Short-term Caloric Restriction Research Articles

Mitigating the effects of time in the heart and liver: The variable effects of short- and long-term caloric restriction

Caloric restriction (CR) is known for its anti-aging benefits, partly due to reduced oxidative stress and enhanced antioxidant defense. However, CR outcomes vary based on its intensity, timing, and duration. This study explored CR's effects on antioxidant activity in the heart and liver of male Wistar rats during aging. We investigated two CR paradigms: long-term CR (LTCR), started early in life, and short-term CR (STCR), initiated in middle or old age for 3 months. Contrary to previous findings of short-term CR deleterious effects of on the nervous system, our results revealed increased levels of key antioxidants after STCR. More specifically, we found an increase in GSH-Px and GSH under STCR that was particularly pronounced in the liver, while an increase in CAT and GR activities was observed in the heart of the STCR groups. Catalase was characterized as an enzyme particularly responsive to CR, as its activity was also increased in both the liver and heart after long-term caloric restriction. Our results highlight a significant tissue-specific response to CR and contribute to our understanding of the dynamic effects of CR, which in turn has implications for refining its therapeutic potential in combating age-related decline.

Calorie restriction-induced leptin reduction and T-lymphocyte activation in blood and adipose tissue in men with overweight and obesity

BackgroundT-Lymphocyte activation is modulated by the adipokine leptin and serum concentrations of this hormone can be reduced with short-term calorie restriction. The aim of this study was to understand whether leptin per se is important in determining levels of T-lymphocyte activation in humans, by investigating whether the reduction in leptin concentration following calorie restriction is associated with a decrease in T-Lymphocyte activation in blood and adipose tissue.MethodsTwelve men with overweight and obesity (age 35–55 years, waist circumference 95–115 cm) reduced their calorie intake by 50% for 3 consecutive days. Blood and subcutaneous adipose tissue were obtained for isolation of immune cells and cytokine analysis. CD4+ and CD8 + T-Lymphocytes were identified and characterised according to their expression of activation markers CD25 and CD69 by flow cytometry.ResultsSerum leptin was reduced by (mean ± SEM) 31 ± 16% (p < 0.001) following calorie restriction. The percentage of blood CD4 + CD25 + T-lymphocytes and level of CD25 expression on these lymphocytes were significantly reduced by 8 ± 10% (p = 0.016) and 8 ± 4% (p = 0.058), respectively. After calorie restriction, ex vivo leptin secretion from abdominal subcutaneous adipose tissue explants was not changed, and this corresponded with a lack of change in adipose tissue resident T-Lymphocyte activation.ConclusionsSerum leptin was reduced after calorie restriction and this was temporally associated with a reduction in activation of blood CD4 + CD25 + T-Lymphocytes. In abdominal subcutaneous adipose tissue, however, leptin secretion was unaltered, and there were no observed changes in adipose resident T-Lymphocyte activation.

Post-restriction hyperphagia and metabolic responses to short-term calorie restriction in C57BL/6 mice

Aims: To evaluate post-restriction hyperphagia (PRH) responses to short-term calorie restriction (CR) and the potential drivers of this behaviour. Methods: Adult male C57BL/6J mice underwent 30% CR for 5 to 30 days, then refed for 12 days. Energy intake, body mass, fat mass, fat-free mass, body temperature, and physical activity were measured continuously throughout the CR and re-feeding phases and daily energy expenditure was measured over final 2 days of CR and the first 5 days of re-feeding. Results: Following restriction, energy intake, body mass, fat free mass, body temperature and daily energy expenditure were reduced in all groups compared to controls (P&lt;0.05). Only the 20d and 25d groups had significantly lower fat mass than controls (P=0.004). Total physical activity and dark-phase physical activity did not differ between control and CR groups (P=0.446 and 0.380 respectively); but light-phase physical activity of groups 20d, 25d and 30d increased significantly (P&lt;0.001) due to food anticipatory activity. All CR groups displayed peak PRH on day1 of refeeding. Total energy intake over the following 2-5 days of refeeding was also greater than the controls (P=0.002). The magnitude of PRH increased with CR duration and body mass loss at the individual level (P&lt;0.001). In a multiple regression analysis fat free mass loss was the main factor that was correlated with the level of PRH (Multiple regression R2=32.7%, fat mass P=0.036, fat free mass P=0.003). Conclusion: Hunger (reflected by PRH) was mostly related to body mass and fat free mass loss. The effect of fat free mass loss was the opposite of that expected if fat free mass is a key driver of food intake as recently postulated. Developing restriction protocols that minimize loss of fat free mass may reduce the level of hunger that emerges when individuals are under restriction.

Crosstalk between short- and long-term calorie restriction transcriptomic signatures with anxiety-like behavior, aging, and neurodegeneration: implications for drug repurposing

Calorie restriction (CR) is considered an effective intervention for anxiety, aging, and obesity. We investigated the effects of short- and long-term CR on behavior as well as transcriptome profiles in the hypothalamus, amygdala, prefrontal cortex, pituitary, and adrenal glands of Hooded Wistar and Long Evans male rats. A reduction in anxiety-like behavior, as assessed via the elevated plus maze, was observed in both short- and long-term CR. Despite this, short- and long-term CR regulated different sets of genes, leading to distinct transcriptomic signatures. The employed models were able to simultaneously analyze categorical and numerical variables, evaluating the effect of tissue type along with expression data. In all tissues, transcription factors, zinc finger protein 45-like and zinc finger BTB domain-containing two, were the top selected genes by the models in short and long-term CR treatments, respectively. Text mining identified associations between genes of the short-term CR signature and neurodegeneration, stress, and obesity and between genes of the long-term signature and the nervous system. Literature mining-based drug repurposing showed that alongside known CR mimetics such as resveratrol and rapamycin, candidates not typically associated with CR mimetics may be repurposed based on their interaction with transcriptomic signatures of CR. This study goes some way to unravelling the global effects of CR and opens new avenues for treatment for emotional disorders, neurodegeneration, and obesity.

FRI005 Appetite Response To Short-term Energy Restriction In Young Healthy Women

Abstract Disclosure: G.E. Choi: None. C. Okigbo: None. J. Tessa Tonleu: None. S. Shekhar: None. H.F. Leka: None. A.E. Kim: None. B. Purse: None. K.R. Hisch: None. A.E. Smith-Ryan: None. J.E. Hall: None. Short-term caloric restriction, also referred to as energy restriction (ER), is commonly used by women across the weight spectrum to address their weight or health. Chronic ER is associated with increased appetite, but the relationship is poorly characterized in short-term ER or in the absence of obesity. We investigated the impact of controlled short-term ER on appetite and relevant hormone mediators in young women. In the early follicular phase of two menstrual cycles, 19 healthy non-obese women aged 23.36 ± 2.08 years (mean ± SD) with a BMI of 23.15 ± 2.34 kg/m2 (mean ± sem) underwent two five-day diet and exercise interventions: neutral energy availability (NEA) = 45 kcal/kg lean body mass (LBM)/day and deficient energy availability (DEA) = 20 kcal/kg LBM/day. On day 5 of both interventions, a visual analog scale (VAS) appetite questionnaire, body weight, fasting leptin and orexin-A were measured. We used paired t-tests for comparisons of changes from NEA to DEA. Principal-component factor analysis divided VAS items into appetite, satiety, and hunger (Cronbach alphas &amp;gt;0.80). We utilized linear regression models to determine how changes (Δ) in body weight, leptin, and orexin-A affect appetite, satiety, hunger, and cravings. From NEA to DEA, appetite and hunger increased (55% vs 76%; p&amp;lt;0.001 and 52% vs 71%; p&amp;lt;0.001, respectively), while satiety and cravings decreased (42% vs 19%; p &amp;lt;0.01 and 49% to 38%; p&amp;lt;0.01, respectively). DEA resulted in a weight loss of 1.0±0.22 kg (p&amp;lt;0.001), a decrease in leptin of 3.13±0.95 ng/ml, p=0.002), and increased orexin-A (0.06±0.02 ng/ml, p=0.018). Δ body weight was positively associated with Δ leptin (p=0.001) but not Δ orexin-A. When adjusting for leptin and orexin-A, increased appetite was associated with weight loss (p=0.011). Δ satiety was independently correlated with Δ body weight (p=0.002) and Δ leptin (p=0.033). Δ hunger was positively correlated with Δ body weight (p=0.043), independent of Δ orexin-A). Δ leptin, orexin-A, or body weight did not correlate with Δ craving. Thus, even in non-obese women, short-term ER results in a profound effect on homeostatic mechanisms designed to maintain weight; increased appetite and decreased satiety are mediated by even a minor degree of weight loss, both independently and through decreased leptin. It is likely that changes in ghrelin also contribute to these adaptations to ER, however it was not measured in this study for technical reasons. Interestingly, the effect of short-term ER on specific food cravings is overwhelmed by the overall increase in appetite. Presentation: Friday, June 16, 2023

Assessment of the Protective Effect of Resveratrol and Short Term Caloric Restriction on Diabetic Nephropathy in Rats Via SIRT1/AMPK Pathway

Assessment of the Protective Effect of Resveratrol and Short Term Caloric Restriction on Diabetic Nephropathy in Rats Via SIRT1/AMPK Pathway

The Beneficial and Adverse Effects of Autophagic Response to Caloric Restriction and Fasting.

Each cell is equipped with a conserved housekeeping mechanism, known as autophagy, to recycle exhausted materials and dispose of injured organelles via lysosomal degradation. Autophagy is an early-stage cellular response to stress stimuli in both physiological and pathological situations. It is thought that the promotion of autophagy flux prevents host cells from subsequent injuries by removing damaged organelles and misfolded proteins. As a correlate, the modulation of autophagy is suggested as a therapeutic approach in diverse pathological conditions. Accumulated evidence suggests that intermittent fasting or calorie restriction can lead to the induction of adaptive autophagy and increase longevity of eukaryotic cells. However, prolonged calorie restriction with excessive autophagy response is harmful and can stimulate a type II autophagic cell death. Despite the existence of a close relationship between calorie deprivation and autophagic response in different cell types, the precise molecular mechanisms associated with this phenomenon remain unclear. Here, we aimed to highlight the possible effects of prolonged and short-term calorie restriction on autophagic response and cell homeostasis.

Short-Term Caloric Restriction and Subsequent Re-Feeding Compromise Liver Health and Associated Lipid Mediator Signaling in Aged Mice.

Aging is characterized by alterations in the inflammatory microenvironment, which is tightly regulated by a complex network of inflammatory mediators. Excessive calorie consumption contributes to age- and lifestyle-associated diseases like obesity, type 2 diabetes, cardiovascular disorders, and cancer, while limited nutrient availability may lead to systemic health-promoting adaptations. Geroprotective effects of short-term caloric restriction (CR) can beneficially regulate innate immune receptors and interferon signaling in the liver of aged mice, but how CR impacts the hepatic release of immunomodulatory mediators like cytokines and lipid mediators (LM) is elusive. Here, we investigated the impact of aging on the inflammatory microenvironment in the liver and its linkage to calorie consumption. The livers of female young and aged C57BL/6JRj mice, as well as of aged mice after caloric restriction (CR) up to 28 days, with and without subsequent re-feeding (2 days), were evaluated. Surprisingly, despite differences in the hepatic proteome of young and old mice, aging did not promote a pro-inflammatory environment in the liver, but it reduced lipoxygenase-mediated formation of LM from polyunsaturated fatty acids without affecting the expression of the involved lipoxygenases and related oxygenases. Moreover, CR failed to ameliorate the secretion of pro-inflammatory cytokines but shifted the LM production to the formation of monohydroxylated LM with inflammation-resolving features. Unexpectedly, re-feeding after CR even further decreased the inflammatory response as LM species were markedly downregulated. Our findings raise the question of how short-term CR is indeed beneficial as a nutritional intervention for healthy elderly subjects and further stress the necessity to address tissue-specific inflammatory states.

P16-014-23 Postprandial Glycemic Response and Glycemic Variability During a Short-Term Caloric and Carbohydrate Restriction

P16-014-23 Postprandial Glycemic Response and Glycemic Variability During a Short-Term Caloric and Carbohydrate Restriction

Higher untrained fitness exerts a neuroprotection in Independence to caloric restriction or exercise in high-fat diet-induced obesity

We investigated whether weight maintenance following short-term caloric restriction or exercise exerted neuroprotective effects on obesity induced by a high-fat diet. We also sought to identify whether the neuroprotective effects of higher untrained fitness persisted in the obese condition, both with and without caloric restriction or exercise. Male Wistar rats were fed with either a normal diet (ND) or a high-fat diet (HFD) for 12 weeks. At week 12, untrained fitness and blood metabolic parameters were measured. The ND-fed rats continuously received a ND for 16 additional weeks. HFD-fed rats were randomly assigned to 5 groups as of the followings: 1) an additional 16 weeks of HFD without intervention, 2) 10-week weight maintenance following 6-week short-term caloric restriction, 3) long-term caloric restriction (16 weeks), 4) 10-week weight maintenance following 6 weeks of HFD plus short-term exercise, and 5) HFD plus long-term exercise (16 weeks). Untrained fitness, blood metabolic parameters, and behavioral tests were then determined. Thereafter, the rats were euthanized for molecular studies. Our results demonstrated that long-term caloric restriction had the greatest systemic metabolic benefit among all interventions. Long-term caloric restriction and exercise equally attenuated HFD-induced cognitive impairment by improving synaptic function, blood-brain barrier integrity, mitochondrial health, and neurogenesis, and reducing oxidative stress, neuroinflammation, apoptosis, and Alzheimer's-related pathology. Weight maintenance following short-term caloric restriction showed no benefit to neurogenesis. Weight maintenance following short-term exercise exerted no benefit on synaptic function, neuronal insulin signaling and metabolism, autophagy, and neurogenesis. Interestingly, we found that higher untrained fitness level at week 12 showed positive correlations with more favorable brain profiles at week 28 in HFD-fed rats, both with and without caloric restriction or exercise. All of these findings suggested that higher untrained fitness exerts neuroprotection in HFD-induced obesity independently of caloric restriction or exercise. Therefore, targeting enhancement of untrained fitness may lead to more effective treatment of neurodegeneration in obese condition.

Short term starvation potentiates the efficacy of chemotherapy in triple negative breast cancer via metabolic reprogramming

BackgroundChemotherapy (CT) is central to the treatment of triple negative breast cancer (TNBC), but drug toxicity and resistance place strong restrictions on treatment regimes. Fasting sensitizes cancer cells to a range of chemotherapeutic agents and also ameliorates CT-associated adverse effects. However, the molecular mechanism(s) by which fasting, or short-term starvation (STS), improves the efficacy of CT is poorly characterized.MethodsThe differential responses of breast cancer or near normal cell lines to combined STS and CT were assessed by cellular viability and integrity assays (Hoechst and PI staining, MTT or H2DCFDA staining, immunofluorescence), metabolic profiling (Seahorse analysis, metabolomics), gene expression (quantitative real-time PCR) and iRNA-mediated silencing. The clinical significance of the in vitro data was evaluated by bioinformatical integration of transcriptomic data from patient data bases: The Cancer Genome Atlas (TCGA), European Genome-phenome Archive (EGA), Gene Expression Omnibus (GEO) and a TNBC cohort. We further examined the translatability of our findings in vivo by establishing a murine syngeneic orthotopic mammary tumor-bearing model.ResultsWe provide mechanistic insights into how preconditioning with STS enhances the susceptibility of breast cancer cells to CT. We showed that combined STS and CT enhanced cell death and increased reactive oxygen species (ROS) levels, in association with higher levels of DNA damage and decreased mRNA levels for the NRF2 targets genes NQO1 and TXNRD1 in TNBC cells compared to near normal cells. ROS enhancement was associated with compromised mitochondrial respiration and changes in the metabolic profile, which have a significant clinical prognostic and predictive value. Furthermore, we validate the safety and efficacy of combined periodic hypocaloric diet and CT in a TNBC mouse model.ConclusionsOur in vitro, in vivo and clinical findings provide a robust rationale for clinical trials on the therapeutic benefit of short-term caloric restriction as an adjuvant to CT in triple breast cancer treatment.

Whole Transcriptome Analysis of Hypothalamus in Mice during Short-Term Starvation

Molecular profiling of the hypothalamus in response to metabolic shifts is a critical cue to better understand the principle of the central control of whole-body energy metabolism. The transcriptional responses of the rodent hypothalamus to short-term calorie restriction have been documented. However, studies on the identification of hypothalamic secretory factors that potentially contribute to the control of appetite are lacking. In this study, we analyzed the differential expression of hypothalamic genes and compared the selected secretory factors from the fasted mice with those of fed control mice using bulk RNA-sequencing. We verified seven secretory genes that were significantly altered in the hypothalamus of fasted mice. In addition, we determined the response of secretory genes in cultured hypothalamic cells to treatment with ghrelin and leptin. The current study provides further insights into the neuronal response to food restriction at the molecular level and may be useful for understanding the hypothalamic control of appetite.

Caloric restriction reinforces the stem cell pool in the aged brain without affecting overall proliferation status

Overfeeding (OF) and obesity increase the risk for brain aging and neurodegenerative diseases due to increased oxidative stress and neuroinflammation, which likely contribute to cellular dysfunction. In contrast, caloric restriction (CR) is an intervention known for its effects on extending both life- and health-span. In the current study, the effects on the aging brain of two short-term feeding regimens, OF and CR, were investigated. We applied these diets for 12 weeks to both young and aged zebrafish. We performed protein and mRNA level analysis to examine diet-mediated effects on any potential age-related alterations in the brain. Markers implicated in the regulation of brain aging, cell cycle, proliferation, inflammation, and cytoskeleton were analyzed. The most prominent result observed was a downregulation in the expression levels of the stem cell marker, Sox2, in CR-fed animals as compared to OF-fed fish. Furthermore, our data highlighted significant age-related downregulations in Tp53, Myca, and L-plastin levels. The multivariate analyses of all datasets suggested that as opposed to OF, the adaptive mechanisms increasing lifespan via CR are likely exerting their effects by reinforcing the stem cell pool and downregulating inflammation. The data reveal important therapeutic targets with respect to the state of nutrient uptake for the slowing down of the detrimental effects of aging, resulting in a healthy and extended lifespan, as well as lowering the risk for neurodegenerative disease.

Long-term caloric restriction ameliorates T cell immunosenescence in mice

Aging is associated with a decrease in the function of the immune system, a phenomenon known as immunosenescence, which results in reduced resistance to infection. Caloric restriction (CR) is known to prolong lifespan and to regulate immune function. However, whether and how CR affects immunosenescence remains unclear. Here, we evaluated the effect of long- and short-term CR on immunosenescence by subjecting wild-type mice to CR between 6 and 18 months of age or between 17 and 18 months of age, respectively. Compared with a normal diet or short-term CR, long-term CR induced marked or complete attenuation of age-related decreases in the frequency of spleen NK cells and NKT cells; naïve CD4+ and CD8+ T cells; and cytokine- and granzyme B-secreting T cells. In contrast, both long- and short-term CR significantly suppressed age-related upregulation of the T cell exhaustion markers PD-1, Tim-3, and KLRG1, as well as the transcription factors NR4A1 and TOX, which regulate the expression of genes associated with the T cell exhaustion phenotype. These results suggest that CR might suppress age-associated immunosenescence by regulating the expression of transcription factors and target genes that control T cell exhaustion.

Intermittent Caloric Restriction Promotes Erythroid Development and Ameliorates Phenylhydrazine-Induced Anemia in Mice.

BackgroundDietary restriction has a profound effect in altering immune system and promoting metabolic health and aging. However, how dietary restriction impacts erythroid system is largely unknown. We found that a short-term caloric restriction (CR) stimulates expression of KLF1, a master regulator of erythroid development, in the spleen of mouse, and thus explored the potential effect of CR on erythropoiesis.MethodsWe analyzed the effects of intermittent CR and continuous CR for different lengths of time on parameters of peripheral blood and erythroid profiles in the spleen and bone marrow in C57BL/6 mice. We next assessed how different types of CR affect phenylhydrazine-induced anemia in the mice. Colony formation assay was also used to analyze LK + progenitors and BFU-E in the bone marrow.ResultsIntermittent CR for 2 weeks raised the number of reticulocytes in the blood, while continuous CR for 2 weeks elevated red blood cells and hemoglobin level. Intermittent CR for 2 weeks promoted extramedullary hematopoiesis in the spleen, while continuous CR mainly promoted erythropoiesis in the bone marrow. Interestingly, a short-term intermittent CR but not continuous CR was able to ameliorate phenylhydrazine-induced anemia. Intermittent CR reduced early-stage erythroblasts and increased late-stage erythroblasts/mature RBCs in the spleen, indicating an accelerated transition from early-stage to late-stage erythroblasts/mature red blood cells. Furthermore, a short-term intermittent CR elevated LK + progenitors and the committed erythroid progenitor cells BFU-E in the bone marrow.ConclusionOur study demonstrated that a short-term intermittent CR, but not continuous CR, has a significant effect to promote hematopoiesis and such activity can ameliorate phenylhydrazine-induced acute anemia in the mouse.

Caloric restriction reduces the pro-inflammatory eicosanoid 20-hydroxyeicosatetraenoic acid to protect from acute kidney injury

Acute kidney injury is a frequent complication in the clinical setting and associated with significant morbidity and mortality. Preconditioning with short-term caloric restriction is highly protective against kidney injury in rodent ischemia reperfusion injury models. However, the underlying mechanisms are unknown hampering clinical translation. Here, we examined the molecular basis of caloric restriction-mediated protection to elucidate the principles of kidney stress resistance. Analysis of an RNAseq dataset after caloric restriction identified Cyp4a12a, a cytochrome exclusively expressed in male mice, to be strongly downregulated after caloric restriction. Kidney ischemia reperfusion injury robustly induced acute kidney injury in male mice and this damage could be markedly attenuated by pretreatment with caloric restriction. In females, damage was significantly less pronounced and preconditioning with caloric restriction had only little effect. Tissue concentrations of the metabolic product of Cyp4a12a, 20-hydroxyeicosatetraenoic acid (20-HETE), were found to be significantly reduced by caloric restriction. Conversely, intraperitoneal supplementation of 20-HETE in preconditioned males partly abrogated the protective potential of caloric restriction. Interestingly, this effect was accompanied by a partial reversal of caloric restriction--induced changes in protein but not RNA expression pointing towards inflammation, endoplasmic reticulum stress and lipid metabolism. Thus, our findings provide an insight into the mechanisms underlying kidney protection by caloric restriction. Hence, understanding the mediators of preconditioning is an important prerequisite for moving towards translation to the clinical setting.

Aging and short-term calorie restriction differently affect the cardiac and skeletal muscle expression of genes regulating energy substrate utilization in male rats

Aging affects the energy metabolism differently in the cardiac and skeletal muscles. The study aim was to assess the effects of short-term calorie restriction (SCR) and refeeding on the expression of genes involved in the control of cardiac and skeletal muscle energy metabolism in old vs. young male rats. Young (4 mo) and old (24 mo) rats were subjected to 60% SCR for 30 days, and refed ad libitum for 2 or 4 days. In the cardiac (CM) and skeletal muscles (SM) we compared the gene expression (qPCR) of carnitine palmitoyltransferase-I (Cpt-I), peroxisome proliferator-activated receptor beta/delta (Ppar-β/δ), glucose transporter 4 (Glut4), peroxisome proliferator-activated receptor-γ coactivator-1α (Pgc-1α), and sirtuin 3 (Sirt3). In CM, aging increased Cpt-I expression but did not affect the other genes. In SM, Cpt-I, Glut4, Pgc-1α, and Sirt3 mRNA levels were lower in old than young rats. In CM of only young rats SCR increased Cpt-I expression which remained elevated after refeeding. Upon SCR, the expression of Ppar-β/δ, Glut4, Pgc-1α, and Sirt3 in CM increased in young but not old rats, and refeeding re-established control levels. In SM of young rats SCR increased Ppar-β/δ and Pgc-1α, and decreased Sirt3 expression, whereas refeeding generally decreased these mRNA levels. In SM of old rats SCR decreased only Pgc-1α expression. The adaptive response to SCR and subsequent refeeding is muscle tissue-specific and differs in young and old male rats. SCR appears to increase the efficiency of glucose and fatty acid utilization in the cardiac muscle of young, but not old male rats.

Short-term moderate caloric restriction in a high-fat diet alleviates obesity via AMPK/SIRT1 signaling in white adipocytes and liver.

BackgroundObesity is a growing problem for public health worldwide. Calorie restriction (CR) is a safety and effective life intervention to defend against obesity. Short-term moderate CR may be a more favorable strategy against this pathology. However, the mechanisms behind the effects of CR remain to be clarified. Increased energy expenditure in the liver and brown adipose tissue could potentially be manipulated to modulate and improve metabolism in obesity. Moreover, nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin-1 (SIRT1) and AMP-activated protein kinase (AMPK) are well-characterized metabolic modulators. We aim to explore the anti-obesity effects of short-term moderate CR by improving energy metabolism via the SIRT1/AMPK pathway in white adipocytes and liver in a mouse model of obesity.MethodsMale C57BL/6 mice were randomized into two groups receiving either a standard or a high-fat diet (HFD) for 8 weeks to induce obesity. The HFD-induced obese mice were further randomized into two groups: HFD group or CR group (received 75% of the food eaten by HFD group). Their energy metabolism, white adipose tissue (WAT) contents, hepatic fat deposition, the expression of AMPK, SIRT1, peroxisome proliferators γ-activated receptor coactivator-1α (PGC-1α), nuclear factor kappa B (NF-κB), endothelial nitric oxide synthase (eNOS) in WAT, and hepatic tissues were determined.ResultsAfter 4 weeks, body weight, total serum cholesterol, fasting blood glucose, and insulin levels were significantly lower in the CR group. Moreover, CR ameliorated hepatocyte steatosis, attenuated white adipogenesis, and increased energy expenditure and expressions of SIRT1, PGC-1α, and phosphorylated AMPK in subcutaneous WAT and the hepatic tissues. In addition, CR reduced the protein levels of NF-κB and increased the eNOS expression.ConclusionShort-term moderate CR decreases obesity, increases the thermogenesis, and inhibits inflammation in a mouse model of obesity, probably via the activation of the AMPK/SIRT1 pathway in WAT and liver.

Calorie restriction and calorie dilution have different impacts on body fat, metabolism, behavior, and hypothalamic gene expression.

Caloric restriction is a robust intervention to increase lifespan. Giving less food (calorie restriction [CR]) or allowing free access to a diluted diet with indigestible components (calorie dilution [CD]) are two methods to impose restriction. CD does not generate the same lifespan effect as CR. We compare responses of C57BL/6 mice with equivalent levels of CR and CD. The two groups have different responses in fat loss, circulating hormones, and metabolic rate. CR mice are hungrier, as assessed by behavioral assays. Although gene expression of Npy, Agrp, and Pomc do not differ between CR and CD groups, CR mice had a distinctive hypothalamic gene-expression profile with many genes related to starvation upregulated relative to CD. While both result in lower calorie intake, CR and CD are not equivalent procedures. Increased hunger under CR supports the hypothesis that hunger signaling is a key process mediating the benefits of CR.

Sulfur Amino Acid Supplementation Abrogates Protective Effects of Caloric Restriction for Enhancing Bone Marrow Regrowth Following Ionizing Radiation.

Radiation therapy damages and depletes total bone marrow (BM) cellularity, compromising safety and limiting effective dosing. Aging also strains total BM and BM hematopoietic stem and progenitor cell (HSPC) renewal and function, resulting in multi-system defects. Interventions that preserve BM and BM HSPC homeostasis thus have potential clinical significance. Here, we report that 50% calorie restriction (CR) for 7-days or fasting for 3-days prior to irradiation improved mouse BM regrowth in the days and weeks post irradiation. Specifically, one week of 50% CR ameliorated loss of total BM cellularity post irradiation compared to ad libitum-fed controls. CR-mediated BM protection was abrogated by dietary sulfur amino acid (i.e., cysteine, methionine) supplementation or pharmacological inhibition of sulfur amino acid metabolizing and hydrogen sulfide (H2S) producing enzymes. Up to 2-fold increased proliferative capacity of ex vivo-irradiated BM isolated from food restricted mice relative to control mice indicates cell autonomy of the protective effect. Pretreatment with H2S in vitro was sufficient to preserve proliferative capacity by over 50% compared to non-treated cells in ex vivo-irradiated BM and BM HSPCs. The exogenous addition of H2S inhibited Ten eleven translocation 2 (TET2) activity in vitro, thus providing a potential mechanism of action. Short-term CR or fasting therefore offers BM radioprotection and promotes regrowth in part via altered sulfur amino acid metabolism and H2S generation, with translational implications for radiation treatment and aging.