SCFA transport in rat duodenum.

Area of Science:

• Gastroenterology
• Molecular Biology
• Physiology

Background:

• Short-chain fatty acids (SCFAs) are present in the duodenal lumen from bacteria and food.
• Acetate, the most abundant SCFA, is rapidly absorbed, but the mechanism is unclear.

Purpose of the Study:

• Investigate the distribution and function of SCFA transporters in the rat duodenum.
• Elucidate the mechanism of acetate absorption and its physiological consequences.

Main Methods:

• Localization of candidate SCFA transporters (SMCT1, MCT1, MCT4) in rat duodenum.
• Ussing chamber experiments to measure short-circuit current (Isc) in response to luminal acetate.
• Duodenal loop perfusion studies to assess acetate absorption and portal venous concentration.
• Measurement of duodenal bicarbonate (HCO3-) secretion.

Main Results:

• SMCT1 localized to the brush border; MCT1 and MCT4 to the basolateral membrane.
• Luminal acetate increased Isc via a Na(+)-dependent mechanism, inhibited by SMCT1 inhibitor ibuprofen, indicating electrogenic absorption via SMCT1.
• Acetate perfusion increased portal venous acetate and stimulated duodenal HCO3- secretion via nerve and cyclooxygenase activation.

Conclusions:

• Duodenal SCFA absorption occurs via SMCT1 and MCTs, leading to increased bicarbonate secretion.
• Rapid SCFA absorption may suppress bacterial colonization and play a role in functional dyspepsia associated with bacterial overgrowth.