Failure of short-term feed restriction to affect luteinizing hormone and leptin secretion or subcutaneous adipose tissue expression of leptin in the prepuberal gilt

Hart, H. A., Azain, M. J., Hausman, G. J., Reeves, D. E. and Barb, C. R. 2007. Failure of short-term feed-restriction to affect luteinizing hormone and leptin secretion or subcutaneous adipose tissue expression of leptin in the prepuberal gilt. Can. J. Anim. Sci. 87: 191–197. Previously we reported that 24-h fast increased serum non-esterified fatty acids (NEFA) concentrations, and decreased leptin pulse frequency, but not mean serum leptin concentrations in the OVX prepuberal gilt. The present study was conducted to determine if short-term feed restriction in the prepuberal gilt would reduce BF gene transcript expression, pulsatile LH secretion and serum leptin concentrations. OVX prepuberal gilts 79 ± 4 kg BW were control fed 3 kg (CF; n = 6) or feed restricted (RST; 33% of CF diet; n = 6) for 8 d to determine the effects of RST on leptin and LH secretion, metabolism, leptin, Ob-rb and transcription factor expression in BF. Blood samples were collected on day 8 and BF on day 9. RST gilts lost BW (–2.5 vs. +8.2 kg; SE = 0.6 kg; P < 0.001) and BF (–3 vs. +2 mm; SE = 1mm; P < 0.02) compared with CF gilts. Postprandial serum T4 concentrations increased (P < 0.04) in CF, but not in RST pigs. Postprandial serum insulin and BHBA concentrations were similar between treatments. A treatment × time interaction was detected for plasma glucose (P < 0.02) and NEFA (P < 0.04) concentrations. Feed restriction failed to affect leptin or LH secretion except for LH pulse amplitude was greater (P < 0.01) in RST gilts. RST failed to affect BF leptin, Ob-rb, AFABP, C/EBPα, or PPARγ2 expression. In conclusion, the ability of the prepuberal gilt to maintain energy level in the normal range suggests the prepuberal animal is resistant to moderate reduction in nutrition. Thus, leptin may not play a primary role in the regulation of LH secretion in the prepuberal gilt, but may serve as a metabolic signal reflecting the amount of stored energy, which may be necessary for activation of the reproductive axis during puberal development in the gilt.