Renal Compensation for Impaired Hepatic Glucose Release During Hypoglycemia in Type 2 Diabetes

Abstract

During liver transplantation and after both meal ingestion and prolonged fasting, renal glucose release (RGR) increases while hepatic glucose release (HGR) decreases. These and other observations have led to the concept of hepatorenal reciprocity. According to this concept, reciprocal changes in hepatic and renal glucose release may occur to minimize deviations from normal glucose homeostasis. We further assessed this concept by testing the hypothesis that during counterregulation of hypoglycemia in patients with type 2 diabetes, who would be expected to have reduced HGR, RGR would be increased. Accordingly, we performed hypoglycemic hyperinsulinemic clamp experiments (∼3.1 mmol/l) in 12 type 2 diabetic and in 10 age-weight-matched nondiabetic volunteers and measured total endogenous glucose release (TEGR) and RGR using a combined isotopic net balance approach. HGR was calculated as the difference between TEGR and RGR since only these organs are capable of releasing glucose. We found that during comparable hypoglycemia and hyperinsulinemia, TEGR was reduced in type 2 diabetes (6.6 ± 0.6 vs. 10.2 ± 1.1 μmol · kg⁻¹ · min⁻¹ in nondiabetic volunteers, P = 0.01) due to reduced HGR (3.9 ± 0.5 vs. 8.6 ± 1.0 μmol · kg⁻¹ · min⁻¹ in nondiabetic volunteers, P = 0.0015). In contrast, RGR was increased approximately twofold in type 2 diabetes (3.3 ± 0.5 vs. 1.6 ± 0.3 μmol · kg⁻¹ · min⁻¹ in nondiabetic volunteers, P = 0.015). Plasma epinephrine, lactate, and free fatty acid concentrations, which would promote RGR, were also greater in type 2 diabetes (all P < 0.01). Our results provide further support for hepatorenal reciprocity and may explain at least in part the relatively low occurrence of severe hypoglycemia in type 2 diabetes compared with type 1 diabetes where both HGR and RGR counterregulatory responses are reduced.