Impact of pregnancy on underlying renal disease

Sex dimorphism in kidney health and disease: mechanistic insights and clinical implication

Sex is a key variable in the regulation of human physiology and pathology. Many diseases disproportionately affect one sex: autoimmune diseases, such as systemic lupus erythematosus, are more common in women but more severe in men, whereas the incidence of other disorders such as gouty arthritis and malignant cancers is higher in men. Besides the pathophysiology, sex may also influence the efficacy of therapeutics; participants in clinical trials are still predominately men, and the side effects of drugs are more common in women than in men. Sex dimorphism is a prominent feature of kidney physiology and function, and consequently affects the predisposition to many adult kidney diseases. These differences subsequently influence the response to immune stimuli, hormones, and therapies. It is highly likely that these responses differ between the sexes. Therefore, it becomes imperative to consider sex differences in translational science from basic science to preclinical research to clinical research and trials. Under-representation of one sex in preclinical animal studies or clinical trials remains an issue and key reported outcomes of such studies ought to be presented separately. Without this, it remains difficult to tailor the management of kidney disease appropriately and effectively. In this review, we provide mechanistic insights into sex differences in rodents and humans, both in kidney health and disease, highlight the importance of considering sex differences in the design of any preclinical animal or clinical study, and propose guidance on how to optimal design and conduct preclinical animal studies in future research.

Multiple metal exposure and platelet counts during pregnancy: A repeated measure study

BACKGROUND

Evidence from animal and in vitro studies suggest that some metals interfere with normal platelet counts (PLT). However, limited human studies have investigated the association of metals and PLT, a marker of hematologic and hemostatic, particularly in susceptible populations such as pregnant women.

OBJECTIVES

Our purpose was to investigate the associations of repeated measures of 13 urinary metals with PLT during pregnancy.

METHODS

The present study involved 3911 pregnant women participating in a prospective cohort study in Wuhan, China, from 2013 to 2016. We measured 13 metals in urine and PLT in blood samples collected in the first, second, and third trimester (median = 13, 24, and 35 weeks of gestation, respectively). Mixed linear models and general linear models were applied to analyze the associations between multiple metals and PLT during pregnancy. The odds ratio (OR) for gestational thrombocytopenia was examined using generalized estimating equations.

RESULTS

After adjusting for other metals and covariates, the repeated measure analyses showed that decreased levels of PLT were associated with a 10-fold increase in urinary concentration of cadmium (Cd) [percent difference (%Δ) = -5.02, 95%CI = -9.53, -0.29], manganese (Mn) [percent difference (%Δ) = -4.63, 95%CI = -7.50, -1.67], and arsenic (As) [percent difference (%Δ) = -4.56, 95%CI = -8.11, -0.86]. Cross-sectional analyses by trimesters revealed that Cd was inversely associated with PLT through the three trimesters. In addition, Cd was associated with an increased OR of 1.80 (95%CI: 1.26, 2.56), 1.65 (95%CI: 1.05, 2.59), 1.54 (95%CI: 1.02, 2.33) for gestational thrombocytopenia in the first, second, and third trimester, respectively.

CONCLUSIONS

Our study suggested an association of Cd, Mn, and As with decreased PLT during pregnancy. Particularly, Cd may increase the risk of gestational thrombocytopenia.

Pregnancy management and outcome in women with chronic kidney disease

An increasing number of pregnancies occur in the presence of chronic kidney diseases (CKD), mainly including chronic glomerulonephritis (GN), diabetic nephropathy (DN), and lupus nephritis (LN). The most important factor affecting fetal and maternal prognosis is the degree of renal function at conception. In the majority of patients with mild renal function impairment, and well-controlled blood pressure, pregnancy is usually successful and does not alter the natural course of maternal renal disease. Conversely, fetal outcome and long-term maternal renal function might be seriously threatened by pregnancy in women with moderate or severe renal function impairment. The last few years, advances in our knowledge about the interaction of pregnancy and renal function resulted in the improvement of fetal outcome in patients with chronic renal failure and also in the management of pregnant women with end-stage renal disease (ESRD) maintained on dialysis. However, women with impaired renal function and those on dialysis should be carefully counseled about the risks of pregnancy.

Postpartum persistent proteinuria after preeclampsia: a single-center experience

BACKGROUND

Many studies have investigated preexistent renal disease during pregnancy. However, insufficient data regarding the new onset of glomerulonephritis in the course of gestation, especially in patients with preeclampsia, exist. The aim of this study was to investigate underlying renal disease in preeclamptic Turkish women with persistent proteinuria after delivery.

METHODS

Between 2005 and 2010, 463 patients with preeclampsia were admitted to our hospital. The symptoms of proteinuria persisted in 34 women (0.7 %). Thirteen of these patients refused a kidney biopsy. Seven of these patients had a history of documented kidney disease. Kidney biopsies were performed on 14 women who were diagnosed with persistent proteinuria in the postpartum period and the specimens were examined by light and immunofluorescence microscopy.

RESULTS

Ten of 14 patients (71 %) were diagnosed with underlying renal disease. Four patients were diagnosed with idiopathic preeclampsia (29 %). Histopathological findings existed for ten patients with underlying renal disease; four patients (29 %) were diagnosed with membranoproliferative glomerulonephritis (MPGN), four patients (29 %) were diagnosed with IgA nephropathy (IgAN), one patient (7 %) was diagnosed with focal segmental glomerulosclerosis (FSGS), and one patient (7 %) was diagnosed with amyloidosis. Hematuria was detected in eight patients (57 %), and high serum creatinin levels were observed in five (36 %).

CONCLUSIONS

Persistent proteinuria is the most important predictor of underlying renal disease after delivery. All patients with preeclampsia should be evaluated with respect to continuing proteinuria, persistent hematuria, or impaired renal functions after postpartum period and a percutaneous renal biopsy should be performed in those patients who have positive signs of underlying renal disease.

Chronic Renal Disease in Pregnancy

The purpose of this review was to examine the impact of varying degrees of renal insufficiency on pregnancy outcome in women with chronic renal disease. Our search of the literature did not reveal any randomized clinical trials or meta-analyses. The available information is derived from opinion, reviews, retrospective series, and limited observational series. It appears that chronic renal disease in pregnancy is uncommon, occurring in 0.03-0.12% of all pregnancies from two U.S. population-based and registry studies. Maternal complications associated with chronic renal disease include preeclampsia, worsening renal function, preterm delivery, anemia, chronic hypertension, and cesarean delivery. The live birth rate in women with chronic renal disease ranges between 64% and 98% depending on the severity of renal insufficiency and presence of hypertension. Significant proteinuria may be an indicator of underlying renal insufficiency. Management of pregnant women with underlying renal disease should ideally entail a multidisciplinary approach at a tertiary center and include a maternal-fetal medicine specialist and a nephrologist. Such women should receive counseling regarding the pregnancy outcomes in association with maternal chronic renal disease and the effect of pregnancy on renal function, especially within the ensuing 5 years postpartum. These women will require frequent visits and monitoring of renal function during pregnancy. Women whose renal disease is further complicated by hypertension should be counseled regarding the increased risk of adverse outcome and need for blood pressure control. Some antihypertensives, especially angiotensin-converting enzyme inhibitors and angiotensin-receptor blockers, should be avoided during pregnancy, if possible, because of the potential for both teratogenic (hypocalvaria) and fetal effects (renal failure, oliguria, and demise).

Effects of a reduction in maternal renal mass on pregnancy and cardiovascular and renal function of the pregnant ewe

Maternal renal disease is associated with high maternal and fetal morbidity. To establish an animal model to study renal dysfunction in pregnancy and its potential role in programming for renal disease and hypertension in adult life, a kidney was removed from each of 16 nonpregnant ewes, and a branch of the renal artery of the remaining kidney was ligated (STNx ewes). The 16 STNx and 15 intact ewes were time mated 2.5-17 mo later and studied at 119-132 days of gestation. STNx ewes demonstrated renal hypertrophy and glomerular hyperfiltration. They had higher diastolic arterial pressures (P < 0.05) and larger left ventricles (P < 0.0005), drank more water (P < 0.01), were hypochloremic (P < 0.01) and hyperglycemic (P < 0.0005), and had higher plasma creatinine levels (P < 0.0005) than intact ewes. Effective renal plasma flows and glomerular filtration rates were lower (P < 0.01) and protein excretion was greater (P < 0.05) in STNx than in intact ewes. Glomerulotubular balance was impaired in STNx ewes. Proximal tubular Na(+) reabsorption was reduced (P < 0.05), so Na(+) excretion was increased (P < 0.05). In STNx ewes, filtered K(+) loads were reduced (P < 0.005), but K(+) excretion was the same as in intact ewes. There was net K(+) secretion in STNx ewes; in intact ewes, there was net reabsorption. Plasma renin and angiotensinogen concentrations in STNx and intact ewes were similar, so the hypertension in STNx ewes was not renin dependent. STNx fetuses grew normally, and their blood gases, blood pressure, and heart rates were normal. These alterations in maternal fluid and electrolyte balance and the potential risk of maternal salt depletion or hyperkalemia may adversely affect the fetus.

Changes in renal hemodynamics and structure in the aging kidney; sexual dimorphism and the nitric oxide system

With advancing age the kidney shows both functional declines (falls in GFR) and development of structural damage. In most individuals this occurs slowly and does not lead to severe renal impairment unless additional insults are superimposed. There is a pronounced sexual dimorphism with females protected, due both to beneficial effects of the estrogens and damaging effects of androgens, some of which act directly on the glomerular mesangial cell to regulate growth and extracellular matrix production. Nitric oxide is a major factor in regulation of vascular tone and growth and becomes deficient with advancing age, as endothelial dysfunction develops. Although the abundance of the substrate, L-arginine, is well maintained during aging, there are increases in the concentration of circulating endogenous nitric oxide synthase (nNOS) inhibitors, which will contribute, to the endothelial dysfunction. There is a clear sexual dimorphism in the NO system, with pre-menopausal females producing more NO than men. Within the kidney, declines in the abundance and activity of the neuronal form of the nitric oxide synthase (nNOS) correlate with development of disease. In the male rat where injury and dysfunction occurs, nNOS abundance declines markedly, whereas in the protected female, renal nNOS abundance is maintained. Taken together, it is likely that age-dependent declines in NO generation contribute to age-dependent kidney damage.

Role of nitric oxide in the natriuretic and diuretic responses in pregnant rats

Normal pregnancy is characterized by sodium conservation and increase in plasma volume, yet the natriuretic response to acute saline volume expansion (VE) is intact in pregnant rats. Nitric oxide (NO) has been suggested to play a role in renal and cardiovascular adaptations to normal pregnancy. The objective of this study was to determine the role of NO in the natriuretic and diuretic responses to VE during pregnancy. Infusion of NG-monomethyl-l-arginine (l-NMMA) was used to inhibit NO synthesis. Nine groups of Sprague-Dawley (SD) rats were studied: nonpregnant (NP-VE, n = 7), midterm pregnant (MP-VE, n = 8), and late-term pregnant (LP-VE, n = 7) SD groups that underwent VE alone after a control period; NP-l-NMMA (n = 7), MP-l-NMMA (n = 8), and LP-l-NMMA (n = 7) SD groups that were infused with l-NMMA after a control period; and another three groups of SD rats (NP-VE-l-NMMA, n = 8; MP-VE-l-NMMA, n = 7; and LP-VE-l-NMMA, n = 12) that underwent simultaneous VE and l-NMMA infusion after a control period. The change in fractional excretion of sodium was 7.22 +/- 1.03% for NPVE, 9.89 +/- 1.85% for NP-l-NMMA, and 17.66 +/- 1.85% for NP-VE-l-NMMA (P < 0.05 vs. NP-VE and NP-l-NMMA); 6.61 +/- 1.07% for MP-VE, 7.99 +/- 1.92% for MP-l-NMMA, and 10.24 +/- 1.91% for MP-VE-l-NMMA [not significant (NS) vs. MP-VE and MP-l-NMMA]; 8.20 +/- 1.92% for LP-VE, 8.09 +/- 0.70% for LP-l-NMMA, and 7.57 +/- 1.11% for LP-VE-l-NMMA (both NS vs. LP-VE and LP-l-NMMA). The increase in renal interstitial hydrostatic pressure was significantly greater in all NP compared with pregnant groups with similar experimental intervention (i.e., VE, l-NMMA, or VE-l-NMMA). In conclusion, the natriuretic and diuretic responses to VE and l-NMMA infusion were additive in NP but not in pregnant rats, indicating a possible lower ability of pregnant rats to respond to combined significant natriuretic and diuretic stimuli.