Adipocyte biology and insulin resistance

We are identifying genes and proteins involved in development of insulin resistance and stress responses in adipose cells, including their responses to reactive oxygen species.

A kinase important for immune cells in the development of adipocytes

Marko Knoll, together with Heide Christine Patterson, is investigating how this specific kinase regulates the development of adipocytes using a floxed mice for the kinase and breeding these mice to a mouse expressing a fat cell specific Cre under the control of the adiponectin promoter. Identified as a top hit in a screen against the kinome, inhibition of this kinase and/or its deletion diminished whereas enhanced expression and activity increased β – agonist- triggered thermogenesis; this was measured my induced expression of the mitochondrial uncoupling protein Ucp1 in brown adipocytes in vitro. Further, this kinase promoted protein kinase B (Akt) activation, mitochondrial respiration, and expression of genes critically required for mitochondrial biogenesis and function in response to induction of thermogenesis. Kinase deletion in adipose tissue resulted in partial lethality of the mice that was rescued by thermoneutrality, as well as impaired expansion of brown preadipocytes, decreased brown fat mass, and impaired cold-induced browning. The only brown and beige adipocytes that developed were those that escaped kinase deletion. On a high fat diet, these mice displayed severe glucose intolerance and insulin resistance associated with obesity and decreased energy expenditure. These results establish this kinase as an essential mediator of brown fat formation and function, suggesting that pharmacological modulation of kinase activity and its targets has the potential to treat diabetes.

A novel kinase that mediates signaling by oxidative stress and in vivo insulin resistance

Heide Christine Patterson, a post-doc in the laboratory and a pathologist at Brigham and Women's Hospital, together with Marko Knoll, a post-doc, are investigating whether a kinase important for signal transduction in immune cells also mediates activation of oxidative stress induced pathways. They are determining in what subcellular compartment the signaling occurs and what components regulate activation of this kinase, as well as its in vivo relevance for function of brown adipocytes. They are using a combination of approaches that include genetic and pharmacological manipulation of primary B cells, fibroblasts, and adipocytes as well as bioinformatics and in vivo functional assays using conditional gene targeting in mice.