Differential effects of calorie restriction and exercise on the adipose transcriptome in diet-induced obese mice

Plant-Derived Nutraceuticals Involved in Body Weight Control by Modulating Gene Expression

Obesity is the most prevalent health problem in the Western world, with pathological body weight gain associated with numerous co-morbidities that can be the main cause of death. There are several factors that can contribute to the development of obesity, such as diet, sedentary lifestyle, and genetic make-up. Genetic predispositions play an important role in obesity, but genetic variations alone cannot fully explain the explosion of obesity, which is why studies have turned to epigenetics. The latest scientific evidence suggests that both genetics and environmental factors contribute to the rise in obesity. Certain variables, such as diet and exercise, have the ability to alter gene expression without affecting the DNA sequence, a phenomenon known as epigenetics. Epigenetic changes are reversible, and reversibility makes these changes attractive targets for therapeutic interventions. While anti-obesity drugs have been proposed to this end in recent decades, their numerous side effects make them not very attractive. On the other hand, the use of nutraceuticals for weight loss is increasing, and studies have shown that some of these products, such as resveratrol, curcumin, epigallocatechin-3-gallate, ginger, capsaicin, and caffeine, can alter gene expression, restoring the normal epigenetic profile and aiding weight loss.

Dieting reverses histone methylation and hypothalamic AgRP regulation in obese rats

INTRODUCTION

Although dieting is a key factor in improving physiological functions associated with obesity, the role by which histone methylation modulates satiety/hunger regulation of the hypothalamus through weight loss remains largely elusive. Canonically, H3K9me2 is a transcriptional repressive post-translational epigenetic modification that is involved in obesity, however, its role in the hypothalamic arcuate nucleus (ARC) has not been thoroughly explored. Here we explore the role that KDM4D, a specific demethylase of residue H3K9, plays in energy balance by directly modulating the expression of AgRP, a key neuropeptide that regulates hunger response.

METHODS

We used a rodent model of diet-induced obesity (DIO) to assess whether histone methylation malprogramming impairs energy balance control and how caloric restriction may reverse this phenotype. Using ChIP-qPCR, we assessed the repressive modification of H3K9me2 at the site of AgRP. To elucidate the functional role of KDM4D in reversing obesity via dieting, a pharmacological agent, JIB-04 was used to inhibit the action of KDM4D in vivo.

RESULTS

In DIO, downregulation of Kdm4d mRNA results in both enrichment of H3K9me2 on the AgRP promoter and transcriptional repression of AgRP. Because epigenetic modifications are dynamic, it is possible for some of these modifications to be reversed when external cues are altered. The reversal phenomenon was observed in calorically restricted rats, in which upregulation of Kdm4d mRNA resulted in demethylation of H3K9 on the AgRP promoter and transcriptional increase of AgRP. In order to verify that KDM4D is necessary to reverse obesity by dieting, we demonstrated that in vivo inhibition of KDM4D activity by pharmacological agent JIB-04 in naïve rats resulted in transcriptional repression of AgRP, decreasing orexigenic signaling, thus inhibiting hunger.

DISCUSSION

We propose that the action of KDM4D through the demethylation of H3K9 is critical in maintaining a stable epigenetic landscape of the AgRP promoter, and may offer a target to develop new treatments for obesity.

An Overview of Epigenetics in Obesity: The Role of Lifestyle and Therapeutic Interventions

Obesity has become a global epidemic that has a negative impact on population health and the economy of nations. Genetic predispositions have been demonstrated to have a substantial role in the unbalanced energy metabolism seen in obesity. However, these genetic variations cannot entirely explain the massive growth in obesity over the last few decades. Accumulating evidence suggests that modern lifestyle characteristics such as the intake of energy-dense foods, adopting sedentary behavior, or exposure to environmental factors such as industrial endocrine disruptors all contribute to the rising obesity epidemic. Recent advances in the study of DNA and its alterations have considerably increased our understanding of the function of epigenetics in regulating energy metabolism and expenditure in obesity and metabolic diseases. These epigenetic modifications influence how DNA is transcribed without altering its sequence. They are dynamic, reflecting the interplay between the body and its surroundings. Notably, these epigenetic changes are reversible, making them appealing targets for therapeutic and corrective interventions. In this review, I discuss how these epigenetic modifications contribute to the disordered energy metabolism in obesity and to what degree lifestyle and weight reduction strategies and pharmacological drugs can restore energy balance by restoring normal epigenetic profiles.

Impact of Physical Activity and Exercise on the Epigenome in Skeletal Muscle and Effects on Systemic Metabolism

Exercise and physical activity induces physiological responses in organisms, and adaptations in skeletal muscle, which is beneficial for maintaining health and preventing and/or treating most chronic diseases. These adaptations are mainly instigated by transcriptional responses that ensue in reaction to each individual exercise, either resistance or endurance. Consequently, changes in key metabolic, regulatory, and myogenic genes in skeletal muscle occur as both an early and late response to exercise, and these epigenetic modifications, which are influenced by environmental and genetic factors, trigger those alterations in the transcriptional responses. DNA methylation and histone modifications are the most significant epigenetic changes described in gene transcription, linked to the skeletal muscle transcriptional response to exercise, and mediating the exercise adaptations. Nevertheless, other alterations in the epigenetics markers, such as epitranscriptomics, modifications mediated by miRNAs, and lactylation as a novel epigenetic modification, are emerging as key events for gene transcription. Here, we provide an overview and update of the impact of exercise on epigenetic modifications, including the well-described DNA methylations and histone modifications, and the emerging modifications in the skeletal muscle. In addition, we describe the effects of exercise on epigenetic markers in other metabolic tissues; also, we provide information about how systemic metabolism or its metabolites influence epigenetic modifications in the skeletal muscle.

Adiponectin and Asthma: Knowns, Unknowns and Controversies

Adiponectin is an adipokine associated with the healthy obese phenotype. Adiponectin increases insulin sensitivity and has cardio and vascular protection actions. Studies related to adiponectin, a modulator of the innate and acquired immunity response, have suggested a role of this molecule in asthma. Studies based on various asthma animal models and on the key cells involved in the allergic response have provided important insights about this relation. Some of them indicated protection and others reversed the balance towards negative effects. Many of them described the cellular pathways activated by adiponectin, which are potentially beneficial for asthma prevention or for reduction in the risk of exacerbations. However, conclusive proofs about their efficiency still need to be provided. In this article, we will, briefly, present the general actions of adiponectin and the epidemiological studies supporting the relation with asthma. The main focus of the current review is on the mechanisms of adiponectin and the impact on the pathobiology of asthma. From this perspective, we will provide arguments for and against the positive influence of this molecule in asthma, also indicating the controversies and sketching out the potential directions of research to complete the picture.

Transcriptomic Effects of Healthspan-Promoting Dietary Interventions: Current Evidence and Future Directions

Aging is the greatest risk factor most diseases, including cardiovascular disorders, cancers, diabetes, and neurodegeneration, but select nutritional interventions may profoundly reduce the risk for these conditions. These interventions include calorie restriction, intermittent fasting, protein restriction, and reducing intake of certain amino acids. Certain ad libitum diets, including the Mediterranean, Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability, and Okinawan diets also promote healthy aging. Evidence indicates that these dietary strategies influence aging and healthspan by acting on the biological "hallmarks of aging" and especially upstream nutrient sensing pathways. Recent advances in "omics" technologies, including RNA-sequencing (transcriptomics), have increased our understanding of how such nutritional interventions may influence gene expression related to these biological mediators of aging, primarily in pre-clinical studies. However, whether these effects are also reflected in the human transcriptome, which may provide insight on other downstream/related cellular processes with aging, is an emerging topic. Broadly, the investigation of how these nutritional interventions influence the transcriptome may provide novel insight into pathways associated with aging, and potential targets to treat age-associated disease and increase healthspan. Therefore, the purpose of this mini review is to summarize what is known about the transcriptomic effects of key dietary/nutritional interventions in both pre-clinical models and humans, address gaps in the literature, and provide insight into future research directions.

Protective effects of calorie restriction on insulin resistance and islet function in STZ-induced type 2 diabetes rats

Background

Caloric restriction (CR) has become increasingly attractive in the treatment of type 2 diabetes mellitus (T2DM) because of the increasingly common high-calorie diet and sedentary lifestyle. This study aimed to evaluate the role of CR in T2DM treatment and further explore its potential molecular mechanisms.

Methods

Sixty male Sprague–Dawley rats were used in this study. The diabetes model was induced by 8 weeks of high-fat diet (HFD) followed by a single dose of streptozotocin injection (30 mg/kg). Subsequently, the diabetic rats were fed HFD at 28 g/day (diabetic control) or 20 g/day (30% CR regimen) for 20 weeks. Meanwhile, normal rats fed a free standard chow diet served as the vehicle control. Body mass, plasma glucose levels, and lipid profiles were monitored. After diabetes-related functional tests were performed, the rats were sacrificed at 10 and 20 weeks, and glucose uptake in fresh muscle was determined. In addition, western blotting and immunofluorescence were used to detect alterations in AKT/AS160/GLUT4 signaling.

Results

We found that 30% CR significantly attenuated hyperglycemia and dyslipidemia, leading to alleviation of glucolipotoxicity and thus protection of islet function. Insulin resistance was also markedly ameliorated, as indicated by notably improved insulin tolerance and homeostatic model assessment for insulin resistance (HOMA-IR). However, the improvement in glucose uptake in skeletal muscle was not significant. The upregulation of AKT/AS160/GLUT4 signaling in muscle induced by 30% CR also attenuated gradually over time. Interestingly, the consecutive decrease in AKT/AS160/GLUT4 signaling in white adipose tissue was significantly reversed by 30% CR.

Conclusion

CR (30%) could protect islet function from hyperglycemia and dyslipidemia, and improve insulin resistance. The mechanism by which these effects occurred is likely related to the upregulation of AKT/AS160/GLUT4 signaling.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-021-00575-y.

Understanding Dietary Intervention-Mediated Epigenetic Modifications in Metabolic Diseases

The global prevalence of metabolic disorders, such as obesity, diabetes and fatty liver disease, is dramatically increasing. Both genetic and environmental factors are well-known contributors to the development of these diseases and therefore, the study of epigenetics can provide additional mechanistic insight. Dietary interventions, including caloric restriction, intermittent fasting or time-restricted feeding, have shown promising improvements in patients' overall metabolic profiles (i.e., reduced body weight, improved glucose homeostasis), and an increasing number of studies have associated these beneficial effects with epigenetic alterations. In this article, we review epigenetic changes involved in both metabolic diseases and dietary interventions in primary metabolic tissues (i.e., adipose, liver, and pancreas) in hopes of elucidating potential biomarkers and therapeutic targets for disease prevention and treatment.

Calorie restriction promotes remyelination in a Cuprizone-Induced demyelination mouse model of multiple sclerosis

Over the past few decades several attempts have been made to introduce a potential and promising therapy for Multiple sclerosis (MS). Calorie restriction (CR) is a dietary manipulation to reduce calorie intake which has been shown to improve neuroprotection and attenuate neurodegenerative disorders. Here, we evaluated the effect of 33% CR regimen for 4 weeks on the remyelination capacity of Cuprizone (CPZ) induced demyelination in a mouse model of MS. Results showed that CR induced a significant increase in motor coordination and balance performance in CPZ mice. Also, luxol fast blue (LFB) staining showed that CR regimen significantly improved the remyelination in the corpus callosum of CPZ + CR mice compared to the CPZ group. In addition, CR regimen significantly increased the transcript expression levels of BDNF, Sox2, and Sirt1 in the corpus callosum of CPZ mice, while decreasing the p53 levels. Moreover, CR regimen significantly decreased the apoptosis rate. Furthermore, astrogliosis (GFAP + astrocytes) and microgliosis (Iba-1 + microglia) were significantly decreased by CR regimen while oligodendrogenesis (Olig2+) and Sirt1 + cell expression were significantly increased in the corpus callosum of CPZ + CR mice compared to the CPZ group. In conclusion, CR regimen can promote remyelination potential in a CPZ-demyelinating mouse model of MS by increasing oligodendrocyte generation while decreasing their apoptosis.

Dietary restriction and/or exercise training impairs spermatogenesis in normal rats

Dietary restriction and/or exercise has been shown to have multiple benefits for health. However, its effects on reproductive health and the mechanisms by which it regulates reproductive function remain unclear. Here, to evaluate its effects on spermatogenesis and sperm function, rats were divided into 4 groups: ad libitum-fed sedentary control, dietary restriction (DR), exercise training (ET), and dietary restriction plus exercise training (DR+ET) groups. Results indicated that body weight, epididymal fat pad weight, and sperm counts were significantly reduced in the DR, ET, and DR+ET groups. Moreover, sperm motility and capacitation-associated protein tyrosine phosphorylation were suppressed in the DR and DR+ET groups, but not the ET group. Microarray analysis revealed that the number of downregulated genes was higher than that of upregulated genes in the DR and/or ET groups. About half of the downregulated genes are common after exercise training and/or diet restriction. Gene ontology analysis showed that downregulated genes in the DR, ET, and DR+ET groups affected spermatogenesis through overlapping pathways, including glucocorticoid, corticosteroid, extracellular structure organization, and estradiol responses. Our findings suggest that diet restriction and/or exercise training may present potential risks to male reproductive dysfunction by disrupting normal gene expression patterns in the testis. Novelty: Dietary restriction and/or exercise can lead to the damage of spermatogenesis as well as sperm maturation. Sperm functional changes are more sensitive to dietary restriction than exercise training. Dietary restriction and exercise impair spermatogenesis through overlapping biological pathways in the testis.

Life-long control of cytomegalovirus (CMV) by T resident memory cells in the adipose tissue results in inflammation and hyperglycemia

Cytomegalovirus (CMV) is a ubiquitous herpesvirus infecting most of the world’s population. CMV has been rigorously investigated for its impact on lifelong immunity and potential complications arising from lifelong infection. A rigorous adaptive immune response mounts during progression of CMV infection from acute to latent states. CD8 T cells, in large part, drive this response and have very clearly been demonstrated to take up residence in the salivary gland and lungs of infected mice during latency. However, the role of tissue resident CD8 T cells as an ongoing defense mechanism against CMV has not been studied in other anatomical locations. Therefore, we sought to identify additional locations of anti-CMV T cell residency and the physiological consequences of such a response. Through RT-qPCR we found that mouse CMV (mCMV) infected the visceral adipose tissue and that this resulted in an expansion of leukocytes in situ. We further found, through flow cytometry, that adipose tissue became enriched in cytotoxic CD8 T cells that are specific for mCMV antigens from day 7 post infection through the lifespan of an infected animal (> 450 days post infection) and that carry markers of tissue residence. Furthermore, we found that inflammatory cytokines are elevated alongside the expansion of CD8 T cells. Finally, we show a correlation between the inflammatory state of adipose tissue in response to mCMV infection and the development of hyperglycemia in mice. Overall, this study identifies adipose tissue as a location of viral infection leading to a sustained and lifelong adaptive immune response mediated by CD8 T cells that correlates with hyperglycemia. These data potentially provide a mechanistic link between metabolic syndrome and chronic infection.

Mouse cytomegalovirus (mCMV) infection results in initial systemic viremia that is thereafter controlled by the adaptive immune system. Control is mediated in part by T cells that render the virus undetectable systemically, and latent in specific organs, including the lungs and salivary glands. It remains unclear how latent virus is controlled across tissues given the large pool of systemic mCMV-specific T cells. We explored mCMV control in the adipose tissue, whose cellular constituents are potentially susceptible to infection. We found that mCMV infects the adipose tissue during the acute phase, causing local inflammation and a lifelong mCMV-specific CD8 T cell immune response. The response consisted largely from non-recirculating, tissue-resident T cells. The infected adipose tissue showed signs of metabolic changes, that may potentially predispose the infected host to metabolic dysregulation as evidenced by hyperglycemia. Accumulation and persistence of mCMV specific non-circulating resident CD8 T cells (Trm) in adipose tissue reveal a likely generalized mechanism of mCMV tissue reservoir control by Trm cells and identify the adipose tissue as a persistent mCMV reservoir, with potential implications for metabolic health.

Histone Modifications as an Intersection Between Diet and Longevity

Histone modifications are key epigenetic regulators that control chromatin structure and gene transcription, thereby impacting on various important cellular phenotypes. Over the past decade, a growing number of studies have indicated that changes in various histone modifications have a significant influence on the aging process. Furthermore, it has been revealed that the abundance and localization of histone modifications are responsive to various environmental stimuli, such as diet, which can also affect gene expression and lifespan. This supports the notion that histone modifications can serve as a main cellular platform for signal integration. Hence, in this review we focus on the role of histone modifications during aging, report the data indicating that diet affects histone modification levels and explore the idea that histone modifications may function as an intersection through which diet regulates lifespan. A greater understanding of the epigenetic mechanisms that link environmental signals to longevity may provide new strategies for therapeutic intervention in age-related diseases and for promoting healthy aging.

Elevated leptin disrupts epithelial polarity and promotes premalignant alterations in the mammary gland

Obesity is a highly prevalent and modifiable breast cancer risk factor. While the role of obesity in fueling breast cancer progression is well established, the mechanisms linking obesity to breast cancer initiation are poorly understood. A hallmark of breast cancer initiation is the disruption of apical polarity in mammary glands. Here we show that mice with diet-induced obesity display mislocalization of Par3, a regulator of cellular junctional complexes defining mammary epithelial polarity. We found that epithelial polarity loss also occurs in a 3D coculture system that combines acini with human mammary adipose tissue, and establish that a paracrine effect of the tissue adipokine leptin causes loss of polarity by overactivation of the PI3K/Akt pathway. Leptin sensitizes non-neoplastic cells to proliferative stimuli, causes mitotic spindle misalignment, and expands the pool of cells with stem/progenitor characteristics, which are early steps for cancer initiation. We also found that normal breast tissue samples with high leptin/adiponectin transcript ratio characteristic of obesity have an altered distribution of apical polarity markers. This effect is associated with increased epithelial cell layers. Our results provide a molecular basis for early alterations in epithelial architecture during obesity-mediated cancer initiation.

Precision Physical Therapy: Exercise, the Epigenome, and the Heritability of Environmentally Modified Traits

One of the newest frontiers of physical therapy is the field of epigenetics, which examines how pervasive environmental factors such as exercise regulate the expression of genes. The epigenome may be one of the most powerful systems through which exercise exerts its beneficial effects on health and longevity. Large epidemiology studies show that individuals who regularly exercise demonstrate a lower "epigenetic age," experience fewer metabolic diseases, and enjoy greater longevity. However, the dose, mode, intensity, and duration of exercise required to achieve a healthy epigenetic profile is unknown. As experts in exercise prescription, physical therapists are ideally suited to contribute to the discovery of this dose-response relationship. This perspective makes a case for the genesis of "precision physical therapy," which capitalizes on epigenetic discoveries to optimize exercise-based interventions. Summarized here is the emerging body of knowledge supporting epigenetic adaptations to exercise in humans, including the intriguing possibility that these environmentally modified traits could be passed down to offspring. In the future, it is likely that epigenetic data will enhance our understanding of individual disease risk and individual response to prescribed exercise. The profession of physical therapy must be alert to new epigenetic knowledge that can enhance the specificity and efficacy of movement-based treatments.

Histone deacetylase-mediated regulation of endolysosomal pH

The pH of the endolysosomal system is tightly regulated by a balance of proton pump and leak mechanisms that are critical for storage, recycling, turnover, and signaling functions in the cell. Dysregulation of endolysosomal pH has been linked to aging, amyloidogenesis, synaptic dysfunction, and various neurodegenerative disorders, including Alzheimer's disease. Therefore, understanding the mechanisms that regulate luminal pH may be key to identifying new targets for managing these disorders. Meta-analysis of yeast microarray databases revealed that nutrient-limiting conditions inhibited the histone deacetylase (HDAC) Rpd3 and thereby up-regulated transcription of the endosomal Na⁺/H⁺ exchanger Nhx1, resulting in vacuolar alkalinization. Consistent with these findings, Rpd3 inhibition by the HDAC inhibitor and antifungal drug trichostatin A induced Nhx1 expression and vacuolar alkalinization. Bioinformatics analysis of Drosophila and mouse databases revealed that caloric control of the Nhx1 orthologs DmNHE3 and NHE6, respectively, is also mediated by HDACs. We show that NHE6 is a target of the transcription factor cAMP-response element-binding protein (CREB), a known regulator of cellular responses to low-nutrient conditions, providing a molecular mechanism for nutrient- and HDAC-dependent regulation of endosomal pH. Of note, pharmacological targeting of the CREB pathway to increase NHE6 expression helped regulate endosomal pH and correct defective clearance of amyloid Aβ in an apoE4 astrocyte model of Alzheimer's disease. These observations from yeast, fly, mouse, and cell culture models point to an evolutionarily conserved mechanism for HDAC-mediated regulation of endosomal NHE expression. Our insights offer new therapeutic strategies for modulation of endolysosomal pH in fungal infection and human disease.

Nutrition and Ageing

The ageing trajectory is plastic and can be slowed down by lifestyle factors, including good nutrition, adequate physical activity and avoidance of smoking. In humans, plant-based diets such as the Mediterranean dietary pattern are associated with healthier ageing and lower risk of age-related disease, whereas obesity accelerates ageing and increases the likelihood of most common complex diseases including CVD, T2D, dementia, musculoskeletal diseases and several cancers. As yet, there is only weak evidence in humans about the molecular mechanisms through which dietary factors modulate ageing but evidence from cell systems and animal models suggest that it is probable that better dietary choices influence all 9 hallmarks of ageing. It seems likely that better eating patterns retard ageing in at least two ways including (i) by reducing pervasive damaging processes such as inflammation, oxidative stress/redox changes and metabolic stress and (ii) by enhancing cellular capacities for damage management and repair. From a societal perspective, there is an urgent imperative to discover, and to implement, cost-effective lifestyle (especially dietary) interventions which enable each of us to age well, i.e. to remain physically and socially active and independent and to minimise the period towards the end of life when individuals suffer from frailty and multi-morbidity.

SORLA facilitates insulin receptor signaling in adipocytes and exacerbates obesity

In humans, genetic variation of sortilin-related receptor, L(DLR class) A repeats containing (SORL1), which encodes the intracellular sorting receptor SORLA, is a major genetic risk factor for familial and sporadic forms of Alzheimer's disease. Recent GWAS analysis has also associated SORL1 with obesity in humans and in mouse models, suggesting that this receptor may play a role in regulating metabolism. Here, using mouse models with genetic loss or tissue-specific overexpression of SORLA as well as data from obese human subjects, we observed a gene-dosage effect that links SORLA expression to obesity and glucose tolerance. Overexpression of human SORLA in murine adipose tissue blocked hydrolysis of triacylglycerides and caused excessive adiposity. In contrast, Sorl1 gene inactivation in mice accelerated breakdown of triacylglycerides in adipocytes and protected animals from diet-induced obesity. We then identified the underlying molecular mechanism whereby SORLA promotes insulin-induced suppression of lipolysis in adipocytes. Specifically, we determined that SORLA acts as a sorting factor for the insulin receptor (IR) that redirects internalized receptor molecules from endosomes to the plasma membrane, thereby enhancing IR surface expression and strengthening insulin signal reception in target cells. Our findings provide a molecular mechanism for the association of SORL1 with human obesity and confirm a genetic link between neurodegeneration and metabolism that converges on the receptor SORLA.

Obesity: epigenetic regulation – recent observations

Genetic and environmental factors, especially nutrition and lifestyle, have been discussed in the literature for their relevance to epidemic obesity. Gene-environment interactions may need to be understood for an improved understanding of the causes of obesity, and epigenetic mechanisms are of special importance. Consequences of epigenetic mechanisms seem to be particularly important during certain periods of life: prenatal, postnatal and intergenerational, transgenerational inheritance are discussed with relevance to obesity. This review focuses on nutrients, diet and habits influencing intergenerational, transgenerational, prenatal and postnatal epigenetics; on evidence of epigenetic modifiers in adulthood; and on animal models for the study of obesity.

Six-month Calorie Restriction in Overweight Individuals Elicits Transcriptomic Response in Subcutaneous Adipose Tissue That is Distinct From Effects of Energy Deficit

Calorie restriction confers health benefits distinct from energy deficit by exercise. We characterized the adipose-transcriptome to investigate the molecular basis of the differential phenotypic responses. Abdominal subcutaneous fat was collected from 24 overweight participants randomized in three groups (N = 8/group): weight maintenance (control), 25% energy deficit by calorie restriction alone (CR), and 25% energy deficit by calorie restriction with structured exercise (CREX). Within each group, gene expression was compared between 6 months and baseline with cutoffs at nominal p ≤ .01 and absolute fold-change ≥ 1.5. Gene-set enrichment analysis (false discovery rate < 5%) was used to identify significantly regulated biological pathways. CR and CREX elicited similar overall clinical response to energy deficit and a comparable reduction in gene transcription specific to oxidative phosphorylation and proteasome function. CR vastly outweighed CREX in the number of differentially regulated genes (88 vs 39) and pathways (28 vs 6). CR specifically downregulated the chemokine signaling-related pathways. Among the CR-regulated genes, 27 functioned as transcription/translation regulators (eg, mRNA processing or transcription/translation initiation), whereas CREX regulated only one gene in this category. Our data suggest that CR has a broader effect on the transcriptome compared with CREX which may mediate its specific impact on delaying primary aging.

Insights from space: potential role of diet in the spatial organization of chromosomes

We can now sequence and identify genome wide epigenetic patterns and perform a variety of "genomic experiments" within relatively short periods of time-ranging from days to weeks. Yet, despite these technological advances, we have a poor understanding of the inter-relationships between epigenetics, genome structure-function, and nutrition. Perhaps this limitation lies, in part, in our propensity to study epigenetics in terms of the linear arrangement of elements and genes. Here we propose that a more complete understanding of how nutrition impacts on epigenetics and cellular development resides within the inter-relationships between DNA and histone modification patterns and genome function, in the context of spatial organization of chromatin and the epigenome.

Risk determination and prevention of breast cancer

Breast cancer is an increasing public health problem. Substantial advances have been made in the treatment of breast cancer, but the introduction of methods to predict women at elevated risk and prevent the disease has been less successful. Here, we summarize recent data on newer approaches to risk prediction, available approaches to prevention, how new approaches may be made, and the difficult problem of using what we already know to prevent breast cancer in populations. During 2012, the Breast Cancer Campaign facilitated a series of workshops, each covering a specialty area of breast cancer to identify gaps in our knowledge. The risk-and-prevention panel involved in this exercise was asked to expand and update its report and review recent relevant peer-reviewed literature. The enlarged position paper presented here highlights the key gaps in risk-and-prevention research that were identified, together with recommendations for action. The panel estimated from the relevant literature that potentially 50% of breast cancer could be prevented in the subgroup of women at high and moderate risk of breast cancer by using current chemoprevention (tamoxifen, raloxifene, exemestane, and anastrozole) and that, in all women, lifestyle measures, including weight control, exercise, and moderating alcohol intake, could reduce breast cancer risk by about 30%. Risk may be estimated by standard models potentially with the addition of, for example, mammographic density and appropriate single-nucleotide polymorphisms. This review expands on four areas: (a) the prediction of breast cancer risk, (b) the evidence for the effectiveness of preventive therapy and lifestyle approaches to prevention, (c) how understanding the biology of the breast may lead to new targets for prevention, and (d) a summary of published guidelines for preventive approaches and measures required for their implementation. We hope that efforts to fill these and other gaps will lead to considerable advances in our efforts to predict risk and prevent breast cancer over the next 10 years.

Short-term rapamycin treatment in mice has few effects on the transcriptome of white adipose tissue compared to dietary restriction

Rapamycin, a drug that has been shown to increase lifespan in mice, inhibits the target of rapamycin (TOR) pathway, a major pathway that regulates cell growth and energy status. It has been hypothesized that rapamycin and dietary restriction (DR) extend lifespan through similar mechanisms/pathways. Using microarray analysis, we compared the transcriptome of white adipose tissue from mice fed rapamycin or DR-diet for 6 months. Multidimensional scaling and heatmap analyses showed that rapamycin had essentially no effect on the transcriptome as compared to DR. For example, only six transcripts were significantly altered by rapamycin while mice fed DR showed a significant change in over 1000 transcripts. Using ingenuity pathway analysis, we found that stearate biosynthesis and circadian rhythm signaling were significantly changed by DR. Our findings showing that DR, but not rapamycin, has an effect on the transcriptome of the adipose tissue, suggesting that these two manipulations increase lifespan through different mechanisms/pathways.

The pathogenesis of obesity from a genomic and systems biology perspective

The recent obesity epidemic has imposed significant health, economical, and societal concerns. However, effective preventive and therapeutic strategies are currently lacking, primarily due to a lack of comprehensive understanding of the underlying molecular mechanisms. Recent genome-wide scans of genetic variants, transcriptome, and epigenome have uncovered >50 genetic loci that predispose individuals to obesity and revealed hundreds of genes with altered transcriptional activity and/or epigenetic variations in obesity-related tissues upon various environmental challenges such as high caloric diets, lack of physical activity, and environmental chemicals. These discoveries highlight the importance of genes involved in the control of energy homeostasis and food intake by the central nervous system, as well as genes contributing to lipid metabolism, adipogenesis, fat cell differentiation, and immune response in peripheral tissues, in obesity development. Future studies that are directed to obtain a more comprehensive, systems-level understanding of disease mechanisms and that test novel therapeutic strategies aiming at systems-level normalization of the obesity-related molecular alterations are warranted.

Adiponectin and energy homeostasis

White adipose tissue (WAT) is the premier energy depot. Since the discovery of the hormonal properties of adipose-secreted proteins such as leptin and adiponectin, WAT has been classified as an endocrine organ. Although many regulatory effects of the adipocyte-derived hormones on various biological systems have been identified, maintaining systemic energy homeostasis is still the essential function of most adipocyte-derived hormones. Adiponectin is one adipocyte-derived hormone and well known for its effect in improving insulin sensitivity in liver and skeletal muscle. Unlike most other adipocyte-derived hormones, adiponectin gene expression and blood concentration are inversely associated with adiposity. Interestingly, recent studies have demonstrated that, in addition to its insulin sensitizing effects, adiponectin plays an important role in maintaining energy homeostasis. In this review, we summarize the progress of research about 1) the causal relationship of adiposity, energy intake, and adiponectin gene expression; and 2) the regulatory role of adiponectin in systemic energy metabolism.

Effects of interventions on adiponectin and adiponectin receptors

Adiponectin secreted from adipose tissue binds to two distinct adiponectin receptors (AdipoR1 and AdipoR2) identified and exerts its anti-diabetic effects in insulin-sensitive organs including liver, skeletal muscle and adipose tissue as well as amelioration of vascular dysfunction in the various vasculatures. A number of experimental and clinical observations have demonstrated that circulating levels of adiponectin are markedly reduced in obesity, type 2 diabetes, hypertension, and coronary artery disease. Therapeutic interventions which can improve the action of adiponectin including elevation of circulating adiponectin concentration or up-regulation and/or activation of its receptors, could provide better understanding of strategies to ameliorate metabolic disorders and vascular disease. The focus of the present review is to summarize accumulating evidence showing the role of interventions such as pharmacological agents, exercise, and calorie restriction in the expression of adiponectin and adiponectin receptors.

Leucine supplementation differentially enhances pancreatic cancer growth in lean and overweight mice

Background

The risk of pancreatic cancer, the 4th deadliest cancer for both men and women in the United States, is increased by obesity. Calorie restriction (CR) is a well-known dietary regimen that prevents or reverses obesity and suppresses tumorigenesis in a variety of animal models, at least in part via inhibition of mammalian target of rapamycin (mTOR) signaling. Branched-chain amino acids (BCAA), especially leucine, activate mTOR and enhance growth and proliferation of myocytes and epithelial cells, which is why leucine is a popular supplement among athletes. Leucine is also increasingly being used as a treatment for pancreatic cancer cachexia, but the effects of leucine supplementation on pancreatic tumor growth have not been elucidated.

Results

Supplementation with leucine increased pancreatic tumor growth in both lean (104 ± 17 mm³ versus 46 ± 13 mm³; P <0.05) and overweight (367 ± 45 mm³ versus 230 ± 39 mm³; P <0.01) mice, but tumor enhancement was associated with different biological outcomes depending on the diet. In the lean mice, leucine increased phosphorylation of mTOR and downstream effector S6 ribosomal protein, but in the overweight mice, leucine reduced glucose clearance and thus increased the amount of circulating glucose available to the tumor.

Conclusions

These findings show that leucine supplementation enhances tumor growth in both lean and overweight mice through diet-dependent effects in a murine model of pancreatic cancer, suggesting caution against the clinical use of leucine supplementation for the purposes of skeletal muscle enhancement in cachectic patients.

Genistein exposure during the early postnatal period favors the development of obesity in female, but not male rats

Genistein (Gen), the primary isoflavone in soy, has been shown to adversely affect various endocrine-mediated endpoints in rodents and humans. Soy formula intake by human infants has been associated with early age at menarche and decreased female-typical behavior in girls. Adipose deposition and expansion are also hormonally regulated and Gen has been shown to alter these processes. However, little is known about the impact of early-life soy intake on metabolic homeostasis in adulthood. The current study examined the impact of early-life Gen exposure on adulthood body composition (by magnetic resonance imaging) and the molecular signals mediating adipose expansion. From postnatal day (PND) 1 to 22, rat pups were daily orally dosed with 50mg/kg Gen to mimic blood Gen levels in human infants fed soy formula. Female but not male Gen-exposed rats had increased fat/lean mass ratio, fat mass, adipocyte size and number, and decreased muscle fiber perimeter. PND22 Gen-exposed females, but not males, had increased expression of adipogenic factors, including CCAAT/enhancer binding protein alpha (Cebpα), CCAAT/enhancer binding protein beta (Cebpβ), and peroxisome proliferator-activated receptor gamma (Pparγ). Furthermore, Wingless-related MMTV integration site 10b (Wnt10b), a critical regulator of adipogenic cell fate determination, was hypermethylated and had decreased expression in adipose of PND22 Gen-exposed females. These data suggest that developmental Gen exposure in rats has gender-specific effects on adiposity that closely parallel the effects of a postweaning high-fat diet and underscore the importance of considering timing of exposure and gender when establishing safety recommendations for early-life dietary Gen intake.

Epigenetic regulation in obesity

PURPOSE OF REVIEW

Research suggests that 65% of variation in obesity is genetic. However, much of the known genetic associations have little known function and their effect size small, thus the gene-environment interaction, including epigenetic influences on gene expression, is suggested to be an important factor in the susceptibilty to obesity. This review will explore the potential of epigenetic markers to influence expression of genes associated with obesity.

RECENT FINDINGS

Epigenetic changes in utero are known to have direct implications on the phenotype of the offspring. More recently work has focused on how such epigenetic changes continue to regulate risk of obesity from infancy through to adulthood. Work has shown that, for example, hypomethylation of the MC4 gene causes an increase in expression, and has a direct impact on appetite and intake, and thus influences risk of obesity. Similar influences are also seen in other aspects of obesity including inflammation and adiposity.

SUMMARY

Maternal diet during foetal development has many epigenetic implications, which affect the offspring's risk factors for obesity during childhood and adulthood, and even in subsequent generations. Genes associated with risk of obesity, are susceptible to epigenetic mutations, which have subsequent effects on disease mechanisms, such as appetite and impaired glucose and insulin tolerance.

What obesity research tells us about epigenetic mechanisms

The pathophysiology of obesity is extremely complex and is associated with extensive gene expression changes in tissues throughout the body. This situation, combined with the fact that all gene expression changes are thought to have associated epigenetic changes, means that the links between obesity and epigenetics will undoubtedly be vast. Much progress in identifying epigenetic changes induced by (or inducing) obesity has already been made, with candidate and genome-wide approaches. These discoveries will aid the clinician through increasing our understanding of the inheritance, development and treatment of obesity. However, they are also of great value for epigenetic researchers, as they have revealed mechanisms of environmental interactions with epigenetics that can produce or perpetuate a disease state. Here, we will review the evidence for four mechanisms through which epigenetics contributes to obesity: as downstream effectors of environmental signals; through abnormal global epigenetic state driving obesogenic expression patterns; through facilitating developmental programming and through transgenerational epigenetic inheritance.

Peroxisome proliferator-activated receptor-γ activation enhances insulin-stimulated glucose disposal by reducing ped/pea-15 gene expression in skeletal muscle cells: evidence for involvement of activator protein-1

The gene network responsible for inflammation-induced insulin resistance remains enigmatic. In this study, we show that, in L6 cells, rosiglitazone- as well as pioglitazone-dependent activation of peroxisome proliferator-activated receptor-γ (PPARγ) represses transcription of the ped/pea-15 gene, whose increased activity impairs glucose tolerance in mice and humans. Rosiglitazone enhanced insulin-induced glucose uptake in L6 cells expressing the endogenous ped/pea-15 gene but not in cells expressing ped/pea-15 under the control of an exogenous promoter. The ability of PPARγ to affect ped/pea-15 expression was also lost in cells and in C57BL/6J transgenic mice expressing ped/pea-15 under the control of an exogenous promoter, suggesting that ped/pea-15 repression may contribute to rosiglitazone action on glucose disposal. Indeed, high fat diet mice showed insulin resistance and increased ped/pea-15 levels, although these effects were reduced by rosiglitazone treatment. Both supershift and ChIP assays revealed the presence of the AP-1 component c-JUN at the PED/PEA-15 promoter upon 12-O-tetradecanoylphorbol-13-acetate stimulation of the cells. In these experiments, rosiglitazone treatment reduced c-JUN presence at the PED/PEA-15 promoter. This effect was not associated with a decrease in c-JUN expression. In addition, c-jun silencing in L6 cells lowered ped/pea-15 expression and caused nonresponsiveness to rosiglitazone, although c-jun overexpression enhanced the binding to the ped/pea-15 promoter and blocked the rosiglitazone effect. These results indicate that PPARγ regulates ped/pea-15 transcription by inhibiting c-JUN binding at the ped/pea-15 promoter. Thus, ped/pea-15 is downstream of a major PPARγ-regulated inflammatory network. Repression of ped/pea-15 transcription might contribute to the PPARγ regulation of muscle sensitivity to insulin.

Epigenetic manifestation of metabolic syndrome and dietary management

SIGNIFICANCE

Metabolic syndrome constitutes a group of disorders such as insulin resistance, hypertension, and hypertriglyceridemia, predisposing an individual to risk factors such as cardiovascular disease, diabetes, obesity, and dyslipidemia. A majority of these diseases are influenced by the environmental factors, nutrient uptake, and genetic profile of an individual that together dysregulate gene function. These genetic and nongenetic factors are reported to introduce epigenetic cues that modulate the gene function which is inherited by the offspring.

RECENT ADVANCES

Considering the epigenetic modulation of the metabolic disorders, nutrigenomics has been distinctly categorized as a branch that deals with modulatory effect of nutrients on metabolic disorders and disease progression by supplementing the individuals with key nutrient-enriched diets which are derived from plant and animal sources.

CRITICAL ISSUES

Nutritional components of the diet regulate the metabolic health of an individual either by controlling the expression of some key genes related to metabolic pathways or by modulating the epigenetic events on such genes. The present article discusses various metabolic disorders in detail and the effect of nutrients on the specific genes causing those disorders. We also highlight the molecular mechanisms of some metabolic disorders through epigenetic modifications and possible therapeutic interventions.

FUTURE DIRECTIONS

With the advent of high-throughput technologies and epigenetic modulation of the metabolic disorders, an altered epigenetic code that is programmed due to improper nutrients can be reverted back by supplementing the diet with various plant-derived compounds. The implication of small molecular drugs is also of utmost significance for challenging the metabolic disorders.

Nutrigenomics: implications for breast and colon cancer prevention

Nutrigenomics refers to the interaction between one's diet and his/her genes. These interactions can markedly influence digestion, absorption, and the elimination of bioactive food components, as well as influence their site of actions/molecular targets. Nutrigenomics comprises nutrigenetics, epigenetics, and transcriptomics, coupled with other "omic," such as proteomics and metabolomics, that apparently account for the wide variability in cancer risk among individuals with similar dietary habits. Multiple food components including essential nutrients, phytochemical, zoochemicals, fungochemical, and bacterochemicals have been implicated in cancer risk and tumor behavior, admittedly with mixed results. Such findings suggest that not all individuals respond identically to a diet. This chapter highlights the influence of single-nucleotide polymorphism, copy number, epigenetic events, and transcriptomic homeostasis as factors influencing the response to food components and ultimately health, including cancer risk. Both breast and colorectal cancers are reviewed as examples about how nutrigenomics may influence the response to dietary intakes. As the concept that "one size fits all" comes to an end and personalized approaches surface, additional research data will be required to identify those who will benefit most from dietary change and any who might be placed at risk because of an adjustment.