Dietary Deprivation Research Articles

Plasma zinc's alter ego is a low‐molecular‐weight humoral factor

Mild dietary zinc deprivation in humans and rodents has little effect on blood plasma zinc levels, and yet cellular consequences of zinc depletion can be detected in vascular and other tissues. We proposed that a zinc-regulated humoral factor might mediate the effects of zinc deprivation. Using a novel approach, primary rat vascular smooth muscle cells (VSMCs) were treated with plasma from zinc-deficient (<1 mg Zn/kg) or zinc-adequate (35 mg Zn/kg, pair-fed) adult male rats, and zinc levels were manipulated to distinguish direct and indirect effects of plasma zinc. Gene expression changes were analyzed by microarray and qPCR, and incubation of VSMCs with blood plasma from zinc-deficient rats strongly changed the expression of >2500 genes, compared to incubation of cells with zinc-adequate rat plasma. We demonstrated that this effect was caused by a low-molecular-weight (∼2-kDa) zinc-regulated humoral factor but that changes in gene expression were mostly reversed by adding zinc back to zinc-deficient plasma. Strongly regulated genes were overrepresented in pathways associated with immune function and development. We conclude that zinc deficiency induces the production of a low-molecular-weight humoral factor whose influence on VSMC gene expression is blocked by plasma zinc. This factor is therefore under dual control by zinc.

Treating metastatic castration-resistant prostate cancer with novel polyamine-free oral nutritional supplementation: Phase I study

BackgroundPolyamine (PA) dietary deprivation may be of clinical interest in castration-resistant prostate cancer (CRPC). PurposeWe assessed tolerance and side effects of PA-free oral nutritional supplement (ONS) combined with partial intermittent intestinal decontamination (PIID) in a Phase I trial. MethodsTen volunteers of mean age 68 ± 12 years and with symptomatic, metastatic CRPC were enrolled. PA-free ONS was given as the only food source three times daily during the first 2 weeks; twice daily with one PA-reduced meal for 3 weeks; and then once daily with two PA-reduced meals for 7 weeks. Oral neomycin was administered at 0.75 g/day as PIID every other week. Toxicity, performance, and pain status were rated on World Health Organization and European Organisation for Research and Treatment of Cancer scales. Prostate-specific antigen, blood counts, ionograms, and hepatic transaminases were regularly assessed. Bone and computed tomography scans were performed at weeks 0, 5 and 12. ResultsOne patient disliked the taste and stopped on Day 4. Nine patients experienced transient Grade I diarrhea. Performance status and pain score were significantly improved in five patients and maintained in three patients. No significant differences in body weight, hemoglobin, serum proteins, and ionograms were noted. Four patients had 20–40% prostate-specific antigen baseline decline during the first 5 weeks of the trial. Five patients had bone and computed tomography scan stabilization. ConclusionThis PA-free ONS was safe and well tolerated with PIDD. It seemed to benefit quality of life and control pain. The effects were dose dependent, with maximum improvement observed during the first 5 weeks when PA depletion was maximal.

The disruption of CREB/BDNF/TrkB signaling. Dynamic changes induced by zinc deficiency

Background Our previous studies indicated that expression of several proteins involved in numerous aspects of plasticity in the central nervous system (CNS) is modulated by four-week dietary deprivation of trace element zinc. The levels of the phosphorylated forms of transcription factor cyclic AMP response-element binding (pCREB) protein, neurotrophin brain derived neurotrophic factor (BDNF) protein and high-affinity tropomyosine-related kinase B receptor (TrkB) protein were significantly decreased in the hippocampus of rats fed a zinc-deficient diet for four weeks. However, no changes of these proteins between rats subjected to four-week zinc restriction and the control animals were found in the prefrontal cortex. Aims Here we examined whether six-week dietary zinc deprivation induces changes in the protein levels of pCREB, BDNF and TrkB in the prefrontal cortex and hippocampus of rats. Methods Male Sprague Dowley rats (5-week-old) were fed a 50 mg Zn/kg (control group) or a 3 mg Zn/kg (zinc deficient group) diet for six weeks. The protein levels of pCREB, BDNF and TrkB were measured using western blotting. Results The levels of pCREB and BDNF proteins were significantly decreased (by 46% and 52%) in the prefrontal cortex and (by 44% and 54%) in the hippocampus of rats subjected to six-week zinc-deficient diet when compared with that of the control animals. Interestingly, at the same time point an increase (by 153%) in TrkB protein was observed in the prefrontal cortex of group fed zinc-deficient diet for six weeks compared to the control group. Conclusions The present data reports that six-week dietary zinc deprivation, unlike four-week zinc restriction, influences not only the hippocampus, but also the prefrontal cortex of rats. One can assume that CREB/ BDNF/TrkB proteins levels changes are dynamic in response to zinc deprivation and vary not only across brain regions but also in the course of time.

Combined vitamin C and E deficiency induces motor defects in gulo−/−/SVCT2+/− mice

ObjectivesKey antioxidants, vitamins C and E, are necessary for normal brain development and neuronal function. In this study, we depleted both of these vitamins in two mouse models to determine if oxidative stress due to combined vitamin C and E dietary deficiency altered their neurological phenotype. The first model lacked both alleles for the Gulonolactone oxidase gene (Gulo−/−) and therefore was unable synthesize vitamin C. To obtain an additional cellular deficiency of vitamin C, the second model also lacked one allele for the cellular vitamin C transporter gene (Gulo−/−/SVCT2+/−).MethodsThe experimental treatment was 16 weeks of vitamin E deprivation followed by 3 weeks of vitamin C deprivation. Mice were assessed for motor coordination deficits, vitamin levels, and oxidative stress biomarkers.ResultsIn the first model, defects in motor performance were more apparent in both vitamin C-deficient groups (VE+VC−, VE−VC−) compared to vitamin C-supplemented groups (VE+VC+, VE−VC+) regardless of vitamin E level. Analysis of brain cortex and liver confirmed decreases of at least 80% for each vitamin in mice on deficient diets. Vitamin E deficiency doubled oxidative stress biomarkers (F2-isoprostanes and malondialdehyde). In the second model, Gulo−/−/SVCT2+/− mice on the doubly deficient diets showed deficits in locomotor activity, Rota-rod performance, and other motor tasks, with no concomitant change in anxiety or spatial memory.DiscussionVitamin E deficiency alone caused a modest oxidative stress in brain that did not affect motor performance. Adding a cellular deficit in vitamin C to dietary deprivation of both vitamins significantly impaired motor performance.

Enalapril attenuates the exaggerated sympathetic response to physical stress in prenatally programmed hypertensive rats

Prenatal programming induced by maternal dietary protein deprivation (6% vs 20% protein diet) results in hypertension in adult rat offspring. We have shown that the hypertension with prenatal programming (PPH) is due to increased sympathetic nerve activity. The purpose of this study was to examine if angiotensin‐converting enzyme (ACE) inhibition would attenuate the enhanced sympathetic response to acute physical stress in PPH. To test this postulate, changes in renal sympathetic nerve activity (RSNA) to stimulation of the skeletal muscle exercise pressor reflex (EPR) were assessed in controls and PPH rats chronically treated (from age 4 wks) with either vehicle or enalapril (an ACE inhibitor) in their drinking water. Adult male offspring (age 16–20 wks) were studied. Resting systolic blood pressure (SBP) was greater in PPH than control in vehicle treated groups and the blood pressure was normalized by enalapril in the PPH group. The RSNA response to EPR stimulation was significantly higher in PPH than control in vehicle treated groups. Enalapril treatment significantly attenuated the RSNA response to EPR activation in PPH but had no effect in control rats. These results suggest that angiotensin II contributes to the generation of stress‐induced sympathetic overactivity in PPH. Further, this enhanced sympathetic responsiveness can be reduced by ACE inhibition. Supported by NIH HL‐088422, DK41612 and DK078596

La restriction sodée prévient le remodelage cardiovasculaire dans l’insulinorésistance chez le rat

Aim of the studyIn the present work, the objective was to evaluate the influence of a dietary sodium restriction on cardiovascular morphology changes associated with insulin-resistance. Animals and protocolAt 8 weeks of age, rats were fed for 12 weeks a 60%-fructose diet containing a regular sodium content (0.64%) or totally lacking in sodium chloride (<0.01%). A group of rats fed a wheat starch-based diet with regular sodium content served as control group. ResultsElevated HOMA index and plasma insulin confirm the presence of insulin-resistance in fructose-fed rats. Concomitantly, an increase in cardiac mass and in cardiac collagen (Sirius red staining) was detected without obvious change in arterial pressure or cardiac aldosterone synthase mRNA expression. In addition, cross-sectional area of the carotid artery was higher in fructose-fed rats. Production of superoxide anion, equated with dihydroethidium (DHE) staining, was enhanced in cardiac tissue of rats with insulin-resistance. Withdrawal of sodium from the fructose diet prevented all the cardiovascular effects of fructose consumption, including DHE staining. ConclusionThese results are in favor of the participation of oxidative stress normalization in the beneficial influence of dietary sodium deprivation on cardiovascular remodeling in this model of insulin-resistance in rats.

P.1.021 Chronic administration of haloperidol in rats and its effect on microglial cell density and whole brain weight and volume

BDNF and TrkB in the hippocampus but not in the prefrontal cortex. The level of pCREB protein was decreased by 91% whereas the level of BDNF protein was decreased by 73% in the hippocampus of the zinc-deficient rats when compared with that of the control animals. At the same time point a decrease (by 40%) in TrkB protein was observed in the hippocampus of the zinc-deficient group compared to the control group. Conclusions: The previous studies indicated that dietary-induced zinc deficiency leads to the development of depressive like behaviour (e.g. increase in the immobility time in the forced swim test) and that experimentally induced zinc deficiency might be a model of depression. The present data suggests that pCREB, BDNF and TrkB expression is modulated by zinc deficiency and that the decreased expression of these proteins after dietary zinc deprivation is linked to the depressive like behaviour in the zinc deficiency paradigm. It seems that the hippocampus, the region of the brain that plays a critical role in neurogenesis, is more susceptible to the biochemical changes caused by zinc deficiency than the prefrontal cortex. This is consistent with data obtained during experiments where acute and chronic stress paradigms were found to decrease the expression of BDNF in the rodent hippocampus [1].

Retinol deprivation partially rescues the skeletal mineralization defects of Phex-deficient Hyp mice

X-linked hypophosphatemic rickets (XLH) is a genetic disorder caused by mutational inactivation of the PHEX gene, encoding a transmembrane endopeptidase expressed in osteoblasts. Since several experiments involving Phex-deficient Hyp mice have demonstrated that an increased expression of Fgf23 in osteoblasts is causative for the renal phosphate loss characteristic of XLH, we performed genome-wide expression analysis to compare differentiated osteoblasts from wildtype and Hyp mice. Here we did not only observe the expected increase of Fgf23 expression in the latter ones, but also a differential expression of genes that are either induced by or involved in retinoic acid signaling, which led us to analyze whether dietary retinol deprivation would influence the phenotype of Hyp mice. Unexpectedly, feeding a retinol-free diet resulted in a partial rescue of the growth plate and bone mineralization defects in 6weeks old Hyp mice. When we fed the same diet for 24weeks the amount of non-mineralized bone matrix (osteoid) was reduced by more than 70%, although phosphate homeostasis was unaffected. In contrast, a dietary normalization of serum phosphate levels in Hyp mice reduced the osteoid amount by less than 30%, thereby demonstrating a previously unknown impact of retinol on the cell-autonomous mineralization defect of Phex-deficient osteoblasts.

Economic and Social Factors in the Etiology of Childhood Rickets over the Past Four Centuries

Economic and social factors can determine the prevalence and severity of a health condition, as well as enhance co-morbidities. This article reviews forces that have influenced the appearance and persistence of nutritional rickets over the past 400 years. Childhood rickets first appeared from 1600 to 1640 as an epidemic disorder in the south and west of England when the woolen trade developed as a home labor industry. Later, with the coal-fueled factory system, agrarian laborers migrated to cities, creating a wage earner class. Their children were raised in smog-ridden and crowded conditions and were victims of an urban-based form of rickets lasting from the 1640s to the 1930s. With the discovery of vitamin D, arising from both dietary sources and from photocutaneous biosynthesis by exposure to ultraviolet B wavelengths from the sun, and recognition of its use as a therapeutic agent, epidemic rickets largely disappeared. The pro-sunshine era was ushered in between 1930 and 1965. Since, rising rates of skin cancer have greatly tempered enthusiasm for sun exposure and led to recommendations for sun protection strategies. Beginning in the 1960s, examples of nutritional rickets have been seen in dark-skinned immigrants moving to northern latitudes. Often rickets occurred in association with vitamin D-deficient mothers who exclusively breast-fed their offspring. Also, vitamin D deficiency is more evident in young children, adolescents, pregnant mothers and the elderly, many of who remain indoors and do not use vitamin supplements. These factors - child labor, the almost universal use of coal as a fuel, dietary deprivations during wars, migration of dark-skinned populations to regions where sunshine is scarce, and cancer-associated fear of sun exposure - have resulted in the persistence of nutritional rickets despite the knowledge of medical practitioners, nutritionists, and even parents. This manuscript reviews these factors and their impact on the health of children.

Prenatal Programming of Hypertension Induces Sympathetic Overactivity in Response to Physical Stress

Small-for-gestational-age infants are known to develop hypertension in adulthood. This prenatal programming of hypertension (PPH) can result from several insults including maternal dietary protein deprivation, uteroplacental insufficiency, and prenatal administration of glucocorticoids. The mechanisms underlying the development of hypertension remain unclear although the sympathetic nervous system has been indirectly implicated. This study was designed to directly measure renal sympathetic nerve activity both at rest and during physical stress in an animal model of PPH. The adult male offspring of rats fed either a 6% (PPH) or 20% protein diet (control) were investigated. Conscious systolic blood pressure measured by tail cuff was significantly higher in PPH compared with control (140 ± 3 versus 128 ± 3 mm Hg; P<0.05). Baseline mean arterial pressure, heart rate, and renal sympathetic activity were not different between groups during isoflurane anesthesia or after decerebration. Physical stress was induced in decerebrate animals by activating the exercise pressor reflex during static muscle contraction. Stimulation of the exercise pressor reflex evoked significantly larger changes from baseline in mean arterial pressure (40 ± 7 versus 20 ± 4 mm Hg; P<0.05), heart rate (19 ± 3 versus 5 ± 1 bpm; P<0.05), and renal sympathetic activity (198 ± 29% versus 68 ± 14%; P<0.05) in PPH as compared with control. The data demonstrate that the sympathetic response to physical stress is markedly exaggerated in PPH and may play a significant role in the development of hypertension in adults born small for gestational age.

Impact of dietary carotenoid deprivation on macular pigment and serum concentrations of lutein and zeaxanthin

Impact of dietary carotenoid deprivation on macular pigment and serum concentrations of lutein and zeaxanthin

S6K1 in the Central Nervous System Regulates Energy Expenditure via MC4R/CRH Pathways in Response to Deprivation of an Essential Amino Acid

It is well established that the central nervous system (CNS), especially the hypothalamus, plays an important role in regulating energy homeostasis and lipid metabolism. We have previously shown that hypothalamic corticotropin-releasing hormone (CRH) is critical for stimulating fat loss in response to dietary leucine deprivation. The molecular mechanisms underlying the CNS regulation of leucine deprivation–stimulated fat loss are, however, still largely unknown. Here, we used intracerebroventricular injection of adenoviral vectors to identify a novel role for hypothalamic p70 S6 kinase 1 (S6K1), a major downstream effector of the kinase mammalian target of rapamycin, in leucine deprivation stimulation of energy expenditure. Furthermore, we show that the effect of hypothalamic S6K1 is mediated by modulation of Crh expression in a melanocortin-4 receptor–dependent manner. Taken together, our studies provide a new perspective for understanding the regulation of energy expenditure by the CNS and the importance of cross-talk between nutritional control and regulation of endocrine signals.

Multiple Menkes copper ATPase (Atp7a) transcript and protein variants are induced by iron deficiency in rat duodenal enterocytes

The Menkes copper ATPase (Atp7a) pumps copper into the trans-Golgi for cuproenzyme synthesis, and translocates to the basolateral membrane of enterocytes for copper export. Recent studies demonstrated that three 5′ end splice variants of the Atp7a transcript exist in rat duodenum, all of which are strongly induced during iron deprivation. To explore a possible role for Atp7a (and copper) in intestinal iron absorption, the current studies were undertaken to test the hypothesis that multiple Atp7a transcript and protein variants exist in intestinal epithelial cells. Northern blot analyses using probes generated from the full-length Atp7a cDNA revealed several specific hybridization bands, all of which were more intense in RNA samples extracted from duodenal enterocytes isolated from iron-deficient rats. A PCR-based approach, using forward primers specific for the alternative 5′ end splice variants and a reverse primer in exon 23, demonstrated that 3 full-length transcripts exist in rat IEC-6 cells. To identify possible Atp7a protein variants, three distinct polyclonal antisera were utilized. The specificity of the antisera was first established by western blotting and immunoprecipitation studies using samples derived from isolated rat enterocytes and Atp7a knockdown IEC-6 cells. Several specific immunoreactive bands were documented, and a unique Atp7a protein distribution in cytosolic vesicle-like structures was noted. In conclusion, multiple Atp7a transcript and protein variants exist in rodent intestinal epithelial cells and are induced by dietary iron deprivation. Further studies will be designed to determine the subcellular distribution of Atp7a protein variants and possible unique functions of each.

CHILDHOOD DIET: A CLOSER EXAMINATION OF THE EVIDENCE FROM DENTAL TISSUES USING STABLE ISOTOPE ANALYSIS OF INCREMENTAL HUMAN DENTINE*

Incremental dentine analysis utilizes tissue that does not remodel and that permits comparison, at the same age, of those who survived infancy with those who did not at high temporal resolution. Here, we present a pilot study of teeth from a 19th‐century cemetery in London, comparing the merits of two methods of obtaining dentine increments for subsequent isotope determination. Covariation in δ13C and δ15N values suggests that even small variations have a physiological basis. We show that high‐resolution intra‐dentine isotope profiles can pinpoint short‐duration events such as dietary change or nutritional deprivation in the juvenile years of life.

Physiologic Role of the Menkes Copper ATPase (Atp7a) in Intestinal Iron Transport

Atp7a is a copper transporting ATPase involved in intestinal copper export that is strongly induced in the intestine of iron deficient rats. We evaluated the possible role of Atp7a in iron homeostasis in Atp7a knock down (KD) rat intestinal epithelial (IEC‐6) cells and Brindle mice that express a mutant, inactive form of Atp7a. In KD cells with &gt;90% decrease in Atp7a protein levels, copper loading led to significantly increased intracellular Cu levels, demonstrating a reduction in the copper export function of Atp7a. Iron (59Fe) transport studies in IEC‐6 cells grown in bicameral cell culture inserts revealed significant transepithelial iron flux when cells were deprived of iron. Transport in Atp7a KD cells showed that 59Fe transported into cells and transferred to the basolateral chamber was reduced. Next, Brindled mice were rescued by perinatal copper injection and studies were done to consider the in vivo role of Atp7a in iron absorption. Brindled mice were anemic compared to wild type littermates, and Dmt1, TfR1 and Atp7a expression was induced by dietary iron deprivation. Furthermore, serum ferroxidase activity, reflecting ceruloplasmin, was decreased in Brindled mice as was activity of a novel cytosolic ferroxidase in enterocytes. These data demonstrate a physiologic role for Atp7a in intestinal iron transport possibly related to copper delivery to multi‐copper ferroxidases involved in iron homeostasis.Grant Funding Source : NIH

S6K links cell fate, cell cycle and nutrient response in C. elegans germline stem/progenitor cells

Coupling of stem/progenitor cell proliferation and differentiation to organismal physiological demands ensures the proper growth and homeostasis of tissues. However, in vivo mechanisms underlying this control are poorly characterized. We investigated the role of ribosomal protein S6 kinase (S6K) at the intersection of nutrition and the establishment of a stem/progenitor cell population using the C. elegans germ line as a model. We find that rsks-1 (which encodes the worm homolog of mammalian p70S6K) is required germline-autonomously for proper establishment of the germline progenitor pool. In the germ line, rsks-1 promotes cell cycle progression and inhibits larval progenitor differentiation, promotes growth of adult tumors and requires a conserved TOR phosphorylation site. Loss of rsks-1 and ife-1 (eIF4E) together reduces the germline progenitor pool more severely than either single mutant and similarly to reducing the activity of let-363 (TOR) or daf-15 (RAPTOR). Moreover, rsks-1 acts in parallel with the glp-1 (Notch) and daf-2 (insulin-IGF receptor) pathways, and does not share the same genetic dependencies with its role in lifespan control. We show that overall dietary restriction and amino acid deprivation cause germline defects similar to a subset of rsks-1 mutant phenotypes. Consistent with a link between diet and germline proliferation via rsks-1, loss of rsks-1 renders the germ line largely insensitive to the effects of dietary restriction. Our studies establish the C. elegans germ line as an in vivo model to understand TOR-S6K signaling in proliferation and differentiation and suggest that this pathway is a key nutrient-responsive regulator of germline progenitors.

Zinc deficiency as a possible model of depression – behavioral evaluation

Background There is much evidence supporting a link between serum zinc level and mood disorders [McLoughlin and Hodge, Acta Psychiatr Scand, 1990; Maes et al., J Affect Disord, 1994, Maes et al., Biol Psychiatry, 1997, Siwek et al., J Affect Disord, 2010]. It has been also reported that zinc deficiency induced by zinc – deficient diet elicits behavioral disturbances in animals, e.g., enhanced depressive – like behavior was found after dietary zinc deprivation in the forced swim test (FST) [Tamano et al., Neurochem Int, 2009; Whittle et al., Amino Acids, 2009]. Since there is a relationship between zinc homeostasis and depression in humans and since zinc deprivation induces depressive – like behavior in animals it seems interesting to evaluate if procedure of zinc deprivation might be useful on preclinical level as a model of depression. The aim of the present study was to examine behavioral changes induced by zinc deficiency as a possible model of depression. Methods Male Sprague Dowley rats were fed the control (30 mg Zn/kg) or zinc deficient (3 mg Zn/kg) diet for 4 weeks. Behavior of the control and zinc deficient rats was assessed in the forced swim test (FST) and the open field test. Locomotor activity was also measured. Results Zinc deficiency resulted in a significant increase in immobility time and decreased swimming and climbing in the FST. The spontaneous locomotor activity was significantly increased in zinc deficient rats compared to control animals. Four weeks of zinc deprivation seems to influence also exploratory activity of rats (the number of rearing was decreased in zinc deficient rats while the number of line crossing were not different between the control and zinc deprived animals). Conclusions This data indicated that dietary-induced zinc – deficiency leads to the development of depressive – like behavior and that experimentally induced zinc – deficiency might be a useful model of depression.

S6K links cell fate, cell cycle and nutrient response inC. elegansgermline stem/progenitor cells

Coupling of stem/progenitor cell proliferation and differentiation to organismal physiological demands ensures the proper growth and homeostasis of tissues. However, in vivo mechanisms underlying this control are poorly characterized. We investigated the role of ribosomal protein S6 kinase (S6K) at the intersection of nutrition and the establishment of a stem/progenitor cell population using the C. elegans germ line as a model. We find that rsks-1 (which encodes the worm homolog of mammalian p70S6K) is required germline-autonomously for proper establishment of the germline progenitor pool. In the germ line, rsks-1 promotes cell cycle progression and inhibits larval progenitor differentiation, promotes growth of adult tumors and requires a conserved TOR phosphorylation site. Loss of rsks-1 and ife-1 (eIF4E) together reduces the germline progenitor pool more severely than either single mutant and similarly to reducing the activity of let-363 (TOR) or daf-15 (RAPTOR). Moreover, rsks-1 acts in parallel with the glp-1 (Notch) and daf-2 (insulin-IGF receptor) pathways, and does not share the same genetic dependencies with its role in lifespan control. We show that overall dietary restriction and amino acid deprivation cause germline defects similar to a subset of rsks-1 mutant phenotypes. Consistent with a link between diet and germline proliferation via rsks-1, loss of rsks-1 renders the germ line largely insensitive to the effects of dietary restriction. Our studies establish the C. elegans germ line as an in vivo model to understand TOR-S6K signaling in proliferation and differentiation and suggest that this pathway is a key nutrient-responsive regulator of germline progenitors.

Prenatal programming of rat cortical collecting tubule sodium transport

Prenatal insults have been shown to lead to elevated blood pressure in offspring when they are studied as adults. Prenatal administration of dexamethasone and dietary protein deprivation have demonstrated that there is an increase in transporter abundance for a number of nephron segments but not the subunits of the epithelial sodium channel (ENaC) in the cortical collecting duct. Recent studies have shown that aldosterone is elevated in offspring of protein-deprived mothers when studied as adults, but the physiological importance of the increase in serum aldosterone is unknown. As an indirect measure of ENaC activity, we compared the natriuretic response to benzamil in offspring of mothers who ate a low-protein diet (6%) with those who ate a normal diet (20%) for the last half of pregnancy. The natriuretic response to benzamil was greater in the 6% group (821.1 ± 161.0 μmol/24 h) compared with the 20% group (279.1 ± 137.0 μmol/24 h), consistent with greater ENaC activity in vivo (P < 0.05). In this study, we also directly studied cortical collecting tubule function from adult rats using in vitro microperfusion. There was no difference in basal or vasopressin-stimulated osmotic water permeability. However, while cortical collecting ducts of adult offspring whose mothers ate a 20% protein diet had no sodium transport (-1.9 ± 3.1 pmol·mm(-1)·min(-1)), the offspring of rats that ate a 6% protein diet during the last half of pregnancy had a net sodium flux of 10.7 ± 2.6 pmol·mm(-1)·min(-1) (P = 0.01) in tubules perfused in vitro. Sodium transport was measured using ion-selective electrodes, a novel technique allowing measurement of sodium in nanoliter quantities of fluid. Thus we directly demonstrate that there is prenatal programming of cortical collecting duct sodium transport.

Prenatal Programming of Hypertension in the Rat: Effect of Postnatal Rearing

Background/Aims: Dietary protein deprivation during pregnancy causes hypertension in offspring when they become adults. This study examined if postnatal rearing had an effect on blood pressure and glomerular number in male rats whose mothers were fed either a control diet or a low protein diet. Methods: Neonates were cross fostered at 1 day of age to a different mother. After birth, all nursing and weaned rats were fed a control diet. Blood pressure and glomerular number were measured in adult offspring. Results: Control rats cross fostered to another control mother had a lower blood pressure than low protein rats cross fostered to another low protein mother (133 ± 4 vs. 151 ± 4 mm Hg, p < 0.05) and a greater number of glomeruli (28,388 ± 989 vs. 25,045 ± 851, p < 0.05). Fostering pups from the 20% group to mothers that were fed a 6% diet during pregnancy did not cause hypertension or a reduction in the number of glomeruli. However, fostering the 6% group on to mothers that were fed a 20% protein diet during pregnancy resulted in normalization of the blood pressure and number of glomeruli. Conclusion: The hypertension and reduced glomerular number resulting from prenatal dietary protein deprivation can be normalized by improving the postnatal environment.