Finally, we discovered that pre-operation HbA1c levels and age accurately predicted HbA1c change in the one to three months following surgery [29], indicating that aging is associated with a loss of pancreatic function and increased insulin resistance. The greater the HbA1c and the younger the patient, the better glycemic control or diabetes remission. The changes in gastrointestinal hormonal response [30] and gut microbiota with aging may be the additional causes for the effects we identified in this investigation. Here, INS is linked to diabetes mellitus.