Sodium-lithium Transport in Adolescents With IDDM: Relationship to incipient nephropathy and glycemic control

Charles H Crompton; J Williamson Balfe; Judith A Balfe; Alice Chatzilias; Denis Daneman

doi:10.2337/diacare.17.7.704

Original Articles

Sodium-lithium Transport in Adolescents With IDDM: Relationship to incipient nephropathy and glycemic control

Charles H Crompton, MB, BS, FRACP,
J Williamson Balfe, MD, FRCP(C),
Judith A Balfe,
Alice Chatzilias and
Denis Daneman, MB, BCH, FRCP(C)

Divisions of Endocrinology and Nephrology, Department of Pediatrics, The Hospital for Sick Children and University of Toronto Toronto, Canada

Address correspondence and reprint requests to Denis Daneman, MB, BCh, FRCP(C), Division of Endocrinology, The Hospital for Sick Children, 555 University Avenue, Toronto, Canada M5G 1X8.

Diabetes Care 1994 Jul; 17(7): 704-710. https://doi.org/10.2337/diacare.17.7.704

Abstract

OBJECTIVE The aims of this study were to examine genetic and environmental influences in the development of early diabetic nephropathy and to assess the value of measuring membrane sodium transport as a marker for early nephropathy.

RESEARCH DESIGN AND METHODS We measured erythrocyte sodium- lithium (Na-Li) countertransport, blood pressure (BP), HbA_1c, and microalbuminuria (MA) in 84 adolescents with insulin-dependent diabetes mellitus (IDDM), 29 of whom had MA. Twenty-nine non-MA patients were selected and matched for age, sex, and IDDM duration with the 29 diabetic subjects with MA. The 84 diabetic adolescents were also compared with 85 nondiabetic siblings.

RESULTS The erythrocyte Na-Li countertransport was significantly greater in the IDDM group than in the sibling group (mean ± SD, 0.41 ± 0.14 vs. 0.30 ±0.11 mmol Li · liters of erythrocytes^–1 · h^–1, respectively, P < 0.0001), but a significant correlation was noted between the results in IDDM subjects and their siblings (r = 0.42, P < 0.0008). Na-Li countertransport was not different in the diabetic subjects with or without MA (0.43 ± 0.13 vs. 0.37 ± 0.13 mmol Li · liters of erythrocytes^–1 · h^–1, respectively). There was a significant correlation in the IDDM group between recent diabetic control (HbA^1c) and Na-Li countertransport (r = 0.37, P < 0.003). Diastolic BP was significantly higher in the IDDM group with MA than in those without MA (60 ± 6 vs. 55 ± 6 mmHg, respectively, P < 0.03).

CONCLUSIONS These results suggest that erythrocyte Na-Li countertransport is influenced by the diabetic milieu. However, there was also evidence in our subjects of a genetic contribution to Na-Li countertransport as seen by the correlation between levels in the IDDM subjects and their siblings. Using Na-Li countertransport, we were not able to segregate those IDDM adolescents with and without early nephropathy.