Lipid metabolism in human skeletal muscle cells: effects of palmitate and chronic hyperglycaemia

This review focuses on the effect of exogenous factors known to be of importance for the development of insulin resistance in differentiated human myotubes. Recent data from our laboratory on the effects of fatty acid pre-treatment and chronic glucose oversupply on fatty acid and glucose metabolism, without and with acute insulin are presented, and discussed in the context of other recent publications in the field. Pre-treatment of myotubes with palmitate, chronic hyperglycaemia, and acute high concentrations of insulin changed fatty acid metabolism in favour of accumulation of intracellular lipids. Acute insulin exposure increased C-14-oleate uptake and levels of free fatty acids (FFA) and triacylglycerol (TAG). Palmitate pre-treatment further increased oleate uptake, both under basal conditions and in the presence of insulin, with a marked increase in the phospholipid (PL) fraction, with a concomitant reduction in oleate oxidation. Chronic hyperglycaemia also promoted increased lipogenesis and elevated levels of cellular lipids. Changes in fatty acid metabolism in human muscle, in particular fatty acid oxidation, are probably crucial for the molecular mechanism behind skeletal muscle insulin resistance and impaired glucose metabolism. Differentiated human skeletal muscle cells may be an ideal system to further explore the mechanisms regulating lipid metabolism.