What is the relationship between beta cell and insulin in the context of the input sentence. Choose an answer from: 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.

No new safety signals or data were presented at this year's ADA conference, but data was presented that confirmed the preservation and restoration of beta cell function as determined by C-peptide, which is a measure of a person's own insulin production.

Answer: product_or_material_produced