Nora Martínez

Leptin modulates nitric oxide production and lipid metabolism in human placenta

Leptin has significant effects on appetite, energy expenditure, lipid mobilisation and reproduction. During pregnancy, leptin is produced in the placenta, a tissue in which leptin receptors are highly expressed, suggesting autocrine/paracrine functions for this hormone. In the present study, a putative role of leptin as a regulator of nitric oxide (NO) production and lipid metabolism was evaluated in term human placenta. We demonstrated that leptin enhanced NO production in human placental explants (P < 0.01). Although leptin did not modify the placental levels of cholesteryl esters and phospholipids, leptin decreased levels of triglycerides (P < 0.01) and cholesterol (P < 0.001) in term human placenta. The effect of leptin on lipid mass seems to be independent of the modulation of de novo lipid synthesis because leptin did not modify the incorporation of (14)C-acetate into any of the lipids evaluated. We investigated the effects of leptin on placental lipid catabolism and found that in both term human placental explants and primary cultures of trophoblastic cells, leptin increased glycerol release, an index of the hydrolysis of esterified lipids, in a dose-dependent manner. In conclusion, we have shown that leptin affects NO production and lipid catabolism in human placenta, providing supportive evidence for a role of leptin in placental functions that would determine the transfer of nutrients to the developing fetus.

Safflower and olive oil dietary treatments rescue aberrant embryonic arachidonic acid and nitric oxide metabolism and prevent diabetic embryopathy in rats.

Aberrant arachidonic acid and nitric oxide (NO) metabolic pathways are involved in diabetic embryopathy. Previous works have found diminished concentrations of PGE(2) and PGI(2) in embryos from diabetic rats, and that PGI(2) is capable of increasing embryonic PGE(2) concentrations through the activation of the nuclear receptor PPARdelta. PPARdelta activators are lipid molecules such as oleic and linoleic acids, present in high concentrations in olive and safflower oils, respectively. The aim of this study was to analyze the capability of dietary supplementation with either 6% olive or 6% safflower oils to regulate PGE(2), PGI(2) and NO concentrations in embryos and deciduas from control and diabetic rats during early organogenesis. Diabetes was induced by a single injection of streptozotocin (55 mg/kg) 1 week before mating. Animals were fed with the oil-supplemented diets from Days 0.5 to 10.5 of gestation. PGI(2) and PGE(2) were measured by EIA and NO through the evaluation of its stable metabolites nitrates-nitrites in 10.5 day embryos and deciduas. We found that the olive and safflower oil-supplemented treatments highly reduced resorption and malformation rates in diabetic animals, and that they were able to prevent maternal diabetes-induced alterations in embryonic and decidual PGI(2) and PGE(2) concentrations. Moreover, these dietary treatments prevented NO overproduction in embryos and deciduas from diabetic rats. These data indicate that in maternal diabetes both the embryo and the decidua benefit from the olive and safflower oil supplementation probably through mechanisms that involve the rescue of aberrant prostaglandin and NO generation and that prevent developmental damage during early organogenesis.

Activation of the nuclear receptor PPARα regulates lipid metabolism in foetal liver from diabetic rats: implications in diabetes-induced foetal overgrowth

Peroxisome proliferator‐activated receptor α (PPARα) is a crucial regulator of liver lipid metabolism. As maternal diabetes impairs foetal lipid metabolism and growth, we aimed to determine whether PPARα activation regulates lipid metabolism in the foetal liver from diabetic rats as well as foetal weight and foetal liver weight.

Effects of natural ligands of PPARγ on lipid metabolism in placental tissues from healthy and diabetic rats

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent nuclear receptor that plays an important role in placental development and function metabolism in diabetic and control rats after midpregnancy, as well as the concentrations of the PPARgamma endogenous agonist 15deoxyDelta(12,14)Prostaglandin J(2) (15dPGJ(2)). In vitro experiments showed that 15dPGJ(2) did not regulate placental concentrations of triglycerides, cholesteryl esters, phospholipids and free fatty acids, but decreased the de novo synthesis of these lipid species. PPAR agonists were administered in vivo through dietary supplementation with either 6% olive oil or 6% safflower oil. These treatments led to increases in placental lipid mass in control tissues and more markedly in diabetic tissues. In addition, they led to reductions in the de novo lipid synthesis both in control and in diabetic placental tissues. In the placenta from diabetic rats fed with the standard diet, 15dPGJ(2) concentrations were greatly reduced. Both dietary supplementations increased the concentrations of 15dPGJ(2) in placentas from control and diabetic rats. These data indicate that, in the placenta, PPARgamma natural ligands regulate the concentration of their own endogenous ligands. In addition, they increase the placental capacity to accumulate maternal-derived lipids, and reduce the de novo lipid synthesis, thus regulating metabolic pathways that are altered in the placenta from diabetic rats and involved in the lipid transfer to the developing fetus.

PPAR activation as a regulator of lipid metabolism, nitric oxide production and lipid peroxidation in the placenta from type 2 diabetic patients

Peroxisome proliferator activated receptors (PPARs) are ligand activated transcription factors with crucial functions in lipid homeostasis, anti-inflammatory processes and placental development. Maternal diabetes induces a pro-inflammatory environment and alters placental development. We investigated whether PPARs regulate lipid metabolism and nitric oxide (NO) production in placental explants from healthy and type 2 diabetic (DM2) patients. We found decreased PPARα and PPARγ concentrations, no changes in PPARδ concentrations, and increased lipids, lipoperoxides and NO production in placentas from DM2 patients. PPARα agonists reduced placental concentrations of triglycerides and both PPARα and PPARδ agonists reduced concentrations of phospholipids, cholesteryl esters and cholesterol. PPARγ agonists increased lipid concentrations in placentas from DM2 patients and more markedly in placentas from healthy patients. Endogenous ligands for the three PPAR isotypes reduced NO production and lipoperoxidation in placentas from DM2 patients. We conclude that PPARs play a role in placental NO and lipid homeostasis and can regulate NO production, lipid concentrations and lipoperoxidation in placentas from DM2 patients.

Carbaprostacyclin, a PPARδ agonist, ameliorates excess lipid accumulation in diabetic rat placentas

AIMS Maternal diabetes impairs placental development and metabolism. Peroxisome proliferator-activated receptors (PPARs) are ligand-activated nuclear receptors relevant in metabolic homeostasis. We investigated the concentrations of PPARdelta and its endogenous agonist prostacyclin (PGI2), as well as the effects of carbaprostacylin (cPGI(2,) a PPARdelta agonist) on lipid metabolism in placentas from control and streptozotocin-induced diabetic rats on day 13.5 of gestation. MAIN METHODS The placentas were explanted to evaluate PPARdelta expression and PGI2 concentrations, and cultured with cPGI2 for further analysis of lipid metabolism (concentrations and (14)C-acetate derived synthesis of triglycerides, cholesteryl esters, phospholipids, cholesterol and free fatty acids; release of glycerol and lipid peroxidation). KEY FINDINGS Reduced PGI2 concentrations were found in the placentas from diabetic rats when compared to controls. cPGI2 additions reduced the concentrations and synthesis of several lipid species, increased lipid catabolism and reduced lipid peroxidation in the placenta. These effects were more marked in diabetic tissues, which presented alterations in the lipid metabolic parameters evaluated. cPGI2 additions increased placental PPARdelta and acyl-CoA oxidase expression, which are changes possibly involved in the catabolic effects observed. SIGNIFICANCE The present study reveals the capability of cPGI2 to regulate placental lipid metabolism and PPARdelta expression, and suggests that preserving appropriate PGI2 concentrations in the placenta may help to metabolize maternal derived lipid overload in diabetic gestations.

MMP/ TIMP balance is modulated in vitro by 15dPGJ2 in fetuses and placentas from diabetic rats

Background  Maternal diabetes is associated with morphological placental abnormalities and foeto‐placental impairments. These alterations are linked with a dysregulation of the activity of matrix metalloproteinases (MMPs). We investigated the action of 15deoxyΔ12,14 prostaglandin J2 (15dPGJ2), a natural ligand of the peroxisome proliferator activated receptor (PPAR) γ, on MMP‐2 and MMP‐9 activities and tissue inhibitors of matrix metalloproteinases (TIMP) levels in foetuses and placentas from diabetic rats.

Dietary treatments enriched in olive and safflower oils regulate seric and placental matrix metalloproteinases in maternal diabetes.

OBJECTIVES Matrix metalloproteinases (MMPs) are proteolytic enzymes involved in placental development and function, although related to the pro-inflammatory environment when produced in excess. Previous studies have identified MMP-2 and MMP-9 overactivities in the placenta from diabetic rats. In this study, we aimed to determine whether diets supplemented with olive and safflower oil, enriched in natural PPAR ligands, are able to regulate MMP-2 and MMP-9 activities in the placenta and serum from diabetic rats. STUDY DESIGN Diabetes was induced in rat neonates by streptozotocin administration (90mg/kg s.c.). Control and diabetic rats were fed with 6% olive oil- or 6% safflower oil-supplemented diets from days 0.5-13.5 of gestation. MAIN OUTCOME MEASURES On day 13.5 of gestation, placentas and sera were isolated for further determination of matrix metalloproteinases (MMPs) 2 and 9 activities by zymography. Placental MMP-2 and MMP-9 protein concentration and immunolocalization were also determined. RESULTS Sera from diabetic pregnant animals showed MMP-2 and MMP-9 overactivities when compared to controls. Serum MMP-9 activity was significantly decreased when the diabetic animals received the olive and safflower oil dietary treatments. Placentas from diabetic rats showed increased MMP-2 and MMP-9 activities and protein concentrations, and both were decreased when diabetic rats received the olive and safflower dietary treatments. CONCLUSIONS This study demonstrates that both olive and safflower oil-supplemented diets were able to prevent MMPs overactivities in the placenta from diabetic rats, and that these beneficial effects are reflected in rat sera.

Altered matrix metalloproteinases and tissue inhibitors of metalloproteinases in embryos from diabetic rats during early organogenesis.

Maternal diabetes increases the risks for embryo malformations. Matrix metalloproteinase-2 (MMP-2) and MMP-9 are two relevant MMPs for embryo development. Here, we addressed whether changes in these MMPs and in tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-2 are altered in embryos and decidua from type 1 diabetic rats during early organogenesis. Our results demonstrate MMP-2 and MMP-9 overactivities and overexpression, together with increases in lipid peroxidation and nitric oxide production in embryos and decidua from diabetic animals. There is a concomitant increase in the inhibitory activity of TIMP-1 and TIMP-2 in embryos and decidua, and an increase in protein expression of embryonic TIMP-1 and TIMP-2. In situ zymography demonstrated MMPs overactivities despite increased TIMPs in embryos and decidua in maternal diabetes during early organogenesis. This study reveals that maternal diabetes leads to profound alterations in MMPs/TIMPs balance during embryo organogenesis, the gestational period during which most malformations are induced.

The effects of maternal dietary treatments with natural PPAR ligands on lipid metabolism in fetuses from control and diabetic rats

Maternal diabetes impairs fetal development and growth. We studied the effects of maternal diets enriched in unsaturated fatty acids capable of activating peroxisome proliferator-activated receptors (PPARs) on the concentrations of 15deoxyDelta12,14PGJ2 (15dPGJ2), lipid mass, and the de novo lipid synthesis in 13.5-day fetuses from control and diabetic rats. Diabetes was induced by neonatal streptozotocin administration (90 mg/kg). Rats were treated with a standard diet supplemented or not with 6% olive oil or 6% safflower oil from days 0.5 to 13.5 of gestation. Fetuses from diabetic rats fed with the standard diet showed reduced 15dPGJ2 concentrations, whereas maternal treatments with olive and safflower oils increased 15dPGJ2 concentrations. Fetuses from diabetic rats showed increased concentrations of phospholipids and increased synthesis of triglycerides, phospholipids, cholesterol and free fatty acids. Diabetic rat treatments with olive and safflower oils reduced phospholipids, cholesterol, and free fatty acid concentrations and the de novo lipid synthesis in the fetuses. These effects were different from those observed in fetuses from control rats, and seem not to involve PPARgamma activation. In conclusion, olive oil- and safflower oil-supplemented diets provide beneficial effects in maternal diabetes, as they prevent fetal impairments in 15dPGJ2 concentrations, lipid synthesis and lipid accumulation.