Restriction of dietary protein and progression of renal failure in diabetic nephropathy

Poultry Consumption and Human Cardiometabolic Health-Related Outcomes: A Narrative Review

Poultry meats, in particular chicken, have high rates of consumption globally. Poultry is the most consumed type of meat in the United States (US), with chicken being the most common type of poultry consumed. The amounts of chicken and total poultry consumed in the US have more than tripled over the last six decades. This narrative review describes nutritional profiles of commonly consumed chicken/poultry products, consumption trends, and dietary recommendations in the US. Overviews of the scientific literature pertaining to associations between, and effects of consuming chicken/poultry on, body weight and body composition, cardiovascular disease (CVD), and type II diabetes mellitus (T2DM) are provided. Limited evidence from randomized controlled trials indicates the consumption of lean unprocessed chicken as a primary dietary protein source has either beneficial or neutral effects on body weight and body composition and risk factors for CVD and T2DM. Apparently, zero randomized controlled feeding trials have specifically assessed the effects of consuming processed chicken/poultry on these health outcomes. Evidence from observational studies is less consistent, likely due to confounding factors such as a lack of a description of and distinctions among types of chicken/poultry products, amounts consumed, and cooking and preservation methods. New experimental and observational research on the impacts of consuming chicken/poultry, especially processed versions, on cardiometabolic health is sorely needed.

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.

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.

Nutritional support for patients with chronic kidney disease at pre-dialysis stages

Chronic kidney disease (CKD) is characterized by poor outcomes, an increasing frequency of new cases, the need for expensive method of renal replacement therapy at the terminal stage. The main task facing the doctor is slowing the progression of CKD and delay the start of dialysis by applying the nephroprotective strategy, of which diet therapy is an essential part. The key components of the diet for CKD patients are reducing sodium intake to 2.3 g per day in order to improve control of blood pressure (BP), dietary protein restriction adequate to renal function from 0.8 to 0.3 g/kg of body weight per day combined with the prescribing of ketoanalogues of essential amino acids, hyperglycemia control. With the progression of CKD, the main objectives of the diet therapy are the prevention/correction of complications: protein-energy waisting, metabolic acidosis, ensuring sufficient calories, corresponding to the bodys energy expenditures (3035 kcal/kg of body weight per day), limiting phosphate intake to 0.81 g a day, restriction of food potassium. Low-protein diet in combination with ketoanalogues of amino acids, regular monitoring and correction of the nutritional status of patients at the pre-dialysis stages of CKD is an effective and safe method of nephroprotection, which allows delaying the start of dialysis.

Insights on Medical Nutrition Therapy for Type 2 Diabetes Mellitus: An Indian Perspective

It is critical to integrate medical nutrition therapy (MNT) provided by a registered dietician (RD) into primary care of type 2 diabetes mellitus (T2DM). This is necessary to achieve the goals of improving overall metabolic measures beyond calorie restriction and weight loss. Misconceptions about nutrition in T2DM add to the challenges of executing MNT in a culturally sensitive population. The current review provides insights into MNT for the prevention and management of T2DM in India, based on both evidence and experience. It revisits historical Indian studies and provides information on appropriate dietary intake of carbohydrates (60-70%), proteins (~ 20%) and fats (10%) that will be acceptable and beneficial in an Indian T2DM population. It discusses nuances of types of carbohydrates and fats and explains associations of increased dietary fiber intake, balanced intake of low and high glycemic index foods and substitution of saturated fats with plant-based polyunsaturated fats in improving outcomes of T2DM and attenuating risk factors. The article also deliberates upon special patient populations with comorbid conditions and diseases and the necessary adjustments needed in their nutritional care. It outlines a step-wise approach to MNT involving a careful interplay of nutrition assessment, diagnosis, individualization and patient counseling. Overall, the success of MNT relies on providing accurate, acceptable and appropriate dietary choices for continued patient adherence. Collaborative efforts from diabetologists, endocrinologists, internists and RDs are required to prioritize and implement MNT in diabetes practice in India.Funding: Signutra Inc.

Dietary Approaches in the Management of Diabetic Patients with Kidney Disease

Chronic kidney disease (CKD) is one of the most prevalent complications of diabetes, and patients with diabetic kidney disease (DKD) have a substantially higher risk of cardiovascular disease and death compared to their non-diabetic CKD counterparts. In addition to pharmacologic management strategies, nutritional and dietary interventions in DKD are an essential aspect of management with the potential for ameliorating kidney function decline and preventing the development of other end-organ complications. Among DKD patients with non-dialysis dependent CKD, expert panels recommend lower dietary protein intake of 0.8 g/kg of body weight/day, while higher dietary protein intake (>1.2 g/kg of body weight/day) is advised among diabetic end-stage renal disease patients receiving maintenance dialysis to counteract protein catabolism, dialysate amino acid and protein losses, and protein-energy wasting. Carbohydrates from sugars should be limited to less than 10% of energy intake, and it is also suggested that higher polyunsaturated and monounsaturated fat consumption in lieu of saturated fatty acids, trans-fat, and cholesterol are associated with more favorable outcomes. While guidelines recommend dietary sodium restriction to less than 1.5-2.3 g/day, excessively low sodium intake may be associated with hyponatremia as well as impaired glucose metabolism and insulin sensitivity. As patients with advanced DKD progressing to end-stage renal disease may be prone to the "burnt-out diabetes" phenomenon (i.e., spontaneous resolution of hypoglycemia and frequent hypoglycemic episodes), further studies in this population are particularly needed to determine the safety and efficacy of dietary restrictions in this population.

Higher protein intake is associated with increased risk for incident end-stage renal disease among blacks with diabetes in the Southern Community Cohort Study

BACKGROUND AND AIMS

Diabetes, a risk factor for end-stage renal disease (ESRD), is associated with impaired protein metabolism. We investigated whether protein intake is associated with ESRD and whether the risk is higher among blacks with diabetes.

METHODS AND RESULTS

We conducted a nested case-control study of ESRD within the Southern Community Cohort Study, a prospective study of low-income blacks and whites in the southeastern US (2002-2009). Through 2012, 1057 incident ESRD cases were identified by linkage with the United States Renal Data System and matched to 3198 controls by age, sex, and race. Dietary intakes were assessed from a validated food frequency questionnaire at baseline. Odds ratios (ORs) and 95% confidence intervals (CIs) were computed from logistic regression models that included matching variables, BMI, education, income, hypertension, total energy intake, and percent energy from saturated and polyunsaturated fatty acids. Mean (±SD) daily energy intake from protein was higher among ESRD cases than controls (15.7 ± 3.3 vs. 15.1 ± 3.1%, P < 0.0001). For a 1% increase in percent energy intake from protein, the adjusted ORs (95% CIs) for ESRD were 1.06 (1.02-1.10) for blacks with diabetes, 1.02 (0.98-1.06) for blacks without diabetes, 0.99 (0.90-1.09) for whites with diabetes and 0.94 (0.84-1.06) for whites without diabetes. Protein intake in g/kg/day was also associated with ESRD (4th vs. 1st quartile OR = 1.76; 95% CI: 1.17-2.65).

CONCLUSION

Our results raise the possibility that among blacks with diabetes, increased dietary protein is associated with increased incidence of ESRD. Studies on how protein intake and metabolism affect ESRD are needed.

Rice endosperm protein slows progression of fatty liver and diabetic nephropathy in Zucker diabetic fatty rats

We previously reported that rice endosperm protein (REP) has renoprotective effects in Goto-Kakizaki rats, a non-obese diabetic model. However, whether these effects occur in obese diabetes remains unclear. This study aimed to clarify the effects of REP on obese diabetes, especially on fatty liver and diabetic nephropathy, using the obese diabetic model Zucker diabetic fatty (ZDF) rats. In total, 7-week-old male ZDF rats were fed diets containing 20 % REP or casein (C) for 8 weeks. Changes in fasting blood glucose levels and urinary markers were monitored during the experimental period. Hepatic lipids and metabolites were measured and renal glomeruli were observed morphologically. HbA1c levels were significantly lower in rats fed REP, compared with C (P<0·05). Compared with C in the liver, REP prevented lipid accumulation (total lipid, TAG and total cholesterol, P<0·01). Liver metabolome analysis indicated that levels of metabolites associated with glycolysis, the pentose phosphate pathway and carnitine metabolism were significantly greater in the REP group than in the C group (P<0·05), suggesting activation of both glucose catabolism and fatty acid oxidation. The metabolite increases promoted by REP may contribute to suppression of liver lipid accumulation. Urinary excretion of albumin and N-acetyl-β-d-glucosaminidase was significantly reduced in rats fed REP for 8 weeks (P<0·01). In addition, there was a distinct suppression of mesangial matrix expansion and glomerular hypertrophy in response to REP (P<0·01). Thus, REP had preventive effects on obese diabetes, fatty liver and diabetic nephropathy.

Insulin dependence as an independent predictor of perioperative morbidity after ventral hernia repair: a National Surgical Quality Improvement Program analysis of 45,759 patients

BACKGROUND

Although diabetes mellitus has been identified as a predictor of perioperative morbidity after ventral hernia repair (VHR), it is unclear whether insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM) confer the same degree of risk. We examined the variable effect of IDDM and NIDDM on 30-day medical and surgical complications after VHR.

METHODS

We performed a retrospective analysis of patients in the National Surgical Quality Improvement Program database from 2005 to 2012 undergoing VHR. After perioperative variable comparison, regression analysis was performed to determine whether IDDM and/or NIDDM independently predicted increased complications after proper risk adjustment.

RESULTS

A total of 45,759 patients were identified to have undergone VHR. Of these, 38,026 patients (83.1%) were not diabetic, 5,252 (11.5%) were NIDDM patients, and 2,481 (5.4%) were IDDM patients. After controlling for other risk factors, we found that IDDM independently predicted increased rates of overall, surgical, and medical complications (odds ratio, 1.284, 1.251, 1.263, respectively) in open repair. IDDM independently predicted increased overall and medical complications (odds ratio, 1.997, 1.889, respectively) but not surgical complications in laparoscopic repair. NIDDM was not significantly associated with any complication type in either procedure type.

CONCLUSIONS

Our present study suggests that much of the perioperative risk associated with diabetes is attributable to IDDM. The effect of IDDM on laparoscopic and open repair is subtly different. IDDM demonstrates increased overall and medical complications in laparoscopic repair and increased overall, medical, and surgical complications in open repair. Of note, IDDM does not independently predict increased risk for surgical complications in laparoscopic repair.

Euglycemia in Diabetic Rats Leads to Reduced Liver Weight via Increased Autophagy and Apoptosis through Increased AMPK and Caspase-3 and Decreased mTOR Activities

Euglycemia is the ultimate goal in diabetes care to prevent complications. However, the benefits of euglycemia in type 2 diabetes are controversial because near-euglycemic subjects show higher mortality than moderately hyperglycemic subjects. We previously reported that euglycemic-diabetic rats on calorie-control lose a critical liver weight (LW) compared with hyperglycemic rats. Here, we elucidated the molecular mechanisms underlying the loss of LW in euglycemic-diabetic rats and identified a potential risk in achieving euglycemia by calorie-control. Sprague-Dawley diabetic rats generated by subtotal-pancreatectomy were fed a calorie-controlled diet for 7 weeks to achieve euglycemia using 19 kcal% (19R) or 6 kcal% (6R) protein-containing chow or fed ad libitum (19AL). The diet in both R groups was isocaloric/kg body weight to the sham-operated group (19S). Compared with 19S and hyperglycemic 19AL, both euglycemic R groups showed lower LWs, increased autophagy, and increased AMPK and caspase-3 and decreased mTOR activities. Though degree of insulin deficiency was similar among the diabetic rats, Akt activity was lower, and PTEN activity was higher in both R groups than in 19AL whose signaling patterns were similar to 19S. In conclusion, euglycemia achieved by calorie-control is deleterious in insulin deficiency due to increased autophagy and apoptosis in the liver via AMPK and caspase-3 activation.

The impact of hyperfiltration on the diabetic kidney

More than two decades ago, hyperfiltration (HF) in diabetes was postulated to be a maladaptive response observed early in the course of diabetic kidney disease (DKD), which may eventually predispose to irreversible damage to nephrons and development of progressive renal disease. Despite this, the potential mechanisms leading to renal HF in diabetes are not fully understood, although several hypotheses have been proposed, including alterations in glomerular haemodynamic function and tubulo-glomerular feedback. Furthermore, the role of HF as a causative factor in renal disease progression is still unclear and warrants further prospective longer-term studies. Although HF has been entrenched as the first stage in the classic albuminuric pathway to end-stage renal disease in DKD, and HF has been shown to predict the progression of albuminuria in many, but not all studies, the concept that HF predisposes to the development of chronic kidney disease (CKD) stage 3, that is, glomerular filtration rate (GFR) decline to<60mL/min/1.73m(2), remains to be proved. Further long-term studies of GFR gradients therefore are required to establish whether HF ultimately leads to decreased kidney function, after adjustment for glycaemic control and other confounders. Whether reversal of HF with therapeutic agents is protective against reducing the risk of development of albuminuria and renal impairment is also worth investigating in prospective randomized trials.

Expert opinion of nephrologists about the effectiveness of low-protein diet in different stages of chronic kidney disease (CKD)

No clinical trials have specifically explored the benefits of low-protein diet in patients with different stages of chronic kidney disease (CKD) 3B. In the absence of RCTs, expert opinion may be a valid surrogate to estimate treatment effectiveness. A questionnaire-based survey of a large sample of nephrologists from Southern Italy was conducted to explore benefits of low-protein diet (LPD) in delaying dialysis entry in different CKD stages. For the case vignettes describing eight different patient profiles with various CKD stages, nephrologists reported expected benefits as time delay of dialysis entry. Information was collected through questionnaires filled by 88 nephrologists from different Southern Italian hospitals. On average, nephrologists estimated the highest delay in starting dialysis due to LPD in stages 3B (15 months) and 3A (14 months), and the lowest for 5 stage (3 months). According to opinion of a large sample of Southern Italian nephrologists, low-protein diet may be more efficacious if started in CKD stage 3B than 4 and 5.

Socioeconomic factors and racial disparities in kidney disease outcomes

African Americans suffer disproportionately from advanced and progressive chronic kidney disease (CKD). Socioeconomic factors are believed to play an important role in this disparity, and likely influence African Americans' increased risk of CKD through multiple pathways. Low socioeconomic status (SES) may contribute to racial disparities in CKD because of the greater prevalence of poverty, for example, among African Americans as compared with whites. However, low SES has a stronger relation with CKD among African Americans than among whites, underscoring that the context and magnitude of socioeconomic influences on CKD outcomes varies between these populations. These socioeconomic influences may produce new or potentiate existing racial differences in biology. This review discusses what is known about the role of SES in explaining racial disparities in CKD, highlights several knowledge gaps in this area, and suggests future directions toward the elimination of disparities in CKD.

Low-protein diet for diabetic nephropathy

Diabetic nephropathy is the leading cause of progressive kidney disease, leading to end-stage renal disease and renal replacement therapy. Angiotensin-converting enzyme inhibitors and/or angiotensin receptor blockers have been considered effective at slowing the progression of kidney function deterioration. However, these drugs cannot sufficiently halt the progression of nephropathy to the extent that is required. A low-protein diet (LPD) is believed to be a nutritional intervention that may slow kidney disease progression. In fact, preclinical animal experiments have demonstrated excellent renoprotective effects of an LPD. However, in human clinical trials, analyses of the effects of protein restriction on diabetic nephropathy have not yet revealed consistently positive outcomes of this nutritional intervention. In this review, we analyze the potential renoprotective effects of an LPD on diabetic nephropathy and summarize the outcomes of clinical trials that have systematically investigated the efficacy of an LPD in diabetic nephropathy. In addition, we discuss some potential approaches associated with nutritional interventions to combat progressive kidney disease.

Weight loss for reduction of proteinuria in diabetic nephropathy: Comparison with angiotensin-converting enzyme inhibitor therapy

Reduction of weight in obese type 2 diabetes mellitus (T2DM) individuals is emerging as a significant strategy in the reduction of proteinuria in diabetic nephropathy along with control of hyperglycemia, hypertension, and dyslipidemia. The objective was to evaluate the reduction in 24-h proteinuria in T2DM patients with nephropathy by weight loss, with conventional therapy (angiotensin-converting enzyme [ACE] inhibitors) as the control arm. A prospective, randomized controlled trial was conducted between June 2010 and May 2011. T2DM patients with confirmed nephropathy by 24-h urinary protein estimation with a body mass index (BMI) of >25 kg/m² were studied. Patients who had nondiabetic nephropathy, uncontrolled hypertension (>125/75 mmHg) irrespective of antihypertensive drugs, excess weight due to edema or obesity due to other specific diseases, alcoholics, smokers, and patients who were on hemodialysis were excluded from the study. The patients were divided into three groups, namely, group A, patients on ACE inhibitor therapy; group B, patients on lifestyle modifications for weight loss; and group C, patients on an antiobesity drug (orlistat) and lifestyle modifications. At the end of 6 months, all the three groups were compared. Data were analyzed using software SPSS version 15.0. This study encompassed a total of 88 patients; 12 patients were dropped during the study period and 76 (group A: 22, group B: 23, and group C: 31) patients remained. The mean age of the patients was 58.36 ± 10.87 years (range: 30-70 years). At baseline, age, gender, mean BMI, waist-to-hip ratio (WHR), and 24-h proteinuria did not vary significantly among the three groups. At 6 months, the mean BMI significantly decreased in group C (P < 0.001) compared to that in the other two groups. Among the parameters BMI and WHR, the proportional form of BMI correlated well with the degree of reduction in proteinuria (r = 0.397, P = 0.01). Reduction in weight using lifestyle modifications and antiobesity drugs might improve renal function and proteinuria safely as observed in obese patients with diabetic nephropathy.

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

OBJECTIVE

To evaluate the effect of low-protein diet on kidney function in patients with diabetic nephropathy.

DESIGN

A systematic review and a meta-analysis of randomised controlled trials.

DATA SOURCES

MEDLINE, EMBASE, Cochrane Library, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number (ISRCTN) Register and University Hospital Medical Information Network-Clinical Trials Registry (UMIN-CTR) from inception to 10 December 2012. Internet searches were also carried out with general search engines (Google and Google Scholar).

STUDY SELECTION

Randomised controlled trials that compared low-protein diet versus control diet and assessed the effects on kidney function, proteinuria, glycaemic control or nutritional status.

PRIMARY AND SECONDARY OUTCOME MEASURES AND DATA SYNTHESIS

The primary outcome was a change in the glomerular filtration rate (GFR). The secondary outcomes were changes in proteinuria, post-treatment value of glycated haemoglobin A1C (HbA1c) and post-treatment value of serum albumin. The results were summarised as the mean difference for continuous outcomes and pooled by the random effects model. Subgroup analyses and sensitivity analyses were conducted regarding patient characteristics, intervention period, methodological quality and assessment of diet compliance. The assessment of diet compliance was performed based on the actual protein intake ratio (APIR) of the low-protein diet group to the control group.

RESULTS

We identified 13 randomised controlled trials enrolling 779 patients. A low-protein diet was associated with a significant improvement in GFR (5.82 ml/min/1.73 m(2), 95% CI 2.30 to 9.33, I(2)=92%; n=624). This effect was consistent across the subgroups of type of diabetes, stages of nephropathy and intervention period. However, GFR was improved only when diet compliance was fair (8.92, 95% CI 2.75 to 15.09, I(2)=92% for APIR <0.9 and 0.03, 95% CI -1.49 to 1.56, I(2)=90% for APIR ≥0.9). Proteinuria and serum albumin were not differed between the groups. HbA1c was slightly but significantly decreased in the low-protein diet group (-0.26%, 95% CI -0.35 to -0.18, I(2)=0%; n=536).

CONCLUSIONS

Low-protein diet was significantly associated with improvement of diabetic nephropathy. The adverse effects of low-protein diet were not apparent such as worsening of glycaemic control and malnutrition.

Nephropathy in diabetes

The most common cause of end stage renal disease (ESRD) requiring dialysis is diabetes. Both environmental and genetic factors have been postulated as the risk factors of Diabetic Nephropathy (DN). Hyperglycemia-induced metabolic and hemodynamic pathways are recognized to be mediators of kidney injury. Multiple biochemical pathways have been postulated that explain how hyperglycemia causes tissue damage: Non-enzymatic glycation that generates advanced glycation end products, activation of protein kinase C, acceleration of the polyol pathway and oxidative stress. Three major histologic pathological changes occur in DN: Mesangial expansion, GBM thickening, and glomerular sclerosis. It now seems clear in targeting a therapeutic regimen to achieve blood glucose, blood pressure and proteunuric goals, dietary protein and salt restriction, weight reduction, aggressive lipid lowering, smoking cessation and exercise. Multiple intensive interventions reduce cardiovascular events as well as nephropathy by about half when compared with conventional multifactorial treatment.

Optimal nutrition for predialysis chronic kidney disease

Diet potentially plays a major role in the progression and complications of predialysis CKD. Moderate protein consumption along with a diet low in sodium might slow kidney disease progression. Increasing vegetable protein intake might decrease serum phosphorus, uremic toxins, and kidney damage. Because obesity might be an important factor in the increasing prevalence of CKD, dietary strategies targeting obesity might also benefit CKD progression. In those with more advanced CKD, dietary calcium and phosphorus restriction could minimize vascular calcification. Dietary fiber and vitamin D supplementation might also be important to decrease inflammation in CKD.

Serum phosphorus predicts incident chronic kidney disease and end-stage renal disease

BACKGROUND

Elevations in serum phosphorus are associated with renal decline in animal models and progression of established chronic kidney disease (CKD) in human observational studies. We examined whether serum phosphorus levels increase the risk of incident CKD or end-stage renal disease (ESRD) in two population-based prospective cohort studies.

METHODS

Overall, 2269 participants free of CKD [estimated glomerular filtration rate (eGFR) <60 mL/min/1.73(2)] from the Framingham Heart Study (FHS; mean age 42 years; 53% women) and 13,372 participants from the Third National Health and Nutrition Examination Survey (NHANES III; mean age 44.3 years, 52% women) contributed to the present study. In the FHS, we evaluated the relationship between baseline phosphorus category (<2.5 mg/dL, 2.5-3.49 mg/dL, 3.5-3.99 mg/dL and ≥4 mg/dL) and incident CKD (n = 267). In NHANES, we examined the relationship between phosphorus below and above 4 mg/dL in relation to incident ESRD (n = 65).

RESULTS

FHS participants in the highest phosphorus category had an increased risk of CKD [odds ratio 2.14; 95% confidence interval (CI), 1.07-4.28; P = 0.03] in multivariable-adjusted models when compared to the referent group (2.5-3.49 mg/dL). Similarly, NHANES III participants with phosphorus levels ≥4 mg/dL demonstrated an increased risk of incident ESRD compared to those <4 mg/dL (relative risk 1.90; 95% CI 1.03-3.53; P = 0.04).

CONCLUSIONS

In prospective studies of the general population, serum phosphorus levels in the upper-normal range were associated with a doubling in the risk of developing incident CKD and ESRD.

The clinical significance of hyperfiltration in diabetes

Glomerular filtration rate is commonly elevated in early diabetes and patients with this symptom are arbitrarily considered to have hyperfiltration. The prevalence of hyperfiltration in type 1 diabetes varies from less than 25% to more than 75%. The corresponding figures in type 2 diabetes are significantly lower, ranging between 0% and more than 40%. Several factors, methodological and biological, may contribute to the wide variation in estimates of hyperfiltration prevalence. Methodological differences in measurement and evaluation of GFR apply in particular to the handling of plasma disappearance curves of filtration markers. Biological factors that may influence GFR in the hyperfiltration range include glycaemic control, diabetes duration, BMI, sex, pubertal status in type 1 diabetes and age in type 2 diabetes. Hyperglycaemia may influence GFR and albuminuria, and may therefore confound the evaluation of hyperfiltration as an independent risk factor for diabetic nephropathy. Adequate assessment of the relationship between glycaemic control, GFR and AER therefore requires serial measurements of all three variables followed by multivariate analysis. A recent meta-analysis of ten type 1 diabetes studies concluded that the presence of hyperfiltration at baseline more than doubled the risk of developing micro- or macroalbuminuria at follow-up. However, not all studies allowed for confounding factors or regression dilution bias. Future studies will therefore need to address the independent role of hyperfiltration, not only in the evolution of albuminuria, but also in the subsequent decline of GFR.

Protein restriction for diabetic renal disease

BACKGROUND

Diabetic renal disease (diabetic nephropathy) is a leading cause of end-stage renal failure. Once the process has started, it cannot be reversed by glycaemic control, but progression might be slowed by control of blood pressure and protein restriction.

OBJECTIVES

To assess the effects of dietary protein restriction on the progression of diabetic nephropathy in patients with diabetes.

SEARCH STRATEGY

We searched The Cochrane Library, MEDLINE, EMBASE, ISI Proceedings, Science Citation Index Expanded and bibliographies of included studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and before and after studies of the effects of a modified or restricted protein diet on diabetic renal function in people with type 1 or type 2 diabetes following diet for at least four months were considered.

DATA COLLECTION AND ANALYSIS

Two reviewers performed data extraction and evaluation of quality independently. Pooling of results was done by means of random-effects model.

MAIN RESULTS

Twelve studies were included, nine RCTs and three before and after studies. Only one study explored all-cause mortality and end-stage renal disease (ESRD) as endpoints. The relative risk (RR) of ESRD or death was 0.23 (95% confidence interval (CI) 0.07 to 0.72) for patients assigned to a low protein diet (LPD). Pooling of the seven RCTs in patients with type 1 diabetes resulted in a non-significant reduction in the decline of glomerular filtration rate (GFR) of 0.1 ml/min/month (95% CI -0.1 to 0.3) in the LPD group. For type 2 diabetes, one trial showed a small insignificant improvement in the rate of decline of GFR in the protein-restricted group and a second found a similar decline in both the intervention and control groups. Actual protein intake in the intervention groups ranged from 0.7 to 1.1 g/kg/day. One study noted malnutrition in the LPD group. We found no data on the effects of LPDs on health-related quality of life and costs.

AUTHORS' CONCLUSIONS

The results show that reducing protein intake appears to slightly slow progression to renal failure but not statistically significantly so. However, questions concerning the level of protein intake and compliance remain. Further longer-term research on large representative groups of patients with both type 1 and type 2 diabetes mellitus is necessary. Because of the variability amongst patients, there might perhaps be a six month therapeutic trial of protein restriction in all individuals, with continuation only in those who responded best. Trials are required of different types of protein.

Regional Differences in End-Stage Renal Disease and Amount of Protein Intake in Japan

OBJECTIVE

We recently showed regional differences in the incidence of end-stage renal disease (ESRD) within Japan, which is generally ethnically homogenous, suggesting that factors other than genetic may contribute to the difference. We examined regional differences in the amounts of dietary nutrient intake, especially protein in our search for an explanation.

DESIGN AND SETTING

Annually, the Japanese Society for Dialysis Therapy reports the numbers of patients entering maintenance dialysis in each prefecture of Japan. We used these numbers from 1984 to 2002 to calculate the annual ESRD incidence in each of 12 regions of Japan. The regional differences were analyzed in relation to the amounts of nutrient intake reported annually by National Nutrition Survey in corresponding regions for these 19 years. Each year, approximately 15,000 subjects from 5000 households in randomly selected 300 districts were included to obtain a representative sample of the entire population of Japanese in a manner of age, sex, and body mass matched.

RESULTS

There were marked regional differences in the annual ESRD incidence and small regional differences in dietary intake of each nutrient. Multiple regression analysis showed that the annual ESRD incidence was negatively correlated with energy intake (r = -0.65, F = 240, n = 228) and positively correlated with animal protein intake (r = 0.25, F = 30). Across 12 regions in the values averaged for 19 years in each region, however, the incidence of ESRD was negatively correlated only with the amounts of energy intake (r = -0.74, F = 12, n = 12), but not with animal protein (r = 0.07, F = 0.04).

CONCLUSION

The present study, relating regional differences between ESRD dynamics and the amounts of nutrient intake in a nationwide population of Japan, revealed that the renal protective effects of dietary restriction of protein, suggested by animal models of progressive nephropathies but yet unproved by large-scale clinical trials, remained unestablished even on a macro level of whole Japan through mapping approaches.

Proposal for mapping renal failure in Japan and its application for strategy to arrest endstage renal disease

Remarkable regional differences in the annual incidence of endstage renal disease (ESRD) was found within Japan, which has a relatively homogeneous ethnic composition. In addition, there existed no regional difference in the incidence of ESRD due to polycystic kidney disease, the major genetic disorder of the kidneys. These findings suggest that the presence of factors other than genetic disposition contribute to the differences. On the other hand, there were similar regional variations in the incidences of ESRD between two causes of ESRD: chronic glomerulonephritis and diabetic nephropathy. Because it is unlikely that the regional distribution of underlying disease incidence and the disease-specific progression rate would be similar for two different causes, this observation suggests that factors governing the progression rate, which operate commonly for all causes of ESRD but differ among regions, may play an important role in generating the regional differences. Finally, we examined regional differences in the amounts of inhibitors of the renin-angiotensin system used, especially angiotensin-converting enzyme (ACE) inhibitors, in our search for an explanation of the regional differences in ESRD dynamics. Among antihypertensive agents examined, only ACE inhibitors were negatively correlated with the annual incidence of ESRD. The renal protective effects of ACE inhibitors have been established by results with animal models of progressive nephropathy and by large-scale clinical trials. Our epidemiological results for Japan as a whole show the same protective effects still more convincingly from a different approach. It is not completely clear yet at present, however, how regional variations in the incidence of ESRD are generated. If we could identify in future the factors that contribute to the regional differences, strategies for the treatment of renal disease will become available from different angles. Thus, much effort will be encouraged for the further analysis of regional differences in ESRD dynamics.

Effect of weight loss using formula diet on renal function in obese patients with diabetic nephropathy

OBJECTIVE

To evaluate the effect and safety of treatment with low-calorie formula diet on renal function and proteinuria in obese patients with diabetic nephropathy.

DESIGN

Prospective study on safety and efficacy of a 4-week low-calorie (11-19 kcal/kg/day) normal-protein (0.9-1.2 g/kg/day) diet partly supplemented with formula diet.

SUBJECTS

In all, 22 obese patients with diabetic nephropathy (BMI: 30.4+/-5.3 kg/m(2), HbA1c: 7.1+/-1.4%, serum creatinine: 172.4+/-57.5 micromol/l, urinary protein: 3.3+/-2.6 g/day).

RESULTS

The mean body weight decreased by 6.2+/-3.0 kg. The mean systolic blood pressure, creatinine, blood urea nitrogen, urinary protein, and 8-hydroxydeoxyguanosine decreased significantly by 7.5+/-12.7 mmHg, 41.6+/-23.9 micromol/l, 1.50+/-1.61 mmol/l, 1.8+/-1.7 g/day, and 3.1+/-3.6 ng/mg creatinine, respectively. No patient had increased serum creatinine and urinary protein. Mean creatinine clearance (40.6+/-17.9 to 46.1+/-14.6 ml/s/1.73 m(2)) and serum albumin showed no significant changes. Delta serum creatinine and Delta urinary protein correlated with Delta body weight (r=0.62 and 0.49, respectively) and Delta visceral fat area (r=0.58 and 0.58, respectively), but did not correlate with Delta systolic blood pressure, Delta fasting blood glucose and Delta subcutaneous fat area.

CONCLUSION

These results suggested that weight reduction using formula diet might improve renal function and proteinuria safely for a short term in obese patients with diabetic nephropathy.

[The role of the diet as a risk factor for the development and progression of diabetic nephropathy]

Diabetic nephropathy (DN) is the leading cause of kidney disease in patients starting renal replacement therapy, and affects up to 40% of type 1 and type 2 diabetic patients. Diet seems to play an important role in the development of the disease. There are evidences supporting the concept that not only the amount but also the origin of dietary protein are associated with DN. Few studies analyzed the role of dietary lipids. A low-protein diet slows down the decline of renal function and ameliorates the DN prognosis and death in patients with type 1 diabetes with micro- and macroalbuminuria. Studies in type 2 diabetic patients are scanty but short-term studies suggest that this approach decreases albuminuria. However, the use of low-protein diet for long periods is compromised by poor compliance and its long-term safety is not firmly established. Enthusiastic results come up when comparing the effect of different sources of animal protein on renal function and lipid profile in patients with DN, which may represent an alternative strategy for low-protein diet on medical nutritional therapy in patients with DN and in cardiovascular risk factors and endothelial function.

Proteasome production in human muscle during nutritional inhibition of myofibrillar protein degradation

Protein undernutrition inhibits adenosine triphosphate (ATP)-dependent muscle protein degradation-a hallmark of the proteasome system. Here we report decreased myofibrillar protein degradation during dietary protein restriction without a concomitant decrease in proteasome gene expression, proteasome protein abundance, or proteasome in vivo fractional synthesis rate. Healthy human subjects consuming the average minimum adult protein requirement (0.71 g x kg(-1) fat-free mass x d(-1)) exhibited substantially lower (68%) excretion of 3-methylhistidine, an indicator of myofibrillar protein breakdown, when compared with subjects consuming an ample, American-style protein intake (1.67 g x kg(-1) fat-free mass x d(-1)). However, they displayed no difference in the expression of mRNA for proteasome subunits C2 or C3, in the content of C2 protein, or in the rate of incorporation of stable isotopically labeled l-[1-(13)C]-leucine into proteasome proteins. The results demonstrate that nutritional inhibition of myofibrillar protein degradation does not involve suppression in vivo of proteasome production in man. This suggests that other elements of the ubiquitin-proteasome system, such as ubiquitination pathways, are more important than proteasome abundance in the nutritional regulation of skeletal muscle mass.

Cost-effective strategies in the prevention of diabetic nephropathy

A significant subgroup of patients with diabetes mellitus are predisposed to developing diabetic nephropathy and it is in this subgroup that other diabetes- related complications, and in particular greatly increased cardiovascular disease risk, are concentrated. The high personal, social and financial costs of managing end-stage renal failure and the other complications associated with diabetic nephropathy make a powerful case for screening and effective intervention programmes to prevent the condition or retard its progression. As major breakthroughs in finding genetic susceptibility factors remain elusive, screening efforts continue to be based on microalbuminuria testing, despite increasing recognition of its limitations as a positive predictor of nephropathy. Interventions have been extensively studied, but results remain conflicting. Economic evaluations of such screening and intervention programmes are essential for health planners, yet models of the cost/benefit ratio of such interventions often rely on a rather slim evidence base. Where economic models are developed, they are frequently based on those papers that propound the greatest clinical benefits of a given intervention, leading to a possible over-estimation of the advantages of the chosen approach. Furthermore, the benefits of even such generally accepted interventions as ACE inhibitor treatment are less firmly established than generally appreciated. Lifestyle interventions are instinctively attractive, but are by no means a low-cost option (as is often assumed by both medical professionals and politicians). This review critically assesses the evidence for clinical efficacy and economic benefit of microalbuminuria screening and interventions such as intensive glycaemic control, antihypertensive treatment, ACE inhibition and angiotensin receptor blockade, dietary protein restriction and lipid-modifying therapy. The various costs associated with diabetic nephropathy are so great that even expensive interventions may have a favourable cost/benefit ratio, provided they are truly effective.

Nutrition therapy for diabetic nephropathy

Human observational studies report no association between protein intakes less than 20% of energy intake and the development of renal disease. With protein intakes greater than 20% of energy intake there is an association between protein with increased albumin excretion rate. Once albuminuria is present, intervention studies suggest a beneficial effect on renal function with a reduction of protein to 0.8 to 1.0 g/kg/d with microalbuminuria and to 0.8 g/kg/d with macroalbuminuria. Restriction of sodium to 2400 mg/d or possibly for some to 2000 mg/d assists in the control of hypertension. In macroalbuminuria, there may be additional benefits in lowering phosphorus intake to 500 to 1000 mg/d. There is no strong evidence to suggest benefit from vegetable or plant proteins over animal protein, but there is evidence for benefit on renal function, glucose, lipids, and blood pressure from weight-maintaining diets meeting guidelines for a healthy diet.

Optimizing target-organ protection in patients with diabetes mellitus: angiotensin-converting enzyme inhibitors or angiotensin receptor blockers?

High blood pressure in the setting of type 1 and type 2 diabetes is commonly associated with the earlier development of target-organ damage, including cardiovascular and cerebrovascular disease and progressive renal insufficiency. The major goal of treating high blood pressure in this population is to prevent or reduce the likelihood of target-organ damage. The treatment goal for high blood pressure, therefore, has to be defined based on optimal means of preventing cardiovascular and renal events. The reduction of high blood pressure with pharmacologic therapy is associated with reduction of cardiovascular events, renal disease, and associated mortality. However, many questions remain. Some of the basic and important questions include the following: What should be the goal of treated blood pressure in the diabetic, and are there preferred agents that should be used in the hypertensive diabetic population? How do angiotensin-converting enzyme inhibitors and angiotensin receptor blockers fit in? Are there advantages of one class over the other? The goal of this review is to summarize the recent clinical trial findings and try to provide recommendations based on the evidence of these trials to help the clinician better choose blood pressure goals and treatment strategies in the diabetic population.

Effect of dietary protein restriction on prognosis in patients with diabetic nephropathy

BACKGROUND

Recent data suggest that dietary protein restriction improves survival and delays the progression to end-stage renal disease (ESRD) in non-diabetic nephropathies. The purpose of our study was to determine the effect of dietary protein restriction on survival and progression to ESRD in diabetic nephropathy.

METHODS

A four-year prospective, controlled trial with concealed randomization was performed comparing the effects of a low-protein diet (0.6 g/kg/day) with a usual-protein diet. The study included 82 type 1 diabetic patients with progressive diabetic nephropathy [pre-study mean decline in glomerular filtration rate (GFR) 7.1 mL/min/year (95% CI, 5.8 to 8.5)]. The main outcome measures were decline in GFR and development of ESRD or death.

RESULTS

During the follow-up period the usual-protein diet group consumed 1.02 g/kg/day (95% CI; 0.95 to 1.10) as compared with 0.89 (0.83 to 0.95) in the low-protein diet group (P = 0.005). The mean declines in GFR were 3.9 mL/min/year (2.7 to 5.2) in the usual-protein diet group and 3.8 (2.8 to 4.8) in the low-protein diet group. ESRD or death occurred in 27% of patients on a usual-protein diet as compared with 10% on a low-protein diet (log-rank test; P = 0.042). The relative risk of ESRD or death was 0.23 (0.07 to 0.72) for patients assigned to a low-protein diet, after an adjustment at baseline for the presence of cardiovascular disease (P = 0.01). Blood pressure and glycemic control were comparable in the two diet groups during the follow-up period.

CONCLUSION

Moderate dietary protein restriction improves prognosis in type 1 diabetic patients with progressive diabetic nephropathy in addition to the beneficial effect of antihypertensive treatment.

Favorable impact of a vegan diet with exercise on hemorheology: implications for control of diabetic neuropathy

A little-noticed clinical report indicates that a low-fat, whole-food vegan diet, coupled with daily walking exercise, leads to rapid remission of neuropathic pain in the majority of type 2 diabetics expressing this complication. Concurrent marked improvements in glycemic control presumably contribute to this benefit, but are unlikely to be solely responsible. Consideration should be given to the possibility that improved blood rheology - decreased blood viscosity and increased blood filterability - plays a prominent role in mediating this effect. There is considerable evidence that neural hypoxia, secondary to impaired endoneurial microcirculatory perfusion, is a crucial etiologic factor in diabetic neuropathy; the unfavorable impact of diabetes on hemorheology would be expected to exacerbate endoneurial ischemia. Conversely, measures which improve blood fluidity would likely have a beneficial impact on diabetic neuropathy. There is indeed evidence that vegan diets, as well as exercise training, tend to decrease the viscosity of both whole blood and plasma; reductions in hematocrit and in fibrinogen may contribute to this effect. The fact that vegan diets decrease the white cell count is suggestive of an improvement in blood filterability as well; filterability improves with exercise training owing to an increase in erythrocyte deformability. Whether these measures influence the activation of leukocytes in diabetics - an important determinant of blood filterability - remains to be determined. There are various reasons for suspecting that a vegan diet can reduce risk for other major complications of diabetes - retinopathy, nephropathy, and macrovascular disease - independent of its tendency to improve glycemic control in type 2 patients. The vegan diet/exercise strategy represents a safe, 'low-tech' approach to managing diabetes that deserves far greater attention from medical researchers and practitioners.

Severe dietary protein restriction in overt diabetic nephropathy: benefits or risks?

OBJECTIVE

To evaluate whether restricting protein intake may delay the progression of chronic renal failure caused by overt diabetic nephropathy and also whether this increases the risk of malnutrition.

DESIGN

Prospective clinical trial.

SETTING

Nephrology outpatients.

PATIENTS

Sixty-nine patients (32 affected by type 1 and 37 by type 2 diabetes, all treated with insulin) affected by both overt diabetic nephropathy and hypertension.

INTERVENTION

The study was started once hypertension and glycemia had been under control for at least 3 months. Two groups of patients, matched for similar mean glomerular filtration rate value and nutritional status, were studied: a low-protein diet (0.6 g/kg/d) was randomly prescribed to 35 patients, whereas in the other 34 patients a free diet intake was maintained for 12 months.

MAIN OUTCOME MEASURE

Renal function and nutritional status.

RESULTS

The protein intake was significantly different in the 2 groups of patients, whereas the average decline of glomerular filtration rate during the follow-up was comparable. In the low-protein diet group, serum prealbumin concentration significantly decreased after 9 months, whereas serum albumin decreased at the end of the study.

CONCLUSION

Severe dietary protein restriction does not seem to delay the progression of renal disease in patients with overt diabetic nephropathy, whereas it may induce malnutrition.