Greater Dietary Inflammatory Index score is associated with higher likelihood of chronic kidney disease

Chronic kidney disease (CKD) is described as a progressive alteration of kidney function, resulting from multiple factors, including behaviours. We investigated the association of the Dietary Inflammatory Index (DII®) with prevalent CKD in adult Americans. National Health and Nutrition Examination Survey participants with measured data on kidney function markers from 2005 to 2012 were included in this study. Prevalent CKD was based on an estimated glomerular filtration rate (eGFR) <60 ml/min per 1·73 m2 or urinary albumin/creatinine≥30 mg/g. Energy-adjusted DII (E-DIITM) scores were calculated from 24-h dietary recalls. Statistical analyses accounted for the survey design and sample weights. We included 21 649 participants, with 1634 (6·8 %) having prevalent CKD. Participants with high E-DII scores had greater BMI, fasting blood glucose and systolic blood pressure, and were more likely to be diabetic or hypertensive (all P<0·001) compared with those with lower E-DII scores. In regression models adjusted for age, sex, race, fasting blood glucose, blood pressure, BMI, hypertension and diabetes status, mean eGFR significantly decreased across increasing quartiles of E-DII, whereas serum uric acid level and log urinary albumin:creatinine ratio significantly increased (all P<0·001). Prevalent CKD increased from 5·3 % in the lowest to 9·3 % in the highest E-DII quartile (P=0·02). In multivariable-adjusted logistic regression models, the odds of prevalent CKD were 29 % higher in the highest compared with the lowest E-DII quartile. Pro-inflammatory diet is associated with declining kidney function and high prevalence of CKD. Dietary changes that reduce inflammation have a potential to prevent CKD.

A higher ratio of refined grain to whole grain is associated with a greater likelihood of chronic kidney disease: a population-based study

A growing number of studies suggest that diet and renal function are related. However, little is known about the link between both whole grain (WG) and refined grain (RG) consumption and kidney function parameters. Thus, we investigated the association of WG and RG with urinary albumin to creatinine ratio (ACR) and prevalent chronic kidney disease (CKD). Data from participants of the National Health and Nutrition Examination Surveys (NHANES) from 2005 to 2010 were collected. Estimated glomerular filtration rate (eGFR) was calculated by the CKD Epidemiology Collaboration equation. Survey design and sample weights were taken into consideration for statistical analyses. Finally, we included 16 325 participants from NHANES, 6·9 % of whom had prevalent CKD. In models adjusted for age, sex, race, fasting blood glucose, blood pressure, adiposity, hypertension and diabetes status, mean eGFR significantly increased across increasing quartiles of WG (Q1: 88·2 v. Q4: 95·4 ml/min per 1·73 m2, P&lt;0·001), whereas it significantly decreased across increasing quartiles of RG (Q1: 97·2 v. Q4: 88·4 ml/min per 1·73 m2, P&lt;0·001). Furthermore, serum uric acid levels and ACR significantly decreased across quartiles of WG (both P&lt;0·001). In multivariable-adjusted logistic regression models, the likelihood of prevalent CKD was 21 % lower in the highest WG quartile compared with the lowest one. In conclusion, our results shed light on the beneficial impact of WG on kidney function and CKD, whereas RG is adversely associated with eGFR.

Dietary fibre intake in relation to the risk of incident chronic kidney disease

The purpose of this study was primarily to evaluate the association of total fibre intake with the risk of incident chronic kidney disease (CKD). We also evaluated the association of dietary fibre from fruits, vegetables, cereals and legumes with the incidence of CKD in a population-based prospective study. We followed up 1630 participants of the Tehran Lipid and Glucose Study for 6·1 years, who were initially free of CKD. Baseline diet was assessed by a valid and reliable FFQ. Estimated glomerular filtration rate (eGFR) was calculated, using the Modification of Diet in Renal Disease Study equation, and CKD was defined as eGFR <60 ml/min per 1·73 m2. OR using multivariable logistic regression was reported for the association of incident CKD with tertiles of dietary fibre intake. After adjustment for age, sex, smoking, total energy intake, physical activity, diabetes and using angiotensin-converting-enzyme inhibitor, the OR for subjects in the highest compared with the lowest tertile of total fibre intake was 0·47 (95 % CI 0·27, 0·86). In addition, for every 5 g/d increase in total fibre intake, the risk of incident CKD decreased by 11 %. After adjusting for potential confounders, OR for participants in the highest compared with the lowest tertile of fibre from vegetables was 0·63 (95 % CI 0·43, 0·93) and from legumes it was 0·68 (95 % CI 0·47, 0·98). We observed inverse associations between total fibre intake and risk of incident CKD, which demonstrate that high fibre intake, mainly from legumes and vegetables, may reduce the occurrence of CKD.

Low-protein diet supplemented with ketoacids delays the progression of diabetic nephropathy by inhibiting oxidative stress in the KKAy mice model

Diabetic nephropathy (DN) is a major cause of chronic kidney disease. We aimed to investigate the effect of the low-protein diets (LPD) supplemented with ketoacids (LPD+KA) in KKAy mice, an early type 2 DN model. KKAy mice were treated with normal protein diet (NPD), LPD or LPD+KA from 12 to 24 weeks of age. A period of 12-week treatment with LPD significantly reduced albuminuria as compared with that observed after NPD treatment. Treatment with LPD+KA further reduced albuminuria as compared with that observed with LPD treatment alone. Moreover, LPD treatment reduced mesangial expansion, thickness of glomerular basement membrane and the severity of the podocyte foot process effacement in KKAy mice; these effects were more pronounced in KKAy mice treated with LPD+KA. Both LPD and LPD+KA treatments slightly reduced total body weight, but had no significant effect on kidney weight and blood glucose concentrations when compared with NPD-treated KKAy mice. LPD treatment slightly attenuated oxidative stress in kidneys as compared with that observed in NPD-treated KKAy mice; however, LPD+KA treatment remarkably ameliorated oxidative stress in diabetic kidneys as shown by decreased malondialdehyde concentrations, protein carbonylation, nitrotyrosine expression and increased superoxide dismutase expression. Nutritional therapy using LPD+KA confers additional renal benefits as compared with those of LPD treatment alone in early type 2 DN through inhibition of oxidative stress.

Consumption of whole grains, fruit and vegetables is not associated with indices of renal function in the population-based longitudinal Doetinchem study

Emerging evidence suggests that diet and renal function are related. Little is known, however, about the association of consumption of whole grains, fruit and vegetables with urinary albumin:creatinine ratio (ACR) and changes in estimated glomerular filtration rate (eGFR). We investigated this in a population-based cohort aged 26-65 years. Data were from 3787 participants from the Doetinchem cohort study, who were examined ≥3 times, 5 years apart. Consumption of food groups was assessed at each round with a validated FFQ. GFR was estimated at each round from routinely measured cystatin C and creatinine using the Chronic Kidney Disease-Epidemiology (CKD-EPI) equation. ACR was measured at the last round. Generalised estimated equation models were performed to examine associations with changes in eGFR. Linear regression was used to examine associations with ACR. Adjustments were made for covariates related to lifestyle, biological factors and diet. Mean baseline eGFR was 104·5 (sd 13·7) and mean annual decline was -0·95 (sd 0·67) ml/min per 1·73 m2 over a 15-year follow-up. A trend was observed towards slightly less annual decline in eGFR among those with higher consumption of whole grains (P=0·06). This association, however, was attenuated and no longer significant in multivariate models (P=0·29). Consumption of fruit and vegetables was not associated with changes in eGFR and urinary ACR. In conclusion, consumption of whole grains, fruit and vegetables is not associated with changes in eGFR and mean ACR. As this was the first longitudinal study into this association in the general population, and as results are only partially in line with related studies, further research is recommended.

Waist circumference as a predictor of mortality in peritoneal dialysis patients: a follow-up study of 48 months

Body-fat gain is a common finding among peritoneal dialysis (PD) patients, and the accumulation of adipose tissue occurs predominantly in the abdominal area. Waist circumference (WC) is a reliable marker of abdominal obesity and its association with worse outcomes has been demonstrated in non-dialysis and haemodialysis patients. We aimed at investigating whether WC measurements as well as the changes over time in WC were able to predict mortality in PD patients. This prospective study included 109 patients undergoing PD (57 % male, age 52 (sd 16) years, 32 % diabetics, 48 % BMI≥25 kg/m2). WC was measured at the umbilicus level (empty abdominal cavity), and values >88 cm for women and >102 cm for men were considered high. Nutritional status and laboratory parameters were also evaluated. WC was measured at baseline and after 6 months, and mortality was registered during a period of 48 months. High WC was observed in 55 % of women and in 23 % of men at baseline. After 6 months, 61 % of the patients showed an increased WC. At the end of the study, twenty-seven deaths were registered. A significant increase in WC was observed only in the non-survivor group. In the Cox regression analysis adjusting for sex, age, duration on dialysis, diabetes, BMI, serum albumin and C-reactive protein, high WC at baseline as well as the 6-month increase in WC were independently associated with mortality. This study demonstrated that a high WC and the increase over time in WC were both predictors of mortality in PD patients.

Hb level, iron intake and mortality in Chinese adults: a 10-year follow-up study

Anaemia is prevalent in developing countries and is commonly Fe deficiency related. We aimed to assess the association between Fe status, Fe intake and mortality among Chinese adults. We prospectively studied 8291 adults aged 20-98 years with a mean follow-up of 9·9 years. All participants were measured for Hb at baseline in 2002. Food intake, measured by 3-d weighed food record (n 2832), and fasting serum ferritin were measured. We documented 491 deaths (including 192 CVD and 165 cancer deaths) during 81 527 person-years of follow-up. There was a U-shaped association between Hb levels and all-cause mortality. Compared with the second quartile of Hb (121 g/l), the first (105) and fourth quartile (144) had hazard ratios (HR) of 2·29 (95 % CI 1·51, 3·48) and 2·31 (95 % CI 1·46, 3·64) for all-cause mortality in women. In men, compared with third quartile of Hb (143 g/l), first (122) and fourth quartiles (154) had 61 and 65 % increased risk of all-cause mortality. Anaemia was associated with an increased risk of all-cause and CVD mortality in men but not in women after adjusting for potential confounders. Low and high Fe intake as percentage of Chinese recommended nutrient intake (RNI) were positively associated with all-cause mortality in women but not in men. In women, across quartiles of relative Fe intake, HR for all-cause mortality were 2·55 (95 % CI 0·99, 6·57), 1·00, 3·12 (95 % CI 1·35, 7·18) and 2·78 (95 % CI 1·02, 7·58). Both low and high Hb levels are related to increased risk of all-cause mortality. Both low and high intake of Fe as percentage of RNI was positively associated with mortality in women.

Cholecalciferol v. ergocalciferol for 25-hydroxyvitamin D (25(OH)D) repletion in chronic kidney disease: a randomised clinical trial

Patients with chronic kidney disease (CKD) demonstrate complex mineral metabolism derangements and a high prevalence of vitamin D deficiency. However, the optimal method of 25-hydroxyvitamin D (25(OH)D) repletion is unknown, and trials analysing the comparative efficacy of cholecalciferol and ergocalciferol in this population are lacking. We conducted a randomised clinical trial of cholecalciferol 1250μg (50 000 IU) weekly v. ergocalciferol 1250μg (50 000 IU) weekly for 12 weeks in forty-four non-dialysis-dependent patients with stage 3-5 CKD. The primary outcome was change in total 25(OH)D from baseline to week 12 (immediately after therapy). Secondary analyses included the change in 1,25-dihydroxyvitamin D (1,25(OH)2D), parathyroid hormone (PTH), D2 and D3 sub-fractions of 25(OH)D and 1,25(OH)2D and total 25(OH)D from baseline to week 18 (6 weeks after therapy). Cholecalciferol therapy yielded a greater change in total 25(OH)D (45·0 (sd 16·5) ng/ml) v. ergocalciferol (30·7 (sd 15·3) ng/ml) from baseline to week 12 (P<0·01); this observation partially resulted from a substantial reduction in the 25(OH)D3 sub-fraction with ergocalciferol. However, following cessation of therapy, no statistical difference was observed for total 25(OH)D change from baseline to week 18 between cholecalciferol and ergocalciferol groups (22·4 (sd 12·7) v. 17·6 (sd 8·9) ng/ml, respectively; P=0·17). We observed no significant difference between these therapies with regard to changes in serum PTH or 1,25(OH)2D. Therapy with cholecalciferol, compared with ergocalciferol, is more effective at raising serum 25(OH)D in non-dialysis-dependent CKD patients while active therapy is ongoing. However, levels of 25(OH)D declined substantially in both arms following cessation of therapy, suggesting the need for maintenance therapy to sustain levels.

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.

Reduction in sodium intake is independently associated with improved blood pressure control in people with chronic kidney disease in primary care

Decreasing sodium intake has been associated with improvements in blood pressure (BP) and proteinuria, two important risk factors for CVD and chronic kidney disease (CKD) progression. We aimed to investigate the role of sodium intake by examining the effect of changes in sodium intake over 1 year on BP and proteinuria in people with early stage CKD. From thirty-two general practices, 1607 patients with previous estimated glomerular filtration rate of 59-30 ml/min per 1.73 m² and mean age of 72.9 (sd 9.0) years were recruited. Clinical assessment, urine and serum biochemistry testing were performed at baseline and after 1 year. Sodium intake was estimated from early morning urine specimens using an equation validated for this study population. We found that compared with people who increased their sodium intake from ≤ 100 to >100 mmol/d over 1 year, people who decreased their intake from >100 to ≤ 100 mmol/d evidenced a greater decrease in all BP variables (Δmean arterial pressure (ΔMAP) = -7.44 (SD 10.1) v. -0.23 (SD 10.4) mmHg; P<0.001) as well as in pulse wave velocity (ΔPWV = -0.47 (SD 1.3) v. 0.08 (SD 1.88) m/s; P<0.05). Albuminuria improved only in albuminuric patients who decreased their sodium intake. BP improved in people who maintained low sodium intake at both times and in those with persistent high intake, but the number of anti-hypertensive increased only in the higher sodium intake group, and PWV improved only in participants with lower sodium intake. Decreasing sodium intake was an independent determinant of ΔMAP. Although more evidence is needed, our results support the benefits of reducing and maintaining sodium intake below 100 mmol/d (2.3-2.4 g/d) in people with early stages of CKD.