Effect of antioxidants and betaine supplementation on serum HSPs and stress hormone during long-term heat stress adaptation in goat

Menacing global rise in surface temperature compelled more focus of research over decoding heat stress response mechanism of animals and mitigation of heat stress. Thirty female goats were taken and randomly divided into 5 groups (n=6) such as NHS (Non heat stressed), HS (Heat stressed supplemented with normal saline- 5mL I/M), HS+B (Heat stressed supplemented with betaine- 0.2g/kg BW I/M), HS+VC (Heat stressed supplemented with Vitamin C- 40mg/kg BW I/M), HS+VE+Se (Heat stressed supplemented with Vitamin E- 50 mg and Selenium- 1.5 mg I/M). After 14 days acclimatization, except NHS group, other groups were supplemented and 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, 6, 11 and 16. Stress hormones and extracellular HSPs concentration were measured by RIA and ELISA, respectively. The body weight (BW) and body condition score (BCS) was decreased by considerable amount in heat stressed goats except HS+B group. Stress hormones responses to heat stress in goats between groups on study days: On first day, cortisol concentration decreased significantly (P<0.05) in HS+VC group in comparison to HS and HS+VE+Se groups. On day 6, T3 level in HS group and T4 level in HS+VC group was found significantly (P<0.05) lower than HS+VE+Se group. Cortisol level in HS and HS+VE+Se group was investigated significantly (P<0.05) higher than NHS and HS+VC groups. On day 11, T3 concentration in HS+VC and HS+VE+Se group and cortisol concentration in HS+B group increased (P<0.05) in comparison to other groups. On day 16, T3 and T4 concentration in antioxidants and betaine administered groups was found significantly (P<0.05) higher in comparison to HS group. T3 concentration in HS group decreased (P<0.05) than NHS group. Stress hormones responses to heat stress in goats between study days within groups: In HS group, T3 concentration decreased (P<0.05) on day 16 in comparison to day 1 through day 6. A non significant (P>0.05) decrease was observed in T4 concentration. Cortisol concentration increased (P<0.05) to reach at peak on day 6 and thereafter decreased to basal level on day 11. In HS+B group, T3 concentration was observed significantly higher (P<0.05) on day 6 and 16 in comparison to day 1 and 11. Its concentration on day 6 was significantly (P<0.05) lower than day 16. T4 concentration increased (P<0.05) on day 16 in comparison to day 1. Cortisol concentration increased (P<0.05) to reach at peak level on day 11 through day 6 in comparison to day 1. Thereafter, it decreased (P<0.05) towards basal level on day 16. In HS+VC group, concentration of T3 on day 11 and 16, and T4 on day 16 was found significantly (P<0.05) higher in comparison to day 1 and 6. Cortisol concentration increased (P<0.05) on day 11 than day 1. In HS+VE+Se group, T3 concentration increased (P<0.05) on day 6 in comparison to day 1 and maintained at higher level on subsequent days. T4 on day 16 was found significantly (P<0.05) higher in comparison to day 1. Cortisol concentration was recorded significantly (P<0.05) higher on day 6 than day 1, 11 and 16. T3 mean concentration was increased (P<0.05) in antioxidants supplemented groups and decreased (P<0.05) in HS group in comparison to NHS and HS+B groups. Vitamin E with Se increased (P<0.05) the T4 mean concentration than HS group. Cortisol concentration was found significantly (P<0.05) higher in HS and HS+B group in comparison to other groups. Responses of extracellular HSP70 to heat stress quantified by ELISA: Six hour heat stress at 42 °C on first day was found to have no effect on the extracellular HSP70 (eHSP70) in all groups. On day 6, eHSP concentration was found significantly (P<0.05) higher in heat stress exposed animals in comparison to control animals. On day 11, eHSP70 level in serum was differed (P<0.05) in all groups and the increasing order of eHSP70 concentration was follows: - NHS < HS+VC < HS+VE+Se < HS group. On day 16, there was observed higher (P<0.05) level of eHSP70 only in HS group animals than other groups. The eHSP70 increased significantly (P<0.05) after day 1 in all groups in comparison to NHS group and reached to peak value on day 11. After that, it decreased (P<0.05) towards basal level concentration in heat stressed animals. Mean eHSP70 increased (P<0.05) in all heat stressed groups in comparison to NHS group and in HS group it was significantly (P<0.05) higher than HS+B, HS+VC and HS+VE+Se groups. Responses of extracellular HSP90 to heat stress quantified by ELISA: On day 1, extracellular HSP90 (eHSP90) concentration was significantly (P<0.05) higher in HS, HS+B and HS+VE+Se group in comparison to NHS and HS+VC groups. However on day 6, no significant (P>0.05) difference was observed between groups. Concentration of eHSP90 increased (P<0.05) in HS group than NHS group on day 11. On day 16, eHSP90 level increased (P<0.05) in HS, HS+VC and HS+VE+Se in comparison to NHS and HS+B group. In antioxidants administered groups, eHSP90 concentration was significantly (P<0.05) lower than HS group. In HS group, the expression of eHSP90 declined (P<0.05) on day six in comparison to day 1; gradually increased (P<0.05) through day 11 and reached again at second peak on day 16. In contrast, the eHSP90 concentration in antioxidant administered groups remained at basal level up to day 11 and thereafter, increased significantly (P<0.05) on day 16. However, we could not observe any difference in betaine administered group on eHSP90 between days. Mean eHSP90 increased (P<0.05) in HS group in comparison to all other groups. In conclusion, betaine and antioxidants supplementation significantly affect the BW, BCS, cortisol, T3, T4, extracellular HSP70 and HSP90 during heat stress. eHSP70 and eHSP90 may be used as a useful biomarker of heat stress in animals.