Maternal high-sodium intake alters the responsiveness of the renin–angiotensin system in adult offspring

High dietary salt intake attenuates nitric oxide mediated endothelium-dependent vasodilation and increases oxidative stress in pregnancy

OBJECTIVE

This study aimed to investigate the impact of dietary salt intake during normal pregnancy on maternal microvascular and macrovascular endothelium-dependent reactivity and oxidative stress level.

MATERIALS AND METHODS

In this cross-sectional study, based on their 24-h urinary sodium excretion, pregnant women (37-40 weeks of gestation) were divided into three groups: normal salt (<5.75 g/day, N  = 12), high salt (5.75-10.25 g/day, N  = 36), and very high salt (VHS;>10.25 g/day, N  = 17). Forearm skin microvascular reactivity in response to vascular occlusion, local heating (LTH) and iontophoresis of acetylcholine (AChID), as well as brachial artery flow mediated dilation (FMD) were measured. Serum nitric oxide, endocan, 8-iso-prostaglandin F2α (8-iso-PGF2α), thiobarbituric acid reactive substances (TBARS), and ferric-reducing ability of plasma assay were measured as biomarkers of endothelial function/activation and oxidative stress.

RESULTS

Brachial artery FMD, microvascular AChID, and LTH were significantly decreased in VHS compared with NS group, while LTH was also decreased in normal salt compared with high salt group. Nitric oxide was significantly decreased in both high salt and VHS groups compared with normal salt. Endocan, 8-iso-PGF2α, and TBARS were significantly increased in VHS compared with the normal salt group.

CONCLUSION

High dietary salt intake is associated with decreased nitric oxide mediated endothelium-dependent vasodilation in peripheral microcirculation and macrocirculation of healthy pregnant women due to increased oxidative stress.

Translational insights into mechanisms and preventive strategies after renal injury in neonates

Adverse perinatal circumstances can cause acute kidney injury (AKI) and contribute to chronic kidney disease (CKD). Accumulating evidence indicate that a wide spectrum of perinatal conditions interferes with normal kidney development and ultimately leads to aberrant kidney structure and function later in life. The present review addresses the lack of mechanistic knowledge with regard to perinatal origins of CKD and provides a comprehensive overview of pre- and peri-natal insults, including genetic predisposition, suboptimal nutritional supply, obesity and maternal metabolic disorders as well as placental insufficiency leading to intrauterine growth restriction (IUGR), prematurity, infections, inflammatory processes, and the need for life-saving treatments (e.g. oxygen supplementation, mechanical ventilation, medications) in neonates. Finally, we discuss future preventive, therapeutic, and regenerative directions. In summary, this review highlights the perinatal vulnerability of the kidney and the early origins of increased susceptibility toward AKI and CKD during postnatal life. Promotion of kidney health and prevention of disease require the understanding of perinatal injury in order to optimize perinatal micro- and macro-environments and enable normal kidney development.

Excessive maternal salt intake gives rise to vasopressin-dependent salt sensitivity of blood pressure in male offspring

Salt sensitivity of blood pressure (SSBP) is a trait carrying strong prognostic implications for various cardiovascular diseases. To test the hypothesis that excessive maternal salt intake causes SSBP in offspring through a mechanism dependent upon arginine-vasopressin (AVP), we performed a series of experiments using offspring of the rat dams salt-loaded during pregnancy and lactation with 1.5% saline drink ("experimental offspring") and those with normal perinatal salt exposure ("control offspring"). Salt challenge, given at 7-8 weeks of age with either 2% saline drink (3 days) or 8% NaCl-containing chow (4 weeks), had little or no effect on systolic blood pressure (SBP) in female offspring, whereas the salt challenge significantly raised SBP in male offspring, with the magnitude of increase being greater in experimental, than control, rats. Furthermore, the salt challenge not only raised plasma AVP level more and caused greater depressor responses to V1a and V2 AVP receptor antagonists to occur in experimental, than control, males, but it also made GABA excitatory in a significant proportion of magnocellular AVP neurons of experimental males by depolarizing GABA equilibrium potential. The effect of the maternal salt loading on the salt challenge-elicited SBP response in male offspring was precluded by maternal conivaptan treatment (non-selective AVP receptor antagonist) during the salt-loading period, whereas it was mimicked by neonatal AVP treatment. These results suggest that the excessive maternal salt intake brings about SSBP in male offspring, both the programming and the expression of which depend on increased AVP secretion that may partly result from excitatory GABAergic action.

Impact of early-life diet on long-term renal health

In the last years, great advances have been made in the effort to understand how nutritional influences can affect long-term renal health. Evidence has accumulated that maternal nutrition before and during pregnancy and lactation as well as early postnatal nutrition is of special significance. In this review, we summarize epidemiologic and experimental data on the renal effects of perinatal exposure to energy restriction, low-protein diet, high-fat diet, high-fructose diet, and high- and low-salt diet as well as micronutrient deficiencies. Interestingly, different modifications during early-life diet may end up with similar sequelae for the offspring. On the other hand, molecular pathways can be influenced in opposite directions by different dietary interventions during early life. Importantly, postnatal nutrition significantly modifies the phenotype induced by maternal diet. Sequelae of altered macro- or micronutrient intakes include altered nephron count, blood pressure dysregulation, altered sodium handling, endothelial dysfunction, inflammation, mitochondrial dysfunction, and oxidative stress. In addition, renal prostaglandin metabolism as well as renal AMPK, mTOR, and PPAR signaling can be affected and the renin-angiotensin-aldosterone system may be dysregulated. Lately, the influence of early-life diet on gut microbiota leading to altered short chain fatty acid profiles has been discussed in the etiology of arterial hypertension. Against this background, the preventive and therapeutic potential of perinatal nutritional interventions regarding kidney disease is an emerging field of research. Especially individuals at risk (e.g., newborns from mothers who suffered from malnutrition during gestation) could disproportionately benefit from well-targeted dietary interventions.

N-acetyl-l-cysteine exacerbates kidney dysfunction caused by a chronic high-sodium diet in renal ischemia and reperfusion rats

AIMS

To investigate the effect of long-term N-acetyl-l-cysteine (NAC) treatment in Wistar rats subjected to renal ischemia and reperfusion (IR) and a chronic high‑sodium diet (HSD).

MAIN METHODS

Adult male Wistar rats received an HSD (8.0% NaCl) or a normal‑sodium diet (NSD; 1.3% NaCl) and NAC (600 mg/L) or normal drinking water starting at 8 weeks of age. At 11 weeks of age, the rats from both diet and NAC or water treatment groups underwent renal IR or Sham surgery and were followed for 10 weeks. The study consisted of six animal groups: NSD + Sham + water; NSD + IR + water; NSD + IR + NAC; HSD + Sham + water; HSD + IR + water; and HSD + IR + NAC.

KEY FINDINGS

Tail blood pressure (tBP) increased with IR and NAC treatment in the NSD group but not in the HSD group. The serum creatinine level was higher after NAC treatment in both diet groups, and creatinine clearance was decreased in only the HSD + IR + NAC group. Albuminuria increased in the HSD + IR + water group and decreased in the HSD + IR + NAC group. Kidney mass was increased in the HSD + IR group and decreased with NAC treatment. Renal fibrosis was prevented with NAC treatment and cardiac fibrosis was decreased with NAC treatment in the HSD + IR group.

SIGNIFICANCE

NAC treatment promoted structural improvements, such as decreased albuminuria and fibrosis, in the kidney and heart. However, NAC could not recover kidney function or blood pressure from the effects of IR associated with an HSD. Therefore, in general, long-term NAC treatment is not effective and is deleterious to recovery of function after kidney injury.

Maternal high-sodium intake affects the offspring' vascular renin-angiotensin system promoting endothelial dysfunction in rats

Perinatal sodium overload induces endothelial dysfunction in adult offspring, but the underlying mechanisms are not fully known. The involvement of tissue renin-angiotensin system on high sodium-programmed endothelial dysfunction was examined. Acetylcholine and angiotensin I and II responses were analyzed in aorta and mesenteric resistance arteries from 24-week-old male offspring of normal-salt (O-NS, 1.3% NaCl) and high-salt (O-HS, 8% NaCl) fed dams. COX-2 expression, O₂^- production and angiotensin converting enzyme (ACE) activity were determined. A separated O-HS was treated with losartan (15 mg kg^-1/day) for eight weeks. Compared to O-NS, O-HS were normotensive. Acetylcholine-induced relaxation was impaired in O-HS arteries, which was improved by tempol, apocynin or indomethacin. The angiotensin I-induced contraction was greater in O-HS arteries, whereas the angiotensin II responses were unchanged. ACE activity, O₂^- production and COX-2 expression were increased in O-HS arteries. In this group, the increased O₂^- production was inhibited by apocynin or losartan. Chronic losartan decreased COX-2 expression and restored the endothelium-dependent vasodilation in O-HS. Our findings reiterate that perinatal sodium overload programs endothelial dysfunction in adult offspring through a blood pressure-independent mechanism. Our results also suggest that vascular angiotensin II is the main mediator of high sodium-programmed endothelial dysfunction, promoting COX-2 expression and oxidative stress.

High maternal sodium intake alters sex-specific renal renin-angiotensin system components in newborn Wistar offspring

This study aimed to evaluate the systemic and renal renin-angiotensin-aldosterone system (RAAS) at birth in male and female offspring and in mothers fed a high sodium diet (HSD) before and during gestation. Female Wistar rats were fed a HSD (8.0% NaCl) or a normal sodium diet (1.3% NaCl) from 8 weeks of age until delivery of their first litter. Maternal body weight, tail blood pressure, and food and water intake were evaluated. The litter sizes were assessed, and the body and kidney weights of the offspring were measured. Both mothers and offspring were euthanized immediately following the birth of the pups to evaluate plasma renin activity (PRA), renal renin content (RRC), renal angiotensin-converting enzyme (ACE) activity, renal angiotensin (Ang) II content, serum aldosterone (ALDO) levels, and renal cortical and medullary renin messenger RNA expression. In mothers in the HSD group, water intake and kidney mass were higher, whereas renal ACE activity, Ang II, PRA, ALDO and RRC were decreased. In the offspring of HSD-fed dams, the body and kidney mass were lower in both genders, renal ACE activity was lower in females and renal Ang II was lower in males. PRA, RRC, renin gene expression and ALDO levels did not differ between the groups of offspring. The data presented herein showed that a maternal HSD during pregnancy induces low birth weight and a sex-specific response in the RAAS in offspring.

Maternal high-salt intake during pregnancy reprogrammed renin-angiotensin system-mediated cardiomyocyte apoptosis in the adult offspring heart

AIMS

Excess salt intake during pregnancy may alter fetal organ structures and functions leading to increased risks in the development of cardiovascular diseases in later life. The present study determined whether and how the prenatal high-salt (HS) diets affect renin-angiotensin system (RAS) that may mediate cardiac cell death.

METHODS AND RESULTS

Angiotensin II receptors, AT1 and AT2, protein expression was increased in the myocardium of the offspring exposed to prenatal HS; apoptotic cells appeared in the myocardium of the adult offspring. Mitochondrion was isolated in cell experiments, and the data showed cardiomyocyte apoptosis requiring cytochrome C release. Pretreating H9C2 cells with AT2 agonist CGP42112A induced cell apoptosis in DNA fragments and activated caspase 3. CGP42112A increased mitochondrion cytochrome C release and apoptosis in the cells.

CONCLUSION

Both in vitro and in vivo study demonstrated that cardiomyocyte apoptosis was related to AT2 activation. Prenatal HS diets may reprogram RAS that mediates apoptosis in the offspring myocardium, and AT2 may contribute to cardiomyocyte apoptosis via the cytochrome C release pathway.