Forearm insulin- and non-insulin-mediated glucose uptake and muscle metabolism in man: role of free fatty acids and blood glucose levels.
Muscle can utilize glucose by two different mechanisms, one non-insulin-mediated and the other insulin-mediated. The aim of this study was to investigate and to quantify the influence of high and low free fatty acids (FFA) levels on muscle non-insulin-mediated glucose uptake (MNIMGU) and muscle insulin-mediated glucose uptake (MIMGU) and on muscle metabolism during euglycemia and hyperglycemia. Six healthy volunteers were submitted, in a random order, to a 2-hour euglycemic clamp (EC) followed by a 2-hour hyperglycemic (11 mmol/L) clamp (HC) under five different conditions: (1) somatostatin infusion (SRIF, 500 micrograms/h); (2) SRIF infusion preceded by a nicotinic acid analogue (acipimox, 250 mg orally, (3) SRIF plus insulin infusion; (4) SRIF plus insulin plus intralipid infusion; and (5) SRIF plus insulin infusion plus acipimox. In the postabsorptive state MNIMGU represented 71% of the total muscle glucose uptake (MGU) and during the EC a sharp reduction of FFA levels increased the MNIMGU by 10% (P less than .05), and an acute increase in FFA levels decreased the MNIMGU by 26% (P less than .05). MIMGU was significantly increased by 103% after acipimox administration (P less than .05) and was decreased by 65% during intralipid infusion (P less than .05). During HC, MNIMGU was not significantly influenced by low or high FFA levels, and MIMGU was not affected by a sharp lowering of FFA levels, but was significantly decreased (85%) during intralipid infusion. There was no significant difference in the lactate, pyruvate, and alanine balance across the forearm during EC and HC.(ABSTRACT TRUNCATED AT 250 WORDS)
Piatti
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PM
Instituto Scientifico S. Raffaele, Cattedra di Clinica Medica, Università di Milano, Italy.
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D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D005230:Fatty Acids, Nonesterified / Q000502:physiology*; D005542:Forearm; D005947:Glucose / Q000378:metabolism*; D015309:Glucose Clamp Technique; D006801:Humans; D006943:Hyperglycemia / Q000097:blood; D007328:Insulin / Q000502:physiology*; D008297:Male; D009132:Muscles / Q000378:metabolism*
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D005947:Glucose