Up-regulation of leptin in adipocytes exposed to high glucose and its effect in peritoneal angiogenesis

Objective By simulating a high-glucose condition of peritoneal dialysis (PD) fluid, to explore the effect of high glucose on the expression of leptin and its relationship with peritoneal angiogenesis. Methods Adipocytes differentiated from 3T3-L1 were divided into high glucose group (139 mmol/l glucose) and high mannitol group. Leptin levels in supernatant collected at 0 h, 12 h, 24 h and 48 h were measured by ELISA. Endothelial cells (ECs) were respectively cultured with normal glouse, high glucose, high mannitol condition, supernatants of adipocyte induced by normal glouse, high glucose and high mannitol, high glucose supernatants+leptin antibody, and high mannitol supernatants+leptin antibody. Tubular structure formation and migration of ECs were detected. Results Adipocytes exposed to high glucose for 48 h produced more leptin as compared with control group, high mannitol group, 12 h-high glucose group and 24 h-high glucose group (all P＜0.05). Compared with ECs in normal group, ECs in high glucose had less tubular structure formation and increased migration (all P＜0.01). Compared with those of ECs in high glucose, the tubular structure formation and the migration of ECs in adipocyte supernatants induced by high glucose had increased (all P＜0.01), and these effects were reduced by leptin antibody (all P＜0.01). Conclusion There is an up-regulation of leptin in adipocytes exposed to high glucose, which may be an alternative way to prevent peritoneal angiogenesis.     

脂肪来源干细胞体外成骨和成脂及成神经的诱导分化研究

目的 探讨脂肪组织来源干细胞 (adipose stem cell,ADSC) 的表面表型及向成骨、成脂和成神经多向分化的生物学特性.方法 取SD大鼠的腹股沟、附睾垫和腹膜后脂肪,Ⅰ型胶原酶消化、分离培养ADSC,检测第3代ADSC的CD29、CD44和CD45的表达情况.将ADSC加入成骨诱导剂,通过茜素红S染色鉴定成骨细胞;成脂诱导剂利用油红O染色鉴定脂肪细胞;神经干培养基诱导,免疫荧光染色鉴定诱导的神经元.结果 ADSC表达CD29(99.07±0.12)%、CD44(95.82±0.68)%和CD45(0.11±0.12)%.其经成骨诱导4周,茜素红S染色显示聚集的细胞团中央形成红色钙化结节,碱性磷酸酶染色可见到细胞的胞质内有紫红色颗粒;成脂诱导1周,油红O染色可见细胞质内有橙红色脂滴;经过神经干培养基诱导6 d后,免疫荧光染色显示诱导的细胞Nestin、NF-200及GFAP阳性表达.结论 ADSC表达间质干细胞的表面表型,体外经诱导培养后可向成骨细胞、脂肪细胞和神经元多向分化,表明 ADSC具有干细胞的多向分化潜能.     

膝关节滑膜间质干细胞分离、培养及其多向分化潜能特性的研究

目的 探讨晚期骨关节炎患者膝关节滑膜间质干细胞(synovium-derived mesenchymalstem cells,SMSCs)体外分离、培养的可行性及其在体外向脂肪细胞、成骨细胞和软骨细胞定向分化的特性.方法 取膝关节滑膜组织,胶原酶消化获得有核细胞.挑选单细胞克隆,筛选获得SMSCs.流式细胞技术检测细胞表面特异性抗原标志.培养至第三代,分别向脂肪细胞、成骨细胞和软骨细胞诱导分化.油红O染色鉴定向脂肪细胞分化;碱性磷酸酶染色、茜素红染色鉴定向成骨细胞分化;甲苯胺蓝染色鉴定向软骨细胞分化.RT-PCR检测脂肪细胞、成骨细胞标志基因.Ⅱ型胶原免疫组化染色检测软骨细胞Ⅱ型胶原的表达.结果 原代SMSCs体外培养呈葵花样细胞集落,传代后可见圆形巨噬样细胞和纺锤形成纤维样细胞,融合后呈成纤维细胞样生长.CD44、CD90呈阳性,CD34、CD71和CD45呈阴性.向脂肪细胞诱导21d,油红O染色阳性;RT-PCR检测有脂蛋白酶、乙二腈及PPARγ2表达;向成骨细胞诱导7、28 d,ALP,茜素红染色阳性,有ALP、Osteopontin及Osteocalcin表达;向软骨细胞诱导21d,甲苯胺蓝染色阳性,Ⅱ型胶原免疫组化染色阳性.结论 晚期骨关节炎患者膝关节滑膜组织可以分离、培养获得SMSCs. SMSCs具有向脂肪细胞、成骨细胞和软骨细胞发生定向分化的潜能.     

Metabolic disruption in male mice due to fetal exposure to low but not high doses of bisphenol A (BPA): Evidence for effects on body weight,food intake,adipocytes, leptin,adiponectin, insulin and glucose regulation

Exposure to bisphenol A (BPA) is implicated in many aspects of metabolic disease in humans and experimental animals. We fed pregnant CD-1 mice BPA at doses ranging from 5 to 50,000 μg/kg/day, spanning 10-fold below the reference dose to 10-fold above the currently predicted no adverse effect level (NOAEL). At BPA doses below the NOAEL that resulted in average unconjugated BPA between 2 and 200 pg/ml in fetal serum (AUC_0–24 h), we observed significant effects in adult male offspring: an age-related change in food intake, an increase in body weight and liver weight, abdominal adipocyte mass, number and volume, and in serum leptin and insulin, but a decrease in serum adiponectin and in glucose tolerance. For most of these outcomes non-monotonic dose–response relationships were observed; the highest BPA dose did not produce a significant effect for any outcome. A 0.1-μg/kg/day dose of DES resulted in some but not all low-dose BPA outcomes.     

Effects of estrogen therapy on bone marrow adipocytes in postmenopausal osteoporotic women

Summary  One-year treatment of osteoporotic postmenopausal women with transdermal estrogen resulted in significant decreases in bone marrow adipocyte volume and prevented increases in adipocyte number as compared to placebo-treated controls. Estrogen treatment also prevented increases in mean adipocyte size over 1 year. Introduction  Aging is associated not only with bone loss but also with increases in bone marrow adipocytes. Since osteoblasts and adipocytes are derived from a common precursor, it is possible that with aging, there is a preferential “switch” in commitment of this precursor to the adipocyte over the osteoblast lineage. We tested the hypothesis that the apparent “age-related” increase in marrow adipocytes is due, at least in part, to estrogen (E) deficiency. Methods  Reanalysis of bone biopsies from a randomized, placebo-controlled trial involving 56 postmenopausal osteoporotic women (mean age, 64 years) treated either with placebo (PL, n = 27) or transdermal estradiol (0.1 mg/d, n = 29) for 1 year. Results  Adipocyte volume/tissue volume (AV/TV) and adipocyte number (Ad#) increased (by ∼20%, P < 0.05) in the PL group, but were unchanged (Ad#) or decreased (AV/TV, by −24%, P < 0.001) in the E group. E treatment also prevented increases in mean adipocyte size over 1 year. Conclusions  These findings represent the first in vivo demonstration in humans that not only ongoing bone loss, but also the increase in bone marrow adipocyte number and size in postmenopausal osteoporotic women may be due, at least in part, to E deficiency. Supported by NIH Grants AG004875 and AG028936.     

高密度脂蛋白对3T3-L1脂肪细胞分泌白细胞介素8的影响

分别用不同浓度高密度脂蛋白(HDL,0、10、50和100μg/ml)孵育3T3-L1脂肪细胞16 h,再加入100 ng/ml脂多糖共同孵育6 h.用酶联免疫吸附法(ELISA)检测各组脂肪细胞培养液中的白细胞介素8水平,半定量逆转录多聚酶链式反应(RT-PCR)测定脂肪细胞PPARγmRNA的表达.结果 显示,脂多糖刺激使脂肪细胞分泌白细胞介素8增加(P＜0.05).不同浓度HDL干预的脂肪细胞分泌的白细胞介素8水平均低于脂多糖刺激组,并且呈剂量依赖性.不同浓度HDL干预的脂肪细胞PPARγmRNA表达较单用脂多糖刺激组显著升高.这些结果提示HDL可能通过上调PPARγ的表达、抑制脂肪细胞分泌白细胞介素8分泌.     

Fat cell enlargement is an independent marker of insulin resistance and ‘hyperleptinaemia’

Aims/hypothesis The aim of this study was to explore whether fat cell size in human subcutaneous and omental adipose tissue is independently related to insulin action and adipokine levels. Materials and methods Fat cells were prepared from abdominal subcutaneous biopsies obtained from 49 type 2 diabetic and 83 non-diabetic subjects and from omental biopsies obtained from 37 non-diabetic subjects. Cell size and insulin action on glucose uptake capacity in vitro were assessed in isolated fat cells. Insulin sensitivity in vivo was assessed with euglycaemic-hyperinsulinaemic clamps. Fasting blood samples were collected and adipokines and NEFA were measured. Results Negative correlations were found between subcutaneous fat cell size and insulin sensitivity assessed as M-value during clamp and as insulin action on glucose uptake in fat cells in vitro. This was seen in non-diabetic subjects after including age, sex and BMI in the analyses. No such relationship was found in type 2 diabetic subjects. In both groups, subcutaneous fat cell size correlated positively and independently with plasma levels of leptin but not to any of the other assessed adipokines. In non-diabetic subjects, omental fat cell size was independently and negatively correlated with insulin action in subcutaneous, but not omental, fat cells in vitro. Conclusions/interpretation Fat cell enlargement is associated with insulin resistance in non-diabetic individuals independently of BMI. This was not seen in type 2 diabetic subjects, suggesting that after development of type 2 diabetes other factors, not related to fat cell size, become more important for the modulation of insulin resistance.     

Fatty acid-induced mitochondrial uncoupling in adipocytes as a key protective factor against insulin resistance and beta cell dysfunction: a new concept in the pathogenesis of obesity-associated type 2 diabetes mellitus

Type 2 diabetes is associated with excessive food intake and a sedentary lifestyle. Local inflammation of white adipose tissue induces cytokine-mediated insulin resistance of adipocytes. This results in enhanced lipolysis within these cells. The fatty acids that are released into the cytosol can be removed by mitochondrial β-oxidation. The flux through this pathway is normally limited by the rate of ADP supply, which in turn is determined by the metabolic activity of the adipocyte. It is expected that the latter does not adapt to an increased rate of lipolysis. We propose that elevated fatty acid concentrations in the cytosol of adipocytes induce mitochondrial uncoupling and thereby allow mitochondria to remove much larger amounts of fatty acids. By this, release of fatty acids out of adipocytes into the circulation is prevented. When the rate of fatty acid release into the cytosol exceeds the β-oxidation capacity, cytosolic fatty acid concentrations increase and induce mitochondrial toxicity. This results in a decrease in β-oxidation capacity and the entry of fatty acids into the circulation. Unless these released fatty acids are removed by mitochondrial oxidation in active muscles, these fatty acids result in ectopic triacylglycerol deposits, induction of insulin resistance, beta cell damage and diabetes. Thiazolidinediones improve mitochondrial function within adipocytes and may in this way alleviate the burden imposed by the excessive fat accumulation associated with the metabolic syndrome. Thus, the number and activity of mitochondria within adipocytes contribute to the threshold at which fatty acids are released into the circulation, leading to insulin resistance and type 2 diabetes.     

Recombinant C3adesArg/acylation stimulating protein (ASP) is highly bioactive: A critical evaluation of C5L2 binding and 3T3-L1 adipocyte activation

C5L2 is a recently identified receptor for C5a/C5adesArg, C3a and C3adesArg (ASP). C5a/C5adesArg bind with high affinity, with no identified activation. By contrast, some studies demonstrate C3a/ASP binding/activation to C5L2; others do not. Our aim is to critically evaluate ASP/C3adesArg-C5L2 binding and bioactivity.Cell-associated fluorescent-ASP (Fl-ASP) binding to C5L2 increased from transiently transfected < stably transfected < Fl-ASP-sorted C5L2-HEK for both human C5L2 and mouse C5L2. Transfected C5L2-CHO cells had similar results. Endogenous C5L2 expression increased from 3T3-L1 preadipocytes < 3T3-L1 adipocytes < primary mouse adipocytes. Non-transfected cells ± Fl-ASP demonstrated background fluorescence only.In adherent C5L2-HEK (Fl-ASP sorted) and 3T3-L1 cells, blocking with 10% fetal calf serum, protamine sulfate or ovalbumin prevented ¹²⁵I-ASP non-specific binding (NSB, no cells), while albumin increased NSB. Binding to non-transfected HEK was comparable to NSB. Optimal specific binding was obtained at 20 °C (vs. 4 °C) in PBS or serum-free medium with K_d 83.7 ± 23.7 nM (C5L2-HEK), 66 ± 15 nM (C5L2-CHO) and 76 ± 14.3 nM (3T3-L1 preadipocytes); ¹²⁵I-C5a binding had greater affinity. Fl-ASP-C5L2 binding was comparable and concentration dependent (K_d 31 nM (direct binding) and IC₅₀ 35 nM (competition binding) regardless of conditions).Recombinant ASP (rASP) produced in modified Escherichia coli Origami (DE3) (allowing folding and disulphide bridge formation), purified under non-denaturing conditions demonstrated 10× greater bioactivity vs. proteolytically derived plasma ASP for triglyceride synthesis and fatty acid uptake in 3T3-L1 adipocytes and preadipocytes while adipose tissue from C5L2 KO mice was non-responsive. rASP stimulation of adipocyte BODIPY-fatty acid uptake demonstrated EC₅₀ 115 ± 93 nM and maximal stimulation of 413 ± 33%, p < 0.001. ASP binding has distinct characteristics that lead to C5L2 activation and increased bioactivity.