Haptoglobin 1-1 phenotype: A risk factor for 24-hours polyuria.

Area of Science:

• Nephrology
• Genetics
• Internal Medicine

Background:

• Haptoglobin (Hp) exhibits three phenotypes: Hp 1-1, Hp 2-2, and Hp 2-1.
• The Hp 1-1 phenotype is associated with hypertension and salt sensitivity, potentially contributing to increased urine production.

Purpose of the Study:

• To investigate the association between haptoglobin (Hp) polymorphisms and the occurrence of polyuria, defined as urine output exceeding 40 mL/kg/24 hours.

Main Methods:

• A post hoc analysis of a prospective observational study involving 170 subjects who underwent renal function profiling.
• Haptoglobin phenotypes were identified using starch gel electrophoresis.
• Comparison of Hp phenotype distribution and renal function parameters (diuresis rate, sodium and free water clearance) between subjects with and without polyuria, and a reference group.

Main Results:

• The Hp1 allele frequency was significantly higher in polyuric subjects (0.500) compared to the reference group (0.400).
• The Hp 1-1 phenotype was more prevalent in subjects with polyuria (28%) versus the reference group (16%).
• Hp 1-1 subjects showed no circadian variation in diuresis or clearance rates and a positive correlation between plasma Hp concentration and 24-hour sodium clearance in non-polyuric individuals.

Conclusions:

• The Hp1 allele and Hp 1-1 phenotype are associated with an increased risk of polyuria.
• Individuals with the Hp 1-1 phenotype exhibit impaired urine concentrating ability and continuous sodium excretion.
• Plasma Hp concentration in Hp 1-1 subjects correlates with sodium clearance, suggesting a role in renal sodium handling.