Insulin activates phospholipase C in fat cells: similarity with the activation of pyruvate dehydrogenase.

Phospholipase C (PHL-C) activity determined in homogenates of fat cells treated with physiological concentrations of insulin showed a 2-3-fold increase as compared to controls in the absence of insulin. The changes of PHL-C and pyruvate dehydrogenase (PDH) activity which was measured concomitantly exhibited very similar characteristics as to insulin sensitivity, saturability, time dependence and glucose requirement. Exogenous PHL-C as an activator of PDH in fat cells (Honeyman et al., 1983) also showed a striking similarity to insulin. Our findings strongly suggest that, in fat cells, PHL-C is susceptible to short-term activation by insulin. This effect may be relevant to the mechanism of PDH activation and perhaps to other metabolic actions of insulin.