Modulatory effect of betaine on expression dynamics of HSPs during heat stress acclimation in goat (Capra hircus).

Changing climatic scenario with expected global rise in surface temperature compelled more focus of research over decoding heat stress response mechanism of animals and mitigation of heat stress. Recently betaine, a trimethyl form of glycine has been found to ameliorate heat stress in some species of animals. To overcome deleterious effect of heat stress, an attempt was taken to investigate the effect of betaine supplementation on heat stress mitigation in goats. Eighteen female Barbari goats were taken and randomly divided into 3 groups (n=6) such as control, HS (Heat stressed), HS+B (Heat stressed administered with betaine). Except for the control group, other groups were exposed to repeated heat stress (42 °C) for 6 h for sixteen consecutive days. Blood samples were collected at the end of heat exposure on day 1 (Initial heat stress acclimation - IHSA), day 6 (Short term heat stress acclimation - STHSA) and day 16 (Long term heat stress acclimation - LTHSA). When the groups were compared between different heat stress acclimatory phases, expression of all HSPs (HSP60, HSP70, HSP90 and HSP105/110) showed a similar pattern with a first peak on IHSA, reaching a basal level on STHSA followed by second peak on LTHSA. The messenger RNA (mRNA) and protein expression of HSPs was observed to be higher (P<0.05) in HS group than HS+B group except HSP90 on IHSA and HSP60 on STHSA. HSP105/110 expression was highest (P<0.05) on LTHSA. Immunocytochemical analysis revealed that HSPs were mainly localized both in nucleus and cytoplasm of PBMCs. In conclusion, heat stress increases HSPs expression and betaine administration was shown to have a dwindling effect on expression of HSPs, suggesting a possible role of this chemical chaperone on heat stress amelioration.