Changes in skeletal muscle vascular resistance with weight gain: associations with insulin and sympathetic activity

This study was designed to characterize changes in peripheral vascular resistance with weight gain, and whether these changes are correlated with insulin and/or sympathetic activity.

Femoral vascular resistance (FVR), mean arterial pressure, heart rate, and plasma insulin were measured before and during overfeeding in seven dogs with unilateral lumbar ganglionectomy (L3 to L6). Measurements were taken standing and while walking on a treadmill.

There was a significant main effect of weight gain to increase mean arterial pressure (16.5+/-8.4 mmHg and 12.5+/-6.8 mmHg increase for standing and walking baseline, respectively) and heart rate (increase from week 1 of 31.6+/-10.6 beats/minute standing and 38.3+/-9.1 walking beat/minute). FVR increased immediately with overfeeding/ weight gain [standing: denervated (DNX):1.32+/-0.3 to 2.34+/-0.5; intact: 0.88+/-0.17 to 1.9+/-0.33 mmHg/mL.min(-1)], but returned to baseline with continued weight gain. Return of FVR to baseline occurred between weeks 2 and 3 of overfeeding in the DNX limb, but did not return to baseline until week 6 in the innervated limb. These changes were not correlated with plasma insulin levels.

These data suggest that vascular resistance may be normal in the obese, but increases in vascular resistance occur early with weight gain (before changes in arterial pressure). This initial increase in vascular resistance could initiate the series of events leading to obesity-associated hypertension. Additionally, changing vascular resistance during weight gain may be influenced by sympathetic activity, because DNX limb FVR returned to baseline approximately 3 weeks earlier than the innervated limb.