Intestinal lipid dysregulation is a common feature of insulin-resistant states. The present study investigated alterations in gene expression of key proteins involved in the active absorption of dietary fat and cholesterol in response to development of insulin resistance. Studies were conducted in two diet-induced animal models of insulin resistance: fructose-fed hamster and high-fat-fed mouse. Changes in the mRNA abundance of lipid transporters, adenosine triphosphate cassette (ABC) G5, ABCG8, FA-CoA ligase fatty acid translocase P4, Niemann-Pick C1-Like1 (NPC1L1), fatty acid transport protein 4 (FATP4), and Scavenger Receptor Class B Type I (SR-BI), were assessed in intestinal fragments (duodenum, jejunum, and ileum) using quantitative real-time PCR. Of all the transporters evaluated, SR-B1 showed the most significant changes in both animal models examined. A marked stimulation of SR-B1 expression was observed in all intestinal segments examined in both insulin-resistant animal models. The link between SR-BI expression and intestinal lipoprotein production was then examined in the Caco-2 cell model. SR-B1 overexpression in Caco-2 cells increased apolipoprotein B (apoB) 100 and apoB48 secretion, whereas RNAi knock down of SR-B1 decreased secretion of both apoB100 and apoB48. We also observed changes in subcellular distribution of SR-B1 in response to exogenous lipid and insulin. Confocal microscopy revealed marked changes in SR-BI subcellular distribution in response to both exogenous lipids (oleate) and insulin. In summary, marked stimulation of intestinal SR-BI occurs in vivo in animal models of diet-induced insulin resistance, and modulation of SR-BI in vitro regulates production of apoB-containing lipoprotein particles. We postulate that apical and/or basolateral SR-BI may play an important role in intestinal chylomicron production and may contribute to chylomicron overproduction normally observed in insulin-resistant states.
BACKGROUND
Simulation-based surgical skills training during preclinical education is a persistent challenge due to time constraints of trainees and instructors alike. Self-directed practice is resource-efficient and flexible; however, insight into technical proficiency among trainees is often lacking. The purpose of this study is to prospectively assess the accuracy of self-assessments among medical students learning basic surgical suturing.
METHODS
Over seven weekly practice sessions, preclinical medical students performed serial repetitions of a simulation-based suturing task under one-on-one observation by one of four trainers. Following each task repetition, self- and trainer-assessments were performed using a 36-point weighted checklist of technical standards developed a priori by expert consensus. Upon study completion, agreement between self- and trainer-assessments was measured using weighted Cohen’s kappa coefficients.
RESULTS
Twenty-nine medical students each performed a median of 25 suture task repetitions (IQR 21.5–28). Self-assessments tended to overestimate proficiency during the first tertile of practice attempts. Agreement between self- and trainer-assessments improved with experience, such that the weighted kappa statistics for the two-handed and instrument ties were greater than 0.81 after 18 to 21 task attempts.
CONCLUSIONS
Inexperienced trainees frequently overestimate technical proficiency through self-assessments. However, this bias diminishes with repetitive practice. Only after trainees have attained the capacity to accurately self-assess can effective self-directed learning take place.
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