SODIUM-LITHIUM COUNTERTRANSPORT AND TRIGLYCERIDES IN DIABETIC NEPHROPATHY

Elevated erythrocyte sodium-lithium countertransport (SLC) activity is an intermediate phenotype of essential hypertension among Caucasians, and is controversially associated with nephropathy in Type 1 (insulin -dependent) diabetes. Hypertriglyceridemia is a frequent concomitant o f elevated SLC in the general population, and may be found in diabetic nephropathy. The present study was designed to investigate the influe nce of kidney disease, serum triglycerides and blood pressure on the i nterindividual variability of SLC in Type 1 diabetes. SLC and fasting major serum lipids were studied in 35 Type 1 diabetic patients with pe rsistently elevated urinary albumin excretion and in a group of patien ts matched for age, sex and duration of diabetes, but with normoalbumi nuria. SLC was elevated in patients with clinical nephropathy (N = 10; median: 420 mumol . 1RBC-1 . hr-1) and in patients with microalbuminu ria (N = 25; median: 405 mumol . 1RBC-1 . hr-1) compared with normoalb uminuric patients (median: 296 mumol . 1RBC-1 . hr 0.01 vs. both group s). Hypertriglyceridemia and hypercholesterolemia were found only amon g patients with macroalbuminuria. Analysis of covariance indicated tha t the association of elevated SLC with kidney disease (P < 0.006 in al l models) was largely independent of serum triglycerides, but also of total cholesterol, insulin dose and measures of glycemic control. Only diastolic blood pressure was positively associated with SLC (P < 0.02 ) independently from nephropathy (P < 0.005) also after restricting an alysis to the normoalbuminuric patients. Kidney disease and raised blo od pressure remain major concomitants of elevated SLC in Type 1 diabet ics.