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Reduced glomerular size- and charge-selectivity in clinically healthy individuals with microalbuminuria
J S Jensen1, K Borch-Johnsen, T Deckert
1Steno Diabetes Center, Gentofte, Denmark.
Abstract:
The pathophysiologic mechanism behind microalbuminuria, a potential atherosclerotic risk factor, was explored by measuring fractional clearances of four endogenous plasma proteins of different size and electric charge (albumin, beta 2-microglobulin, immunoglobulin G, and immunoglobulin G4). Twenty-eight clinically healthy individuals with microalbuminuria, defined as a urinary albumin excretion of 6.6-150 micrograms min-1, and 60 matched control subjects were studied. Fractional immunoglobulin G clearance was higher (geometric means (95% confidence intervals)) 3.0 (2.3-3.9) x 10(-6), n = 28, vs. 2.1 (1.8-2.4) x 10(-6), n = 60; P = 0.02), whereas the ratio immunoglobulin G clearance/immunoglobulin G4 clearance was lower (geometric means (95% confidence intervals)) 1.8 (1.4-2.2), n = 28, vs. 2.3 (2.0-2.5), n = 60; P = 0.03) in microalbuminuric than in normoalbuminuric individuals. Fractional beta 2-microglobulin clearance was similar in the two groups. Since total IgG and the IgG4 subclass are of similar size and configuration but electrically neutral and negative, respectively; these findings indicate that microalbuminuria is associated with decreased size- and charge-selectivity of the glomerular vessel wall. Hypothetically, such alterations may reflect generalized vascular abnormalities linking microalbuminuria to atherogenesis.
Insights
Microalbuminuria, an early sign of kidney disease and potential atherosclerosis risk, is linked to reduced kidney filter selectivity. This suggests generalized vascular issues may connect microalbuminuria to heart disease development.
Area of Science:
- Nephrology
- Cardiovascular Medicine
- Vascular Biology
Background:
- Microalbuminuria is a marker for kidney damage and a risk factor for atherosclerosis.
- The exact pathophysiological mechanisms underlying microalbuminuria are not fully understood.
Purpose of the Study:
- To investigate the pathophysiologic basis of microalbuminuria by assessing glomerular filtration selectivity.
- To explore the relationship between microalbuminuria and potential generalized vascular abnormalities.
Main Methods:
- Measured fractional clearances of albumin, beta 2-microglobulin, immunoglobulin G (IgG), and IgG4 in 28 individuals with microalbuminuria and 60 controls.
- Analyzed protein size and charge selectivity of the glomerular filtration barrier.
Main Results:
- Individuals with microalbuminuria showed higher fractional IgG clearance compared to controls (P=0.02).
- The ratio of IgG clearance to IgG4 clearance was lower in microalbuminuric individuals (P=0.03), indicating altered charge selectivity.
- Fractional beta 2-microglobulin clearance remained similar between groups, suggesting size selectivity was less affected.
Conclusions:
- Microalbuminuria is associated with impaired size- and charge-selectivity of the glomerular filtration barrier.
- These findings suggest that microalbuminuria may reflect broader vascular dysfunction, potentially linking it to atherogenesis.
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