Early researchers studying pancreatic function isolated an active substance from islet tissues, which they named "insularin".

To investigate its role in hormonal communication and homeostasis, they administered controlled doses of insularin to healthy mammalian subjects and continuously monitored their blood glucose levels.

The graph below summarizes the results of these experiments.

Which of the following statements is/are correct interpretations of these experimental findings?

1. Insularin is synthesized and secreted by the $\beta$ cells in the islets of Langerhans.
2. Insularin causes a reduction in the concentration of blood glucose.
3. The glucose-lowering effect of a single injection of insularin is transient, with blood glucose returning to baseline within approximately 40 minutes.