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BACKGROUND@#High levels of plasma homocysteine occur almost uniformly in patients with end-stage renal disease (ESRD). IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis and a common cause of ESRD in young adults. Here, we aimed to detect whether homocysteine was elevated and associated with clinical-pathologic manifestations of IgAN patients and tested its causal effects using a two-sample Mendelian randomization (MR) approach.@*METHODS@#For observational analysis, 108 IgAN patients, 30 lupus nephritis (LN) patients, 50 minimal change disease (MCD) patients, and 206 healthy controls were recruited from April 2014 to April 2015. Their plasma homocysteine was measured and clinical-pathologic manifestations were collected from medical records. For MR analysis, we further included 1686 IgAN patients. The missense variant methylenetetrahydrofolate reductase C677T (rs1801133) was selected as an instrument, which was genotyped by TaqMan allele discrimination assays.@*RESULTS@#Majority of IgAN patients (93.52%, 101/108) showed elevated levels of plasma homocysteine (>10 μmol/L). Plasma homocysteine in IgAN patients was significantly higher than that in MCD patients (median: 18.32 vs. 11.15 μmol/L, Z = -5.29, P < 0.01) and in healthy controls (median: 18.32 vs. 10.00 μmol/L, Z = -8.76, P < 0.01), but comparable with those in LN patients (median: 18.32 L vs. 14.50 μmol/L, Z = -1.32, P = 0.19). Significant differences were observed in sub-groups of IgAN patients according to quartiles of plasma homocysteine for male ratio (22.22% vs. 51.85% vs. 70.37% vs. 70.37%, χ = 14.29, P < 0.01), serum creatinine (median: 77.00 vs. 100.00 vs. 129.00 vs. 150.00 μmol/L, χ = 34.06, P < 0.01), estimated glomerular filtration rate (median: 100.52 vs. 74.23 vs. 52.68 vs. 42.67 mL·min·1.73 m, χ = 21.75, P < 0.01), systolic blood pressure (median: 120.00 vs. 120.00 vs. 125.00 vs. 130.00 mmHg, χ = 2.97, P = 0.05), diastolic blood pressure (median 80.00 vs. 75.00 vs. 80.00 vs. 81.00 mmHg, χ = 11.47, P < 0.01), and pathologic tubular atrophy and interstitial fibrosis (T) (T0/T1/T2: 62.96%/33.33%/3.70% vs. 29.63%/40.74%/29.63% vs. 24.00%/48.00%/28.00% vs. 14.81%/37.04%/48.15%, χ = 17.66, P < 0.01). The coefficient of each rs1801133-T allele on homocysteine levels after controlling age and sex was 7.12 (P < 0.01). MR estimates showed causal positive effects of homocysteine on serum creatine (β = 0.76, P = 0.02), systolic blood pressure (β = 0.26, P = 0.02), diastolic blood pressure (β = 0.20, P = 0.01), and pathologic T lesion (β = 0.01, P = 0.01) in IgAN.@*CONCLUSIONS@#By observational and MR analyses, consistent results were observed for associations of plasma homocysteine with serum creatinine, blood pressures, and pathologic T lesion in IgAN patients.
ABSTRACT
Immunometabolism, focusing on the changes in intracellular metabolic pathways in immune cells that alter their function, is one of the most important research fields in recent years. Researches on the metabolism of carbohydrates, lipids,and proteins of immune cells shed important light on a better understanding of the physiological and pathological mechanisms of several diseases. For example, innate and adaptive immunity have been recently confirmed to be involved in obesity, further increasing risk of type 2 diabetes, cardiovascular disease, cancer and neurodegenerative disease. Interactions between metabolic aberrations and chronic kidney diseases always lead to a vicious spiral in disease etiology and progression. Up to date, emerging evidence has also indicated a therapeutic role of immune-metabolism. In this perspective,we aim to discuss some of these novel findings, with a special focus on how protein metabolism shaping immune system and gut microbiome in kidney disease. We hope the readers find our account understandable, interesting and thought-provoking for their own research.
ABSTRACT
OBJECTIVE@#To compare the genetic architecture of susceptibility variants of IgA nephropathy (IgAN) in Chinese and Europeans.@*METHODS@#We selected the independent genome-wide significant variants of IgAN in European population as candidate variants. Their associations, risk alleles, risk allele frequencies, odds ratios and population attributable risk scores were derived and calculated, then compared with those in the current Chinese population, including 1 194 IgAN patients and 902 controls. Using the significant variants, genetic risk scores were calculated and compared between the East Asians and the Europeans. The correlation between the genetic risk scores and clinical manifestations was also evaluated.@*RESULTS@#There were 16 independent single nucleotide polymorphisms (SNPs) located in 11 loci showing significantly association with susceptibility to IgAN in the Europeans. 93.75% (15/16) of them also showed significant associations in the Chinese (P<0.05). The effects of all the associated SNPs were in the same direction, either risk or being protective for IgAN, between the Chinese and the Europeans. On the contrary, remarkable higher risk allelic odds ratio (P=1.94×10-2), higher risk allele frequency (P=3.09×10-2), and higher population attributable risk (P=3.03×10-4) were observed for most of the associated SNPs in the Chinese than in the Europeans. Furthermore, genetic risk scores were significantly larger in the Asian populations compared with the Europeans (P=1.78×10-163). While there was no significance among the subpopulations in both the East Asians and the Europeans. Compared with the healthy controls, the genetic risk score in the IgAN patients was significantly larger (P=3.60×10-27). Clinical analysis showed the genetic risk score was positively associated with serum levels of IgA and IgA1, phases of chronic kidney disease and Haas grades.@*CONCLUSION@#Our study provides further evidence in the shared genetic architecture between Chinese and Europeans, while differences with respect to the effect sizes and risk allele frequencies across ethnicities, contributing partially to the differences of disease prevalence.
Subject(s)
Humans , Asian People , Case-Control Studies , Gene Frequency , Genetic Predisposition to Disease , Glomerulonephritis, IGA , Polymorphism, Single NucleotideABSTRACT
<p><b>BACKGROUND</b>A previous study has shown that rs548234 polymorphism at PRDM1-ATG5 region is associated with rheumatoid arthritis (RA) in Caucasian populations. The aim of this study was to investigate the effect of rs548234 polymorphism at PRDM1-ATG5 region on susceptibility to RA in Chinese Han population.</p><p><b>METHODS</b>We genotyped 848 RA patients and 1431 matched healthy controls for rs548234 single-nucleotide polymorphism (SNP) with a predesigned TaqMan SNP genotyping assay. Association analyses were performed on the whole data set and on rheumatoid factors (RF) and anti-cyclic citrullinated peptides (anti-CCP) antibody. Finally, we carried out combined analysis of rs548234 association with RA based on the published data.</p><p><b>RESULTS</b>No significant difference in the genotype distribution between RA patients and healthy controls for rs548234 (C/T) polymorphism was found in Chinese Han population, neither in whole data set nor in stratified subsets, e.g. RF and anti-CCP status. Association analysis in different ethnic groups showed that rs548234 at PRDM1-ATG5 region was associated with RA in Caucasian ancestry but not in East Asian population.</p><p><b>CONCLUSIONS</b>Our results showed no involvement of rs548234 at PRDM1-ATG5 region in the susceptibility or clinical relevance of RA in Chinese Han population.</p>