Lipolytic and Antilipolytic Effects of Human Growth Hormone, Its 20-Kilodalton Variant, A Reduced and Carboxymethylated Derivative, and Human Placental Lactogen on Chicken Adipose Tissue In Vitro

Abstract

The lipolytic and antilipolytic effects of human growth hormone (22K-hGH), its 20-kilodalton variant (20K-hGH), a reduced and S-carboxymethylated derivative (RCM-hGH), and human placental lactogen were examined using chicken adipose tissue explants in vitro. Lipolysis, as determined by glycerol release, was stimulated by 22K-hGH (biosynthetic and pituitary derived), 20K-hGH (pituitary derived), and RCM-hGH (modified biosynthetic). These growth hormone preparations also exhibited similar antilipolytic activity (i.e., transient inhibition of glucagon-induced lipolysis). However, unlike human growth hormone, human placental lactogen neither stimulated lipolysis nor inhibited glucagon-stimulated lipolysis. Some augmentation of glucagon-stimulated lipolysis was observed in the presence of human placental lactogen. These results indicate that the disulfide bridges (Cys53----Cys165; Cys182----Cys189) and amino acid residues 32-46 of hGH are not required for lipolytic or antilipolytic activities of human growth hormone on chicken adipose tissue.

Complete Solubilization and Purification of Recombinant Human Growth Hormone Produced in Escherichia coli

“…Although for some proteins disulfide bonds are crucial for their folding as reducing disulfide bonds can result in inactive protein, previous studies indicate that the disulfide bonds in hGH do not appear to be necessary for biological activity [30], [31], [32], [33]. Although hGH was expressed as a reduced form in the E. coli cytoplasmic space, we found that the cystein residues of hGH were spontaneously oxidized and formed intramolecular disulfide bonds under our purification conditions.…”

Endocrine Regulation of Fetal Adipose Tissue Metabolism in the Pig: Interaction of Porcine Growth Hormone and Thyroxine

“…8 and 27). Although acute lipolytic effects of GH have been observed in adipose tissue from rats (28.29) and chickens (30). such studies of human.…”

Structure‐Function Relationships of Growth Hormone and Other Members of the Growth Hormone Gene Family

“…When both disulfide bonds of hGH were split and the sulfur atoms carbamidomethylated, total hGH potency was retained in the rat tibia and pigeon crop sac bioassays (32). In a similar manner, Campbell et al (14) found that the two disulfide bridges of hGH are not required for lipolytic or antilipolytic activities on chicken adipose tissue. However, it was found that when hGH was reduced and alkylated, there was substantial loss of biological activity, with up to 25 % retention of its diabetogenic and lactogenic activities (13,96).…”