1. Figure 1 Candidate signalling pathways of irisin in adipocytes
Figure 1 | Candidate signalling pathways of irisin in adipocytes. Irisin stimulates the browning of white adipose tissue (WAT) by inducing the expression of UCP1 gene and, consequently, of UCP1 protein via the p38 mitogen-activated protein kinase (MAPK) and extracellular-signal regulated kinase (ERK) pathway. Brown adipose tissue (BAT) has an increased number of mitochondria and increased energy expenditure due to elevated oxygen consumption, and accumulates smaller lipids than do white adipocytes. After cold exposure, BAT has higher glucose uptake and GLUT4 (also known as SLC2A4) expression than WAT. Irisin, which is also secreted from muscle after cold exposure, can stimulate browning; a possible involvement of irisin in glucose uptake and GLUT4 expression seems to be plausible but has not yet been investigated. Irisin also stimulates lipolysis via the cyclic AMP (cAMP)–protein kinase A (PKA)–perilipin–hormone-sensitive lipase (HSL) pathway and through the upregulation of the expression of PNPLA2 (also known as ATGL), HSL and FABP4.
Perakakis, N. et al. (2017) Physiology and role of irisin in glucose homeostasis
Nat. Rev. Endocrinol. doi: /nrendo