Spotlight on Kylie Kavanagh, DVM
Twice weekly hot tub sessions reduced blood pressure in monkeys
The single therapy known to improve all aspects of metabolic health in people is exercise. However a significant proportion of the population is unable to undertake intense exercise due to obesity, arthritis, diabetic neuropathy, and other comorbidities that accompany aging and metabolic disease.
Hot tub therapy induces increases in core body temperature, heart rate, and blood pressure in a similar manner to that of exercise. Heat is known to induce tissue expression of proteins (HSP70 and 90) known to protect cells from the metabolic stress.
Four adult monkeys were submerged to neck level in a heated whirlpool with continuous rectal temperature monitoring, and maintained between 39 and 41C for 30 minutes. Muscle biopsies were taken prior to, immediately following, and 1 and 4 hours post-hot tub in 4 monkeys. Hot tub therapy significantly induced gene expression of HSP70 nine-fold (p<0.01), and HSP90 two-fold (p<0.05) with elevations persisting to 4 hours.
We then conducted a pilot clinical trial in aged primates (average age 17 years) to determine the vascular and glycemic effects of repeated heat therapy. Four monkeys underwent twice weekly hot tub sessions for 5 weeks and 3 control [CTL] monkeys had normal body temperature maintained under sedation. Muscle biopsies, blood pressure (BP) measurements, and glucose tolerance tests were performed one week before and one week after the trial. In the hot tub monkeys, tissue levels of the protective HSP protein were variable but showed a trend towards elevation even 5 days after the final session. Systolic BP was reduced by > 40mmHg and diastolic BP by >20mmHg (p=0.06 for both) with a notable trend towards reduced heart rate (p=0.11).
This effect is the equivalent of taking 4 separate antihypertensive medications. Glucose tolerance worsened in control monkeys, but hot tub monkeys were stable with signs of improved insulin secretion. We conclude that hot tub therapy in aged monkeys induces protective HSP proteins in muscle tissue and shows promise for the treatment of hypertension and insulin resistance.
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