Metabolic and adrenergic characteristics of young men with insulin resistance

The primary site of insulin resistance, as measured by the euglycaemic glucose clamp technique, is skeletal muscle. We used the euglycaemic hyperinsulinaemic glucose clamp technique to assess insulin sensitivity (glucose disposal rate, GDR). We aimed at clarifying the demographic, metabolic, haemorrheological, haemodynamic, and by mental stress test the adrenergic characteristics of 21-year-old men grouped in tertiles according to their insulin (I) sensitivity index (GDR/I); insulin resistant group (GDR/I < 5.5 a.u., n = 17), intermediate group (5.5 < GDR/I < 9.5 a.u., n = 16) and insulin sensitive group (GDR/I > 9.5 a.u., n = 17). Insulin resistance was characterized by higher body mass index (p = 0.002, analysis of variance), triglycerides (p = 0.001), total cholesterol/high density lipoprotein cholesterol ratio (p = 0.002), haemoglobin (p = 0.013), haematocrit (p = 0.017) and resting heart rate (p = 0.041) but not resting blood pressure or catecholamines in arterialized blood. However, the mental stress caused by announcement of a forthcoming arithmetic stress test increased diastolic blood pressure and plasma epinephrine dependent on insulin resistance (p = 0.006 and p = 0.012, respectively) with a similar trend also for the maximal increases in heart rate and plasma norepinephrine during arithmetic. Thus, in healthy young men, insulin resistance is not associated with differences in baseline blood pressure but is characterized by higher body weight, disorders in blood lipids and haemorrheology and a hyperadrenergic response to mental stress that even involves blood pressure. We suggest that the sympathetic nervous system may be involved in the pathophysiology of the characteristic insulin resistance or metabolic cardiovascular syndrome in young men.