Phytanic acid

 ( Alkanoic Acids ) 

Phytanic acid (or 3,7,11,15-tetramethyl hexadecanoic acid) is a branched-chain fatty acid that humans can obtain through the consumption of dairy products, ruminant animal fats, and certain fish. Western diets are estimated to provide 50–100 mg of phytanic acid per day.Steinberg, D. Phytanic acid storage disease (Refsum's disease). In: Metabolic Basis of Inherited Disease. Edited by Stanbury JB, Wyngarden JB, Fredericksen DS, Goldstein JL, Brown MS, 5th edn. New York: McGraw Hill; 1983: 731-747. In a study conducted in Oxford, individuals who consumed meat had, on average, a 6.7-fold higher geometric mean plasma phytanic acid concentration than did vegans.

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Human pathology Unlike most fatty acids, phytanic acid cannot be metabolized by beta oxidation. Instead, it undergoes alpha oxidation in the peroxisome, where it is converted into pristanic acid by the removal of one carbon. Pristanic acid can undergo several rounds of β-oxidation in the peroxisome to form medium chain fatty acids that can be converted to carbon dioxide and water in mitochondria.

Individuals with adult Refsum disease, an autosomal recessive neurological disorder caused by mutations in the PHYH gene, have impaired α-oxidation activity and accumulate large stores of phytanic acid in their blood and tissues. This frequently leads to peripheral polyneuropathy, cerebellar ataxia, retinitis pigmentosa, anosmia, and hearing loss. Reduced exposure to phytanic acid

Phytanic acid is a branched-chain fatty acid found almost exclusively in the fat and dairy products of ruminants (cattle, sheep, goats). It is derived from phytol—released from chlorophyll and converted into phytanic acid by the rumen microbiota. Humans do not convert chlorophyll to phytanic acid in any significant amount, so the only substantial source is consumption of ruminant-derived foods.

In the general population, phytanic acid can activate nuclear receptors such as PPARα and RXR, thereby modulating gene expression and influencing lipid metabolism, inflammation, and cellular proliferation.Wanders RJA, Komen JC, Ferdinandusse S. Phytanic acid metabolism in health and disease. Biochim Biophys Acta. 2011;1811(9):498-507. doi:10.1016/j.bbalip.2011.06.006Hellgren LI. Phytanic acid–an overlooked bioactive fatty acid in dairy fat? Ann N Y Acad Sci. 2010;1190:42-49. doi:10.1111/j.1749-6632.2009.05273.x Epidemiological studies have found that higher estimates of phytanic acid intake are associated with an increased risk of aggressive prostate cancer—for example, in the Finnish Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, elevated intake was linked to a relative risk of approximately 1.4–1.8 for advanced disease (p-trend ≈ 0.06).Bradshaw PT, et al. Phytanic acid, dairy consumption, and prostate cancer risk in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Am J Clin Nutr. 2010;91(3):712-719. doi:10.3945/ajcn.2009.28202 Although evidence is not conclusive, the association is biologically plausible.

In individuals with peroxisomal disorders such as adult Refsum disease, impaired α-oxidation results in accumulation of phytanic acid in serum and tissues, which leads to peripheral neuropathy, cerebellar ataxia, retinitis pigmentosa, anosmia, and hearing loss.Jansen GA, Wanders RJ. Alpha-oxidation. Biochim Biophys Acta. 2006;1763(12):1403-1412. doi:10.1016/j.bbamcr.2006.08.038Poulos A. Very long chain fatty acids in higher animals—a review. Lipids. 1995;30(1):1-14. doi:10.1007/BF02537036 However, the potential risk of metabolic and proliferative alterations applies to the general population as well—not only to those with such rare diseases.

A plant-based diet that excludes ruminant-derived products reduces dietary phytanic acid intake to near zero, effectively eliminating this avoidable exposure

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Presence in other organisms In ruminant animals, the gut fermentation of ingested plant materials liberates phytol, a constituent of chlorophyll, which is then converted to phytanic acid and stored in fats. In contrast to observations made in , there is indirect evidence that diverse non-human , including the other than humans (, , and ), can derive significant amounts of phytanic acid from the hindgut fermentation of plant materials.

Freshwater sea sponge contain terpenoid acids such as 4,8,12-trimethyltridecanoic, phytanic and pristanic acids, which indicates that these acids may have chemotaxonomy significance for both marine and freshwater sponges.

Insects, such as the sumac flea beetle, are reported to use phytol and its metabolites (e.g. phytanic acid) as chemical deterrents against predation. These compounds originate from host plants.

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Modulator of transcription Phytanic acid and its metabolites have been reported to bind to and/or activate the transcription factors PPAR-alpha and retinoid X receptor (RXR).

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