Utilize the input text as a context reference, choose the right relationship between 'beta cell' and 'insulin' from the options.
Options: headquarters location, owner of, operator, product/material produced

In contrast, patients receiving a single course of teplizumab demonstrated a relative increase in C-peptide levels, suggesting not only a delay in beta cell destruction, but also the recovery of sick or dying beta cells and the restoration of their functionality and insulin secretion.
product/material produced