AJP - Endocrinology and Metabolism, Vol 259, Issue 4 E542-E547, Copyright © 1990 by American Physiological Society
Lack of effect of hyperglycemia on lipolysis in humans
M. Caruso, G. D. Divertie, M. D. Jensen and J. M. Miles
Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota 55905.
Controversy exists regarding whether plasma glucose concentrations are
independently involved in the regulation of adipose tissue lipolysis. In
the present study, six subjects with insulin-dependent diabetes and six
nondiabetic volunteers were studied during infusion of somatostatin, growth
hormone, and insulin at rates designed to maintain basal rates of
lipolysis, which was traced using a constant infusion of [1-14C]palmitate.
A euglycemic (approximately 5 mmol/l) clamp was performed for 3 h, followed
by 3 h of hyperglycemia (approximately 9 and approximately 11 mmol/l in
nondiabetic and diabetic subjects, respectively). Ten nondiabetic subjects
were studied during 6 h of euglycemia to exclude time-dependent changes in
lipolysis. The results showed that palmitate concentrations did not change
between euglycemia and hyperglycemia in either group [118 +/- 10 vs. 132
+/- 14 mumol/l and 145 +/- 21 vs. 134 +/- 15 mumol/l in nondiabetic and
diabetic subjects, respectively; both P = not significant (NS)]. Similarly,
palmitate rate of appearance (Ra) did not change during hyperglycemia (1.0
+/- 0.1 and 1.7 +/- 0.4 mumol.kg-1.min-1 in nondiabetic and diabetic
subjects, respectively) compared with euglycemia (1.0 +/- 0.1 and 1.6 +/-
0.4 mumol.kg-1.min-1 in nondiabetic and diabetic subjects, respectively; P
= NS). Palmitate concentrations and Ra did not change during 6 h of
euglycemia in nondiabetic volunteers. Thus hyperglycemia per se has no
effect on free fatty acid turnover. Changes in lipolysis that occur
coincident with hyperglycemia are probably due to changes in other
circulating substrates or hormones known to affect lipolysis.
