Importance of early initiation of dietary protein restriction for the prevention of experimental progressive renal disease

Importance of early and continuous use of protein restriction on the progression of adriamycin nephropathy

Three experimental protocols were carried out with the aim of evaluating the role of protein restriction on the progression of the established adriamycin-induced nephropathy, and whether the protective effect of the diet persists after the diet is discontinued. The effect of a low protein diet (LPD) was studied for 6 weeks in protocol 1, 16 weeks in protocol 2 and for 28 weeks in protocol 3. In protocol 3, one group (LL) received LPD and another (NN) was given a normal protein diet (NPD). A third group (LN) received LPD for 16 weeks and then NPD for 12 weeks and a fourth group (NL) was fed NPD for 16 weeks and then LPD for 12 weeks. In protocol 1 the tubulo-interstitial index (TILI) of rats on LPD (Md = 2, P25 = 0.0; P75 = 3.5) after six weeks, was smaller than that of the animals on NPD (Md = 6.0; P25 = 3.0; P75 = 8.0; p < 0.05). In protocol 2, the group taking LPD presented an area of interstitial fibrosis (IF) (Md = 0.5%, P25 0.2%; P75 = 1.9%) smaller than that of the NPD group (Md = 6.8%; P25 = 5.2%; P75 = 7.1%; p < 0.05). No significant difference in the area of glomerulosclerosis (GSA) was observed between the animals on LPD (Md = 0.0%; P25 = 0.0%, P75 = 0.0%) and NPD (Md = 0.37%; P25 = 02%, P75 = 1.25%; p > 0.05). In protocol 3, the group LL showed GSA (Md = 1.3%; P25 0.6%, P75 = 2.5%) and IF (Md = 3.6%; P25 = 1.6%; P75 = 5.9%) smaller that those of LN (GSA Md = 10.1%; P25 = 6.6%; P75 = 14.8%; IF: Md = 17.3%; P25 = 14.1%; P75 = 24.5%), NL (GSA: Md = 9.1%; P25 = 5.8%; P75 = 11.7%; IF: Md = 25.0%; P25 = 20.4%; P75 = 30%), and NN (GSA: Md = 6.75%; P25 = 4.9%; P75 = 11.7%; IF: Md = 20.9%; P25 = 16.2%; P75 = 32.4%). In conclusion, in order to be effective, LPD must be introduced early and maintained for a long period of tune.

Sodium bicarbonate treatment reduces renal injury, renal production of transforming growth factor-beta, and urinary transforming growth factor-beta excretion in rats with doxorubicin-induced nephropathy

The aim of this study is to investigate the effect of sodium bicarbonate on doxorubicin-injected rats. Thirty female Wistar rats were injected with doxorubicin (3.5 mg/kg of body weight, intravenously) and 30 rats with 0.15 mol/L of sodium chloride solution (group C). Fifteen days later, we replaced the drinking water with a 0.15-mol/L sodium bicarbonate solution for 10 of the animals injected with doxorubicin (group AD-B). Three months after the beginning of treatment, urine samples were collected to quantify albumin, creatinine, and transforming growth factor-beta (TGF-beta). The rats were killed, and the kidneys were removed for histological, morphometric, immunohistochemical, and RNA studies. All doxorubicin-injected animals showed structural renal changes. However, these alterations were less intense in rats treated with doxorubicin plus sodium bicarbonate (P < 0.05). The percentage of glomerulosclerosis was 0.11% +/- 0.08% in group C, 14.7% +/- 12.8% in group AD (rats treated with doxorubicin only), and 4.38% +/- 1.9% in group AD-B, and the percentage of tubulointerstitial damage was 0. 01% +/- 0.03% in group C, 54.6% +/- 20.3% in group AD, and 16.6% +/- 10.3% in group AD-B. The immunostaining for TGF-beta in the renal cortex and glomeruli was more intense in the animals injected with doxorubicin only. A greater renal cortical TGF-beta messenger RNA content was observed in the animals injected with only doxorubicin that did not receive sodium bicarbonate (P < 0.05). These animals also presented a greater rate of urinary TGF-beta excretion reported as picograms of TGF-beta per milligram of urinary creatinine (P < 0.05), which was 202 +/- 11 pg/mg in group C, 1, 103 +/- 580 pg/mg in group AD, and 299 +/- 128 pg/mg in group AD-B. However, albuminuria was more intense in the sodium bicarbonate-treated animals (P < 0.05). The animals from group AD also showed higher immunostaining scores for vimentin and albumin in tubule cells (P < 0.05). In conclusion, treatment with sodium bicarbonate reduces structural renal damage, albumin reabsorption, and renal TGF-beta production in rats with doxorubicin-induced nephropathy.

Analysis of factors influencing chronic renal failure progression

One of the most important characteristics of chronic renal failure (CRF) is its progression to end stage renal disease. CRF progression depends of many factors indicated in numerous experimental and clinical studies. The present study was undertaken with the aim to examine the role of sex, etiology of CRF, renal function at the beginning of the study, hypertension and protein intake on CRF progression. Ninety-two patients (47 female and 45 male) aged between 17 and 70, with various underlying kidney diseases and various degrees of CRF were followed for 8 years. CRF progression was expressed as Creatinine clearance (CCr) and reciprocal values of serum Creatinine (SCr) against time. CRF progression was slower in women than in men, but not significantly. Patients with diabetic nephropathy (b = 0.00006) and glomerulonephritis (b = 0.00005) had faster progression of CRF than patients with nephrosclerosis (b = 0.00002), tubulointerstitial nephritis (b = 0.00003) and polycystic kidney disease (b = 0.00003). The fastest progression of CRF was in patients with the lowest SCr values at the beginning of the study. Proper regulation of blood pressure was the most important factor in slowing down CRF progression, independently of kind of antihypertensive drugs. Neither angiotensin converting enzyme inhibitors (b = -0.00001) nor calcium channel blockers (b = -0.00002) showed better effects on CRF progression slowing down in comparison with other antihypertensive drugs (b = -0.00001). Low protein diet slowed down CRF progression, but not significantly. In conclusion, our retrospective study confirms that CRF progression depends on sex, underlying renal diseases and serum Creatinine levels at the beginning of the study. Good regulation of blood pressure and low protein diet can slow down CRF progression.

Randomised multicentre study of a low-protein diet on the progression of chronic renal failure in children. European Study Group of Nutritional Treatment of Chronic Renal Failure in Childhood

BACKGROUND

Some studies have suggested that a low-protein diet slows the deterioration of renal function in patients with chronic renal failure (CRF). The effects of a low-protein diet on renal function and growth, have not been assessed in a large, prospective randomised trial in children with CRF.

METHODS

A 2-year prospective, stratified, and randomised multicentre study recruited 191 patients aged 2-18 years. After a run-in period of at least 6 months, patients were stratified into either a progressive or non-progressive category based on the change in creatinine clearance in this period. The patients were also stratified into three renal-disease categories and then randomly assigned to a control or diet group. In the diet group, the protein intake was the lowest, safe WHO recommendation--i.e., 0.8-1.1 g/kg daily adjusted for age. All patients were advised to have a calorie intake of at least 70% of the WHO recommendations. Glomerular filtration rate (GFR) was measured every 2 months by creatinine clearance; dietary compliance was checked by urinary urea-nitrogen excretion and dietary diaries (weighing method). 112 patients completed an optional third year of the study.

FINDINGS

The low-protein diet did not affect growth. However, there was no effect of diet on the mean decline in creatinine clearance over 2 years (diet vs control: progressive group -9.7 [SD 8.0] vs -10.7 [11.8] mL/min per 1.73 m2; non-progressive group -2.5 [7.5] vs -4.3 [10.0] mL/min per 1.73 m2). Patients classified as having progressive disease were older and had a lower creatinine clearance and a higher blood pressure at randomisation, and had a greater decrease in creatinine clearance than non-progressive patients. On multivariate regression analysis proteinuria (partial R2 = 0.259) and systolic blood pressure (partial R2 = 0.087) were independent predictors of the change in GFR. Similar results were found after the study was extended for a third year.

INTERPRETATION

A low-protein diet for 3 years did not affect the decrease in renal function in children with CRF. Proteinuria and blood pressure explain a large part of the variability of, and may be causally related to the decline in the GFR.

Proteinuria and albumin homeostasis in the nephrotic syndrome: effect of dietary protein intake

Nephrotic syndrome is analyzed in the light of interventions designed to decrease proteinuria and renal injury. The effect of dietary protein intake on urinary protein losses and albumin homeostasis are discussed on the basis of the pathophysiologic mechanisms known to account for changes in renal function of nephrotic patients. In addition, the effect of angiotensin-converting enzyme inhibitors for reduction of proteinuria is discussed in terms of the modulation of glomerular permselectivity and hemodynamics.

Short- or long-term effects of a low-protein diet on fibronectin and transforming growth factor-beta synthesis in Adriamycin-induced nephropathy

Increased synthesis and gene expression of fibronectin or transforming growth factor-beta (TGF-beta) have been reported to be involved in the progressive process of doxorubicin hydrochloride (Adriamycin)-induced nephropathy. In the present study, the effects of dietary protein restriction on the synthesis and gene expression of fibronectin or TGF-beta were investigated by immunoprecipitation, Northern blotting, and TGF-beta bioassay in this model after subjects were given either short- or long-term low-protein diets. In the long-term diet experiment, either a normal protein diet (NPD, 20%) or low-protein diet (LPD, 5%) was fed to the Adriamycin rats for 8 weeks after the injection of Adriamycin. An 8-week LPD significantly ameliorated kidney destruction and remarkably reduced the fibronectin synthesis. Furthermore, the significant decreases of the latent TGF-beta secretion and the expression of TGF-beta 1 mRNA were observed in the Adriamycin rats fed an 8-week LPD. In the short-term diet experiment, an NPD or LPD was fed to the Adriamycin rats for 2 weeks at weeks 4, 8, or 16 after the injection of Adriamycin. A 2-week LPD did not ameliorate kidney damage. Although fibronectin synthesis by the renal cortex in the Adriamycin rats was remarkably reduced by a 2-week LPD, there was no significant decrease in the latent TGF-beta secretion in the Adriamycin rats. The mRNA expressions of fibronectin or TGF-beta 1 were not affected by a 2-week LPD in the Adriamycin rats at any stage. In conclusion, decreased fibronectin and TGF-beta synthesis may be one of the mechanisms by which the long-term dietary protein restriction ameliorates kidney damage. On the other hand, a 2-week LPD affected the only fibronectin synthesis, which thus suggested that an LPD might exert a quicker influence on the protein synthesis of fibronectin than on the transcriptional events of fibronectin.

Energy and nutrient intake of patients with mild-to-moderate chronic renal failure compared with healthy children: an Italian multicentre study

Nutritional counselling is important in the management of children with chronic renal failure (CRF). In 1988, a controlled European multicentre study was started to evaluate the effects of a low-protein diet on the progression of CRF in children. To assess the energy, macro- and micronutrient intake, 4-day weighed dietary records were obtained from 50 children with low to moderate CRF (creatinine clearance 65 to 15 ml/min per 1.73 m2) and from 93 healthy children. The mean energy intake was 90%-93% of the recommended dietary allowance for Italian children in controls and 76%-88% in CRF patients. The mean protein intake was 2.1-3.1 g/kg per day in controls and 1.6-2.7 g/kg per day in CRF patients. Overall, the energy intake was 10% and the protein intake 33% lower in CRF patients than in healthy children. Children with CRF consumed less cholesterol, calcium and phosphorus than healthy children. The lower spontaneous intake of energy, protein and other nutrients should be taken into account when planning the nutrition of children with CRF.

Low-protein diet in children with chronic renal failure--1-year results. European Study Group for Nutritional Treatment of Chronic Renal Failure in Childhood

In 1988 the European Study for Nutritional Treatment of Children with Chronic Renal Failure started its multicentre randomized trial to investigate the influence of protein intake on the progression of renal failure. A total of 284 children had been registered. Of these 221 were accepted for the study. The data from 105 patients after 1 year of study are available for preliminary analysis. Fifty children were randomized for the diet group and 55 for the control group. Both groups were comparable concerning age, glomuerlar filtration rate (GFR) and height standard deviation score for chronological age at the start of the study period and the distribution of primary renal diseases and sex. Limits for protein and energy intake were set according to the safe levels and recommendations given by the World Health Organization. The compliance with dietary prescriptions as calculated from dietary diaries was good. A low-protein diet did not do any harm to the children with respect to length gain and weight gain. The progression of renal failure was minimal in the diet group (mean loss of GFR 3.6 ml/min per 1.73 m2 per year) as well as in the control group (2.3 ml/min per 1.73 m2 per year). The differences between the diet group and the control group were statistically not significant when either all patients or only subgroups of various primary renal diseases were analysed. When only patients with a good compliance were considered (documented by dietary diaries or by urea nitrogen excretion) the same results were obtained. In summary, reduction of protein intake was accepted by the majority of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute loading with proteins from different sources in healthy volunteers and diabetic patients

To evaluate the effects of protein loading on glomerular filtration rate (GFR), urinary excretion rate of albumin (AER), and plasma concentration of amino acids, 10 healthy volunteers and six diabetics were studied before and after eating tuna fish, egg white, cheese, or tofu. Furthermore, to study the possible role of glucagon, growth hormone (GH), atrial natriuretic peptide (ANP), or kallikrein in the responses of GFR, these substances were measured before and after protein loading. GFR increased significantly (p less than .001) after ingestion of tuna fish. No significant differences were seen between the GFR before and that after ingestion of the other foods. AER was unchanged following protein loading. Plasma concentrations of alanine, glycine, and arginine increased to a greater degree after ingestion of tuna fish than after digestion of the other foods. This result suggests that the response of GFR after protein loading may differ from one protein to another, and that these responses may not be directly mediated by glucagon, GH, ANP, or kallikrein.