Phytanic acid

Human pathology

Unlike most fatty acids, phytanic acid cannot be metabolized by β-oxidation. Instead, it undergoes α-oxidation in the peroxisome, where it is converted into pristanic acid by the removal of one carbon.{{Cite journal

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.{{Cite journal 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. 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). 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. 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

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.{{Cite journal | doi-access = free | doi-access = free

Freshwater sponges contain terpenoid acids such as 4,8,12-trimethyltridecanoic, phytanic and pristanic acids, which indicates that these acids may have chemotaxonomical 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.

Modulator of transcription

Phytanic acid and its metabolites have been reported to bind to and/or activate the transcription factors PPAR-alpha{{Cite journal | doi-access = free

References

References

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2. 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.
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5. 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
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8. (1993). "Isoprenoid polyunsaturated fatty acids from freshwater sponges". Journal of Natural Products.
9. (1998). "The shield defense of the sumac flea beetle, Blepharida rhois (Chrysomelidae: Alticinae)". Chemoecology.