Characterization of skeletal muscle pericytes in health, insulin resistance and type 2 diabetes
Authors: Attrill Emily , Mayne Sophie , Perera Sathya , Ross Renee , Richards Stephen , Sutherland Brad , Premilovac Dino 
Published: May 2023

The skeletal muscle microvasculature is a key regulator of peripheral resistance and plays a major role in determining muscle function. In insulin resistance and type 2 diabetes (T2D), blood flow is disrupted contributing to metabolic dysfunction. Pericytes are contractile cells known to regulate capillary diameter and microvascular blood flow in several organs, however little is known about their role in skeletal muscle. In this study, we developed a novel mouse model of T2D to characterize pericytes in healthy, insulin resistant and T2D skeletal muscle.Male Tg(Cspg4-DsRed.T1)1Akik/J mice were allocated to control diet (CD; 6% fat wt/wt, n=5) or high fat diet (HFD; 23% fat wt/wt, n=17) for 17wks to model insulin resistance. To model T2D, we infused streptozotocin (STZ) across 14 days using osmotic mini-pumps to generate moderate (MOD, 200mg/kgSTZ, n=5) and severe (SEV, 250-300mg/kgSTZ, n=7) hyperglycaemia. In week 17, mice underwent a 2hr glucose tolerance test (GTT; 2.0g/kg IP glucose) after which mice were euthanized and cardiac perfused with 4% paraformaldehyde. The gastrocnemius and soleus were excised, processed for staining, and imaged. HFD mice were obese (CD 33.0±3.5, HFD 38.7±4.1g, p=0.011) and had elevated fasting glucose regardless of STZ dose (CD 9.6±0.9, HFD 14.7±5.1mmol/L, p=0.036). HFD mice had elevated plasma insulin (CD 166±18, HFD 242±109pmol/L, p=0.003) which was reduced to CD levels with STZ (MOD 99±44, SEV 126±46pmol/L, p<0.001 vs HFD). HFD and STZ induced a stepwise increase in blood glucose at the end of the 2hr GTT (CD 11.0±0.9, HFD 15.9±3.4, MOD 23.5±3.7, SEV 31.2±2.6mmol/L, p<0.001 for group effect). Although HFD did not change capillary density in the gastrocnemius (CD 1311±190, HFD 1263±200cap/mm2, p=0.641), capillary density was reduced in MOD (1158±315cap/mm2, p=0.007 vs HFD) and increased in SEV (1553±174cap/mm2, p=0.035 vs HFD). There was no change in pericyte density in the gastrocnemius (CD 61±21 vs HFD 63±22 vs MOD 64±15 vs SEV 81±27cells/mm2, p=0.484 for group effect). Similarly, pericyte density in the soleus was unchanged between CD (175±43 cells/mm2), HFD (147±18 cells/mm2) and MOD (118±25 cells/mm2). In contrast, SEV had a ~40% increase in pericyte density compared to all other groups (SEV 242±36cells/mm2, p<0.05). Perhaps most importantly, we observed distinct changes in pericyte morphology in both muscles in the HFD, MOD and SEV mice compared with CD mice. These changes include swelling and fragmentation of pericyte cytoplasmic processes that normally cover 95% of skeletal muscle capillaries.In summary, changes in pericyte density and morphology occur in insulin resistance and T2D. Given microvascular dysfunction is a hallmark of insulin resistance and T2D, this work suggests pericyte damage may contribute to blood flow dysregulation and the progression of disease. Further work is needed to understand the functional consequences of pericyte changes to skeletal muscle health in insulin resistance and T2D. This work has been supported by the Tasmanian School of Medicine and the University of Tasmania. This is the full abstract presented at the American Physiology Summit 2023 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.