Effect of chronic food restriction on pulsatile luteinizing hormone secretion and hypothalamic neuropeptide Y gene expression in castrate male sheep

Clare Lesley Adam, P.A. Findlay, C E Kyle, Pauline Young, Julian Mercer

Research output: Contribution to journalArticle

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Abstract

Castrate male sheep (wethers, average liveweight 38 +/- 0.6 kg) were given one of the following diets for 10 weeks followed by euthanasia (n=8/group): high-energy high-protein providing 1.5 times the energy required to maintain Liveweight (maintenance) (group 1.5M), low-energy low-protein at 0.5 maintenance (0.5M), or low-energy high-protein at 0.5 maintenance (0.5M+P). 1.5M wethers gained 22% liveweight whereas 0.5M and 0.5M+P wethers lost 18 and 13% liveweight respectively. Relative to the 15M group, the 0.5M and 0.5M+P soups had similar plasma concentrations of glucose and cortisol throughout, but elevated non-esterified fatty acids (P<0.001) and reduced IGF-I and insulin (P<0.05, 0.01 or 0.001) from 1 week onwards. Each week blood samples were taken every 12 min for 4 h and plasma assayed for LH. Mean concentration over 4 h, LH pulse frequency and LH pulse amplitude showed no progressive change in 1.5M sheep. However, in both 0.5M and 0.5M+P groups mean LH increased (P<0.001 and P<0.01 respectively), pulse frequency decreased (P<0.01 and P<0.01) and pulse amplitude increased (P<0.001 and P<0.01) over the 10-week period. Anterior pituitary LH content was greater in 0.5M (P<0.01) and 0.5M+P (P<0.05) than in 15M sheep. Coronal sections (20 mu m) of hypothalamic brain tissue were subjected to in situ hybridisation to determine gene expression for neuropeptide Y (NPY). NPY mRNA was concentrated in the arcuate nucleus and median eminence, with total amounts greater in both 0.5M (310%, P<0.001) and 0.5M+P (333%, P<0.01) groups than in 1.5M sheep (100%). These data reveal that chronic low dietary energy intake by long-term castrates, with high or low protein intake, reduces LH pulse frequency but increases the circulating levels of LH by virtue of an increase in pulse amplitude, and concomitantly increases hypothalamic NPY gene expression.

Original languageEnglish
Pages (from-to)329-337
Number of pages9
JournalJournal of Endocrinology
Volume152
Issue number2
DOIs
Publication statusPublished - Feb 1997

Keywords

  • GROWTH-FACTOR-I
  • GONADOTROPIN-RELEASING-HORMONE
  • DEER CERVUS-ELAPHUS
  • REPRODUCTIVE DEVELOPMENT
  • NUTRITIONAL MODULATION
  • OVARIECTOMIZED LAMBS
  • PITUITARY-GLANDS
  • MESSENGER-RNAS
  • BODY CONDITION
  • ESTROUS-CYCLE

Cite this

Effect of chronic food restriction on pulsatile luteinizing hormone secretion and hypothalamic neuropeptide Y gene expression in castrate male sheep. / Adam, Clare Lesley; Findlay, P.A.; Kyle, C E ; Young, Pauline; Mercer, Julian.

In: Journal of Endocrinology, Vol. 152, No. 2, 02.1997, p. 329-337.

Research output: Contribution to journalArticle

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author = "Adam, {Clare Lesley} and P.A. Findlay and Kyle, {C E} and Pauline Young and Julian Mercer",
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T1 - Effect of chronic food restriction on pulsatile luteinizing hormone secretion and hypothalamic neuropeptide Y gene expression in castrate male sheep

AU - Adam, Clare Lesley

AU - Findlay, P.A.

AU - Kyle, C E

AU - Young, Pauline

AU - Mercer, Julian

PY - 1997/2

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N2 - Castrate male sheep (wethers, average liveweight 38 +/- 0.6 kg) were given one of the following diets for 10 weeks followed by euthanasia (n=8/group): high-energy high-protein providing 1.5 times the energy required to maintain Liveweight (maintenance) (group 1.5M), low-energy low-protein at 0.5 maintenance (0.5M), or low-energy high-protein at 0.5 maintenance (0.5M+P). 1.5M wethers gained 22% liveweight whereas 0.5M and 0.5M+P wethers lost 18 and 13% liveweight respectively. Relative to the 15M group, the 0.5M and 0.5M+P soups had similar plasma concentrations of glucose and cortisol throughout, but elevated non-esterified fatty acids (P<0.001) and reduced IGF-I and insulin (P<0.05, 0.01 or 0.001) from 1 week onwards. Each week blood samples were taken every 12 min for 4 h and plasma assayed for LH. Mean concentration over 4 h, LH pulse frequency and LH pulse amplitude showed no progressive change in 1.5M sheep. However, in both 0.5M and 0.5M+P groups mean LH increased (P<0.001 and P<0.01 respectively), pulse frequency decreased (P<0.01 and P<0.01) and pulse amplitude increased (P<0.001 and P<0.01) over the 10-week period. Anterior pituitary LH content was greater in 0.5M (P<0.01) and 0.5M+P (P<0.05) than in 15M sheep. Coronal sections (20 mu m) of hypothalamic brain tissue were subjected to in situ hybridisation to determine gene expression for neuropeptide Y (NPY). NPY mRNA was concentrated in the arcuate nucleus and median eminence, with total amounts greater in both 0.5M (310%, P<0.001) and 0.5M+P (333%, P<0.01) groups than in 1.5M sheep (100%). These data reveal that chronic low dietary energy intake by long-term castrates, with high or low protein intake, reduces LH pulse frequency but increases the circulating levels of LH by virtue of an increase in pulse amplitude, and concomitantly increases hypothalamic NPY gene expression.

AB - Castrate male sheep (wethers, average liveweight 38 +/- 0.6 kg) were given one of the following diets for 10 weeks followed by euthanasia (n=8/group): high-energy high-protein providing 1.5 times the energy required to maintain Liveweight (maintenance) (group 1.5M), low-energy low-protein at 0.5 maintenance (0.5M), or low-energy high-protein at 0.5 maintenance (0.5M+P). 1.5M wethers gained 22% liveweight whereas 0.5M and 0.5M+P wethers lost 18 and 13% liveweight respectively. Relative to the 15M group, the 0.5M and 0.5M+P soups had similar plasma concentrations of glucose and cortisol throughout, but elevated non-esterified fatty acids (P<0.001) and reduced IGF-I and insulin (P<0.05, 0.01 or 0.001) from 1 week onwards. Each week blood samples were taken every 12 min for 4 h and plasma assayed for LH. Mean concentration over 4 h, LH pulse frequency and LH pulse amplitude showed no progressive change in 1.5M sheep. However, in both 0.5M and 0.5M+P groups mean LH increased (P<0.001 and P<0.01 respectively), pulse frequency decreased (P<0.01 and P<0.01) and pulse amplitude increased (P<0.001 and P<0.01) over the 10-week period. Anterior pituitary LH content was greater in 0.5M (P<0.01) and 0.5M+P (P<0.05) than in 15M sheep. Coronal sections (20 mu m) of hypothalamic brain tissue were subjected to in situ hybridisation to determine gene expression for neuropeptide Y (NPY). NPY mRNA was concentrated in the arcuate nucleus and median eminence, with total amounts greater in both 0.5M (310%, P<0.001) and 0.5M+P (333%, P<0.01) groups than in 1.5M sheep (100%). These data reveal that chronic low dietary energy intake by long-term castrates, with high or low protein intake, reduces LH pulse frequency but increases the circulating levels of LH by virtue of an increase in pulse amplitude, and concomitantly increases hypothalamic NPY gene expression.

KW - GROWTH-FACTOR-I

KW - GONADOTROPIN-RELEASING-HORMONE

KW - DEER CERVUS-ELAPHUS

KW - REPRODUCTIVE DEVELOPMENT

KW - NUTRITIONAL MODULATION

KW - OVARIECTOMIZED LAMBS

KW - PITUITARY-GLANDS

KW - MESSENGER-RNAS

KW - BODY CONDITION

KW - ESTROUS-CYCLE

U2 - 10.1677/joe.0.1520329

DO - 10.1677/joe.0.1520329

M3 - Article

VL - 152

SP - 329

EP - 337

JO - Journal of Endocrinology

JF - Journal of Endocrinology

SN - 0022-0795

IS - 2

ER -