Department of Molecular Biology, School of Veterinary Medicine, University of California, Davis, CA, USA.
Division of Endocrinology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA.
Int J Obes (Lond). 2019 Jun;43(6):1164-1173. doi: 10.1038/s41366-018-0191-1. Epub 2018 Aug 20.
BACKGROUND/OBJECTIVES: African-American women have the greatest prevalence of obesity in the United States, and higher rates of type 2 diabetes than Caucasian women, yet paradoxically lower plasma triglycerides (TG), visceral fat and intrahepatic fat, and higher high-density lipoprotein (HDL)-cholesterol. Visceral fat has not been evaluated against insulin resistance in African-American women, and TG/HDL-cholesterol has been criticized as a poor biomarker for insulin resistance in mixed-sex African-American populations. Adipocyte hypertrophy, reflecting adipocyte dysfunction, predicts insulin resistance in Caucasians, but has not been studied in African-Americans. Our goal was to assess whether traditional correlates of insulin resistance, measures of adiposity and adipocyte characteristics similarly predict peripheral insulin resistance in African-American and Caucasian women.
SUBJECTS/METHODS: Thirty-four healthy African-American (n = 17) and Caucasian (n = 17) women, matched for age (mean = 53.0 yrs) and body mass index (BMI) (mean = 30 kg/m), underwent a steady-state plasma glucose test to measure insulin sensitivity; computed tomography (fat distribution); and a periumbilical scalpel biopsy (adipocyte characterization). By-race analyzes utilized analysis of covariance; linear regressions evaluated relationships between metabolic/adipose variables. All analyses adjusted for BMI and menopausal status.
Insulin sensitivity did not differ between groups (p = 0.65). Neither BMI, nor %body fat or thigh fat predicted insulin resistance in African-American women. Fasting TG (p = 0.046), HDL-cholesterol (p = 0.0006) and TG/HDL-cholesterol ratio (p = 0.009) strongly predicted insulin resistance in African-American women. Despite being lower in African-American women, hepatic fat and visceral adipose tissue (VAT) correlated with insulin resistance in both groups, as did fasting glucose, VAT/SAT (subcutaneous adipose tissue) ratio, and %SAT (inverse).
Total adiposity measures and adipocyte hypertrophy did not predict insulin resistance in African-American women, but did in Caucasian women. Plasma TG and HDL-cholesterol were significant predictors of insulin resistance in African-American women. Our findings demonstrate the need to identify race and sex-specific biomarkers for metabolic risk profiling.
背景/目的：非裔美国女性是美国肥胖率最高的人群，患 2 型糖尿病的比率高于白种女性，但她们的血浆甘油三酯（TG）、内脏脂肪和肝内脂肪水平较低，高密度脂蛋白（HDL）-胆固醇水平较高。尚未在非裔美国女性中评估内脏脂肪与胰岛素抵抗之间的关系，并且 TG/HDL-胆固醇已被批评为混合性别非裔美国人中胰岛素抵抗的不良生物标志物。脂肪细胞肥大反映了脂肪细胞功能障碍，可预测白种人的胰岛素抵抗，但尚未在非裔美国人中进行研究。我们的目标是评估传统的胰岛素抵抗相关指标、肥胖程度测量值和脂肪细胞特征是否同样可以预测非裔美国人和白种女性的外周胰岛素抵抗。
受试者/方法：34 名健康的非裔美国女性（n=17）和白种女性（n=17），年龄（平均=53.0 岁）和体重指数（BMI）（平均=30kg/m）相匹配，进行稳态血糖测试以测量胰岛素敏感性；计算机断层扫描（脂肪分布）；以及脐周手术刀活检（脂肪细胞特征）。按种族进行分析时使用协方差分析；线性回归评估代谢/脂肪变量之间的关系。所有分析均根据 BMI 和绝经状态进行调整。
两组之间的胰岛素敏感性没有差异（p=0.65）。非裔美国女性的 BMI 或体脂肪百分比或大腿脂肪均不能预测胰岛素抵抗。空腹 TG（p=0.046）、HDL-胆固醇（p=0.0006）和 TG/HDL-胆固醇比值（p=0.009）强烈预测了非裔美国女性的胰岛素抵抗。尽管非裔美国女性的肝脂肪和内脏脂肪组织（VAT）水平较低，但在两组中都与胰岛素抵抗相关，空腹血糖、VAT/SAT（皮下脂肪组织）比值和 %SAT（倒数）也是如此。
在非裔美国女性中，总脂肪量和脂肪细胞肥大不能预测胰岛素抵抗，但在白种女性中可以预测。血浆 TG 和 HDL-胆固醇是非裔美国女性胰岛素抵抗的重要预测指标。我们的研究结果表明，需要确定种族和性别特异性的代谢风险分析生物标志物。
