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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #237280
Title: Effects of fasting on IGF-I, IGF-II, and IGF-binding protein mRNA concentrations in channel catfish (Ictalurus punctatus)

Author
item Peterson, Brian
item Waldbieser, Geoffrey - Geoff

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2009
Publication Date: 8/1/2009
Citation: Peterson, B.C., Waldbieser, G.C. 2009. Effects of fasting on IGF-I, IGF-II, and IGF-binding protein mRNA concentrations in channel catfish (Ictalurus punctatus). Domestic Animal Endocrinology. 37:74-83.

Interpretive Summary: The effects of fasting on insulin like growth factor-I (IGF-I), IGF-II, and insulin like growth factor binding proteins (IGFBPs) in channel catfish were examined. Fed control fish (Fed) were compared to fish that had been fasted for 30 days followed by 15 days of additional feeding (Restricted). Prolonged fasting (30 days) reduced body weight ~60% and decreased IGF-I mRNA in the liver and muscle. Fifteen days of re-feeding restored levels of hepatic and muscle IGF-I mRNA. Liver IGF-II mRNA was not affected by fasting but was increased 2.2 fold after 15 days of re-feeding. Abundance of muscle IGF-II mRNA was similar between the fed control and restricted group throughout the experimental period. Fasting also increased liver IGFBP-1 mRNA and decreased IGFBP-3 mRNA whereas abundance of IGFBP-2 mRNA was not affected. Interestingly, re-feeding for 15 days did not restore levels of IGFBP-1 and IGFBP-3 mRNA relative to fed control levels. The IGF results suggest that IGF-I and IGF-II are regulated by nutritional status and probably have a differential effect in promoting muscle growth during recovery from fasting. Similar to mammals, IGFBP-1 and IGFBP-3 are regulators of catfish growth. These results provide additional evidence of the conserved nature of the IGF-IGFBP-growth axis in catfish.

Technical Abstract: The effects of fasting on IGF-I, IGF-II, and IGF-binding proteins (IGFBPs) in channel catfish were examined. Fed control fish (Fed) were compared to fish that had been fasted for 30 days followed by 15 days of additional feeding (Restricted). Sequence alignment and similarity to orthologous proteins in other vertebrates provided structural evidence that the three catfish sequences identified in the present research were IGFBP-1, -2, and -3. Prolonged fasting (30 days) reduced body weight ~60% (P < 0.001) and decreased IGF-I mRNA in the liver and muscle (P < 0.01). Fifteen days of re-feeding restored levels of hepatic and muscle IGF-I mRNA. Liver IGF-II mRNA was not affected by fasting but was increased 2.2 fold after 15 days of re-feeding (P < 0.05). Abundance of muscle IGF-II mRNA was similar between the fed control and restricted group throughout the experimental period. Fasting also increased liver IGFBP-1 mRNA (P < 0.05) and decreased IGFBP-3 mRNA (P < 0.01) whereas abundance of IGFBP-2 mRNA was not significantly affected. Interestingly, re-feeding for 15 days did not restore levels of IGFBP-1 and IGFBP-3 mRNA relative to fed control levels. The IGF results suggest that IGF-I and IGF-II are differently regulated by nutritional status and probably have a differential effect in promoting muscle growth during recovery from fasting. Similar to mammals, IGFBP-1 mRNA in catfish is increased during catabolism whereas IGFBP-3 mRNA is decreased during inhibited somatic growth. The IGFBP results provide additional evidence of the conserved nature of the IGF-IGFBP-growth axis in catfish.