L-arginine administration exacerbates myocardial injury in diabetics via prooxidant and proinflammatory mechanisms along with myocardial structural disruption

Figure 1 Schematic diagram illustrating the major steps of the experiments in the study. HFD: High-fat diet; STZ: Streptozotocin.

Figure 2 Analysis of biochemical parameters in normal and treated rat groups, whereas animal weights, alanine aminotransferase, aspartate aminotransferase, serum creatine kinase, serum cardiac troponin I, lactate dehydrogenase. A: Animal weights; B: Alanine aminotransferase; C: Aspartate aminotransferase; D: Serum creatine kinase; E: Serum cardiac troponin I; F: Lactate dehydrogenase. G1 = Control group, G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg), G3 = Normal rats received 1 g/kg/day of L-Arg, G4 = Normal rats received 1.5 g/kg/day of L-Arg, G5 = Diabetic group, G6 = Diabetic rats received 0.5 g/kg/day of L-Arg, G7 = Diabetic rats received 1 g/kg/day of L-Arg, G8 = Diabetic rats received 1.5 g/kg/day of L-Arg. The data presented as means ± SE (n = 12). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group. AST: Aspartate aminotransferase; ALT: Alanine aminotransferase; LDH: Lactate dehydrogenase.

Figure 3 Effect of L-arginine on the activities of serum total antioxidant capacity, reduced glutathione, low density lipoprotein, very low density lipoprotein, triglyceride, and total cholesterol levels in the normal and treated rat groups. A: Total antioxidant capacity; B: Reduced glutathione; C: Low density lipoprotein; D: Very low density lipoprotein; E: Triglyceride; F: Total cholesterol levels. G1 = Control group, G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg), G3 = Normal rats received 1 g/kg/day of L-Arg, G4 = Normal rats received 1.5 g/kg/day of L-Arg, G5 = Diabetic group, G6 = Diabetic rats received 0.5 g/kg/day of L-Arg, G7 = Diabetic rats received 1 g/kg/day of L-Arg, G8 = Diabetic rats received 1.5 g/kg/day of L-Arg. The data presented as means ± SE (n = 12). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group. TAC: Total antioxidant capacity; GSH: Glutathione; LDL: Low density lipoprotein; VLDL: Very low density lipoprotein.

Figure 4 Effect of L-arginine on the activities of serum tumor necrosis factor-alpha, interleukin-1 beta, superoxide dismutase and glutathione peroxidase, malondialdehyde, nitric oxide, in the normal and treated rat groups. A: Tumor necrosis factor-alpha; B: Interleukin-1 beta; C: Superoxide dismutase; D: Glutathione peroxidase; E: Malondialdehyde; F: Nitric oxide. G1 = Control group, G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg), G3 = Normal rats received 1 g/kg/day of L-Arg, G4 = Normal rats received 1.5 g/kg/day of L-Arg, G5 = Diabetic group, G6 = Diabetic rats received 0.5 g/kg/day of L-Arg, G7 = Diabetic rats received 1 g/kg/day of L-Arg, G8 = Diabetic rats received 1.5 g/kg/day of L-Arg. The data presented as means ± SE (n = 12). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs to the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-arg 1 g/kg group. TNF-α: Tumor necrosis factor-alpha; IL-1β: interleukin-1 beta; SOD: superoxide dismutase; GSH-Px: Glutathione peroxidase; MDA: Malondialdehyde.

Figure 5 Histopathology of rats’ heart hematoxylin eosin. A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Cardiac injury score. Results are presented as mean ± SEM (n = 6). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the L-Arg diabetic + 0.5 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group.

Figure 6 Histopathology of rats’ heart (Masson trichrome stain). A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Cardiac fibrosis. Results are presented as mean ± SEM (n = 6). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group.

Figure 7 Immunohistochemistry results of desmin in cardiac tissues. A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Immunostaning area. ^aP < 0.05 vs the control group. Results are presented as mean ± SEM (n = 6). ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group). Results are presented as mean ± SEM (n = 6).

Figure 8 Immunohistochemistry results of alpha smooth muscle actin in cardiac tissues. A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Immunostaning area. Results are presented as mean ± SEM (n = 6). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group).

Figure 9 Immunohistochemistry results of nuclear factor erythroid 2 in cardiac tissues. A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Immunostaning area. Results are presented as mean ± SEM (n = 6). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg 05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group.

Figure 10  Immunohistochemistry results of Inducible nitric oxide synthase in cardiac tissues. A: G1 = Control group; B: G2 = Normal rats received 0.5 g/kg/day of L-arginine (L-Arg); C: G3 = Normal rats received 1 g/kg/day of L-Arg; D: G4 = Normal rats received 1.5 g/kg/day of L-Arg; E: G5 = Diabetic group; F: G6 = Diabetic rats received 0.5 g/kg/day of L-Arg; G: G7 = Diabetic rats received 1 g/kg/day of L-Arg; H: G8 = Diabetic rats received 1.5 g/kg/day of L-Arg; I: Immunostaning area. Results are presented as mean ± SEM (n = 6). ^aP < 0.05 vs the control group. ^bP < 0.05 vs the diabetic group. ^cP < 0.05 vs the diabetic + L-Arg05 g/kg group. ^dP < 0.05 vs the diabetic + L-Arg 1 g/kg group.