NUTRITION – SANTE
Coenzyme Q10: multiple benefits in one ingredient
1 Gian Paolo LITTARRU Abstract: Coenzyme Q is a lipid molecule widely diffused in nature; in humans and Peter LAMBRECHTS2 other mammals it is present as coenzyme Q10. (CoQ10). The first recognized role of CoQ was in mitochondrial bioenergetics, where it plays a central role in the production 1 Department of Biochemistry, Biology & 10 of ATP. It is also present in other subcellular organelles, both in its oxidized and in its Genetics, Polytechnic University of the reduced state (ubiquinol-10). The reduced form of CoQ10 is endowed with powerful Marche, 60131 Ancona, Italy, phone antioxidant activity: it acts as a chain-breaking antioxidant and is also capable of
Key words: Coenzyme Q10, bioenergetics, antioxidation, skin metabolism, fermenta- tion, nutritional claims
Coenzyme Q (CoQ) also known as food supplement is natural CoQ10, New progress has been made in eluci- ubiquinone, is a lipid molecule widely extracted from some microorganisms dating CoQ10 in metabolism and nutri- distributed in nature. In mitochondria, which synthesize CoQ10, identical to the tion. This short chapter is mainly focused like in other cellular compartments, it one which is found in humans and other on recent findings which will hopefully is present both in its oxidised state mammals. This issue will be commented contribute to better understand the (ubiquinone) and in its reduced one later on in the text. relationship between basic biochemical (ubiquinol). The first homolog to be mechanisms and certain physiological discovered about 50 years ago, in beef For a certain number of years CoQ was and clinical effects. mitochondria, was coenzyme Q10 (Crane known for its key role in mitochondrial et al., 1957). In fact, CoQ is made of bioenergetics; later studies demon- benzoquinone moiety and an isoprenoid strated its presence in other subcellular CoQ10 and mitochondrial side chain the length of which is 10 units fractions and in plasma, and extensively bioenergetics both in man and many mammals; there- investigated its antioxidant role. The fore we talk about CoQ10 and reduced rationale supporting the use of CoQ10 The essential role of CoQ10 in bioen- CoQ10 (ubiquinol-10). Other living organ- as a food supplement is mainly based on ergetics was postulated since the years isms possess different species of CoQ, for these two functions. More recent data of its discovery. In fact several years instance Saccharomyces cerevisiae produ- reveal that CoQ10 affects the expression later, the studies of Nobel Prize winner ces CoQ6, other microorganisms CoQ7, of genes involved in human cell signalling, Peter Mitchell highlighted the central and many mammals CoQ9.Eachorgan- metabolism and transport (Groneberg role of this quinone in the chemo- ism possesses a dominant homolog of et al., 2005) and some of the effects of osmotic production of ATP. Therefore 10.1684/ocl.2011.0374 doi: CoQ, and minor amounts of other exogenously administered CoQ10 may be CoQ10 is a key component of the homologs. Most of CoQ10 available as a due to this property. mitochondrial machinery, the main
To cite this article: Littarru GP, Lambrechts P. Coenzyme Q10: multiple benefits in one ingredient. OCL 2011 ; 18(2) : 76-82. doi : 10.1684/ ocl.2011.0374
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Article disponible sur le site http://www.ocl-journal.org ou http://dx.doi.org/10.1051/ocl.2011.0374 energy plant of our cells. At this level it A minor part is however introduced widely used anticholesterolemic drugs, operates as a redox couple (ubiquinone/ through the diet; moreover a series of also inhibit CoQ10 biosynthesis and this ubiquinol), responsible for proton and dietary components is essential for the could have important practical implica- electron transport. If mitochondria are proper functioning of CoQ10 biosyn- tions. devoid of CoQ10 they cannot produce thesis (figure 2). Coenzyme Q10 concentration greatly ATP; in some conditions we can have The synthesis of the quinone moiety of varies in different tissues, probably partial CoQ10 deficiencies. CoQ10 starts from phenylalanine or related to different metabolic demands Even though the concentration of CoQ10 from tyrosine and the isoprenoid side (figure 3). in mitochondria is rather high compared chain derives from mevalonate. A series Tissue concentrations of CoQ10 also to the corresponding concentration of of vitamin cofactors is needed for this vary with age: for different organs an other mitochondrial components, it is biosynthesis. According to Karl Folkers increase of CoQ10 has been found in the not saturating. This practically means that the dominant source of CoQ10 in man initial decades with a subsequent at the actual concentrations of CoQ10 in is biosynthesis. This complex, 17 step decrease (figure 4). these membranes the velocity of the process, requiring at least seven vitamins respiratory complexes is not the maximal (vitamin B2 – riboflavin, vitamin B3 – one. In fact, small variations in the niacinamide, vitamin B6, folic acid, CoQ as an antioxidant concentration of CoQ10 in these mem- vitamin B12, vitamin C, and pantothenic branes leads to remarkable changes in acid) and several trace elements, is, by its In its reduced form (ubiquinol) coen- the respiratory rates of these cells. This nature, highly vulnerable. Karl Folkers zyme Q acts as a phenolic antioxidant, can explain why, even though a small argues that suboptimal nutrient intake in undergoing hydrogen abstraction by part of the exogenously administered man is highly possible and that there free radicals, therefore it acts like a chain breaking antioxidant. This evidence has CoQ10 is uptaken by our cells, the effect is subsequent secondary impairment in been produced by numerous experi- is not negligible (figure 1). CoQ10 biosynthesis. It was highlighted that in a vitamin B6 deficiency plasma mental models, both in vivo and in vitro, using artificial membranes, isolated sub- CoQ10 levels are also low and they incre- Ubiquinone biosynthesis: ase upon improvement of the vitamin B6 cellular organelles, cultured cells, iso- biochemical and clinical deficiency status (Willis et al., 1999). In lated perfused organs and clinical implications eukaryotes the isoprenoid side chain of models (Dallner and Stocker, 2005). coenzyme Q is synthesized through the Ubiquinol may act by slowing down the Strictly speaking CoQ10 is not a vitamin, mevalonate pathway, which also leads to chain propagation reaction, with a as mammals and lower animals are the synthesis of cholesterol. As we will mechanism that is common to the co- capable of synthesizing this molecule. comment below statins, the potent and called ‘‘chain breaking antioxidants’’. Reduced Coenzyme Q is also able to regenerate a-tocopherol, the active form of Vitamin E: in this sense CoQ10 and vitamin E are considered as a lipophilic antioxidant duo of primary importance. In order to act as an antioxidant CoQ Vmax must be in the reduced state; several enzymes exert this function of CoQ reductases. There are some conditions where the reducing capacity of the cell might be impaired: in these conditions Exogenous supplementation supplementing CoQ10 already in the reduced state (QH2, ubiquinol-10) might be particularly relevant. Physiological levels Antioxidant function of
CoQ10deficit CoQ10 in plasma lipoproteins It is currently believed that high levels of LDL, as well as smoking and hyper- tension, are primary risk factors, among [Coenzyme Q10] Km those contributing to cardiovascular disease. Biochemical mechanisms responsible for the atherogenicity of LDL have been extensively addressed, Figure 1. The physiological range of CoQ10 in the mitochondrial respiratory chain is close to the Km, the concentration supporting 50% of the maximum velocity (Source: Estornell E, et al. FEBS and experimental evidence bas been Lett 1992; 311 : 107-9). produced indicating that oxidatively
OCL VOL. 18 N8 2 MARS-AVRIL 2011 77 penetrate the endothelial cell lining and reach the subendothelial space, where Coenzyme Q10 contents in foodstuffs they undergo oxidative attack. Oxida- 8 tively modified LDL are capable of Average daily intake through diet = 3 to 5 mg (Weber 1997a) triggering further events, including pla- 7 telet activation, and exert a chemotactic attraction on circulating monocytes, 6 which migrate to the subendothelial space, where they become macro- 5 phages. These cells have only low levels 4 of the classical LDL receptor, nonetheless they are able to take up more rapidly mg/100gr 3 oxidatively modified LDL, and this uptake involves a different receptor, 2 called the ‘‘scavenger receptor’’. As dis- cussed above, oxidatively modified LDL 1 are easily recognized by the scavenger receptors. These events lead to an accu- 0 mulation of lipids, mainly cholesterol and Sardine Pork Beef Olive oil Poultry Broccoli ButterSunflower Cheese cholesterol esters, in the macrophages, oil which will become lipid-laden foam cells. Foam cells may be considered the essence of the atheromatous lesions. Figure 2. Coenzyme Q10 content of different foods (Source: Kamei et al. The Distribution and Content of Ubiquinone in Foods. Internat J Vit Nutr Res 1986; 56: 57-63). LDL are endowed with a number of lipid soluble antioxidants capable of prevent- ing or minimizing lipid peroxidation. Plasma levels of CoQ10 have been extensive investigated (Tomasetti et al., modified LDL become atherogenic. It a consequence of these changes LDL are 1999). Most plasma CoQ is trans- was found that endothelial cells are no longer ‘‘recognized’’ by the normal 10 ported by LDL where, together with involved in the oxidative attack against receptors, and are taken up more readily vitamin E, it exerts its antioxidant pro- LDL. Oxidative attack on LDL deeply by the scavenger receptors of macro- tection. Ubiquinol-10 is the most reactive affects the apoprotein moiety as well. As phages. LDL leave the blood stream, antioxidant in LDL, and although it is present at lower concentrations com- pared to vitamin E, it is able to regenerate a-tocopherol from the tocopheril radical, Connentration of Coenzyme Q10 making the vitamin E-ubiquinol duo the most important antioxidant system in Heart LDL. CoQ10 enriched LDL, isolated from Kidney plasma of healthy volunteers orally treated with CoQ for a few days, were Liver 10 less susceptible to peroxidizability in Q10 Muscle vitro, compared to the same LDL in basal Brain conditions (Mohr et al., 1992). Pancreas Blood CoQ10 is mainly transported by LDL, Lung although it is also present in the other Thyroid gland classes of lipoproteins and in blood cells. Its Testicle concentration is usually reported in micro- Intestine grams/litre of plasma or micromoles/litre. But it is worthwhile to normalize these Skin(epithelial) valuesaccordingtothebloodLDLcontent Skin(dermal) or at least to plasma cholesterol levels. The Blood plasma CoQ10/total cholesterol level could have a 0 20 40 60 80 100 120 predictive value in cardiovascular disease Connentration (µg/g tissue) (Molyneux et al., 2008). Besides decreas- ing LDL peroxidizability, CoQ10 could have a direct antiatherosclerotic effect, in fact animal studies have shown that Figure 3. Concentration of coenzymeQ10 in different human tissues (Source: Okamoto T, et al. Internat J Vit Nutr Res 59; 288-92; Aberg et al. Archives of Biochemistry and CoQ10 administration attenuates aortic Biophysics and Biophysics 1992; 295: 230-4; Shindo Y, et al. J Invets Dermatol 1994; atherosclerotic lesions (Witting et al. 102 : 122-4. 2000 ; Singh et al. 2000).
78 OCL VOL. 18 N8 2 MARS-AVRIL 2011 is a double blind study where a group of kendo athletes showed lower levels of CK, myoglobin and lipid peroxides 100% compared to the corresponding values 100% 95,3% in the placebo group (Kon et al., 2008). Liver 83,0% In a study where CoQ10 had been taken in combination with vitamin C and E, administration of this antioxidant cocktail 72,6% Lungs further increased the eNOS and uncou- 68,2% pling protein 3 (UCP3) mRNA content 65,3% Kidneys after exercise (Hellsten et al., 2007). For the first time a study examined the 51,7% acute effects of CoQ and placebo on Heart 10 42,9% autonomic nervous activity and energy metabolism at rest and during exercise 20 years 40 years 80 years (Zheng and Moritani, 2008). Fat oxida- tion significantly increased during exer- ciseintheCoQ10group;resultssuggested that CoQ10 increases autonomic nervous activity during low intensity exercise. Figure 4. The concentration of coenzyme Q10 in the body decreases year by year, indicating that it has a close relationship with aging (Kalen A, et al. Lipids1989; 24: 579). In a double blind pilot study patients with post-polio syndrome were treated with 200 mg of CoQ10/day. Muscle strength, CoQ10: analytical aspects (and other CoQs) in vegetable oils and muscle endurance and quality of life generally in fatty samples, due to inter- increased statistically significantly in all CoQ10 is commonly assayed in plasma, ferences mainly with triacylglycerides. A 14 patients but there was no significant both in basal conditions and after oral clean, efficient separation and quantifi- difference between the CoQ10 and pla- supplementation. Basal CoQ10 levels cation procedure was recently proposed cebo groups (Kough et al., 2008). might reflect CoQ10 deficiency and, as and applied to the determination of pointed out above, they might have a CoQ9 and CoQ10 contents in different predictive value in cardiac failure. Post vegetable oil samples (Rodriguez-Acuna Effects on skin supplementation levels of CoQ10 are et al.,2008). metabolism also important, since a clinical response is much more common if some thresh- The bioenergetic and antioxidant prop- old values are reached. Several studies Physiological effects: erties of CoQ10 have also been studied at have highlighted that a plasma level of CoQ and physical skin level. The first report was by 10 Hoppe et al. (1999). This paper demon- at least 2.5 mg/mL should be reached to exercise have a consistent physiological response strated that CoQ10 penetrates into the (Belardinelli et al., 2006). Of course The key role of coenzyme Q in viable layers of the epidermis and reduces 10 the levels of oxidation measured by weak quantification of plasma CoQ10 is also mitochondrial bioenergetics has sug- important to assess bioavailability of gested its use in an attempt to improve photon emission. CoQ10 was also effec- tive in human keratinocytes against UVA different CoQ10 formulations. Methods aerobic capacity and physical perform- are usually based on HPLC separation: a ance. Some studies have highlighted an mediated oxidative stress and in sup- simple, yet precise and accurate ergogenic effect while others did not. pressing the expression of collagenase in method is the one which appears in These issues have recently been human dermal fibroblasts following UVA irradiation. A reduction in wrinkle depth the website of the International CoQ10 addressed in 3 papers published in Association (Littarru et al., 2004). 2008 (Cooke et al., 2008, following CoQ10 application was also Mizuno et al., 2008, Kon et al., 2008). shown, an effect confirmed by Ashida Coenzyme Q can also be quantitatively 10 One of these articles shows that following et al. (2005). The combined effect of assayed in cells and in biological fluids. a single administration of CoQ plasma creatine and CoQ10 on skin’s energy CoQ cellular levels are particularly 10 10 levels significantly correlated with metabolism was highlighted by Blatt important in some ‘‘primary CoQ 10 muscle CoQ levels, maximal oxygen et al. (2005). Recently Inui and collabo- deficiencies’’. These are conditions where, 10 consumption and treadmill time to rators showed that cytokine production due to genetic reasons one or more of the exhaustion. A trend for increased time in keratinocytes is inhibited by CoQ10, steps involved in CoQ biosynthesis are 10 to exhaustion was observed following resulting in a decrease of metalloprotei- impaired. In some cases there is a dra- two weeks of CoQ supplementation nases leading to wrinkle reduction. matic positive response to exogenous 10 (p = 0.06) (Cooke et al., 2008). In CoQ administration (Quinzii et al., 10 another trial, oral administration of 2008). Reproductive medicine CoQ10 improved subjective fatigue sen- Some analytical problems have been sation and physical performance Impairment of mitochondrial bioener- found in the quantification of CoQ10 (Mizuno et al., 2008). The third article getics and oxidative stress are known to
OCL VOL. 18 N8 2 MARS-AVRIL 2011 79 be involved in sperm motility. After a cases quality of life, clinical symptoms 2007 ; Marcoff and Thompson, 2007). series of studies highlighting the impli- and the frequency of hospitalization A small-sized, yet double-blind study cations of CoQ10 in male infertility a were ameliorated upon CoQ10 admin- also points out that CoQ10 exogenous more recent publication confirmed, in a istration. In some protocols there was administration reduced myopathic placebo controlled double-blind also an improvement of ejection fraction symptoms in statin treated patients randomized trial, the efficacy of and other functional parameters. (Caso et al., 2007). Of course a large CoQ10 treatment in improving semen double blind clinical trail would be Cardiovascular effects of CoQ10 can be quality in men with idiopathic infertility ascribed to its bioenergetic role, to its necessary in order to assess the capability (Balercia et al., 2009). Oxidized and capability of antagonizing oxidation of of CoQ10 in mitigating statin side effects. reduced CoQ10 concentration signifi- plasma LDL and to its effect in amelio- cantly increased both in seminal plasma rating endothelial function. This effect Neurodegenerative and sperm cells, together with sperm was first seen by Watts et al. in patients motility, after 6 months of therapy with affected by Type II diabetes (Watts et al., disease 200 mg/day CoQ . The increased con- 10 2002) and then further explored by The positive effect of oral administration centration of CoQ10 and QH2 (reduced Belardinelli et al. in patients affected by CoQ ) in seminal plasma and sperm of CoQ10 to patients affected by Parkin- 10 ischemic heart disease (Belardinelli son’s disease was investigated in 2002 cells, the improvement of semen kinetic et al., 2006). Endothelial dysfunction features and treatment, and the evi- by Shults et al. (2002). Friedreich’s ataxia is commonly believed as an early sign of is another condition where treatment dence of a direct correlation between vascular impairment and the capability with CoQ10 and vitamin E caused a CoQ10 concentrations and sperm motil- of CoQ10 in counteracting it represents prolonged improvement in cardiac and ity strongly support a cause-effect a promising field. The mild hypotensive relationship. Similar results were found skeletal muscle bioenergetics and clinical effect of CoQ10 is probably related to scores (Cooper and Schapira, 2007). by Safarinejad (2009). In this study 212 this property. infertile men with idiopathic oligoas- In 2005 Sandor et al. studied the effect thenoteratospermia were treated with of CoQ10 (300 mg/day for 3 months) in 300 mg/day CoQ10 or placebo for 26 Human CoQ10 42 migraine patients in a double-blind, weeks. Statistically significant improve- deficiencies randomized, placebo-controlled trial. ment was found, in the CoQ10 group, The primary outcome variable in this regarding sperm count and motility Already in the past CoQ10 had been study was a change of attack frequency values, with a positive correlation shown to be effective in a number of in the third month of treatment com- between treatment duration of CoQ10 cases of mitochondrial myopathies, pared to baseline. The authors showed and sperm count as well as mean sperm which were sometimes associated with that responders were 47.6% in the motility. The CoQ10 group had a low CoQ10 muscle levels. With the CoQ10 treated group vs 14.4% in the significant decrease in serum FSH and progress in molecular biology techni- placebo group. A positive effect of LH at the 26 week treatment phase. The ques primary CoQ10 deficiencies, due to CoQ10 was also demonstrated in a large authors highlight that a lower serum mutations in ubiquinone biosynthetic group of pediatric patients suffering FSH implies a better spermatogenesis. genes, have been identified and some of from migraine (Hershey et al., 2007). Moreover, Inhibin B, which reflects these syndromes have shown excellent responses to oral CoQ treatment Sertoli’s cell function, increased in the 10 Sourcing: main natural CoQ group. (Quinzii et al., 2008). 10 origins, Kaneka’s process These studies did not address the key (yeast fermentation) issue of pregnancy rate; they were simply Statins and CoQ10 aimed at determining an effect of CoQ10 There are 3 methods used for the on sperm motility and quality. Other Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase manufacturing of CoQ10: yeast fermen- variables should of course be taken into tation, bacteria fermentation and chem- account in order to determine whether inhibitors which decrease synthesis of mevalonate, a key metabolic step in the ical synthesis. The latter was the first CoQ10 has an influence on pregnancy industrial method, introduced by Nis- rate. cholesterol synthesis pathway. These efficient drugs can produce a variety shin in the early 70s. Greater amounts of of muscle-related complaints or myo- CoQ10 became available when Japan- based Kaneka Corporation began pro- CoQ10 supports pathies. Since the mevalonate pathway also leads to the biosynthesis of the ducing natural CoQ10 (also called cardiovascular function KANEKA Q10TM) via patented yeast isoprenoid side chain of coenzyme Q10, fermentation in 1977. Kaneka is now CoQ10 deficiency at myocardial level different studies have addressed the the world’s largest manufacturer of has been documented in different possibility of CoQ10 being an etiologic studies. Although in most cases the factor in statin myopathy. There is no CoQ10 and is the only producer to deficiency was not the cause of the doubt that statins decrease plasma and manufacture CoQ10 in US market. cardiopathy this might have contrib- leukocyte CoQ10 levels; a few studies The yeast-fermentation method, along uted to the severity of the disorder. also report a decrease of muscle CoQ10 with Kaneka’s rigorous manufacturing Numerous trials have been conducted level upon statin treatment. This con- standards, makes KanekaQ10TM the on the effect of CoQ10 as coadjuvant in troversial issue has been extensively purest commercial-grade CoQ10 avail- the treatment of cardiac failure. In many investigated (Littarru and Langsjoen, able on the market today. The process
80 OCL VOL. 18 N8 2 MARS-AVRIL 2011 results in CoQ10 with the so-called all- a dossier of Kaneka that provided cause and effect. Moreover, for Vitamins trans configuration, which means that it scientific arguments to substantiate and Minerals EFSA accepts ‘‘textbook’’ is identical to naturally occurring CoQ10 the safety of CoQ10 up to 200 mg/day knowledge as evidence. found in meat, fish and other products and higher. The 200 mg level is being As a general rule, EFSA does not accept and also bio-identical to CoQ10 pro- followed by other European Union human studies conducted on patients, duced in the human body (figure 5). countries, and potentially all of them, yet medicinal paradigms are expected. by the legal principle of new Mutual The Kaneka yeast fermentation process Unfortunately, up to now, many CoQ10 is in accordance with pharmaceutical Recognition Regulation. This Regulation health benefits (as for other nutraceut- GMP standards and does not contain requires products lawfully marketed in icals) have been studied in patients. impurities found in synthetic material. one EU member state to be permitted Because of this evolution, most generic TM entry into another member state’s claims for Other Substances have not Kaneka Q10 is the only CoQ10 backed market. The mutual recognition regu- been accepted by EFSA. This is also true by published human safety studies and is lation plays a key role in the future EU for the generic CoQ10 claims: energy, the primary CoQ10 used in most scientific market for CoQ10. studies. As purest, most rigorously tested antioxidant, and blood pressure nor- malizing. We are facing a situation CoQ10 available, KanekaQ10 has been According the new European Health where study designs, which are accept- used in all major CoQ10 clinical trials Claim regulation (EC 1924/2006) the approved by the FDA and funded by the generic health claims were planned to able in the scientific community, are not NIH (e.g. Phase III Clinical Trial on be disclosed in a positive list that EU usable for marketing purposes. Coenzyme Q10’s Effects on Huntington’s would give access to by end of January Only in 2011 and 2012, which is more and Parkinson Disease in US). 2010. Yet, early 2011 there is still no list than 4 years after publication of the available. In the meanwhile, national health claim regulation, EFSA will organ- regulation still applies and all health ise guidance meetings and publish Regulatory status claims that are well supported by documents to provide more clarity on science can continue to be used. their idea of how health claims should CoQ10 is a well-established ingredient that is present in many food supple- EFSA has started to deliver scientific be substantiated for different fields such ments, fortified foods and cosmetic opinions on art. 13 regarding generic as weight management, cardiovascular brands all over Europe. There is an health claims. EFSA is taking the stance to health, joint health, physical perform- increasing acceptance of the role of treat Vitamins and Minerals very differ- ance, etc. Guidelines specifying the type non-vitamin and mineral ingredients, ently from Other Substances - examples of of studies, the proper biomarkers to be used and other pertinent issues should such as CoQ10 and its levels move the latter areCoQ10, glucosamine,lutein, towards higher levels than were consid- lycopene, carnitine, etc. For Vitamins and also be established. The scientific com- ered a decade ago based on risk Minerals a ‘‘scientific consensus’’ is usu- munity is just beginning to come to assessment approach and supportive ally sufficient to substantiate a health terms with health claim regulations and data. A Belgian ministerial order deter- claim, whereas for Other Substances, this process is ongoing. The full impact of the regulations is still evolving and mined CoQ10 was safe for use in food golden standard human trials are supplements at 200 mg after reviewing required with conclusive evidence of many grey areas are apparent. An independent economic impact assess- ment of existing and potential effects of the health claims regulation concluded
O that all initial objectives of the health Trans-isomer = Natural occurring CoQ O 10 claims regulation, notably relating to objectives such as consumer protection, O O fair competition, and promotion of R&D, were only poorly or weakly O addressed (Brookes, 2010). O Cis-isomer O O Ubiquinol
Ubiquinol, the reduced form of CoQ10 has recently become available in stable form, and is manufactured exclusively by Kaneka. Ubiquinol represents 93- 95% of CoQ10 pool in plasma of healthy human and is the predominant Coen- zyme Q10 form in a healthy cell. Several studies suggest that ubiquinol-ratio in human plasma may represent a sensitive index of oxidative stress in vivo espe- cially indicative of early oxidative dam- age. CoQ10 researchers from around the Figure 5. The trans and cis isomers of coenzyme Q10. world are working to advance the
OCL VOL. 18 N8 2 MARS-AVRIL 2011 81 understanding of the newly available Cooper JM, Schapira AH. Friedreich’s ataxia: in increased levels of ubiquinol-10 within ubiquinol. Recently, Japanese research- coenzyme Q10 and vitamin E therapy. circulating lipoproteins and increased resist- ers showed protective effects of ubiq- Mitochondrion 2007; 7: S127-35. ance of human low-density lipoprotein to the uinol on influenza virus infection Crane FL, Hatefi Y, Lester RL, Widmer C. initiation of lipid peroxidation. Biochim Bio- in mice. Isolation of a quinone from beef heart phys Acta 1992; 1126: 247-54. mitochondria. Biochim Biophys Acta 1957; Molyneux SL, Florkowski CM, George PM, 25: 220-1. et al. Coenzyme Q : an independent Conclusion 10 Dallner G, and Stocker R. Coenzyme Q. In: predictor of mortality in chronic heart failure. J Am Coll Cardiol 2008; 52: 1435-41. CoQ is a highly studied nutrient Encyclopedia of dietary supplements. 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