Obesity/Type II Diabetes Promotes Function-Limiting Changes In Flexor Tendon Extracellular Matrix Organization That Are Not Reversed By Restoring Normal Metabolic Function

Abstract

Type II Diabetes (T2DM) negatively alters baseline tendon function, including decreased range of motion and mechanical properties; however, the biological mechanisms that promote diabetic tendinopathy are unknown. To facilitate identification of therapeutic targets we developed a novel murine model of diabetic tendinopathy. Mice fed a High Fat Diet (HFD) developed diet induced obesity and T2DM. Obesity/ T2DM resulted in progressive impairments in tendon gliding function and mechanical properties, relative to mice fed a Low Fat Diet (LFD), as well as a decrease in collagen fibril diameter by transmission electron microscopy. We then determined if restoration of normal metabolic function, by switching mice from HFD to LFD, is sufficient to halt the pathological changes in tendon due to obesity/T2DM. However, switching from a HFD to LFD resulted in greater impairments in tendon gliding function than mice maintained on a HFD. Mechanistically, IR{beta} signaling is decreased in obese/T2DM murine tendons, suggesting altered IR{beta} signaling as a driver of diabetic tendinopathy. However, knock-down of IR{beta} expression in S100a4-lineage cells (IRcKOS100a4) was not sufficient to induce diabetic tendinopathy as no impairments in tendon gliding function or mechanical properties were observed in IRcKOS100a4 relative to WT. Collectively, these data define a murine model of diabetic tendinopathy, and demonstrate that tendon-specific, rather than systemic treatment approaches are needed.