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United States Department of Agriculture

Agricultural Research Service

Title: Plasma Acylcarnitine Profiles Suggest Incomplete Fatty Acid ß-Oxidation and Altered Tricarboxylic Cycle Activity in Type 2 Diabetic African-American Women

Authors
item Adams, Sean
item Hoppel, Charles - CASE WESTERN RESERVE UNIV
item Lok, Kerry - UNIV. OF ALABAMA
item Zhao, Ling - UC DAVIS, NUTR. DEPT.
item Wong, Scott
item Minkler, Paul - CASE WESTERN RESERVE UNIV
item Hwang, Daniel
item Newman, John
item Garvey, W. - UNIV. OF ALABAMA

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2009
Publication Date: March 10, 2009
Repository URL: http://jn.nutrition.org/cgi/reprint/139/6/1073
Citation: Adams, S.H., Hoppel, C.L., Lok, K.H., Zhao, L., Wong, S.W., Minkler, P.E., Hwang, D.H., Newman, J.W., Garvey, W.T. 2009. Plasma Acylcarnitine Profiles Suggest Incomplete Fatty Acid ß-Oxidation and Altered Tricarboxylic Cycle Activity in Type 2 Diabetic African-American Women. Journal of Nutrition, 139:1073-1081.

Interpretive Summary: Inefficient muscle long-chain fatty acid (LCFA) combustion is associated with insulin resistance, but molecular links between mitochondrial fat catabolism and insulin action remain controversial. We hypothesized that plasma acylcarnitine profiling would identify distinct metabolite patterns reflective of muscle fat catabolism when comparing individuals bearing a missense G304A uncoupling protein 3 (UCP3 g/a) polymorphism to controls, since UCP3 is predominantly expressed in skeletal muscle and g/a individuals have reduced whole-body fat oxidation. Mass-spectroscopy analyses of 42 acylcarnitine moieties in plasma samples from overnight-fasted type 2 diabetics (n=44) and non-diabetics (n=12) with or without the UCP3 g/a polymorphism (n=28/genotype: 22 diabetic, 6 non-diabetic/genotype) were conducted. Contrary to our hypothesis, genotype had negligible impact on plasma metabolite patterns. However, a comparison of non-diabetics vs. type 2 diabetics revealed a striking increase in the concentrations of fatty acylcarnitines reflective of incomplete LCFA ß-oxidation in the latter (i.e., summed C10- to C14-carnitine concentrations were ~300% of controls, p=0.004). Across all volunteers (n=56), acetylcarnitine rose and propionylcarnitine decreased with increasing hemoglobin A1c (HbA1c; r = 0.544, P<0.0001 and r = -0.308, P<0.05, respectively) and with increasing total plasma acylcarnitine concentration. In proof-of-concept studies, we made the novel observation that C12-C14 acylarnitines significantly stimulated NF'B activity (up to 200% of controls) in RAW264.7 cells. These results are consistent with the working hypothesis that inefficient tissue LCFA ß-oxidation, due in part to a relatively low tricarboxylic acid (TCA) cycle capacity, increases tissue accumulation of acetyl-CoA and generates chain-shortened acylcarnitine molecules that activate pro-inflammatory pathways implicated in insulin resistance.

Technical Abstract: Inefficient muscle long-chain fatty acid (LCFA) combustion is associated with insulin resistance, but molecular links between mitochondrial fat catabolism and insulin action remain controversial. We hypothesized that plasma acylcarnitine profiling would identify distinct metabolite patterns reflective of muscle fat catabolism when comparing individuals bearing a missense G304A uncoupling protein 3 (UCP3 g/a) polymorphism to controls, since UCP3 is predominantly expressed in skeletal muscle and g/a individuals have reduced whole-body fat oxidation. Mass-spectroscopy analyses of 42 acylcarnitine moieties in plasma samples from overnight-fasted type 2 diabetics (n=44) and non-diabetics (n=12) with or without the UCP3 g/a polymorphism (n=28/genotype: 22 diabetic, 6 non-diabetic/genotype) were conducted. Contrary to our hypothesis, genotype had negligible impact on plasma metabolite patterns. However, a comparison of non-diabetics vs. type 2 diabetics revealed a striking increase in the concentrations of fatty acylcarnitines reflective of incomplete LCFA ß-oxidation in the latter (i.e., summed C10- to C14-carnitine concentrations were ~300% of controls, p=0.004). Across all volunteers (n=56), acetylcarnitine rose and propionylcarnitine decreased with increasing hemoglobin A1c (HbA1c; r = 0.544, P<0.0001 and r = -0.308, P<0.05, respectively) and with increasing total plasma acylcarnitine concentration. In proof-of-concept studies, we made the novel observation that C12-C14 acylarnitines significantly stimulated NF'B activity (up to 200% of controls) in RAW264.7 cells. These results are consistent with the working hypothesis that inefficient tissue LCFA ß-oxidation, due in part to a relatively low tricarboxylic acid (TCA) cycle capacity, increases tissue accumulation of acetyl-CoA and generates chain-shortened acylcarnitine molecules that activate pro-inflammatory pathways implicated in insulin resistance.

Last Modified: 4/18/2014
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