Combined prenatal and postnatal protein restriction influences adult kidney structure, function, and arterial pressure

The effects of prenatal protein restriction on adult renal and cardiovascular function have been studied in considerable detail. However, little is known about the effects of life-long protein restriction, a common condition in the developing world. Therefore, we determined in rats the effects of combined pre- and postnatal protein restriction on adult arterial pressure and renal function and responses to increased dietary sodium. Nephron number was also determined. Male Sprague-Dawley rats were born to mothers fed a low [8% (wt/wt), LP] or normal [20% (wt/wt), NP] isocaloric protein diet throughout pregnancy and maintained on these diets after birth. At postnatal day 135, nephron number, mean arterial pressure (MAP), and renal function were determined. A high-NaCl [8.0% (wt/wt), high-salt] diet was fed to a subset of rats from weaning. MAP was less in LP than in NP rats (120 +/- 2 vs. 128 +/- 2 mmHg, P < 0.05) and was not significantly altered by increased salt intake. Nephron number was 31% less in LP than in NP rats (P < 0.001). The volume of individual glomeruli was also less in LP than in NP rats, as were calculated effective renal plasma flow and glomerular filtration rate. Glomerular filtration rate, but not effective renal plasma flow, appeared to be increased by high salt intake, particularly in LP rats. In conclusion, protein restriction induced a severe nephron deficit, but MAP was lower, rather than higher, in protein-restricted than in control rats in adulthood. These findings indicate that the postnatal environment plays a key role in determining the outcomes of developmental programming.     

Early renal structure alteration in rat offspring from dams fed low protein diet

To investigate the early renal alterations due to severe maternal protein restriction (MPR) Wistar dams received 23% (normal protein, NP) or 5% (low protein, LP) chow during gestation and lactation periods. In NP offspring at birth, the cortex-to-medulla (C/M) ratio was 35% greater in female than in male offspring and the mature/immature glomeruli ratio was lower in both sexes of LP offspring than in the matched NP ones (by 20%). At birth and at weaning the kidney of the LP offspring showed fewer glomeruli (40% less) than the age-matched NP offspring. The NP female offspring had almost 20% fewer glomeruli than the matched male offspring. At weaning, the number of glomeruli was positively correlated with BM at birth (R=0.86; P<0.001). The effects of gender and maternal protein restriction, both individually and overall, based on biometrical and stereological parameters were: day 1, MPR largely responsible for the majority of alterations observed in LP groups, however gender influenced C/M ratio; day 21, MPR and gender interacted and modified the number of glomeruli per kidney. The early adverse of MPR effect on renal development is disproportionate between mature and immature glomeruli at birth leading to fewer glomeruli at weaning. This supports epidemiological data in humans underlying why fetuses with low birth weight carry an increased risk of mortality from chronic diseases in adulthood, including hypertension.     

Modest maternal protein restriction fails to program adult hypertension in female rats

Modest maternal dietary protein restriction in the rat leads to hypertension in adult male offspring. The purpose of this study was to determine whether female rats are resistant to developing the increased blood pressure seen in male rats after maternal protein restriction. Pregnant rats were fed a normal protein (19%, NP) or low-protein (8.5%, LP) diet throughout gestation. Renal renin protein and ANG II levels were reduced by 50-65% in male LP compared with NP pups, but were not suppressed in female LP compared with female NP. Mean arterial pressure in conscious, chronically instrumented adult female offspring (22 wk) was not different in LP (LP: 120 +/- 3 mmHg vs. NP: 121 +/- 2 mmHg), and glomerular filtration rate was also not different in LP vs. NP. The number of glomeruli per kidney was similar in adult LP and NP female offspring (LP: 26,050 +/- 2,071 vs. NP: 26,248 +/- 1,292, NP), and individual glomerular volume was also not different (LP: 0.92 +/- 0.11 10(6) microm(3), LP vs. NP: 1.07 +/- 0.11 10(6) microm(3)); the total volume of all glomeruli per kidney was also not significantly different. Thus female rats are relatively resistant to the programming for adult hypertension by perinatal protein restriction that we have described in males. This resistance may be due to the fact that modest maternal protein restriction does not reduce the number of glomeruli with which females are endowed as it does in males. The intrarenal renin-angiotensin system during development may play a key role in this protective effect of female gender.     

Birth weight and postnatal dietary protein level affect performance, muscle metabolism and meat quality in pigs

Intrauterine growth restriction (IUGR), resulting in low birth body weight (LBW) occurs naturally in pigs. However, IUGR may also cause persistent changes in physiology and metabolism resulting in poorer performance, organogenesis and meat quality. As IUGR pigs have a lower daily gain from birth to slaughter they may differ in utilization of nutrients and requirements for dietary protein compared with their larger littermates. Thus, the objective in this study was to examine the interaction between birth body weight (BW) and the postnatal dietary protein level, in relation to postnatal performance, organogenesis, muscle metabolism and meat quality. The experiment was carried out with offspring from 16 purebred Danish Landrace gilts mated to Danish Landrace boars. The female and entire male pigs with LBW that survived at weaning were compared with the female and male pigs with the highest/high birth body weight (HBW) within each litter. The offspring were reared individually from weaning and were fed ad libitum a diet containing either a normal level of protein (NP) for optimal growth or an isocaloric diet containing a 30% lower protein content (LP) from 3 weeks to 150 days of age. At slaughter, we found no interactions between birth weight group and dietary protein level for any of the measured traits. The relative crown-rump length (cm/kg) at birth indicates that LBW pigs were thinner than HBW pigs. Daily gain and feed intake were reduced by 14% and 10%, respectively, while the kg feed/kg gain was slightly increased by 3% in LBW pigs compared with HBW pigs. The LP diet reduced daily gain by 27% due to reduced feed intake and increased kg feed/kg gain by 12% and 21%, respectively compared with the NP diet. LBW male pigs produced meat with a higher shear force than male HBW pigs and also LP pigs produced meat with higher shear force than NP pigs. The activity of lactate dehydrogenase in the Longissimus dorsi muscle (LD) was reduced in pigs fed the LP diet. Calpastatin was increased in LD of LBW pigs and decreased in pigs fed the NP diet. In conclusion, these results suggest a rejection of our hypothesis that low birth weight littermates have a lower requirement for dietary protein compared with heavy weight littermates. Furthermore, LBW male pigs and LP fed pigs of both genders produced less tender meat than HBW pigs or NP fed pigs, respectively.     

Protein-restriction diet during the suckling phase programs rat metabolism against obesity and insulin resistance exacerbation induced by a high-fat diet in adulthood

Protein restriction during the suckling phase can malprogram rat offspring to a lean phenotype associated with metabolic dysfunctions later in life. We tested whether protein-caloric restriction during lactation can exacerbate the effect of a high-fat (HF) diet at adulthood. To test this hypothesis, we fed lactating Wistar dams with a low-protein (LP; 4% protein) diet during the first 2 weeks of lactation or a normal-protein (NP; 23% protein) diet throughout lactation. Rat offspring from NP and LP mothers received a normal-protein diet until 60 days old. At this time, a batch of animals from both groups was fed an HF (35% fat) diet, while another received an NF (7% fat) diet. Maternal protein-caloric restriction provoked lower body weight and fat pad stores, hypoinsulinemia, glucose intolerance, higher insulin sensitivity, reduced insulin secretion and altered autonomic nervous system (ANS) function in adult rat offspring. At 90 days old, NP rats fed an HF diet in adulthood displayed obesity, impaired glucose homeostasis and altered insulin secretion and ANS activity. Interestingly, the LP/HF group also presented fat pad and body weight gain, altered glucose homeostasis, hyperleptinemia and impaired insulin secretion but at a smaller magnitude than the NP-HF group. In addition, LP/HF rats displayed elevated insulin sensitivity. We concluded that protein-caloric restriction during the first 14 days of life programs the rat metabolism against obesity and insulin resistance exacerbation induced by an obesogenic HF diet.     

Role of maternal glucocorticoid inducible kinase SGK1 in fetal programming of blood pressure in response to prenatal diet

Maternal stress and malnutrition modify intrauterine fetal development with impact on postnatal blood pressure, nutrient, water, and electrolyte metabolism. The present study explored the possible involvement of maternal serum- and glucocorticoid-inducible kinase (SGK)-1 in fetal programming of blood pressure. To this end, wild-type (sgk1(+/+)) male mice were mated with SGK1 knockout (sgk1(-/-)) female mice, and sgk1(-/-) males with sgk1(+/+) females, resulting in both cases in heterozygotic (sgk1(-/+)) offspring. Following prenatal protein restriction, the offspring of sgk1(+/+) mothers gained weight significantly slower and had significantly higher blood pressure after birth. Moreover, a sexual dimorphism was apparent in fasting blood glucose and plasma corticosterone concentrations, with higher levels in female offspring. In contrast, prenatal protein restriction of sgk1(-/-) mothers had no significant effect on postnatal weight gain, blood pressure, plasma glucose concentration, or corticosterone levels, irrespective of offspring sex. Plasma aldosterone concentration, urinary flow rates, and urinary excretions of Na(+) and K(+) were not significantly modified by either maternal genotype or nutritional manipulation. In conclusion, maternal signals mediated by SGK1 may play a decisive role in fetal programming of hypertension induced by prenatal protein restriction.     

Effect of maternal feed restriction during pregnancy on glucose tolerance in the adult guinea pig

Maternal nutrient restriction and impaired fetal growth are associated with postnatal insulin resistance, hyperinsulinemia, and glucose intolerance in humans but not consistently in other species, such as the rat or sheep. We therefore determined the effect of mild (85% ad libitum intake/kg body wt) or moderate (70% ad libitum intake/kg body wt) maternal feed restriction throughout pregnancy on glucose and insulin responses to an intravenous glucose tolerance test (IVGTT) in the young adult guinea pig. Maternal feed restriction reduced birth weight (mild and moderate: both P < 0.02) in male offspring. Moderate restriction increased plasma glucose area under the curve (P < 0.04) and decreased the glucose tolerance index (K(G)) (P < 0.02) during the IVGTT in male offspring compared with those of mildly restricted but not of ad libitum-fed mothers. Moderate restriction increased fasting plasma insulin (P < 0.04, adjusted for litter size) and the insulin response to IVGTT (P < 0.001), and both moderate and mild restriction increased the insulin-to-glucose ratio during the IVGTT (P < 0.003 and P < 0.02) in male offspring. When offspring were classed into tertiles according to birth weight, glucose tolerance was not altered, but fasting insulin concentrations were increased in low compared with medium birth weight males (P < 0.03). The insulin-to-glucose ratio throughout the IVGTT was increased in low compared with medium (P < 0.01) or high (P < 0.05) birth weight males. Thus maternal feed restriction in the guinea pig restricts fetal growth and causes hyperinsulinemia in young adult male offspring, suggestive of insulin resistance. These findings suggest that mild to moderate prenatal perturbation programs postnatal glucose homeostasis adversely in the guinea pig, as in the human.     

Gestational low protein diet selectively induces the amino acid response pathway target genes in the liver of offspring rats through transcription factor binding and histone modifications

The amino acid response (AAR) pathway detects a deficiency of dietary amino acid or protein. To investigate the impact of gestational protein restriction on the AAR pathway in offspring, pregnant Sprague-Dawley rats were fed a control (C) or low protein (LP) diet during gestation. Livers of female offspring were collected on postnatal d 38. The mRNA amount of Atf3 in LP offspring increased significantly compared with C offspring, while Asns did not differ between the two groups. ATF4 and p-eIF2α were both induced in LP offspring, whereas p-ERK was significantly decreased. Additionally, amino acid limitation (-AA) in HepG2 cells increased p-ERK and AAR pathway-related genes, while U0126 decreased p-ERK but did not completely reverse the activation of AAR pathway-related genes. Chromatin immunoprecipitation assay demonstrated an increased association of both RNA polymerase II (Pol II) and ATF4 at the Atf3 promoter in LP offspring, while acetylated histone H4, tri-methyl histone H3 at lysine 9, ATF4, ATF3, C/EBPβ, and CHOP, but not Pol II, were all increased at the Asns promoter in LP offspring. In -AA HepG2 cells, C/EBPβ siRNA treatment did not prevent the activation of either ATF3 or ASNS in response to -AA, while ATF4 siRNA prevented the activation of ASNS but not ATF3. Our data demonstrates that a maternal LP diet programs the AAR pathway in the liver of offspring rats. The differential priming of the downstream target genes of the AAR pathway in response to maternal LP diet presents a novel regulatory mechanism related to nutrient-gene interactions.     

Does Early Mismatched Nutrition Predispose to Hypertension and Atherosclerosis,in Male Mice?

Background

A link between early mismatched nutritional environment and development of components of the metabolic syndrome later in life has been shown in epidemiological and animal data. The aim of this study was to investigate whether an early mismatched nutrition produced by catch-up growth after fetal protein restriction could induce the appearance of hypertension and/or atherosclerosis in adult male mice.

Methodology/Principal Findings

Wild-type C57BL6/J or LDLr−/− dams were fed a low protein (LP) or a control (C) diet during gestation. Catch-up growth was induced in LP offspring by feeding dams with a control diet and by culling the litter to 4 pups against 8 in controls. At weaning, male mice were fed either standard chow or an obesogenic diet (OB), leading to 4 experimental groups. Blood pressure (BP) and heart rate (HR) were assessed in conscious unrestrained wild-type mice by telemetry. Atherosclerosis plaque area was measured in aortic root sections of LDLr−/− mice. We found that: (1) postnatal OB diet increased significantly BP (P<0.0001) and HR (P<0.008) in 3-month old OB-C and OB-LP offspring, respectively; (2) that maternal LP diet induced a significant higher BP (P<0.009) and HR (P<0.004) and (3) an altered circadian rhythm in addition to higher plasma corticosterone concentration in 9 months-old LP offspring; (4) that, although LP offspring showed higher plasma total cholesterol than control offspring, atherosclerosis assessed in aortic roots of 6-mo old mice featured increased plaque area due to OB feeding but not due to early mismatched nutrition.

Conclusions/Significance

These results indicate a long-term effect of early mismatched nutrition on the appearance of hypertension independently of obesity, while no effect on atherosclerosis was noticed at this age.     

Maternal green tea polyphenol intake during lactation attenuates kidney injury in high-fat-diet-fed male offspring programmed by maternal protein restriction in rats

Maternal malnutrition is known to increase the risk of obesity in offspring. We investigated whether green tea extract (GTE) intake during lactation affects obesity-related fibrosis and inflammation in the kidney of high-fat-diet-fed adult offspring of protein-restricted-diet-fed dams during pregnancy and lactation. Pregnant Wistar rats received diets containing 20% (normal-protein, NP) or 8% (low-protein, LP) casein, and they received 0%-, 0.12%- or 0.24%-GTE-containing LP diets (LP/LP, LP/LGT and LP/HGT, respectively) during lactation. At weaning, the pups that received a diet providing 13% (normal-fat, NF) or 45% (high-fat, HF) energy from fat were divided into five groups: NP/NP/NF, LP/LP/NF, LP/LP/HF, LP/LGT/HF and LP/HGT/HF. At week 45, the degree of fibrosis; macrophage infiltration; protein expression levels of TGF-β; and mRNA levels of TNF-α, DNMT, UHRF1 and histone lysine methyltransferase (G9a) in the kidneys of male offspring were examined. The area of fibrosis and TGF-βlevels increased in the LP/LP/HF group. Conversely, the fibrotic areas and TGF-β levels in the LP/HGT/HF group decreased (33% and 31%, respectively) compared with those in the LP/LP/HF group. The number of macrophages and mRNA levels of TNF-α in the LP/HGT/HF group decreased (34% and 29%, respectively) compared with those in the LP/LP/HF group. DNMT1, UHRF1 and G9a mRNA levels in the LP/HGT/HF group decreased compared with those in the LP/LP/HF group. In conclusion, GTE intake during lactation attenuated tubulointerstitial fibrosis and macrophage infiltration by down-regulating epigenetic modulators such as DNMT1, UHRF1 and G9a in the kidney of HF-diet-fed adult offspring programmed by maternal protein restriction.     

Maternal protein restriction induce skeletal muscle changes without altering the MRFs MyoD and myogenin expression in offspring

Stimuli during pregnancy, such as protein restriction, can affect morphophysiological parameters in the offspring with consequences in adulthood. The phenomenon known as fetal programming can cause short- and long-term changes in the skeletal muscle phenotype. We investigated the morphology and the myogenic regulatory factors (MRFs) MyoD and myogenin expression in soleus, SOL; oxidative and slow twitching and in extensor digitorum longus, EDL; glycolytic and fast twitching muscles in the offspring of dams subjected to protein restriction during pregnancy. Four groups of male Wistar offspring rats were studied. Offspring from dams fed a low-protein diet (6?% protein, LP) and normal protein diet (17?% protein, NP) were euthanized at 30 and 112?days old, and their muscles were removed and kept at ?80?°C. Muscles histological sections (8?μm) were submitted to a myofibrillar adenosine triphosphatase histochemistry reaction for morphometric analysis. Gene and protein expression levels of MyoD and myogenin were determined by RT-qPCR and western blotting. The major findings observed were distinct patterns of morphological changes in SOL and EDL muscles in LP offspring at 30 and 112?days old without changes in MRFs MyoD and myogenin expression. Our results indicate that maternal protein restriction followed by normal diet after birth induced morphological changes in muscles with distinct morphofunctional characteristics over the long term, but did not alter the MRFs MyoD and myogenin expression. Further studies are necessary to better understand the mechanisms underlying the maternal protein restriction response on skeletal muscle.     

Adult cardiorenal benefits from postnatal fish oil supplement in rat offspring of low-protein pregnancies

We investigated the effect of fish oil (FO) treatment on cardiorenal structure of adult offspring from low-protein pregnancies. Three month old offspring were assigned to eight groups (four male groups and four female groups, n=8 each) (NP=normal-protein diet, LP=low-protein diet): NP, LP, NP plus FO, and LP plus FO. Left ventricle and kidney were analyzed with light microscopy and stereology. The both sexes of LP offspring showed 30% lower birth weights than the respective NP offspring and high blood pressure (BP) levels in adulthood which was efficiently reduced by FO treatment. In the heart, FO treated the cardiomyocyte hypertrophy, the vascularization impairment, and decreased the cardiomyocyte loss usually observed in adult LP offspring. In the kidney, FO treated, in the male, the imbalance of the cortex-to-medulla ratio observed in both sexes of LP offspring, and reduced the glomeruli loss in the LP offspring. The positive correlation between the number of cardiomyocyte nuclei later in life and the body mass (BM) at birth was significant only in both sexes of LP offspring and this correlation disappeared in LP plus fish oil offspring. The positive correlation between the number of glomeruli later in life and the BM at birth was significant in NP male offspring and in both sexes of LP offspring. In conclusion, FO supplement, which is a rich source of n-3 fatty acids (DHA and EPA), has beneficial effects on BP control and cardiac and renal adverse remodeling usually seen in offspring of the LP pregnancies.     

Repeated ethanol exposure during late gestation decreases nephron endowment in fetal sheep

Maternal alcohol consumption during pregnancy can affect fetal development, but little is known about the effects on the developing kidney. Our objectives were to determine the effects of repeated ethanol exposure during the latter half of gestation on glomerular (nephron) number and expression of key genes involved in renal development or function in the ovine fetal kidney. Pregnant ewes received daily intravenous infusion of ethanol (0.75 g/kg, n=5) or saline (control, n=5) over 1 h from 95 to 133 days of gestational age (DGA; term is approximately 147 DGA). Maternal and fetal arterial blood samples were taken before and after the start of the daily ethanol infusions for determination of blood ethanol concentration (BEC). Necropsy was performed at 134 DGA, and fetal kidneys were collected for determination of total glomerular number using the physical disector/fractionator technique; at this gestational age nephrogenesis is completed in sheep. Maximal maternal and fetal BECs of 0.12+/-0.01 g/dl (mean+/-SE) and 0.11+/-0.01 g/dl, respectively, were reached 1 h after starting maternal ethanol infusions. Ethanol exposure had no effect on fetal body weight, kidney weight, or the gene expression of members of the renin-angiotensin system, insulin-like growth factors, and sodium channels. However, fetal glomerular number was lower after ethanol exposure (377,585+/-8,325) than in controls (423,177+/-17,178, P<0.001). The data demonstrate that our regimen of fetal ethanol exposure during the latter half of gestation results in an 11% reduction in nephron endowment without affecting the overall growth of the kidney or fetus or the expression of key genes involved in renal development or function. A reduced nephron endowment of this magnitude could have important implications for the cardiovascular health of offspring during postnatal life.     

Excess of Methyl Donor in the Perinatal Period Reduces Postnatal Leptin Secretion in Rat and Interacts with the Effect of Protein Content in Diet

Methionine, folic acid, betaine and choline interact in the one-carbon metabolism which provides methyl groups for methylation reactions. An optimal intake of these nutrients during pregnancy is required for successful completion of fetal development and evidence is growing that they could be involved in metabolic long-term programming. However, the biological pathways involved in the action of these nutrients are still poorly known. This study investigated the interaction between methyl donors and protein content in maternal diet during the preconceptual, pregnancy and lactation periods and the consequences on the rat offspring in the short and long term. Methyl donor supplementation reduced leptin secretion in offspring, whereas insulin levels were mostly affected by protein restriction. The joint effect of protein restriction and methyl donor excess strongly impaired postnatal growth in both gender and long term weight gain in male offspring only, without affecting food intake. In addition, rats born from protein restricted and methyl donor supplemented dams gained less weight when fed a hypercaloric diet. Methylation of the leptin gene promoter in adipose tissue was increased in methyl donor supplemented groups but not affected by protein restriction only. These results suggest that maternal methyl donor supplementation may influence energy homeostasis in a gender-dependent manner, without affecting food intake. Moreover, we showed that macronutrients and micronutrients in maternal diet interact to influence the programming of the offspring.     

Effects of Maternal Diet and Exercise during Pregnancy on Glucose Metabolism in Skeletal Muscle and Fat of Weanling Rats

Obesity during pregnancy contributes to the development of metabolic disorders in offspring. Maternal exercise may limit gestational weight gain and ameliorate these programming effects. We previously showed benefits of post-weaning voluntary exercise in offspring from obese dams. Here we examined whether voluntary exercise during pregnancy influences lipid and glucose homeostasis in muscle and fat in offspring of both lean and obese dams. Female Sprague-Dawley rats were fed chow (C) or high fat (F) diet for 6 weeks before mating. Half underwent voluntary exercise (CE/FE) with a running wheel introduced 10 days prior to mating and available until the dams delivered; others remained sedentary (CS/FS). Male and female pups were killed at postnatal day (PND)19 and retroperitoneal fat and gastrocnemius muscle were collected for gene expression. Lean and obese dams achieved similar modest levels of exercise. At PND1, both male and female pups from exercised lean dams were significantly lighter (CE versus CS), with no effect in those from obese dams. At PND19, maternal obesity significantly increased offspring body weight and adiposity, with no effect of maternal exercise. Exercise significantly reduced insulin concentrations in males (CE/FE versus CS/FS), with reduced glucose in male FE pups. In males, maternal obesity significantly decreased muscle myogenic differentiation 1 (MYOD1) and glucose transporter type 4 (GLUT4) mRNA expressions (FS vs CS); these were normalized by exercise. Maternal exercise upregulated adipose GLUT4, interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and peroxisome proliferator activated receptor gamma coactivator 1 alpha (PGC1α) mRNA expression in offspring of dams consuming chow. Modest voluntary exercise during pregnancy was associated with lower birth weight in pups from lean dams. Maternal exercise appeared to decrease the metabolic risk induced by maternal obesity, improving insulin/glucose metabolism, with greater effects in male than female offspring.     

Protein malnutrition after weaning disrupts peripheral clock and daily insulin secretion in mice

Changes in nutritional state may alter circadian rhythms through alterations in expression of clock genes. Protein deficiency has a profound effect on body metabolism, but the effect of this nutrient restriction after weaning on biological clock has not been explored. Thus, this study aims to investigate whether the protein restriction affects the daily oscillation in the behavior and metabolic rhythms, as well as expression of clock genes in peripheral tissues. Male C57BL/6 J mice, after weaning, were fed a normal-protein (NP) diet or a low-protein (LP) diet for 8 weeks. Mice fed an LP diet did not show difference in locomotor activity and energy expenditure, but the food intake was increased, with parallel increased expression of the orexigenic neuropeptide Npy and disruption of the anorexigenic Pomc oscillatory pattern in the hypothalamus. LP mice showed disruption in the daily rhythmic patterns of plasma glucose, triglycerides and insulin. Also, the rhythmic expression of clock genes in peripheral tissues and pancreatic islets was altered in LP mice. In pancreatic islets, the disruption of clock genes was followed by impairment of daily glucose-stimulated insulin secretion and the expression of genes involved in exocytosis. Pharmacological activation of REV-ERBα could not restore the insulin secretion in LP mice. The present study demonstrates that protein restriction, leading to development of malnutrition, alters the peripheral clock and metabolic outputs, suggesting that this nutrient provides important entraining cues to regulate the daily fluctuation of biological clock.     

Role of the renin-angiotensin-aldosterone system in the enhancement of salt sensitivity caused by prenatal protein restriction in stroke-prone spontaneously hypertensive rats

We previously demonstrated that maternal protein restriction during pregnancy enhanced salt sensitivity and shortened life span in stroke-prone spontaneously hypertensive rats (SHRSP). The present study was conducted to investigate the participation of the renin-angiotensin-aldosterone system in the development of salt sensitivity in the offspring of dams fed a low-protein diet during pregnancy. We used SHRSP offspring from dams fed a 20% casein diet (CN) or a 9% casein diet (LP) during pregnancy. The CN and LP SHRSP offspring were further subdivided into tap-water-drinking and 1%-saline-drinking groups from the postnatal 10th week. A remarkable elevation in blood pressure in response to salt loading was observed in the LP SHRSP offspring. The protein levels of CYP11B2, an enzyme for aldosterone synthesis, were markedly elevated in response to salt loading in the kidneys of LP offspring. Treatment of the LP offspring with an aldosterone receptor antagonist prevented the blood pressure from elevating and lengthened the average life span in LP offspring in response to the drinking of 1% saline. No difference in the activity of angiotensin-converting enzyme or in the protein level of the angiotensin type 1 receptor was found between the CN and LP offspring in either the tap-water-drinking or saline-drinking conditions. In conclusion, the increment of aldosterone production in response to high-salt loading may contribute to the elevated salt sensitivity of the offspring of protein-restricted dams.     

Induction of hyperglycemia in adult intrauterine growth-restricted rats: effects on renal function

Intrauterine growth restriction (IUGR) leads to a reduction in nephron endowment at birth and is linked to renal dysfunction in adulthood. The aim of the present study was to determine whether kidneys of IUGR rat offspring are more vulnerable to a secondary insult of hyperglycemia. IUGR was induced in Wistar-Kyoto rats by maternal protein restriction. At 24 wk of age, diabetes was induced in male IUGR and non-IUGR offspring by streptozotocin injection; insulin was injected daily to maintain blood glucose levels at either a mild (7-10 mmol/l; n=8/group) or a moderate (10-15 mmol/l; n=8/group) level. At 32 wk of age, renal function was assessed using ultrasound and [(3)H]inulin and [(14)C]para-aminohippurate clearance techniques. Conscious mean arterial blood pressure and heart rate were unchanged in IUGR offspring. Relative kidney length was increased significantly in IUGR offspring, and renal function was altered significantly; of importance, there was a significant increase in filtration fraction, indicative of glomerular hyperfiltration. Induction of hyperglycemia led to marked impairment of renal function. However, the response to hyperglycemia was not different between IUGR and non-IUGR offspring. Maintaining blood glucose levels at a mild hyperglycemic level led to marked improvement in all measures of renal function in IUGR and non-IUGR offspring. In conclusion, while the IUGR offspring showed evidence of hyperfiltration, the response to hyperglycemia was similar in IUGR and non-IUGR kidneys in adulthood. Importantly, maintaining blood glucose levels at a mild hyperglycemic level markedly attenuated the renal dysfunction associated with diabetes, even in IUGR offspring.