Evidence for a role of proteins, lipids, and phytochemicals in the prevention of polycystic kidney disease progression and severity

Diet and Polycystic Kidney Disease: Nutrients, Foods, Dietary Patterns, and Implications for Practice

Polycystic kidney disease (PKD) is a chronic, progressive hereditary condition characterized by abnormal development and growth of cysts in the kidneys and other organs. There is increasing interest in exploring whether dietary modifications may prevent or slow the disease course in people with PKD. Although vasopressin-receptor agonists have emerged as a novel drug treatment in advancing care for people with PKD, several recent landmark trials and clinical discoveries also have provided new insights into potential dietary-related therapeutic strategies. In this review, we summarize the current evidence pertaining to nutrients, foods, dietary patterns, cyst growth, and progression of PKD. We also describe existing evidence-based dietary care for people with PKD and outline the potential implications for advancing evidence-based dietary interventions. Semin Nephrol 43:x-xx © 2023 Elsevier Inc. All rights reserved.

The Clinical and Mutational Spectrum of 69 Turkish Children with Autosomal Recessive or Autosomal Dominant Polycystic Kidney Disease: A Multicenter Retrospective Cohort Study

INTRODUCTION

Autosomal recessive polycystic kidney disease (ARPKD) is associated with pathogenic variants in the PKHD1 gene. Autosomal dominant polycystic kidney disease (ADPKD) is mainly associated with pathogenic variants in PKD1 or PKD2. The present study aimed to identify the clinical and genetic features of Turkish pediatric ARPKD and ADPKD patients.

METHODS

This multicenter, retrospective cohort study included 21 genetically confirmed ARPKD and 48 genetically confirmed ADPKD patients from 7 pediatric nephrology centers. Demographic features, clinical, and laboratory findings at presentation and during 12-month intervals were recorded.

RESULTS

The median age of the ARPKD patients at diagnosis was lower than the median age of ADPKD patients (10.5 months [range: 0-15 years] vs. 5.2 years [range: 0.1-16 years], respectively, [p = 0.014]). At the time of diagnosis, the median eGFR in the ARPKD patients was lower compared to that of ADPKD patients (81.6 [IQR: 28.7-110.5] mL/min/1.73 m2 and 118 [IQR: 91.2-139.8] mL/min/1.73 m2, respectively, [p = 0.0001]). In total, 11 (52.4%) ARPKD patients had malnutrition; 7 (33.3%) patients had growth retardation at presentation; and 4 (19%) patients had both malnutrition and growth retardation. At diagnosis, 8 (16.7%) of the ADPKD patients had malnutrition, and 5 (10.4%) patients had growth retardation. The malnutrition, growth retardation, and hypertension rates at diagnosis were higher in the ARPKD patients than the ADPKD patients (p = 0.002, p = 0.02, and p = 0.0001, respectively). ARPKD patients with malnutrition and growth retardation had worse renal survival compared to the patients without (p = 0.03 and p = 0.01). Similarly, ADPKD patients with malnutrition had worse renal survival compared to the patients without (p = 0.002). ARPKD patients with truncating variants had poorer 3- and 6-year renal outcome than those carrying non-truncating variants (p = 0.017).

CONCLUSION

Based on renal survival analysis, type of genetic variant, growth retardation, and/or malnutrition at presentation were observed to be factors associated with progression to chronic kidney disease (CKD). Differentiation of ARPKD and ADPKD, and identification of the predictors of the development of CKD are vital for optimal management of patients with ARPKD or ADPKD.

Renoprotective potentials of small molecule natural products targeting mitochondrial dysfunction

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), have become critical clinical, socioeconomic, and public health concerns worldwide. The kidney requires a lot of energy, and mitochondria act as the central organelle for the proper functioning of the kidney. Mitochondrial dysfunction has been associated with the pathogenesis of AKI and CKD. Natural products and their structural analogs have been sought as an alternative therapeutic strategy despite the challenges in drug discovery. Many studies have shown that small-molecule natural products can improve renal function and ameliorate kidney disease progression. This review summarizes the nephroprotective effects of small-molecule natural products, such as berberine, betulinic acid, celastrol, curcumin, salidroside, polydatin, and resveratrol. Treatment with small-molecule natural products was shown to attenuate renal oxidative stress and mitochondrial DNA (mtDNA) damage and restore mitochondrial biogenesis and dynamics in the kidneys against various injury stimuli. Therefore, small-molecule natural products should be recognized as multi-target therapeutics and promising drugs to prevent kidney diseases, particularly those with mitochondrial dysfunction.

Dietary Interventions in Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the progressive growth of renal cysts, leading to the loss of functional nephrons. Recommendations for individuals with ADPKD to maintain a healthy diet and lifestyle are largely similar to those for the general population. However, recent evidence from preclinical models suggests that more tightly specified dietary regimens, including caloric restriction, intermittent fasting, and ketogenic diets, hold promise to slow disease progression, and the results of ongoing human clinical trials are eagerly awaited. These dietary interventions directly influence nutrient signaling and substrate availability in the cystic kidney, while also conferring systemic metabolic benefits. The present review focuses on the importance of local and systemic metabolism in ADPKD and summarizes current evidence for dietary interventions to slow disease progression and improve quality of life.

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.

Feeding soy protein isolate and n-3 PUFA affects polycystic liver disease progression in a PCK rat model of autosomal polycystic kidney disease

OBJECTIVE

In polycystic liver disease (PCLD), multiple cysts cause liver enlargement, structural damage, and loss of function. Soy protein and dietary ω-3 polyunsaturated fatty acids (n-3 PUFAs) have been found to decrease cyst proliferation and inflammation in polycystic kidney disease. Therefore, the aim of the study was to investigate whether soy protein and n-3 PUFA supplementation attenuates PCLD.

METHODS

Young (age 28 days) female PCK rats were fed (n = 12 per group) either casein + corn oil (casein + CO), casein + soybean oil (casein + SO), soy protein isolate + soybean oil (SPI + SO), or SPI + 1:1 soybean/salmon oil blend (SPI + SB) diet for 12 weeks. Liver histology, gene expression by real-time quantitative polymerase chain reaction, and serum markers of liver injury were determined.

RESULTS

Diet had no effect on PCLD progression as indicated by no significant differences in liver weight and hepatic proliferation gene expression between diet groups. PCK rats fed SPI + SB diet, however, had the greatest (P < 0.05) histological evidence of hepatic cyst obstruction, portal inflammation, steatosis, and upregulation (P = 0.03) of fibrosis-related genes. Rats fed SPI + SB diet also had the lowest (P < 0.001) serum cholesterol and higher (P < 0.05) serum alkaline phosphatase and bilirubin concentrations.

CONCLUSIONS

Feeding young female PCK rats SPI and n-3 PUFA failed to attenuate PCLD progression. Furthermore, feeding SPI + SB diet resulted in complications of hepatic steatosis attributable to cysts obstruction of bile duct and hepatic vein. Based on the results, it was concluded that diet intervention alone was not effective at attenuating PCLD associated with autosomal recessive polycystic kidney disease.

Feeding soy protein isolate and oils rich in omega-3 polyunsaturated fatty acids affected mineral balance, but not bone in a rat model of autosomal recessive polycystic kidney disease

Background

Polycystic kidney disease (PKD), a genetic disorder characterized by multiple cysts and renal failure at an early age. In children, kidney disease is often accompanied by disordered mineral metabolism, failure to achieve peak bone mass, and reduced adult height. Optimizing bone health during the growth stage may preserve against bone loss associated with early renal dysfunction in PKD. Dietary soy protein and omega-3 polyunsaturated fatty acid (n-3 PUFA) have been reported to ameliorate PKD and to promote bone health. The study objective was to determine the bone effects of feeding soy protein and/or n-3 PUFAs in a rat model of PKD.

Methods

Weanling female PCK rats (n = 12/group) were randomly assigned to casein + corn oil (Casein + CO), casein + soybean oil (Casein + SO), soy protein isolate + soybean oil (SPI + SO) or soy protein isolate + 1:1 soybean oil:salmon oil blend (SPI + SB) for 12 weeks.

Results

Rats fed SPI + SO diet had shorter (P = 0.001) femur length than casein-fed rats. Rats fed SPI + SO and SPI + SB diet had higher (P = 0.04) calcium (Ca) and phosphorus (P) retention. However, there were no significant differences in femur and tibial Ca, P or bone mass between diet groups. There were also no significant difference in bone microarchitecture measured by micro-computed tomography or bone strength determined by three-point bending test between diet groups.

Conclusions

Early diet management of PKD using SPI and/or n-3 PUFAs influenced bone longitudinal growth and mineral balance, but neither worsened nor enhanced bone mineralization, microarchitecture or strength.

Dietary n-3 polyunsaturated fatty acids or soy protein isolate did not attenuate disease progression in a female rat model of autosomal recessive polycystic kidney disease

Polycystic kidney disease (PKD) is an incurable genetic disorder that is characterized by multiple benign cysts. As PKD advances, cyst growth increases kidney volume, decreases renal function, and may lead to end-stage renal disease; however, in a PKD rat model, feeding soy protein isolate (SPI) reduced cyst proliferation and growth. The n-3 polyunsaturated fatty acids (PUFAs) are noted for their anti-inflammatory actions. Therefore, diet therapy could offer a potentially efficacious, safe, and cost-effective strategy for treating PKD. The objective of this study was to investigate the role of soy protein and/or n-3 PUFAs on PKD progression and severity in the rat model of autosomal recessive PKD. We hypothesized that the antiproliferative and anti-inflammatory actions associated with soy protein and n-3 PUFA supplementation will attenuate PKD progression in female PCK rats. For 12 weeks, young (age, 28 days) female PCK rats were randomly assigned (n=12/group) to 4 different diets: casein±corn oil, casein±soybean oil, SPI±soybean oil, or SPI±1:1 soybean/salmon oil (SPI±SB). The feeding of the different protein and lipid sources had no significant effect on relative kidney weight. Histologic evaluation showed no significant differences in cortical or medullary cyst size, interstitial inflammation, and fibrosis among diet groups. However, rats fed SPI±SB diet had cortical cyst obstruction and the highest (P<.01) serum blood urea nitrogen concentration. Rats fed SPI±SB diet had the highest (P<.001) renal docosahexaeonic acid, but there were no significant differences in renal tissue inflammation and proliferation gene expression among the diet groups. Based on these results, dietary soy protein and/or n-3 PUFAs did not attenuate disease progression or severity in the female PCK rat model of autosomal recessive PKD.