Short-term effects of a very-low-protein diet supplemented with ketoacids in nondialyzed chronic kidney disease patients

Effects of Plant-Based Protein Consumption on Kidney Function and Mineral Bone Disorder Outcomes in Adults With Stage 3-5 Chronic Kidney Disease: A Systematic Review

INTRODUCTION

Plant-based protein is of growing interest for dietary management of chronic kidney disease (CKD) and is hypothesized to preserve kidney function and reduce CKD-mineral bone disorder (MBD) complications, among other benefits. This systematic review aimed to summarize the available clinical trial evidence for the effect of plant-based protein on kidney function and CKD-MBD outcomes in adults with stage 3-5 CKD not on dialysis.

METHODS

Searches of Medline, Embase, Agricola, CAB abstracts, Web of Science, Scopus, and hand searching were performed. Clinical trials with ≥8 participants ≥18 years of age with an estimated glomerular filtration rate <60 mL/min/1.73 m2 but not on dialysis were included. Additionally, only clinical trials with ≥1-week interventions with ≥50% dietary protein from plant-based sources and reported at least one outcome for both kidney function and CKD-MBD outcomes were included. Of the 10,962 identified abstracts, 32 met inclusion criteria and were assessed for risk of bias.

RESULTS

Results for kidney function and CKD-MBD outcomes were heterogenous, with most studies having suboptimal methodological quality. In most of the studies (27/32), protein source was altered only secondarily to low-protein diet interventions. Thus, data synthesis and interpretation were focused on a subset of five studies that investigated a change in protein source only (i.e., animal vs. plant). Of this subset, four studies reported no change in kidney function, while one study reported a decrease. Three studies reported no change in serum phosphorus, and one study reported lower serum phosphorus following a vegetarian diet. Further, limited data and inconclusive results were observed for phosphaturic hormones, parathyroid hormone, and fibroblast growth factor-23.

CONCLUSION

Current clinical trial evidence on plant-based protein interventions for preserving kidney function and preventing CKD-MBD is limited to inform clinical guidelines at this time. This systematic review emphasizes the ongoing need to research the effects of plant-based protein on kidney function and CKD-MBD outcomes.

The Role of Plant-Based Diets in Preventing and Mitigating Chronic Kidney Disease: More Light than Shadows

Chronic kidney disease (CKD) is a non-communicable disease that affects >10% of the general population worldwide; the number of patients affected by CKD is increasing due in part to the rise in risk factors such as obesity, hypertension, and diabetes mellitus. As many studies show, diet can be an important tool for preventing and mitigating the onset of non-communicable diseases. Plant-based diets (PBDs) are those that emphasize the consumption of plant foods and may or may not include small or moderate amounts of animal foods. Recently, these diets have received increasing interest because they have been associated with favourable effects on health and also appear to protect against the development and progression of CKD. PBDs, which are associated with protein restrictions, seem to offer adjunctive advantages in patients with chronic kidney disease, as compared to conventional low-protein diets that include animal proteins. The principal aims of this review are to provide a comprehensive overview of the existing literature regarding the role of plant-based diets and low-protein, plant-based diets in the context of chronic kidney disease. Moreover, we try to clarify the definition of plant-based diets, and then we analyse possible concerns about the use of PBDs in patients with chronic kidney disease (nutritional deficiency and hyperkalaemia risk). Finally, we offer some strategies to increase the nutritional value of plant-based low-protein diets. In the Materials and Methods section, many studies about plant-based diets and low-protein plant-based diets (e.g., the very-low-protein diet and vegan low-protein diet, LPD) in chronic kidney disease were considered. In the Results and Conclusion section, current data, most from observational studies, agree upon the protective effect of plant-based diets on kidney function. Moreover, in patients with advanced CKD, low-protein plant-based options, especially a very-low-protein diet supplemented with heteroanalogues (VLPDs), compared to a conventional LPD appear to offer adjunctive advances in terms of delaying dialysis and mitigating metabolic disturbances. However, further studies are necessary to better investigate the possible metabolic and cardiovascular advantages of plant-based LPDs versus conventional LPDs.

The Microbiome and Protein Carbamylation: Potential Targets for Protein-Restricted Diets Supplemented with Ketoanalogues in Predialysis Chronic Kidney Disease

In chronic kidney disease (CKD), metabolic derangements resulting from the interplay between decreasing renal excretory capacity and impaired gut function contribute to accelerating disease progression and enhancing the risk of complications. To protect residual kidney function and improve quality of life in conservatively managed predialysis CKD patients, current guidelines recommend protein-restricted diets supplemented with essential amino acids (EAAs) and their ketoanalogues (KAs). In clinical studies, such an approach improved nitrogen balance and other secondary metabolic disturbances, translating to clinical benefits, mainly the delayed initiation of dialysis. There is also increasing evidence that a protein-restricted diet supplemented with KAs slows down disease progression. In the present review article, recent insights into the role of KA/EAA-supplemented protein-restricted diets in delaying CKD progression are summarized, and possible mechanistic underpinnings, such as protein carbamylation and gut dysbiosis, are elucidated. Emerging evidence suggests that lowering urea levels may reduce protein carbamylation, which might contribute to decreased morbidity and mortality. Protein restriction, alone or in combination with KA/EAA supplementation, modulates gut dysbiosis and decreases the generation of gut-derived uremic toxins associated, e.g., with cardiovascular disease, inflammation, protein energy wasting, and disease progression. Future studies are warranted to assess the effects on the gut microbiome, the generation of uremic toxins, as well as markers of carbamylation.

Optimizing Nutrition in Renal Patients: Effects of a Low-Protein Diet Supplemented With Ketoacids

Background Chronic kidney disease (CKD) is a non-communicable disease; it is a major cause of morbidity and mortality in Nigeria as the incidence has been increasing in Nigeria over the last few years. A low-protein diet supplemented with ketoacids has been duly documented to reduce the malnutrition associated with CKD as well as improve estimated glomeruli filtration rate while delaying the onset of dialysis in predialysis CKD patients. Objective The aim of this study was to determine the effects of a low-protein diet supplemented with ketoacids compared to a conventional low protein on nutritional indices in predialysis CKD patients. Methods and materials A randomized controlled trial with a total of 60 participants was conducted at Delta State University Teaching Hospital (DELSUTH), Oghara, Nigeria. Participants were patients older than 18 years with CKD stage 3-5 who were not on dialysis. They were recruited and randomized into the intervention group (low-protein diet supplemented with ketoacids) with 30 participants and the non-intervention group (low protein with placebo) with 30 participants. The mean outcome was changed in the nutritional indices from baseline till the end of the study. Results A total of 60 patients were randomly allocated to receive a low-protein diet supplemented with ketoacids (n=30) or control (n=30). All participants were included in the analysis of all outcomes. The mean change score in serum total protein, albumin, and triglycerides between the intervention and non-intervention groups were 1.1±1.1 g/dL vs 0.1±1.1 g/dL (p<0.001), 0.2±0.9 g/dL vs -0.3±0.8 g/dL (p<0.001), and 3.0±3.5 g/dL vs 1.8±3.7 g/dL, respectively. Conclusion and recommendation The use of low-protein diet supplemented with ketoacids improved the anthropometric and nutritional indices in patients with stage 3-5 CKD.

Isobutanol production by combined in vivo and in vitro metabolic engineering

The production of the biofuel, isobutanol, in E. coli faces limitations due to alcohol toxicity, product inhibition, product recovery, and long-term industrial feasibility. Here we demonstrate an approach of combining both in vivo with in vitro metabolic engineering to produce isobutanol. The in vivo production of α-ketoisovalerate (KIV) was conducted through CRISPR mediated integration of the KIV pathway in bicistronic design (BCD) in E. coli and inhibition of competitive valine pathway using CRISPRi technology. The subsequent in vitro conversion to isobutanol was carried out with engineered enzymes for 2-ketoacid decarboxylase (KIVD) and alcohol dehydrogenase (ADH). For the in vivo production of KIV and subsequent in vitro production of isobutanol, this two-step serial approach resulted in yields of 56% and 93%, productivities of 0.62 and 0.074 g L^-1 h^-1, and titers of 5.6 and 1.78 g L^-1, respectively. Thus, this combined biosynthetic system can be used as a modular approach for producing important metabolites, like isobutanol, without the limitations associated with in vivo production using a consolidated bioprocess.

Obesity-Related Chronic Kidney Disease: Principal Mechanisms and New Approaches in Nutritional Management

Obesity is the epidemic of our era and its incidence is supposed to increase by more than 30% by 2030. It is commonly defined as a chronic and metabolic disease with an excessive accumulation of body fat in relation to fat-free mass, both in terms of quantity and distribution at specific points on the body. The effects of obesity have an important impact on different clinical areas, particularly endocrinology, cardiology, and nephrology. Indeed, increased rates of obesity have been associated with increased risk of cardiovascular disease (CVD), cancer, type 2 diabetes (T2D), dyslipidemia, hypertension, renal diseases, and neurocognitive impairment. Obesity-related chronic kidney disease (CKD) has been ascribed to intrarenal fat accumulation along the proximal tubule, glomeruli, renal sinus, and around the kidney capsule, and to hemodynamic changes with hyperfiltration, albuminuria, and impaired glomerular filtration rate. In addition, hypertension, dyslipidemia, and diabetes, which arise as a consequence of overweight, contribute to amplifying renal dysfunction in both the native and transplanted kidney. Overall, several mechanisms are closely related to the onset and progression of CKD in the general population, including changes in renal hemodynamics, neurohumoral pathways, renal adiposity, local and systemic inflammation, dysbiosis of microbiota, insulin resistance, and fibrotic process. Unfortunately, there are no clinical practice guidelines for the management of patients with obesity-related CKD. Therefore, dietary management is based on the clinical practice guidelines for the nutritional care of adults with CKD, developed and published by the National Kidney Foundation, Kidney Disease Outcome Quality Initiative and common recommendations for the healthy population. Optimal nutritional management of these patients should follow the guidelines of the Mediterranean diet, which is known to be associated with a lower incidence of CVD and beneficial effects on chronic diseases such as diabetes, obesity, and cognitive health. Mediterranean-style diets are often unsuccessful in promoting efficient weight loss, especially in patients with altered glucose metabolism. For this purpose, this review also discusses the use of non-classical weight loss approaches in CKD, including intermittent fasting and ketogenic diet to contrast the onset and progression of obesity-related CKD.

The effect of the diet of nitrogen-free analogs of essential amino acids on chronic kidney disease deterioration: A meta-analysis

INTRODUCTION

We performed a meta-analysis to evaluate the effect of the diet of nitrogen-free analogs of essential amino acids on chronic kidney disease deterioration.

METHODS

A systematic literature search up-to September 2021 was done and 14 studies included 1574 subjects with chronic kidney disease at the start of the study; 786 of them had the very low-protein diets supplemented with nitrogen-free analogs and 788 had the conventional low-protein diet.

RESULTS

Very low-protein diet supplemented with nitrogen-free analogs had significantly higher estimated glomerular filtration rate, lower serum creatinine, and lower blood urea nitrogen; however, it had no significant difference in serum albumin, serum cholesterol, serum phosphorous, serum calcium, and parathyroid hormone compared to conventional low-protein diet in subjects with chronic kidney disease.

CONCLUSION

The very low-protein diets supplemented with nitrogen-free analogs had significantly better kidney functions results compared to the conventional low-protein diets in subjects with chronic kidney disease. Further studies are required to validate these findings.

Optimizing Diet to Slow CKD Progression

Due to the unique role of the kidney in the metabolism of nutrients, patients with chronic kidney disease (CKD) lose the ability to excrete solutes and maintain homeostasis. Nutrient intake modifications and monitoring of nutritional status in this population becomes critical, since it can affect important health outcomes, including progression to kidney failure, quality of life, morbidity, and mortality. Although there are multiple hemodynamic and metabolic factors involved in the progression and prognosis of CKD, nutritional interventions are a central component of the care of patients with non-dialysis CKD (ND-CKD) and of the prevention of overweight and possible protein energy-wasting. Here, we review the reno-protective effects of diet in adults with ND-CKD stages 3-5, including transplant patients.

Nutrition in Chronic Kidney Disease-The Role of Proteins and Specific Diets

Chronic kidney disease (CKD) is a global public health burden, needing comprehensive management for preventing and delaying the progression to advanced CKD. The role of nutritional therapy as a strategy to slow CKD progression and uremia has been recommended for more than a century. Although a consistent body of evidence suggest a benefit of protein restriction therapy, patients' adherence and compliance have to be considered when prescribing nutritional therapy in advanced CKD patients. Therefore, these prescriptions need to be individualized since some patients may prefer to enjoy their food without restriction, despite knowing the potential importance of dietary therapy in reducing uremic manifestations, maintaining protein-energy status.

Ketoanalogs' Effects on Intestinal Microbiota Modulation and Uremic Toxins Serum Levels in Chronic Kidney Disease (Medika2 Study)

Nutritional therapy (NT) is a therapeutic option in the conservative treatment of chronic kidney disease (CKD) patients to delay the start of dialysis. The aim of this study was to evaluate the specific effect of ketoanalogs (KA)-supplemented diets for gut microbiota modulation. In a previous study we observed that the Mediterranean diet (MD) and a KA-supplemented very-low-protein diet (VLPD) modulated beneficially gut microbiota, reducing indoxyl- and p-cresyl-sulfate (IS, PCS) serum levels, and ameliorating the intestinal permeability in CKD patients. In the current study, we added a third diet regimen consisting of KA-supplemented MD. Forty-three patients with CKD grades 3B–4 continuing the crossover clinical trial were assigned to six months of KA-supplemented MD (MD + KA). Compared to MD, KA-supplementation in MD + KA determined (i) a decrease of Clostridiaceae, Methanobacteriaceae, Prevotellaceae, and Lactobacillaceae while Bacteroidaceae and Lachnospiraceae increased; (ii) a reduction of total and free IS and PCS compared to a free diet (FD)—more than the MD, but not as effectively as the VLPD. These results further clarify the driving role of urea levels in regulating gut integrity status and demonstrating that the reduction of azotemia produced by KA-supplemented VLPD was more effective than KA-supplemented MD in gut microbiota modulation mainly due to the effect of the drastic reduction of protein intake rather than the effect of KA.

Ketoanalogue supplements reduce mortality in patients with pre-dialysis advanced diabetic kidney disease: A nationwide population-based study

BACKGROUND & AIMS

Metabolism dysregulation and protein energy wasting occur in patients with chronic kidney disease (CKD) and are associated with poor survival, especially in patients prior to starting dialysis. Accumulating evidence indicates that dietary supplementation with ketoanalogues (KAs, a mixture of branched-chain amino acids) exerts a variety of beneficial effects for patients with CKD. However, the role of KAs in diabetic kidney disease (DKD), one of the major causes of CKD, is still controversial. The aim of this study was to explore the impact of KA supplements on survival in patients with stage 5 DKD who have not yet started dialysis (DKD-5-ND).

METHODS

We analyzed a nationwide cohort retrieved from the National Health Insurance Research Database in Taiwan to study the long-term impact of KA supplements in patients with DKD-5-ND. We enrolled 15,782 incident pre-dialysis DKD patients between January 1, 2004 and December 31, 2007. Landmark analysis was used to eliminate immortal bias, and overlap weighting was used to balance differences between the KA users and nonusers in the beginning. The primary study endpoint was all-cause mortality, and the occurrence of permanent dialysis (presenting the end-stage renal disease, ESRD) and major adverse cardiovascular events (MACEs) was also evaluated. All patients were followed for five years or until death.

RESULTS

The prevalence of KA usage in the DKD-5-ND patients was 6.3%. The 5-year all-cause mortality rate in the KA users was lower than that in the nonusers (34.7% vs 42.7%). After adjusting for known covariates, the KA users still had a lower risk of mortality (adjusted hazard ratio [aHR]: 0.73, 95% confidence interval [CI]: 0.66-0.82). In addition, the incidence of ESRD was also slightly lower among the KA users (90.9% for users vs 91.2% for nonusers, adjusted cause-specific hazard ratio [aCSHR]: 0.65, 95% CI: 0.61-0.69), and the occurrence of MACEs was lower (adjusted incidence rate ratios [aIRR]: 0.76, 95% CI: 0.67-0.86). Although the all-cause mortality was higher among patientsolder than 70 years (60.5% for KA users vs 46.5% for nonusers) the risk reduction seemed prominent among older patients (aHR: 0.65, 95% CI: 0.56-0.76 for patients aged ≥70 years; aHR: 0.82, 95% CI: 0.71-0.96 for patients aged < 70 years). The reduction in risks of mortality was consistent in subgroup analysis and sensitivity tests.

CONCLUSIONS

The use of KA supplements seemed to be beneficial for patients with DKD-5-ND; further in-depth analysis of using KA for these patients is warranted.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Revising Dietary Phosphorus Advice in Chronic Kidney Disease G3-5D

We summarize how practicing dietitians combined available evidence with clinical experience, to define revised dietary recommendations for phosphorus in chronic kidney disease G3-5D. As well as a review of the evidence base, 4 priority topics were reviewed. These were translated into 3 nutrient level recommendations: the introduction of some plant protein where phosphorus is largely bound by phytate; consideration of protein intake in terms of phosphorus load and the phosphorus to protein ratio; and an increased focus on avoiding phosphate additives. This review summarizes and interprets the available evidence in order to support the development of practical food-based advice for patients with chronic kidney disease.

The Effects of Restricted Protein Diet Supplemented With Ketoanalogue on Renal Function, Blood Pressure, Nutritional Status, and Chronic Kidney Disease-Mineral and Bone Disorder in Chronic Kidney Disease Patients: A Systematic Review and Meta-Analysis

OBJECTIVE

To systemically review the meta-analysis exploring the effectiveness and safety of restricted protein diet supplemented with ketoanalogues (KAs) when compared with regular diet or low protein diet (LPD) without KAs in chronic kidney disease (CKD) patients.

STUDY DESIGN AND METHODS

We conducted electronic searches in PubMed, Scopus, Cochrane Central Register of Controlled Trials, and ClinicalTrials.gov from January 1960 to May 2018 to identify randomized controlled clinical trials that explored the effects of restricted protein diet including vegetarian and mixed type of protein with KAs on kidney endpoints including the changes in estimated glomerular filtration rate (eGFR) and proteinuria, nutritional status, and CKD-mineral bone disorder.

RESULTS

Seventeen RCTs with 1,459 participants were included in our meta-analysis. Restricted protein diet with KAs significantly preserved eGFR and reduced proteinuria, serum phosphate, parathyroid hormone (PTH) level, systolic blood pressure, diastolic blood pressure, and serum cholesterol. By subgroup analysis, very low protein diet (VLPD) with KAs was plausibly superior to LPD with KAs in slowing the decline in eGFR. Only VLPD with KAs significantly improved serum PTH, systolic blood pressure, and diastolic blood pressure while both regimens significantly decreased serum phosphate. Only LPD with KAs significantly raised serum albumin and serum calcium.

CONCLUSION

Restricted protein diet supplemented with KAs could effectively improve kidney endpoints including preserving eGFR and diminishing proteinuria, blood pressure levels, and CKD-mineral bone disorder parameters without causing malnutrition. VLPD with KAs appears to provide more effectiveness in slowing the decline in eGFR, lowering blood pressure, reducing serum PTH, and less increasing serum calcium level.

Ketoacid Analogues Supplementation in Chronic Kidney Disease and Future Perspectives

Diet is a key component of care during chronic kidney disease (CKD). Nutritional interventions, and, specifically, a restricted protein diet has been under debate for decades. In order to reduce the risk of nutritional disorders in very-low protein diets (VLDP), supplementation by nitrogen-free ketoacid analogues (KAs) have been proposed. The aim of this review is to summarize the potential effects of this dietary therapy on renal function, uremic toxins levels, and nutritional and metabolic parameters and propose future directions. The purpose of this paper is also to select all experimental and randomized clinical studies (RCTs) that have compared VLDP + KA to normal diet or/and low protein diet (LPD). We reviewed the SCOPUS, WEB of SCIENCES, CENTRAL, and PUBMED databases from their inception to 1 January, 2019. Following duplicate removal and application of exclusion criteria, 23 RCTs and 12 experimental studies were included. LPD/VLPD + KAs appear nutritionally safe even if how muscle protein metabolism adapts to an LPD/VLPD + KAs is still largely unknown. VLPD + KAs seem to reduce uremic toxins production but the impact on intestinal microbiota remains unexplored. All studies observed a reduction of acidosis, phosphorus, and possibly sodium intake, while still providing adequate calcium intake. The impact of this diet on carbohydrate and bone parameters are only preliminary and need to be confirmed with RCTs. The Modification of Diet in Renal Disease study, the largest RCTs, failed to demonstrate a benefit in the primary outcome of the decline rate for the glomerular filtration rate. However, the design of this study was challenged and data were subsequently reanalyzed. However, when adherent patients were selected, with a rapid rate of progression and a long-term follow up, more recent meta-analysis and RCTs suggest that these diets can reduce the loss of the glomerular filtration rate in addition to the beneficial effects of renin-angiotensin-aldosterone system (RAAS) inhibitors. The current evidence suggests that KAs supplemented LPD diets should be included as part of the clinical recommendations for both the nutritional prevention and metabolic management of CKD. More research is needed to examine the effectiveness of KAs especially on uremic toxins. A reflection about the dose and composition of the KAs supplement, the cost-effective features, and their indication to reduce the frequency of dialysis needs to be completed.

The Effect of Ketoanalogues on Chronic Kidney Disease Deterioration: A Meta-Analysis

The effects of ketoanalogues (KA) on chronic kidney disease (CKD) deterioration have not yet been fully confirmed. To strengthen the evidence of the role of KA in CKD, PubMed and Embase were searched for studies published through February 2019. Effect sizes from ten randomized control trials (RCTs) and two non-RCTs comprising a total of 951 patients were pooled and analyzed. A restricted protein diet supplemented with ketoanalogues (RPKA) was found to significantly delay the progression of CKD (p = 0.008), particularly in patients with an estimated glomerular filtration rate (eGFR) > 18 mL/min/1.73 m² (p < 0.0001). No significant change in eGFR was found when comparing a very-low-protein diet and a low-protein diet (p = 0.10). In addition, compared with the placebo, RPKA did not cause malnutrition (albumin: p = 0.56; cholesterol: p = 0.50). Moreover, RPKA significantly decreased phosphorous levels (p = 0.001), increased calcium levels (p = 0.04), and decreased parathyroid hormone (PTH) levels (p = 0.05) in patients with eGFR < 18 mL/min/1.73 m². In conclusion, RPKA could slow down the progression of CKD in patients with eGFR > 18 mL/min/1.73 m² without causing malnutrition and reverse CKD-MBD in patients with eGFR < 18 mL/min/1.73 m².

Very low protein diet plus ketoacid analogs of essential amino acids supplement to retard chronic kidney disease progression

Background

A very low protein diet (VLPD) with ketoacid analogs of essential amino acids (KA/EAA) administration can remarkably influence protein synthesis and metabolic disturbances of patients with advanced chronic kidney disease (CKD), and may also slow the decline in renal function.

Methods

A retrospective cohort study was carried out to monitor renal progression and metabolic and nutritional status among 140 patients with CKD stage III or IV. One group (n = 70) was on a low protein diet (LPD) with 0.6 g of protein intake, and another group (n = 70) was on a VLPD with 0.3 g of protein and KA/EAA supplementation of 100 mg/kg/day for 12 months.

Results

At 12-month follow-up, estimated glomerular filtration rate (GFR) significantly decreased from 41.6 ± 10.2 to 36.4 ± 8.8 mL/min/1.73 m² (P < 0.001) and urine protein increased from 0.6 ± 0.5 to 0.9 ± 1.1 g/day (P = 0.017) in the LPD group, but no significant changes in estimated GFR and urine protein were found in the VLPD plus KA/EAA group. A significant mean difference in rate of change in estimated GFR (-5.2 ± 3.6 mL/min/1.73 m² per year; P < 0.001) was observed between the two groups. After Cox regression analysis, treatment with VLPD plus KA/EAA significantly protected against the incidence of declining GFR > 10% annually (adjusted hazard ratio, 0.42; 95% confidence interval, 0.23-0.79; P = 0.006) and significant correlations were found between using VLPD plus KA/EEA and increased GFR.

Conclusion

VLPD supplementation with KA/EAA is associated with delayed renal progression while preserving the nutritional status in the patients with CKD. Co-administration of VLPD and KA/EAA may prove an effective alternative to conservative management of CKD.

Dietary supplementation with ketoacids protects against CKD-induced oxidative damage and mitochondrial dysfunction in skeletal muscle of 5/6 nephrectomised rats

Background

A low-protein diet supplemented with ketoacids (LPD + KA) maintains the nutritional status of patients with chronic kidney disease (CKD). Oxidative damage and mitochondrial dysfunction associated with the upregulation of p66SHC and FoxO3a have been shown to contribute to muscle atrophy. This study aimed to determine whether LPD + KA improves muscle atrophy and attenuates the oxidative stress and mitochondrial damage observed in CKD rats.

Methods

5/6 nephrectomy rats were randomly divided into three groups and fed with either 22% protein (normal-protein diet; NPD), 6% protein (low-protein diets; LPD) or 5% protein plus 1% ketoacids (LPD + KA) for 24 weeks. Sham-operated rats with NPD intake were used as the control.

Results

KA supplementation improved muscle atrophy and function in CKD + LPD rats. It also reduced the upregulation of genes related to the ubiquitin-proteasome system and 26S proteasome activity, as well as protein and mitochondrial oxidative damage in the muscles of CKD + LPD rats. Moreover, KA supplementation prevented the drastic decrease in activities of mitochondrial electron transport chain complexes, mitochondrial respiration, and content in the muscles of CKD + LPD rats. Furthermore, KA supplementation reversed the elevation in p66Shc and FoxO3a expression in the muscles of CKD + LPD rats.

Conclusions

Our results showed that KA supplementation to be beneficial to muscle atrophy in CKD + LPD, which might be associated with improvement of oxidative damage and mitochondrial dysfunction through suppression of p66Shc and FoxO3a.

Phosphate stimulates myotube atrophy through autophagy activation: evidence of hyperphosphatemia contributing to skeletal muscle wasting in chronic kidney disease

Background

Accelerated muscle atrophy is associated with a three-fold increase in mortality in chronic kidney disease (CKD) patients. It is suggested that hyperphosphatemia might contribute to muscle wasting, but the underlying mechanisms remain unclear. Although evidence indicates that autophagy is involved in the maintenance of muscle homeostasis, it is not known if high phosphate levels can result in activation of autophagy, leading to muscle protein loss.

Methods

Immortalized rat L6 myotubes were exposed to a high concentration of phosphate, with or without autophagy inhibition. Myotube atrophy was examined by phase contrast microscopy. Autophagic activity was assessed by measuring the expression of microtubule-associated protein 1 light chain 3 (LC3) and p62 using quantitative real-time polymerase chain reaction and western blot.

Results

Phosphate induced cell atrophy in L6 myotubes in a dose- and time-dependent manner, and these responses were not associated with calcification or osteogenesis. Phosphate also dose- and time-dependently increased the LC3-II/LC3-I ratio. Inhibition of autophagy with wortmannin or knockdown of Atg5 significantly suppressed myotube atrophy caused by high phosphate concentration.

Conclusions

High phosphate concentration induces muscle cell atrophy through the activation of autophagy. Targeting autophagy could be a therapeutic strategy for preventing muscle wasting caused by hyperphosphatemia.

Very low protein diets supplemented with keto-analogues in ESRD predialysis patients and its effect on vascular stiffness and AVF Maturation

Background

Native arteriovenous fistula (AVF) is the most appropriate type of vascular access for chronic dialysis. Its patency rates depend on vascular wall characteristics. Ketoacid analogues of essential amino acids (KA/EAA) are prescribed in end-stage renal disease (ESRD) pre-dialysis patients to lower toxic metabolic products generation and improve nutritional status. We hypothesized that very-low protein diet (VLPD) supplemented with KA/EAA may influence arterial wall stiffness and affect AVF maturation rates and duration in pre-dialysis ESRD patients.

Methods

In a prospective, cohort, 3 years study we enrolled 67 consecutive non-diabetic early referral ESRD patients that underwent AVF creation in our hospital. Patients were divided in two groups based on their regimen 12 months prior to surgery: a VLPD supplemented with KA/EAA study group versus a low protein diet non-KA/EAA-supplemented control group. For each patient we performed serum analysis for the parameters of bone mineral disease, inflammation and nutritional status, one pulse wave velocity (PWV) measurement and one Doppler ultrasound (US) determination prior the surgery, followed by consequent Doppler US assessments at 4, 6, 8 and 12 weeks after it. Rates and duration of mature AVF achievement were noted. We used logistic regression to analyze the association between AVF maturation and KA/EAA administration, by comparing rates and durations between groups, unadjusted and adjusted for systolic blood pressure, C-reactive protein, PWV, phosphorus values. All parameters in the logistic model were transformed in binary variables. A p-value < α = 0.05 was considered significant; data were processed using SPSS 16 software and Excel.

Results

In the study group (n = 28, aged 57 ± 12.35, 13 females) we registered better serum phosphate (p = 0.022) and C-reactive protein control (p = 0.021), lower PWV (p = 0.007) and a higher percent of AVF creation success (33.3 % versus 17.8 %, p < 0.05). AVF maturation duration was lower in study group (5.91 versus 7.15 weeks, p < 0.001).

Conclusions

VLPD supplemented with KA/EAA appear to improve the native AVF primary outcome, decreasing the initial vascular stiffness, possible by preserving vascular wall quality in CKD patients through a better serum phosphate levels control and the limitation of inflammatory response.

"Dietaly": practical issues for the nutritional management of CKD patients in Italy

Evidence exists that nutritional therapy induces favorable metabolic changes, prevents signs and symptoms of renal insufficiency, and is able to delay the need of dialysis. Currently, the main concern of the renal diets has turned from the efficacy to the feasibility in the daily clinical practice.Herewith we describe some different dietary approaches, developed in Italy in the last decades and applied in the actual clinical practice for the nutritional management of CKD patients.A step-wise approach or simplified dietary regimens are usually prescribed while taking into account not only the residual renal function and progression rate but also socio-economic, psychological and functional aspects.The application of the principles of the Mediterranean diet that covers the recommended daily allowances for nutrients and protein (0.8 g/Kg/day) exert a favorable effect at least in the early stages of CKD. Low protein (0.6 g/kg/day) regimens that include vegan diet and very low-protein (0.3-0.4 g/Kg/day) diet supplemented with essential amino acids and ketoacids, represent more opportunities that should be tailored on the single patient's needs.Rather than a structured dietary plan, a list of basic recommendations to improve compliance with a low-sodium diet in CKD may allow patients to reach the desired salt target in the daily eating.Another approach consists of low protein diets as part of an integrated menu, in which patients can choose the "diet" that best suits their preferences and clinical needs.Lastly, in order to allow efficacy and safety, the importance of monitoring and follow up of a proper nutritional treatment in CKD patients is emphasized.

A practical approach to dietary interventions for nondialysis-dependent CKD patients: the experience of a reference nephrology center in Brazil

This paper describes the 30-year experience on nutritional management of non-dialysis dependent chronic kidney disease (CKD) patients in a public outpatient clinic located in the city of São Paulo, Brazil. A team of specialized dietitians in renal nutrition is responsible to provide individual dietary counseling for patients on stages 3 to 5 of CKD. Two different types of nutrition care protocols are employed depending on the level of renal function. For patients with CKD stage 3 a simplified nutritional assessment is performed and the main dietary focus is on the control of protein intake particularly from animal sources. A more complete nutritional assessment as well as a detailed dietary plan focusing not only on the control of protein but also on energy supply and on specific micronutrients is provided for patients on stages 4 or 5 of CKD. Practical approaches and tools used by the dietitians in our clinic for improving patient´s adherence to protein, sodium and potassium restriction while maintaining a healthy diet are described in detail in the sections of the article.

Keto-supplemented Low Protein Diet: A Valid Therapeutic Approach for Patients with Steroid-resistant Proteinuria during Early-stage Chronic Kidney Disease

BACKGROUND AND OBJECTIVES

Low protein diets supplemented with keto acid (sLPD) are recommended for patients with stage 3-5 chronic kidney disease (CKD). This study assessed whether sLPD is beneficial for patients with steroid-resistant proteinuria during early-stage CKD.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

A 1-year randomized controlled trial was conducted from 2010 to 2012. In this study, 108 proteinuric patients who were steroid-resistant were assigned to a sLPD group (0.6 g/kg/d with 0.09 g/kg/d keto acids) or a normal protein diet group (NPD, 1.0 g/kg/d). Estimated dietary protein intake, urinary protein excretion, remission rate, renal function, nutritional status, and blood pressure were measured.

RESULTS

Baseline characteristics were comparable between the sLPD group (47 patients) and the NPD group (49 patients). Urinary protein excretion significantly decreased in sLPD compared to NPD in months 6, 9, and 12 (P<0.05). Proteinuria reduction was higher in sLPD than in NPD (P<0.001) at the end of the study. Complete remission and partial remission rates were higher in sLPD than in NPD. Serum albumin and pre-albumin levels were higher in sLPD than in NPD in months 9 and 12 (P<0.05). Serum total cholesterol and triglyceride levels declined more significantly in sLPD than in NPD (P<0.01) at the end of the study. There were no differences in nutritional status, renal function, hemoglobin, or blood pressure between the two groups.

CONCLUSIONS

sLPD is both nutritionally safe and beneficial, providing nephroprotective effects for early-stage CKD patients with steroid-resistant proteinuria.

Is there a role for ketoacid supplements in the management of CKD?

Ketoacid (KA) analogues of essential amino acids (EAAs) provide several potential advantages for people with advanced chronic kidney disease (CKD). Because KAs lack the amino group bound to the α carbon of an amino acid, they can be converted to their respective amino acids without providing additional nitrogen. It has been well established that a diet with 0.3 to 0.4 g of protein per kilogram per day that is supplemented with KAs and EAAs reduces the generation of potentially toxic metabolic products, as well as the burden of potassium, phosphorus, and possibly sodium, while still providing calcium. These KA/EAA-supplemented very-low-protein diets (VLPDs) can maintain good nutrition, but the appropriate dose of the KA/EAA supplement has not been established. Thus, a KA/EAA dose-response study for good nutrition clearly is needed. Similarly, the composition of the KA/EAA supplement needs to be reexamined; for example, some KA/EAA preparations contain neither the EAA phenylalanine nor its analogue. Indications concerning when to inaugurate a KA/EAA-supplemented VLPD therapy also are unclear. Evidence strongly suggests that these diets can delay the need for maintenance dialysis therapy, but whether they slow the loss of glomerular filtration rate in patients with CKD is less clear, particularly in this era of more vigorous blood pressure control and use of angiotensin/aldosterone blockade. Some clinicians prescribe KA/EAA supplements for patients with CKD or treated with maintenance dialysis, but with diets that have much higher protein levels than the VLPDs in which these supplements have been studied. More research is needed to examine the effectiveness of KA/EAA supplements with higher protein intakes.

Nutrition prescription to achieve positive outcomes in chronic kidney disease: a systematic review

In Chronic Kidney Disease (CKD), management of diet is important in prevention of disease progression and symptom management, however evidence on nutrition prescription is limited. Recent international CKD guidelines and literature was reviewed to address the following question “What is the appropriate nutrition prescription to achieve positive outcomes in adult patients with chronic kidney disease?” Databases included in the search were Medline and CINAHL using EBSCOhost search engine, Embase and the Cochrane Database of Systematic Reviews published from 2000 to 2009. International guidelines pertaining to nutrition prescription in CKD were also reviewed from 2000 to 2013. Three hundred and eleven papers and eight guidelines were reviewed by three reviewers. Evidence was graded as per the National Health and Medical Research Council of Australia criteria. The evidence from thirty six papers was tabulated under the following headings: protein, weight loss, enteral support, vitamin D, sodium, fat, fibre, oral nutrition supplements, nutrition counselling, including protein and phosphate, nutrients in peritoneal dialysis solution and intradialytic parenteral nutrition, and was compared to international guidelines. While more evidence based studies are warranted, the customary nutrition prescription remains satisfactory with the exception of Vitamin D and phosphate. In these two areas, additional research is urgently needed given the potential of adverse outcomes for the CKD patient.

Bio-based production of organic acids with Corynebacterium glutamicum

The shortage of oil resources, the steadily rising oil prices and the impact of its use on the environment evokes an increasing political, industrial and technical interest for development of safe and efficient processes for the production of chemicals from renewable biomass. Thus, microbial fermentation of renewable feedstocks found its way in white biotechnology, complementing more and more traditional crude oil-based chemical processes. Rational strain design of appropriate microorganisms has become possible due to steadily increasing knowledge on metabolism and pathway regulation of industrially relevant organisms and, aside from process engineering and optimization, has an outstanding impact on improving the performance of such hosts. Corynebacterium glutamicum is well known as workhorse for the industrial production of numerous amino acids. However, recent studies also explored the usefulness of this organism for the production of several organic acids and great efforts have been made for improvement of the performance. This review summarizes the current knowledge and recent achievements on metabolic engineering approaches to tailor C. glutamicum for the bio-based production of organic acids. We focus here on the fermentative production of pyruvate, L- and D-lactate, 2-ketoisovalerate, 2-ketoglutarate, and succinate. These organic acids represent a class of compounds with manifold application ranges, e.g. in pharmaceutical and cosmetics industry, as food additives, and economically very interesting, as precursors for a variety of bulk chemicals and commercially important polymers.

Metabolic engineering of Corynebacterium glutamicum for 2-ketoisovalerate production

2-Ketoisovalerate is used as a therapeutic agent, and a 2-ketoisovalerate-producing organism may serve as a platform for products deriving from this 2-keto acid. We engineered the wild type of Corynebacterium glutamicum for the growth-decoupled production of 2-ketoisovalerate from glucose by deletion of the aceE gene encoding the E1p subunit of the pyruvate dehydrogenase complex, deletion of the transaminase B gene ilvE, and additional overexpression of the ilvBNCD genes, encoding the l-valine biosynthetic enzymes acetohydroxyacid synthase (AHAS), acetohydroxyacid isomeroreductase, and dihydroxyacid dehydratase. 2-Ketoisovalerate production was further improved by deletion of the pyruvate:quinone oxidoreductase gene pqo. In fed-batch fermentations at high cell densities, the newly constructed strains produced up to 188 ± 28 mM (21.8 ± 3.2 g liter(-1)) 2-ketoisovalerate and showed a product yield of about 0.47 ± 0.05 mol per mol (0.3 ± 0.03 g per g) of glucose and a volumetric productivity of about 4.6 ± 0.6 mM (0.53 ± 0.07 g liter(-1)) 2-ketoisovalerate per h in the overall production phase. In studying the influence of the three branched-chain 2-keto acids 2-ketoisovalerate, 2-ketoisocaproate, and 2-keto-3-methylvalerate on the AHAS activity, we observed a competitive inhibition of the AHAS enzyme by 2-ketoisovalerate.

Leucine and alpha-ketoisocaproic acid, but not norleucine, stimulate skeletal muscle protein synthesis in neonatal pigs

The branched-chain amino acid, leucine, acts as a nutrient signal to stimulate protein synthesis in skeletal muscle of young pigs. However, the chemical structure responsible for this effect has not been identified. We have shown that the other branched-chain amino acids, isoleucine and valine, are not able to stimulate protein synthesis when raised in plasma to levels within the postprandial range. In this study, we evaluated the effect of leucine, alpha-ketoisocaproic acid (KIC), and norleucine infusion (0 or 400 micromol kg(-1) h(-1) for 60 min) on protein synthesis and activation of translation initiation factors in piglets. Infusion of leucine, KIC, and norleucine raised plasma levels of each compound compared with controls. KIC also increased (P < 0.01) and norleucine reduced (P < 0.02) plasma levels of leucine compared with controls. Administration of leucine and KIC resulted in greater (P < 0.006) phosphorylation of eukaryotic initiation factor (eIF) 4E binding protein-1 (4E-BP1) and eIF4G, lower (P < 0.04) abundance of the inactive 4E-BP1.eIF4E complex, and greater (P < 0.05) active eIF4G.eIF4E complex formation in skeletal muscle compared with controls. Protein synthesis in skeletal muscle was greater (P < 0.02) in leucine- and KIC-infused pigs than in those in the control group. Norleucine infusion did not affect muscle protein synthesis or translation initiation factor activation. In liver, neither protein synthesis nor activation of translation initiation factors was affected by treatment. These results suggest that the ability of leucine to act as a nutrient signal to stimulate skeletal muscle protein synthesis is specific for leucine and/or its metabolite, KIC.

Intestinal metabolism of sulfur amino acids

The gastrointestinal tract (GIT) is a metabolically significant site of sulfur amino acid (SAA) metabolism in the body and metabolises about 20 % of the dietary methionine intake which is mainly transmethylated to homocysteine and trans-sulfurated to cysteine. The GIT accounts for about 25 % of the whole-body transmethylation and trans-sulfuration. In addition, in vivo studies in young pigs indicate that the GIT is a site of net homocysteine release and thus may contribute to the homocysteinaemia. The gut also utilises 25 % of the dietary cysteine intake and the cysteine uptake by the gut represents about 65 % of the splanchnic first-pass uptake. Moreover, we recently showed that SAA deficiency significantly suppresses intestinal mucosal growth and reduces intestinal epithelial cell proliferation, and increases intestinal oxidant stress in piglets. These recent findings indicate that intestinal metabolism of dietary methionine and cysteine is nutritionally important for intestinal mucosal growth. Besides their role in protein synthesis, methionine and cysteine are precursors of important molecules. S-adenosylmethionine, a metabolite of methionine, is the principal biological methyl donor in mammalian cells and a precursor for polyamine synthesis. Cysteine is the rate-limiting amino acid for glutathione synthesis, the major cellular antioxidant in mammals. Further studies are warranted to establish how SAA metabolism regulates gut growth and intestinal function, and contributes to the development of gastrointestinal diseases. The present review discusses the evidence of SAA metabolism in the GIT and its functional and nutritional importance in gut function and diseases.

Acidose metabólica na doença renal crônica: abordagem nutricional

A acidose metabólica é uma das complicações da doença renal crônica e está associada ao aumento do catabolismo protéico, à diminuição da síntese de proteínas e ao balanço nitrogenado negativo. A dieta tem forte influência sobre a geração de ácidos, podendo contribuir, portanto, para determinar a gravidade da acidose no paciente com doença renal crônica. Alguns pesquisadores têm observado que é possível estimar a excreção ácida renal, e que o cálculo dessa carga ácida a partir de alguns componentes da dieta, permitiria uma predição apropriada dos efeitos da dieta na acidose metabólica. Este artigo é uma comunicação sobre as bases fisiológicas, bem como as implicações clínicas da acidose em pacientes com doença renal crônica e a influência da dieta no balanço ácido-básico desses pacientes.

Nutrition and Metabolism in Kidney Disease

Nutritional and metabolic derangements are highly prevalent in patients with chronic kidney disease (CKD) and patients on renal replacement therapy. These derangements, which can be termed uremic malnutrition, significantly affect the high morbidity and mortality rates observed in this patient population. Uremic malnutrition clearly is related to multiple factors encountered during the predialysis stage and during chronic dialysis therapy. Several preliminary studies suggested that interventions to improve the nutritional status and metabolic status of uremic patients actually may improve the expected outcome in these patients, although their long-term efficacy is not well established. It therefore is important to emphasize that uremic malnutrition is a major comorbid condition in CKD and renal replacement therapy patients, and that all efforts should be made to try to understand better and treat these conditions effectively to improve not only mortality but also the quality of life of chronically uremic patients. In this article we review the current state of knowledge in the field of nutrition and metabolism in all stages of CKD and renal replacement therapy, including kidney transplant. We also address questions that face investigators in this field and suggest where future research might be headed.