Low Sirt1 expression, which is upregulated by fasting, in human adipose tissue from obese women

Piceatannol Upregulates SIRT1 Expression in Skeletal Muscle Cells and in Human Whole Blood: In Vitro Assay and a Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Comparison Trial

Piceatannol (PIC), a polyphenol abundant in passion fruit seeds, is reported to promote fat metabolism. This study investigated whether PIC affects sirtuin 1 (SIRT1) expression and metabolic factors in C2C12 skeletal muscle cells. C2C12 myotubes were stimulated with PIC, and alterations in gene expression, protein levels, mitochondrial DNA content, and fatty acid levels were assessed using real-time PCR, Western blotting, and Nile red staining. Furthermore, we examined changes in SIRT1 expression following the consumption of a test food containing 100 mg PIC for 2 weeks among adults with varying age and body mass index ranges. Both PIC and passion fruit seed extract induced SIRT1 expression in C2C12 myotubes to a greater extent than resveratrol. PIC also increased the expression of genes associated with mitochondrial biogenesis and fatty acid utilization, increased mitochondrial DNA content, and suppressed oleic acid-induced fat accumulation. Moreover, participants who consumed PIC exhibited significantly higher SIRT1 mRNA expression in whole blood compared to those in the placebo group. These findings suggest that PIC induces SIRT1 expression both in vitro and in the human body, which may promote mitochondrial biosynthesis and fat metabolism.

Caloric restriction, Sirtuins, and cardiovascular diseases

ABSTRACT

Caloric restriction (CR) is a well-established dietary intervention known to extend healthy lifespan and exert positive effects on aging-related diseases, including cardiovascular conditions. Sirtuins, a family of nicotinamide adenine dinucleotide (NAD + )-dependent histone deacetylases, have emerged as key regulators of cellular metabolism, stress responses, and the aging process, serving as energy status sensors in response to CR. However, the mechanism through which CR regulates Sirtuin function to ameliorate cardiovascular disease remains unclear. This review not only provided an overview of recent research investigating the interplay between Sirtuins and CR, specifically focusing on their potential implications for cardiovascular health, but also provided a comprehensive summary of the benefits of CR for the cardiovascular system mediated directly via Sirtuins. CR has also been shown to have considerable impact on specific metabolic organs, leading to the production of small molecules that enter systemic circulation and subsequently regulate Sirtuin activity within the cardiovascular system. The direct and indirect effects of CR offer a potential mechanism for Sirtuin modulation and subsequent cardiovascular protection. Understanding the interplay between CR and Sirtuins will provide new insights for the development of interventions to prevent and treat cardiovascular diseases.

Novel targets of β-TrCP cooperatively accelerate carbohydrate and fatty acid consumption

Cellular energy is primarily produced from glucose and fat through glycolysis and fatty acid oxidation (FAO) followed by the tricarboxylic acid cycle in mitochondria; energy homeostasis is carefully maintained via numerous feedback pathways. In this report, we uncovered a new master regulator of carbohydrate and lipid metabolism. When ubiquitin E3 ligase β-TrCP2 was inducibly knocked out in β-TrCP1 knockout adult mice, the resulting double knockout mice (DKO) lost fat mass rapidly. Biochemical analyses of the tissues and cells from β-TrCP2 KO and DKO mice revealed that glycolysis, FAO, and lipolysis were dramatically upregulated. The absence of β-TrCP2 increased the protein stability of metabolic rate-limiting enzymes including 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1A (CPT1A), and carnitine/acylcarnitine translocase (CACT). Our data suggest that β-TrCP is a potential regulator for total energy homeostasis by simultaneously controlling glucose and fatty acid metabolism and that targeting β-TrCP could be an effective strategy to treat obesity and other metabolic disorders.

Obesity under the moonlight of c-MYC

The moonlighting protein c-Myc is a master regulator of multiple biological processes including cell proliferation, differentiation, angiogenesis, apoptosis and metabolism. It is constitutively and aberrantly expressed in more than 70% of human cancers. Overwhelming evidence suggests that c-Myc dysregulation is involved in several inflammatory, autoimmune, metabolic and other non-cancerous diseases. In this review, we addressed the role of c-Myc in obesity. Obesity is a systemic disease, accompanied by multi-organ dysfunction apart from white adipose tissue (WAT), such as the liver, the pancreas, and the intestine. c-Myc plays a big diversity of functions regulating cellular proliferation, the maturation of progenitor cells, fatty acids (FAs) metabolism, and extracellular matrix (ECM) remodeling. Moreover, c-Myc drives the expression of a wide range of metabolic genes, modulates the inflammatory response, induces insulin resistance (IR), and contributes to the regulation of intestinal dysbiosis. Altogether, c-Myc is an interesting diagnostic tool and/or therapeutic target in order to mitigate obesity and its consequences.

The complex relationship between obesity and neurodegenerative diseases: an updated review

Obesity is a global epidemic, affecting roughly 30% of the world's population and predicted to rise. This disease results from genetic, behavioral, societal, and environmental factors, leading to excessive fat accumulation, due to insufficient energy expenditure. The adipose tissue, once seen as a simple storage depot, is now recognized as a complex organ with various functions, including hormone regulation and modulation of metabolism, inflammation, and homeostasis. Obesity is associated with a low-grade inflammatory state and has been linked to neurodegenerative diseases like multiple sclerosis (MS), Alzheimer's (AD), and Parkinson's (PD). Mechanistically, reduced adipose expandability leads to hypertrophic adipocytes, triggering inflammation, insulin and leptin resistance, blood-brain barrier disruption, altered brain metabolism, neuronal inflammation, brain atrophy, and cognitive decline. Obesity impacts neurodegenerative disorders through shared underlying mechanisms, underscoring its potential as a modifiable risk factor for these diseases. Nevertheless, further research is needed to fully grasp the intricate connections between obesity and neurodegeneration. Collaborative efforts in this field hold promise for innovative strategies to address this complex relationship and develop effective prevention and treatment methods, which also includes specific diets and physical activities, ultimately improving quality of life and health.

Cardioprotective effects of calorie restriction against inflammation and apoptosis in ovariectomized obese rats: Role of classical estrogen receptors and SIRT1

AIM

Obesity is a metabolic complication linked with bad eating habits and a sedentary lifestyle, and the heart is one of the target organs damaged by it. Estrogen deficiency during menopause worsens the situation. Calorie restriction (CR) can contribute to reducing cardiovascular disease (CVD) in postmenopausal conditions. Thus, the effects of CR on inflammation and apoptosis in ovariectomized rats' hearts with obesity were studied.

METHOD

Female Wistar rats were categorized into Sham and OVX (ovariectomized) groups and received a standard diet (SD) or high-fat diet (60%HFD) or calorie restriction (30% CR) for 16 weeks. The real-time PCR method was used to evaluate the inflammatory markers and estrogen receptors gene expression. Western-blot and ELISA methods were respectively used for the measurement of apoptosis and SIRT1 protein expression.

RESULTS

HFD led to the elevation of body weight, IL-6 (interleukin-6) and TNF-α (tumor necrosis factor-α) and reduction of IL-10 (interleukin-10) gene expressions, and also an increment in protein levels of cleaved caspase-3, Bax and Bax/Bcl2 ratio and decrement in Bcl-2 in OVX rats (P < 0.001). Additionally, HFD reduced SIRT1 (sirtuin1) protein levels, ERα (estrogen receptor α), and ERβ (estrogen receptor β) gene expressions (P < 0.001). In contrast, CR declined body weight, IL-6 and TNF-α (P < 0.001), increased IL-10 expressions (P < 0.05), decreased cleaved caspase-3 (P < 0.001), Bax (P < 0.01), and Bax/Bcl2 ratio (P < 0.05), enhanced Bcl-2 (P < 0.001), increased SIRT1 (P < 0.05) and ERα (P < 0.001) and ERβ (P < 0.01) expressions.

CONCLUSION

CR through the SIRT1 regulation and estrogen receptors attenuate obesity-induced-cardiac inflammation and apoptosis. CR can be a cardioprotective candidate in postmenopausal conditions.

Predictors of Survival Among the Oldest Old Following Acute Hospital Admission: Insights From Clinical and Biochemical Factors

Understanding the factors influencing survival in oldest old population is crucial for providing appropriate care and improving outcomes. This prospective observational study aimed to investigate the determinants of survival in acutely ill oldest old patients during acute hospitalization and 1-month follow-up. Various geriatric domains and biochemical markers were assessed. Among the 70 included patients with a median age of 87 (Inter quartile range: 85-90), the presence of diabetes, delirium, tachypnea, and high sirtuin-5 levels were associated with reduced in-hospital survival. Non-survivors had raised levels of Sirtuin 1 and Sirtuin 5, with an increase of 43% and 70%, respectively. At 1 month, delirium and diabetes were still associated with reduced survival. These findings suggest that type-2 diabetes, delirium, tachypnea, and high sirtuin-5 levels could serve as predictors of reduced survival in acutely ill, hospitalized oldest old patients.

Changes in circulating sirtuin 1 after bariatric surgery

BACKGROUND AND AIMS

Obesity is associated with chronic inflammation and oxidative stress. Weight loss after bariatric surgery improves the inflammatory state and risk of cardiovascular disease. Improvement in metabolic dysfunction might be associated with changes in the activity of sirtuin 1 (SIRT1) and we aimed to investigate the effect of bariatric surgery on its circulating levels.

METHODS AND RESULTS

This is a sub-study of a prospective cohort study, including 110 subjects with morbid obesity. The surgical procedure was either laparoscopic Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). Blood was sampled at inclusion and six and 12 months after surgery. SIRT1 was measured in EDTA plasma with an enzyme-linked immunosorbent assay. The mean age in the population was 43 years, 80% were women and mean body mass index (BMI) was 38.8 kg/m². RYGB and SG were performed in 89 and 21 subjects, respectively. SIRT1 concentration was significantly reduced from baseline to six and 12 months after surgery, with mean values (SD) 156.8 (82.6), 119.5 (65.6) and 94.9 (45.6) ng/mL, respectively, (p ≤ 0.002, all), accompanied by significant reductions in C-reactive protein (CRP), BMI and triglycerides from inclusion (p < 0.001, all). Type of surgery did not differently modify SIRT1 levels (p = 0.09). CRP and triglycerides were both positively predictive of SIRT1 levels (p ≤ 0.001, both).

CONCLUSION

SIRT1 concentration was significantly lower six and 12 months after bariatric surgery. CRP and triglycerides independently predicted SIRT1 levels, suggesting that reduction in SIRT1 levels might not intrinsically be related to weight reduction, but to improvement in metaflammation.

Molecular mechanisms of dietary restriction promoting health and longevity

Dietary restriction with adequate nutrition is the gold standard for delaying ageing and extending healthspan and lifespan in diverse species, including rodents and non-human primates. In this Review, we discuss the effects of dietary restriction in these mammalian model organisms and discuss accumulating data that suggest that dietary restriction results in many of the same physiological, metabolic and molecular changes responsible for the prevention of multiple ageing-associated diseases in humans. We further discuss how different forms of fasting, protein restriction and specific reductions in the levels of essential amino acids such as methionine and the branched-chain amino acids selectively impact the activity of AKT, FOXO, mTOR, nicotinamide adenine dinucleotide (NAD⁺), AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21), which are key components of some of the most important nutrient-sensing geroprotective signalling pathways that promote healthy longevity.

Sirtuin function and metabolism: Role in pancreas, liver, and adipose tissue and their crosstalk impacting bone homeostasis

Mammalian sirtuins (SIRT1-7) are members of the nicotine adenine dinucleotide (NAD+)-dependent family of enzymes critical for histone deacetylation and posttranslational modification of proteins. Sirtuin family members regulate a wide spectrum of biological processes and are best known for maintaining longevity. Sirtuins are well characterized in metabolic tissues such as the pancreas, liver and adipose tissue (AT). They are regulated by a diverse range of stimuli, including nutrients and metabolic changes within the organism. Indeed, nutrient-associated conditions, such as obesity and anorexia nervosa (AN), were found to be associated with bone fragility development in osteoporosis. Interestingly, it has also been demonstrated that sirtuins, more specifically SIRT1, can regulate bone activity. Various studies have demonstrated the importance of sirtuins in bone in the regulation of bone homeostasis and maintenance of the balance between bone resorption and bone formation. However, to understand the molecular mechanisms involved in the negative regulation of bone homeostasis during overnutrition (obesity) or undernutrition, it is crucial to examine a wider picture and to determine the pancreatic, liver and adipose tissue pathway crosstalk responsible for bone loss. Particularly, under AN conditions, sirtuin family members are highly expressed in metabolic tissue, but this phenomenon is reversed in bone, and severe bone loss has been observed in human subjects. AN-associated bone loss may be connected to SIRT1 deficiency; however, additional factors may interfere with bone homeostasis. Thus, in this review, we focus on sirtuin activity in the pancreas, liver and AT in cases of over- and undernutrition, especially the regulation of their secretome by sirtuins. Furthermore, we examine how the secretome of the pancreas, liver and AT affects bone homeostasis, focusing on undernutrition. This review aims to lead to a better understanding of the crosstalk between sirtuins, metabolic organs and bone. In long term prospective it should contribute to promote improvement of therapeutic strategies for the prevention of metabolic diseases and the development of osteoporosis.

Redox Regulation of Lipid Mobilization in Adipose Tissues

Lipid mobilization in adipose tissues, which includes lipogenesis and lipolysis, is a paramount process in regulating systemic energy metabolism. Reactive oxygen and nitrogen species (ROS and RNS) are byproducts of cellular metabolism that exert signaling functions in several cellular processes, including lipolysis and lipogenesis. During lipolysis, the adipose tissue generates ROS and RNS and thus requires a robust antioxidant response to maintain tight regulation of redox signaling. This review will discuss the production of ROS and RNS within the adipose tissue, their role in regulating lipolysis and lipogenesis, and the implications of antioxidants on lipid mobilization.

Effect of intermittent and continuous caloric restriction on Sirtuin1 concentration depends on sex and body mass index

BACKGROUND & AIMS

The favorable effect of caloric restriction (CR) on health span is well known and partly mediated by the sirtuin system. Sirtuin1, a regulator of energy homeostasis in response to nutrient availability, is activated by CR. We therefore investigated effects of two different CR regimens on Sirtuin1 concentrations.

METHODS & RESULTS

The study included 112 abdominally obese subjects, randomized to intermittent or continuous CR for 1 year. Blood samples and anthropometric measures were collected at baseline and after 12 months. Sirtuin1 concentrations were measured by ELISA. Sirtuin1 correlated significantly to BMI at baseline (r = .232, p = 0.019). Mean reduction in body-weight was 8.0 and 9.0 kg after intermittent and continuous CR, respectively. After 1 year, no significant between-group differences in Sirtuin1 levels were observed according to regimen (p = 0.98) and sex (p = 0.41). An increase in median Sirtuin1 concentrations (pg/mL) [25, 75 percentiles] from baseline was observed after intermittent CR in the total population (884 [624, 1285] vs.762 [530, 1135]; p = 0.041), most marked in men (820 [623, 1250] vs. 633 [524, 926]; p = 0.016). Improvement in BMI after 1 year correlated to Sirtuin1 changes, but varied according to sex. In women, Spearman's rho = .298, p = 0.034, with stronger correlation in the intermittent CR group (r = .424, p = 0.049). In men, there was an inverse relation to Sirtuin1 changes, only in the intermittent CR group (r = -.396, p = 0.045).

CONCLUSIONS

Effects on Sirtuin1 concentrations after 1 year of CR are sex and BMI-related. Intermittent CR regimen affected Sirtuin1 to a stronger extent than continuous CR, suggesting individualized dietary intervention.

Modulatory Effect of Intermittent Fasting on Adipose Tissue Inflammation: Amelioration of Cardiovascular Dysfunction in Early Metabolic Impairment

Cardiometabolic syndrome (CMS) is a cluster of maladaptive cardiovascular, renal, thrombotic, inflammatory, and metabolic disorders. It confers a high risk of cardiovascular mortality and morbidity. CMS is triggered by major shifts in lifestyle and dietary habits with increased consumption of refined, calorie-dense diets. Evidence indicates that diet-induced CMS is linked to Adipose tissue (AT) inflammation. This led to the proposal that adipose inflammation may be involved in metabolic derangements, such as insulin resistance and poor glycemic control, as well as the contribution to the inflammatory process predisposing patients to increased cardiovascular risk. Therefore, in the absence of direct pharmacological interventions for the subclinical phase of CMS, time restricted feeding regimens were anticipated to alleviate early metabolic damage and subsequent comorbidities. These regimens, referred to as intermittent fasting (IF), showed a strong positive impact on the metabolic state of obese and non-obese human subjects and animal models, positive AT remodeling in face of overnutrition and high fat diet (HFD) consumption, and improved CV outcomes. Here, we summarize the available evidence on the role of adipose inflammation in triggering cardiovascular impairment in the context of diet induced CMS with an emphasis on the involvement of perivascular adipose tissue. As well, we propose some possible molecular pathways linking intermittent fasting to the ameliorative effect on adipose inflammation and cardiovascular dysfunction under such circumstances. We highlight a number of targets, whose function changes in perivascular adipose tissue inflammation and could be modified by intermittent fasting acting as a novel approach to ameliorate the inflammatory status.

Bariatric surgery can acutely modulate ER-stress and inflammation on subcutaneous adipose tissue in non-diabetic patients with obesity

BACKGROUND

Bariatric surgery, especially Roux-en-Y gastric bypass (RYGB), is the most effective and durable treatment option for severe obesity. The mechanisms involving adipose tissue may be important to explain the effects of surgery.

METHODS

We aimed to identify the genetic signatures of adipose tissue in patients undergoing RYGB. We evaluated 13 obese, non-diabetic patients (mean age 37 years, 100% women, Body mass index (BMI) 42.2 kg/m²) one day before surgery, 3 and 6 months (M) after RYGB.

RESULTS

Analysis of gene expression in adipose tissue collected at surgery compared with samples collected at 3 M and 6 M Post-RYGB showed that interleukins [Interleukin 6, Tumor necrosis factor-α (TNF-α), and Monocyte chemoattractant protein-1(MCP1)] and endoplasmic reticulum stress (ERS) genes [Eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3) and Calreticulin (CALR)] decreased during the follow-up (P ≤ 0.01 for all). Otherwise, genes involved in energy homeostasis [Adiponectin and AMP-activated protein kinase (AMPK)], cellular response to oxidative stress [Sirtuin 1, Sirtuin 3, and Nuclear factor erythroid 2-related factor 2 (NRF2)], mitochondrial biogenesis [Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α)] and amino acids metabolism [General control nonderepressible 2 (GCN2)] increased from baseline to all other time points evaluated (P ≤ 0.01 for all). Also, expression of Peroxisome proliferator-activated receptor gamma (PPARϒ) (adipogenesis regulation) was significantly decreased after RYGB (P < 0.05). Additionally, we observed that PGC1α, SIRT1 and AMPK strongly correlated to BMI at 3 M (P ≤ 0.01 for all), as well as ADIPOQ and SIRT1 to BMI at 6 M (P ≤ 0.01 for all).

CONCLUSIONS

Our findings demonstrate that weight loss is associated with amelioration of inflammation and ERS and increased protection against oxidative stress in adipose tissue. These observations are strongly correlated with a decrease in BMI and essential genes that control cellular energy homeostasis, suggesting an adaptive process on a gene expression level during the caloric restriction and weight loss period after RYGB. Trial registration CAAE: 73,585,317.0.0000.5440.

Heme Oxygenase-1 in liver transplant ischemia-reperfusion injury: From bench-to-bedside

Hepatic ischemia-reperfusion injury (IRI), a major risk factor for early allograft dysfunction (EAD) and acute or chronic graft rejection, contributes to donor organ shortage for life-saving orthotopic liver transplantation (OLT). The graft injury caused by local ischemia (warm and/or cold) leads to parenchymal cell death and release of danger-associated molecular patterns (DAMPs), followed by reperfusion-triggered production of reactive oxygen species (ROS), activation of inflammatory cells, hepatocellular damage and ultimate organ failure. Heme oxygenase 1 (HO-1), a heat shock protein-32 induced under IR-stress, is an essential component of the cytoprotective mechanism in stressed livers. HO-1 regulates anti-inflammatory responses and may be crucial in the pathogenesis of chronic diseases, such as arteriosclerosis, hypertension, diabetes and steatosis. An emerging area of study is macrophage-derived HO-1 and its pivotal intrahepatic homeostatic function played in IRI-OLT. Indeed, ectopic hepatic HO-1 overexpression activates intracellular SIRT1/autophagy axis to serve as a key cellular self-defense mechanism in both mouse and human OLT recipients. Recent translational studies in rodents and human liver transplant patients provide novel insights into HO-1 mediated cytoprotection against sterile hepatic inflammation. In this review, we summarize the current bench-to-bedside knowledge on HO-1 molecular signaling and discuss their future therapeutic potential to mitigate IRI in OLT.

Dietary natural products as epigenetic modifiers in aging-associated inflammation and disease

Covering: up to 2020Chronic, low-grade inflammation is linked to aging and has been termed "inflammaging". Inflammaging is considered a key contributor to the development of metabolic dysfunction and a broad spectrum of diseases or disorders including declines in brain and heart function. Genome-wide association studies (GWAS) coupled with epigenome-wide association studies (EWAS) have shown the importance of diet in the development of chronic and age-related diseases. Moreover, dietary interventions e.g. caloric restriction can attenuate inflammation to delay and/or prevent these diseases. Common themes in these studies entail the use of phytochemicals (plant-derived compounds) or the production of short chain fatty acids (SCFAs) as epigenetic modifiers of DNA and histone proteins. Epigenetic modifications are dynamically regulated and as such, serve as potential therapeutic targets for the treatment or prevention of age-related disease. In this review, we will focus on the role for natural products that include phytochemicals and short chain fatty acids (SCFAs) as regulators of these epigenetic adaptations. Specifically, we discuss regulators of methylation, acetylation and acylation, in the protection from chronic inflammation driven metabolic dysfunction and deterioration of neurocognitive and cardiac function.

MR (Mineralocorticoid Receptor) Induces Adipose Tissue Senescence and Mitochondrial Dysfunction Leading to Vascular Dysfunction in Obesity

Adipose tissue (AT) senescence and mitochondrial dysfunction are associated with obesity. Studies in obese patients and animals demonstrate that the MR (mineralocorticoid receptor) contributes to obesity-associated cardiovascular complications through its specific role in AT. However, underlying mechanisms remain unclear. This study aims to elucidate whether MR regulates mitochondrial function in obesity, resulting in AT premature aging and vascular dysfunction. Obese (db/db) and lean (db/+) mice were treated with an MR antagonist or a specific mitochondria-targeted antioxidant. Mitochondrial and vascular functions were determined by respirometry and myography, respectively. Molecular mechanisms were probed by Western immunoblotting and real-time polymerase chain reaction in visceral AT and arteries and focused on senescence markers and redox-sensitive pathways. db/db mice displayed AT senescence with activation of the p53-p21 pathway and decreased SIRT (sirtuin) levels, as well as mitochondrial dysfunction. Furthermore, the beneficial anticontractile effects of perivascular AT were lost in db/db via ROCK (Rho kinase) activation. MR blockade prevented these effects. Thus, MR activation in obesity induces mitochondrial dysfunction and AT senescence and dysfunction, which consequently increases vascular contractility. In conclusion, our study identifies novel mechanistic insights involving MR, adipose mitochondria, and vascular function that may be of importance to develop new therapeutic strategies to limit obesity-associated cardiovascular complications.

Histological and Molecular Adipose Tissue Changes Are Related to Metabolic Syndrome Rather Than Lipodystrophy in Human Immunodeficiency Virus-Infected Patients: A Cross-Sectional Study

Background

In human immunodeficiency virus (HIV)-infected patients on combination antiretroviral therapy (cART), lipodystrophy shares many similarities with metabolic syndrome, but only metabolic syndrome has objective classification criteria. We examined adipose tissue changes related to lipodystrophy and metabolic syndrome to clarify whether it may be acceptable to focus diagnosis on metabolic syndrome rather than lipodystrophy.

Methods

This is a cross-sectional study of 60 HIV-infected men on cART and 15 healthy men. We evaluated lipodystrophy (clinical assessment) and metabolic syndrome (JIS-2009). We compared adipocyte size, leukocyte infiltration, and gene expression in abdominal subcutaneous adipose tissue biopsies of patients with and without lipodystrophy and with and without metabolic syndrome.

Results

Lipodystrophy was only associated with increased macrophage infiltration (P = .04) and adiponectin messenger ribonucleic acid ([mRNA] P = .008), whereas metabolic syndrome was associated with larger adipocytes (P < .0001), decreased expression of genes related to adipogenesis and adipocyte function (P values between <.0001 and .08), increased leptin mRNA (P = .04), and a trend towards increased expression of inflammatory genes (P values between .08 and .6).

Conclusions

Metabolic syndrome rather than lipodystrophy was associated with major unfavorable abdominal subcutaneous adipose tissue changes. In a clinical setting, it may be more relevant to focus on metabolic syndrome diagnosis in HIV-infected patients on cART with regards to adipose tissue dysfunction and risk of cardiometabolic complications.

The Effect of Resveratrol Supplementation on Cardio-Metabolic Risk Factors in Patients with Type 2 Diabetes: A Randomized, Double-Blind Controlled Trial

The aim of the present randomized controlled trial was to evaluate the effect of a micronized resveratrol supplement on glycemic status, lipid profile, and body composition in patients with type 2 diabetes mellitus (T2DM). A total of 71 overweight patients with T2DM (body mass index ranged 25-30) were randomly assigned to receive 1000 mg/day trans-resveratrol or placebo (methyl cellulose) for 8 weeks. Anthropometric indices and biochemical indices including lipid and glycemic profile were measured before and after the intervention. In adjusted model (age, sex, and baseline body mass index), resveratrol decreased fasting blood sugar (-7.97±13.6 mg/dL, p=0.05) and increased high density lipoprotein (3.62±8.75 mg/dL, p=0.01) levels compared with placebo. Moreover, the mean difference in insulin levels reached significance (-0.97±1.91, μIU/mL, p= 0.02). However, no significant differences were observed for anthropometric measures. It was found that 8-week resveratrol supplementation produced useful effects on some cardio-metabolic parameters in patients with T2DM. More studies are needed to confirm these findings.

Pharmacologic or genetic activation of SIRT1 attenuates the fat-induced decrease in beta-cell function in vivo

Background

There is evidence that sirtuin 1 (SIRT1), a key regulator of nutrient metabolism, increases β-cell secretory function. Excess circulating fat, as seen in obesity, has been shown to decrease β-cell function, an effect that may involve decreased SIRT1 activity. Consequently, SIRT1 activation may increase β-cell function in conditions of elevated plasma-free fatty acid levels. Here we attempted to attenuate the lipid-induced decrease in β-cell function in vivo using pharmacological and genetic models of SIRT1 activation.

Methods

Our pharmacologic model involved 48 h intravenous infusion of Wistar rats with either saline or oleate with or without the SIRT1 activator resveratrol. Additionally, we used β-cell-specific SIRT1 overexpressing (BESTO) mice and wild-type littermates infused for 48 h intravenously with either saline or oleate. In both models, the infusion period was followed by assessment of β-cell function using the hyperglycemic clamp method.

Results

Lipid infusion resulted in a significant decrease in β-cell function as expected in both rats (p < 0.05) and mice (p < 0.001). Both models of SIRT1 activation, which did not alter β-cell function in the absence of fat, resulted in partial protection from the fat-induced decrease in β-cell function (NS vs. control).

Conclusion

These results suggest that SIRT1 is a therapeutic target in decreased β-cell function specifically induced by fat.

Epigenetic modifications induced by exercise: Drug-free intervention to improve cognitive deficits associated with obesity

Obesity and metabolic disorders are increasing worldwide and are associated with brain atrophy and dysfunction, which are risk factors for late-onset dementia and Alzheimer's disease. Epidemiological studies demonstrated that changes in lifestyle, including the frequent practice of physical exercise are able to prevent and treat not only obesity/metabolic disorders, but also to improve cognitive function and dementia. Several biochemical pathways and epigenetic mechanisms have been proposed to understand the beneficial effects of physical exercise on cognition. This manuscript revised central ongoing research on epigenetic mechanisms induced by exercise and the beneficial effects on obesity-associated cognitive decline, highlighting potential mechanistic mediators.

Palmitate-induced IL6 expression ameliorated by chicoric acid through AMPK and SIRT1-mediated pathway in the PBMCs of newly diagnosed type 2 diabetes patients and healthy subjects

Inhibition of inflammation is one of the possible therapeutic approaches for Insulin resistance (IR) during type 2 diabetes mellitus (T2DM). In the current study we investigated the effects of palmitate and chicoric acid (CA) on inflammation in peripheral blood mononuclear cells (PBMCs) of newly diagnosed T2DM patients and healthy subjects and explored the mechanism by which palmitate and CA influence inflammation. 20 newly diagnosed T2DM patients and 20 healthy subjects were recruited in our study. Blood sample were collected and PBMCs were isolated. Interleukin 6 (IL6), silent information regulator type 1 (SIRT1), AMP-activated protein kinase (AMPK) and phospho-AMPK (pAMPK) were evaluated both in vivo and in vitro. PBMCs were treated with palmitate and CA to investigate their effects on inflammation. IL6 and SIRT1 genes expression were evaluated by real-time PCR. The levels of IL6 in culture medium were measured by ELISA. Proteins levels of AMPK and pAMPK in PBMCs were detected by western blotting. IL6 expression was higher and SIRT1 expression and pAMPK levels were lower in PBMCs of diabetic patients and obese subjects compared to healthy subjects and non-obese subjects, respectively. CA significantly prevented against increased IL6 levels as well as its gene expression in PBMCs induced by palmitate. Also, CA returned reduction in SIRT1 expression and pAMPK levels mediated via palmitate to near control level. These findings reveal that CA reduces inflammation in PBMCs probably through upregulation of SIRT1 and pAMPK. Therefore, CA would be suggested as a novel agent for the treatment of T2DM.

Obesity May Accelerate the Aging Process

Lines of evidence from several studies have shown that increases in life expectancy are now accompanied by increased disability rate. The expanded lifespan of the aging population imposes a challenge on the continuous increase of chronic disease. The prevalence of overweight and obesity is increasing at an alarming rate in many parts of the world. Further to increasing the onset of metabolic imbalances, obesity leads to reduced life span and affects cellular and molecular processes in a fashion resembling aging. Nine key hallmarks of the aging process have been proposed. In this review, we will review these hallmarks and discuss pathophysiological changes that occur with obesity, that are similar to or contribute to those that occur during aging. We present and discuss the idea that obesity, in addition to having disease-specific effects, may accelerate the rate of aging affecting all aspects of physiology and thus shortening life span and health span.

Prostaglandin E2 down-regulates sirtuin 1 (SIRT1), leading to elevated levels of aromatase, providing insights into the obesity-breast cancer connection

Obesity increases the risk of hormone receptor-positive breast cancer in postmenopausal women. Levels of aromatase, the rate-limiting enzyme in estrogen biosynthesis, are increased in the breast tissue of obese women. Both prostaglandin E₂ (PGE₂) and hypoxia-inducible factor 1α (HIF-1α) contribute to the induction of aromatase in adipose stromal cells (ASCs). Sirtuin 1 (SIRT1) binds, deacetylates, and thereby inactivates HIF-1α. Here, we sought to determine whether SIRT1 also plays a role in regulating aromatase expression. We demonstrate that reduced SIRT1 levels are associated with elevated levels of acetyl-HIF-1α, HIF-1α, and aromatase in breast tissue of obese compared with lean women. To determine whether these changes were functionally linked, ASCs were utilized. In ASCs, treatment with PGE₂, which is increased in obese individuals, down-regulated SIRT1 levels, leading to elevated acetyl-HIF-1α and HIF-1α levels and enhanced aromatase gene transcription. Chemical SIRT1 activators (SIRT1720 and resveratrol) suppressed the PGE₂-mediated induction of acetyl-HIF-1α, HIF-1α, and aromatase. Silencing of p300/CBP-associated factor (PCAF), which acetylates HIF-1α, blocked PGE₂-mediated increases in acetyl-HIF-1α, HIF-1α, and aromatase. SIRT1 overexpression or PCAF silencing inhibited the interaction between HIF-1α and p300, a coactivator of aromatase expression, and suppressed p300 binding to the aromatase promoter. PGE₂ acted via prostaglandin E2 receptor 2 (EP₂) and EP₄ to induce activating transcription factor 3 (ATF3), a repressive transcription factor, which bound to a CREB site within the SIRT1 promoter and reduced SIRT1 levels. These findings suggest that reduced SIRT1-mediated deacetylation of HIF-1α contributes to the elevated levels of aromatase in breast tissues of obese women.

SIRT1 overexpression attenuates offspring metabolic and liver disorders as a result of maternal high-fat feeding

KEY POINTS

Maternal high-fat diet (MHF) consumption led to metabolic and liver disorders in male offspring, which are associated with reduced sirtuin (SIRT)1 expression and activity in the offspring liver SIRT1 overexpression in MHF offspring reduced their body weight and adiposity and normalized lipid metabolic markers in epididymal and retroperitoneal adipose tissues SIRT1 overexpression in MHF offspring improved glucose tolerance, as well as systemic and hepatic insulin sensitivity SIRT1 overexpression ameliorated MHF-induced lipogenesis, oxidative stress and fibrogenesis in the liver of offspring.

ABSTRACT

Maternal obesity can increase the risk of metabolic disorders in the offspring. However, the underlying mechanism responsible for this is not clearly understood. Previous evidence implied that sirtuin (SIRT)1, a potent regulator of energy metabolism and stress responses, may play an important role. In the present study, we have shown, in C57BL/6 mice, that maternal high-fat diet (HFD) consumption can induce a pre-diabetic and non-alcoholic fatty liver disease phenotype in the offspring, associated with reduced SIRT1 expression in the hypothalamus, white adipose tissues (WAT) and liver. Importantly, the overexpression of SIRT1 in these offspring significantly attenuated the excessive accumulation of epididymal (Epi) white adipose tissue (WAT) and retroperitoneal (Rp)WAT (P < 0.001), glucose intolerance and insulin resistance (both P < 0.05) at weaning age. These changes were associated with the suppression of peroxisome proliferator-activated receptor gamma (PPAR)γ (P < 0.01), PPARγ-coactivator 1-alpha (P < 0.05) and sterol regulatory element-binding protein-1c in EpiWAT (P < 0.01), whereas there was increased expression of PPARγ in RpWAT (P < 0.05). In the liver, PPARγ mRNA expression, as well as Akt protein expression and activity, were increased (P < 0.05), whereas fatty acid synthase and carbohydrate response element binding protein were downregulated (P < 0.05), supporting increased insulin sensitivity and reduced lipogenesis in the liver. In addition, hepatic expression of endogenous anti-oxidants, including glutathione peroxidase 1 and catalase, was increased (P < 0.01 and P < 0.05 respectively), whereas collagen and fibronectin deposition was suppressed (P < 0.01). Collectively, the present study provides direct evidence of the mechanistic significance of SIRT1 in maternal HFD-induced metabolic dysfunction in offspring and suggests that SIRT1 is a promising target for fetal reprogramming.

Moderate weight loss attenuates chronic endoplasmic reticulum stress and mitochondrial dysfunction in human obesity

OBJECTIVE

In obese patients undergoing caloric restriction, there are several potential mechanisms involved in the improvement of metabolic outcomes. The present study further explores whether caloric restriction can modulate endoplasmic reticulum (ER) stress and mitochondrial function, as both are known to be mechanisms underlying inflammation and insulin resistance (IR) during obesity.

METHODS

A total of 64 obese patients with BMI ≥35 kg/m² underwent a dietary program consisting of 6 weeks of a very-low-calorie diet followed by 18 weeks of low-calorie diet. We evaluated changes in the metabolic and inflammatory markers -TNFα, hsCRP, complement component 3 (C3c), and retinol binding protein 4 (RBP4)-, in the ER stress markers and modulators -eIF2α-P, sXBP1, ATF6, JNK-P, CHOP, GRP78, and SIRT1-, and in mitochondrial function parameters -mitochondrial reactive oxygen species (mROS), glutathione peroxidase 1 (GPX1), cytosolic Ca²⁺, and mitochondrial membrane potential.

RESULTS

The dietary intervention produced an 8.85% weight loss associated with enhanced insulin sensitivity, a less marked atherogenic lipid profile, and a decrease in systemic inflammation (TNFα, hsCRP) and adipokine levels (RBP4 and C3c). Chronic ER stress was significantly reduced (ATF6-CHOP, JNK-P) and expression levels of SIRT1 and GRP78 - a Ca²⁺-dependent chaperone - were increased and accompanied by the restoration of Ca²⁺ depots. Furthermore, mROS production and mitochondrial membrane potential improvement were associated with the up-regulation of the antioxidant enzyme GPX1.

CONCLUSIONS

Our data provide evidence that moderate weight loss attenuates systemic inflammation and IR and promotes the amelioration of ER stress and mitochondrial dysfunction, increasing the expression of chaperones, SIRT1 and antioxidant GPX1.

Adipose tissue, but not skeletal muscle, sirtuin 1 expression is decreased in obesity and related to insulin sensitivity

PURPOSE

Sirtuin 1 may regulate glucose and lipid metabolism. We aimed to assess adipose tissue and skeletal muscle sirtuin 1 expression in relation to insulin sensitivity, the expression of proinflammatory and metabolic genes, and to study the regulation of sirtuin 1 expression by hyperinsulinemia and circulating free fatty acids elevation.

METHODS

We examined 60 normal-weight, 42 overweight and 15 obese young subjects. The hyperinsulinemic-euglycemic clamp technique was applied throughout to measure insulin sensitivity. In 20 subjects, two 6 h clamps were performed, one of them with concurrent Intralipid/heparin infusion. Biopsies of subcutaneous adipose tissue and skeletal muscle were collected for the measurement of gene and protein expression.

RESULTS

Obese subjects had lower adipose sirtuin 1 in comparison with normal-weight and overweight participants. Muscle sirtuin 1 did not differ between the groups. Adipose tissue sirtuin 1 was related to insulin sensitivity, adipose tissue SLC2A4. The relationship between adipose tissue sirtuin 1 and insulin sensitivity was still present after controlling for BMI, however, it disappeared after controlling for adipose tissue SLC2A4. Muscle sirtuin 1 was not related to insulin sensitivity. Hyperisulinemia decreased adipose tissue and increased muscle sirtuin 1 expression. Intralipid/heparin infusion negated these effects.

CONCLUSIONS

Adipose tissue, but not muscle, sirtuin 1 is associated with insulin sensitivity in humans, possibly because of its correlation with adipose tissue SLC2A4 expression. Insulin differentially regulates adipose tissue and skeletal muscle sirtuin 1 expression in the short-term and circulating free fatty acids elevation negates these effects, which may be associated with lipid-induced insulin resistance.

The variable role of SIRT1 in the maintenance and differentiation of mesenchymal stem cells

SIRT1 is an NAD+-dependent deacetylase that acts as a nutrient sensitive regulator of longevity. SIRT1 also acts as a key regulator of mesenchymal stem cells (MSCs), adult stem cells that give rise to tissues such as bone, fat, muscle and cartilage. This review focuses on how SIRT1 regulates the self-renewal, multipotency and differentiation of MSCs. The variable role of SIRT1 in promoting the differentiation of MSCs towards certain lineages, while repressing others, will be examined within the broader context of aging, calorie restriction, and regenerative medicine. Finally, recent animal and human studies will be highlighted which paint an overall salutary role for SIRT1 in protecting MSCs (and resulting tissues) from age-related atrophy and dysfunction.

High Levels of SIRT1 Expression as a Protective Mechanism Against Disease-Related Conditions

SIRT1 protein, a member of Silent Information Regulator 2 (Sir2) protein family, have gained considerable attention as epigenetic regulators for a great area in the human physiology. Changes in sirtuin expression are critical in several diseases, including metabolic syndrome, cardiovascular diseases, cancer and neurodegeneration. Here, we provide an overview of the association of the increasing level of SIRT1 protein for regulating some disease related conditions such as obesity, cardiovascular diseases and neurodegeneration. This review also provides a detailed molecular understanding of the interaction of the some basic molecules with increasing SIRT1 levels rather than reduction of the SIRT1 expression. In this context, the current approaches to enhancing the expression of SIRT1 points the importance of epigenetics in several age-related diseases to provide a healthy aging by developing novel therapies which can prevent or damp the progression of some diseases.

Distinctive Roles of Sirtuins on Diabetes, Protective or Detrimental?

Dysregulation of metabolic pathways leads to type 2 diabetes, characteristic of high glucose concentration caused by insulin resistance. The histone deacetylases sirtuins exhibit remarkable enzymatic activities. Accumulating evidence indicates that sirtuins can be pharmacologically activated to ameliorate diabetes. Here, we evaluated different roles of sirtuins (SIRT1-SIRT7) in diabetes progression and described their involvement in metabolic pathways of skeletal muscle, adipose tissue and liver. The nuclear sirtuins, SIRT1, SIRT6, and SIRT7, regulate the activity of key transcription factors and cofactors in almost all tissues with the cellular responses to energy demands. The mitochondrial sirtuins, SIRT3, SIRT4, and SIRT5, regulate the activity of mitochondrial enzymes in response to fasting and calorie restriction. Moreover, genetic polymorphisms of SIRT1 and SIRT2 have been reported to associate with diabetes development. It's worth noting that SIRT1, SIRT2, SIRT3, and SIRT6 are positive regulators of insulin resistance in most cases. In the opposite, SIRT4 and SIRT7 inhibit insulin secretion and fatty acid oxidation. Identification of SIRT1 activators for diabetes has gained wide attention, such as metformin, resveratrol, and resveratrol derivatives. Randomized, prospective, and large-scale clinical trials are warrant to uncover the responsibilities of SIRTs modulators on diabetes progress.

Circulating SIRT1 Increases After Intragastric Balloon Fat Loss in Obese Patients

BACKGROUND

Sirtuins (SIRTs), ubiquitous deacetylases, are main regulators of energy homeostasis and metabolism. SIRT1 has a positive impact on obesity, diabetes mellitus, liver steatosis, and other metabolic disorders. Lean subjects have higher expression of SIRT1 in the adipose tissue compared to obese. However, it is not known whether weight loss associates with changes in blood SIRT1. We evaluated the effect of weight loss on circulating SIRT1, metabolic parameters, and body composition.

METHODS

Thirty-two obese subjects were studied before and 6 months after BioEnterics® Intragastric Balloon (BIB®) [22 patients, BMI 41.82 ± 6.28 kg/m(2)] or hypocaloric diet [10 patients, BMI 38.95 ± 6.90 kg/m(2)]. Plasma SIRT1, body composition, measures of metabolic syndrome (waist circumference, fasting plasma glucose, blood pressure, HDL cholesterol, triglycerides), and inflammation markers (ESR, CRP, fibrinogen) were recorded.

RESULTS

SIRT1 levels showed a significant increase, together with a significant reduction of BMI, excess body weight, and total fat mass either after BIB or diet intervention. The percent excess body weight loss was 33.73 ± 19.06 and 22.08 ± 11.62 % after BIB and diet, respectively, a trend toward a metabolic and inflammatory amelioration was observed with both treatments. Negative correlation between SIRT1 and % fat mass (BIB, ρ = -0.537, p = 0.017; diet, ρ = -0.638, p = 0.047) was also seen.

CONCLUSIONS

The reduction of fat mass associates with increased plasma SIRT1 indicating that, besides tissue levels, circulating SIRT1 is stimulated by a negative caloric balance. The rise of plasma SIRT1 may represent a parameter associating with fat loss rather than weight lowering regardless of the weight reduction system method used.

Reduced gene expression of sirtuins and active AMPK levels in children and adolescents with obesity and insulin resistance

BACKGROUND

Sirtuins, including SIRT1 and SIRT2, are longevity-associated deacetylase enzymes that modulate metabolic homeostasis in response to the cellular energy state. Adenosine monophosphate activated protein kinase (AMPK) and SIRT1 are interrelated and share several common target pathways. This study aimed to evaluate the SIRT1 and SIRT2 gene expression in peripheral blood mononuclear cells (PBMCs) as well as plasma levels of AMPK, in obese children and adolescents.

MATERIALS AND METHODS

Participants included 60 children and adolescents (30 obese and 30 age- and gender-matched control subjects). Real-time polymerase chain reaction (PCR) was used to assess the SIRT1 and SIRT2 gene expression in PBMCs. Serum phospho-AMPK and insulin were measured using enzyme-linked immunosorbent assay (ELISA), and insulin resistance (IR) was calculated by the Homeostasis Model of Assessment of Insulin Resistance (HOMA-IR). Glucose and lipid profile were also measured.

RESULTS

SIRT1 gene expression and phospho-AMPK plasma levels were significantly diminished in obese subjects compared to the control group, and both SIRT1 and SIRT2 were significantly lower in obese children with IR compared to those without IR. SIRT1 expression revealed significant negative correlations with body mass index and waist circumference as well as insulin and HOMA-IR and a positive correlation with AMPK. SIRT2 negatively correlated with SIRT1 and positively correlated with high density lipoprotein-cholesterol (HDL-C).

CONCLUSION

SIRT1 and SIRT2 expression and AMPK levels decrease in children with obesity and IR. Targeting SIRT1 can be valuable in preventing obesity-associated IR in childhood and adolescence.

Sirtuins 1-7 expression in human adipose-derived stem cells from subcutaneous and visceral fat depots: influence of obesity and hypoxia

The sirtuin family comprises seven NAD⁺-dependent deacetylases which control the overall health of organisms through the regulation of pleiotropic metabolic pathways. Sirtuins are important modulators of adipose tissue metabolism and their expression is higher in lean than obese subjects. At present, the role of sirtuins in adipose-derived stem cells has not been investigated yet. Therefore, in this study, we evaluated the expression of the complete panel of sirtuins in adipose-derived stem cells isolated from both subcutaneous and visceral fat of non-obese and obese subjects. We aimed at investigating the influence of obesity on sirtuins' levels, their role in obesity-associated inflammation, and the relationship with the peroxisome proliferator-activated receptor delta, which also plays functions in adipose tissue metabolism. The mRNA levels in the four types of adipose-derived stem cells were evaluated by quantitative polymerase chain reaction, in untreated cells and also after 8 h of hypoxia exposure. Correlations among sirtuins' expression and clinical and molecular parameters were also analyzed. We found that sirtuin1-6 exhibited significant higher mRNA expression in visceral adipose-derived stem cells compared to subcutaneous adipose-derived stem cells of non-obese subjects. Sirtuin1-6 levels were markedly reduced in visceral adipose-derived stem cells of obese patients. Sirtuins' expression in visceral adipose-derived stem cells correlated negatively with body mass index and C-reactive protein and positively with peroxisome proliferator-activated receptor delta. Finally, only in the visceral adipose-derived stem cells of obese patients hypoxia-induced mRNA expression of all of the sirtuins. Our results highlight that sirtuins' levels in adipose-derived stem cells are consistent with protective effects against visceral obesity and inflammation, and suggest a transcriptional mechanism through which acute hypoxia up-regulates sirtuins in the visceral adipose-derived stem cells of obese patients.

Adipose tissue NAD+ biology in obesity and insulin resistance: From mechanism to therapy

Nicotinamide adenine dinucleotide (NAD⁺ ) biosynthetic pathway, mediated by nicotinamide phosphoribosyltransferase (NAMPT), a key NAD⁺ biosynthetic enzyme, plays a pivotal role in controlling many biological processes, such as metabolism, circadian rhythm, inflammation, and aging. Over the past decade, NAMPT-mediated NAD⁺ biosynthesis, together with its key downstream mediator, namely the NAD⁺ -dependent protein deacetylase SIRT1, has been demonstrated to regulate glucose and lipid metabolism in a tissue-dependent manner. These discoveries have provided novel mechanistic and therapeutic insights into obesity and its metabolic complications, such as insulin resistance, an important risk factor for developing type 2 diabetes and cardiovascular disease. This review will focus on the importance of adipose tissue NAMPT-mediated NAD⁺ biosynthesis and SIRT1 in the pathophysiology of obesity and insulin resistance. We will also critically explore translational and clinical aspects of adipose tissue NAD⁺ biology.

Comprehensive Metabolomic Analysis in Blood, Urine, Fat, and Muscle in Men with Metabolic Syndrome: A Randomized, Placebo-Controlled Clinical Trial on the Effects of Resveratrol after Four Months' Treatment

Resveratrol possesses several beneficial metabolic effects in rodents, while the effects of resveratrol in humans remain unclear. Therefore, we performed a non-targeted comprehensive metabolomic analysis on blood, urine, adipose tissue, and skeletal muscle tissue in middle-aged men with metabolic syndrome randomized to either resveratrol or placebo treatment for four months. Changes in steroid hormones across all four matrices were the most pronounced changes observed. Resveratrol treatment reduced sulfated androgen precursors in blood, adipose tissue, and muscle tissue, and increased these metabolites in urine. Furthermore, markers of muscle turnover were increased and lipid metabolism was affected, with increased intracellular glycerol and accumulation of long-chain saturated, monounsaturated, and polyunsaturated (n3 and n6) free fatty acids in resveratrol-treated men. Finally, urinary derivatives of aromatic amino acids, which mainly reflect the composition of the gut microbiota, were altered upon resveratrol treatment. In conclusion, the non-targeted metabolomics approach applied to four different matrices provided evidence of subtle but robust effects on several metabolic pathways following resveratrol treatment for four months in men with metabolic syndrome—effects that, for the most part, would not have been detected by routine analyses. The affected pathways should be the focus of future clinical trials on resveratrol’s effects, and perhaps particularly the areas of steroid metabolism and the gut microbiome.

Adipose tissue NAD+-homeostasis, sirtuins and poly(ADP-ribose) polymerases -important players in mitochondrial metabolism and metabolic health

Obesity, a chronic state of energy overload, is characterized by adipose tissue dysfunction that is considered to be the major driver for obesity associated metabolic complications. The reasons for adipose tissue dysfunction are incompletely understood, but one potential contributing factor is adipose tissue mitochondrial dysfunction. Derangements of adipose tissue mitochondrial biogenesis and pathways associate with obesity and metabolic diseases. Mitochondria are central organelles in energy metabolism through their role in energy derivation through catabolic oxidative reactions. The mitochondrial processes are dependent on the proper NAD⁺/NADH redox balance and NAD⁺ is essential for reactions catalyzed by the key regulators of mitochondrial metabolism, sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs). Notably, obesity is associated with disturbed adipose tissue NAD⁺ homeostasis and the balance of SIRT and PARP activities. In this review we aim to summarize existing literature on the maintenance of intracellular NAD⁺ pools and the function of SIRTs and PARPs in adipose tissue during normal and obese conditions, with the purpose of comprehending their potential role in mitochondrial derangements and obesity associated metabolic complications. Understanding the molecular mechanisms that are the root cause of the adipose tissue mitochondrial derangements is crucial for developing new effective strategies to reverse obesity associated metabolic complications.

Synchronized human skeletal myotubes of lean, obese and type 2 diabetic patients maintain circadian oscillation of clock genes

Cell and animal studies have demonstrated that circadian rhythm is governed by autonomous rhythmicity of clock genes. Although disturbances in circadian rhythm have been implicated in metabolic disease development, it remains unknown whether muscle circadian rhythm is altered in human models of type 2 diabetes. Here we used human primary myotubes (HPM) to investigate if rhythmicity of clock- and metabolic gene expression is altered in donors with obesity or type 2 diabetes compared to metabolically healthy donors. HPM were obtained from skeletal muscle biopsies of four groups: type 2 diabetic patients and their BMI- and age-matched obese controls and from lean, healthy and young endurance trained athletes and their age-matched sedentary controls. HPM were differentiated for 7 days before synchronization by serum shock followed by gene expression profiling over the next 72 hours. HPM display robust circadian rhythms in clock genes, but REVERBA displayed dampened rhythmicity in type 2 diabetes. Furthermore, rhythmicity in NAMPT and SIRT1 expression was only observed in HPM from trained athletes. Rhythmicity in expression of key-regulators of carbohydrate and lipid metabolism was modest. We demonstrate that in human skeletal muscle REVERBA/B, NAMPT and SIRT1 circadian rhythms are affected in donors of sedentary life style and poor health status.

Effects of self-reported calorie restriction on correlations between SIRT1 polymorphisms and body mass index and long-term weight change

SIRT1 acts as a cellular sensor to detect energy availability and modulates fat and glucose metabolism. This study assessed the effects of self-reported calorie restriction (CR) and exercise on correlations between SIRT1 polymorphisms and body mass index (BMI) and long-term weight change. This cross-sectional study enrolled 4023 subjects aged 35-69years (1847 men and 2176 women) selected from participants in the Japan Multi-Institutional Collaborative Cohort Study. This study was based on a self-administered questionnaire. No significant correlations between SIRT1 polymorphisms and BMI or long-term weight change were found in either the CR or the active groups. In the no-CR group, women with the rs1467568 G allele had a higher BMI than women without (p=0.02). Moreover, women with the rs7895833 A or rs1467568 G allele gained more weight from the age of 20years than women without these alleles (p=0.03 for rs7895833 and p=0.003 for rs1467568). In addition, the odds ratios (95% confidence intervals) of these alleles for overweight (BMI >27.5kg/m²) were significantly high in the no-CR women group (1.78 (1.06-2.99) for rs7895833 and 1.88 (1.13-3.15) for rs1467568) but not in the CR group. The results of this study suggest that CR might override the genetic contributions of the SIRT1 rs7895833 A and rs1467568 G alleles to BMI and long-term weight change.

SIRT1 and SIRT7 expression in adipose tissues of obese and normal-weight individuals is regulated by microRNAs but not by methylation status

BACKGROUND/OBJECTIVE

Given their importance in the regulation of metabolism, sirtuins (SIRTs) constitute promising subjects of research on the pathogenesis of obesity and the metabolic syndrome. The aim of this study was to assess whether obesity in humans is associated with changes in the expression of SIRT genes in adipose tissue and whether epigenetic mechanisms, DNA methylation and microRNA (miRNA) interference, mediate in this phenomenon.

SUBJECTS/METHODS

The expression of SIRTs and of SIRT1 and SIRT7 mRNA-interacting miRNAs was evaluated by real-time PCR in visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) of 58 obese (body mass index (BMI) >40 kg m^-2) and 31 normal-weight (BMI 20-24.9 kg m^-2) individuals. The methylation status of SIRTs was studied by the methylation-sensitive digestion/real-time PCR method.

RESULTS

SIRT1 mRNA levels were lower in adipose tissues of obese patients than of normal-weight controls (VAT: P=0.0002, SAT: P=0.008). In contrast, expression of SIRT7 was higher in adipose tissues of obese patients than in the control group (VAT: P=0.001, SAT: P=0.008). The mean methylation of the SIRT1 and SIRT7 CpG islands was similar in tissues with high and low expression of these genes, and there was no correlation between the level of expression and the level of methylation. On the other hand, expression of SIRT1 in VAT of obese subjects correlated negatively with the expression of miR-22-3p (P<0.0001, r_s=-0.514), miR-34a-5p (P=0.01, r_s=-0.326) and miR-181a-3p (P<0.0001, r_s=-0.536). In turn, expression of SIRT7 in VAT of slim individuals correlated negatively with the expression of miR-125a-5p (P=0.003, r_s=-0.562) and miR-125b-5p (P=0.018, r_s=-0.460).

CONCLUSIONS

We observed obesity-associated downregulation of SIRT1 and upregulation of SIRT7 mRNA levels that were not associated with the methylation status of their promoters. We found a negative correlation between mRNA levels of SIRT1 in VAT of obese individuals and SIRT7 in VAT of the normal-weight subjects and expression of the relevant miRNAs.

SILAC-MS Based Characterization of LPS and Resveratrol Induced Changes in Adipocyte Proteomics - Resveratrol as Ameliorating Factor on LPS Induced Changes

Adipose tissue inflammation is believed to play a pivotal role in the development obesity-related morbidities such as insulin resistance. However, it is not known how this (low-grade) inflammatory state develops. It has been proposed that the leakage of lipopolysaccharides (LPS), originating from the gut microbiota, through the gut epithelium could drive initiation of inflammation. To get a better understanding of which proteins and intracellular pathways are affected by LPS in adipocytes, we performed SILAC proteomic analysis and identified proteins that were altered in expression. Furthermore, we tested the anti-inflammatory compound resveratrol. A total of 927 proteins were quantified by the SILAC method and of these 57- and 64 were significantly up- and downregulated by LPS, respectively. Bioinformatic analysis (GO analysis) revealed that the upregulated proteins were especially involved in the pathways of respiratory electron transport chain and inflammation. The downregulated proteins were especially involved in protein glycosylation. One of the latter proteins, GALNT2, has previously been described to regulate the expression of liver lipases such as ANGPTL3 and apoC-III affecting lipid metabolism. Furthermore, LPS treatment reduced the protein levels of the insulin sensitizing adipokine, adiponectin, and proteins participating in the final steps of triglyceride- and cholesterol synthesis. Generally, resveratrol opposed the effect induced by LPS and, as such, functioning as an ameliorating factor in disease state. Using an unbiased proteomic approach, we present novel insight of how the proteome is altered in adipocytes in response to LPS as seen in obesity. We suggest that LPS partly exerts its detrimental effects by altering glycosylation processes of the cell, which is starting to emerge as important posttranscriptional regulators of protein expression. Furthermore, resveratrol could be a prime candidate in ameliorating dysfunctioning adipose tissue induced by inflammatory stimulation.

Feast and famine: Adipose tissue adaptations for healthy aging

Proper adipose tissue function controls energy balance with favourable effects on metabolic health and longevity. The molecular and metabolic asset of adipose tissue quickly and dynamically readapts in response to nutrient fluctuations. Once delivered into cells, nutrients are managed by mitochondria that represent a key bioenergetics node. A persistent nutrient overload generates mitochondrial exhaustion and uncontrolled reactive oxygen species ((mt)ROS) production. In adipocytes, metabolic/molecular reorganization is triggered culminating in the acquirement of a hypertrophic and hypersecretory phenotype that accelerates aging. Conversely, dietary regimens such as caloric restriction or time-controlled fasting endorse mitochondrial functionality and (mt)ROS-mediated signalling, thus promoting geroprotection. In this perspective view, we argued some important molecular and metabolic aspects related to adipocyte response to nutrient stress. Finally we delineated hypothetical routes by which molecularly and metabolically readapted adipose tissue promotes healthy aging.

In Search of New Therapeutic Targets in Obesity Treatment: Sirtuins

Most of the available non-invasive medical therapies for obesity are non-efficient in a long-term evaluation; therefore there is a constant need for new methods of treatment. Research on calorie restriction has led to the discovery of sirtuins (silent information regulators, SIRTs), enzymes regulating different cellular pathways that may constitute potential targets in the treatment of obesity. This review paper presents the role of SIRTs in the regulation of glucose and lipid metabolism as well as in the differentiation of adipocytes. How disturbances of SIRTs’ expression and activity may lead to the development of obesity and related complications is discussed. A special emphasis is placed on polymorphisms in genes encoding SIRTs and their possible association with susceptibility to obesity and metabolic complications, as well as on data regarding altered expression of SIRTs in human obesity. Finally, the therapeutic potential of SIRTs-targeted strategies in the treatment of obesity and related disorders is discussed.

Weight Loss Is Associated With Increased NAD(+)/SIRT1 Expression But Reduced PARP Activity in White Adipose Tissue

CONTEXT

Sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs) are 2 important nicotinamide adenine dinucleotide (NAD)(+)-dependent enzyme families with opposing metabolic effects. Energy shortage increases NAD(+) biosynthesis and SIRT activity but reduces PARP activity in animals. Effects of energy balance on these pathways in humans are unknown.

OBJECTIVE

We compared NAD(+)/SIRT pathway expressions and PARP activities in sc adipose tissue (SAT) between lean and obese subjects and investigated their change in the obese subjects during a 12-month weight loss.

DESIGN, SETTING AND PARTICIPANTS

SAT biopsies were obtained from 19 clinically healthy obese subjects (mean ± SE body mass index, 34.6 ± 2.7 kg/m(2)) during a weight-loss intervention (0, 5, and 12 mo) and from 19 lean reference subjects (body mass index, 22.7 ± 1.1 kg/m(2)) at baseline.

MAIN OUTCOME MEASURES

SAT mRNA expressions of SIRTs 1-7 and the rate-limiting gene in NAD(+) biosynthesis, nicotinamide phosphoribosyltransferase (NAMPT) were measured by Affymetrix, and total PARP activity by ELISA kit.

RESULTS

SIRT1, SIRT3, SIRT7, and NAMPT expressions were significantly lower, whereas total PARP activity was increased in obese compared with lean subjects. SIRT1 and NAMPT expressions increased in obese subjects between 0 and 5 months, after a mean weight loss of 11.7%. In subjects who continued to lose weight between 5 and 12 months, SIRT1 expression increased progressively, whereas in subjects with weight regain, SIRT1 reverted to baseline levels. PARP activity significantly decreased in all subjects upon weight loss.

CONCLUSIONS

Calorie restriction is an attractive strategy to improve the NAD(+)/SIRT pathway and decrease PARPs in SAT in human obesity.

Polymorphism in the SIRT1 gene and parameters of metabolic syndrome in a sample of the adult Brazilian population

ABSTRACT Objective: To evaluate whether the single nucleotide polymorphism rs7895833 (A/G) of the gene SIRT1 is associated with metabolic syndrome criteria in a sample of Brazilian adults. Methods: Serum samples and oral mucosal cells were collected from 243 subjects aged 30 to 70 years. Biochemical, hormonal, and anthropometric data were obtained. The single nucleotide polymorphism rs7895833 (A/G) was analyzed by polymerase chain reaction using the amplification refractory mutation system. Results: Among the 243 study subjects, 100 (41.15%) were classified as non-metabolic syndrome and 143 (58.85%), as metabolic syndrome. The frequency of the single nucleotide polymorphism rs7895833 (A/G) did not differ between the groups. However, 111 patients (45.67%) were overweight (body mass index: 25-29.9 kg/m2). Blood glucose, total cholesterol, triglycerides, very low density lipoprotein, low density lipoprotein, waist and hip circumferences, and blood pressure were higher in the metabolic syndrome group than in the non-metabolic syndrome group. Free thyroxine 4, grown hormone, and insulin levels were within the normal range. The metabolic conditions of the patients with metabolic syndrome indicate biochemical, anthropometric, and hormonal changes characteristic of overweight and obesity. Conclusion: The SIRT1 polymorphism rs7895833 (A/G) is not associated with the metabolic syndrome in the adult Brazilian population.

Plasma levels of SIRT1 associate with non-alcoholic fatty liver disease in obese patients

Sirtuins (SIRTs) are master metabolic regulators with protective roles against obesity and obesity-associated metabolic disorders, including non-alcoholic fatty liver disease (NAFLD) and type-2 diabetes. We aimed to ascertain whether there is a relationship between serum SIRT1 and liver steatosis severity in obese patients. Seventy-two obese patients (BMI ≥ 30 kg/m(2)), 18 males and 54 females, mean age 39.66 ± 12.34 years, with ultrasonographic evidence of NAFLD, were studied. BMI, transaminases, insulin, HOMA-index, HbA1c, body composition (DXA), plasma SIRT1 levels (ELISA) and representative measures of metabolic syndrome (waist circumference, fasting plasma glucose, blood pressure, HDL-cholesterol, triglycerides) and inflammation (ESR, CRP, fibrinogen) were evaluated. Thirty healthy lean patients were included as controls. SIRT1 was significantly lower in severe liver steatosis obese group compared to the mild steatosis group, both had lower SIRT1 plasma values compared to control lean patients (P = 0.0001). SIRT1 showed an inverse correlation with liver steatosis and HbA1c in univariate analysis (ρ = -0.386; P = 0.001; ρ = -0.300; P = 0.01, respectively). Multiple linear regression analysis showed that liver steatosis was the independent correlate of SIRT1 even after adjustment for potentially relevant variables (β = -0.442; P = 0.003). Serum SIRT1 might be a novel clinical/biochemical parameter associated with fat liver infiltration. Further studies in larger cohorts are warranted.

Sirtuin-1 regulation of mammalian metabolism

Sirtuin-1 (SirT1) is a nutrient-sensing deacetylase whose levels and activity increase with caloric restriction to preserve euglycemia and promote efficient energy utilization. Focusing on data obtained in vivo, we review how SirT1 orchestrates the adaptive response to fasting by stimulating hepatic gluconeogenesis and fatty acid oxidation, increasing circulating adiponectin levels and limiting immune activation. Finally, we consider its viability as a therapeutic target for the treatment of type 2 diabetes.

Resveratrol ameliorates imiquimod-induced psoriasis-like skin inflammation in mice

Background

The polyphenol resveratrol has anti-inflammatory effects in various cells, tissues, animals and human settings of low-grade inflammation. Psoriasis is a disease of both localized and systemic low-grade inflammation. The Sirtuin1 enzyme thought to mediate the effects of resveratrol is present in skin and resveratrol is known to down regulate NF-κB; an important contributor in the development of psoriasis. Consequently we investigated whether resveratrol has an effect on an Imiquimod induced psoriasis-like skin inflammation in mice and sought to identify candidate genes, pathways and interleukins mediating the effects.

Methods

The study consisted of three treatment groups: A control group, an Imiquimod group and an Imiquimod+resveratrol group. Psoriasis severity was assessed using elements of the Psoriasis Area Severity Index, skin thickness measurements, and histological examination. We performed an RNA microarray from lesional skin and afterwards Ingenuity pathway analysis to identify affected signalling pathways. Our microarray was compared to a previously deposited microarray to determine if gene changes were psoriasis-like, and to a human microarray to determine if findings could be relevant in a human setting.

Results

Imiquimod treatment induced a psoriasis-like skin inflammation. Resveratrol significantly diminished the severity of the psoriasis-like skin inflammation. The RNA microarray revealed a psoriasis-like gene expression-profile in the Imiquimod treated group, and highlighted several resveratrol dependent changes in relevant genes, such as increased expression of genes associated with retinoic acid stimulation and reduced expression of genes involved in IL-17 dependent pathways. Quantitative PCR confirmed a resveratrol dependent decrease in mRNA levels of IL-17A and IL-19; both central in developing psoriasis.

Conclusions

Resveratrol ameliorates psoriasis, and changes expression of retinoic acid stimulated genes, IL-17 signalling pathways, IL-17A and IL-19 mRNA levels in a beneficial manner, which suggests resveratrol, might have a role in the treatment of psoriasis and should be explored further in a human setting.

SIRT1 gene variants are related to risk of childhood obesity

Obesity is a multifactorial disorder resulting from the interaction between genetic, psychological, physical, environmental, and socioeconomic factors. SIRT1 gene has important effects on the regulation of adiponectin, caloric restriction, insulin sensitivity, coronary atherosclerosis, and cardiovascular diseases. The aim of this study was to investigate the association between childhood obesity and SIRT1 gene polymorphisms regarding rs7895833 A > G in the promoter region, rs7069102 C > G in intron 4, and rs2273773 C > T in exon 5 using PCR-CTPP method in 120 obese and 120 normal weight children. In this study, BMI, systolic and diastolic blood pressure, LDL cholesterol, triglyceride, and insulin levels were significantly higher and HDL-cholesterol levels were significantly lower in obese children compared to normal weight children. For rs7895833 A > G, the rate of having AG genotype and G allele was significantly higher in obese children compared to non-obese group (p < 0.001). The risk for obesity was increased by 1.9 times in G allele carriers; therefore, A allele may be protective against obesity. Both study groups had CT heterozygote genotype for rs2273773 C > T. There was no significant difference for rs7069102 C > G gene polymorphism between groups.

CONCLUSION

This is the first study reporting an association between SIRT1 gene polymorphisms and obesity in children.