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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #166478
Title: LIPOPOLYSACCHARIDE REGULATES MYOSTATIN AND MYOD INDEPENDENTLY OF AN INCREASE IN PLASMA CORTISOL IN CHANNEL CATFISH (ICTALURUS PUNCTATUS)

Author
item Weber, Thomas
item Small, Brian
item Bosworth, Brian

Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2004
Publication Date: 1/1/2005
Citation: Weber, T.E., Small, B.C., Bosworth, B.G. 2005. Lipopolysaccharide regulates myostatin and myod independently of an increase in plasma cortisol in channel catfish (Ictalurus punctatus). Domestic Animal Endocrinology 28(1):64-73.

Interpretive Summary: Muscle growth is an economically important trait in catfish. Understanding how events such as pathogen exposure and the associated stress response affect regulation of genes involved in muscle growth could provide information useful in the development of catfish germplasm with superior growth and disease resistance. In this study we determined the effects of injecting catfish with lipopolysaccharide (LPS - a component of bacterial cell walls which produces an inflammatory response in mammals) and the glucocorticoid (a class of hormones produced during stress), dexamethasone on expression of two genes, MyoD and myostatin, involved in muscle growth in mammals. Unlike mammals, LPS did not increase cortisol in channel catfish. It was also found that LPS upregulated MyoD and downregulated myostatin, again, opposite of what is found in mammalian species in regards to MyoD regulation. As found in other fish species, glucocorticoid injection decreased the expression of myostatin, but did not affect MyoD expression. The lack of a cortisol response due to LPS injection suggests that the regulation of myostatin and MyoD in response to inflammatory stimuli is independent of glucocorticoids. Furthermore, the results of this study indicate that the regulation of genes involved in muscle growth in fish following pathogen exposure or stress is different from that observed in mammals. The results of this research demonstrate the need for fish specific models of growth regulation by pathogen exposure.

Technical Abstract: The effects of lipopolysaccharide (LPS) on plasma cortisol and the expression of MyoD and myostatin (MSTN) mRNAs, and the effect of dexamethasone (Dex) on MyoD and MSTN mRNAs were evaluated in channel catfish. For the LPS injection experiments, juvenile channel catfish were injected with 1.5 mg/kg LPS or sterile PBS. Blood was collected at 1h, 3 h, 12h, and 24 h postinjection for cortisol determination, and muscle samples were collected at 3 h, 12 h, and 24 h for mRNA analysis. For the Dex injection experiment, fish were injected with 1.0 mg/kg Dex or saline and muscle samples were collected at 12 h and 24 h. There was no effect of LPS on plasma cortisol at any of the time points measured. Injection with LPS increased the abundance of MyoD mRNA at 3 and 12 h, and decreased the abundance of MSTN mRNA at 24 h. There was no effect of Dex injection on the abundance of MyoD mRNA. However, Dex injection decreased the abundance of MSTN mRNA at 12 h postinjection. These results suggest that LPS regulates the expression of MyoD and MSTN independently of an increase in plasma cortisol, and that the regulation of MyoD in the channel catfish differs from mammals in response to inflammatory stimuli. These results also confirm that exogenous glucocorticoids decrease the expression of MSTN as shown in other fish species.