1. Biosynthesis of docosahexaenoic acid (DHA, 22:6-4, 7,10,13,16,19): two distinct pathways
Xiao Qiu Prostaglandins Leukot Essent Fatty Acids. 2003 Feb;68(2):181-6.doi: 10.1016/s0952-3278(02)00268-5.
Docosahexaenoic acid (DHA) has long been recognized for its beneficial effect in humans, but its biosynthetic pathway has not been clearly established until recently. According to Sprecher, in mammals, DHA is synthesized via a retro-conversion process in peroxisomes-the aerobic delta4 desaturation-independent pathway. Recent identification of a Thraustochytrium delta4 desaturase indicates that delta4 desaturation is indeed involved in DHA synthesis in Thraustochytrium. More interestingly, an alternative pathway for DHA biosynthesis-the anaerobic polyketide synthase pathway was also reported recently to occur in Schizochytrium, another member of the Thraustochytriidae. This mini-review attempts to assess the latest research on these distinct pathways for DHA biosynthesis.
2. Development of certified reference materials for four polyunsaturated fatty acid esters
Weizhu Chen, Wenhui Jin, Yiping Zhang, Hua Fang, Hui Chen, Zhuan Hong, Xiaoyan Huang Food Chem. 2022 Sep 30;389:133006.doi: 10.1016/j.foodchem.2022.133006.Epub 2022 Apr 20.
Certified reference materials (CRMs) with high accuracy and traceability are essential tools for the validation of analytical methods and calibration of equipment. In this study, purity CRMs for four polyunsaturated fatty acids (PUFAs) esters, namely, cis-(4,7,10,13,16,19)- Docosahexaenoic acid methyl ester (DHA-ME), cis-4,7,10,13,16,19- Docosahexaenoic acid ethyl ester (DHA-EE), cis-(5,8,11,14,17)- Eicosapentaenoic acid methyl ester (EPA-ME) and cis-(5,8,11,14,17)- Eicosapentaenoic acid ethyl ester (EPA-EE), were first developed according to the ISO Guide. The CRMs' purity values were assigned based on the average of quantitative nuclear magnetic resonance and mass balance approaches. The certified value with expanded uncertainties (k = 2, 95% confidence interval) were determined to be (98.8 ± 0.4) %, (99.0 ± 0.3) %, (98.9 ± 0.4) % and (98.9 ± 0.4) % for DHA-ME, DHA-EE, EPA-ME and EPA-EE, respectively. The four PUFAs esters were homogeneous and stable for 12 months at -4 °C and 7 days at 50 °C.
3. Effect of 4,7,10,13,16,19-docosahexaenoic acid on triglyceride accumulation and secretion in rat hepatocytes in culture
L J Martin, G B Reaidi, G R Gavino, V C Gavino Lipids. 1991 May;26(5):374-80.doi: 10.1007/BF02537202.
We have investigated the effect of oleic (18:1) and 4,7,10,13,16,19-docosahexaenoic (22:6 omega 3) acids on triglyceride (TG) accumulation, secretion and reuptake in rat hepatocytes in culture. We also calculated the percentage of total TG, TG-esterified 18:1 and TG-esterified 22:6 omega 3 that were secreted relative to the total accumulation (intra + extracellular TG). Both fatty acids were incorporated mainly in the intracellular TG fraction. Treatment with 18:1 but not with 22:6 omega 3 increased the quantity of TG secreted into the culture medium relative to controls. Treatment with 22:6 omega 3 caused a greater accumulation of intracellular TG than 18:1. This arises in part from the preferential retention of 22:6 omega 3-enriched TG by the hepatocytes. At 24 hr, there was no longer any difference in the net secretion of TG by 18:1 and 22:6 omega 3-treated cells, which may be a consequence of the reuptake of TG-esterified 18:1. There was no reuptake of TG-esterified 22:6 omega 3. We conclude that inhibition of hepatocyte TG synthesis is not obligatory for 22:6 omega 3-induced diminution of TG secretion.
