Transport and utilization of amino acids and glucose in human monocytes: activation of glucose metabolism by insulin.

The influence of insulin on transport and utilization of amino acids and glucose in purified human peripheral blood monocytes has been studied. Insulin had an immediate stimulating effect on the uptake of 3-O-methylglucose and 2-deoxyglucose; the maximal effects were 55% and 47% increases, respectively, during the first 2 min, in which energy-dependent hexose uptake dominates. Later, with advancing free diffusion, values declined to 16% and 25%. After a lag of 30 min, the rise in glucose uptake was followed by a small rise in glucose oxidation, documented by an 18% increase of 14CO2 production from [1-14C]glucose in the presence of hormone. No effect of insulin on sodium dependent alpha-aminoisobutyric acid or sodium-independent leucine uptake in monocytes could be found. The incorporation of amino acids into monocyte protein remained unchanged as well. Our results prove that the well documented binding of insulin to human monocytes initiates specific cellular reactions. The increased hexose monophosphate shunt activity may result in increased immune reactivity of the monocyte.