Impact of Gastric Banding Versus Metformin on β-Cell Function in Adults With Impaired Glucose Tolerance or Mild Type 2 Diabetes

Abstract

Objective: Type 2 diabetes (T2D) results from progressive loss of β-cell function. The BetaFat study compared gastric banding and metformin for their impact on β-cell function in adults with moderate obesity and impaired glucose tolerance (IGT) or recently diagnosed, mild T2D.

Research design and methods: Eighty-eight people aged 21-65 years, BMI 30-40 kg/m2, with IGT or diabetes known for <1 year, were randomized to gastric banding or metformin for 2 years. Hyperglycemic clamps (11.1 mmol/L) followed by arginine injection at maximally potentiating glycemia (>25 mmol/L) were performed at baseline, 12 months, and 24 months to measure steady-state C-peptide (SSCP) and acute C-peptide response to arginine at maximum glycemic potentiation (ACPRmax) and insulin sensitivity (M/I).

Results: At 24 months, the band group lost 10.7 kg; the metformin group lost 1.7 kg (P < 0.01). Insulin sensitivity increased 45% in the band group and 25% in the metformin group (P = 0.30 between groups). SSCP adjusted for insulin sensitivity fell slightly but not significantly in each group (P = 0.34 between groups). ACPRmax adjusted for insulin sensitivity fell significantly in the metformin group (P = 0.002) but not in the band group (P = 0.25 between groups). HbA1c fell at 12 and 24 months in the band group (P < 0.004) but only at 12 months (P < 0.01) in the metformin group (P > 0.14 between groups). Normoglycemia was present in 22% and 15% of band and metformin groups, respectively, at 24 months (P = 0.66 between groups).

Conclusions: Gastric banding and metformin had similar effects to preserve β-cell function and stabilize or improve glycemia over a 2-year period in moderately obese adults with IGT or recently diagnosed, mild T2D.

Trial registration: ClinicalTrials.gov NCT01763346.

© 2018 by the American Diabetes Association.

Figures

Figure 1

Body weight (A), HbA1c (B), OGTT fasting (C), and 2-h (D) glucose concentrations over the course of the study in participants who were randomized to gastric banding (open circles, n = 36) or metformin (solid circles, n = 34) and who participated in 24-month glucose clamp studies. Metformin was withheld on the day of each visit. Asterisks denote within-group differences from baseline (*P < 0.05, **P < 0.01). P values listed as text in the top of each figure denote intergroup differences. Data are mean ± SE.

Figure 2

Relationship between insulin sensitivity (M/I) and each of the two coprimary outcomes from clamp studies: SSCP (A) and ACPRmax (B) in participants randomized to gastric banding (red circles) or metformin (green circles). “B,” “12,” and “24” denote data collected at baseline, 12 months, and 24 months on trial, respectively. The black line depicts the model fit of the data at baseline for all 70 participants, in the format y = xb *ea where “a” and “b” were the intercept and slope, respectively, for the linear model of log-transformed “y” (SSCP or ACPRmax) against log-transformed “x” (M/I). Changes that parallel the black line indicate stable β-cell compensation for insulin sensitivity. Changes downward compared with the slope of the black line indicate declining β-cell compensation; changes upward compared with that slope indicate increasing compensation. P values for changes from baseline within groups and for differences between groups appear in Table 2 and Results.