Insulin-stimulated glucose uptake partly relies on p21-activated kinase (PAK)2, but not PAK1, in mouse skeletal muscle

The group I p21‐activated kinase (PAK) isoforms PAK1 and PAK2 are activated in response to insulin in skeletal muscle and PAK1/2 signalling is impaired in insulin‐resistant mouse and human skeletal muscle. Interestingly, PAK1 has been suggested to be required for insulin‐stimulated glucose transporter 4 translocation in mouse skeletal muscle. Therefore, the present study aimed to examine the role of PAK1 in insulin‐stimulated muscle glucose uptake. The pharmacological inhibitor of group I PAKs, IPA‐3 partially reduced (–20%) insulin‐stimulated glucose uptake in isolated mouse soleus muscle (P < 0.001). However, because there was no phenotype with genetic ablation of PAK1 alone, consequently, the relative requirement for PAK1 and PAK2 in whole‐body glucose homeostasis and insulin‐stimulated muscle glucose uptake was investigated. Whole‐body respiratory exchange ratio was largely unaffected in whole‐body PAK1 knockout (KO), muscle‐specific PAK2 KO and in mice with combined whole‐body PAK1 KO and muscle‐specific PAK2 KO. By contrast, glucose tolerance was mildly impaired in mice lacking PAK2 specifically in muscle, but not PAK1 KO mice. Moreover, while PAK1 KO muscles displayed normal insulin‐stimulated glucose uptake in vivo and in isolated muscle, insulin‐stimulated glucose uptake was slightly reduced in isolated glycolytic extensor digitorum longus muscle lacking PAK2 alone (–18%) or in combination with PAK1 KO (–12%) (P < 0.05). In conclusion, glucose tolerance and insulin‐stimulated glucose uptake partly rely on PAK2 in glycolytic mouse muscle, whereas PAK1 is dispensable for whole‐body glucose homeostasis and insulin‐stimulated muscle glucose uptake.