Measures of tubular function in normoalbuminuric insulin-dependent diabetic patients and their relationship with sodium lithium countertransport activity.
The aim of this study was to assess the relationship between markers of tubular function, markers of glycaemic control and erythrocyte sodium-lithium countertransport activity (SLC) in 40 normotensive, normoalbuminuric insulin-dependent diabetic (IDDM) subjects and 11 normal control subjects. Nine IDDM subjects had SLC > 0.40 mmol lithium h-1 litre RBC-1. Glomerular filtration rate (GFR) and the excretion rate of retinol-binding protein (RBP), N-acetyl-beta-D-glucosaminidase (beta-NAG) and glucose were significantly higher in IDDM subjects compared to control subjects (Mann-Whitney test, p = 0.02, < 0.001, < 0.001 and < 0.001, respectively), whilst the two groups had similar SLC and TmPO4 levels. There was no significant relationship between SLC and the other variables in IDDM subjects, even when comparing IDDM subjects with normal and high SLC. beta-NAG excretion rate was correlated to urinary glucose (rs 0.47, p = 0.001) and, weakly, to the other markers of glycaemic control (fasting blood glucose rs = 0.31, p = 0.03, fructosamine rs 0.28, p = 0.04, HbA1 rs 0.27, p = 0.04). RBP excretion rate was correlated to the excretion rate of beta-NAG (rs 0.38; p = 0.007) and albumin (rs 0.45; p = 0.002); the excretion rates of beta-NAG and albumin were significantly associated (rs 0.37, p = 0.009). Diabetes duration did not correlate to any of the aforementioned variables. In this study, beta-NAG and RBP overnight excretion rates were higher in normoalbuminuric IDDM subjects compared to control subjects but no relationship was present between SLC and tubular function in IDDM patients without complications. Excretion rates of different proteins appear to be interrelated and, in IDDM, beta-NAG excretion is associated with glycaemic control.
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Centro di Fisiologia Clinica del Consiglio Nazionale delle Ricerche e Divisione Nefrologica, Reggio Calabria, Italy.
Winocour
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Parlongo
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Gibb
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Gillespie
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Alberti
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KG
D000293:Adolescent; D000328:Adult; D000419:Albuminuria / Q000378:metabolism; D017920:Antiporters / Q000378:metabolism*; D015415:Biomarkers; D001786:Blood Glucose / Q000378:metabolism; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000378:metabolism* / Q000503:physiopathology*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007328:Insulin / Q000097:blood; D007677:Kidney Function Tests; D007684:Kidney Tubules / Q000378:metabolism / Q000503:physiopathology*; D008094:Lithium / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000097:blood; D012964:Sodium / Q000378:metabolism
D017920:Antiporters; D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin; D010710:Phosphates; C045885:sodium-lithium countertransporter; D008094:Lithium; D012964:Sodium