Intramyocellular triglyceride (IMTG) level correlates with insulin resistance. Paradoxically, trained humans and obese, sedentary, insulin-resistant humans have high IMTG levels despite discrepant clinical phenotypes. We hypothesize that higher IMTG turnover in trained humans explains this paradox.

Methods: Obese, insulin-resistant subjects [n=47, mean (SD), BMI:36.2 kg/m2(5.7), VO2max 25.4 ml/kg/min (5.7)] and lean trained subjects [n=15, BMI:22.2 kg/m2(1.8), VO2max 55ml/kg/min (10.1)] were fasted overnight. Two muscle biopsies (Bx) were acquired during a pulse-chase experiment using [U-13C]palmitate and [9-2H]palmitate infusions (6 h each), overlapping by 1 hour. Bx#1 was performed during the infusion overlap [last hour of 6 h [U-13C]palmitate infusion, 1 hour after starting [9-2H]palmitate. Bx#2 was performed at study conclusion [last hour of [9-2H]palmitate infusion, 6 hours after stopping [U-13C]palmitate]. Palmitate enrichment and concentration were measured. [9-2H]palmitate IMTG incorporation at Bx#1 and [U-13C] IMTG loss at Bx#2 indicated the interplay between plasma and muscle fatty acids.

Results: Palmitate IMTG incorporation positively correlated between measures of IMTG turnover and negatively with insulin sensitivity. No correlation seen for VO2max/BMI.

Conclusion: Muscle-level IMTG measures dictates higher resting IMTG turnover more than training related phenotype.


L.S.Chow: Research Support; Dexcom, Inc. A.Bantle: None. A.C.Alvear: None. D.G.Mashek: None. M.D.Jensen: Other Relationship; Novo Nordisk, Elsevier.


National Institutes of Health (R01DK098203)

Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. More information is available at