Zonation of acetate labeling across the liver: implications for studies oflipogenesis by MIDA

Citation
Ma. Puchowicz et al., Zonation of acetate labeling across the liver: implications for studies oflipogenesis by MIDA, AM J P-ENDO, 277(6), 1999, pp. E1022-E1027
Citations number
30
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
ISSN journal
01931849 → ACNP
Volume
277
Issue
6
Year of publication
1999
Pages
E1022 - E1027
Database
ISI
SICI code
0193-1849(199912)277:6<E1022:ZOALAT>2.0.ZU;2-X
Abstract
Measurement of fractional lipogenesis by mass isotopomer distribution analy sis (MIDA) of fatty acids or cholesterol labeled from [C-13]acetate assumes constant enrichment of lipogenic acetyl-CoA in all hepatocytes. This would not be the case if uptake and release of acetate by the liver resulted in transhepatic gradients of acetyl-CoA enrichment. Conscious dogs, prefitted with transhepatic catheters, were infused with glucose and [1,2-C-13(2)]ace tate. Stable concentrations and enrichments of acetate were measured in art ery (17 mu M, 36%), portal vein (61 mu M, 5.4%), and hepatic vein (17 mu M, 1.0%) and were computed for mixed blood entering the liver (53 mu M, 7.4%) . We also measured balances of propionate and butyrate across gut and liver . All gut release of propionate and butyrate is taken up, by the liver. The threefold decrease in acetate concentration and the sevenfold decrease in acetate enrichment across the Liver strongly suggest that the enrichment of lipogenic acetyl-CoA decreases across the liver. Thus fractional hepatic l ipogenesis measured in vivo by MIDA may be underestimated.