A relation between non-esterified fatty acids in plasma and the metabolism of glucose.

The concentration of non-esterified fatty acids (NEFA) in plasma increases after an injection of heparin (1). Apparently a lipase released into the blood (2, 3) hydrolyzes the neutral fat in chylomicrons (4) and promotes both the reduction of turbidity in the plasma and removal of fatty acids to tissues. If the small amounts of NEFA normally present in blood arise from hydrolysis of circulating triglycerides, the concentration should remain constant or increase to some extent during spontaneous clearing of alimentary lipemia, depending on relative rates of liberation and removal. This expectation was not supported by the present work. In every case, after a mixed meal, NEFA fell sharply and remained below the fasting value for 2 or more hours; fat alone, when fed in sufficient quantity to produce gross lipemia, had no demonstrable effect on circulating NEFA. Feeding of glucose or injection of insulin caused a fall in concentration comparable to that occurring after the mixed meals, while the injection of epinephrine caused a marked rise.