The influence of supplemental docosahexaenoic and arachidonic acids during pregnancy and lactation on neurodevelopment at eighteen months

Docosahexaenoic acid (DHA) and arachidonic acid (AA) are important for neurodevelopment. The effects of DHA (220 mg/day, n=41), DHA+AA (220 mg/day, n=39) or placebo (n=34) during pregnancy and lactation on neurodevelopment at 18 months, and the relations between umbilical cord DHA, AA and Mead acid and neurodevelopment were studied. An age-specific, standardized neurological assessment for the evaluation of minor neurological dysfunction (MND), and the Bayley Scales of Infant Development (BSID) were used. The intervention did not influence any of the outcomes. Umbilical venous (UV) Mead acid was negatively and n-6 fatty acids were weakly positively associated to the BSID mental developmental index. Children with simple MND had lower UV DHA compared to normally classified children. We conclude that relatively short-term maternal DHA or DHA+AA supplementation does not influence neurodevelopment at toddler age, although some parameters of brain development are related to perinatal DHA and AA status.     

Motor, mental and behavioral developments in infancy are associated with fatty acid pattern in breast milk and plasma of premature infants

The objective of this study was to investigate any association between infants' early development and PUFA concentrations in early breast milk and infants' plasma phospholipids at 44 weeks gestational age. Fifty-one premature infants were included. The quality of general movement was assessed at 3 months, and motor, mental and behavioral development at 3, 6, 10 and 18 months corrected age using Bayley's Scales of Infant Development (BSID-II). Linoleic acid, the major n-6/n-3 FA ratios, Mead acid and the EFA deficiency index in early breast milk were negatively associated with development up to 18 months of age. DHA and AA, respectively, in infants' plasma phospholipids was positively, but the AA/DHA ratio negatively, associated with development from 6 to 18 months of age. Our data suggest that the commonly found high n-6 concentration in breast milk is associated with less favorable motor, mental and behavioral development up to 18 months of age.     

Gestational age dependent changes of the fetal brain, liver and adipose tissue fatty acid compositions in a population with high fish intakes

IntroductionThere are no data on the intrauterine fatty acid (FA) compositions of brain, liver and adipose tissue of infants born to women with high fish intakes.Subjects and methodsWe analyzed the brain (n=18), liver (n=14) and adipose tissue (n=11) FA compositions of 20 stillborn infants with different gestational ages (range 8–38 weeks) born to Tanzanian women with low linoleic acid (LA) intakes and high intakes of docosahexaenoic (DHA) and arachidonic (AA) acids from local fish.Results and discussionWith advancing gestation, brain saturated-FA (SAFA; in g/100 g FA), polyunsaturated-FA (PUFA), DHA, 20:3ω6, 22:4ω6 and 22:5ω6 increased, while monounsaturated-FA (MUFA), 20:3ω9, 22:3ω9 and AA decreased. Decreasing brain AA might be caused by increasing AA-metabolism to 20:3ω6, 22:4ω6 and 22:5ω6. In the liver, SAFA, PUFA and LA increased, while MUFA decreased with gestation. The steep increase of (mostly de novo synthesized) SAFA in adipose tissue coincided with relative decreases of MUFA, PUFA, DHA, LA and AA with advancing gestation. Compared to Western infants, the currently studied African infants had higher DHA, lower AA, and a higher DHA/AA-ratio in brain and adipose tissue, while the LA content of adipose tissue was lower.ConclusionThe low LA and high DHA and AA intakes by the mothers of these infants might support optimal α-linolenic (ALA) vs. LA competition for Δ5D and Δ6D-activities and DHA vs. AA antagonism. Conversely, the Western diet, characterized by high LA and lower DHA and AA intakes, might disturb these evolutionary conserved mechanisms aiming at an optimal ω3/ω6-balance.     

Maternal and fetal brain contents of docosahexaenoic acid (DHA) and arachidonic acid (AA) at various essential fatty acid (EFA), DHA and AA dietary intakes during pregnancy in mice

We investigated essential fatty acids (EFA) and long-chain polyunsaturated fatty acids (LCP) in maternal and fetal brain as a function of EFA/LCP availability to the feto-maternal unit in mice. Diets varying in parent EFA, arachidonic acid (AA), and docosahexaenoic acid (DHA) were administered from day 3 prior to conception till day 15 of pregnancy. We concentrated on DHA, AA, Mead acid, and EFA-index [(omega-3+omega-6)/(omega-7+omega-9)] in maternal erythrocytes, maternal brain, and fetal brain. It was found that erythrocyte EFA/LCP sensitively reflects declining EFA/LCP status in pregnancy, although this decline was not apparent in maternal brain. Differences in erythrocyte EFA/LCP coincided with larger differences in fetal brain EFA/LCP as compared to EFA/LCP in maternal brain. Both maternal and fetal brains were affected by short-term EFA/LCP intake, but the developing fetal brain proved most sensitive. The inverse relationship between fetal brain AA and DHA suggests the need of a maternal dietary DHA/AA balance, at least in mice.     

Lower fetal status of docosahexaenoic acid, arachidonic acid and essential fatty acids is associated with less favorable neonatal neurological condition

Long-chain polyunsaturated fatty acids, notably arachidonic (AA) and docosahexaenoic (DHA) acids are abundant in brain and may be conditionally essential in fetal life. We investigated umbilical artery (UA) and vein (UV) fatty acid compositions and early neonatal neurological condition in 317 term infants. Neurological condition was summarized as a clinical classification and a 'neurological optimality score' (NOS). Neurologically abnormal infants (n=27) had lower UV DHA and essential fatty acid (EFA) status. NOS correlated positively with AA (UV), and EFA (UV) and DHA status (UV and UA) and negatively with 18:2omega6 and omega9 (UV), and 20:3omega9, omega7 and C18 trans fatty acids (UV and UA). UV DHA, AA, saturated fatty acids, gestational age and obstetrical optimality score explained 16.2% of the NOS variance. Early postnatal neurological condition seems negatively influenced by lower fetal DHA, AA and EFA status. C18 trans fatty acids and 18:2omega6 may exert negative effects by impairment of LCP status.     

Contrasting effects of arachidonic acid and docosahexaenoic acid membrane incorporation into cardiomyocytes on free cholesterol turnover

The preservation of a constant pool of free cholesterol (FC) is critical to ensure several functions of cardiomyocytes. We investigated the impact of the membrane incorporation of arachidonic acid (C20:4 ω6, AA) or docosahexaenoic acid (C22:6 ω3, DHA) as ω6 or ω3 polyunsaturated fatty acids (PUFAs) on cholesterol homeostasis in primary cultures of neonatal rat cardiac myocytes. We measured significant alterations to the phospholipid FA profiles, which had markedly different ω6/ω3 ratios between the AA and DHA cells (13 vs. 1). The AA cells showed a 2.7-fold lower cholesterol biosynthesis than the DHA cells. Overall, the AA cells showed 2-fold lower FC masses and 2-fold higher cholesteryl ester masses than the DHA cells. The AA cells had a lower FC to phospholipid ratio and higher triglyceride levels than the DHA cells. Moreover, the AA cells showed a 40% decrease in ATP binding cassette transporter A1 (ABCA1)-mediated and a 19% decrease in ABCG1-mediated cholesterol efflux than the DHA cells. The differences in cholesterol efflux pathways induced by AA or DHA incorporation were not caused by variations in ABCs transporter expression and were reduced when ABC transporters were overexpressed by exposure to LXR/RXR agonists. These results show that AA incorporation into cardiomyocyte membranes decreased the FC turnover by markedly decreasing the endogenous cholesterol synthesis and by decreasing the ABCA1- and ABCG1-cholesterol efflux pathways, whereas DHA had the opposite effects. We propose that these observations may partially contribute to the beneficial effects on the heart of a diet containing a high ω3/ω6 PUFA ratio.     

Effect of two doses of docosahexaenoic acid (DHA) in the diet of preterm infants on infant fatty acid status: results from the DINO trial

Formula supplemented with docosahexaenoic acid (DHA) improves retinal function of preterm infants but the optimal dose is unknown. In a randomized controlled trial we examined the effect of increasing the DHA concentration of human milk and formula on circulating fatty acids of preterm infants. Infants born <33 weeks gestation were fed high-DHA milk (1% total fat as DHA) or standard-DHA milk (0.2-0.3% DHA) until reaching their estimated due date (EDD). Milk arachidonic acid (AA) concentration was approximately 0.5% for both groups. At EDD, erythrocyte membrane phospholipid DHA was elevated in the high-DHA group compared with standard-DHA (mean+/-SD, high-DHA 6.8+/-1.2, standard-DHA 5.2+/-0.7, p<0.0005) but AA was lower (high-DHA 14.9+/-1.3, standard-DHA 16.0+/-1.2, p<0.0005). Feeding preterm infants human milk and formula with 1% DHA raises but does not saturate erythrocyte phospholipids with DHA. Milk exceeding 1% DHA may be required to increase DHA status to levels seen in term infants.     

Intrauterine, postpartum and adult relationships between arachidonic acid (AA) and docosahexaenoic acid (DHA)

Erythrocyte (RBC) fatty acid compositions from populations with stable dietary habits but large variations in RBC-arachidonic (AA) and RBC-docosahexaenoic acid (DHA) provided us with insight into relationships between DHA and AA. It also enabled us to estimate the maternal RBC-DHA (mRBC-DHA) status that corresponded with no decrease in mRBC-DHA during pregnancy, or in infant (i) RBC-DHA or mRBC-DHA during the first 3 months postpartum (DHA-equilibrium) while exclusively breastfeeding. At delivery, iRBC-AA is uniformly high and independent of mRBC-AA. Infants born to mothers with low RBC-DHA exhibit higher, but infants born to mothers with high RBC-DHA exhibit lower RBC-DHA than their mothers. This switch from ‘biomagnification’ into ‘bioattenuation’ occurs at 6 g% mRBC-DHA. At 6 g%, mRBC-DHA is stable throughout pregnancy, corresponds with postpartum infant DHA-equilibrium of 6 and 0.4 g% DHA in mature milk, but results in postpartum depletion of mRBC-DHA to 5 g%. Postpartum maternal DHA-equilibrium is reached at 8 g% mRBC-DHA, corresponding with 1 g% DHA in mature milk and 7 g% iRBC-DHA at delivery that increases to 8 g% during lactation. This 8 g% RBC-DHA concurs with the lowest risks of cardiovascular and psychiatric diseases in adults. RBC-data from 1866 infants, males and (non-)pregnant females indicated AA vs. DHA synergism at low RBC-DHA, but antagonism at high RBC-DHA. These data, together with high intakes of AA and DHA from our Paleolithic diet, suggest that bioattenuation of DHA during pregnancy and postnatal antagonism between AA and DHA are the physiological standard for humans across the life cycle.     

Gender-specific fatty acid profiles in platelet phosphatidyl-choline and -ethanolamine

Previous studies suggested that women synthesise docosahexaenoic acid (DHA) more efficiently from their precursors than men. This study investigated the relationship between diet, platelet phospholipids fatty acids and gender. Dietary intake and platelet phosphatidyl-choline (PC) and phosphatidylethanolamine (PE) fatty acids were determined in Caucasian 40 men and 34 women. Absolute and %energy intakes of arachidonic acid (AA), eicosapentaenoic acid (EPA), and DHA, and the ratios of total n-6/n-3 PUFA and linoleic/alpha-linolenic acids did not differ between the sexes. However, women had higher DHA in PC (1.19 vs 1.05 wt%, p<0.05) and PE (3.62 vs 3.21 wt%, p<0.05) than men. Also EPA (1.10 vs 0.93 wt%, p<0.05) was higher in women's PE. Conversely, men had elevated AA and total n-6 fatty acids in PC. The higher platelet DHA levels and lower platelet AA/EPA and AA/DHA ratios in women of child-bearing age compared with men, may lead to less platelet aggregation and vaso-occlusion.     

Fatty acid composition of the postmortem prefrontal cortex of adolescent male and female suicide victims

Prior epidemiological, prospective intervention, and peripheral and central fatty acid composition studies suggest that omega-3 fatty acid deficiency may be associated with the pathoaetiology of depression and suicide. In the present study, we determined the fatty acid composition of the postmortem prefrontal cortex (PFC) of adolescent male and female suicide victims and age-matched controls. Fatty acid composition (wt% total fatty acids) and concentrations (μmol/g) were determined in the postmortem PFC (Brodmann area 10) of male and female adolescent (aged 13–20 years) suicide victims (n=20) and age-matched controls (n=20) by gas chromatography. None of the major polyunsaturated fatty acids including the principle brain omega-3 fatty acid, docosahexaenoic acid (DHA), monounsaturated fatty acids, or saturated fatty acids differed significantly between adolescent suicide victims and controls before or after segregation by gender. The arachidonic acid (AA, 20:4n-6): DHA ratio and adrenic acid (22:4n-6) composition were negatively correlated with age at death in controls but not in suicides, and males exhibited a greater AA:DHA ratio irrespective of cause-of-death. These results demonstrate that adolescent male and female suicide victims do not exhibit DHA deficits in the postmortem PFC relative to age-matched controls, and suggest that suicide victims do not exhibit the normal age-related decrease in adrenic acid composition and the AA:DHA ratio.     

Plasma fatty acids of neonates born to mothers with and without gestational diabetes

Women with gestational diabetes mellitus (GDM) and their neonates have lower levels of arachidonic (AA) and docosahexaenoic (DHA) acids in red cell membranes. It is not clear if this abnormality is restricted to red cells or is a generalised problem. We have investigated plasma fatty acids of neonates (venous cord) of GDM (n=37), and non-diabetic (n=31) women. The GDMs had lower levels of dihomogamma-linolenic (20:3n-6, DHGLA) acid, summation operator n-6 metabolites, DHA and summation operator n-3 metabolites (p<0.05) in choline phosphoglycerides (CPG). They also had lower levels of AA (-4.5%), adrenic acid (22:4n-6, -13%), osbond acid (22:5n-6, -7%) and summation operator n-6 (-2.5%). There was a similar pattern in triglycerides (TG) and cholesterol esters (CE). Mead acid, a marker of generalised shortage of derived and parent essential fatty acids, was higher in CPG and TG of the GDM group by 73% and 76%. The adrenic/osbond acid (22:4n-6/22:5n-6) ratio, a biochemical marker of DHA insufficiency, was reduced in CPG (-4.5%), TG (-63%) and CE (-75%) of the GDM group. These findings, which are consistent with the previous red cell data, suggest that the neuro-visual and vascular development and function of the offspring of GDM women may be adversely affected if the levels of AA and DHA are compromised further by other factors, pre- or post-natally. Studies are required to elucidate the underlying mechanism for the reduction of the two fatty acids and to evaluate the developmental and health implications.     

Eicosapentaenoic acid decreases expression of anandamide synthesis enzyme and cannabinoid receptor 2 in osteoblast-like cells

Anandamide (AEA) is an endogenous agonist for the cannabinoid receptor 2 (CB2) which is expressed in osteoblasts. Arachidonic acid (AA) is the precursor for AEA and dietary n-3 polyunsaturated fatty acids (PUFA) are known to reduce the concentrations of AA in tissues and cells. Therefore, we hypothesized that n-3 PUFA, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which reduce AA in cells, could lower AEA in osteoblasts by altering enzyme expression of the endocannabinoid (EC) system. MC3T3-E1 osteoblast-like cells were grown for 6, 10, 15, 20, 25 or 30 days in osteogenic medium. Osteoblasts were treated with 10 μM of AA, EPA, DHA, oleic acid (OA) or EPA+DHA (5 μM each) for 72 h prior to their collection for measurement of mRNA and alkaline phosphatase (ALP) activity. Compared to vehicle control, osteoblasts treated with AA had higher levels of AA and n-6 PUFA while those treated with EPA and DHA had lower n-6 but higher n-3 PUFA. Independent of the fatty acid treatments, osteoblasts matured normally as evidenced by ALP activity. N-acyl phosphatidylethanolamine-selective phospholipase D (NAPE-PLD), fatty acid amide hydrolase (FAAH) and CB2 mRNA expression were higher at 20 days compared to 10 days. NAPE-PLD and CB2 mRNA was lower in osteoblasts treated with EPA compared to all other groups. Thus, mRNA expression for NAPE-PLD, FAAH, and CB2 increased during osteoblast maturation and EPA reduced mRNA for NAPE-PLD and CB2 receptor. In conclusion, EPA lowered mRNA levels for proteins of the EC system and mRNA for AEA synthesis/degradation is reported in osteoblasts.     

Dietary docosahexaenoic acid but not arachidonic acid influences central nervous system fatty acid status in baboon neonates

The influence of dietary docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (AA, 20:4n-6) on infant central nervous system (CNS) composition has implications for neural development, including vision, cognition, and motor function. We consider here combined results of three published studies of DHA/AA-containing formulas and breastfeeding to evaluate the CNS tissue response of baboon neonates with varied concentration and duration of DHA/AA consumption [G.Y. Diau, A.T. Hsieh, E.A. Sarkadi-Nagy, V. Wijendran, P.W. Nathanielsz, J.T. Brenna, The influence of long chain polyunsaturate supplementation on docosahexaenoic acid and arachidonic acid in baboon neonate central nervous system, BMC Med. 3 (2005) 11; A.T. Hsieh, J.C. Anthony, D.A. Diersen-Schade, et al., The influence of moderate and high dietary long chain polyunsaturated fatty acids (LCPUFA) on baboon neonate tissue fatty acids, Pediatr. Res. 61 (2007) 537–45; E. Sarkadi-Nagy, V. Wijendran, G.Y. Diau, et al., The influence of prematurity and long chain polyunsaturate supplementation in 4-week adjusted age baboon neonate brain and related tissues, Pediatr. Res. 54 (2003) 244–252]. A total of 43 neonates born spontaneously at term, or preterm by Cesarean section, consumed diets with DHA–AA (%w/w) at several levels: none (0,0), moderate (0.3, 0.6), or high (>0.6, 0.67 or 1.2). CNS fatty acids were analyzed at 4 and 12 weeks postpartum for term baboons and 7.5 weeks for preterm neonates. CNS DHA was consistently greater by 5–30% in neonates consuming DHA and nearer 30% for cortex. In contrast, CNS AA was unaffected by dietary AA and decreased in all structures with age. Dietary DHA consistently supports greater CNS DHA and maintenance of cortex DHA concentration with feeding duration, while CNS AA is not related to dietary supply. These data on structure-specific LCPUFA accretion may provide insight into neural mechanisms responsible for suboptimal functional outcomes in infants consuming diets that do not support the highest tissue DHA levels.     

Comparison of bloodstream fatty acid composition from African-American women at gestation, delivery, and postpartum

Our aim was to examine the docosahexaenoic acid (DHA; 22:6n-3) status of pregnant African-American women reporting to the antenatal clinic at Wayne State University in a longitudinal study design. Fatty acid compositions of plasma and erythrocyte total lipid extracts were determined and food frequency surveys were administered at 24 weeks of gestation, delivery, and 3 months postpartum for participants (n = 157). DHA (mean +/- SD) in the estimated total circulating plasma was similar at gestation (384 +/- 162 mg) and delivery (372 +/- 155 mg) but was significantly lower at 3 months postpartum (178 +/- 81 mg). The relative weight percentage of DHA and docosapentaenoic acid n-6 (DPAn-6; 22:5n-6) decreased postpartum, whereas their respective metabolic precursors, eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (AA; 20:4n-6), increased. Similar results were found in erythrocytes. Dietary intake of DHA throughout the study was estimated at 68 +/- 75 mg/day. The relative amounts of circulating DHA and DPAn-6 were increased during pregnancy compared with 3 months postpartum, possibly via increased synthesis from EPA and AA. The low dietary intake and blood levels of DHA in this population compared with others may not support optimal fetal DHA accretion and subsequent neural development.     

Arachidonic acid and Docosahexanoic acid enhance platelet formation from human apheresis-derived CD34+ cells

An Aberration in megakaryopoiesis and thrombopoiesis, 2 important processes that maintain hemostasis, leads to thrombocytopenia. Though platelet transfusions are used to treat this condition, blood banks frequently face a shortage of platelets. Therefore, methods to generate platelets on a large scale are strongly desirable. However, to generate megakaryocytes (MKs) and platelets (PLTs) in numbers sufficient for clinical application, it is essential to understand the mechanism of platelet production and explore efficient strategies accordingly. We have earlier reported that the N-6 and N-3 poly-unsaturated fatty acids (PUFAs), Arachidonic acid (AA)/Docosahexanoic acid (DHA) have beneficial effect on the generation of MKs and PLTs from umbilical cord blood derived CD34⁺ cells. Here we tested if a similar effect is observed with peripheral blood derived CD34⁺ cells, which are more commonly used in transplantation settings. We found a significant enhancement in cell numbers, surface marker expression, cellular ploidy and expression of cytoskeletal components during PLT biogenesis in cultures exposed to media containing AA/DHA than control cultures that were not exposed to these PUFAs. The test cells engrafted more efficiently in NOD/SCID mice than control cells. AA/DHA appears to have enhanced MK/PLT generation through upregulation of the NOTCH and AKT pathways. Our data show that PUFAs could be valuable additives in the culture system for large scale production of platelets for clinical applications.     

Reduction of dehydroascorbic acid by homocysteine

To determine the reductive process of extracellular dehydroascorbic acid (DHA), molecules (homocysteine, homocysteine thiolactone, methionine, cysteine, and homoserine) were tested to identify those with the potential to reduce DHA to ascorbic acid (AA). Homocysteine (Hcy) was the most potent of the molecules tested. The efficacy of Hcy was compared with that of other molecules able to reduce DHA (reduced glutathione (GSH) and cysteine (Cy)). Although all three molecules were able to reduce DHA, GSH and Cy were not to reduce DHA to AA at concentrations lower than 100 micromol/l, and only less than 5% DHA was reduced to AA at concentrations of 200-300 micromol/l. In contrast, Hcy reduced DHA to AA stoichiometrically at concentrations as low as 10 micromol/l. In Jurkat and U937 cells, the increasing concentrations of extracellular Hcy suppressed intracellular dehydroascorbic acid uptake, indicating that extracellular reduction of DHA by Hcy leads to decreasing extracellular DHA available for its intracellular uptake. Simultaneous oxidation and reduction of Hcy and DHA were accelerated extracellularly in the presence of quercetin, an inhibitor of DHA uptake, suggesting that extracellular ascorbic acid concentration increased via blocking DHA uptake by quercetin and reducing extracellular DHA by Hcy. The effect of homocysteine on DHA reduction and uptake was confirmed with human umbilical vein endothelial cells. The oxidation of Hcy also prevented the decrease in DNA synthesis in human umbilical vein endothelial cells, which would occur following exposure to Hcy.     

Effect of supplementation of arachidonic acid (AA) or a combination of AA plus docosahexaenoic acid on breastmilk fatty acid composition

We investigated whether supplementation with arachidonic acid (20:4 omega 6; AA), or a combination of AA and docosahexaenoic acid (22:6 omega 3; DHA) would affect human milk polyunsaturated fatty acid (PUFA) composition. Ten women were daily supplemented with 300 mg AA, eight with 300 mg AA, 110 mg eicosapentaenoic acid (20:5 omega 3; EPA) and 400 mg DHA, for one week and eight women served as unsupplemented controls. Milk samples were collected on days 0, 1 and 7. The fatty acid composition of the milk was analyzed by capillary gas chromatography with flame ionisation detection. Supplementation with AA alone had no effect on breastmilk AA, but tended to reduce EPA and DHA levels. Administration of a combination of AA, EPA and DHA tended to increase both milk AA and long chain PUFA (LCPUFA)omega 3 content. A larger simultaneous increase of milk AA, DHA and EPA than observed in the present study can probably be accomplished by the use of a combination of a lower LCPUFA omega 6/LCPUFA omega 3 ratio and higher AA, EPA and DHA dosages.     

Ascorbic acid and development of xylem and phloem cells in the pine trunk

Changes in the levels of ascorbic acid (AA), its oxidized form, dehydroascorbic acid (DHA), and uronic acids as initial precursors for the AA synthesis were studied as related to the degree of xylem and phloem cell development in the course of early and late wood formation in the trunks of Scots pine (Pinus sylvestris L.). The cells of mature and conducting phloem, cambial zone, differently developed cells in the zones of cell enlargement and maturation were obtained by successive scraping tissue layers from trunk segments of 20–25-year-old trees; tissue identification was checked anatomically and histochemically. The contents of compounds tested were calculated per dry weight and per cell basis. We found great differences in the contents of AA and DHA and also in their ratio in dependence of the wood type developing in the pine trunks during growth period and on the stage of differentiation of xylem and phloem cells. Changes in the AA content during xylem cell differentiation were accompanied by changes in the content of uronic acids. The amounts of AA, DHA, and uronic acids were the highest at the stage of early lignification and reduced with tracheid maturation. The AA to DHA ratio changed differently in the course of early and late xylem lignification. It reduced from the start of lignification to the formation of early mature xylem and, in contrast, increased in mature late wood; this indicates a difference in the level of redox processes in these tissues.