Involvement of non-esterified fatty acid oxidation in glucocorticoid-induced peripheral insulin resistance in vivo in rats.
The mechanism by which glucocorticoids induce insulin resistance was studied in normal rats administered for 2 days with corticosterone then tested by euglycaemic hyperinsulinaemic clamps. Corticosterone administration induced a slight hyperglycaemia, hyperinsulinaemia and increased non-esterified fatty acid levels. It impaired insulin-stimulated total glucose utilization (corticosterone 15.7 +/- 0.7; controls 24.6 +/- 0.8 mg.kg-1 x min-1), as well as residual hepatic glucose production (corticosterone 4.9 +/- 1.0; controls 2.0 +/- 0.7 mg.kg-1 x min-1). During the clamps, insulin did not decrease the elevated non-esterified fatty acid levels in corticosterone-administered rats (corticosterone 1.38 +/- 0.15, controls 0.22 +/- 0.04 mmol/l). Corticosterone administration decreased the in vivo insulin-stimulated glucose utilization index by individual muscles by 62 +/- 6%, and the de novo glycogen synthesis by 78 +/- 2% (n = 8-9 muscles). GLUT4 protein and mRNA levels were either unchanged or slightly increased by corticosterone administration. Inhibition of lipid oxidation by etomoxir prevented corticosterone-induced muscle but not hepatic insulin resistance. In conclusion, glucocorticoid-induced muscle insulin resistance is due to excessive non-esterified fatty acid oxidation, possibly via increased glucose fatty-acid cycle ultimately inhibiting glucose transport, or via decreased glycogen synthesis, or by a direct effect on glucose transporter translocation or activity or both.
Guillaume-Gentil
C
C
Laboratories de Recherches Métaboliques, Faculty and Department of Medicine, University of Geneva, Switzerland.
Assimacopoulos-Jeannet
F
F
Jeanrenaud
B
B
D000818:Animals; D001786:Blood Glucose / Q000187:drug effects / Q000378:metabolism; D002334:Carnitine O-Palmitoyltransferase / Q000037:antagonists & inhibitors; D003345:Corticosterone / Q000494:pharmacology*; D004852:Epoxy Compounds / Q000494:pharmacology; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005943:Gluconeogenesis / Q000187:drug effects; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D051275:Glucose Transporter Type 4; D006003:Glycogen / Q000096:biosynthesis; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D007333:Insulin Resistance / Q000502:physiology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis; D009124:Muscle Proteins; D009132:Muscles / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D011924:Rats, Zucker
D001786:Blood Glucose; D004852:Epoxy Compounds; D005230:Fatty Acids, Nonesterified; D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; C495694:Slc2a4 protein, rat; D006003:Glycogen; D002334:Carnitine O-Palmitoyltransferase; D005947:Glucose; C054207:etomoxir; D003345:Corticosterone