Are serum nitric oxide metabolites associated with fasting insulin among Iranian adults? (Tehran Lipid and Glucose Study)

Aim: It has been suggested that insulin resistance is associated with altered nitric oxide (NO) homeostasis. There is however no population-based study documenting an association between fasting serum insulin and serum NO metabolites (NOx) with multivariable adjustment. This study was therefore designed to determine the association between serum NOx and fasting insulin levels and insulin resistance/sensitivity indices in a sample of a population-based study in Iran. Materials and methods: This study, performed within the framework of the Tehran Lipid and Glucose Study (TLGS), analyzed the data of 1518 non-diabetic subjects (955 women), aged 20-87 years, who had participated in phase III of the TLGS (2006-2008). Serum NOx concentrations were measured using the Griess method. Fasting serum insulin was measured by the electrochemiluminescence immunoassay method. Multiple regression analysis was used to determine the association between serum NOx concentration and quartiles of insulin and insulin resistance/sensitivity indices (HOMA1-IR, HOMA2-IR, and QUICKI). Results: NOx concentration in women only was weakly correlated with HOMA1-IR (r = 0.07, P = 0.03) and QUICKI (r = -0.07, P = 0.03), whereas no significant association was observed in men (P > 0.05). Marginally significant correlations were also found between serum NOx and fasting insulin concentration (r = 0.062, p = 0.057) and HOMA2-IR (r = 0.063, p = 0.053) in women. NOx concentration differed significantly between quartiles of insulin and insulin resistance/sensitivity indices among women and the total population (P < 0.05), associations which remained significant after age adjustment (P < 0.05), but not after adjustment for other confounding variables (P > 0.05). Conclusions: Fasting serum insulin level and insulin resistance/sensitivity indices are not associated with serum NOx level after multivariable adjustment.