Therapeutic Potential of N-acetylcysteine and Glycine in Reducing Pulmonary Injury in Diabetic Rats

Diabetes mellitus is associated with systemic complications, including the development of pulmonary injury, characterized mainly by excessive accumulation of extracellular matrix components and inflammatory cell infiltration in lung tissue. This process is driven by oxidative stress and chronic inflammation, both caused and exacerbated by hyperglycemia. N-acetylcysteine (NAC) and glycine, known for their antioxidant and anti-inflammatory effects, offer potential therapeutic benefits in mitigating diabetes-induced lung injury.

The study aimed to investigate the effects of supplementation by either NAC or glycine or their combination on reducing lung injury in rats with type 1 diabetes Materials and methods: The study used 30 adult Wistar albino rats (10 weeks old, weighing between 180 g and 380 g). Six of them were used as controls, while 24 adult rats (10 weeks old, 180-380 g) with type 1 diabetes, induced through a single intraperitoneal injection of streptozotocin (STZ) at a dose of 55 mg/kg, were randomly assigned to four experimental groups: control (CTL), diabetic (Db), NAC treatment (diabetic+NAC), glycine treatment (diabetic+glycine), and combined NAC and glycine treatment (diabetic+NAC+glycine). NAC (100 mg/kg) and glycine (250 mg/kg) were administered orally for 12 weeks. At the end of the study, lung tissues were collected for histopathological examination. Qualitative, semi-quantitative, and stereological histological analysis was used to analyze structural changes in the lung tissue. Semi-quantitative scoring was carried out to evaluate the extent of inflammation, while stereological analysis was performed to determine the volume density of alveolar spaces and septal connective tissue. The semi-quantitative scoring included scores ranging from 0 (absent), 1 (minimal), 2 (mild), 3 (moderate), to 4 (severe).

Qualitative histological analysis revealed pronounced inflammation and fibrosis in the lungs of untreated diabetic rats, characterized by thickened alveolar septa and immune cell infiltration. Both treatments with NAC and glycine individually reduced inflammation and fibrosis compared to untreated diabetic rats. The greatest improvement was observed in the NAC+glycine group, where the alveolar structure appeared almost normal, with minimal inflammation. Semiquantitative analysis showed statistically significant differences in peribronchial and peribrochiolar infiltrates between the diabetic group (2.16±0.47) and the control group (0.33±0.21, p=0.026). The combination of NAC and glycine significantly reduced peribronchial and peribronchiolar infiltrates (0.33±0.33, p=0.026) compared to the diabetic group. Similarly, septal inflammatory infiltrates were significantly lower in the NAC+glycine group (1±0.36) compared to diabetic rats (3.33±0.33, p=0.004). Total airway inflammatory infiltration was also significantly reduced in the NAC+glycine group (1.33±0.33, p=0.002) compared to the diabetic group (5.5±0.5).

As the combination of NAC and glycine demonstrated protective effects against lung inflammation and fibrosis in diabetic rats, a synergistic effect of NAC and glycine in mitigating pulmonary complications associated with type 1 diabetes may be suggested. These findings warrant further exploration of the combination for managing diabetic lung disease and potentially other fibrotic conditions.