Resveratrol enhances fatty acid oxidation capacity and reduces resistin and Retinol-Binding Protein 4 expression in white adipocytes

Sirt1-mediated deacetylation of PGC-1α alleviated hepatic steatosis in type 2 diabetes mellitus via improving mitochondrial fatty acid oxidation

Being activated by deacetylation, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) has become an important regulator of metabolic-related diseases. The activation of Sirtuin 1 (Sirt1) by resveratrol was likely to deacetylate PGC-1α. However, the role of deacetylated PGC-1α in the alleviation of activated Sirt1 on type 2 diabetes mellitus (T2DM)-related fatty liver disease (FLD) remained unexplored. The aim of this study was to investigate the potential impact of Sirt1-mediated deacetylation of PGC-1α on T2DM-associated FLD and its underlying mechanisms. Our findings revealed that, along with the decreased Sirt1, the levels of acetylated PGC-1α were up-regulated in hepatocytes co-stimulated with high glucose (HG) and free fatty acids (FFA). Down-regulated Sirt1 inactivated PGC-1α by inhibiting its deacetylation, while activating Sirt1 improved hepatic injury by reducing lipid droplet accumulation through the deacetylation of PGC-1α. However, the beneficial effects of Sirt1 activation on hepatic steatosis were inhibited by PGC-1α antagonist in vitro. Mechanistically, activating Sirt1 enhanced mitochondrial function by promoting PGC-1α activity, thereby facilitating hepatic fatty acid oxidation (FAO). In conclusion, Sirt1-mediated deacetylation of PGC-1α mitigated hepatic lipotoxicity by enhancing mitochondrial FAO, which contributed to the restoration of mitochondrial function in T2DM. The activation of Sirt1-mediated PGC-1α deacetylation might represent a promising therapeutic approach for T2DM-associated FLD.

Exercise-Induced cytokines, diet, and inflammation and their role in adipose tissue metabolism

Background

Obesity poses a significant global health challenge, necessitating effective prevention and treatment strategies. Exercise and diet are recognized as pivotal interventions in combating obesity. This study reviews the literature concerning the impact of exercise-induced cytokines, dietary factors, and inflammation on adipose tissue metabolism, shedding light on potential pathways for therapeutic intervention.

Methodology

A comprehensive review of relevant literature was conducted to elucidate the role of exercise-induced cytokines, including interleukin-6 (IL-6), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), irisin, myostatin, fibroblast growth factor 21 (FGF21), follistatin (FST), and angiopoietin-like 4 (ANGPTL4), in adipose tissue metabolism. Various databases were systematically searched using predefined search terms to identify relevant studies. Articles selected for inclusion underwent thorough analysis to extract pertinent data on the mechanisms underlying the influence of these cytokines on adipose tissue metabolism.

Results and Discussion

Exercise-induced cytokines exert profound effects on adipose tissue metabolism, influencing energy expenditure (EE), thermogenesis, fat loss, and adipogenesis. For instance, IL-6 activates AMP-activated protein kinase (AMPK), promoting fatty acid oxidation and reducing lipogenesis. IL-15 upregulates peroxisome proliferator-activated receptor delta (PPARδ), stimulating fatty acid catabolism and suppressing lipogenesis. BDNF enhances AMPK-dependent fat oxidation, while irisin induces the browning of white adipose tissue (WAT), augmenting thermogenesis. Moreover, myostatin, FGF21, FST, and ANGPTL4 each play distinct roles in modulating adipose tissue metabolism, impacting factors such as fatty acid oxidation, adipogenesis, and lipid uptake. The elucidation of these pathways offers valuable insights into the complex interplay between exercise, cytokines, and adipose tissue metabolism, thereby informing the development of targeted obesity management strategies.

Conclusion

Understanding the mechanisms by which exercise-induced cytokines regulate adipose tissue metabolism is critical for devising effective obesity prevention and treatment modalities. Harnessing the therapeutic potential of exercise-induced cytokines, in conjunction with dietary interventions, holds promise for mitigating the global burden of obesity. Further research is warranted to delineate the precise mechanisms underlying the interactions between exercise, cytokines, and adipose tissue metabolism.

The anti-obesity effects of resveratrol on the 3T3-L1 adipocytes

Obesity is a severe health problem worldwide due to its association with various adverse health consequences. The present study aims to evaluate the anti-obesity effects of resveratrol, as a natural polyphenol, on the 3T3-L1 adipocytes. PubMed, Scopus, ScienceDirect, Web of Sciences, and Google Scholar databases were searched up to March 2022 using relevant keywords. All original articles, written in English, evaluating the anti-obesity effects of resveratrol on the 3T3-L1 adipocytes were eligible for this review. Initially, 4361 records were found in the electronic search databases. After removing duplicates and irrelevant studies according to the title and abstract, the full text of the 51 articles was critically screened and 38 in vitro studies were included in this review. Except for one case, all of these studies reported that different doses (ranged 1-200 μM) of resveratrol treatment have anti-obesity effects on 3T3L1 adipocytes through various mechanisms such as induction of apoptosis, a decrease of fat accumulation and adipogenesis, promotion of white adipocytes browning, inhibition of preadipocyte proliferation and consequent differentiation, and up-regulation of miRNA that involved in the antiadipogenic and triacylglycerol metabolism in white adipose tissue. The findings indicate that resveratrol has anti-obesity effects. Therefore, resveratrol treatment could be used to prevent and treat obesity and its related disorders. Well-designed randomized clinical trials with different doses of resveratrol are recommended to be performed on obese subjects.

Targeting Retinol-Binding Protein 4 (RBP4) in the Management of Cardiometabolic Diseases

The ancient use of herbs for the treatment of various human diseases have been documented, with several scientific literatures supporting the use of medicinal plants. There is however a major concern about the phyto-constituents in the plants that performs the healing function and the mechanism by which it works for different ailments are still a research prospect. Cardiometabolic disease (CMD) is no doubt becoming more frequent globally and this is due to poor approach in therapy, contrary effects linked with intensive control, inept strategies with old drugs, inadequate control of some risk factors and lack of knowledge of the pathophysiological mechanisms that lead to this malaise. Retinol-binding protein 4 (RBP4) are predominantly secreted in the liver and adipose tissues and several researches have observed that elevation in serum levels of RBP4 often observed in obese experimental animals and human subjects causes CMD (obesity, insulin resistance, hyperlipidemia, etc.). RBP4 has gained special attention in the last 20 years in the field of metabolism research. This review aims to show research interaction of some medicinal plants targeting RBP4 in treating CMD and to encourage researchers, who are interested in CMD drug design, to focus on medicinal plants that inhibit the secretion of serum RBP4 in the adipose tissue for therapeutic approach to CMD. It also aims to identify the major bioactive compounds of plants that serves as a better and cheaper drug candidate for CMD and also study the signaling pathway which the plant material uses to regulate the metabolic consequences.

The Preventive Mechanisms of Bioactive Food Compounds against Obesity-Induced Inflammation

Dietary patterns are promising strategies for preventing and treating obesity and its coexisting inflammatory processes. Bioactive food compounds have received considerable attention due to their actions against obesity-induced inflammation, with limited harmful side effects. They are perceived as food ingredients or dietary supplements other than those necessary to meet basic human nutritional needs and are responsible for positive changes in the state of health. These include polyphenols, unsaturated fatty acids, and probiotics. Although the exact mechanisms of bioactive food compounds' action are still poorly understood, studies have indicated that they involve the modulation of the secretion of proinflammatory cytokines, adipokines, and hormones; regulate gene expression in adipose tissue; and modify the signaling pathways responsible for the inflammatory response. Targeting the consumption and/or supplementation of foods with anti-inflammatory potential may represent a new approach to obesity-induced inflammation treatment. Nevertheless, more studies are needed to evaluate strategies for bioactive food compound intake, especially times and doses. Moreover, worldwide education about the advantages of bioactive food compound consumption is warranted to limit the consequences of unhealthy dietary patterns. This work presents a review and synthesis of recent data on the preventive mechanisms of bioactive food compounds in the context of obesity-induced inflammation.

Biological function of resveratrol and its application in animal production: a review

With the prohibition of antibiotics in feed, plant functional substances have been widely studied as feed additives. Resveratrol, a natural stilbene, and a non-flavonoid polyphenol found in plants, possesses antioxidant, anti-inflammatory, and metabolic regulatory features. Resveratrol generated intense scientific and public interest, primarily due to its widely reported ability to prevent cancer, delay aging and alleviate related metabolic diseases. Recently, resveratrol has been studied and applied as a feed additive in animal production. This review focuses on the outline of the absorption and metabolism and biological functions of resveratrol and summarizes the application of dietary resveratrol in animal production up to the present, including pigs, poultry, and ruminants. In pigs, dietary resveratrol improved intestinal health, mitochondrial function, meat quality, and more. In poultry, studies have shown that dietary resveratrol improves growth performance and meat and egg quality and alleviates heat stress induced adverse effects. There are few studies on dietary resveratrol in ruminants; however previous studies have indicated that dietary resveratrol increases nutrient digestibility and reduces methane emissions in sheep. It is hoped that this review could provide a specific theoretical basis and research ideas for the research and application of resveratrol.

The effect of a fruit-rich diet on liver biomarkers, insulin resistance, and lipid profile in patients with non-alcoholic fatty liver disease: a randomized clinical trial

BACKGROUND

Despite confirmed dietary approaches to improve the Non-Alcoholic Fatty Liver Disease (NAFLD), the effect of fruits on NAFLD is not clear. The present study aimed to investigate the effect of a fruit rich diet (FRD) on liver steatosis, liver enzymes, Insulin resistance, and lipid profile in patients with NAFLD.

METHODS

Eighty adults with NAFLD participated in this randomized controlled trial. The participants were randomly assigned to the FRD group with consumption of at least 4 servings of fruits daily or the control group with fruits consumption of less than 2 servings/day. The grade of steatosis, serum levels of liver enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT), total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), glucose, and homeostatic model assessment for insulin resistance (HOMA-IR) were measured at the baseline and at the end of the study.

RESULTS

After 6 months of intervention, the FRD group had significantly higher BMI (31.40 ± 2.61 vs. 25.68 ± 2.54, p < .001), WC (113.5 ± 10.7 vs. 100.5 ± 7.5, p < .001), the grade of steatosis, ALT (89.1 ± 92.9 vs. 32.0 ± 19.2, p < .001), AST (74.5 ± 107.8 vs. 24.0 ± 8.5, p < .001), ALP (273.4 ± 128.5 vs. 155.0 ± 43.9, p < .001), GGT (92.7 ± 16.2 vs. 21.2 ± 7.7, p < .001), TC (206.1 ± 40.5 vs. 172.7 ± 42.4, p < .01), LDL (126.9 ± 32.3 vs. 99.8 ± 29.8, p < .001), glucose (115.5 ± 30.0 vs. 97.7 ± 19.0, p < .01), and insulin resistance (7.36 ± 4.37 vs. 2.66 ± 1.27, p < .001), and lower HDL (41.4 ± 8.9 vs. 53.8 ± 15.1, p < .001) compared to the control group. Adjusting for BMI and calorie intake did not change the results.

CONCLUSION

The results of the present study indicated that consumption of fruits more than 4 servings/day exacerbates steatosis, dyslipidemia, and glycemic control in NAFLD patients. Further studies are needed to identify the underlying mechanisms of the effects of fruits on NAFLD.

CLINICAL TRIAL REGISTRATION

This trial was registered at Iranian randomized clinical trial website with IRCT registration no. IRCT20201010048982N1on October 15, 2020.

Benefits and Implications of Resveratrol Supplementation on Microbiota Modulations: A Systematic Review of the Literature

Resveratrol is a polyphenol that has been shown to possess many applications in different fields of medicine. This systematic review has drawn attention to the axis between resveratrol and human microbiota, which plays a key role in maintaining an adequate immune response that can lead to different diseases when compromised. Resveratrol can also be an asset in new technologies, such as gene therapy. PubMed, Cochrane Library, Scopus, Web of Science, and Google Scholar were searched to find papers that matched our topic dating from 1 January 2017 up to 18 January 2022, with English-language restriction using the following Boolean keywords: ("resveratrol" AND "microbio*"). Eighteen studies were included as relevant papers matching the purpose of our investigation. Immune response, prevention of thrombotic complications, microbiota, gene therapy, and bone regeneration were retrieved as the main topics. The analyzed studies mostly involved resveratrol supplementation and its effects on human microbiota by trials in vitro, in vivo, and ex vivo. The beneficial activity of resveratrol is evident by analyzing the changes in the host's genetic expression and the gastrointestinal microbial community with its administration. The possibility of identifying individual microbial families may allow to tailor therapeutic plans with targeted polyphenolic diets when associated with microbial dysbiosis, such as inflammatory diseases of the gastrointestinal tract, degenerative diseases, tumors, obesity, diabetes, bone tissue regeneration, and metabolic syndrome.

Retinol binding protein 4 antagonists and protein synthesis inhibitors: Potential for therapeutic development

Retinol-binding protein 4 (RBP4) is a serum protein that transports Vitamin A. RBP4 is correlated with numerous diseases and metabolic syndromes, including insulin resistance in type 2 diabetes, cardiovascular diseases, obesity, and macular degeneration. Recently, RBP4 antagonists and protein synthesis inhibitors are under development to regulate the effect of RBP4. Several RBP4 antagonists, especially BPN-14136, have demonstrated promising safety profiles and potential therapeutic benefits in animal studies. Two RBP4 antagonists, specifically tinlarebant (Belite Bio) and STG-001 (Stargazer) are currently undergoing clinical trials. Some antidiabetic drugs and nutraceuticals have been reported to reduce RBP4 expression, but more clinical data is needed to evaluate their therapeutical benefits. As regulating RBP4 levels or its activities would benefit a wide range of patients, further research is highly recommended to develop clinically useful RBP4 antagonists or protein synthesis inhibitors.

Natural Antioxidant Application on Fat Accumulation: Preclinical Evidence

Obesity represents one of the most important challenges in the contemporary world that must be overcome. Different pathological consequences of these physical conditions have been studied for more than 30 years. The most nagging effects were found early in the cardiovascular system. However, later, its negative impact was also investigated in several other organs. Damage at cellular structures due to overexpression of reactive oxygen species together with mechanisms that cause under-production of antioxidants leads to the development of obesity-related complications. In this view, the negative results of oxidant molecules due to obesity were studied in various districts of the body. In the last ten years, scientific literature has reported reasonable evidence regarding natural and synthetic compounds' supplementation, which showed benefits in reducing oxidative stress and inflammatory processes in animal models of obesity. This article attempts to clarify the role of oxidative stress due to obesity and the opposing role of antioxidants to counter it, reported in preclinical studies. This analysis aims to clear-up different mechanisms that lead to the build-up of pro-oxidants during obesity and how various molecules of different origins hinder this phenomenon, behaving as antioxidants.

N-acetylcysteine delivery with silica nanoparticles into 3T3-L1 adipocytes

Background: The addition of 5 mM N-acetylcysteine (NAC) to 3T3-L1 adipocytes culture inhibits the accumulation of triglycerides (Tg) by 50%, but after 48 h uptake was only 16% of total NAC available. Based on these results, the aim of this study is to increase the NAC cellular uptake by encapsulating it in silica nanoparticles (NPs). Materials & methods: Silica NPs, 20 ± 4.5 nm in size, were developed, with an inner cavity loaded with 5 mM NAC. At 48 h after treatment, there was a dose-dependent cytotoxic effect. We attempted to reduce the cytotoxicity of silica NPs by coating them with bovine serum albumin. Results: While we obtained nontoxic bovine serum albumin coated NPs, their effect on Tg cellular accumulation was also reduced.

Precision Nutrition to Activate Thermogenesis as a Complementary Approach to Target Obesity and Associated-Metabolic-Disorders

Simple Summary

Regarding the pandemic of obesity and chronic diseases associated to metabolic alterations that occur nowadays worldwide, here, we review the most recent studies related to bioactive compounds and diet derived ingredients with potential effects to augment the systemic energy expenditure. We specifically focus in two processes: the activation of thermogenesis in adipose tissue and the enhancement of the mitochondrial oxidative phosphorylation capacity in muscles. This may provide relevant information to develop diets and supplements to conduct nutritional intervention studies with the objective to ameliorate the metabolic and chronic inflammation in the course of obesity and related disorders.

Abstract

Obesity is associated to increased incidence and poorer prognosis in multiple cancers, contributing to up to 20% of cancer related deaths. These associations are mainly driven by metabolic and inflammatory changes in the adipose tissue during obesity, which disrupt the physiologic metabolic homeostasis. The association between obesity and hypercholesterolemia, hypertension, cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM) is well known. Importantly, the retrospective analysis of more than 1000 epidemiological studies have also shown the positive correlation between the excess of fatness with the risk of cancer. In addition, more important than weight, it is the dysfunctional adipose tissue the main driver of insulin resistance, metabolic syndrome and all cause of mortality and cancer deaths, which also explains why normal weight individuals may behave as “metabolically unhealthy obese” individuals. Adipocytes also have direct effects on tumor cells through paracrine signaling. Downregulation of adiponectin and upregulation of leptin in serum correlate with markers of chronic inflammation, and crown like structures (CLS) associated to the adipose tissue disfunction. Nevertheless, obesity is a preventable risk factor in cancer. Lifestyle interventions might contribute to reduce the adverse effects of obesity. Thus, Mediterranean diet interventional studies have been shown to reduce to circulation inflammatory factors, insulin sensitivity and cardiovascular function, with durable responses of up to 2 years in obese patients. Mediterranean diet supplemented with extra-virgin olive oil reduced the incidence of breast cancer compared with a control diet. Physical activity is another important lifestyle factor which may also contribute to reduced systemic biomarkers of metabolic syndrome associated to obesity. In this scenario, precision nutrition may provide complementary approaches to target the metabolic inflammation associated to “unhealthy obesity”. Herein, we first describe the different types of adipose tissue -thermogenic active brown adipose tissue (BAT) versus the energy storing white adipose tissue (WAT). We then move on precision nutrition based strategies, by mean of natural extracts derived from plants and/or diet derived ingredients, which may be useful to normalize the metabolic inflammation associated to “unhealthy obesity”. More specifically, we focus on two axis: (1) the activation of thermogenesis in BAT and browning of WAT; (2) and the potential of augmenting the oxidative capacity of muscles to dissipate energy. These strategies may be particularly relevant as complementary approaches to alleviate obesity associated effects on chronic inflammation, immunosuppression, angiogenesis and chemotherapy resistance in cancer. Finally, we summarize main studies where plant derived extracts, mainly, polyphenols and flavonoids, have been applied to increase the energy expenditure.

Effects of Oral Resveratrol Supplementation on Glycogen Replenishment and Mitochondria Biogenesis in Exercised Human Skeletal Muscle

The present study aimed to investigate the effect of oral resveratrol supplementation on the key molecular gene expressions involved in mitochondria biogenesis and glycogen resynthesis in human skeletal muscle. Nine young male athletes participated in the single-blind and crossover designed study. All subjects completed a 4-day resveratrol and placebo supplement in a randomized order while performing a single bout of cycling exercise. Immediately after the exercise challenge, the subjects consumed a carbohydrate (CHO) meal (2 g CHO/Kg body mass) with either resveratrol or placebo capsules. Biopsied muscle samples, blood samples and expired gas samples were obtained at 0 h and 3 h after exercise. The muscle samples were measured for gene transcription factor expression by real-time PCR for glucose uptake and mitochondria biogenesis. Plasma glucose, insulin, glycerol, non-esterified fatty acid concentrations and respiratory exchange ratio were analyzed during post-exercise recovery periods. The results showed that the muscle glycogen concentrations were higher at 3 h than at 0 h; however, there were no difference between resveratrol trial and placebo trial. There were no significantly different concentrations in plasma parameters between the two trials. Similarly, no measured gene expressions were significant between the two trials. The evidence concluded that the 4-day oral resveratrol supplementation did not improve post-exercise muscle glycogen resynthesis and related glucose uptake and mitochondrial biosynthesis gene expression in men.

Synthesis and Characterization of Novel Resveratrol Butyrate Esters That Have the Ability to Prevent Fat Accumulation in a Liver Cell Culture Model

To facilitate broad applications and enhance bioactivity, resveratrol was esterified to resveratrol butyrate esters (RBE). Esterification with butyric acid was conducted by the Steglich esterification method at room temperature with N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide (EDC) and 4-dimethyl aminopyridine (DMAP). Our experiments demonstrated the synthesis of RBE through EDC- and DMAP-facilitated esterification was successful and that the FTIR spectra of RBE revealed absorption (1751 cm⁻¹) in the ester region. ¹³C-NMR spectrum of RBE showed a peak at 171 ppm corresponding to the ester group and peaks between 1700 and 1600 cm⁻¹ in the FTIR spectra. RBE treatment (25 or 50 μM) decreased oleic acid-induced lipid accumulation in HepG2 cells. This effect was stronger than that of resveratrol and mediated through the downregulation of p-ACC and SREBP-2 expression. This is the first study demonstrating RBE could be synthesized by the Steglich method and that resulting RBE could inhibit lipid accumulation in HepG2 cells. These results suggest that RBE could potentially serve as functional food ingredients and supplements for health promotion.

Modulation of adipocyte size and fat pad weight via resveratrol releasing scaffolds implanted into the epididymal adipose tissue

Lipid overload of the adipose tissue, which can be caused by overnutrition, underlies metabolic disease. We hypothesized that increasing the energy demand of adipose tissue is a promising strategy to combat excessive lipid accumulation. Resveratrol, a natural polyphenol, activates lipid catabolism in fat tissue; however, its clinical success is hindered by poor bioavailability. Here, we implanted resveratrol releasing poly(lactide-co-glycolide) scaffolds into epididymal fat to overcome its poor bioavailability with the goal of enhancing local lipid catabolism. In lean mice, resveratrol scaffolds decreased adipocyte size relative to scaffolds with no drug, a response that correlated with AMP kinase activation. Immunohistochemistry indicated that macrophages and multinucleated giant cells within the scaffold expressed carnitine palmitoyltransferase 1 (CPT1) at higher levels than other cells in the adipose tissue. Furthermore, resveratrol increased CPT1 levels in cultured macrophages. Taken together, we propose that resveratrol scaffolds decrease adipocyte size because resveratrol increases lipid utilization in scaffold-infiltrating immune cells, possibly through elevating CPT1 levels or activity. In a follow-up study, mice that received resveratrol scaffolds 28-day prior to a high-fat diet exhibited decreased weight gain, adipose tissue expansion, and adipocyte hypertrophy compared to mice with control scaffolds. Notably, this scaffold-based strategy required a single resveratrol administration compared to the daily regiment generally needed for oral administration. These results indicate that localized delivery of metabolism modulating agents to the adipose tissue may overcome issues with bioavailability and that the role of biomaterials should be further investigated in this therapeutic strategy for metabolic disease.

Scaffold Implant Into the Epididymal Adipose Tissue Protects Mice From High Fat Diet Induced Ectopic Lipid Accumulation and Hyperinsulinemia

Ectopic lipid accumulation, the deposition of lipids in lean tissue, is linked to type 2 diabetes through an association with insulin resistance. It occurs when adipose tissue fails to meet lipid storage needs and there is lipid spillover into tissues not equipped to store them. Ectopic lipid contributes to organ dysfunction because lipids can interfere with insulin signaling and other signaling pathways. Clinical studies indicate that decreasing ectopic lipids through diet and exercise is effective in treating type 2 diabetes; however, its prevalence continues to rise. We propose that strategies to improve lipid handling in the adipose tissue would be adjunctive to healthy lifestyle modification and may address difficulties in treating type 2 diabetes and other syndromes spurred by ectopic lipid. Herein, we investigate biomaterial implants as a means to increase lipid utilization in adipose tissue through the recruitment of highly metabolic cells. Poly(lactide-co-glycolide) scaffolds were implanted into the epididymal fat of mice fed a high fat diet that overwhelms the adipose tissue and promotes ectopic lipid accumulation. Over 5 weeks, mice with scaffolds gained less weight compared to mice without scaffolds and were protected from hyperinsulinemia. These effects correlated with a 53% decrease in triglyceride in the gastrocnemius and a 25% decrease in the liver. Scaffolds increased CPT1A protein levels in the epididymal fat and histology revealed high expression of CTP1A in the cells infiltrating the scaffold relative to the rest of the fat pad. In addition, lacing the scaffold with resveratrol increased CPT1A expression in the epididymal fat over scaffolds with no drug; however, this did not result in further decreases in weight gain or ectopic lipid. Mechanistically, we propose that the cellular activity caused by scaffold implant mitigates the lipid load imposed by the high fat diet and leads to a substantial decrease in lipid accumulation in the muscle and liver. In conclusion, this study establishes that a tissue engineering approach to modulate lipid utilization in the epididymal fat tissue can mitigate ectopic lipid accumulation in mice fed a high fat diet with positive effects on weight gain and whole-body insulin resistance.

Microencapsulation as a tool to counteract the typical low bioavailability of polyphenols in the management of diabetes

Polyphenols are secondary metabolites widely distributed in many plant foods, such a tea, coffee, chocolate and fruits. The consumption of these compounds is related to the improvement or amelioration of many diseases, including diabetes. Nevertheless, the great barrier to the therapeutic use of polyphenols is the low bioavailability of these compounds once ingested. For that reason, the encapsulation of polyphenols in different matrices may protect them from digestion and improve their release and subsequent absorption to obtain target-specific health effects. Some studies have reported the beneficial effect of encapsulation to increase both bioavailability and bioaccessibility. However, these works have mostly been carried out in vitro and few studies are specifically addressed at improving diabetes. In the current work, an overview of the knowledge related to nanoparticles and their use in the diabetic condition has been reviewed.

Resveratrol Reduces Lipid Accumulation through Upregulating the Expression of MicroRNAs Regulating Fatty Acid Bet Oxidation in Liver Cells: Evidence from In-vivo and In-vitro Studies

MicroRNAs have been shown to regulate lipogenesis in liver. The aim of the present study was to investigate whether the effects of resveratrol (RSV) on lipogenesis are associated with the changes in the expression of two miRNAs (miR-107 and miR-10b) that regulate lipogenic pathways. 30 wild type C57BL/6j male mice were randomly fed three diets: a standard chow diet (ND), a high fat diet (HFD, 60% fat) and the high fat diet supplemented with 0.4% RSV (HFD-RSV) for 16 weeks. HepG2 cells were treated with high glucose (33 mM) and RSV (20 µM) for 24 h. The expression of the genes and miRNAs were measured by real-time PCR. Triglyceride level was increased in the liver of mice and HepG2 cells. In both animal and In-vitro experiments, triglyceride level was significantly decreased in groups treated with RSV. The expression of the miR-107 and miR-10b was significantly upregulated in the liver of HFD mice, whereas HFD-RSV group demonstrated a significant lower expression of both miRNAs compared to HFD group. In addition, RSV treatment significantly upregulated the expression of CPT-1a and PPARα genes in the liver of HFD mice. Moreover, treatment with RSV could reduce the expression of miR-107 and miR-10b and increase the expression of CPT-1a and PPARα in HG-treated HepG2 cells. These evidence, as a whole, suggest that RSV could exert its anti-lipogenic effect partially through alterations in the expression of miR-107 and miR-10b in liver cells.

Modulatory Role of SIRT1 and Resistin as Therapeutic Targets in Patients with Aortic Valve Stenosis

BACKGROUND

Inflammatory is one of the main cause of aortic valve stenosis (AS), so discovering novel biomarkers for the targeted therapy of inflammation could be an attractive strategy in AS prevention. The objectives of our study were to clarify the modulatory role of resistin and silent information regulator 1 (SIRT1) before and after surgery and also to evaluate the therapeutic effects of resveratrol.

METHODS

Nineteen AS patients and 15 healthy subjects were studied as the case and control groups, respectively. Peripheral blood mononuclear cells (PBMCs) were isolated and cultured to determine the levels of resistin and SIRT1 and the effects of resveratrol on them.

RESULTS

Significant increase in resistin expression was observed in the patients compare to the control (p ≤0.01), and this upregulation was augmented 72 h following surgery (p ≤0.01). The SIRT1 expression decreased in the AS group compare to the control but this reduction was not significant. Aortic valve replacement caused a higher decrease in the protein (p ≤0.01) and mRNA level (p ≤0.05) of SIRT1. Resveratrol in the AS group significantly diminished the resistin level (p ≤0.05) but increased the SIRT1 level (p ≤0.001).

CONCLUSIONS

In our patients with AS, the resistin level was increased, whereas the expression of SIRT1 was reduced and surgery augmented these alterations. Resveratrol improved inflammation in the PBMCs of the patients through the SIRT1/resistin pathway. These findings suggest that pharmacological therapy with resveratrol might be a novel approach to alleviating inflammation in patients with AS.

Resveratrol Anti-Obesity Effects: Rapid Inhibition of Adipocyte Glucose Utilization

Studies in animal models of diabetes and obesity have shown that resveratrol mitigates complications of metabolic diseases, beyond those resulting from oxidative stress. Furthermore, results obtained with cultured preadipocytes have also revealed that prolonged resveratrol treatment impairs adipogenesis. Considering the role of adipocytes in the hypertrophy of fat stores, and keeping in mind that insulin is the main trigger of excessive energy storage during post-prandial periods, the present study aimed to investigate how short-term effects of resveratrol can limit glucose disposal in a gut-adipose tissue axis. We found that resveratrol exhibits a more potent inhibitory capacity towards α-glucosidase than pancreatic lipase activity. Resveratrol also rapidly blunts glucose transport in mature fat cells by counteracting the effect of insulin and insulin-like lipogenic agents. Within two hours, resveratrol also inhibited the incorporation of glucose into lipids of adipocytes, which was unaffected by membrane cholesterol depletion. Moreover, the comparison between adipocytes with invalidated semicarbazide-sensitive amine oxidase activity and their control, or between resveratrol and several inhibitors, did not indicate that the recently described interaction of resveratrol with amine oxidases was involved in its antilipogenic effect. Caffeine and piceatannol, previously said to interact with glucose carriers, also inhibit lipogenesis in adipocytes, whereas other antioxidant phytochemicals do not reproduce such an antilipogenic effect. This study highlights the diverse first steps by which resveratrol impairs excessive fat accumulation, indicating that this natural molecule and its derivatives deserve further studies to develop their potential anti-obesity properties.

Resveratrol, Metabolic Syndrome, and Gut Microbiota

Resveratrol is a polyphenol which has been shown to have beneficial effects on metabolic syndrome-related alterations in experimental animals, including glucose and lipid homeostasis improvement and a reduction in fat mass, blood pressure, low-grade inflammation, and oxidative stress. Clinical trials have been carried out to address its potential; however, results are still inconclusive. Even though resveratrol is partly metabolized by gut microbiota, the relevance of this “forgotten organ” had not been widely considered. However, in the past few years, data has emerged suggesting that the therapeutic potential of this compound may be due to its interaction with gut microbiota, reporting changes in bacterial composition associated with beneficial metabolic outcomes. Even though data is still scarce and for the most part observational, it is promising nevertheless, suggesting that resveratrol supplementation could be a useful tool for the treatment of metabolic syndrome and its associated conditions.

Dietary polyphenols and their roles in fat browning

Discovery of the presence of brown adipose tissue (BAT) in newborn babies and adult humans, especially constitutively active brown fat or inducible beige fat, has led to the investigation of strategies employing BAT aimed at the development of novel therapeutic avenues for combating obesity and diabetes. Such antiobesity therapeutic tools include pharmaceutical and nutraceutical dietary polyphenols. Although there have been emerging notable advances in knowledge of and an increased amount of research related to brown and beige adipocyte developmental lineages and transcriptional regulators, current knowledge regarding whether and how food factors and environmental modifiers of BAT influence thermogenesis has not been extensively investigated. Therefore, in this review, we summarized recent updates on the exploration of dietary polyphenols while paying attention to the activation of BAT and thermogenesis. Specifically, we summarized findings pertaining to BAT metabolism, white adipose tissue (WAT) browning and thermogenic function of polyphenols (e.g., flavan-3-ols, green tea catechins, resveratrol, capsaicin/capsinoids, curcumin, thymol, chrysin, quercetin and berberine) that may foster a relatively safe and effective therapeutic option to improve metabolic health. We also deciphered the underlying proposed mechanisms through which these dietary polyphenols facilitate BAT activity and WAT browning. Characterization of thermogenic dietary factors may offer novel insight enabling revision of nutritional intervention strategies aimed at obesity and diabetes prevention and management. Moreover, identification of polyphenolic dietary factors among plant-derived natural compounds may provide information that facilitates nutritional intervention strategies against obesity, diabetes and metabolic syndrome.

Programming of the Beige Phenotype in White Adipose Tissue of Adult Mice by Mild Resveratrol and Nicotinamide Riboside Supplementations in Early Postnatal Life

SCOPE

Resveratrol (RSV) and nicotinamide riboside (NR) are food compounds with anti-obesity actions in adult rodents. Here, the long-term effects of RSV and NR mild supplementation throughout lactation on adiposity-related parameters and the appearance of the beige phenotype in white adipose tissue (WAT) in adulthood are assessed.

METHODS AND RESULTS

Newborn mice received orally RSV or NR from day 2 to 20 of life. Control littermates received the vehicle. All animals are weaned onto a chow diet on day 21. On day 90, half the animals of each group are assigned to a high-fat diet (HFD) for 10 weeks, while the other remained on a normal-fat diet. Energy-balance-related parameters, blood parameters, and gene expression and immunohistochemical analysis of WAT are assessed. Treated male mice show an improved response to the HFD, such as delayed body weight gain, a blunted increase in the plasma leptin/adiponectin ratio, and a decreased lipolytic response, together with signs of white-to-brown fat remodeling in inguinal WAT. These effects are absent in female mice.

CONCLUSION

RSV and NR supplementations in early postnatal life affect WAT's thermogenic/oxidative transcriptional phenotype and metabolic responses in adulthood, with upregulatory and beneficial effects evidenced in male animals.

Weight Loss Associated With Consumption of Apples: A Review

Apples are known as a major source of polyphenols, dietary fiber, carotenoids, and other nutrients. There are many documents and studies that show fruit polyphenols likely promote anti-obesity effects and exert their beneficial effects via scavenging free radicals, regulating gene expression, and altering signal transduction in target cells and tissues, especially fat tissues.The goal of this review is to presenti the major components of apple and the evidence that indicates its potential to diminution weight gain risk from in vitro, animal, and epidemiological and clinical studies. This review summarizes data about the apple and apple products that been have reported to reduce weight gain by various mechanisms, including antioxidant, antiproliferative, and cell signaling pathways. An extensive search was performed in PubMed, Science Direct, Scopus, and Google Scholar to identify human, animal, and cell culture studies on the association between weight loss and apple consumption, published from inception up to journey 15, 2017. The feeding of apples rats (7-10 mg/kg/d) in different forms in 8 experiments have shown that this caused weight loss during 3 to 28 weeks. In agreement with this, the obtained results from 5 experiments on humans have revealed that consumption of the whole apple or apple juice (240-720 mg/d) in 4-12 weeks by fat people can cause weight loss. Experiments on animals and humans have shown that the consumption of apples in different forms can cause weight loss in overweight ones. However, the main questions are which kind of apple, which part of it, how much, and how long overweight persons should consume them to reduce their body fat and body mass index (BMI). Then, it is necessary to do a meta-analysis to show how these factors affect the body fat percentage and whether this weight-lowering effect is statistically significant or not.

Serum Carotenoids Are Inversely Associated with RBP4 and Other Inflammatory Markers in Middle-Aged and Elderly Adults

(1) Background: Carotenoids may be inversely associated with inflammatory markers (i.e., TNF-α, IL-6, IL-1β). However, data are scarce on retinol binding protein 4 (RBP4) in humans. We examined the associations among serum carotenoids, RBP4 and several inflammatory markers in a Chinese population. (2) Methods: This community-based cross-sectional study included 3031 participants (68% males) aged 40-75 years in Guangzhou, China. Serum concentrations of carotenoids, RBP4, and inflammatory markers were measured. (3) Results: Generally, serum individual and total carotenoids were significantly and inversely associated with retinol-adjusted RBP4, RBP4, hsCRP, MCP1, and TNF-alpha levels. Age- and gender-adjusted partial correlation coefficients between total carotenoids and the above inflammatory markers were -0.129, -0.097, -0.159, -0.079, and -0.014 (all p < 0.01, except for TNF-alpha with p >0.05), respectively. The multivariate-adjusted values of partial correlation coefficients for these inflammation-related markers were -0.098, -0.079, -0.114, -0.090, and -0.079 (all p < 0.01), respectively. Among the individual carotenoids, those with the most predominant association were lutein-zeaxanthin and total carotenoids for retinol-adjusted RBP4 and RBP4, alpha- and beta-carotene for hsCRP, and alpha-carotene for MCP1 and TNF-alpha. No significant associations were observed for IL-6 and IL-1beta. (4) Conclusions: Serum carotenoids were inversely associated with RBP4, hsCRP, MCP1 and TNF-alpha among middle-aged and elderly Chinese adults.

Involvement of RBP4 in Diabetic Atherosclerosis and the Role of Vitamin D Intervention

The purposes of this study were to evaluate the expression of retinol-binding protein 4 (RBP4) in diabetic rats with atherosclerosis and to investigate the role of vitamin D intervention. Male Wistar rats were randomly divided into 4 groups, including the control group (NC), the diabetic rats (DM1), the untreated diabetic atherosclerosis rats (DM2), and the vitamin D-treated diabetic atherosclerosis rats (DM3). The levels of serum and adipose RBP4, fasting insulin (FINS), fasting plasma glucose (FPG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), triglycerides (TG), low-density lipoprotein cholesterol (LDL-c), 25-hydroxyvitamin D [25(OH)D], C-reactive protein (CRP), and systolic blood pressure (SBP) were measured. Homeostasis model assessment of insulin resistance (HOMA-IR), homeostasis model assessment β-cell function index (HOMA-β), and atherogenic indexes (AI) were calculated. Compared with group NC, the levels of RBP4, TG, LDL-c, FPG, FINS, CRP, AI1, AI2, SBP, and HOMA-IR increased, while the levels of HDL-c, 25(OH)D, and HOMA-β decreased in groups DM1 and DM2. After 8 weeks of vitamin D supplementation in group DM3, the levels of 25(OH)D and HOMA-β increased and the levels of LDL-c, TC, HOMA-IR, FINS, CRP, RBP4, AI1, AI2, and SBP decreased significantly when compared with group DM2 (P < 0.05); Pearson analysis showed that serum RBP4 was positively correlated with TG, FINS, HOMA-IR, SBP, CRP, and AI and negatively correlated with 25(OH)D. In addition, multivariable logistic regression analysis showed that serum RBP4, SBP, and HDL-c were predictors for the presence of diabetic atherosclerosis. These findings suggested that RBP4 could involve in the improvement of diabetic atherosclerosis; vitamin D had the ability to decrease the level of RBP4 and eventually played an important role in preventing atherosclerosis in diabetes.

Anti-Inflammatory and Anti-Obesity Properties of Food Bioactive Components: Effects on Adipose Tissue

Obesity is an epidemic and costly disease affecting 13% of the adult population worldwide. Obesity is associated with adipose tissue hypertrophy and hyperplasia, as well as pathologic endocrine alterations of adipose tissue including local and chronic systemic low-grade inflammation. Moreover, this inflammation is a risk factor for both metabolic syndrome (MetS) and insulin resistance. Basic and clinical studies demonstrate that foods containing bioactive compounds are capable of preventing both obesity and adipose tissue inflammation, improving obesity-associated MetS in human subjects and animal models of obesity. In this review, we discuss the anti-obesity and anti-inflammatory protective effects of some bioactive polyphenols of plant origin and omega-3 polyunsaturated fatty acids, available for the customers worldwide from commonly used foods and/or as components of commercial food supplements. We review how these bioactive compounds modulate cell signaling including through the nuclear factor-κB, adenosine monophosphate-activated protein kinase, mitogen-activated protein kinase, toll-like receptors, and G-protein coupled receptor 120 intracellular signaling pathways and improve the balance of pro- and anti-inflammatory mediators secreted by adipose tissue and subsequently lower systemic inflammation and risk for metabolic diseases.

Phyllodulcin, a Natural Sweetener, Regulates Obesity-Related Metabolic Changes and Fat Browning-Related Genes of Subcutaneous White Adipose Tissue in High-Fat Diet-Induced Obese Mice

Phyllodulcin is a natural sweetener found in Hydrangea macrophylla var. thunbergii. This study investigated whether phyllodulcin could improve metabolic abnormalities in high-fat diet (HFD)-induced obese mice. Animals were fed a 60% HFD for 6 weeks to induce obesity, followed by 7 weeks of supplementation with phyllodulcin (20 or 40 mg/kg body weight (b.w.)/day). Stevioside (40 mg/kg b.w./day) was used as a positive control. Phyllodulcin supplementation reduced subcutaneous fat mass, levels of plasma lipids, triglycerides, total cholesterol, and low-density lipoprotein cholesterol and improved the levels of leptin, adiponectin, and fasting blood glucose. In subcutaneous fat tissues, supplementation with stevioside or phyllodulcin significantly decreased mRNA expression of lipogenesis-related genes, including CCAAT/enhancer-binding protein α (C/EBPα), peroxisome proliferator activated receptor γ (PPARγ), and sterol regulatory element-binding protein-1C (SREBP-1c) compared to the high-fat group. Phyllodulcin supplementation significantly increased the expression of fat browning-related genes, including PR domain containing 16 (Prdm16), uncoupling protein 1 (UCP1), and peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), compared to the high-fat group. Hypothalamic brain-derived neurotrophic factor-tropomyosin receptor kinase B (BDNF-TrkB) signaling was upregulated by phyllodulcin supplementation. In conclusion, phyllodulcin is a potential sweetener that could be used to combat obesity by regulating levels of leptin, fat browning-related genes, and hypothalamic BDNF-TrkB signaling.

Dietary (Poly)phenols, Brown Adipose Tissue Activation, and Energy Expenditure: A Narrative Review

The incidence of overweight and obesity has reached epidemic proportions, making the control of body weight and its complications a primary health problem. Diet has long played a first-line role in preventing and managing obesity. However, beyond the obvious strategy of restricting caloric intake, growing evidence supports the specific antiobesity effects of some food-derived components, particularly (poly)phenolic compounds. The relatively new rediscovery of active brown adipose tissue in adult humans has generated interest in this tissue as a novel and viable target for stimulating energy expenditure and controlling body weight by promoting energy dissipation. This review critically discusses the evidence supporting the concept that the antiobesity effects ascribed to (poly)phenols might be dependent on their capacity to promote energy dissipation by activating brown adipose tissue. Although discrepancies exist in the literature, most in vivo studies with rodents strongly support the role of some (poly)phenol classes, particularly flavan-3-ols and resveratrol, in promoting energy expenditure. Some human data currently are available and most are consistent with studies in rodents. Further investigation of effects in humans is warranted.

Antioxidant dietary approach in treatment of fatty liver: New insights and updates

Non-alcoholic fatty liver disease (NAFLD) is a common clinicopathological condition, encompassing a range of conditions caused by lipid deposition within liver cells. To date, no approved drugs are available for the treatment of NAFLD, despite the fact that it represents a serious and growing clinical problem in the Western world. Identification of the molecular mechanisms leading to NAFLD-related fat accumulation, mitochondrial dysfunction and oxidative balance impairment facilitates the development of specific interventions aimed at preventing the progression of hepatic steatosis. In this review, we focus our attention on the role of dysfunctions in mitochondrial bioenergetics in the pathogenesis of fatty liver. Major data from the literature about the mitochondrial targeting of some antioxidant molecules as a potential treatment for hepatic steatosis are described and critically analysed. There is ample evidence of the positive effects of several classes of antioxidants, such as polyphenols (i.e., resveratrol, quercetin, coumestrol, anthocyanins, epigallocatechin gallate and curcumin), carotenoids (i.e., lycopene, astaxanthin and fucoxanthin) and glucosinolates (i.e., glucoraphanin, sulforaphane, sinigrin and allyl-isothiocyanate), on the reversion of fatty liver. Although the mechanism of action is not yet fully elucidated, in some cases an indirect interaction with mitochondrial metabolism is expected. We believe that such knowledge will eventually translate into the development of novel therapeutic approaches for fatty liver.

Resveratrol derivative BTM-0512 mitigates obesity by promoting beige remodeling of subcutaneous preadipocytes

Recent studies revealed that sirtuin 1 (SIRT1) is involved in the regulation of energy metabolism and its agonist resveratrol showed anti-obesity effect. This study aims to determine whether BTM-0512, a novel derivative of resveratrol, acts as an antagonist of obesity and to explore its possible mechanisms. High-fat diet (HFD)-induced obese mice were intragastrically administered with BTM-0512 (5, 10, and 20 mg/kg/day) or resveratrol (10 mg/kg/day). It was found that the body weight, Lee's index, ratio of visceral adipose tissue (VAT) to body weight, and blood glucose were significantly reduced in BTM-0512-treated mice when compared with those in mice treated with resveratrol. BTM-0512 up-regulated the expressions of SIRT1, full length PRDM16 (fPRDM16), total PRDM16 (tPRDM16, including fPPRDM16 and other PRDM16 isoforms), and uncoupling protein 1 (UCP1) in both brown and subcutaneous adipose tissues. Although BTM-0512 and resveratrol also up-regulated SIRT1 and tPRDM16 levels in VAT of HFD-induced obese mice, the expressions of fPRDM16, UCP1, and TMEM26 were down-regulated. In mouse primary subcutaneous preadipocytes cultured with or without adipogenic medium, BTM-0512 up-regulated fPRDM16, tPRDM16, and UCP1 expressions, which was reversed by SIRT1 antagonists. But in cultured brown and visceral adipocytes, the UCP1 protein level showed no significant change after treatment with 1 μM of BTM-0512. Moreover, transfection with human SIRT1 plasmid reduced lipid deposit, as well as the mRNA levels of fPRDM16, UCP1, and TMEM26, in cultured human visceral adipose-derived stem cells. In conclusion, BTM-0512 has stronger anti-obesity effect than resveratrol, which might be associated with activation of beige remodeling in subcutaneous adipose tissue.

Influence of resveratrol on endoplasmic reticulum stress and expression of adipokines in adipose tissues/adipocytes induced by high-calorie diet or palmitic acid

PURPOSE

This study aimed to determine whether resveratrol treatment alleviates endoplasmic reticulum stress and changes the expression of adipokines in adipose tissues and cells.

METHODS

8-week-old male C57BL/6 mice were fed a high-calorie diet (HCD group) or high-calorie diet supplemented with resveratrol (high-calorie diet  + resveratrol group) for 3 months. Insulin resistance, serum lipids and proinflammatory indices, the size and inflammatory cell infiltration in subcutaneous and visceral adipose tissues were analyzed. The gene expressions of endoplasmic reticulum stress, adipokines, and inflammatory cytokines were determined. The induced mature 3T3-L1 cells were pretreated with resveratrol and then palmitic acid, and the gene expressions of endoplasmic reticulum stress, adipokines, and inflammatory cytokines were determined.

RESULTS

Subcutaneous and visceral adipose tissues in the high-calorie diet-fed mice exhibited adipocyte hypertrophy, inflammatory activation, and endoplasmic reticulum stress. Resveratrol alleviated high-calorie diet-induced insulin resistance and endoplasmic reticulum stress, increased expression of SIRT1, and reversed expression of adipokines in varying degrees in both subcutaneous and visceral adipose tissues. The effects of resveratrol on palmitic acid-treated adipocytes were similar to those shown in the tissues.

CONCLUSIONS

Resveratrol treatment obviously reversed adipocyte hypertrophy and insulin resistance by attenuating endoplasmic reticulum stress and inflammation, thus increasing the expression of SIRT1 and inverting the expression of adipokines in vivo and in vitro.

Resveratrol attenuates mitochondrial dysfunction in the liver of intrauterine growth retarded suckling piglets by improving mitochondrial biogenesis and redox status

SCOPE

Emerging evidence has identified mitochondrial biogenesis and oxidative phosphorylation as potential targets for the prevention and treatment of metabolic syndrome. This study investigated the effect of resveratrol (RSV) on hepatic mitochondrial function in intrauterine growth-retarded (IUGR) suckling piglets.

METHODS AND RESULTS

Seven normal birth weight (NBW) and fourteen IUGR neonatal male piglets were selected. Piglets were fed control diets supplemented with 0 (NBW-CON), 0 (IUGR-CON), and 1.0 (IUGR-RSV) g RSV per kg of milk dry matter from 7 to 21 days of age (n = 7), respectively. Mitochondrial function, swelling, and redox status in the liver were assessed. Compared with NBW, IUGR impaired hepatic mitochondrial biogenesis and energy homeostasis of the control piglets. IUGR control piglets showed overproduction of superoxide radicals, increased concentration of malondialdehyde, and marked swelling in the mitochondria. RSV improved mitochondrial DNA content, ATP production, and fatty acid oxidation in the liver of IUGR piglets, along with an increased activity of sirtuin 1. RSV inhibited mitochondrial superoxide anion accumulation, increased complex III and manganese superoxide dismutase activities, and ameliorated mitochondrial swelling and lipid peroxidation in the IUGR piglets.

CONCLUSION

RSV may have beneficial effects in improving hepatic mitochondrial function and redox status in the IUGR piglets.

Browning of white adipose tissue: lessons from experimental models

Beige or brite (brown-in-white) adipocytes are present in white adipose tissue (WAT) and have a white fat-like phenotype that when stimulated acquires a brown fat-like phenotype, leading to increased thermogenesis. This phenomenon is known as browning and is more likely to occur in subcutaneous fat depots. Browning involves the expression of many transcription factors, such as PR domain containing 16 (PRDM16) and peroxisome proliferator-activated receptor (PPAR)-γ, and of uncoupling protein (UCP)-1, which is the hallmark of thermogenesis. Recent papers pointed that browning can occur in the WAT of humans, with beneficial metabolic effects. This fact indicates that these cells can be targeted to treat a range of diseases, with both pharmacological and nutritional activators. Pharmacological approaches to induce browning include the use of PPAR-α agonist, adrenergic receptor stimulation, thyroid hormone administration, irisin and FGF21 induction. Most of them act through the induction of PPAR-γ coactivator (PGC) 1-α and the consequent mitochondrial biogenesis and UCP1 induction. About the nutritional inducers, several compounds have been described with multiple mechanisms of action. Some of these activators include specific amino acids restriction, capsaicin, bile acids, Resveratrol, and retinoic acid. Besides that, some classes of lipids, as well as many plant extracts, have also been implicated in the browning of WAT. In conclusion, the discovery of browning in human WAT opens the possibility to target the adipose tissue to fight a range of diseases. Studies have arisen showing promising results and bringing new opportunities in thermogenesis and obesity control.

Resveratrol enhances brown adipocyte formation and function by activating AMP-activated protein kinase (AMPK) α1 in mice fed high-fat diet

SCOPE

Enhancing the formation and function of brown adipose tissue (BAT) increases thermogenesis and hence reduces obesity. Thus, we investigate the effects of resveratrol (Resv) on brown adipocyte formation and function in mouse interscapular BAT (iBAT).

METHODS AND RESULTS

CD1 mice and stromal vascular cells (SVCs) isolated from iBAT were treated with Resv. Expression of brown adipogenic and thermogenic markers, and involvement of AMP-activated protein kinase (AMPK)α1 were assessed. In vivo, Resv-enhanced expression of brown adipogenic markers, PR domain-containing 16 (PRDM16) and thermogenic genes, uncoupling protein 1 (UCP1) and cytochrome C in iBAT, along with smaller lipid droplets, elevated AMPKα activity and increased oxygen consumption. Meanwhile, Resv promoted expression of PRDM16, UCP1, PGC1α, cytochrome C and pyruvate dehydrogenase (PDH) in differentiated iBAT SVCs, suggesting that Resv enhanced brown adipocyte formation and function in vitro. In addition, Resv stimulated AMPKα and oxygen consumption in differentiated iBAT SVCs. However, the promotional effects of Resv were diminished by AMPK inhibition or AMPKα1 knockout, implying the involvement of AMPKα1 in this process.

CONCLUSION

Resv enhanced brown adipocyte formation and thermogenic function in mouse iBAT by promoting the expression of brown adipogenic markers via activating AMPKα1, which contributed to the anti-obesity effects of Resv.

A combination of resveratrol and quercetin induces browning in white adipose tissue of rats fed an obesogenic diet

OBJECTIVE

To analyze whether a combination of quercetin (Q) and resveratrol (RSV) would induce a white adipose tissue (WAT) browning effect.

METHODS

Thirty-six rats were fed an obesogenic diet and divided into four groups: control, treated with RSV (15 mg/kg body weight/day; RSV group), treated with Q (30 mg/kg body weight/day; Q group), or treated with both polyphenols (RSV + Q group).

RESULTS

After 6 weeks, body and WAT weights were significantly reduced in the RSV + Q group. In perirenal WAT of the control, RSV, and Q groups, white unilocular adipocytes appeared in the majority of cells, while in the RSV + Q group numerous multilocular adipocytes with positive immunostaining for UCP1 were observed. The presence of UCP1 was confirmed by Western blot. This group also revealed increased mRNA levels of Cidea, Hocx9, Bmp4, Slc27a1, Pat2, Atgl, and Atp5d. Interscapular brown adipose tissue weight showed no differences between groups, but the Cidea mRNA level was increased in the RSV group, the Cox-2 mRNA level in the RSV + Q group, and UCP1 protein expression in the RSV and the RSV + Q groups.

CONCLUSIONS

This study demonstrated that the RSV + Q combination produces a brown-like remodeling effect in perirenal WAT, as well as increased UCP1 protein expression in interscapular brown adipose tissue.

Combinations of bio-active dietary constituents affect human white adipocyte function in-vitro

Background

Specific bio-active dietary compounds modulate numerous metabolic processes in adipose tissue (AT), including pre-adipocyte proliferation and differentiation. AT dysfunction, rather than an increased fat mass per se, is strongly associated with the development of insulin resistance and is characterized by impaired adipogenesis, hypertrophic adipocytes, inflammation, and impairments in substrate metabolism. A better understanding of mechanisms underlying AT dysfunction may provide new strategies for the treatment of obesity-associated metabolic diseases. Here we evaluated the role of (all-E)-lycopene (Lyc), eicosapentaenoic acid (EPA) or trans-resveratrol (Res) and combinations thereof on human white adipocyte function.

Methods

In-vitro differentiating human pre-adipocytes were treated with EPA, Lyc and Res or their combinations for 14 days. The effects on intracellular lipid droplet (LD) accumulation, secreted anti- and pro-inflammatory cyto-/adipokines (e.g. adiponectin, IL-6, IL-8/CXCL-8 and MCP-1/CCL2) and on gene expression of markers of adipocyte differentiation and substrate metabolism (e.g. PPAR-gamma, C/EBP-alpha, GLUT-4, FAS, ATGL, HSL, and PLIN-1) were measured by fluorescent microscopy (Cellomics™), multi-parametric LiquiChip® technology and quantitative RT-PCR, respectively.

Results

Treatment of differentiating adipocytes for 14 days with the combination of Lyc/Res and EPA/Res resulted in significantly inhibited LD formation (~ -25 and -20%, respectively) compared to the effects of the single compounds. These morphological changes were accompanied by increased mRNA levels of the adipogenic marker PPAR-gamma and the lipase ATGL and by decreased expression levels of lipogenic markers (LPL, FAS, GLUT-4) and the LD-covering protein PLIN-1. In addition, a blunted adipocyte secretion of pro-inflammatory cytokines (IL-6 and MCP-1) and adiponectin was observed following treatment with these compounds.

Conclusion

The combination of the dietary bio-actives Lyc and EPA with Res might influence adipocyte function by affecting the balance between adipogenic, lipogenic and lipolytic gene expression, resulting in a reduced LD storage and a less inflammatory secretion profile. Taken together, our results indicate that combinations of dietary compounds may be beneficial for the prevention and treatment of metabolic disorders via effects on human white adipocyte function.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0143-5) contains supplementary material, which is available to authorized users.

Hormonal and nutritional signalling in the control of brown and beige adipose tissue activation and recruitment

Recent research has revealed that the activity of adipose tissue (BAT) in adult humans is higher than previously thought, and that obese patients show abnormally low levels of brown fat activity. Studies in experimental animals have shown that BAT is a site of energy expenditure, and that BAT activity protects against obesity and associated metabolic diseases. The action of the sympathetic nervous activity on BAT depots is considered the main regulator of BAT activity in rodent models and possibly also in humans. However, recent research has revealed the existence of additional hormonal factors, produced by distinct peripheral tissues or present in the diet, that influence the amount and activity of BAT. These hormonal factors may act on BAT directly, but also indirectly by targeting the brain and determining the intensity of sympathetic action upon BAT. Identification and characterization of novel factors that control BAT may provide clues for the development of new strategies to treat obesity and metabolic diseases.

GLP-1 receptor agonist promotes brown remodelling in mouse white adipose tissue through SIRT1

AIMS/HYPOTHESIS

Accumulating evidence has revealed the significant role of glucagon-like peptide-1 (GLP-1) in weight loss. Sirtuin 1 (SIRT1) plays a vital role in the regulation of lipid metabolism. Here, we investigated the contribution of lipolytic and oxidative changes in white adipose tissue (WAT) to the weight-lowering effect induced by the GLP-1 receptor (GLP-1R) agonist exenatide (exendin-4) in mice. We also looked at the role of SIRT1 in this process.

METHODS

C57BL/6J mice and Sirt1 (+/-) mice were treated with exenatide (24 nmol/kg) or an NaCl solution (154 mmol/l) control i.p. for 8 weeks while receiving a high-fat diet (HFD) after a 12 week HFD challenge. Systemic phenotypic evaluations were carried out during and after the intervention. A lentivirus-mediated short hairpin (sh)RNA vector of the Sirt1 gene was transfected into differentiated 3T3-L1 adipocytes. An in vitro model system used adipocytes induced from Sirt1-null mouse embryonic fibroblasts (MEFs).

RESULTS

Exenatide reduced fat mass and enhanced the lipolytic and oxidative capacity of WAT in diet-induced obese C57BL/6J mice. However, these effects were significantly impaired in Sirt1 (+/-) mice compared with wild-type controls. In vitro, exendin-4 increased lipolysis and fatty acid oxidation by upregulating SIRT1 expression and activity in differentiated 3T3-L1 adipocytes. Conversely, RNA interference (i)-induced knockdown of SIRT1 attenuated the lipolytic and oxidative responses to exendin-4 in differentiated 3T3-L1 adipocytes. Again, these responses were entirely abolished in Sirt1-null MEFs after induction into adipocytes.

CONCLUSIONS/INTERPRETATION

These data highlight that a GLP-1R agonist promotes brown remodelling of WAT in a SIRT1-dependent manner; this might be one of the mechanisms underlying its effect on weight loss.

Mitochondrial dysfunction in fatty acid oxidation disorders: insights from human and animal studies

Patients affected by FAOD commonly present with hepatopathy, cardiomyopathy, skeletal myopathy and encephalopathy. Human and animal evidences indicate that mitochondrial functions are disrupted by fatty acids and derivatives accumulating in these disorders, suggesting that lipotoxicity may contribute to their pathogenesis.

Mitochondrial fatty acid oxidation (FAO) plays a pivotal role in maintaining body energy homoeostasis mainly during catabolic states. Oxidation of fatty acids requires approximately 25 proteins. Inherited defects of FAO have been identified in the majority of these proteins and constitute an important group of inborn errors of metabolism. Affected patients usually present with severe hepatopathy, cardiomyopathy and skeletal myopathy, whereas some patients may suffer acute and/or progressive encephalopathy whose pathogenesis is poorly known. In recent years growing evidence has emerged indicating that energy deficiency/disruption of mitochondrial homoeostasis is involved in the pathophysiology of some fatty acid oxidation defects (FAOD), although the exact underlying mechanisms are not yet established. Characteristic fatty acids and carnitine derivatives are found at high concentrations in these patients and more markedly during episodes of metabolic decompensation that are associated with worsening of clinical symptoms. Therefore, it is conceivable that these compounds may be toxic. We will briefly summarize the current knowledge obtained from patients and genetic mouse models with these disorders indicating that disruption of mitochondrial energy, redox and calcium homoeostasis is involved in the pathophysiology of the tissue damage in the more common FAOD, including medium-chain acyl-CoA dehydrogenase (MCAD), long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and very long-chain acyl-CoA dehydrogenase (VLCAD) deficiencies. We will also provide evidence that the fatty acids and derivatives that accumulate in these diseases disrupt mitochondrial homoeostasis. The elucidation of the toxic mechanisms of these compounds may offer new perspectives for potential novel adjuvant therapeutic strategies in selected disorders of this group.

Cell Systems to Investigate the Impact of Polyphenols on Cardiovascular Health

Polyphenols are a diverse group of micronutrients from plant origin that may serve as antioxidants and that contribute to human health in general. More specifically, many research groups have investigated their protective effect against cardiovascular diseases in several animal studies and human trials. Yet, because of the excessive processing of the polyphenol structure by human cells and the residing intestinal microbial community, which results in a large variability between the test subjects, the exact mechanisms of their protective effects are still under investigation. To this end, simplified cell culture systems have been used to decrease the inter-individual variability in mechanistic studies. In this review, we will discuss the different cell culture models that have been used so far for polyphenol research in the context of cardiovascular diseases. We will also review the current trends in cell culture research, including co-culture methodologies. Finally, we will discuss the potential of these advanced models to screen for cardiovascular effects of the large pool of bioactive polyphenols present in foods and their metabolites.

Retinol binding protein 4 in relation to diet, inflammation, immunity, and cardiovascular diseases

Retinol binding protein 4 (RBP4), previously called retinol binding protein (RBP), is considered a specific carrier of retinol in the blood. It is also an adipokine that has been implicated in the pathophysiology of insulin resistance. RBP4 seems to be correlated with cardiometabolic markers in inflammatory chronic diseases, including obesity, type 2 diabetes, metabolic syndrome, and cardiovascular diseases (CVDs). It has recently been suggested that inflammation produced by RBP4 induces insulin resistance and CVD. The clinical relevance of this hypothesis is discussed in this review. Knowledge concerning the association of RBP4 with inflammation markers, oxidative stress, and CVDs as well as concerning the role of diet and antioxidants in decreasing RBP4 concentrations are discussed. Special attention is given to methodologies used in previously published studies and covariates that should be controlled when planning new studies on this adipokine.

Prevention of obesity by dietary resveratrol: how strong is the evidence?

Obesity is a pandemic problem worldwide. Dietary polyphenolic compounds show promise in preventing obesity. Resveratrol (RSV), one of the most extensively studied polyphenol compounds, has been shown to exert anti-obesity effects in various animal studies and also in several human studies. The fat-lowering effects of RSV may result from its ability to inhibit adipogenesis, suppress lipogenesis, stimulate lipolysis, promote apoptosis, and increase fatty acid oxidation and thermogenesis, as well as the recently demonstrated induction of the browning of white adipose tissue (WAT). These anti-obesity effects of RSV likely depend on its ability to activate AMP-activated protein kinase (AMPK), a key enzyme regulating cellular energy metabolism. Consumption of fruits such as berries, grapes and nuts, which contain high levels of RSV and other polyphenols, might help to reduce obesity.