Ubiquinone

This oil-soluble vitamin-like substance is present in most eukaryotic cells, primarily in the mitochondria. It is a component of the electron transport chain and participates in aerobic cellular respiration, generating energy in the form of ATP. Ninety-five percent of the human body?s energy is generated this way.^[1][2] Therefore, those organs with the highest energy requirements ? such as the heart and the liver ? have the highest CoQ₁₀ concentrations.^[3][4][5]

History

Coenzyme Q was first discovered by professor Fred L. Crane and colleagues at the University of Wisconsin-Madison Enzyme Institute in 1957.^[6][7] In 1958, its chemical structure was reported by Professor Karl Folkers and coworkers at Merck.^[8][7]

Chemical properties

The oxidized structure of CoQ, or Q, is given here. The various kinds of Coenzyme Q can be distinguished by the number of isoprenoid side-chains they have. The most common CoQ in human mitochondria is Q10. The image to the right has three isoprenoid units and would be called Q3.  




If Coenzyme Q is reduced by one equivalent, the following structure results, a ubisemiquinone, and is denoted QH. Note the free-radical on one of the ring oxygens (either oxygen may become a free-radical, in this case the top oxygen is shown as such).  



 
If Coenzyme Q is reduced by two equivalents, the compound becomes a ubiquinol, denoted QH2:  

Biochemical role

Electron transport chain ("UQ" visible in green near center.)

Supplementation

Because of its ability to transfer electrons and therefore act as an antioxidant, Coenzyme Q is also used as a dietary supplement. When one is younger the body can synthesize Q₁₀ from the lower-numbered ubiquinones such as Q₆ or Q₈. The elderly^[9][10] and sick may not be able to make enough, thus Q₁₀ becomes a vitamin later in life and in illness.

Mitochondrial disorders

Supplementation of Coenzyme Q₁₀ is a treatment for some of the very rare and serious mitochondrial disorders and other metabolic disorders, where patients are not capable of producing enough coenzyme Q₁₀ because of their disorder. Coenzyme Q₁₀ is then prescribed by a physician.^[11]

Migraine headaches

Supplementation of Coenzyme Q₁₀ has been found to have a beneficial effect on the condition of some sufferers of migraine headaches. So far, three studies have been done, of which two were small, did not have a placebo group, were not randomized, and were open-label,^[12] and one was a double-blind, randomized, placebo-controlled trial, which found statistically significant results despite its small sample size of 42 patients.^[13] Dosages were 150 to 300 mg/day.

Cancer

It is also being investigated as a treatment for cancer, and as relief from cancer treatment side-effects.^[14]

Brain health and neurodegenerative diseases

Recent studies have shown that the antioxidant properties of coenzyme Q₁₀ benefit the body and the brain in animal models.^[15] Some of these studies indicate that coenzyme Q₁₀ protects the brain from neurodegenerative disease such as Parkinson's,^[16] although it does not relieve the symptoms.^[17] Dosage was 300 mg per day.

Cardiac arrest

Another recent study shows a survival benefit after cardiac arrest if coenzyme Q₁₀ is administered in addition to commencing active cooling (to 32–34 degrees Celsius).^[18]

Blood pressure

There are several reports concerning the effect of CoQ₁₀ on blood pressure in human studies.^[19] In a recent meta-analysis of the clinical trials of CoQ₁₀ for hypertension, a research group led by Professor Frank Rosenfeldt (Director, Cardiac Surgical Research Unit, Alfred Hospital, Melbourne, Australia) reviewed all published trials of Coenzyme Q₁₀ for hypertension, and assessed overall efficacy, consistency of therapeutic action, and side-effect incidence. Meta-analysis was performed in 12 clinical trials (362 patients) comprising three randomized controlled trials, one crossover study, and eight open-label studies. The research group concluded that coenzyme Q₁₀ has the potential in hypertensive patients to lower systolic blood pressure by up to 17 mm Hg and diastolic blood pressure by up to 10 mm Hg without significant side-effects.^[20]

Lifespan

Studies have shown that low dosages of coenzyme Q₁₀ reduce oxidation and DNA double-strand breaks, and a combination of a diet rich in polyunsaturated fatty acids and coenzyme Q₁₀ supplementation leads to a longer lifespan in rats.^[21]

Biosynthesis

The benzoquinone portion of Coenzyme Q₁₀ is synthesized from tyrosine, whereas the isoprene sidechain is synthesized from acetyl-CoA through the mevalonate pathway. The mevalonate pathway is also used for the first steps of cholesterol biosynthesis.

Inhibition by statins and beta blockers

Coenzyme Q₁₀ shares a common biosynthetic pathway with cholesterol. The synthesis of an intermediary precursor of Coenzyme Q₁₀, mevalonate, is inhibited by some beta blockers, blood pressure-lowering medication,^[22] and statins, a class of cholesterol-lowering drugs.^[23] Statins can reduce serum levels of coenzyme Q₁₀ by up to 40%.^[24] Some research suggests the logical option of supplementation with coenzyme Q₁₀ as a routine adjunct to any treatment that may reduce endogenous production of coenzyme Q₁₀, based on a balance of likely benefit against very small risk.^[25][26]

Occurrence in nature

CoQ10 occurs in mackerel and herring fresh heart tissue in concentrations of 105-148 ?g/g. In fresh mackerel "red and white tissue," CoQ10 concentrations of 67 and 15 ?g/g, respectively, have been reported. In fresh herring tissue, an amount of 15?24 ?g/g of CoQ10 has been reported.^[27]

CoQ10 Content of various foods:^[28]

Cooking by frying reduces Q10 content from 14-32%.^[30]

References

See also

• Idebenone - synthetic analog with reduced oxidant generating properties

External links

• Coenzyme Q10 general details, treatment methods, and side effects
• An Introduction to Coenzyme Q₁₀ at University of Washington
• Possible Health Benefits of Coenzyme Q₁₀ at Oregon State University
• Study Suggests Coenzyme Q₁₀ Slows Functional Decline in Parkinson's Disease at National Institute of Neurological Disorders and Stroke

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