The present invention provides a compound which has a PDHK-inhibiting activity and is useful for the treatment or prevention of diabetes (type 1 diabetes, type 2 diabetes, etc.), insulin resistance syndrome, metabolic syndrome, hyperglycemia, hyperlactatemia, diabetes complications (diabetic neuropathy, diabetic retinopathy, diabetic nephropathy, cataract, etc.), heart failure (acute heart failure, chronic heart failure), cardiomyopathy, myocardial ischemia, myocardial infarction, angina pectoris, dyslipidemia, atherosclerosis, peripheral arterial disease, intermittent claudication, chronic obstructive pulmonary disease, brain ischemia, stroke, mitochondrial disease, mitochondrial encephalomyopathy, cancer, pulmonary hypertension or Alzheimer's disease. The present invention relates to a compound represented by formula [I-a] or [II] or a pharmaceutically acceptable salt thereof. [In the formulae, each symbol is as defined in the description.]
