Effects Of Short-term Caloric Restriction Research Articles

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.

Free Fatty Acids’ Level and Nutrition in Critically Ill Patients and Association with Outcomes: A Prospective Sub-Study of PermiT Trial

Objectives: The objectives of this study were to evaluate the clinical and nutritional correlates of high free fatty acids (FFAs) level in critically ill patients and the association with outcomes, and to study the effect of short-term caloric restriction (permissive underfeeding) on FFAs level during critical illness. Patients/Method: In this pre-planned sub-study of the PermiT (Permissive Underfeeding vs. Target Enteral Feeding in Adult Critically Ill Patients) trial, we included critically ill patients who were expected to stay for ≥14 days in the intensive care unit. We measured FFAs level on day 1, 3, 5, 7, and 14 of enrollment. Of 70 enrolled patients, 23 (32.8%) patients had high FFAs level (baseline FFAs level >0.45 mmol/L in females and >0.6 mmol/L in males). Results: Patients with high FFAs level were significantly older and more likely to be females and diabetics and they had lower ratio of partial pressure of oxygen to the fraction of inspired oxygen, higher creatinine, and higher total cholesterol levels than those with normal FFAs level. During the study period, patients with high FFAs level had higher blood glucose and required more insulin. On multivariable logistic regression analysis, the predictors of high baseline FFAs level were diabetes (adjusted odds ratio (aOR): 5.36; 95% confidence interval (CI): 1.56, 18.43, p = 0.008) and baseline cholesterol level (aOR, 4.29; 95% CI: 11.64, 11.19, p = 0.003). Serial levels of FFAs did not differ with time between permissive underfeeding and standard feeding groups. FFAs level was not associated with 90-day mortality (aOR: 0.49; 95% CI: 0.09, 2.60, p = 0.40). Conclusion: We conclude that high FFAs level in critically ill patients is associated with features of metabolic syndrome and is not affected by short-term permissive underfeeding.

Differential Gene Expression in Peripheral White Blood Cells with Permissive Underfeeding and Standard Feeding in Critically Ill Patients: A Descriptive Sub-study of the PermiT Randomized Controlled Trial

The effect of short-term caloric restriction on gene expression in critically ill patients has not been studied. In this sub-study of the PermiT trial (Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults Trial- ISRCTN68144998), we examined gene expression patterns in peripheral white blood cells (buffy coat) associated with moderate caloric restriction (permissive underfeeding) in critically ill patients compared to standard feeding. Blood samples collected on study day 1 and 14 were subjected to total RNA extraction and gene expression using microarray analysis. We enrolled 50 patients, 25 in each group. Among 1751 tested genes, 332 genes in 12 pathways were found to be significantly upregulated or downregulated between study day 1 and 14 (global p value for the pathway ≤ 0.05). Using the heatmap, the differential expression of genes from day 1 to 14 in the permissive underfeeding group was compared to the standard feeding group. We further compared gene expression signal intensity in permissive underfeeding compared standard feeding by constructing univariate and multivariate linear regression models on individual patient data. We found differential expression of several genes with permissive underfeeding, most notably those related to metabolism, autophagy and other cellular functions, indicating that moderate differences in caloric intake trigger different cellular pathways.

Metabolic effects of short-term caloric restriction in mice with reduced insulin gene dosage.

Caloric restriction (CR) is the only environmental intervention with robust evidence that it extends lifespan and delays the symptoms of aging, but its mechanisms are incompletely understood. Based on the prolonged longevity of knockout models, it was hypothesized that the insulin-IGF pathway could be a target for developing a CR mimic. This study aimed to test whether CR has additive effects on glucose homeostasis and beta-cell function in mice with reduced insulin gene dosage. To study models with a range of basal insulin levels, wild-type C57BL/6J and mice on an Ins2-/- background, were put on 8 weeks of 40% CR at various ages. Both male and female mice rapidly lost weight due to a reduced WAT mass. Glucose tolerance was improved and fasting glucose levels were reduced by CR in both wild type and 45- and 70-week-old Ins2-/- mice. The effects of CR and reduced insulin on glucose tolerance were non-additive in 20-week-old mice. Interestingly, mice on CR generally exhibited an inability to further depress blood glucose after insulin injection, pointing to possible alterations in insulin sensitivity. In conclusion, our results demonstrate that CR can cause weight loss in the context of reduced insulin production, but that CR-improved glucose homeostasis does not occur near the 'insulin floor' in young mice. Collectively, these data shed further light on the relationships between CR, insulin and glucose homeostasis.

Cardioprotective Signature of Short-Term Caloric Restriction.

ObjectiveTo understand the molecular pathways underlying the cardiac preconditioning effect of short-term caloric restriction (CR).BackgroundLifelong CR has been suggested to reduce the incidence of cardiovascular disease through a variety of mechanisms. However, prolonged adherence to a CR life-style is difficult. Here we reveal the pathways that are modulated by short-term CR, which are associated with protection of the mouse heart from ischemia.MethodsMale 10-12 wk old C57bl/6 mice were randomly assigned to an ad libitum (AL) diet with free access to regular chow, or CR, receiving 30% less food for 7 days (d), prior to myocardial infarction (MI) via permanent coronary ligation. At d8, the left ventricles (LV) of AL and CR mice were collected for Western blot, mRNA and microRNA (miR) analyses to identify cardioprotective gene expression signatures. In separate groups, infarct size, cardiac hemodynamics and protein abundance of caspase 3 was measured at d2 post-MI.ResultsThis short-term model of CR was associated with cardio-protection, as evidenced by decreased infarct size (18.5±2.4% vs. 26.6±1.7%, N=10/group; P=0.01). mRNA and miR profiles pre-MI (N=5/group) identified genes modulated by short-term CR to be associated with circadian clock, oxidative stress, immune function, apoptosis, metabolism, angiogenesis, cytoskeleton and extracellular matrix (ECM). Western blots pre-MI revealed CR-associated increases in phosphorylated Akt and GSK3ß, reduced levels of phosphorylated AMPK and mitochondrial related proteins PGC-1α, cytochrome C and cyclooxygenase (COX) IV, with no differences in the levels of phosphorylated eNOS or MAPK (ERK1/2; p38). CR regimen was also associated with reduced protein abundance of cleaved caspase 3 in the infarcted heart and improved cardiac function.

Effects of short-term very-low calorie diet on islet β-cell function, glucose and lipid metabolism in type 2 diabetic patients

Objective To study the effects of short-term caloric restriction (CR) on insulin secretion and glucose and lipid metabolism in type 2 diabetic patients.Methods Oral glucose tolerance test,insulin releasing test,and other biochemical tests were performed in 20 type 2 diabetic patients whose body mass index(BMI) was less than 40 kg/m2before and after 9 days with CR(300-600 kcal/d).Results (1) After short-term CR,the patients' mean body weight was reduced from (70.5 ± 11.0) kg to (65.9 ± 10.5) kg(P＜0.01),and their waist circumference from (86.68 ± 10.26) cm to (81.03 ± 9.77) cm (P＜0.001).Moreover,BM1 was reduced from (25.99 ± 2.78) kg/m2 to (23.89 ± 2.66) kg/m2 (P＜0.01),the visceral fat mass area decreased from (104.79 ± 29.65) cm2 to (97.44 ± 29.14) cm2 (P =0.015),and the weight of body fat mass was reduced from (22.8 ± 4.9) kg to (20.9 ± 4.5) kg(P＜ 0.01).(2) After 9 days of CR,there were significant reductions in fasting blood glucose [from (8.47 ± 1.77) mmol/L to (6.30± 1.82) mmol/L,P＜0.01],fasting insulin [from (10.8±4.0) mIU/L to (7.1 ±4.2) mIU/L,P＜ 0.01),and blood triglyceride [from (2.36 ± 1.71) mmol/L to (1.28 ± 0.50) mmol/L,P＜0.05),as well as lowering of systolic blood pressure[from (127 ± 11) mmHg(1 mmHg=0.133 kPa) to (117 ± 10) mmHg,P＜0.01),and diastolic blood pressure [from (80 ± 7) mmHg to (73 ± 10) mmHg,P＜0.01],though,no significant difference was found in total eholesterol and low density lipoprotein levels before and after CR.(3) The first-phase insulin response,which was represented by acute insulin response,was increased from (62.37 ± 40.28) mIU/L to (98.1 8 ± 77.17) mIU/L(P＜0.05) during the study period,while changes in insulin area under the curve showed no significant differences before and after CR.HOMA-IR,which was a parameter of insulin resistance,was decreased from 4.12 ± 1.87 to 2.02 ± 1.25 (P＜0.01).Conclusion Short-term CR can effectively improve islet β cell function,glucose and lipid metabolism in patients with type 2 diabetes. Key words: Caloric restriction ; Diabetes mellitus, type 2 ; Insulin secretion ; Glucose ; Lipid

Effects of brief perturbations in energy balance on indices of glucose homeostasis in healthy lean men

Little is known about the effects of short-term caloric restriction (CR) and overfeeding (OF) on glucose homeostasis in healthy lean individuals. In addition, it remains unclear whether the effects of CR and OF are reversed by a complementary feeding period. Ten healthy men participated in two cycles of controlled 7-day periods of CR and refeeding (RF; protocol A), and OF and CR (protocol B) at ±60% energy requirement. At baseline, insulin sensitivity (IS) was assessed by euglycemic clamp (M). Before and during each feeding cycle, fasting and oral glucose tolerance test-derived indices were used to estimate glucose tolerance, IS and glucose-stimulated insulin secretion. Clamp tests revealed normal IS at baseline (M-values 9.4±2.1 mg kg⁻¹ min⁻¹, coefficient of variation (CV)(inter) 22%). M-values were significantly correlated with indices of IS. In protocol A, CR-induced weight loss (-3.0±0.4 kg) was associated with an increase in fasting IS. Postprandial IS and glucose-stimulated insulin secretion remained unchanged, but glucose tolerance decreased. RF decreased fasting and postprandial IS at increased glucose-stimulated insulin secretion. In protocol B, OF significantly increased the body weight (+1.6±0.9 kg). Concomitantly, fasting and postprandial IS decreased at increased glucose-stimulated insulin secretion. Subsequent CR reversed these effects. Inter-individual variability in indices of glucose metabolism was high with coefficients of variation ranging from 9 to 59%. Significant changes in glucose metabolism are evident within 7-day periods of controlled OF and underfeeding. Although IS was impaired at the end of the CR-RF cycle, IS was normalized after the OF-CR cycle. At different feeding regimens, homeostatic responses of glucose metabolism were highly variable.

The Ischemic Heart

Caloric restriction has emerged as an effective strategy for lengthening lifespan in a variety of species.1 In mammals, one mechanism for this phenomenon may be the prevention of detrimental age-related alterations in cellular function1 and presumably subsequent improvement in organ function. The effects of caloric restriction on the heart, at least in rats and mice, involve a number of changes in gene expression that are beneficial to the aged cardiomyocyte2 and/or protect the heart from ischemic injury.3 Although it is likely that all of the beneficial mediators of caloric restriction have not been identified, a number of proteins in the mammalian sirtuin family may play key roles in the regulation of health and longevity.4 In addition, recent evidence has suggested that alterations in whole-body energy metabolism contribute to the beneficial effects of caloric restriction.5 Indeed, caloric restriction in mammals leads to loss of adipose tissue and dramatically alters the action of this endocrine organ.6 As such, caloric restriction contributes to changes in adipose tissue–derived hormone (adipokine) secretion, which can govern whole-body metabolism.7 Furthermore, studies using isolated cardiac myocytes suggest that these adipokines may exert direct end-organ effects that are independent from alterations in whole-body metabolism.8–10 One adipokine that is significantly increased during caloric restriction is adiponectin.11 Previous work has shown that adiponectin exerts a host of protective effects on the cardiovascular system12 and as such may be an essential component mediating the effects of caloric restriction. Article p 2809 The focus on adiponectin in the cardiovascular system has been due largely to the fact that in humans, circulating adiponectin levels are negatively correlated with increased body mass index.13 Because increased body mass index is associated with a number of obesity-linked disorders, including cardiovascular disease, the reduction in serum …

Cardioprotective Effects of Short-Term Caloric Restriction Are Mediated by Adiponectin via Activation of AMP-Activated Protein Kinase

Overeating and obesity are major health problems in developed countries. Caloric restriction (CR) can counteract the deleterious aspects of obesity-related diseases and prolong lifespan. We have demonstrated that short-term CR improves myocardial ischemic tolerance and increases adiponectin levels. Here, we investigated the specific role of adiponectin in CR-induced cardioprotection. Adiponectin antisense transgenic (Ad-AS) mice and wild-type (WT) mice were randomly assigned to a group fed ad libitum and a CR group (90% of caloric intake of ad libitum for 3 weeks, then 65% for 2 weeks). Isolated perfused mouse hearts were subjected to 25 minutes of ischemia, followed by 60 minutes of reperfusion. CR increased serum adiponectin levels by 84% in WT mice. Gel filtration analysis of the oligomeric complex distribution showed that CR produced a marked increase in the high-molecular-weight complex of adiponectin in WT mice; in contrast, CR did not change serum adiponectin levels or their oligomeric pattern in Ad-AS mice. CR improved the recovery of left ventricular function after ischemia/reperfusion and limited infarct size in WT mice; these effects were completely abrogated in Ad-AS mice. CR also increased the phosphorylated form of AMP-activated protein kinase and acetyl-CoA carboxylase in WT but not in Ad-AS mice. Recombinant adiponectin restored CR-induced cardioprotection in Ad-AS mice, and inhibition of AMP-activated protein kinase phosphorylation completely abrogated CR-induced cardioprotection in WT mice. The cardioprotective effects of short-term CR are mediated by increased production of adiponectin and the associated activation of AMP-activated protein kinase.

Effects of short-term caloric restriction on circulating free IGF-I, acid-labile subunit, IGF-binding proteins (IGFBPs)-1–4, and IGFBPs-1–3 protease activity in obese subjects

Decreased levels of GH and total IGF-I have been reported in obesity. It has been hypothesized that increased free (biologically active) IGF-I levels generated from IGF-binding protein (IGFBP) protease activity could be the mechanism for the low GH release in dieting obese subjects. However, no published data exist on free IGF-I levels, acid labile subunit (ALS), or IGFBP protease activity in relation to GH release during a hypocaloric diet. The main purpose of this study was to determine free IGF-I, ALS, IGFBPs-1-4, and IGFBPs-1-3 protease activity in relation to 24-h GH release before and after a short-term very low-calorie diet (VLCD). Six obese subjects before weight loss, five after an average weight loss of 36.1 kg, and five age-and sex-matched lean controls underwent a 4-day VLCD. All subjects were studied on two occasions, once during normal basic diet and again during the last day of the VLCD (1.6 MJ). Free IGF-I was determined by a non-competitive immunoradiometric assay. Free IGF-I levels decreased in concert with increased ALS and unchanged blunted GH release after a VLCD in the obese subjects. IGFBPs-1-3 proteolytic activity was found to be unchanged by hypocaloric diet in all groups. We conclude that free IGF-I decreases after a short-term hypocaloric diet in obese subjects with no concomitant change in 24-h GH release. Circulating free IGF-I per se cannot be the main mechanism of the attenuated GH release in dieting obese subjects.

Short-term caloric restriction and sites of oxygen radical generation in kidney and skeletal muscle mitochondria.

Mitochondrial free radical generation is believed to be one of the principal factors determining aging rate, and complexes I and III have been described as the main sources of reactive oxygen species (ROS) within mitochondria in heart, brain, and liver. Moreover, complex I ROS generation of heart and liver mitochondria seems especially linked to aging rate both in comparative studies between animals with different longevities and in caloric restriction models. Caloric restriction (CR) is a well-documented manipulation that extends mean and maximum longevity. One of the factors that appears to be involved in such life span extension is the reduction in mitochondrial free radical generation at complex I. We have performed two parallel investigations, one studying the effect of short-term CR on oxygen radical generation in kidney and skeletal muscle (gastrocnemius) mitochondria and a second one regarding location of mitochondrial ROS-generating sites in these same tissues. In the former study, no effect of short-term caloric restriction was observed in mitochondrial free radical generation in either kidney or skeletal muscle. The latter study ruled out complex II as a principal source of free radicals in kidney and in skeletal muscle mitochondria, and, similar to previous investigations in heart and liver organelles, the main free radical generators were located at complexes I and III within the electron transport system.

Caloric restriction reverses the deficits in leptin receptor protein and leptin signaling capacity associated with diet-induced obesity: role of leptin in the regulation of hypothalamic long-form leptin receptor expression.

The objectives of this study were to determine if reduced long-form leptin receptor (ObRb) expression in diet-induced obese (DIO) animals is associated with deficits in maximal leptin signaling and, secondly, to establish the effects of short-term caloric restriction (CR) on ObRb expression and function. Groups of DIO and life-long chow-fed (CHOW) F344xBN male rats, aged 6 months, were given an i.c.v. injection containing 2 micro g leptin or artificial cerebrospinal fluid (ACSF) vehicle. Leptin induced a >6-fold increase in STAT3 phosphorylation in CHOW rats, but less than 2-fold increase in DIO. Reduced maximal leptin-stimulated STAT3 phosphorylation in DIO rats was coupled with a decline in both ObRb expression and protein. At this point, subgroups of DIO and CHOW animals underwent CR for 30 days and were then tested for acute leptin responsiveness. CR resulted in a 45 and 85% increase respectively in leptin-stimulated STAT3 phosphorylation in CHOW and DIO animals. Similarly, CR increased ObRb expression and protein in both CHOW and DIO animals. To explore the role of leptin in regulating ObRb expression, we reversibly overexpressed leptin in the hypothalamus and found that ObRb mRNA inversely follows central leptin expression. By enhancing both ObRb expression and signaling capacity, CR may enhance leptin responsiveness in leptin-resistant DIO animals.

Effect of short-term caloric restriction on H2O2 production and oxidative DNA damage in rat liver mitochondria and location of the free radical source.

Oxygen free radicals (ROS) of mitochondrial origin seem to be involved in aging. Whereas in other tissues complexes I or III of the respiratory chain contain the ROS generators, in this study we find that rat liver mitochondria generate oxygen radicals at complexes I, II, and III. Short-term (6 weeks) caloric restriction significantly decreased H2O2 production in rat liver mitochondria. This decrease in ROS production was located at complex I because it occurred with complex I-linked substrates (pyruvate/malate), but did not reach statistical significance with the complex II-linked substrate succinate. The mechanism responsible for the lowered ROS production was not a decrease in oxygen consumption. Instead, the mitochondria of caloric-restricted animals released less ROS per unit electron flow. This was due to a decrease in the degree of reduction of the complex I generator. Furthermore, oxidative damage to mitochondrial and nuclear DNA was also decreased in the liver by short-term caloric restriction. The results agree with the idea that caloric restriction delays aging, at least in part, by decreasing the rate of mitochondrial ROS generation and thus the rate of attack to molecules, like DNA, highly relevant for the accumulation of age-dependent changes.

FABPPB CONTENT DECREASES WITH 20 DAY CALORIC RESTRICTION IN MUSCLE OF YOUNG FISCHER 344 RATS

779 Long-term caloric restriction has been shown to prolong life span in rats. However, the effects of short-term caloric restriction on younger animals has not been examined. It has been shown that long-term caloric restriction increases glucose transport in adult rat muscle tissue, but the effects of caloric restriction on free fatty acid (FFA) transport have not been examined. Therefore, we examined the effect of short-term caloric restriction on changes in the muscle content of the plasma membrane fatty acid-binding protein(FABPPM) in young adult rats. Male Fischer 344 rats were randomly assigned to either an ad libitum (AL) or a 20 day caloric restriction (CR) feeding group. The CR diet consisted of a 40% reduction from baseline food intake supplemented with minerals and vitamins. At 5.5 months of age, blood samples were taken and the flexor digitorum brevis (FDB) muscles were rapidly excised. Crude membrane fractions were prepared and analyzed for FABPPM by SDS PAGE analysis. CR resulted in a significant decrease in body weight (AL: 330 ± 6 g vs. CR: 280 ± 4 g, p<0.01), but no difference in FDB muscle weights (68.5 ± 5 mg, p>0.05) was observed. Blood glucose (G) and plasma FFA concentrations were significantly lower in CR rats (G: 95.8 ± 3.6 mg/dl, FFA: 350 ± 30 μmol/L) than in AL rats (G: 113.3 ± 4.4 mg/dl, FFA: 520 ± 60 μmol/L, p<0.05). FABPPM content was significantly decreased in CR rats versus AL rats(AL: 36.4 ± 1.1 units vs. CR: 30.7 ± 2.6 units, p<0.05). It is concluded that 20 days of caloric restriction results in significant decreases in FABPPM content in FDB muscles and plasma FFA concentration. These findings indicate that short-term caloric restriction induces rapid changes in FFA metabolism in young adult rats.

Caloric restriction causes secretagogue specific changes of gastric acid secretion in rats

The purpose of this study was to examine the effects of short-term caloric restriction (CR) for 4, 8 and 16 weeks on gastric acid secretion in rats. CR rats were fed 60% of normal food intake for 4, 8 or 16 weeks and then prepared with gastric fistulas. Histamine- and carbachol-stimulated gastric acid secretion were significantly ( P<0.05) decreased after more than 4 weeks and 8 weeks of caloric restriction, respectively. In contrast, gastrin-stimulated acid secretion was unaffected by CR. The 1-h-integrated acid output to a submaximal dose of gastrin (40 μg·kg −1) was significantly higher than that of histamine (5 mg·kg −1) after 8 weeks of CR (63±13 and 27±4 μEq·h −1, respectively). Gastrin treatment (5 μg·kg −1·h −1) of CR rats restored the gastric acid responses to both histamine and carbachol. These results suggest that CR can selectively decrease the gastric acid responses to both histamine and carbachol by depletion of the endogenous tissue stores of gastrin. More importantly, these results indicate that under an in vivo gastrin-diminished condition, histamine is not the final secretagogue for gastric acid secretion.

Short-term caloric restriction augments age-related decreases in gastrin content and release

Aging is assciated with significant structural and functional changes in the gastrointestinal tract. Gastrin, a hormone produced by G cells in the antrum of the stomach, stimulates proliferation of gastric mucosa; its synthesis appears to decrease with age. Life-long restriction of caloric intake is the only experimental manipulation that has been shown to retard aging processes in rats. The purpose of this study was to examine the effect of short-term caloric restriction (CR) on the production and release of the hormone gastrin with aging. Aging causes a fall in both fasting plasma levels of gastrin and antral content of gastrin in Fischer 344 rats; short-term CR appears to augment this age-related decrease. Steady state levels of antral gastrin mRNA were decreased with aging, and short-term CR resulted in an augmented decrease in aged, but not in young rats. Our findings indicate that gastrin release, synthesis and gene expression decrease with age. Restriction of the caloric intake for a short period (i.e. 8 weeks) augments this age-related decrease in antral gastrin and fasting plasma levels. Short-term CR appears to decrease the production of gastrin at the level of gene expression.