebral blood prior to harvesting the hippocampus. Our results demonstrated that although the plasma IGF-I levels were decreased in the CR and AOGHD rats compared to controls, the hippocampal IGF-I levels did not differ among the groups. These data suggest that local brain IGF-I levels are regulated in a different manner than plasma IGF-I levels.

Influence of nutritional state on leptin effects in rats

Event Abstract Back to Event Influence of nutritional state on leptin effects in rats Miklos Szekely1*, Marta Balasko1, Tore Schjottelvik1, Szilvia Soos1 and Erika Petervari1 1 University of Pécs, Department of Pathophysiology and Gerontology, Hungary The main target of white adipose tissue-derived leptin is the arcuate nucleus: it inhibits the expression or production of anorexigenic peptides and stimulates the activity of orexigenic ones. Lack of leptin or presence of defective leptin-receptor is accompanied by severe obesity. With aging a decreased responsiveness to leptin develops, which might be connected with age-related obesity. It is also possible, however, that the obesity is responsible for the decreased responsiveness. In the present studies the effect of a 7-day-long, 1 µg/h dose intracerebroventricular infusion of recombinant leptin was studied on body weight (BW) and food intake (FI) in 2- or 6-months-old normally fed (NF2 or NF6; 282±15 or 456±13 g) male Wistar rats and 6-months-old rats made obese by calorie-rich food (OB6; 588±12 g) or 6-months-old calorie-restricted (CR6; 361±7 g) rats (2/3 of normal diet = 16 g/day). By the end of the infusion period BW decreased by 8.6% in NF2, 10.2% in NF6, 5.6% in OB6 and 0.1% in CR rats. FI decreased by ca. 50% in the NF groups, 7.6% in OB6 rats, while CR6 rats ate all the 16 g of food. It is concluded that obesity rather than age contributes to the decreased leptin responsiveness. In later ages this may be even more pronounced. In contrast, in CR6 animals leptin had no effect on FI: this might be due to low responsiveness to anorexigenic peptides (as we have earlier demonstrated for melanocortins in lean juvenile rats) or enhanced responsiveness to orexigenic ones. (Support: OTKA 49321). Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Homeostatic regulatory mechanisms Citation: Szekely M, Balasko M, Schjottelvik T, Soos S and Petervari E (2009). Influence of nutritional state on leptin effects in rats. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.002 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 24 Feb 2009; Published Online: 24 Feb 2009. * Correspondence: Miklos Szekely, University of Pécs, Department of Pathophysiology and Gerontology, Pecs, Hungary, miklos.szekely@aok.pte.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Miklos Szekely Marta Balasko Tore Schjottelvik Szilvia Soos Erika Petervari Google Miklos Szekely Marta Balasko Tore Schjottelvik Szilvia Soos Erika Petervari Google Scholar Miklos Szekely Marta Balasko Tore Schjottelvik Szilvia Soos Erika Petervari PubMed Miklos Szekely Marta Balasko Tore Schjottelvik Szilvia Soos Erika Petervari Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The effect on renal structure and function of late-life-introduced caloric restriction (CR) in rats

Previous studies have shown that life-long caloric restriction in rats protects the kidneys from age-dependent injury. In this study, we analyzed whether late-life-introduced caloric restriction has a similar effect. The study lasted 12 months. Three groups of animals were analyzed: rats fed "ad libitum" (AD, n = 9), rats on 60% caloric restriction (CR, n = 9), and rats fed "ad libitum" for the first six months of their life then switched to 60% caloric restriction thereafter (LCR, n = 9). At the end of the study kidney function was assessed and kidney samples were analyzed histologically. Serum creatinine and urine albumin were higher in AD than in both CR and LCR (P < 0.001). Creatinine clearance (Cl(cr)) corrected for body weight was lowest in AD and comparable in CR and LCR. Similarly Cl(cr) corrected for kidney weight was lower in AD than in both CR and LCR (P < 0.05). Severe albuminuria was observed only in AD. In CR and LCR the amount of albumin excreted was comparable (AD vs. CR, P < 0.0001; AD vs. LCR, P < 0.001). In morphometric analysis, the mean size of the glomeruli was higher in AD than in both CR and LCR (P < 0.01). Similar results were found for the mesangial area (AD vs. CR, P < 0.001; AD vs. LCR, P < 0.01) and for mesangial cell counts (AD vs. CR, P < 0.001; AD vs. LCR, P < 0.05). No difference was found between CR and LCR in morphometry. In conclusion, our study indicates that late-life introduction of caloric restriction reverses most of the structural and functional changes observed in the kidneys of "ad libitum"-fed rats.

Localization of Abasic Sites and Single-Strand Breaks in Mitochondrial DNA from Brain of Aged Rat, Treated or not with Caloric Restriction Diet

According to the "mitochondrial theory of aging" the lifelong accumulation of various kinds of damage to mitochondrial DNA (mtDNA) has been related to the age-dependent mitochondrial bioenergetic dysfunction. Caloric restriction (CR) diet is able to prevent or delay the onset of several age-related damages to mtDNA. The effects of aging and CR on the presence of abasic sites and single-strand breaks of the sugar-phosphate backbone in mtDNA have been analyzed by applying Ligation Mediated-PCR to a H strand region of brain mtDNA from young and old ad libitum-fed and old CR-treated rats. The region, encompassing the Direct Repeat 1 of the 4,834 bp-long deletion, is highly damaged in the old ad libitum-fed animals with respect to the young ones, whereas in the CR rats it shows a much lower extent of damage. The data confirm, at single nucleotide resolution, the protective effect of CR on the age-related mtDNA damage.

Caloric restriction optimizes the proteasome pathway with aging in rat plantaris muscle: implications for sarcopenia

To gain insight into the significance of alterations in the proteasome pathway for sarcopenia and its attenuation by calorie restriction, we examined protein oxidation and components of the proteasome pathway in plantaris muscle in 8-, 30-, and 35-mo-old ad libitum-fed (AL) rats; and in 8-, 35-, and 40-mo-old calorie-restricted (CR) rats. We hypothesized that CR rats would exhibit a lesser accumulation of protein carbonyls with aging and that this would be associated with a better maintenance of skeletal muscle proteasome activity and function with aging. Consistent with this view, whereas AL rats had a significant increase in protein carbonylation with aging, there was no such increase in CR rats. Protein levels of the ubiquitin ligases MuRF1 and MAFbx increased similarly with aging in both AL and CR rats. On the other hand, chymotrypsin-like activity of the proteasome increased with aging more gradually in CR rats, and this increase was paralleled by increases in the expression of the C2 subunit in both groups, suggesting that differences in activity were not related to differences in proteasome function with aging. Interestingly, the plot of muscle mass vs. proteasome activity showed that the oldest animals in both diets had a lower muscle mass than would be predicted by their proteasome activity, suggesting that other factors explain the acceleration of sarcopenia at advanced age. Since calorie restriction better protects skeletal muscle function than muscle mass with aging (Hepple RT, Baker DJ, Kaczor JJ, Krause DJ, FASEB J 19: 1320-1322, 2005), and our current results show that this protection of function is associated with a prevention of oxidative protein damage accumulation, we suggest that calorie restriction optimizes the proteasome pathway to preserve skeletal muscle function at the expense of modest muscle atrophy.

R403 – Epidermal Proliferating Cell Nuclear Antigen in Aging Rats

Problem To determine if epidermal cell proliferation in colony-raised Fischer 344 rats changes with age and diet. Methods Fischer 344 rats fed ad libitum and calorie-restricted (CR) diets were obtained from the NIA colonies, and young, young adult, and old animals from both groups were used for this study (six in each group). Tissue sections from the dorsal skin (DS) and foot plate (FP) were used for immunohistochemical staining of proliferating cell nuclear antigen (PCNA). The proliferation index (PCNA-I) was computed from counts of stained and total number of keratinocytes. Simultaneous measurements of epidermal thickness were obtained from same sections. Data were analyzed with Excel and SPSS 14.0 software for statistics. Results Two-way analysis of variance (ANOVA) was applied to the data to probe the effect of age, diet, and age-diet interaction. A significant effect of age was noticed in the two parameters i.e., DS PCNA (F 3.96, P .011), FP epidermal width (F 3.37, P .021) and FP PCNA-I (F 9.0, P .000). A significant correlation between DS width and PCNA values was also noted (r 0.5, P .01). Conclusion There is a trend of reduction of PCNA positive cells with increasing age irrespective of thickness of epidermis, and this trend is more apparent in CR rats. Significance This cell proliferation study has implications in relation to CR effect on age-related disease conditions, and biogerontology. Support The study was partially funded by the 2007 Leslie Bernstein grant from AAFPRS foundation.

Enhanced activation of a “nutrient‐sensing” pathway with age contributes to insulin resistance

Calorie restriction improves life span whereas nutrient excess leads to obesity and unfavorable metabolic consequences, supporting the role for a cellular "nutrient sensor" in aging. Hexosamine biosynthetic pathway (HBP) is a candidate nutrient-sensing pathway. We hypothesized that altered nutrient sensing (by HBP) with age may provide a link among aging, nutrient flux, and insulin resistance. Using a hyperinsulinemic clamp in young rats, we show that experimental activation of HBP, through the systemic infusion of glucosamine, induced severe insulin resistance (36% decline in peripheral insulin action; P<0.05), increased adipose tissue gene expression of fat-derived peptides (PAI-1 by 4-fold, angiotensinogen 3-fold, leptin 2-fold, resistin 4-fold, and adiponectin 4-fold; P<0.01 compared with young saline-infused), and enhanced glycosylation of transcription factors, thus mimicking a physiological and biological phenotype of aging. We further demonstrate a greater activation of nutrient-sensing HBP with age in both old ad libitum-fed and calorie-restricted rats. Interestingly, old calorie-restricted animals rapidly develop insulin resistance when exposed to glucosamine, despite their "young" phenotype. These results suggest that altered nutrient sensing by HBP with age may be the link among nutrients, insulin resistance, and age-related diabetes.

Combined Effect of Gender and Caloric Restriction on Liver Proteomic Expression Profile

We analyzed the combined effect of gender and CR on protein expression profile in liver. We identified 27 differentially expressed proteins involved in several cellular functions such as substrate metabolism, antioxidant systems, stress response, iron homeostasis and cardiovascular protection. This study reveals new cellular pathways liable to be similarly regulated in females and calorie restricted rats and which could be related with the greater longevity in these animals.