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

Background: SUSPPUP, calculated as serum sodium [Na] to urinary Na divided by (serum potassium [K]) 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.