Influence of Lactate Infusion on Glucose and FFA Metabolism in Man

Abstract

Sodium L(+)-lactate was infused at rates of 5 to 12 mmol/min intravenously for 30 min in healthy volunteers, and the exchange of lactate, glucose, and free fatty acids (FFA) was measured in the leg, the forearm muscle, and the splanchnic region. Arterial lactate levels were 3 to 5 mmol/1 during the infusion. Leg blood flow increased about 2.5-fold and leg oxygen uptake rose by 35%. Blood flow, oxygen uptake, and glucose production in the splanchnic area remained unaltered. The fractional uptake of lactate by the leg, the splanchnic region, and the forearm decreased during the course of the infusion. Skeletal muscle metabolized 35% and the splanchnic area 10% of the lactate administered. Arterial FFA fell during the first half of the infusion period. [¹⁴C]oleic acid was used as a tracer, and no change in its specific activity was observed during the lactate infusion, indicating that the decrease in FFA concentration was due to an increase in the rate of removal. No significant change was seen in the rates of uptake and release of oleic acid in the leg or the splanchnic region. It is concluded that infusion of sodium lactate to man (a) is accompanied by an increase in leg blood flow and a stimulation of the oxidative metabolism of leg tissues and (b) causes a fall in arterial FFA due to an augmented removal of FFA from the plasma pool but (c) has no effect on mobilization of FFA from adipose tissue. The data further indicate that skeletal muscle is quantitatively more important than the liver in the disposal of lactate in the resting state.

Key Words:

• FFA turnover
• glucose
• lactate
• lipolysis
• liver
• regional blood flow
• skeletal muscle