Majority of researches have proven that bariatric surgery is an alternative for improving glucose and lipid metabolism. Remission of diabetes correlates with weight reduction [19]. Bariatric surgery is an excellent solution to Diabetes remission and weight reduction in most cases [20]. However, only few studies had researched on the impact of sleeve gastrectomy on pre-diabetics. In this study, the changes of glucose, lipid profile, bile acids of pre-diabetes, who underwent LSG, were explored and discussed.
Having a large meta-analysis [21] and recent observational studies [20] proven improvement in glucose metabolism had a correlation with weight reduction. Similarly, reduction of food intake capacity via bariatric surgery aided to weight loss as seen as continuous loss of weight in all groups, non-diabetics, diabetics, pre-diabetics, during the course of a year post-op. In terms of glycemic status, expectedly initial HbA1c and fasting glucose of prediabetics appeared to be significantly different in comparison to non-diabetics alone and T2DM alone. Improvement of glycemic control and body weight in pre-diabetics and diabetics began at the first month post-op and persisted in the next 12 months. This corresponded to Rubio-Almanza et al, who suggested that bariatric surgery improved glycemic control and obesity comorbidities in the pre-diabetes patient [22]. Besides, nearly 70% of pre-diabetics in our centre was treated by LSG. Within the course of study, remarkably improvement of glycemic state was observed in both diabetics and pre-diabetics. LSG therefore is an effective alternative for pre-diabetics, whom failing managed by lifestyle modification, to assist with both weight loss and glycemic control, thus delaying and preventing the progression of T2DM [23]. The advantage of LSG is minimal invasive, relatively low risks and few complications, and cost effective meanwhile highly effective in delaying and preventing the obesity and T2DM comorbidities and theirs irreversible neurovascular complications in advance [24]. Hence, LSG shall be encouraged in pre-diabetics. However, our study was a short-term follow-up study, long-term follow up will be continued and necessary, especially, these favourable results are related to weight loss.
Epidemiological and clinical studies have not only shown that HDL-C is negatively correlated with the incidence of atherosclerotic related disease, but also recently suggests that some effects of bariatric surgery take place speedily after surgery as it may involve increased HDL levels [25-27]. Similarly, HDL, ‘good cholesterol’ was significantly increased in prediabetics after 6 months LSG operation. HDL increased is thought to associate with improvement of hepatic insulin sensitivity [28]. This perhaps explains the improved glycemic status after bariatric surgery. Further research may be necessary to reveal the mechanism of how HDL affect glucose metabolism.
Bile acids are derivatives of cholesterol synthesized in the hepatocyte, thus bile acid synthesis is a regulator of body cholesterol. Initial mean concentration of TBA in diabetics and prediabetics was 3 µmol/L higher than the western [29-32]. The cause of high level of bile acid reminded unclear. Fatty liver, race, glycemic control or lipid profile may possibly contribute to the cause, resulting as compensatory bile acid secretion. Bile acid of prediabetics significantly reduced by the first year post-op. Some literatures indicated an increase in bile acids strongly correlates with the improvement in glucose and lipid metabolism [29, 30], but Robert E et al [32]do not support the hypothesis that bile acids are key mediators of the early increase in postprandial GLP-1 and PYY secretion for improvement in glucose metabolism in post-bariatric patients. Besides, Hilde Risstad et al [31] indicated form data that bile acids had no significant change in 1-year post-bariatric patients but significantly increased after 5 years. It is proved that bile acids are not key mediators for the improvement of glucose in early post-bariatric patients. Similarly, our results do not suggest that bile acid attributed to the rapid improvement in glycemic control seen shortly after surgery.
Regarding to lipid change, this study revealed that triglyceride (TG) significantly continued to decrease. The fact that bile acid was synthesized and secreted by hepatocytes, therefore, liver function directly affected synthesis of bile acids. Clinically, ALT and AST are sensitive indicators of liver damage. ALT and AST reduced in this study, indicating an improvement of liver function after metabolic surgery. Additionally, there is a correlation between the change of bile acid and ALT in pre-diabetics.
Some limitations are included in this study. At first, bariatric surgery is still in the developing stage in China, postoperative regular follow-up has not been paid close attention to some patients, resulting in a high rate of loss to follow-up. 35% of the patients were followup at 1 year post-operation in this study; therefore, the small postoperative sample size was shown. Besides, our study was a short-term follow-up study, but long-term follow up will be continued. Third, our result only reveals some clinical phenomenon, further researches are necessary to consider pre-diabetes as a criterion for metabolic surgery and long-term effect after metabolic surgery.