The effect of dietary supplementation of N-acetyl-L-cysteine on glutathione concentration and lipid peroxidation in cigarette smoke-exposed rats fed a low-protein diet

OBJECTIVE: The aim of the study is to investigate the modulatory effects of dietary supplementation of N-acetyl-L-cysteine (NAC) on glutathione (GSH) concentration in liver and lung, and lipid peroxidation in cigarette smoke-exposed rats fed a low-protein diet.

METHODS: Rats were divided randomly into 4 dietary groups; 8 per group. The control group (Group 1) was fed a normal-protein diet and received room air as a sham-smoke exposure. Group 2 was fed a normal-protein diet, Group 3 was fed with a low-protein diet and Group 4 was fed with a low-protein diet supplemented with NAC, and exposed to the smoke of 10 cigarettes/hour/day until the end of the experiment (4 weeks) period. Glutathione in liver and lung and serum albumin level were measured. Also, thiobarbituric acid reactive substances (TBARS) were measured, as an indication of oxidative stress. The study was conducted in the College of Applied Medical Sciences, King Saud University, Riyadh, Kingdom of Saudi Arabia, in the year 2003.

RESULTS: Smoke-exposed rats fed with the low-protein diet had significantly lower hepatic GSH concentration compared to other dietary groups. Moreover, NAC supplementation to the low-protein diet, in the smoke-exposed rats, significantly increased hepatic GSH concentration compared to the corresponding animals fed the same amount of protein, but without NAC supplementation. No reduction in lung GSH concentration occurred in cigarette-smoke rats fed a low-protein diet supplemented with NAC. Cigarette smoking significantly increased the level of TBARS in serum in all dietary groups compared to the control. However, the elevation in the TBARS level was higher in the low protein dietary group.

CONCLUSION: The results show no significant reduction in the lung and hepatic GSH concentration in cigarette smoke-exposed rats fed a normal-protein diet compared with the corresponding control rats fed a same level of protein. The study indicates the efficiency of NAC supplementation in scavenging free-radicals and enhancing GSH concentration in smoke-exposed rats fed a low-protein diet.