Leptin Concentrations in Plasma and Follicular Fluid from Prepubertal Gilts as Influenced by Fasting, Refeeding and Insulin

Abstract

This study’s aim was to examine whether fasting and refeeding would influence leptin levels in both plasma and follicular fluid from prepubertal gilts, and whether insulin affects leptin levels in fasting gilts. In experiment 1, four gilts were fasted for 72 h and then refed. Blood samples were withdrawn during normoalimentation, at the end of fasting, and for 4 h after refeeding. All samples were assayed for leptin; alternate samples were assayed for insulin, glucose and non-esterified fatty acids (NEFA). Fasting caused a decrease in leptin, glucose and insulin levels in plasma, while NEFA concentrations increased. In experiment 2, four gilts were given insulin as a bolus (0.2 IU/kg body weight) after 68 h of fasting. Blood samples were collected every 15 min around insulin administration and were assayed for leptin, insulin and glucose. This experiment shows that insulin administration increases leptin levels during fasting. In experiment 3, gilts were ovariectomized during normal alimentation (n = 4), after 48 h of fasting (n = 4), and after 48 h of realimentation following 48 h of fasting (n = 4). Leptin levels in both plasma and follicular fluid collected after 48 h of fasting were significantly lower than those observed during normoalimentation or refeeding. In conclusion, a transient increase in insulin during fasting is effective in restoring leptin concentrations; in addition, leptin levels in follicular fluid parallel those in plasma.

Glucose - Non-esterified fatty acids - Metabolism - Ovary

References

• 1 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
• 2 Ahima R S, Flier J S. Leptin.  Annu Rev Physiol. 2000;  62 413-437
• 3 Brichard S M, Delporte M L, Lambert M. Adipocytokines in anorexia nervosa: a review focusing on leptin and adiponectin.  Horm Metab Res. 2003;  35 337-342
• 4 Kolaczynski J W, Considine R V, Ohannesian J, Marco C, Opentanova I, Nyce M R, Myint M, Caro J F. Responses to leptin in short-term fasting and refeeding in humans: a link with ketogenesis but not ketones themselves.  Diabetes. 1996;  45 1511-1515
• 5 Ahima R S, Prabakaran D, Mantzoros C, Qu D Q, Lowell B, Maratos-Flier E, Flier J S. Role of leptin in the neuroendocrine response to fasting.  Nature. 1996;  382 250-252
• 6 Amstalden M, Garcia M R, Williams S W, Stanko R L, Nizielski S E, Morrison C D, Keisler D H, Williams G L. Leptin gene expression, circulating leptin, and luteinizing hormone pulsatility are acutely responsive to short-term fasting in prepubertal heifers: relationships to circulating insulin and insulin-like growth factor 1.  Biol Reprod. 2000;  63 127-133
• 7 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
• 8 Whisnant C S, Harrell R J. Effect of short-term feed restriction and refeeding on serum concentrations of leptin, luteinizing hormone and insulin in ovariectomized gilts.  Domest Anim Endocrinol. 2002;  22 73-80
• 9 Cawthorne M A, Morton N M, Pallett A L, Liu Y L, Emilsson V. Peripheral metabolic actions of leptin.  Proceedings of the Nutrition Society. 1998;  57 449-453
• 10 Saladin R, de Vos P, Guerre-Millio M, Leturque A, Girard J, Staels B, Auwerx J. Transient increase in obese gene expression after food intake or insulin administration.  Nature. 1995;  377 527-529
• 11 Zheng D, Jones J P, Usala J S, Dohm G L. Differential expression of ob mRNA in rat adipose tissues in response to insulin.  Biochem Biophys Res Commun. 1996;  218 434-437
• 12 Ramsay T G, White M E. Insulin regulation of leptin expression in streptozotocin diabetic pigs.  J Anim Sci. 2000;  78 1479-1503
• 13 Cunningham M J, Clifton D K, Steiner R A. Leptin’s actions on the reproductive axis: Perspectives and mechanisms.  Biol Reprod. 1999;  60 216-222
• 14 Ruiz-Cortes Z T, Men T, Palin M F, Downey B R, Lacroix D A, Murphy B D. Porcine leptin receptor: molecular structure and expression in the ovary.  Mol Reprod Dev. 2000;  56 465-474
• 15 National Research Council .Nutrient requirements of Swine. 9 ed. Washington, DC; National Academy Press 1988
• 16 Arai T, Kawakami Y, Matsushima T, Okuda Y, Yamashita K. Intracellular fatty acid downregulates ob gene expression in 3T3-L1 adipocytes.  Biochem Biophys Res Commun. 2002;  297 1291-1296
• 17 Utriainen T, Malmstrom R, Makimattila S, Yki-Jarvinen H. Supraphysiological hyperinsulinemia increases concentrations after 4 h in normal subjects.  Diabetes. 1996;  45 1364-1366
• 18 Koopmans S J, Frolich M, Gribnau E H, Westendorp R GJ, Defronzo R A. Effect of hyperinsulinemia on concentrations and food intake in rats.  Am J Physiol. 1998;  274 E998-E1001
• 19 Block S S, Rhoads R P, Bauman D E, Ehrhardt R A, McGuire M A, Crooker B A, Griinari J M, Mackle TR , Weber W J, van Amburgh M E, Boisclair Y R. Demonstration of a role for insulin in the regulation of leptin in lactating dairy cows.  J Dairy Sci. 2003;  86 3508-3515
• 20 Leury B J, Baumgard L H, Block S S, Segoale N, Ehrhardt R A, Rhoads R P, Bauman D E, Bell A W, Boisclair Y R. Effect of insulin and growth hormone on plasma leptin in periparturient dairy cows.  Am J Physiol Regul Integr Comp Physiol. 2003;  285 R1107-R1115
• 21 Laferrere B, Caixas A, Fried SK, Bashore C, Kim J, Pi-Sunyer FX. A pulse of insulin and dexamethasone stimulates serum leptin in fasting human subjects.  Eur J Endocrinol. 2002;  146 839-845
• 22 Mizuno T, Bergen H, Kleopoulos S, Bauman W A, Mobbs C V. Effects of nutritional status and aging on leptin gene expression in mice: importance of glucose.  Horm Metab Res. 1996;  28 679-684
• 23 Mueller W M, Gregoire F M, Stanhope K L. et al . Evidence that glucose metabolism regulates leptin secretion from cultured rat adipocytes.  Endocrinology. 1998;  139 551-558
• 24 Yu W H, Kimura M, Walczewska A, Karanth S, McCann S M. Role of leptin in hypothalamic-pituitary function.  Proc Natl Acad Sci USA. 1997;  94 1023-1028
• 25 Barb C R, Barrett J B, Kraeling R R. Role of leptin in modulating the hypothalamic-pituitary axis and luteinizing hormone secretion in the prepubertal gilt.  Domestic Animal Endocrinol. 2004;  26 201-214
• 26 Cioffi J A, van Blerkom J, Antczak M, Shafer A, Wittmer S, Snodgrass H R. The expression of leptin and ist receptors in pre-ovulatory human follicles.  Mol Hum Reprod. 1997;  3 467-472
• 27 Loffler S, Aust G, Kohler U, Spanel-Borowski K. Evidence of leptin expression in normal and polycystic human ovaries.  Mol Hum Reprod. 2001;  7 1143-1149
• 28 Butzow T L, Moilanen J M, Lehtovirta M, Tuomi T, Hovatta O, Siegberg R, Nilsson C G, Apter D. Serum and follicular fluid leptin during in vitro fertilization: relationship among leptin increase, body fat mass, and reduced ovarian response.  J Clin Endocrinol Metab. 1999;  84 3135-3139
• 29 Ferguson E M, Ashworth C J, Edwards S A, Hawkins N, Hepburn N, Hunter M G. Effect of different nutritional regimens before ovulation on plasma concentrations of metabolic and reproductive hormones and oocyte maturation in gilts.  Reproduction. 2003;  126 61-71
• 30 Ruiz-Cortes Z T, Martel-Kennes Y, Gevry N Y, Downey B R, Palin M F, Murphy B D. Biphasic effects of leptin in porcine granulosa cells.  Biol Reprod. 2003;  68 789-796
• 31 Spicer L J, Francisco C C. The adipose obese gene product, leptin: evidence of a direct inhibitory role in ovarian function.  Endocrinology. 1997;  138 3374-3379
• 32 Spicer L J, Francisco C C. Adipose obese gene product, leptin, inhibits bovine ovarian thecal cell steroidogenesis.  Biol Reprod. 1998;  58 207-212
• 33 Nicklin L T, Glister C, Robinson R S, Marsters P, Campbell B K, Knight P G, Mann G E, Hunter M G. Leptin in the bovine corpus luteum: receptor expression and effects on progesterone production. Reproduction 2004; Abs series n° 31, O2, 6, Ghent 5 - 7 April.