Glucose absorbed in the digestive system goes directly to muscle and to adipose tissue, where it is stored, and also to the pancreas. The flow of glucose in the body and its regulation by insulin. Heterozygous GLUT4+/- mice that display decreased GLUT4 protein in muscle and adipose tissue are insulin resistant and develop diabetes later in life. 76,77 A central role for GLUT4 in whole-body metabolism is strongly supported by a variety of genetically engineered mouse models. The transport step is rate limiting for glucose uptake into fat and muscle under most conditions. Glucose transport in insulin-sensitive tissues has received considerable attention because of the importance of this process in the maintenance of whole body glucose disposal in the adult. GLUT4, unlike other facilititave GLUTs, is primarily localized intracellularly in the unstimulated state and is acutely redistributed to the plasma membrane in response to insulin and other stimuli. 74 GLUT4 contains unique sequences in its N- and C-terminal cytoplasmic domains that direct its characteristic membrane trafficking capability. The sequence of human GLUT4 is highly conserved, and 95% and 96% identity exists between the sequences of human and rat or mouse GLUT4. 72 Compared with the adult, little GLUT4 is expressed in fetal muscle 47 and brown fat, 73 and levels do not increase until well after birth. 49 Low levels are also expressed in fetal rat brain. GLUT4 is primarily expressed in adult tissues that exhibit insulin-stimulated glucose transport, such as adipose tissue and skeletal and cardiac muscle. ![]() Simmons, in Fetal and Neonatal Physiology (Fifth Edition), 2017 Glucose Transporter 4
0 Comments
Leave a Reply. |