Mild renal dysfunction is associated with insulin resistance in chronic glomerulonephritis

Background: Insulin resistance is associated with advanced and moderate chronic renal failure (CRF). However, insulin resistance in chronic glomerulonephritis (CGN) before onset of frank renal dysfunction is not fully evaluated. We attempted to investigate the association of insulin resistance with mild renal dysfunction and with abnormal calcium homeostasis. Patients and methods: Eighteen young, lean non-diabetic male patients with biopsy-proven CGN (age 30 ± 7 years, body mass index 23.0 ± 2.5 kg/m²) were enrolled. Insulin sensitivity was estimated by the glucose infusion rate (M value) during euglycemic hyperinsulinemic clamping for 60 to 120 min. Calcium-related parameters including intracellular calcium concentrations ([Ca²⁺](i)) in platelets were also measured. Renal function was normal or slightly impaired (serum creatinine, 1.0 ± 0.2 mg/dl; glomerular filtration rate (GFR), 68 to 131 ml/min/1.48 m²). We divided subjects into an insulin-sensitive (IS) group (M value > 7.3 mg/kg/min, the overall mean) and an insulin-resistant (IR) group (M value < 7.3 mg/kg/min). Results: During a 75 g oral glucose tolerance test, the plasma glucose concentration at 120 min after glucose loading and the immunoreactive insulin concentration at 60 min were significantly higher in the IR group. GFR was notably lower in the IR group than in the IS group (p = 0.0003), and was significantly correlated with insulin sensitivity (p < 0.02, r = 0.58). The basal [Ca²⁺](i) was significantly higher in the IR than in the IS group (39 ± 9 vs. 30 ± 9 nM, p < 0.05). Conclusion: Mild renal dysfunction and elevated basal [Ca²⁺](i) are associated with insulin resistance in CGN.