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Effects of posthatch feed deprivation on heparan sulfate proteoglycan, syndecan-1, and glypican expression: implications for muscle growth potential in chickens.

The heparan sulfate proteoglycans, syndecan-1 and glypican-1 (glypican), are low affinity receptors for fibroblast growth factor 2 (FGF2). Because FGF2 stimulates skeletal muscle cell proliferation but inhibits differentiation, changes in FGF2 signaling due to early posthatch feed deprivation may play a significant role in modulating muscle growth. To study the effect of early posthatch feed deprivation in chickens on heparan sulfate proteoglycan relative protein concentration, syndecan-1 expression, and glypican mRNA expression, pectoralis major muscle tissue was isolated from pretreatment d 0 chicks and chicks fed or feed deprived for 3 d, and after d 3 feeding was resumed in the feed-deprived birds until d 7. Heparan sulfate proteoglycan protein concentration was measured by ELISA analysis and was significantly decreased in the feed-deprived birds beginning at d 2 (P < 0.05). The expression of syndecan-1 and glypican was measured by semi-quantitative reverse transcription PCR. Syndecan-1 expression was unaffected by feed withdrawal and refeeding (P > 0.05). Glypican mRNA expression was decreased in the muscle tissue from feed-deprived birds at d 3 (P < 0.05), but by d 7, after initiating feeding on d 4, it was significantly elevated compared with in muscle tissue from chicks maintained on feed (P < 0.05). The results from the present study demonstrate that the heparan sulfate proteoglycan protein concentration and syndecan-1 and glypican mRNA expressions are differentially affected by early posthatch feed deprivation, which may alter signaling events associated with muscle growth.