Hypothalamic Inflammaging-Related miRNA Dysregulation after Weight Regain Is Associated with Systemic Inflammation and Intestinal Ultrastructural Damage

Weight regain after weight loss is a major challenge in obesity management and may promote inflammatory responses distinct from sustained obesity. Whether these alterations involve intestinal, systemic, and hypothalamic inflammatory changes remains unclear. This study evaluated intestinal ultrastructural alterations, systemic inflammation, and hypothalamic inflammation following weight loss and regain in adult C57BL/6 mice. Male mice underwent an 18-week dietary protocol (chow or HFHS) and were allocated to Control (C), Obesity (Ob), Weight Loss (WL), and Weight Regain (WR) groups (n=10/group). Plasma, intestine, and hypothalamus were analyzed by biochemical, ultrastructural, immunofluorescence, and molecular approaches. Data were analyzed by one-way ANOVA and miRNA expression by principal component analysis. WR showed disrupted microvilli, altered junctional complexes, and mitochondrial abnormalities, accompanied by elevated circulating LPS (+287% vs C). Compared with Ob, WR showed higher circulating TNF-α (+75%), IL-1β (+148%), and IL-6 (+39%). In the hypothalamus, WR and Ob exhibited comparable inflammatory activation, with increased Tlr4, Il1b, Il6, and Nlrp3 expression and IBA-1/NF-κB immunoreactivity. WR also displayed a distinct inflammaging-related miRNA profile and increased p53, a cellular senescence marker (+57% vs Ob). WL, however, attenuated intestinal ultrastructural and inflammatory alterations. In summary, WR induced intestinal ultrastructural damage and exacerbated systemic inflammation, accompanied by hypothalamic inflammatory activation, a distinct inflammaging-related miRNA profile, and increased cellular senescence, supporting an inflammatory phenotype distinct from sustained obesity.