腎素與血管張力素系統抑制劑對於脂肪細胞功能的影響

Effects of Renin-Angiotensin System Blockers on Adipocyte Function

洪薇雯(Wei-Wen Hung)

指導教授 ： 辛錫璋

高雄醫學大學/醫學院/醫學研究所/碩士(2008年)

https://doi.org/10.6832/KMU.2008.00119

摘要

前言：肥胖是第2型糖尿病的主要危險因子，肥胖者的脂肪細胞產生病變，造成胰島素阻抗性，導致糖尿病。大規模的臨床研究已證實腎素與血管張力素系統抑制劑(RAS blockers)的使用，包括血管張力素轉換酵素抑制劑(ACEI)與血管張力素第一型接受器阻斷劑(AT1R blocker)可以降低第2型糖尿病的發生率；因此，RAS blockers是否能調控脂肪細胞的分化與脂肪細胞激素的分泌，並改善脂肪細胞的胰島素阻抗性，是我們研究的重點所在。
研究方法：以3T3-L1前驅脂肪細胞進行細胞培養，並分為對照組(未誘發分化)、誘發組、與誘發並加入ACEI、AT1R blocker、或AT2R blocker，觀察在不同分化天數的脂肪細胞分化與脂肪油滴聚集，以Oil-red O方法進行細胞染色，以real-time聚合酶連鎖反應分析欲觀察的脂肪細胞激素之mRNA，以蛋白質電泳(西方點墨法)分析欲瞭解的蛋白質濃度變化。
研究結果：隨著3T3-L1脂肪細胞分化天數的增加，脂肪細胞逐漸變大且脂肪油滴在細胞內堆積，脂肪細胞激素mRNA的表現隨之上升；血管張力素原的mRNA表現也是；AT1R mRNA的表現反而下降；ACE與AT2R的mRNA表現則在分化第二天升到最高。ACEI、AT1R blocker、和AT2R blocker可以改變脂肪細胞分化的程度與脂肪油滴聚集的情形，同時降低脂肪細胞激素分泌；且AT1R blocker與AT2R blocker可以修復脂肪細胞的IRS-1與Akt蛋白質之磷酸化，ACEI則沒有影響。
討論：ACEI可能是經由IRS-1與Akt以外的機轉而改變脂肪細胞分化；AT1R blocker與AT2R blocker則透過修復IRS-1與Akt的磷酸化改善胰島素在脂肪細胞訊息傳遞路徑；但是這兩個接受器本身在脂肪細胞分化過程中可能以不同方式進行調控，一是AT1R的接受器活性增強，另一則是AT2R的mRNA表現增加；AT1R blocker與AT2R blocker則阻斷各自的接受器作用並改善胰島素阻抗性。我們的研究結果是RAS blockers降低糖尿病發生率的理論基礎，冀望應用於臨床上治療並預防肥胖及其相關併發症的產生。

關鍵字

腎素與血管張力素系統 ； 脂肪細胞激素 ； 血管張力素轉換酵素抑制劑 ； 血管張力素接受器阻斷劑

並列摘要

Background: Obesity has been regarded as a major risk factor for type 2 diabetes. In the adipocytes of obese subjects, pathologic changes lead to insulin resistance and cause diabetes. Many large clinical outcome trials have shown blockade of the rennin-angiotensin system (RAS) with angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) reduces the incidence of type 2 diabetes. The aim of our study is to determine the effects of RAS blockers on adipocyte differentiation and adipokine secretion.
Material and Method: The 3T3-L1 preadipocytes were used for cell culture and divided into Control group (no induction), Induction group，Induction plus ACEI or AT1R blocker or AT2R blocker. We described the state of adipocyte differentiation and fat accumulation. Oil-red O stain for cell staining, real-time PCR for mRNA analysis, and Western blot for protein analysis were performed.
Results: We found that as 3T3-L1 adipocytes differentiate, the cells enlarge with fat accumulation. The expressions of adipokine mRNA increased and so did angiotensinogen mRNA. AT1R mRNA was down-regulated. Expressions of ACE mRNA and AT2R mRNA reached the peak at day 2 of adipocyte differentiation. Additions of ACEI, AT1R blocker, or AT2R blocker changed the extents of adipocyte differentiation and fat accumulation with down-regulation of adipokine secretions. Besides, AT1R blocker and AT2R blocker but not ACEI restored the phosphorylation of IRS-1 and Akt proteins.
Discussion: ACEI might modulate adipocyte differentiations via mechanisms other than the IRS-1 and Akt pathways. AT1R blocker and AT2R blocker improved insulin signaling by restoring IRS-1 and Akt phosphorylation. The two receptors might have different ways of modulation, either to increase receptor activity (AT1R) or to increase mRNA expression (AT2R), which were blocked by its blockers to improve insulin resistance. Our results is the rationale that RAS blockers decrease the incidence of diabetes, which may be applied clinically to treat or even prevent obesity and its realted complications.

並列關鍵字

Renin-Angiotensin System ； Adipokine ； angiotensin-converting enzyme inhibitor ； angiotensin II receptor blocker

參考文獻

1. Sharma AM. The obese patient with diabetes mellitus: from research targets to treatment options. Am J Med. 2006;119(5 Suppl 1):S17-23.

2. Kopelman PG. Obesity as a medical problem. Nature. 2000;404(6778):635-643.

3. Lin YC, Yen LL, Chen SY, Kao MD, Tzeng MS, Huang PC, Pan WH. Prevalence of overweight and obesity and its associated factors: findings from National Nutrition and Health Survey in Taiwan, 1993-1996. Prev Med. 2003;37(3):233-241.

4. Pan WH, Flegal KM, Chang HY, Yeh WT, Yeh CJ, Lee WC. Body mass index and obesity-related metabolic disorders in Taiwanese and US whites and blacks: implications for definitions of overweight and obesity for Asians. Am J Clin Nutr. 2004;79(1):31-39.

5. Zimmet P, Alberti KG, Shaw J. Global and societal implications of the diabetes epidemic. Nature. 2001;414(6865):782-787.