Effect of Ichnocarpus frutescens (L.) R. Br. hexane extract on preadipocytes viability and lipid accumulation in 3T3-L1 cells

ObjectiveTo investigate the crude extracts of Ichnocarpus frutescens (I. frutescens) for antiobesity effect.MethodsLeaves of I. frutescens were sequentially extracted with hexane, ethyl acetate, and methanol and their effect on viability of 3T3-L1 preadipocytes were evaluated. Based on this the apoptosis on preadipocytes was confirmed by DNA fragmentation and LDH (Lactate dehydrogenase) leakage assays. Anti-adipogenesis was performed by oil red O (ORO) staining and free glycerol release in the medium of differentiated adipocytes.ResultsThe hexane extract of I. frutescens (IFHE) inhibited cell viability in a time- and dose-related manner. An increased release of LDH, as a marker of membrane integrity, was observed at a dose of 200 μ g/mL. The discontinuous DNA fragments on agarose gel electrophoresis showed the apoptotic effect of the IFHE. Morphological observations of cells stained with ORO showed a decrease in cellular lipid content at the concentrations tested compared to the induced control cells. In the experiment of lipolytic activity, treatment with IFHE enhanced glycerol secretion with the rates of approximately 28%, 55%, and 46% at the concentrations of 100, 200 and 300 μ g/mL, respectively.ConclusionsThe observed properties clearly revealed the medicinal property of I. frutescens in the treatment of obesity.     

Duration and magnitude of extracellular signal-regulated protein kinase phosphorylation determine adipogenesis or osteogenesis in human bone marrow-derived stem cells

Purpose

Imbalances between osteogenic and adipogenic differentiation leads to diseases such as osteoporosis. The aim of our study was to demonstrate the differences in extracellular signal-regulated kinase (ERK) phosphorylation during both adipogenesis and osteogenesis of human bone marrow-derived stem cells (BMSCs).

Materials and Methods

Using troglitazone, GW9662 and U0126, we investigated their role in hBMSC differentiation to adipogenic and osteogenic fates.

Results

ERK1/2 inhibition by U0126 suppressed proliferator-activated receptor (PPAR)γ expression and lipid accumulation, while it decreased the mRNA expression of adipogenic genes (lipoprotein lipase, PPARγ, and adipocyte protein) and osteogenic genes (type I collagen and osteopontin). ERK phosphorylation was transient and decreased during adipogenesis, whereas it occurred steadily during osteogenesis. Troglitazone, a PPARγ agonist, induced adipogenesis by inhibiting ERK phosphorylation even in an osteogenic medium, suggesting that ERK signaling needs to be shut off in order to proceed with adipose cell commitment. Cell proliferation was greatly increased in osteogenesis but was not changed during adipogenesis, indicating that ERK might play different roles in cellular proliferation and differentiation between the two committed cell types.

Conclusion

The duration and magnitude of ERK activation might be a crucial factor for the balance between adipogenesis and osteogenesis in human bone marrow-derived stem cells.     

Beta-adrenergic signals regulate adipogenesis of mouse mesenchymal stem cells via cAMP/PKA pathway

The adipogenic capacity of mesenchymal stem cells (MSCs) and the involvement of β-adrenergic signals in lipolysis and thermogenesis have been well established. However, little is known about the development of β-adrenergic receptor (β-AR) systems and the role of β-adrenergic signals in adipogenic differentiation of MSCs. In this study, we demonstrated that both the mRNA and protein levels of β2- and β3-AR were up-regulated following adipogenesis of mouse bone marrow derived MSCs. We also established that β-AR agonists negatively while antagonists positively affected MSC adipogenesis. Both the β2- and β3-AR were involved in MSC adipogenesis, with β3-AR being the predominant subtype. The effect of β-ARs on MSC adipogenesis was at least partly mediated via the cAMP/PKA signaling pathway. These findings suggested that MSC is also a target for β-adrenergic regulation, and β-adrenergic signaling (major β3-signaling) plays a role in MSC adipogenesis.     

Role of microRNAs in obesity and the metabolic syndrome

Obesity and the metabolic syndrome are major public health concerns, and present a formidable therapeutic challenge. Many patients remain recalcitrant to conventional lifestyle changes and medical therapies. Bariatric surgery has made laudable progress in the treatment of obesity and its related metabolic disorders, yet carries inherent risks. Unravelling the molecular mechanisms of metabolic disorders is essential in order to develop novel, valid therapeutic strategies. Mi(cro)RNAs play important regulatory roles in a variety of biological processes including adipocyte differentiation, metabolic integration, insulin resistance and appetite regulation. Investigation of these molecules and their genetic targets may potentially identify new pathways involved in complex metabolic disease processes, improving our understanding of metabolic disorders and influence future approaches to the treatment of obesity. This review discusses the role of miRNAs in obesity and related components of the metabolic syndrome, and highlights the potential of using miRNAs as novel biomarkers and therapeutic targets for these diseases.     

CCNG2 and CDK4 is associated with insulin resistance in adipose tissue

BackgroundThe involvement of cyclin G2 (CCNG2) and cyclin-dependent kinase-4 (CDK4), cell cycle regulatory proteins, in adipose tissue metabolism and insulin resistance is still unknown. The objective of this study was to analyze CCNG2 and CDK4 levels in visceral (VAT) and subcutaneous adipose tissue (SAT) from nonobese and morbidly obese patients and their relationship with insulin resistance.MethodsWe studied the mRNA and protein levels of CCNG2 and CDK4 in VAT and SAT from 12 nonobese and 23 morbidly obese patients (11 with low [MO-L-IR] and 12 with high insulin resistance [MO-H-IR]).ResultsThe nonobese patients had a significantly greater CCNG2 expression in VAT (P = .004) and SAT (P<.001) than the MO-L-IR and MO-H-IR patients. The MO-H-IR patients had a significantly lower CDK4 expression in VAT than the MO-L-IR (P = .026), but similar to the nonobese patients. CDK4 and CCNG2 expression correlated significantly in VAT (r = 0.511, P<.001) and SAT (r = .535, P = .001). In different multiple regression analysis models, CCNG2 and CDK4 expression in VAT was mainly predicted by glucose (P = .047 and P = .008, respectively), and CCNG2 expression in SAT was mainly predicted by body mass index (P = .041). No significant associations were found with CDK4 expression in SAT. Moreover, VAT CCNG2 expression was the main determinant of the improvement in the homeostasis model assessment of insulin resistance index at 3 months after bariatric surgery (B = -271.7, P = .026).ConclusionOur data show for the first time that the human CCNG2 and CDK4 expression of VAT are inversely associated with glucose and insulin resistance.     

New concepts in white adipose tissue physiology

Numerous studies address the physiology of adipose tissue (AT). The interest surrounding the physiology of AT is primarily the result of the epidemic outburst of obesity in various contemporary societies. Briefly, the two primary metabolic activities of white AT include lipogenesis and lipolysis. Throughout the last two decades, a new model of AT physiology has emerged. Although AT was considered to be primarily an abundant energy source, it is currently considered to be a prolific producer of biologically active substances, and, consequently, is now recognized as an endocrine organ. In addition to leptin, other biologically active substances secreted by AT, generally classified as cytokines, include adiponectin, interleukin-6, tumor necrosis factor-alpha, resistin, vaspin, visfatin, and many others now collectively referred to as adipokines. The secretion of such biologically active substances by AT indicates its importance as a metabolic regulator. Cell turnover of AT has also recently been investigated in terms of its biological role in adipogenesis. Consequently, the objective of this review is to provide a comprehensive critical review of the current literature concerning the metabolic (lipolysis, lipogenesis) and endocrine actions of AT.     

骨髓脂肪细胞在激素性骨坏死发生过程中的时序变化特点

目的血管外脂肪堆积如何参与激素性骨坏死的发病机制目前仍然不清楚。本课题应用建立的激素性骨坏死家兔模型研究骨髓脂肪细胞在骨坏死发生过程中组织病理形态学上的时序变化特点。方法32只28-32周龄成年新西兰大白兔分为正常对照组（n=16）和激素处理组（n=16）。激素处理组动物接受1次耳静脉内毒素注射和连续3次肌内糖皮质激素注射诱导骨坏死,正常对照组注射相应剂量的生理盐水。各组动物在最后一次注射糖皮质激素2周（早期）和4周（晚期）以后分别处死8只动物,获取双侧近端股骨,应用组织形态计量学技术分别测定股骨髓内脂肪细胞密度、脂肪细胞直径和脂肪细胞面积,同时进行骨坏死的组织病理学评价。结果激素处理早期组和晚期组骨髓脂肪细胞密度分别明显高于正常对照组67.1%和54.4%,但是早期组与晚期组之间差异不显著。激素处理晚期组骨髓脂肪细胞直径明显高于正常对照组,但是早期组骨髓脂肪细胞直径与正常对照组比较有减小趋势;激素处理早期组和晚期组骨髓脂肪细胞面积都分别明显高于正常对照组44%和83.6%,且晚期组亦显著高于早期组;脂肪细胞直径的频数分布显示,正常对照组峰值介于40-50μm,激素处理早期组较正常对照组增多的脂肪细胞直径介于30-40μm,晚期组较正常对照组增多的脂肪细胞直径介于50-60μm。组织病理学评价显示早期组骨坏死发生率为25%（2/8）,晚期组骨坏死发生率为87.5%（7/8）。结论在激素性骨坏死发生过程中,早期血管外脂肪堆积表现为大量生成的小脂肪细胞,后期血管外脂肪堆积表现为脂肪细胞出现肥大。     

Effects of sulfonylurea drugs on adiponectin production from 3T3-L1 adipocytes: implication of different mechanism from pioglitazone

Adiponectin is a fat-derived cytokine with anti-diabetic and anti-atherogenic properties. In this study, effects of sulfonylureas (SUs) on adiponectin production and the action mechanism were evaluated using 3T3-L1 adipocytes. The cells were incubated with glimepiride, glibenclamide, gliclazide, pioglitazone, metformin and the medium only as the control. In the control, the adiponectin level evaluated as the production rate per 24 h was not changed, while pioglitazone significantly increased the adiponectin level. SUs also increased the adiponectin level, but metformin failed to show any increase in adiponectin production. SUs induced adiponectin gene expression as well as pioglitazone. Pioglitazone significantly increased adipogenesis, but glimepiride did not. The aP2 gene expression was increased by pioglitazone, but not by glimepiride. Forskolin, a protein kinase A stimulator, reduced the adiponectin production stimulated by glimepiride but not by pioglitazone. These observations strongly suggest that SUs stimulate the adiponectin production through a different mechanism from pioglitazone, namely an interaction with protein kinase A activity. The significance of the extrapancreatic action of SUs observed in this study should be further evaluated in the clinical field.     

Adipose tissue and adipocyte dysregulation

Obesity-associated insulin resistance is a complex disorder involving a number of candidate molecules, pathways and transduction systems possessing potential causal actions. Inflammation in adipose tissue (AT) is one mechanism proposed to explain the development of insulin resistance, while identification of factors that lead to or cause AT dysfunction when it reaches its limit of expansion represents an important challenge. Pathological expansion of AT is characterized by changes in its blood flow, and the presence of enlarged and dysfunctional adipocytes that begin an inflammatory campaign of altered adipokine and cytokine secretions. Adipocyte senescence, necrosis and death are associated with increased immune cell and macrophage infiltration of AT in obesity. This can boost inflammation and reinforce fat cell dysfunction and death. In addition, pathological fat mass expansion is also related to limited recruitment of fat cell progenitors able to proliferate and differentiate into healthy small fat cells to compensate for cell death and preserve adipocyte numbers. Limiting vascular development and enhancing fibrotic processes worsen inflammation towards chronic irreversibility. The AT expandability hypothesis states that failure of AT expansion is one of the key factors linking positive energy balance and cardiometabolic risks, not obesity per se. Besides the usual treatment of obesity based on behavioral approaches (specific dietary/nutritional approaches together with increased physical activity), a number of questions remain concerning the possible recovery of metabolic health after inflammation-preventing interventions.