Effect of restricting dietary protein on the progression of renal failure in patients with insulin-dependent diabetes mellitus

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.

Dietary protein restriction and preservation of kidney function in chronic kidney disease

Dietary protein augmentation elicits an increase in single nephron glomerular filtration rate (GFR) and increased transglomerular pressure. This is similar to the hemodynamic response to reduction in renal mass. Among patients and experimental animals with proteinuric renal disease, these changes also cause an increase in glomerular permselectivity, which in experimental animals accelerates loss of renal function. A meta-analysis of a group of prospective randomized trials including over 2,000 patients found a significant effect on reducing dietary protein decreasing the risk of end-stage renal disease or death (defined as renal death). This differs somewhat in the outcomes of clinical trials using intermediate outcomes, such as the Modification of Diet in Renal Disease study that used change in GFR in part because of the initial hemodynamic effect of reduction in GFR mediated by dietary protein restriction.

Nonprotein calorie supplement improves adherence to low-protein diet and exerts beneficial responses on renal function in chronic kidney disease

OBJECTIVE

Malnutrition is common in patients with chronic kidney disease (CKD) who are on low-protein diets and is a powerful predictor of morbidity and mortality in CKD. Studies have shown that patients on low-protein diets often have difficulty meeting nutritional energy requirements. Our study evaluated the effects of a nonprotein calorie (NPC) supplement on renal function and nutritional status in patients on a low-protein diet.

DESIGN

This was a prospective, randomized, open-label, controlled clinical trial.

SUBJECTS

A total of 109 patients with CKD (men, 67%; mean age, 54.5 ± 13 years) with stage 3 to 4 disease were randomly assigned to the intervention group (n = 55) or the control group (n = 54).

INTERVENTION

All participants received individualized dietary counseling aimed at achieving a daily protein intake of 0.6 to 0.8 g and a daily energy intake of 30 to 35 kcal/kg. The intervention group consumed a 200-kcal NPC supplement daily. The control group received dietary counseling only.

MAIN OUTCOME MEASURE

The estimated glomerular filtration rate (eGFR) was calculated using the 4-variable Modification of Diet in Renal Disease (MDRD) Study equation. Urine protein excretion, dietary protein and energy intake, and serum levels of creatinine, urea nitrogen, cholesterol, triglycerides, and albumin were assessed at baseline, at 12 weeks, and at 24 weeks.

RESULTS

Dietary protein intake and urine protein excretion levels decreased significantly in the intervention group and were significantly lower than those of the control group. In addition, serum levels of creatinine and urea nitrogen decreased significantly, and eGFR increased significantly in the intervention group compared with baseline assessments. No significant differences were observed in the control group.

CONCLUSIONS

The NPC supplement improved patient adherence to the low-protein diet and reduced urine protein excretion in patients with 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.

Phosphate Metabolism in CKD Stages 3-5: Dietary and Pharmacological Control

When compared to the available information for patients on dialysis (CKD stage 5D), data on the epidemiology and appropriate treatment of calcium and phosphate metabolism in the predialysis stages of chronic kidney disease (CKD) are quite limited. Perceptible derangements of calcium and phosphate levels start to become apparent when GFR falls below 30 mL/min in some, but not all, patients. However, hyperphosphatemia may be a significant morbidity and mortality risk predictor in predialysis CKD stages. The RIND study, evaluating progression of coronary artery calcification in incident hemodialysis patients, indirectly demonstrated that vascular calcification processes start to manifest in CKD patients prior to the dialysis stage, which may be closely linked to early and invisible derangements in calcium and phosphate homeostasis. Novel insights into the pathophysiology of calcium and phosphate handling such as the discovery of FGF23 and other phosphatonins suggest that a more complex assessment of phosphate balance is warranted, possibly including measurements of fractional phosphate excretion and phosphatonin levels in order to appropriately evaluate disordered metabolism in earlier stages of kidney disease. As a consequence, early and preventive treatment approaches may have to be developed for patients in CKD stages 3-5 to halt progression of CKD-MBD.

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.

In patients with type 1 diabetes and new-onset microalbuminuria the development of advanced chronic kidney disease may not require progression to proteinuria

We sought to study new-onset microalbuminuria, its progression, and the decline of renal function in patients with type 1 diabetes. Using a cohort of 109 patients who developed new-onset microalbuminuria in the first 4 years following enrollment in the 1st Joslin Kidney Study, we simultaneously tracked the change in their renal function and urinary albumin excretion. Of these, 79 patients were followed for an average of 12 years after microalbuminuria onset, wherein their glomerular filtration rate was estimated by the Modification of Diet in Renal Disease Study formula and compared with their microalbuminuria and proteinuria. The concordance between these outcomes was weak. Only 12 of the 23 patients who progressed to advanced (stage 3-5) chronic kidney disease developed proteinuria, which, in general, did not precede but accompanied the progression to advanced chronic kidney disease. The remaining 11 patients who developed advanced disease had persistent microalbuminuria or returned to normal albuminuria. Thus, we found that one-third of patients with type 1 diabetes developed advanced chronic kidney disease relatively soon after the onset of microalbuminuria and this was not conditional on the presence of proteinuria. Contrary to the existing concept of early nephropathy in type 1 diabetes, less emphasis should be placed on the mechanisms of progression to proteinuria and more placed on mechanisms initiating and promoting the early decline of renal function that eventually progresses to advanced chronic kidney disease.

Hypertriglyceridemia: an independent risk factor of chronic kidney disease in Taiwanese adults

BACKGROUND

The prevalence and incidence of chronic kidney disease (CKD) are relatively high in Taiwanese patients than in patients of other countries, particularly in the older age groups. Dyslipidemia in patients with CKD has been recognized as a risk factor for disease progression but the role of triglycerides (TGs) remains controversial. With this regard, we evaluated the effects of hypertriglyceridemia on renal function in Taiwanese adults (aged >or=40 years).

METHODS

From January 2002 to December 2006, we conducted a community-based medical screening program in Chiayi County with 18,422 subjects (aged >or=40 years). The CKD was defined as an estimated glomerular filtration rate of <60 mL min 1.73 m. Age, body mass index, systolic blood pressure, fasting plasma glucose, and serum total cholesterol were considered as potential confounders.

RESULT

The CKD was prevalent in 24.2% of the middle-aged and elderly population. By using multiple logistic regression models, we determined that old age and elevated levels of body mass index, systolic blood pressure, fasting plasma glucose, and cholesterol were associated with CKD. The adjusted odds ratios of CKD in participants with serum TG >==200 mg/dL was 1.901 (95% confidence interval: 1.07-3.36; P < 0.05) and in participants with serum TG > 500 mg/dL it increased to 2.205 (1.33-3.64, P < 0.05).

CONCLUSION

Hypertriglyceridemia is an independent risk factor for CKD in Taiwanese adults. Thus, an effective screening program that identifies people with hypertriglyceridemia is warranted.

Low protein diets for chronic kidney disease in non diabetic adults

BACKGROUND

For more than fifty years, low protein diets have been proposed to patients with kidney failure. However, the effects of these diets in preventing severe kidney failure and the need for maintenance dialysis have not been resolved.

OBJECTIVES

To determine the efficacy of low protein diets in delaying the need to start maintenance dialysis.

SEARCH STRATEGY

Cochrane Renal Group studies register, the Cochrane Central Register of Controlled studies, MEDLINE, and EMBASE. Congress abstracts (American Society of Nephrology since 1990, European Dialysis Transplant Association since 1985, International Society of Nephrology since 1987). Direct contacts with investigators.

SELECTION CRITERIA

Randomised studies comparing two different levels of protein intake in adult patients suffering from moderate to severe kidney failure, followed for at least one year.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies and extracted data. Statistical analyses were performed using the random effects model and the results expressed as risk ratio (RR) for dichotomous outcomes with 95% confidence intervals (CI). Collection of the number of "renal deaths" defined as the need for starting dialysis, the death of a patient or a kidney transplant during the study.

MAIN RESULTS

Ten studies were identified from over 40 studies. A total of 2000 patients were analysed, 1002 had received reduced protein intake and 998 a higher protein intake. There were 281 renal deaths recorded, 113 in the low protein diet and 168 in the higher protein diet group (RR 0.68, 95% CI 0.55 to 0.84, P = 0.0002). To avoid one renal death, 2 to 56 patients need to be treated with a low protein diet during one year.

AUTHORS' CONCLUSIONS

Reducing protein intake in patients with chronic kidney disease reduces the occurrence of renal death by 32% as compared with higher or unrestricted protein intake. The optimal level of protein intake cannot be confirmed from these studies.

The effect of low-protein diet supplemented with ketoacids in patients with chronic renal failure

Ismert, hogy az étrendi fehérjemegszorítás lassítja a krónikus vesebetegség progresszióját. Ha a fehérjebevitel kevesebb mint 0,5-0,6 g/ttkg/nap, a diétát esszenciális aminosavakkal/ketosavakkal szükséges kiegészíteni. A szerzők tanulmányukban a hosszú időn keresztül ketosavakkal kiegészített fehérjeszegény diéta hatását vizsgálták krónikus veseelégtelenségben szenvedő betegekben a veseelégtelenség progressziójára, a kalcium- és foszforanyagcserére, a betegek tápláltsági állapotára, továbbá felmérték a betegek complience-ét. Ötvenegy beteget kezeltek 12–57 hónapig (átlagos kezelési idő: 26 hónap). A szérumkreatinin-érték átlaga 349,72±78,04 µmol/l-ről 460,66±206,66 µmol/l-re emelkedett, amely 27 µmol/l/év, illetve 2,3 µmol/l/hó szérumkreatinin-növekedést jelentett. A Cockroft–Gault-formula alapján számolt glomerulusfiltrációs ráta (GFR) 21,52±7,84 ml/min-ról 18,22±7,76 ml/min-ra csökkent, ami 0,83 ml/min/év, illetve 0,07 ml/min/hó GFR-csökkenést jelentett. Lineáris regressziós analízissel az 1/szérumkreatinin versus időegyenes dőlésszöge 0,0018 volt. A szérumparathormon-szint szignifikánsan csökkent, a szérumkalcium, -foszfor szintje nem változott. A betegek tápláltsági állapota (a BMI, szérumalbumin, szubjektív tápláltsági felmérés alapján) a folyamatos és intenzív diétás edukációnak köszönhetően nem romlott, a betegek tartani tudták az alacsony fehérjetartalmú diétát a kezelés hosszú időtartama alatt. Eredményeik igazolják, hogy a ketosavakkal kiegészített fehérjeszegény diéta hatásos a veseelégtelenség progressziójának csökkentésében, előnyösen befolyásolja a kalcium- és foszforanyagcserét, nem rontja a betegek tápláltsági állapotát.

Slowing chronic kidney disease progression: results of prospective clinical trials in adults

Chronic kidney disease is generally thought to be a progressive disorder regardless of etiology. Over the past 15 years, investigations into the mechanisms of disease progression and treatment designed to slow or halt disease progression have been conducted, largely in the adult kidney disease population. Intervention trials have demonstrated that lowering blood pressure in hypertensive patients and administration of drugs that block the renin-angiotensin aldosterone system are effective at slowing kidney disease progression, including diabetes, hypertension, and various glomerular diseases. In addition, novel strategies including anemia therapy with erythropoietin-stimulating agents have been conducted to determine whether treatment of this common complication of kidney disease can stabilize kidney function. Whereas substantial success has been achieved in more common forms of adult kidney disease such as diabetes and hypertension, slowing progression of some immune-mediated glomerular disease such as lupus nephritis and immunoglobulin A (IgA) nephropathy remain a great challenge. Moreover, there is no proven strategy, including multifactorial interventions, that clearly halts progressive chronic kidney disease that has been studied prospectively in a large-scale, long-term trial. The purpose of this review is to discuss these trials, as they form the underpinnings for current clinical practice guidelines in adults with chronic kidney disease.

Effects of dietary protein restriction on albumin and fibrinogen synthesis in macroalbuminuric type 2 diabetic patients

AIMS/HYPOTHESIS

Diabetic nephropathy is associated with hypoalbuminaemia and hyperfibrinogenaemia. A low-protein diet has been recommended in patients with diabetic nephropathy, but its effects on albumin and fibrinogen synthesis are unknown.

METHODS

We compared the effects of a normal (NPD; 1.38 +/- 0.08 g kg(-1) day(-1)) or low (LPD; 0.81 +/- 0.04 g kg(-1) day(-1)) -protein diet on endogenous leucine flux (ELF), albumin and fibrinogen synthesis (L-[5,5,5,-2H3]leucine infusion), and markers of inflammation in nine type 2 diabetic patients with macroalbuminuria. Six healthy participants on NPD served as control participants.

RESULTS

In comparison with healthy participants, type 2 diabetic patients on an NPD had similar ELF, reduced serum albumin (38 +/- 1.1 vs 42 +/- 0.8 g/l; p < 0.05), similar fractional synthesis rates (FSR) and absolute synthesis rates (ASR) of albumin, and both increased plasma fibrinogen concentration [10.7 +/- 0.6 vs 7.2 +/- 0.5 micromol/l (3.64 +/- 0.22 vs 2.45 +/- 0.18 g/l); p < 0.05] and fibrinogen ASR [11.03 +/- 1.17 vs 6.0 +/- 1.8 micromol 1.73 m(-2) day(-1) (3.7 +/- 0.4 vs 1.9 +/- 0.3 g 1.73 m(-2) day(-1)); p < 0.01]. After LPD, type 2 diabetic patients had the following changes in comparison with NPD: reduced proteinuria (2.74 +/- 0.4 vs 4.51 +/- 0.8 g/day; p < 0.05), ELF (1.93 +/- 0.08 vs 2.11 +/- 0.08 micromol kg(-1) min(-1); p < 0.05) and total fibrinogen pool; increased serum albumin (42 +/- 1 vs 38 +/- 1 g/l; p < 0.01) and albumin ASR (14.1 +/- 1 vs 9.9 +/- 1 g 1.73 m(-2) day(-1); p < 0.05); and reduced plasma IL-6 levels, which were correlated with albumin ASR (r = -0.749; p < 0.05).

CONCLUSIONS/INTERPRETATION

LPD in type 2 diabetic patients with diabetic nephropathy reduces low-grade inflammatory state, proteinuria, albuminuria, whole-body proteolysis and ASR of fibrinogen, while increasing albumin FSR, ASR and serum concentration.

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.

The impact of HIV on chronic kidney disease outcomes

Chronic kidney disease (CKD) is a known complication of the human immunodeficiency virus (HIV) but outcomes among HIV-infected patients with kidney disease are unknown. We studied a national sample of 202,927 patients with CKD (stage 3 or higher) for death, end-stage renal disease (ESRD) and the mean annual rate of decline in estimated glomerular filtration rate (eGFR) over a median period of 3.8 years. Within this sample, 0.3% of the patients were diagnosed with HIV, 43.5% were diabetic, whereas the remainder had neither disease. In this national CKD cohort, HIV-infected black patients were at higher risk of death, a similar risk for ESRD and loss of eGFR than black patients with diabetes. HIV-infected white patients experienced higher rates of death but a lower risk of ESRD than their counterparts with diabetes. Our results highlight a need to study mortality and mechanisms of ESRD in the HIV infected population.

Protektion der Nierenfunktion bei Diabetikern

The course of diabetic nephropathy is affected by several factors that can be manipulated. In primary prevention, near normal metabolic control beginning at the time of the diagnosis of diabetes diminishes the risk of microalbuminuria to an extent depending on the HbA1c level attained. Hypertensive diabetics should be consistently treated with renin-angiotensin system (RAS)-blocking agents. In secondary prevention, a multifactorial therapy is able to stop or retard further progression. Its components are a sustained decrease of blood pressure in the normotensive range using RAS-blocking agents (normotensive patients should also be treated) as well as near normal metabolic control that takes into account the changing pharmacokinetic and pharmacodynamic properties of blood glucose-lowering drugs in renal insufficiency. Consideration of further factors (smoking, protein intake, anemia) and several general nephroprotective measures complete the treatment spectrum. Therapy for dyslipidemia and the administration of aspirin are important in view of the high cardiovascular morbidity. It is essential to monitor kidney function and the therapeutic components at short intervals.

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.

Microalbuminuria and the risk for early progressive renal function decline in type 1 diabetes

This study aimed to establish the time of initiation and the determinants of renal function decline in type 1 diabetes. Until now, such decline has been assumed to be a late-occurring event associated with proteinuria. A total of 267 patients with normoalbuminuria and 301 patients with microalbuminuria were followed for 8 to 12 yr. Linear trends (slopes) in GFR were estimated by serial measurement of serum cystatin C. Cases of early renal function decline were defined by loss in cystatin C GFR that exceeded -3.3%/yr, a threshold that corresponds to the 2.5th percentile of the distribution of GFR slopes in an independent nondiabetic normotensive population. Cases of early renal function decline occurred in 9% (mean slope -4.4; range -5.9 to -3.3%/yr) of the normoalbuminuria group and 31% (mean slope -7.1; range -23.8 to -3.3%/yr) of the microalbuminuria group (P < 0.001). Risk for early renal function decline depended on whether microalbuminuria regressed, remained stable, or progressed, rising from 16 to 32 and 68%, respectively (P < 0.001). In multivariate analysis, risk for decline was higher after age 35 yr or when glycosylated hemoglobin exceeded 9% but did not vary with diabetes duration, smoking, BP, or angiotensin-converting enzyme inhibitor treatment. Contrary to the existing paradigm of diabetic nephropathy, progressive renal function decline in type 1 diabetes is an early event that occurs in a large proportion of patients with microalbuminuria. Together with testing for microalbuminuria, clinical protocols using cystatin C to diagnose early renal function decline and track response to therapeutic interventions should be developed.

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.

Low protein diets for chronic kidney disease in non diabetic adults

BACKGROUND

For more than fifty years, low protein diets have been proposed to patients with kidney failure. However, the effects of these diets in preventing severe renal failure and the need for maintenance dialysis have not been resolved.

OBJECTIVES

To determine the efficacy of low protein diets in delaying the need to start maintenance dialysis.

SEARCH STRATEGY

Cochrane Renal Group trials register, the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE. Congress abstracts (American Society of Nephrology since 1990, European Dialysis Transplant Association since 1985, International Society of Nephrology since 1987). Direct contacts with investigators. Date of most recent search: December 2004.

SELECTION CRITERIA

Randomised trials comparing two different levels of protein intake in adult patients suffering from moderate to severe renal failure, followed for at least one year.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected studies and extracted data. Statistical analyses were performed using the random effects model and the results expressed as relative risk (RR) for dichotomous outcomes with 95% confidence intervals (CI). Collection of the number of "renal deaths" defined as the need for starting dialysis, the death of a patient or a kidney transplant during the trial.

MAIN RESULTS

Eight trials were identified from over 40 studies. A total of 1524 patients were analysed, 763 had received reduced protein intake and 761 a higher protein intake. Two hundred and fifty one renal deaths were recorded, 103 in the low protein diet and 148 in the higher protein diet group (RR 0.69, 95% CI 0.56 to 0.86, P = 0.0007). To avoid one renal death, 2 to 56 patients need to be treated with a low protein diet during one year.

AUTHORS' CONCLUSIONS

Reducing protein intake in patients with chronic kidney disease reduces the occurrence of renal death by 31% as compared with higher or unrestricted protein intake. The optimal level of protein intake cannot be confirmed from these studies.

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.

Dietary protein restriction as a treatment for slowing chronic kidney disease progression: The case against (Review Article)

Low-protein diets (<or=0.7 g/kg per day) have been advocated for over 70 years as a means of slowing the rate of progression of kidney disease and delaying the appearance of uraemic symptoms and need for dialysis. However, the available evidence to date suggests that the benefit : risk ratio of dietary protein restriction is not favourable in that: (i) compliance is generally sub-optimal; (ii) most of the published randomised controlled trials demonstrate that low-protein diets do not significantly slow the rate of kidney disease progression; (iii) meta-analyses of controlled trials have demonstrated strong evidence of publication bias favouring studies with positive, rather than negative, results; (iv) the optimal level and duration of dietary protein intake have not been defined; (v) there is no convincing clinical evidence that dietary protein restriction provides any benefit beyond that afforded by angiotensin blockade; and (vi) low-protein diets are associated with both statistically and clinically significant declines in nutritional markers in chronic kidney disease populations, which already have a high prevalence of malnutrition. Patients with progressive kidney disease are therefore likely to be better served by avoiding dietary protein restriction (thereby ensuring optimal preservation of their nutrition) and instituting alternative, proven renoprotective measures (e.g. renin-angiotensin system blockade, blood pressure reduction and statin therapy).

Early nephropathy in type 1 diabetes: a new perspective on who will and who will not progress

Impaired renal function and end-stage renal disease (ESRD) affect up to a third of patients with type 1 diabetes. Thus, strategies for early detection and for preventative interventions are of critical importance. A model of diabetic nephropathy was developed in the 1980s that placed paramount importance on the finding of microalbuminuria as an early marker of a committed process of progressive kidney disease in diabetes. However, recent studies have provided evidence that microalbuminuria is a marker of dynamic, rather than fixed, kidney injury. Preliminary studies into early renal function decline, a process measured in early nephropathy using a simple assay for cystatin C to calculate the slope of glomerular filtration rate change over time, suggest that it is a more proximal marker than microalbuminuria of a person's trajectory toward impaired renal function and ESRD. Therefore, early renal function decline, rather than microalbuminuria, may be considered as the early marker of the committed process underlying progressive 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.

A Dipstick Protein and Specific Gravity Algorithm Accurately Predicts Pathological Proteinuria

BACKGROUND

The proper strategy to screen for early chronic kidney disease is debatable, but protein-creatinine ratio from a random urine sample (UPC) commonly is used. The purpose is to determine whether dipstick data effectively identify patients with increased UPC ratios. Because urine concentration affects proteinuria interpretation, we hypothesized that dipstick protein (DSP) and specific gravity (SG) are sufficient for screening.

METHODS

A hospital laboratory database was searched for urine samples simultaneously assayed for UPC ratio, DSP, and SG (n = 2,098). A random 70% of the cohort was used to generate a development model, which was validated in the remaining 30%. Samples were stratified according to DSP and SG values. A DSP versus SG matrix was created, and each sample was allocated to a discrete DSP-SG category. Proportions of samples with overt (UPC ratio > or = 500 mg/g) and nephrotic-range proteinuria (UPC ratio > or = 3,000 mg/g) were calculated for all 40 cells.

RESULTS

Optimum correlations between DSP-SG cells and UPC ratios were determined for the development model, yielding 97.0% negative predictive value (NPV) for a UPC ratio of 500 mg/g or less and 97.5% positive predictive value (PPV) for a UPC ratio of 500 mg/g or greater. NPV for a UPC ratio of 3,000 mg/g or less was 99.7%. Application of the model to the validation sample showed a 96.5% NPV for a UPC ratio of 500 mg/g or less, 99.4% PPV for a UPC ratio of 500 mg/g or greater, and 99.0% NPV for a UPC ratio of 3,000 mg/g or less.

CONCLUSION

DSP and SG values effectively identify patients requiring proteinuria quantification by means of UPC ratio. A Web-based tool was developed that allows DSP and SG value entry and provides a recommendation regarding the need for proteinuria quantification.

Urinary excretion of transferrin and orosomucoid are increased after acute protein loading in healthy subjects

BACKGROUND/AIMS

The aim of this study was to elucidate what kind of plasma proteins would change their urinary excretions when the glomerular filtration rate (GFR) was increased.

METHODS

We measured urinary excretions of three plasma proteins with different molecular radii (MR) and isoelectric points (pI): albumin, orosomucoid (OM) and transferrin (Tf), after acute protein loading in healthy subjects.

RESULTS

Urinary excretion of OM with more anioic charge and smaller MR than albumin, and Tf with more cationic charge and slightly larger molecular weight than albumin, significantly increased in parallel with increased creatinine clearances after acute protein loading. These renal responses returned to basal levels 9 h after protein ingestion. In contrast, increases in urinary excretion of albumin were not observed.

CONCLUSION

Because these findings could not be explained by changes in either size or charge selectivity of shunt pores in the glomerular capillary wall, it is suggested that urinary excretion of albumin may have a special property that distinguishes it from other plasma proteins and may be a less sensitive marker to reflect changes in renal hemodynamics than the other plasma proteins.

Intensified treatment of patients with type 2 diabetes mellitus and overt nephropathy

BACKGROUND

Diabetic nephropathy is the single most common cause of chronic renal failure requiring dialysis. Effective treatment exists, but no clinical audit or large trial has reduced the rate of loss of renal function as effectively as in small groups of intensively managed patients.

AIM

To determine the effect of intensive vs. standard medical management on the rate of progression of renal failure in patients with diabetic nephropathy.

DESIGN

Prospective randomized controlled study.

METHODS

Patients with type 2 diabetes and nephropathy were randomly allocated to an intensive group (n = 47) or control group (n = 43). Treatment targets were the same for both groups, but the intensive group were seen as often as required to meet the targets; controls were seen at their normal clinics. The primary end-point was the rate of progression of renal disease in the second year.

RESULTS

The groups were well matched at baseline. During follow-up, the intensive group had lower mean SBP, DBP and cholesterol. Median rate of progression of renal failure in the intensive group fell from 0.44 ml/min/month in the first year to 0.14 ml/min/month in the second year, compared to 0.49 ml/min/month and 0.53 ml/min/month in the control group (p = 0.04 for second year). Patients in the intensive group spent significantly less time in hospital.

DISCUSSION

Intensive treatment slowed progression of renal disease within 2 years in patients with established diabetic nephropathy. Mean creatinine clearance at the start of the trial was 55 ml/min, so assuming that the rates of progression achieved at the end of the second year persisted, onset of dialysis would be delayed by 20 years in the intensive group compared with the control group.

Preventing cardiovascular events in patients with diabetes mellitus

Diabetes mellitus and obesity are becoming increasingly prevalent in the United States. Patients with diabetes are 2 to 3 times more likely to develop cardiovascular disease (CVD) than are individuals without diabetes, but proper diabetes management and metabolic control can reduce this risk. Nonpharmacologic interventions, such as diet and exercise, can help to reduce weight and control insulin resistance, blood glucose levels, and lipid abnormalities, thereby lowering the risk of adverse cardiovascular outcomes. However, diet and exercise can provide particular challenges for the patient with diabetes. Antiobesity drugs, such as sibutramine and orlistat, can help individuals with diabetes lose weight and can have some effect on metabolic control. Alcohol use and hormone replacement therapy are still controversial topics with regard to reducing the risk of CVD. Smoking is known to be particularly dangerous for those with diabetes, and it is important for health care providers to help their patients stop smoking. Early and aggressive intervention in treating risk factors can reduce the risk of developing diabetes and prevent CVD in the patient with diabetes.

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.