Effects of Dietary Menthol on Autonomic Thermoregulation in a Cold Environment

Human body temperature homeostasis is regulated by both behavioral and autonomic thermoregulation. The transient receptor potential melastatin 8 (TRPM8) channel, a cold receptor, plays a critical role in cold perception and thermoregulation. Menthol, which activates TRPM8, has been shown to promote the "browning" of white adipocytes, enhancing thermogenesis. However, its effect on autonomic thermoregulation has remained unclear. To address this, the present study examines the influence of dietary menthol intake on autonomic thermoregulation in mice, with a focus on body temperature regulation under cold conditions. In this experiment, mice were fed diets containing 0.25% and 0.5% menthol for either 2 or 4 wk. The results indicated that the 0.5% menthol diet significantly reduced food intake, body weight, and visceral fat. In contrast, the 0.25% menthol diet showed no significant impact on these factors. Notably, mice treated with the 0.25% menthol diet for 4 wk suppressed the decrease in rectal and interscapular brown adipose tissue (IBAT) temperatures in a cold environment under anesthesia. Additionally, TRPM8 gene expression in IBAT was upregulated after 4 wk of 0.25% menthol diet consumption. These findings suggest that dietary menthol, especially at low concentrations, improves autonomic thermoregulation by activating TRPM8 without significantly affecting food intake or body weight.