Fluid-phase pinocytosis of LDL by macrophages is regarded as a novel promising target to reduce macrophage cholesterol accumulation in atherosclerotic lesions. The mechanisms of regulation of fluid-phase pinocytosis in macrophages and, specifically, the role of Akt kinases are poorly understood. We have found previously that increased lipoprotein uptake via the receptor-independent process in Akt3 kinase-deficient macrophages contributes to increased atherosclerosis in mice. The mechanism by which Akt3 deficiency promotes lipoprotein uptake in macrophages is unknown. We now report that Akt3 constitutively suppresses macropinocytosis in macrophages through a novel WNK1/SGK1/Cdc42 pathway. Mechanistic studies have demonstrated that the lack of Akt3 expression in murine and human macrophages results in increased expression of with-no-lysine kinase 1 (WNK1), which, in turn, leads to increased activity of serum and glucocorticoid-inducible kinase 1 (SGK1). SGK1 promotes expression of the Rho family GTPase Cdc42, a positive regulator of actin assembly, cell polarization, and pinocytosis. Individual suppression of WNK1 expression, SGK1, or Cdc42 activity in Akt3-deficient macrophages rescued the phenotype. These results demonstrate that Akt3 is a specific negative regulator of macropinocytosis in macrophages.

Aims Post-operative atrial fibrillation (POAF) is associated with stroke and mortality. It is unknown if POAF is associated with subsequent heart failure (HF) hospitalization. This study aims to examine the association between POAF and incident HF hospitalization among patients undergoing cardiac and non-cardiac surgeries. Methods and results A retrospective cohort study was conducted using all-payer administrative claims data that included all non-federal emergency department visits and acute care hospitalizations across 11 states in the USA. The study population included adults aged at least 18 years hospitalized for surgery without a prior diagnosis of HF. Cox proportional hazards regression models were used to examine the association between POAF and incident HF hospitalization after making adjustment for socio-demographics and comorbid conditions. Among 76 536 patients who underwent cardiac surgery, 14 365 (18.8%) developed incident POAF. In an adjusted Cox model, POAF was associated with incident HF hospitalization [hazard ratio (HR) 1.33; 95% confidence interval (CI) 1.25–1.41]. In a sensitivity analysis excluding HF within 1 year of surgery, POAF remained associated with incident HF hospitalization (HR 1.15; 95% CI 1.01–1.31). Among 2 929 854 patients who underwent non-cardiac surgery, 23 763 (0.8%) developed incident POAF. In an adjusted Cox model, POAF was again associated with incident HF hospitalization (HR 2.02; 95% CI 1.94–2.10), including in a sensitivity analysis excluding HF within 1 year of surgery (HR 1.49; 95% CI 1.38–1.61). Conclusions Post-operative atrial fibrillation is associated with incident HF hospitalization among patients without prior history of HF undergoing both cardiac and non-cardiac surgeries. These findings reinforce the adverse prognostic impact of POAF and suggest that POAF may be a marker for identifying patients with subclinical HF and those at elevated risk for HF.