Associations between serum insulin and homocysteine in a Swedish population—a potential link between the metabolic syndrome and hyperhomocysteinemia: The Skaraborg project

The objective of this study is to examine the association between serum levels of insulin and homocysteine (Hcy) in a population-based sample of Swedish men and women. Men and women (537 and 571, respectively) 40 years or older, who were randomly selected from the population in Skara, southwestern Sweden, with valid information on serum levels of Hcy and insulin, were subject to a physical examination, including anthropometric measurement. Lifestyle factors were assessed by a questionnaire, and venous blood samples were drawn after an overnight fast. Insulin resistance was estimated by the homeostasis model assessment index. Homocysteine was higher in men (11.0 μmol/L) than in women (9.7 μmol/L) (P < .001) and was positively associated with age (P < .001 in both sexes) and serum creatinine (P = .009 in men, P < .001 in women), but inversely associated with leisure time physical activity (P = .012 in men, P = .001 in women). There was a positive association between serum insulin and serum Hcy independent of age and sex (P = .004). Upon exclusion of patients with diabetes and individuals with serum creatinine level greater than 130 μcat/L, this association was significant in the remaining 999 individuals also after adjustment for age, sex, serum creatinine, leisure time physical activity, body mass index, and smoking status (P = .003). A 1 SD difference in serum insulin corresponded to a difference of 0.5 μmol/L in serum Hcy. A similar association was found between insulin resistance and serum Hcy. In conclusion, there is an association between serum insulin and Hcy that may constitute a link between the metabolic syndrome and Hcy, either unilaterally or as part of a vicious circle.