Investigation of Acute Physiological Effects of Aspiration Therapy

It is generally agreed that the increasing incidence of obesity mainly is caused by the adoption of a sedentary lifestyle combined with excessive caloric intake. So far, preventive measures and interventions based on lifestyle modifications have not been able to affect the western lifestyle to a degree that remedies the increasing prevalence of obesity. Likewise, no medical interventions have yet been able to induce and maintain significant major weight loss in obese populations. In contrast, bariatric surgery prompts a significant and often sustained weight loss, which frequently triggers remission of obesity-related comorbidities. However, bariatric surgery is invasive, irreversible and costly. Aspiration therapy was introduced as a less invasive and cheaper treatment for obesity. According to some studies, aspiration therapy is nearly as effective as Roux-en-Y gastric bypass in terms of excess weight loss after one year. Thus, aspiration therapy may aspire as an alternative treatment option for obesity with lower risk of complications than bariatric surgery.

The risk of developing impaired glucose tolerance and overt type 2 diabetes rises along with increasing obesity. The estimated risk of developing type 2 diabetes increases 3-fold with a body mass index (BMI) of 25-29.9 kg/m2 (overweight) and \~20-fold with a BMI >35 kg/m2 (severely obese) compared to a normal BMI (\<25 kg/m2) (6). Type 2 diabetes is a complex, multi-organ metabolic disorder and is associated with serious complications, reduced quality of life and early death. The disease is characterized by hyperglycaemia and, thus, elevated haemoglobinA1c (HbA1c) (>6.5% or >48mmol/mol), which is a blood parameter used clinically as a measure of mean blood glucose over time (\~3 months). Studies have shown that up to 70% of the mean plasma glucose levels is caused by postprandial plasma glucose excursions. Moreover, postprandial hyperglycaemia in itself seems to be associated with an elevated risk of cardiovascular disease due to unfavourable effect on both small and large blood vessels. Accordingly, postprandial hyperglycaemia has been suggested to constitute a better predictor of mortality risk than fasting plasma glucose concentrations in both patients with type 2 diabetes and individuals with normal glucose tolerance. Since the prevalence of impaired glucose tolerance is \~2-fold higher in obese compared to lean individuals, postprandial hyperglycaemia poses a great risk of developing severe comorbidities such as cardiovascular disease and type 2 diabetes for obese individuals and may increase mortality in this group. It is yet unknown whether aspiration therapy can attenuate the plasma glucose response to a meal. Due to the reduced amount of food reaching the intestine after aspiration, it seems likely that aspiration therapy reduces postprandial plasma glucose excursions and thereby prevents potential postprandial hyperglycaemia.

It is well known that an orally administered glucose load elicits a greater insulin secretion response compared to an intravenous infusion of glucose resulting in identical plasma glucose elevations. This phenomenon is called the incretin effect. The incretin effect is primarily driven by the insulinotropic gut hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These so-called incretin hormones play crucial roles in regulation of glucose homeostasis and appetite. GLP-1 is produced in the intestinal mucosa by the so-called enteroendocrine L cells, which are predominantly localised in the distal part of the small intestine and the colon. GIP originates from enteroendocrine K 5 cells in the gut mucosa. K cells are assumed to be predominant in the proximal part of the small intestine. Both GLP-1 and GIP are secreted in response to ingestion of nutrients and have strong glucose-dependent insulinotropic effects on pancreatic beta cells. The incretin hormones are of interest in the present study, because impaired incretin effect is an early sign of dysmetabolism in obese individuals and a distinctive feature of type 2 diabetes, suggesting that the impaired glucose tolerance of these patients is, at least in part, due to a defective incretin system. Whether aspiration of gastric content after a meal affects postprandial incretin hormone response has not been elucidated. The investigators plan to investigate meal-induced incretin hormone excursions in plasma with and without aspiration therapy and compare the results to a matched control group.

In addition to GLP-1 and GIP, several other gut-related hormones are known to regulate glucose homeostasis and appetite. Glucagon is a peptide hormone secreted from the pancreatic alpha cells. Glucagon acts opposite to insulin by promoting hepatic gluconeogenesis and glycogenolysis causing increased plasma glucose concentrations. Oxyntomodulin and pancreatic peptide YY3-36 (PYY) are peptide hormones secreted by the enteroendocrine L cells in response to feeding and both suppress appetite. Gastrin is a hormone secreted by G cells localised in the pyloric antrum, duodenum and pancreas. Gastrin stimulates acid (HCl) secretion and gastric emptying by increasing gastric motility. Cholecystokinin (CCK) is a peptide hormone secreted by the enteroendocrine I cells in the duodenum. CCK promotes bile release from the gallbladder and also acts as an appetite suppressant. To this point, it is unknown how aspiration therapy affects these appetite- and glucose-regulating hormones during a meal. The investigators aim to investigate this during standardised mixed meal tests with and without aspiration.

Furthermore, it is relevant to examine the effect of aspiration therapy on satiety. Thus, the investigators aim to evaluate the effect of aspiration therapy on satiety before, during and after a mixed meal as well as food intake after the MMT with and without aspiration evaluated through an ad libitum meal provided at the end of the experimental days.