The Effect of N-Acetylcysteine on Respiratory Enzymes, ADP/ATP Ratio, Glutathione Metabolism, and Nitrosative Stress in the Salivary Gland Mitochondria of Insulin Resistant Rats.

Anna Zalewska,Mateusz Maciejczyk,Izabela Szarmach,Małgorzata Żendzian-Piotrowska

doi:10.3390/nu12020458

Abstract

This is the first study to assess the effect of N-acetylcysteine (NAC) on the mitochondrial respiratory system, as well as free radical production, glutathione metabolism, nitrosative stress, and apoptosis in the salivary gland mitochondria of rats with high-fat diet (HFD)-induced insulin resistance (IR). The study was conducted on male Wistar rats divided into four groups of 10 animals each: C (control, rats fed a standard diet containing 10.3% fat), C + NAC (rats fed a standard diet, receiving NAC intragastrically), HFD (rats fed a high-fat diet containing 59.8% fat), and HFD + NAC (rats fed HFD diet, receiving NAC intragastrically). We confirmed that 8 weeks of HFD induces systemic IR as well as disturbances in mitochondrial complexes of the parotid and submandibular glands of rats. NAC supplementation leads to a significant increase in the activity of complex I, II + III and cytochrome c oxidase (COX), and also reduces the ADP/ATP ratio compared to HFD rats. Furthermore, NAC reduces the hydrogen peroxide production/activity of pro-oxidant enzymes, increases the pool of mitochondrial glutathione, and prevents cytokine formation, apoptosis, and nitrosative damage to the mitochondria in both aforementioned salivary glands of HFD rats. To sum up, NAC supplementation enhances energy metabolism in the salivary glands of IR rats, and prevents inflammation, apoptosis, and nitrosative stress.

Highlights

N-acetyl-cysteine (NAC) is a derivative of a thiol-containing amino acid, which—directly or indirectly, by increasing the concentration of glutathione—demonstrates antioxidant properties
We proved that NAC supplementation strengthens both enzymatic and non-enzymatic antioxidant mechanisms of parotid as well as submandibular glands, and prevents oxidative damage to and dysfunction of the parotid gland of rats with insulin resistance (IR) induced by high-fat diet [15]
An eight-week high-fat diet resulted in a considerable increase in the level of glucose (p < 0.0001 and p < 0.0001, respectively), insulin (p < 0.0001 and p < 0.0001, respectively) and fatty acids (p < 0.0001 and p < 0.0001, respectively) compared to both the group fed standard diet and rats fed HFD + NAC

Summary

Introduction

N-acetyl-cysteine (NAC) is a derivative of a thiol-containing amino acid, which—directly or indirectly, by increasing the concentration of glutathione—demonstrates antioxidant properties. NAC is a cysteine donor for the synthesis of reduced glutathione (GSH). GSH is the most important intracellular antioxidant maintaining a reduced state of protein thiol groups, which is a prerequisite for sustaining the activity of these proteins. GSH can directly deactivate oxygen free radicals (ROS) or be used by glutathione peroxidase as a cofactor in the detoxification of hydrogen peroxide and peroxynitrite. NAC stimulates the activity of glutathione reductase (GR), an enzyme that restores the reduced form of glutathione, using NADPH [1]. It has been evidenced that NAC reacts rapidly with highly reactive oxygen and nitrogen radicals

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