Effect of low-protein diet on kidney function in diabetic nephropathy: meta-analysis of randomised controlled trials

Lower energy intake associated with higher risk of cardiovascular mortality in chronic kidney disease patients on a low-protein diets

OBJECTIVE

An increasing number of studies shown that inadequate energy intake causes an increase in adverse incidents in chronic kidney disease (CKD) patients on low-protein diets (LPD). The study aimed to investigate the relationship between energy intake and cardiovascular mortality in CKD patients on a LPD.

METHODS

This was a cross-sectional study, a total of 4264 CKD patients were enrolled from the NHANES database between 2009 and 2018. Restricted cubic spline plots and Cox regression analysis were used to analyze the association between energy intake and cardiovascular mortality in CKD patients on a LPD. Additionally, a nomogram was constructed to estimate cardiovascular survival in CKD patients on a LPD.

RESULTS

Among CKD patients on a LPD in the United States, 90.05% had an energy intake of less than 25 kcal/kg/day, compared to 36.94% in CKD patients on a non-LPD. Energy intake and cardiovascular mortality showed a linear relationship in CKD patients on a LPD, while a 'U-shaped' relationship was observed in CKD patients on a non-LPD. Multifactorial Cox regression models revealed that for Per-standard deviation (Per-SD) decrement in energy intake, the risk of cardiovascular mortality increased by 41% (HR: 1.41, 95% CI: 1.12, 1.77; P = 0.004) in CKD patients on a LPD. The concordance index of the nomogram was 0.79 (95% CI, 0.75, 0.83).

CONCLUSION

CKD patients, especially those on a LPD, have significantly inadequate energy intake. Lower energy intake is associated with higher cardiovascular mortality in CKD patients on a LPD.

Association between dietary protein intake and mortality among patients with diabetic kidney disease

AIMS

This study aimed to investigate the association between dietary protein intake and mortality among patients with diabetic kidney disease.

METHODS

The research encompassed a total of 2901 participants diagnosed with diabetic kidney disease, drawn from the National Health and Nutrition Examination Survey (NHANES). To determine outcomes related to all-cause and cardiovascular mortality, connections were established with the National Death Index up until December 31, 2019. Estimations of hazard ratios (HRs) and their corresponding 95 % confidence intervals (CIs) were conducted using Cox proportional hazard ratio models.

RESULTS

During the 261,239 person-years of follow-up, 1236 deaths were recorded. After multivariate adjustment, the weighted hazard ratio (HR) and 95 % CIs for participants with 1.0-1.2 g/kg of protein intake was 0.65 (0.44, 0.96) for all-cause mortality. A higher proportion of animal protein intake was found to be associated with an increased mortality risk. Stratified analyses showed that higher protein intake benefited older participants.

CONCLUSIONS

In diabetic kidney disease patients, 1.0-1.2 g/kg of protein was associated with lower mortality and 0.6-1.2 g/kg of protein especially benefitted patients ≥60 years.

Intermittent protein restriction before but not after the onset of diabetic kidney disease attenuates disease progression in mice

Background

High dietary protein intake exacerbates proteinuria in individuals with diabetic kidney disease (DKD). However, studies on the impacts of low protein diet (LPD) on DKD have yielded conflicting results. Furthermore, patient compliance to continuous protein restriction is challenging.

Objective

The current study aims to investigate the effects of intermittent protein restriction (IPR) on disease progression of DKD.

Methods

Diabetic KK-Ay mice were used in this study. For the IPR treatment, three consecutive days of LPD were followed by four consecutive days of normal protein diet (NPD) within each week. For early intervention, mice received IPR before DKD onset. For late intervention, mice received IPR after DKD onset. In both experiments, age-matched mice fed continuous NPD served as the control group. Kidney morphology, structure and function of mice in different groups were examined.

Results

Intermittent protein restriction before DKD onset ameliorated pathological changes in kidney, including nephromegaly, glomerular hyperfiltration, tubular injuries and proteinuria, without improving glycemic control. Meanwhile, IPR initiated after DKD onset showed no renoprotective effects despite improved glucose homeostasis.

Conclusion

Intermittent protein restriction before rather than after DKD onset protects kidneys, and the impacts of IPR on the kidneys are independent of glycemic control. IPR shows promise as an effective strategy for managing DKD and improving patient compliance.

Low Protein Diet Reduces Proteinuria and Decline in Glomerular Filtration Rate in Advanced, Heavy Proteinuric Diabetic Kidney Disease

Low protein diet (LPD) seems beneficial in ameliorating the complications of chronic kidney disease (CKD), in reducing proteinuria and the decline in kidney function, thus postponing the need for kidney replacement therapy (KRT). However, this type of intervention was less investigated in diabetic kidney disease (DKD). This is a single-center, prospective, interventional study that aims to assess the efficacy of reducing proteinuria and the rate of decline in the estimated glomerular filtration rate (eGFR). Patients with advanced DKD (stable proteinuria > 3 g/g and eGFR < 30 mL/min) with a good nutritional status and accepting a LPD were evaluated for inclusion. Ninety-two of the 452 screened patients (66% males, median age 61 years, proteinuria 4.8 g/g creatininuria, eGFR 11.7 mL/min/1.73 m2) completed the study. Intervention consisted of LPD supplemented with ketoanalogues of essential amino acids (KA) along with conventional nephroprotective therapy. Efficacy parameters were the variation in proteinuria and in eGFR from baseline to the end of the study. Proteinuria decreased 3-fold, and the rate of decline in eGFR decreased 5-fold in the intervention phase. No patient initiated KRT or died. LPD supplemented with KA seems effective in safely postponing KRT by reducing proteinuria and the decline in kidney function in advanced 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.

Plant-based diets in patients with chronic kidney disease

Dietary protein restriction has been considered to be a nutritional-related strategy to reduce risk for end-stage kidney disease among patients with non-dialysis-dependent chronic kidney disease (CKD). However, there is insufficient evidence to recommend a particular type of protein to slow down the CKD progression. Recently, various plant-based diets could demonstrate some additional benefits such as a blood pressure-lowering effect, a reduction of metabolic acidosis as well as hyperphosphatemia, and gut-derived uremic toxins. Furthermore, the former concerns about the risk of undernutrition and hyperkalemia observed with plant-based diets may be inconsistent in real clinical practice. In this review, we summarize the current evidence of the proposed pleiotropic effects of plant-based diets and their associations with clinical outcomes among pre-dialysis CKD patients.

Effect of Nonsupplemented Low-Protein Diet on the Initiation of Renal Replacement Therapy in Stage 4 and 5 Chronic Kidney Disease: A Retrospective Multicenter Cohort Study in Japan

OBJECTIVE

In subjects with chronic kidney disease (CKD), the effect of low-protein diet (LPD) is expected to alleviate uremic symptoms. However, whether LPD is effective in preventing loss of kidney function is controversial. The aim of this study was to evaluate the association between LPD and renal outcomes.

METHODS

We conducted a multicenter cohort study of 325 patients who suffered CKD stage 4 and 5 with eGFR ≥10 mL/min/1.73 m,2 between January 2008 and December 2014. The primary diseases of the patients were chronic glomerulonephritis (47.7%), nephrosclerosis (16.9%), diabetic nephropathy (26.2%), and others (9.2%). The patients were divided into four groups, based on the mean protein intake (PI)/day, group 1 (n = 76): PI < 0.5 g/kg ideal body weight/day, group 2 (n = 56): 0.5 ≤ PI < 0.6 g/kg/day, group 3 (n = 110): 0.6 ≤ PI < 0.8 g/kg/day, group 4 (n = 83): PI ≥ 0.8 g/kg/day. Dietary supplementation with essential amino acids and ketoanalogues was not used. The outcome measure was occurrence of renal replacement therapy (RRT) (hemodialysis, peritoneal dialysis, renal transplantation (excluding preemptive transplantation)) and all-cause mortality until December 2018. Cox regression models were used to examine whether LPD was associated with the risk of outcomes.

RESULTS

During a mean follow-up of 4.1 ± 2.2 years. Thirty-three patients (10.2%) died of all causes, 163 patients (50.2%) needed to start RRT, and 6 patients (1.8%) received a renal transplant. LPD therapy of 0.5 g/kg/day or less was significantly related to a lower risk of RRT and all-cause mortality [Hazard ratio = 0.656; 95% confidence interval, 0.438 to 0.984, P = .042].

CONCLUSIONS

These results suggest that non-supplemented LPD therapy of 0.5 g/kg/day or less may prolong the initiation of RRT in stage 4 and 5 CKD patients.

Protein supplementation changes gut microbial diversity and derived metabolites in subjects with type 2 diabetes

High-protein diets are promoted for individuals with type 2 diabetes (T2D). However, effects of dietary protein interventions on (gut-derived) metabolites in T2D remains understudied. We therefore performed a multi-center, randomized-controlled, isocaloric protein intervention with 151 participants following either 12-week high-protein (HP; 30Energy %, N = 78) vs. low-protein (LP; 10 Energy%, N = 73) diet. Primary objectives were dietary effects on glycemic control which were determined via glycemic excursions, continuous glucose monitors and HbA1c. Secondary objectives were impact of diet on gut microbiota composition and -derived metabolites which were determined by shotgun-metagenomics and mass spectrometry. Analyses were performed using delta changes adjusting for center, baseline, and kidney function when appropriate. This study found that a short-term 12-week isocaloric protein modulation does not affect glycemic parameters or weight in metformin-treated T2D. However, the HP diet slightly worsened kidney function, increased alpha-diversity, and production of potentially harmful microbiota-dependent metabolites, which may affect host metabolism upon prolonged exposure.

The Role of Protein Restriction in the Progression of Chronic Kidney Disease

Even though nephrology has made much progress, reducing the progression of the chronic kidney disease remains, in fact, one of the biggest challenges. Long before the renal replacement therapy (RRT), it was known that limiting the protein could help almost all uremia symptoms. Although it was proposed as early as the 1960s, it only became widely used in the 1980s. By lowering the urea and other nitrogen wastes and lowering the metabolic acidosis, oxidative stress, and insulin resistance, limiting the amount of protein in your diet can help improve uremic symptoms. Also, limiting the protein in the diet positively controls the cardiovascular complications, including the arterial blood pressure and proteinuria reduction, which are risk factors for CKD progression. This mini-review examines the impact of protein restriction on the possibility of slowing CKD progression in depth.

Protein restriction in adults with chronic kidney disease, with or without diabetes: Integrated Diabetes and Endocrine Academy (IDEA) consensus statement for Indian patients

BACKGROUND AND AIMS

Most guidelines recommend protein restriction in adults with chronic kidney disease (CKD), with or without diabetes. However, advising protein restriction for every person with CKD is controversial. We aim to arrive at a consensus on this topic, especially among Indian adults with CKD.

METHODS

A systematic literature search in the PubMed electronic database was undertaken using specific keywords and MeSH terms until May 1, 2022. All the retrieved literature was circulated and rigorously deliberated upon by the panel members.

RESULTS

Seventeen meta-analyses that evaluated the outcomes of protein restriction in adults with CKD, with or without diabetes, met our inclusion criteria and were analyzed. A low-protein diet (LPD) in people with stages 3-5 of CKD (who are not on haemodialysis [HD]) reduces the severity of uremic symptoms and the rate of decline in glomerular filtration rate, leading to a delay in dialysis initiation. However, LPD in patients on maintenance HD may not be desirable because HD-induced protein catabolism may lead to protein-energy malnutrition. Since the average protein intake among Indians is much lower than recommended, this must be taken into consideration before recommending LPD for all Indian adults with CKD, particularly those on maintenance HD.

CONCLUSION

It is essential to assess the nutritional status of people with CKD, particularly in countries like India where average daily protein intake is poor, before recommending guideline-directed protein restriction. The prescribed diet, including the quantity and quality of proteins, should be tailored to the person's habits, tastes, and needs.

The nitrogen load is affected by high protein provision according to kidney function in critically ill patients

Adequate protein delivery is recommended in the acute phase of critical illness with kidney dysfunction. However, the influence of the protein and nitrogen loads has not yet been clarified. Patients admitted to the intensive care unit were included. In the former period, patients received standard care (0.9 g/kg/day protein). In the latter, patients received the intervention of active nutrition therapy with high protein delivery (1.8 g/kg/day protein). Fifty patients in the standard care group and 61 in the intervention group were examined. Maximum blood urea nitrogen (BUN) on days 7-10 were 27.9 (17.3, 38.6) vs 33 (26.3, 51.8) (mg/dl) (p = 0.031). The maximum difference in BUN increased [31.3 (22.8, 55) vs 50 (37.3, 75.9) mg/dl (p = 0.047)] when patients were limited to an estimated glomerular filtration rate (eGFR) <50 ml/min/1.73 m². This difference increased further when patients were limited to eGFR <30 ml/min/1.73 m². No significant differences were observed in maximum Cre or in the use of RRT. In conclusion, the provision of 1.8 g/kg/day protein was associated with an increase in BUN in critically ill patients with kidney dysfunction; however, it was tolerated without the need for RRT.

Efficacy of Low-Protein Rice for Dietary Protein Restriction in CKD Patients: A Multicenter, Randomized, Controlled Study

Background

The benefits of dietary protein restriction in CKD remain unclear, largely due to inadequate adherence in most clinical trials. We examined whether low-protein rice (LPR) previously developed to reduce the protein content of rice, a major staple food, would help improve adherence to dietary protein restriction.

Methods

This open-label, multicenter, randomized, controlled trial evaluated the efficacy of LPR use for reducing dietary protein intake (DPI) in patients with CKD stages G3aA2-G4. Participants were randomly assigned in a 1:1 ratio to an LPR or control group and were followed up for 24 weeks. Both groups received regular counseling by dietitians to help achieve a target DPI of 0.7 g/kg ideal body weight (IBW) per day. The amount of protein in LPR is about 4% of that in ordinary rice, and the participants in the LPR group were instructed to consume LPR with at least two meals per day. The primary outcome was estimated dietary protein intake (eDPI) determined using the Maroni formula. The secondary outcomes included creatinine clearance (CCr) and urinary protein on the basis of 24-hour urine collection.

Results

In total, 51 patients were randomized to either the LPR group or the control group. At baseline, mean age was 62.5 years, 70% were men, mean CCr was 52.0 ml/min, and mean eDPI was 0.99 g/kg IBW per day. At 24 weeks, mean eDPI decreased to 0.80 g/kg IBW per day in the LPR group and to 0.91 g/kg IBW per day in the control group, giving a between-group difference of 0.11 g/kg IBW per day (95% confidence interval, 0.03 to 0.19 g/kg IBW per day; P=0.006). There was no significant between-group difference in CCr, but urinary protein was lower at 24 weeks in the LPR group than in the control group.

Conclusions

LPR is a feasible tool for efficiently reducing DPI in patients with CKD.

Clinical Trial registry name and registration number

Randomized, Multicenter, Controlled Study for the Efficacy of Low-Protein Rice Diet in Patients with Chronic Kidney Disease, UMIN000015630.

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

AIM

To assess the efficacy of low-protein diets (LPD) on cardiovascular risk factors and kidney function in diabetic nephropathy (DN) based on randomized controlled trials (RCTs).

METHODS

A comprehensive systematic search was undertaken in PubMed/MEDLINE, Web of Science, SCOPUS and Embase databases from inception until January 2022 without using time or language restrictions. RCTs which reported the effects of LPD on cardiovascular risk factors and kidney function in DN were considered.

RESULTS

The results of the present study showed that a LPD significantly reduces urinary urea (WMD: -244.49 g/day, 95 % CI: -418.83, -70.16, P = 0.006) and HbA1c (WMD: -0.20, 95 % CI: -0.39, -0.01, P = 0.036) levels. However, the results did not show neither significant nor beneficial effect on other renal function and cardiovascular risk factors. Furthermore, the results of subgroup analysis showed LPD caused a further decrease in HbA1c during the follow-up period of ≤ 24 weeks, protein intake less than 0.8 g/kg/d and in individuals younger than 50 years. Albuminuria also showed a greater reduction in people under the age of 50 with type 1 diabetes (DMT1) following a LPD.

CONCLUSION

The results of the present study showed that LPD significantly reduces urinary urea and HbA1c.

The 2021-2022 position of Brazilian Diabetes Society on diabetic kidney disease (DKD) management: an evidence-based guideline to clinical practice. Screening and treatment of hyperglycemia, arterial hypertension, and dyslipidemia in the patient with DKD

BACKGROUND

Diabetic kidney disease is the leading cause of end-stage renal disease and is associated with increased morbidity and mortality. This review is an authorized literal translation of part of the Brazilian Diabetes Society (SBD) Guidelines 2021-2022. This evidence-based guideline provides guidance on the correct management of Diabetic Kidney Disease (DKD) in clinical practice.

METHODS

The methodology was published elsewhere in previous SBD guidelines and was approved by the internal institutional Steering Committee for publication. Briefly, the Brazilian Diabetes Society indicated 14 experts to constitute the Central Committee, designed to regulate methodology, review the manuscripts, and make judgments on degrees of recommendations and levels of evidence. SBD Renal Disease Department drafted the manuscript selecting key clinical questions to make a narrative review using MEDLINE via PubMed, with the best evidence available including high-quality clinical trials, metanalysis, and large observational studies related to DKD diagnosis and treatment, by using the MeSH terms [diabetes], [type 2 diabetes], [type 1 diabetes] and [chronic kidney disease].

RESULTS

The extensive review of the literature made by the 14 members of the Central Committee defined 24 recommendations. Three levels of evidence were considered: A. Data from more than 1 randomized clinical trial or 1 metanalysis of randomized clinical trials with low heterogeneity (I2 < 40%). B. Data from metanalysis, including large observational studies, a single randomized clinical trial, or a pre-specified subgroup analysis. C: Data from small or non-randomized studies, exploratory analyses, or consensus of expert opinion. The degree of recommendation was obtained based on a poll sent to the panelists, using the following criteria: Grade I: when more than 90% of agreement; Grade IIa 75-89% of agreement; IIb 50-74% of agreement, and III, when most of the panelist recommends against a defined treatment.

CONCLUSIONS

To prevent or at least postpone the advanced stages of DKD with the associated cardiovascular complications, intensive glycemic and blood pressure control are required, as well as the use of renin-angiotensin-aldosterone system blocker agents such as ARB, ACEI, and MRA. Recently, SGLT2 inhibitors and GLP1 receptor agonists have been added to the therapeutic arsenal, with well-proven benefits regarding kidney protection and patients' survival.

Development and validation of a simple equation to evaluate dietary protein intake using the blood urea nitrogen/serum creatinine ratio in patients with stage 3 chronic kidney disease

PURPOSE

The aim of this research was to develop a simple equation to evaluate dietary protein intake (DPI) in patients with stage 3 chronic kidney disease (CKD) using the blood urea nitrogen (BUN)/serum creatinine (SCr) ratio (BUN/SCr).

METHODS

In a prospective cohort of 136 inpatients with stage 3 CKD from 2 centres, the estimated dietary protein intake (DPI) was calculated using Maroni's formula after the patients implemented a 7 day protein-restricted diet. We developed estimation equations based on BUN/SCr and the spot urinary urea nitrogen (UUN)/urinary creatinine (UCr) ratio (UUN/UCr) in combination with sex and body mass index (BMI). These equations were then internally and externally validated.

RESULTS

The following candidate parameters were derived from univariate regression analysis for 5 established models: sex, BMI, BUN/SCr, UUN and UUN/UCr. Sex and BMI were included in all models after variable evaluation using multiple regression analysis. UUN, UUN/UCr and BUN/SCr were included in model 3, model 4 and model 5, respectively. Both internal and external validation indicated that model 5 resulted in the lowest values for bias and root mean square error and the highest P₃₀ compared with model 3 and model 4. Therefore, the model 5 equation, DPI =  - 5.18 (- 14.49 if the patient is female) + 1.89 × BMI + 1.38 × BUN/SCr, was selected because of the higher correlation (r = 0.498) between the estimated DPI and predicted DPI.

CONCLUSION

The DPI equation developed using BUN/SCr, sex and BMI may be used to estimate protein intake for patients with stage 3 CKD.

TRIAL REGISTRATION

Chinese Clinical Trial Registry Center (ChiCTR-ROC-17011363). Registered on 11 May 2017, Retrospectively registered, http://www.chictr.org.cn/index.aspx .

Dietary carbohydrate restriction augments weight loss-induced improvements in glycaemic control and liver fat in individuals with type 2 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

Lifestyle modification and weight loss are cornerstones of type 2 diabetes management. However, carbohydrate restriction may have weight-independent beneficial effects on glycaemic control. This has been difficult to demonstrate because low-carbohydrate diets readily decrease body weight. We hypothesised that carbohydrate restriction enhances the beneficial metabolic effects of weight loss in type 2 diabetes.

METHODS

This open-label, parallel RCT included adults with type 2 diabetes, HbA_1c 48-97 mmol/mol (6.5-11%), BMI >25 kg/m², eGFR >30 ml min^-1 [1.73 m]^-2 and glucose-lowering therapy restricted to metformin or dipeptidyl peptidase-4 inhibitors. Participants were randomised by a third party and assigned to 6 weeks of energy restriction (all foods were provided) aiming at ~6% weight loss with either a carbohydrate-reduced high-protein diet (CRHP, percentage of total energy intake [E%]: CH30/P30/F40) or a conventional diabetes diet (CD, E%: CH50/P17/F33). Fasting blood samples, continuous glucose monitoring and magnetic resonance spectroscopy were used to assess glycaemic control, lipid metabolism and intrahepatic fat. Change in HbA_1c was the primary outcome; changes in circulating and intrahepatic triacylglycerol were secondary outcomes. Data were collected at Copenhagen University Hospital (Bispebjerg and Herlev).

RESULTS

Seventy-two adults (CD 36, CRHP 36, all white, 38 male sex) with type 2 diabetes (mean duration 8 years, mean HbA_1c 57 mmol/mol [7.4%]) and mean BMI of 33 kg/m² were enrolled, of which 67 (CD 33, CRHP 34) completed the study. Body weight decreased by 5.8 kg (5.9%) in both groups after 6 weeks. Compared with the CD diet, the CRHP diet further reduced HbA_1c (mean [95% CI] -1.9 [-3.5, -0.3] mmol/mol [-0.18 (-0.32, -0.03)%], p = 0.018) and diurnal mean glucose (mean [95% CI] -0.8 [-1.2, -0.4] mmol/l, p < 0.001), stabilised glucose excursions by reducing glucose CV (mean [95% CI] -4.1 [-5.9, -2.2]%, p < 0.001), and augmented the reductions in fasting triacylglycerol concentration (by mean [95% CI] -18 [-29, -6]%, p < 0.01) and liver fat content (by mean [95% CI] -26 [-45, 0]%, p = 0.051). However, pancreatic fat content was decreased to a lesser extent by the CRHP than the CD diet (mean [95% CI] 33 [7, 65]%, p = 0.010). Fasting glucose, insulin, HOMA2-IR and cholesterol concentrations (total, LDL and HDL) were reduced significantly and similarly by both diets.

CONCLUSIONS/INTERPRETATION

Moderate carbohydrate restriction for 6 weeks modestly improved glycaemic control, and decreased circulating and intrahepatic triacylglycerol levels beyond the effects of weight loss itself compared with a CD diet in individuals with type 2 diabetes. Concurrent differences in protein and fat intakes, and the quality of dietary macronutrients, may have contributed to these results and should be explored in future studies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03814694.

FUNDING

The study was funded by Arla Foods amba, The Danish Dairy Research Foundation, and Copenhagen University Hospital Bispebjerg Frederiksberg.

Plant-Based versus Animal-Based Low Protein Diets in the Management of Chronic Kidney Disease

Recent data reiterate low-protein diets (LPDs) as cornerstones in the conservative management of chronic kidney disease (CKD). The reduction in proteinuria, better blood pressure control and the reduction in the rate of decline in kidney function with LPDs were reported, both in non-diabetics and diabetics patients. Supplemented, vegetarian, very-low-protein diets (sVLPD, 0.3 g/kg-day) could postpone kidney replacement therapy (KRT) initiation, mainly through the better control of metabolic disorders of advanced CKD in non-diabetic patients. Plant-based diets could ameliorate gut microbiota and appear to be superior to mixed hypoproteic diets in treating advanced CKD: better control of nitrogen balance, acid-base metabolism and bone mineral disorders. Vegetarian diets generate fewer uremic toxins and reduce salt intake and acid overload. At the same time, they can improve lipid metabolism, providing a high ratio of unsaturated to saturated fatty acids, as well as insulin resistance.

Dietary protein sources and risk of diabetic nephropathy in women: A case-control study

BACKGROUND

Several studies have investigated the association between dietary protein and the risk of diabetic nephropathy (DN); however, there is no agreement on the type of dietary protein sources that might increase the risk of DN. This study was conducted to investigate the associations between different protein sources and the odds of DN developing in Iranian women with existing type 2 diabetes.

METHODS

In this case-control study, 105 women with DN and 105 controls, matched for age and diabetes duration, were selected from the Kowsar Diabetes Clinic in Semnan, Iran. Dietary intake was assessed using a validated and reliable food frequency questionnaire. Dietary protein patterns were estimated using the factor analysis method. Multivariate logistic regression was performed to examine the association between protein patterns and the odds of developing DN.

RESULTS

Two patterns were identified: the Mediterranean-based Dietary Protein Sources (MDPS) pattern which is rich in low-fat dairy, fish, poultry, soy, and legumes, and the Western-based Dietary Protein Sources (WDPS) pattern, rich in red and processed meats, eggs, and high-fat dairy. After adjusting for several confounders, greater adherence (third vs. the first tertile) to the MDPS pattern was associated with lower odds of DN (OR = 0.03; 95 % CI: 0.00, 0.10). In contrast, a strong positive association was observed between adherence to the WDPS pattern and DN (OR = 2.81; 95 % CI: 1.09-7.21).

CONCLUSIONS

Our results show that there is a potential association between the type of protein sources consumed and the odds of DN development in women with type 2 diabetes. Further studies are needed to confirm these findings.

Diabetic nephropathy: A twisted thread to unravel

Diabetic nephropathy (DN), a persistent microvascular problem of diabetes mellitus is described as an elevated level of albumin excretion in urine and impaired renal activity. The morbidity and mortality of type-1 diabetics and type-2 diabetics due to end stage renal disease is also a result of the increased prevalence of DN. DN typically occurs as a consequence of an association among metabolic and hemodynamic variables, activating specific pathways leading to renal injury. According to current interventions, intensive glucose regulation decreases the threat of DN incidence and growth, and also suppressing the renin-angiotensin system (RAS) is a significant goal for hemodynamic and metabolism-related deformities in DN. However, the pathogenesis of DN is multifactorial so novel approaches other than glucose and blood pressure control are required for treatment. This review briefly summarizes the reported pathogenesis of DN, current interventions for its treatment, and possible novel interventions to unweave the thread of DN.

The Importance of Phosphate Control in Chronic Kidney Disease

A series of problems including osteopathy, abnormal serum data, and vascular calcification associated with chronic kidney disease (CKD) are now collectively called CKD-mineral bone disease (CKD-MBD). The pathophysiology of CKD-MBD is becoming clear with the emerging of αKlotho, originally identified as a progeria-causing protein, and bone-derived phosphaturic fibroblast growth factor 23 (FGF23) as associated factors. Meanwhile, compared with calcium and parathyroid hormone, which have long been linked with CKD-MBD, phosphate is now attracting more attention because of its association with complications and outcomes. Incidentally, as the pivotal roles of FGF23 and αKlotho in phosphate metabolism have been unveiled, how phosphate metabolism and hyperphosphatemia are involved in CKD-MBD and how they can be clinically treated have become of great interest. Thus, the aim of this review is reconsider CKD-MBD from the viewpoint of phosphorus, its involvement in the pathophysiology, causing complications, therapeutic approach based on the clinical evidence, and clarifying the importance of phosphorus management.

Probiotics ameliorates glycemic control of patients with diabetic nephropathy: A randomized clinical study

OBJECTIVE

This research aimed to explore the effects of probiotic administration on glycemic control and renal function in patients with diabetic nephropathy (DN).

METHODS

The 101 participants were randomly divided into two treatment groups and 76 patients were included in the final analysis. In 76 patients with diabetic nephropathy of type 2 diabetes, a randomized double-blind and placebo-controlled clinical trial was conducted to evaluate the administration of 3.2 × 109  CFU probiotic supplements per day (Bifidobacterium bifidum, 1.2 × 109  CFU, Lactobacillus acidophilus 4.2 × 109  CFU, Streptococcus thermophilus 4.3 × 109  CFU) for 12 weeks on glycemic control of patients, including fasting blood glucose, 2 h postprandial blood glucose, glycosylated hemoglobin (HbA1c), microalbuminuria/creatinine (mAlb/Cr) and estimated glomerular filtration rate (eGFR) levels. The placebo group daily received empty capsules filled with starch.

RESULTS

After 12 weeks, the administration of probiotics demonstrated a significant reduction in fasting blood glucose (10.68 ± 3.24 mmol/L before vs. 7.81 ± 2.77 mmol/L after, p < 0.05), HbA1c (8.19 ± 1.60% before vs. 7.32 ± 1.20% after, p < 0.05) and mAlb/Cr (101.60 ± 22.17 mg/g before vs. 67.53 ± 20.11 mg/g after, p < 0.05), while only mAlb/Cr level was significantly lower in the probiotic group than in the placebo group after intervention (67.53 ± 20.11 mg/g vs. 87.71 ± 23.01, p < 0.05). Meanwhile, there was no significant reduction of 2 h postprandial blood glucose level (18.95 ± 5.23 mmol/L vs. 17.35 ± 6.28 mmol/L, p = 0.24) and eGFR (84.34 ± 6.97 ml/min vs. 82.8 ± 8.72 ml/min, p = 0.45) in patients before and after probiotic intake. In addition, the placebo group failed to show any significant change of these parameters.

CONCLUSION

This clinical study revealed probiotic administration could ameliorate glycemic control of patients with diabetic nephropathy, potentiating its therapeutic potential in clinical application.

Admission kidney function is a strong predictor for the response to nutritional support in patients at nutritional risk

BACKGROUND

Patients with chronic kidney disease (CKD) are at substantial risk of malnutrition, which negatively affects clinical outcomes. We investigated the association of kidney function assessed at hospital admission and effectiveness of nutritional support in hospitalized medical patients at risk of malnutrition.

METHODS

This is a secondary analysis of an investigator-initiated, randomized-controlled, Swiss multicenter trial (EFFORT) that compared individualised nutritional support with usual hospital food on clinical outcomes. We compared effects of nutritional support on mortality in subgroups of patients stratified according to kidney function at the time of hospital admission (estimated glomerular filtration rates [eGFR] <15, 15-29, 30-59, 60-89 and ≥ 90 ml/min/1.73 m²).

RESULTS

We included 1943 of 2028 patients (96%) from the original trial with known admission creatinine levels. Admission eGFR was a strong predictor for the beneficial effects of nutritional support in regard to lowering of 30-day mortality. Patients with an eGFR <15, 15-29 and 30-59 had the strongest mortality benefit (odds ratios [95%CI] of 0.24 [0.05 to 1.25], 0.37 [0.14 to 0.95] and 0.39 [0.21 to 0.75], respectively), while patients with less severe impairment in kidney function had a less pronounced mortality benefits (p for interaction 0.001). A similar stepwise association of kidney function and response to nutritional support was found also for other secondary outcomes.

CONCLUSION

In medical inpatients at nutritional risk, admission kidney function was a strong predictor for the response to nutritional therapy. Initial kidney function may help to individualize nutritional support in the future by identification of patients with most clinical benefit.

CLINICAL TRIAL REGISTRATION

Registered under ClinicalTrials.gov Identifier no. NCT02517476.

Role of Albuminuria in Detecting Cardio-Renal Risk and Outcome in Diabetic Subjects

The clinical significance of albuminuria in diabetic subjects and the impact of its reduction on the main cardiorenal outcomes by different drug classes are among the most interesting research focuses of recent years. Although nephrologists and cardiologists have been paying attention to the study of proteinuria for years, currently among diabetics, increased urine albumin excretion ascertains the highest cardio-renal risk. In fact, diabetes is a condition by itself associated with a high-risk of both micro/macrovascular complications. Moreover, proteinuria reduction in diabetic subjects by several treatments lowers both renal and cardiovascular disease progression. The 2019 joint ESC-EASD guidelines on diabetes, prediabetes and cardiovascular (CV) disease assign to proteinuria a crucial role in defining CV risk level in the diabetic patient. In fact, proteinuria by itself allows the diabetic patient to be staged at very high CV risk, thus affecting the choice of anti-hyperglycemic drug class. The purpose of this review is to present a clear update on the role of albuminuria as a cardio-renal risk marker, starting from pathophysiological mechanisms in support of this role. Besides this, we will show the prognostic value in observational studies, as well as randomized clinical trials (RCTs) demonstrating the potential improvement of cardio-renal outcomes in diabetic patients by reducing proteinuria.

Low-salt low-protein diet and blood pressure control in patients with advanced diabetic kidney disease and heavy proteinuria

PURPOSE

To assess the associations between effects of low salt, low protein diet supplemented with keto-analogues (sLPD)-on salt intake, blood pressure (BP) and cardiovascular events (CVEs) in patients with advanced diabetic kidney disease (DKD) and heavy proteinuria.

METHODS

Prospective, single-center study (total duration of 15 months), enrolling 92 patients with advanced DKD (median eGFR 11.7 ml/min) and heavy proteinuria (median 4.8 g/g creatininuria). The intervention consisted in a low salt-low protein (0.6 g/kg-day) diet (sLPD) under intensive nutritional counselling, and adjustment of antihypertensive therapy. The endpoints of this sub-analysis were a salt intake ≤ 5 g/day, a mean blood pressure (MAP) ≤ 97 mmHg, corresponding to KDIGO target of 130/80 mmHg, and the rate of CVEs.

RESULTS

Salt intake decreased with 2.5 g/day and the proportion of patients reaching the salt intake endpoint increased with 58%. A salt intake ≤ 5 g/day was associated with a reduced MAP, BMI, proteinuria, fractional excretion of sodium, and eGFR, suggesting a salt-related volume contraction but was not related to protein intake. Mean arterial pressure decreased with 13 mmHg. MAP ≤ 97 mmHg was associated with lower proteinuria, salt, and protein intake, but the contribution of salt intake cannot be differentiated from that of protein intake. CVEs occurred in 20% of patients and were independently related to a lower age and MAP, and increased comorbidities. eGFR only minimally declined and no renal adverse events were noted. sLPD was nutritionally safe.

CONCLUSIONS

The multifactorial personalized intervention allowed a stable MAP reduction to KDIGO recommended levels (≤ 97 mmHg), related to the decrease in salt and protein intake. However, BP lower than 130/80 mmHg increased the cardiovascular but not the renal risk in heavy proteinuric patients with advanced DKD.

TRIAL REGISTRATION NUMBER

0341507433: NCT03415074. Registered 02/02/2015 in US National Library of Medicine, ClinicalTrials.gov (NCT).

Diabetic Kidney Disease Benefits from Intensive Low-Protein Diet: Updated Systematic Review and Meta-analysis

A dietary protein intake (DPI) of between 0.6 and 0.8 g protein per kilogram body weight per day (g/kg/day) is frequently recommended for adults with moderate-to-advanced chronic kidney disease (CKD). However, evidence on whether patients with diabetic kidney disease (DKD) actually benefit from a DPI of ≤ 0.8 g/kg/day and from a low-protein diet (LPD) at CKD stages 1-3 has not been consistent. We systematically searched MEDLINE, EMBASE, Cochrane Library, Web of Knowledge, as well as the bibliographies of articles identified in the search, for eligible randomized controlled trials that had investigated the effects of LPD (prescribed DPI < 0.8 g/kg/day) versus control diet on the progression of DKD. Nine trials that included 506 participants and follow-up periods varying from 4.5 to 60 months were included in the subsequent systematic review and meta-analysis. The data showed that patients with DKD who consumed < 0.8 g protein/kg/day had a significantly reduced decline in glomerular filtration rate (GFR) (mean difference [MD] 22.31 mL/min/1.73 m², 95% confidence interval [CI] 17.19, 27.42; P  < 0.01) and a significant decrease in proteinuria (standard mean difference [SMD] - 2.26 units, 95% CI - 2.99, - 1.52; P  < 0.001) versus those on the control diet. The benefits of LPD to patients with DKD at CKD stages 1-3 were a markedly decreased proteinuria (SMD - 0.96 units, 95% CI - 1.81, - 0.11; P  = 0.03) and slight but significant decreases in glycated hemoglobin (- 0.42%) and cholesterol levels (- 0.22 mmol/L). Our meta-analysis indicated that a DPI of < 0.8 g/kg/day was strongly associated with a slow decline in GFR and decreased proteinuria in the patients with DKD. Patients with CKD stages CKD 1-3 benefited from LPD in terms of a marked decrease of proteinuria and slight but significant improvements in lipid and glucose control.

Medical Nutritional Therapy for Patients with Chronic Kidney Disease not on Dialysis: The Low Protein Diet as a Medication

The 2020 Kidney Disease Outcome Quality Initiative (KDOQI) Clinical Practice Guideline for Nutrition in chronic kidney disease (CKD) recommends protein restriction to patients affected by CKD in stages 3 to 5 (not on dialysis), provided that they are metabolically stable, with the goal to delay kidney failure (graded as evidence level 1A) and improve quality of life (graded as evidence level 2C). Despite these strong statements, low protein diets (LPDs) are not prescribed by many nephrologists worldwide. In this review, we challenge the view of protein restriction as an "option" in the management of patients with CKD, and defend it as a core element of care. We argue that LPDs need to be tailored and patient-centered to ensure adherence, efficacy, and safety. Nephrologists, aligned with renal dietitians, may approach the implementation of LPDs similarly to a drug prescription, considering its indications, contra-indications, mechanism of action, dosages, unwanted side effects, and special warnings. Following this framework, we discuss herein the benefits and potential harms of LPDs as a cornerstone in CKD management.

Nutritional management in patients with chronic kidney disease

The global prevalence of chronic kidney disease (CKD) is increasing with the aging of populations worldwide. As kidney function declines, the accumulation of metabolic waste products and excessive electrolytes can significantly impair the health of patients with CKD. As nutritional management of patients with CKD is thought to control uremic symptoms and provide beneficial effects on the progression of kidney dysfunction, the diet of patients with CKD should be an important consideration in their care. Many guidelines recommend limiting protein intake in these patients, as high-protein diets aggravate kidney dysfunction. Excess sodium may be associated with CKD progression and all-cause mortality and, therefore, limiting salt intake is generally recommended. Low potassium is associated with muscle weakness and hypertension, whereas high potassium is associated with cardiac arrhythmia. Therefore, recent guidelines recommend adjusting dietary potassium intake on an individual basis to maintain serum potassium levels within the normal range. Appropriate dietary calcium intake is recommended to maintain calcium balance in patients with CKD G3, G4. Given the many dietary considerations for patients with CKD, effective nutritional management is challenging. Individualized strategies are needed to ensure the best outcome for patients with CKD.

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.

Association between Low Protein Intake and Mortality in Patients with Type 2 Diabetes

The aim of this study was to investigate the association between protein intake and mortality risk in patients with type 2 diabetes. We analyzed a pooled data of 2494 diabetic patients from two prospective longitudinal studies. Nutritional intake was assessed using a Food Frequency Questionnaire at baseline. Protein intake per body weight (kg) per day was categorized into quartile groups. Adjusted hazard ratios (HRs) and 95% confidence interval (CI) were calculated using Cox regression analysis. During the six-year follow-up, there were 152 incidents of all-cause mortality. The HR for mortality in the lowest quartile of protein intake per body weight compared with the highest quartile was 2.26 (95% CI: 1.34–3.82, p = 0.002) after adjustment for covariates. Subgroup analyses revealed significant associations between low protein intake and mortality in patients aged over 75 years or under 65 years. After further adjustment of the total energy intake, a significant association between protein intake and mortality remained in patients aged ≥ 75 years, whereas the association was attenuated in those aged < 65 years. Our results suggest that adequate protein intake is necessary in older diabetic patients over 75 years, whereas with diabetes, whereas whole optimal total energy intake is required in younger patients with type 2 diabetes.

Physiological Multifunctions of Rice Proteins of Endosperm and Bran

Although it is considered a staple food, rice intake is under serious debate for its physiological usefulness, especially for diabetic patients, because of starch content. However, rice protein, the second major component of rice, has gained attention recently for its newly-discovered functions, which were previously unknown. Rice protein, a plant protein, shows multiple beneficial functions on lipid metabolism and diabetes and its complications, nephropathy, fatty liver and osteoporosis. Rice proteins of endosperm and bran, an ingredient of white rice and an unused product of brown rice, respectively, are valuable components for human health.

The Effects of Different Quantities and Qualities of Protein Intake in People with Diabetes Mellitus

The recommended amount and quality of protein in diets of diabetic patients are highly controversial. In order to provide evidence-based information, the Diabetes Nutrition Study Group (DNSG) used a grading procedure used for quality of evidence and strength of recommendations (GRADE). A protein intake of 10% to 20% of energy intake (E%) or about 0.8 to 1.3 g/kg body weight in people below 65 years of age, and 15% to 20% of E% in people above 65 years of age appeared safe in weight-stable conditions. There were no intervention studies addressing metabolic effects, mortality, or cardiovascular events over prolonged periods. Body weight is closely linked to metabolic control and high protein diets are often recommended. Weight-loss diets that include 23% to 32% of E% as protein for up to one year reduced blood pressure and body weight slightly but significantly more than lower protein diets, whereas blood lipids, fasting blood glucose, and HbA1c improved similarly with higher or lower protein intakes in participants with a glomerular filtration rate (GFR) >60 mL/min/1.73 m². Patients with a GFR <60 mL/min/1.73 m² did not show a faster decline of GFR or kidney function with protein intakes around 0.8 g/kg body weight as compared with lower intakes, thereby arguing against a restriction. The effects of protein intake on diabetic eye or nerve disease have not been reported. There are a number of studies that have compared different types of animal proteins (milk, chicken, beef, pork, and fish) or compared animal with plant protein in diabetic patients and have reported a greater reduction of serum cholesterol with plant protein. In summary, the suggested range of protein intake appears to be safe and can be adapted according to personal dietary preferences.

Association of unhealthy dietary behaviors with renal function decline in patients with diabetes

OBJECTIVE

Balanced nutrition is important for patients with diabetes, and nutrition might well influence diabetes-related complications, although there is limited evidence for this supposition at present. Consequently, we investigate the association between dietary behaviors and renal function decline among patients with diabetes.

RESEARCH DESIGN AND METHODS

From 2011 to 2013, a total of 2797 patients with type 2 diabetes participated in the Diabetes Shared Care Program at Chang Gung Memorial Hospital. All received nutritional consulting by dieticians and an eight-item list of unhealthy dietary behaviors, which included the excessive intake of carbohydrates, fats, protein, fruit, pickled foods, dessert and alcohol, as well as inadequate dietary vegetable. Estimated glomerular filtration rate (eGFR) decline ≥40% was defined as a surrogate end point for kidney damage. Independent dietary risk factors predicting poor renal outcomes were assessed.

RESULTS

Stable mean glycated hemoglobin (A_1c) (7.78% to 7.75%, p=0.151), improved cholesterol (174.04 to 170.13 mg/dL, p<0.001) and low-density lipoprotein (104.19 to 98.07 mg/dL, p<0.001) were found in patients throughout 2 years of therapy. However, significant eGFR decline was noted (94.20 to 88.08 mL/min/1.73 m², p<0.001). A total of 125 subjects had eGFR decline ≥40% and 2672 had stable renal progression.In regression analysis, 625 stable renal patients (selected via propensity score matching) and 125 subjects with eGFR decline ≥40% demonstrated excessive pickled foods to be predictive of poor renal outcomes (OR 1.861, 95% CI 1.230 to 2.814, p=0.003).

CONCLUSIONS

Our study suggests that excessive pickled foods deteriorate renal function more than other unhealthy dietary behaviors in patients with diabetes.

A carbohydrate-reduced high-protein diet improves HbA1c and liver fat content in weight stable participants with type 2 diabetes: a randomised controlled trial

AIMS/HYPOTHESIS

Dietary recommendations for treating type 2 diabetes are unclear but a trend towards recommending a diet reduced in carbohydrate content is acknowledged. We compared a carbohydrate-reduced high-protein (CRHP) diet with an iso-energetic conventional diabetes (CD) diet to elucidate the effects on glycaemic control and selected cardiovascular risk markers during 6 weeks of full food provision of each diet.

METHODS

The primary outcome of the study was change in HbA_1c. Secondary outcomes reported in the present paper include glycaemic variables, ectopic fat content and 24 h blood pressure. Eligibility criteria were: men and women with type 2 diabetes, HbA_1c 48-97 mmol/mol (6.5-11%), age >18 years, haemoglobin >6/>7 mmol/l (women/men) and eGFR >30 ml min^-1 (1.73 m)^-2. Participants were randomised by drawing blinded ballots to 6 + 6 weeks of an iso-energetic CRHP vs CD diet in an open label, crossover design aiming at body weight stability. The CRHP/CD diets contained carbohydrate 30/50 energy per cent (E%), protein 30/17E% and fat 40/33E%, respectively. Participants underwent a meal test at the end of each diet period and glycaemic variables, lipid profiles, 24 h blood pressure and ectopic fat including liver and pancreatic fat content were assessed at baseline and at the end of each diet period. Data were collected at Copenhagen University Hospital, Bispebjerg and Copenhagen University Hospital, Herlev.

RESULTS

Twenty-eight participants completed the study. Fourteen participants carried out 6 weeks of the CRHP intervention followed by 6 weeks of the CD intervention, and 14 participants received the dietary interventions in the reverse order. Compared with a CD diet, a CRHP diet reduced the primary outcome of HbA_1c (mean ± SEM: -6.2 ± 0.8 mmol/mol (-0.6 ± 0.1%) vs -0.75 ± 1.0 mmol/mol (-0.1 ± 0.1%); p < 0.001). Nine (out of 37) pre-specified secondary outcomes are reported in the present paper, of which five were significantly different between the diets, (p < 0.05); compared with a CD diet, a CRHP diet reduced the secondary outcomes (mean ± SEM or medians [interquartile range]) of fasting plasma glucose (-0.71 ± 0.20 mmol/l vs 0.03 ± 0.23 mmol/l; p < 0.05), postprandial plasma glucose AUC (9.58 ± 0.29 mmol/l × 240 min vs 11.89 ± 0.43 mmol/l × 240 min; p < 0.001) and net AUC (1.25 ± 0.20 mmol/l × 240 min vs 3.10 ± 0.25 mmol/l × 240 min; p < 0.001), hepatic fat content (-2.4% [-7.8% to -1.0%] vs 0.2% [-2.3% to 0.9%]; p < 0.01) and pancreatic fat content (-1.7% [-3.5% to 0.6%] vs 0.5% [-1.0% to 2.0%]; p < 0.05). Changes in other secondary outcomes, i.e. 24 h blood pressure and muscle-, visceral- or subcutaneous adipose tissue, did not differ between diets.

CONCLUSIONS/INTERPRETATION

A moderate macronutrient shift by substituting carbohydrates with protein and fat for 6 weeks reduced HbA_1c and hepatic fat content in weight stable individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02764021.

FUNDING

The study was funded by grants from Arla Food for Health; the Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen; the Department of Clinical Medicine, Aarhus University; the Department of Nutrition, Exercise and Sports, University of Copenhagen; and Copenhagen University Hospital, Bispebjerg.

Effects of dietary protein intake on renal outcome and mortality in patients with advanced diabetic nephropathy

BACKGROUND

The difficulty of adhering to a low-protein diet is a serious limitation of randomized controlled trials aimed at validating the efficacy of this therapy. In this observational study of patients with diabetic nephropathy, we examined the association of dietary protein intake (DPI) with renal outcome and mortality, taking into account the nutritional status.

METHODS

We conducted a single-center historical cohort study of 449 adult Japanese patients with type 2 diabetes and the urinary albumin-to-creatinine ratio of ≥ 300 mg/g or estimated glomerular filtration rate of < 30 mL/min/1.73 m². DPI was estimated with a formula using nitrogen levels in spot urine and body mass index. Malnutrition was defined as the Geriatric Nutritional Risk Index of ≤ 98. The primary and secondary endpoints were renal replacement therapy (RRT) initiation and mortality before RRT initiation, respectively. The Fine and Gray subdistribution hazard model was used to determine the relative effects of DPI on the respective endpoint.

RESULTS

Decreased DPI was associated with lower incidence of RRT with an adjusted hazard ratio of 0.81 (95% confidence interval: 0.72-0.92, p < 0.001). The interaction between DPI and nutritional status with respect to mortality was significant (p interaction = 0.047). Decreased DPI was a risk factor for mortality in patients with malnutrition (p = 0.009) but not in those without malnutrition (p = 0.559).

CONCLUSIONS

In patients with type 2 diabetic nephropathy, lower DPI was associated with lower incidence of RRT initiation, suggesting beneficial effects of a low-protein diet on kidneys. Conversely, lower DPI might lead to increased mortality in patients with malnutrition.

Dietary intake in type 1 diabetes at different stages of diabetic kidney disease

AIM

Diet plays an important role in the kidney health of individuals with type 1 diabetes. However, not much is known about dietary practices at different stages of diabetic nephropathy. We aimed at investigating food intake, dietary patterns, and nutrient intakes in individuals with type 1 diabetes differing in renal status.

METHODS

Data were available from 1874 individuals with type 1 diabetes (45% men, age 48 ± 13 years). Diet was assessed at the levels of food items and diet patterns (diet questionnaire), and energy and nutrient intakes (food record). Six groups were formed based on the eGFR or dialysis and transplantation status.

RESULTS

Reductions in liquid-milk product and salt consumption, and increase in special diet adherence were observed at the early stages of eGFR decline. Reduced coffee consumption was observed after eGFR was <30 ml/min/1.73 m². With advancing kidney failure, rye bread consumption decreased, but that of wheat bread increased. Compared to those with intact kidney function (the index group), the Fish and vegetable diet pattern scores were higher in individuals with mildly-to-severely decreased eGFR. Instead, the Sweet pattern scores were lower than in the index group in all other groups. Energy intake was lower in all groups compared to those with intact kidney function. Advancing kidney failure was associated with reductions in protein intake per body weight, and in the intakes of sodium, potassium, calcium, and phosphorus.

CONCLUSIONS

Differences in the dietary intake are seen already at the early stages of kidney function decline.

High rates of protein intake are associated with an accelerated rate of decline of residual kidney function in incident peritoneal dialysis patients

BACKGROUND

Preservation of residual kidney function (RKF) is a relevant objective in peritoneal dialysis (PD) patients. The influence of dietary protein intake (PI) on this variable has not been adequately investigated.

METHODS

Following an observational design, we studied 336 patients incident on PD, with a minimum follow-up of 6 months. The main study variable was the mean PI [normalized rate of protein nitrogen appearance (nPNA)] during the first 4 months on PD. The main outcome variables were the absolute rate of decline of RKF and the proportion of patients presenting a >50% decay of their RKF during the first year of follow-up. We applied univariate and multivariate strategies of analysis, taking into consideration the main control variables bearing a correlation with nPNA and/or RKF.

RESULTS

Mean nPNA (first 4 months) was 1.23 ± 0.33 g/kg/day, while the overall rate of decline of RKF was -0.13 ± 0.29 mL/min/month; 69 patients (25.1%) had lost >50% of their initial RKF by the end of the first year. Univariate analysis disclosed consistent associations between the main study variable on one hand and baseline RKF (r = 0.32, P < 0.0005) and its rate of decline (r = -0.23, P < 0.0005) on the other. The latter two variables were also significantly correlated (r = -0.36, P < 0.0005). Multivariate analysis identified mean nPNA as an independent predictor of the rate of decline of RKF [odds ratio 1.09 per 0.10 g/kg/day, 95% confidence interval (CI) 0.99-1.19, P = 0.058] and, in particular, of the probability of losing >50% of the baseline RKF during the first year of treatment (odds ratio 1.15 per 0.10 g/kg/day, 95% CI 1.04-1.27, P = 0.006).

CONCLUSION

Higher rates of PI during the first months of therapy are associated with a faster decline of RKF among patients incident on PD. Our results underline the convenience of keeping an adequate balance between sufficient protein ingestion, to prevent malnutrition and wasting, and sensible restriction in stable, adequately nourished individuals with rates of intake in the higher range or above-recommended allowances.

Protein intake is not associated with progression of diabetic kidney disease in patients without macroalbuminuria

BACKGROUND

Diabetic kidney disease is an important problem in individuals with diabetes. The effect of dietary protein intake on the renal function of patients with diabetes is controversial. Here, we sought to clarify the association between dietary protein intake and changes in the urinary albumin excretion (UAE) or estimated glomerular filtration rate (eGFR) in patients with type 2 diabetes.

METHODS

In this retrospective cohort study, we included 144 patients (70 men, mean ± standard deviation of age 64 ± 10 years, and median (interquartile range) of UAE 15.0 (7.0-38.9) mg/gCr) without an eGFR less than 30 mL/min/1.73 m² and/or UAE greater than or equal to 300 mg/gCr. Changes in the UAE or eGFR were defined as (logarithms [UAE+1] or eGFR at follow-up minus logarithms [UAE+1] or eGFR at baseline examination)/follow-up duration (years). Habitual protein intake was estimated by a self-administered diet history questionnaire.

RESULTS

The median follow-up duration was 5 years. Protein intake (g/kg ideal body weight/day) was not associated with the change in the UAE (r = -0.130, p = 0.120) or change in the eGFR (r = -0.074, p = 0.381). Multiple linear regression analyses showed that after adjusting for covariates, the patients' protein intake was not associated with change in their UAE (standardized regression coefficient: 0.044, p = 0.732) or change in their eGFR (standardized regression coefficient: 0.250, p = 0.085).

CONCLUSIONS

Dietary protein intake does not influence changes in the UAE or eGFR among patients with type 2 diabetes without macroalbuminuria.

Dietary Protein Intake, Protein Energy Wasting, and the Progression of Chronic Kidney Disease: Analysis from the KNOW-CKD Study

Studies on the effect of dietary protein intake (DPI) on chronic kidney disease (CKD) progression, along with the potential hazard of protein-energy wasting (PEW), are scarce. We evaluated the association between DPI and kidney function both cross-sectionally and longitudinally, particularly emphasizing the role of PEW, in a large-scale, observational, multicenter, prospective study. We enrolled 1572 patients with non-dialysis CKD between 2011 and 2016. CKD progression was defined by a >50% estimated glomerular filtration rate (eGFR) decrease, serum creatinine doubling, or dialysis initiation. A Cox proportional hazard regression analysis was conducted. During the mean follow-up period of 41.6 months, CKD progression was observed in 296 patients. Cross-sectionally, increased DPI was significantly associated with increased eGFR. Similarly, increased DPI tertile was significantly associated with increased renal survival in a Kaplan–Meier curve analysis. In the multivariate Cox proportional hazard regression analysis, the statistical significance of the DPI tertile group in CKD progression was lost when PEW-related variables were added as covariates. In penalized spline curve analysis, the adjusted odds ratio of PEW significantly increased as DPI decreased. DPI, per se was not a major determinant of CKD progression. An intimate association between reduced DPI and PEW may be a more important predictor of CKD progression than DPI.

Effect of diet protein restriction on progression of chronic kidney disease: A systematic review and meta-analysis

Background

Dietary protein restriction has long been thought to play an important role in the progression of chronic kidney disease (CKD); however, the effect of dietary protein on the rate of decline in kidney function remains controversial.

Objective

We undertook a systematic review and meta-analysis of randomized controlled trials (RCTs) to assess the influence of protein restriction on chronic kidney disease.

Method

Ovid MEDLINE (from 1946 to March 5, 2016), EMBASE (from 1966 to March 5, 2016), and the Cochrane Library (Inception to March 5, 2016) were searched to identify RCTs comparing different levels of protein intake for at least 24 weeks in adult patients with CKD. The outcomes included kidney failure events, the rate of change in estimated glomerular filtration rate (eGFR) per year, all cause death events, and changes in proteinuria, serum phosphorus concentration, serum albumin, and body mass index (BMI).

Results

Nineteen trials with 2492 subjects were analyzed. A low protein diet reduced the risk of kidney failure (odds ratio (OR) = 0.59, 95% CI: 0.41 to 0.85) and end-stage renal disease (ESRD) (OR = 0.64, 95% CI: 0.43 to 0.96), but did not produce a clear beneficial effect for all cause death events (OR = 1.17, 95% CI: 0.67 to 2.06). The change in the mean difference (MD) for the rate of decline in the eGFR was significant (MD: −1.85, P = 0.001), and for proteinuria (MD: −0.44, P = 0.02). A low protein diet also reduced the serum phosphorus concentration (MD: −0.37, 95% CI: −0.5 to −0.24) and BMI (MD: −0.61, 95% CI: −1.05 to −0.17). However the change in albumin presented no significant difference between two groups (MD: 0.23, 95% CI: −0.51 to 0.97).

Conclusions

Based on the findings of our meta-analysis, protein-restricted diet may reduce the rate of decline in renal function and the risk of kidney failure for CKD populations, but did not produce a clear beneficial effect for all cause death events. Besides However, the optimal level of protein intake in different participants is left unanswered, and the nutritional status should be regarded with caution.