Insulin causes vasoconstriction but does not increase blood pressure in the elderly

Objective: Acute increases in plasma insulin (pINS) produce both sympathoexcitation and vasodilation in normal young adults. However, aging is associated with insulin resistance and maybe altered vascular and/or sympatheticresponses to insulin. Degign and Methods: Muscle sympathetic nerve activity (MSNA, microneurogaphy), forearm blood flow (FBF), blood pressure (HP) and heart rate (HR) responses to acute pINS increases were assessed in healthy, lean, normotensive elderly (ELD, N=l 1, BMI=25±lkg/m2, age=64±2y) and young (YNG. N=8, BMI=26±lkg/m2, age=27±2y) subjects. Data were collected during a 90 min insulin clamp. Data are mean ±SE. Results pINS(μU/ml) M-Value Mean, BP(mmHg) HR(beats/min) MSHA(b/min) Gruop control clamp (mg/kg mini control clamp ccptrot clamp control clamp ELD 9±2 88±104.3±0.4 95±2 94±2 62±2 63±2 33±3 44+4YNG 9±2 83+. 68,3±1.5t 84±2 a 86±2 a 61±3 65±315±2t 3l±4,ap<0.05 (clamp vs control) a p<0.05 (ELD vs YNG) Conclusions: 1) ELD show vasoconstriction, noi vasodifation, with insulin. 2) ELD have elevated resting MSNA but attenuated insulin-induced increases in MSNA. 3} BP did not increase with insulin in either group. 4) ELD lack the increased HR observed in the YNG. 5) ELD are more insulin resistant. The absence of vasodilation with insulin in the ELD may contribute to their insulin resistance by reducing glucose delivery. The vasoconstriction in the ELD is not due to exaggerated MSNA but to a failure of insulin's vasodilator action.