Utilize the input text as a context reference, choose the right relationship between beta cell and insulin from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

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.

Answer: product_or_material_produced