Key result
Fat emulsion infusion did not attenuate insulin-induced increases in calf blood flow (35% vs 35%) or muscle sympathetic nerve activity in lean healthy subjects.
Why the study?
Does acute induction of insulin resistance via fat emulsion infusion attenuate insulin-induced vasodilation and sympathetic activation in healthy lean subjects?
Does acute induction of insulin resistance via fat emulsion infusion attenuate insulin-induced vasodilation and sympathetic activation in healthy lean subjects?
Absolute Event Rate: 35% vs 35%
Acute induction of insulin resistance does not impair insulin-mediated vasodilation and sympathetic activation in lean subjects, suggesting hyperinsulinemia itself is the primary stimulus for these responses.
Acute fat emulsion does not blunt insulin's vascular or sympathetic effects in healthy subjects; leaves open relevance to chronic insulin resistance.
Insulin-induced stimulation of blood flow and sympathetic nerve activity in skeletal muscle tissue is impaired in obesity, but the underlying mechanism is unknown. To determine whether insulin resistance alters sympathetic and vasodilatory responses to euglycemic hyperinsulinemia, in eight healthy subjects we measured calf blood flow and muscle sympathetic nerve activity (MSNA) (n = 5) during insulin/glucose infusion (euglycemic hyperinsulinemic [6 pmol.kg-1.min-1] clamp) performed alone and performed during concomitant fat emulsion infusion, a maneuver designed to induce insulin resistance. The major new finding is that fat emulsion infusion, which attenuated insulin-induced stimulation of carbohydrate oxidation by 39 +/- 7% (P < 0.01), did not have any detectable effect on insulin-induced vasodilatory and sympathetic responses: at the end of the 2-h clamp, blood flow and MSNA had increased by 35 +/- 6% (P < 0.01) and 152 +/- 58% (P < 0.01), respectively, during insulin infusion alone and by 35 +/- 7% (P < 0.01) and 244 +/- 90% (P < 0.01), respectively, during insulin infusion superimposed on free fatty acid infusion. These observations in lean healthy subjects indicate that induction of resistance to the stimulatory effects of insulin on carbohydrate metabolism does not attenuate muscle blood flow and MSNA responses evoked by acute euglycemic hyperinsulinemia. These findings provide further evidence that hyperinsulinemia per se is the primary stimulus that triggers stimulation of muscle blood flow and MSNA during insulin/glucose infusion in humans and suggest that the impaired insulin-induced vasodilation in obese subjects is not related primarily to impaired stimulation of muscle carbohydrate metabolism.
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Vollenweider et al. (1995) studied Healthy (n=8). Fat emulsion infusion during euglycemic hyperinsulinemic clamp vs. Euglycemic hyperinsulinemic clamp alone was evaluated on Increase in calf blood flow. Fat emulsion infusion did not attenuate insulin-induced increases in calf blood flow (35% vs 35%) or muscle sympathetic nerve activity in lean healthy subjects.
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