Tirzepatide and Intermittent Cold Exposure Independently Improve Glucose Homeostasis in DIO Mice Housed at Thermoneutrality
Obesity is considered a risk factor for metabolic diseases, including type 2 diabetes, and results from an imbalance between energy intake and energy expenditure. While pharmacological approaches such as tirzepatide, a dual GIP/GLP-1 receptor agonist, effectively reduce food intake and body weight, strategies that enhance energy expenditure (EE) may provide complementary metabolic benefits. Intermittent cold exposure (ICE) is one such approach that enhances EE and improves glucose homeostasis independent of weight loss. However, the combined effects of these interventions remain unexplored. In this study, we investigated the individual and combined effects of tirzepatide and ICE on body composition, energy metabolism, and glucose homeostasis in diet-induced obese (DIO) male and female mice housed at thermoneutrality. After 8 weeks of 45% high-fat diet feeding, mice received tirzepatide (10 nmol/kg) or vehicle and were exposed to ICE (4{degrees}C, 1 h/day, 5 days/week) or remained at thermoneutrality for 3 weeks. Energy expenditure and substrate utilization were assessed using indirect calorimetry at thermoneutrality and during an acute 1 h cold challenge. Tirzepatide reduced body weight, food intake, and adiposity in both sexes, with a greater reduction in lean mass in males. ICE did not affect body weight but improved glucose homeostasis. At thermoneutrality, tirzepatide did not alter total EE but lowered respiratory exchange ratio (RER), indicating a shift toward lipid utilization. In contrast, ICE increased energy expenditure and fat oxidation, with no additive effects observed when combined with tirzepatide. Together, these findings highlight that targeting both energy intake and expenditure represents complementary, but not necessarily additive approaches to improving metabolic health.