RESUMO
Mexican Americans (MA) exhibit high risk for the insulin resistance syndrome characterized by subclinical inflammation and greater risk for type 2 diabetes compared with non-Hispanic white (NHW) adults. The reasons for this phenomenon remain obscure. Because the inflammatory cytokine, tumor necrosis factor-alpha (TNF alpha), is associated with insulin resistance in various models of obesity and diabetes, we sought to determine whether circulating concentrations of this cytokine and its soluble receptors are higher in MA than NHW, and also to determine if the TNF alpha system is related to the lower insulin sensitivity in MA. Fasting blood samples were used to determine concentrations of TNF alpha, soluble TNF receptors 1 (sTNFR1) and 2 (sTNFR2) in the same 13 MA (7 women, 6 men, age=27.0+/-2.0 years, BMI=23.0+/-0.7) and 13 NHW (7 women, 6 men, age=24.8+/-1.5 years, BMI=22.8+/-0.6) previously shown to exhibit differences in insulin sensitivity. Circulating TNF alpha was significantly higher (3.11+/-0.38 vs. 2.10+/-0.24 pg/ml, p<0.05) and sTNFR2 was significantly lower (1324+/-85 vs. 1925+/-127 pg/ml, p<0.05) among MA compared with NHW subjects. Soluble TNFR1 was not different between groups (MA: 970+/-111 pg/ml vs. NHW: 1218+/-73 pg/ml, p=0.07). TNF alpha, sTNFR1 and sTNFR2 were not correlated with HOMA-IR when the two groups were analyzed in aggregate. This study documents higher circulating TNF alpha concentrations in non-obese, non-diabetic MA, a population group at increased risk for the metabolic syndrome and the untoward effects of sub-clinical inflammation. The clinical implications of this difference, if any, are not yet known.
Assuntos
Resistência à Insulina/etnologia , Fator de Necrose Tumoral alfa/biossíntese , Adolescente , Adulto , Estatura , Índice de Massa Corporal , Peso Corporal , Feminino , Glucose/metabolismo , Humanos , Inflamação , Insulina/metabolismo , Masculino , Americanos Mexicanos , México , Obesidade/sangue , Receptores Tipo I de Fatores de Necrose Tumoral/sangue , Receptores Tipo II do Fator de Necrose Tumoral/sangue , Risco , Estados UnidosRESUMO
We determined whether lower insulin sensitivity persists in young, nonobese, nondiabetic Mexican-American [MA; n = 13, 27.0 +/- 2.0 yr, body mass index (BMI) 23.0 +/- 0.7] compared with non-Hispanic white (NHW; n = 13, 24.8 +/- 1.5 yr, BMI 22.8 +/- 0.6) males and females after accounting for cardiorespiratory fitness (maximal O(2) uptake), abdominal fat distribution (computed tomography scans), dietary intake (4-day records), and skeletal muscle insulin-signaling protein abundance from muscle biopsies (Western blot analysis). MA were significantly less insulin sensitive compared with their NHW counterparts when estimated by homeostatic model assessment of insulin resistance (MA: 1.53 +/- 0.22 vs. NHW: 0.87 +/- 0.16, P < 0.05) and the revised quantitative insulin sensitivity check index (MA: 0.45 +/- 0.08 vs. NHW: 0.58 +/- 0.19, P = 0.05). However, skeletal muscle protein abundance of insulin receptor-beta (IRbeta), phosphatidylinositol 3-kinase p85 subunit, Akt1, Akt2, and GLUT4 were not significantly different. Differences in indexes of insulin sensitivity lost significance after percent dietary intake of palmitic acid, palmitoleic acid, and skeletal muscle protein abundance of IRbeta were accounted for. We conclude that differences in insulin sensitivity between nonobese, nondiabetic MA and NHW persist after effects of chronic and acute exercise and total and abdominal fat distribution are accounted for. These differences may be mediated, in part, by dietary fat intake.