Heat Therapy Sessions Previously To High-Fat Diet Consumption In Female Rats: Effects on Metabolic Markers And eHSP72 Plasma Levels

Background: The development of type 2 diabetes mellitus (T2DM) involves a pro-inflammatory profile, marked by higher plasma 72-KDa heat shock proteins (eHSP72) levels. Experimental and clinical studies have shown that heat therapy (HT) helps subjects with established T2DM to control body weight and glycemia by improving heat shock response. However, whether HT has benefits when applied as a preventive strategy is unknown. Objective: We aim to test whether HT can prevent weight gain, adiposty, improve glycemia, and decrease eHSP72 levels. Methods: Adult (2-month-old) female Wistar rats (n=24) were divided into four groups: Control (4 months without intervention + standard diet, 16.6 MJ/kg, 11.4% fat); HFD (2 months without intervention + 2 months of HFD consumption, (22.8 MJ/kg, 58.3% fat); HT1x+HFD (2 months of HT, 1x/week + 2 months of HFD consumption); and, HT3x+HFD (2 months HT, 3x/week + 2 months of HFD consumption). HT was performed for 20 minutes in an immersive chamber inside a water bath at 41°C. Rectal temperature (°C) was registered during HT sessions, and the body weight gain (BWG) and fasting glycemia were evaluated before and after interventions. At the end of the study, adipose tissue was collected, and plasma eHSP72 levels were assessed with an ELISA kit (Enzo Life Sciences). Data were expressed as mean±s.d., One-way or Two-way ANOVA followed by Tukey's multiple comparisons test were applied (p<0.05). All procedures were approved by the Committee of Animal Welfare (0052021-CEUA-UNIJUI). Results: All groups presented similar basal temperature (mean range between 37.3°C and 37.5°C, P=0.883), and heat sessions increased ~2.5°C (Control=38.7±0.8; HFD=38.7±0.7; HT1x+HFD=39.7±0.8*; HT3x+HFD=40.2±0.3*, *p<0.008 vs. Control and HFD groups.) All groups started with similar body weight (P=0.407), and in the first 2 months increased approximately 17g in body weight compared to their basal levels (p<0.0001), without difference between groups (P=0.395). After the HFD consumption (last 2 months), all groups increased body weight in comparison to their previous levels (p<0.0001), without difference between groups (BWG%: Control=14.5±6.8; HFD=20.2±9.1; HT1x+HFD=27.1±8.8; HT3x+HFD=16.7±10.0, P=0.162). No differences in glycemia were found at the beginning of the experimental protocol (means range from 69 to 73 mg/dl, P=0.995) and at the 2-month mark (means range from 71 to 77 mg/dl, P = 0.924). At the end of the study, all HFD groups presented higher glycemia and adiposity in comparison to the Control group (Glycemia mg/dl: Control=86.2±3.5; HFD=98.5±10.6; HT1x+HFD=98.3±8.7; HT3x+HFD=99.8±8.3, p<0,006), (Adiposity %: Control=2.1±1.2; HFD=4.05±1.0; HT1x+HFD=5.7±1.5; HT3x+HFD=3.9±1.5, P=0.031). Levels of eHSP72 were decreased in the HT3x+HFD group compared to the HFD group. (Plasma eHSP72 ng/ml: Control=0.13±0.04; HFD=0.19±0.08; HT1x+HFD=0.18±0.07; HT3x+HFD=0.10±0.04, P=0.042 vs HFD). Conclusion: Preventive heat therapy sessions attenuated the pro-inflammatory profile induced by a high-fat diet; however, the tested HT protocol was ineffective in preventing the metabolic effects of diet consumption. The Brazilian National Council for Scientific and Technological Development (CNPq, 407329/2016-1, 444286/2024-1, 403136/2024-5, 405546/2023-8, 307926/2022-2 to TGH) This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.