2.1. Animals and animal care
C57BL/6J male mice (CLEA Japan, Tokyo, Japan) aged 8 weeks were fed standard chow (Oriental Yeast, Tokyo, Japan) and were allowed free access to food and water at room temperature (25°C) under a 12-h light cycle. The mice were randomly divided into four groups, and treated with the vehicle, linagliptin (Lina), OSI-906, or OSI-906 in combination with linagliptin (OSI-906 + Lina) for 7 days. This study was approved by the Yokohama City University Institutional Animal Care and Use Committee (IACUC) (Permit Number: F-A-14-041) and was conducted in accordance with the guidelines of the Animal Care Committee of Yokohama City University.