Adiponectin reduces glomerular endothelial glycocalyx disruption and restores glomerular barrier function in a mouse model of type 2 diabetes

Adiponectin has vascular anti-inflammatory and protective effects. Whilst adiponectin is known to protect against the development of albuminuria, historically the focus has been on podocyte protection within the glomerular filtration barrier (GFB). The first barrier to albumin in the GFB is the endothelial glycocalyx (eGlx), a surface gel-like barrier covering glomerular endothelial cells (GEnC). In diabetes, eGlx dysfunction occurs before podocyte damage, hence we hypothesized that adiponectin could protect from eGlx damage to prevent early vascular damage in diabetic kidney disease (DKD). Globular adiponectin (gAd) activated AMPK signalling in human GEnC through AdipoR1. It significantly reduced eGlx shedding and the TNFα-mediated increase in syndecan-4 (SDC4) and MMP2 mRNA expression in GEnC in vitro. It protected against increased TNFα mRNA expression in glomeruli isolated from db/db mice, and genes associated with glycocalyx shedding (SDC4, MMP2 and MMP9). In addition, gAd protected against increased glomerular albumin permeability (Ps’alb) in glomeruli isolated from db/db mice, when administered to mice (i.p) and when applied directly to glomeruli (ex vivo). Ps’alb was inversely correlated with eGlx depth in vivo. In summary, adiponectin restored eGlx depth, which was correlated with improved glomerular barrier function, in diabetes.