Metabolism of gut

Function of the small intestine

Absorption (monosaccharides, fat, aminoacids, vitamines, water, metals and trace elements)Defence against bacteria, toxines and antigen entryHormone productionMotility – transit of nutrients

Absorption in small intestine

Jejunum:Glucose and monosaccharidesFA, glycerol, mono- acylglycerol,phospholipidsAminoacidsVitaminesElectrolytes, Ca, Fe

Ileum:Cholic acidsB12 vitH2O, Na, K, ….

Investigation of intestinal function:

Test of carbohydrate absorption: monosaccharides (D-xylose, L-rhamnose) are not metabolized in the body are excreted and in the urin is measured the contentTest of fat absorption: normaly is dietary fat absorbed in the small intestine. Pancreatic, hepatic and intestinal disease increased the fat content in faeces( normaly must be lower than 6g/24h).

Triolein breath test: 13C-triolein substrate is metabolized and samples of expired 13CO2 : 12CO2 are measured.

Aminoacid absorption: malabsorption of specific AA occures in inherited metabolis diseases

Decreased absorption of nutrients: malabsorption

Deficit microvillar enzymes: alactasia,sucrase-isomaltase deficitPancreatic enzymes deficiency:protein lossing enterophaty Bile salt deficiency: steatorhea

Deficit of transport mechanism:Anemia (Fe, folic acid, B12)Osteomalacia (Ca, D vitamin)Aminoacids

Most ingestet food is absorbed in small intestine, the residue passes into large intestine:

Bacteria produce gases: CO2, CH4, H2, H2S, NH3, acetic, lactic, propionic and butyric acidH2O is absorbed

Ions are absorbedEnd material is excreated in form of stool

The main role of the colon is the absorption of water and electrolytes. Input and output of water and electrolytes in the GI over 24 h

INPUT Water ml Na mmol K mmol

Diet 1500 150 80

GI secretion

7500 1000 40

Total 9000 1150 120

Out putFaeces 150 5 12

Stool

Volume: <200g/d (higher volume is in malabsorption)Dry weight make 30%Composition:25% minerals (Na, K, Cl, Ca, PO4, Fe, Cu, Mn, Zn, I)

25% intestinal flora 50% organic components

Stool

pH-neutral:(acidic pH 5,5 by microbial dyspepsia)Color: from bile pigments – urobilin and stercobilin. Newborns – bilirubinOdour: gases and scatol, indol, thiomethanEnzymes: trypsin, chymotrypsin, elastaseToxic and neurotoxic metabolites: H2S, NH3, diamines, tyramin, neurin