Circadian Blood Pressure Rhythm Is Changed by Improvement in Hypoalbuminemia and Massive Proteinuria in Patients with Minimal Change Nephrotic Syndrome

Abstract

Background: Proteinuria and nighttime blood pressure (BP) elevation are notable risk markers of chronic kidney disease and correlate closely with each other. However, daily urinary protein excretion (UPE) always fluctuates. In patients with minimal change nephrotic syndrome (MCNS), serum albumin concentrations (SAC) decrease but fluctuate less than UPE. We evaluated whether SAC is a reliable marker for proteinuria, and compared the relations among circadian BP changes, SAC, and UPE. Methods: In patients with MCNS (12 men and 11 women, 43 ± 18 years), blood and spot urine samples were collected on three consecutive days before treatment, and 24-hour BP was also measured on the three days. Then, an intervention study was conducted in the patients to examine circadian BP changes induced by treatment. Sleeping/waking BP ratio was analyzed as an indicator of circadian BP rhythm. Results: In the three-day measurements before treatment, mean coefficient of variation, an index of dispersion of data, for SAC was 7.4 ± 7.4%, which was markedly lower (p < 0.01) than 35.7 ± 15.4% for UPE. SAC correlated inversely with sleeping/waking systolic and diastolic BP ratios on all three days, whereas UPE did not correlate significantly with sleeping/waking diastolic BP ratio on day 3. Sleeping/waking systolic and diastolic BP ratios were 96 ± 5 and 95 ± 6%, and were higher (p < 0.05) than in healthy subjects (89 ± 8 and 88 ± 10%). Treatment improved hyperproteinuria and hypoalbuminemia, and was accompanied by decreases (p < 0.05) in sleeping and waking systolic/diastolic BP ratio to 91 ± 8 and 89 ± 9%. Conclusion: These findings suggest that reduced SAC in patients with proteinuria is associated with disrupted circadian BP rhythm.