Studies on the Effect of Growth Hormone in vivo and in vitro on Lipogenic Enzymes and Transaminases in a Teleost Anabas Testudineus (Bloch)

Abstract

The specific activities of three lipogenic enzymes, malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PDH) and isocitrate dehydrogenase (ICDH), in liver and heart and two transaminases (AST & ALT) in liver and muscle, were studied in response to the in vivo and in vitro administration of growth hormone (GH) in a teleost Anabas testudineus. Ovine growth hormone (oGH) in vivo significantly reduced the activities of lipogenic enzymes, except for heart G6PDH, which showed an increase at the highest dose of hormone. Transaminase activity either increased or decreased depending on the dose of GH. The lowest dose of hormone employed (0.1 microg/gm b/w) exhibited a stimulatory effect and the highest dose (0.5 microg/gm. b/w) an inhibitory effect on transaminase activity. Both ovine GH and carp GH (oGH and cGH) in vitro significantly reduced the activities of ME, G6PDH and ICDH. Activities of AST and ALT were increased by oGH and cGH in vitro. The present study reveals that irrespective of origin, GH in vitro has a direct inhibitory effect on lipogenic enzymes ME, G6PDH, ICDH and a stimulatory effect on transaminases AST and ALT in A. testudineus, thus favoring gluconeogenesis.

The co-existence of two growth hormone receptors in teleost fish and their differential signal transduction, tissue distribution and hormonal regulation of expression in seabream

“…It has been reported recently that cortisol could elicit metabolic changes in seabream liver by decreasing the glucose-6-phosphate dehydrogenase (G6PDH) activity (Laiz-Carrion et al 2003). The enhanced expression of sbGHR1 by cortisol might provide a possible explanation for this report since GH has been shown to reduce hepatic G6PDH activity in fish (Leena et al 1999).…”

Fasting modulates metabolic responses to cortisol, GH and IGF‐I in Arctic charr hepatocytes

“…As the GH/IGF‐I axis is modulated by extended fasting in wild, anadromous Arctic charr, these hormones seem likely to play a major role in the seasonal regulation of energy re‐partitioning (Aas‐Hansen et al ., 2005). This is further exemplified by the fact that piscine GH stimulates hepatocyte metabolism, including oxygen consumption [ Anguilla anguilla (L.), Peyon et al ., 1998], and lipid and amino acid metabolism [ O. mykiss , O’Connor et al ., 1993; Anabas testudineus (Bloch), Leena et al ., 1999].…”

“…Previous studies have shown that GH treatment increased hepatic lipolysis in vivo (Mommsen, 1998) and in vitro (O’Connor et al ., 1993; Leena et al ., 1999, 2001). Also, GH was shown to decrease hepatic lipogenesis in vivo (Leena et al ., 1999), all of which supports a lipolytic role for GH in teleosts. No effect of GH nor of IGF‐I on enzymes involved in lipid metabolism was seen in the present study.…”

“…This increased amino acid catabolism may be to fuel hepatic metabolism (oxidation; Walton & Cowey, 1982) but may also provide C3 precursors for gluconeogenesis and glyconeogenesis (Suarez & Mommsen, 1987). The results support the increase in liver transaminase activities reported in A. testudineus treated with GH in vivo as well as in vitro using hepatocytes (Leena et al ., 1999, 2001; Leena & Oommen, 2001). Although GH and IGF‐I exerted effects singly on hepatocyte amino acid metabolism, the reason for the lack of any effect when they were given in combination is not clear.…”

Depletion of suppressor of cytokine signaling-1a causes hepatic steatosis and insulin resistance in zebrafish

“…GH signaling is known to stimulate gluconeogenesis, lipolysis, and adipose tissue mobilization in mammals and teleosts (26,28,36). A central role of the JAK2-STAT5 pathway in mediating the growth-stimulating action of GH signaling has been reported in teleosts (23).…”