This book introduces the recent topics regarding the involvement of regucalcin in metabolic regulation and its related diseases. Cell signaling system may be potent interest in the fields of biomedical research. Regucalcin, which was discovered as a calcium-binding protein in 1978, is demonstrated to play a potential role as a suppressor in manifold intracellular signaling process linked to transcription activity. With growing studies, regucalcin has been demonstrated to play a multifunctional role in the regulation of the function of various types of cells and tissues, including the regulation of intracellular calcium homeostasis, various enzymes activity, cell signal transduction, nuclear function and gene expression, cell proliferation, apoptosis, and other cellular events. Regucalcin plays a pivotal role in maintaining cell homeostasis and protecting from disorders with ageing. This book focuses recent highlighted information regarding the role of regucalcin in metabolic regulation and its related diseases with aging. This book is constituted of 6 chapters as described in the following. This book will be of interest to graduate students, researchers, scientists and physicians focused on the fields of molecular and cellular biology, biomedical sciences, and clinical challenges.