Most animals including humans are experiencing fasting-feeding cycles throughout their lives. Upon feeding, the rise of blood glucose level is reduced by increasing glucose uptake in peripheral tissues such as liver and skeletal muscles. Dysregulation in blood glucose homeostasis is associated with many disorders such as diabetes and cardiovascular diseases. As a glucose sensor, liver is actively involved in removal of postprandial blood glucose via glycogen synthesis. However, how hepatic glycogenesis is coupled with the fasting-feeding cycle to control postprandial blood glucose homeostasis remains unclear. Recently, scientists from the Chinese Academy of Sciences have provided insight into the role of glycogen metabolism in glucose homeostasis and lipid metabolism in the liver. 

Earlier study at Dr. CHEN Yan’s lab at the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, CAS found that PPP1R3G, a novel glycogen-targeting regulatory subunit of a protein phosphatase 1, is actively involved in the control of blood glucose homeostasis by regulating hepatic glycogenesis in a manner closely coordinated with the fasting–feeding cycle. In a recent study, a PhD student ZHANG Yongxian and his colleagues, under the supervision of Dr. CHEN, used a mouse model with liver-specific overexpression of PPP1R3G to further explore the physiological function of PPP1R3G.   

Overexpression of PPP1R3G could markedly enhance hepatic glycogen accumulation and increase the clearance rate of postprandial blood glucose. In addition, the transgenic mice have a reduced fat composition, together with decreased triglyceride level in the liver and blood. Interestingly, PPP1R3G overexpression in the liver could also improve fasting-induced fatty liver. Collectively, these findings reveal that PPP1R3G plays a critical role in glucose homeostasis. In addition, this work indicates that glycogen metabolism in the liver is closely associated with lipid metabolism in the body.   

This work entitled “Regulation of glucose homeostasis and lipid metabolism by PPP1R3G-mediated hepatic glycogenesis“ was published online in Molecular Endocrinology on Nov 21, 2013. This work was supported by grants from National Natural Science Foundation of China, the Ministry of Science and Technology of China, and the Chinese Academy of Science. 

CONTACT:
CHEN Yan, Principle Investigator
Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences,
Shanghai 200031, China.
Tel: 86-21-54920916
Fax: 86-21-54920291
Email: ychen3@sibs.ac.cn 
Website: http://press.endocrine.org/doi/pdf/10.1210/me.2013-1268