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

Alpha-tocopherol prevents intrauterine undernutrition-induced oligonephronia in rats

The role of alpha-tocopherol during nephrogenesis was investigated in rats subjected to maternal undernutrition, which reduces the number of nephrons. alpha-tocopherol (350 mg/kg, p.o.) was administered daily to well-nourished or malnourished Wistar dams during pregnancy, or to prenatal undernourished rats during lactation. The kidneys of 1- and 25-day-old offspring were removed to evaluate expression of angiotensin II (Ang II) and to correlate this with expression of proliferating cell nuclear antigen, alpha-smooth muscle actin, fibronectin and vimentin in the glomeruli and tubulointerstitial space. One-day-old prenatally undernourished rats had reduced expression of Ang II and of kidney development markers, and presented with an enlarged nephrogenic zone. Maternal administration of alpha-tocopherol restored the features of normal kidney development in undernourished rats. Twenty-five-day-old prenatally undernourished progeny had fewer glomeruli than the control group. Conversely, animals from mothers that received alpha-tocopherol during lactation presented with the same number of glomeruli and the same glomerular morphometrical profile as the control group. Analyzing the levels of thiobarbituric acid reactive substances in the liver in conjunction with kidney development markers, it is plausible that alpha-tocopherol had antioxidant and non-antioxidant actions. This study provides evidence that alpha-tocopherol treatment restored Ang II expression, and subsequently restored renal structural development.Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior[CAPES/PROCAD-NF 519/2010]Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)[IBPG-1228-2.07/08]Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)[BIC-0408-2.07/09]Fundacao de Amparo a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)[AMD-0017-2.00/10]CNPq Conselho Nacional de Desenvolvimento Cientifico e Tecnologic

Perinatal Na+ overload programs raised renal proximal Na+ transport and enalapril-sensitive alterations of Ang II signaling pathways during adulthood.

BACKGROUND: High Na(+) intake is a reality in nowadays and is frequently accompanied by renal and cardiovascular alterations. In this study, renal mechanisms underlying perinatal Na(+) overload-programmed alterations in Na(+) transporters and the renin/angiotensin system (RAS) were investigated, together with effects of short-term treatment with enalapril in terms of reprogramming molecular alterations in kidney. METHODOLOGY/PRINCIPAL FINDINGS: Male adult Wistar rats were obtained from dams maintained throughout pregnancy and lactation on a standard diet and drinking water (control) or 0.17 M NaCl (saline group). Enalapril (100 mg/l), an angiotensin converting enzyme inhibitor, was administered for three weeks after weaning. Ninety day old offspring from dams that drank saline presented with proximal tubules exhibiting increased (Na(+)+K(+))ATPase expression and activity. Ouabain-insensitive Na(+)-ATPase activity remained unchanged but its response to angiotensin II (Ang II) was lost. PKC, PKA, renal thiobarbituric acid reactive substances (TBARS), macrophage infiltration and collagen deposition markedly increased, and AT(2) receptor expression decreased while AT(1) expression was unaltered. Early treatment with enalapril reduced expression and activity of (Na(+)+K(+))ATPase, partially recovered the response of Na(+)-ATPase to Ang II, and reduced PKC and PKA activities independently of whether offspring were exposed to high perinatal Na(+) or not. In addition, treatment with enalapril per se reduced AT(2) receptor expression, and increased TBARS, macrophage infiltration and collagen deposition. The perinatally Na(+)-overloaded offspring presented high numbers of Ang II-positive cortical cells, and significantly lower circulating Ang I, indicating that programming/reprogramming impacted systemic and local RAS. CONCLUSIONS/SIGNIFICANCE: Maternal Na(+) overload programmed alterations in renal Na(+) transporters and in its regulation, as well as severe structural lesions in adult offspring. Enalapril was beneficial predominantly through its influence on Na(+) pumping activities in adult offspring. However, side effects including down-regulation of PKA, PKC and AT(2) receptors and increased TBARS could impair renal function in later life

Water balance and excretion of Na⁺ by the offspring ¹.

1<p>n = 7–8; 30 and 90 indicate postnatal day of life.</p>2<p>In ml/24 h per 100 g BW.</p>3<p>In ml/24 h per 100 g BW; * P<0.05 with respect to C.</p>4<p>In ml/24 h per 100 g BW; * P<0.05 with respect to C; ^† P<0.05 with respect to S.</p

Responsiveness of ouabain-insensitive Na⁺-ATPase activity to Ang II.

<p>Panels C (upper left) and S (upper right) correspond to the offspring from control and perinatally Na⁺-overloaded mothers, respectively. Panels CE (lower left) and SE (lower right) correspond to the previous two groups treated with enalapril. Values are means ± S.E.M.; (n = 5–26 depending on the group and Ang II concentrations shown on the <i>abscissae</i>). Different lowercase letters above the circles indicate differences (P<0.05) calculated by comparing mean values within and among figures. Two or three letters above the same bar (a, d; a, c, d) relate to the fact that the corresponding mean value is not different from the others.</p

PKC activity and PKA activity in proximal tubule cell membranes.

<p>PKC activity (A) and PKA activity (B). Values are means ± S.E.M. (n = 3 for PKC and n = 4–5 for PKA). Different lowercase letters above bars indicate statistically different values (P<0.05).</p

AT₁ receptors and AT₂ receptors expression in membranes of the proximal tubule cells.

<p>AT₁ (A) and AT₂ (B) receptores. Upper panels: representative immunodetections. Lower panels: densitometric representations of receptor immunosignals corrected for protein loading (ponceau red) after immunoprecipitation. Values are means ± S.E.M.; (n = 5 for AT₁; n = 3–5 for AT₂). C values were taken as 100% and those from S, CE and SE groups in the same gel were expressed as a percentage of C (n = 3–5 for AT₂; n = 5 for AT₁). Different lowercase letters above bars indicate statistical differences (P<0.05).</p