FIGURE 3.

Metabolic turnover analysis of Epi WAT in C57 and ob/ob mice. Four-hour-fasted 11-week-old male C57 and ob/ob mice were administered [¹³C₆]glucose (0.2 mg/μl in saline, 1 mg/g of body weight) intraperitoneally. 15 and 30 min after [¹³C₆]glucose administration, Epi WAT, liver, and skeletal muscle were harvested for analysis. C57 and ob/ob mice of the non-administered (C57–0 min and ob-0 min), 15 min-administered (C57–15 min and ob-15 min), and 30 min-administered (C57–30 min and ob-30 min) (n = 6 for each of the six groups) were analyzed for isotopomer levels of metabolites using LC/MS. A, representation of potential ¹³C-labeled glutamate isotopomers derived from [¹³C₆]glucose. Green circles, ¹³C-labeled carbons in the isotopomers from pyruvate via PC flux; yellow circles, ¹³C-labeled carbons in the isotopomers from pyruvate via PDH flux. B, changes in plasma glucose levels. C, changes in plasma insulin levels. D, [¹³C₆]glucose-derived constitutive metabolites of the TCA cycle, pyruvate and glutamate, in Epi WAT. The level of each M+2 isotopomer in C57 mice was set at 1. Data are mean ± S.E. *, p < 0.05; **, p < 0.01; ***, p < 0.001; C57 versus ob/ob mice at the same time after [¹³C₆]glucose administration.