Although women and men have about an equal prevalence of type 2 diabetes (DM), DM imposes a clinically significant excess relative risk of coronary heart disease (44% higher), stroke (27% higher) and vascular dementia (19% higher) in women compared to men. Understanding these sex differences could inform research to improve DM outcomes for both women and men. Postulated reasons for the ?female disadvantage? include an adverse cardiometabolic profile (particularly greater obesity) and disparities in aggressiveness of CV preventive treatments (e.g. use of statins). In addition, differences in endogenous sex hormones, including estradiol (E2), testosterone (T) and sex hormone binding globulin (SHBG), may contribute to the excess risk for women conferred by DM. Although lifestyle changes (diet, exercise and weight loss) are the cornerstone of diabetes management, it is not known if weight loss and healthier lifestyle can modulate the trajectory of sex hormones over time, and the role of these hormonal changes on cardiometabolic risk factors. The Action for Health In Diabetes (Look AHEAD) Study was a randomized controlled trial among 5,145 overweight individuals with obesity and type 2 diabetes designed to evaluate the effect of an Intensive Lifestyle Intervention (ILI) compared to a control group on incident CVD events. A major strength of Look AHEAD is its capacity to address questions of causation, because study participants were followed over 8 years (~3000 with longitudinal biospecimens for sex hormone measurements), with significant and well-characterized alterations in weight and with adjudicated clinical outcomes. In this proposal, we will first analyze the stored biospecimens for sex hormones (E2, T), SHBG and albumin. We will then 1) Test whether the ILI improves endogenous sex hormones over time and whether the effect of ILI is moderated by sex; 2) Evaluate the longitudinal associations between endogenous sex hormones and cardiometabolic risk factors (HbA1c, lipid levels, body mass index and weight, waist circumference, body composition, blood pressure) (primary outcomes); 3) Test the effect of the time-trajectory of endogenous sex hormones on improving cardio-metabolic risk factors and long term DM outcomes (i.e. CVD, stroke, chronic kidney disease and vascular dementia) over 8 years of followup, and whether differences exist by sex. Our overall hypothesis is that ILI improves the sex hormone profile, and that an unfavorable sex hormone profile, i.e. high free T in women and low free T in men, is associated with an adverse cardiometabolic risk profile. Ultimately, understanding the biological role of sex hormones in DM could target treatments, particularly lifestyle modification, and inform the prevention of CVD and other DM complications, to reduce DM-related morbidity and mortality for both women and men.
Type 2 diabetes confers a greater excess risk of cardiovascular disease in women than in men. We propose to use The Look AHEAD (Action for Health In Diabetes) Study to examine the association between endogenous sex hormones (testosterone, estradiol and sex hormone binding globulin) and cardiovascular disease risk factors, over 8 years, by sex, and in response to the intensive lifestyle intervention among 3000 study participants with type 2 diabetes.
