Background: Phosphoinositide 3-kinases (PI3Ks) are critical regulators of cellular processes including membrane trafficking, nutrient signaling, and metabolic homeostasis. While Class I and III PI3Ks are well-characterized, the functions of Class II PI3Ks remain poorly understood. PIK3C2B is enriched in skeletal muscle (SkM) and regulates endosomal trafficking and protein sorting. Emerging evidence implicates PIK3C2B as a modulator of both skeletal muscle function and systemic energy metabolism. Here, we investigate how skeletal muscle-specific ablation of Pik3c2b influences whole-body energy metabolism and muscle bioenergetics and evaluate the therapeutic potential of targeting Pik3c2b via a novel gene therapy approach. Methods: Skeletal muscle-specific Pik3c2b knockout (KO) mice were generated using an ACTA1 Cre-lox system and maintained on a standard chow diet up to 40 weeks for longitudinal assessment of body weight, food intake, body composition (Echo-MRI), energy expenditure (CLAMS), and in vivo insulin sensitivity. Muscle, liver, and adipose tissues were analyzed histologically, and muscle phosphoinositide levels were quantified by LC-MS/MS. Primary mouse myotubes were used for mitochondrial bioenergetic studies (Oroboros) and co-culture experiments with 3T3L1 adipocytes. For therapeutic studies, a MYOAAV3A vector delivering a Pik3c2b-targeted miRNA or PBS control was administered to juvenile wild-type mice followed by metabolic phenotyping. Results: Pik3c2b KO mice exhibited favorable metabolic adaptations throughout aging as compared to WT (Cre+) controls, including lower body weight independent of changes in food intake, reduced adiposity and smaller adipocytes that express a ‘myogenic-like’ profile. While SkM structure remained largely unremarkable, Pik3c2b deletion selectively remodeled phosphoinositide pools and enhanced mitochondrial respiratory capacity. In-direct co-culture experiments recapitulated in vivo our findings, supporting a role for Pik3c2b in mediating SkM-adipose crosstalk. In gene therapy experiments, MYOAAV-miRNA delivery effectively reduced Pik3c2b mRNA and protein levels in skeletal muscle compared to PBS controls (p< 0.05). Treated mice displayed lower body weight and total fat mass throughout adulthood (p< 0.05), with no differences in cumulative food intake. Conclusion: Skeletal muscle-specific Pik3c2b ablation improves body composition throughout aging, highlighting a previously unrecognized role for Pik3c2b in muscle-driven energy homeostasis. Targeting PIK3C2B via genetic therapy may represent a promising strategy to mitigate adverse metabolic factors associated with obesity and related comorbidities. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Han et al. (Fri,) studied this question.