Diabetes
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Hyaluronic acid (HA) is a major component of the glycocalyx involved in the vascular wall and endothelial glomerular permeability barrier. Endocytosed hyaluronidase HYAL1 is known to degrade HA into small fragments in different cell types, including endothelial cells. In diabetes, the size and permeability of the glycocalyx are altered. ⋯ We observed that 4 weeks after STZ injections, the lack of HYAL1 1) prevents diabetes-induced increases in soluble P-selectin concentrations and limits the impact of the disease on endothelium-dependent hyperpolarization (EDH)-mediated vasorelaxation; 2) increases glycocalyx thickness and maintains glycocalyx structure and HA content during diabetes; and 3) prevents diabetes-induced glomerular barrier dysfunction assessed using the urinary albumin-to-creatinine ratio and urinary ratio of 70- to 40-kDa dextran. Our findings suggest that HYAL1 contributes to endothelial and glycocalyx dysfunction induced by diabetes. HYAL1 inhibitors could be explored as a new therapeutic approach to prevent vascular complications in diabetes.
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Emerging insulin resistance is normally compensated by increased insulin production of pancreatic β-cells, thereby maintaining normoglycemia. However, it is unclear whether this is achieved by adaptation of β-cell function, mass, or both. Most importantly, it is still unknown which of these adaptive mechanisms fail when type 2 diabetes develops. ⋯ Prior to prediabetes, β-cell function displays decreased stimulated calcium dynamics, whereas islet mass continues to increase through prediabetes onset. Thus, our data reveal a predominant role of islet function with distinct contributions of triggering and amplifying pathway in the in vivo processes preceding diabetes onset. These findings support protection and recovery of β-cell function as primary goals for prevention and treatment of diabetes and provide insight into potential therapeutic targets.