Xu Fen, Lin Beisi, Zhou Yinli, Deng Hongrong, Bi Yan, Liang Hua
Department of Endocrinology, Third Affiliated Hospital, Sun Yat-sen University, Guangzhou 510630, China.
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Zhonghua Yi Xue Za Zhi. 2014 Oct 21;94(38):2992-5.
To explore the effects of insulin therapy on the expression of pigment epithelium-derived factor (PEDF) in adipocytes of type 2 diabetic mellitus (T2DM) in rats.
A total of 22 newly diagnosed type 2 diabetics received a 2-week intensive insulin therapy. The levels of fasting plasma glucose (FPG), serum triglyceride and PEDF were measured before and after therapy. T2DM was induced by a high-fat diet and a low-dose streptozotocin (STZ). The Spraque-Dawley rats were divided randomly into diabetic, insulin treatment and gliclazide treatment groups. Another group with a chow diet was designated as normal controls. Differentiated 3T3-L1 adipocytes were then incubated with tumor necrosis factor-alpha (TNF-α) and (or) insulin for 24 h. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot were used to detect the expression of PEDF in adipose tissue or adipocytes. The PEDF levels in both sera and cell supernatant were measured by enzyme-linked immunosorbent assay (ELISA). Glucose uptake was detected after treatment of PEDF or anti-PEDF antibody simultaneously together with insulin in mature 3T3-L1 adipocytes.
Insulin therapy decreased the serum levels of FPG and triglyceride of T2DM patients ((12.9 ± 2.8) vs (5.9 ± 1.4) mmol/L, (3.1 ± 1.8) vs (1.7 ± 0.8) mmol/L, P < 0.05) while the serum level of PEDF decreased significantly after therapy ((22.85 ± 5.73) vs (18.38 ± 5.28) µg/L, P < 0.05). Consistently the serum level of PEDF of diabetic rats was remarkably higher than that of normal controls and insulin-treated group ((28.6 ± 0.5) vs (25.4 ± 0.6) and (25.3 ± 0.6) µg/L, P < 0.05). And the elevated levels of PEDF, TNF-α mRNA and protein in adipose tissue (P < 0.05) could be reduced by insulin treatment (P < 0.05). However, no obvious change was detected in gliclazide treatment group. Further evidences suggested that TNF-α could induce more secretion and expression of PEDF in 3T3-L1 adipocyte while this effect became ameliorated by insulin treatment. Furthermore, decreased capacity of glucose uptake by PEDF might be reversed by anti-PEDF antibody in 3T3-L1 adipocytes (P < 0.05).
Insulin can down-regulate the expression of PEDF in adipocytes of T2DM and improve the glucose uptake of adipocytes. It may be one of the mechanisms through which insulin therapy improves peripheral insulin resistance.
探讨胰岛素治疗对2型糖尿病（T2DM）大鼠脂肪细胞中色素上皮衍生因子（PEDF）表达的影响。
22例新诊断的2型糖尿病患者接受为期2周的强化胰岛素治疗。治疗前后测量空腹血糖（FPG）、血清甘油三酯和PEDF水平。通过高脂饮食和低剂量链脲佐菌素（STZ）诱导T2DM。将Spraque-Dawley大鼠随机分为糖尿病组、胰岛素治疗组和格列齐特治疗组。另一组给予普通饮食作为正常对照组。然后将分化的3T3-L1脂肪细胞与肿瘤坏死因子-α（TNF-α）和（或）胰岛素孵育24小时。采用定量逆转录-聚合酶链反应（qRT-PCR）和蛋白质印迹法检测脂肪组织或脂肪细胞中PEDF的表达。采用酶联免疫吸附测定（ELISA）法检测血清和细胞上清液中的PEDF水平。在成熟的3T3-L1脂肪细胞中，同时用PEDF或抗PEDF抗体与胰岛素处理后检测葡萄糖摄取。
胰岛素治疗降低了T2DM患者的血清FPG和甘油三酯水平（（12.9±2.8）对（5.9±1.4）mmol/L，（3.1±1.8）对（1.7±0.8）mmol/L，P<0.05），而治疗后血清PEDF水平显著降低（（22.85±5.73）对（18.38±5.28）μg/L，P<0.05）。同样，糖尿病大鼠的血清PEDF水平显著高于正常对照组和胰岛素治疗组（（28.6±0.5）对（25.4±0.6）和（25.3±0.6）μg/L，P<0.05）。胰岛素治疗可降低脂肪组织中升高的PEDF、TNF-α mRNA和蛋白水平（P<0.05）。然而，格列齐特治疗组未检测到明显变化。进一步的证据表明，TNF-α可诱导3T3-L1脂肪细胞中更多的PEDF分泌和表达，而胰岛素治疗可改善这种作用。此外，抗PEDF抗体可逆转3T3-L1脂肪细胞中PEDF降低的葡萄糖摄取能力（P<0.05）。
胰岛素可下调T2DM脂肪细胞中PEDF的表达，改善脂肪细胞的葡萄糖摄取。这可能是胰岛素治疗改善外周胰岛素抵抗的机制之一。
