1. Universidad San Pablo-CEU

Aims/hypothesis Both arachidonic acid (AA, 20:4 n-6) and docosahexaenoic acid (DHA,22:6 n-3), long-chain polyunsaturated fatty acids (LCPUFA), are involved in fetal development and, based on their percentage compositions, appear to be specifically accumulated in fetal circulation in a proposed phenomenon known as biomagnification. Discrepancies exist in the literature concerning the effect of gestational diabetes mellitus (GDM) on circulating fatty acids. Our objective was to analyse individual fatty acid concentrations in a large cohort of maternal and cord paired serum samples from pregnant women with and without GDM. Methods Overnight fasted maternal and cord blood paired samples from 84 women with GDM and well controlled blood glucose levels and 90 healthy pregnant women (controls) were drawn at term. Individual fatty acids within total serum lipids were analysed by gas chromatography and expressed both as concentrations of fatty acid (mmol/l) and as a percentage of total fatty acids. Results In the serum of overnight fasted pregnant women with GDM, the concentrations of most fatty acids were lower than in control women, except for AA and DHA, which remained the same. The concentrations of most fatty acids in cord serum were also lower in the GDM group than in the control group, except for α-linolenic acid (ALA,18:3 n-3), which was higher in the GDM group. In both groups, the concentrations of all fatty acids were lower in cord serum than in maternal serum. In GDM participants only, a positive and significant correlation between cord and maternal serum concentration of AA and DHA was observed. Conclusions/interpretation The expression of fatty acids in molar concentrations reveals that GDM decreases the concentration of most fatty acids in both maternal and cord serum. There is a high fetal dependence on maternal AA and DHA, but our findings do not support the existence of a fetal biomagnification of those two LCPUFA.

Backgroud: Higher accretion of prenatal fat is associated with a higher proportion of obesity in children. However, most of the data on regulatory factors involved in fetal adipogenesis come from animal studies; in humans there is no evidence on how fetal insulin affects fatty acid concentrations and fetal adiposity. Objective: We evaluate the relationship between fetal adipose tissue accretion with insulin and fetal consumption of circulating fatty acid (FA). Methods: In fasting maternal blood at term and cord samples, from 41 gestational diabetes mellitus women (GDM) and 68 non-diabetic controls, serum compounds were determined. Individual FA were analyzed and expressed as concentrations of FA (mmol/L). Results: Both groups had similar maternal serum glucose, insulin, triacylglycerol (TAG), non-esterified FA (NEFA), glycerol and leptin concentrations, but most individual maternal serum FA were lower in GDM than controls. Neonatal fat mass (FM) was higher in the GDM group even though neonatal birth weights were similar. In GDM cord serum glucose, insulin, NEFA and leptin were higher than controls, but glycerol and all individual FA were lower. In GDM neonates only, a negative correlation was found between each FA and FM, and there was a strong negative correlation between the concentrations of umbilical blood insulin and five major FA. Conclusion: Our results show for the first time that hyperinsulinemia in fetuses of GDM women increases FA utilization, which may contribute to to their increased adiposity.

Context Angiopoietin-like protein 6 (ANGPTL6) is a hepatokine, which, in animal studies, improves insulin sensitivity and increases energy expenditure to counteract insulin resistance. Objective Evaluate in a human population, the role of serum ANGPTL6 in gestational diabetes mellitus (GDM) or its presence in fetal circulation. Research design and methods A total of 190 women (115 controls and 75 GDM) and their offspring were studied. Insulin, glucose, ANGPTL6, retinol binding protein 4 (RBP4), and retinol, as well as leptin and adiponectin, were determined in maternal serum obtained at term and from umbilical artery blood at delivery. Results At term, pregnant women with GDM showed higher serum concentrations of ANGPTL6, insulin, homeostatic model assessment, and apo-RBP4 (free RBP4) than controls but not of glucose, which remained similar in both groups. Also, in arterial cord serum, ANGPTL6 concentration was increased in GDM neonates with respect to the control group (201 ± 12 ng/mL vs 119 ± 8 ng/mL, respectively). No effect of maternal insulin treatment of some GDM mothers in neonates of either sex on ANGPTL6 levels was observed. In GDM, circulating ANGPTL6 showed no correlation with glucose or insulin concentration or with neonatal adiposity. However, in control pregnancies, the variation in glucose concentration was positively correlated with ANGPTL6 concentration, both in maternal and in cord samples, and cord ANGPTL6 was negatively correlated with neonatal fat mass. Furthermore, in control pregnant women, serum concentrations of ANGPTL6 and apo-RBP4 were negatively correlated. Conclusion Serum ANGPTL6 levels are associated with maternal glucose homeostasis and fetal adiposity in normal pregnancy. ANGPTL6 levels in maternal and cord serum GDM pregnancy at term are increased, although its mechanism and physiological role are unknown yet.

Certain limitations exist for animals to modify fatty acid changes. Besides the role of arachidonic acid (AA), docosahexaenoic acid (DHA) and other 20-carbon long-chain polyunsaturated fatty acids (LCPUFAs) for the synthesis of inflammatory mediators as eicosanoids, different LCPUFAs have many other effects, including their abilities to regulate gene expression and downstream events. LCPUFAs are susceptible to autoxidation, which is prevented by the action of antioxidants in the form of enzymes like superoxide dismutases, catalases and peroxidases, as well as antioxidant compounds that protect against oxidation or repair the damage caused. Under normal conditions, the fetus needs both essential fatty acids (EFAs) and LCPUFAs, which are obtained from its mother by placental transfer. In early pregnancy, dietary derived fatty acids are accumulated in maternal adipose tissue. However, during late pregnancy, corresponding to the period of the highest fetal growth, maternal adipose tissue becomes catabolic and LCPUFAs are released into the circulation by adipose lipolytic activity. The released LCPUFAs are taken up by maternal liver to be esterified and released back to the circulation as triacylglycerides (TAGs) in very-low-density lipoprotein (VLDL) that become available to the placenta to be transferred to the fetus in the form of non-esterified fatty acids (NEFAs). An enhanced adipose tissue lipolysis is maintained around parturition and esterified LCPUFAs are diverted to mammary glands thanks to an increased activity of lipoprotein lipase for milk production. Throughout this process, LCPUFAs become available to the newborn during suckling. The important role of both DHA and AA for the development of the nervous system and for growth has motivated their dietary supplement during different postnatal stages. This has been especially important in preterm infants both because under normal conditions, the fetus acquires most of these fatty acids during late pregnancy, and because the immaturity of the enzyme systems for the synthesis of AA and DHA from their respective EFAs.

Background: Ligands of peroxisome-proliferator activated receptors (PPARs), such as non-esterified fatty acids (NEFAs), induce expression of angiopoietin-like protein 4 (ANGPTL4). Recently ANGPTL4 has been reported to be a mediator of intracellular adipose lipolysis induced by glucocorticoids. Objective: To determine the concentrations of ANGPTL4 in cord serum of neonates born by spontaneous vaginal delivery (SVD) and by pre-labor cesarean section (CS) from healthy women, and to relate them to parameters of neonatal lipolytic activity at birth. Measurements: In 54 neonates born by SVD and in 56 neonates born by CS, arterial cord blood was drawn to determine insulin, cortisol, triacylglycerols (TAGs), glycerol, non-esterified fatty acids (NEFAs), individual fatty acids, ANGPTL4, adiponectin, retinol binding protein 4 (RBP4) and leptin. Results: Birth weight and neonatal fat mass in SVD and CS showed no difference, but the concentrations of glycerol, adiponectin, RBP4, NEFAs and most individual fatty acids were higher in cord serum of neonates born by SVD compared to CS, indicating a higher adipose tissue breakdown in the SVD group. The concentrations of TAG and cortisol were also higher and that of insulin was lower in cord serum of SVD compared to the CS group. However, the concentration in cord serum of ANGPTL4 did not differ between the two groups and no positive correlation with either NEFA or glycerol concentrations were detected. Conclusion: ANGPTL4 is known to stimulate lipolysis in adults, but does not appear to mediate the increased activity in SVD, indicating the presence of different regulatory inputs.

The amount of peroxisome proliferator-activated receptor-ex (PPARcx) protein was markedly augmented in the liver of suckling rats compared to adult rats. This different PPARcx abundance was used to study the sensitivity to nutritional changes in the expression and activity of this receptor. Thus, 10-day-old and adult rats were orally given either glucose, Intralipid or a combination of both diets, and liver mRNA levels of PPARcx and the PPAR related genes, acyl-CoA oxidase (ACO) and phosphoenolpyruvate carboxykinase (PEPCK), and plasma metabolites were measured. In neonates, the expression of PPARcx and ACO was seen to increase when the level of FF A in plasma was also high, unless an elevated level of insulin was also present. However, this fatty acid-induced effect was not detected in adult rats. On the contrary, the hepatic expression of PEPCK was modulated by the nutritional changes similarly in both neonates and adult rats. Thus, it may be concluded that the expression of the PPARcx gene in adult rats seems to be less sensitive to nutritional changes than in neonates.

Hepatectomy and nephrectomy in the rat produced an increase in blood glycerol levels which was observed before the fall in blood glucose. The disappearance of total radioactivity from plasma after the i.v. injection of either (U- 14C)-glycerol or (U- 14C)-glucose in these animals was slower than in their sham operated controls. Total radioactivity in plasma was always lower after (U- 14C)-glycerol administration than after (U- 14C)-glucose. The loss of either tracer from plasma in the eviscerated animals was followed by the appearance of 14C-lactate, demonstrating their rapid metabolism. The radioactivity appearing in the water soluble fraction of lumbar fat pads was increased in eviscerated animals while in the lipid fraction it was reduced from both tracers. These results show that adipose tissue is able to metabolize small quantities of glycerol directly in viva. The use of both (1 4C)-glycerol and (14C)- glucose by skeletal and heart muscles was enhanced in hepatectomized rats but the effect on synthesis of labelled glyceride glycerol was greater for (1 4C)-glycerol, suggesting its important role in the esterification of fatty acids in these tissues.

Postnatal development of the glucose and insulin balance in offspring of ethanol-treated and control rats has been studied. Newborn rats were separated from their mothers and placed with normal lactating, nonethanol-treated dams. Prenatal exposure to ethanol led to hypoglycemia on the first day of extrauterine life and a general tendency to hyperinsulinemia during the entire postnatal period studied. The glucose-tolerance test in weaned rats (30 days old) gave a greater and faster increase than controls in levels of both glucose and plasma insulin. At adult age (90 days) the response of blood glucose to an oral glucose load in offspring from ethanol-treated mothers was not different from that in offspring from controls, but the insulin response was higher. This abnormal insulin response, such a long time after the end of ethanol exposure, suggests either a permanent alteration in the pancreatic response, or a peripheral insulin resistance and/or differences in the rate of insulin degradation in these animals.