The proliferation and migration of vascular smooth muscle cells(VSMCs)play an essential role during the development of atherosclerosis and restenosis.While many factors potentially contribute to the abnormal activation of VSMCs,hyperglycemia is generally believed to be a major causative factor.On the other hand,FAM3B(named PANDER for its secretory form)is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas.FAM3B is co-secreted with insulin from the β-cell upon glucose stimulation and regulates glucose homeostasis.However,the roles of FAM3B in the regulation of VSMC physiology,especially under the hyperglycemic condition,remain unknown.Here,we showed that FAM3B was significantly induced in the VSMC layer of hyperglycemic rats and high glucose-treated VSMCs.Knockdown of FAM3B by small interfering RNA transduction markedly inhibited,whereas FAM3B overexpression significantly accelerated VSMC proliferation and migration.At the molecular level,enforced expression of miR-322-5p significantly antagonized FAM3B-induced VSMC proliferation and migration,suggesting that FAM3B facilitated VSMC pathological activation through inhibition of miR-322-5p.Taken together,FAM3B mediates high glucose-induced VSMC proliferation and migration and may therefore serve as a novel therapeutic target for related cardiovascular diseases such as atherosclerosis.