Diagnosis of albuminuria by tryptic digestion and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry

The potassium puzzle: exploring the intriguing connection to albuminuria

Background

Studies have revealed a relationship between dietary potassium intake and albuminuria, despite the fact that the human body needs a lot of potassium. Our study concentrated on the link between dietary potassium intake and albuminuria.

Methods

This study used subgroup analysis and weighted multivariate regression analysis. Data from the National Health and Nutrition Examination Survey (NHANES) were examined to determine the urinary albumin-to-creatinine ratio (ACR) and participant age (20 years or older). ACR >30 mg/g was the threshold for albuminuria.

Results

7,564 individuals in all were included in the study. The link between the two was significant in both our original model (OR = 0.99; 95% CI, 0.98-0.99, p < 0.0001) and the minimum adjusted model (OR = 0.99; 95% CI, 0.98-0.99, p < 0.0001). A fully adjusted model did not change the significance of the negative correlation between potassium consumption and albuminuria (OR = 0.99; 95% CI, 0.98-1.00, p = 0.0005), indicating that each unit increase in potassium intake was related with a 1% decrease in the chance of developing albuminuria. The negative correlation between potassium intake and albuminuria was not significantly influenced by sex, age, BMI, hypertension, diabetes, or smoking, according to interaction tests (p for interaction >0.05).

Conclusion

Reduced risk of albuminuria was linked to higher dietary potassium intake. The particular mechanism linking the two still has to be explained by several inventive and prospective studies.

Association between dietary inflammation index and albuminuria: results from the National Health and Nutrition Examination Survey

Background

The Dietary Inflammation Index (DII) is a tool for evaluating the potential for dietary inflammation, and inflammation is a major cause of exacerbation in chronic kidney disease. Our study aimed to investigate the relationship between DII and albuminuria.

Methods

Data were obtained from the 2005-2018 National Health and Nutrition Examination Survey (NHANES) after excluding pregnant, minors, and missing data of urinary albumin-creatinine ratio (ACR), estimated glomerular filtration rate (eGFR), and DII were enrolled in our study. Albuminuria was defined as ACR > 30 mg/g. DII was calculated and divided into tertiles. After fully adjusted, multivariate logistic regression analysis and subgroup analysis were performed to investigate the association between DII and albuminuria.

Results

A total of 22,607 participants including 2,803 (12.40%) with and 19,804 (87.60%) without albuminuria were enrolled in our study. The albuminuria increased with the increasing DII tertiles (Tertile 1: 10.81%; Tertile 2: 12.41%; Tertile 3:13.97%, P < 0.001). After fully adjusting for covariates, multivariate logistic regression showed that the higher the DII, the greater the odds of albuminuria (OR = 1.19; 95% CI, 1.00-1.41, P < 0.001). Subgroup analysis and interaction test of participants found that the positive correlation between DII and albuminuria was not significantly related to gender, age, BMI, hypertension, diabetes, and eGFR (P for interaction >0.05).

Conclusion

Elevated DII is associated with high odds of albuminuria. Further large-scale prospective studies are still needed to analyze the role of DII in albuminuria.

Association of domain-specific physical activity with albuminuria among prediabetes and diabetes: a large cross-sectional study

BACKGROUND

Albuminuria, the presence of excess of protein in urine, is a well-known risk factor for early kidney damage among diabetic/prediabetic patients. There is a complex interaction between physical activity (PA) and albuminuria. However, the relationship of specific-domain PA and albuminuria remained obscure.

METHODS

Albuminuria was defined as urinary albumin/creatinine ratio (ACR) > 30 mg/g. PA was self-reported by participants and classified into transportation-related PA (TPA), occupation-related PA (OPA), and leisure-time PA (LTPA). Weighted logistic regression was conducted to compute the odds ratios (ORs) and 95% confidence intervals (CIs). Restricted cubic spline (RCS) was used to evaluate the dose-response of PA domains with the risk of albuminuria.

RESULTS

A total of 6739 diabetic/prediabetic patients (mean age: 56.52 ± 0.29 years) were enrolled in our study, including 3181 (47.20%) females and 3558 (52.80%) males. Of them, 1578 (23.42%) were identified with albuminuria, and 5161(76.58%) were without albuminuria. Diabetic/prediabetic patients who adhered the PA guidelines for total PA had a 22% decreased risk of albuminuria (OR = 0.78, 95%CI 0.64-0.95), and those met the PA guidelines for LTPA had a 28% decreased of albuminuria (OR = 0.72, 95%CI 0.57-0.92). However, OPA and TPA were both not associated with decreased risk of albuminuria. RCS showed linear relationship between the risk of albuminuria with LTPA.

CONCLUSIONS

Meeting the PA guideline for LTPA, but not OPA and TPA, was inversely related to the risk of albuminuria among diabetic/prediabetic patients. Additionally, achieving more than 300 min/week of LTPA conferred the positive effects in reducing albuminuria among diabetic/prediabetic patients.

Impaired sensitivity to thyroid hormones is associated with albuminuria in the euthyroid population: results from NHANES

PURPOSE

The relationship between thyroid hormone sensitivity and albuminuria remains unclear. We aimed to investigate the association between thyroid hormone sensitivity and the risk of albuminuria in a euthyroid population.

METHODS

This cross-sectional study included 7634 euthyroid adults collected from the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2012. Central sensitivity to thyroid hormones was evaluated using the thyroid-stimulating hormone index (TSHI), the thyrotrophic thyroxine resistance index (TT4RI), and the thyroid feedback quantile-based index (TFQI). Peripheral sensitivity to thyroid hormones was measured using the free triiodothyronine/free thyroxine (FT3/FT4) ratio. Furthermore, the independent relationship between sensitivity to thyroid hormones and albuminuria was assessed.

RESULTS

The proportion of albuminuria increased with a higher interquartile range of TFQI levels (7.31% vs. 7.89% vs. 7.95% vs. 9.89%, P = 0.024). Furthermore, TFQI was found to be independently associated with the risk of albuminuria after adjusting for confounding factors (OR = 1.28, 95% CI 1.01-1.60, P = 0.037). Subgroup analysis revealed a significant relationship between TFQI and albuminuria, especially among individuals over 60.

CONCLUSIONS

In euthyroid subjects, impaired central sensitivity to thyroid hormones is associated with albuminuria. TFQI holds significant potential as an epidemiological tool for quantifying the impact of impaired central sensitivity on the risk of albuminuria.

The relationship between triglyceride-glucose index and albuminuria in United States adults

Purpose

Triglyceride-glucose (TyG) index is a simple and reliable indicator of metabolic dysfunction. We aimed to investigate a possible relationship between TyG index and albuminuria in the United States adult population.

Methods

This cross-sectional study was conducted among adults with complete TyG index and urinary albumin/urinary creatinine (UACR) from 2011-2018 National Health and Nutrition Examination Survey (NHANES). The independent relationship between TyG index and albuminuria (UACR>30mg/g) was evaluated. TyG index was compared with insulin resistance represented by homeostatic model assessment of insulin resistance (HOMA-IR), and metabolic syndrome. Subgroup analysis was also performed.

Results

A total of 9872 participants were included in this study, and the average TyG index was 8.53 ± 0.01. The proportion of albuminuria gradually increased with the increase of TyG index quartile interval. Elevated TyG index was independently associated with albuminuria, and this association persisted after additional adjustments for HOMA-IR or dichotomous metabolic syndrome. The area under the ROC curve (AUC) of TyG index was larger than that of log (HOMA-IR). Subgroup analysis suggested that the relationship between TyG index and albuminuria is of greater concern in age<60, overweight/obese, diabetic, and metabolic syndrome patients.

Conclusion

The TyG index may be a potential epidemiological tool to quantify the role of metabolic dysfunction, rather than just insulin resistance, in albuminuria in the United States adult population. Further large-scale prospective studies are needed to confirm our findings.

The association between weight-adjusted-waist index and increased urinary albumin excretion in adults: A population-based study

Aims

The negative effect of obesity on kidney health has been reported. The association between weight-adjusted-waist index (WWI, a newly developed adiposity index) and albuminuria has not been reported earlier.

Methods

This cross-sectional study was conducted among adults with complete data about WWI and urinary albumin-to-creatinine ratio (ACR) in 2005–2018 National Health and Nutrition Examination Survey (NHANES). WWI was calculated as waist circumference (WC) divided by the square root of weight. Weighted multivariable logistic regression and generalized additive model were employed to explore the independent relationship between WWI with albuminuria and its non-linearity. A two-piecewise linear regression model was used to calculate the threshold effect. Subgroup analysis and interaction tests were also performed.

Results

A total of 36,921 participants were enrolled with a prevalence of albuminuria of 9.32%. The prevalence of albuminuria increased with the higher WWI tertiles (Tertile 1: 5.31%, Tertile 2: 8.23%, Tertile 3: 15.65%). WWI was positively associated with a higher likelihood of albuminuria (OR = 1.28, 95% CI: 1.15–1.43), and this relationship remains stable in subgroups (all P for trend > 0.05). Non-linear positive relationships were detected in females with a breakpoint of 10.93. A positive association between WWI and albuminuria (OR = 1.39, 95% CI: 1.20–1.61) was observed on the right of the breakpoint, while the association on the left was of no statistical significance. WWI showed a stronger correlation with albuminuria (OR = 1.28) than other markers of obesity including body mass index (BMI, OR = 1.02) and WC (OR = 1.01).

Conclusion

Weight-adjusted-waist index levels were positively related to an increased likelihood of albuminuria in United States adults and showed a stronger relationship than BMI and WC. Our findings indicated that WWI may serve as a simple anthropometric index to predict albuminuria.

Systemic Immune-Inflammation Index Is Associated With Increased Urinary Albumin Excretion: A Population-Based Study

Background

Systemic immune-inflammation index (SII) is a novel inflammatory marker, and inflammation has been reported to be related with renal damage. We aimed to investigate the possible relationship between SII and albuminuria.

Methods

The present cross-sectional study was conducted among adults with complete data about SII and urinary albumin-to-creatinine ratio (ACR) in 2005–2018 National Health and Nutrition Examination Survey (NHANES). SII was calculated as the platelet count × neutrophil count/lymphocyte count. Albuminuria was defined as ACR >30mg/g. Weighted multivariable regression analysis and subgroup analysis were conducted to explore the independent relationship between SII and albuminuria.

Results

A total of 36,463 individuals were included in our analysis; 9.56% participants were categorized as having albuminuria overall and increased with the higher SII tertiles (tertile 1, 7.83%; tertile 2, 8.49%; tertile 3, 12.13%; p for trend <0.0001). Multivariable logistic regression showed that a higher SII level was associated with increased likelihood of albuminuria independently (OR = 1.31; 95% CI, 1.17–1.48, p<0.0001) after full adjustment. Subgroup analysis and interaction test showed that there was no significant dependence of gender, age, body mass index, hypertension, diabetes, non‐alcoholic fatty liver disease, and estimated glomerular filtration rate (eGFR) on this positive association (all p for interaction >0.05).

Conclusions

SII was positively associated with increased urinary albumin excretion in US adults. Further large-scale prospective studies are still needed to analyze the role of SII in albuminuria.

Applications of MALDI-TOF mass spectrometry in clinical proteomics

INTRODUCTION

The development of precision medicine requires advanced technologies to address the multifactorial disease stratification and to support personalized treatments. Among omics techniques, proteomics based on Mass Spectrometry (MS) is becoming increasingly relevant in clinical practice allowing a phenotypic characterization of the dynamic functional status of the organism. From this perspective, Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) MS is a suitable platform for providing a high-throughput support to clinics. Areas covered: This review aims to provide an updated overview of MALDI-TOF MS applications in clinical proteomics. The most relevant features of this analysis have been discussed, highlighting both pre-analytical and analytical factors that are crucial in proteomics studies. Particular emphasis is placed on biofluids proteomics for biomarkers discovery and on recent progresses in clinical microbiology, drug monitoring, and minimal residual disease (MRD). Expert commentary: Despite some analytical limitations, the latest technological advances together with the easiness of use, the low time and low cost consuming and the high throughput are making MALDI-TOF MS instruments very attractive for the clinical practice. These features offer a significant potential for the routine of the clinical laboratory and ultimately for personalized medicine.

Superhydrophobic candle soot/PDMS substrate for one-step enrichment and desalting of peptides in MALDI MS analysis

Superhydrophobic substrate is applied in matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) detection due to its confinement effect. The weak interaction of superhydrophobic surface with water/salts makes it potential in one-step enrichment and desalting of peptide in MALDI MS analysis. We fabricate a superhydrophobic substrate by spin-coating poly(dimethyl siloxane) (PDMS) on a candle soot layer. On this substrate, the peptide analytes can be confined and enriched in a small area due to the confinement effect and its strong hydrophobic interactions with PDMS. Meanwhile, the desalting can be easily realized by removing the residual solution after the absorption of analyst molecules due to the weak interaction between water/salt contaminants and the superhydrophobic surface. Using this substrate, angiotensin III (Ang III) in the presence of salt with high concentration (2 M or saturated) can be analyzed, and the peptide sequence coverage of 10 μg/mL myoglobin (MYO) and bovine serum albumin (BSA) digests is enhanced to 51% and 26%, which is 37% and 21% analyzed with the commercial ZipTipC₁₈ pipette tips. The LOD of bacitracin A (Bac A) in milk with this substrate is 100 pM and nearly 360 times lower than the LOD of standard testing method. This substrate has potential practical applications in proteomics research and actual sample analysis.

A novel paper-based colorimetry device for the determination of the albumin to creatinine ratio

A novel paper-based analytical device (PAD) was fabricated and developed for the simple and rapid determination of the albumin to creatinine ratio (ACR) in urine samples.

Urinary proteomics and metabolomics studies to monitor bladder health and urological diseases

Background

Assays of molecular biomarkers in urine are non-invasive compared to other body fluids and can be easily repeated. Based on the hypothesis that the secreted markers from the diseased organs may locally release into the body fluid in the vicinity of the injury, urine-based assays have been considered beneficial to monitoring bladder health and urological diseases. The urine proteome is much less complex than the serum and tissues, but nevertheless can contain biomarkers for diagnosis and prognosis of diseases. The urine metabolome has a much higher number and concentration of low-molecular metabolites than the serum or tissues, with a far lower lipid concentration, yet informs directly about dietary and microbial metabolism.

Discussion

We here discuss the use of mass spectrometry-based proteomics and metabolomics for urine biomarker assays, specifically with respect to the underlying mechanisms that trigger the pathological condition.

Conclusion

Molecular biomarker profiles, based on proteomics and metabolomics studies, reliably distinguish patients from healthy controls, stratify sub-populations with respect to treatment options, and predict therapeutic response of patients with urological disease.

Applications of MALDI Mass Spectrometry in Clinical Chemistry

BACKGROUND

MALDI-TOF mass spectrometry (MS) is set to make inroads into clinical chemistry because it offers advantages over other analytical platforms. These advantages include low acquisition and operating costs, ease of use, ruggedness, and high throughput. When coupled with innovative front-end strategies and applied to important clinical problems, it can deliver rapid, sensitive, and cost-effective assays.

CONTENT

This review describes the general principles of MALDI-TOF MS, highlights the unique features of the platform, and discusses some practical methods based upon it. There is substantial potential for MALDI-TOF MS to make further inroads into clinical chemistry because of the selectivity of mass detection and its ability to independently quantify proteoforms.

SUMMARY

MALDI-TOF MS has already transformed the practice of clinical microbiology and this review illustrates how and why it is now set to play an increasingly important role in in vitro diagnostics in particular, and clinical chemistry in general.

Biomarker Characterization by MALDI-TOF/MS

Mass spectrometric techniques frequently used in clinical diagnosis, such as gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, ambient ionization mass spectrometry, and matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF/MS), are discussed. Due to its ability to rapidly detect large biomolecules in trace amounts, MALDI-TOF/MS is an ideal tool for characterizing disease biomarkers in biologic samples. Clinical applications of MS for the identification and characterization of microorganisms, DNA fragments, tissues, and biofluids are introduced. Approaches for using MALDI-TOF/MS to detect various disease biomarkers including peptides, proteins, and lipids in biological fluids are further discussed. Finally, various sample pretreatment methods which improve the detection efficiency of disease biomarkers are introduced.