Cortisol, resposta glicêmica e secreção de insulina em equinos clinicamente sadios submetidos a sessões de hipóxia normobárica

Abstract

Many studies pointed out to the effects of acute or chronic hypoxia in order to study the adaptation in response to high altitudes. Recently, some studies have tried to unravel the effects of exposure to intermittent hypoxia (IH), to explore the therapeutic value to patients and potential influence on the performance of athletes. Same studies show that exposure to acute or chronic hypoxia can influence the metabolism of glucose and related hormones, however, the results are still inconsistent. In horses affected with polysaccharide storage myopathy, in which horses show enhanced glucose uptake by muscle cells and increase insulin sensitivity may be the target of future studies for the potential use of IH in veterinary medicine. The aim of this study is to evaluate the effect of normobaric intermittent hypoxia in serum cortisol, blood glucose levels and insulin secretion in non-exercised horses. Healthy adult horses (n=8) were selected after physical examination and underwent an intravenous glucose tolerance test (0.5gr/kg) (IVGTT). Blood samples (n=11) were collected between 0 and 180 minutes after glucose administration to evaluate glycemic response and insulin secretion. Then, they were exposed to 1-hour hypoxia sessions twice a day, reaching a total of 43 hypoxia sessions. From first to last session the [O2] was gradually decreased from 17% to 12%. The heart rate and the samples to measure serum cortisol were collected before and every 15 minutes during the sessions 1, 4, 6, 8, 10, 14, 22 and 43. The IVGTT was repeated at the end of the study. The serum cortisol levels were higher in session 1 (S1) (17% O2) when compared to the levels of S10 (13% O2) and S43 (12% O2) (P<0.05). The glycemic response was not significantly altered in resting horses submitted to normobaric hypoxia sessions from 17% to 12% [O2], however, required higher insulin secretion, suggesting a decrease in sensitivity to this hormone. The decline in serum cortisol and heart rate suggests an adaption to the stimulus of hypoxia. IH is a resource that provides a wide area for further studies in horses, both as a therapeutic tool, about the potential benefits on athletic performance.