Daily rhythms of diabetogenic factors in men: role of type 2 diabetes and body weight

Obesity is a major cause of type 2 diabetes. Transition from obesity to type 2 diabetes manifests in the dysregulation of hormones controlling glucose homeostasis and inflammation. As metabolism is a dynamic process that changes across 24-hours, we assessed diurnal rhythmicity in a panel of 10 diabetes-related hormones. Plasma hormones were analysed every 2-hours over 24-hours in a controlled laboratory study with hourly isocaloric drinks during wake. To separate effects of body mass from type 2 diabetes, we recruited 3 groups of middle-aged men; an overweight group with type 2 diabetes and 2 control groups (lean and overweight). Average daily concentrations of glucose, triacylglycerol and all the hormones except visfatin were significantly higher in the overweight group compared to the lean group (P < 0.001). In type 2 diabetes, glucose, insulin, C-peptide, glucose-dependent insulinotropic peptide and glucagon-like peptide-1 increased further (P < 0.05), whereas triacylglycerol, ghrelin and plasminogen activator inhibitor-1 concentrations were significantly lower compared to the overweight group (P < 0.001). Insulin, C-peptide, glucose-dependent insulinotropic peptide and leptin exhibited significant diurnal rhythms in all study groups (P < 0.05). Other hormones were only rhythmic in 1 or 2 groups. In every group, hormones associated with glucose regulation (insulin, C-peptide, glucose-dependent insulinotropic peptide, ghrelin and plasminogen activator inhibitor-1), triacylglycerol and glucose peaked in the afternoon whereas glucagon and hormones associated with appetite and inflammation peaked at night. Thus being overweight with or without type 2 diabetes significantly affected hormone concentrations but did not affect the timing of the hormonal rhythms.