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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Fasting on IGF-Binding Proteins, Glucose, and Cortisol in Channel Catfish (Ictalurus punctatus)

Authors
item Peterson, Brian
item Small, Brian

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 17, 2003
Publication Date: March 1, 2004
Citation: Peterson, B.C., Small, B.C. 2004. Effects of Fasting on IGF-Binding Proteins, Glucose, and Cortisol in Channel Catfish (Ictalurus punctatus). Domestic Animal Endocrinology. 26:231-240.

Interpretive Summary: The effects of fasting on IGF-binding proteins (IGFBPs), glucose, and cortisol in channel catfish were examined. Fed fish (controls) were compared to 14-, 30-, and 45-day fasted fish and 45-day fasted fish refed for 15 additional days. Body length and body weight changes, condition factor(CF), hepatosomatic index (HSI), and plasma glucose and cortisol were assessed to determine growth and metabolic status. Body length and body weight growth rates were inhibited after 14, 30, and 45 days of fasting. The 14-, 30-, and 45-day fasted fish exhibited hypoglycemia and reduced CF and HSI. Cortisol levels were significantly increased in 30-day fasted fish compared to fed controls. Associated with the increase in cortisol was a concomitant increase in plasma levels of approximately 20-kDa IGFBP (cf-IGFBP-1). At the end of 15 days of refeeding, cf-IGFBP-1, glucose, and cortisol levels were similar to fed controls. These results suggest that cf-IGFBP-1 is increased during fasting-induced growth inhibition of channel catfish and cortisol is probably involved in regulating this IGFBP.

Technical Abstract: The effects of fasting on IGF-binding proteins, glucose, and cortisol in channel catfish were examined. Fed fish (controls) were compared to 14-, 30-, and 45-day fasted fish and 45-day fasted fish refed for 15 additional days. Body length and body weight changes, condition factor(CF), hepatosomatic index (HSI), and plasma glucose and cortisol were assessed to determine growth and metabolic status. Plasma IGFBP concentrations were measured using digoxigenin-3-o-methylcarbonyl-E-aminocaproic acid-N-hydroxysuccimimide ester labeled human IGF-I. Body length and body weight growth rates were inhibited (P < 0.05) after 14, 30, and 45 days of fasting. The 14-, 30-, and 45-day fasted fish exhibited hypoglycemia and reduced CF and HSI. Cortisol levels were increased (22.8 +/- 15.2 vs. 4.7 +/- 3.9) in 30-day fasted fish compared to fed controls (P < 0.05). Associated with the increase in cortisol was a concomitant increase in plasma levels of approximately 20-kDa IGFBP (cf-IGFBP-1). The increase in levels of cf-IGFBP-1 was observed through day 45. Levels of approximately 35 and 45 kDa IGFBP were also identified but were similar between fed and unfed fish throughout the experiment. At the end of 15 days of refeeding, cf-IGFBP-1, glucose, and cortisol levels were similar to fed controls. Refeeding also caused an increase in growth rates. These results suggest that a catfish counterpart to mammalian IGFBP-1 may exist which is similar to what has been reported in other species of fish. These results also suggest that cf-IGFBP1 is upregulated during fasting-induced growth inhibition of channel catfish and cortisol may be involved in regulating this IGFBP.

Last Modified: 8/22/2014
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