Effects of stimulated growth hormone secretion on age-related changes in plasma cholesterol and hepatic low density lipoprotein messenger RNA concentrations.
Mech Ageing Dev
; 75(3): 215-26, 1994 Sep.
Article
em En
| MEDLINE
| ID: mdl-7845055
ABSTRACT
Growth hormone (GH) secretion declines during aging. Since GH alters plasma cholesterol (PC) concentrations, it was of interest to determine how GH secretagogues affect age-related hypercholesterolemia. Fischer 344 rats (3 and 14 months old) were co-administered (s.c.) GH releasing hormone (3 micrograms/kg; GHRH) and GH releasing hexapeptide (100 micrograms/kg; GHRP) for 120 consecutive days. Aging was associated with a progressive increase in PC, which was reduced in rats administered GHRH and GHRP compared to those administered vehicle, i.e. changes in PC during the study were 26.5 +/- 1.2 mg/dl vs. 40.1 +/- 0.9 mg/dl (P < 0.05) in the younger rats and 17.6 +/- 2.3 mg/dl vs. 31.6 +/- 5.3 mg/dl (P < 0.05) in the older rats, respectively. The lower concentrations of PC in GH secretagogue-treated older rats were associated with higher mean concentrations of hepatic LDL receptor mRNA (1.27 +/- 0.4 vs. 0.4 +/- 0.1; P < 0.05) but not cholesterol 7-alpha hydroxylase mRNA. Although GH secretagogue treatment was also associated with lower plasma cholesterol in the younger rats, it was not accompanied by quantitative changes in mean group concentrations of hepatic LDL receptor mRNA. Instead, daily administration of GHRH and GHRP in the younger rats correlated with a significant reciprocal relationship (P < 0.05) between PC and hepatic LDL receptor mRNA for individual group members. The results of this study suggest that reduced GH secretion during aging contributes, at least in part, to a progressive increase in plasma cholesterol that can be partially prevented with GH secretagogues. Furthermore, the effects on PC may result from GH-mediated, qualitative and quantitative changes in hepatic LDL receptor mRNA that increase receptor-mediated cholesterol clearance.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Envelhecimento
/
RNA Mensageiro
/
Receptores de LDL
/
Hormônio do Crescimento
/
Colesterol
/
Fígado
Tipo de estudo:
Qualitative_research
Limite:
Animals
Idioma:
En
Revista:
Mech Ageing Dev
Ano de publicação:
1994
Tipo de documento:
Article