Altered materno-fetal transfer of 13C-polyunsaturated fatty acids in obese pregnant women

Placental Epigenome Impacts Fetal Development: Effects of Maternal Nutrients and Gut Microbiota

Evidence is emerging on the role of maternal diet, gut microbiota, and other lifestyle factors in establishing lifelong health and disease, which are determined by transgenerationally inherited epigenetic modifications. Understanding epigenetic mechanisms may help identify novel biomarkers for gestation-related exposure, burden, or disease risk. Such biomarkers are essential for developing tools for the early detection of risk factors and exposure levels. It is necessary to establish an exposure threshold due to nutrient deficiencies or other environmental factors that can result in clinically relevant epigenetic alterations that modulate disease risks in the fetus. This narrative review summarizes the latest updates on the roles of maternal nutrients (n-3 fatty acids, polyphenols, vitamins) and gut microbiota on the placental epigenome and its impacts on fetal brain development. This review unravels the potential roles of the functional epigenome for targeted intervention to ensure optimal fetal brain development and its performance in later life.

Gestational Diabetes Mellitus Remodels the Fetal Brain Fatty Acid Profile Through Placenta-Brain Lipid Axis in C57BL/6J Mice

BACKGROUND

Polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA), are critical for proper fetal brain growth and development. Gestational diabetes mellitus (GDM) could affect maternal-fetal fatty acid metabolism.

OBJECTIVE

This study aimed to explore the effect of GDM and high-fat (HF) diet on the DHA transport signaling pathway in the placenta-brain axis and fatty acid concentrations in the fetal brain.

METHODS

Insulin receptor antagonist (S961) and HF diet were used to establish an animal model of GDM. Eighty female C57BL/6J mice were randomly divided into control (CON), GDM, HF, and HF+GDM groups. The fatty acid profiles of the maternal liver and fetal brain were analyzed by gas chromatography. In addition, we analyzed the protein amounts of maternal liver fatty acid desaturase (FADS1/3), elongase (ELOVL2/5) and the regulatory factor sterol-regulatory element-binding protein (SREBP)-1c, and the DHA transport signaling pathway (Wnt3/β-catenin/MFSD2a) of the placenta and fetal brain using western blotting.

RESULTS

GDM promoted the decrease of maternal liver ELOVL2, ELOVL5, and SREBP-1c. Accordingly, we observed a significant decrease in the amount of maternal liver arachidonic acid (AA), DHA, and total n-3 PUFA and n-6 PUFA induced by GDM. GDM also significantly decreased the amount of DHA and n-3 PUFA in the fetal brain. GDM downregulated the Wnt3/β-catenin/MFSD2a signaling pathway, which transfers n-3 PUFA in the placenta and fetal brain. The HF diet increased n-6 PUFA amounts in the maternal liver, correspondingly increasing linoleic acid, gamma-linolenic acid, AA, and total n-6 PUFA in the fetal brain, but decreased DHA amount in the fetal brain. However, HF diet only tended to decrease placental β-catenin and MFSD2a amounts (P = 0.074 and P = 0.098, respectively).

CONCLUSIONS

Maternal GDM could affect the fatty acid profile of the fetal brain both by downregulating the Wnt3/β-catenin/MFSD2a pathway of the placental-fetal barrier and by affecting maternal fatty acid metabolism.

Effects of a High-Fat Diet and Docosahexaenoic Acid during Pregnancy on Fatty Acid Composition in the Fetal Livers of Mice

A high-fat diet (HFD) during pregnancy promotes fat accumulation and reduces docosahexaenoic acid (DHA) levels in the liver of the offspring at postnatal ages, which can depend on fetal sex. However, the prenatal mechanisms behind these associations are still unclear. Thus, we analyzed if an HFD alters DHA content and the expression of molecules related to fatty acid (FA) metabolism in the fetal liver. Female C57BL/6 mice were fed a control diet or HFD for 4-6 weeks before pregnancy until the gestational day (GD) 17.5. A subgroup of each diet received DHA (100 mg/Kg) orally from GD 6.5 until 16.5. On GD 17.5, maternal livers, placentas, and livers from male and female fetuses were collected for FA profiling with gas-chromatography and gene expression of molecules related to FA metabolism using qPCR. PPAR-α protein expression was evaluated using Western blot. The gene expression of placental FA transporters was also assessed. An HFD increased eicosapentaenoic acid (EPA) and decreased DHA levels and protein expression of PPAR-α in the fetal livers of both sexes. DHA increased the gene expression of Ppara, Cpt1, and Acsl1 in the livers of female fetuses. Therefore, an HFD reduces DHA levels and PPAR-α, a master regulator of gene expression, in the fetal liver. In turn, the livers of female fetuses seem to be more sensitive to DHA action.

The Placenta: A Maternofetal Interface

The placenta is the gatekeeper between the mother and the fetus. Over the first trimester of pregnancy, the fetus is nourished by uterine gland secretions in a process known as histiotrophic nutrition. During the second trimester of pregnancy, placentation has evolved to the point at which nutrients are delivered to the placenta via maternal blood (hemotrophic nutrition). Over gestation, the placenta must adapt to these variable nutrient supplies, to alterations in maternal physiology and blood flow, and to dynamic changes in fetal growth rates. Numerous questions remain about the mechanisms used to transport nutrients to the fetus and the maternal and fetal determinants of this process. Growing data highlight the ability of the placenta to regulate this process. As new technologies and omics approaches are utilized to study this maternofetal interface, greater insight into this unique organ and its impact on fetal development and long-term health has been obtained.

Maternal Obesity and Gut Microbiota Are Associated with Fetal Brain Development

Obesity in pregnancy induces metabolic syndrome, low-grade inflammation, altered endocrine factors, placental function, and the maternal gut microbiome. All these factors impact fetal growth and development, including brain development. The lipid metabolic transporters of the maternal-fetal-placental unit are dysregulated in obesity. Consequently, the transport of essential long-chain PUFAs for fetal brain development is disturbed. The mother’s gut microbiota is vital in maintaining postnatal energy homeostasis and maternal-fetal immune competence. Obesity during pregnancy changes the gut microbiota, affecting fetal brain development. Obesity in pregnancy can induce placental and intrauterine inflammation and thus influence the neurodevelopmental outcomes of the offspring. Several epidemiological studies observed an association between maternal obesity and adverse neurodevelopment. This review discusses the effects of maternal obesity and gut microbiota on fetal neurodevelopment outcomes. In addition, the possible mechanisms of the impacts of obesity and gut microbiota on fetal brain development are discussed.

Human placental lipid content and lipid metabolic enzyme abundance in obesity and across gestation

Changes in placental lipid metabolism influence the delivery of lipids critical for fetal development and fetal requirements for lipids change across gestation. We hypothesized that placental lipid content and metabolic enzyme protein levels increase across gestation and are elevated in obesity. Placentas (4-40 weeks' gestation) were collected from control (body mass index, BMI = 18.5-24.9, n=37) and obese (BMI > 30, n=19) pregnant women. Trophoblast villous tissue was homogenized and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS) for phospholipid and triacylglycerol (TAG) analysis and western blot for protein quantification. The placental content of TAG species and nine of 35 identified phosphatidylcholines (PC) were significantly higher (P<0.05) in first trimester (28-79%, 10-47%, respectively). Furthermore, two TAG and three PC differed by maternal BMI and were significantly increased (P<0.05) in the obese group in first trimester (72-87%, 88-119%, respectively). Placental protein abundance of glycerol-2-phosphate (GPAT3) and 1-acyl-sn-glycerol-3-phosphate acyltransferase 2 (AGPAT2), involved in de novo synthesis of PC and TAG, were higher (P<0.05) in the first trimester (66 and 74%, respectively). The protein abundance of the PC-remodeling enzyme PLA2G4c was also higher (63%) in first trimester (P<0.05). In conclusion, the placental content of many phospholipid and TAG species and the protein level of associated synthesis enzymes are higher in first-trimester human placenta. The high PC content may be related to the rapid membrane expansion in early pregnancy and the low placental oxygen tension may promote the accumulation of tissue TAGs in first trimester. Maternal obesity had only limited impact on placental lipid content and metabolic enzyme protein abundance.

Maternal obesity: new placental paradigms unfolded

The prevalence of maternal obesity is increasing at an alarming rate, and is providing a major challenge for obstetric practice. Adverse effects on maternal and fetal health are mediated by complex interactions between metabolic, inflammatory, and oxidative stress signaling in the placenta. Endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR) are common downstream pathways of cell stress, and there is evidence that this conserved homeostatic response may be a key mediator in the pathogenesis of placental dysfunction. We summarize the current literature on the placental cellular and molecular changes that occur in obese women. A special focus is cast onto placental ER stress in obese pregnancy, which may provide a novel link for future investigation.

Myo-inositol moderates maternal BMI and glycemia related variations in in-vitro placental 13C-DHA-metabolism, altering their relationships with birthweight

Transplacental docosahexaenoic-acid (DHA) supply for fetal development is regulated by placental DHA-lipid metabolism. Both maternal diabetes and obesity are linked to possible decreased fetal circulating DHA and increased placental DHA-lipids. Since myo-inositol is a promising intervention for gestational diabetes (GDM), we aimed to determine whether myo-inositol could rectify perturbations in placental DHA metabolism associated with maternal increasing glycemia and obesity and examine links with birthweight. Term placental villous explants from 17 women representing a range of BMIs and mid-gestational glycemia, were incubated with ¹³C-labeled-DHA for 48 h, in 0.3 µmol/L (control) or 60 µmol/L myo-inositol. Individual newly synthesized ¹³C-DHA-labeled lipid species were quantified by liquid-chromatography-mass-spectrometry. Compared with controls, incubation with myo-inositol decreased most ¹³C-DHA-lipids in placental explants from women with higher BMI or higher glycemia, but increased ¹³C-DHA-lipids with normal BMI or lower glycemia. Myo-inositol also increased ¹³C-DHA-labeled lipids in cases of lower birthweight centile, but induced decreases at higher centiles. Myo-inositol therefore lowered DHA-lipids in placenta with high basal placental DHA-lipid production (higher BMI and glycemia) but increased DHA-lipids where basal processing capacity is low. Myo-inositol thus moderates placental DHA metabolism towards a physiological mean which may in turn moderate birthweight.

Sex-Dependent Regulation of Placental Oleic Acid and Palmitic Acid Metabolism by Maternal Glycemia and Associations with Birthweight

Pregnancy complications such as maternal hyperglycemia increase perinatal mortality and morbidity, but risks are higher in males than in females. We hypothesized that fetal sex-dependent differences in placental palmitic-acid (PA) and oleic-acid (OA) metabolism influence such risks. Placental explants (n = 22) were incubated with isotope-labeled fatty acids (¹³C-PA or ¹³C-OA) for 24 or 48 h and the production of forty-seven ¹³C-PA lipids and thirty-seven ¹³C-OA lipids quantified by LCMS. Linear regression was used to investigate associations between maternal glycemia, BMI and fetal sex with ¹³C lipids, and between ¹³C lipids and birthweight centile. Placental explants from females showed greater incorporation of ¹³C-OA and ¹³C-PA into almost all lipids compared to males. Fetal sex also influenced relationships with maternal glycemia, with many ¹³C-OA and ¹³C-PA acylcarnitines, ¹³C-PA-diacylglycerols and ¹³C-PA phospholipids positively associated with glycemia in females but not in males. In contrast, several ¹³C-OA triacylglycerols and ¹³C-OA phospholipids were negatively associated with glycemia in males but not in females. Birthweight centile in females was positively associated with six ¹³C-PA and three ¹³C-OA lipids (mainly acylcarnitines) and was negatively associated with eight ¹³C-OA lipids, while males showed few associations. Fetal sex thus influences placental lipid metabolism and could be a key modulator of the impact of maternal metabolic health on perinatal outcomes, potentially contributing toward sex-specific adaptions in which females prioritize survival.

Maternal obesity causes fetal cardiac hypertrophy and alters adult offspring myocardial metabolism in mice

Obesity in pregnant women causes fetal cardiac dysfunction and increases offspring cardiovascular disease risk, but its effect on myocardial metabolism is unknown. We hypothesized that maternal obesity alters fetal cardiac expression of metabolism-related genes and shifts offspring myocardial substrate preference from glucose towards lipids. Female mice were fed control or obesogenic diets before and during pregnancy. Fetal hearts were studied in late gestation (embryonic day (E) 18.5; term ≈ E21), and offspring were studied at 3, 6, 9 or 24 months postnatally. Maternal obesity increased heart weight and peroxisome proliferator activated receptor gamma (Pparg) expression in female and male fetuses and caused left ventricular diastolic dysfunction in the adult offspring. Cardiac dysfunction worsened progressively with age in female, but not male, offspring of obese dams, in comparison to age-matched control animals. In 6-month-old offspring, exposure to maternal obesity increased cardiac palmitoyl carnitine-supported mitochondrial respiration in males and reduced myocardial 18 F-fluorodeoxyglucose uptake in females. Cardiac Pparg expression remained higher in adult offspring of obese dams than control dams and was correlated with contractile and metabolic function. Maternal obesity did not affect cardiac palmitoyl carnitine respiration in females or 18 F-fluorodeoxyglucose uptake in males and did not alter cardiac 3 H-oleic acid uptake, pyruvate respiration, lipid content or fatty acid/glucose transporter abundance in offspring of either sex. The results support our hypothesis and show that maternal obesity affects offspring cardiac metabolism in a sex-dependent manner. Persistent upregulation of Pparg expression in response to overnutrition in utero might underpin programmed cardiac impairments mechanistically and contribute to cardiovascular disease risk in children of women with obesity. KEY POINTS: Obesity in pregnant women causes cardiac dysfunction in the fetus and increases lifelong cardiovascular disease risk in the offspring. In this study, we showed that maternal obesity in mice induces hypertrophy of the fetal heart in association with altered expression of genes related to nutrient metabolism. Maternal obesity also alters cardiac metabolism of carbohydrates and lipids in the adult offspring. The results suggest that overnutrition in utero might contribute to increased cardiovascular disease risk in children of women with obesity.

Association of Prepregnancy Obesity and Remodeled Maternal-Fetal Plasma Fatty Acid Profiles

Background

Fatty acids, especially polyunsaturated fatty acid (PUFA), are found abundantly in the brain and are fundamental for a fetus's growth. The fatty acid profiles of mothers and fetuses may be affected by maternal prepregnancy body mass index (pre-BMI), thus affecting fetal growth and development.

Methods

A total of 103 mother-fetus pairs were divided into overweight/obese (OW, n = 26), normal weight (NW, n = 60), and underweight (UW, n = 17) groups according to pre-BMI. Fatty acid profiles in maternal and umbilical cord plasma were analyzed by gas chromatography.

Results

The infant birth BMI z-score of the OW group was higher than that of the NW and UW groups (p < 0.05). The OW mothers had significantly higher plasma n-6 PUFA and n-6/n-3, but lower docosahexaenoic acid (DHA) and n-3 PUFA (p < 0.05). In cord plasma, the proportions of DHA and n-3 PUFA were lower in the OW group (p < 0.05), whereas the n-6/n-3 ratio was higher in the OW group (p < 0.05). The pre-BMI was negatively correlated with cord plasma DHA in all subjects (r = −0.303, p = 0.002), and the same negative correlation can be observed in the OW group (r = −0.561, p = 0.004), but not in the NW and UW groups (p > 0.05). The pre-BMI was positively correlated with cord plasma n-6/n-3 in all subjects (r = 0.325, p = 0.001), and the same positive correlation can be found in the OW group (r = 0.558, p = 0.004), but not in NW and UW groups (p > 0.05).

Conclusions

Maternal pre-BMI was associated with the maternal-fetal plasma fatty acid profiles, whereas the adverse fatty acid profiles are more noticeable in the prepregnancy OW mothers.

Reduced n-3 and n-6 PUFA (DHA and AA) Concentrations in Breast Milk and Erythrocytes Phospholipids during Pregnancy and Lactation in Women with Obesity

Obesity during pregnancy is a worrying public health problem worldwide. Maternal diet is critical for fatty acid (FA) placental transport and FA content in breast milk (BM). We evaluated FA composition in erythrocytes phospholipids (EP) and BM in pregnant women with (OBE, n = 30) and without (non-OBE, n = 31) obesity. Sixty-one healthy women were evaluated at their 20-24th gestational week and followed until 6th month of lactation. Diet was evaluated through a food frequency questionnaire. FA composition of EP and BM was assessed by gas-liquid chromatography. The OBE group showed lower diet quality, but total n-6 and n-3 polyunsaturated FA (PUFA), ALA, EPA, and DHA dietary intake was similar between groups. N-3 PUFA, ALA, DHA, and the n-6/n-3 PUFA ratio in EP were lower at the 6th lactation month in the OBE group. In BM, the arachidonic acid (AA) concentration was lower at the end of the lactation, and DHA content showed an earlier and constant decline in the OBE group compared to the non-OBE group. In conclusion, n-3 PUFA and AA and DHA levels were reduced in EP and BM in pregnant women with obesity. Strategies to increase n-3 PUFA are urgently needed during pregnancy and lactation, particularly in women with obesity.

How the placenta-brain lipid axis impacts the nutritional origin of child neurodevelopmental disorders: Focus on attention deficit hyperactivity disorder and autism spectrum disorder

Dietary fish is a rich source of omega-3 (n-3) fatty acids, and as such, is believed to have played an important role in the evolution of the human brain and its advanced cognitive function. The long chain polyunsaturated fatty acids, particularly the n-3 docosahexanoic acid (DHA), are critical for proper neurological development and function. Both low plasma DHA and obesity in pregnancy are associated with neurodevelopmental disorders such as attention deficit and hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in childhood, and n-3 supplementation has been shown to improve symptoms, as reviewed herein. The mechanisms underlying the connection between maternal obesity, n-3 fatty acid levels and offspring's neurological outcomes are poorly understood, but we review the evidence for a mediating role of the placenta in this relationship. Despite promising data that n-3 fatty acid supplementation mitigates the effect of maternal obesity on placental lipid metabolism, few clinical trials or animal studies have considered the neurological outcomes of offspring of mothers with obesity supplemented with n-3 FA in pregnancy.

Decreased Fatty Acid Transporter FABP1 and Increased Isoprostanes and Neuroprostanes in the Human Term Placenta: Implications for Inflammation and Birth Weight in Maternal Pre-Gestational Obesity

The rise in prevalence of obesity in women of reproductive age in developed and developing countries might propagate intergenerational cycles of detrimental effects on metabolic health. Placental lipid metabolism is disrupted by maternal obesity, which possibly affects the life-long health of the offspring. Here, we investigated placental lipid metabolism in women with pre-gestational obesity as a sole pregnancy complication and compared it to placental responses of lean women. Open profile and targeted lipidomics were used to assess placental lipids and oxidised products of docosahexaenoic (DHA) and arachidonic acid (AA), respectively, neuroprostanes and isoprostanes. Despite no overall signs of lipid accumulation, DHA and AA levels in placentas from obese women were, respectively, 2.2 and 2.5 times higher than those from lean women. Additionally, a 2-fold increase in DHA-derived neuroprostanes and a 1.7-fold increase in AA-derived isoprostanes were seen in the obese group. These changes correlated with a 70% decrease in placental FABP1 protein. Multivariate analyses suggested that neuroprostanes and isoprostanes are associated with maternal and placental inflammation and with birth weight. These results might shed light on the molecular mechanisms associated with altered placental fatty acid metabolism in maternal pre-gestational obesity, placing these oxidised fatty acids as novel mediators of placental function.

Placental 13C-DHA metabolism and relationship with maternal BMI, glycemia and birthweight

BACKGROUND

Fetal docosahexaenoic acid (DHA) supply relies on preferential transplacental transfer, which is regulated by placental DHA lipid metabolism. Maternal hyperglycemia and obesity associate with higher birthweight and fetal DHA insufficiency but the role of placental DHA metabolism is unclear.

METHODS

Explants from 17 term placenta were incubated with 13C-labeled DHA for 48 h, at 5 or 10 mmol/L glucose treatment, and the production of 17 individual newly synthesized 13C-DHA labeled lipids quantified by liquid chromatography mass spectrometry.

RESULTS

Maternal BMI positively associated with 13C-DHA-labeled diacylglycerols, triacylglycerols, lysophospholipids, phosphatidylcholine and phosphatidylethanolamine plasmalogens, while maternal fasting glycemia positively associated with five 13C-DHA triacylglycerols. In turn, 13C-DHA-labeled phospholipids and triacylglycerols positively associated with birthweight centile. In-vitro glucose treatment increased most 13C-DHA-lipids, but decreased 13C-DHA phosphatidylethanolamine plasmalogens. However, with increasing maternal BMI, the magnitude of the glucose treatment induced increase in 13C-DHA phosphatidylcholine and 13C-DHA lysophospholipids was curtailed, with further decline in 13C-DHA phosphatidylethanolamine plasmalogens. Conversely, with increasing birthweight centile glucose treatment induced increases in 13C-DHA triacylglycerols were exaggerated, while glucose treatment induced decreases in 13C-DHA phosphatidylethanolamine plasmalogens were diminished.

CONCLUSIONS

Maternal BMI and glycemia increased the production of different placental DHA lipids implying impact on different metabolic pathways. Glucose-induced elevation in placental DHA metabolism is moderated with higher maternal BMI. In turn, findings of associations between many DHA lipids with birthweight suggest that BMI and glycemia promote fetal growth partly through changes in placental DHA metabolism.

Self-Reported DHA Supplementation during Pregnancy and Its Association with Obesity or Gestational Diabetes in Relation to DHA Concentration in Cord and Maternal Plasma: Results from NELA, a Prospective Mother-Offspring Cohort

Maternal supplementation of docosahexaenoic acid (DHA) during pregnancy has been recommended due to its role in infant development, but its effect on materno-fetal DHA status is not well established. We evaluated the associations between DHA supplementation in pregnant women with obesity or gestational diabetes mellitus (GDM) and maternal and neonatal DHA status. Serum fatty acids (FA) were analyzed in 641 pregnant women (24 weeks of gestation) and in 345 venous and 166 arterial cord blood samples of participants of the NELA cohort. Obese women (n = 47) presented lower DHA in serum than those lean (n = 397) or overweight (n = 116) before pregnancy. Linoleic acid in arterial cord was elevated in obese women, which indicates lower fetal retention. Maternal DHA supplementation (200 mg/d) during pregnancy was associated with enhanced maternal and fetal DHA levels regardless of pre-pregnancy body mass index (BMI), although higher arterial DHA in overweight women indicated an attenuated response. Maternal DHA supplementation was not associated with cord venous DHA in neonates of mothers with GDM. The cord arteriovenous difference was similar for DHA between GDM and controls. In conclusion, maternal DHA supplementation during pregnancy enhanced fetal DHA status regardless of the pre-pregnancy BMI while GDM may reduce the effect of DHA supplementation in newborns.

Sex-specific responses in placental fatty acid oxidation, esterification and transfer capacity to maternal obesity

Fatty acid metabolism and oxidation capacity in the placenta, which likely affects the rate and composition of lipid delivered to the fetus remains poorly understood. Long chain polyunsaturated fatty acids, such as docosahexaenoic acid (DHA), are critical for fetal growth and brain development. We determined the impact of maternal obesity on placental fatty acid oxidation, esterification and transport capacity by measuring PhosphatidylCholine (PC) and LysoPhosphatidylCholine (LPC) containing DHA by mass spectrometry in mother-placenta-baby triads as well as placental free carnitine and acylcarnitine metabolites in women with normal and obese pre-pregnancy BMI. Placental protein expression of enzymes involved in beta-oxidation and esterification pathways, MFSD2a (lysophosphatidylcholine transporter) and OCTN2 (carnitine transporter) expression in syncytiotrophoblast microvillous (MVM) and basal (BM) membranes were determined by Western Blot. Maternal obesity was associated with decreased umbilical cord plasma DHA in LPC and PC fractions in male, but not female, fetuses. Basal membrane MFSD2a protein expression was increased in placenta of males of obese mothers. In female placentas, despite an increased MVM OCTN2 expression, maternal obesity was associated with a reduced MUFA-carnitine levels and increased esterification enzymes. We speculate that lower DHA-PL in fetal circulation of male offspring of obese mothers, despite a significant increase in transporter expression for LPC-DHA, may lead to low DHA needed for brain development contributing to neurological consequences that are more prevalent in male children. Female placentas likely have reduced beta-oxidation capacity and appear to store FA through greater placental esterification, suggesting impaired placenta function and lipid transfer in female placentas of obese mothers.

Placental mobilization of free fatty acids contributes to altered materno-fetal transfer in obesity

BACKGROUND

Metabolic changes in obese pregnant women, such as changes of plasma lipids beyond physiological levels, may subsequently affect fetal development in utero. These metabolic derangements may remain in the offspring and continue throughout life. The placenta mediates bidirectional exchange of nutrients between mother and fetus. The impact of prepregnancy obesity on placental transfer of lipids is still unknown.

OBJECTIVE

We aimed to examine materno-to-fetal free fatty acid (FFA) transfer by a combined experimental and modeling approach. Flux of ¹³C-labeled FFA was evaluated by ex vivo perfusion of human placentae as a function of prepregnancy obesity. Mathematical modeling complemented ex vivo results by providing FFA kinetic parameters.

RESULTS

Obesity was strongly associated with elevated materno-to-fetal transfer of applied ¹³C-FFA. Clearance of polyunsaturated ¹³C-docosahexaenoic acid (DHA) was most prominently affected. The use of the mathematical model revealed a lower tissue storage capacity for DHA in obese compared with lean placentae.

CONCLUSION

Besides direct materno-to-fetal FFA transfer, placental mobilization accounts for the fetal FA supply. Together, with metabolic changes in the mother and an elevated materno-fetal FFA transfer shown in obesity, these changes suggest that they may be transmitted to the fetus, with yet unknown consequences.

Impact of Maternal Obesity on the Metabolism and Bioavailability of Polyunsaturated Fatty Acids during Pregnancy and Breastfeeding

Prenatal and postnatal development are closely related to healthy maternal conditions that allow for the provision of all nutritional requirements to the offspring. In this regard, an appropriate supply of fatty acids (FA), mainly n-3 and n-6 long-chain polyunsaturated fatty acids (LCPUFA), is crucial to ensure a normal development, because they are an integral part of cell membranes and participate in the synthesis of bioactive molecules that regulate multiple signaling pathways. On the other hand, maternal obesity and excessive gestational weight gain affect FA supply to the fetus and neonate, altering placental nutrient transfer, as well as the production and composition of breast milk during lactation. In this regard, maternal obesity modifies FA profile, resulting in low n-3 and elevated n-6 PUFA levels in maternal and fetal circulation during pregnancy, as well as in breast milk during lactation. These modifications are associated with a pro-inflammatory state and oxidative stress with short and long-term consequences in different organs of the fetus and neonate, including in the liver, brain, skeletal muscle, and adipose tissue. Altogether, these changes confer to the offspring a higher risk of developing obesity and its complications, as well as neuropsychiatric disorders, asthma, and cancer. Considering the consequences of an abnormal FA supply to offspring induced by maternal obesity, we aimed to review the effects of obesity on the metabolism and bioavailability of FA during pregnancy and breastfeeding, with an emphasis on LCPUFA homeostasis.

Nutrition and Metabolic Adaptations in Physiological and Complicated Pregnancy: Focus on Obesity and Gestational Diabetes

Pregnancy offers a window of opportunity to program the future health of both mothers and offspring. During gestation, women experience a series of physical and metabolic modifications and adaptations, which aim to protect the fetus development and are closely related to both pre-gestational nutritional status and gestational weight gain. Moreover, pre-gestational obesity represents a challenge of treatment, and nowadays there are new evidence as regard its management, especially the adequate weight gain. Recent evidence has highlighted the determinant role of nutritional status and maternal diet on both pregnancy outcomes and long-term risk of chronic diseases, through a transgenerational flow, conceptualized by the Development Origin of Health and Diseases (Dohad) theory. In this review we will analyse the physiological and endocrine adaptation in pregnancy, and the metabolic complications, thus the focal points for nutritional and therapeutic strategies that we must early implement, virtually before conception, to safeguard the health of both mother and progeny. We will summarize the current nutritional recommendations and the use of nutraceuticals in pregnancy, with a focus on the management of pregnancy complicated by obesity and hyperglycemia, assessing the most recent evidence about the effects of ante-natal nutrition on the long-term, on either maternal health or metabolic risk of the offspring.

Exploring the metabolic fate of medium-chain triglycerides in healthy individuals using a stable isotope tracer

BACKGROUND & AIMS

Medium chain triglyceride (MCT) supplementation is often recommended as treatment for patients with long-chain fatty acid β-oxidation (lcFAO) disorders, since they can be utilized as an energy source without the use of the defective enzyme. However, studies in mice and preterm infants suggest that not all medium-chain fatty acids (MCFA) are oxidized and may undergo elongation to long-chain fatty acids (LCFA). In this single blinded study, we explored the metabolic fates of MCT in healthy individuals using a ¹³C-labeled MCT tracer.

METHOD

Three healthy males in rest received on two test days a primed continuous infusion of glyceryl tri[1,2,3,4-¹³C₄]-octanoate with either an isocaloric supplementation of 1) exclusively MCT (MCT-only) or 2) a mixture of MCT, proteins and carbohydrates (MCT-mix). Gas chromatography - combustion - isotope ratio mass spectrometry (GC-C-IRMS) was used to determine ¹³C-enrichment of long-chain fatty acids in plasma and of ¹³CO₂ in exhaled air.

RESULTS

When provided as single energy source, an estimated 42% of administered MCT was converted to CO₂. In combination with carbohydrates and proteins in the diet, oxidation of MCT was higher (62%). In both diets <1% of ¹³C-label was incorporated in LCFA in plasma, indicating that administered MCT underwent chain-elongation to LCT.

CONCLUSIONS

Although the relative MCT oxidation rate was higher when combined with carbohydrates and protein, quantitatively more MCT was oxidized when given an isocaloric meal with solely MCT. As these results were obtained in the resting state opposed to during exercise, it is too early to give a recommendation concerning the use of MCT in lcFAO disorders. The data show that in resting healthy individuals only a very small part of the MCT is traced back as LCFA in plasma, suggesting that MCT treatment does not result in a large LCFA burden, however further research on storage of MCT in tissues is warranted.

REGISTRATION

The study was registered in the Nederlands Trialregister. Protocol ID: Trial NL7417 (NTR7650).

Development and validation of a gas chromatography-mass spectrometry method to analyze octanoate enrichments at low concentrations in human plasma

A new method for accurately analyzing octanoate enrichment in plasma was developed and validated. Samples were derivatized directly in plasma by transesterification with isobutanol and were analyzed by gas chromatography-mass spectrometry (GC-MS). This method was developed to analyze the precursor enrichment in a stable isotope tracer protocol. Glyceryl tri[1,2,3,4-¹³C₄] octanoate, a stable isotope-labeled medium-chain triglyceride (MCT), was orally administered in combination with (1) exclusively MCT or (2) a combination of protein, carbohydrates, and MCT to investigate the metabolic route of oral MCT under various conditions. Accurate analysis of octanoate enrichment in plasma at concentrations as low as 0.43 μM (lower limit of quantification, LLOQ) was performed. This is an improvement of about twenty times for the LLOQ for analysis of the enrichment of octanoate when compared with the gold-standard method for fatty acid analysis (methyl esterification). Moreover, we found that' with this gold-standard method, study samples were easily contaminated with (unlabeled) octanoate from other sources, leading to biased, incorrect results. The precision and linearity obtained using the new method were good (coefficient of variation intraday < 9.1%, interday < 9.3%, R² of the calibration curve > 0.99). The sensitivity was sufficient for analyzing samples obtained using the stable isotope protocol. This new method is more sensitive than methyl esterification and it minimizes the risk of contamination. Graphical abstract.

Diabetes Mellitus, Obesity, and the Placenta

The placenta is exposed to metabolic derangements in the maternal and fetal circulation. The effects of the early placental "exposome" determine further trajectories. Overstimulation of the fetal pancreas in early gestation results in fetal hyperinsulinemia, augmenting glucose transfer with adverse effects on the fetus. The manifold placental changes at the end of pregnancy can be regarded as adaptive responses to protect the fetus from diabetes and obesity. The causal role of the placenta, if any, in mediating long-term effects on offspring development is an important area of current and future research.