Lipid Accumulation In Adipose Tissue Research Articles

Platycodon D reduces obesity and non-alcoholic fatty liver disease induced by a high-fat diet through inhibiting intestinal fat absorption.

Platycodin D (PD) has been reported to treat metabolic diseases, including non-alcoholic fatty liver disease. In addition, platycodin D has been reported to activate intestinal 5'AMP-activated protein kinase (AMPK) phosphorylation levels, thereby reducing lipid absorption. Therefore, the aim of this study is to explore whether PD activation of intestinal AMPK and reduced lipid absorption can improve non-alcoholic fatty liver disease. Clean-grade male C57/BL mice were fed a high-fat diet (HFD) (containing 60% calories) for 16 weeks, and oral PD (10mg/kg/day) was administered at the same time. The liver and intestines were the collected, and the intestines were tested. The expressions of lipid absorption genes (CD36, NPC1L1, and ApoB), the serum total triglyceride (TG) and total cholesterol (TC) levels in the intestines and livers, the fecal free fatty acid (FFA) levels, and the expression of AMPK phosphorylated proteins in the intestines were examined using Western blot analyses. The lipid distribution in the livers, intestines, and fat was detected using Oil Red O and hematoxylin and eosin (H&E) staining. A colon cancer cell line (Caco2) was used to confirm the effect of PD on the cellular lipid uptake in vitro. In addition, serum inflammatory factors and liver enzymes were measured to clarify the impact of PD on the circulation of metabolic syndrome. Leptin-deficient mice (OB) were then used to further explore the improvement of PD on body weight and blood lipids. PD had a very significant therapeutic or preventive effect on metabolic syndrome and fatty liver induced by a high-fat diet. PD improved body weight, insulin sensitivity, and glucose tolerance in mice fed a high-fat diet and also prevented non-alcoholic fatty liver disease, reduced blood lipid levels, and increased fecal lipid excretion. In addition, PD reduced lipid absorption by activating the intestinal AMPK protein, which may have involved the inhibition of the gene expression levels of intestinal lipid absorption genes (CD36, NPC1L1, and ApoB). The combined effect of these factors improved hepatic lipid accumulation and lipid accumulation in adipose tissue. It was further found that PD also improved the body weights and blood lipid levels of leptin-deficient mice (OB) mice. PD had a very strong therapeutic effect on mice under a high-fat diet. PD reduced high-fat diet-induced obesity and non-alcoholic fatty liver disease by inhibiting intestinal fat absorption.

Deciphering adipose development: Function, differentiation and regulation.

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

CD73-dependent generation of extracellular adenosine by vascular endothelial cells modulates de novo lipogenesis in adipose tissue.

Next to white and brown adipocytes present in white and brown adipose tissue (WAT, BAT), vascular endothelial cells, tissue-resident macrophages and other immune cells have important roles in maintaining adipose tissue homeostasis but also contribute to the etiology of obesity-associated chronic inflammatory metabolic diseases. In addition to hormonal signals such as insulin and norepinephrine, extracellular adenine nucleotides modulate lipid storage, fatty acid release and thermogenic responses in adipose tissues. The complex regulation of extracellular adenine nucleotides involves a network of ectoenzymes that convert ATP via ADP and AMP to adenosine. However, in WAT and BAT the processing of extracellular adenine nucleotides and its relevance for intercellular communications are still largely unknown. Based on our observations that in adipose tissues the adenosine-generating enzyme CD73 is mainly expressed by vascular endothelial cells, we studied glucose and lipid handling, energy expenditure and adaptive thermogenesis in mice lacking endothelial CD73 housed at different ambient temperatures. Under conditions of thermogenic activation, CD73 expressed by endothelial cells is dispensable for the expression of thermogenic genes as well as energy expenditure. Notably, thermoneutral housing leading to a state of low energy expenditure and lipid accumulation in adipose tissues resulted in enhanced glucose uptake into WAT of endothelial CD73-deficient mice. This effect was associated with elevated expression levels of de novo lipogenesis genes. Mechanistic studies provide evidence that extracellular adenosine is imported into adipocytes and converted to AMP by adenosine kinase. Subsequently, activation of the AMP kinase lowers the expression of de novo lipogenesis genes, most likely via inactivation of the transcription factor carbohydrate response element binding protein (ChREBP). In conclusion, this study demonstrates that endothelial-derived extracellular adenosine generated via the ectoenzyme CD73 is a paracrine factor shaping lipid metabolism in WAT.

Design, synthesis and evaluation of 2-pyrimidinylindole derivatives as anti-obesity agents by regulating lipid metabolism

Obesity, a global pandemic posing a growing threat to human health, necessitates the development of effective and safe anti-obesity agents. Our previous studies highlighted the lipid-lowering effects of indolylquinazoline Bouchardatine and its derivatives. In this study, we employed scaffold hopping and simplification strategies to design and synthesize two new series derivatives by modifying the D ring. Extensive discussions have been conducted regarding the structure-activity relationship between lipid-lowering activity and the new compounds. These discussions have resulted in the discovery of 2-pyrimidinylindole derivatives as a promising scaffold for anti-obesity treatment. The new 2-pyrimidinylindole derivatives exhibited comparable lipid-lowering activity to the previously reported indolylquinazoline derivatives, including SYSU-3d and R17, with reduced toxicity. The most potent compound, 5a, demonstrated a larger therapeutic index, improved aqueous solubility and oral bioavailability compared to the previous lead compounds. In vivo evaluation indicated that 5a effectively reduced lipid accumulation in adipose tissue, improved glucose tolerance, and mitigated insulin resistance and liver function damage caused by a high-fat and high-cholesterol diet. Mechanism studies indicated that 5a may regulate lipid metabolism through the modulation of the PPARγ signaling pathway. Overall, our study has identified a highly active compound 5a, and provided the basis for further development of 2-pyrimidinylindole as a promising scaffold for obesity treatment.

HM-chromanone suppresses lipid accumulation by modulating AMPK/SREBP-1c pathway in ob/ob mice

This study investigated whether HM-chromanone, a bioactive compound isolated from Portulaca oleracea L., inhibits lipid accumulation in adipose tissue and liver of C57BL/6J ob/ob mice. C57BL/6J mice were used for the normal group and C57BL/6J ob/ob mice were randomly divided into three groups: ob/ob, metformin and HM-chromanone. In the HM-chromanone group, body and liver weight, fat mass and fat size were significantly lower than that in the ob/ob group. The HM-chromanone group also showed lower serum lipid levels and hepatic lipid accumulation compared with the ob/ob group. HM-chromanone administration significantly activated adenosine monophosphate-activated protein kinase (AMPK) and inhibited sterol regulatory element binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) in adipose tissue and liver. These results suggest that HM-chromanone potentially suppresses lipid accumulation by modulating AMPK/SREBP-1c pathway in adipose tissue and liver of ob/ob mice.

Breast cancer cell-derived exosome-delivered microRNA-155 targets UBQLN1 in adipocytes and facilitates cancer cachexia-related fat loss.

Cachexia occurrence and development are associated with loss of white adipose tissues, which may be involved with cancer-derived exosomes. This study attempted to characterize the functional mechanisms of bc cell-derived exosomes-loaded microRNA (miR)-155 in cancer cachexia-related fat loss. Exosomes were incubated with preadipocytes and cellular lipid droplet accumulation was observed using oil red O staining. Western blots evaluated the cellular levels of lipogenesis marker peroxisome proliferator activated receptor gamma (PPARγ) and adiponectin, C1Q and collagen domain containing (AdipoQ). Differentiated adipocytes were incubated with exosomes, and phosphate hormone sensitive lipase (P-HSL), adipose triglyceride lipase (ATGL), and glycerol were detected in adipocytes, in addition to uncoupling protein 1 (UCP1) and leptin levels. A mouse model of cancer cachexia was established where cancer exosomes were injected intravenously. The changes in body weight and tumor-free body weights were recorded and serum glycerol levels and lipid accumulation in adipose tissues were determined. Also, the relationship between miR-155 and UBQLN1 was predicted and verified. bc exosome treatment reduced PPARγ and AdipoQ protein levels, promoted the levels of P-HSL and ATGL proteins, facilitated glycerol release, increased UCP1 expression, and lowered leptin expression in adipocytes. Exosomal miR-155 inhibited lipogenesis in preadipocytes and boosted the browning of white adipose tissues. miR-155 downregulation alleviated cancer exosome-induced browning of white adipose tissues and fat loss. Mechanistically, miR-155 targeted UBQLN1, and UBQLN1 upregulation reversed the impacts of cancer exosomes. miR-155 loaded by bc cell-derived exosomes significantly affects white adipose browning and inhibition of cancer-derived exosomes.

Novel Insight into the Role of the Kiss1/GPR54 System in Energy Metabolism in Major Metabolic Organs.

The Kiss1/GPR54 system is a multifunctional genetic system with an essential role in regulating energy balance and metabolic homeostasis. In the mammalian hypothalamus, two major populations of neurons, the rostral periventricular region of the third ventricle (RP3V) and the arcuate nucleus (ARC), produced kisspeptin. Kiss1ARC neurons input kisspeptin and glutamate to feeding-associated neurons to regulate energy intake and expenditure balance. Kisspeptin in the peripheral circulation is involved in lipid accumulation in adipose tissue. In the hepatic and pancreatic circuits, kisspeptin signaling affects insulin secretion, suggesting the critical role of the Kiss1/GPR54 system in regulating glucose and lipid metabolism. In addition, this review also predicts the role of the Kiss1/GPRS4 system in skeletal muscle in association with exercise performance. Recent studies have focused on the link between kisspeptin signaling and energy homeostasis, further investigation of potential function is warranted. Therefore, this review summarizes the role of the Kiss1/GPRS4 system in the major metabolic organs in relation to energy metabolism homeostasis, aiming to endow the reader with a critical and updated view of the Kiss1/GPR54 system in energy metabolism.

Inhibitory Effects of Hydrolysable Tannins on Lipid Accumulation in 3T3-L1 Cells.

Obesity is currently the most common cause of metabolic diseases including type 2 diabetes and hyperlipidemia. Obesity results from excess lipid accumulation in adipose tissue. Several studies have investigated the inhibitory effects of natural plant-derived products on adipocyte differentiation and lipid accumulation. In this study, we examined the effect of hydrolysable tannins composed of gallic acid and glucose on adipocyte differentiation in 3T3-L1 cells. 1,2,3,4,6-Penta-O-galloyl-β-D-glucose (PGG) (1), a representative gallotannin, inhibited lipid accumulation in 3T3-L1 cells, whereas ellagitannins (tellimagrandin I, eugeniin and casuarictin) did not. The expression of adipocyte differentiation-related genes, including peroxisome proliferator activator γ2 (Pparγ2), CCAAT/enhancer binding protein α (C/EBPα) and adipocyte fatty acid binding protein (aP2), was significantly suppressed in PGG (1)-treated 3T3-L1 cells beginning at day 2 after induction of differentiation. While PGG (1) did not directly reduce Pparγ2 expression, it reduced the expression of its target genes in mature adipocytes. In addition, PGG (1) treatment inhibited mitotic clonal expansion, one of earliest events of adipocyte differentiation. These findings indicate that PGG (1) has an inhibitory effect on adipocyte differentiation through the suppression of mitotic clonal expansion.

Effects of Chemical Structures Interacting with Amine Oxidases on Glucose, Lipid and Hydrogen Peroxide Handling by Human Adipocytes.

Benzylamine is a natural molecule present in food and edible plants, capable of activating hexose uptake and inhibiting lipolysis in human fat cells. These effects are dependent on its oxidation by amine oxidases present in adipocytes, and on the subsequent hydrogen peroxide production, known to exhibit insulin-like actions. Virtually, other substrates interacting with such hydrogen peroxide-releasing enzymes potentially can modulate lipid accumulation in adipose tissue. Inhibition of such enzymes has also been reported to influence lipid deposition. We have therefore studied in human adipocytes the lipolytic and lipogenic activities of pharmacological entities designed to interact with amine oxidases highly expressed in this cell type: the semicarbazide-sensitive amine oxidase (SSAO also known as PrAO or VAP-1) and the monoamine oxidases (MAO). The results showed that SZV-2016 and SZV-2017 behaved as better substrates than benzylamine, releasing hydrogen peroxide once oxidized, and reproduced or even exceeded its insulin-like metabolic effects in fat cells. Additionally, several novel SSAO inhibitors, such as SZV-2007 and SZV-1398, have been evidenced and shown to inhibit benzylamine metabolic actions. Taken as a whole, our findings reinforce the list of molecules that influence the regulation of triacylglycerol assembly/breakdown, at least in vitro in human adipocytes. The novel compounds deserve deeper investigation of their mechanisms of interaction with SSAO or MAO, and constitute potential candidates for therapeutic use in obesity and diabetes.

Role of insulin action in the pathogenesis of diabetic complications.

Among the various pathological conditions associated with type 2 diabetes, insulin resistance has long been reported to be a potent risk factor for diabetic complications. The liver, skeletal muscle, and adipose tissue are the major organs of action of insulin in systemic glucose metabolism, but insulin receptors and their downstream insulin signaling molecules are also constitutively expressed in vascular endothelial cells, vascular smooth muscle, and monocytes/macrophages. Forkhead box class O family member proteins (FoxOs) of transcription factors are essential regulators of cellular homeostasis, including glucose and lipid metabolism, oxidative stress response and redox signaling, cell cycle progression and apoptosis. In vascular endothelial cells, FoxOs strongly promote atherosclerosis via suppressing nitric oxide production and enhancing inflammatory responses. In liver sinusoidal endothelial cells, FoxOs induces hepatic insulin resistance by inducing nitration of insulin receptor in hepatocytes. Insulin resistance in adipose tissue limits capacity of lipid accumulation in adipose tissue, which promotes ectopic lipid accumulation and organ dysfunction in liver, vascular, and kidney. Modulation of insulin sensitivity in adipose tissue to induce healthy adipose expansion is expected to be a promising strategy for diabetic complications.

TRIM67 Deficiency Exacerbates Hypothalamic Inflammation and Fat Accumulation in Obese Mice.

Obesity has achieved the appearance of a global epidemic and is a serious cause for concern. The hypothalamus, as the central regulator of energy homeostasis, plays a critical role in regulating food intake and energy expenditure. In this study, we show that TRIM67 in the hypothalamus was responsive to body-energy homeostasis whilst a deficiency of TRIM67 exacerbated metabolic disorders in high-fat-diet-induced obese mice. We found exacerbated neuroinflammation and apoptosis in the hypothalamus of obese TRIM67 KO mice. We also found reduced BDNF in the hypothalamus, which affected the fat sympathetic nervous system innervation and contributed to lipid accumulation in adipose tissue under high-fat-diet exposure. In this study, we reveal potential implications between TRIM67 and the hypothalamic function responding to energy overuptake as well as a consideration for the therapeutic diagnosis of obesity.

RANKL elevation activates the NIK/NF-κB pathway, inducing obesity in ovariectomized mice.

Menopausal women are susceptible to visceral obesity, which increases the risk of metabolic disorders. However, the mechanisms of menopause-induced visceral fat accumulation are not fully understood. Circulating levels of receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) are elevated in an animal model of menopause. RANKL, a multifunctional cytokine, activates the NF-κB pathway, which serves as a pivotal mediator of inflammatory responses. Here, we investigated whether RANKL-induced non-canonical NF-κB pathway activation induces inflammation and lipid accumulation in adipose tissues. RANKL induced Tnfa expression via the non-canonical NF-κB pathway in bone marrow cells. We therefore analyzed aly/aly mice, in which the non-canonical NF-κB pathway is not activated, owing to an inactive form of NF-κB-inducing kinase. A postmenopausal obesity model was generated by ovariectomy and subsequent high-fat and high-sucrose diet feeding. In aly/aly mice with postmenopausal obesity, serum RANKL levels were elevated, and hepatic lipid accumulation and adipocyte hypertrophy were suppressed, resulting in reduced macrophage infiltration and inflammatory cytokine mRNA expression in visceral adipose tissue. Furthermore, aly/aly mice showed protection from glucose intolerance and insulin resistance, which were observed in ovariectomized WT obese mice. These findings indicate that non-canonical NF-κB pathway activation via serum RANKL elevation contributes to postmenopausal obesity.

Fructose-mediated NLRP3 activation induces inflammation and lipogenesis in adipose tissue

Adipose tissue plays a crucial role in energy intake and regulation of metabolic homeostasis. Fructose consumption implicates in development and progression of metabolic dysfunctions. Fructose is a lipogenic sugar known to induce inflammatory response. However, the role of specific inflammatory signal such as nucleotide-binding and oligomerization domain-like receptor, leucine-rich repeat and pyrin domain containing protein 3 (NLRP3) in fructose-induced inflammatory response and its relevance to lipogenesis in adipose tissue are elusive. We assessed NLRP3 activation and its significance in inflammatory response and lipogenesis in epididymal adipose tissue of 60% fructose diet (HFrD)-fed rats. The long-term consumption of HFrD led to impairment of glucose metabolism, development of visceral adiposity, insulin resistance, and elevation of serum triglycerides level, accompanied by activation of NLRP3 in adipose tissue. NLRP3 inflammasome activation in adipose tissue was associated with up-regulated expression of Nlrp3, Asc, and Caspase-1, and raised caspase-1 activity, which resulted in increased expression of IL-1β and IL-18 and secretion of IL-1β. Moreover, lipid accumulation and expression of transcription factors exacerbating accumulation of lipids were augmented in adipose tissue of HFrD-fed rats. Treatment with glyburide, quercetin or allopurinol corrected HFrD-induced dyslipidemia or hyperuricemia, and blocked NLRP3 activation, leading to mitigated inflammatory signaling and lipid accumulation in adipose tissue, improved glucose tolerance and insulin sensitivity in HFrD-fed rats. These data suggest the role of NLRP3 inflammasome to establish linkage among inflammation, lipid accumulation and insulin resistance in adipose tissue, and targeting NLRP3 inflammasome may be a plausible approach for prevention and management for fructose-induced metabolic impairments.

Panax notoginseng Saponin Protects Against Diabetic Cardiomyopathy Through Lipid Metabolism Modulation.

BackgroundPeople with diabetes are more likely to develop cardiovascular diseases. Lipotoxicity plays a key role in the development of diabetic cardiomyopathy. Panax notoginseng saponin (PNS) has been used to treat diabetes and obesity. However, the role of PNS in diabetic cardiomyopathy remains unclear.Methods and ResultsDiabetic db/db mice received high‐dose (200 mg/kg per day) or medium‐dose (100 mg/kg per day) PNS by gavage for 12 weeks until week 36. Lipid accumulation and cardiac function in diabetic mice were detected and possible mechanisms involved were explored. PNS significantly improved body weight, body fat content, serum lipids, adipocytokines, and antioxidative function in db/db mice. Lipid accumulation in adipose tissue, liver, and heart were also alleviated by PNS treatment. Cardiac function and mitochondrial structure were also improved by PNS. H9c2 cells were treated with palmitate acid, and PNS pretreatment reduced lipid accumulation, mitochondrial reactive oxygen species, as well as improved mitochondrial membrane potential and mitochondrial oxygen consumption rate. Levels of proteins and expression of genes related to glucose and lipid metabolism, antioxidative function, and mitochondrial dynamics were also improved by PNS administration.ConclusionsPNS attenuated heart dysfunction in diabetic mice by reducing lipotoxicity as well as modulating oxidative stress and improving mitochondrial function.

Oolong tea extract alleviates weight gain in high-fat diet-induced obese rats by regulating lipid metabolism and modulating gut microbiota.

Obesity is a serious global health issue, and the societal interventions during the COVID-19 pandemic may have perturbed energy homeostasis, which affects the condition of obesity. Tea is a traditional beverage in Asia and has been shown to provide many beneficial health effects. Oolong tea is semifermented, with its chemical composition comprising features of green (unfermented) and black (fermented) tea. Although green tea has anti-obesity properties, studies on the anti-obesity ability of oolong tea are still scarce. In this study, we analyzed the chemical composition of oolong tea extract (OTE) and investigated the effects of OTE on high-fat diet-induced obese rats. OTE contained more (-)-epigallocatechin-3-gallate, (-)-epigallocatechin, and (-)-gallocatechin-3-gallate than theaflavins and theasinensins. Rats fed with a high-fat diet (HFD) and treated with 0.5% OTE exhibited significantly reduced body weight and visceral fat weight compared with the HFD-only group. OTE also decreased adipocyte size, lipogenesis-related protein sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FASN) protein expression and increased thermogenesis-related protein peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and uncoupling protein 1 (UCP1) protein expression in epididymal adipose tissue compared with the HFD group. Moreover, the OTE groups had a significantly higher abundance of Candidatus arthromitus and Hydrogenoanaerobacterium and a lower abundance of Ruminococcus1, Oscillibacter, and Odoribacter compared with the HFD group. All these results show that OTE can alleviate weight gain by regulating lipid metabolism and modulating the distribution of the gut microbiota to decrease lipid accumulation in adipose tissue.

Lupinus angustifolius Protein Hydrolysates Reduce Abdominal Adiposity and Ameliorate Metabolic Associated Fatty Liver Disease (MAFLD) in Western Diet Fed-ApoE-/- Mice.

Metabolic-associated fatty liver disease (MAFLD) is the most important cause of liver disease worldwide. It is characterized by the accumulation of fat in the liver and is closely associated with abdominal obesity. In addition, oxidative stress and inflammation are significant features involved in MAFLD. Recently, our group demonstrated that lupin protein hydrolysates (LPHs) had lipid lowering, antioxidant, and anti-inflammatory effects. Sixty male mice fed with a Western diet were intragastrically treated with LPHs (or vehicle) for 12 weeks. Liver and adipose tissue lipid accumulation and hepatic inflammatory and oxidant status were evaluated. A significant decrease in steatosis was observed in LPHs-treated mice, which presented a decreased gene expression of CD36 and LDL-R, crucial markers in MAFLD. In addition, LPHs increased the hepatic total antioxidant capacity and reduced the hepatic inflammatory status. Moreover, LPHs-treated mice showed a significant reduction in abdominal adiposity. This is the first study to show that the supplementation with LPHs markedly ameliorates the generation of the steatotic liver caused by the intake of a Western diet and reduces abdominal obesity in ApoE−/− mice. Future clinical trials should shed light on the effects of LPHs on MAFLD.

SCFJFK is functionally linked to obesity and metabolic syndrome.

Dysregulation of lipid metabolism could lead to the development of metabolic disorders. We report here that the F-box protein JFK promotes excessive lipid accumulation in adipose tissue and contributes to the development of metabolic syndrome. JFK transgenic mice develop spontaneous obesity, accompanied by dyslipidemia, hyperglycemia, and insulin resistance, phenotypes that are further exacerbated under high-fat diets. In contrast, Jfk knockout mice are lean and resistant to diet-induced metabolic malfunctions. Liver-specific reconstitution of JFK expression in Jfk knockout mice leads to hepatic lipid accumulation resembling human hepatic steatosis and nonalcoholic fatty liver disease. We show that JFK interacts with and destabilizes ING5 through assembly of the SCF complex. Integrative transcriptomic and genomic analysis reveals that the SCFJFK -ING5 axis interferes with AMPK activity and fatty acid β-oxidation, leading to the suppression of hepatic lipid catabolism. Significantly, JFK is upregulated and AMPKα1 is down-regulated in liver tissues from NAFLD patients. These results reveal that SCFJFK is a bona fide E3 ligase for ING5 and link the SCFJFK -ING5 axis to the development of obesity and metabolic syndrome.

Emodin inhibits lipid accumulation and inflammation in adipose tissue of high‐fat diet‐fed mice by inducing M2 polarization of adipose tissue macrophages

Adiposetissuemacrophages(ATMs)representthemostabundantleukocytes in adipose tissue (AT). An increase in number and a phenotypical switch of ATMs during the development of obesity contributetochronicinflammationand metabolic disorders, which have been regarded as potential therapeutic targets to restore AT homeostasis. Emodin has been shown to exert strong anti-inflammatory property via acting on macrophages in a range of disease models. However, whether emodin exerts a beneficial effect on obesity via modulating ATMs has not been reported. In high-fat diet (HFD)-induced obese mice, emodin significantly inhibited the increase of body weight and lipid accumulation in ATs. Emodin apparently reduced glucose and insulin levels and ameliorated serum lipid profiles in HFD-fed mice. Moreover, the local and systemic inflammation was dramatically alleviated by emodin. We next discovered that M2 macrophage percentage was greatly increased by emodin although total ATMs was not altered, which resulted in a net increase of M2 macrophages in AT. In vitro studies confirmed that emodin promoted the polarization of macrophages towards M2. Gene ontology (GO) analysis showed that myeloid leukocyte differentiation and activation were among the most significant biological processes in emodin-treated ATMs. We further identified that TREM2 was the most dramatically upregulated molecule by emodin and emodin-induced M2 macrophage polarization was dependent on TREM2. Furthermore, silencing TREM2 apparently abrogated the effect of emodin on AT inflammation and adipogenesis. We, for the first time, disclosed that emodin inhibited obesity by promoting M2 macrophage polarization via TREM2, suggesting that emodin may be explored as a clinical and translational candidate in preventing obesity and its related metabolic diseases.

Feprazone Displays Antiadipogenesis and Antiobesity Capacities in in Vitro 3 T3-L1 Cells and in Vivo Mice

Background and purpose: Excessive lipid accumulation in adipose tissues and deregulation of adipogenesis-induced obesity affect millions of people worldwide. Feprazone, a nonsteroidal anti-inflammatory drug, has a wide clinical use. However, it is unknown whether Feprazone possesses an antiadipogenic ability. The aim of this study is to investigate whether Feprazone possesses an antiadipogenic ability in 3 T3-L1 cells and an antiobesity capacity in mouse models. Methods: An MTT assay was used to determine the optimized incubation concentrations of Feprazone in 3 T3-L1 cells. The lipid accumulation was evaluated using Oil Red O staining. The concentrations of triglyceride and glycerol release were detected to check the lipolysis during 3 T3-L1 adipogenesis. A quantitative real-time polymerase chain reaction (qRT-PCR) was used to determine the expressions of sterol regulatory element-binding protein-1C (SREBP-1C) and fatty acid binding protein 4 (FABP4) in treated cells. The expressions of peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT/enhancer-binding protein α (C/EBP-α), adipose triglyceride lipase (ATGL), and aquaporin-7 (AQP-7) were detected using qRT-PCR and Western blot analysis. After the high-fat diet (HFD) mice were treated with Feprazone, the pathological state of adipocyte tissues was evaluated using HE staining. The adipocyte size, visceral adipocyte tissue weight, and bodyweights were recorded. Results: According to the proliferation result, 30 and 60 μM Feprazone were used as the optimized concentrations of Feprazone. In the in vitro study, lipid accumulation, elevated production of triglycerides, the release of glycerol, upregulated SREBP-1C, FABP4, PPAR-γ, and C/EBP-α and downregulated ATGL and AQP-7 in the 3 T3-L1 adipocytes induced by the adipocyte differentiation cocktail medium were significantly reversed by treatment with Feprazone. In the in vivo experiment, we found that the increased adipocyte size, visceral adipocyte tissue weight, and body weights induced by HFD feeding in mice were significantly suppressed by the administration of Feprazone. Conclusion: Feprazone might display anti-adipogenic and antiobesity capacities in in vitro 3 T3-L1 cells and in vivo mice.

Lipoprotein receptor SR-B1 deficiency enhances adipose tissue inflammation and reduces susceptibility to hepatic steatosis during diet-induced obesity in mice

Scavenger receptor class B type 1 (SR-B1) is a membrane lipoprotein receptor/lipid transporter involved in the pathogenesis of atherosclerosis, but its role in obesity and fatty liver development is unclear. Here, we determined the effects of SR-B1 deficiency on plasma metabolic and inflammatory parameters as well as fat deposition in adipose tissue and liver during obesity. To induce obesity, we performed high-fat diet (HFD) exposure for 12 weeks in male SR-B1 knock-out (SR-B1−/−, n = 14) and wild-type (WT, n = 12) mice. Compared to HFD-fed WT mice, plasma from HFD-fed SR-B1−/− animals exhibited increased total cholesterol, triglycerides (TG) and tumor necrosis factor-α (TNF-α) levels. In addition, hypertrophied adipocytes and macrophage-containing crown-like structures (CLS) were observed in adipose tissue from HFD-fed SR-B1 deficient mice. Remarkably, liver from obese SR-B1−/− mice showed attenuated TG content, dysregulation in hepatic peroxisome proliferator-activated receptors (PPARs) expression, increased hepatic TG secretion, and altered hepatic fatty acid (FA) composition. In conclusion, we show that SR-B1 deficiency alters the metabolic environment of obese mice through modulation of liver and adipose tissue lipid accumulation. Our findings provide the basis for further elucidation of SR-B1's role in obesity and fatty liver, two major public health issues that increase the risk of advanced chronic diseases and overall mortality.