MURINE ILEAL INTERPOSITION INDUCES SUBCUTANEOUS WHITE ADIPOSE TISSUE REMODELING WITH ENHANCED LIPOLYSIS, FATTY ACID OXIDATION, AND MITOCHONDRIAL TRANSPORT Michael Kachmar, DO (1,2,3); Hari Naga Sai Kiran Suryadevara, MS (3); R Leigh Townsend, BS (3); Teresa H Schauer, BS (3); David A Hughes, PhD (3); Sujoy Ghosh, PhD (3); Vance L Albaugh, MD, PhD (3)

(1) Morsani College of Medicine, University of South Florida, Tampa FL; (2) Tampa General Hospital, Tampa FL; (3) Pennington Biomedical Research Center, Baton Rouge LA

INTRODUCTION: Metabolic surgery improves obesity-associated comorbidities through weight-dependent and weight-independent mechanisms, although these mechanisms remain incompletely understood. Ileal interposition (I-I) is a simplified metabolic operation that uses gastrointestinal rearrangement to mimic these effects. I-I was used to test the hypothesis that transcriptional remodeling of subcutaneous white adipose tissue (scWAT) is at least one contributing mechanism of the benefits associated with gastrointestinal rearrangement.

METHODS: Male C57BL/6J mice (n=27) were maintained on either a high-fat semi-purified diet (60% kcal; diet-induced obesity, HF) or a semi-purified, matched low-fat diet (10% kcal; lean controls, LF) and then randomized to I-I or ad libitum diet controls (HF-C, n = 5; HF-II, n = 6; LF-C, n = 8; LF-II, n = 8). Four weeks post-intervention, scWAT was harvested for standard guanidinium thiocyanate RNA isolation and bulk RNA sequencing. Differential expression was modeled using limma (R/Bioconductor) across pre-specified contrasts: high-fat surgery versus high-fat control, low-fat surgery versus low-fat control, pooled surgery versus pooled control, diet (high-fat versus low-fat, collapsing surgery and control), and surgery-by-diet interaction. Genes were considered significant at an adjusted p-value (FDR) ≤ 0.05. Post-processing evaluated for concordant significance in the high-fat, low-fat, and pooled surgery comparisons with the constant direction of effect, and exclusion if significant in the diet or surgery-by-diet contrasts.

RESULTS: Across scWAT, 382 genes met the concordance criteria. Of these 382 genes, 50 were consistently upregulated and significant in the pooled surgery contrast. The median log2 fold-change across the 50 upregulated genes was 0.76 (IQR 0.41), with values ranging from 0.32–2.19. Using magnitude thresholds, 39 of 50 upregulated genes showed an average log2 fold-change ≥0.58 (~1.5-fold), and 13 of 50 had an average log2 fold-change ≥1 (~2-fold). Three genes (Mc5r, Acsm3, and Slc25a34) exceeded a log2 fold-change >2 (~4-fold) in at least one comparison, while remaining concordantly upregulated across all three surgery contrasts and non-significant in diet-related effects.

CONCLUSION(S): Ileal interposition triggers transcriptional reprogramming of scWAT, with concordant upregulation of 50 genes, including robust signals in lipolysis (Mc5r), fatty acid activation (Acsm3), and mitochondrial transport (Slc25a34). These effects appear independent of diet, supporting an operation-driven mechanism. This data highlight scWAT’s role in systemic metabolic improvements after metabolic surgery and suggest potential therapeutic targets in peripheral adipose remodeling. These findings warrant investigation of gut-derived signals, including incretin hormones and bile acids, which may serve as candidate upstream mediators coordinating adipose tissue reprogramming and cross-talk across intestinal, hepatic, and adipose tissues.