Plerocercoid growth factor (PGF), a human growth hormone (hGH) analogue produced by the tapeworm Spirometra mansonoides, has direct insulin-like action in adipose tissue of normal rats in vitro

The metabolic actions of GH can be divided into acute (insulin-like) and chronic (lipolytic/anti-insulin). The insulin-like actions of GH are most readily elicited in GH-deficient animals as GH induces resistance to its own insulin-like action. Like GH, PGF stimulates growth and cross-reacts with anti-hGH antibodies. Independent experiments were conducted comparing the direct actions of PGF to insulin or hGH in vitro. Insulin-like effects were determined by the ability of PGF, insulin or hGH to stimulate (U-/sup 14/C)glucose metabolism in epidydimal fat pads from normal rats and by inhibition of epinephrine-stimulated lipolysis. Direct stimulation of lipolysis was used as anti-insulin activity. To determine if PGF competes for insulin or GH receptors, adipocytes (3 x 10/sup 5/ cells/ml) were incubated with either (/sup 125/I)insulin or (/sup 125/I)hGH +/- PGF, +/- insulin or +/- hGH. PGF stimulated glucose oxidation and /sup 14/C-incorporation into lipids. Insulin, hGH and PGF inhibited lipolysis (33%, 29% and 34%, respectively). Adipose tissue was very sensitive to the lipolytic effect of hGH but PGF was neither lipolytic nor did it confer refractoriness to its insulin-like action. PGF bound to GH but not to insulin receptors. Therefore, PGF had direct insulin-like effects but did not stimulate lipolysis in tissue frommore » normal rats in vitro.« less