Lipid Deposition In Adipocytes Research Articles

LBODP005 Gper Modulates Multiple Functions In Adipose Tissue To Promote An Anti-obese Phenotype

Abstract Obesity and metabolic syndrome are major health issues of modern society and their incidence is increasing at alarming rates worldwide. Obesity and associated chronic diseases exhibit sexual disparity with pre-menopausal females displaying better protection compared to age-matched males. These beneficial effects on metabolism in females are predominantly attributed to the female hormone estrogen, specifically 17β-estradiol (E2). E2 exerts its actions via multiple receptors, nuclear and extra-nuclear estrogen receptor (ER) α and ERβ, and the G protein-coupled estrogen receptor (GPER). GPER is present in diverse cells types and tissues and has been implicated in numerous physiological processes via multiple cellular signaling pathways. We have combined in vivo studies in an ovariectomized (OVX) mouse model along with in vitro assays in 3T3-L1 cells to investigate the role of GPER in modulating adipocyte function. Our studies reveal that loss of GPER increased adiposity in female mice on high fat diet and activation of GPER by its selective agonist G-1 attenuates adiposity in OVX mice. G-1 activated AMPK, increased cellular respiration and expression of mitochondrial and antioxidant genes and reduced lipid deposition in adipocytes. Furthermore, G-1 treatment promoted an anti-inflammatory phenotype in mice. Thus, our findings establish a role of GPER agonist G-1 in exerting anti-lipogenic and anti-inflammatory effects in adipocytes, which may have potential therapeutic implications in treatment of obesity. Presentation: No date and time listed

Lipedema and the Potential Role of Estrogen in Excessive Adipose Tissue Accumulation.

Lipedema is a painful fat disorder that affects ~11% of the female population. It is characterized by bilateral, disproportionate accumulation of subcutaneous adipose tissue predominantly in the lower body. The onset of lipedema pathophysiology is thought to occur during periods of hormonal fluctuation, such as puberty, pregnancy, or menopause. Although the identification and characterization of lipedema have improved, the underlying disease etiology remains to be elucidated. Estrogen, a key regulator of adipocyte lipid and glucose metabolism, and female-associated body fat distribution are postulated to play a contributory role in the pathophysiology of lipedema. Dysregulation of adipose tissue accumulation via estrogen signaling likely occurs by two mechanisms: (1). altered adipocyte estrogen receptor distribution (ERα/ERß ratio) and subsequent metabolic signaling and/or (2). increased release of adipocyte-produced steroidogenic enzymes leading to increased paracrine estrogen release. These alterations could result in increased activation of peroxisome proliferator-activated receptor γ (PPARγ), free fatty acid entry into adipocytes, glucose uptake, and angiogenesis while decreasing lipolysis, mitochondriogenesis, and mitochondrial function. Together, these metabolic alterations would lead to increased adipogenesis and adipocyte lipid deposition, resulting in increased adipose depot mass. This review summarizes research characterizing estrogen-mediated adipose tissue metabolism and its possible relation to excessive adipose tissue accumulation associated with lipedema.

BKCa channel participates in insulin-induced lipid deposition in adipocytes by increasing intracellular calcium.

Storing energy in the form of triglyceride (TG) is one of the basic functions of adipose tissue. Large-conductance calcium-activated potassium channels (BKCa channels) are expressed in adipose tissue and adipocyte-specific BKCa deficiency resists obesity in mice, but the role of BKCa channels in lipid deposition and the underlying mechanisms have not been elucidated. In the present study, we generated BKCa knockout (KO) rats and performed a transcriptome analysis of adipose tissue. We found that the phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) signaling pathway, which is important for lipid deposition, exhibited the most notable reduction among various signaling pathways in BKCa KO rats compared to wild-typerats. Insulin-induced TG deposition, glucose uptake, and Akt (Ser473) phosphorylation were significantly reduced in cultured adipocytes differentiated from adipose-derived stem cellsof BKCa KO rats. Furthermore, we found that the insulin-induced increase of intracellular calcium resulting from extracellular calcium influx was significantly impaired in BKCa KO adipocytes. Finally, insulin activated BKCa currents through PI3K, which was independent of Akt and intracellular calcium. The results of this study suggested that BKCa channels participate in the insulin signaling pathway and promote TG deposition by increasing extracellular calcium influx in adipocytes.

The Effect of Simvastatin on Gut Microbiota and Lipid Metabolism in Hyperlipidemic Rats Induced by a High-Fat Diet.

The objective of this study was to investigate the effects of simvastatin (SIM) on lipid metabolism disorders and gut microbiota in high-fat diet-induced hyperlipidemic rats. The obtained results revealed that feeding rats with SIM (20 mg/kg/day) significantly decreased serum lipid level and inhibited hepatic lipid accumulation and steatosis. Histological analysis further indicated that SIM reduced lipid deposition in adipocytes and hepatocytes in comparison with that of the HFD group. The underlying mechanisms of SIM administration against HFD-induced hyperlipidemia were also studied by UPLC-Q-TOF/MS-based liver metabonomics coupled with pathway analysis. Metabolic pathway enrichment analysis of liver metabolites with significant difference in abundance indicated that fatty acids metabolism and amino acid metabolism were the main metabolic pathways altered by SIM administration. Meanwhile, operational taxonomic units (OTUs) analysis revealed that oral administration of SIM altered the composition of gut microbiota, including Ruminococcaceae (OTU960) and Lactobacillus (OTU152), and so on. Furthermore, SIM treatment also regulated the mRNA levels of the genes involved in lipid and cholesterol metabolism. Immunohistochemistry (IHC) analysis of the liver-related proteins (CD36, CYP7A1 and SREBP-1C) showed that oral administration of SIM could regulate the levels of the protein expression related to hepatic lipid metabolism.

SIRT5 inhibits bovine preadipocyte differentiation and lipid deposition by activating AMPK and repressing MAPK signal pathways

SIRT5 (sirtuin 5) is located in the mitochondria and plays an important role in biological processes such as maintaining the balance of lipid metabolism and promoting fatty acid oxidation mobilization. In this study, the bovine preadipocyte differentiation and obese mouse models were constructed; combined with transcriptome sequencing (RNA-seq) and morphological identification, the regulatory and molecular mechanisms underlying the effects of SIRT5 on bovine preadipocyte differentiation and lipid metabolism were studied. The results reveal that during the differentiation of preadipocytes, SIRT5 inhibited the expression of key genes that promote lipid formation and differentiation in fatty acid biosynthesis and PPAR pathways. SIRT5 significantly activated the adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) pathway and repressed the mitogen-activated protein kinase (MAPK) pathway. Eventually, SIRT5 significantly inhibited the differentiation of bovine preadipocytes and simultaneously inhibited lipid synthesis and lipid deposition in adipocytes. The verification experiments performed using obese mice also yielded consistent results in vivo.

Role of silibinin in the management of diabetes mellitus and its complications.

Diabetes mellitus is globally approaching epidemic proportions and acts as a major cause of a number of serious health problems diagnosed as diabetic complications. The current oral drugs in the treatment of diabetes and its complications could meet some but not all of the patients' needs, and the development of novel drugs with a hypoglycemic effect is urgently required. Silibinin, a flavonolignan traditionally used for the treatment of gallbladder and hepatic diseases, was reported to improve glycemic homeostasis by improving the activity of pancreatic β-cells, increasing insulin sensitivity of liver and muscle cells, and decreasing lipid deposition in adipocytes. Researches also indicated the effectiveness of silibinin in controlling several diabetic complications including neuropathy, retinopathy, impaired healing, hepatopathy, cardiomyopathy, nephropathy, and osteoporosis. In this review, we summarize the recent anti-diabetes findings of silibinin and clarify the underlying pharmacological mechanisms, and update the knowledge in understanding the role of silibinin in control of diabetic complications.

Sequential induction of beta cell rest and stimulation using stable GIP inhibitor and GLP-1 mimetic peptides improves metabolic control in C57BL/KsJ db/db mice.

GIP(6-30)Cex-K(40)[Pal] has been characterised as a fatty-acid-derived gastric inhibitory polypeptide (GIP) inhibitor that can induce pancreatic beta cell rest by diminishing the incretin effect. We investigated its therapeutic efficacy with and without the glucagon-like peptide-1 (GLP-1) beta cell cytotropic agent liraglutide. The therapeutic efficacy of GIP(6-30)Cex-K(40)[Pal] alone, and in combination with liraglutide, was determined in C57BL/KsJ db/db mice using a sequential 12 h administration schedule. GIP(6-30)Cex-K(40)[Pal] was devoid of cAMP-generating or insulin-secretory activity, and inhibited GIP-induced cAMP production and insulin secretion. GIP(6-30)Cex-K(40)[Pal] also inhibited GIP-induced glucose-lowering and insulin-releasing actions in mice. Dose- and time-dependent studies in mice revealed that 2.5 nmol/kg GIP(6-30)Cex-K(40)[Pal], and 0.25 nmol/kg liraglutide, imparted distinct biological effects for 8-12 h post administration. When GIP(6-30)Cex-K(40)[Pal] (2.5 nmol/kg) and liraglutide (0.25 nmol/kg) were administered sequentially at 12 h intervals (at 08:00 and 20:00 hours) to db/db mice for 28 days, mice treated with GIP(6-30)Cex-K(40)[Pal] (08:00 hours) and liraglutide (20:00 hours) displayed pronounced reductions in circulating glucose and insulin. Both oral and intraperitoneal glucose tolerance and glucose-stimulated plasma insulin concentrations were improved together with enhanced insulin sensitivity. The expression of genes involved in adipocyte lipid deposition was generally decreased. The other treatment modalities, including GIP(6-30)Cex-K(40)[Pal] (08:00 and 20:00 hours), liraglutide (08:00 and 20:00 hours) and liraglutide (08:00 hours) combined with GIP(6-30)Cex-K(40)[Pal] (20:00 hours), also imparted beneficial effects but these were not as prominent as those of GIP(6-30)Cex-K(40)[Pal] (08:00 hours) and liraglutide (20:00 hours). These data demonstrate that periods of beta cell rest combined with intervals of beta cell stimulation benefit diabetes control and should be further evaluated as a potential treatment option for type 2 diabetes.

Adiponectin‐impaired adipocyte differentiation negatively regulates fat deposition in chicken

Adiponectin is a protein hormone secreted exclusively by adipocytes that plays an important role in the modulation of glucose and lipid metabolism. To investigate the effect of adiponectin on lipid metabolism in chicken, rosiglitazone (agonist of adiponectin) and dexamethasone (inhibitor of adiponectin) were used to treat 23-day-old broilers in vivo. To verify the functionality of adiponectin on fat deposition, chicken pre-adipocytes were cultured in the medium containing 10 μg/ml adiponectin. Serum adiponectin and lipids and fat distribution were analysed. Oil Red O staining was used to determine lipid deposition in adipocytes. The expression levels of adiponectin, adiponectin receptors (AdipoR) and lipid metabolism-related genes in different tissues and pre-adipocytes were measured using real-time PCR, and the abundance of lipid metabolism-related proteins was measured by Western blot. Rosiglitazone increased serum adiponectin concentration and the expression levels of adiponectin and adiponectin receptor 1 (AdipoR1) in tissues and significantly decreased levels of serum lipids and fat deposition. Rosiglitazone significantly increased the expression levels of adipose triglyceride lipase (ATGL) and AdipoR1 and decreased the expression levels of fatty acid synthase (FAS). Dexamethasone had the converse effects compared with rosiglitazone. Oil red O staining results showed a marked decrease in fat deposition in cells treated with adiponectin. In adipocytes, adiponectin could decrease the expression levels of CCAAT/enhancer-binding protein α (C/EBPα) and FAS and increased the expression levels of ATGL and AdipoR1. These results indicate that adiponectin has a remarkable effect on impairment of adipocyte differentiation, which contributes to the negative regulation of fat deposition in chicken.

Zebrafish obesogenic test: a tool for screening molecules that target adiposity

Dietary and xenobiotic compounds may alter endocrine signaling and lipid homeostasis, thus inducing obesity. We describe a short-term assay method, the zebrafish obesogenic (ZO) test, for examining the effects of diet, drugs, and environmental contaminants, singly or in combination, on white adipose tissue (WAT) dynamics in live larvae. The ZO test is an intermediate step in obesity research, between in vitro and rodent assays, and may be also used to study the effect of environmental toxicants on the adiposity of aquatic species. The procedure, using Nile Red (NR) fluorescent probe to reveal adipocyte lipid droplets, is suitable for pharmaceutical or toxicological screening. Larvae treated at an environmentally-relevant concentration of tributyltin chloride (TBT), an environmental obesogen, exhibited a remarkable increase in adiposity, irrespective of the lipid composition of the background diet. Exogenous compounds, e.g., rosiglitazone or TBT, known to increase adiposity in the fasting state, were classified as obesogenic. Anti-obesogenic compounds favored a decrease in adiposity in the fasting state. The ZO test, using adipocyte lipid droplet size and adiposity as its endpoints, is a whole-organism alternative testing assay for obesogenic and anti-obesogenic compounds and mixtures and provides relevant information for environmental and human risk assessments.

Novel Mechanism of the Vascular Protector Prostacyclin: Regulating MicroRNA Expression

Prostacyclin (PGI(2)) is a key vascular protector, metabolized from endogenous arachidonic acid (AA). Its actions are mediated through the PGI(2) receptor (IP) and nuclear receptor, peroxisome proliferator-activated receptor γ (PPARγ). Here, we found that PGI(2) is involved in regulating cellular microRNA (miRNA) expression through its receptors in a mouse adipose tissue-derived primary culture cell line expressing a novel hybrid enzyme gene (COX-1-10aa-PGIS), cyclooxygenase-1 (COX-1) and PGI(2) synthase (PGIS) linked with a 10-amino acid linker. The triple catalytic functions of the hybrid enzyme in these cells successfully redirected the endogenous AA metabolism toward a stable and dominant production of PGI(2). The miRNA microarray analysis of the cell line with upregulated PGI(2) revealed a significant upregulation (711, 148b, and 744) and downregulation of miRNAs of interest, which were reversed by antagonists of the IP and PPARγ receptors. Furthermore, we also found that the insulin-mediated lipid deposition was inhibited in the PGI(2)-upregulated adipocytes. The study also initiated a discussion that suggested that the endogenous PGI(2) inhibition of lipid deposition in adipocytes could involve miRNA-mediated inhibition of expression of the targeted genes. This indicated that PGI(2)-miRNA regulation could exist in broad pathophysiological processes involving PGI(2) (i.e., apoptosis, vascular inflammation, cancer, embryo implantation, and obesity).

Interleukin‐15 Contributes to the Regulation of Murine Adipose Tissue and Human Adipocytes

An alarming global rise in the prevalence of obesity and its contribution to the development of chronic diseases is a serious health concern. Recently, obesity has been described as a chronic low-grade inflammatory condition, influenced by both adipose tissue and immune cells suggesting proinflammatory cytokines may play a role in its etiology. Here we examined the effects of interleukin-15 (IL-15) on adipose tissue and its association with obesity. Over expression of IL-15 (IL-15tg) was associated with lean body condition whereas lack of IL-15 (IL-15(-/-)) results in significant increase in weight gain without altering appetite. Interestingly, there were no differences in proinflammatory cytokines such as IL-6 and tumor necrosis factor-alpha (TNF-alpha) in serum between the three strains of mice. In addition, there were significant numbers of natural killer (NK) cells in fat tissues from IL-15tg and B6 compared to IL-15(-/-) mice. IL-15 treatment results in significant weight loss in IL-15(-/-) knockout and diet-induced obese mice independent of food intake. Fat pad cross-sections show decreased pad size with over expression of IL-15 is due to adipocyte shrinkage. IL-15 induces weight loss without altering food consumption by affecting lipid deposition in adipocytes. Treatment of differentiated human adipocytes with recombinant human IL-15 protein resulted in decreased lipid deposition. In addition, obese patients had significantly lower serum IL-15 levels when compared to normal weight individuals. These results clearly suggest that IL-15 may be involved in adipose tissue regulation and linked to obesity.

Adaptations of adipose tissue metabolism and number of insulin receptors in pregnant sheep

1. 1. The endocrine control of adipose tissue metabolism during pregnancy in sheep has been investigated. 2. 2. The number of insulin receptors of sheep adipocytes was increased during pregnancy. 3. 3. There was no apparent change in the concentration of serum insulin during pregnancy in sheep while the rise in serum progesterone concentration was smaller and more gradual than in rats. 4. 4. Net lipid deposition in adipocytes occurred during the first 55 days of pregnancy, probably due primarily to increased lipoprotein lipase activity. 5. 5. Net deposition of lipid had ceased by mid-pregnancy while by 125 days of pregnancy, the rate of fatty acid synthesis in adipose tissue was decreased and the serum fatty acid concentration had risen, suggesting the onset of net lipid mobilization in the tissue. 6. 6. Results are compared with those from other studies with rats; it would appear that different mechanisms regulate lipid deposition during pregnancy in sheep and rats.