Differences in the regulation of adipose tissue and liver lipogenesis by carbohydrates in humans.
We assessed the contributions of human liver and adipose tissue de novo lipogenesis (DNL) to triacylglycerol (TAG) synthesis. Volunteers were fed a high-energy, high-carbohydrate diet (HC, n = 5) or a normocaloric diet (NC, n = 10). NC subjects remained in the fasting state (Study 1, n = 5) or received oral glucose (Study 2, n = 5) throughout the test (12 h). HC subjects remained in the fasting state (Study 3). They ingested deuterated water and [U-13C]acetate to trace lipogenesis. Adipose tissue fatty-acid (FA) synthase (FAS), acetyl-CoA carboxylase 1 (ACC1), and SREBP-1c mRNA were measured. Plasma TAG-FA was labeled by 13C and deuterium showing active liver lipogenesis, which was stimulated (P < 0.05) by oral glucose and HC diet. Adipose tissue TAG had no detectable 13C enrichment in any test, showing no significant incorporation of TAG-FA provided by liver lipogenesis, but were labeled by deuterium in all tests, showing active DNL in situ; however, rough quantitative estimates showed that adipose DNL was minimal (<1 g), and poorly stimulated by oral glucose or HC diet. mRNA levels were not increased by the HC diet. Adipose DNL is active in humans, but contributes little to TAG stores and is less responsive than liver DNL to stimulation by carbohydrates.
Diraison
Frédérique
F
INSERM U 499 and GENALYS, Faculté RTH Laennec, 69008, Lyon, France.
Yankah
Vivienne
V
Letexier
Dominique
D
Dusserre
Eric
E
Jones
Peter
P
Beylot
Michel
M
D000103:Acetyl-CoA Carboxylase / Q000235:genetics; D000273:Adipose Tissue / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics; D002241:Carbohydrates / Q000008:administration & dosage / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics; D064429:Fatty Acid Synthases / Q000235:genetics; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D008055:Lipids / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D012333:RNA, Messenger / Q000032:analysis; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors / Q000235:genetics
D022762:CCAAT-Enhancer-Binding Proteins; D002241:Carbohydrates; D004268:DNA-Binding Proteins; D008055:Lipids; D012333:RNA, Messenger; C497387:SREBF1 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D064429:Fatty Acid Synthases; D000103:Acetyl-CoA Carboxylase