What is the relationship between 'beta cell' and 'insulin' in the context of the input sentence.
Options: product/material produced, operator, owner of, headquarters location

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