Associations between renal hyperfiltration and serum alkaline phosphatase

Area of Science:

• Nephrology
• Metabolic Health
• Biochemistry

Background:

• Renal hyperfiltration, a state of excessive kidney filtration, is linked to kidney injury and commonly observed in individuals with diabetes (DM) and metabolic syndrome (MS).
• Elevated serum alkaline phosphatase (ALP) levels are prevalent in patients with DM or MS.
• While increased urinary ALP excretion is noted in hyperfiltration with tubular damage, the direct association between serum ALP and hyperfiltration remains under-investigated.

Purpose of the Study:

• To investigate the association between serum alkaline phosphatase (ALP) levels and renal hyperfiltration in a general adult population.
• To explore the relationship between serum ALP, renal hyperfiltration, and metabolic disorders like diabetes and metabolic syndrome.

Main Methods:

• A retrospective observational study utilizing data from 21,308 adults from the Korea National Health and Nutrition Examination Survey IV-V (2008-2011).
• Renal hyperfiltration was defined as exceeding the age- and sex-specific 97.5th percentile of estimated glomerular filtration rate (eGFR).
• Participants were categorized into four eGFR groups: >120, 90-119, 60-89, and <60 mL/min/1.73 m²; serum ALP levels were analyzed across quartiles.

Main Results:

• Participants with eGFR >120 mL/min/1.73 m² in the highest ALP quartile showed significantly increased risks for metabolic syndrome (Odds Ratio [OR] 3.848) and diabetes (OR 2.166) compared to the lowest quartile.
• Higher ALP quartiles were significantly associated with albuminuria in participants with eGFR ≥ 60 mL/min/1.73m² (OR 1.631, adjusted for age and sex).
• After adjustment, the highest ALP quartile was significantly associated with an increased risk of renal hyperfiltration (OR 1.624). Hyperfiltration was also linked to hemoglobin, triglyceride, white blood cell count, DM, smoking, and alcohol consumption.

Conclusions:

• Higher serum ALP levels are significantly associated with renal hyperfiltration in the Korean general population.
• The relationship between serum ALP and metabolic disorders is more pronounced in individuals with upper-normal eGFR levels.
• Elevated serum ALP may serve as a potential indicator for renal hyperfiltration and associated metabolic risks, especially in individuals with preserved kidney function.