Cadmium-Induced Proteinuria: Mechanistic Insights from Dose-Effect Analyses

Area of Science:

• Environmental Health
• Nephrology
• Toxicology

Background:

• Cadmium (Cd) is a toxic metal that accumulates in the kidneys, specifically targeting proximal tubular epithelial cells responsible for protein reabsorption.
• Kidney function, including estimated glomerular filtration rate (eGFR) and protein handling, can be compromised by heavy metal exposure.

Purpose of the Study:

• To analyze the association between cadmium exposure and kidney function markers, including eGFR and urinary protein excretion.
• To investigate the impact of cadmium on tubular protein reabsorption and identify potential differential effects on various proteins.

Main Methods:

• Archived data from residents in a cadmium-contaminated area and a control area in Thailand were analyzed.
• Excretion rates of cadmium (E_Cd), total protein (E_Prot), albumin (E_alb), β₂-microglobulin (E_β2M), and α1-microglobulin (E_α1M) were normalized to creatinine clearance (C_cr).
• Statistical analyses were performed to assess correlations between cadmium excretion, eGFR, and protein excretion markers.

Main Results:

• Cadmium excretion (E_Cd/C_cr) was directly associated with increased total protein excretion (E_Prot/C_cr) and inversely associated with eGFR.
• Elevated cadmium excretion levels significantly increased the odds of proteinuria and low eGFR.
• Cadmium excretion showed stronger correlations with total protein, β₂-microglobulin, and α1-microglobulin excretion than with albumin excretion.

Conclusions:

• Cadmium exposure simultaneously diminishes kidney filtration (eGFR) and tubular protein reabsorption.
• The findings suggest that cadmium differentially affects tubular reabsorption, potentially leading to preferential loss of certain proteins over albumin.
• This study highlights the detrimental impact of cadmium on kidney health and underscores the importance of monitoring environmental cadmium exposure.