Metabolic programming during lactation stimulates renal Na+ transport in the adult offspring due to an early impact on local angiotensin II pathways.

BACKGROUND: Several studies have correlated perinatal malnutrition with diseases in adulthood, giving support to the programming hypothesis. In this study, the effects of maternal undernutrition during lactation on renal Na(+)-transporters and on the local angiotensin II (Ang II) signaling cascade in rats were investigated. METHODOLOGY/PRINCIPAL FINDINGS: Female rats received a hypoproteic diet (8% protein) throughout lactation. Control and programmed offspring consumed a diet containing 20% protein after weaning. Programming caused a decrease in the number of nephrons (35%), in the area of the Bowman's capsule (30%) and the capillary tuft (30%), and increased collagen deposition in the cortex and medulla (by 175% and 700%, respectively). In programmed rats the expression of (Na(+)+K(+))ATPase in proximal tubules increased by 40%, but its activity was doubled owing to a threefold increase in affinity for K(+). Programming doubled the ouabain-insensitive Na(+)-ATPase activity with loss of its physiological response to Ang II, increased the expression of AT(1) and decreased the expression of AT(2) receptors), and caused a pronounced inhibition (90%) of protein kinase C activity with decrease in the expression of the α (24%) and ε (13%) isoforms. Activity and expression of cyclic AMP-dependent protein kinase decreased in the same proportion as the AT(2) receptors (30%). In vivo studies at 60 days revealed an increased glomerular filtration rate (GFR) (70%), increased Na(+) excretion (80%) and intense proteinuria (increase of 400% in protein excretion). Programmed rats, which had normal arterial pressure at 60 days, became hypertensive by 150 days. CONCLUSIONS/SIGNIFICANCE: Maternal protein restriction during lactation results in alterations in GFR, renal Na(+) handling and in components of the Ang II-linked regulatory pathway of renal Na(+) reabsorption. At the molecular level, they provide a framework for understanding how metabolic programming of renal mechanisms contributes to the onset of hypertension in adulthood.

Venous thrombosis risk: effects of palm oil and hydrogenated fat diet in rats.

OBJECTIVE: We tested whether diets containing partially hydrogenated fat (PHVO, rich in trans fatty acids) or palm oil (PO, rich in saturated fat-C16 palmitic fatty acid) had different effects on the propensity for venous thrombosis, a marker of haemostatic cardiovascular risk. METHODS: Female Wistar rats were fed normolipidic diets containing PHVO or PO during lactation, and their young male pups were fed the same diets from weaning until the 180th day of life. We evaluated platelet fatty acid composition, serum lipids, platelet aggregation, clotting time, and venous thrombus formation. RESULTS: A significant and cumulative incorporation of trans fatty acid was observed only in the platelet lipids from the PHVO group, associated with an increased sensitivity to adenosine diphosphate (ADP) and venous thrombus formation in vivo. Platelets from rats raised on the PO diet also exhibited platelet aggregation induced by ADP and an increase in venous thrombus weight, with a concomitant increase in serum triglycerides. CONCLUSION: The prolonged replacement of dietary hydrogenated fat by PO impaired platelet aggregability and venous thrombosis, suggesting an increased risk of thromboembolic diseases.

Betaine protects urea-induced denaturation of myosin subfragment-1.

We have demonstrated previously that urea inhibits the activity and alters the tertiary structure of skeletal muscle myosin in a biphasic manner. This was attributed to differential effects on its globular and filamentous portion. The inhibition of catalytic activity was counteracted by methylamines. With the aim of comprehending the effects of urea on the catalytic (globular) portion of myosin, this study examines the effects of urea and the countereffects of betaine on the catalytic activity and structure of myosin subfragment-1. It is shown that urea inactivates subfragment-1 in parallel with its ability to induce exposure of the enzyme hydrophobic domains, as assessed using intrinsic and extrinsic fluorescence. Both effects are counteracted by betaine, which alone does not significantly affect subfragment-1. Urea also enhances the accessibility of thiol groups, promotes aggregation and decreases the alpha-helix content of S1, effects that are also counteracted by betaine. We conclude that urea-induced inactivation of the enzyme is caused by partial unfolding of the myosin catalytic domain.

Dietary fatty acids early in life affect lipid metabolism and adiposity in young rats.

The purpose of this study was to evaluate the effects of four isoenergetic diets of differing fat composition on blood lipid profile and adiposity in young rats. Diets containing different lipid sources--partially hydrogenated vegetable oil (PHVO), palm oil (PO), canola oil (CO), and soy oil (SO)--were fed to lactating rats during the 21 days of lactation, and then fed to young males following weaning until the 45th day of life. In vivo lipogenesis rate (LR), lipid content (LC), relative level of FA, and the activity of lipoprotein lipase (LPL) enzyme were measured in epididymal adipose tissue (EPI). Fasting blood lipoproteins and LC in the carcass were also appraised. Body weight of PO and PHVO groups was significantly higher than CO and SO groups from day 14 of lactation to day 45, despite the lower food intake in the PHVO group. PO and PHVO groups presented higher LR and LC in EPI than SO and CO groups. Carcass fat content was significantly higher in PHVO and PO groups than in CO and SO groups. The LPL activity in EPI was unaffected by dietary lipids. PHVO group had increased total cholesterol and TAG concentrations in comparison with the PO group, and significantly lower HDL level compared with the other groups. These results show that the kind of FA in the dietary lipid offered early in life can affect lipid metabolism and adiposity.

Antithrombotic properties of Ixolaris, a potent inhibitor of the extrinsic pathway of the coagulation cascade.

Ixolaris is a two-Kunitz tick salivary gland protein identified in Ixodes scapularis that presents extensive sequence homology to TFPI. It binds to FXa or FX as scaffolds and inhibits tissue factor/FVIIa complex (extrinsic Xnase). Differently from TFPI, ixolaris does not bind to the active site cleft of FXa. Instead, complex formation is mediated by the FXa heparin-binding exosite, which may also results in decreased FXa activity into the prothrombinase complex. In this report, we show that recombinant (125)I-ixolaris interacts with rat and human FX in plasma and prolongs the prothrombin time (PT) and activated partial thromboplastin time (aPTT) in vitro. We have also investigated the effects of ixolaris in vivo, using a venous thrombosis model. Subcutaneous (s.c.) or intravenous (i.v.) administration of ixolaris in rats caused a dose-dependent reduction in thrombus formation, with complete inhibition attained at 20 microg/kg and 10 microg/kg, respectively. Antithrombotic effects were observed 3 h after s.c. administration of ixolaris and lasted for 24 h thereafter. Ex vivo experiments showed that ixolaris (up to 100 microg/kg) did not affect the aPTT, while the PT was increased by approximately 0.4-fold at the highest ixolaris concentration. Remarkably, effective antithrombotic doses of ixolaris (20 microg/kg) was not associated with bleeding which was significant only at higher doses of the anticoagulant (40 microg/kg). Our experiments demonstrate that ixolaris is an effective and possibly safe antithrombotic agent in vivo.

Counteracting effects of urea and methylamines in function and structure of skeletal muscle myosin.

Myosin is an asymmetric protein that comprises two globular heads (S1) and a double-stranded alpha-helical rod. We have investigated the effects of urea and the methylamines trimethylamine oxide (TMA-O) and glycine betaine (betaine) on activity and structure of skeletal muscle myosin. K(+) EDTA ATPase activity of myosin was almost completely inhibited by urea (2M); TMA-O stimulated myosin activity, whereas betaine had no effect. When combined with urea (0-2M), TMA-O or betaine (1 M) effectively protected the ATPase activity of myosin against inhibition. Intrinsic fluorescence measurements showed that in urea or TMA-O (0-2M), there were no shifts in the center of mass of the fluorescence spectrum of myosin, despite a decrease in fluorescence intensity. However, these osmolytes at concentrations above 2M produced a red shift in the emission spectrum. Betaine alone did not alter the center of mass at any concentration tested up to 5.2M. Thus, modifications in ATPase activity induced by low concentrations of solutes (<2M) are not directly correlated with the modifications in myosin structure detected by fluorescence. Both methylamines (>or=1M) were also able to protect myosin structure against urea-induced effects (2-8M). Protection was not observed for S1, supporting the hypothesis that these osmolytes have a biphasic effect on myosin: at lower concentrations there is an effect on the globular portion (S1), and at higher concentrations there is an effect on the coiled-coil (rod) portion of myosin.