Niacin in patients with chronic kidney disease: Is it effective and safe?

Vitamin Supplement Use in Patients With CKD: Worth the Pill Burden?

All vitamins play essential roles in various aspects of body function and systems. Patients with chronic kidney disease (CKD), including those receiving dialysis, may be at increased risk of developing vitamin deficiencies due to anorexia, poor dietary intake, protein energy wasting, restricted diet, dialysis loss, or inadequate sun exposure for vitamin D. However, clinical manifestations of most vitamin deficiencies are usually subtle or undetected in this population. Testing for circulating levels is not undertaken for most vitamins except folate, B12, and 25-hydroxyvitamin D because assays may not be available or may be costly to perform and do not always correlate with body stores. The last systematic review through 2016 was performed for the Kidney Disease Outcome Quality Initiative (KDOQI) 2020 Nutrition Guideline update, so this article summarizes the more recent evidence. We review the use of vitamins supplementation in the CKD population. To date there have been no randomized trials to support the benefits of any vitamin supplementation for kidney, cardiovascular, or patient-centered outcomes. The decision to supplement water-soluble vitamins should be individualized, taking account the patient's dietary intake, nutritional status, risk of vitamins deficiency/insufficiency, CKD stage, comorbid status, and dialysis loss. Nutritional vitamin D deficiency should be corrected, but the supplementation dose and formulation need to be personalized, taking into consideration the degree of 25-hydroxyvitamin D deficiency, parathyroid hormone levels, CKD stage, and local formulation. Routine supplementation of vitamins A and E is not supported due to potential toxicity. Although more trial data are required to elucidate the roles of vitamin supplementation, all patients with CKD should undergo periodic assessment of dietary intake and aim to receive various vitamins through natural food sources and a healthy eating pattern that includes vitamin-dense foods.

Neuroprotective Effects of Nicotinamide against MPTP-Induced Parkinson's Disease in Mice: Impact on Oxidative Stress, Neuroinflammation, Nrf2/HO-1 and TLR4 Signaling Pathways

Nicotinamide (NAM) is the amide form of niacin and an important precursor of nicotinamide adenine dinucleotide (NAD), which is needed for energy metabolism and cellular functions. Additionally, it has shown neuroprotective properties in several neurodegenerative diseases. Herein, we sought to investigate the potential protective mechanisms of NAM in an intraperitoneal (i.p) 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) mouse model (wild-type mice (C57BL/6N), eight weeks old, average body weight 25-30 g). The study had four groups (n = 10 per group): control, MPTP (30 mg/kg i.p. for 5 days), MPTP treated with NAM (500 mg/kg, i.p for 10 days) and control treated with NAM. Our study showed that MPTP increased the expression of α-synuclein 2.5-fold, decreased tyrosine hydroxylase (TH) 0.5-fold and dopamine transporters (DAT) levels up to 0.5-fold in the striatum and substantia nigra pars compacta (SNpc), and impaired motor function. However, NAM treatment significantly reversed these PD-like pathologies. Furthermore, NAM treatment reduced oxidative stress by increasing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) between 0.5- and 1.0-fold. Lastly, NAM treatment regulated neuroinflammation by reducing Toll-like receptor 4 (TLR-4), phosphorylated nuclear factor-κB, tumor (p-NFκB), and cyclooxygenase-2 (COX-2) levels by 0.5- to 2-fold in the PD mouse brain. Overall, these findings suggest that NAM exhibits neuroprotective properties and may be an effective therapeutic agent for PD.

Urinary metabolic characterization with nephrotoxicity for residents under cadmium exposure

Cadmium is a well-known hazardous pollutant that mainly comes from dietary, tobacco and occupational exposure, posing threat to kidney. However, there is still a lack of systematic study on metabolic pathways and urinary biomarkers related to its nephrotoxicity under cadmium exposure for both females and males. In this study, a mass spectrometry-based metabolomics investigation of a cohort of 144 volunteers was conducted to explore sex-specific metabolic alteration and to screen biomarkers related to cadmium-induced nephrotoxicity. When the concentration of urinary cadmium increased, creatine pathway, amino acid metabolism especially the tryptophan metabolism, aminoacyl-tRNA biosynthesis, and purine metabolism were primarily influenced regardless of the gender. Also, the most specific biomarkers linked with nephrotoxicity based on the statistical analysis were detected including creatine, creatinine, l-tryptophan, adenine and uric acid. The study outcome might provide information to reflect the body burden and help improve health policy for risk assessment.

Urinary Excretion of N1-Methylnicotinamide and N1-Methyl-2-Pyridone-5-Carboxamide and Mortality in Kidney Transplant Recipients

It is unclear whether niacin nutritional status is a target for improvement of long-term outcome after renal transplantation. The 24-h urinary excretion of N¹-methylnicotinamide (N¹-MN), as a biomarker of niacin status, has previously been shown to be negatively associated with premature mortality in kidney transplant recipients (KTR). However, recent evidence implies higher enzymatic conversion of N¹-MN to N¹-methyl-2-pyridone-5-carboxamide (2Py) in KTR, therefore the need exists for interpretation of both N¹-MN and 2Py excretion for niacin status assessment. We assessed niacin status by means of the 24-h urinary excretion of the sum of N¹-MN and 2Py (N¹-MN + 2Py), and its associations with risk of premature mortality in KTR. N¹-MN + 2Py excretion was measured in a longitudinal cohort of 660 KTR with LS-MS/MS. Prospective associations of N¹-MN + 2Py excretion were investigated with Cox regression analyses. Median N¹-MN + 2Py excretion was 198.3 (155.9–269.4) µmol/day. During follow-up of 5.4 (4.7–6.1) years, 143 KTR died, of whom 40 due to an infectious disease. N¹-MN + 2Py excretion was negatively associated with risk of all-cause mortality (HR 0.61; 95% CI 0.47–0.79; p < 0.001), and infectious mortality specifically (HR 0.47; 95% CI 0.29–0.75; p = 0.002), independent of potential confounders. Secondary analyses showed effect modification of hs-CRP on the negative prospective association of N¹-MN + 2Py excretion, and sensitivity analyses showed negative and independent associations of N¹-MN and 2Py excretion with risk of all-cause mortality separately. These findings add further evidence to niacin status as a target for nutritional strategies for improvement of long-term outcome in KTR.