Key result
Growth hormone restores IGF-I and IGFBP-3 mRNA in dwarf rats, whereas fasting reduces IGF-I independently.
Why the study?
Does growth hormone administration or fasting alter hepatic expressions of IGF-I and IGFBPs in spontaneous dwarf rats?
Does growth hormone administration or fasting alter hepatic expressions of IGF-I and IGFBPs in spontaneous dwarf rats?
Growth hormone regulates hepatic expression of IGF-I, IGFBP-1, and IGFBP-3, while fasting-induced changes in IGF-I and IGFBP-2 mRNA appear to be mediated by factors other than reduced serum GH.
GH selectively regulates hepatic IGF-I/IGFBP mRNAs in deficient rats; leaves open fasting mechanisms and human translation.
Effects of growth hormone (GH) and fasting on hepatic expressions of insulin-like growth factor I (IGF-I) and IGF-I-binding protein (IGFBP)-1, -2, -3, and -4 were examined in spontaneous dwarf rats (SDR), which completely and specifically lack GH among pituitary hormones. The hepatic expressions of mRNA encoding IGF-I and IGFBP-3 were reduced and IGFBP-1 mRNA was elevated in the SDR. Both chronic and acute administration of GH restored these changes, indicating the association of GH but not other pituitary hormones with hepatic expressions of these genes. In addition, the present examination revealed that mRNA level of IGFBP-2 was elevated in SDR, which could not be attenuated by exogenous GH, and that GH may not be directly relevant to the regulation of hepatic IGFBP-4 expression. Fasting for 2 days reduced IGF-I mRNA level and increased IGFBP-2 mRNA level in the SDR, as well as in the normal rat, suggesting the presence of factors other than reduced serum GH responsible for fasting-induced alteration in the expression of these mRNAs. On the other hand, fasting resulted in little change or even a reduction of IGFBP-1 mRNA level in the SDR.
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Nogami et al. (1994) studied Growth hormone deficiency (Spontaneous dwarf rats). Growth hormone (GH) administration and fasting vs. Normal rats / baseline SDR was evaluated on Hepatic expressions of mRNA encoding IGF-I and IGFBP-1, -2, -3, and -4. Growth hormone administration restored reduced IGF-I and IGFBP-3 mRNA and elevated IGFBP-1 mRNA in spontaneous dwarf rats, while fasting reduced IGF-I and increased IGFBP-2 mRNA independently of GH.
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