Effect of carbohydrate overfeeding on whole body and adipose tissue metabolism in humans.
OBJECTIVE
To evaluate the effect of a 4-day carbohydrate overfeeding on whole body net de novo lipogenesis and on markers of de novo lipogenesis in subcutaneous adipose tissue of healthy lean humans.


METHODS
Nine healthy lean volunteers (five men and four women) were studied after 4 days of either isocaloric feeding or carbohydrate overfeeding. On each occasion, they underwent a metabolic study during which their energy expenditure and net substrate oxidation rates (indirect calorimetry), and the fractional activity of the pentose-phosphate pathway in subcutaneous adipose tissue (subcutaneous microdialysis with 1,6(13)C2,6,6(2)H2 glucose) were assessed before and after administration of glucose. Adipose tissue biopsies were obtained at the end of the experiments to monitor mRNAs of key lipogenic enzymes.


RESULTS
Carbohydrate overfeeding increased basal and postglucose energy expenditure and net carbohydrate oxidation. Whole body net de novo lipogenesis after glucose loading was markedly increased at the expense of glycogen synthesis. Carbohydrate overfeeding also increased mRNA levels for the key lipogenic enzymes sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase, and fatty acid synthase. The fractional activity of adipose tissue pentose-phosphate pathway was 17% to 22% and was not altered by carbohydrate overfeeding.


CONCLUSIONS
Carbohydrate overfeeding markedly increased net de novo lipogenesis at the expense of glycogen synthesis. An increase in mRNAs coding for key lipogenic enzymes suggests that de novo lipogenesis occurred, at least in part, in adipose tissue. The pentose-phosphate pathway is active in adipose tissue of healthy humans, consistent with an active role of this tissue in de novo lipogenesis.
Minehira
Kaori
K
Institute of Physiology, University of Lausanne, Lausanne, Switzerland.
Bettschart
Vincent
V
Vidal
Hubert
H
Vega
Nathalie
N
Di Vetta
Véronique
V
Rey
Valentine
V
Schneiter
Philippe
P
Tappy
Luc
L
D000273:Adipose Tissue / Q000254:growth & development / Q000378:metabolism*; D000328:Adult; D001481:Basal Metabolism / Q000502:physiology; D002153:Calorimetry, Indirect; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology*; D005232:Fatty Acids, Volatile / Q000097:blood; D005260:Female; D006801:Humans; D008055:Lipids / Q000096:biosynthesis* / Q000097:blood; D008297:Male; D009765:Obesity / Q000209:etiology / Q000378:metabolism; D010101:Oxygen Consumption; D012333:RNA, Messenger / Q000378:metabolism; D014280:Triglycerides / Q000096:biosynthesis / Q000097:blood
D004040:Dietary Carbohydrates; D005232:Fatty Acids, Volatile; D008055:Lipids; D012333:RNA, Messenger; D014280:Triglycerides