坎地沙坦对自发性高血压大鼠胰岛素抵抗及血清脂联素的影响

目的: 探讨血管紧张素II受体拮抗剂坎地沙坦对自发性高血压大鼠(SHR)糖代谢及血清脂联素的影响。方法: SHR大鼠分为两组:高血压组(SHR,n=30);坎地沙坦组(坎地沙坦,1 mg·kg^-1·d^-1,n=30, 灌胃法给药),另设同种系WKY大鼠为对照组,给予同等量安慰剂, 12周后分别用生化方法和放射免疫方法测定空腹血糖(FBG)和胰岛素水平(FINS),计算IR指数(HOMA-IR),用生化方法进行口服葡萄糖耐量试验(OGTT),ELISA分析法测定血清脂联素水平。结果: 空腹血糖高血压组和对照组大鼠差异无统计学意义(P>0.05);空腹胰岛素水平和HOMA-IR与高血压组大鼠相比,对照组和坎地沙坦组要明显降低 (P<0.05);OGTT结果显示,30 min 和 120 min 血糖水平与高血压组相比,对照组和坎地沙坦给药组明显降低(P<0.05)。血清脂联素的水平与高血压组相比,对照组和坎地沙坦大鼠明显较高(P<0.05)。结论: 血管紧张素II 受体拮抗剂坎地沙坦可以升高高血压血清脂联素水平,改善IR,降低30、120 min 餐后血糖水平。     

Hepatic and Adipose Tissue Depot-Specific Changes in Lipid Metabolism in Late-Onset Obese (LOB) Rats

Transgenic Late-onset OBesity (LOB) rats slowly develop a male-specific, autosomal dominant, obesity phenotype with a specific increase in peri-renal white adipose tissue (WAT) depot and preserved insulin sensitivity (Bains et al. in Endocrinology 145:2666–2679, 2004). To better understand the remarkable phenotype of these rats, the lipid metabolism was investigated in male LOB and non-transgenic (NT) littermates. Total plasma cholesterol (C) levels were normal but total plasma triacylglycerol (TAG) (2.8-fold) and hepatic TAG content (25%) was elevated in LOB males. Plasma VLDL-C and VLDL-TAG levels were higher while plasma apoB levels were 60% lower in LOB males. Increased hepatic TAG secretion explained the increased VLDL levels in LOB males. The hepatic gene expression of FAS, SCD-1, mitochondrial (mt)GPAT, and DGAT2 was up-regulated in both old obese and young non-obese LOB rats. Lipoprotein lipase (LPL) activity in heart and epididymal white adipose tissue (WAT) was unchanged, while LPL activity was increased in peri-renal WAT (30%) and decreased in soleus muscle (40%). Moreover, FAS, SCD-1 and DGAT2 gene expression was increased in peri-renal, but not in epididymal WAT. Basal lipolysis was reduced or unchanged and β-adrenergic stimulated lipolysis was reduced in WAT from both old obese and young non-obese LOB rats. To summarize, the obese phenotype of LOB male rats is associated with increased hepatic TAG production and secretion, a shift in LPL activity from skeletal muscle to WAT, reduced lipolytic response in WAT depots and a specific increase in expression of genes responsible for fatty acid and TAG synthesis in the peri-renal depot. F. Frick and R. Hume contributed equally to this work.     

Dietary Supplementation of Calcium may Counteract Obesity in Mice Mediated by Changes in Plasma Fatty Acids

The scope of this study was to assess the impact of calcium and conjugated linoleic acid (CLA) supplementation on plasma fatty acid profiles and to evaluate potential synergistic effects of both compounds against dietary obesity. Mice separated into five experimental groups were followed: control (C), high-fat diet (HF), HF with calcium (Ca), HF plus CLA and HF with both Ca and CLA. Plasma metabolites and fatty acids were determined by commercial kits and gas chromatography, respectively. Both dietary calcium and CLA supplementation contributed to lower body fat gain under a HF diet. Maximum efficacy was seen with calcium; no additional effect was associated with the combined treatment with CLA. Plasma leptin, adiponectin and HOMA index were in accordance with an altered glucose/insulin homeostasis in the HF and HF + CLA groups, whereas control levels were attained under Ca-enriched diets. Plasma fatty acids showed minor changes associated to CLA treatment, but a high impact on PUFA was observed under Ca-enriched diets. Our results show that the mechanism underlying the anti-obesity effects of calcium supplementation is mediated mainly by changes in PUFA plasma profile. In addition, the lack of synergy on body weight reduction in combination with associated lipid profiles of calcium and CLA suggests that calcium may interfere with absorption and/or bioactivity of CLA, which can be of relevance when using CLA-fortified dairy products against human obesity.     

Regulation of adiponectin secretion and expression by insulin and β‐agonists in rat

The adipocytokines, including adiponectin, are important factors in the regulation of insulin sensitivity and carbohydrate and lipid metabolism. It is proved that concentrations of adiponectin are decreased in obesity, an insulin resistant state. The current study is to address potential mechanisms regulating adiponectin secretion and expression in vivo. To observe the regulation of adiponectin by fasting‐refeeding and β‐agonists, male Wistar rats were fasted for 18 h and allowed to refeed with/without a β3‐adrenergic receptor agonist infused into refeeding rats. We also investigated the effects of insulin clamp on adiponectin secretion and expression, including euglycemic–hyperinsulinemic clamp and hyperglycemic–hyperinsulinemic clamp. Plasma adiponectin levels were determined by radioimmunoassay. Using real‐time PCR assays, we analyzed the expression of adiponectin genes in rat primary adipocytes. Refeeding of 18‐h fasted rats increased plasma adiponectin concentration (～2‐fold) and adipose tissue adiponectin expression (～3‐fold), and these effects were mimicked by hyperinsulinemia in the absence of refeeding and completely blocked by administration of β‐agonists during refeeding. We conclude that (i) adiponectin secretion and expression are acutely regulated in vivo by nutritional status; (ii) in vivo, insulin and β‐agonists act directly at the adipocyte to regulate adiponectin secretion and expression.     

The signaling pathway in modulating bone metabolism after dental implant in diabetes

Diabetes Mellitus is a systematic disease with complications in multi-organs, including decreased implant osseointegration and a high failure rate of dental transplants. Accumulating evidence indicates that the signaling pathway directly impacts the process of bone metabolism and inflammatory response implicated with dental implants in diabetic patients. This review summarizes the recent advance in signaling pathways regulate osseointegration and inflammatory response in dental transplantation, aiming to identify the potential therapeutic target to reduce the dental transplant failure in diabetes patients, with emphasis on the surface characteristics of the implant, inflammatory signaling, AMPK, PPARγ, WNT, ROS, and adiponectin signaling.     

Syzygium aqueum leaf extract and its bioactive compounds enhances pre-adipocyte differentiation and 2-NBDG uptake in 3T3-L1 cells

The insulin-like and/or insulin-sensitising effects of Syzygium aqueum leaf extract and its six bioactive compounds; 4-hydroxybenzaldehyde, myricetin-3-O-rhamnoside, europetin-3-O-rhamnoside, phloretin, myrigalone-G and myrigalone-B were investigated in 3T3-L1 adipocytes. We observed that, S. aqueum leaf extract (0.04–5 μg/ml) and its six bioactive compounds (0.08–10 μM) at non-cytotoxic concentrations were effectively enhance adipogenesis, stimulate glucose uptake and increase adiponectin secretion in 3T3-L1 adipocytes. Clearly, the compounds myricetin-3-O-rhamnoside and europetin-3-O-rhamnoside showed insulin-like and insulin-sensitising effects on adipocytes from a concentration of 0.08 μM. These compounds were far better than rosiglitazone and the other isolated compounds in enhancing adipogenesis, stimulating 2-NBDG uptake and increasing adiponectin secretion at all the concentrations tested. These suggest the antidiabetic potential of S. aqueum leaf extract and its six bioactive compounds. However, further molecular interaction studies to explain the mechanisms of action are highly warranted.     

Trans-Cinnamic Acid Increases Adiponectin and the Phosphorylation of AMP-Activated Protein Kinase through G-Protein-Coupled Receptor Signaling in 3T3-L1 Adipocytes

Adiponectin and intracellular 5′adenosine monophosphate-activated protein kinase (AMPK) are important modulators of glucose and fat metabolism. Cinnamon exerts beneficial effects by improving insulin sensitivity and blood lipids, e.g., through increasing adiponectin concentrations and AMPK activation. The underlying mechanism is unknown. The G_i/G_o-protein-coupled receptor (GPR) 109A stimulates adiponectin secretion after binding its ligand niacin. Trans-cinnamic acid (tCA), a compound of cinnamon is another ligand. We hypothesize whether AMPK activation and adiponectin secretion by tCA is transmitted by GPR signaling. Differentiated 3T3-L1 cells were incubated with pertussis toxin (PTX), an inhibitor of G_i/G_o-protein-coupling, and treated with different tCA concentrations. Treatment with tCA increased adiponectin and the pAMPK/AMPK ratio (p ≤ 0.001). PTX incubation abolished the increased pAMPK/AMPK ratio and adiponectin secretion. The latter remained increased compared to controls (p ≤ 0.002). tCA treatment stimulated adiponectin secretion and AMPK activation; the inhibitory effect of PTX suggests GPR is involved in tCA stimulated signaling.     

脂联素与肥胖的相关性的meta分析

目的本研究拟探讨脂联素与肥胖的相关性及其在肥胖相关的2型糖尿病中的可能作用。方法对上溯至2000年的脂联素与糖尿病及肥胖的前瞻性及横断面研究进行检索。数据分析采用Cochrane协作网提供的RevMan4.2软件进行meta分析。危险度分析采用比值比作为效应量表示结果,连续性变量采用加权均数差值分析。两者均以95%可信区间(CI)表示。应用固定效应模型和随机效应模型分析结果。结果(1)脂联素四分位最低组与最高组相比,男性(P<0.00001)和女性(P=0.0001)BMI都有明显差异。女性差异比男性更大些;(2)在男性肥胖者中,脂联素的水平与非肥胖组差异不明显(P=0.64);在女性肥胖者中,两者差异也不明显(P=0.20)。结论脂联素与肥胖具有明显关联,但其机制较复杂,且可能在肥胖在2型糖尿病的早期作用机制中起到作用。     

Linoleic Acid Decreases Leptin and Adiponectin Secretion from Primary Rat Adipocytes in the Presence of Insulin

Obesity rates have dramatically increased over the last few decades and, at the same time, major changes in the type of fatty acid intake have occurred. Linoleic acid, an n-6 polyunsaturated fatty acid, is an essential fatty acid occurring in high amounts in several western diets. A potential role of this fatty acid on obesity has been suggested. Controversial effects of linoleic acid on insulin sensitivity have also been reported. Thus, the aim of this study was to examine the direct effects of linoleic acid on leptin and adiponectin production, two adipokines known to influence weight gain and insulin sensitivity. Because insulin-stimulated glucose metabolism is an important regulator of leptin production, the effects of linoleic acid on adipocyte metabolism were also examined. For this purpose, isolated rat adipocytes were incubated with linoleic acid (1–200 μM) in the absence or presence of insulin. Linoleic acid (1–200 μM) significantly decreased insulin-stimulated leptin secretion and expression (P < 0.05), however, no changes in basal leptin production were observed. Linoleic acid also induced a significant decrease (~20%) in adiponectin secretion (P < 0.05), but only in the presence of insulin and at the highest concentration tested (200 μM). This fatty acid did not modify either glucose uptake or lactate production and the percentage of glucose metabolized to lactate was not changed either. Together, these results suggest that linoleic acid seems to interfere with other insulin signalling pathway different from those controlling glucose uptake and metabolism, but involved in the regulation of leptin and adiponectin production.