To evaluate the roles of hyperglycemia and increased plasma FFA level in the development of insulin resistance, we examined the effects of phlorizin and acipimox treatments on tissue sensitivity to insulin in streptozotocin(STZ)-diabetic rats. Insulin sensitivity was assessed with the glucose-insulin clamp technique. Blood glucose concentration was clamped at basal levels of control and diabetic states, and plasma insulin concentrations were clamped at the levels of basal, approximately 60 and approximately 1500 microU/ml. In diabetic rats, the basal blood glucose and plasma FFA levels in the fasting state were elevated, while the plasma insulin concentration was lower than in normal controls. Moreover, diabetic rats became glucose intolerant after intravenous injection of glucose. The metabolic clearance rate(MCR) of glucose showed a decrease of basal and insulin stimulated response in diabetic rats. As results of the glucose-insulin clamp study and intravenous glucose tolerance test, insulin resistance was developed in STZ-diabetic rats. Phlorizin treatment of diabetic rats recovered insulin sensitivity to nearly normal levels and improved glucose tolerance, but had no effect on insulin action in controls. Insulin sensitivity was also improved by acipimox treatment in diabetic rats, but did not reach normal levels. These results show that hyperglycemia is an obvious causative factor of insulin resistance, and increased FFA level may also act on the development of insulin resistance in STZ-diabetic rats.
Animal ; Antilipemic Agents/*pharmacology ; Blood Glucose/analysis ; Diabetes Mellitus, Experimental/*metabolism ; Fatty Acids, Nonesterified/blood ; Female ; *Insulin Resistance ; Phlorhizin/*pharmacology ; Pyrazines/*pharmacology ; Rats ; Rats, Sprague-Dawley ; Streptozocin

To investigate the role of glucose transporter 1 (GLUT1) and sodium-glucose cotransporter 1 (SGLT1) in high glucose dialysate-induced peritoneal fibrosis.Thirty six male SD rats were randomly divided into 6 groups (6 in each):normal control group, sham operation group, peritoneal dialysis group (PD group), PD+phloretin group (PD+T group), PD+phlorizin group (PD+Z group), PD+phloretin+phlorizin group (PD+T+Z group). Rat model of uraemia was established using 5/6 nephrotomy, and 2.5% dextrose peritoneal dialysis solution was used in peritoneal dialysis. Peritoneal equilibration test was performed 24 h after dialysis to evaluate transport function of peritoneum in rats; HE staining was used to observe the morphology of peritoneal tissue; and immunohistochemistry was used to detect the expression of GLUT1, SGLT1, TGF-β1 and connective tissue growth factor (CTGF) in peritoneum. Human peritoneal microvascular endothelial cells (HPECs) were divided into 5 groups:normal control group, peritoneal dialysis group (PD group), PD+phloretin group (PD+T group), PD+phlorezin group (PD+Z group), and PD+phloretin+phlorezin group (PD+T+Z group). Real time PCR and Western blotting were used to detect mRNA and protein expressions of GLUT1, SGLT1, TGF-β1, CTGF in peritoneal membrane and HPECs., compared with sham operation group, rats in PD group had thickened peritoneum, higher ultrafiltration volume, and the mRNA and protein expressions of GLUT1, SGLT1, CTGF, TGF-β1 were significantly increased (all<0.05); compared with PD group, thickened peritoneum was attenuated, and the mRNA and protein expressions of GLUT1, SGLT1, CTGF, TGF-β1 were significantly decreased in PD+T, PD+Z and PD+T+Z groups (all<0.05). Pearson's correlation analysis showed that the expressions of GLUT1, SGLT1 in peritoneum were positively correlated with the expressions of TGF-β1 and CTGF (all<0.05)., the mRNA and protein expressions of GLUT1, SGLT1, TGF-β1, CTGF were significantly increased in HPECs of peritoneal dialysis group (all<0.05), and those in PD+T, PD+Z, and PD+T+Z groups were decreased (all<0.05). Pearson's correlation analysis showed that the expressions of GLUT1, SGLT1 in HPECs were positively correlated with the expressions of TGF-β1 and CTGF (all<0.05).High glucose peritoneal dialysis fluid may promote peritoneal fibrosis by upregulating the expressions of GLUT1 and SGLT1.
Animals ; Cells, Cultured ; Connective Tissue Growth Factor ; analysis ; drug effects ; Dialysis Solutions ; adverse effects ; chemistry ; pharmacology ; Gene Expression Regulation ; drug effects ; Glucose ; adverse effects ; pharmacology ; Glucose Transporter Type 1 ; analysis ; drug effects ; physiology ; Hemodiafiltration ; adverse effects ; methods ; Humans ; Male ; Peritoneal Dialysis ; adverse effects ; methods ; Peritoneal Fibrosis ; chemically induced ; genetics ; physiopathology ; Peritoneum ; chemistry ; drug effects ; pathology ; Phloretin ; Phlorhizin ; RNA, Messenger ; Rats ; Rats, Sprague-Dawley ; Sodium-Glucose Transporter 1 ; analysis ; drug effects ; physiology ; Transforming Growth Factor beta1 ; analysis ; drug effects ; Uremia ; chemically induced