CIDE Family-Mediated Unique Lipid Droplet Morphology in White Adipose Tissue and Brown Adipose Tissue Determines the Adipocyte Energy Metabolism

Detraining after short-term exercise induces hyperphagia and obesity with fatty liver and brown adipose tissue whitening in young male OLETF rats

This study examined the effects of exercise and detraining at a young age on fat accumulation in various organs. Four-week-old male Otsuka Long-Evans Tokushima Fatty (OLETF) rats were assigned to either the non-exercise sedentary (OLETF Sed) or exercise groups. The exercise group was subdivided into two groups: exercise between 4 and 12 weeks of age (OLETF Ex) and exercise between 4 and 6 weeks of age followed by non-exercise between 6 and 12 weeks of age (OLETF DT). Body weight was significantly lower in the OLETF Ex group than in the OLETF Sed group at 12 weeks of age. Fat accumulation in the epididymal white adipose tissue, liver, and brown adipose tissue was suppressed in the OLETF Ex group. During the exercise period, body weight and food intake in the OLETF DT group were significantly lower than those in the OLETF Sed group. However, food intake was significantly higher in the OLETF DT group than in the OLETF Sed group after exercise cessation, resulting in extreme obesity with fatty liver and brown adipose tissue whitening. Detraining after early-onset exercise promotes hyperphagia, causing extreme obesity. Overeating should be avoided during detraining periods in cases of exercise cessation at a young age.

Mitochondria isolated from lipid droplets of white adipose tissue reveal functional differences based on lipid droplet size

Recent studies in brown adipose tissue (BAT) described a unique subpopulation of mitochondria bound to lipid droplets (LDs), which were termed PeriDroplet Mitochondria (PDM). PDM can be isolated from BAT by differential centrifugation and salt washes. Contrary to BAT, this approach has so far not led to the successful isolation of PDM from white adipose tissue (WAT). Here, we developed a method to isolate PDM from WAT with high yield and purity by an optimized proteolytic treatment that preserves the respiratory function of mitochondria. Using this approach, we show that, contrary to BAT, WAT PDM have lower respiratory and ATP synthesis capacities compared with WAT cytoplasmic mitochondria (CM). Furthermore, by isolating PDM from LDs of different sizes, we found a negative correlation between LD size and the respiratory capacity of their PDM in WAT. Thus, our new isolation method reveals tissue-specific characteristics of PDM and establishes the existence of heterogeneity in PDM function determined by LD size.

Effects of allicin on human Simpson-Golabi-Behmel syndrome cells in mediating browning phenotype

INTRODUCTION

Obesity is a major health problem because it is associated with increased risk of cardiovascular disease, diabetes, hypertension, and some cancers. Strategies to prevent or reduce obesity focus mainly on the possible effects of natural compounds that can induce a phenotype of browning adipocytes capable of releasing energy in the form of heat. Allicin, a bioactive component of garlic with numerous pharmacological functions, is known to stimulate energy metabolism.

METHODS

In the present study, the effects of allicin on human Simpson-Golabi-Behmel Syndrome (SGBS) cells were investigated by quantifying the dynamics of lipid droplets (LDs) and mitochondria, as well as transcriptomic changes after six days of differentiation.

RESULTS

Allicin significantly promoted the reduction in the surface area and size of LDs, leading to the formation of multilocular adipocytes, which was confirmed by the upregulation of genes related to lipolysis. The increase in the number and decrease in the mean aspect ratio of mitochondria in allicin-treated cells indicate a shift in mitochondrial dynamics toward fission. The structural results are confirmed by transcriptomic analysis showing a significant arrangement of gene expression associated with beige adipocytes, in particular increased expression of T-box transcription factor 1 (TBX1), uncoupling protein 1 (UCP1), PPARG coactivator 1 alpha (PPARGC1A), peroxisome proliferator-activated receptor alpha (PPARA), and OXPHOS-related genes. The most promising targets are nuclear genes such as retinoid X receptor alpha (RXRA), retinoid X receptor gamma (RXRG), nuclear receptor subfamily 1 group H member 3 (NR1H3), nuclear receptor subfamily 1 group H member 4 (NR1H4), PPARA, and oestrogen receptor 1 (ESR1).

DISCUSSION

Transcriptomic data and the network pharmacology-based approach revealed that genes and potential targets of allicin are involved in ligand-activated transcription factor activity, intracellular receptor signalling, regulation of cold-induced thermogenesis, and positive regulation of lipid metabolism. The present study highlights the potential role of allicin in triggering browning in human SGBS cells by affecting the LD dynamics, mitochondrial morphology, and expression of brown marker genes. Understanding the potential targets through which allicin promotes this effect may reveal the underlying signalling pathways and support these findings.

CLSTN3β enforces adipocyte multilocularity to facilitate lipid utilization

Multilocular adipocytes are a hallmark of thermogenic adipose tissue1,2, but the factors that enforce this cellular phenotype are largely unknown. Here, we show that an adipocyte-selective product of the Clstn3 locus (CLSTN3β) present in only placental mammals facilitates the efficient use of stored triglyceride by limiting lipid droplet (LD) expansion. CLSTN3β is an integral endoplasmic reticulum (ER) membrane protein that localizes to ER-LD contact sites through a conserved hairpin-like domain. Mice lacking CLSTN3β have abnormal LD morphology and altered substrate use in brown adipose tissue, and are more susceptible to cold-induced hypothermia despite having no defect in adrenergic signalling. Conversely, forced expression of CLSTN3β is sufficient to enforce a multilocular LD phenotype in cultured cells and adipose tissue. CLSTN3β associates with cell death-inducing DFFA-like effector proteins and impairs their ability to transfer lipid between LDs, thereby restricting LD fusion and expansion. Functionally, increased LD surface area in CLSTN3β-expressing adipocytes promotes engagement of the lipolytic machinery and facilitates fatty acid oxidation. In human fat, CLSTN3B is a selective marker of multilocular adipocytes. These findings define a molecular mechanism that regulates LD form and function to facilitate lipid utilization in thermogenic adipocytes.

Cordyceps guangdongensis lipid-lowering formula alleviates fat and lipid accumulation by modulating gut microbiota and short-chain fatty acids in high-fat diet mice

Obesity has caused serious health and economic problems in the world. Cordyceps guangdongensis is a high-value macrofungus with broad application potential in the food and bio-medicine industry. This current study aimed to estimate the role of C. guangdongensis lipid-lowering compound formula (CGLC) in regulating fat and lipid accumulation, gut microbiota balance, short-chain fatty acid (SCFA) contents, and expression levels of genes involved in fat and lipid metabolism in high-fat diet (HFD) mice. The results showed that CGLC intervention markedly reduced body weights and fat accumulation in HFD mice, improved glucose tolerance and blood lipid levels, and decreased lipid droplet accumulation and fat vacuole levels in the liver. CGLC decreased the ratio of Firmicutes and Bacteroidetes and increased the relative abundances of Bacteroides (B. acidifaciens) and Bifidobacterium (B. pseudolongum). In addition, CGLC treatment significantly promoted the production of SCFAs and regulated the relative expression levels of genes involved in fat and lipid metabolism in liver. Association analysis showed that several species of Bacteroides and most of SCFAs were significantly associated with serum lipid indicators. These results suggested that CGLC is a novel candidate formulation for treating obesity and non-alcohol fatty liver by regulating gut microbiota, SCFAs, and genes involved in fat and lipid metabolism.

The emerging roles of PHOSPHO1 and its regulated phospholipid homeostasis in metabolic disorders

Emerging evidence suggests that phosphoethanolamine/phosphocholine phosphatase 1 (PHOSPHO1), a specific phosphoethanolamine and phosphocholine phosphatase, is involved in energy metabolism. In this review, we describe the structure and regulation of PHOSPHO1, as well as current knowledge about the role of PHOSPHO1 and its related phospholipid metabolites in regulating energy metabolism. We also examine mechanistic evidence of PHOSPHO1- and phospholipid-mediated regulation of mitochondrial and lipid droplets functions in the context of metabolic homeostasis, which could be potentially targeted for treating metabolic disorders.

Regulatory networks determining substrate utilization in brown adipocytes

Brown adipose tissue (BAT) is often considered as a sink for nutrients to generate heat. However, when the complex hormonal and nervous inputs and intracellular signaling networks regulating substrate utilization are considered, BAT appears much more as a tightly controlled rheostat, regulating body temperature and balancing circulating nutrient levels. Here we provide an overview of key regulatory circuits, including the diurnal rhythm, determining glucose, fatty acid, and amino acid utilization and the interdependency of these nutrients in thermogenesis. Moreover, we discuss additional factors mediating sympathetic BAT activation beyond β-adrenergic signaling and the limitations of glucose-based BAT activity measurements to foster a better understanding and interpretation of BAT activity data.

Tanshinone 1 prevents high fat diet-induced obesity through activation of brown adipocytes and induction of browning in white adipocytes

AIM

Increasing brown adipocytes activity and inducting browning of white adipocytes are potential therapeutic targets for the treatment of obesity. In the present study, we investigated the effects of Tanshinone 1 (Tan 1), a major compound from Salvia miltiorrhiza Bunge, on the activation of brown adipocytes and browning of white adipocytes in vivo and in vitro.

MATERIALS AND METHODS

Expression of genes associated with brown adipocyte function including thermogenesis, mitochondria biogenesis and fatty acid oxidation was examined in brown adipose tissue (BAT) and white adipose tissue (WAT) of high fat diet (HFD)-fed obese mice administrated with Tan 1 or in immortalized brown adipocytes (iBAs) and 3T3-L1 adipocytes treated with Tan 1. Mitochondria DNA (mtDNA) content, lipolysis and phosphorylated AMP-activated protein kinase (AMPK) were further assessed in Tan 1 treated-iBAs and 3T3-L1 adipocytes.

KEY FINDINGS

The administration of Tan 1 protected against HFD-induced obesity in mice, which was associated with enhanced expression of brown adipocyte function-related genes in BAT and WAT. Tan 1 treatment also upregulated brown adipocyte function-related genes in iBA and induced beige adipocytes genes in 3T3-L1 adipocytes, resulting in increased mtDNA content and lipolysis. Tan 1 activated AMPK in BAT and WAT of HFD-fed obese mice as well as in iBAs and 3T3-L1 adipocytes. Inhibition of AMPK by compound C prevented Tan 1-induced expression of beige adipocytes genes.

SIGNIFICANCE

These results indicate that Tan 1 activates brown adipocytes and induces browning of white adipocytes, which may contribute to anti-obesity activity of Tan 1.

Crude Polysaccharide Extracted From Moringa oleifera Leaves Prevents Obesity in Association With Modulating Gut Microbiota in High-Fat Diet-Fed Mice

Moringa oleifera is a commonly used plant with high nutritional and medicinal values. M. oleifera leaves are considered a new food resource in China. However, the biological activities of M. oleifera polysaccharides (MOP) in regulating gut microbiota and alleviating obesity remain obscure. In the present study, we prepared the MOP and evaluated its effects on obesity and gut microbiota in high-fat diet (HFD)-induced C57BL/6J mice. The experimental mice were supplemented with a normal chow diet (NCD group), a high-fat diet (HFD group), and HFD along with MOP at a different dose of 100, 200, and 400 mg/kg/d, respectively. Physiological, histological, biochemical parameters, genes related to lipid metabolism, and gut microbiota composition were compared among five experimental groups. The results showed that MOP supplementation effectively prevented weight gain and lipid accumulation induced by HFD, ameliorated blood lipid levels and insulin resistance, alleviated the secretion of pro-inflammatory cytokines, and regulated the expression of genes related to lipid metabolism and bile acid metabolism. In addition, MOP positively reshaped the gut microbiota composition, significantly increasing the abundance of Bacteroides, norank_f_Ruminococcaceae, and Oscillibacter, while decreasing the relative abundance of Blautia, Alistipes, and Tyzzerella, which are closely associated with obesity. These results demonstrated that MOP supplementation has a protective effect against HFD-induced obesity in mice, which was associated with reshaping the gut microbiota. To the best of our knowledge, this is the first report on the potential of MOP to prevent obesity and modulating gut microbiota, which suggests that MOP can be used as a potential prebiotic.

Cinnamaldehyde treatment during adolescence improves white and brown adipose tissue metabolism in a male rat model of early obesity

Early obesity is a serious health problem and nutritional therapeutic strategies during young age may improve health outcomes throughout life. Cinnamaldehyde, major component of cinnamon, exhibits several beneficial metabolic effects....

Zeaxanthin Remodels Cytoplasmic Lipid Droplets via β3-Adrenergic Receptor Signaling and Enhances Perilipin 5-Mediated Lipid Droplet–Mitochondria Interactions in Adipocytes

Cytoplasmic lipid droplets (LDs), which are remarkably dynamic, neutral lipid storage organelles, play fundamental roles in lipid metabolism and energy homeostasis. Both the dynamic remodeling of LDs and LD–mitochondria interactions...

Lipoxin A4 promotes adipogenic differentiation and browning of mouse embryonic fibroblasts

Recently, it has been irrefutably discovered that brown adipocytes dissipate energy as heat and protect against obesity. Researchers make great efforts to explore approaches for its activation. Lipoxin A4 (LXA4) has been proven to reverse adipose tissue inflammation and improve insulin resistance, but its function on brown adipocyte differentiation has been poorly understood, which therefore to be investigated in the present study. Mouse embryonic fibroblasts (MEFs) were induced and differentiated to model brown adipocytes, and treated with LXA4 at 0, 1, 5, and 10 nM for 0-14 d. Afterwards, Oil Red O staining detected lipid droplets. In differentiated MEFs with or without LXA4 (10 nM) treatment, western blot and quantitative real-time polymerase chain reaction (qRT-PCR) assessed adipocyte browning marker uncoupling protein 1 (UCP-1), and brown adipogenesis markers peroxisome proliferator-activated receptor gamma (PPARγ), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), cyclooxygenase-2 (COX-2), and positive regulation domain containing 16 (PRDM16) as well as lipogenic genes of stearoyl-CoA desaturase 1 (SCD1), fatty acid synthase (FASN), glucose transporter type 4 (GLUT4), and carbohydrate response element binding protein (ChREBP). The induced differentiation of MEFs toward brown adipocytes was successful. LXA4 promoted intracellular accumulation of lipid droplets of induced cells and increased UCP-1 expression in a dose- or time-dependent manner. Under the administration of LXA4, brown adipogenesis markers and lipogenic genes were further upregulated. LXA4 made a contribution to induce differentiation of MEFs to brown adipocytes, which could be regarded a new drug target for obesity management.

High-Glucose and Free Fatty Acid-Induced Adipocytes Generate Increasing of HMGB1 and Reduced GLUT4 Expression

Background High-mobility group box 1 protein (HMGB1) is released from necrotic adipocytes into the extracellular milieu as an inflammatory alarmin in obesity. Although the impact of excess nutrient on adipocytes is well known, it is not clear how specific its component drive cell-size and damaged of adipocytes, and how this relates to the risk of insulin resistance. Objectives The aim of this study was to determine HMGB1 level in adipocytes cultures after high glucose and/or FFA exposures and to assess GLUT4 expression. We determined cellular features of adipocytes that correlates to HMGB1 released and insulin resistance. Methods Differentiated adipocytes were exposed to high glucose and/or FFAs for 7 days. ELISA was performed on supernatant to assess the HMGB1 level. Total GLUT4 expression were quantified by immunofluorescense. Results High glucose and FFA-exposed cells have significant increase of HMGB1 level with decreased of cell size and necrotic adipocytes features.  The total GLUT4 were reduced in HG-cells (p <0,045), but not in FFA cells. Hypertrophic adipocytes (p <0.05) and slight decrease of GLUT4 expression were showed on HG+FFA exposures with no increase of HMGB1 level. There was a significant correlation between cell size and HMGB1 level (R -0,637, p < 0.026) Conclusion The expression level studies between high glucose, FFA, and a combination of both on adipocytes results strongly suggest that high glucose is more damaging to adipocyte compared to FFA. Nevertheless, the combination of the two causes adipocyte dysfunction with general features of adipose tissue in obesity, suggested it can be used as a hypertrophic adipocytes model to study obesity in vitro.

Dietary Iron Deficiency Modulates Adipocyte Iron Homeostasis, Adaptive Thermogenesis, and Obesity in C57BL/6 Mice

BACKGROUND

Adaptive thermogenesis is an iron-demanding pathway, significantly contributing to whole-body energy expenditure. However, the effects of iron-deficient diets on adaptive thermogenesis and obesity remain unknown.

OBJECTIVES

We aimed to determine the impact of dietary iron deficiency on iron homeostasis in adipocytes, adaptive thermogenic capacity, and metabolic consequences in obesity.

METHODS

C57BL/6 male mice were assigned to either the iron-adequate (IA, 35 ppm) or the iron-deficient group (ID, 3 ppm) at weaning. Upon 8 wk of age, both IA and ID groups received an isocaloric high-fat diet (45% kcal from fat) for 10 wk, maintaining the same iron content. Mice (n = 8) were used to determine the iron status at the systemic and tissue levels and lipid metabolism and inflammatory signaling in adipose tissue. The same mice were used to evaluate cold tolerance (4°C) for 3 h. For assessing adaptive thermogenesis, mice (n = 5) received an intraperitoneal injection of β3-adrenoceptor agonist CL316243 (CL) for 5 d.

RESULTS

Compared with the IA group, the ID group had nonanemic iron deficiency, lower serum ferritin (42.8%, P < 0.01), and greater weight gain (8.67%, P < 0.05) and insulin resistance (159%, P < 0.01), partly due to reduced AMP-activated protein kinase activation (61.0%, P < 0.05). Upon cold exposure, the ID group maintained a core body temperature 2°C lower than the IA group. The ID group had lower iron content (47.0%, P < 0.01) in the inguinal adipose tissue (iWAT) than the IA group, which was associated with impaired adaptive thermogenesis. In response to CL, ID mice showed decreased heat production (P < 0.01) and defective upregulation of beige adipocyte-specific markers, including uncoupling protein 1 (41.1%, P < 0.001), transferrin receptor 1 (47.5%, P < 0.001), and mitochondrial respiratory chain complexes (P < 0.05) compared with IA mice.

CONCLUSIONS

Dietary iron deficiency deregulates iron balance in the iWAT and impairs adaptive thermogenesis, thereby escalating the diet-induced weight gain in C57BL/6 mice.

Impaired brown adipose tissue is differentially modulated in insulin-resistant obese wistar and type 2 diabetic Goto-Kakizaki rats

Brown adipose tissue (BAT) is a potential target to treat obesity and diabetes, dissipating energy as heat. Type 2 diabetes (T2D) has been associated with obesogenic diets; however, T2D was also reported in lean individuals to be associated with genetic factors. We aimed to investigate the differences between obese and lean models of insulin resistance (IR) and elucidate the mechanism associated with BAT metabolism and dysfunction in different IR animal models: a genetic model (lean GK rats) and obese models (diet-induced obese Wistar rats) at 8 weeks of age fed a high-carbohydrate (HC), high-fat (HF) diet, or high-fat and high-sugar (HFHS) diet for 8 weeks. At 15 weeks of age, BAT glucose uptake was evaluated by 18F-FDG PET under basal (saline administration) or stimulated condition (CL316,243, a selective β3-AR agonist). After CL316, 243 administrations, GK animals showed decreased glucose uptake compared to HC animals. At 16 weeks of age, the animals were euthanized, and the interscapular BAT was dissected for analysis. Histological analyses showed lower cell density in GK rats and higher adipocyte area compared to all groups, followed by HFHS and HF compared to HC. HFHS showed a decreased batokine FGF21 protein level compared to all groups. However, GK animals showed increased expression of genes involved in fatty acid oxidation (CPT1 and CPT2), BAT metabolism (Sirt1 and Pgc1-α), and obesogenic genes (leptin and PAI-1) but decreased gene expression of glucose transporter 1 (GLUT-1) compared to other groups. Our data suggest impaired BAT function in obese Wistar and GK rats, with evidence of a whitening process in these animals.

Endothelial cell crosstalk improves browning but hinders white adipocyte maturation in 3D engineered adipose tissue

Central to the development of adipose tissue (AT) engineered models is the supporting vasculature. It is a key part of AT function and long-term maintenance, but the crosstalk between adipocytes and endothelial cells is not well understood. Here, we directly co-culture the two cell types at varying ratios in a 3D Type I collagen gel. Constructs were evaluated for adipocyte maturation and function and vascular network organization. Further, these constructs were treated with forskolin, a beta-adrenergic agonist, to stimulate lipolysis and browning. Adipocytes in co-cultures were found to be less mature than an adipocyte-only control, shown by smaller lipid droplets and downregulation of key adipocyte-related genes. The most extensive vascular network formation was found in the 1:1 co-culture, supported by vascular endothelial growth factor (VEGF) upregulation. After forskolin treatment, the presence of endothelial cells was shown to upregulate PPAR coactivator 1 alpha (PGC-1α) and leptin, but not uncoupling protein 1 (UCP1), suggesting a specific crosstalk that enhances early stages of browning.

Uncovering the Role of Glycogen in Brown Adipose Tissue

The presence of glycogen in the brown adipose tissue (BAT) has been described 60 years ago. However, the role of this energetic storage in brown adipocytes has been long time underestimated. We have recently shown that during brown adipocyte differentiation in the embryo, glycogen accumulates and is degraded by glycophagy, a dynamic essential for lipid droplets biogenesis. Recent studies have shown that the storage and degradation of triglycerides in BAT are not essential for the activation of BAT in response to cold exposure in adults, and that glycogen can compensate for their absence. In this review, we report the recent advances related to the importance of glycogen in brown adipocytes.

Metabolism and Metabolic Disorders and the Microbiome: The Intestinal Microbiota Associated With Obesity, Lipid Metabolism, and Metabolic Health-Pathophysiology and Therapeutic Strategies

Changes in the intestinal microbiome have been associated with obesity and type 2 diabetes, in epidemiological studies and studies of the effects of fecal transfer in germ-free mice. We review the mechanisms by which alterations in the intestinal microbiome contribute to development of metabolic diseases, and recent advances, such as the effects of the microbiome on lipid metabolism. Strategies have been developed to modify the intestinal microbiome and reverse metabolic alterations, which might be used as therapies. We discuss approaches that have shown effects in mouse models of obesity and metabolic disorders, and how these might be translated to humans to improve metabolic health.

Ad36 promotes differentiation of hADSCs into brown adipocytes by up-regulating LncRNA ROR

AIMS

This study is to investigate the role of adenovirus type 36 (Ad36) in inducing differentiation of human adipose-derived stem cells (hADSCs) into brown adipocytes.

MAIN METHODS

The hADSCs were induced to differentiate into adipocytes by a cocktail method and Ad36, respectively. They were collected on the 2nd, 4th, 6th, and 8th day, respectively. LncRNA ROR was silenced by siRNA. RT-qPCR and Western-blot were used to detect the mRNA and protein levels. Transmission electron microscopy was used to observe the mitochondria.

KEY FINDINGS

The mRNA and protein expression levels of LncRNA ROR, Cidea, Dio2, Fgf21, Ucp1, Prdm16, Cox5b, Atp5o, Atp6, and Nd2 in the Ad36 induction group were significantly higher than those in the cocktail induction group. The expression levels of Leptin mRNA and protein in the Ad36 induction group were significantly lower than those in the cocktail induction group. After siRNA knockdown of LncRNA ROR, mRNA and protein expression levels of Cidea, Dio2, Fgf21, Ucp1, Prdm16, Cox5b, Atp5o, Atp6 and Nd2 were significantly lower than the control group during the induction of hADSC differentiation into adipocytes by Ad36. Additionally, mitochondria in the Ad36 induction group was increased compared to that in the cocktail induction group.

SIGNIFICANCE

Ad36 may promote the differentiation of hADSCs into brown adipocytes by up-regulating LncRNA ROR.

Effects of 1,25(OH)2 D3 on lipid droplet growth in adipocytes

This study aimed to explore the effects of 1,25(OH)₂ D₃ on lipid droplet (LD) growth in 3T3-L1 adipocytes of hypertrophy model. Cocktail method was used to induce differentiation in 3T3-L1 cells. After 8 days, the cells were modeled by 100, 300, 600, and 900 μM palmitic acid (PA) for 24 hr. The best concentration of modeling was screened by MTT results and triglycerides (TG) content. The model cells were intervened by 1, 10, and 100 nM 1,25(OH)₂ D₃ for 24 hr. Then, the TG content of cells were detected and stained by oil red O. The diameter and quantity of LDs were analyzed. mRNA relative expression levels of genes related to LD (CIDE-a, Fsp27, PLIN-1), upstream response factor (PPAR-α, PPAR-γ, and VDR), and TG metabolism (long chain acyl-CoA synthetase 3, 1-acylglycerol-3-phosphate O-acyltransferase 1, adipose triglyceride lipase, diacylglycerol acyltransferase 1, diacylglycerol acyltransferase 2, glycerol-3-phosphate O-acyltransferase 3, glycerol-3-phosphate O-acyltransferase 4, hormone-sensitive lipase, mannosyl (alpha-1,3-)-glycoprotein beta-1,2-N-acetyl glucosaminyl transferase, phosphatidic acid phosphatase, and uncoupling protein-1) were detected by RT-qPCR. A total of 300 μM PA was selected as the optimum concentration. Compared with model group, 10 and 100 nM 1,25(OH)₂ D₃ decreased the average diameter, increased the quantity of LDs, upregulated PPAR-α and PLIN-1 mRNA expression levels, and downregulated CIDE-a and Fsp27 mRNA expression levels significantly (p < .05). However, 1 nM 1,25(OH)₂ D₃ did not alter LD morphology and TG content. mRNA expression levels of long chain acyl-CoA synthetase 3, 1-acylglycerol-3-phosphate O-acyltransferase 1, diacylglycerol acyltransferase 2, glycerol-3-phosphate O-acyltransferase 3, and glycerol-3-phosphate O-acyltransferase 4 in 10 and 100 nM groups were significantly lower than those in the model group (p < .05); mRNA expression levels of adipose triglyceride lipase, diacylglycerol acyltransferase 1, hormone-sensitive lipase, mannosyl (alpha-1,3-)-glycoprotein beta-1,2-N-acetyl glucosaminyl transferase, phosphatidic acid phosphatase, and uncoupling protein-1 were significantly increased in the 100 nM group (p < .05). The 10 and 100 nM 1,25(OH)₂ D₃ can inhibit LD fusion, promote LD decomposition, reduce LD volume, and inhibit lipogenesis through the PPAR-α signaling pathway.

Fasting and refeeding cycles alter subcutaneous white depot growth dynamics and the morphology of brown adipose tissue in female rats

Intermittent food restriction (IFR) is used mainly for weight loss; however, its effects on adipose tissue are not known when alternating with an obesogenic diet. To demonstrate its effects on morphological dynamics of fat deposits, female Wistar rats were distributed into groups: standard control (ST-C), with commercial diet; DIO control (DIO-C), with a diet that induces obesity (DIO) during the first and last 15 d, replaced by a standard diet for thirty intermediate days; standard restricted (ST-R), with standard diet during the first and last 15 d, with six cycles of IFR at 50 % of ST-C; and DIO restricted (DIO-R), in DIO during the first and last 15 d, with six cycles of IFR at 50 % of DIO-C. At 105 d of life, white adipose tissue (WAT) and brown adipose tissue (BAT) deposits were collected, weighed and histology performed. The DIO-R group showed higher total food intake (DIO-R 10 768·0 (SEM 357·52) kJ/g v. DIO-C 8868·6 (SEM 249·25) kJ/g, P < 0·0001), energy efficiency during RAI (DIO-R 2·26 (SEM 0·05) g/kJ v. DIO-C 0·70 (SEM 0·03) g/kJ, P < 0·0001) and WAT (DIO-R 5·65 (SEM 0·30) g/100 g v. DIO-C 4·56 (SEM 0·30) g/100 g) than their respective control. Furthermore, IFR groups presented hypertrophy of WAT and BAT, as well as fibrosis in BAT. Thus, IFR can establish prospective resistance to weight loss by favouring changes in adipose tissue morphology, increased energy intake and efficiency. Finally, the DIO diet before and after IFR aggravates the damages caused by the restriction.

Metformin alleviates hyperuricaemia-induced serum FFA elevation and insulin resistance by inhibiting adipocyte hypertrophy and reversing suppressed white adipose tissue beiging

Hyperuricaemia (HUA) significantly increases the risk of metabolic syndrome and is strongly associated with the increased prevalence of high serum free fatty acids (FFAs) and insulin resistance. However, the underlying mechanisms are not well established, especially the effect of uric acid (UA) on adipose tissue, a vital organ in regulating whole-body energy and FFA homeostasis. In the present study, we noticed that adipocytes from the white adipose tissue of patients with HUA were hypertrophied and had decreased UCP1 expression. To test the effects of UA on adipose tissue, we built both in vitro and in vivo HUA models and elucidated that a high level of UA could induce hypertrophy of adipocytes, inhibit their hyperplasia and reduce their beige-like characteristics. According to mRNA-sequencing analysis, UA significantly decreased the expression of leptin in adipocytes, which was closely related to fatty acid metabolism and the AMPK signalling pathway, as indicated by KEGG pathway analysis. Moreover, lowering UA using benzbromarone (a uricosuric agent) or metformin-induced activation of AMPK expression significantly attenuated UA-induced FFA metabolism impairment and adipose beiging suppression, which subsequently alleviated serum FFA elevation and insulin resistance in HUA mice. Taken together, these observations confirm that UA is involved in the aetiology of metabolic abnormalities in adipose tissue by regulating leptin-AMPK pathway, and metformin could lessen HUA-induced serum FFA elevation and insulin resistance by improving adipose tissue function via AMPK activation. Therefore, metformin could represent a novel treatment strategy for HUA-related metabolic disorders.

Adropin stimulates proliferation but suppresses differentiation in rat primary brown preadipocytes

Adropin is a peptide hormone encoded by Energy Homeostasis Associated (Enho) gene. Adropin modulates glucose and lipid metabolism, and adiposity. Recently, we found that adropin suppresses differentiation of rodent white preadipocytes into mature fat cells. By contrast, the role of adropin in controlling brown adipogenesis is largely unknown. Therefore, in the present study we evaluated the effects of adropin on proliferation and differentiation of adipocyte precursor cells in rats. Brown adipocyte precursor cells were isolated from male Wistar rats. Cell replication was measured by BrdU incorporation. Gene expression was studied using real time PCR. Protein phosphorylation and production was assessed by Western blot. Lipid accumulation was evaluated by Oil Red O staining. Colorimetric kits were used to evaluate glycerol and free fatty acids release. We report here that adropin stimulates proliferation of brown preadipocytes. Moreover, in brown preadipocytes, adropin suppresses mRNA expression of adipogenic genes (C/ebpα, C/ebpβ, Pgc1α, Pparγ and Prdm16) during differentiation process. In addition, adropin suppresses UCP1 protein production in brown adipocytes. Finally, adropin reduces intracellular lipid content in brown adipocytes. These results indicate that adropin stimulates proliferation of brown preadipocytes and suppresses their differentiation into mature adipocytes.

Comparison of the Effects of Browning-Inducing Capsaicin on Two Murine Adipocyte Models

The increasing prevalence of obesity and its associated comorbidities has gained attention in developing effective treatments and strategies that promote energy expenditure and the conversion of fat from a white to a brite phenotype. Capsaicin, bioactive component of chili peppers and a transient receptor potential channel vanilloid 1 (TRPV1) agonist, has been known to stimulate the process of thermogenesis. In this study, the effects of capsaicin were assessed on two murine cellular models by quantifying the dynamic of lipid droplets (LDs) and the expression of genes involved in adipocyte browning. Present findings demonstrated that treatment with norepinephrine or capsaicin combined with norepinephrine on 3T3-L1 cells and X9 cells significantly promoted the reduction of LDs area surface and size. The transcription of browning related genes such as uncoupling protein 1 (Ucp1), T-box transcription factor 1 (Tbx1), PR domain containing 16 (Prdm16), peroxisome proliferator-activated receptor γ coactivator 1α (Ppargc1a) and cell death-inducing DNA fragmentation factor A-like effector A (Cidea) was up-regulated by chronic capsaicin treatment on differentiated 3T3-L1 cells. Instead, X9 cells were significantly responsive only to the treatment with norepinephrine, used as positive control.

Fat-specific protein 27α inhibits autophagy-dependent lipid droplet breakdown in white adipocytes

AIMS/INTRODUCTION

Fat-specific protein 27 (FSP27) α is the major isoform of FSP27 in white adipose tissue (WAT), and is essential for large unilocular lipid droplet (LD) formation in white adipocytes. In contrast, FSP27β is abundantly expressed in brown adipose tissue (BAT), and plays an important role in small multilocular LD formation. In FSP27 KO mice in which FSP27α and β are both depleted, WAT is characterized by multilocular LD formation, and by increased mitochondrial abundance and energy expenditure, whereas BAT conversely manifests large oligolocular LDs and reduced energy expenditure.

MATERIALS AND METHODS

We investigated the effects of autophagy in WAT and BAT of wild type (WT) and FSP27 knockout (KO) mice. In addition, we examined the effects of FSP27α and FSP27β to the induction of autophagy in COS cells.

RESULTS

Food deprivation induced autophagy in BAT of WT mice, as well as in WAT of FSP27 KO mice, suggesting that enhanced autophagy is characteristic of adipocytes with small multilocular LDs. Pharmacological inhibition of autophagy attenuated the fasting-induced loss of LD area in adipocytes with small multilocular LDs (BAT of WT mice and WAT of FSP27 KO mice), without affecting that in adipocytes with large unilocular or oligolocular LDs (WAT of WT mice or in BAT of FSP27 KO mice). Overexpression of FSP27α inhibited autophagy induction by serum deprivation in COS cells, whereas that of FSP27β had no such effect.

CONCLUSIONS

The present results thus showed that FSP27α inhibits autophagy and might thereby contribute to the energy-storage function of WAT.

Black Raspberry (Rubus coreanus Miquel) Promotes Browning of Preadipocytes and Inguinal White Adipose Tissue in Cold-Induced Mice

The alteration of white adipose tissue (WAT) "browning", a change of white into beige fat, has been considered as a new therapeutic strategy to treat obesity. In this study, we investigated the browning effect of black raspberry (Rubus coreanus Miquel) using in vitro and in vivo models. Black raspberry water extract (BRWE) treatment inhibited lipid accumulation in human mesenchymal stem cells (hMSCs) and zebrafish. To evaluate the thermogenic activity, BRWE was orally administered for 2 weeks, and then, the mice were placed in a 4 °C environment. As a result, BRWE treatment increased rectal temperature and inguinal WAT (iWAT) thermogenesis by inducing the expression of beige fat specific markers such as PR domain zinc-finger protein 16 (PRDM16), uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), and t-box protein 1 (TBX1) in cold-exposed mice. Furthermore, ellagic acid (EA), a constituent of BRWE, markedly promoted beige specific markers: UCP1, PGC1α, TBX1, and nuclear respiratory factor 1 in beige differentiation media (DM)-induced 3T3-L1 adipocytes. Our findings indicate that BRWE can promote beige differentiation/activation, and EA is the active compound responsible for such effect. Thus, we suggest the nature-derived agents BRWE and EA as potential agents for obesity treatment.

Lyophilized Maqui (Aristotelia chilensis) Berry Induces Browning in the Subcutaneous White Adipose Tissue and Ameliorates the Insulin Resistance in High Fat Diet-Induced Obese Mice

Maqui (Aristotelia Chilensis) berry features a unique profile of anthocyanidins that includes high amounts of delphinidin-3-O-sambubioside-5-O-glucoside and delphinidin-3-O-sambubioside and has shown positive effects on fasting glucose and insulin levels in humans and murine models of type 2 diabetes and obesity. The molecular mechanisms underlying the impact of maqui on the onset and development of the obese phenotype and insulin resistance was investigated in high fat diet-induced obese mice supplemented with a lyophilized maqui berry. Maqui-dietary supplemented animals showed better insulin response and decreased weight gain but also a differential expression of genes involved in de novo lipogenesis, fatty acid oxidation, multilocular lipid droplet formation and thermogenesis in subcutaneous white adipose tissue (scWAT). These changes correlated with an increased expression of the carbohydrate response element binding protein b (Chrebpb), the sterol regulatory binding protein 1c (Srebp1c) and Cellular repressor of adenovirus early region 1A-stimulated genes 1 (Creg1) and an improvement in the fibroblast growth factor 21 (FGF21) signaling. Our evidence suggests that maqui dietary supplementation activates the induction of fuel storage and thermogenesis characteristic of a brown-like phenotype in scWAT and counteracts the unhealthy metabolic impact of an HFD. This induction constitutes a putative strategy to prevent/treat diet-induced obesity and its associated comorbidities.

An Ancient Chinese Herbal Decoction Containing Angelicae Sinensis Radix, Astragali Radix, Jujuba Fructus, and Zingiberis Rhizoma Recens Stimulates the Browning Conversion of White Adipocyte in Cultured 3T3-L1 Cells

Background

Abnormal storage of white adipocyte tissue (WAT) is the major factor causing obesity. The promising strategies for obesity treatment are building up the brown adipocyte tissue (BAT) and/or expedite fatty acid catabolism. Traditional Chinese Medicine (TCM) sheds light on preventing obesity. Ginger is one of the most effective herbs for antiobesity by accelerating browning WAT. To fortify the antiobesity effect of ginger, an ancient Chinese herbal decoction composed of four herbs, Angelicae Sinensis Radix (ASR), Astragali Radix (AR), Jujuba Fructus (JF), and Zingiberis Rhizoma Recens (ZRR; ginger), was tested here: this herbal formula was written in AD 1155, named as Danggui Buxue Tang (DBT₁₁₅₅). Therefore, the antiobesity function of this ancient herbal decoction was revealed in vitro by cultured 3T3-L1 cells.

Materials and Method

The lipid accumulation was detected by Oil Red O staining. Furthermore, the underlying working mechanisms of antiobesity functions of DBT₁₁₅₅ were confirmed in 3T3-L1 cells by confocal microscopy, western blot, and RT-PCR.

Results

DBT₁₁₅₅ was able to actuate brown fat-specific gene activations, which included (i) expression of PPARγ, UCP1, and PCG1α and (ii) fatty acid oxidation genes, i.e., CPT1A and HSL. The increase of browning WAT, triggered by DBT₁₁₅₅, was possibly mediated by a Ca²⁺-AMPK signaling pathway, because the application of Ca²⁺ chelator, BAMPTA-AM, reversed the effect.

Conclusion

These findings suggested that the herbal mixture DBT₁₁₅₅ could potentiate the antiobesity functions of ginger, which might have potential therapeutic implications.

Repression of adipose vascular endothelial growth factor reduces obesity through adipose browning

Obesity is the result of excessive energy accumulation and is associated with many diseases. We previously reported that universal repression of vascular endothelial growth factor (VEGF) leads to brown-like adipocyte development in white adipose tissues, and that these mice are resistant to obesity (Lu X et al. Endocrinology 153: 3123-3132, 2012). Using an adipose-specific VEGF repression mouse model (aP2-rtTR-krab^tg/+/VEGF^tetO/tetO), we show that adipose-specific VEGF repression can repeat the previous phenotypes, including adipose browning, increased energy consumption, and reduction in body weight. Expression of brown adipose-associated genes is increased, and white adipose-associated genes are downregulated under VEGF repression. Our study demonstrates that adipose-specific VEGF repression can lead to antiobesity activity through adipose browning and has potential clinical value.

Pyridostigmine protects against cardiomyopathy associated with adipose tissue browning and improvement of vagal activity in high-fat diet rats

Obesity, a major contributor to the development of cardiovascular diseases, is associated with an autonomic imbalance characterized by sympathetic hyperactivity and diminished vagal activity. Vagal activation plays important roles in weight loss and improvement of cardiac function. Pyridostigmine is a reversible acetylcholinesterase inhibitor, but whether it ameliorates cardiac lipid accumulation and cardiac remodeling in rats fed a high-fat diet has not been determined. This study investigated the effects of pyridostigmine on high-fat diet-induced cardiac dysfunction and explored the potential mechanisms. Rats were fed a normal or high-fat diet and treated with pyridostigmine. Vagal discharge was evaluated using the BL-420S system, and cardiac function by echocardiograms. Lipid deposition and cardiac remodeling were determined histologically. Lipid utility was assessed by qPCR. A high-fat diet led to a significant reduction in vagal discharge and lipid utility and a marked increase in lipid accumulation, cardiac remodeling, and cardiac dysfunction. Pyridostigmine improved vagal activity and lipid metabolism disorder and cardiac remodeling, accompanied by an improvement of cardiac function in high-fat diet-fed rats. An increase in the browning of white adipose tissue in pyridostigmine-treated rats was also observed and linked to the expression of UCP-1 and CIDEA. Additionally, pyridostigmine facilitated activation of brown adipose tissue via activation of the SIRT-1/AMPK/PGC-1α pathway. In conclusion, a high-fat diet resulted in cardiac lipid accumulation, cardiac remodeling, and a significant decrease in vagal discharge. Pyridostigmine ameliorated cardiomyopathy, an effect related to reduced cardiac lipid accumulation, and facilitated the browning of white adipose tissue while activating brown adipose tissue.