NAC Supplementation of Hyperglycemic Rats Prevents the Development of Insulin Resistance and Improves Antioxidant Status but Only Alleviates General and Salivary Gland Oxidative Stress

Abstract

Previous studies based on animal models demonstrated that N-acetylcysteine (NAC) prevents oxidative stress and improves salivary gland function when the NAC supplementation starts simultaneously with insulin resistance (IR) induction. This study is the first to evaluate the effect of a 4-week NAC supply on the antioxidant barrier and oxidative stress in Wistar rats after six weeks of high-fat diet (HFD) intake. Redox biomarkers were evaluated in the parotid (PG) and submandibular (SMG) salivary glands and stimulated whole saliva (SWS), as well as in the plasma and serum. We demonstrated that the activity of salivary peroxidase and superoxide dismutase and total antioxidant capacity were significantly higher in PG, SMG, and SWS of IR rats treated with NAC. It appears that in PG and SMG of rats fed an HFD, N-acetylcysteine supplementation abolishes oxidative modifications to proteins (evidenced by decreased content of advanced oxidation protein products (AOPP) and advanced glycation end products (AGE)). Simultaneously, it does not reverse oxidative modifications of lipids (as seen in increased concentration of 8-isoprostanes and 4-hydroxynonenal vs. the control), although it reduces the peroxidation of salivary lipids in relation to the group fed a high-fat diet alone. NAC administration increased protein levels in PG and SMG but did not affect saliva secretion, which was significantly lower compared to the controls. To sum up, the inclusion of NAC supplementation after six weeks of HFD feeding was effective in improving the general and salivary gland antioxidant status. Nevertheless, NAC did not eliminate salivary oxidative stress and only partially prevented salivary gland dysfunction.

N-acetylcysteine supplementation did not reverse mitochondrial oxidative stress, apoptosis, and inflammation in the salivary glands of hyperglycemic rats

“…Previous studies demonstrated that rats fed the high-fat diet for 6 weeks developed hyperglycemia [ 2 , 3 , 33 ]. The inclusion of a 4-week NAC supplementation at this stage, despite the continuation of the HFD, prevented the development of IR and strengthened the cytoplasmic antioxidant systems of salivary glands [ 33 ].…”

“…Previous studies demonstrated that rats fed the high-fat diet for 6 weeks developed hyperglycemia [ 2 , 3 , 33 ]. The inclusion of a 4-week NAC supplementation at this stage, despite the continuation of the HFD, prevented the development of IR and strengthened the cytoplasmic antioxidant systems of salivary glands [ 33 ]. Interestingly, NAC blocked oxidative modifications of proteins and carbohydrates and did not reduce lipid peroxidation in the cytoplasm of acinar cells of the submandibular glands of rats fed the HFD vs. the control rats.…”

“…Interestingly, NAC blocked oxidative modifications of proteins and carbohydrates and did not reduce lipid peroxidation in the cytoplasm of acinar cells of the submandibular glands of rats fed the HFD vs. the control rats. In the cytoplasm of acinar cells of the parotid glands, NAC supplementation reduced the intensity of lipid peroxidation compared to the HFD group, but these values were significantly higher than those observed in the control group [ 33 ]. NAC supplementation did not entail the reduction of carbohydrate and protein oxidation in the cytoplasm of acinar cells of the parotid glands.…”

“…NAC supplementation did not entail the reduction of carbohydrate and protein oxidation in the cytoplasm of acinar cells of the parotid glands. In conclusion, NAC-dependent reduction of cytoplasmic OS was only partial and dependent on the type of the salivary gland [ 33 ]. The persistence of OS despite NAC administration is probably a result of excessive ROS formation, but this hypothesis needs to be examined and explained.…”

Salivary Redox Biomarkers in Insulin Resistance: Preclinical Studies in an Animal Model

“…Next, whole blood was collected from the abdominal aorta into glass tubes (to obtain serum) and EDTA tubes (to obtain plasma) and centrifuged (3000 × g, 4°C, 10 min). To protect against sample oxidation and proteolysis, the antioxidant butylated hydroxytoluene (BHT, ten μ L of 0.5 M BHT in acetonitrile per 1 mL sample; Sigma-Aldrich, Steinheim, Germany) and a protease inhibitor (Complete Mini Roche, France) were added to the collected saliva and plasma samples [ 72 , 73 ]. All samples were stored at -80°C but for no longer than six months.…”