A study of size-selective renal elimination using a novel human model

Area of Science:

• Nephrology
• Physiology
• Biochemistry

Background:

• Selective glomerular hypofiltration syndromes highlight the need to understand renal molecule elimination.
• Direct measurement of single-pass renal elimination is crucial for assessing kidney function.

Purpose of the Study:

• To introduce and validate a novel human model for directly measuring the renal elimination ratio (RER) of molecules with increasing sizes.
• To investigate the relationship between molecular size and renal elimination.
• To explore the correlation between RER of key biomarkers and estimated glomerular filtration rate (eGFR).

Main Methods:

• Analysis of plasma concentrations of 11 molecules (urea to IgG) in arterial and renal venous blood from 45 Transcatheter Aortic Valve Implantation (TAVI) patients.
• Calculation of Renal Elimination Ratio (RER) as the arteriovenous concentration difference divided by arterial concentration.
• Computation of eGFR using CKD-EPI equations for creatinine and cystatin C.

Main Results:

• Creatinine (0.11 kDa) exhibited the highest RER (21.0 ± 6.3%).
• Renal elimination decreased with increasing molecular size, with cystatin C (13 kDa) at 14.4 ± 5.3% and troponin-T (36 kDa) at 11.3 ± 4.6%.
• A renal elimination threshold was identified between 36 and 44 kDa, with orosomucoid (44 kDa) showing a negative RER (-0.2 ± 4.7%).
• RERs of creatinine and cystatin C showed a significant positive linear relationship with eGFR (r=0.48 and 0.40, respectively).

Conclusions:

• A novel human model effectively demonstrated that renal elimination declines as molecular size increases.
• The RERs of creatinine and cystatin C correlate with eGFR, validating the model's utility.
• This model holds potential for studying selective glomerular hypofiltration syndromes and refining kidney function assessments.