Depot-Specific White Adipose Tissue Remodeling Supports Non-Thermogenic Metabolic Homeostasis During Shallow Hibernation in Raccoon Dogs.

White adipose tissue (WAT) is essential for maintaining energy homeostasis during hibernation by supplying lipolysis-derived fatty acids as a major fuel source. In raccoon dogs (Nyctereutes procyonoides), the activity of brown adipose tissue is diminished, providing a unique model to investigate how WAT supports metabolic homeostasis in a largely non-thermogenic state. Here, we integrated physiological, histological, transcriptomic, and molecular analyses of back-fat and tail-fat depots during autumn fattening and winter sleep. Despite reduced food intake, body weight loss, and mild hypothermia, raccoon dogs maintained systemic glucose and lipid homeostasis. Both WAT depots exhibited adipocyte atrophy and the coordinated suppression of core metabolic and biosynthetic pathways, indicating a shared program of metabolic depression. However, the two depots adopted distinct remodeling strategies. Back-fat showed collagen densification and vascular-associated remodeling, suggesting a structural adaptation that may preserve tissue integrity during winter sleep. In contrast, tail-fat displayed enhanced innate immune signaling and M2 macrophage enrichment, indicating immune niche remodeling that may support tissue protection during prolonged lipid mobilization. Together, these findings reveal that raccoon dogs maintain metabolic homeostasis during shallow hibernation through a non-thermogenic, WAT-centered strategy characterized by shared metabolic depression and depot-specific structural and immunometabolic remodeling.