腹部和大腿皮下脂肪组织抵抗素蛋白的表达

背景：抵抗素是脂肪细胞分泌的一种多肽激素。而中心性肥胖时可引起胰岛素抵抗和导致2型糖尿病。 目的：比较正常人腹部和大腿皮下脂肪组织抵抗素蛋白表达的情况，探讨抵抗素在中心性肥胖引起胰岛素抵抗中的作用。 设计：对照观察实验。 单位：华中科技大学同济医学院附属同济医院内分泌科。 对象：选择2003-01／04华中科技大学同济医学院附属同济医院外科住院患者20例，根据留取脂肪组织的部位分腹部皮下脂肪组织组12例和大腿皮下脂肪组织组8例。 方法：①所有患者测量血压、身高、体质量，计算体质量指数，体内脂肪百分比（按白种人数据推导的公式）：男性：1．2&;#215;体质量（kg）＋身高^-2（m^-2）＋0．23&;#215;年龄-16．2；女性：1．2&;#215;体质量（kg）＋身高^-2（m^-2）＋0．23&;#215;年龄-5．4。②葡萄糖氧化酶法测定空腹血糖。③留取的脂肪组织标本用单去污裂解液提取脂肪组织中的蛋白质，考马斯亮蓝法测定蛋白质浓度，Western-blot测量脂肪组织抵抗素蛋白的表达水平。 主要观察指标：两组患者的血压、体质量指数，体内脂肪百分比，空腹血糖，抵抗素蛋白的表达水平。 结果：纳入患者20例，均进入结果分析。①两组的空腹血糖、收缩压、舒张压、体质量指数、体内脂肪百分比差异无显著性（P〉0．05）。②腹部皮下脂肪组织抵抗素蛋白表达（A）为14942&;#177;6076。明显高于大腿皮下脂肪组织组39421&;#177;6087，二者比较差异显著（P〈0．01）。 结论：抵抗素蛋白在腹部皮下脂肪组织的表达高于腿部皮下脂肪组织，此结果对中心性肥胖并引起胰岛素抵抗和2型糖尿病的发生具有参考价值。     

2型糖尿病大鼠大网膜和皮下脂肪组织抵抗素基因的表达

目的:观察实验性2型糖尿病大鼠大网膜与皮下脂肪组织抵抗素基因的表达,探讨抵抗素与胰岛素抵抗的关系。方法:实验于2003-09/2004-06在郑州大学第一附属医院内分泌实验室完成。选择雌性Wistar大鼠30只,随机抽签法分为普通饲料组(8只)和高脂饲料组(22只),高脂饲料组大鼠采用0.1mol/L链脲佐菌素尾静脉注射加高脂喂养的方法建立2型糖尿病模型15只,随机抽取8只作为糖尿病组,普通饲料组为正常对照组。检测两组大鼠的空腹血糖、胰岛素、胰岛素敏感性指数、血清胆固醇及三酰甘油。采用反转录-聚合酶链反应检测两组大鼠大网膜和皮下脂肪组织中抵抗素基因的表达。结果:纳入动物16只,均进入结果分析。①糖尿病组大鼠胰岛素敏感性指数与正常对照组大鼠相比明显降低(分别为-4.89±0.20,-2.63±0.42,P<0.01),空腹血糖、胰岛素、三酰甘油和胆固醇明显升高[空腹血糖分别为(12.89±1.18),(4.86±0.68)mmol/L;胰岛素分别为(10.51±1.93),(3.07±1.15)μU/L;三酰甘油分别为(2.63±0.71),(1.13±0.17)mmol/L;胆固醇分别为(1.73±0.15),(1.25±0.17)mmol/L,P<0.01]。②以A值比表示,糖尿病组大网膜脂肪组织的抵抗素基因表达与正常对照组皮下和大网膜脂肪组织、糖尿病组皮下脂肪组织比较明显升高(分别为0.27±0.03,0.15±0.02,0.15±0.03,0.17±0.02,P<0.01),而后三者间相比差异无显著性(P>0.01)。结论:抵抗素基因在2型糖尿病大鼠大网膜脂肪组织中表达升高,可能是腹型肥胖更易导致胰岛素抵抗的重要原因之一。     

肥胖人群抵抗素表达与血清游离脂肪酸、肿瘤坏死因子α、脂联素水平的研究

目的了解3种脂肪细胞因子(游离脂肪酸、肿瘤坏死因子α和脂联素)与肥胖人群抵抗素表达的关系。方法选取19例肥胖和29例非肥胖受试者,采用逆转录聚合酶链反应(RT-PCR)方法,检测腹部皮下与大网膜脂肪组织中抵抗素mRNA的表达,同时测定血清抵抗素、肿瘤坏死因子α(TNF-α)、游离脂肪酸(FFA)和脂联素等指标,计算胰岛素敏感性指数及胰岛素抵抗指数(HOMA-IR)。结果肥胖组的血清FFA、TNF-α和抵抗素水平高于非肥胖组(均P<0.05);而血清脂联素水平却低于非肥胖组(P<0.05);抵抗素在各组皮下及网膜脂肪组织中的表达差异均无统计学意义;以血清抵抗素为因变量进行多元逐步回归分析,显示脂联素、TNF-α、皮下脂肪组织中抵抗素表达、FFA进入回归方程;相关分析显示,血清抵抗素与体质量指数、FFA、TNF-α、HOMA-IR呈正相关(分别r=0.457,P=0.008;r=0.708,P=0.000;r=0.520,P=0.006;r=0.703,P=0.000),与血清脂联素水平呈负相关(r=-0.928,P=0.000);皮下脂肪中抵抗素表达与TNF-α呈负相关(r=-0.352,P=0.039),与网膜脂肪中抵抗素的表达呈正相关(r=0.285,P=0.05),与血清FFA和脂联素水平无相关性。结论提示TNF-α、皮下脂肪组织中抵抗素表达和FFA对血清抵抗素水平具有正性影响,而脂联素对抵抗素水平产生负性作用;TNF-α可能下调皮下脂肪中抵抗素的表达。     

胰岛素抵抗人群皮下脂肪组织中脂肪甘油三酯脂酶和激素敏感性脂肪酶表达减低

目的 通过检测胰岛素抵抗人群皮下脂肪组织中脂肪甘油三酯脂酶(ATGL)和激素敏感性脂肪酶(HSL)的表达,探讨脂肪动员异常与胰岛素抵抗的关系及在胰岛素抵抗中的作用.方法 选则本院择期行腹腔镜胆囊切除术的住院患者55例,根据胰岛素抵抗指数,将患者分为胰岛素敏感组27例和胰岛素抵抗组28例.在手术过程中取皮下脂肪组织.采用半定量逆转录聚合酶链反应测定脂肪组织中ATGL、HSLmRNA的表达,采用Westernblot法测定脂肪组织中ATGL、HSL蛋白的表达.结果 胰岛素抵抗组的体质量指数、腰臀比、血清甘油三酯、血清空腹胰岛素及游离脂肪酸水平均明显高于胰岛素敏感组,体质量指数25.31±1.54 vs 23.11±1.03,腰臀比0.98±0.24 vs 0.75±0.15,甘油三酯(1.98±0.56)mmol/L VS(1.04±0.24)mmol/L,空腹胰岛素(25.87±14.21)mU/LVS(11.15±4.67)mU/L.游离脂肪酸(1.35±0.46)mmol/L vs (0.66±0.23)mmol/ L(P<0.01).胰岛素抵抗组皮下脂肪组织中ATGL mRNA和蛋白表达均明显低于胰岛素敏感组,0.92±0.13 vs 2.03±0.21、1.03±0.08 vs 1.98±0.11(P<0.01);HSL mRNA和蛋白表达也均明显低于胰岛素敏感组,1.35±0.21 vs 1.64±0.12、1.25±0.09 VS 1.42±0.15(P<0.01).ATGL的蛋白表达与空腹胰岛素、胰岛素抵抗指数及游离脂肪酸呈负相关(r=-0.235、-0.356和-0.214,P<0.01或<0.05);HSL 的蛋白表达与空腹胰岛素、游离脂肪酸和腰臀比呈负相关(r=-0.185、-0.246和-0.145,P<0.01或<0.05).结论 胰岛素抵抗状态时皮下脂肪组织中ATGL和HsL的表达减低.     

过氧化物酶体增殖物激活受体γ2在妊娠期糖尿病患者腹部皮下脂肪组织中的表达

目的:探讨过氧化物酶体增殖物激活受体(PPAR)γ2的表达变化在妊娠期糖尿病(GDM)发病机制中的作用.方法:正常妊娠和GDM孕妇各40例,每组各有20例体质指数正常者和20例肥胖或超重者.收集腹部皮下脂肪组织,分别用RT-PCR技术和Western blot印迹法检测组织中PPARγ2 mRNA及其蛋白的表达,同时测定空腹血糖、空腹胰岛素、体质指数等临床指标.结果:与正常妊娠妇女比较,孕前体质指数匹配的GDM患者均存在明显的胰岛素抵抗,但GDM两组间的胰岛素抵抗程度差异无显著性(P＞0.05);GDM患者腹部皮下脂肪组织中的PPARγ2mRNA及其蛋白质的表达水平均显著升高,肥胖或超重GDM患者尤为显著,其差异均有显著性(P＜0.05).此外,PPARγ2 mRNA及其蛋白质的表达水平与体质指数、空腹胰岛素水平呈正相关(r值分别为0.67、0.59、0.63、0.56,均P＜0.01).结论:PPARγ2表达升高参与了胰岛素抵抗的发生,与GDM的发病关系密切;PPARγ2的表达除了与血胰岛素水平显著相关外,还会受到肥胖因素的影响.     

代谢综合征患者与抵抗素的相关性研究

目的探讨代谢综合征(MS)患者血清抵抗素水平与血脂、肥胖和胰岛素抵抗的关系。方法88例MS患者和26例年龄相匹配的正常对照组按体质量指数(BMI)将MS患者分为肥胖组和非肥胖组,采用酶联免疫吸附测定(ELISA)法测定受试者空腹血清抵抗素水平,同时检测其身高、体质量、腰围、臀围、血压、血糖、血脂及胰岛素水平,并计算其BMI、腰臀比和胰岛素抵抗指数。结果MS患者肥胖组与正常对照组相比其血清抵抗素水平明显升高,分别为[(28.08±11.92)μg/L vs(18.96±6.27)μg/L,P<0.01],非肥胖组与对照组比血清抵抗素水平明显升高分别为[(25.96±12.08)μg/L vs(18.96±6.27)μg/L,P<0.01],肥胖组和非肥胖组相比其血清抵抗素水平差异亦有统计学意义(P<0.05),相关分析显示空腹血清抵抗素水平与BMI、腰臀比、胰岛素抵抗指数呈正相关(r值分别为0.31、0.21、0.23,均P<0.05),与血糖、血压、血脂无相关性(P>0.05)。结论MS患者血清抵抗素水平明显升高,且与肥胖及胰岛素抵抗程度有明显的相关性,因而抵抗素可能为肥胖和胰岛素抵抗、MS、2型糖尿病及心血管疾病的主要连接点。     

肥胖人群脂联素、抵抗素和胰岛素抵抗水平的研究

目的 探讨肥胖患者血清脂联素、抵抗素和胰岛素抵抗水平的变化及意义.方法 分别测定106例肥胖者和107名健康对照者的体重指数(BMI)、腰围、臀围、空腹胰岛素、空腹血糖、血脂、脂联素和抵抗素水平,计算胰岛素抵抗指数(HOMA-IRI). 结果 肥胖者的体重指数(BMI)、体脂分布百分比(BF)、HOMA-IRI、抵抗素...     

大网膜脂肪组织中胰岛素受体底物1、葡萄糖转运蛋白4和抵抗素mRNA表达水平与代谢综合征的关系

目的:分析代谢综合征患者大网膜脂肪组织胰岛素受体底物1、葡萄糖转运蛋白4和抵抗素mRNA表达水平及其与代谢综合征相关指标的关系。方法:选择2003-02/08在青岛大学医学院附属医院普通外科及妇科择期手术的患者53例,均知情同意。根据代谢综合征的诊断标准分为两组:①代谢综合征组28例,分为两个亚组:2型糖尿病组13例,非糖尿病组15例。②对照组25例。手术前当天抽取患者空腹血,测定空腹血糖、三酰甘油、空腹胰岛素。手术中取大网膜脂肪组织约200mg,用于RNA提取。采用一步法半定量反转录聚合酶链反应技术,测定患者大网膜脂肪组织中胰岛素受体底物1、葡萄糖转运蛋白4以及抵抗素的mRNA表达水平。结果:代谢综合征组28例,对照组25例患者全部进入结果分析,无脱落。①代谢综合征组患者大网膜脂肪组织胰岛素受体底物1、葡萄糖转运蛋白4mRNA表达均显著低于对照组(P<0.01)。2型糖尿病患者的胰岛素受体底物1mRNA、葡萄糖转运蛋白4mRNA表达显著低于非糖尿病患者(P<0.01)。②代谢综合征组与对照组患者胰岛素受体底物1与葡萄糖转运蛋白4的mRNA表达呈显著正相关(r=0.661,0.621,P<0.01)。③多因素逐步回归分析显示腰臀比与胰岛素抵抗指数及胰岛素受体底物1、葡萄糖转运蛋白4mRNA表达均有明显的相关性。④抵抗素mRNA表达阳性率和表达量在2型糖尿病代谢综合征患者、非糖尿病代谢综合征患者与对照组之间差异均无显著性意义(P=0.121,P=0.228),与腰臀比、体质量指数、胰岛素抵抗指数、空腹血糖、空腹胰岛素、三酰甘油以及血压均无相关性(P>0.05)。结论:代谢综合征患者大网膜脂肪组织胰岛素受体底物1与葡萄糖转运蛋白4mRNA表达明显降低,其中以2型糖尿病患者表现最为显著。大网膜脂肪组织抵抗素mRNA表达与代谢综合征及2型糖尿病无关。胰岛素受体底物1、葡萄糖转运蛋白4的mRNA表达和腰臀比可联合预测胰岛素抵抗的程度。     

高脂饮食肥胖模型小鼠脂肪组织受体相互作用蛋白140基因的表达

背景：受体相互作用蛋白140基因敲除小鼠可通过增加线粒体生物功能、脂肪酸氧化、氧化磷酸化等代谢途径来抵抗高脂饮食诱导的肥胖。 目的：构建高脂饮食致肥胖模型小鼠,观察脂肪组织受体相互作用蛋白140 mRNA表达水平变化及胰岛素抵抗的关系。 方法：将C57BL/6J雄性小鼠随机分为对照组和高脂饮食组,分别喂养14周后,测量2组小鼠体质量,选取高脂饮食组中体质量大于对照组小鼠平均体质量20%的小鼠作为肥胖组小鼠。 结果与结论：高脂饮食组小鼠中有12只符合标准计入肥胖组。肥胖组小鼠三酰甘油、总胆固醇、空腹血糖、空腹胰岛素水平和胰岛素抵抗指数均明显高于对照组（P＜0.05或P＜0.01）;肥胖组小鼠脂肪组织中受体相互作用蛋白140 mRNA的表达高于对照组（P＜0.05）;且小鼠脂肪组织受体相互作用蛋白140 mRNA表达水平与三酰甘油水平、胰岛素抵抗指数呈正相关（r=0.526,P＜0.05;r=0.465,P＜0.05）,而与总胆固醇、空腹血糖、空腹胰岛素水平无相关性（P＞0.05）。     

代谢综合征患者血清抵抗素和瘦素与2型糖尿病相关性研究

目的探讨代谢综合征(metabolic syndrome,MS)患者血清抵抗素、瘦素与2型糖尿病(type 2diabetes mellitus,T2DM)的关系。方法选取T2DM并MS患者29例(T2DM+MS组)、非T2DM的MS患者28例(单纯MS组)、体检健康者30例(对照组),采用放射免疫方法检测血清抵抗素、瘦素水平,同时检测身高、体质量、血压、空腹血糖、血脂、血尿酸、胰岛素,并计算体质指数和胰岛素抵抗指数。结果 T2DM+MS组、单纯MS组与对照组空腹血糖、收缩压、舒张压、高密度脂蛋白胆固醇、三酰甘油、瘦素、胰岛素水平和胰岛素抵抗指数比较差异均有统计学意义(P<0.05);T2DM+MS组与单纯MS组空腹血糖、收缩压、瘦素和胰岛素水平比较差异有统计学意义(P<0.05);抵抗素水平升高与体质量指数、血尿酸、收缩压和胰岛素抵抗指数相关;瘦素水平升高与体质量指数、空腹血糖、胰岛素和胰岛素抵抗指数相关。结论血清瘦素和抵抗素水平与MS密切相关,高血清瘦素水平在MS和T2DM形成及发展中起重要作用。     

2型糖尿病大鼠模型抵抗素基因表达与胰岛素敏感指数的相关性

背景:抵抗素作为一种蛋白质激素,具有直接对抗胰岛素的作用,其可能是肥胖者易发2型糖尿病的关键分子.目的:构建2型糖尿病大鼠模型并观察大鼠抵抗素的基因表达与胰岛素敏感指数的关系,观察罗格列酮对抵抗素基因表达的影响.设计:随机对照,动物实验.单位:郑州大学第一附属医院老年病科.材料:选用健康雌性Wistar大鼠30只,鼠龄2个月,购自华中科技大学同济医学院动物中心.实验用普通饲料由华中科技大学同济医学院动物中心提供,总热量为14..8 J/g(质量分数:蛋白质0.2,碳水化合物0.61,脂肪0.17);高脂饲料由普通饲料加蔗糖、炼猪油、鸡蛋、奶粉混合而成,总热量为20.083 J/g(蛋白质0.09,碳水化合物0.51,脂肪0.38).大鼠抵抗素及β-actin引物由北京赛百盛公司合成.方法:实验于2006-10/2007-10在郑州大学第一附属医院完成.实验过程中对动物的处置符合动物伦理学要求.适应性喂养大鼠2周后,随机分为普通饲料组8只和高脂饲料组22只.高脂饲料组大鼠尾静脉注射链脲佐菌素25 mg/kg,注射后第2人开始给予高脂饮食;普通饲料组给予柠檬酸钠一柠檬酸缓冲液1 mL/kg尾静脉注射,继续普通饲料喂养.高脂饲料喂养12周后有15只大鼠符合2型糖尿病模型标准,被随机分为罗格列酮组8只和模型组7只,前组用罗格列酮2 mg/(kg·d)灌胃,后组用蒸馏水8 mL/(kg·d)灌胃;普通饲料组灌胃等量蒸馏水,干预4周.主要观察指标:应用葡萄糖氧化酶法测定血糖;采用磁性分离酶联免疫法测定胰岛素;采用酶法测定血清三酰甘油和总胆固醇.计算胰岛素敏感指数(1/空腹血糖×空腹胰岛素).用反转录-聚合酶链反应检测大网膜脂肪组织抵抗素mRNA的表达.应用Spearman相关分析和多元逐步回归分析显示抵抗素基因与胰岛素敏感指数的关系.结果:造模成功15只和对照组大鼠8只进入结果分析.①大网膜脂肪组织抵抗素基因表达(A值):模型组为0.27±0.031,明显高于普通饲料和罗格列酮组(0.15±0.018和0.20±0.024,P<0.01).②Spearman相关分析和多元逐步回归分析结果:抵抗素基因与空腹血糖、空腹胰岛素和胰岛素敏感指数分别呈正相关(r=0.271、0.283和0.323,P<0.01);多元逐步回归分析显示,胰岛素敏感指数对抵抗素基因的作用最显著(R2=0.081).结论:2型糖尿病大鼠抵抗素基因表达升高,且与胰岛素敏感指数相关;罗格列酮可逆转此状况.     

健康体检人群体脂肪含量与血压水平的关系

目的 探讨体脂肪含量(BF%)与血压水平之间的关系.方法 采用横断面研究的方法对健康体检者904例测量身高、体重、血压,检测血糖、血脂及血尿酸,利用生物电阻抗(BIA)原理进行BF%测定.结果 高血压组BF%高于正常组.按BF%四分位分组,结果显示男女两性的收缩压、舒张压、平均动脉压及高血压检出率均随BF%水平升高而增高的趋势.多因素Logistic回归分析显示性别、甘油三酯、血糖、BF%、年龄和尿酸是高血压的危险因素.男性BF%、BMI和WHR判定高血压的ROC曲线下面积分别为0.696(95% CI:0.651~0.740)、0.707(95% CI:0.664~0.751)和0.762(95% CI:0.722~0.802).女性分别为0.780(95% CI:0.720~0.840)、0.797(95% CI:0.735~0.859)和0.844(95% CI:0.796~0.893).结论 BF%是高血压的危险因素,BF%对高血压诊断价值与BMI相近,略低于WHR.     

BMI and objectively measured body fat and body fat distribution in prepubertal children

BACKGROUND: Body Mass Index (BMI) is often used as a surrogate estimate of body fat in epidemiological studies. This study explores the association between BMI, body fat and body fat distribution assessed by Dual-Energy X-Ray Absorptiometry (DXA) in younger children. METHODS: Cross-sectional study of 246 children (138 boys and 108 girls) aged 8-11 years. DXA was used to quantify abdominal fat mass (AFM), total body fat (TBF) and also total body fat as percentage of total body mass (BF%). Body fat distribution was calculated as AFM/TBF. RESULTS: We found close correlations between BMI vs. TBF, BF% and AFM (r = 0.94, r = 0.92 and r = 0.93) for boys and (r = 0.95, r = 0.92 and r = 0.95) for girls, respectively (P<0.05 for all r-values). However, significantly lower correlation (P<0.001 for difference between the r-values) existed for body fat distribution (r = 0.64 for boys and 0.73 for girls). CONCLUSION: Percentage body fat, TBF and AFM were all closely associated with BMI, suggesting that BMI serves as a good surrogate marker for obesity in population studies. However, a significantly lower correlation existed for BMI vs. body fat distribution, which may be a limitation when BMI is used to study cardiovascular risk factors in epidemiological studies.     

Prdm16 determines the thermogenic program of subcutaneous white adipose tissue in mice

The white adipose organ is composed of both subcutaneous and several intra-abdominal depots. Excess abdominal adiposity is a major risk factor for metabolic disease in rodents and humans, while expansion of subcutaneous fat does not carry the same risks. Brown adipose produces heat as a defense against hypothermia and obesity, and the appearance of brown-like adipocytes within white adipose tissue depots is associated with improved metabolic phenotypes. Thus, understanding the differences in cell biology and function of these different adipose cell types and depots may be critical to the development of new therapies for metabolic disease. Here, we found that Prdm16, a brown adipose determination factor, is selectively expressed in subcutaneous white adipocytes relative to other white fat depots in mice. Transgenic expression of Prdm16 in fat tissue robustly induced the development of brown-like adipocytes in subcutaneous, but not epididymal, adipose depots. Prdm16 transgenic mice displayed increased energy expenditure, limited weight gain, and improved glucose tolerance in response to a high-fat diet. shRNA-mediated depletion of Prdm16 in isolated subcutaneous adipocytes caused a sharp decrease in the expression of thermogenic genes and a reduction in uncoupled cellular respiration. Finally, Prdm16 haploinsufficiency reduced the brown fat phenotype in white adipose tissue stimulated by β-adrenergic agonists. These results demonstrate that Prdm16 is a cell-autonomous determinant of a brown fat-like gene program and thermogenesis in subcutaneous adipose tissues.     

Effects of weight loss on visceral and abdominal subcutaneous adipose tissue blood-flow and insulin-mediated glucose uptake in healthy obese subjects

Objective. Rapid weight loss with very-low-calorie diet (VLCD) is known to improve insulin sensitivity and decrease adipose tissue masses. The aim was to investigate the effects of VLCD on adipose tissue regional glucose uptake (rGU) and perfusion and their association with adipokines.

Research design and methods. Sixteen healthy obese (body mass index 33±1.1 kg/m²) subjects underwent VLCD for 6 weeks. RGU and perfusion were measured using [¹⁸F]-fluoro-deoxy-glucose, [¹⁵O]H₂O and positron emission tomography.

Results. Blood-flow and rGU expressed per gram of adipose tissue were higher in visceral fat compared to abdominal subcutaneous fat (P<0.01 for both). Dieting decreased weight by 11±0.9 kg (P<0.0001). Visceral adipose fat decreased by 25% (P<0.001) and abdominal subcutaneous fat by 16% (P<0.001). Whole body insulin sensitivity increased by 33% (P<0.01). Perfusion of both fat depots decreased (P<0.001), while rGU remained unchanged. Among the adipokines, leptin and interleukin-6 levels seemed to be associated with abdominal subcutaneous and intra-abdominal adipose tissue insulin resistance but not with adipose tissue perfusion.

Conclusions. Abdominal adipose tissue perfusion and rGU are not related in obesity. Rapid weight loss decreases perfusion through adipose tissue depots but has no influence on rGU demonstrating the ‘sink’ role of adipose tissue.     

Aging per se does not influence glucose homeostasis: in vivo and in vitro evidence

OBJECTIVE: To assess the effect of age on glucose metabolism by examining 1) glucose metabolism in young and middle-aged subjects when total or regional adiposity is taken into account and 2) in vitro glucose transport in adipose tissue explants from young and middle-aged women paired for total and abdominal adiposity. RESEARCH DESIGN AND METHODS: Study 1: body composition, subcutaneous abdominal and visceral adipose tissue areas, and fasting and oral glucose-stimulated glucose and insulin were measured in 84 young and 81 middle-aged men and in 110 young and 91 middle-aged women. Study 2: glucose uptake in subcutaneous abdominal and visceral adipose tissue explants were measured in eight young and eight middle-aged women. RESULTS: Study 1: young and middle-aged men showed similar subcutaneous abdominal tissue area, whereas fat mass and visceral adipose tissue were greater in middle-aged than in young men (P < 0.01). Fat mass and subcutaneous and visceral adipose tissue areas were greater in middle-aged as compared with young women (P < 0.01). Fasting plasma glucose and the glucose response to an oral glucose tolerance test were significantly higher in middle-aged than in young men and women (P < 0.001). Statistical control for visceral adipose tissue area eliminated the difference seen in glucose response in men and women. Study 2: glucose transport in subcutaneous and omental adipose tissue did not differ between young and middle-aged women. CONCLUSIONS: 1) Visceral obesity, more than age per se, correlates with glucose intolerance in middle-aged subjects; 2) aging does not influence in vitro adipose tissue glucose uptake.     

Visceral adiposity and the risk of impaired glucose tolerance: a prospective study among Japanese Americans

OBJECTIVE: Greater visceral adiposity, higher insulin resistance, and impaired insulin secretion increase the risk of type 2 diabetes. Whether visceral adiposity increases risk of impaired glucose tolerance (IGT) independent of other adipose depots, insulin resistance, and insulin secretion is not known. RESEARCH DESIGN AND METHODS: Study subjects included 128 Japanese Americans with normal glucose tolerance at entry. Baseline variables included plasma glucose and insulin measured after an overnight fast and during a 75-g oral glucose tolerance test, fat areas by computed tomography, insulin secretion (incremental insulin response [IIR] [30 min insulin - fasting insulin]/30 min glucose), and insulin resistance index (homeostasis model assessment for insulin resistance [HOMA-IR]). RESULTS: During the 10- to 11-year follow-up period, we confirmed 57 cases of IGT. Significant predictors of IGT included intra-abdominal fat area (IAFA) (odds ratio [OR] for a 1 SD increase 3.82, 95% CI 1.63-8.94 at a fasting plasma glucose [FPG] level of 4.5 mmol/l), HOMA-IR (2.41, 1.15-5.04), IIR (0.30, 0.13-0.69 at an FPG level of 4.5 mmol/l), the interactions of IAFA by FPG (P = 0.003), and IIR by FPG (P = 0.030) after adjusting for age, sex, FPG, and BMI. The multiple-adjusted OR of IAFA increased and that of IIR decreased as FPG level decreased because of these interactions. Even after adjustment for total fat area, total subcutaneous fat area, or abdominal subcutaneous fat area, all of these associations remained a significant predictor of IGT incidence. CONCLUSIONS: Greater visceral adiposity increases the risk of IGT independent of insulin resistance, insulin secretion, and other adipose depots in Japanese Americans.