Effects of fat availability on acetyl-CoA and acetylcarnitine metabolism in rat skeletal muscle.

Abstract

This study was designed to examine the effects of stimulation and fat availability on the contents of acetyl coenzyme A (acetyl-CoA), free CoA (CoASH), acetylcarnitine, and free carnitine in the oxidative fiber types of rat skeletal muscle. Hindlimb muscles were perfused with no exogenous free fatty acids (FFA) or high FFA (0.93 +/- 0.03 mM) for 10 min at rest and during isometric, tetanic stimulation. Soleus (SOL) and red gastrocnemius (RG) muscles were sampled prior to perfusion and following rest perfusion and 1 and 5 min of stimulation. The SOL muscle contains predominantly slow oxidative (SO) fibers and the RG contains 56% fast oxidative-glycolytic (FOG) and 35% SO fibers. O2 uptake and tetanic tension production were similar in the fat-free and high FFA treatments. Rest perfusion with high FFA increased acetyl-CoA from 14.6 +/- 1.0 to 20.1 +/- 2.5 nmol/g dry muscle (dm) and acetylcarnitine from 0.12 +/- 0.01 to 0.78 +/- 0.18 mumol/g dm in the RG, while fat-free perfusion had no effect. The SOL results were similar as high FFA increased acetyl-CoA from 7.7 +/- 1.0 to 14.2 +/- 3.1 nmol/g dm and acetylcarnitine from 0.14 +/- 0.02 to 0.49 +/- 0.09 mumol/g dm. Stimulation increased acetyl-CoA and acetylcarnitine to values above rest in SOL and RG in both treatments and removed all fat-free and high-fat differences. The decreases in CoASH and free carnitine were reciprocal to the increases in acetyl-CoA and acetylcarnitine at all time points in both muscles such that total CoA and carnitine were constant.(ABSTRACT TRUNCATED AT 250 WORDS)