Thursday, July 10, 2014
1. Pathway for driving beige fat formation. Cold stimulus promotes beige fat
formation and thermogenesis, but the pathways involved in such processes were
unclear. The recently hypothesized immune system-mediated pathway for driving
these processes could yield new ways to treat obesity, type 2 diabetes and
related metabolic disorders.
this pathway, cold stimulus triggers recruitment of CC chemokine receptor 2
(CCR2; CD192)+ monocytes
to white adipose tissues, where they differentiate into macrophages. Cold
stimulus also induces eosinophils in those tissues to release type 2 cytokines,
such as IL-4 (BSF1) and IL-13 (small yellow
cytokines induce alternative activation of macrophages. This process leads to
increased expression of tyrosine hydroxylase in myeloid cell populations found
in white adipose tissues, including the macrophages themselves.
increased expression of tyrosine hydroxylase results in more secretion of
catecholamines (small purple circles) from myeloid cells, which in turn drives
the formation of beige adipocytes and increases their thermogenesis activity.
these beige adipocytes are formed from white adipocytes or some precursor cell
population in white adipose tissue has not been determined.
least two points of intervention (red dashed arrows) have been identified. As
reported in Rao et al., the hormone meteorin glial cell differentiation
regulator-like (METRNL) (gray circles)
can induce expression of IL-4 and IL-13 and promote beige fat formation and thermogenesis
activity. Separately, Qiu et al. report that infusion of IL-4 itself has