The most critical considerations are a larger cohort of participants with T2D treated with metformin monotherapy; a longer duration of intervention; the inclusion of a companion prebiotic or additional butyrate-producing taxa; the direct measurement of GLP-1; and the collection of additional blood plasma specimens, especially during the oral meal tolerance tests to allow for identification of transient phenomena that manifest only during the postprandial period. The gene discussed is GCG; the disease is type 2 diabetes mellitus.