Water intake attenuates the hyperglycemic effect of chronic exposure to high environmental temperature without improving oxidative stress and cardiovascular outcome in animal models

Abstract

Background: It is unclear if water intake during exposure to high environmental temperature (HET) attenuates hyperthermia-induced cardiovascular event.
Objectives: This study investigated the influence of chronic exposure to HET on cardiovascular parameters, oxidative stress and blood glucose homeostasis in the presence and absence of water rehydration in animal models.
Methods: Eighteen Male Sprague-Dawley rats (n=6/group) were either exposed to high o environmental temperature (38.5 ± 0.5 C, relative humidity of 65-75%,) 4hrs daily for 8 weeks without (H) or with water rehydration (RH), compared with control (C) rats maintained at room temperature of 25^o ± 0.5 C. Fasting Blood Glucose (FBG), oral Glucose Tolerance Test (OGTT), liver glycogen, blood
pressure (BP), heart rates (HR) and oxidative parameters were determined.
Results: In comparison with control rats, FBG and 60min-post OGTT blood glucose were significantly higher in rats exposed to HET alone (H) (P<0.05), but unaltered in rats exposed to HET + rehydrated (RH) . However, liver glycogen was significantly (P<0.05) depleted in RH rats. SBP, MAP and HR were significantly (P<0.05, P<0.01, P<0.001) elevated in H and RH rats. Similarly, plasma Malondialdehyde
(MDA) concentration was significantly elevated in both H and RH groups (P<0.001), with associated suppression of superoxide dismutase (SOD) (P<0.05) and catalase activities (P<0.05) as well as Reduced Glutathione(GSH) level (P<0.01) in H rats, but with only GSH (P<0.01) suppressed in RH rats.
Conclusion: Overall, HET impaired peripheral glucose uptake with associated increase in BP, myocardial workload and oxidative stress. Peripheral glucose uptake was enhanced by water intake during exposure to HET with no improvement in BP, HR, myocardial workload and oxidative stress parameters.

Keys: high environmental temperature, environmental heat, rehydration, oxidative stress, hyperglyceamia