Improvement of beta-cell function in conjunction with glycemic control after medical nutrition therapy in newly-diagnosed type 2 diabetes mellitus

BACKGROUND: The current study aimed to reveal the correlation of beta-cell function and insulin sensitivity with glycemic control and weight control before and after medical nutrition therapy (MNT) in patients with newly-diagnosed type 2 diabetes mellitus. METHODS: We retrospectively analyzed consecutive 68 patients with newly-diagnosed type 2 diabetes mellitus who started MNT without antihyperglycemic medications and underwent a 75-g oral glucose tolerance test (OGTT) before and after the therapy. Beta-cell function was evaluated by the OGTT-derived disposition index, whereas insulin sensitivity was evaluated by Matsuda’s insulin sensitivity index. RESULTS: After 4.0 ± 1.5 months of MNT, mean HbA1c and body mass index significantly decreased from 9.6 ± 1.8% to 7.2 ± 1.0% and from 26.9 ± 4.1 to 25.4 ± 3.7 kg/m(2) (both P < 0.001), while the median disposition index and Matsuda’s index significantly increased from 0.34 (0.20–0.68) to 0.88 (0.53–1.52) (P < 0.001) and from 4.70 (2.95–5.93) to 5.17 (3.48–6.89) (P = 0.003), respectively. The disposition index was significantly correlated with HbA1c levels both before and after MNT (r = -0.61 and -0.68; both P < 0.001). The magnitude of the correlation after MNT was not different from that before MNT (P = 0.42). Matsuda’s index was correlated not with HbA1c levels but with body mass index, both before (r = 0.07 [P = 0.57] and r = -0.58 [P < 0.001]) and after MNT (r = -0.01 [P = 0.95] and r = -0.52 [P < 0.001]). CONCLUSIONS: Beta-cell function was improved in conjunction with glycemic control after MNT in patients with newly-diagnosed type 2 diabetes mellitus. Insulin sensitivity was linked with weight control rather than glycemic control. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-022-01064-w.