g(m3)-ganglioside and Diabetic-Nephropathies

Despite scientific advances, diabetic nephropathy remains both a therapeutical challenge, and one of the major diabetic complications. Chemical structure of gangliosides, the most complex of glycosphingolipids, is characterised by one or more sialic acids and carbohydrate groups linked to a ceramide structure. Their potential pathogenetic role in a number of disorders linked to diabetes mellitus has recently been conjectured, due to evidence of their negative modulation of the insulin-mediated signaling and general effects on key cell functions like proliferation, differentiation, apoptosis, cellular signaling and adhesion. Elevated levels of advanced glycation products (AGE) usually found in diabetic conditions seem to be responsible for increased concentration of a-series gangliosides in tissues, most notably GM3. GM3 was shown to compromise the renal pericyte and mesangial cell regeneration via the inactivation of VEGF receptor and the receptor-associated Akt signaling pathway. Likewise, the lipid raft theory opened a new research area for GM3 influence, since in the glycosynapse model glycosphingolipids have a key cell-to-cell communication unit with modulating capabilities on signaling receptors. The goal of this review is to provide insight into currently available theories on proposed mechanisms that mark the GM3 as a pathophysiological mediator in the development of diabetic nephropathy.

Topics: Animals; Diabetic Nephropathies; G(M3) Ganglioside; Humans; Kidney; Membrane Microdomains

Ganglioside GM3 is particularly abundant in the kidney tissue and is thought to play an important role in the maintenance of the charge-selective filtration barrier of glomeruli. Altered expression of ganglioside GM3 was pathologically related with glomerular hypertrophy occurring in diabetic human and rat kidneys. Considering the role of GM3 ganglioside in kidney function, the aim of this study was to determine the difference in expression of GM3 ganglioside in glomeruli and tubules using immunofluorescence microscopy both in rat models of types 1 and 2 diabetes mellitus. Diabetes was induced with streptozotocin (55 mg/kg for type 1 diabetes and 35 mg/kg for type 2 diabetes) injection to male Sprague-Dawley rats which were fed with normal pellet diet (type 1 diabetes) or high-fat diet (type 2 diabetes). Rats were sacrificed 2 weeks after diabetes induction, frozen renal sections were stained with primary antibody GM3(Neu5Ac) and visualized by secondary antibody coupled with Texas red. In addition, renal gangliosides GM3 were analyzed by high-performance thin-layer chromatography followed by GM3 immunostaining. Immunofluorescent microscopy detected 1.7-fold higher GM3 expression in tubules and 1.25-fold higher GM3 in glomeruli of type 1 diabetes mellitus compared with control group. Type 2 diabetes mellitus rats showed slight GM3 increase in whole kidney, unchanged GM3 in glomeruli, but significant higher GM3 expression in tubules, compared with control animals. Taking into consideration increased tubular GM3 content in both types of diabetes, we could hypothesize the role of GM3 in early pathogenesis of diabetic nephropathy.

Topics: Animals; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetic Nephropathies; Diet, High-Fat; G(M3) Ganglioside; Humans; Immunohistochemistry; Kidney Glomerulus; Kidney Tubules; Male; Rats; Rats, Sprague-Dawley; Streptozocin

Advanced glycation end products (AGEs) are involved in the development of microvascular complications, including alterations of retinal pericyte and renal mesangial cell growth occurring during diabetic retinopathy and diabetic nephropathy, respectively. Because gangliosides are implicated in the regulation of cell proliferation, we hypothesized that AGEs could exert cellular effects in part by modulating ganglioside levels. Results of the present study indicate that AGEs caused an inhibition of both bovine retinal pericyte (BRP) and rat renal mesangial cell (RMC) proliferation, associated with an increase of a-series gangliosides consecutive to GM3 synthase activity increase and GD3 synthase activity inhibition. Similar modifications were also found in the renal cortex of diabetic db/db mice compared with controls. Treatment of BRP and RMC with exogenous a-series gangliosides decreased proliferation and blockade of a-series gangliosides with specific antibodies partially protecting the two cell types from the AGE-induced proliferation decrease. Further, inhibition of GM3 synthase using specific SiRNA partially reversed the AGE effects on mesangial cell proliferation. These results suggest that a-series gangliosides are mediators of the adverse AGE effects on BRP and RMC proliferation. They also raise the hypothesis of common mechanisms involved in the development of diabetic retinopathy and diabetic nephropathy.

Topics: Animals; Cattle; Cell Division; Cells, Cultured; Diabetes Mellitus, Type 1; Diabetic Nephropathies; Diabetic Retinopathy; Disease Models, Animal; G(M1) Ganglioside; G(M3) Ganglioside; Gangliosides; Glomerular Mesangium; Glycation End Products, Advanced; Kidney Cortex; Mice; Microcirculation; Pericytes; Rats; Retinal Vessels; RNA, Small Interfering; Sialyltransferases

Ganglioside GM(3) (NeuAcalpha3Galbeta4Glcbeta1Cer) is known to regulate the proliferation of many cell types and to maintain the charge-selective filtration barrier of glomeruli. Based on these, this study examined whether altered expression of ganglioside GM(3) was pathologically related with glomerular hypertrophy and proteinuria occurring in diabetic human and rat kidneys. Diabetic rats were produced by intraperitoneal injection of streptozotocin (80 mg/kg, I.P.). At 15 days after the induction of diabetes, glomerular volume and fibrotic matrix were dramatically elevated, whereas glomerular sialic acid contents were significantly reduced compared with control. Based upon mobility on high-performance thin-layer chromatography (HPTLC) and reactivity to anti-GM(3) monoclonal antibody, normal glomeruli showed a complex ganglioside pattern that consisted of six different components of gangliosides, mainly GM(3), and diabetes caused a severe reduction of these gangliosides with apparent changes in the composition of major ganglioside GM(3). Semi-quantitative analysis by HPTLC showed that ganglioside GM(3) was reduced to 57% of control in diabetic glomeruli. A prominent immunofluorescence microscopy showed a dramatic disappearance of GM(3) expression in diabetic glomeruli. These results indicate that diabetic glomeruli can be characterized by decreases of glomerular sialic acid content and ganglioside GM(3) expression, which may cause loss of charge-selective filtration barrier in renal glomeruli. These changes may be account, at least in part, for the development of glomerular hypertrophy and proteinuria seen in the early stage of diabetic glomerulopathy.

Topics: Animals; Chromatography, Thin Layer; Diabetes Mellitus, Experimental; Diabetic Nephropathies; G(M3) Ganglioside; Hypertrophy; Kidney Glomerulus; Male; Microscopy, Fluorescence; Proteinuria; Rats; Rats, Sprague-Dawley; Sialic Acids