Kidney dysfunction in the low-birth weight murine adult: implications of oxidative stress

Fetuin-B and oxidative stress disrupt placental trophoblasts during maternal undernourishment

BACKGROUND

Insufficient nutrition during pregnancy can lead to negative health outcomes for both mother and foetus. Maternal undernourishment (MUN) can be due to many factors like hyperemesis gravidarum or poor access to nutrition. Just as MUN can affect the mother and foetus, it can adversely affect the vital placental interface between the two. We suspect an observed increase in fetuin-B and oxidative stress in MUN placentas could be major players responsible for the placental insufficiency often seen with MUN.

METHODS

To establish a model of MUN during pregnancy, a reduced protein chow was fed to pregnant dams at a caloric deficit. We examined the MUN placentas and the downstream effects of fetuin-B and oxidative stress at the whole organ and trophoblast levels. We examined fetuin-B's role in trophoblast pathology by measuring apoptosis, proliferation, TLR4 activation, expression of NF-ΚB p65, oxidative stress, and mitochondrial superoxide production. The effects of MUN and fetuin-B on mitochondrial superoxide production, antioxidant levels, metabolism, and electron transport chain complex activity were compared directly. Pharmaceutical interventions were utilised to narrow down specific pathways involved.

RESULTS

Studies indicated that MUN and oxidative stress upregulated fetuin-B in the placenta. This relationship displayed a positive feedback loop as fetuin-B, in turn, promoted oxidative stress through activation of TLR4. Consequently, MUN, fetuin-B, and oxidative stress promoted apoptosis and reduced proliferative expansion of trophoblast, thereby reducing their quantity. MUN and fetuin-B reduced mitochondrial metabolism and function, promoting mitochondrial dysregulation and superoxide generation in MUN trophoblasts.

CONCLUSIONS

Our study sheds light on the mechanisms responsible for MUN-induced placental insufficiency while identifying therapeutic agents as possible add-on interventions.

Renal and Vascular Functional Decline in Aged Low Birth Weight Murine Adults

INTRODUCTION

Maternal undernutrition (MUN)-induced low birth weight (LBW) neonates are susceptible to the development of high blood pressure and kidney disease later in life, although the underlying pathological causes remain unclear. The study here investigated the role of renal oxidative stress, impairment of vascular function, and altered sensitivity to angiotensin II (Ang II) as factors that contribute to these pathologies in aged LBW mice.

METHODS

LBW offspring were generated using a combined protein and caloric restricted MUN mouse model. The resulting LBW offspring were examined 1 year after birth for mean arterial blood pressure (MABP) (carotid artery catheterization), renal blood flow (RBF) (laser Doppler flowmetry), glomerular filtration rate (GFR) (sinistrin clearance), vasoreactivity (myograph), renal vascular density (CD31 staining), and reactive oxygen species (ROS) (ROS probes). Immunoblotting examined Ang II type 1 receptor (AT1R), soluble guanylate cyclase (sGC), and antioxidant systems. Pharmacological agents delivered to animals included the sGC stimulator δ-aminolevulinic acid (ALA), the AT1R inhibitor losartan, the antioxidant ethyl pyruvate (EP), and the toll-like receptor 4 inhibitor TAK242.

RESULTS

After 1 year, MABP was increased, while RBF, GFR, vascular reactivity, renal vascular density, and sGC were all reduced in the LBW aged adult. All four pharmacological agents improved MABP, RBF, GFR, vascular density, and vascular reactivity. Renal ROS was increased in the LBW adult but was reduced by ALA, EP, and TAK242 treatment. AT1R was upregulated in the LBW adult, while sGC was decreased, an effect reversed by ALA treatment. Endogenous antioxidant systems, including SOD1, catalase, and glutathione were downregulated in the LBW adult.

CONCLUSION

MUN-induced LBW mice experience increased Ang II sensitivity and oxidative stress. The increased Ang II sensitivity and ROS generation influences vascular density and reactivity, which drive an increase in MABP, and a concomitantly decrease in RBF and glomerular filtration. Pharmacological intervention that inhibits AT1R, enhances levels of sGC, reduces ROS, or inhibits toll-like receptor 4 improves vascular and renal function in the LBW adult.

Stromal Vascular Fraction Restores Vasodilatory Function by Reducing Oxidative Stress in Aging-Induced Coronary Microvascular Disease

Aims: The objective of this study is to identify mechanisms for adipose stromal vascular fraction's (SVF) restorative effects on vasodilation in aging-induced coronary microvascular disease (CMD). We hypothesize that reactive oxygen species (ROS) diminish β1-adrenergic receptor (β1ADR)- and flow-mediated dilation (FMD) in coronary arterioles, reversible by SVF and adipose-derived stem cells (ADSCs). Results: SVF attenuates aging-induced chronic accumulation of ROS and pro-oxidant gene and protein expression with enhancement of antioxidant gene and protein expression and glutathione, but not nitric oxide. ADSCs attenuate hydrogen peroxide while restoring nitric oxide and glutathione. Mass spectrometry of SVF- and ADSC-conditioned media reveals abundant antioxidant proteins suggesting a paracrine mechanism. FMD and β1ADR-mediated dilation diminished with aging, restored with SVF and ADSCs. FMD was restored by a switch in the acute signaling mediator from hydrogen peroxide in aging to peroxynitrite with SVF and ADSCs. Vasorelaxation to β1ADR-agonism was mechanistically linked with hydrogen peroxide, nitric oxide, and glutathione. Exogenous ROS eliminates isoproterenol-mediated dilation in youth that is blocked by inhibition of pro-desensitization and internalization proteins while nitric oxide enhances isoproterenol-mediated dilation in aging. Innovation: We introduce a novel mechanism by which ROS impacts β1ADR trafficking: the ROS/RNS-β1ADR desensitization and internalization axis. Aging-induced ROS shunts β1ADR from the plasma membrane into endosomes. SVF reduces oxidative burden, restoring functional β1ADR. Conclusions: SVF (and ADSCs to a lesser extent) reduce oxidative stress, and restore flow- and β1ADR-mediated vasodilation in aging. SVF represents a promising therapeutic strategy for CMD by addressing root cause of pathology; that is, oxidative stress-mediated hyperconstriction. Antioxid. Redox Signal. 38, 261-281.

Structural and functional changes in the kidney caused by adverse fetal and neonatal environments

Health and disease risk in the adulthood are known to be affected by the early developmental environment. Kidney diseases are one of these diseases, and kidneys are altered both structurally and functionally by adverse pre- and perinatal events. The most known structural change is low nephron number seen in subjects born low birth weight and/or preterm. In various animal models of intrauterine growth restriction (IUGR), one of the causes of low birth weight, the mechanism of low nephron number was investigated. While apoptosis of metanephric mesenchyme has been suggested to be the cause, I showed that suppression of ureteric branching, global DNA methylation, and caspase-3 activity also contributes to the mechanism. Other structural changes caused by adverse fetal and neonatal environments include peritubular and glomerular capillary rarefaction and low podocyte endowment. These are aggravated by postnatal development of focal glomerulosclerosis and tubulointerstitial fibrosis that result from low nephron number. Functional changes can be seen in tubules, endothelium, renin-angiotensin system, sympathetic nervous system, oxidative stress, and others. As an example, I reported that aggravated nitrosative stress in a rat IUGR model resulted in more severe tubular necrosis and tubulointerstitial fibrosis after unilateral ureteral obstruction. The mechanism of various functional changes needs to be clarified but may be explained by epigenetic modifications.

Effects of intrauterine growth restriction during late pregnancy on the ovine fetal renal function and antioxidant capacity

This study investigated the effects of intrauterine growth restriction during late pregnancy on the ovine fetal renal function and renal antioxidant capacity. Eighteen ewes pregnant were randomly divided into control group (CG, ad libitum, 0.67 MJ ME·BW^-0.75 ·day^-1 , n = 6), restricted group 1 (RG1, 0.18 MJ ME·BW^-0.75 ·day^-1 , n = 6), and restricted group 2 (RG2, 0.33 MJ ME·BW^-0.75 ·day^-1 , n = 6). At 140 days, the fetal blood, allantoic fluid and kidney tissue were collected to determinate fetal renal function and renal antioxidant capacity. The results showed that the fetal weight, kidney weight, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), aquaporin-2 (AQP-2) and aquaporin-3 (AQP-3), and total antioxidant capacity (T-AOC) in RG1 group were decreased compared with the CG (P < 0.05), but the contents of β2-Microglobulin (β 2-MG), cystatin C (Cys-C), filtered sodium excretion fraction (FENa), malondialdehyde (MDA), and hydroxyl radical (OH) in RG1 group were increased (P < 0.05). The impaired ovine fetal renal growth, antioxidant imbalance and dysfunction of glomerulus ultrafiltration, and the renal tubules reabsorption were induced by maternal malnutrition during late pregnancy.

Low birth weight trends: possible impacts on the prevalences of hypertension and chronic kidney disease

Worldwide, hypertension and chronic kidney disease (CKD) are highly prevalent disorders and are strong risk factors for cardiovascular disease and end-stage renal disease (ESRD). The developmental origins of health and disease (DOHAD) concept suggests that undesirable perinatal environmental conditions, such as malnutrition, contribute to disease development in adults. Among the known hypertension and CKD risk factors, DOHAD plays a potential role in determining susceptibility to the onset of these diseases in later adulthood. Since low birth weight (LBW) is a surrogate marker for adverse fetal environmental conditions, the high incidence of LBW in developing countries and its increasing incidence in most developed countries (attributed to multiple pregnancies and prepregnancy maternal factors, such as undernutrition, advanced maternal age, and smoking) is concerning. Thus, LBW is an important public health problem not only because of the associated infant mortality and morbidity but also because it is a risk factor for adult-onset hypertension/CKD. During their reproductive years, pregnant women who were born with LBWs have an increased risk of hypertensive disorders of pregnancy, which contribute to the risk of developing cardiovascular disease and ESRD. The offspring of LBW females are also likely to be LBW, which suggests that susceptibility to hypertension/CKD may reflect transgenerational inheritance. Therefore, there is global concern about the increasing prevalence of LBW-related diseases. This review summarizes the relevance of hypertension and CKD in conjunction with DOHAD and discusses recent studies that have examined the impact of the upward LBW trend on renal function and blood pressure.

Resilience to acute kidney injury in offspring of maternal protein restriction

Protein restriction (PR) during pregnancy induces morphofunctional alterations related to deficient nephrogenesis. We studied the renal functional and morphological significance of PR during pregnancy and/or lactation in adult male rat offspring and the repercussions on acute kidney injury (AKI) severity. Female rats were randomly assigned to the following groups: control diet during pregnancy and lactation (CC), control diet during pregnancy and PR diet during lactation (CR), PR during pregnancy and control diet during lactation (RC), and PR during pregnancy and lactation (RR). Three months after birth, at least 12 male offspring of each group randomly underwent either bilateral renal ischemia for 45 min [ischemia-reperfusion (IR)] or sham surgery. Thus, eight groups were studied 24 h after reperfusion: CC, CC + IR, CR, CR + IR, RC, RC + IR, RR, and RR + IR. Under basal conditions, the CR, RC, and RR groups exhibited a significant reduction in nephron number that was associated with a reduction in renal blood flow. Glomerular hyperfiltration was present as a compensatory mechanism to maintain normal renal function. mRNA levels of several vasoactive, antioxidant, and anti-inflammatory molecules were decreased. After IR, renal function was similarly reduced in all of the studied groups. Although all of the offspring from maternal PR exhibited renal injury, the magnitude was lower in the RC and RR groups, which were associated with faster renal blood flow recovery, differential vasoactive factors, and hypoxia-inducible factor-1α signaling. Our results show that the offspring from maternal PR are resilient to AKI induced by IR that was associated with reduced tubular injury and a differential hemodynamic response.

Individual and Environmental Factors Associated with Proteinuria in Korean Children: A Multilevel Analysis

Proteinuria is a significant sign of childhood renal disorders. However, little is known about how sociodemographic and environmental factors are related to the presence of proteinuria among children and adolescents. This paper focuses on the prevalence of proteinuria and its risk factors among children and adolescents. This study conducted a secondary analysis of data from the 2016 Sample Schools Raw Data of Health Examination for School Students (SSRDHESS). Data collected from 27,081 students who had undergone a health screening were analyzed using Chi-square tests, independent t-tests, and multilevel logistic regression analysis. The prevalence of proteinuria was higher in the thin group than in the normal weight group (adjusted odds ratio (aOR) = 1.77; 95% confidence interval (CI) = 1.34–2.33) and lower in the overweight/obese group (aOR = 0.64; 95% CI = 0.51–0.80). Additionally, those in metropolitan and small–medium sized cities had a proteinuria prevalence about 1.5-fold higher than that of those in rural areas (95% CI = 1.08–2.02, 95% CI = 1.19–1.92, respectively). Proteinuria was associated with environmental pollution, including smoking rate, ambient particulate matter and heavy metals in drinking water (aOR = 1.10; 95% CI = 1.01–1.20; aOR = 1.06; 95% CI = 1.01–1.11, aOR = 1.001; 95% CI = 1.0001–1.0015). These results suggest that to improve health management effectiveness, kidney disease prevention efforts for children and adolescents should focus on geographical area and environmental pollution, as well as body weight as individual factors.