Intrauterine low-protein diet disturbs metanephric gene expression and induces urinary tract developmental abnormalities in mice

Gestational diabetes mellitus induces congenital anomalies of the kidney and urinary tract in mice by altering RET/MAPK/ERK pathway

Gestational diabetes mellitus (GDM) presents a substantial population health concern. Previous studies have revealed that GDM can ultimately influence nephron endowment. In this study, we established a GDM mouse model to investigate the embryological alterations and molecular mechanisms underlying the development of congenital anomalies of the kidney and urinary tract (CAKUT) affected by GDM. Our study highlights that GDM could contribute to the manifestation of CAKUT, with prevalent phenotypes characterized by isolated hydronephrosis and duplex kidney complicated with hydronephrosis in mice. Ectopic ureteric buds (UBs) and extended length of common nephric ducts (CNDs) were noted in the metanephric development stage. The expression of Ret and downstream p-ERK activity were enhanced in UBs, which indicated the alteration of RET/MAPK/ERK pathway may be one of the mechanisms contributing to the increased occurrence of CAKUT associated with GDM.

Pro-inflammatory Polarization of Macrophages Causes Intestinal Inflammation in Low-Birth-Weight Piglets and Mice

BACKGROUND

Low-birth-weight (LBW) animals suffer from intestinal damage and inflammation in their early life.

OBJECTIVES

The aim of this study was to investigate the role of macrophages in intestinal inflammation in LBW piglets and mice.

METHODS

Major genes involved in intestinal barrier function such as claudin-1, zonula occludens-1 (ZO-1), occludin, and mucin 2 and inflammatory cytokines such as IL-1β, TNF-α, IL-10, and IL-13 were evaluated in 21-day-old, normal birth weight (NBW) and LBW piglets and mice. Macrophage markers such as CD16/32, CD163, and CD206 were also assessed by immunofluorescence and flow cytometry. Polarized and unpolarized macrophages were further transferred into NBW and LBW mice, followed by evaluation of intestinal permeability and inflammation.

RESULTS

Claudin-1 mRNA in LBW piglets as well as claudin-1, occludin, ZO-1 and mucin 2 mRNAs in LBW mice was significantly downregulated. IL-1β and TNF-α were significantly upregulated in LBW piglets (P < 0.05). LBW mice showed a reduced expression of IL-10 and IL-13 (P < 0.05), with a heightened IL-6 level (P < 0.01) in the jejunum. CD16, a marker for M1 macrophages, was significantly elevated in the jejunum of LBW piglets, whereas CD163, a marker for M2 macrophages, was significantly decreased (P < 0.05). Similarly, LBW mice had more CD11b+CD16/32+ M1 macrophages (P < 0.05) and fewer CD206+ M2 macrophages (P < 0.01) than NBW mice. Moreover, transfer of M1 macrophages exacerbated intestinal inflammation in LBW mice. Furthermore, two major glycolysis-associated genes, hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA), were significantly upregulated in LBW piglets and mice (P < 0.05).

CONCLUSIONS

This study revealed for the first time that the intestinal macrophages are polarized towards a pro-inflammatory phenotype in LBW piglets and mice, contributing to intestinal inflammation. The findings of this study provide new options for the management of intestinal inflammation in LBW animals.

Regulation of nephron progenitor cell lifespan and nephron endowment

Low nephron number - resulting, for example, from prematurity or developmental anomalies - is a risk factor for the development of hypertension, chronic kidney disease and kidney failure. Considerable interest therefore exists in the mechanisms that regulate nephron endowment and contribute to the premature cessation of nephrogenesis following preterm birth. The cessation of nephrogenesis in utero or shortly after birth is synchronized across multiple niches in all mammals, and is coupled with the exhaustion of nephron progenitor cells. Consequently, no nephrons are formed after the cessation of developmental nephrogenesis, and lifelong renal function therefore depends on the complement of nephrons generated during gestation. In humans, a tenfold variation in nephron endowment between individuals contributes to differences in susceptibility to kidney disease; however, the mechanisms underlying this variation are not yet clear. Salient advances in our understanding of environmental inputs, and of intrinsic molecular mechanisms that contribute to the regulation of cessation timing or nephron progenitor cell exhaustion, have the potential to inform interventions to enhance nephron endowment and improve lifelong kidney health for susceptible individuals.

Low Nephron Number Induced by Maternal Protein Restriction Is Prevented by Nicotinamide Riboside Supplementation Depending on Sirtuin 3 Activation

A reduced nephron number at birth, due to critical gestational conditions, including maternal malnutrition, is associated with the risk of developing hypertension and chronic kidney disease in adulthood. No interventions are currently available to augment nephron number. We have recently shown that sirtuin 3 (SIRT3) has an important role in dictating proper nephron endowment. The present study explored whether SIRT3 stimulation, by means of supplementation with nicotinamide riboside (NR), a precursor of the SIRT3 co-substrate nicotinamide adenine dinucleotide (NAD⁺), was able to improve nephron number in a murine model of a low protein (LP) diet. Our findings show that reduced nephron number in newborn mice (day 1) born to mothers fed a LP diet was associated with impaired renal SIRT3 expression, which was restored through supplementation with NR. Glomerular podocyte density, as well as the rarefaction of renal capillaries, also improved through NR administration. In mechanistic terms, the restoration of SIRT3 expression through NR was mediated by the induction of proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α). Moreover, NR restored SIRT3 activity, as shown by the reduction of the acetylation of optic atrophy 1 (OPA1) and superoxide dismutase 2 (SOD2), which resulted in improved mitochondrial morphology and protection against oxidative damage in mice born to mothers fed the LP diet. Our results provide evidence that it is feasible to prevent nephron mass shortage at birth through SIRT3 boosting during nephrogenesis, thus providing a therapeutic option to possibly limit the long-term sequelae of reduced nephron number in adulthood.

Effect of maternal curcumin supplementation on intestinal damage and the gut microbiota in male mice offspring with intra-uterine growth retardation

PURPOSE

The present study investigated whether maternal curcumin supplementation might protect against intra-uterine growth retardation (IUGR) induced intestinal damage and modulate gut microbiota in male mice offspring.

METHODS

In total, 36 C57BL/6 mice (24 females and 12 males, 6-8 weeks old) were randomly divided into three groups based on the diet before and throughout pregnancy and lactation: (1) normal protein (19%), (2) low protein (8%), and (3) low protein (8%) + 600 mg kg-1 curcumin. Offspring were administered a control diet until postnatal day 35.

RESULTS

Maternal curcumin supplementation could normalize the maternal protein deficiency-induced decrease in jejunal SOD activity (NP = 200.40 ± 10.58 U/mg protein; LP = 153.30 ± 5.51 U/mg protein; LPC = 185.40 ± 9.52 U/mg protein; P < 0.05) and T-AOC content (NP = 138.90 ± 17.51 U/mg protein; LP = 84.53 ± 5.42 U/mg protein; LPC = 99.73 ± 12.88 U/mg protein; P < 0.05) in the mice offspring. Maternal curcumin supplementation increased the maternal low protein diet-induced decline in the ratio of villus height-to-crypt depth (NP = 2.23 ± 0.19; LP = 1.90 ± 0.06; LPC = 2.56 ± 0.20; P < 0.05), the number of goblet cells (NP = 12.72 ± 1.16; LP = 7.04 ± 0.53; LPC = 13.10 ± 1.17; P < 0.05), and the ratio of PCNA-positive cells (NP = 13.59 ± 1.13%; LP = 2.42 ± 0.74%; LPC = 6.90 ± 0.96%; P < 0.05). It also reversed the maternal protein deficiency-induced increase of the body weight (NP = 13.00 ± 0.48 g; LP = 16.49 ± 0.75 g; LPC = 10.65 ± 1.12 g; P < 0.05), the serum glucose levels (NP = 5.32 ± 0.28 mmol/L; LP = 6.82 ± 0.33 mmol/L; LPC = 4.69 ± 0.35 mmol/L; P < 0.05), and the jejunal apoptotic index (NP = 6.50 ± 1.58%; LP = 10.65 ± 0.75%; LPC = 5.24 ± 0.71%; P < 0.05). Additionally, maternal curcumin supplementation enhanced the gene expression level of Nrf2 (NP = 1.00 ± 0.12; LP = 0.73 ± 0.10; LPC = 1.34 ± 0.12; P < 0.05), Sod2 (NP = 1.00 ± 0.04; LP = 0.85 ± 0.04; LPC = 1.04 ± 0.04; P < 0.05) and Ocln (NP = 1.00 ± 0.09; LP = 0.94 ± 0.10; LPC = 1.47 ± 0.09; P < 0.05) in the jejunum. Furthermore, maternal curcumin supplementation normalized the relative abundance of Lactobacillus (NP = 31.56 ± 6.19%; LP = 7.60 ± 2.33%; LPC = 17.79 ± 2.41%; P < 0.05) and Desulfovibrio (NP = 3.63 ± 0.93%; LP = 20.73 ± 3.96%; LPC = 13.96 ± 4.23%; P < 0.05), and the ratio of Firmicutes/Bacteroidota (NP = 2.84 ± 0.64; LP = 1.21 ± 0.30; LPC = 1.79 ± 0.15; P < 0.05). Moreover, Lactobacillus was positively correlated with the SOD activity, and it was negatively correlated with Il - 1β expression (P < 0.05). Desulfovibrio was negatively correlated with the SOD activity and the jejunal expression of Sod1, Bcl - 2, Card11, and Zo - 1 (P < 0.05).

CONCLUSIONS

Maternal curcumin supplementation could improve intestinal integrity, oxidative status, and gut microbiota in male mice offspring with IUGR.

Disparate phenotypes in two unfavorable pregnancies due to maternal mosaicism of a novel RET gene mutation

Mutations in RET have been found in multiple diseases including isolated and associated congenital anomalies. Here, we report a case presented with disparate phenotypes in each pregnancy but caused by the same novel mutation. Whole-exome sequencing (WES) was performed on the proband/abortion product-parental trio and a novel missense variant in RET (chr10:43615610C>G; c.2689C>G; p.Arg897Gly) was identified. The mother was a low-level somatic carrier of this new mutation, with 17.3% in blood, 19.1% in oralmucous membrane, and 15.7% in urine by droplet digital polymerase chain reaction (dd PCR). Our finding not only broadens the mutation spectrum of RET but also gives supportive genetic counseling and timely guidance on fertility choices.

Intrauterine Low-Protein Diet Exacerbates Abnormal Development of the Urinary System in Gen1-Mutant Mice

BACKGROUND

Gen1 mutation can cause various phenotypes of congenital anomaly of the kidney and urinary tract (CAKUT). An intrauterine low-protein isocaloric diet can also cause CAKUT phenotypes in offspring. However, single factors such as gene mutation or abnormal environmental factor during pregnancy can only explain part of the pathogenesis of CAKUT.

OBJECTIVES

A low-protein isocaloric diet was fed to Gen1-mutant mice throughout pregnancy to establish a Gen1-mutant mouse model exposed to a low-protein isocaloric intrauterine environment. The mice were divided into 4 groups: normal (22%) protein diet (ND) + wild-type mice (CON group), ND + Gen1^PB/+ mice (Gen1^PB/+ group), low (6%)-protein isocaloric diet (LD) + wild-type mice (LD group), and the LD + Gen1^PB/+ groups.

METHODS

The experimental design included observing proportion and distribution of CAKUT phenotypes of neonatal mice; evaluating the number of ureteric buds (UBs) on embryonic day (E) 11.5, the location of UBs on E11.5, and length of the common nephric duct (CND); isolating embryonic kidneys on E11.5 from the Gen1^PB/+ group and culturing embryonic kidneys in medium containing 10% serum or serum-free medium to observe the branching of UBs; and detecting the p-PLCγ, p-Akt, and p-ERK1/2 in UBs and CND on E11.5, as well as the apoptosis and proliferation of tissues by immunofluorescence staining.

RESULTS

We found that the incidence of CAKUT in offspring of Gen1^PB/+ mice under an intrauterine low-protein isocaloric diet environment was significantly increased, and a duplicated collecting system was the dominant phenotype of CAKUT. During the early stage of metanephric development, ectopic protrusion of UBs may appear and lower locations of UBs in Gen1^PB/+ mice under an intrauterine low-protein isocaloric diet environment and the number of UB branches in the serum-free culture condition significantly decreased. Further examination revealed that p-PLCγ signaling and tissue apoptosis were abnormal in UBs and the CND at the early stage of kidney development.

CONCLUSIONS

The aforementioned findings suggest that an intrauterine low-protein isocaloric diet can aggravate the occurrence of CAKUT in Gen1-mutant mice, which might affect key steps in the metanephric development, such as the protrusion of UBs, which might be related to mediate UBs and CND apoptosis through p-PLCγ signaling.

Microanatomy of the developing nephron in the fetal human kidney during late gestation

BACKGROUND

Clinical experiences reveal that the kidneys of preterm and low birth weight infants are highly vulnerable. Noxae of various molecular composition can damage the outer renal cortex, resulting in an early termination of nephron formation. However, in contrast to what is known about the rodent kidney, with reference to the damage on the early stages of nephron anlage such as the comma-shaped body, renal vesicles, pretubular aggregate or nephrogenic niche, this information in the fetal human kidney is not available. The few documented pathological alterations in the fetal human kidney during late gestation are glomeruli with a dilated Bowman's space and a shrunken tuft, the reduction in width of the nephrogenic zone and the lack of here contained S-shaped bodies. The latter points out that the shaping, folding or expansion of the developing nephron must be disrupted. Since these specific aspects have been little investigated, the aim of the present microanatomical contribution is to highlight it.

METHODS

Firstly, the individual stages of nephron anlage in the fetal human kidney during late gestation were documented by microscopic images. Then, as a stylistic tool for the pointing to specific sites of the running developmental process, a series of true to scale sketches were produced.

RESULTS

The generated sketches depict the spatial expansion of the transiently appearing stages of nephron anlage. These are restricted to the nephrogenic zone and are framed by the inner side of the renal capsule, the related collecting duct ampulla and a perforating radiate artery. Practical hints and a consequent nomenclature explain the developmental course and help us to identify the precise location of the proximal - distal poles, medial - lateral profiles, connecting points, adhesion sites or folds at the developing nephron on microscopic specimens.

CONCLUSIONS

The impairment of nephrogenesis in preterm and low birth weight babies is an unsolved biomedical issue. To contribute, by provided true to scale sketches, numerous practical hints and a consequent nomenclature typical features of nephron formation in the fetal human kidney at late gestation are demonstrated.

Analysis of structure and gene expression in developing kidneys of male and female rats exposed to low protein diets in utero

A maternal low protein (LP) diet in rodents often results in low nephron endowment and renal pathophysiology in adult life, with outcomes often differing between male and female offspring. Precisely how a maternal LP diet results in low nephron endowment is unknown. We conducted morphological and molecular studies of branching morphogenesis and nephrogenesis to identify mechanisms and timepoints that might give rise to low nephron endowment. Sprague-Dawley rats were fed a normal protein (19.4% protein, NP) or LP (9% protein) diet for 3 weeks prior to mating and throughout gestation. Embryonic day 14.25 (E14.25) kidneys from males and females were either cultured for 2 days after which branching morphogenesis was quantified, or frozen for gene expression analysis. Real-time PCR was used to quantify expression of key nephrogenesis and branching morphogenesis genes at E14.25 and 17.25. At E17.25, nephron number was determined in fixed tissue. There was no effect of either maternal diet or sex on branching morphogenesis. Nephron number at E17.25 was 14% lower in male and female LP offspring than in NP controls. At E14.25 expression levels of genes involved in branching morphogenesis (Gfrα1, Bmp4, Gdnf) and nephrogenesis (Hnf4a, Pax2, Wnt4) were similar in the dietary groups, but significant differences between sexes were identified. At E17.25, expression of Gfrα1, Gdnf, Bmp4, Pax2 and Six2 was lower in LP offspring than NP offspring, in both male and female offspring. These findings provide new insights into how a LP diet leads to low nephron endowment and renal sexual dimorphism.

Shaping of the nephron - a complex, vulnerable, and poorly explored backdrop for noxae impairing nephrogenesis in the fetal human kidney

Background

The impairment of nephrogenesis is caused by noxae, all of which are significantly different in molecular composition. These can cause an early termination of nephron development in preterm and low birth weight babies resulting in oligonephropathy. For the fetal human kidney, there was no negative effect reported on the early stages of nephron anlage such as the niche, pretubular aggregate, renal vesicle, or comma-shaped body. In contrast, pathological alterations were identified on subsequently developing S-shaped bodies and glomeruli. While the atypical glomeruli were closely analyzed, the S-shaped bodies and the pre-stages received little attention even though passing the process of nephron shaping. Since micrographs and an explanation about this substantial developmental period were missing, the shaping of the nephron in the fetal human kidney during the phase of late gestation was recorded from a microanatomical point of view.

Results

The nephron shaping starts with the primitive renal vesicle, which is still part of the pretubular aggregate at this point. Then, during extension of the renal vesicle, a complex separation is observed. The medial part of its distal pole is fixed on the collecting duct ampulla, while the lateral part remains connected with the pretubular aggregate via a progenitor cell strand. A final separation occurs, when the extended renal vesicle develops into the comma-shaped body. Henceforth, internal epithelial folding generates the tubule and glomerulus anlagen. Arising clefts at the medial and lateral aspect indicate an asymmetrical expansion of the S-shaped body. This leads to development of the glomerulus at the proximal pole, whereas in the center and at the distal pole, it results in elongation of the tubule segments.

Conclusions

The present investigation deals with the shaping of the nephron in the fetal human kidney. In this important developmental phase, the positioning, orientation, and folding of the nephron occur. The demonstration of previously unknown morphological details supports the search for traces left by the impairment of nephrogenesis, enables to refine the assessment in molecular pathology, and provides input for the design of therapeutic concepts prolonging nephrogenesis.

Intrauterine low-protein diet aggravates developmental abnormalities of the urinary system via the Akt/Creb3 pathway in Robo2 mutant mice

The offspring of Robo2 mutant mice usually present with variable phenotypes of congenital anomalies of the kidney and urinary tract (CAKUT). An intrauterine low-protein diet can also cause CAKUT in offspring, dominated by the duplicated collecting system phenotype. A single genetic or environment factor can only partially explain the pathogenesis of CAKUT. The present study aimed to establish an intrauterine low-protein diet roundabout 2 (Robo2) mutant mouse model and found that the intrauterine low-protein diet led to significantly increased CAKUT phenotypes in Robo2^PB/+ mice offspring, dominant by a duplicated collecting system. At the same time, more ectopic and lower located ureteric buds (UBs) were observed in the intrauterine low-protein diet-fed Robo2 mutant mouse model, and the number of UB branches was reduced in the serum-free culture. During UB protrusion, intrauterine low-protein diet reduced the expression of Slit2/Robo2 in Robo2 mutant mice and affected the expression of glial cell-derived neurotrophic factor/Ret, which is a key molecule for metanephric development, with increasing phospho-Akt and phospho-cAMP responsive element-binding protein 3 activity and a reduction of apoptotic cells in embryonic day 11.5 UB tissues. The mechanism by which an intrauterine low-protein diet aggravates CAKUT in Robo2 mutant mice may be related to the disruption of Akt/cAMP responsive element-binding protein 3 signaling and a reduction in apoptosis in UB tissue.