Short-chain Fatty Acid Transport Research Articles

Segmental differences of short-chain fatty acid transport across guinea-pig large intestine.

Unidirectional fluxes of short-chain fatty acids (SCFAs) were measured under short-circuit current conditions across guinea-pig caecum, proximal and distal colon. Fluxes increased linearly with concentration. In the caecum with equal concentrations on both sides of the mucosa the serosal-to-mucosal (sm) fluxes were nearly twice the mucosal-to-serosal (ms) fluxes for all SCFAs; in the distal colon ms fluxes were always higher than sm fluxes. Thus, in the caecum the net effect was secretion while in the distal colon net absorption occurred. In caecum, ms fluxes decreased with chain length while sm fluxes were similar for the three fatty acids, acetic, propionic and butyric acid. In the distal colon both unidirectional fluxes increased with chain length. Fluxes across the mucosa of the proximal colon were intermediate to those in caecum and distal colon. A paracellular transport of short-chain fatty acids is not present. The results indicate that other processes are involved in transcellular transport of SCFA besides non-ionic diffusion.

Transport of propionate by human ileal brush-border membrane vesicles

Human ileal brush-border membrane vesicles were employed to study the mechanisms of short-chain fatty acid (propionate) absorption especially to determine the effects of intravesicular HCO3- and the component of nonionic diffusion. Preloading the vesicles with HCO3- resulted in up to 20-fold "overshoots" of transport, and this effect was not seen with other intravesicular anions. This transport process was very fast (peak uptake 6 s) and was not due to intravesicular buffering by HCO3-. Radiolabeled propionate transport demonstrated transstimulation when the vesicles were preloaded with unlabeled propionate. An inward H+ gradient led to stimulation of propionate transport much smaller than in the presence of trans-HCO3-, whereas an inward Na+ gradient had no effect. Propionate transport was attenuated by the anion exchange inhibitors SITS and DIDS. Under HCO3- gradient conditions, propionate transport exhibited saturation kinetics with an apparent Km of 21 +/- 3 mM and a Vmax of 50 +/- 3 nmol.mg protein-1.3 s-1. Propionate transport was inhibited up to 40% by 2-5 carbon short-chain fatty acids (10 mM) but not by other organic anions. Short-chain fatty acid transport in the human ileum is Na+ independent and occurs mostly via a specific anion exchange mechanism with HCO3-. Our results also demonstrate a small component of nonionic diffusion of the protonated fatty acid (or anion exchange for OH-).

Short-chain fatty acid absorption in rabbit colon in vitro

Short-chain fatty acids are the predominant luminal anion in the colon and are generally absorbed rapidly in vivo. However, the mechanisms of in vitro transport of short-chain fatty acids have not been fully delineated. Therefore, we examined [14C]propionate fluxes in rabbit proximal colon under shortcircuit conditions. There was minimal metabolism of propionate (<10%), permitting accurate flux measurements using a radioisotopic tracer. In a 20 mmol/L propionate Ringer's solution at pH 7.4, there was a significant rate of propionate secretion (−0.58 ± 0.08 μEq · cm−2 · h−1). Decreasing pH to 6.8 by decreasing bicarbonate concentration in the bathing medium resulted in increases in unidirectional fluxes but no change in net transport. Reversal of propionate secretion to propionate absorption was elicited by HEPES substitution for bicarbonate at pH 6.8 or by serosal addition of epinephrine, which increases apical Na+-H+ exchange in this epithelium. Propionate absorption was blocked by both amiloride, an Na+-H+ exchange inhibitor, and ouabain. Under basal conditions, there was a concentration-dependent increase in basal unidirectional propionate fluxes with no change in net transport as the concentration of propionate increased from 10 to 60 mmol/L. In contrast, a concentration-dependent saturation of epinephrine-stimulated propionate absorption was apparent. Transepithelial propionate gradients did not yield a significant diffusion potential. These results suggest that, in rabbit proximal colon, (a) there is bidirectional diffusion of propionate, most probably in the protonated rather than the ionized form; (b) a component of propionate transport is active and linked to electroneutral Na+ absorption through apical Na+-H+ exchange; and (c) changes in composition of the fluid bathing the proximal colon in vitro may significantly alter both rates and direction of short-chain fatty acid transport. Regulation of transcellular active transport may play an important role in colonic short-chain fatty acid conservation.

Short-chain fatty acid transport in the intestine of a herbivorous teleost.

Short-chain fatty acid (SCFA) concentrations of intestinal contents from the herbivorous tilapia, Oreochromis mossambicus, were analysed by gas and high-performance liquid chromatography. Concentrations of acetate ranging from 3 to 18 mmol l-1 were found along the full length of the intestinal tract, as were trace amounts of propionate. Characteristics of [3H]acetate transport by the intestinal brush-border membrane were analysed in isolated brush-border membrane vesicles (BBMV). Influx of [3H]acetate into BBMV occurred by apparent anion exchange and was not enhanced by inwardly directed gradients of sodium or potassium, indicating the lack of sodium-dependent coupling for acetate transport. Competition and stimulation studies with various organic and inorganic anions revealed the likelihood of a transport system in which [3H]acetate is exchanged specifically for intracellular bicarbonate or other SCFA. Other anions tested had only limited or negligible effects on [3H]acetate uptake. Kinetic analysis over a concentration range of external acetate from 0.1 to 35 mmol l-1 yielded a carrier transport Km of 6.4 mmol l-1 and a Jmax of 5.3 nmol mg protein-1 10 s-1. Transport of [3H]acetate was not significantly affected by inhibitory drugs specific for anion exchangers. This study suggests that there is a specific antiport system for anions that is shared by bicarbonate and short-chain volatile fatty acids in the intestinal brush-border membrane of this herbivorous teleost.

Fermentation of polysaccharides and absorption of short chain fatty acids in the mammalian hindgut

1. 1. Hindgut volume varies considerably between carnivores, omnivores and herbivores. But a common feature in all mammals is an extensive microbial fermentation of polysaccharides in the hindgut. Large amounts of short chain fatty acids (SCFA) are produced. Total concentrations of SCFA are generally ca 100mmol/l. SCFA metabolism contributes considerably to the energy metabolism of the animal. 2. 2. In hindgut fermenting herbivores ileal outflow provides fluid and the buffering capacity essential for microbial metabolism. 3. 3. SCFA are rapidly absorbed. Absorption is passive and, unexpectedly, nearly independent from luminal pH. This is attributed to the presence of a constant pH-microclimate at the epithelial surface. 4. 4. The permeability of the proximal compared to the distal colon of guinea pig is higher for acetate, equal for propionate and lower for butyrate. This difference is due to partial absorption of SCFA in the dissociated form in the proximal segment. 5. 5. Protons required for SCFA transport in the undissociated form may be partially explained by HCO 3 accumulation or by Na-H exchange. Findings are controversial.

Short-chain fatty acid transport and its effects on ion transport by rabbit cecum.

Short-chain fatty acid (SCFA) metabolism and transport were examined in vitro across isolated rabbit cecal epithelia whose primary function is absorption of these solutes. This study shows that although there was some low-level metabolism of SCFAs to ketone bodies by the isolated cecum, a significantly higher oxygen consumption was sustained for a longer time period by tissues incubated in glucose-containing salines. The cecum supported a significant net secretory flux of acetate (J net Ac- = -1.13 +/- 0.13 mu eq X cm-2 X h-1) and propionate (J net Pr- = -0.61 +/- 0.14 mu eq X cm-2 X h-1). This study also shows that glucose significantly enhanced short-circuit current (Isc), tissue conductance (Gt), and sodium transport across this tissue. Neither Ac- nor Pr- enhanced net sodium flux (J net Ac-) but Pr- significantly reduced net chloride flux (J net Cl-), whereas Ac- had no effect. The increase in Isc and Gt observed in the presence of SCFAs was attributable to the presence of SCFA in the serosal bathing solution alone. To explain the latter finding and the unexpected finding of SCFA secretion, the existence of an electrogenic anion (HCO3-) secretory pathway is postulated. It is suggested that this system can accommodate SCFAs in vitro and that it is a Na+-dependent system located on the basolateral membrane of the cecal cell.

Traditions and new trends in cell physiology

EDITORIALTraditions and new trends in cell physiologyPhilip A. KnaufPhilip A. KnaufPublished Online:01 Jul 1984https://doi.org/10.1152/ajpcell.1984.247.1.C1MoreSectionsPDF (272 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail "Traditions and new trends in cell physiology." American Journal of Physiology-Cell Physiology, 247(1), p. C1 Back to Top Next FiguresReferencesRelatedInformationCited ByCT-Based Diagnosis of Low Vertebral Bone Mineral Density Is Associated with Hypercalciuria and Hypocitraturia on Opportunistic ImagingJournal of Endourology, Vol. 32, No. 9Increased risk of bone fracture among patients with urinary calculi: a nationwide longitudinal population-based study19 December 2014 | Osteoporosis International, Vol. 26, No. 4Acid–Base Balance and Bone Health28 November 2014Safety of carbonic anhydrase inhibitors10 March 2014 | Expert Opinion on Drug Safety, Vol. 13, No. 4Renal calculus disease4 March 2013How Permissive Should Hypercapnia Be?Local and Systemic Effects of HypercapniaThe effects of acid on boneCurrent Opinion in Nephrology and Hypertension, Vol. 9, No. 4Highly Efficient Adenovirus-Mediated Gene Transfer to Cardiac Myocytes after Single-Pass Coronary DeliveryHuman Gene Therapy, Vol. 11, No. 7Pathogenesis of Idiopathic Calcium Nephrolithiasis: Update 199729 September 2008 | Critical Reviews in Clinical Laboratory Sciences, Vol. 35, No. 2PERMEABILITY OF MYOCARDIAL CAPILLARIES TO HYDROPHILIC DRUGS: THE PARACELLULAR PATHWAYClinical and Experimental Pharmacology and Physiology, Vol. 23, No. 10-11The Pathophysiology of DiarrheaStructure and Regulation of the Amiloride-Sensitive Epithelial Sodium ChannelUrinary calcium and oxalate excretion in childrenPediatric Nephrology, Vol. 9, No. 1Famine, Fiber, Fatty Acids, and Failed Colonic Absorption: Does Fiber Fermentation Ameliorate Diarrhea?29 November 2016 | Journal of Parenteral and Enteral Nutrition, Vol. 18, No. 1Segmental differences in short-chain fatty acid transport in rabbit colon: Effect of pH and Na1 November 1993 | The Journal of Membrane Biology, Vol. 136, No. 2Structure-Function Correlations of Colon and Distal NephronThe Pathogenesis and Treatment of Kidney StonesNew England Journal of Medicine, Vol. 327, No. 16Parathyroid Function in Relation to Intestinal Function and Renal Calcium Reabsorption in Patients with Nephrolithiasis15 February 2010 | Scandinavian Journal of Urology and Nephrology, Vol. 26, No. 1The risk of nephrolithiasis with oral calciumsupplementationCalcified Tissue International, Vol. 48, No. 2Screening for HypercalciuriaPediatrics International, Vol. 32, No. 6An assessment of plasma histamine concentrations during documented endotoxic shockAgents and Actions, Vol. 31, No. 3-4Genetics of UrolithiasisEffects of Heat-Stable Escherichia coli Enterotoxin on Intestinal Alkaline Secretion and Transepithelial Potential Difference in the Rat Intestines in Vivo8 July 2009 | Scandinavian Journal of Gastroenterology, Vol. 25, No. 1Response to Exogenous 1,25(OH)2D during a Low-Calcium Diet in Normal Subjects and Idiopathic Renal-Stone FormersUrolithiasis in children: Current medical managementPediatric Nephrology, Vol. 3, No. 3Evidence for a prostaglandin-mediated bone resorptive mechanism in subjects with fasting hypercalciuriaCalcified Tissue International, Vol. 43, No. 2Methods of Studying Sympathoadrenal Activity in Man24 April 2009 | Acta Medica Scandinavica, Vol. 223, No. 6NaCl Transport in the Vertebrate IntestineIdiopathic Hypercalciuria in Children.Acta Paediatrica, Vol. 76, No. 2Peroraler Calcium-Belastungstest unter freier Diät bei idiopathischer Calcium-Nephrolithiasis — Möglichkeiten und GrenzenKlinische Wochenschrift, Vol. 64, No. 20Glucose Counterregulation, Hypoglycemia, and Intensive Insulin Therapy in Diabetes MellitusNew England Journal of Medicine, Vol. 313, No. 4Prospects for Gene Therapy for the Fibrosed Heart: Targeting Regulators of Extracellular Matrix Turnover More from this issue > Volume 247Issue 1July 1984Pages C1-C1 Copyright & PermissionsCopyright © 1984 the American Physiological Societyhttps://doi.org/10.1152/ajpcell.1984.247.1.C1History Published online 1 July 1984 Published in print 1 July 1984 PDF download Metrics Downloaded 16 times

Short-chain fatty acid transport by the rat colon in vitro

Short-chain fatty acid transport by the rat colon in vitro

Metabolism of volatile fatty acids by liver and portal-drained viscera in sheep.

Metabolism of volatile fatty acids by liver and portal-drained viscera in sheep.

Factors affecting the transport of volatile fatty acids across rumen epithelium.

Factors affecting the transport of volatile fatty acids across rumen epithelium.