Characterization of Diabetic Intramuscular Adipose Tissue and its Impact on Skeletal Muscle
Authors: Gui Chang , Bohnert Kathryn , McCormick Jeremy , Bakus Jonathon , Johnson Jeffrey , Klein Sandra , Meyer Gretchen 
Published: May 2024

Obesity and type 2 Diabetes exhibit a muscle pathology called fatty infiltration where adipocytes develop between muscle fibers in the intramuscular space. This is associated with reduced contractile strength and physical function in these populations. However, the mechanisms governing this phenomenon are not well understood. In this study, we aim to characterize intramuscular adipose tissue (IMAT) in both healthy and diabetic patients and explore its impact on muscle regeneration. We hypothesized that diabetes would alter the secretory profile of IMAT and hinder muscle regeneration. Finally, we treated IMAT-derived progenitor cells with a browning agent to determine whether this intervention could modulate IMAT-muscle cross-talk. We collected human IMAT from the abductor hallucis muscle and subcutaneous fat from patients during elective below-knee amputation, both with and without type 2 Diabetes. All participants gave informed consent to participate in this study. Samples were divided and processed for RNA sequencing and adipose progenitor cell (APC) isolation. Following sequencing, we identified top differentially expressed genes (DEGs) encoding secretory proteins that differed between IMAT and subcutaneous fat across participants, including WNT2, BMP5, OSTN. Additionally, IPA analysis revealed that the Wound Healing Signaling pathway is more activated in IMAT under diabetic conditions. We then screened these target genes using a co-culture system in vitro. In this system, APCs were cultured under different conditions and then used to condition media which was applied to separate cultures of isolated human muscle myoblasts. Cultured ASCs were additionally collected for qPCR analysis and a sample of the media was collected for screening. The impact of the conditioned media on myogenesis was assayed by Myosin Heavy Chain (MHC) immunostaining. Myogenesis was not affected by treatment with any conditioned media, including that from Diabetic IMAT. Furthermore, no improvement of myogenesis was observed by treating the APCs with a browning agent. We were able to confirm that WNT2 is differentially expressed in IMAT APCs treated with a browning agent, compared with SQ (p=0.0406, n=4, FC=0.47) and diabetic conditions (p=0.1581, n=5), in line with our intact tissue RNAseq. This study highlights the distinct transcriptional profile of IMAT compared to subcutaneous fat, with WNT2 identified as a potential mediator between adipose tissue and skeletal muscle. The failure to observe decreased myogenesis implies the crosstalk between muscle and muscle-associated fat might involve a more complex cell-cell network than a simple ASC-myoblast interaction. 1R01AR075773-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.