New research published in Diabetes reveals that even small rises in blood glucose—less than 0.5 mmol/L—can significantly suppress endogenous glucose production (EGP), but only when insulin secretion is intact. This finding, published following controlled glucose infusion experiments, provides new insight into the subtle but potent regulatory role of insulin in glucose metabolism and suggests implications for β-cell function and diabetes management.

Researchers infused glucose at a low rate (1 mg/kg/min) into two groups: healthy individuals without diabetes and individuals with type 1 diabetes (T1D), who lack endogenous insulin production. In non-diabetic participants, the minor glycemic increase led to a ~20% rise in insulin secretion, which in turn resulted in ~40% suppression of EGP. These effects occurred without any change in glucose disposal, while free fatty acids (FFAs) and glucagon were gradually suppressed by 30%.

In contrast, T1D participants receiving glucose infusions under constant basal insulin levels showed only a brief, modest suppression of EGP. Blood glucose continued to rise steadily, eventually increasing by nearly 2 mmol/L after 90 minutes. FFAs and glucagon remained unchanged, and glucose disposal showed only minimal improvement.

These findings demonstrate that the observed suppression of liver glucose output and lipolysis in healthy individuals is mediated by small, physiologically appropriate increases in insulin. The absence of a similar effect in people with T1D underscores insulin's essential role in these processes.

Importantly, the data also suggest that such minor glucose elevations could act as signaling mechanisms to support β-cell adaptation, which may have broader implications in understanding how the body maintains glucose homeostasis and in the early stages of diabetes development.