The effect of hot-tub therapy on serum Hsp70 level and its benefit on diabetic rats: A preliminary report

Purpose: To carry out a preliminary study examining the efficacy of long-term hot-tub therapy (HTT) in the improvement of diabetic complications on streptozotocin-induced diabetic rats. Materials and methods: Male Wistar rats were immersed mid-sternum in a circulating water bath (42 degrees C for 30 min) to obtain a core body temperature of 41 degrees C; this process was repeated three times a week for 5 months. The blood was collected every month. Multiple parameters were examined for all rats including heat shock protein (Hsp70) level, serum glucose and insulin concentrations, advanced glycation end product (AGE) and glycated haemoglobin (HbA1c) formation, lipid profile and antioxidant defence system. Additionally, the chaperoning capacity of glycated Hsp70 was evaluated based on in vitro studies in which the refolding of denatured luciferase was compared to refolding by native Hsp70. Results: HTT-treated diabetic rats showed a significant improvement in lipid profile, antioxidant capacity, insulin secretion and serum Hsp70 level and a significant decrease in AGE formation compared to the untreated diabetic rats. However, HTT had a borderline significant effect on weight and fasting blood glucose. Glycated Hsp70 lost its chaperoning ability to reactivate the denatured luciferase. Conclusion: A decrease in complications in diabetic rats after hot-tub therapy is shown here. An increase in the extracellular Hsp70 level due to HTT was observed. This increase may serve to protect the structure of proteins (e.g. preventing AGE formation), and the observed beneficial effects may be related to it.