Renal glucose excretion as a function of blood glucose concentration in subjects with type 2 diabetes--results of a hyperglycaemic glucose clamp study.
BACKGROUND
The purpose of this study was to investigate renal glucose excretion as a function of blood glucose concentration and to evaluate the within-subject variability and between-subject variability in subjects with type 2 diabetes.


METHODS
Twenty-two subjects with type 2 diabetes [age 58 (12) years, diabetes duration 7 (6) years, endogenous creatinine clearance 117 (38) ml min(-1) 1.73 m(-2); median (inter-quartile range, IQR)] underwent two five-period hyperglycaemic glucose clamp experiments at intervals of 7-21 days. Starting from an initial blood glucose level of 12.2 mmol l(-1), subsequent glucose clamp levels were chosen using an algorithm based on urinary glucose concentrations measured at the end of the preceding glucose clamp period. That is, blood glucose was either stepwise decreased or increased depending on whether urinary glucose concentration was above or below 11.1 mmol l(-1), respectively.


RESULTS
As expected, increasing the blood glucose from 7.8 to 13.3 mmol l(-1) during the glucose clamps resulted in a steep increase of urinary glucose excretion from 0.06 to 0.77 mmol min(-1). With decreasing blood glucose, a measurable glucosuria persisted up to a blood glucose level of 7.8 mmol l(-1). When defining the (pseudo)threshold for renal glucose excretion (PRT(G)) as the highest blood glucose level during glucose clamps associated with a concomitant glucose concentration in urine of <2.8 mmol l(-1), median (IQR) PRT(G) was 11.0 (1.1) mmol l(-1). The within-subject variability of PRT(G), i.e. the difference between two assessments, was low, 0.1 (0.0) mmol l(-1) while the between-subject variability of PRT(G) was high, ranging from 7.7 to 12.2 mmol l(-1).


CONCLUSIONS
Renal glucose excretion increases in a proportional manner with increasing blood glucose. When decreasing blood glucose to euglycaemic blood glucose levels, glucosuria persists so that the classical concept of a renal threshold for glucose excretion cannot be upheld in subjects with type 2 diabetes.
Rave
Klaus
K
Profil Institut für Stoffwechselforschung GmbH, Neuss, Germany. klaus.rave@profil-research.de
Nosek
Leszek
L
Posner
John
J
Heise
Tim
T
Roggen
Kerstin
K
van Hoogdalem
Ewoud-Jan
EJ
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004231:Diuresis; D005260:Female; D014644:Genetic Variation; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology; D015309:Glucose Clamp Technique; D006029:Glycosuria / Q000097:blood / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000503:physiopathology*; D007668:Kidney / Q000503:physiopathology*; D007687:Kidney Tubules, Proximal / Q000503:physiopathology; D008297:Male; D008875:Middle Aged
D001786:Blood Glucose; D005947:Glucose