Measurement of TG synthesis and turnover in vivo by 2H2O incorporation into the glycerol moiety and application of MIDA

被引:108
作者
Turner, SM
Murphy, EJ
Neese, RA
Antelo, F
Thomas, T
Agarwal, A
Go, C
Hellerstein, MK [1 ]
机构
[1] Univ Calif Berkeley, Dept Nutr Sci & Toxicol, Berkeley, CA 94720 USA
[2] Univ Calif San Francisco, Div Endocrinol & Metab, Dept Med, San Francisco Gen Hosp, San Francisco, CA 94101 USA
来源
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM | 2003年 / 285卷 / 04期
关键词
triglyceride; mass isotopomer distribution analysis; kinetics stable isotopes;
D O I
10.1152/ajpendo.00402.2002
中图分类号
R5 [内科学];
学科分类号
1002 ; 100201 ;
摘要
A method is presented for measurement of triglyceride (TG) synthesis that can be applied to slow-turnover lipids. The glycerol moiety of TG is labeled from (H2O)-H-2, and mass isotopomer distribution analysis (MIDA) is applied. Mice and rats were given 4-8% (H2O)-H-2 in drinking water; TG-glycerol was isolated from adipose and liver during less than or equal to 12- wk of (H2O)-H-2 labeling. Mass isotopomer abundances in the glycerol moiety of TG were measured by GC-MS. The combinatorial pattern of isotopomers revealed the number of H atoms in glycerol incorporating label from 2H2O (n) to be 3.8 - 4.0 of a possible 5 for adipose tissue and 4.6 - 4.8 for liver TG. Hepatic TG-glycerol in fact reached 97% predicted maximal value of label incorporation (4.4 - 4.6 x body (H2O)-H-2 enrichment), indicating near-complete replacement of the liver TG pool. Label incorporation into adipose tissue revealed turnover of mesenteric TG to be faster (k = 0.21 day(-1)) than other depots (k = 0.04 - 0.06 day(-1)) in mice. TG isolated from subcutaneous depots of growing adult rats plateaued at 85 - 90% of calculated maximal values at 12 wk (k = 0.05 day(-1)), excluding significant dilution by unlabeled alpha-glycerol phosphate. Turnover of plasma TG, modeled from H-2 incorporation over 60 min, was 0.06 min(-1) (half-life 11.5 min). In summary, use of (H2O)-H-2 labeling with MIDA of TG-glycerol allows measurement of new alpha-glycerol phosphate- derived TG synthesis and turnover. The hypothesis that mesenteric TG is more lipolytically active than other depots, previously difficult to prove by isotope dilution techniques, was confirmed by this label incorporation approach.
引用
收藏
页码:E790 / E803
页数:14
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