Soy protein preserves basement membrane integrity through a synergistic effect on nephrin, matrix metalloproteinase and vascular endothelial growth factor

Sex Differences in Glomerular Protein Expression and Effects of Soy-Based Diet on Podocyte Signaling

Background:

Kidney disease is a major public health issue arising from loss of glomerular podocyte function, and there are considerable sex differences in its prognosis. Evidence suggests a renoprotective effect of estrogen and soy diet-derived phytoestrogens, although the molecular basis for this is poorly understood.

Objective:

Here, we aim to assess sex differences in expression of key proteins associated with podocyte survival and determine the effects of dietary soy on glomerular and podocyte signaling.

Methods:

Male and female FVB mice were fed control, low (1%), and high (20%) doses of isolated soy protein (ISP) in utero and until 100 days of age. Spot urine was collected to measure proteinuria and isolated glomeruli were used to quantify activated and total levels of nephrin, Akt, and ERK1/2. To investigate protective effects of specific soy phytoestrogens, cultured podocytes were treated with or without daidzein and subject to control or high glucose as a model of podocyte injury.

Results:

Nephrin and Akt were elevated at baseline in glomeruli from females compared to males. Both sexes that were fed 1% and 20% ISP displayed robust increases in total glomerular Akt compared to controls, and these effects were more prominent in females. A similar trend at both doses in both sexes was observed with activated Akt and total nephrin. Notably, males exclusively showed increased phosphorylation of nephrin and extracellular signal-regulated kinase (ERK) at the 1% ISP dose; however, no overt changes in urinary albumin excretion or podocin levels were observed, suggesting that the soy diets did not impair podocyte function. Finally, in cultured male and female podocytes, daidzein treatment suppressed high glucose-induced ERK activation.

Conclusions:

Together, our findings reveal a putative mechanism to explain the protective influence of sex on kidney disease progression, and they provide further evidence to support a beneficial role for dietary soy in preserving glomerular function.

The Protective Effects of Ropivacaine Against High Glucose-induced Brain Microvascular Endothelial Injury by Reducing MMPs and Alleviating Oxidative Stress

Diabetes is undoubtedly affecting global health. Considerable attention has been directed to brain complications caused by diabetes, which are reported to be related to the injury on brain microvascular endothelial cells. Oxidative stress and degradation of vascular basement membrane contribute to the injury of vascular endothelia by diabetes. The present study aims to investigate the effects of ropivacaine on high glucose-induced brain microvascular endothelial injury, as well as the underlying mechanism. Cell viability was determined by (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The production of reactive oxygen species (ROS) was evaluated by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Quantitative real-time PCR (QRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to determine the expression levels of matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9), intercellular cell adhesion molecule-1 (ICAM-1), and vascular endothelial growth factor (VEGF). The production of nitric oxide (NO) was detected by DAF-FM DA staining. The expression of inducible nitric oxide synthase (iNOS) was evaluated by qRT-PCR and Western blot analysis. Western blot was used to determine the expression of nuclear factor erythroid 2-related factor 2 (Nrf-2) and heme oxygenase 1 (HO-1).The cell viability of bEnd.3 brain endothelial cells was inhibited by high glucose, which was rescued by ropivacaine. The elevated production of ROS and MDA by high glucose was reversed by ropivacaine. Ropivacaine suppressed the expression of up-regulated iNOS, NO, MMP-2, MMP-9, ICAM-1, and VEGF induced by high glucose incubation. The expression of Nrf-2 and HO-1 by high glucose incubation was significantly inhibited by ropivacaine treatment.Ropivacaine might alleviate high glucose-induced brain microvascular endothelial injury by suppressing oxidative stress and down-regulating MMPs.

Soy-based renoprotection

Chronic kidney disease (CKD) is a significant public health problem as risk factors such as advanced age, obesity, hypertension and diabetes rise in the global population. Currently there are no effective pharmacologic treatments for this disease. The role of diet is important for slowing the progression of CKD and managing symptoms in later stages of renal insufficiency. While low protein diets are generally recommended, maintaining adequate levels of intake is critical for health. There is an increasing appreciation that the source of protein may also be important. Soybean protein has been the most extensively studied plant-based protein in subjects with kidney disease and has demonstrated renal protective properties in a number of clinical studies. Soy protein consumption has been shown to slow the decline in estimated glomerular filtration rate and significantly improve proteinuria in diabetic and non-diabetic patients with nephropathy. Soy’s beneficial effects on renal function may also result from its impact on certain physiological risk factors for CKD such as dyslipidemia, hypertension and hyperglycemia. Soy intake is also associated with improvements in antioxidant status and systemic inflammation in early and late stage CKD patients. Studies conducted in animal models have helped to identify the underlying molecular mechanisms that may play a role in the positive effects of soy protein on renal parameters in polycystic kidney disease, metabolically-induced kidney dysfunction and age-associated progressive nephropathy. Despite the established relationship between soy and renoprotection, further studies are needed for a clear understanding of the role of the cellular and molecular target(s) of soy protein in maintaining renal function.

Whey versus soy protein diets and renal status in rats

Different dietary protein sources can promote different renal statuses. We examined the effects of whey protein (WP) and soy protein (SP) intake on plasma, urinary, and morphological renal parameters in rats. One hundred and twenty Wistar rats were randomly distributed into 2 experimental groups fed with either WP or SP diets over 12 weeks. These diets were based on commercial WP or SP isolates. The urinary calcium content was higher in the WP diet compared to the SP diet group (P<.001) whereas the urinary citrate level was lower (P<.001). The urinary pH was more acidic in the WP diet group compared to the SP diet group (P<.001); however, no differences were observed between the groups for any of the renal morphological parameters analyzed (all, P>.05) or other plasma renal markers such as albumin or urea concentrations. The increase of acid and urinary calcium and the lower urinary citrate level observed in the WP diet group could increase the incidence of nephrolithiasis compared to the SP diet group. Despite the WP showed poorer acid-base profile, no significant morphological renal changes were observed. These results suggest that the use of SP instead of WP appears to promote a more alkaline plasma and urinary profile, with their consequent renal advantages.