Hyocholic acid

Hyocholic acid or 3α,6α,7α-trihydroxy-5β-cholan-24-oic acid is a bile acid found as one of the main forms in pig,^[1] and at low concentrations in other species including humans.^[2][3] Hyocholic acid differs from the primary bile acids found in humans by having a third hydroxyl group in the α-conformation at the 6-position, unlike cholic acid, which has a 12-hydroxyl, and chenodeoxycholic acid which has neither a 6- or 12-hydroxyl. It also differs from the muricholic acids found in rodents, as they are 6β-hydroxylated, and can have the 7-hydroxyl in either the α- or β- positions, forming α- or β-muricholic acids.

Hyocholic acid

Names
IUPAC name 3α,6α,7α-Trihydroxy-5β-cholan-24-oic acid
Systematic IUPAC name (4R)-4-[(1R,3aS,3bS,4S,5R,5aR,7R,9aR,9bS,11aR)-4,5,7-Trihydroxy-9a,11a-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-1-yl]pentanoic acid
Other names γ-Muricholic acid; Iocholic acid
Identifiers
CAS Number	547-75-1
3D model (JSmol)	Interactive image
ChEBI	CHEBI:81244
ChEMBL	ChEMBL1908063
ECHA InfoCard	100.008.124
EC Number	208-935-8
KEGG	C17649
PubChem CID	92805
UNII	2H5H0Q47FL
CompTox Dashboard (EPA)	DTXSID20862167
InChI InChI=1S/C24H40O5/c1-13(4-7-19(26)27)15-5-6-16-20-17(9-11-23(15,16)2)24(3)10-8-14(25)12-18(24)21(28)22(20)29/h13-18,20-22,25,28-29H,4-12H2,1-3H3,(H,26,27)/t13-,14-,15-,16+,17+,18+,20+,21-,22+,23-,24-/m1/s1 Key: DKPMWHFRUGMUKF-KWXDGCAGSA-N
SMILES C[C@H](CCC(=O)O)[C@H]1CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2[C@@H]([C@@H]([C@H]4[C@@]3(CC[C@H](C4)O)C)O)O)C
Properties
Chemical formula	C24H40O5
Molar mass	408.579 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Hyocholic acid is conjugated in the liver before secretion with taurine or with glycine to give taurohyocholate or glycohyocholates. Bacterial 7α-dehydroxylation in the colon produces the secondary bile acid, hyodeoxycholic acid. Epimerization of the 7-hydroxyl to the β-position is found in ω-muricholic acid (also known as β-hyocholic acid).^[4]

The enzyme responsible for the 6-hydroxylation reaction of chenodeoxycholic acid in the pig is the cytochrome P450 CYP4A21.^[5]

Hyocholic acid can be found in humans with cholestasis^[6] and may be increased after sleeve gastrectomy for obesity.^[7]

References

1. Haslewood, GA (June 1971). "Bile salts of germ-free domestic fowl and pigs". The Biochemical Journal. 123 (1): 15–8. doi:10.1042/bj1230015. PMC 1176895. PMID 5128663.
2. Bathena, SP; Mukherjee, S; Olivera, M; Alnouti, Y (30 December 2013). "The profile of bile acids and their sulfate metabolites in human urine and serum". Journal of Chromatography B. 942–943: 53–62. doi:10.1016/j.jchromb.2013.10.019. PMID 24212143.
3. Russell DW (2003). "The enzymes, regulation, and genetics of bile acid synthesis". Annu. Rev. Biochem. 72: 137–74. doi:10.1146/annurev.biochem.72.121801.161712. PMID 12543708.
4. Hofmann, AF; Sjövall, J; Kurz, G; Radominska, A; Schteingart, CD; Tint, GS; Vlahcevic, ZR; Setchell, KD (April 1992). "A proposed nomenclature for bile acids". Journal of Lipid Research. 33 (4): 599–604. doi:10.1016/S0022-2275(20)41624-4. PMID 1527482.
5. Lundell, K; Hansson, R; Wikvall, K (30 March 2001). "Cloning and expression of a pig liver taurochenodeoxycholic acid 6alpha-hydroxylase (CYP4A21): a novel member of the CYP4A subfamily". The Journal of Biological Chemistry. 276 (13): 9606–12. doi:10.1074/jbc.M006584200. PMID 11113117.
6. van Berge Henegouwen, GP; Brandt, KH; Eyssen, H; Parmentier, G (November 1976). "Sulphated and unsulphated bile acids in serum, bile, and urine of patients with cholestasis". Gut. 17 (11): 861–9. doi:10.1136/gut.17.11.861. PMC 1411206. PMID 1001976.
7. Kindel, TL; Krause, C; Helm, MC; McBride, CL; Oleynikov, D; Thakare, R; Alamoudi, J; Kothari, V; Alnouti, Y; Kohli, R (February 2018). "Increased glycine-amidated hyocholic acid correlates to improved early weight loss after sleeve gastrectomy". Surgical Endoscopy. 32 (2): 805–812. doi:10.1007/s00464-017-5747-y. PMC 5844265. PMID 28779240.