Recent data have indicated the emerging role of glomerular autophagy in diabetic kidney disease. We aimed to assess the effect of the SGLT2 inhibitor empagliflozin, the DPP4 inhibitor linagliptin, and their combination, on glomerular autophagy in a model of type 2 diabetes. Eight-week-old male db/db mice were randomly assigned to treatment with empagliflozin, linagliptin, empagliflozin-linagliptin or vehicle for 8 weeks. Age-matched non-diabetic db/+ mice acted as controls. To estimate glomerular autophagy, immunohistochemistry for beclin-1 and LAMP-1 was performed. Podocyte autophagy was assessed by counting the volume density (Vv) of autophagosomes, lysosomes and autolysosomes by transmission electron microscopy. LC3B and LAMP-1, autophagy markers, and caspase-3 and Bcl-2, apoptotic markers, were evaluated in renal cortex by western blot. Vehicle-treated db/db mice had weak glomerular staining for beclin-1 and LAMP-1 and reduced Vv of autophagosomes, autolysosomes and lysosomes in podocytes. Empagliflozin and linagliptin, both as monotherapy and in combination, enhanced the areas of glomerular staining for beclin-1 and LAMP-1 and increased Vv of autophagosomes and autolysosomes in podocytes. Renal LC3B and Bcl-2 were restored in actively treated animals. LAMP-1 expression was enhanced in the empagliflozin group; caspase-3 expression decreased in the empagliflozin-linagliptin group only. Mesangial expansion, podocyte foot process effacement and urinary albumin excretion were mitigated by both agents. The data provide further explanation for the mechanism of the renoprotective effect of SGLT2 inhibitors and DPP4 inhibitors in diabetes.Int. J. Mol. Sci. 2020, 21, 2987 2 of 22 dedifferentiation. In its turn, the loss or damage of podocytes causes dysfunction of the filtration barrier and increases albuminuria [2]. Some recent studies have indicated an emerging role of autophagy downregulation in diabetic podocytopathy [4][5][6]. Autophagy is a cellular recycling process involving self-degradation and reconstruction of damaged organelles and proteins [6]. The process is vital for highly differentiated post-mitotic cells, such as neurons and podocytes [7]. A growing body of evidence indicates a critical role of autophagy in maintaining podocyte integrity and renal function [6]. Mice with podocyte-specific deletion of autophagic regulators, such as class III PI3K vacuolar protein sorting 34 (Vps34) and the Atg5 gene, develop early proteinuria, progressive glomerulosclerosis, and renal failure [6]. Accordingly, autophagy is considered a potential therapeutic target for renal protection [8,9].Sodium-glucose cotransporter-2 (SGLT2) inhibitors and dipeptidylpeptidase-4 (DPP4) inhibitors are promising antidiabetic agents introduced into clinical practice in the last decade. The antihyperglycemic effect of SGLT2 inhibitors is mediated by increment of glucosuria, while DPP4 inhibitors realize their activity through an increase in the half-life of incretin hormones. Both SGLT2 and DPP4 inhibitors demonstrated renal protective...

Background Wnt1-inducible signaling pathway protein 1, or cellular communication network factor 4 (CCN4), a member of CCN family of secreted, extracellular matrix associated signaling proteins, recently was validated as a novel adipose tissue derived cytokine. Objective To assess the relationships between circulating CCN4, adipose tissue distribution and function, and chronic low-grade inflammation in subjects with type 2 diabetes. Methods We observed 156 patients with type 2 diabetes and 24 healthy controls. Serum levels of CCN4, hsCRP and alpha1-acid glycoprotein (alpha1-AGP) were measured by ELISA. Serum concentrations of leptin, resistin, visfatin, adipsin, adiponectin, IL-6, IL-8, IL-18 and TNF-alpha were determined by multiplex analysis. Fat mass and distribution was assessed by DEXA. Mean diameter of adipocytes was estimated in samples of subcutaneous adipose tissue. Results Patients with diabetes had higher levels of circulating CCN4, leptin, resistin, adipsin, visfatin, hsCRP, alpha1-AGP, and IL-6 (all p < 0.02). The CCN4 concentration correlated positively with percentage of fat mass in central abdominal area, as well as with leptin, resistin and visfatin levels; negative correlation was found between CCN4 and mean adipocyte diameter. In multiple regression analysis fat mass in central abdominal area was independent predictor for CCN4 concentration. Conclusion In subjects with type 2 diabetes serum levels of CCN4 are associated with central abdominal fat mass and adipose tissue dysfunction. Keywords WISP-1/CCN4. Type 2 diabetes. Cytokines. Obesity. Adipose tissue Olga Pivovarova-Ramich and Natalia Rudovich contributed equally to this work.