Effects of an acute bout of passive hyperthermia therapy on glycemic control and blood pressure response in healthy individuals and type 2 diabetics

While exercise is beneficial, obese Type 2 diabetics (T2D) have very low exercise capacities. Research using passive heat stress utilizing hot tubs and saunas have reported improvements in cardiovascular and glycemic control in animal models. This project tested the hypothesis that an acute bout of hyperthermia will improve glucose and insulin responses and reduce arterial blood pressure during and following the exposure. Nine obese Type 2 diabetics (T2D; 50.1 ± 12 years, 7.5 ± 1.8% HbA1C) and nine similarly aged healthy controls (HC; 41.1 ± 13.7 years; p = .185, 5.3 ± 0.4%, HbA1C; p =.007) with similar resting blood pressures (T2D: 125 ± 27/ 77 ± 14, HC: 122 ± 14/ 81 ± 10 mmHg, p >.05) volunteered. Subjects underwent a whole body passive heated stress (1 hr resting in 39.4 ± 0.4 °C water) followed by 1 hr post immersion sitting recovery under normal ambient temperatures. Both groups were similarly heat stressed (?, core body, Tre, 1.4 ± 0.4°; ? mean skin temperature, Tsk, 6.5 ± 0.8; and ? heart rate, HR from rest, 33.5 ± 8.3 bpm) at the end of warm water immersion. No main interaction was found for group and condition for glucose, C-peptide, insulin, and leptin during a glucose tolerance test (p > .05). Additionally, in comparison to preimmersion values, there was no interactive effect for mean arterial blood pressure (MAP, time x group; p = .145). In both groups MAP was reduced (p < .01) from min 10 (? MAP, T2D: 10.2 ± 5.5, HC: 14.8 ± 8.4 mmHg) through minute 60 of immersion (T2D: 12.8 ± 8.1, HC: 13.9 ± 11.2 mmHg) and remained below pre-immersion values (p = .004) up to 20 min post immersion (T2D: 10.8 ± 9.6, HC 7.6 ± 6.8 mmHg). These data indicate that an acute 1 hr bout of warm water immersion does not improve glucose and insulin responses 24 hr post treatment. However, passive hyperthermia results in similar hypotensive responses between groups and may offer a acute therapeutic benefit to both healthy and diabetic populations.