coenzyme Q10

{{See also|Q cycle}}

CoQ₁₀ is a component of the mitochondrial electron transport chain (ETC), where it plays a role in oxidative phosphorylation, a process required for the biosynthesis of adenosine triphosphate, the primary energy source of cells.{{cite journal |vauthors=Pradhan N, Singh C, Singh A |title=Coenzyme Q10 a mitochondrial restorer for various brain disorders |journal=Naunyn Schmiedebergs Arch Pharmacol |volume=394 |issue=11 |pages=2197–2222 |date=November 2021 |pmid=34596729 |doi=10.1007/s00210-021-02161-8}}

CoQ₁₀ is a lipophilic molecule that is located in all biological membranes of human body and serves as a component for the synthesis of ATP and is a life-sustaining cofactor for the three complexes (complex I, complex II, and complex III) of the ETC in the mitochondria. CoQ₁₀ has a role in the transport of protons across lysosomal membranes to regulate pH in lysosome functions.

The mitochondrial oxidative phosphorylation process occurs in the inner mitochondrial membrane of eukaryotic cells. This membrane is highly folded into structures called cristae, which increase the surface area available for oxidative phosphorylation. CoQ₁₀ plays a role in this process as an essential cofactor of the ETC located in the inner mitochondrial membrane and serves the following functions:

• electron transport in the mitochondrial ETC, by shuttling electrons from mitochondrial complexes like nicotinamide adenine dinucleotide (NADH), ubiquinone reductase (complex I), and succinate ubiquinone reductase (complex II), the fatty acids and branched-chain amino acids oxidation (through flavin-linked dehydrogenases) to ubiquinol–cytochrome-c reductase (complex III) of the ETC: CoQ₁₀ participates in fatty acid and glucose metabolism by transferring electrons generated from the reduction of fatty acids and glucose to electron acceptors;{{cite journal |vauthors=Manzar H, Abdulhussein D, Yap TE, Cordeiro MF |title=Cellular Consequences of Coenzyme Q10 Deficiency in Neurodegeneration of the Retina and Brain |journal=Int J Mol Sci |volume=21 |issue=23 |date=December 2020 |page=9299 |pmid=33291255 |pmc=7730520 |doi=10.3390/ijms21239299 |doi-access=free}}{{Creative Commons text attribution notice|cc=by4|from this source=yes}}
• antioxidant activity as a lipid-soluble antioxidant together with vitamin E, scavenging reactive oxygen species and protecting cells against oxidative stress, inhibiting the oxidation of proteins, DNA, and use of vitamin E.{{cite journal |vauthors=Di Lorenzo A, Iannuzzo G, Parlato A, Cuomo G, Testa C, Coppola M, D'Ambrosio G, Oliviero DA, Sarullo S, Vitale G, Nugara C, Sarullo FM, Giallauria F |title=Clinical Evidence for Q10 Coenzyme Supplementation in Heart Failure: From Energetics to Functional Improvement |journal=J Clin Med |volume=9 |issue=5 |date=April 2020 |page=1266 |pmid=32349341 |pmc=7287951 |doi=10.3390/jcm9051266 | doi-access=free}}{{Creative Commons text attribution notice|cc=by4|from this source=yes}}

{{Expert needed|biochemistry|talk=Biological function|date=April 2024}}

Coenzymes Q is a coenzyme family that is ubiquitous in animals and many Pseudomonadota,{{cite journal | vauthors = Nowicka B, Kruk J | title = Occurrence, biosynthesis and function of isoprenoid quinones | journal = Biochimica et Biophysica Acta (BBA) - Bioenergetics | volume = 1797 | issue = 9 | pages = 1587–1605 | date = September 2010 | pmid = 20599680 | doi = 10.1016/j.bbabio.2010.06.007 | doi-access = free }} a group of gram-negative bacteria. The fact that the coenzyme is ubiquitous gives the origin of its other name, ubiquinone.{{Include-USGov|agency=National Center for Biotechnology Information|title=Ubidecarenone |url=https://pubchem.ncbi.nlm.nih.gov/compound/5281915 | work = PubChem | publisher = US National Library of Medicine |access-date=4 April 2024 |date=30 March 2024}} In humans, the most common form of coenzymes Q is coenzyme Q₁₀, also called CoQ₁₀ ({{IPAc-en|ˌ|k|oʊ|k|j|uː|ˈ|t|ɛ|n}}) or ubiquinone-10.

Coenzyme Q₁₀ is a 1,4-benzoquinone, in which "Q" refers to the quinone chemical group and "10" refers to the number of isoprenyl chemical subunits (shown enclosed in brackets in the diagram) in its tail. In natural ubiquinones, there are from six to ten subunits in the tail, with humans having a tail of 10 isoprene units (50 carbon atoms) connected to its benzoquinone "head".

This family of fat-soluble substances is present in all respiring eukaryotic cells, primarily in the mitochondria. Ninety-five percent of the human body's energy is generated this way.{{cite journal | vauthors = Ernster L, Dallner G | title = Biochemical, physiological and medical aspects of ubiquinone function | journal = Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease | volume = 1271 | issue = 1 | pages = 195–204 | date = May 1995 | pmid = 7599208 | doi = 10.1016/0925-4439(95)00028-3 | doi-access = free }} Organs with the highest energy requirements—such as the heart, liver, and kidney—have the highest CoQ₁₀ concentrations.{{cite journal | vauthors = Okamoto T, Matsuya T, Fukunaga Y, Kishi T, Yamagami T | title = Human serum ubiquinol-10 levels and relationship to serum lipids | journal = International Journal for Vitamin and Nutrition Research | volume = 59 | issue = 3 | pages = 288–292 | year = 1989 | pmid = 2599795 }}{{cite journal | vauthors = Aberg F, Appelkvist EL, Dallner G, Ernster L | title = Distribution and redox state of ubiquinones in rat and human tissues | journal = Archives of Biochemistry and Biophysics | volume = 295 | issue = 2 | pages = 230–234 | date = June 1992 | pmid = 1586151 | doi = 10.1016/0003-9861(92)90511-T }}{{cite journal | vauthors = Shindo Y, Witt E, Han D, Epstein W, Packer L | title = Enzymic and non-enzymic antioxidants in epidermis and dermis of human skin | journal = The Journal of Investigative Dermatology | volume = 102 | issue = 1 | pages = 122–124 | date = January 1994 | pmid = 8288904 | doi = 10.1111/1523-1747.ep12371744 | doi-access = }}{{cite journal|vauthors=Žmitek J, ŽMitek K, Pravs I|title=Improving the bioavailability of coenzyme q10 from theory to practice|year=2008|journal=Agro Food Industry Hi-Tech|url=https://www.scopus.com/inward/record.uri?eid=2-s2.0-53849139131&partnerID=40&md5=25ac2ff16eec9fc4a8b52430316bfbd8|access-date=5 April 2024|archive-date=23 April 2024|archive-url=https://web.archive.org/web/20240423075336/https://www.scopus.com/record/display.uri?eid=2-s2.0-53849139131&origin=inward&txGid=4f4a035686dfee6b6fbde3099b06b518|url-status=live}}

There are three redox states of CoQ: fully oxidized (ubiquinone), semiquinone (ubisemiquinone), and fully reduced (ubiquinol). The capacity of this molecule to act as a two-electron carrier (moving between the quinone and quinol form) and a one-electron carrier (moving between the semiquinone and one of these other forms) is central to its role in the electron transport chain due to the iron–sulfur clusters that can only accept one electron at a time and as a free radical–scavenging antioxidant.

There are two major pathways of deficiency of CoQ₁₀ in humans: reduced biosynthesis, and increased use by the body.{{cite journal |vauthors=Desbats MA, Lunardi G, Doimo M, Trevisson E, Salviati L |title=Genetic bases and clinical manifestations of coenzyme Q10 (CoQ 10) deficiency |journal=J Inherit Metab Dis |volume=38 |issue=1 |pages=145–56 |date=January 2015 |pmid=25091424 |doi=10.1007/s10545-014-9749-9 |url=}} Biosynthesis is the major source of CoQ₁₀. Biosynthesis requires at least 15 genes, and mutations in any of them can cause CoQ deficiency. CoQ₁₀ levels also may be affected by other genetic defects (such as mutations of mitochondrial DNA, ETFDH, APTX, FXN, and BRAF, genes that are not directly related to the CoQ₁₀ biosynthetic process). Some of these, such as mutations in COQ6, can lead to serious diseases such as steroid-resistant nephrotic syndrome with sensorineural deafness.{{cite journal|doi=10.1172/JCI45693 |title=COQ6 mutations in human patients produce nephrotic syndrome with sensorineural deafness |date=2011 |journal=Journal of Clinical Investigation |volume=121 |issue=5 |pages=2013–2024 |pmid=21540551 |pmc=3083770 |vauthors = Heeringa SF, Chernin G, Chaki M, Zhou W, Sloan AJ, Ji Z, Xie LX, Salviati L, Hurd TW, Vega-Warner V, Killen PD, Raphael Y, Ashraf S, Ovunc B, Schoeb DS, McLaughlin HM, Airik R, Vlangos CN, Gbadegesin R, Hinkes B, Saisawat P, Trevisson E, Doimo M, Casarin A, Pertegato V, Giorgi G, Prokisch H, Rötig A, Nürnberg G, Becker C }}{{cite journal|doi=10.1002/jmd2.12068 |title=COQ6 mutation in patients with nephrotic syndrome, sensorineural deafness, and optic atrophy |date=2020 |journal=Jimd Reports |volume=54 |issue=1 |pages=37–44 |pmid=32685349 |pmc=7358665 | vauthors = Justine Perrin R, Rousset-Rouvière C, Garaix F, Cano A, Conrath J, Boyer O, Tsimaratos M }}{{cite web | url=https://www.ncbi.nlm.nih.gov/medgen/886260 | title=Nephrotic Syndrome - COQ6 Associated (Concept Id: C4054393) - MedGen - NCBI | access-date=6 April 2024 | archive-date=6 April 2024 | archive-url=https://web.archive.org/web/20240406102811/https://www.ncbi.nlm.nih.gov/medgen/886260 | url-status=live }}

Although CoQ₁₀ may be measured in blood plasma, these measurements reflect dietary intake rather than tissue status. Currently, most clinical centers measure CoQ₁₀ levels in cultured skin fibroblasts, muscle biopsies, and blood mononuclear cells.{{cite journal | vauthors = Trevisson E, DiMauro S, Navas P, Salviati L | title = Coenzyme Q deficiency in muscle | journal = Current Opinion in Neurology | volume = 24 | issue = 5 | pages = 449–456 | date = October 2011 | pmid = 21844807 | doi = 10.1097/WCO.0b013e32834ab528 | hdl-access = free | hdl = 10261/129020 }} Culture fibroblasts can be used also to evaluate the rate of endogenous CoQ₁₀ biosynthesis, by measuring the uptake of ¹⁴C-labeled p-hydroxybenzoate.{{cite journal | vauthors = Montero R, Sánchez-Alcázar JA, Briones P, Hernández AR, Cordero MD, Trevisson E, Salviati L, Pineda M, García-Cazorla A, Navas P, Artuch R | title = Analysis of coenzyme Q10 in muscle and fibroblasts for the diagnosis of CoQ₁₀ deficiency syndromes | journal = Clinical Biochemistry | volume = 41 | issue = 9 | pages = 697–700 | date = June 2008 | pmid = 18387363 | doi = 10.1016/j.clinbiochem.2008.03.007 | hdl-access = free | hdl = 11577/2447079 }}

CoQ₁₀ is studied as an adjunctive therapy to reduce inflammation in periodontitis.{{cite journal |vauthors=Fawzy El-Sayed KM, Cosgarea R, Sculean A, Doerfer C |title=Can vitamins improve periodontal wound healing/regeneration? |journal=Periodontol 2000 |volume=94 |issue=1 |pages=539–602 |date=February 2024 |pmid=37592831 |doi=10.1111/prd.12513 |url=|doi-access=free }}

Although statins may reduce CoQ₁₀ in the blood it is unclear if they reduce CoQ₁₀ in muscle. Evidence does not support that supplementation improves statin side effects.{{cite journal | vauthors = Tan JT, Barry AR | title = Coenzyme Q10 supplementation in the management of statin-associated myalgia | journal = American Journal of Health-System Pharmacy | volume = 74 | issue = 11 | pages = 786–793 | date = June 2017 | pmid = 28546301 | doi = 10.2146/ajhp160714 | s2cid = 3825396 | doi-access = free }}{{Cite journal |last1=Kennedy |first1=Cormac |last2=Köller |first2=Yasmin |last3=Surkova |first3=Elena |date=2020-04-01 |title=Effect of Coenzyme Q10 on statin-associated myalgia and adherence to statin therapy: A systematic review and meta-analysis |journal=Atherosclerosis |language=en |volume=299 |pages=1–8 |doi=10.1016/j.atherosclerosis.2020.03.006 |pmid=32179207 |doi-access=free }}

The oxidized structure of CoQ₁₀ is shown below. The various kinds of coenzyme Q may be distinguished by the number of isoprenoid subunits in their side-chains. The most common coenzyme Q in human mitochondria is CoQ₁₀. Q refers to the quinone head and "10" refers to the number of isoprene repeats in the tail. The molecule below has three isoprenoid units and would be called Q₃.

:File:Unibuinone3.svg

In its pure state, it is an orange-colored lipophile powder and has no taste or odor.

Biosynthesis occurs in most human tissue. There are three major steps:

1. Creation of the benzoquinone structure (using phenylalanine or tyrosine, via 4-hydroxybenzoate)
2. Creation of the isoprene side chain (using acetyl-CoA)
3. The joining or condensation of the above two structures

The initial two reactions occur in mitochondria, the endoplasmic reticulum, and peroxisomes, indicating multiple sites of synthesis in animal cells.{{cite journal | vauthors = Bentinger M, Tekle M, Dallner G | title = Coenzyme Q--biosynthesis and functions | journal = Biochemical and Biophysical Research Communications | volume = 396 | issue = 1 | pages = 74–79 | date = May 2010 | pmid = 20494114 | doi = 10.1016/j.bbrc.2010.02.147 }}

An important enzyme in this pathway is HMG-CoA reductase, usually a target for intervention in cardiovascular complications. The "statin" family of cholesterol-reducing medications inhibits HMG-CoA reductase. One possible side effect of statins is decreased production of CoQ₁₀, which may be connected to the development of myopathy and rhabdomyolysis. However, the role statins play in CoQ deficiency is controversial. Although statins reduce blood levels of CoQ, studies on the effects of muscle levels of CoQ are yet to come. CoQ supplementation also does not reduce side effects of statin medications.

Genes involved include PDSS1, PDSS2, COQ2, and ADCK3 (COQ8, CABC1).{{Cite book | vauthors = Espinós C, Felipo V, Palau F |url=https://books.google.com/books?id=uxQ_pjKNhE8C&pg=PA122 |title=Inherited Neuromuscular Diseases: Translation from Pathomechanisms to Therapies |date=2009 |publisher=Springer |isbn=978-90-481-2812-9 |pages=122ff |access-date=4 January 2011}}

Organisms other than humans produce the benzoquinone and isoprene structures from somewhat different source chemicals. For example, the bacteria E. coli produces the former from chorismate and the latter from a non-mevalonate source. The common yeast S. cerevisiae, however, derives the former from either chorismate or tyrosine and the latter from mevalonate. Most organisms share the common 4-hydroxybenzoate intermediate, yet again uses different steps to arrive at the "Q" structure.{{cite journal | vauthors = Meganathan R | title = Ubiquinone biosynthesis in microorganisms | journal = FEMS Microbiology Letters | volume = 203 | issue = 2 | pages = 131–139 | date = September 2001 | pmid = 11583838 | doi = 10.1111/j.1574-6968.2001.tb10831.x | doi-access = free }}

Although neither a prescription drug nor an essential nutrient, CoQ₁₀ is commonly used as a dietary supplement with the intent to prevent or improve disease conditions, such as cardiovascular disorders.{{cite journal | vauthors = Arenas-Jal M, Suñé-Negre JM, García-Montoya E | title = Coenzyme Q10 supplementation: Efficacy, safety, and formulation challenges | journal = Comprehensive Reviews in Food Science and Food Safety | volume = 19 | issue = 2 | pages = 574–594 | date = March 2020 | pmid = 33325173 | doi = 10.1111/1541-4337.12539 | hdl-access = free | hdl = 2445/181270 }} CoQ₁₀ is naturally produced by the body and plays a crucial role in cell growth and protection. Despite its significant role in the body, it is not used as a drug to treat any specific disease.

Nevertheless, CoQ₁₀ is widely available as an over-the-counter dietary supplement and is recommended by some healthcare professionals, despite a lack of definitive scientific evidence supporting these recommendations, especially when it comes to cardiovascular diseases.{{cite journal |vauthors=Bjørklund G, Semenova Y, Gasmi A, Indika NR, Hrynovets I, Lysiuk R, Lenchyk L, Uryr T, Yeromina H, Peana M |title=Coenzyme Q10 for Enhancing Physical Activity and Extending the Human Life Cycle |journal=Curr Med Chem |volume=31 |issue=14 |pages=1804–1817 |date=2024 |pmid=36852817 |doi=10.2174/0929867330666230228103913}}

CoQ₁₀ is not approved by the U.S. Food and Drug Administration (FDA) for the treatment of any medical condition.{{Include-USGov|agency=National Cancer Institute|url=http://www.cancer.gov/cancertopics/pdq/cam/coenzymeQ10/patient|publisher=National Cancer Institute|title=Coenzyme Q₁₀|date=April 2022}}{{cite book|pmid=26389329 |date=2002 |publisher=PDQ Integrative, Alternative, and Complementary Therapies Editorial Board |title=Coenzyme Q10: Health Professional Version |author=((PDQ Integrative, Alternative, and Complementary Therapies Editorial Board)) }}{{Include-USGov|agency=National Cancer Institute| vauthors = White J |date= 14 May 2014 |title=PDQ Coenzyme Q₁₀ |url=http://www.cancer.gov/cancertopics/pdq/cam/coenzymeQ10/HealthProfessional |publisher= National Cancer Institute, National Institutes of Health, U.S. Dept. of Health and Human Services |access-date= 29 June 2014}}{{Cite web |url=https://www.nice.org.uk/advice/es11/resources/mitochondrial-disorders-in-children-coenzyme-q10-pdf-1158110303173 |title=Mitochondrial disorders in children: Co-enzyme Q10 |date=28 March 2017 |website=nice.org.uk |publisher=National Institute for Health and Care Excellence |location=UK |access-date=10 October 2019 |archive-date=10 October 2019 |archive-url=https://web.archive.org/web/20191010120754/https://www.nice.org.uk/advice/es11/resources/mitochondrial-disorders-in-children-coenzyme-q10-pdf-1158110303173 |url-status=live }} However, it is sold as a dietary supplement not subject to the same regulations as medicinal drugs, and is an ingredient in some cosmetics.{{cite journal | vauthors = Hojerová J | title = [Coenzyme Q10--its importance, properties and use in nutrition and cosmetics] | journal = Ceska a Slovenska Farmacie | volume = 49 | issue = 3 | pages = 119–123 | date = May 2000 | pmid = 10953455 }} The manufacture of CoQ₁₀ is not regulated, and different batches and brands may vary significantly.

A 2014 Cochrane review found insufficient evidence to make a conclusion about its use for the prevention of heart disease.{{cite journal | vauthors = Flowers N, Hartley L, Todkill D, Stranges S, Rees K | title = Co-enzyme Q10 supplementation for the primary prevention of cardiovascular disease | journal = The Cochrane Database of Systematic Reviews | volume = 2014 | issue = 12 | pages = CD010405 | date = 4 December 2014 | pmid = 25474484 | pmc = 9759150 | doi = 10.1002/14651858.CD010405.pub2 }} A 2016 Cochrane review concluded that CoQ₁₀ had no effect on blood pressure.{{cite journal | vauthors = Ho MJ, Li EC, Wright JM | title = Blood pressure lowering efficacy of coenzyme Q10 for primary hypertension | journal = The Cochrane Database of Systematic Reviews | volume = 2016 | issue = 3 | pages = CD007435 | date = March 2016 | pmid = 26935713 | pmc = 6486033 | doi = 10.1002/14651858.CD007435.pub3 }} A 2021 Cochrane review found "no convincing evidence to support or refute" the use of CoQ₁₀ for the treatment of heart failure.{{cite journal | vauthors = Al Saadi T, Assaf Y, Farwati M, Turkmani K, Al-Mouakeh A, Shebli B, Khoja M, Essali A, Madmani ME | title = Coenzyme Q10 for heart failure | journal = The Cochrane Database of Systematic Reviews | volume = 2021 | issue = 2 | pages = CD008684 | date = February 2021 | pmid = 35608922 | pmc = 8092430 | doi = 10.1002/14651858.CD008684.pub3 | collaboration = Cochrane Heart Group }}

A 2017 meta-analysis of people with heart failure taking 30–100 mg/d of CoQ₁₀ found a 31% lower mortality and increased exercise capacity, with no significant difference in the endpoints of left heart ejection fraction.{{cite journal | vauthors = Lei L, Liu Y | title = Efficacy of coenzyme Q10 in patients with cardiac failure: a meta-analysis of clinical trials | journal = BMC Cardiovascular Disorders | volume = 17 | issue = 1 | pages = 196 | date = July 2017 | pmid = 28738783 | pmc = 5525208 | doi = 10.1186/s12872-017-0628-9 | doi-access = free }}{{Creative Commons text attribution notice|cc=by4|from this source=yes}} A 2021 meta-analysis found that coenzyme Q10 was associated with a 31% lower all-cause mortality in HF patients.{{Cite journal |last1=Khan |first1=Muhammad Shahzeb |last2=Khan |first2=Fiza |last3=Fonarow |first3=Gregg C. |last4=Sreenivasan |first4=Jayakumar |last5=Greene |first5=Stephen J. |last6=Khan |first6=Safi U. |last7=Usman |first7=Muhammad Shariq |last8=Vaduganathan |first8=Muthiah |last9=Fudim |first9=Marat |last10=Anker |first10=Stefan D. |last11=Butler |first11=Javed |date=June 2021 |title=Dietary interventions and nutritional supplements for heart failure: a systematic appraisal and evidence map |url=https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2278 |journal=European Journal of Heart Failure |language=en |volume=23 |issue=9 |pages=1468–1476 |doi=10.1002/ejhf.2278 |pmid=34173307 |issn=1388-9842 |access-date=10 June 2024 |archive-date=2 January 2023 |archive-url=https://web.archive.org/web/20230102122936/https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2278 |url-status=live }} In a 2023 meta-analysis of older people, ubiquinone had evidence of a cardiovascular effect, but ubiquinol did not.{{cite journal | vauthors = Fladerer JP, Grollitsch S | title = Comparison of Coenzyme Q10 (Ubiquinone) and Reduced Coenzyme Q10 (Ubiquinol) as Supplement to Prevent Cardiovascular Disease and Reduce Cardiovascular Mortality | journal = Current Cardiology Reports | volume = 25 | issue = 12 | pages = 1759–1767 | date = December 2023 | pmid = 37971634 | pmc = 10811087 | doi = 10.1007/s11886-023-01992-6 | doi-access = free }}

Although CoQ₁₀ has been studied as a potential remedy to treat purported muscle-related side effects of statin medications, the results were mixed. Although a 2018 meta-analysis concluded that there was preliminary evidence for oral CoQ₁₀ reducing statin-associated muscle symptoms, including muscle pain, muscle weakness, muscle cramps, and muscle tiredness,{{cite journal | vauthors = Qu H, Guo M, Chai H, Wang WT, Gao ZY, Shi DZ | title = Effects of Coenzyme Q10 on Statin-Induced Myopathy: An Updated Meta-Analysis of Randomized Controlled Trials | journal = Journal of the American Heart Association | volume = 7 | issue = 19 | pages = e009835 | date = October 2018 | pmid = 30371340 | pmc = 6404871 | doi = 10.1161/JAHA.118.009835 }}{{Creative Commons text attribution notice|cc=by4|from this source=yes}} 2015 and 2024 meta-analysis found that CoQ₁₀ had no effect on statin myopathy.{{cite journal | vauthors = Banach M, Serban C, Sahebkar A, Ursoniu S, Rysz J, Muntner P, Toth PP, Jones SR, Rizzo M, Glasser SP, Lip GY, Dragan S, Mikhailidis DP | title = Effects of coenzyme Q10 on statin-induced myopathy: a meta-analysis of randomized controlled trials | journal = Mayo Clinic Proceedings | volume = 90 | issue = 1 | pages = 24–34 | date = January 2015 | pmid = 25440725 | doi = 10.1016/j.mayocp.2014.08.021 | type = Systematic Review and Meta-Analysis }}

CoQ₁₀ is studied as an adjunctive therapy to reduce inflammation in periodontitis.

CoQ₁₀ in the pure form is a crystalline powder insoluble in water. Absorption as a pharmacological substance follows the same process as that of lipids; the uptake mechanism appears to be similar to that of vitamin E, another lipid-soluble nutrient. This process in the human body involves secretion into the small intestine of pancreatic enzymes and bile, which facilitates emulsification and micelle formation required for absorption of lipophilic substances.{{cite journal | vauthors = Bhagavan HN, Chopra RK | title = Coenzyme Q10: absorption, tissue uptake, metabolism and pharmacokinetics | journal = Free Radical Research | volume = 40 | issue = 5 | pages = 445–453 | date = May 2006 | pmid = 16551570 | doi = 10.1080/10715760600617843 | s2cid = 39001523 }} Food intake (and the presence of lipids) stimulates bodily biliary excretion of bile acids and greatly enhances absorption of CoQ₁₀. Exogenous CoQ₁₀ is absorbed from the small intestine and is best absorbed if taken with a meal. Serum concentration of CoQ₁₀ in fed condition is higher than in fasting conditions.{{cite book | vauthors = Bogentoft C, Edlund PO, Olsson B, Widlund L, Westensen K | chapter = Biopharmaceutical aspects of intravenous and oral administration of coenzyme Q10. | title = Biomedical and clinical aspects of coenzyme Q | date = 1991 | volume = 6 | pages = 215–224 }}{{cite journal | vauthors = Ochiai A, Itagaki S, Kurokawa T, Kobayashi M, Hirano T, Iseki K | title = Improvement in intestinal coenzyme q10 absorption by food intake | journal = Yakugaku Zasshi | volume = 127 | issue = 8 | pages = 1251–1254 | date = August 2007 | pmid = 17666877 | doi = 10.1248/yakushi.127.1251 | hdl-access = free | doi-access = free | hdl = 2115/30144 }}{{Verify source|date=November 2010}}

CoQ₁₀ is metabolized in all tissues, with the metabolites phosphorylated in cells. CoQ10 is reduced to ubiquinol during or after absorption in the small intestine. It is absorbed by chylomicrons, and redistributed in the blood within lipoproteins. Its elimination occurs via biliary and fecal excretion.

Some reports have been published on the pharmacokinetics of CoQ₁₀. The plasma peak can be observed 6–8 hours after oral administration when taken as a pharmacological substance. In some studies, a second plasma peak was observed approximately 24 hours after administration, probably due to enterohepatic recycling and redistribution from the liver to circulation.

Deuterium-labeled crystalline CoQ₁₀ was used to investigate pharmacokinetics in humans to determine an elimination half-time of 33 hours.{{cite journal | vauthors = Tomono Y, Hasegawa J, Seki T, Motegi K, Morishita N | title = Pharmacokinetic study of deuterium-labeled coenzyme Q10 in man | journal = International Journal of Clinical Pharmacology, Therapy, and Toxicology | volume = 24 | issue = 10 | pages = 536–541 | date = October 1986 | pmid = 3781673 }}

In contrast to the intake of CoQ₁₀ as a constituent of food, such as nuts or meat, from which CoQ₁₀ is normally absorbed, there is a concern about CoQ₁₀ bioavailability when it is taken as a dietary supplement.{{cite journal|doi=10.3390/antiox9050386|doi-access=free |title=Bioavailability of Coenzyme Q10: An Overview of the Absorption Process and Subsequent Metabolism |date=2020 |journal=Antioxidants |volume=9 |issue=5 |page=386 |pmid=32380795 | vauthors = Mantle D, Dybring A |pmc=7278738 }}{{cite journal|doi=10.3390/nu11030527|doi-access=free |title=Bioavailability and Sustained Plasma Concentrations of CoQ10 in Healthy Volunteers by a Novel Oral Timed-Release Preparation |date=2019 |journal=Nutrients |volume=11 |issue=3 |page=527 |pmid=30823449 |pmc=6471387 | vauthors = Martucci A, Reurean-Pintilei D, Manole A }} Bioavailability of CoQ₁₀ supplements may be reduced due to the lipophilic nature of its molecule and large molecular weight.

Nanoparticles have been explored as a delivery system for various drugs, such as improving the oral bioavailability of drugs with poor absorption characteristics.{{cite journal | vauthors = Mathiowitz E, Jacob JS, Jong YS, Carino GP, Chickering DE, Chaturvedi P, Santos CA, Vijayaraghavan K, Montgomery S, Bassett M, Morrell C | title = Biologically erodable microspheres as potential oral drug delivery systems | journal = Nature | volume = 386 | issue = 6623 | pages = 410–414 | date = March 1997 | pmid = 9121559 | doi = 10.1038/386410a0 | s2cid = 4324209 | bibcode = 1997Natur.386..410M }} However, this has not proved successful with CoQ₁₀, although reports have differed widely.{{cite journal | vauthors = Hsu CH, Cui Z, Mumper RJ, Jay M | title = Preparation and characterization of novel coenzyme Q10 nanoparticles engineered from microemulsion precursors | journal = AAPS PharmSciTech | volume = 4 | issue = 3 | pages = E32 | year = 2003 | pmid = 14621964 | pmc = 2750625 | doi = 10.1208/pt040332 }}{{Verify source|date=November 2010}}{{cite journal | vauthors = Joshi SS, Sawant SV, Shedge A, Halpner AD | title = Comparative bioavailability of two novel coenzyme Q10 preparations in humans | journal = International Journal of Clinical Pharmacology and Therapeutics | volume = 41 | issue = 1 | pages = 42–48 | date = January 2003 | pmid = 12564745 | doi = 10.5414/CPP41042 }}{{Verify source|date=November 2010}} The use of aqueous suspension of finely powdered CoQ₁₀ in pure water also reveals only a minor effect.{{cite journal | vauthors = Ozawa Y, Mizushima Y, Koyama I, Akimoto M, Yamagata Y, Hayashi H, Murayama H | title = Intestinal absorption enhancement of coenzyme Q10 with a lipid microsphere | journal = Arzneimittel-Forschung | volume = 36 | issue = 4 | pages = 689–690 | date = April 1986 | pmid = 3718593 }}

Facilitating drug absorption by increasing its solubility in water is a common pharmaceutical strategy and also is successful for CoQ₁₀. Various approaches have been developed to achieve this goal, with many of them producing significantly better results over oil-based soft gel capsules despite the many attempts to optimize their composition. Examples of such approaches are use of the aqueous dispersion of solid CoQ₁₀ with the polymer tyloxapol,{{cite patent |inventor = Westesen K, Siekmann B |title=Particles with modified physicochemical properties, their preparation and uses |country=US |number=6197349 |publication-date=2001}} formulations based on various solubilising agents, such as hydrogenated lecithin,{{cite patent| inventor = Ohashi H, Takami T, Koyama N, Kogure Y, Ida K |title=Aqueous solution containing ubidecarenone |country=US |number=4483873 |publication-date=1984}} and complexation with cyclodextrins; among the latter, the complex with β-cyclodextrin has been found to have highly increased bioavailability{{cite journal | vauthors = Zmitek J, Smidovnik A, Fir M, Prosek M, Zmitek K, Walczak J, Pravst I | title = Relative bioavailability of two forms of a novel water-soluble coenzyme Q10 | journal = Annals of Nutrition & Metabolism | volume = 52 | issue = 4 | pages = 281–287 | year = 2008 | pmid = 18645245 | doi = 10.1159/000129661 | s2cid = 825159 }}{{cite journal |vauthors = Kagan D, Madhavi D |year=2010 |title=A Study on the Bioavailability of a Novel Sustained-Release Coenzyme Q₁₀-β-Cyclodextrin Complex |journal=Integrative Medicine |volume=9 |issue=1}} and also is used in pharmaceutical and food industries for CoQ₁₀-fortification.

Generally, oral CoQ₁₀ supplementation is well tolerated. The most common side effects are gastrointestinal symptoms (nausea, vomiting, appetite suppression, and abdominal pain), rashes, and headaches.{{cite journal | vauthors = Wyman M, Leonard M, Morledge T | title = Coenzyme Q10: a therapy for hypertension and statin-induced myalgia? | journal = Cleveland Clinic Journal of Medicine | volume = 77 | issue = 7 | pages = 435–442 | date = July 2010 | pmid = 20601617 | doi = 10.3949/ccjm.77a.09078 | s2cid = 26572524 | doi-access = free }} Some adverse effects, largely gastrointestinal, are reported with intakes. Doses of 100–300 mg per day may induce insomnia or elevate liver enzymes. The observed safe level risk assessment method indicated that the evidence of safety is acceptable at intakes up to 1200 mg per day.{{cite journal | vauthors = Hathcock JN, Shao A | title = Risk assessment for coenzyme Q10 (Ubiquinone) | journal = Regulatory Toxicology and Pharmacology | volume = 45 | issue = 3 | pages = 282–288 | date = August 2006 | pmid = 16814438 | doi = 10.1016/j.yrtph.2006.05.006 }}

Caution should be observed in the use of CoQ₁₀ supplementation in people with bile duct obstruction and during pregnancy or breastfeeding.

CoQ₁₀ taken as a pharmacological substance has potential to inhibit the effects of theophylline as well as the anticoagulant warfarin; CoQ₁₀ may interfere with warfarin's actions by interacting with cytochrome p450 enzymes thereby reducing the INR, a measure of blood clotting.{{cite journal | vauthors = Sharma A, Fonarow GC, Butler J, Ezekowitz JA, Felker GM | title = Coenzyme Q10 and Heart Failure: A State-of-the-Art Review | journal = Circulation: Heart Failure | volume = 9 | issue = 4 | pages = e002639 | date = April 2016 | pmid = 27012265 | doi = 10.1161/CIRCHEARTFAILURE.115.002639 | s2cid = 2034503 | doi-access = free }} The structure of CoQ₁₀ is similar to that of vitamin K, which competes with and counteracts warfarin's anticoagulation effects. CoQ₁₀ is not recommended in people taking warfarin due to the increased risk of clotting.

Detailed reviews on occurrence of CoQ₁₀ and dietary intake were published in 2010.{{cite journal | vauthors = Pravst I, Zmitek K, Zmitek J | title = Coenzyme Q10 contents in foods and fortification strategies | journal = Critical Reviews in Food Science and Nutrition | volume = 50 | issue = 4 | pages = 269–280 | date = April 2010 | pmid = 20301015 | doi = 10.1080/10408390902773037 | s2cid = 38779392 }} Besides the endogenous synthesis within organisms, CoQ₁₀ also is supplied by various foods. CoQ₁₀ concentrations in various foods are:

Vegetable oils, meat, and fish are rich in CoQ₁₀. Dairy products are much poorer sources of CoQ₁₀ than animal tissues. Among vegetables, broccoli and cauliflower are good sources of CoQ₁₀. Most fruits and berries are poor sources of CoQ₁₀, except avocados, which have relatively high oil and CoQ₁₀ content.

In the developed world, the estimated daily intake of CoQ₁₀ has been determined at 3–6 mg per day, derived primarily from meat.

South Koreans have an estimated average daily CoQ (Q₉ + Q₁₀) intake of 11.6 mg/d, derived primarily from kimchi.{{cite journal|doi=10.1016/j.jfca.2011.03.018 |title=Ubiquinone contents in Korean fermented foods and average daily intakes |date=2011 |journal=Journal of Food Composition and Analysis |volume=24 |issue=8 |pages=1123–1129 | vauthors = Pyo Y, Oh H }}

Cooking by frying reduces CoQ₁₀ content by 14–32%.{{cite journal | vauthors = Weber C, Bysted A, Hłlmer G | title = The coenzyme Q10 content of the average Danish diet | journal = International Journal for Vitamin and Nutrition Research | volume = 67 | issue = 2 | pages = 123–129 | year = 1997 | pmid = 9129255 }}

In 1950, a small amount of CoQ₁₀ was isolated from the lining of a horse's gut, a compound initially called substance SA, but later deemed to be quinone found in many animal tissues.{{cite journal | vauthors = Morton RA | title = Ubiquinone | journal = Nature | volume = 182 | issue = 4652 | pages = 1764–1767 | date = December 1958 | pmid = 13622652 | doi = 10.1038/1821764a0 | bibcode = 1958Natur.182.1764M }} In 1957, the same compound was isolated from mitochondrial membranes of beef heart, with research showing that it transported electrons within mitochondria. It was called Q-275 as a quinone.{{cite journal | vauthors = Crane FL, Hatefi Y, Lester RL, Widmer C | title = Isolation of a quinone from beef heart mitochondria | journal = Biochimica et Biophysica Acta | volume = 25 | issue = 1 | pages = 220–221 | date = July 1957 | pmid = 13445756 | doi = 10.1016/0006-3002(57)90457-2 }} The Q-275/substance SA was later renamed ubiquinone as it was a ubiquitous quinone found in all animal tissues. In 1958, its full chemical structure was reported.{{Cite journal|vauthors=Wolf DE|date=1958|title=Coenzyme Q. I. structure studies on the coenzyme Q group|journal=Journal of the American Chemical Society|volume= 80|issue=17|page=4752|doi=10.1021/ja01550a096|bibcode=1958JAChS..80.4752W |issn=0002-7863}} Ubiquinone was later called either mitoquinone or coenzyme Q due to its participation to the mitochondrial electron transport chain. In 1966, a study reported that reduced CoQ₆ was an effective antioxidant in cells.{{cite journal | vauthors = Mellors A, Tappel AL | title = Quinones and quinols as inhibitors of lipid peroxidation | journal = Lipids | volume = 1 | issue = 4 | pages = 282–284 | date = July 1966 | pmid = 17805631 | doi = 10.1007/BF02531617 | s2cid = 2129339 }}

• Idebenone – synthetic analog with reduced oxidant-generating properties
• Mitoquinone mesylate – synthetic analog with improved mitochondrial permeability

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{{Electron transport chain}}

{{Enzyme cofactors}}

{{Antioxidants}}

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{{DISPLAYTITLE:Coenzyme Q₁₀}}

Category:Antioxidants

Category:1,4-Benzoquinones

Category:Cellular respiration

Category:Coenzymes

Category:Glycolysis

Category:Meroterpenoids

Category:Phenol ethers

Category:Polyenes