**8. Glutathione and sleep**

Glutathione is a tripeptide (gamma-glutamylcysteinylglycine) that performs many vital functions in every cell of the body [57]. It is present in two forms in the body; in a "reduced (GSH)" or an "oxidized (GSSG)" form. The majority of glutathione in the body is present in its reduced form because this is the only way it can perform its critical role. Certain tissues are more susceptible to GSH depletion than others. The reduced form of glutathione is the most active form and is found in healthy cells. GSH plays an important role in the protection of cells against damage from free radicals and other electrophiles. Several steps in the metabolism of arachidonic acid may be normally regulated by GSH-enzymes [58]. It was an early observation that GSH may function as a chemical cofactor or coenzyme in the formation of some PGs, particularly PGEs [59]. Measuring glutathione levels in specific areas of the brain of sleepdeprived animals reveals that the thalamus and hypothalamus are particularly susceptible [60]. It is essential for detoxifying cells and this process is more active during sleep [61]. The

vulnerability of these tissues may contribute to some of the functional effects of sleep depri‐ vation. The relationship between Glutathione (GSH) and sleep has been shown that it defends the cells from destructive agents such as free radicals, chemical toxins, and heavy metals that constantly assault the cells and inhibit their optimum function, causing disease and acceler‐ ating the aging process. Studies have shown that sleep deprived animals have lower gluta‐ thione levels in certain parts of the brain. The two brain areas involved in sleep are the thalamus and hypothalamus. These areas are particularly vulnerable to glutathione depletion and can lead to sleeping problems [60]. It has been reported that GSH is the only antioxidant that does not become a free radical itself after donating a free electron [62]. Further research suggested that high blood GSH concentrations correlates with long lifespan both in animals and humans [63]. Mancuso et al [64] observed that GSH levels were lower in patients with OSAS than in controls and suggests that antioxidant defences are impaired in patients with Obstructive sleep apnea syndrome (OSAS). Recently, Ntalapascha et al (2012) reported that overnight changes (%) in plasma biomarkers were significantly different between OSAS and controls for GSH/ GSSG, controls had increased GSH levels overnight whereas OSAS did not.
