Pharmaceutical compositions and methods for protecting against atrophy of pancreatic islets in a mammal with metabolic syndrome, prediabetes or diabetes are disclosed. The method comprises administering to the mammal a pharmaceutical composition comprising a compound having a chemical structure of formula (I) in an effective amount and a pharmaceutically acceptable carrier: wherein R is H or COCH2COOH; m=3 or 4; n=0 or 1; o=2; and p=1 or 2.