Diabetes Mellitus, Experimental/complications; Diabetes Mellitus, Experimental/drug therapy; Diabetic Nephropathies/drug therapy; Dipeptidyl-Peptidase IV Inhibitors/therapeutic use; 8-Hydroxy-2'-Deoxyguanosine; Adamantane/administration & dosage; Adamantane/analogs & derivatives; Adamantane/pharmacology; Adamantane/therapeutic use; Animals; Blood Glucose/drug effects; Blood Glucose/metabolism; Body Weight/drug effects; Caspase 3/metabolism; Cyclic AMP/urine; Deoxyguanosine/analogs & derivatives; Deoxyguanosine/urine; Diabetes Mellitus, Experimental/pathology; Diabetes Mellitus, Experimental/physiopathology; Diabetic Nephropathies/metabolism; Diabetic Nephropathies/pathology; Diabetic Nephropathies/physiopathology; Dipeptidyl Peptidase 4/metabolism; Dipeptidyl-Peptidase IV Inhibitors/administration & dosage; Dipeptidyl-Peptidase IV Inhibitors/pharmacology; Eating/drug effects; Gene Expression/drug effects; Gene Expression/genetics; Glomerular Basement Membrane/drug effects; Glomerular Basement Membrane/pathology; Glucagon-Like Peptide 1/blood; Glucagon-Like Peptide-1 Receptor; Glycated Hemoglobin/metabolism; Insulin/blood; Kidney/drug effects; Kidney/metabolism; Kidney/pathology; Kidney/physiopathology; Male; Pyrrolidines/administration & dosage; Pyrrolidines/pharmacology; Pyrrolidines/therapeutic use; Rats; Rats, Sprague-Dawley; Receptors, Glucagon/genetics; Receptors, Glucagon/metabolism; Transforming Growth Factor beta1/metabolism