The fate of [U-(13)C]palmitate extracted by skeletal muscle in subjects with type 2 diabetes and control subjects.
The current study investigated the fate of a [U-(13)C]palmitate tracer extracted by forearm muscle in type 2 diabetic and control subjects. We studied seven healthy lean male subjects and seven obese male subjects with type 2 diabetes using the forearm muscle balance technique with continuous intravenous infusion of the stable isotope tracer [U-(13)C]palmitate under baseline conditions and during intravenous infusion of the nonselective beta-agonist isoprenaline (ISO; 20 ng *kg(-1) lean body mass* min(-1)). In skeletal muscle of control subjects, there was a significant release of (13)C-labeled oxidation products in the form of (13)CO(2) (15% of (13)C uptake from labeled palmitate) and a significant release of (13)C-labeled glutamine (release of (13)C-labeled atoms from glutamine was 6% of (13)C uptake from labeled palmitate), whereas in type 2 diabetic subjects there was no detectable release of (13)CO(2) and (13)C-glutamine, despite a significant uptake of [U-(13)C]palmitate (60% of control value). There was net uptake of arterial (13)C-labeled glutamate by forearm muscle in both groups. Also, the ISO-induced increase in arterial glutamine enrichment and arterial concentration of (13)C-glutamine was more pronounced in the diabetic group relative to control subjects. In view of the diminished ISO-induced release of (13)C-glutamine from type 2 diabetic muscle, the latter data indicate that more [U-(13)C]palmitate entered the liver in the diabetic group and was incorporated into newly synthesized glutamine and glutamate molecules. Thus, the lack of release of (13)C-labeled oxidation products by type 2 diabetic muscle during beta-adrenergic stimulation, despite significant [U-(13)C]palmitate uptake, indicates differences in the handling of fatty acids between type 2 diabetic subjects and healthy control subjects.
Blaak
Ellen E
EE
Department of Human Biology, Nutrition Research Center, Maastricht University, Maastricht, the Netherlands. e.blaak@hb.unimaas.nl
Wagenmakers
Anton J M
AJ
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage; D001158:Arteries; D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000032:analysis; D002247:Carbon Isotopes; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D006801:Humans; D007262:Infusions, Intravenous; D007545:Isoproterenol / Q000008:administration & dosage; D008099:Liver / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010084:Oxidation-Reduction; D019308:Palmitic Acid / Q000097:blood / Q000378:metabolism*
D000318:Adrenergic beta-Agonists; D002247:Carbon Isotopes; D005973:Glutamine; D002245:Carbon Dioxide; D019308:Palmitic Acid; D018698:Glutamic Acid; D005947:Glucose; D007545:Isoproterenol