EFFECT OF DIET ON INSULIN-MEDIATED AND CONTRACTION-MEDIATED GLUCOSE-TRANSPORT AND UPTAKE IN RAT MUSCLE

A diet rich in fat diminishes insulin-mediated glucose uptake in muscl e. This study explored whether contraction-mediated glucose uptake is also affected. Rats were fed a diet rich in fat (FAT, 73% of energy) o r carbohydrate (CHO, 66%) for 5 wk. Hindquarters were perfused, and ei ther glucose uptake or glucose transport capacity {uptake of 3-O-[C-14 ]-methyl-D-glucose (40 mM)} was measured. Amounts of glucose transport er isoform GLUT-1 and GLUT-4 glucose-transporting proteins were determ ined by Western blot. Glucose uptake was lower (P < 0.05) in hindlegs from FAT than from CHO rats at submaximum and maximum insulin [4 +/- 0 .4 vs. 5 +/- 0.3 (SE) mu mol . min(-1). leg(-1) at 150 mu U/ml insulin ] as well as during prolonged stimulation of the sciatic nerve (4.4 +/ - 0.4 vs. 5.6 +/- 0.6 mu mol . min(-1). leg(-1)). Maximum glucose tran sport elicited by insulin (soleus: 1.7 +/- 0.2 vs. 2.6 +/- 0.2 mu mol . g(-1). 5 min(-1), P < 0.05) or contractions (soleus: 1.8 +/- 0.2 vs. 2.6 +/- 0.3, P < 0.05) in red muscle was decreased in parallel in FAT compared with CHO rats. GLUT-4 content was decreased by 13-29% (P < 0 .05) in the various fiber types, whereas GLUT-1 content was identical in FAT compared with CHO rats. It is concluded that a FAT diet reduces both insulin and contraction stimulation of glucose uptake in muscle and that these effects are associated with diminished skeletal muscle glucose transport capacities and GLUT-4 contents.