Effects of Different Culture Conditions and Leptin on GH mRNA Expression and GH Secretion by Pig Pituitary Cells

Abstract

Growth hormone (GH) is enhanced in malnutrition; physiological increments in GH secretion seem to play an important role in regulating metabolism during fasting. Leptin has also been shown to play a role, amongst others, in modulating the somatotropic axis. In this study, we investigated how the composition of culture media could influence basal and leptin-stimulated GH secretion and expression in pig pituitary cells. Pituitary cells from 8-month-old sows were incubated for 48 h in presence and absence of 10 % fetal calf serum, either in DMEM/Ham’s F12, in arginine-free DMEM/Ham’s F-12, or in DMEM/Ham’s F12 Salts. Cells were then treated for 24 h with GHRH or recombinant human leptin (rhLep) individually or in association with GHRH; cell proliferation, nitric oxide (NO) production and GH expression and secretion were determined. The absence of nutritional factors induced a decrease in cell proliferation, but stimulated both GH secretion and expression. Furthermore, rhLep significantly increased GH expression and secretion irrespective of culture conditions. NO production was only significantly enhanced by leptin under DMEM/Ham’s F12 culture conditions. These observations lead us to hypothesize that the adaptive capabilities of pituitary cells may overcome the negative effects of undernutrition; in this context, leptin does not seem to depend on NO pathways in modulating GH secretion.

Pituitary cells - Culture condition - Leptin - Growth hormone - Nitric oxide

References

• 1 Barb C R, Kraeling R R, Rampacek G B. Metabolic regulation of the neuroendocrine axis in pigs.  Reprod Dom Anim. 2002;  59 203-217
• 2 Norrelund H, Riis A L, Moller N. Effects of GH on protein metabolism during dietary restriction in man.  Growth Horm IGF Res. 2002;  12 198-207
• 3 Louveau I, Le D ividich . GH and IGF-I binding in adipose tissue, liver, and skeletal muscle in response to milk intake level in piglets.  Gen Comp Endocrinol. 2002;  126(3) 310-317
• 4 Baranowska B, Wolinska-Witort E, Wasilewska-Dziubinska E, Roguski K, Martynska L, Chmielowska M. The role of neuropeptides in the disturbed control of appetite and hormone secretion in eating disorders.  Neuroendocrinol Lett. 2003;  24(6) 431-434
• 5 Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman J M. Positional cloning of the mouse obese gene and its human homologue.  Nature. 1994;  372 425-432
• 6 Swartz M W, Seeley R, Campfield L A, Burn P, Baskin D G. Identification of leptin action in the rat hypothalamus.  J Clin Invest. 1996;  98 1101-1106
• 7 Jin L, Zhang S, Burguera B G, Couce M E, Osamura R Y, Kulig E, Lloyd R V. Leptin and leptin receptor expression in rat and mouse pituitary cells.  Endocrinology. 2000;  141 333-339
• 8 Lin J, Barb CR, Matteri RL, Kraeling  RR, Chen X, Meinersmann RJ, Rampacek GB. Long form receptor mRNA expression in the brain, pituitary and other tissues in the pig.  Domest Anim Endocrinol. 2000;  19 53-61
• 9 Baratta M, Saleri R, Mainardi G L, Valle D, Giustina A, Tamanini C. Leptin regulates GH gene expression and secretion and nitric oxide production in pig pituitary cells.  Endocrinology. 2002;  143 551-557
• 10 Saleri R, Giustina A, Tamanini C, Valle D, Burattin A, Wehrenberg W B, Baratta M. Leptin stimulates growth hormone secretion via a direct pituitary effect combined with a decreased somatostatin tone in a median eminence-pituitary perifusion study.  Neuroendocrinology. 2004;  79 221-228
• 11 Ramsay T G, Bush J A, McMurtry J P, Thivierge M C, Davis T A. Peripheral leptin administration alters hormone and metabolite levels in the young pig.  Comp Biochem Physiol A Mol Integr Physiol.. 2004;  138(1) 17-25
• 12 Carro E, Senaris R, Considine R V, Casanueva F F, Dieguez C. Regulation of in vivo growth hormone secretion by leptin.  Endocrinology. 1997;  138 2203-2206
• 13 Cocchi D, De Gennaro C olonna , Bagnasco M, Bonacci D, Muller E E. Leptin regulates GH secretion in the rat by acting on GHRH and somatostatinergic functions.  J Endocrinol. 1999;  162 95-99
• 14 Lin J, Barb CR, Kraeling RR, Rampacek GB. Growth hormone releasing factor decreases long form leptin receptor expression in porcine anterior pituitary cells.  Domest Anim Endocrinol. 2003;  24 95-101
• 15 Philip M, Moran O, Lazar L. Growth without growth hormone.  J Pediatr Endocrinol Metab. 2002;  15(5) 1267-1272
• 16 Ozata M, Dieguez C, Casanueva F F. The inhibition of growth hormone secretion presented in obesity is not mediated by the high leptin levels: a study in human leptin deficiency patients.  J Clin Endocrinol Metab. 2003;  88(1) 312-316
• 17 Ghigo E, Bellone J, Aimaretti G, Bellone S, Loche S, Cappa M, Bartolotta E, Dammacco F, Camanni F. Reliability of provocative tests to assess growth hormone secretory status. Study in 472 normally growing children.  J Clin Endocrinol Metab. 1996;  81(9) 3323-3327
• 18 Villalobos C, Nunez L, Garcia-Sancho J. Mechanisms for stimulation of rat anterior pituitary cells by arginine and other amino acids.  J Physiol. 1997;  502 421-431
• 19 Vankelecom H, Matthys P, Denef C. Inducible nitric oxide synthase in the anterior pituitary gland: induction by interferon-gamma in a subpopulation of folliculostellate cells and in an unidentifiable population of non-hormone-secreting cells.  J Histochem Cytochem. 1997;  45 847-857
• 20 Cuttica C M, Giusti M, Bocca L, Sessarego P, de Martini D, Valenti S, Spaziante R, Giordano G. Nitric oxide modulates in vivo and in vitro growth hormone release in acromegaly.  Neuroendocrinology. 1997;  66 426-431
• 21 Saleri R, Baratta M, Tamanini C. β-endorphin directly influences both basal and GnRH-induced LH release by bovine pituitaries in vitro.  Reprod Dom Anim. 1998;  33 27-32
• 22 Baratta M, Saleri R, Mascadri C, Coy D H, Negro-Vilar A, Tamanini C, Giustina A. Modulation by galanin of growth hormone and gonadotropin secretion from perifused pituitary and median eminence of prepubertal male calves.  Neuroendocrinology. 1997;  66 271-277
• 23 Casanueva F F. Physiology of growth hormone secretion and action.  Endocrinol Metab Clin North Am. 1992;  21 483-517
• 24 Casanueva F F, Dieguez C. Neuroendocrine regulation and actions of leptin.  Front Neuroendocrinol. 1999;  20 317-363
• 25 Maccario M, Veldhuis J D, Broglio F, Vito L D, Arvat E, Deghenghi R, Ghigo E. Neuroendocrine and metabolic determinants of the adaptation of GH/IGF-I axis to obesity.  Ann Endocrinol (Paris). 2002;  63 140-144
• 26 Argente J, Caballo N, Barrios V, Munoz M T, Pozo J, Chowen J A, Morande G, Hernandez M. Multiple endocrine abnormalities of the growth hormone and insulin-like growth factor axis in prepubertal children with exogenous obesity: effect of short- and long-term weight reduction.  J Clin Endocrinol Metab. 1997;  82 2076-2083
• 27 Rasmussen M H, Hvidberg A, Juul A, Main K M, Gotfredsen A, Skakkebaek N E, Hilsted J. Massive loss restores 24-hour growth hormone release profiles and serum insulin like growth factor-I levels in obese subjects.  J Clin Endocrinol Metab. 1995;  80 1407-1415
• 28 Considine R V, Sinha M K, Heiman M L, Kriauciunas A, Steophens T W, Nyce M R, Ohannesian J P, Marco C C, Mckee L J, Bauer T L, Caro J F. Serum immunoreactive-leptin concentrations in normal-weight and obese humans.  N Engl J Med. 1996;  334 292-295
• 29 Carro E, Seoane L M, Senaris R, Casanueva F F, Dieguez C. Leptin increases in vivo GH responses to GHRH and GH-releasing peptide-6 in food deprived rats.  Eur J Endocrinol. 2000;  142 66-70
• 30 Britton J S, Edgar B A. Environmental control of the cell cycle in Drosophila: nutrition activates mitotic and endoreplicative cells by distinct mechanisms.  Development. 1998;  125 2149-2158
• 31 Murray A W. Recycling the cell cycle: cyclins revisited.  Cell. 2004;  116(2) 221-234
• 32 Grossman A, Costa A, Forsling M L, Jacobs R, Kostoglou-Athanassiou I, Nappi G, Navarra P, Satta M A. Gaseous neurotransmitters in the hypothalamus. The roles of nitric oxide and carbon monoxide in neuroendocrinology.  Horm Metab Res. 1997;  29 477-82
• 33 Aguila M C. Growth hormone-releasing factor increases somatostatin release and mRNA levels in the rat periventricular nucleus via nitric oxide by activation of guanylate cyclase.  Proc Natl Acad Sci USA. 1994;  91 782-786
• 34 Shimizu Y, Nagaya N, Teranishi Y, Imazu M, Yamamoto H, Shokawa T, Kangawa K, Kohno N, Yoshizumi M. Ghrelin improves endothelial dysfunction through growth hormone-independent mechanisms in rats.  Biochem Biophys Res Commun. 2003;  310 830-835
• 35 Pinilla L, Tena-Sempere M, Aguilar E. Nitric oxide stimulates growth hormone secretion in vitro through a calcium- and cyclic guanosine monophosphate-independent mechanism.  Horm Res. 1999;  51 242-247
• 36 Barb C R, Barrett J B, Kraeling R R, Rampacek G B. Serum leptin concentrations, luteinizing hormone and growth hormone secretion during feed and metabolic fuel restriction in the prepuberal gilt.  Domest Anim Endocrinol. 2001;  20 47-63
• 37 Barb C R, Yan X, Azain M J, Kraeling R R, Rampacek G B, Ramsay T G. Recombinant porcine leptin reduced feed intake and stimulates growth hormone secretion in swine.  Domest Anim Endocrinol. 1998;  15 77-86
• 38 Saleri R, Giustina A, Tamanini C, Valle D, Burattin A, Wehremberg W B, Baratta M. Leptin stimulates growth hormone secretion via a direct pituitari effect combined with a decreased somatostatin tone in a median eminence-pituitary perifusion system.  Neuroendocrinology. 2004;  79 221-228
• 39 Morash B, Wilkinson D, Murphy P, Ur E, Wilkinson M. Developmental regulation of leptin gene expression in rat brain and pituitary.  Mol Cell Endocrinol. 2001;  185 151-159
• 40 Hayashida T, Murakami K, Mogi K, Nishisara M, Nakazato M, Mondal M S, Horii Y, Kojima M, Kangawa K, Murakami N. Ghrelin in domestic animals: distribution in stomach and its possible role.  Domest Anim Endocrinol. 2001;  21 17-24