Topical Area: Obesity
Sucrose Non-Fermenting Related Kinase (SNRK), a serine/threonine kinase, is a novel member of the AMPK/SNF1 family. We previously reported that adipose specific SNRK deficiency induced systemic inflammation and insulin resistance. In this study, we aimed to dissect the role of SNRK in white versus brown adipose tissue in insulin signaling and glucose homeostasis.
The SNRKloxp/loxp mice were mated with adiponectin-Cre (A-Cre) transgenic mice to generate the adipose tissue specific knockout model (SNRK-/-,A-Cre), and with UCP1-Cre (U-Cre) mice to generate the brown adipose tissue (BAT) specific knockout model (SNRK-/-,U-Cre). RNA sequencing and phosphoproteomics analysis were applied to identify the signaling pathways affected by SNRK deficiency and the potential substrate of SNRK.
SNRK deletion exclusively in BAT is sufficient to impair insulin signaling and glucose uptake without inducing local and systemic inflammation. Phosphoproteomic study identified PPP2R5D as the potential substrate of SNRK that regulates insulin signaling through controlling PP2A activity. Dephosphorylated PPP2R5D promotes constitutive assembly of PP2A-Akt complex in SNRK deficient primary brown adipocytes and BAT, therefore reduces insulin stimulated Akt phosphorylation and subsequent glucose uptake. RNA sequencing data provided further evidence to show that the PI3K/AKT signaling pathway is suppressed by SNRK deletion in primary brown adipocytes.
Insulin resistance in BAT alone is not sufficient to impact whole body glucose homeostasis, indicating that the role of SNRK in WAT and inflammation might be critical for observed systemic insulin resistance in SNRK-/-,A-Cre mice.
Funding Sources :
National Institute of Diabetes and Digestive and Kidney Diseases (R01 DK103699).