ObjectiveTo investigate the effect and mechanism of sleeve gastrectomy (SG) on reducing blood glucose level. MethodsThirty GK rats were randomly divided into SG group, sham operation (SO) group, pair-fed (PF) group, and blank control (BC) group. The changes of weight, fasting blood glucose, glucose tolerance (oral glucose tolerance test, OGTT), insulin tolerance (insulin tolerance test, ITT), plasma insulin, ghrelin, and glucagon like peptide-1 (GLP-1) were monitored before and 24 weeks after operation respectively. ResultsFrom the 4th week after operation, weight gain in SG group and PF group began to decrease significantly compared with SO group (Plt;0.01). From the 2nd week after operation, fasting blood glucose level in SG group was lower than that in SO, PF, and BC groups (Plt;005), and the glucose tolerance in SG group obviously improved compared with preoperation and the other 3 groups (Plt;0.01). On the 6th week after operation, the insulin sensitivity in SG group obviously improved compared with SO group (Plt;0.05, Plt;0.01). There was no significant difference of insulin level between SG group and SO group (Pgt;0.05), ghrelin level significantly decreased (Plt;0.01) while GLP-1 level significantly increased (Plt;0.01) in SG group compared with SO group during 2-24 weeks after operation. ConclusionsThe effect of SG on reducing blood glucose is definite. SG can directly lower blood glucose independent with weight loss. Postoperative decreased ghrelin level and increased GLP-1 level may be its primary mechanism.
Randomized controlled trials (RCTs) are often limited because of ethical or operational reasons. Quasi-experimental studies could be an alternative to RCTs to make causal inferences without randomization by controlling the confounding effects of the study. This paper introduced the general statistical analysis methods of quasi-experimental design through basic ideas, characteristics, limitations and applications in medicine, including difference-in-difference models, instrumental variables, regression discontinuity design, interrupted time series, and so on, and to provide references for future research.