Fluorescent visualization and evaluation of NPC1L1- mediated vesicular endocytosis during intestinal cholesterol absorption in mice

Excessive cholesterol absorption from intestinal lumen contributes to the pathogenesis of hypercholesterolemia,which is an independent risk factor for atherosclerotic cardiovascular disease.Niemann-Pick C1-like 1(NPC1L1)is a major membrane protein responsible for cholesterol absorption,in which the physiological role of vesicular endocytosis is still controversial,and it lacks a feasible tool to visualize and evaluate the endocytosis of NPC1L1 vesicles in vivo.Here,we genetically labeled endogenous NPC1L1 protein with EGFP in a knock-in mouse model,and demonstrated fluorescent visualization and evaluation of the endocytic vesicles of NPC1L1-cago during intestinal cholesterol absorption.The homozygous NPC1L1-EGFP mice have normal NPC1L1 expression pattern as well as cholesterol homeostasis on chow or high-cholesterol diets.The fluorescence of NPC1L1-EGFP fusion protein localizes at the brush border membrane of small intestine,and EGFP-positive vesicles is visualized beneath the membrane as early as 5 min post oral gavage of cholesterol.Of note,the vesicles colocalize with the early endosomal marker early endosome antigen 1(EEA1)and the filipin-stained free cholesterol.Pretreatment with NPC1L1 inhibitor ezetimibe inhibits the formation of these cholesterol-induced endocytic vesicles.Our data support the notion that NPC1L1-mediated cholesterol absorption is a vesicular endocytic process.NPC1L1-EGFP mice are a useful model for visualizing cellular NPC1L1-cargo vesicle itineraries and for evaluating NPC1L1 activity in vivo in response to diverse pharmacological agents and nutrients.

Epidemiological Study of Sepsis in China： Protocol of a Cross-sectional Survey

Background： Sepsis is the leading cause of death among critically ill patients. Herein, we conducted a national survey to provide data on epidemiology and treatment of sepsis in the clinical practice in China, which has no detailed epidemiological data available on sepsis. Methods： This was a prospective cross-sectional survey from December 1, 2015 to January 31, 2016 in all provinces/municipalities of the mainland of China. The primary outcome of this study was the incidence of sepsis, and the secondary outcome was its etiology in China. Patients with sepsis admitted to the Intensive Care Units were included in this study. The demographic, physiological, bacteriological, and therapeutic data of these patients were recorded. The incidence of sepsis was estimated using the data from the sixth census in China, reported by the Chinese National Health and Family Planning Commission and the National Bureau of Statistics as the standard population. The independent risk factors for increased mortality from sepsis were calculated. Conclusions： This study indicated the incidence and outcome of sepsis in China. It also showed the most common etiology of different sites and types of infection, which could guide empiric antibiotic therapy. Moreover, it provided information on the independent risk factors for increased mortality due to sepsis. The findings provide evidence to guide clinical management and may help improve the outcome in septic patients.