This study will investigate the effects of gastric bypass surgery on type II diabetes. The study will recruit patients with type II diabetes having Roux-en-Y gastric bypass, patients without type II diabetes having Roux-en-Y gastric bypass, and control subjects (patients having gastroscopy, but no surgery). Targeted enrollment is 30 patients per group. Samples of intestine are taken prior to surgery in gastroscopy, during surgery, and 6 months after surgery during gastroscopy. Meal test with incretin measurements, and feces and blood samplings are performed before and after surgery

Hypotheses are:

• The pathogenesis of type II diabetes is linked to changes in the expression of intestinal endocrine cells
• The changes in the incretine excretion after the gastric bypass surgery partly explain the amelioration of type II diabetes
• The oxidation of lipoprotein is diminished after the gastric bypass surgery slowing the development of atherosclerosis
• The immunologic functions of the intestine are changed by the gastric bypass surgery attenuating systemic inflammation
• The gastric bypass surgery changes cholesterol and bile acid metabolism
• The gastric bypass surgery changes the fecal microbiota

Primary end points are:

• Changes in the amounts of endocrine cells in ventricle, duodenum and jejunum
• Changes in the incretine secretion studied with liquid meal test
• Changes in the oxidation of lipoproteins
• Changes in the immunologic markers in ventricle, duodenum and jejunum
• Changes in the amounts of phytosterols, cholesterol metabolites and bile acids
• Changes in fecal microbiota

Inclusion Criteria (patients with surgery):

• Patients having Roux-en-Y gastric bypass (according to clinical guidelines)
• Age: 18-65 years

Inclusion Criteria (control patients without surgery):

• Patients having gastroscopy (for various clinical reasons)

Exclusion Criteria:

• Diabetes (applies for control patients)
• BMI over 30 (applies for control patients)
• Insulin treatment
• Oral corticosteroid treatment
• Chronic inflammatory disease
• Coeliac disease
• Malignant disease

All patients are recruited from Oulu University Hospital