# Coenzyme Q at the Hinge of Health and Metabolic Diseases
## 6 Supplementation with CoQ: Metabolic Recovery  
The efficacy of CoQ as supplement for the treatment of diseases associated with mitochondrial dysfunction is not completely clear. Many studies and clinical trials have been performed in order to find the positive effects of dietary supplementation with CoQ in different metabolic and age-related diseases [176]. However, the design of the trials and the presence of an important percentage of the population showing a low incorporation of dietary CoQ has not allowed us to obtain clear therapeutic procedures for this compound [177; 178]. The hydrophobicity of CoQ and its large molecular weight reduces the amount of nutritional CoQ that reaches blood plasma [179]. Fat-solubilized formulations are preferred to powder-based presentations as solubilization in the fat matrix permits superior bioavailability [178; 179]. Recently, it has been found that CoQ transport in intestinal epithelium requires Niemann-Pick Like 1 protein, a transporter involved in the intestinal absorption of fat-soluble components such as cholesterol [180]. This is an interesting aspect as people showing low fat absorption from their diet may suffer from an insufficient incorporation of dietary CoQ. In any case, supplementation with CoQ produces null or very low toxicity and no serious side effects in doses up to 1.2 to 3 g/day [181]. This aspect is important, especially in those patients suffering CoQ deficiency syndrome, which needs supplementation with high levels of this compound. CoQ supplementation has shown therapeutic benefits in aging-related disorders, principally in cardiovascular and metabolic diseases in the elderly [182; 183]. Studies on the effect of CoQ supplementation in human aging need to be performed rigorously, but studies in rat life-long supplementation have demonstrated the attenuation of an age-related decrease in total antioxidant activity, and also a reduction in DNA-damage in lymphocytes [184]. The supplementation of a Mediterranean diet with CoQ improves the metabolism of advanced glycation end products in the post-prandial period in elderly people [185], the lipid and glycemic profile in dyslipidemia individuals [186], and the glucose metabolism and oxidative damage markers in the plasma of patients with diabetic nephropathy [187]. In people suffering metabolic syndrome, CoQ supplementation may reduce serum triglyceride levels and improve lipid profiles [188]. Metabolic syndrome courses with a chronic inflammatory profile and CoQ supplementation has demonstrated the capacity to reduce this profile, possibly by improving mitochondrial activity in immune cells. In general, supplementation with CoQ can reduce the levels of plasmonic inflammatory cytokines [189], although the number of studies are limited, and in some cases, the results are conflicting [190; 191; 192]. The effect of supplementation with CoQ in a decrease in inflammation and lipid peroxidation in metabolic syndrome patients has also been associated with an improvement in liver function [193]. Mitochondrial dysfunction is associated with aging-dependent mylalgia, and supplementation with CoQ shows some therapeutic efficacy in reducing inflammation and restoring antioxidant and mitochondrial activities [194]. Interestingly, CoQ and carotene deficiencies, accompanied by metabolic disorders, are common in patients with oral cancer. This deficiency is associated with an increase in the risk of central obesity, hyperglyemia, and metabolic disease [195]. Interestingly, CoQ\({}_{10}\) appears as an efficient reducer of inflammation in people showing chronic inflammation processes, such as ulcerative colitis [196]. In fact, its use has been proposed in the modulation of autoimmune disorders accompanied by inflammatory processes [197], such as antiphospholipid syndrome [198].