Marked recovery from glucotoxicity of β-cell function after medical nutrition therapy without pharmacotherapy in type 2 diabetic outpatients with extreme hyperglycemia: a pilot retrospective study.

We investigated whether glucotoxicity of β-cell function could be eliminated after medical nutrition therapy (MNT) without forced correction of hyperglycemia by anti-diabetic medications including exogenous insulin administration. We analyzed newly diagnosed type 2 diabetic outpatients with hemoglobin A1c (HbA1c) of 10.1 ± 1.5%, who were treated by MNT at least for three months, without any aid of anti-diabetic medications. The β-cell function was calculated as the product of the ΔIns/ΔGlu and the Matsuda index, where ΔIns/ΔGlu represents the ratio of the incremental concentrations of insulin to those of glucose during the 0- to 120-min time periods under a 75-g oral glucose tolerance test. After MNT, HbA1c levels were reduced to 7.0 ± 1.0% (p < 0.001). The β-cell function was significantly improved (n = 13; p = 0.001; effect size d = 1.9). Fasting plasma glucose became below 7.0 mmol/l in 57% (8/13), and 120-minute plasma glucose became below 11.1 mmol/l in 43% (6/13). The β-cell function after MNT was significantly correlated with HbA1c levels achieved after MNT (Pearson's correlation coefficient r = -0.62, p = 0.025). In conclusion, the β-cell dysfunction was ameliorated after MNT without glucose-lowering pharmacotherapy in newly diagnosed type 2 diabetic outpatients who presented extreme hyperglycemia.