Association of a novel electrolyte index, SUSPPUP, based on the measurement of fasting serum and spot urinary sodium and potassium, with prediabetes and diabetes in Chinese population

Abstract

Background: SUSPPUP, calculated as serum sodium [Na⁺] to urinary Na⁺ divided by (serum potassium [K⁺]) ² to urinary K⁺, is a composite electrolyte index that reflects renal Na⁺ retention and K⁺ excretion. It remains unclear whether SUSPPUP and its components including serum or urinary Na⁺ or K⁺, are associated with glucose metabolism. This study aimed to address their associations.

Methods: We conducted a cross-sectional study enrolling 5,581 Chinese adults (1,269 with prediabetes, 1,044 with diabetes, and 3,268 with normoglycemia). Fasting serum and morning spot urine were used to measure electrolytes that included Na⁺ and K⁺.

Results: SUSPPUP was higher in prediabetes and diabetes than normoglycemia. The odds of prediabetes and diabetes were increased by 21% and 39% for every 1-standard deviation increment of SUSPPUP after multivariable-adjustment. Multiple linear regression analysis showed that SUSPPUP correlated positively with fasting plasma glucose, 2 h plasma glucose after OGTT, and glycated hemoglobin A1c. Higher spot urinary Na⁺ was associated with lower odds of prediabetes and diabetes, while spot urinary K⁺ showed the opposite.

Conclusion: Increases in Na⁺ retention and K⁺ excretion in the kidney, as reflected by an elevated SUSPPUP, are associated with increased prevalence of prediabetes and diabetes in Chinese community-dwellers.

Keywords: Glucose Metabolism; SUSPPUP; Serum Electrolytes; Urinary Electrolytes.