Effect of low birth weight on impaired renal development and function and hypertension in rat model

Cardiovascular and renal profiles in rat offspring that do not undergo catch-up growth after exposure to maternal protein restriction

Maternal protein restriction is often associated with structural and functional sequelae in offspring, particularly affecting growth and renal-cardiovascular function. However, there is little understanding as to whether hypertension and kidney disease occur because of a primary nephron deficit or whether controlling postnatal growth can result in normal renal-cardiovascular phenotypes. To investigate this, female Sprague-Dawley rats were fed either a low-protein (LP, 8.4% protein) or normal-protein (NP, 19.4% protein) diet prior to mating and until offspring were weaned at postnatal day (PN) 21. Offspring were then fed a non 'growth' (4.6% fat) which ensured that catch-up growth did not occur. Offspring growth was determined by weight and dual energy X-ray absorptiometry. Nephron number was determined at PN21 using the disector-fractionator method. Kidney function was measured at PN180 and PN360 using clearance methods. Blood pressure was measured at PN360 using radio-telemetry. Body weight was similar at PN1, but by PN21 LP offspring were 39% smaller than controls (P_diet < 0.001). This difference was due to proportional changes in lean muscle, fat, and bone content. LP offspring remained smaller than NP offspring until PN360. In LP offspring, nephron number was 26% less in males and 17% less in females, than NP controls (P_diet < 0.0004). Kidney function was similar across dietary groups and sexes at PN180 and PN360. Blood pressure was similar in LP and NP offspring at PN360. These findings suggest that remaining on a slow growth trajectory after exposure to a suboptimal intrauterine environment does not lead to the development of kidney dysfunction and hypertension.

Effect of L-arginine supplementation on the hepatic phosphatidylinositol 3-kinase signaling pathway and gluconeogenic enzymes in early intrauterine growth-restricted rats

The present study aimed to investigate the response of the phosphatidylinositol 3-kinase (PI3K) signaling pathway and gluconeogenic enzymes in intrauterine growth-restricted rats to dietary L-arginine (L-Arg) supplementation during the lactation period early in life. Pregnant Sprague-Dawley rats were randomly divided into a control group (CON), an intrauterine growth restriction group (IUGR) and an L-Arg group (LA). The pregnant rats in the CON group were fed a 21% protein diet, and those in the IUGR and LA groups were fed a 10% low protein diet, and all rats were fed a 21% protein diet after delivery. Water was available ad libitum to the pregnant rats during the 21-day lactation period, and the water provided to the LA group included 200 mg/kg/day L-Arg. Blood glucose, serum insulin, homeostasis model of assessment for insulin resistance (HOMA-IR), PI3K and protein kinase B (PKB) protein expression, and phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase) mRNA expression in the offspring rats were measured postnatally at 1, 3 and 8 weeks. No significant difference in blood glucose, serum insulin and HOMA-IR were identified at any time point among the three groups. PI3K and PKB expression was lower in the IUGR group offspring compared with that in the CON group offspring, but both were increased by dietary L-Arg supplementation. PEPCK mRNA and G-6-Pase mRNA expression levels in the offspring of the IUGR group were higher compared with those in the CON group but were downregulated following L-Arg supplementation. These results suggest that dietary L-Arg supplementation during the early lactation period promoted catch-up growth and reversed abnormalities in hepatic insulin signaling and gene expression of gluconeogenic enzymes in IUGR offspring rats.

Complications during pregnancy and fetal development: implications for the occurrence of chronic kidney disease

INTRODUCTION

Numerous epidemiological studies indicate an inverse association between birth weight and the risk for chronic kidney disease. Areas covered: Historically, the first studies to address the developmental origins of chronic disease focused on the inverse relationship between birth weight and blood pressure. A reduction in nephron number was a consistent finding in low birth weight individuals and experimental models of developmental insult. Recent studies indicate that a congenital reduction in renal reserve in conjunction with an increase in blood pressure that has its origins in fetal life increases vulnerability to renal injury and disease. Expert commentary: Limited experimental studies have investigated the mechanisms that contribute to the developmental origins of kidney disease. Several studies suggest that enhanced susceptibility to renal injury following a developmental insult is altered by sex and age. More in-depth studies are needed to clarify how low birth weight contributes to enhanced renal risk, and how sex and age influence this adverse relationship.

High and Low Salt Intake during Pregnancy: Impact on Cardiac and Renal Structure in Newborns

INTRODUCTION

Previous studies from our laboratory demonstrated that dietary salt overload and salt restriction during pregnancy were associated with cardiac and renal structural and/or functional alterations in adult offspring. The present study evaluated renal and cardiac structure and the local renin-angiotensin system in newborns from dams fed high-, normal- or low-salt diets during pregnancy.

METHODS

Female Wistar rats were fed low- (LS, 0.15% NaCl), normal- (NS, 1.3% NaCl) or high- (HS, 8% NaCl) salt diets during pregnancy. Kidneys and hearts were collected from newborns (n = 6-8/group) during the first 24 hours after birth to evaluate possible changes in structure using stereology. Protein expression of renin-angiotensin system components was evaluated using an indirect enzyme-linked immunosorbent assay (ELISA).

RESULTS

No differences between groups were observed in total renal volume, volume of renal compartments or number of glomeruli. The transverse diameter of the nuclei of cardiomyocytes was greater in HS than NS males in the left and right ventricles. Protein expression of the AT1 receptor was lower in the kidneys of the LS than in those of the NS and HS males but not females. Protein expression of the AT2 receptor was lower in the kidneys of the LS males and females than in those of the NS males and females.

CONCLUSION

High salt intake during pregnancy induced left and right ventricular hypertrophy in male newborns. Salt restriction during pregnancy reduced the expression of renal angiotensin II receptors in newborns.

Maternal low-protein diet causes body weight loss in male, neonate Sprague-Dawley rats involving UCP-1-mediated thermogenesis

Brown adipose tissue (BAT) plays an important role in regulating body weight (BW) by modifying thermogenesis. Maternal low protein (LP) diets reduce offspring birth weight. Increased BAT thermogenesis in utero may be one mechanism for the lower BW. However, whether maternal LP nutrition alters BAT thermogenesis and BW of offspring in utero is not yet known. We fed obese-prone Sprague-Dawley dams 8% LP or 20% normal protein (NP) diets for 3 weeks prior to breeding and through pregnancy. BW and gene expression of interscapular BAT (iBAT) thermogenic markers were measured in male fetal (gestation day 18) and neonatal (day 0 or 1) offspring. BW of neonatal LP males was lower than NP males but no difference was observed in females. Gene and protein expression of UCP-1 and transcription factors PRDM16 and PPARα in iBAT were 2- to 6-fold greater in LP than in NP male neonatal offspring. FNDC5, a precursor of irisin and activator of thermogenesis, was expressed 2-fold greater in neonatal LP iBAT than NP males. However, fetal iBAT UCP-1, PRDM16, PPARα and irisin mRNA did not differ between LP and NP groups. Maternal LP diet had no effects on placental irisin and UCP-2 expression. These results suggest that prenatal protein restriction increases the risk for low BW through mechanisms affecting full-term offspring iBAT thermogenesis but not greatly altering fetal iBAT or placental thermogenesis.

Antioxidant treatment reverts increased arterial Basal tone and oxidative stress in nephrectomized (5/6) hypertensive rats

Nonischemic 5/6 nephrectomized rat (NefR) is a model of chronic kidney disease. However, little is known about vascular dysfunction and its relation with hypertension in NefR. Aims. To evaluate possible alterations of endothelial function, NO-bioavailability, and basal tone in aorta from NefR and the role of oxidative stress. Sprague Dawley rats were divided into sham rats (SR), NefR, and NefR treated with tempol (NefR-T). Mean arterial pressure (MAP) and renal function were determined. In isolated aortic rings the following was measured: 1-endothelial function, 2-basal tone, 3-NO levels, 4-membrane potential (MP), and 5-oxidative stress. NefR increased MAP (SR: 119 ± 4 mmHg; n = 7; NefR: 169 ± 6; n = 8; P < 0.001). Tempol did not modify MAP (NefR-T: 168 ± 10; n = 6; P < 0.001). NefR showed endothelial dysfunction, increased basal tone and decreased NO levels (SR: 32 ± 2 nA; n = 7, NefR: 10 ± 2; n = 8; P < 0.001). In both in vitro and in vivo tempol improves basal tone, NO levels, and MP. Oxidative stress in NefR was reverted in NefR-T. We described, for the first time, that aorta from NefR presented increased basal tone related to endothelial dysfunction and decreased NO-bioavailability. The fact that tempol improves NO-contents and basal tone, without decrease MAP, indicates that oxidative stress could be implicated early and independently to hypertension, in the vascular alterations.