Correlation of Body Mass Index with Clinicopathologic Parameters in Patients with Idiopathic Membranous Nephropathy

Causal associations between environmental factors and risk of IgA nephropathy and membranous nephropathy: a bidirectional Mendelian randomization and mediation analysis

AIMS

IgA nephropathy (IgAN) and membranous nephropathy (MN) have intricate etiologies that are poorly understood. This study aimed to investigate the impact of genetically predicted environmental factors on IgAN and MN.

METHODS

We used bidirectional two-step Mendelian randomization (MR) analysis utilizing large-scale genome-wide association study (GWAS) data to investigate the relationships between 68 environmental exposures and IgAN and MN. The main method is inverse variance weighted (IVW). Sensitivity analyses were conducted to validate the causal estimates. Furthermore, the two-step MR was used to explore possible mediating effects.

RESULTS

A total of 20 significant causal associations were identified. Genetically predicted educational attainment (EA), average household income, gluten-free diet, cheese intake, fresh fruit intake, cognitive performance, and intelligence were associated with a reduced risk of IgAN (p < 0.05); whereas frequency of alcohol consumption, insomnia, triglycerides, transferrin saturation, percentage body fat, body mass index (BMI), waist circumference, and blood pressure were associated with the risk of IgAN (p < 0.05). Genetically predicted EA and moderate to vigorous physical activity were associated with a reduced risk of MN (p < 0.05); on the other hand, beef intake, waist-to-hip ratio, and nitrogen oxides were associated with the risk of MN (p < 0.05). In addition, we observed that insomnia, BMI, and waist circumference partially mediated the causal link between EA and IgAN, with mediation proportions of 12.52%, 11.06%, and 9.93%, respectively.

CONCLUSIONS

This study provides novel evidence of causal relationships between 20 genetically predicted environmental factors and the risk of IgAN and MN. These findings may inform targeted prevention strategies and contribute to improved disease risk assessment.

Relationship of body mass index and kidney outcomes in patients with primary glomerulonephritis: A systematic review and meta-analysis

BACKGROUND

Primary glomerulonephritis, is a major contributor to the development of chronic kidney disease and end-stage renal disease. Previous studies on the relationship between overweight/obesity with primary glomerulonephritis in the chronic kidney disease was inconsistent. This study aimed to systematically review and meta-analyze the relationship between body mass index and adverse kidney outcomes in patients with primary glomerulonephritis.

METHODS

PubMed, Embase, the Cochrane Library, and the China National Knowledge Infrastructure were searched. Patients were divided into an overweight/obesity group (group O) and a non-overweight/obesity group (group N) according to their body mass index values.

RESULTS

Twenty-six studies with 11,038 patients were selected. Patients in group O had deteriorated baseline characteristics, including worse baseline estimated glomerular filtration rate (weighted mean differences [WMD] = -5.99), higher Scr (WMD = 7.34), uric acid (WMD = 47.53), 24-hour proteinuria (WMD = 0.40), and a higher prevalence rate of hypertension (odds ratio, OR = 2.70) and diabetes mellitus (OR = 2.644). On the histopathologic level, patients in group O had a significantly lower total glomerular number (WMD = -2.30); however, no difference was observed in mesangial cell proliferation, endocapillary hypercellularity, crescents, sclerosis, and tubular atrophy/interstitial fibrosis between the 2 groups. The incidence of adverse renal outcomes in the 2 groups was similar (OR = 0.96). The meta-analysis of hazard ratios from Cox regressions indicated a strong association between overweight/obesity and poor renal outcomes in glomerulonephritis (HR = 1.17).

CONCLUSION

Overweight/obesity glomerulonephritis patients had remarkably poor baseline clinicopathological characteristics. Being overweight or obesity would likely impact the progression of primary glomerulonephritis but not serious enough to contribute to significant poor renal outcomes, which could be prevented by aggressive therapy.

Diagnostic value of renal biopsy in anti-phospholipase A2 receptor antibody-positive patients with proteinuria in China

Renal biopsy remains the gold standard for diagnosing membranous nephropathy (MN). Recent studies have suggested that renal biopsy can be replaced with the serum phospholipase A2 receptor (PLA2R) antibody test for MN diagnosis in patients with nephrotic syndrome. However, this test has not been validated in the Chinese population. In this study, we investigated whether renal biopsy provides additional diagnostic information on patients with proteinuria who are seropositive for PLA2R antibodies (SAb +). We retrospectively reviewed the clinicopathological characteristics of SAb + adult patients (aged ≥ 18 years) with proteinuria (≥ 0.5 g/24 h) assessed at the Department of Nephrology, the First Affiliated Hospital of Zhengzhou University, from June 2021 to March 2022. Among a total of 801 SAb + patients who received renal biopsy, those with incomplete pathological data, diabetes or any potential cause of secondary MN were excluded. Among the 491 remaining patients, 474 had primary MN (PMN), 16 had atypical MN (AMN, 9 patients with "full house" and 2 patients with HBsAg + /HBcAg + immunofluorescence results), and 1 had focal segmental glomerulosclerosis. In patients with an eGFR of ≥ 60 mL/min/1.73 m2 (n = 451), 436 had PMN, and 71 (16.3%) exhibited additional biopsy findings, with obesity-related glomerulopathy being the most common. In patients with an impaired eGFR (n = 40), 38 had PMN, and 31 (81.6%) showed additional findings, with acute tubular injury being the most common. In conclusion, anti-PLA2R antibody positivity is highly predictive of PMN in Chinese adults but often coexists with other pathological diagnoses. The advantages of renal biopsy for detecting other pathologies should be weighed against the potential risks of the biopsy procedure.

Defining the threshold: triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio's non-linear impact on tubular atrophy in primary membranous nephropathy

Background

Hyperlipidemia is common in primary membranous nephropathy (PMN) patients, and tubular atrophy (TA) is an unfavorable prognostic factor. However, the correlation between the triglyceride to high-density lipoprotein cholesterol (TG/HDL-C) ratio and TA is controversial. Therefore, our study aimed to investigate the association between the TG/HDL-C ratio and TA in PMN patients.

Methods

We conducted a cross-sectional study and collected data from 363 PMN patients at Shenzhen Second People's Hospital from January 2008 to April 2023. The primary objective was to evaluate the independent correlation between the TG/HDL-C ratio and TA using binary logistic regression model. We used a generalized additive model along with smooth curve fitting and multiple sensitivity analyses to explore the relationship between these variables. Additionally, subgroup analyses were conducted to delve deeper into the results.

Results

Of the 363 PMN patients, 75 had TA (20.66%). The study population had a mean age of 46.598 ± 14.462 years, with 217 (59.78%) being male. After adjusting for sex, age, BMI, hypertension, history of diabetes, smoking, alcohol consumption, UPRO, eGFR, HB, FPG, and ALB, we found that the TG/HDL-C ratio was an independent risk factor for TA in PMN patients (OR=1.29, 95% CI: 1.04, 1.61, P=0.0213). A non-linear correlation was observed between the TG/HDL-C ratio and TA, with an inflection point at 4.25. The odds ratios (OR) on the left and right sides of this inflection point were 1.56 (95% CI: 1.17, 2.07) and 0.25 (95% CI: 0.04, 1.54), respectively. Sensitivity analysis confirmed these results. Subgroup analysis showed a consistent association between the TG/HDL-C ratio and TA, implying that factors such as gender, BMI, age, UPRO, ALB, hypertension and severe nephrotic syndrome had negligible effects on the link between the TG/HDL-C ratio and TA.

Conclusion

Our study demonstrates a non-linear positive correlation between the TG/HDL-C ratio and the risk of TA in PMN patients, independent of other factors. Specifically, the association is more pronounced when the ratio falls below 4.25. Based on our findings, it would be advisable to decrease the TG/HDL-C ratio below the inflection point in PMN patients as part of treatment strategies.

The thickness of glomerular basement membrane predicts complete remission in primary membranous nephropathy

Objective: Glomerular basement membrane (GBM) thickening is a typical and essential histopathological characteristic for the diagnosis of primary membranous nephropathy (PMN). The present study aimed to explore the relationship between GBM thickness and treatment response in PMN patients.Methods: A total of 128 patients with nephrotic syndrome concurrent with PMN were studied. The highest GBM thickness was measured from at least five glomerular capillary loops using an electron microscope, and the mean value was obtained. Patients were categorized into three groups according to the tertiles of GBM thickness as follows: Group 1 (GBM thickness ≤ 1100 nm, n = 48), Group 2 (1100 nm < GBM thickness ≤ 1300 nm, n = 40), Group 3 (GBM thickness >1300 nm, n = 40). Clinicopathological features and treatment response were compared among the three groups. The associations of GBM thickness with complete remission (CR) were assessed by Cox proportional hazard analyses and a cubic spline curve.Results: During a median follow-up period of 25.80 months, 69 (53.9%) patients achieved CR. Kaplan-Meier analysis showed that the non-CR probability was significantly higher in the highest tertile of GBM thickness (p˂0.001). Univariate Cox proportional hazard analysis indicated that GBM thickness was associated with CR (HR per SD 0.617, 95% CI [0.471-0.809], p˂0.001). After adjusting for age, duration of PMN, estimated glomerular filtration rate (eGFR), urinary protein excretion, grade of C3 deposition, and titer of serum anti-phospholipase A2 receptor (PLA2R) antibody, GBM thickness remained an independent predictor of CR (HR per SD 0.580, 95% CI [0.436-0.772], p˂0.001). Further multivariable-adjusted restricted cubic spline analysis confirmed a significant reverse linear association between GBM thickness and CR (p for nonlinear = 0.1261).Conclusions: GBM thickness is an independent risk factor of CR. PMN patients with an increased level of GBM thickening at diagnosis have a lower probability of achieving CR.

Clinicopathological Characteristics and Risk Factors for Rapid eGFR Decline in Chinese Patients with Biopsy-Proven Obesity-Related Glomerulopathy

AIM

To investigate the clinicopathologic features and the related risk factors for rapid estimated glomerular filtration rate (eGFR) decline in Chinese obesity-related glomerulopathy (ORG) patients.

METHODS

A total of 63 ORG patients, who underwent a renal biopsy and received follow-up for at least 12 months, were recruited in our study. These patients were classified as rapid decliners and slow decliners based on the eGFR slope value (-5.0 mL/min/1.73 m²/year). Logistic regression analysis was used to determine the risk factors for rapid eGFR decline.

RESULTS

Of the 63 ORG patients, 48 (76.2%) were male, the mean age was 38.7 ± 9.0 years, the median of urinary protein excretion was 1.62 g/24 h, 27.0% of them had nephrotic-range proteinuria, while hypoalbuminemia was observed in 7.9% of them. The incidence of obvious hypertriglyceridemia, hypertension, glucose dysmetabolism and hyperuricemia were 71.4%, 60.3%, 36.5% and 27.0%, respectively. 13 (20.6%) patients became rapid decliners during the median 45 months of follow-up. Their mean BMI was 31.8 ± 3.6 kg/m², the median of baseline eGFR and urinary protein excretion were 71.8 (range of 30.5-118.2) mL/min/1.73 m²/year and 3.57 g/24 h, respectively. Multivariate logistic regression analysis showed that smoking (OR 9.205, 95% CI 1.704-49.740, P = 0.01), hyperuricemia (OR 5.541, 95% CI 1.079-28.460, P = 0.04) and nephrotic-range proteinuria (OR 6.128, 95% CI 1.311-28.637, P = 0.021) were the independent risk factors for rapid eGFR decline.

CONCLUSION

Chinese ORG patients were more likely to have clinical characteristics with hypertriglyceridemia, hypertension and hyperuricemia, and mild to severe degrees of urinary protein excretion at diagnosis, while patients with nephrotic-range proteinuria lacked hypoalbuminemia and hypercholesterolemia. Smoking, hyperuricemia and nephrotic-range proteinuria were independent risk factors for rapid eGFR decline in ORG patients.