Diet-restricted Animals Research Articles

The C. elegans Myc-family of transcription factors coordinate a dynamic adaptive response to dietary restriction.

Dietary restriction (DR), the process of decreasing overall food consumption over an extended period of time, has been shown to increase longevity across evolutionarily diverse species and delay the onset of age-associated diseases in humans. In Caenorhabditis elegans, the Myc-family transcription factors (TFs) MXL-2 (Mlx) and MML-1 (MondoA/ChREBP), which function as obligate heterodimers, and PHA-4 (orthologous to FOXA) are both necessary for the full physiological benefits of DR. However, the adaptive transcriptional response to DR and the role of MML-1::MXL-2 and PHA-4 remains elusive. We identified the transcriptional signature of C. elegans DR, using the eat-2 genetic model, and demonstrate broad changes in metabolic gene expression in eat-2 DR animals, which requires both mxl-2 and pha-4. While the requirement for these factors in DR gene expression overlaps, we found many of the DR genes exhibit an opposing change in relative gene expression in eat-2;mxl-2 animals compared to wild-type, which was not observed in eat-2 animals with pha-4 loss. Surprisingly, we discovered more than 2000 genes synthetically dysregulated in eat-2;mxl-2, out of which the promoters of down-regulated genes were substantially enriched for PQM-1 and ELT-1/3 GATA TF binding motifs. We further show functional deficiencies of the mxl-2 loss in DR outside of lifespan, as eat-2;mxl-2 animals exhibit substantially smaller brood sizes and lay a proportion of dead eggs, indicating that MML-1::MXL-2 has a role in maintaining the balance between resource allocation to the soma and to reproduction under conditions of chronic food scarcity. While eat-2 animals do not show a significantly different metabolic rate compared to wild-type, we also find that loss of mxl-2 in DR does not affect the rate of oxygen consumption in young animals. The gene expression signature of eat-2 mutant animals is consistent with optimization of energy utilization and resource allocation, rather than induction of canonical gene expression changes associated with acute metabolic stress, such as induction of autophagy after TORC1 inhibition. Consistently, eat-2 animals are not substantially resistant to stress, providing further support to the idea that chronic DR may benefit healthspan and lifespan through efficient use of limited resources rather than broad upregulation of stress responses, and also indicates that MML-1::MXL-2 and PHA-4 may have distinct roles in promotion of benefits in response to different pro-longevity stimuli.

Behavioral, Hormonal, and Serotonergic Responses to Different Restricted Feeding Schedules in Rats.

To determine the effect of long-term restricted feeding schedules on behavior, serotonergic responses, and neuro-endocrine functions, metabolism of serotonin (5-HT) in the striatum, expression of serotonin-1A (5-HT1A) auto-receptor in the raphe nuclei and circulating levels of leptin and corticosterone were determined in female Wistar rats kept on excessive food restriction schedule. Due to a role of dietary deficiency of tryptophan (Trp) in influencing serotonergic neurotransmission, circulating levels of Trp were also determined. Estimations were done in 2 different restricted feeding models: time-restricted feeding (TRF) and diet restricted (DR). TRF animals were given access to food ad libitum only for 2 hours/day. The DR animals were given a small calculated amount of food each day. We found that chronic food restriction for 5 weeks cause a significant decrease in the body weight and produced hyperactivity in both, TRF and DR animals. Levels of Trp were declined in circulation and in the striatum. Similarly, the levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) were decreased in the striatum. Also, the expression of 5-HT1A auto-receptor was declined in the raphe nuclei. These changes in 5-HT metabolism and 5-HT1A auto-receptor expression were more profound in DR animals as compare to TRF animals. Similarly, hypoleptinemia and increased corticosterone found in both models was higher in DR animals. Effect of dietary deficiency of Trp in the modulation of striatal 5-HT metabolism and its consequences on circulating leptin and corticosterone are discussed.

Lamin regulates the dietary restriction response via the mTOR pathway in Caenorhabditis elegans.

ABSTRACTAnimals subjected to dietary restriction (DR) have reduced body size, low fecundity, slower development, lower fat content and longer life span. We identified lamin as a regulator of multiple dietary restriction phenotypes. Downregulation of lmn-1, the single Caenorhabditis elegans lamin gene, increased animal size and fat content specifically in DR animals. The LMN-1 protein acts in the mTOR pathway, upstream of RAPTOR and S6 kinase β1 (S6K), a key component of and target of the mechanistic target of rapamycin (mTOR) complex 1 (mTORC1), respectively. DR excludes the mTORC1 activator RAGC-1 from the nucleus. Downregulation of lmn-1 restores RAGC-1 to the nucleus, a necessary step for the activation of the mTOR pathway. These findings further link lamin to metabolic regulation.

Nervous System Deletion of Mammalian INDY in Mice Mimics Dietary Restriction-Induced Memory Enhancement.

Reduced expression of the Indy (I'm Not Dead Yet) gene extends life span in Caenorhabditis elegans and Drosophila melanogaster and improves the metabolic heath of Mus musculus through inducing a physiological status akin to dietary restriction (DR). Although the function of Indy in aging and hepatic metabolism has been extensively studied, its role in the mouse nervous system remains unclear. Here, we explore the effect of mammalian Indy (mIndy, SLC13A5) gene deletion on murine cognitive function. Similar to what is seen in DR animals, systemic deletion of the mIndy gene (mIndy knockout [KO]) significantly improves memory performance and motor coordination of mice. Both DR and mIndy KO mice act normally in other behavioral tasks, including emotional, social, and food-seeking behaviors. Moreover, we find that tissue-specific deletion of mIndy in the nervous system is sufficient to improve memory performance, while liver-specific deletion has no effect on memory, and results in tests of motor coordination show no changes in either mutant. Mice with systemic or nervous system deletion of mIndy also exhibit increased hippocampal neurogenesis and dendritic spine formation in dentate granule cells; these changes are well-documented contributors to enhanced memory performance. Together, our studies demonstrate a critical role for brain-derived mIndy expression in the regulation of memory function in animals.

Feed restriction since lactation has reduced anxiety in adult Wistar rats

ABSTRACT Objective To evaluate the effects of macronutrients (protein, carbohydrate and/or lipid) in the diet of young adult (72 days) and adult (182 days) Wistar rats treated ad libitum and with 30% restriction from birth on anxiety in the elevated plus-maze. Methods We used 238 rats treated from birth, composing the groups: Control, Protein, Carbohydrate, Lipid, Carbohydrate and Lipid, Control Restriction, Protein Restriction, Carbohydrate Restriction, Lipid Restriction and Carbohydrate and Lipid Restriction. The animals were weighed at the beginning and at the end of the experiment and tested in the elevated plus-maze. Data were submitted to analysis of variance, followed by the Newman-Keuls Test (p<0.05). Results Among the animals treated ad libitum, the Control, Carbohydrate plus Lipid and Lipid gained more weight than the Carbohydrate and Protein; ad libitum animals gained more weight than those on restriction; among the restrictions, Carbohydrate Restriction rats were the ones that gained less weight. Diet-restricted animals exhibited reduced first-entry latency, greater percentage of entries and time spent, frequency of open arm extremity visits, head dipping (protected and unprotected), and length of stay in the central area of the elevated plus-maze. The animals with 182 days presented greater latency for first entry, reduced frequency of false entries and visits to the ends of the open arms and protected head dipping. Conclusion Food restricted animals, regardless of the macronutrient present in the diet, were less anxious and/or increased their impulsivity and those at 182 days were more anxious and/or with reduced impulsivity.

Bone callus formation is highly disrupted by dietary restriction in growing rats sustaining a femoral fracture

Purpose To evaluate the effects of food restriction on fracture healing in growing rats. Methods Sixty-eight male Wistar rats were assigned to two groups: (1) Control and (2) Dietary restriction. After weaning the dietary restricted animals were fed ad libitum for 42 days with 50% of the standard chow ingested by the control group. Subsequently, the animals underwent bone fracture at the diaphysis of the right femur, followed by surgical stabilization of bone fragments. On days 14 and 28 post-fracture, the rats were euthanized, and the fractured femurs were dissected, the callus was analyzed by dual-energy X-ray absorptiometry, micro-computed tomography, histomorphometry, mechanical tests, and gene expression. Results Dietary restriction decreased body mass gain and resulted in several phenotypic changes at the bone callus (a delay in cell proliferation and differentiation, lower rate of newly formed bone and collagen deposition, reductions in bone callus density and size, decrease in tridimensional callus volume, deterioration in microstructure, and reduction in bone callus strength), together with the downregulated expression of osteoblast-related genes. Conclusion Dietary restriction had detrimental effects on osseous healing, with a healing delay and a lower quality of bone callus formation.

Effects of short-term dietary restriction and glutamine supplementation in vitro on the modulation of inflammatory properties.

Dietary restriction (DR) is a nutritional intervention that exerts profound effects on biochemical and immunologic parameters, modulating some inflammatory properties. Glutamine (GLN) is a conditionally essential amino acid that can modulate inflammatory properties. However, there is a lack of data evaluating the effects of DR and GLN supplementation, especially in relation to inflammatory cytokine production and the expression of transcription factors such as nuclear factor (NF)-κB. We subjected 3-mo-old male Balb/c mice to DR by reducing their food intake by 30%. DR animals lost weight and showed reduced levels of serum triacylglycerols, glucose, cholesterol, and calcium as well as a reduction in bone density. Additionally, blood, peritoneal, and spleen cellularity were reduced, lowering the number of peritoneal F4/80- and CD86-positive cells and the total number of splenic CD4- and CD8-positive cells. The production of interleukin (IL)-10 and the expression of NF-κB in splenic cells were not affected by DR or by GLN supplementation. However, peritoneal macrophages from DR animals showed reduced IL-12 and tumor necrosis factor-α production and increased IL-10 production with reduced phosphorylation of NF-κB expression. Additionally, GLN was able to modulate cytokine production by peritoneal cells from the control group, although no effects were observed in cells from the DR group. DR induces biochemical and immunologic changes, in particular by reducing IL-12 and tumor necrosis factor-α production by macrophages and clearly upregulating IL-10 production, whereas GLN supplementation did not modify these parameters in cells from DR animals.

Dietary restriction reduces hippocampal neurogenesis and granule cell neuron density without affecting the density of mossy fibers

The hippocampal formation undergoes significant morphological and functional changes after prolonged caloric and dietary restriction (DR). In this study we tested whether prolonged DR results in deleterious alterations in hippocampal neurogenesis, density of granule cell neurons and mossy fibers, all of which support plasticity in the dentate gyrus. Young adult animals either experienced free access to food (control condition), or every-other-day feeding regimen (DR condition) for 3months. The number of Ki-67 cells and 28-day old 5-bromo-2′-deoxyuridine (BrdU) cells were quantified in the dorsal and ventral dentate gyrus to determine the effect of DR on cellular proliferation and survival of neural progenitor cells in the anatomically defined regions of the dentate gyrus. The density of granule cell neurons and synaptoporin were also quantified to determine the effect of DR on granule cell neurons and mossy fiber projections in the dentate gyrus. Our results show that DR increases cellular proliferation and concurrently reduces survival of newly born neurons in the ventral dentate gyrus without effecting the number of cells in the dorsal dentate gyrus. DR reduced density of granule cell neurons in the dorsal dentate gyrus. These alterations in the number of granule cell neurons did not affect mossy fiber density in DR animals, which was visualized as no differences in synaptoporin expression. Our findings demonstrate that granule cell neurons in the dentate gyrus are vulnerable to chronic DR and that the reorganization of granule cells in the dentate gyrus subregions is not producing concomitant alterations in dentate gyrus neuronal circuitry with this type of DR.

Cell size and fat content of dietary-restricted Caenorhabditis elegans are regulated by ATX-2, an mTOR repressor

Dietary restriction (DR) is a metabolic intervention that extends the lifespan of multiple species, including yeast, flies, nematodes, rodents, and, arguably, rhesus monkeys and humans. Hallmarks of lifelong DR are reductions in body size, fecundity, and fat accumulation, as well as slower development. We have identified atx-2, the Caenorhabditis elegans homolog of the human ATXN2L and ATXN2 genes, as the regulator of these multiple DR phenotypes. Down-regulation of atx-2 increases the body size, cell size, and fat content of dietary-restricted animals and speeds animal development, whereas overexpression of atx-2 is sufficient to reduce the body size and brood size of wild-type animals. atx-2 regulates the mechanistic target of rapamycin (mTOR) pathway, downstream of AMP-activated protein kinase (AMPK) and upstream of ribosomal protein S6 kinase and mTOR complex 1 (TORC1), by its direct association with Rab GDP dissociation inhibitor β, which likely regulates RHEB shuttling between GDP-bound and GTP-bound forms. Taken together, this work identifies a previously unknown mechanism regulating multiple aspects of DR, as well as unknown regulators of the mTOR pathway. They also extend our understanding of diet-dependent growth retardation, and offers a potential mechanism to treat obesity.

The Effect of Orally Administrated β-glucan and Dietary Restriction on Faecal Microflora in Rats

In this study we aimed to evaluate the effect of orally administered β-glucan and/or dietary restriction on Lactobacillus spp., coliforms, Enterobacteriaceae and enterococci counts in rat faeces. For this aim, rats were divided into three experimental groups: i) first group animals received normal diet for 6 months and administrated orally with β-glucan (20 mg/kg for bodyweigth) over the last 14 day of experiment, ii) second group was dietary restricted animals for 6 months and receiving β-glucan as those of first group animals, iii) last group was the control group rats receiving only ad libitum feed. Compared to control group, numeric increase was observed in the number of coliforms, Enterobacriaceae and lactobacillus counts in first group but this was not statistically important. The increase in coliforms and Enterobacteriaceae counts was nearly 2 log while this was 1 log for lactobacillus counts. Interestingly, dietary restriction + β-glucan administration had no significant influence on the increase of defined bacterial groups. The results of the present study showed that orally administration of the β-glucan, widely used as prebiotic, has the potential to modify faeces microbiota in rat model.

The metabolite α-ketoglutarate extends lifespan by inhibiting ATP synthase and TOR.

Metabolism and ageing are intimately linked. Compared with ad libitum feeding, dietary restriction consistently extends lifespan and delays age-related diseases in evolutionarily diverse organisms. Similar conditions of nutrient limitation and genetic or pharmacological perturbations of nutrient or energy metabolism also have longevity benefits. Recently, several metabolites have been identified that modulate ageing; however, the molecular mechanisms underlying this are largely undefined. Here we show that α-ketoglutarate (α-KG), a tricarboxylic acid cycle intermediate, extends the lifespan of adult Caenorhabditis elegans. ATP synthase subunit β is identified as a novel binding protein of α-KG using a small-molecule target identification strategy termed drug affinity responsive target stability (DARTS). The ATP synthase, also known as complex V of the mitochondrial electron transport chain, is the main cellular energy-generating machinery and is highly conserved throughout evolution. Although complete loss of mitochondrial function is detrimental, partial suppression of the electron transport chain has been shown to extend C. elegans lifespan. We show that α-KG inhibits ATP synthase and, similar to ATP synthase knockdown, inhibition by α-KG leads to reduced ATP content, decreased oxygen consumption, and increased autophagy in both C. elegans and mammalian cells. We provide evidence that the lifespan increase by α-KG requires ATP synthase subunit β and is dependent on target of rapamycin (TOR) downstream. Endogenous α-KG levels are increased on starvation and α-KG does not extend the lifespan of dietary-restricted animals, indicating that α-KG is a key metabolite that mediates longevity by dietary restriction. Our analyses uncover new molecular links between a common metabolite, a universal cellular energy generator and dietary restriction in the regulation of organismal lifespan, thus suggesting new strategies for the prevention and treatment of ageing and age-related diseases.

A Krüppel-like factor downstream of the E3 ligase WWP-1 mediates dietary-restriction-induced longevity in Caenorhabditis elegans.

The HECT ubiquitin E3 ligase WWP-1 is a positive regulator of lifespan in response to dietary restriction (DR) in Caenorhabditis elegans. However, substrates of WWP-1 for ubiquitylation in the DR pathway have not yet been identified. Here we identify the C. elegans Krüppel-like factor, KLF-1, as an essential and specific regulator of DR-induced longevity and a substrate for ubiquitylation by WWP-1. Knockdown of klf-1 suppresses the extended lifespan of both DR animals and wwp-1-overexpressing animals, indicating that KLF-1 functions within the same pathway as WWP-1. In addition, overexpression of klf-1 in the intestine is sufficient to extend the lifespan of WT animals on an ad libitum diet, and requires wwp-1 or pha-4/FoxA. We demonstrate that WWP-1 directly interacts with KLF-1 and mediates multiple monoubiquitylation of KLF-1 in vitro and in cellulo. Our data support a model in which modulation of KLF-1 by WWP-1 regulates diet-restriction-induced longevity.

Mitochondrial efficiency is increased in axenically cultured Caenorhabditis elegans

Culturing Caenorhabditis elegans in axenic medium leads to a twofold increase in lifespan and considering the similar phenotypical traits with dietary restricted animals, it is referred to as axenic dietary restriction (ADR). The free radical theory of aging has suggested a pivotal role for mitochondria in the aging process and previous findings established that culture in axenic medium increases metabolic rate. We asked whether axenic culture induces changes in mitochondrial functionality of C. elegans. We show that ADR induces increased electron transport chain (ETC) capacity, enhanced coupling efficiency and reduced leakiness of the mitochondria of young adult worms but not a decrease of ROS production capacity and in vivo H2O2 levels. The age-dependent increase in leak respiration and decrease in coupling efficiency is repressed under ADR conditions. Although ADR mitochondria experience a decrease in ETC capacity with age, they succeed to maintain highly efficient and well-coupled function compared to fully fed controls. This might be mediated by combination of a limited increase in supercomplex abundance and decreased individual CIV abundance, facilitating electron transport and ultimately leading to increased mitochondrial efficiency.

Sex-Specific Effect of Juvenile Diet on Adult Disease Resistance in a Field Cricket

Food limitation is expected to reduce an individual’s body condition (body mass scaled to body size) and cause a trade-off between growth and other fitness-related traits, such as immunity. We tested the condition-dependence of growth and disease resistance in male and female Gryllus texensis field crickets by manipulating diet quality via nutrient content for their entire life and then subjecting individuals to a host resistance test using the live bacterium Serratia marcescens. As predicted, crickets on a high-quality diet eclosed more quickly, and at a larger body size and mass. Crickets on a high-quality diet were not in better condition at the time of eclosion, but they were in better condition 7–11 days after eclosion, with females also being in better condition than males. Despite being in better condition, however, females provided with a high-quality diet had significantly poorer disease resistance than females on a low-quality diet and in poor condition. Similarly, males on low- and high-quality diets did not differ in their disease resistance, despite differing in their body condition. A sex difference in disease resistance under diet-restriction suggests that females might allocate resources toward immunity during development if they expect harsh environmental conditions as an adult or it might suggest that females allocate resources toward other life history activities (i.e. reproduction) when food availability increases. We do not know what immune effectors were altered under diet-restriction to increase disease resistance, but our findings suggest that increased immune function might provide an explanation for the sexually-dimorphic increase in longevity generally observed in diet-restricted animals.

It's all in the brain—2 neurons mediate increased life span upon various stressors in C. elegans

Work in the nematode Caenorhabditis elegans has led to fundamental insights into key biological mechanisms of ageing, which may be instrumental to develop strategies to increase life span and, more important, health span in humans. Dietary restriction (DR) and its surrogate, mild impairment of nutrient sensing pathways (insulin/IGF and/or mTOR axes) by genetic manipulation in the presence of normal food intake are among the most thoroughly investigated interventions, leading to life span extension in yeast, worms, flies and mice [1]. Surprisingly, it was shown that the effect of dietary restriction depends on the presence of two neurons (ASI) in C. elegans, whose ablation completely abrogates the effect [2]. Energy deprivation following dietary restriction leads to increased mitochondrial respiration, and the resulting, moderate increase in reactive oxygen species formation seems to be instrumental for life span extension as well [3,4] due to a process called “mitohormesis” [5]. Accordingly, moderate disturbance of the mitochondrial respiratory chain by mild mutations in several subunits was shown to be another fountain of youth [6–8]. In this issue of Molecular Metabolism, the Ristow group is closing the circle: They show that low amounts of three bona fide inhibitors of complex I of the respiratory chain extend life and health span in the worm [9]. They also show that this mimics dietary restriction, since it does not further extend survival of dietary restricted animals, and that again the effect of these inhibitors is gone if the two ASI neurons had been ablated [9]. They conclude that redox stress sensing in these two neurons may be the signal for the rest of the body to activate the “survive program”. Interestingly, in the same line the Dillin group had shown before that genetic interference with the respiratory chain specifically in neurons activates a beneficial, mitochondrial unfolded protein response in distant tissues, postulating a diffusible, however still unidentified, “mitokine” [10]. There are numerous other examples showing that neurons are necessary for the life span extending effect of various genetic and dietary interventions, and finally even a small molecule, the antidepressant mianserin, inhibiting neuronal serotonin transmission, let live worms longer [11]. This and the recent study of the Ristow team raises hope that maybe also in humans, pharmacologic interventions – specifically aiming at neuro-endocrine signaling instead of targeting peripheral organs – may be available in the near future to treat ageing-related diseases.

Enhanced Phase II Detoxification Contributes to Beneficial Effects of Dietary Restriction as Revealed by Multi-platform Metabolomics Studies

Dietary restriction (DR) has many beneficial effects, but the detailed metabolic mechanism remains largely unresolved. As diet is essentially related to metabolism, we investigated the metabolite profiles of urines from control and DR animals using NMR and LC/MS metabolomic approaches. Multivariate analysis presented distinctive metabolic profiles and marker signals from glucuronide and glycine conjugation pathways in the DR group. Broad profiling of the urine phase II metabolites with neutral loss scanning showed that levels of glucuronide and glycine conjugation metabolites were generally higher in the DR group. The up-regulation of phase II detoxification in the DR group was confirmed by mRNA and protein expression levels of uridinediphospho-glucuronosyltransferase and glycine-N-acyltransferase in actual liver tissues. Histopathology and serum biochemistry showed that DR was correlated with the beneficial effects of low levels of serum alanine transaminase and glycogen granules in liver. In addition, the Nuclear factor (erythroid-derived 2)-like 2 signaling pathway was shown to be up-regulated, providing a mechanistic clue regarding the enhanced phase II detoxification in liver tissue. Taken together, our metabolomic and biochemical studies provide a possible metabolic perspective for understanding the complex mechanism underlying the beneficial effects of DR.

Dietary restriction attenuates age‐associated muscle atrophy by lowering oxidative stress in mice even in complete absence of CuZnSOD

Age-related loss of muscle mass and function, sarcopenia, has a major impact on the quality of life in the elderly. Among the proposed causes of sarcopenia are mitochondrial dysfunction and accumulated oxidative damage during aging. Dietary restriction (DR), a robust dietary intervention that extends lifespan and modulates age-related pathology in a variety of species, has been shown to protect from sarcopenia in rodents. Although the mechanism(s) by which DR modulates aging are still not defined, one potential mechanism is through modulation of oxidative stress and mitochondrial dysfunction. To directly test the protective effect of DR against oxidative stress-induced muscle atrophy in vivo, we subjected mice lacking a key antioxidant enzyme, CuZnSOD (Sod1) to DR (60% of ad libitum fed diet). We have previously shown that the Sod1(-/-) mice exhibit an acceleration of sarcopenia associated with high oxidative stress, mitochondrial dysfunction, and severe neuromuscular innervation defects. Despite the dramatic atrophy phenotype in the Sod1(-/-) mice, DR led to a reversal or attenuation of reduced muscle function, loss of innervation, and muscle atrophy in these mice. DR improves mitochondrial function as evidenced by enhanced Ca2+ regulation and reduction of mitochondrial reactive oxygen species (ROS). Furthermore, we show upregulation of SIRT3 and MnSOD in DR animals, consistent with reduced mitochondrial oxidative stress and reduced oxidative damage in muscle tissue measured as F2-isoprostanes. Collectively, our results demonstrate that DR is a powerful mediator of mitochondrial function, mitochondrial ROS production, and oxidative damage, providing a solid protection against oxidative stress-induced neuromuscular defects and muscle atrophy in vivo even under conditions of high oxidative stress.

Dietary restriction increases site-specific histone H3 acetylation in rat liver: Possible modulation by sirtuins

We studied dietary restriction (DR) related changes of site-specific acetylation of histone H3 in rat livers to explore a possible link to histone modifications and sirtuin levels with anti-aging effects of DR. The acetylation at lysine residue 9, 27 and 56 in H3 was 20–30% higher in DR animals compared with ad libitum fed counterparts. SIRT6, one of histone deacetylases, was significantly decreased by DR and thereby may be involved in an increase in the histone acetylation. Our findings suggest that upregulation of chromatin activities through increased histone acetylation is a mechanism of anti-aging effects of DR.

A role for neuronal cAMP responsive-element binding (CREB)-1 in brain responses to calorie restriction

Calorie restriction delays brain senescence and prevents neurodegeneration, but critical regulators of these beneficial responses other than the NAD(+)-dependent histone deacetylase Sirtuin-1 (Sirt-1) are unknown. We report that effects of calorie restriction on neuronal plasticity, memory and social behavior are abolished in mice lacking cAMP responsive-element binding (CREB)-1 in the forebrain. Moreover, CREB deficiency drastically reduces the expression of Sirt-1 and the induction of genes relevant to neuronal metabolism and survival in the cortex and hippocampus of dietary-restricted animals. Biochemical studies reveal a complex interplay between CREB and Sirt-1: CREB directly regulates the transcription of the sirtuin in neuronal cells by binding to Sirt-1 chromatin; Sirt-1, in turn, is recruited by CREB to DNA and promotes CREB-dependent expression of target gene peroxisome proliferator-activated receptor-γ coactivator-1α and neuronal NO Synthase. Accordingly, expression of these CREB targets is markedly reduced in the brain of Sirt KO mice that are, like CREB-deficient mice, poorly responsive to calorie restriction. Thus, the above circuitry, modulated by nutrient availability, links energy metabolism with neurotrophin signaling, participates in brain adaptation to nutrient restriction, and is potentially relevant to accelerated brain aging by overnutrition and diabetes.

Dietary restriction of mice on a high-fat diet induces substrate efficiency and improves metabolic health

High energy intake and, specifically, high dietary fat intake challenge the mammalian metabolism and correlate with many metabolic disorders such as obesity and diabetes. However, dietary restriction (DR) is known to prevent the development of metabolic disorders. The current western diets are highly enriched in fat, and it is as yet unclear whether DR on a certain high-fat (HF) diet elicits similar beneficial effects on health. In this research, we report that HF-DR improves metabolic health of mice compared with mice receiving the same diet on an ad libitum basis (HF-AL). Already after five weeks of restriction, the serum levels of cholesterol and leptin were significantly decreased in HF-DR mice, whereas their glucose sensitivity and serum adiponectin levels were increased. The body weight and measured serum parameters remained stable in the following 7 weeks of restriction, implying metabolic adaptation. To understand the molecular events associated with this adaptation, we analyzed gene expression in white adipose tissue (WAT) with whole genome microarrays. HF-DR strongly influenced gene expression in WAT; in total, 8643 genes were differentially expressed between both groups of mice, with a major role for genes involved in lipid metabolism and mitochondrial functioning. This was confirmed by quantitative real-time reverse transcription-PCR and substantiated by increase in mitochondrial density in WAT of HF-DR mice. These results provide new insights in the metabolic flexibility of dietary restricted animals and suggest the development of substrate efficiency.