Impact of low-protein diet on cardiovascular risk factors and kidney function in diabetic nephropathy: A systematic review and meta-analysis of randomized-controlled trials

Diabetes and Glucose Management in People on Hemodialysis

Diabetes is a major cause of end-stage kidney disease (ESKD). Glycemic management is challenging in this population, and A1C, commonly used for monitoring glycemic control, is unreliable. Continuous glucose monitoring indices can be used for glycemic monitoring in people with ESKD. Dipeptidyl peptidase 4 inhibitors, incretin mimetic agents (glucagon-like peptide 1 and glucose-dependent insulinotropic peptide receptor agonists), and insulin using an automated insulin delivery system are preferred to manage diabetes in people with ESKD on hemodialysis.

Relationship between preconception protein intake and gestational diabetes mellitus: The Japan Environment and Children's Study

AIMS

To investigate the relationship between preconception protein intake and the risk of gestational diabetes mellitus (GDM).

METHODS

We analyzed data from the Japan Environment and Children's Study, focusing on 80,346 participants (mean age 31.3 ± 4.9 years; mean body mass index 21.2 ± 3.2 kg/m2) who delivered between 2011 and 2014. These participants had no history of diabetes mellitus, no previous diagnosis of GDM, and did not use steroids during pregnancy. Participants were categorized into five groups based on preconception protein energy ratio quintiles (Q1 and Q5 represent the lowest and highest intake, respectively). Continuous variables were compared using one-way analysis of variance or the Kruskal-Wallis test, and categorical variables using chi-square tests. Primary outcomes were GDM, early-diagnosed GDM (Ed-GDM, diagnosed at <24 weeks), and late-diagnosed GDM (Ld-GDM, diagnosed at >24 weeks). Adjusted odds ratios (aORs) and 95 % confidence intervals (CIs) were calculated using logistic regression analysis with the middle quintile (Q3) as the reference.

RESULTS

Multiple logistic regression analysis revealed that using the Q3 group as the reference, the Q5 group had a higher risk of Ed-GDM (aOR 1.48, 95 % CI 1.06-2.07), whereas the Q1 group had a lower risk of Ed-GDM (aOR 0.69, 95 % CI 0.48-0.996). However, no significant differences were observed in the risk of GDM and Ld-GDM.

CONCLUSIONS

Higher preconception protein intake was associated with increased Ed-GDM risk. Further research is needed to refine dietary recommendations for preconception protein intake.

Effects of a Low-Protein Diet on Kidney Function in Patients With Chronic Kidney Disease: An Umbrella Review of Systematic Reviews and Meta-analyses of Randomized Controlled Trials

CONTEXT

Chronic kidney disease (CKD) stands out as one of the most widespread diseases globally. Dietary interventions, such as adopting a low-protein diet (LPD), play a crucial role as a key approach in impeding the advancement of CKD.

OBJECTIVE

The objective of this umbrella review was to provide understanding into the effects of an LPD on kidney function among individuals with CKD, along with evaluating the certainty of the available evidence.

DATA SOURCES

Searches for relevant studies were conducted without limitations through databases such as PubMed, Scopus, Web of Science, and Google Scholar, encompassing findings up to June 2023.

DATA EXTRACTION

The effect sizes for each meta-analysis were recalibrated using a random-effects model. The certainty of the evidence was evaluated using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

DATA ANALYSIS

Twenty-five meta-analyses including 47 randomized controlled trials were included in this study. Moderate certainty of the evidence suggests that LPDs may reduce glycated hemoglobin (HbA1c) and phosphorus levels, and the risk of progressing to end-stage renal disease in patients with CKD. Moreover, notable outcomes include increased glomerular filtration rate and decreased levels of serum albumin, blood urea nitrogen, and bicarbonate, although the certainty of evidence is low. In addition, LPDs can substantially decrease proteinuria, urine urea, and parathyroid hormone (PTH), although with very low certainty. The effects on serum creatinine, calcium, systolic blood pressure, and diastolic blood pressure are statistically nonsignificant, with the certainty of evidence ranging from low to moderate.

CONCLUSION

LPDs demonstrated beneficial effects on renal function in patients with CKD, which is supported by moderate to very low certainty evidence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023473647.

Adherence to a Mediterranean diet is associated with a lower risk of diabetic kidney disease among individuals with hyperglycemia: a prospective cohort study

BACKGROUND

Type 2 diabetes is associated with a variety of complications, including micro- and macrovascular complications, neurological manifestations and poor wound healing. Adhering to a Mediterranean Diet (MED) is generally considered an effective intervention in individuals at risk for type 2 diabetes mellitus (T2DM). However, little is known about its effect with respect to the different specific manifestations of T2DM. This prompted us to explore the effect of MED on the three most significant microvascular complications of T2DM: diabetic retinopathy (DR), diabetic kidney disease (DKD), and vascular diabetic neuropathies (DN).

METHODS

We examined the association between the MED and the incidence of these microvascular complications in a prospective cohort of 33,441 participants with hyperglycemia free of microvascular complications at baseline, identified in the UK Biobank. For each individual, we calculated the Alternate Mediterranean Diet (AMED) score, which yields a semi-continuous measure of the extent to which an individual's diet can be considered as MED. We used Cox proportional hazard models to analyze hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for demographics, lifestyle factors, medical histories and cardiovascular risk factors.

RESULTS

Over a median of 12.3 years of follow-up, 3,392 cases of microvascular complications occurred, including 1,084 cases of diabetic retinopathy (DR), 2,184 cases of diabetic kidney disease (DKD), and 632 cases of diabetic neuropathies (DN), with some patients having 2 or 3 microvascular complications simultaneously. After adjusting for confounders, we observed that higher AMED scores offer protection against DKD among participants with hyperglycemia (comparing the highest AMED scores to the lowest yielded an HR of 0.79 [95% CIs: 0.67, 0.94]). Additionally, the protective effect of AMED against DKD was more evident in the hyperglycemic participants with T2DM (HR, 0.64; 95% CI: 0.50, 0.83). No such effect, however, was seen for DR or DN.

CONCLUSIONS

In this prospective cohort study, we have demonstrated that higher adherence to a MED is associated with a reduced risk of DKD among individuals with hyperglycemia. Our study emphasizes the necessity for continued research focusing on the benefits of the MED. Such efforts including the ongoing clinical trial will offer further insights into the role of MED in the clinical management of DKD.

Effects of dietary intervention on diabetic nephropathy: an umbrella review of systematic reviews and meta-analyses of randomized controlled trials

Objective

To evaluate the quality of evidence, potential biases, and validity of all available studies on dietary intervention and diabetic nephropathy (DN).

Methods

We conducted an umbrella review of existing meta-analyses of randomized controlled trials (RCTs) that focused on the effects of dietary intervention on DN incidence. The literature was searched via PubMed, Embase, Web of Science, and the Cochrane Database of Systematic Reviews. According to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE), evidence of each outcome was evaluated and graded as "high", "moderate", "low" or "very low" quality to draw conclusions. Additionally, we classified evidence of outcomes into 4 categories.

Results

We identified 36 meta-analyses of RCTs and 55 clinical outcomes of DN from 395 unique articles. Moderate-quality evidence suggested that probiotic supplementation could significantly improve blood urea nitrogen (BUN), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels in DN patients. Low-quality evidence indicated that probiotic supplementation significantly improved the serum creatinine concentration, urinary albumin-creatinine ratio (UACR), fasting blood glucose (FBG), HbA1c and high-density lipoprotein cholesterol (HDL-C) in DN patients. In addition, low-quality evidence suggested that a salt restriction diet could significantly improve the creatinine clearance rate (CrCl) in patients with DN. Low-quality evidence suggested that vitamin D supplementation could significantly improve the UACR in patients with DN. In addition, low-quality evidence has indicated that soy isoflavone supplementation could significantly improve BUN, FBG, total cholesterol (TC), triglyceride (TG) and LDL-C levels in patients with DN. Furthermore, low-quality evidence suggested that coenzyme Q10 supplementation could significantly improve HbA1c, TC and HDL-C in patients with DN, and dietary polyphenols also significantly improved HbA1c in patients with DN. Finally, low-quality evidence suggested that supplementation with antioxidant vitamins could significantly improve the serum creatinine concentration, systolic blood pressure, and HbA1c level in patients with DN. Given the small sample size, all significantly associated outcomes were evaluated as class IV evidence.

Conclusion

Moderate to low amounts of evidence suggest that supplementation with probiotics, vitamin D, soy isoflavones, coenzyme Q10, dietary polyphenols, antioxidant vitamins, or salt-restricted diets may significantly improve clinical outcomes in patients with DN.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024512670.

What is central to renal nutrition: protein or sodium intake?

Historically, nutrition intervention has been primarily focused on limiting kidney injury, reducing generation of uraemic metabolites, as well as maintaining nutrition status and preventing protein-energy wasting in patients with chronic kidney disease (CKD). This forms an important rationale for prescribing restricted protein diet and restricted salt diet in patients with CKD. However, evidence supporting a specific protein intake threshold or salt intake threshold remains far from compelling. Some international or national guidelines organizations have provided strong or 'level 1' recommendations for restricted protein diet and restricted salt diet in CKD. However, it is uncertain whether salt or protein restriction plays a more central role in renal nutrition management. A key challenge in successful implementation or wide acceptance of a restricted protein diet and a restricted salt diet is patients' long-term dietary adherence. These challenges also explain the practical difficulties in conducting randomized trials that evaluate the impact of dietary therapy on patients' outcomes. It is increasingly recognized that successful implementation of a restricted dietary prescription or nutrition intervention requires a highly personalized, holistic care approach with support and input from a dedicated multidisciplinary team that provides regular support, counselling and close monitoring of patients. With the advent of novel drug therapies for CKD management such as sodium-glucose cotransporter-2 inhibitors or non-steroidal mineralocorticoid receptor antagonist, it is uncertain whether restricted protein diet and restricted salt diet may still be necessary and have incremental benefits. Powered randomized controlled trials with novel design are clearly indicated to inform clinical practice on recommended dietary protein and salt intake threshold for CKD in this new era.

Nutrition Management for Chronic Kidney Disease: Differences and Special Needs for Children and Adults

Common goals of nutritional therapy across the spectrum of pediatric and adult chronic kidney disease (CKD) include maintaining normal body mass and composition and reducing associated morbidity and mortality. Adult nephrologists caring for children and adolescents may be challenged by the existing complexities in identifying and interpreting the nutritional status and growth in children. Pediatric nephrologists may face situations that call for a sound knowledge of assessing nutritional status and providing nutrition therapy for adolescents and young adults. One important additional nutrition goal in children is to achieve normal growth and development. Children are growing and therefore need more calories and nutrients than just maintaining their body weight and composition. Lack of weight and height gain actually is considered failure to thrive in children. Some fundamental differences in approaches to nutritional therapy in CKD are necessitated based on the etiology of CKD. A large proportion of adults with CKD are diabetics, so the approach would be a low-carbohydrate diet. Children with CKD, especially young ones, often are anorexic, so calorie supplements that could include quite a lot of carbohydrates often are prescribed. More adults with CKD have hypertension and atherosclerotic comorbidities, which result in recommendations for low-salt and low-fat diets. Children with CKD often have salt and electrolyte wasting disease states and would require normal- or even high-salt diets, and fats often are included in supplements to bolster calorie intake. Low-protein diets often are recommended in adults with predialysis CKD to slow disease progression. Children are growing and have a higher protein daily requirement. Low-protein diets have not been found to be efficacious in children with CKD, in achieving normal growth, or in slowing disease progression. Adult nephrologists caring for children and adolescents may be challenged by the existing complexities in identifying and interpreting nutritional status and growth in children. Pediatric nephrologists may face situations that call for a sound knowledge of assessing nutritional status and providing nutrition therapy for adolescents and young adults. This article discusses the differences in the assessment of nutritional status between children and adults, as well as provides a comprehensive approach to nutritional management for CKD across the age spectrum. Semin Nephrol 43:x-xx © 2023 Elsevier Inc. All rights reserved.

Diet, exercise, and pharmacotherapy for sarcopenia in people with diabetes

Diabetes prevalence is increasing rapidly in older people, and sarcopenia is prevalent as a novel complication, particularly in patients with type 2 diabetes mellitus (T2DM). Therefore, sarcopenia prevention and treatment in these people is necessary. Diabetes accelerates sarcopenia through several mechanisms, such as hyperglycemia, chronic inflammation and oxidative stress. The effects of diet, exercise, and pharmacotherapy on sarcopenia in patients with T2DM need to be considered. In diet, low intake of energy, protein, vitamin D, and ω-3 fatty acid are associated with sarcopenia risk. In exercises, although intervention studies in people, especially older and non-obese patients with diabetes, are few, accumulating evidence shows the usefulness of exercise, particularly resistance exercise for muscle mass and strength, and aerobic exercise for physical performance in sarcopenia. In pharmacotherapy, certain classes of anti-diabetes compounds have possibility of preventing sarcopenia. However, much data on diet, exercise, and pharmacotherapy were obtained in obese and non-elderly patients with T2DM, demanding actual clinical data on non-obese and older patients with diabetes.

Change in albuminuria as a surrogate endpoint for cardiovascular and renal outcomes in patients with diabetes

For the purpose of predicting clinical outcomes in patients with diabetes and chronic kidney disease, change in albuminuria is a good candidate to be a surrogate marker for future cardiovascular events and progression of kidney disease. Spot urine albumin/creatinine ratio is convenient and recognized as a viable alternative to 24-h albumin, with some limitations. Although there is sufficient evidence to validate its use in clinical trials as a surrogate endpoint for renal outcomes, this is not yet the case for cardiovascular outcomes. While change in albuminuria as a primary or secondary endpoint is trial-specific, its use should be encouraged, nonetheless.