Also see:
PUFA Increases Estrogen
PUFA and Liver Toxicity; Protection by Saturated Fats
Protective “Essential Fatty Acid Deficiency”
Quotes by Ray Peat, PhD:
“One of the essential protective functions that decline with aging is the liver’s ability to detoxify chemicals, by combining them with glucuronic acid, making them water soluble so that they can be excreted in the urine. The liver (and also the intestines and stomach) efficiently process DHA by glucuronidation.”
“Two ubiquitous carcinogenic factors that can be manipulated without toxins are the polyunsaturated fatty acids (PUFA) and estrogen. These closely interact with each other, and there are many ways in which they can be modulated.”
“Besides causing a general slowing of metabolism, aging and toxic PUFA have specific actions on the detoxifying system. The enzymes that help to detoxify PUFA and estrogen and serotonin are inhibited by both PUFA and estrogen. All systems, including blood vessels and the intestine, are made leaky by estrogen and the PUFA and their products.”
“But when the endogenous omega-9 fatty acids have been thoroughly displaced by dietary omega-6 and omega -3 fatty acids, the systemic release of fatty acids becomes an amplifier of the stress state initiated by injury or other stress. The liver, for example, decreases its detoxification of estrogen in the presence of polyunsaturated fatty acids.”
Drug Metab Dispos. 2002 May;30(5):531-3.
Glucuronidation of the dietary fatty acids, phytanic acid and docosahexaenoic acid, by human UDP-glucuronosyltransferases.
Little JM, Williams L, Xu J, Radominska-Pandya A.
Linoleic acid has recently been shown to be glucuronidated in vitro by human liver and intestinal microsomes and recombinant UGT2B7. In the present study, the dietary fatty acids (FA), phytanic acid (PA), and docosahexaenoic acid (DHA) have been used as substrates for human UDP-glucuronosyltransferases (UGTs). Both compounds were effectively glucuronidated by human liver microsomes (HLM; 1.25 +/- 0.36 and 1.12 +/- 0.32 nmol/mg x min for PA and DHA, respectively) and UGT2B7 (0.71 and 0.53 nmol/mg x min). Kinetic analysis produced relatively low K(m) values for PA with both HLM and UGT2B7 (149 and 108 microM, respectively). The K(m) for DHA glucuronidation by HLM (460 microM) was considerably higher than that for UGT2B7 (168 microM), suggesting the involvement in microsomes of other UGT isoforms in addition to UGT2B7. Glucuronidation of PA and DHA by gastrointestinal microsomes from 16 human subjects was determined. In general, both PA and DHA were glucuronidated by gastric and intestinal microsomes, and activity toward both substrates was lowest in the stomach, increased in the small intestine, and lower in the colon. However, there were large interindividual variations in UGT activity toward both substrates in all segments of the intestine, as has been seen with other substrates. Thus, PA and DHA are effective in vitro substrates for human liver, gastric and intestinal microsomes, and glucuronidation may play a role in modulating the availability of these FA as ligands for nuclear receptors.
Glucuronidation is inhibited by PUFA increasing accumulation of these fats with aging.
Biochem Pharmacol. 2004 Jan 1;67(1):191-9.
Evidence that unsaturated fatty acids are potent inhibitors of renal UDP-glucuronosyltransferases (UGT): kinetic studies using human kidney cortical microsomes and recombinant UGT1A9 and UGT2B7.
Tsoutsikos P, Miners JO, Stapleton A, Thomas A, Sallustio BC, Knights KM.
Renal ischaemia is associated with accumulation of fatty acids (FA) and mobilisation of arachidonic acid (AA). Given the capacity of UDP-glucuronosyltransferase (UGT) isoforms to metabolise both drugs and FA, we hypothesised that FA would inhibit renal drug glucuronidation. The effect of FA (C2:0-C20:5) on 4-methylumbelliferone (4-MU) glucuronidation was investigated using human kidney cortical microsomes (HKCM) and recombinant UGT1A9 and UGT2B7 as the enzyme sources. 4-MU glucuronidation exhibited Michaelis-Menten kinetics with HKCM (apparent K(m) (K(m)(app)) 20.3 microM), weak substrate inhibition with UGT1A9 (K(m)(app) 10.2 microM, K(si) 289.6 microM), and sigmoid kinetics with UGT2B7 (S(50)(app)440.6 microM) Similarly, biphasic UDP-glucuronic acid (UDPGA) kinetics were observed with HKCM (S(50) 354.3 microM) and UGT1A9 (S(50) 88.2 microM). In contrast, the Michaelis-Menten kinetics for UDPGA observed with UGT2B7 (K(m)(app) 493.2 microM) suggested that kinetic interactions with UGTs were specific to the xenobiotic substrate and the co-substrate (UDPGA). FA (C16:1-C20:5) significantly inhibited (25-93%) HKCM, UGT1A9 or UGT2B7 catalysed 4-MU glucuronidation. Although linoleic acid (LA) and AA were both competitive inhibitors of 4-MU glucuronidation by HKCM (K(i)(app) 6.34 and 0.15 microM, respectively), only LA was a competitive inhibitor of UGT1A9 (K(i)(app) 4.06 microM). In contrast, inhibition of UGT1A9 by AA exhibited atypical kinetics. These data indicate that LA and AA are potent inhibitors of 4-MU glucuronidation catalysed by human kidney UGTs and recombinant UGT1A9 and UGT2B7. It is conceivable therefore that during periods of renal ischaemia FA may impair renal drug glucuronidation thus compromising the protective capacity of the kidney against drug-induced nephrotoxicity.
