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Context: Lactate is the preferred energy substrate for developing testicular germ cells. Diabetes is associated with impaired testicular lactate transport/utilisation, and poor sexual behaviour., Objective: To examine the effects of metformin on parameters involved in testicular lactate production, transport/utilisation, and sexual behaviour in diabetic state., Methods: Male Sprague-Dawley rats were assigned into normal control (NC), diabetic control (DC), and metformin-treated diabetic group ( n  = 6/group). Metformin (300 mg/kg b.w./day) was administrated orally for 4 weeks., Results: Intra-testicular glucose and lactate levels, and lactate dehydrogenase (LDH) activity increased, while the mRNA transcript levels of genes responsible for testicular glucose and lactate transport/utilisation (glucose transporter 3, monocarboxylate transporter 4 (MCT4), MCT2, and LDH type C) decreased in DC group. Furthermore, penile nitric oxide increased, while cyclic guanosine monophosphate decreased, with impaired sexual behaviour in DC group. Treatment with metformin improved these parameters., Conclusions: Metformin increases testicular lactate transport/utilisation and improves sexual behaviour in diabetic state.

Introduction: GLUTs are specific membrane proteins that transport glucose down a concentration gradient. There have been few studies on their expression in the kidney. The aim of this study was to identify the expression of GLUTs 1, 3, and 4 in HGEC and their regulation under diabetic milieu., Material and Methods: An immortalized cell line of HGEC was used. Cells were cultured in medium containing 5 or 25 mM D-glucose. Western blotting and flow cytometry were used to examine the presence of GLUTs (1, 3, 4) and alterations in expression., Results: Western blotting analysis revealed that GLUT-1 levels were increased by 53% in HGEC cultured under experimental diabetes compared to cells grown in 5mM glucose. GLUT-3 levels were also increased by 15% under diabetic conditions. GLUT-4 levels were decreased by 20% in diabetes. Fluorescence Activated Cell Sorting (FACS) analysis demonstrated that cell surface expression of GLUT-1 was increased by 28% in cells grown in 25mM glucose. High glucose concentration did not affect cell surface expression of GLUT-3 and GLUT-4., Discussion: These findings suggest that depressed GLUT4 expression in glomerulus and overexpression of GLUT-1 and in a lesser extent of GLUT-3 may alter the glucose uptake in these cells. It has been suggested that the overexpression of GLUT-1 in glomerulus, being the major isoform, may lead to the initial pathologic hallmarks of diabetic nephropathy.