Beneficial effects of a 6-month dietary restriction are time-dependently abolished within 2 weeks or 6 months of refeeding-genome-wide transcriptome analysis in mouse liver

Metallothionein gene expression in rat tissues: response to dietary restriction after orally dichlorodiphenyldichloroethylene (DDE) exposure and high-fat feeding

Dichlorodiphenyldichloroethylene (DDE) is an environmental pollutant that accumulates in adipose tissue through the food chain. Hypercaloric, high-fat diet is considered to promote the accumulation of toxic lipophilic substances in tissues, whereas the loss of body fat through caloric restriction results in a recirculation of these substances. In rats, oral administration of DDE causes the onset of tissues damage; the concomitant intake of a high-fat diet ameliorates tissues status, probably because of the entrapment of the lipophilic substance in fat depots. Recent evidence demonstrates that DDE alters the expression of metallothioneins, proteins involved in cellular defense from oxidative stress, in a diet- and tissue-specific manner. This study is aimed to verify if 2 weeks of caloric restriction after the oral DDE treatment can modify metallothionein gene expression in tissues of high-fat fed rats. Real-time PCR analysis demonstrates that metallothionein gene expression after calorie restriction is tissue-specific and strongly influenced by both previous dietary conditions and DDE exposure. To avoid misleading conclusions on the interference of toxic xenobiotics on metallothionein gene expression is particularly important to consider the tissue, the cellular conditions, and the nutritional status of the animals, especially when the protein is used as an index of cells health.

Distinct and additive effects of calorie restriction and rapamycin in aging skeletal muscle

Preserving skeletal muscle function is essential to maintain life quality at high age. Calorie restriction (CR) potently extends health and lifespan, but is largely unachievable in humans, making “CR mimetics” of great interest. CR targets nutrient-sensing pathways centering on mTORC1. The mTORC1 inhibitor, rapamycin, is considered a potential CR mimetic and is proven to counteract age-related muscle loss. Therefore, we tested whether rapamycin acts via similar mechanisms as CR to slow muscle aging. Here we show that long-term CR and rapamycin unexpectedly display distinct gene expression profiles in geriatric mouse skeletal muscle, despite both benefiting aging muscles. Furthermore, CR improves muscle integrity in mice with nutrient-insensitive, sustained muscle mTORC1 activity and rapamycin provides additive benefits to CR in naturally aging mouse muscles. We conclude that rapamycin and CR exert distinct, compounding effects in aging skeletal muscle, thus opening the possibility of parallel interventions to counteract muscle aging.

The anti-aging intervention calorie restriction (CR) is thought to act via the nutrient-sensing multiprotein complex mTORC1. Here the authors show that the mTORC1-inhibitor rapamycin and CR use largely distinct mechanisms to slow mouse muscle aging.

Oxidative stress, antioxidants, hormesis and calorie restriction: The current perspective in the biology of aging

Aging, in a large measure, has long been defined as the resultant of oxidative stress acting on the cells. The cellular machinery eventually malfunctions at the basic level by the damage from the processes of oxidation and the system starts slowing down because of intrinsic eroding. To understand the initial destruction at the cellular level spreading outward to affect tissues, organs and the organism, the relationship between molecular damage and oxidative stress is required to understand. Retarding the aging process is a matter of cumulatively decreasing the rate of oxidative damage to the cellular machinery. Along with the genetic reasons, the decrease of oxidative stress is somehow a matter of lifestyle and importantly of diet. In the current review, the theories of aging and the understanding of various levels of molecular damage by oxidative stress have been emphasized. A broader understanding of mechanisms of aging have been elaborated in terms of effects of oxidative at molecular, mitochondrial, cellular and organ levels. The antioxidants supplementation, hormesis and calorie restriction as the prominent anti-aging strategies have also been discussed. The relevance and the efficacy of the antiaging strategies at system level have also been presented.

The effect of energy restriction on development and progression of chronic kidney disease: review of the current evidence

Energy restriction (ER) has anti-ageing effects and probably protects from a range of chronic diseases including cancer, diabetes and chronic kidney disease (CKD). Specifically, ER has a positive impact on experimental kidney ageing, CKD (diabetic nephropathy, polycystic kidney disease) and acute kidney injury (nephrotoxic, ischaemia-reperfusion injury) through such mechanisms as increased autophagy, mitochondrial biogenesis and DNA repair, and decreased inflammation and oxidative stress. Key molecules contributing to ER-mediated kidney protection include adenosine monophosphate-activated protein kinase, sirtuin-1 and PPAR-γ coactivator 1α. However, CKD is a complex condition, and ER may potentially worsen CKD complications such as protein-energy wasting, bone-mineral disorders and impaired wound healing. ER mimetics are drugs, such as metformin and Na-glucose co-transporter-2 which mimic the action of ER. This review aims to provide comprehensive data regarding the effect of ER on CKD progression and outcomes.

In Contrast to Dietary Restriction, Application of Resveratrol in Mice Does not Alter Mouse Major Urinary Protein Expression

Resveratrol (RSV) supplementation in mice has been discussed as partly mimicking the beneficial effects of dietary restriction (DR). However, data on putative benefits from resveratrol application in mice and other model organisms including humans is contradictory. Mouse major urinary proteins (MUPs) are a family of proteins that are expressed in rodent liver and secreted via urine. Impacting (mating) behavior and pheromone communication, they are severely down-regulated upon DR. We carried out two studies in C57BL/6Rj mice where RSV was either supplemented via diet or injected intraperitoneally for 8 weeks. Contrary to −40% DR, RSV did not decrease total MUP protein expression or Mup (amongst others Mup3, Mup5, Mup6, Mup15, and Mup20) mRNA levels in mouse liver when compared to ad-libitum (AL)-fed controls. Since inhibitory glucocorticoid response elements can be found in Mup promoters, we also measured glucocorticoid receptor (GR) levels in nuclear hepatic extracts. Consistent with differential MUP expression, we observed more nuclear GR in DR mice than in RSV-supplemented and AL control mice with no difference between RSV and AL. These findings point to the notion that, in mice, RSV does not mimic DR in terms of differential MUP expression.

The Putative Caloric Restriction Mimetic Resveratrol has Moderate Impact on Insulin Sensitivity, Body Composition, and the Metabolome in Mice

SCOPE

Data on resveratrol-(trans-3,5,4'-trihydroxystilbene)-induced caloric-restriction-(CR)-mimicking effects in mice receiving a high-fat diet (HFD) are contradictory. It is hypothesized that this can possibly stem from different bioactivities of resveratrol (RSV) microbial metabolites.

METHODS AND RESULTS

C57BL/6Rj mice are fed an ad-libitum HFD supplemented with RSV or its metabolites, dihydroresveratrol (DHR) and lunularin (LUN) (≈28 mg (dihydro)stilbene kg^-1 mouse per day). A 40% CR group was included in the study. While CR mice show robust changes in bodyweight and composition, hormone levels and mRNA expression, slight changes are found (more muscle, less adipose tissue) in body composition, leptin, and insulin levels in RSV-supplemented mice compared to ad libitum controls. LUN hardly and DHR does not change the hormone levels measured. Metabolome analysis of serum shows changes in CR mice but only slight, if any, changes in RSV-, DHR-, or LUN-supplemented mice compared to the controls. Evaluating the capability of RSV and its metabolites to inhibit carbohydrate-hydrolyzing enzymes in vitro, it is found that RSV reduced α-glucosidase activity to a stronger extent than DHR and LUN.

CONCLUSION

Decelerated carbohydrate breakdown by RSV may have contributed to the moderate impact of dietary RSV on mouse insulin sensitivity (lowered fasting and post-glucose-bolus insulin levels).

Protein Restriction, Epigenetic Diet, Intermittent Fasting as New Approaches for Preventing Age-associated Diseases

Data from epidemiological and experimental studies have shown that diet and eating patterns have a major role in the pathogenesis of many age-associated diseases. Since 1935, calorie restriction (CR) has been identified as one of the most effective nongenetic dietary interventions that can increase lifespan. It involves reducing calorie intake by about 20%–40% below ad libitum, without malnutrition. Restricting food intake has been observed to increase lifespan and prevent many age-associated diseases in rats, mice, and many other species. Understanding the metabolic, molecular, and cellular mechanisms involved in the anti-aging effects of CR can help us to find dietary interventions that can mimic its effects. Recently, different studies have shown that intermittent fasting, protein restriction, and an epigenetic diet can have similar effects to those of CR. These approaches were selected because it has been indicated that they act through a similar molecular pathway and also, are safe and effective in delaying or preventing diseases. In this review, we focus on the mechanistic pathway involved in CR. Then, we review the mimicking interventions through the mechanistic approach. For this purpose, we reviewed both animal and human articles, mainly available through the PubMed online database. We then selected the most relevant full texts which are summarized in this article.

Plasticity of lifelong calorie-restricted C57BL/6J mice in adapting to a medium-fat diet intervention at old age

Calorie restriction (CR) is a dietary regimen that supports healthy aging. In this study, we investigated the systemic and liver‐specific responses caused by a diet switch to a medium‐fat (MF) diet in 24‐month‐old lifelong, CR‐exposed mice. This study aimed to increase the knowledge base on dietary alterations of gerontological relevance. Nine‐week‐old C57BL/6J mice were exposed either to a control, CR, or MF diet. At the age of 24 months, a subset of mice of the CR group was transferred to ad libitumMF feeding (CR‐MF). The mice were sacrificed at the age of 28 months, and then, biochemical and molecular analyses were performed. Our results showed that, despite the long‐term exposure to the CR regimen, mice in the CR‐MF group displayed hyperphagia, rapid weight gain, and hepatic steatosis. However, no hepatic fibrosis/injury or alteration in CR‐improved survival was observed in the diet switch group. The liver transcriptomic profile of CR‐MF mice largely shifted to a profile similar to the MF‐fed animals but leaving ~22% of the 1,578 differentially regulated genes between the CR and MF diet groups comparable with the expression of the lifelong CR group. Therefore, although the diet switch was performed at an old age, the CR‐MF‐exposed mice showed plasticity in coping with the challenge of a MF diet without developing severe liver pathologies.

Intermittent calorie restriction largely counteracts the adverse health effects of a moderate-fat diet in aging C57BL/6J mice

SCOPE

Calorie restriction (CR) has been shown to extend life- and health-span in model species. For most humans, a life-long CR diet is too arduous to adhere to. The aim of this study was to explore whether weekly intermittent CR can (1) provide long-term beneficial effects and (2) counteract diet-induced obesity in male aging mice.

METHODS AND RESULTS

In this study, we have exposed C57Bl/6J mice for 24 months to an intermittent (INT) diet, alternating weekly between CR of a control diet and ad libitum moderate-fat (MF) feeding. This weekly intermittent CR significantly counteracted the adverse effects of the MF diet on mortality, body weight, and liver health markers in 24-month-old male mice. Hepatic gene expression profiles of INT-exposed animals appeared much more comparable to CR- than to MF-exposed mice. At 12 months of age, a subgroup of MF-exposed mice was transferred to the INT diet. Gene expression profiles in the liver of the 24-month-old diet switch mice were highly similar to the INT-exposed mice. However, a small subset of genes was consistently changed by the MF diet during the first phase of life.

CONCLUSION

Weekly intermittent CR largely, but not completely, reversed adverse effects caused by a MF diet.

Caloric Restriction Protects against Lactacystin-Induced Degeneration of Dopamine Neurons Independent of the Ghrelin Receptor

Parkinson’s disease (PD) is a neurodegenerative disorder, characterized by a loss of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). Caloric restriction (CR) has been shown to exert ghrelin-dependent neuroprotective effects in the 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-based animal model for PD. We here investigated whether CR is neuroprotective in the lactacystin (LAC) mouse model for PD, in which proteasome disruption leads to the destruction of the DA neurons of the SNc, and whether this effect is mediated via the ghrelin receptor. Adult male ghrelin receptor wildtype (WT) and knockout (KO) mice were maintained on an ad libitum (AL) diet or on a 30% CR regimen. After 3 weeks, LAC was injected unilaterally into the SNc, and the degree of DA neuron degeneration was evaluated 1 week later. In AL mice, LAC injection significanty reduced the number of DA neurons and striatal DA concentrations. CR protected against DA neuron degeneration following LAC injection. However, no differences were observed between ghrelin receptor WT and KO mice. These results indicate that CR can protect the nigral DA neurons from toxicity related to proteasome disruption; however, the ghrelin receptor is not involved in this effect.

Multicompartment analysis of protein-restricted phenylketonuric mice reveals amino acid imbalances in brain

BACKGROUND

The mainstay of therapy for phenylketonuria (PKU) remains dietary protein restriction. Developmental and neurocognitive outcomes for patients, however, remain suboptimal. We tested the hypothesis that mice with PKU receiving protein-restricted diets would reveal disruptions of brain amino acids that shed light on these neurocognitive deficits.

METHOD

Phenylalanine hydroxylase-deficient (PKU) mice and parallel controls (both wild-type and heterozygous) were fed custom diets containing 18, 6, and 4 % protein for 3 weeks, after which tissues (brain, liver, sera) were collected for amino acid analysis profiling.

RESULTS

Phenylalanine (phe) was increased in all tissues (p < 0.0001) of PKU mice and improved with protein restriction. In sera, decreased tyrosine (p < 0.01) was corrected (defined as not significantly different from the level in control mice receiving 18 % chow) with protein restriction, whereas protein restriction significantly increased many other amino acids. A similar trend for increased amino acid levels with protein restriction was also observed in liver. In brain, the effects of protein restriction on large neutral amino acids (LNAAs) were variable, with some deficit correction (threonine, methionine, glutamine) and no correction of tyrosine under any dietary paradigm. Protein restriction (4 % diet) in PKU mice significantly decreased lysine, arginine, taurine, glutamate, asparagine, and serine which had been comparable to control mice under 18 % protein intake.

CONCLUSION

Depletion of taurine, glutamate, and serine in the brain of PKU mice with dietary protein restriction may provide new insight into neurocognitive deficits of PKU.

Plasticity of adipose tissue in response to fasting and refeeding in male mice

Background

Fasting is the most widely prescribed and self-imposed strategy for treating excessive weight gain and obesity, and has been shown to exert a number of beneficial effects. The aim of the present study was to determine the exact role of fasting and subsequent refeeding on fat distribution in mice.

Methods

C57/BL6 mice fasted for 24 to 72 h and were then subjected to refeeding for 72 h. At 24, 48 and 72 h of fasting, and 12, 24, 48 and 72 h of refeeding, the mice were sacrificed, and serum and various adipose tissues were collected. Serum biochemical parameters, adipose tissue masses and histomorphological analysis of different depots were detected. MRNA was isolated from various adipose tissues, and the expressions of thermogenesis, visceral signature and lipid metabolism-related genes were examined. The phenotypes of adipose tissues between juvenile and adult mice subjected to fasting and refeeding were also compared.

Results

Fasting preferentially consumed mesenteric fat mass and decreased the cell size of mesenteric depots; however, refeeding recovered the mass and morphology of inguinal adipose tissues preferentially compared with visceral depots. Thermogenesis-related gene expression in the inguinal WAT and interscapular BAT were suppressed. Mitochondrial biogenesis was affected by fasting in a depot-specific manner. Furthermore, a short period of fasting led to an increase in visceral signature genes (Wt1, Tcf21) in subcutaneous adipose tissue, while the expression of these genes decreased sharply as the fasting time increased. Additionally, lipogenesis-related markers were enhanced to a greater extent greater in subcutaneous depots compared with those in visceral adipose tissues by refeeding. Although similar phenotypic changes in adipose tissue were observed between juvenile mice and adult mice subjected to fasting and refeeding, the alterations appeared earlier and more sensitively in juvenile mice.

Conclusions

Fasting preferentially consumes lipids in visceral adipose tissues, whereas refeeding recovers lipids predominantly in subcutaneous adipose tissues, which indicated the significance of plasticity of adipose organs for fat distribution when subject to food deprivation or refeeding.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0159-x) contains supplementary material, which is available to authorized users.

A return to ad libitum feeding following caloric restriction promotes hepatic steatosis in hyperphagic OLETF rats

Hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats develop obesity, insulin resistance, and nonalcoholic fatty liver disease (NAFLD), but lifestyle modifications, such as caloric restriction (CR), can prevent these conditions. We sought to determine if prior CR had protective effects on metabolic health and NAFLD development following a 4-wk return to ad libitum (AL) feeding. Four-week-old male OLETF rats (n = 8-10/group) were fed AL for 16 wk (O-AL), CR for 16 wk (O-CR; ∼70% kcal of O-AL), or CR for 12 wk followed by 4 wk of AL feeding (O-AL4wk). CR-induced benefit in prevention of NAFLD, including reduced hepatic steatosis, inflammation, and markers of Kupffer cell activation/number, was largely lost in AL4wk rats. These findings occurred in conjunction with a partial loss of CR-induced beneficial effects on obesity and serum triglycerides in O-AL4wk rats, but in the absence of changes in serum glucose or insulin. CR-induced increases in hepatic mitochondrial respiration remained significantly elevated (P < 0.01) in O-AL4wk compared with O-AL rats, while mitochondrial [1-(14)C]palmitate oxidation, citrate synthase activity, and β-hydroxyacyl-CoA dehydrogenase activity did not differ among OLETF groups. NAFLD development in O-AL4wk rats was accompanied by increases in the protein content of the de novo lipogenesis markers fatty acid synthase and stearoyl-CoA desaturase-1 and decreases in phosphorylated acetyl-CoA carboxylase (pACC)/ACC compared with O-CR rats (P < 0.05 for each). The beneficial effects of chronic CR on NAFLD development were largely lost with 4 wk of AL feeding in the hyperphagic OLETF rat, highlighting the importance of maintaining energy balance in the prevention of NAFLD.

Restriction on an energy-dense diet improves markers of metabolic health and cellular aging in mice through decreasing hepatic mTOR activity

Dietary restriction (DR) on a normal low-fat diet improves metabolic health and may prolong life span. However, it is still uncertain whether restriction of an energy-dense, high-fat diet would also be beneficial and mitigate age-related processes. In the present study, we determined biomarkers of metabolic health, energy metabolism, and cellular aging in obesity-prone mice subjected to 30% DR on a high-fat diet for 6 months. Dietary-restricted mice had significantly lower body weights, less adipose tissue, lower energy expenditure, and altered substrate oxidation compared to their ad libitum-fed counterparts. Hepatic major urinary proteins (Mup) expression, which is linked to glucose and energy metabolism, and biomarkers of metabolic health, including insulin, glucose, cholesterol, and leptin/adiponectin ratio, were likewise reduced in high-fat, dietary-restricted mice. Hallmarks of cellular senescence such as Lamp2a and Hsc70 that mediate chaperone-mediated autophagy were induced and mechanistic target of rapamycin (mTOR) signaling mitigated upon high-fat DR. In contrast to DR applied in low-fat diets, anti-oxidant gene expression, proteasome activity, as well as 5'-adenosine monophosphate-activated protein kinase (AMPK) activation were not changed, suggesting that high-fat DR may attenuate some processes associated with cellular aging without the induction of cellular stress response or energy deprivation.

Energy restriction and potential energy restriction mimetics

Energy restriction (ER; also known as caloric restriction) is the only nutritional intervention that has repeatedly been shown to increase lifespan in model organisms and may delay ageing in humans. In the present review we discuss current scientific literature on ER and its molecular, metabolic and hormonal effects. Moreover, criteria for the classification of substances that might induce positive ER-like changes without having to reduce energy intake are summarised. Additionally, the putative ER mimetics (ERM) 2-deoxy-d-glucose, metformin, rapamycin, resveratrol, spermidine and lipoic acid and their suggested molecular targets are discussed. While there are reports on these ERM candidates that describe lifespan extension in model organisms, data on longevity-inducing effects in higher organisms such as mice remain controversial or are missing. Furthermore, some of these candidates produce detrimental side effects such as immunosuppression or lactic acidosis, or have not been tested for safety in long-term studies. Up to now, there are no known ERM that could be recommended without limitations for use in humans.

Dietary restriction decreases coenzyme Q and ubiquinol potentially via changes in gene expression in the model organism C. elegans

Dietary restriction (DR) is a robust intervention that extends both health span and life span in many organisms. Ubiquinol and ubiquinone represent the reduced and oxidized forms of coenzyme Q (CoQ). CoQ plays a central role in energy metabolism and functions in several cellular processes including gene expression. Here we used the model organism Caenorhabditis elegans to determine level and redox state of CoQ and expression of genes in response to DR. We found that DR down-regulates the steady-state expression levels of several evolutionary conserved genes (i.e. coq-1) that encode key enzymes of the mevalonate and CoQ-synthesizing pathways. In line with this, DR decreases the levels of total CoQ and ubiquinol. This CoQ-reducing effect of DR is obvious in adult worms but not in L4 larvae and is also evident in the eat-2 mutant, a genetic model of DR. In conclusion, we propose that DR reduces the level of CoQ and ubiquinol via gene expression in the model organism C. elegans.

Nutri-informatics: a new kid on the block?

From an epistemological point of view, nutritional physiology has been developed, like other factual sciences such as physics, from a purely descriptive to a mechanismic-explanatory scientific discipline. Nowadays, nutritional physiology has entered the molecular stage. Based on this micro-reductionism, molecular targets (e.g., transcription factors) of energy intake, certain nutrients (e.g., zinc) and selected plant bioactives (e.g., flavonoids) have been identified. Although these results are impressive, molecular approaches in nutritional physiology are limited by nature since the molecular targets of nutrients seem to have no ontic priority to understand the nutritional phenotype of an organism. Here we define, to the best of our knowledge, for the first time Nutri-informatics as a new bioinformatics discipline integrating large-scale data sets from nutritional studies into a stringent nutritional systems biology context. We suggest that Nutri-informatics, as an emerging field, may bridge the gap between nutritional biochemistry, nutritional physiology and metabolism to understand the interactions between an organism and its environment.

Identifying evolutionarily conserved genes in the dietary restriction response using bioinformatics and subsequent testing in Caenorhabditis elegans

Dietary restriction (DR) increases life span, health span and resistance to stress in a wide range of organisms. Work from a large number of laboratories has revealed evolutionarily conserved mechanisms that mediate the DR response. Here, we analyzed the genome-wide gene expression profiles of Caenorhabditis elegans under DR versus ad libitum conditions. Using the Ortho2ExpressMatrix tool, we searched for C. elegans orthologs of mouse genes that have been shown to be differentially expressed under DR conditions in nearly 600 experiments. Based on our bioinformatic approaches, we obtained 189 DR-responsive genes, and 45 of these are highly conserved from worm to man. Subsequent testing of sixteen genes that are up-regulated under DR identified eight genes that abolish the DR-induced resistance to heat stress in C. elegans. Further analyses revealed that fkb-4, dod-22 and ikb-1 genes also abolish increased life span in response to DR. The identified genes that are necessary for the DR response are sensitive to certain stress signals such as metabolic perturbances (dod-22, fkb-4 and nhr-85), DNA damage (ikb-1), heat shock (hsp-12.6) and cancer-like overgrowth (prk-2 and tsp-15). We propose that most of the DR-responsive genes identified are components of the recently discovered cellular surveillance-activated detoxification and defenses pathway, which is, among others, important for the survival of organisms in times of food deprivation.

Nutrition and healthy ageing: calorie restriction or polyphenol-rich "MediterrAsian" diet?

Diet plays an important role in mammalian health and the prevention of chronic diseases such as cardiovascular disease (CVD). Incidence of CVD is low in many parts of Asia (e.g., Japan) and the Mediterranean area (e.g., Italy, Spain, Greece, and Turkey). The Asian and the Mediterranean diets are rich in fruit and vegetables, thereby providing high amounts of plant bioactives including polyphenols, glucosinolates, and antioxidant vitamins. Furthermore, oily fish which is rich in omega-3 fatty acids is an important part of the Asian (e.g., Japanese) and also of the Mediterranean diets. There are specific plant bioactives which predominantly occur in the Mediterranean (e.g., resveratrol from red wine, hydroxytyrosol, and oleuropein from olive oil) and in the Asian diets (e.g., isoflavones from soybean and epigallocatechin gallate from green tea). Interestingly, when compared to calorie restriction which has been repeatedly shown to increase healthspan, these polyphenols activate similar molecular targets such as Sirt1. We suggest that a so-called "MediterrAsian" diet combining sirtuin-activating foods (= sirtfoods) of the Asian as well as Mediterranean diet may be a promising dietary strategy in preventing chronic diseases, thereby ensuring health and healthy ageing. Future (human) studies are needed which take the concept suggested here of the MediterrAsian diet into account.