The ketone body (KB) ß-hydroxybutyrate will be given to eight fasting healthy volunteers of both sexes in order to observe the effects after an oral glucose tolerance test (OGTT) over 2 h. Then, a standard lunch will be served at 12.00, as well as an afternoon snack at 15.00. Each participant will be its own control and participates in a randomised two-way cross over design; the KB are released in the stomach-duodenum, or in the ileum-colon. Peripheral blood samples are taken for endpoint GLP-1 analyses.

It has been shown in man that a fatty diet in people with obesity stimulated the release of ketone bodies (KB) in the small intestinal mucosa. This observation was partly explained by an increased level of the ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) in the jejunum of the obese people.

Glucagon-like peptide 1 (GLP-1) is a peptide that is released from the intestinal mucosa and mediates among other things, satiation, as well as insulin-secretion and insulin-sensitivity. In patients with obesity, GLP-1 response to food is attenuated, but it increases following bariatric surgery.

The question arose if the increased KB could be linked to the decreased level of meal-induced GLP-1. Indeed, in mice and rats the increased production of KB could be related to a decreased level of GLP-1. However, such a close relationship has never been shown in man.

The present study tests, therefore, if release of the ketone body beta-hydroxybutyric acid into the intestine on two levels (stomach/duodenum and ileum/colon) of healthy volunteers influences the blood concentration of GLP-1 following an oral glucose tolerance test (OGTT). Glucose, insulin and KB are determined in peripheral plasma according to OGTT-routine.

KB are lipid-derived organic molecules that can serve a circulating energy source during starvation/fasting (or pronged exercise). Beta-hydroxybutyrate (BHB), acetoacetate (AcAc) and acetone ("ketone bodies") are products of acetyl-CoA derived from fatty acids converted to via hepatic mitochondria. The three KB are connected to each by proteolytic interconnection. BHB is the most important source of energy, while AcAc is approximately 25-30% of BHB. Acetone is gas-soluble and is exhaled if ketonemia increases.

The present study utilises ingestion of one KB (BHB) to get an acute, rapid increase in ketonemia. An encapsulation technology is used to differentiate the effect of KB on the small intestine from the effect mainly in the colon. Microcapsules with 1./ alginate, will release the KB in proximal stomach/duodenal intestine, and 2./ pea protein will release in the distal part of the intestine, mainly colon. The microcapsules are of food grade and are produced according to Good Manufacturing Process (GMP) standards (AnaBio Technologies LTD, Cork, Ireland). The KB in the microcapsules will contain 18 g BHB- and Ca+, Mg2+. Together with the encapsulation material (alginate or pea-protein) the total weight will be 20g per dose.

Inclusion Criteria:

• 18 to 65 years of both sexes
• healthy and without prescribed pharmaceuticals (anticonceptive drugs allowed)
• no symptoms associated with gastrointestinal dysfunction

Exclusion Criteria:

• pregnancy or breastfeeding
• allergy towards standard meals or treatment
• previous substance abuse

Study Protocol and Informed Consent Form will be delivered to the study personnel.

From the 12th of October 2021, to end of 2022.

Laboratory of Surgical Research, Sahlgrenska Universityhospital, Gothenburg, Sweden