Diabetes develops progressively in β cell–specific frataxin knockout animals. (a) Blood glucose concentrations in knockout animals (indicated by black bars) and control animals (comprising wild-type, heterozygous Ins2-cre, and homozygous loxP genotypes; indicated by gray bars) after overnight ad libitum supply of standard chow (random-fed). (b) Blood glucose concentrations after an overnight fast. Error bars depict SEM. *0.05 > P > 0.005; **P < 0.005.