Towards an Optimized Fetal DHA Accretion: Differences on Maternal DHA Supplementation Using Phospholipids vs. Triglycerides during Pregnancy in Different Models

Docosahexaenoic acid (DHA) supplementation during pregnancy has been recommended by several health organizations due to its role in neural, visual, and cognitive development. There are several fat sources available on the market for the manufacture of these dietary supplements with DHA. These fat sources differ in the lipid structure in which DHA is esterified, mainly phospholipids (PL) and triglycerides (TG) molecules. The supplementation of DHA in the form of PL or TG during pregnancy can lead to controversial results depending on the animal model, physiological status and the fat sources utilized. The intestinal digestion, placental uptake, and fetal accretion of DHA may vary depending on the lipid source of DHA ingested by the mother. The form of DHA used in maternal supplementation that would provide an optimal DHA accretion for fetal brain development, based on the available data obtained most of them from different animal models, indicates no consistent differences in fetal accretion when DHA is provided as TG or PL. Other related lipid species are under evaluation, e.g., lyso-phospholipids, with promising results to improve DHA bioavailability although more studies are needed. In this review, the evidence on DHA bioavailability and accumulation in both maternal and fetal tissues after the administration of DHA supplementation during pregnancy in the form of PL or TG in different models is summarized.     

Dietary long-chain polyunsaturated fatty acids from different sources affect fat and fatty acid excretions in rats.

Several sources of long-chain polyunsaturated fatty acids (LCP) have been evaluated for infant-formula supplementation. These sources differ in their chemical structure [triglyceride (TG) or phospholipid (PL)], arrangement of fatty acids on the TG or PL backbone, fatty acid composition and presence of other lipid components. All of these characteristics influence fat digestion, may affect fat and fatty acid absorption, and hence, LCP bioavailability and metabolism in infancy. The main objective of this work was to establish the influence of different dietary LCP sources on overall fat and LCP absorption in early life. We compared fat and fatty acid excretions at weaning in rats fed control diets or diets supplemented with LCP as TG or PL. Two separate experiments were conducted. In Experiment 1, weanling rats were fed for 3 wk a control diet (C1), a diet with TG from tuna and fungal oils (TF-TG) or a diet with PL from pig brain concentrate (PB-PL). In Experiment 2, weanling rats were fed for 3 wk a control diet (C2), a diet containing egg-TG (EG-TG) or a diet containing egg-PL (EG-PL). Fat, mineral and saturated fatty acid excretions in feces were higher in rats fed PB-PL compared with those fed TF-TG diet. In Experiment 2, groups did not differ in fat and mineral excretions. However, the EG-PL group had lower fecal excretions of saturated fatty acids than the C2 and EG-TG groups. The 16:1(n-7), 18:1(n-9), 18:2(n-6) and 22:6(n-3) levels in feces were higher in the EG-TG group than in the EG-PL group. In summary, total fat and LCP excretions differed among rats fed diets supplemented with LCP from different sources.     

High Fat Diet Administration during Specific Periods of Pregnancy Alters Maternal Fatty Acid Profiles in the Near-Term Rat

Excessive fat intake is a global health concern as women of childbearing age increasingly ingest high fat diets (HFDs). We therefore determined the maternal fatty acid (FA) profiles in metabolic organs after HFD administration during specific periods of gestation. Rats were fed a HFD for the first (HF1), second (HF2), or third (HF3) week, or for all three weeks (HFG) of gestation. Total maternal plasma non-esterified fatty acid (NEFA) concentrations were monitored throughout pregnancy. At day 20 of gestation, maternal plasma, liver, adipose tissue, and placenta FA profiles were determined. In HF3 mothers, plasma myristic and stearic acid concentrations were elevated, whereas docosahexaenoic acid (DHA) was reduced in both HF3 and HFG mothers. In HF3 and HFG mothers, hepatic stearic and oleic acid proportions were elevated; conversely, DHA and linoleic acid (LA) proportions were reduced. In adipose tissue, myristic acid was elevated, whereas DHA and LA proportions were reduced in all mothers. Further, adipose tissue stearic acid proportions were elevated in HF2, HF3, and HFG mothers; with oleic acid increased in HF1 and HFG mothers. In HF3 and HFG mothers, placental neutral myristic acid proportions were elevated, whereas DHA was reduced. Further, placental phospholipid DHA proportions were reduced in HF3 and HFG mothers. Maintenance on a diet, high in saturated fat, but low in DHA and LA proportions, during late or throughout gestation, perpetuated reduced DHA across metabolic organs that adapt during pregnancy. Therefore a diet, with normal DHA proportions during gestation, may be important for balancing maternal FA status.     

Water maze performance is unaffected in artificially reared rats fed diets supplemented with arachidonic acid and docosahexaenoic acid

Four groups of male Long-Evans rats were reared artificially from postnatal d 5 to 18 by being fed through a gastrostomy tube with rat milk substitutes containing oils providing 10% linoleic acid and 1% alpha-linolenic acid (g/100 g fat); with the use of a 2 x 2 design, they were fed one of two levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) (0.0 and 2.5 g/100 g of fatty acids). A fifth artificially reared group was fed a diet high in saturated fat, and a sixth group was reared by dams fed a standard AIN-93M diet. The pups were weaned onto modified AIN-93G diets, with a fat composition similar to that fed during the artificial rearing period. Behavioral testing was conducted between 6 and 9 wk of age; brain lipid composition was then assessed. Relative to the unsupplemented group (0.0 g/100 g AA and DHA), dietary supplementation resulted in a wide range of AA (84-103%) and particularly DHA (86-119%) levels in forebrain membrane phospholipids. AA supplementation increased AA levels and decreased DHA levels, and DHA supplementation increased DHA levels and decreased AA levels, with the magnitude of these effects dependent on the level of the other fatty acid. DHA levels were very low in the saturated fat group. The groups did not differ on the place or cued version of the Morris water-maze, but on a test of working memory, the saturated fat group was impaired relative to the suckled control group. Further correlational analyses in the artificially reared animals did not support a relationship between the wide range of DHA and AA levels in the forebrain and working-memory performance.     

Maternal parity and diet (n-3) polyunsaturated fatty acid concentration influence accretion of brain phospholipid docosahexaenoic acid in developing rats

The long-chain PUFA, docosahexaenoic acid [22:6(n-3), DHA], a major component of neuronal membrane phospholipids, accumulates in brain during late prenatal and early neonatal development and is essential for optimal attentional and cognitive function. Because all nutrition is supplied to the developing fetus/neonate by the mother and maternal DHA status is affected by parity, this study examined the effects of maternal diet and parity on DHA accretion in the developing brain. Whole brain total phospholipid fatty acid composition was determined by TLC and GC in weanling male Long-Evans rats (n = 5) from the 1st, 2nd, 3rd, or 4th litters of dams fed diets containing alpha-linolenic acid (ALA), containing ALA and preformed DHA (ALA + DHA), or lacking ALA (low-ALA). First-litter low-ALA offspring exhibited a decrease in phospholipid fatty acid DHA content to 68% of 1st-litter ALA pups. DHA in 2nd-litter low-ALA pups was further decreased to 55% of 1st-litter ALA pups, but further decreases were not observed in subsequent litters. DHA levels increased 15-20% in 2nd to 4th-litter ALA + DHA pups and 11% in 4th-litter ALA pups compared with 1st-litter ALA pups. These findings demonstrate that maternal diet and parity interact to affect offspring brain DHA status and suggest that maternal multiparity may place offspring at greater risk of decreased accretion of brain DHA if the maternal diet contains insufficient (n-3) PUFA.     

Plasma or red blood cell phospholipids can be used to assess docosahexaenoic acid status in women during pregnancy

The suitability of using plasma phopholipids (PLs) to assess docosahexaenoic acid (DHA) status during pregnancy is well accepted. Recent discussions have centered around whether red blood cells (RBCs) can be used to indicate DHA status. We tested the hypothesis that in pregnant women participating in an intervention study when fed a functional food containing DHA, maternal plasma PL DHA would be positively associated with maternal RBC PL and umbilical cord blood RBC PL DHA. Maternal and umbilical cord blood samples were obtained at delivery from women whose mean dietary intake was 187 mg/d (including the amount consumed from the DHA-functional food). Maternal plasma and RBCs and cord blood RBC lipids were extracted and PLs separated by thin-layer chromatography. Phopholipid lipids were methylated, and fatty acids were identified using gas chromatography. Fifty-nine maternal samples and 30 cord blood samples were analyzed. There were moderate to strong correlations between DHA in all compartments (maternal plasma vs maternal RBC PL DHA weight percent [wt%], r = 0.633, P ≤ .001; maternal plasma vs cord blood RBC PL DHA wt%, r = 0.458, P ≤ .01; maternal RBCs vs cord blood RBC PL DHA wt%, r = 0.376, P ≤ .01). These results support the practice of using either plasma PLs or RBC PLs to assess maternal and infant DHA status.     

孕期补充二十二碳六烯酸对母鼠脂肪代谢及CPT-Ⅰ mRNA表达的影响

目的探讨孕期补充二十二碳六烯酸(DHA)对母鼠脂肪代谢和肉碱棕榈酰转移酶-Ⅰ(CPT-Ⅰ)mRNA表达的影响。方法将SD雌鼠按体重随机分成A、B、C3组,孕期分别食用补充高剂量DHA膳食(A)、补充低剂量DHA膳食(B)、普通膳食(C),待母鼠分娩,实验结束。观察母鼠妊娠期间体重变化及各组子鼠出生数量、出生体重情况,检测母鼠产后肾周脂肪含量、血清甘油三酯(TG)、血清总胆固醇(TC)、血清高密度脂蛋白(HDL-C)水平、瘦素(Leptin)及肝脏组织中CPT-ⅠmRNA的表达丰度。结果各组孕鼠妊娠时间、产子数量、子鼠出生体重均无明显差异,但A、B组的母鼠产后血清甘油三酯水平低于C组;A组母鼠孕期增重量、肾周脂肪含量、总胆固醇、瘦素水平均明显低于C组;A、B组母鼠产后肝脏组织的CPT-ⅠmRNA水平高于C组。结论孕期补充DHA有调节母体血脂、减少体内脂肪含量的作用,而CPT-Ⅰ基因表达的上调可能是其一潜在机制。     

Low arachidonic acid rather than alpha-tocopherol is responsible for the delayed postnatal development in offspring of rats fed fish oil instead of olive oil during pregnancy and lactation

This study was designed to compare in rats the effects of dietary fish oil and olive oil during pregnancy and lactation on offspring development, fatty acid profile and vitamin E concentration. From d 0 of pregnancy, female Sprague-Dawley rats were divided into two groups that were fed purified diets that differed only in their nonvitamin lipid components. One diet contained 10 g fish oil/100 g diet (FOD), whereas the other contained 10 g olive oil/100 g diet (OOD). At d 20 of gestation, maternal adipose tissue fatty acid profile did not differ between rats fed the two diets, whereas both maternal and fetal plasma and liver arachidonic acid (AA) contents were proportionally lower and eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid contents were higher in the FOD group than in the OOD group. alpha-Tocopherol concentration was lower in maternal and fetal plasma, liver and brain in the FOD group than in the OOD group. The postnatal increase in body weight and length was less and body and psychomotor maturation indices were delayed in pups from FOD-fed dams compared with those from OOD-fed dams. This difference was maintained when pups were cross-fostered at birth, with the delay in postnatal development present in the pups suckling dams fed FOD during lactation. At age 21 d, pups suckling dams fed FOD had lower AA and higher EPA and DHA concentrations in brain phospholipids. Although alpha-tocopherol in plasma and liver was lower in pups suckling dams fed FOD rather than OOD, brain alpha-tocopherol concentrations did not differ. Milk yield and milk alpha-tocopherol and AA concentrations were lower and EPA and DHA were higher in the milk of dams fed FOD compared with those fed OOD. Postnatal development indices and the proportion of plasma, liver and brain AA concentrations, although not plasma, liver and brain alpha-tocopherol concentrations, recovered to the values found in dams fed OOD when the FOD was supplemented with gamma-linolenic acid. However, postnatal development indices were not recovered when the FOD was supplemented with sufficient exogenous vitamin E to increase plasma and liver alpha-tocopherol concentrations above those in dams fed OOD. Thus, although feeding FOD during pregnancy and lactation decreases both alpha-tocopherol and AA concentrations, the latter deficiency rather than the former seems to be responsible for delayed postnatal development of rat pups.     

Long-Term Effect of Docosahexaenoic Acid Feeding on Lipid Composition and Brain Fatty Acid-Binding Protein Expression in Rats

Arachidonic (AA) and docosahexaenoic acid (DHA) brain accretion is essential for brain development. The impact of DHA-rich maternal diets on offspring brain fatty acid composition has previously been studied up to the weanling stage; however, there has been no follow-up at later stages. Here, we examine the impact of DHA-rich maternal and weaning diets on brain fatty acid composition at weaning and three weeks post-weaning. We report that DHA supplementation during lactation maintains high DHA levels in the brains of pups even when they are fed a DHA-deficient diet for three weeks after weaning. We show that boosting dietary DHA levels for three weeks after weaning compensates for a maternal DHA-deficient diet during lactation. Finally, our data indicate that brain fatty acid binding protein (FABP7), a marker of neural stem cells, is down-regulated in the brains of six-week pups with a high DHA:AA ratio. We propose that elevated levels of DHA in developing brain accelerate brain maturation relative to DHA-deficient brains.     

Comparison of the effects of dietary glucose versus galactose on porcine feto-placental glucose metabolism

The present study was conducted to determine whether dietary galactose can be used to improve glycogen and lipid accretion in fetal pigs. Pregnant gilts were fed diets containing either 24% glucose (control) or 24% galactose from d 98 to 110 of gestation. Gilts underwent abdominohysterotomy on d 110 of gestation. Slices of fetal subcutaneous adipose tissue and placenta were examined for metabolic capacity for glucose and for galactose utilization. No effects of maternal diet were evident upon glycogen content or enzyme activity of fetal semitendinosus muscle and liver. Maternal dietary galactose had no direct effects upon placental glucose oxidation or use for lipid synthesis. However, galactose supplementation of the incubation medium caused reductions in glucose oxidation (15%) and total lipid synthesis (24%) by the maternal placenta. Maternal dietary galactose caused an increase in total lipid (50%) and fatty acid synthesis (200%) from glucose in fetal subcutaneous adipose tissue; direct supplementation of galactose to the incubation medium had no effect on these parameters. The results of the present study suggest that feeding galactose to the pregnant gilt does not have direct effects upon placental metabolism or fetal glycogen storage. However, these data indicate that use of galactose in the maternal diet can result in an increase in the utilization of glucose for lipogenesis by fetal adipose tissue in swine. This effect is not a direct effect of galactose because transport across the placenta was not apparent.     

孕鼠补充二十二碳六烯酸对仔鼠肝脏肉碱棕榈酰转移酶-I mRNA表达的影响

目的 研究孕鼠补充二十二碳六稀酸(DHA)对仔鼠脂肪代谢及肉碱棕榈酰转移酶-I(CPT-I)mRNA水平的影响.方法 成年SD雌鼠随机分成A、B、C三组,待其妊娠后A组给予基础饲料、B组补充低剂量的DHA(1g/kg bw),C组补充高剂量的DHA(2g/kg bw).所有雄性仔鼠出生后均由A组母鼠哺乳,断乳后给予基础饲料喂饲至出生后第8周.每组8只,动态观察仔鼠的体重、体脂含量、甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白(HDL-C)7L CPT-I mRNA水平.结果 三组仔鼠的出生体重差异无显著性(P>0.05);仔鼠出生后的第8周时,C组的体重显著低于A组(P<0.05),B、C组的体脂含量、TG水平显著低于A组(P<0.05).而C组HDL-C水平显著高于A组(P<0.05),但三组TC水平差异无显著性(P>0.05).动态观察表明,肝脏CPT-I mRNA水平持续性出现B、C高于A组,C组高于B组.结论 孕期补充DHA可能通过持续性上调仔鼠肝脏CPT-I基因表达来增强脂肪酸的氧化,降低血脂水平,但孕期摄入过量的DHA可能对子代产生不利影响.     

Effect of reduced dietary protein intake on hepatic and plasma essential fatty acid concentrations in the adult female rat: effect of pregnancy and consequences for accumulation of arachidonic and docosahexaenoic acids in fetal liver and brain

During pregnancy, the accumulation of long-chain polyunsaturated fatty acids (LCPUFA) in fetal tissues places a substantial demand upon maternal lipid metabolism. As lipid metabolism is intimately linked to aspects of protein metabolism, a reduced protein intake in pregnancy may impair activities of enzymes and transport proteins responsible for supplying LCPUFA to the fetus, thereby compromising fetal development. We have investigated the effect of reduced protein intake on LCPUFA status in the non-pregnant rat and in the pregnant rat, and in fetus at day 20 of gestation. Female rats (n 5 per group) were either mated and fed the control diet (180 g protein/kg) or low-protein diet (90 g protein/kg, LPD) diet throughout pregnancy, or fed the control diet or LPD for 20 d (non-pregnant animals). The fatty acid compositions of maternal liver and plasma, and fetal liver and brain were determined by GC. Feeding the LPD did not lead to any gross changes either in adult or fetal growth, or in total lipid concentrations in adult rat liver. However, the LPD was associated specifically with lower liver (42.6 %) and plasma (19.4 %) phosphatidylcholine (PC), and plasma triacylglycerol (28.6 %) docosahexaenoic acid (DHA) concentrations in pregnant rats and reduced fetal brain PC- (26.1 %) and phosphatidylethanolamine- (25.6 %) DHA concentrations. Together, these results show that variations in maternal dietary protein consumption alter DHA status in pregnancy and modify DHA accumulation into the fetal brain. The present results suggest that lower maternal protein intakes reduce delivery of DHA from the mother to the fetus, which may impair development and function of the fetal brain.     

Maternal docosahexaenoic acid supplementation decreases lung inflammation in hyperoxia-exposed newborn mice

DHA is a long-chain fatty acid that has potent antiinflammatory properties. Whereas maternal DHA dietary supplementation has been shown to improve cognitive development in infants fed DHA-supplemented milk, the antiinflammatory effects of maternal DHA supplementation on the developing fetus and neonate have not been extensively explored. Pregnant C3H/HeN dams were fed purified control or DHA-supplemented diets (~0.25% of total fat) at embryonic d 16 and consumed these diets throughout the study. At birth, the nursing mouse pups were placed in room air (RA; 21% O(2)) or >95% O(2) (hyperoxia) for up to 7 d. These studies tested the hypothesis that maternal DHA supplementation would decrease inflammation and improve alveolarization in the lungs of newborn mouse pups exposed to hyperoxia. Survival, inflammatory responses, and lung growth were compared among control diet/RA, DHA/RA, control/O(2), and DHA/O(2) pups. There were fewer neutrophils and macrophages in lung tissues from pups nursed by DHA-supplemented dams than in those nursed by dams fed the control diet at 7 d of hyperoxia exposure (P < 0.015). Although differences due to hyperoxia exposure were observed, maternal diet did not affect keratinocyte-derived chemokine, macrophage inflammatory protein-2, IL-1β, or TNFα mRNA levels in pup tissues. Hyperoxia also induced NF-κB activity, but maternal diet did not affect NF-κB or PPARγ activities. In mice, DHA supplementation decreases leukocyte infiltration in the offspring exposed to hyperoxia, suggesting a potential role for DHA supplementation as a therapy to reduce inflammation in preterm infants.     

Critical differences between two low protein diet protocols in the programming of hypertension in the rat

Maternal nutrition has been identified as a factor determining fetal growth and risk of adult disease. In rats, the feeding of a low protein diet during pregnancy retards fetal growth and induces hypertension in the resulting offspring. Rat models of low protein feeding have been extensively used to study the mechanisms that may link maternal nutrition with impaired fetal growth and later cardiovascular disease and diabetes. Low protein diets of differing composition used in different laboratories have yielded inconsistent data on the relationship between maternal protein intake and offsprings' blood pressure. Two separate low protein diet protocols were compared in terms of their ability to programme hypertension during fetal life. Pregnant rats were assigned to receive one of four diets. Two diets were obtained from a commercial supplier and provided casein at 22 or 9% by weight (H22, control; H9, low protein). The other two diets, manufactured in our own facility, provided 18% casein (S18, control) or 9% casein (S9, low protein) by weight. The diets differed principally in their overall fat content, fatty acid composition, methionine content and the source of carbohydrate. Feeding of the experimental diets commenced on the first day of pregnancy and continued until the rats delivered their litters. Following weaning all the offspring had blood pressure determined on a single occasion. Both low protein diets reduced maternal weight gain relative to their corresponding control diets. Despite this litter sizes were unaffected by the dietary protocols. Both low protein diets reduced birthweights of the pups. Systolic blood pressure was significantly elevated in the offspring of rats fed a low protein S9 diet relative to all other groups (P < 0.05). Animals exposed to H9 diet in utero had similar blood pressures to their H22 controls. It is concluded from this work that differing low protein diet manipulations in rat pregnancy elicit different programming effects upon the developing cardiovasculature. The balance of protein and other nutrients may be a critical determinant of the long-term health effects of maternal undernutrition in pregnancy.     

Dietary fatty acid and protein effects on plasma and liver lipids

Groups of six-day-old female chicks fed semi-synthetic diets containing 14% free fatty acid were evaluated for plasma and liver cholesterol (C), phospholipid (PL), and triglyceride (TG) content. Six different fatty acids (lauric, myristic, palmitic, stearic, oleic and linoleic) were tested at two levels (12.8% and 24.8%) of protein for two different treatment periods (15 and 30 days) in the form of a 3 factorial experimental design. Analysis of variance, F test revealed that treatment duration, dietary protein level, and difference in dietary fatty acid all had significant (p<.05) effects on plasma and/or liver lipid. Compared to 15 days of treatment, 30 day treatment reduced plasma C and PL, but increased liver C and PL. Compared to 12.8% dietary protein, 24.8% protein reduced plasma C and PL, but had no effect on liver lipid. Differences between the individual fatty acids tested were elicited primarily in plasma and liver TG and PL; no significant effect was found in plasma C. Multiple comparison of group means revealed that the significant dietary fat effects were due primarily to linoleic and palmitic acid in plasma, and to linoleic and lauric acid in liver.     

Effect of low carbohydrate diets during pregnancy on embryogenesis and fetal growth and development in rats

Effects in pregnant rats of feeding diets specifically deficient in carbohydrate were studied. The dietary nonprotein energy source was lipid, provided as intact fat (soybean oil) or a fatty acid mixture (edible oleic acid) or a combination of these. These diets provided 9.5% casein protein, which was shown to be minimally adequate in both the lipid-based experimental diets and the high carbohydrate control diet. The diets were fed from mating through d 21 of pregnancy, and pups were delivered by cesarean section. The soybean oil-based zero-carbohydrate diet supported embryogenesis and produced at term normal numbers of normal appearing pups of body weight lower than that of pups from the high carbohydrate control diet. In contrast, the oleic acid-based zero-carbohydrate diet failed to maintain pregnancy, indicating a requirement for carbohydrate or intact fat or both. To maintain pregnancy to term required both 5-10% intact fat and 4% carbohydrate as glucose or its equivalent amount of glycerol from lipid. From feeding graded levels of glucose in fatty acid based diets containing 5-10% intact fat as soybean oil, the carbohydrate requirement was found to be 6-8% glucose to sustain maternal food intake and weight gain and to produce normal fetal weight at term, and 12% glucose to provide approximately half the fetal liver glycogen levels in controls fed a high carbohydrate diet. These experiments have produced the first evidence of the quantitative requirement for carbohydrate for embryogenesis and fetal growth and development in the pregnant rat dam.     

Conjugated linoleic acid reduces body fat accretion and lipogenic gene expression in neonatal pigs fed low- or high-fat formulas

Childhood obesity is an increasing problem and may predispose children to adult obesity. Weight gain during infancy has been linked to excessive weight later in life. Conjugated linoleic acids (CLA) have been shown to reduce fat gain and body fat mass in animal models and in humans. The effects of CLA in a piglet model of human infancy have not been determined. The objective of this experiment was to examine the regulation of body composition and lipid metabolism in pigs fed low- and high-fat milk formulas supplemented with CLA. Twenty-four piglets were fed low- (3%) or high-fat (25%) diets with or without 1% CLA in a 2 x 2 factorial design. Formulas were fed for 16-17 d. Piglet body weight gains did not differ, although pigs fed the low-fat diets consumed greater amounts of diet. Piglets fed the high-fat formula accreted 50% more body fat during the feeding period than low-fat fed piglets and CLA reduced body fat accretion regardless of dietary fat content. Liver and muscle in vitro oxidation of palmitate was not influenced by dietary treatments. Adipose tissue expression of acetyl-CoA carboxylase-alpha and lipoprotein lipase were significantly reduced by CLA treatment. Overall, CLA reduced body fat accretion without influencing daily gain in a piglet model of human infancy. Results indicate that inhibition of fatty acid uptake and synthesis by adipose tissue, and not increased fatty acid oxidation in liver or muscle, were involved in reducing body fat gain.     

Effect of placental function on fatty acid requirements during pregnancy

The fetus has an absolute requirement for the n-3/n-6 fatty acids and docosahexaenoic acid (22:6 n-3; DHA) in particular is essential for the development of the brain and retina. Most of the fat deposition in the fetus occurs in the last 10 weeks of pregnancy. The likely rate of DHA utilisation during late pregnancy cannot be met from dietary sources alone in a significant proportion of mothers. De novo synthesis makes up some of the shortfall but the available evidence suggests that the maternal adipose tissue makes a significant contribution to placental transport to the fetus. The placenta plays a crucial role in mobilising the maternal adipose tissue and actively concentrating and channelling the important n-3/n-6 fatty acids to the fetus via multiple mechanisms including selective uptake by the syncytiotrophoblast, intracellular metabolic channelling, and selective export to the fetal circulation. These mechanisms protect the fetus against low long-chain polyunsaturated fatty acid (LCPUFA) intakes in the last trimester of pregnancy and have the effect of reducing the maternal dietary requirement for preformed DHA at this time. As a result of these adaptations, small changes in the composition of the habitual maternal diet before pregnancy are likely to be more effective in improving LCPUFA delivery to the fetus than large dietary changes in late pregnancy. There is little evidence that DHA intake/status in the second half of pregnancy affects visual and cognitive function in the offspring, but more studies are needed, particularly in children born to vegetarian and vegan and mothers who may have very low intakes of DHA.     

Dietary Fibre,Coronary Heart Disease and Diabetes Mellitus

Maternal nutrition has been identified as a factor determining fetal growth and risk of adult disease. In rats, the feeding of a low protein diet during pregnancy retards fetal growth and induces hypertension in the resulting offspring. Rat models of low protein feeding have been extensively used to study the mechanisms that may link maternal nutrition with impaired fetal growth and later cardiovascular disease and diabetes. Low protein diets of differing composition used in different laboratories have yielded inconsistent data on the relationship between maternal protein intake and offsprings' blood pressure. Two separate low protein diet protocols were compared in terms of their ability to programme hypertension during fetal life. Pregnant rats were assigned to receive one of four diets. Two diets were obtained from a commercial supplier and provided casein at 22 or 9% by weight (H22, control; H9, low protein). The other two diets, manufactured in our own facility, provided 18% casein (S18, control) or 9% casein (S9, low protein) by weight. The diets differed principally in their overall fat content, fatty acid composition, methionine content and the source of carbohydrate. Feeding of the experimental diets commenced on the first day of pregnancy and continued until the rats delivered their litters. Following weaning all the offspring had blood pressure determined on a single occasion. Both low protein diets reduced maternal weight gain relative to their corresponding control diets. Despite this litter sizes were unaffected by the dietary protocols. Both low protein diets reduced birthweights of the pups. Systolic blood pressure was significantly elevated in the offspring of rats fed a low protein S9 diet relative to all other groups (P < 0.05). Animals exposed to H9 diet in utero had similar blood pressures to their H22 controls. It is concluded from this work that differing low protein diet manipulations in rat pregnancy elicit different programming effects upon the developing cardiovasculature. The balance of protein and other nutrients may be a critical determinant of the long-term health effects of maternal undernutrition in pregnancy.     

Gestational alcoholism and fetal zinc accretion in Long-Evans rats.

An animal study was conducted to examine the effects of alcohol consumption on placental transfer of zinc during late gestation. Throughout pregnancy, rat dams were fed a nutritionally adequate diet with 30% of total kcal as alcohol. On days 18 and 21 of pregnancy, zinc-65 was injected subcutaneously into the dams and the dams were killed 24 hours later; tissues were removed for analyses. Maternal serum, liver, kidney, and heart zinc decreased with gestational age while total fetal zinc increased. Neither the decrease in maternal organ zinc nor fetal accretion were affected by alcohol consumption. Placental zinc concentration also declined with developmental age and was not influenced by alcohol consumption. The decrease in placental zinc was accompanied by a decrease in zinc associated with 4-10-kD proteins of placental cytosol. Our results suggest that zinc flux during late rat gestation is a well-regulated process that is not influenced by alcohol consumption. Coordination of the transfer apparently is influenced by maternal blood concentration of zinc, placental zinc-binding proteins, and fetal demand for zinc.