Effects of lipoic acid on lipolysis in 3T3-L1 adipocytes

The PLAAT family as phospholipid-related enzymes

The phospholipase A and acyltransferase (PLAAT) family is a group of structurally related proteins that are conserved among vertebrates. In humans, the family comprises five members (PLAAT1-5), which share common domain structures, and functions as phospholipase A1/A2 and acyltransferase enzymes. Regarding acyltransferase activities, PLAATs produce N-acyl-phosphatidylethanolamines, which serve as the precursor of bioactive N-acylethanolamines (NAEs). Recent evidence strongly suggests that PLAAT proteins play a crucial role in maintaining homeostasis in various organelles, such as the endoplasmic reticulum, lysosomes, mitochondria, and peroxisomes. In this process, PLAAT proteins bind to organelles and degrade them in an enzyme activity-dependent manner. Their physiological significance was revealed by the inability of PLAAT-deficient animals to degrade organelles during the maturation of the eye lens, resulting in the development of cataracts. Furthermore, the deficiency of PLAAT1, 3, and 5 in mice caused resistance to high-fat diet-induced fatty liver, the lean phenotype represented by a marked decrease in adipose tissue mass, and the exacerbation of testicular inflammation due to decreased levels of anti-inflammatory NAEs, respectively. In addition, human PLAAT3 was identified as a causative gene for lipodystrophy. We herein provide an overview of the molecular and biological properties of PLAAT proteins.

Alpha-lipoic Acid: An Antioxidant with Anti-aging Properties for Disease Therapy

The anti-aging effects of alpha-lipoic acid (αLA), a natural antioxidant synthesized in human tissues, have attracted a growing interest in recent years. αLA is a short- -chain sulfur-containing fatty acid occurring in the mitochondria of all kinds of eukaryotic cells. Both the oxidized disulfide of αLA and its reduced form (dihydrolipoic acid, DHLA) exhibit prominent antioxidant function. The amount of αLA inside the human body gradually decreases with age resulting in various health disorders. Its lack can be compensated by supplying from external sources such as dietary supplements or medicinal dosage forms. The primary objectives of this study were the analysis of updated information on the latest two-decade research regarding the use of αLA from an anti-aging perspective. The information was collected from PubMed, Wiley Online Library, Scopus, ScienceDirect, SpringerLink, Google Scholar, and clinicaltrials.gov. Numerous in silico, in vitro, in vivo, and clinical studies revealed that αLA shows a protective role in biological systems by direct or indirect reactive oxygen/nitrogen species quenching. αLA demonstrated beneficial properties in the prevention and treatment of many age-related disorders such as neurodegeneration, metabolic disorders, different cancers, nephropathy, infertility, and skin senescence. Its preventive effects in case of Alzheimer's and Parkinson's diseases are of particular interest. Further mechanistic and clinical studies are highly recommended to evaluate the wide spectrum of αLA therapeutic potential that could optimize its dietary intake for prevention and alleviation disorders related to aging.

Alpha-Lipoic Acid Induces Adipose Tissue Browning through AMP-Activated Protein Kinase Signaling in Vivo and in Vitro

Background

AMP-activated protein kinase (AMPK) is a key enzyme for cellular energy homeostasis and improves metabolic disorders. Brown and beige adipose tissues exert thermogenesis capacities to dissipate energy in the form of heat. Here, we investigated the beneficial effects of the antioxidant alpha-lipoic acid (ALA) in menopausal obesity and the underlying mechanisms.

Methods

Female Wistar rats (8 weeks old) were subjected to bilateral ovariectomy (Ovx) and divided into four groups: Sham (n=8), Ovx (n=11), Ovx+ALA2 (n=10), and Ovx+ALA3 (n=6) (ALA 200 and 300 mg/kg/day, respectively; gavage) for 8 weeks. 3T3-L1 cells were used for in vitro study.

Results

Rats receiving ALA2 and ALA3 treatment showed significantly lower levels of body weight and white adipose tissue (WAT) mass than those of the Ovx group. ALA improved plasma lipid profiles including triglycerides, total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol. Hematoxylin & eosin staining of inguinal WAT showed that ALA treatment reduced Ovx-induced adipocyte size and enhanced uncoupling protein 1 (UCP1) expression. Moreover, plasma levels of irisin were markedly increased in ALA-treated Ovx rats. Protein expression of brown fat-specific markers including UCP1, PRDM16, and CIDEA was downregulated by Ovx but markedly increased by ALA. Phosphorylation of AMPK, its downstream acetyl-CoA carboxylase, and its upstream LKB1 were all significantly increased by ALA treatment. In 3T3-L1 cells, administration of ALA (100 and 250 μM) reduced lipid accumulation and enhanced oxygen consumption and UCP1 protein expression, while inhibition of AMPK by dorsomorphin (5 μM) significantly reversed these effects.

Conclusion

ALA improves estrogen deficiency-induced obesity via browning of WAT through AMPK signaling.

Limited oxygen in standard cell culture alters metabolism and function of differentiated cells

The in vitro oxygen microenvironment profoundly affects the capacity of cell cultures to model physiological and pathophysiological states. Cell culture is often considered to be hyperoxic, but pericellular oxygen levels, which are affected by oxygen diffusivity and consumption, are rarely reported. Here, we provide evidence that several cell types in culture actually experience local hypoxia, with important implications for cell metabolism and function. We focused initially on adipocytes, as adipose tissue hypoxia is frequently observed in obesity and precedes diminished adipocyte function. Under standard conditions, cultured adipocytes are highly glycolytic and exhibit a transcriptional profile indicative of physiological hypoxia. Increasing pericellular oxygen diverted glucose flux toward mitochondria, lowered HIF1α activity, and resulted in widespread transcriptional rewiring. Functionally, adipocytes increased adipokine secretion and sensitivity to insulin and lipolytic stimuli, recapitulating a healthier adipocyte model. The functional benefits of increasing pericellular oxygen were also observed in macrophages, hPSC-derived hepatocytes and cardiac organoids. Our findings demonstrate that oxygen is limiting in many terminally-differentiated cell types, and that considering pericellular oxygen improves the quality, reproducibility and translatability of culture models.

Low concentrations of α-lipoic acid reduce palmitic acid-induced alterations in murine hypertrophic adipocytes

Obesity is a metabolic disorder with excessive body fat accumulation, increasing incidence of chronic metabolic diseases. Hypertrophic obesity is associated with local oxidative stress and inflammation. Herein, we evaluated the in vitro activity of micromolar concentrations of α-lipoic acid (ALA) on palmitic acid (PA)-exposed murine hypertrophic 3T3-L1 adipocytes, focussing on the main molecular pathways involved in adipogenesis, inflammation, and insulin resistance. ALA, starting from 1 µM, decreased adipocytes hypertrophy, reducing PA-triggered intracellular lipid accumulation, PPAR-γ levels, and FABP4 gene expression, and counteracted PA-induced intracellular ROS levels and NF-κB activation. ALA reverted PA-induced insulin resistance, restoring PI3K/Akt axis and inducing GLUT-1 and glucose uptake, showing insulin sensitizing properties since it increased their basal levels. In conclusion, this study supports the potential effects of low micromolar ALA against hypertrophy, inflammation, and insulin resistance in adipose tissue, suggesting its important role as pharmacological supplement in the prevention of conditions linked to obesity and metabolic syndrome.

Brown Algae Dictyopteris divaricata Attenuates Adipogenesis by Modulating Adipocyte Differentiation and Promoting Lipolysis through Heme Oxygenase-1 Activation in 3T3-L1 Cells

The present study aims to explore the probable anti-adipogenesis effect of Dictyopteris divaricata (D. divaricata) in 3T3-L1 preadipocytes by regulating heme oxygenase-1 (HO-1). The extract of D. divaricata retarded lipid accretion and decreased triglyceride (TG) content in 3T3-L1 adipocytes but increased free glycerol levels. Treatment with the extract inhibited lipogenesis by inhibiting protein expressions of fatty acid synthase (FAS) and lipoprotein lipase (LPL), whereas lipolysis increased by activating phosphorylation of hormone-sensitive lipase (p-HSL) and AMP-activated protein kinase (p-AMPK). The extract inhibited adipocyte differentiation of 3T3-L1 preadipocytes through down-regulating adipogenic transcription factors, including peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP1). This is attributed to the triggering of Wnt/β-catenin signaling. In addition, this study found that treatment with the extract activated HO-1 expression. Pharmacological approaches revealed that treatment with Zinc Protoporphyrin (ZnPP), an HO-1 inhibitor, resulted in an increase in lipid accumulation and a decrease in free glycerol levels. Finally, three adipogenic transcription factors, such as PPARγ, C/EBPα, and SREBP1, restored their expression in the presence of ZnPP. Analysis of chemical constituents revealed that the extract of D. divaricata is rich in 1,4-benzenediol, 7-tetradecenal, fucosterol, and n-hexadecanoic acid, which are known to have multiple pharmacological properties.

α-lipoic acid ameliorates consequences of copper overload by up-regulating selenoproteins and decreasing redox misbalance

α-lipoic acid (LA) is an essential cofactor for mitochondrial dehydrogenases and is required for cell growth, metabolic fuel production, and antioxidant defense. In vitro, LA binds copper (Cu) with high affinity and as an endogenous membrane permeable metabolite could be advantageous in mitigating the consequences of Cu overload in human diseases. We tested this hypothesis in 3T3-L1 preadipocytes with inactivated Cu transporter Atp7a; these cells accumulate Cu and show morphologic changes and mitochondria impairment. Treatment with LA corrected the morphology of Atp7a-/- cells similar to the Cu chelator bathocuproinedisulfonate (BCS) and improved mitochondria function; however, the mechanisms of LA and BCS action were different. Unlike BCS, LA did not decrease intracellular Cu but instead increased selenium levels that were low in Atp7a-/- cells. Proteome analysis confirmed distinct cell responses to these compounds and identified upregulation of selenoproteins as the major effect of LA on preadipocytes. Upregulation of selenoproteins was associated with an improved GSH:GSSG ratio in cellular compartments, which was lowered by elevated Cu, and reversal of protein oxidation. Thus, LA diminishes toxic effects of elevated Cu by improving cellular redox environment. We also show that selenium levels are decreased in tissues of a Wilson disease animal model, especially in the liver, making LA an attractive candidate for supplemental treatment of this disease.

Alpha Lipoic Acid Efficacy in PCOS Treatment: What Is the Truth?

Polycystic ovary syndrome (PCOS) is among the most common female endocrinopathies, affecting about 4-25% of women of reproductive age. Women affected by PCOS have an increased risk of developing metabolic syndrome, type 2 diabetes mellitus, cardiovascular diseases, and endometrial cancer. Given the pivotal role of insulin resistance (IR) in the pathogenesis of PCOS, in the last years, many insulin-sensitizing factors have been proposed for PCOS treatment. The first insulin sensitizer recommended by evidence-based guidelines for the assessment and treatment of PCOS was metformin, but the burden of side effects is responsible for treatment discontinuation in many patients. Inositols have insulin-mimetic properties and contribute to decreasing postprandial blood glucose, acting by different pathways. ALA is a natural amphipathic compound with a very strong anti-inflammatory and antioxidant effect and a very noteworthy role in the improvement of insulin metabolic pathway. Given the multiple effects of ALA, a therapeutic strategy based on the synergy between inositols and ALA has been recently proposed by many groups with the aim of improving insulin resistance, reducing androgen levels, and ameliorating reproductive outcomes in PCOS patients. The purpose of this study is to review the existing literature and to evaluate the existing data showing the efficacy and the limitation of a treatment strategy based on this promising molecule. ALA is a valid therapeutic strategy applicable in the treatment of PCOS patients: Its multiple actions, including antinflammatory, antioxidant, and insulin-sensitizing, may be of utmost importance in the treatment of a very complex syndrome. Specifically, the combination of MYO plus ALA creates a synergistic effect that improves insulin resistance in PCOS patients, especially in obese/overweight patients with T2DM familiarity. Moreover, ALA treatment also exerts beneficial effects on endocrine patterns, especially if combined with MYO, improving menstrual regularity and ovulation rhythm. The purpose of our study is to review the existing literature and to evaluate the data showing the efficacy and the limitations of a treatment strategy based on this promising molecule.

Sudachitin and Nobiletin Stimulate Lipolysis via Activation of the cAMP/PKA/HSL Pathway in 3T3-L1 Adipocytes

Polymethoxyflavones are flavonoids that are abundant in citrus fruit peels and have beneficial effects on human health. Previous studies have demonstrated that the polymethoxyflavones, namely sudachitin and nobiletin, ameliorate obesity and diabetes in humans and rodents. Although nobiletin induces lipolysis in adipocytes, lipolytic pathway activation by sudachitin has not been clarified in adipocytes. In this study, the effect of sudachitin on lipolysis was elucidated in murine 3T3-L1 adipocytes. Glycerol release into the medium and activation of the cyclic AMP (cAMP)/protein kinase A (PKA)/hormone-sensitive lipase (HSL) pathway was evaluated in 3T3-L1-differentiated adipocytes. Treatment with sudachitin and nobiletin for 24 and 48 h did not induce cytotoxicity at concentrations of up to 50 μM. Sudachitin and nobiletin at concentrations of 30 and 50 μM increased intracellular cAMP and medium glycerol levels in 3T3-L1 adipocytes. Western blotting revealed that sudachitin and nobiletin dose-dependently increased protein levels of phosphorylated PKA substrates and phosphorylated HSL. Sudachitin- and nobiletin-induced glycerol release, phosphorylation of PKA substrates, and HSL phosphorylation were suppressed by pharmacological inhibition of adenylate cyclase and PKA. These findings indicated that sudachitin, similar to nobiletin, exerts anti-obesogenic effects, at least in part through the induction of lipolysis in adipocytes.

Efficacy and safety of oral alpha-lipoic acid supplementation for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized trials

OBJECTIVE

To examine the dose-dependent influence of oral alpha-lipoic acid (ALA) supplementation on cardiometabolic risk factors in patients with type 2 diabetes (T2D).

DESIGN

We followed the instructions outlined in the Cochrane Handbook for Systematic Reviews of Interventions and the Grading of Recommendations, Assessment, Development, and Evaluation Handbook to conduct our systematic review. The protocol of the study was registered in PROSPERO (CRD42021260587).

METHOD

We searched PubMed, Scopus, and Web of Science to May 2021 for trials of oral ALA supplementation in adults with T2D. The primary outcomes were HbA1c, weight loss, and LDL cholesterol (LDL-C). Secondary outcomes included fasting plasma glucose (FPG), triglyceride (TG), C-reactive protein (CRP), and blood pressure. We conducted a random-effects dose-response meta-analysis to calculate the mean difference (MD) and 95% CI for each 500 mg/day oral ALA supplementation. We performed a nonlinear dose-response meta-analysis using a restricted cubic spline.

RESULTS

We included 16 trials with 1035 patients. Each 500 mg/day increase in oral ALA supplementation significantly reduced HbA1c, body weight, CRP, FPG, and TG. Dose-response meta-analyses indicated a linear decrement in body weight at ALA supplementation of more than 600 mg/day (MD600 mg/day: -0.30 kg, 95% CI: -0.04, -0.57). A relatively J-shaped effect was seen for HbA1c (MD: -0.32%, 95% CI: -0.45, -0.18). Levels of FPG and LDL-C decreased up to 600 mg/day ALA intake. The point estimates were below minimal clinically important difference thresholds for all outcomes.

CONCLUSION

Despite significant improvements, the effects of oral ALA supplementation on cardiometabolic risk factors in patients with T2D were not clinically important.

Potential lipolytic regulators derived from natural products as effective approaches to treat obesity

Epidemic obesity is contributing to increases in the prevalence of obesity-related metabolic diseases and has, therefore, become an important public health problem. Adipose tissue is a vital energy storage organ that regulates whole-body energy metabolism. Triglyceride degradation in adipocytes is called lipolysis. It is closely tied to obesity and the metabolic disorders associated with it. Various natural products such as flavonoids, alkaloids, and terpenoids regulate lipolysis and can promote weight loss or improve obesity-related metabolic conditions. It is important to identify the specific secondary metabolites that are most effective at reducing weight and the health risks associated with obesity and lipolysis regulation. The aims of this review were to identify, categorize, and clarify the modes of action of a wide diversity of plant secondary metabolites that have demonstrated prophylactic and therapeutic efficacy against obesity by regulating lipolysis. The present review explores the regulatory mechanisms of lipolysis and summarizes the effects and modes of action of various natural products on this process. We propose that the discovery and development of natural product-based lipolysis regulators could diminish the risks associated with obesity and certain metabolic conditions.

Tumor necrosis factor-α promotes lipolysis and reduces insulin sensitivity by activating nuclear factor kappa B and c-Jun N-terminal kinase in primary bovine adipocytes

Sustained lipolysis and insulin resistance increase the risk of metabolic dysfunction in dairy cows during the transition period. Proinflammatory cytokines are key regulators of adipose tissue metabolism in nonruminants, but biological functions of these molecules in ruminants are not well known. Thus, the objective of this study was to investigate whether tumor necrosis factor-α (TNF-α) could affect insulin sensitivity and lipolysis in bovine adipocytes as well as the underlying mechanisms. Bovine adipocytes (obtained from the omental and mesenteric adipose depots) isolated from 5 Holstein female calves (1 d old) with similar body weight (median: 36.9 kg, range: 35.5-41.2 kg) were differentiated and used for (1) treatment with different concentrations of TNF-α (0, 0.1, 1, or 10 ng/mL) for 12 h; (2) pretreatment with 10 μM lipolytic agonist isoproterenol (ISO) for 3 h, followed by treatment with or without 10 ng/mL TNF-α for 12 h; and (3) pretreatment with the c-Jun N-terminal kinase (JNK) inhibitor SP600125 (20 μM for 2 h) and nuclear factor kappa B (NF-κB) inhibitor BAY 11-7082 (10 μM for 1 h) followed by treatment with or without 10 ng/mL TNF-α for 12 h. The TNF-α increased glycerol content in supernatant, decreased triglyceride content and insulin-stimulated phosphorylation of protein kinase B suggesting activation of lipolysis and impairment of insulin sensitivity. The TNF-α reduced cell viability, upregulated mRNA abundance of Caspase 3 (CASP3), an apoptosis marker, and increased activity of Caspase 3. In addition, increased phosphorylation of NF-κB and JNK, upregulation of mRNA abundance of interleukin-6 (IL-6), TNFA, and suppressor of cytokine signaling 3 (SOCS3) suggested that TNF-α activated NF-κB and JNK signaling pathways. Furthermore, ISO plus TNF-α-activated NF-κB and JNK signaling pathway to a greater extent than TNF-α alone. Combining TNF-α and ISO aggravated TNF-α-induced apoptosis, insulin insensitivity and lipolysis. In the absence of TNF-α, inhibition of NF-κB and JNK did not alter glycerol content in supernatant, triglyceride content or insulin-stimulated phosphorylation of protein kinase B. In the presence of TNF-α, inhibition of NF-κB and JNK alleviated TNF-α-induced apoptosis, insulin insensitivity and lipolysis. Overall, TNF-α impairs insulin sensitivity and induces lipolysis and apoptosis in bovine adipocytes, which may be partly mediated by activation of NF-κB and JNK. Thus, the data suggested that NF-κB and JNK are potential therapeutic targets for alleviating lipolysis dysregulation and insulin resistance in adipocytes.

Adipose and non-adipose perspectives of plant derived natural compounds for mitigation of obesity

ETHNOPHARMACOLOGICAL RELEVANCE

Phyto-preparations and phyto-compounds, by their natural origin, easy availability, cost-effectiveness, and fruitful traditional uses based on accumulated experiences, have been extensively explored to mitigate the global burden of obesity.

AIM OF THIS REVIEW

The review aimed to analyse and critically summarize the prospect of future anti-obesity drug leads from the extant array of phytochemicals for mitigation of obesity, using adipose related targets (adipocyte formation, lipid metabolism, and thermogenesis) and non-adipose targets (hepatic lipid metabolism, appetite, satiety, and pancreatic lipase activity). Phytochemicals as inhibitors of adipocyte differentiation, modulators of lipid metabolism, and thermogenic activators of adipocytes are specifically discussed with their non-adipose anti-obesogenic targets.

MATERIALS AND METHODS

PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. The taxonomically accepted name of each plant in this review has been vetted from "The Plant List" (www.theplantlist.org) or MPNS (http://mpns.kew.org).

RESULTS

Available knowledge of a large number of phytochemicals, across a range of adipose and non-adipose targets, has been critically analysed and delineated by graphical and tabular depictions, towards mitigation of obesity. Neuro-endocrinal modulation in non-adipose targets brought into sharp dual focus, both non-adipose and adipose targets as the future of anti-obesity research. Numerous phytochemicals (Berberine, Xanthohumol, Ursolic acid, Guggulsterone, Tannic acid, etc.) have been found to be effectively reducing weight through lowered adipocyte formation, increased lipolysis, decreased lipogenesis, and enhanced thermogenesis. They have been affirmed as potential anti-obesity drugs of future because of their effectiveness yet having no threat to adipose or systemic insulin sensitivity.

CONCLUSION

Due to high molecular diversity and a greater ratio of benefit to risk, plant derived compounds hold high therapeutic potential to tackle obesity and associated risks. This review has been able to generate fresh perspectives on the anti-diabetic/anti-hyperglycemic/anti-obesity effect of phytochemicals. It has also brought into the focus that many phytochemicals demonstrating in vitro anti-obesogenic effects are yet to undergo in vivo investigation which could lead to potential phyto-molecules for dedicated anti-obesity action.

Study of the Lipolysis Effect of Nanoliposome-Encapsulated Ganoderma lucidum Protein Hydrolysates on Adipocyte Cells Using Proteomics Approach

Excessive lipid accumulation is a serious condition. Therefore, we aimed at developing safe strategies using natural hypolipidemic products. Lingzhi is an edible fungus and potential lipid suppression stimulant. To use Lingzhi as a functional hyperlipidemic ingredient, response surface methodology (RSM) was conducted to optimize the time (X₁) and enzyme usage (X₂) for the hydrolysate preparation with the highest degree of hydrolysis (DH) and % yield. We encapsulated the hydrolysates using nanoscale liposomes and used proteomics to study how these nano-liposomal hydrolysates could affect lipid accumulation in adipocyte cells. RSM analysis revealed X₁ at 8.63 h and X₂ at 0.93% provided the highest values of DH and % yields were 33.99% and 5.70%. The hydrolysates were loaded into liposome particles that were monodispersed. The loaded nano-liposomal particles did not significantly affect cell survival rates. The triglyceride (TG) breakdown in adipocytes showed a higher TG increase compared to the control. Lipid staining level upon the liposome treatment was lower than that of the control. Proteomics revealed 3425 proteins affected by the liposome treatment, the main proteins being TSSK5, SMU1, GRM7, and KLC4, associated with various biological functions besides lipolysis. The nano-liposomal Linzghi hydrolysate might serve as novel functional ingredients in the treatment and prevention of obesity

Zyflamend, a unique herbal blend, induces cell death and inhibits adipogenesis through the coordinated regulation of PKA and JNK

The prevalence of obesity and its comorbidities has sparked a worldwide concern to address rates of adipose tissue accrual. Recent studies have demonstrated a novel role of Zyflamend, a blend of natural herbal extracts, in regulating lipid metabolism in several cancer cell lines through the activation of the AMPK signalling pathway. Yet, the role of Zyflamend in adipogenic differentiation and lipid metabolism remains largely unexplored. The objective of this study is to investigate the effects of Zyflamend on white 3T3-MBX pre-adipocyte differentiation and elucidate the molecular mechanisms. We demonstrate that Zyflamend treatment altered cell cycle progression, attenuated proliferation, and increased cell death of 3T3-MBX pre-adipocytes. In addition, treatment with Zyflamend inhibited lipid accumulation during the differentiation of 3T3-MBX cells, consistent with decreased expression of lipogenic genes and increased lipolysis. Mechanistically, Zyflamend-induced alterations in adipogenesis were mediated, at least in part, through the activation of AMPK, PKA, and JNK. Inhibition of AMPK partially reversed Zyflamend-induced inhibition of differentiation, whereas the inhibition of either JNK or PKA fully restored adipocyte differentiation and decreased lipolysis. Taken together, the present study demonstrates that Zyflamend, as a novel anti-adipogenic bioactive mix, inhibits adipocyte differentiation through the activation of the PKA and JNK pathways.

Abbreviation: 7-AAD: 7-amino-actinomycin D; ACC: acetyl-CoA carboxylase; AKT: protein kinase B; AMPK: AMP-activated protein kinase; ATGL: adipose triglyceride lipase; C/EBPα: CCAAT-enhancer binding protein alpha; DMEM: Dulbecco’s Modified Eagle Medium; DMSO: dimethyl sulphoxide; DTT: dithiothreitol; EGTA: ethylene glycol-bis-(2-aminoethyl)-N,N,N’,N’-tetraacetic acid; ERK: extracellular signal–regulated kinases; FASN: fatty acid synthase; FBS: foetal bovine serum; GLUT: glucose transporter; HSL: hormone-sensitive lipase; IR: insulin receptor; IRS: insulin receptor substrate; JNK: c-JUN N-terminal kinase; MGL: monoacylglycerol lipase; NaF: sodium fluoride; NF-κB: nuclear factor kappa-light-chain-enhancer of activated B cells; PBS: phosphate buffered- saline; PCB: pyruvate carboxylase; PDE: phosphodiesterase; PKA: protein kinase cAMP-dependent; PMSF: phenylmethylsulfonyl fluoride; PPARγ: perilipin peroxisome proliferator-activated receptor gamma; PREF-1: pre-adipocyte factor 1; PVDF: polyvinylidene fluoride; RIPA: radio-immunoprecipitation assay; SDS-PAGE: sodium dodecyl sulphate polyacrylamide gel electrophoresis; SEM: standard error of the mean; SOX9: suppressor of cytokine signalling 9; TGs: triacylglycerols.

An in vitro study reveals the anti-obesity effects of 7- methoxy-3-methyl-5-((E)-prop-1-enyl)-2-(3,4,5-trimethoxyphenyl)-2,3-dihydrobenzofuran from Myristica fragrans

Adipogenesis, the maturation process of preadipocytes, is closely associated with the development of obesity and other complex metabolic syndromes. Herein, we investigated the effect of 7- methoxy-3-methyl-5-((E)- prop-1-enyl)-2-(3,4,5-trimethoxyphenyl)-2,3-dihydrobenzofuran (TM), a benzofuran, isolated from the mace of Myristica fragrans Houtt on adipogenesis in 3T3-L1 preadipocytes to extrapolate whether this compound has any anti-obesity potential. For this, 3T3-L1 preadipocytes were induced to differentiate in the presence of various concentrations of TM (1, 5, 10 μM) and analyzed for triglyceride (TG) accumulation and the expression of proteins and genes involved in lipogenesis and lipolysis associated with adipogenesis. Results showed that TM significantly reduced TG accumulation and expression of marker proteins of adipocyte differentiation (peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein α, and fatty acid-binding protein 4) and increased the secretion of glycerol in a dose-dependent manner. There was a significant dose-dependent decrease in the expression of fatty acid synthase, stearoyl-CoA desaturase-1, sterol regulatory element-binding transcription factor 1c, and acetyl-CoA carboxylase 1 and an increase in carnitine palmitoyltransferase 1, acyl-CoA oxidase, and peroxisome proliferator-activated receptor α in TM treated cells. The phosphorylation of cAMP-activated protein kinase was also increased, which in turn activated the phosphorylation of acetyl-CoA carboxylase in mature adipocytes. Also, there was an increase in glucose uptake by TM, suggesting its insulin-sensitizing potential. This is the first report on the anti-obesity effects of TM from Myristica fragrans on adipogenesis and lipid metabolism in 3T3-L1 adipocytes and demands detailed in vivo study for developing TM as anti-obesity therapeutics.

Effects of alpha lipoic acid as a supplement in obese children and adolescents

OBJECTIVES

Obesity is significantly associated with inflammatory process and oxidative stress. Alpha lipoic acid (ALA) is a potent antioxidant that has been reported for reducing weight in animals and obese adults in several studies but no data are available in pediatrics. We investigated the possible beneficial role of ALA in obese children.

PATIENTS AND METHODS

Eighty obese children and adolescents were randomized into two groups; the treatment group (n = 40) who received 300 mg of ALA twice daily for 3 months and the control group (n = 40) who received placebo for 3 months. Measurements of weight, body mass index (BMI), lipid profile, fasting blood glucose (FBG), malondialdhyde (MDA), tumor necrosis factor alpha (TNF-α), leptin and adiponectin were carried out before and 3 months after the treatment.

RESULTS

ALA treatment group had a significant reduction of the weight, BMI, MDA, TNF-α, and leptin levels but a significant increase of adiponectin level (P < 0.05) compared to the control group. However, it had no effect on FBG or lipid profile (P > 0.05).

CONCLUSION

ALA may be a promising supplement in the weight reduction in obese children and adolescents.

1α, 25-dihydroxy Vitamin D3 containing fractions of Catharanthus roseus leaf aqueous extract inhibit preadipocyte differentiation and induce lipolysis in 3T3-L1 cells

BACKGROUND

To investigate the potential of Catharanthus roseus leaf aqueous crude extract (CRACE) as a regulator of adipocyte development and function.

METHODS

3T3-L1 adipogenesis model was used to investigate the effect of CRACE on adipogenesis. 3T3-L1 preadipocytes (for adipogenic differentiation) and mature 3T3-L1 adipocytes (for adipocyte function) were treated with non-toxic doses of CRACE. The outcomes were corroborated by intracellular lipid accumulation, expression of pro-and anti-adipogenic effector molecules. To investigate CRACE mediated lipolysis, cAMP accumulation, glycerol release and phosphorylation of key effector molecules were tested in treated mature adipocytes. Finally, the extract was fractionated to identify the active molecule/s in the extract.

RESULTS

CRACE significantly reduced adipocyte differentiation by modulating PPARγ expression. At early stage CRACE directly targeted Lipin1 expression and consequently impacted KLF7, subsequently expression of GATA2, CEBPα, SREBP1c were targeted, with PPARγ expression, particularly curtailed. While CRACE significantly reduced several lipogenic genes like FAS and GPD1 in mature adipocytes, concomitantly, it greatly increased lipolysis resulting in decreased lipid accumulation in mature adipocytes. The increase in lipolysis was due to decreased Akt activation, increased cAMP level, and PKA activity. The fractionation of CRACE allowed identification of two fractions with potent anti-adipogenic activity. Both the fractions contained 1α, 25-dihydroxy Vitamin D3 as major component.

CONCLUSIONS

1α, 25-dihydroxy Vitamin D3 containing CRACE can be developed into an effective anti-obesity formulation that decreases adipogenesis and increases lipid catabolism.

Clitoria ternatea Flower Petal Extract Inhibits Adipogenesis and Lipid Accumulation in 3T3-L1 Preadipocytes by Downregulating Adipogenic Gene Expression

Clitoria ternatea (commonly known as blue pea) flower petal extract (CTE) is used as a natural colorant in a variety of foods and beverages. The objective of study was to determine the inhibitory effect of CTE on adipogenesis in 3T3-L1 preadipocytes. The phytochemical profiles of CTE were analyzed by liquid chromatography and tandem mass spectrometry (LC-MS/MS). Anti-adipogenesis effect of CTE was measured by using Oil Red O staining, intracellular triglyceride assay, quantitative real-time PCR and western blot analysis in 3T3-L1 adipocytes. Cell cycle studies were performed by flow cytometry. Lipolysis experiments were performed using a colorimetric assay kit. In early stages, CTE demonstrated anti-adipogenic effects through inhibition of proliferation and cell cycle retardation by suppressing expression of phospho-Akt and phospho-ERK1/2 signaling pathway. The results also showed that CTE inhibited the late stage of differentiation through diminishing expression of adipogenic transcription factors including PPARγ and C/EBPα. The inhibitory action was subsequently attenuated in downregulation of fatty acid synthase and acetyl-CoA carboxylase, causing the reduction of TG accumulation. In addition, CTE also enhanced catecholamine-induced lipolysis in adipocytes. These results suggest that CTE effectively attenuates adipogenesis by controlling cell cycle progression and downregulating adipogenic gene expression.

Agaricus bisporus supplementation reduces high-fat diet-induced body weight gain and fatty liver development

Obesity is a global epidemic characterized not only by excessive fat deposition but also by important complications such as nonalcoholic liver steatosis. Beneficial antiobesogenic effects have been described for some mushrooms. The current study aimed to demonstrate the protective effect of Agaricus bisporus (AB) supplementation against the metabolic alterations induced by high-fat-diet (HFD) feeding. Eight-week-old C57BL/6J mice were fed for 10 weeks with one of the following diets: (1) control diet (n = 7), (2) HFD (n = 7), (3) HFD supplemented with 5% AB (n = 9), and (4) HFD supplemented with 10% AB (n = 9). A pair-fed group was also included for the 10% AB group (n = 6). The impact of AB supplementation on food intake, body weight gain, and liver and fat pad weights was examined. Biochemical, histological, and molecular parameters were also analyzed. Dietary supplementation with 10% AB reduced the HFD-induced increase in body, epididymal, and mesenteric fat weights (p < 0.01, p < 0.05, and p < 0.05, respectively). Supplementation with AB also reduced liver damage in a dose-dependent manner (p < 0.01 and p < 0.001). This effect was confirmed by histological analysis that showed that liver steatosis was markedly reduced in mice fed with AB. The beneficial properties of 10% AB supplementation appear to be mediated through a decrease in food intake and via stimulation of mesenteric and hepatic free-fatty acid beta-oxidation, along with a decrease in epidydimal and hepatic expression of CD36. In conclusion, supplementation with AB prevents excessive body weight gain and liver steatosis induced by HFD consumption.

Untargeted metabolomic on urine samples after α-lipoic acid and/or eicosapentaenoic acid supplementation in healthy overweight/obese women

BACKGROUND

Eicosapentaenoic acid (EPA) and α-lipoic acid (α-LA) have been investigated for their beneficial effects on obesity and cardiovascular risk factors. In the current research, the goal was to evaluate metabolomic changes following the dietary supplementation of these two lipids, alone or combined in healthy overweight/obese sedentary women following an energy-restricted diet. For this purpose, an untargeted metabolomics approach was conducted on urine samples using liquid chromatography coupled with time of flight mass spectrometry (HPLC-TOF-MS).

METHODS

This is a short-term double blind placebo-controlled study with a parallel nutritional design that lasted 10 weeks. Participants were assigned to one of the 4 experimental groups [Control, EPA (1.3 g/d), α-LA (0.3 g/d) and EPA+α-LA (1.3 g/d + 0.3 g/d)]. All intervention groups followed an energy-restricted diet of 30% less than total energy expenditure. Clinically relevant biochemical measurements were analyzed. Urine samples (24 h) were collected at baseline and after 10 weeks. Untargeted metabolomic analysis on urine samples was carried out, and principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were performed for the pattern recognition and characteristic metabolites identification.

RESULTS

Urine samples were scattered in the PCA scores plots in response to the supplementation with α-LA. Totally, 28 putative discriminant metabolites in positive ionization, and 6 in negative ionization were identified among groups clearly differentiated according to the α-LA administration. Remarkably is the presence of an ascorbate intermediate metabolite (one of the isomers of trihydroxy-dioxohexanoate, or dihydroxy-oxohexanedionate) in the groups supplemented with α-LA. This fact might be associated with antioxidant properties of both α-LA and ascorbic acid. Correlations between phenotypical parameters and putative metabolites of provided additional information on whether there is a direct or inverse relationship between them. Especially interesting are the negative correlation between ascorbate intermediate metabolite and asymmetric dimethylarginine (ADMA) and the positive one between superoxide dismutase (SOD) and α-LA supplementation.

CONCLUSIONS

This metabolomic approach supports that the beneficial effects of α-LA administration on body weight reduction may be partly explained by the antioxidant properties of this organosulfur carboxylic acid mediated by isomers of trihydroxy-dioxohexanoate, or dihydroxy-oxohexanedionate.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01138774 .

Non-adrenergic control of lipolysis and thermogenesis in adipose tissues

The enormous plasticity of adipose tissues, to rapidly adapt to altered physiological states of energy demand, is under neuronal and endocrine control. In energy balance, lipolysis of triacylglycerols and re-esterification of free fatty acids are opposing processes operating in parallel at identical rates, thus allowing a more dynamic transition from anabolism to catabolism, and vice versa. In response to alterations in the state of energy balance, one of the two processes predominates, enabling the efficient mobilization or storage of energy in a negative or positive energy balance, respectively. The release of noradrenaline from the sympathetic nervous system activates lipolysis in a depot-specific manner by initiating the canonical adrenergic receptor-G_s-protein-adenylyl cyclase-cyclic adenosine monophosphate-protein kinase A pathway, targeting proteins of the lipolytic machinery associated with the interface of the lipid droplets. In brown and brite adipocytes, lipolysis stimulated by this signaling pathway is a prerequisite for the activation of non-shivering thermogenesis. Free fatty acids released by lipolysis are direct activators of uncoupling protein 1-mediated leak respiration. Thus, pro- and anti-lipolytic mediators are bona fide modulators of thermogenesis in brown and brite adipocytes. In this Review, we discuss adrenergic and non-adrenergic mechanisms controlling lipolysis and thermogenesis and provide a comprehensive overview of pro- and anti-lipolytic mediators.

Lipoic Acid Stimulates cAMP Production in Healthy Control and Secondary Progressive MS Subjects

Lipoic acid (LA) exhibits antioxidant and anti-inflammatory properties; supplementation reduces disease severity and T lymphocyte migration into the central nervous system in a murine model of multiple sclerosis (MS), and administration in secondary progressive MS (SPMS) subjects reduces brain atrophy compared to placebo. The mechanism of action (MOA) of LA's efficacy in suppression of MS pathology is incompletely understood. LA stimulates production of the immunomodulator cyclic AMP (cAMP) in vitro. To determine whether cAMP could be involved in the MOA of LA in vivo, we performed a clinical trial to examine whether LA stimulates cAMP production in healthy control and MS subjects, and whether there are differences in the bioavailability of LA between groups. We administered 1200 mg of oral LA to healthy control, relapsing remitting MS (RRMS) and SPMS subjects, and measured plasma LA and cAMP levels in peripheral blood mononuclear cells (PBMCs). There were no significant differences between the groups in pharmacokinetic (PK) parameters. Healthy and SPMS subjects had increased cAMP at 2 and 4 h post-LA treatment compared to baseline, while RRMS subjects showed decreases in cAMP. Additionally, plasma concentrations of prostaglandin E2 (PGE₂, a known cAMP stimulator) were significantly lower in female RRMS subjects compared to female HC and SPMS subjects 4 h after LA ingestion. These data indicate that cAMP could be part of the MOA of LA in SPMS, and that there is a divergent response to LA in RRMS subjects that may have implications in the efficacy of immunomodulatory drugs. This clinical trial, "Defining the Anti-inflammatory Role of Lipoic Acid in Multiple Sclerosis," NCT00997438, is registered at https://clinicaltrials.gov/ct2/show/record/NCT00997438 .

Myoinositol combined with alpha-lipoic acid may improve the clinical and endocrine features of polycystic ovary syndrome through an insulin-independent action

The aim of our study was to investigate the effects of a combined treatment with alpha-lipoic acid (ALA) and myoinositol (MYO) on clinical, endocrine and metabolic features of women affected by polycystic ovary syndrome (PCOS). In this pilot cohort study, forty women with PCOS were enrolled and clinical, hormonal and metabolic parameters were evaluated before and after a six-months combined treatment with ALA and MYO daily. Studied patients experienced a significant increase in the number of cycles in six months (p < 0.01). The free androgen index (FAI), the mean androstenedione and DHEAS levels significantly decreased after treatment (p < 0.05). Mean SHBG levels significantly raised (p < 0.01). A significant improvement in mean Ferriman-Gallwey (F-G) score (p < 0.01) and a significant reduction of BMI (p < 0.01) were also observed. A significant reduction of AMH levels, ovarian volume and total antral follicular count were observed in our studied women (p< 0.05). No significant changes occurred in gluco-insulinaemic and lipid parameters after treatment. The combined treatment of ALA and MYO is able to restore the menstrual pattern and to improve the hormonal milieu of PCOS women, even in the absence of apparent changes in insulin metabolism.

Cardiotrophin-1 Regulates Adipokine Production in 3T3-L1 Adipocytes and Adipose Tissue From Obese Mice

Cardiotrophin-1 (CT-1) belongs to the IL-6 family of cytokines. Previous studies of our group revealed that CT-1 is a key regulator of glucose and lipid metabolism. The aim of the present study was to analyze the in vitro and in vivo effects of CT-1 on the production of several adipokines involved in body weight regulation, nutrient metabolism, and inflammation. For this purpose, 3T3-L1 adipocytes were incubated with recombinant protein CT-1 (rCT-1) (1-40 ng/ml) for 1 and 18 h. Moreover, the acute effects of rCT-1 administration (0.2 mg/kg, i.v.) for 30 min and 3 h on adipokines levels were also evaluated in high-fat fed obese mice. In 3T3-L1 adipocytes, rCT-1 treatment downregulated the expression and secretion of leptin, resistin, and visfatin. However, rCT-1 significantly stimulated apelin mRNA and secretion. rCT-1 (18 h) also promoted the activation by phosphorylation of AKT, ERK 1/2, and STAT3. Interestingly, pre-treatment with the PI3K inhibitor LY294002 reversed the stimulatory effects of rCT-1 on apelin expression, suggesting that this pathway could be mediating the effects of rCT-1 on apelin production. In contrast, acute administration of rCT-1 (30 min and 3 h) to diet-induced obese mice downregulated leptin and resistin, without significantly modifying apelin or visfatin mRNA in adipose tissue. Furthermore, CT-1 null mice exhibited altered expression of adipokines in adipose tissue. The present study demonstrates that rCT-1 modulates the production of adipokines in vitro and in vivo, suggesting that the regulation of the secretory function of adipocytes could be involved in the metabolic actions of this cytokine. J. Cell. Physiol. 232: 2469-2477, 2017. © 2016 Wiley Periodicals, Inc.

Effects of dietary supplementation with EPA and/or α-lipoic acid on adipose tissue transcriptomic profile of healthy overweight/obese women following a hypocaloric diet

In obesity, the increment of adiposity levels disrupts the whole body homeostasis, promoting an over production of oxidants and inflammatory mediators. The current study aimed to characterize the transcriptomic changes promoted by supplementation with eicosapentaenoic acid (EPA, 1.3 g/day), α-lipoic acid (0.3 g/day), or both (EPA + α-lipoic acid, 1.3 g/day + 0.3 g/day) in subcutaneous abdominal adipose tissue from overweight/obese healthy women, who followed a hypocaloric diet (30% of total energy expenditure) during ten weeks, by using a microarray approach. At the end of the intervention, a total of 33,297 genes were analyzed using Affymetrix GeneChip arrays. EPA promoted changes in extracellular matrix remodeling gene expression, besides a rise of genes associated with either chemotaxis or wound repair. α-Lipoic acid decreased expression of genes related with cell adhesion and inflammation. Furthermore, α-lipoic acid, especially in combination with EPA, upregulated the expression of genes associated with lipid catabolism while downregulated genes involved in lipids storage. Together, all these data suggest that some of the metabolic effects of EPA and α-lipoic acid could be related to their regulatory actions on adipose tissue metabolism. © 2016 BioFactors, 43(1):117-131, 2017.

Cardiotrophin-1 decreases intestinal sugar uptake in mice and in Caco-2 cells

AIM

Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT-1 treatment on intestinal sugar absorption in different experimental models.

METHODS

rCT-1 effects on α-Methyl-D-glucoside uptake were assessed in everted intestinal rings from wild-type and CT-1(-/-) mice and in Caco-2 cells. rCT-1 actions on SGLT-1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot.

RESULTS

In vivo administration (0.2 mg kg(-1) ) of rCT-1 caused a significant decrease on α-Methyl-D-glucoside uptake in everted intestinal rings from wild-type and CT-1(-/-) mice after short-term and long-term treatments. Similarly, in vitro treatment (1-50 ng mL(-1) ) with rCT-1 reduced α-Methyl-D-glucoside uptake in everted intestinal rings. In Caco-2 cells, rCT-1 treatment (20 ng mL(-1) , 1 and 24 h) lowered apical uptake of α-Methyl-D-glucoside in parallel with a decrease on SGLT-1 protein expression. rCT-1 promoted the phosphorylation of STAT-3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre-treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT-1 on α-Methyl-D-glucoside uptake. AICAR also prevented the inhibition of SGLT-1 observed in rCT-1-treated cells.

CONCLUSIONS

CT-1 inhibits intestinal sugar absorption by the reduction of SGLT-1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti-obesity properties of CT-1.

Cause-effect relationships in nutritional intervention studies for health claims substantiation: guidance for trial design

The growing worldwide interest on functional food research has been accompanied by increasing regulatory guidelines in this area, with the aim of ensuring that any claimed effect in foods, beyond their nutritional role, is based on scientific unequivocal evidence. In order to assess the cause-effect relationship between the regular consumption of a food or a food component and the beneficial outcome for the consumer, an appropriate study design is required. Previous knowledge and research on the specific claimed food or product may be an adequate basis for defining a hypothesis and accurate objectives. Other key factors to take into account are based on the outcomes studied, the length of the trial, sample size and type, as well as the transparency on reporting the results obtained. Based on the Consolidated Standards on Reporting Trials statement (CONSORT), together with the specific guidelines published by the European Food Safety Authority (EFSA) Panel on Dietetic Products, Nutrition and Allergies, the present article aims at summarizing key questions conducting to the most appropriate study design for solid health claim substantiation.

Effects of alpha-lipoic acid on chemerin secretion in 3T3-L1 and human adipocytes

Chemerin is a novel adipokine associated with obesity and insulin resistance. α-Lipoic acid (α-LA) has shown beneficial properties on diabetes and obesity. The aim of this study was to examine the effects of α-LA on chemerin production in adipocytes in absence or presence of TNF-α, insulin and AICAR. The potential signaling pathways involved in α-LA effects on chemerin were also analyzed. α-LA actions on chemerin were tested in differentiated 3T3-L1 adipocytes and in some cases in human subcutaneous and omental adipocytes. Chemerin mRNA levels were measured by RT-PCR and the amount of chemerin secreted to culture media was determined by ELISA. α-LA induced a concentration-dependent inhibition on both chemerin secretion and mRNA levels in 3T3-L1 adipocytes. The AMPK activator AICAR and the PI3K inhibitor LY294002 dramatically abrogated both chemerin secretion and gene expression, and further potentiated the inhibitory effect of α-LA on chemerin secretion. Insulin was able to partially reverse the inhibitory action of α-LA on chemerin secretion. α-LA also reduced basal chemerin secretion in both subcutaneous and omental adipocytes from overweight/obese subjects. Moreover, α-LA was able to abolish the stimulatory effects of the pro-inflammatory cytokine TNF-α on chemerin secretion. Our data demonstrated the ability of α-LA to inhibit chemerin production, an adipokine associated to obesity and metabolic syndrome, suggesting that the reduction of chemerin could contribute to the antiobesity/antidiabetic properties described for α-LA.

FGF21 mediates alcohol-induced adipose tissue lipolysis by activation of systemic release of catecholamine in mice

Alcohol consumption leads to adipose tissue lipoatrophy and mobilization of FFAs, which contributes to hepatic fat accumulation in alcoholic liver disease. This study aimed to investigate the role of fibroblast growth factor (FGF)21, a metabolic regulator, in the regulation of chronic-binge alcohol-induced adipose tissue lipolysis. FGF21 KO mice were subjected to chronic-binge alcohol exposure, and epididymal white adipose tissue lipolysis and liver steatosis were investigated. Alcohol exposure caused adipose intracellular cAMP elevation and activation of lipolytic enzymes, leading to FFA mobilization in both WT and FGF21 KO mice. However, alcohol-induced systemic elevation of catecholamine, which is known to be a major player in adipose lipolysis by binding to the β-adrenergic receptor, was markedly inhibited in KO mice. Supplementation with recombinant human FGF21 to alcohol-exposed FGF21 KO mice resulted in an increase in fat loss in parallel with an increase of circulating norepinephrine concentration. Furthermore, alcohol consumption-induced fatty liver was blunted in the KO mice, indicating an inhibition of fatty acid reverse transport from adipose to the liver in the KO mice. Taken together, our studies demonstrate that FGF21 KO mice are protected from alcohol-induced adipose tissue excess-lipolysis through a mechanism involving systemic catecholamine release.

Eicosapentaenoic acid upregulates VEGF-A through both GPR120 and PPARγ mediated pathways in 3T3-L1 adipocytes

Vascular endothelial growth factor-A (VEGF-A) released from adipocytes promotes angiogenesis; and thereby ameliorates the local hypoxia-induced adipose inflammation and insulin resistance. Here, we newly found that eicosapentaenoic acid (EPA) upregulated both mRNA expression and release of VEGF-A in mature 3T3-L1 adipocytes. Silencing mRNA of G-protein coupled receptor 120 (GPR120) and specific inhibition of peroxisome proliferator-activated receptor γ (PPARγ) by GW9662 respectively attenuated the EPA-induced augmentation of VEGF-A release by adipocytes. Furthermore, transfection of GPR120 gene alone and PPARγ gene alone to HEK293 cells respectively increased the promoter activity of VEGF-A as assessed by luciferase reporter assay, which was further augmented when both genes were co-transfected. Promoter deletion analysis and chromatin immunoprecipitation assay revealed that co-transfection of GPR120 enhanced EPA-induced PPARγ binding to PPAR-response element in VEGF-A promoter region. Thus, by the synchronized activation of a membrane receptor GRP120 and a nuclear receptor PPARγ, EPA enhances VEGF-A production in adipocytes.

Alpha-lipoic acid affects the oxidative stress in various brain structures in mice with methionine and choline deficiency

Deficiency in methionine or choline can induce oxidative stress in various organs such as liver, kidney, heart, and brain. This study was to examine the effects of alpha-lipoic acid (LA) on oxidative stress induced by methionine and choline deficiency (MCD) in several brain structures. Male mice C57BL/6 (n = 28) were divided into four groups: (1) control - continuously fed with standard chow; (2) LA - fed with standard chow and receiving LA; (3) MCD2 - fed with MCD diet for two weeks, and (4) MCD2+LA - fed with MCD diet for two weeks and receiving LA (100 mg/kg/day intraperitonealy [i.p.]). Brain tissue (cortex, hypothalamus, striatum and hippocampus) was taken for determination of oxidative stress parameters. MCD diet induced a significant increase in malondialdehyde and NOx concentration in all brain regions, while LA restored their content to normal values. Similar to this, in MCD2 group, activity of total SOD, MnSOD, and Cu/ZnSOD was reduced by MCD diet, while LA treatment improved their activities in all brain structures. Besides, in MCD2 group a decrease in catalase activity in cortex and GSH content in hypothalamus was evident, while LA treatment induced an increase in catalase activity in cortex and striatum and GSH content in hypothalamus. LA treatment can significantly reduce lipid peroxidation and nitrosative stress, caused by MCD diet, in all brain regions by restoring antioxidant enzymes activities, predominantly total SOD, MnSOD, and Cu/ZnSOD, and to a lesser extent by modulating catalase activity and GSH content. LA supplementation may be used in order to prevent brain oxidative injury induced by methionine and choline deficiency.

Photoactivation of Dok1/ERK/PPARγ signaling axis inhibits excessive lipolysis in insulin-resistant adipocytes

Insulin resistance is a hallmark of the metabolic syndrome and type 2 diabetes. Increased plasma FFA level is an important cause of obesity-associated insulin resistance. Over-activated ERK is closely related with FFA release from adipose tissues in patients with type 2 diabetes. Nevertheless, there are no effective strategies to lower plasma FFA level. Low-power laser irradiation (LPLI) has been reported to regulate multiple biological processes. However, whether LPLI could ameliorate metabolic disorders and the molecular mechanisms involved remain unknown. In this study, we first demonstrated that LPLI suppresses excessive lipolysis of insulin-resistant adipocytes by activating tyrosine kinases-1(Dok1)/ERK/PPARγ pathway. Our data showed that LPLI inhibits ERK phosphorylation through the activation of Dok1, resulting in decreased phospho-PPARγ level. Non-phosphorylated PPARγ maintains in nucleus to promote the expression of adipogenic genes, reversing excessive lipolysis in insulin-resistant adipocytes. In summary, the present research highlights the important roles of Dok1/ERK/PPARγ pathway in lowering FFA release from adipocytes, and our research extends the knowledge of the biological effects induced by LPLI.

Activation of AMPKα2 in adipocytes is essential for nicotine-induced insulin resistance in vivo

Cigarette smoking promotes body weight reduction in humans while paradoxically also promoting insulin resistance (IR) and hyperinsulinemia. However, the mechanisms behind these effects are unclear. Here we show that nicotine, a major constituent of cigarette smoke, selectively activates AMP-activated protein kinase α2 (AMPKα2) in adipocytes, which in turn phosphorylates MAP kinase phosphatase-1 (MKP1) at serine 334, initiating its proteasome-dependent degradation. The nicotine-dependent reduction of MKP1 induces the aberrant activation of both p38 mitogen-activated protein kinase and c-Jun N-terminal kinase, leading to increased phosphorylation of insulin receptor substrate 1 (IRS1) at serine 307. Phosphorylation of IRS1 leads to its degradation, protein kinase B inhibition, and the loss of insulin-mediated inhibition of lipolysis. Consequently, nicotine increases lipolysis, which results in body weight reduction, but this increase also elevates the levels of circulating free fatty acids and thus causes IR in insulin-sensitive tissues. These results establish AMPKα2 as an essential mediator of nicotine-induced whole-body IR in spite of reductions in adiposity.

Effects of α-lipoic acid and eicosapentaenoic acid in overweight and obese women during weight loss

OBJECTIVE

To evaluate the potential body weight-lowering effects of dietary supplementation with eicosapentaenoic acid (EPA) and α-lipoic acid separately or combined in healthy overweight/obese women following a hypocaloric diet.

METHODS

This is a short-term double-blind placebo-controlled study with parallel design that lasted 10 weeks. Of the randomized participants, 97 women received the allocated treatment [Control, EPA (1.3 g/d), α-lipoic acid (0.3 g/d), and EPA+α-lipoic acid (1.3 g/d+0.3 g/d)], and 77 volunteers completed the study. All groups followed an energy-restricted diet of 30% less than total energy expenditure. Body weight, anthropometric measurements, body composition, resting energy expenditure, blood pressure, serum glucose, and insulin and lipid profile, as well as leptin and ghrelin levels, were assessed at baseline and after nutritional intervention.

RESULTS

Body weight loss was significantly higher (P<0.05) in those groups supplemented with α-lipoic acid. EPA supplementation significantly attenuated (P<0.001) the decrease in leptin levels that occurs during weight loss. Body weight loss improved lipid and glucose metabolism parameters but without significant differences between groups.

CONCLUSIONS

The intervention suggests that α-lipoic acid supplementation alone or in combination with EPA may help to promote body weight loss in healthy overweight/obese women following energy-restricted diets.

EPA-enriched phospholipids ameliorate cancer-associated cachexia mainly via inhibiting lipolysis

EPA-PL rescues the cancer-associated cachexia via inhibiting lipolysis.

11β-Hydroxysteroid dehydrogenase type 1 shRNA ameliorates glucocorticoid-induced insulin resistance and lipolysis in mouse abdominal adipose tissue

Long-term glucocorticoid exposure increases the risk for developing type 2 diabetes. Prereceptor activation of glucocorticoid availability in target tissue by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) coupled with hexose-6-phosphate dehydrogenase (H6PDH) is an important mediator of the metabolic syndrome. We explored whether the tissue-specific modulation of 11β-HSD1 and H6PDH in adipose tissue mediates glucocorticoid-induced insulin resistance and lipolysis and analyzed the effects of 11β-HSD1 inhibition on the key lipid metabolism genes and insulin-signaling cascade. We observed that corticosterone (CORT) treatment increased expression of 11β-HSD1 and H6PDH and induced lipase HSL and ATGL with suppression of p-Thr(172) AMPK in adipose tissue of C57BL/6J mice. In contrast, CORT induced adipose insulin resistance, as reflected by a marked decrease in IR and IRS-1 gene expression with a reduction in p-Thr(308) Akt/PKB. Furthermore, 11β-HSD1 shRNA attenuated CORT-induced 11β-HSD1 and lipase expression and improved insulin sensitivity with a concomitant stimulation of pThr(308) Akt/PKB and p-Thr(172) AMPK within adipose tissue. Addition of CORT to 3T3-L1 adipocytes enhanced 11β-HSD1 and H6PDH and impaired p-Thr(308) Akt/PKB, leading to lipolysis. Knockdown of 11β-HSD1 by shRNA attenuated CORT-induced lipolysis and reversed CORT-mediated inhibition of pThr(172) AMPK, which was accompanied by a parallel improvement of insulin signaling response in these cells. These findings suggest that elevated adipose 11β-HSD1 expression may contribute to glucocorticoid-induced insulin resistance and adipolysis.

α-Lipoic acid treatment increases mitochondrial biogenesis and promotes beige adipose features in subcutaneous adipocytes from overweight/obese subjects

α-Lipoic acid (α-Lip) is a natural occurring antioxidant with beneficial anti-obesity properties. The aim of this study was to investigate the putative effects of α-Lip on mitochondrial biogenesis and the acquirement of brown-like characteristics by subcutaneous adipocytes from overweight/obese subjects. Thus, fully differentiated human subcutaneous adipocytes were treated with α-Lip (100 and 250μM) for 24h for studies on mitochondrial content and morphology, mitochondrial DNA (mtDNA) copy number, fatty acid oxidation enzymes and brown/beige characteristic genes. The involvement of the Sirtuin1/Peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (SIRT1/PGC-1α) pathway was also evaluated. Our results showed that α-Lip increased mitochondrial content in cultured human adipocytes as revealed by electron microscopy and by mitotracker green labeling. Moreover, an enhancement in mtDNA content was observed. This increase was accompanied by an up-regulation of SIRT1 protein levels, a decrease in PGC-1α acetylation and up-regulation of Nuclear respiratory factor 1 (Nrf1) and Mitochondrial transcription factor (Tfam) transcription factors. Enhanced oxygen consumption and fatty acid oxidation enzymes, Carnitine palmitoyl transferase 1 and Acyl-coenzyme A oxidase (CPT-1 and ACOX) were also observed. Mitochondria from α-Lip-treated adipocytes exhibited some morphological characteristics of brown mitochondria, and α-Lip also induced up-regulation of some brown/beige adipocytes markers such as cell death-inducing DFFA-like effector a (Cidea) and T-box 1 (Tbx1). Moreover, α-Lip up-regulated PR domain containing 16 (Prdm16) mRNA levels in treated adipocytes. Therefore, our study suggests the ability of α-Lip to promote mitochondrial biogenesis and brown-like remodeling in cultured white subcutaneous adipocytes from overweight/obese donors.

Cardiotrophin-1 stimulates lipolysis through the regulation of main adipose tissue lipases

Cardiotrophin-1 (CT-1) is a cytokine with antiobesity properties and with a role in lipid metabolism regulation and adipose tissue function. The aim of this study was to analyze the molecular mechanisms involved in the lipolytic actions of CT-1 in adipocytes. Recombinant CT-1 (rCT-1) effects on the main proteins and signaling pathways involved in the regulation of lipolysis were evaluated in 3T3-L1 adipocytes and in mice. rCT-1 treatment stimulated basal glycerol release in a concentration- and time-dependent manner in 3T3-L1 adipocytes. rCT-1 (20 ng/ml for 24 h) raised cAMP levels, and in parallel increased protein kinase (PK)A-mediated phosphorylation of perilipin and hormone sensitive lipase (HSL) at Ser660. siRNA knock-down of HSL or PKA, as well as pretreatment with the PKA inhibitor H89, blunted the CT-1-induced lipolysis, suggesting that the lipolytic action of CT-1 in adipocytes is mainly mediated by activation of HSL through the PKA pathway. In ob/ob mice, acute rCT-1 treatment also promoted PKA-mediated phosphorylation of perilipin and HSL at Ser660 and Ser563, and increased adipose triglyceride lipase (desnutrin) content in adipose tissue. These results showed that the ability of CT-1 to regulate the activity of the main lipases underlies the lipolytic action of this cytokine in vitro and in vivo, and could contribute to CT-1 antiobesity effects.

α-lipoic acid reduces fatty acid esterification and lipogenesis in adipocytes from overweight/obese subjects

OBJECTIVE

α-Lipoic acid (α-LA) is a natural occurring antioxidant with beneficial effects on obesity. The aim of this study was to investigate the putative effects of α-LA on triglyceride accumulation and lipogenesis in subcutaneous adipocytes from overweight/obese subjects and to determine the potential mechanisms involved.

METHODS

Fully differentiated human subcutaneous adipocytes were treated with α-LA (100 and 250 µM) during 24 h for studying triglyceride content, de novo lipogenesis, and levels of key lipogenic enzymes. The involvement of AMP-activated protein kinase (AMPK) activation was also evaluated.

RESULTS

α-LA down-regulated triglyceride content by inhibiting fatty acid esterification and de novo lipogenesis. These effects were mediated by reduction in fatty acid synthase (FAS), stearoyl-coenzyme A desaturase 1, and diacylglycerol O-acyltransferase 1 protein levels. Interestingly, α-LA increased AMPK and acetyl CoA carboxylase phosphorylation, while the presence of the AMPK inhibitor Compound C reversed the inhibition observed on FAS protein levels.

CONCLUSIONS

α-LA down-regulates key lipogenic enzymes, inhibiting lipogenesis and reducing triglyceride accumulation through the activation of AMPK signaling pathway in human subcutaneous adipocytes from overweight/obese subjects.

Nutritional factors affecting abdominal fat deposition in poultry: a review

The major goals of the poultry industry are to increase the carcass yield and to reduce carcass fatness, mainly the abdominal fat pad. The increase in poultry meat consumption has guided the selection process toward fast-growing broilers with a reduced feed conversion ratio. Intensive selection has led to great improvements in economic traits such as body weight gain, feed efficiency, and breast yield to meet the demands of consumers, but modern commercial chickens exhibit excessive fat accumulation in the abdomen area. However, dietary composition and feeding strategies may offer practical and efficient solutions for reducing body fat deposition in modern poultry strains. Thus, the regulation of lipid metabolism to reduce the abdominal fat content based on dietary composition and feeding strategy, as well as elucidating their effects on the key enzymes associated with lipid metabolism, could facilitate the production of lean meat and help to understand the fat-lowering effects of diet and different feeding strategies.

Illudins C2 and C3 stimulate lipolysis in 3T3-L1 adipocytes and suppress adipogenesis in 3T3-L1 preadipocytes

The secondary metabolites illudins C2 (1) and C3 (2), obtained from the culture broth of Coprinus atramentarius, have been shown to possess antimicrobial activity. In the present study, we discovered novel biological activities of 1 and 2 in lipolysis of differentiated 3T3-L1 adipocytes and adipogenesis of 3T3-L1 preadipocytes. Compounds 1 and 2 exhibit a dose-dependent increase in glycerol release and thereby reduce intracellular lipid accumulation. The stimulatory effects of 1 and 2 on lipolysis are prevented by cAMP-dependent protein kinase (PKA) and extracellular signal-regulated kinase (ERK) inhibitors. Compounds 1 and 2 down-regulated perilipin and also affected the mRNA and protein levels of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL). However, 1 and 2 treatment leads to a significant increase in PKA-mediated phosphorylation of HSL at S563 and S660. In addition, 1 and 2 treatment in 3T3-L1 preadipocytes induces down-regulation of the critical transcription factors, CCAAT/enhancer binding protein α and β (C/EBPα and C/EBPβ), and peroxisome proliferator activated receptor γ (PPARγ), which are required for adipogenesis, and accordingly inhibits adipogenesis. These results suggest that 1 and 2 might be useful for treating obesity due to their modulatory effects on fat by affecting adipocyte differentiation and fat mobilization.

The therapy of insulin resistance in other diseases besides type 2 diabetes

Insulin resistance is a clinical condition shared by many diseases besides type 2 diabetes (T2DM) such as obesity, polycystic ovary syndrome (PCOS) and non-alcoholic fatty liver disease (NAFLD). Experimental evidence, produced over the years, suggests that metformin has many benefits in the treatment of these diseases. Metformin is a first-line drug in the treatment of overweight and obese type 2 diabetic patients, offering a selective pathophysiological approach by its effect on insulin resistance. Moreover, a number of studies have established the favorable effect of metformin on body weight, not only when evaluating BMI, but also if body mass composition is considered, through the reduction of fat mass. In addition, it reduces insulin resistance, hyperinsulinemia, lipid parameters, arterial hypertension and endothelial dysfunction. In particular, a new formulation of metformin extended-release (ER) is now available with different formulation in different countries. Metformin ER delivers the active drug through hydrated polymers which expand safe uptake of fluid, prolonging gastric transit and delaying drug absorption in the upper gastrointestinal tract. In addition, Metformin ER causes a small, but statistically significant decrease in BMI, when added to a lifestyle intervention program in obese adolescents. Because of the suggested benefits for the treatment of insulin resistance in many clinical conditions, besides type 2 diabetes, the prospective exists that more indications for metformin treatment are becoming a reality.

Direct and indirect antioxidant properties of α-lipoic acid and therapeutic potential

Diabetes has emerged as a major threat to worldwide health. The exact mechanisms underlying the disease are unknown; however, there is growing evidence that the excess generation of reactive oxygen species (ROS) associated with hyperglycemia, causes oxidative stress in a variety of tissues. In this context, various natural compounds with pleiotropic actions like α-lipoic acid (LA) are of interest, especially in metabolic diseases such as diabetes. LA, either as a dietary supplement or a therapeutic agent, modulates redox potential because of its ability to match the redox status between different subcellular compartments as well as extracellularly. Both the oxidized (disulfide) and reduced (di-thiol: dihydro-lipoic acid, DHLA) forms of LA show antioxidant properties. LA exerts antioxidant effects in biological systems through ROS quenching but also via an action on transition metal chelation. Dietary supplementation with LA has been successfully employed in a variety of in vivo models of disease associated with an imbalance of redox status: diabetes and cardiovascular diseases. The complex and intimate association between increased oxidative stress and increased inflammation in related disorders such as diabetes, makes it difficult to establish the temporal sequence of the relationship.

Lipoic acid inhibits adiponectin production in 3T3-L1 adipocytes

Lipoic acid (LA) is a naturally occurring compound with antioxidant properties. Recent attention has been focused on the potential beneficial effects of LA on obesity and related metabolic disorders. Dietary supplementation with LA prevents insulin resistance and upregulates adiponectin, an insulin-sensitizing adipokine, in obese rodents. The aim of this study was to investigate the direct effects of LA on adiponectin production in cultured adipocytes, as well as the potential signaling pathways involved. For this purpose, fully differentiated 3T3-L1 adipocytes were treated with LA (1-500 μM) during 24 h. The amount of adiponectin secreted to media was detected by ELISA, while adiponectin mRNA expression was determined by RT-PCR. Treatment with LA induced a dose-dependent inhibition on adiponectin gene expression and protein secretion. Pretreatment with the PI3K inhibitor LY294002 inhibited adiponectin secretion and mRNA levels, and significantly potentiated the inhibitory effect of LA on adiponectin secretion. The AMPK activator AICAR also reduced adiponectin production, but surprisingly, it was able to reverse the LA-induced inhibition of adiponectin. The JNK inhibitor SP600125 and the MAPK inhibitor PD98059 did not modify the inhibitory effect of LA on adiponectin. In conclusion, our results revealed that LA reduces adiponectin secretion in 3T3-L1 adipocytes, which contrasts with the stimulation of adiponectin described after in vivo supplementation with LA, suggesting that an indirect mechanism or some in vivo metabolic processing is involved.