Abstract

Objective - Ingestion of a mixed meal recruits flow to muscle capillaries and increases total forearm blood flow in healthy young lean people. We examined whether these vascular responses are blunted by obesity.

Methods - We fed 8 middle-aged lean and 8 obese overnight-fasted volunteers a liquid mixed meal (480 kcal). Plasma glucose and insulin were measured every 30 min, and brachial artery flow and muscle microvascular recruitment (contrast ultrasound) were assessed every 60 min over 2 hrs following the meal.

Results - By 30 min, plasma glucose rose in both the lean (5.1 ± 0.1 vs 6.7 ± 0.4 mM, p<0.05) and the obese groups (5.4 ± 0.2 vs 6.7 ± 0.4 mM, p<0.05). Plasma insulin rose (28 ± 4 vs 241 ± 30 pM, p<0.05) by 30 min in the lean group and remained elevated for 2 hrs. The obese had higher fasting plasma insulin levels (65 ± 8 pM, p<0.001) and a greater post-meal area under the insulin-time curve (p<0.05). Brachial artery flow was increased at 120 min after the meal in the lean (38 ± 6 vs 83 ± 16 ml/min, p<0.05), but not in the obese. Muscle microvascular blood volume rose by 120 min in the lean group (14.4 ± 2.2 vs 24.4 ± 4.2 units, p<0.05) but not in the obese.

Conclusions – A mixed meal recruits muscle microvasculature in lean subjects and this effect is blunted by obesity. This impaired vascular recruitment lessens endothelial surface available and may thereby impair post-prandial glucose disposal.