Vitamin D in kidney transplant recipients
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Kidney transplant recipients (KTRs) are susceptible to low levels of vitamin D, which may be responsible for mineral and bone metabolism disorders and play some role in the occurrence of cardiovascular, metabolic, immunologic, neoplastic, and infectious complications after kidney transplant. Kidney Disease Improving Global Outcomes (KDIGO) guidelines of the year 2017 recommended vitamin D supplementation in the first 12 months after transplant using the same treatment strategies for the general population. However, no recommendations are provided after the first 12 months due to a lack of sufficient data. This review analyses some studies that assessed the vitamin D status of KTRs and the effects of nutritional and active vitamin D supplementation on bone mineral density, cardiovascular disease, proteinuria, and graft function in KTRs.

Vitamin D in patients with chronic kidney disease: a position statement of the Working Group "Trace Elements and Mineral Metabolism" of the Italian Society of Nephrology.

In the late 1970s, calcitriol was introduced into clinical practice for the management of secondary renal hyperparathyroidism in chronic kidney disease (CKD). Since then, the use of calcifediol or other native forms of vitamin D was largely ignored until the publication of the 2009 Kidney Disease Improving Global Outcomes (KDIGO) recommendations. The guidelines suggested that measurement of circulating levels of 25(OH)D (calcifediol) and its supplementation were to be performed on the same basis as for the general population. This indication was based on the fact that the precursors of active vitamin D had provided to CKD patients considerable benefits in survival, mainly due to their pleiotropic effects on the cardiovascular system. However, despite the long-term use of various classes of vitamin D in CKD, a clear definition is still lacking concerning the most appropriate time for initiation of therapy, the best compound to prescribe (active metabolites or analogs), the proper dosage, and the most suitable duration of therapy. The aim of this position statement is to provide and critically appraise the current plentiful evidence on vitamin D in different clinical settings related to CKD, particularly focusing on outcomes, monitoring and treatment-associated risks. However, it should be taken in account that position statements are meant to provide guidance; therefore, they are not to be considered prescriptive for all patients and, importantly, they cannot replace the judgment of clinicians.

Partially hydrolyzed guar gum in the treatment of irritable bowel syndrome with constipation: effects of gender, age, and body mass index.

BACKGROUND/AIMS: Partially hydrolyzed guar gum (PHGG) relieves symptoms in constipation-predominant irritable bowel syndrome (IBS) and may have prebiotic properties. However, the correlation between the effectiveness of PHGG and patient characteristics has not been examined. We aimed to investigate the effect of PHGG in symptom relief on constipation-predominant IBS according to gender, age, and body mass index (BMI). PATIENTS AND METHODS: Sixty-eight patients with IBS entered a 2-week run-in period, followed by a 4-week study period with PHGG. Patients completed a daily questionnaire to assess the presence of abdominal pain/discomfort, swelling, and the sensation of incomplete evacuation. The number of evacuations/day, the daily need for laxatives/enemas and stool consistency-form were also evaluated. All patients also underwent a colonic transit time (CTT) evaluation. RESULTS: PHGG administration was associated with a significant improvement in symptom scores, use of laxatives/enemas, stool form/consistency and CTT. At the end of the study period and compared with baseline, the number of evacuations improved in women, patients aged ≥ 45 years and those with BMI ≥ 25 (P < 0.05 for all comparisons); abdominal bloating improved in males (P < 0.05), patients < 45 years (P < 0.01) and those with BMI < 25 (P < 0.05). A decrease in the number of perceived incomplete evacuations/day was reported in patients with a BMI ≥ 25 (P < 0.05). Reductions in laxative/enema use were recorded in females (P < 0.05), patients < 45 years (P < 0.01), and patients with BMI < 25 (P < 0.05). CONCLUSIONS: Gender, age, and BMI seem to influence the effect of PHGG supplementation in constipated IBS patients. Further studies are needed to clarify the interaction of such parameters with a fiber-enriched diet.

Effects of phosphorus-restricted diet and phosphate-binding therapy on outcomes in patients with chronic kidney disease.

BACKGROUND: Phosphorus is associated with mortality in patients with chronic kidney disease (CKD) not on dialysis, possibly through phosphorus-dependent vascular calcification. Although a phosphorus-restricted diet reduces serum phosphorus, it is unlikely that it reduces vascular calcification progression in CKD. This study evaluated whether a combined strategy of phosphorus-restricted diet and phosphate-binding therapy can reduce the risk of all-cause mortality and/or dialysis initiation by attenuating coronary artery calcification (CAC) progression in non-dialysis CKD patients. METHODS: This was a post hoc analysis of a subgroup of patients from a study that evaluated the impact of two phosphorus binder regimens on hard outcomes in CKD. Patients (n = 113) with stage 3-4 CKD and evidence of CAC on a phosphorus-restricted diet were randomized to receive either calcium carbonate or sevelamer added to their phosphorus-restricted diet. End-points were death for any cause and initiation of dialysis. Patients were monitored to the first event or to conclusion of the 36-month follow-up. RESULTS: Overall, treatment with calcium carbonate was associated with increased CAC progression and occurrence of all-cause mortality, dialysis initiation, and the composite end-point. After adjustment for confounders, sevelamer use was the only independent predictive factor of reduced risk of each endpoint but only if CAC progression was either absent or moderate. Accelerated progression (annual CAC increase >75th percentile of the study cohort) increased the risk of all-cause mortality and composite end-point (p = 0.01) independently of the use of sevelamer. CONCLUSIONS: A significant reduction in all-cause mortality, dialysis initiation, and composite end-point risk was achieved by combining phosphorus-restricted diet and sevelamer in non-dialysis CKD patients with absent or moderate but not accelerated CAC progression. Future studies should investigate the role of serum phosphorus, the usefulness of a phosphorus-restricted diet, and the appropriateness of current normal ranges of serum phosphorus concentration in relation to events in non-dialyzed CKD patients.

Impact of BMI on cardiovascular events, renal function, and coronary artery calcification.

BACKGROUND/AIMS: High BMI increases the risk of cardiovascular events (CVEs) in the general population. Conflicting results have been reported on the role of BMI on CVEs and on decline of renal function in patients with chronic kidney disease not on dialysis (CKD). This study evaluates the impact of BMI on CVEs, dialysis initiation, and coronary artery calcification (CAC) in CKD patients. METHODS: CKD patients were divided in normal-BMI and high-BMI patients. CVEs, initiation of dialysis, and extent and progression of CAC were assessed. Univariate and multivariable analysis were performed (adjustment variables: age, diabetes, hypertension, gender, CKD stage, serum concentration of hemoglobin, parathyroid hormone, calcium, phosphorus, albumin, C-reactive protein, LDL-cholesterol, total calcium score, 24-hour proteinuria). Patients were followed to the first event (CVE, dialysis) or for 2 years. RESULTS: 471 patients were evaluated. A CVE occurred in 13.5 and 21.3% (p < 0.05) of normal-BMI and high-BMI patients, respectively. High BMI did not increase the risk for CVEs in univariate (HR: 1.86; 95% CI: 0.97-3.54; p = 0.06) or multivariable analysis (HR: 1.36; 95% CI: 0.57-3.14; p = 0.50). High BMI did not increase the risk for initiation of dialysis in univariate (HR: 0.96; 95% CI: 0.58-1.60; p = 0.9) or multivariable analysis (HR: 1.77; 95% CI: 0.82-3.81; p = 0.14). Adding the interaction term (between BMI and glomerular filtration rate) to other variables, the risk of dialysis initiation significantly increased (HR: 3.06; 95% CI: 1.31-7.18; p = 0.01) in high-BMI patients. High BMI was not a predictor of CAC extent or progression. CONCLUSIONS: High BMI was not a predictor of CVEs. High BMI increased the risk for dialysis initiation, but high BMI was not associated to CAC extent and progression. The presence of confounders may underestimate the impact of high BMI on dialysis initiation.