An in Vitro Study of Choline Uptake by Intestine from Neonatal and Adult Rats

Abstract

MATERIALS AND METHODSthe developing small intestine are frequently different from those characterized in the intestine of mature animals (9-13).In the present studies, we examined the kinetics of choline uptake in the developing small intestine and compared these transport characteristics with those found in the intestine of mature animals.Animals. Adult, male Sprague-Dawley rats (Charles River Breeding Laboratory, Wilmington, MA), each weighing 100-125 g, were housed in stainless steel cages. Rat Chow (Ralston Purina, St. Louis, MO; 0.16% unesterified choline by our assay) and water were given ad libitum for 1 wk prior to use in our studies. Temperature in the housing facility was 24°C. The light cycle was 12 h long, 0600 to 1800 h.Neonatal animals used in these studies were kept with lactating dams up to the time of the experiment. Litter size was limited to 10 pups per dam. Mothers were fed rat Chow (Ralston Purina; 0.16% unesterified choline by our assay) and water ad libitum. Rat milk contained 100-300 ILM unesterified choline by our assay. Only male rat pups, 10-11 days old, were used in the experiments described. Measurement o/uptake by gut slices. Adult rats were anesthetized with ether, a midline abdominal incision was made, and the small intestine was visualized. Segments taken from the area immediately distal to the end of the stomach were designated as duodenum. Jejunal segments were taken from the area whose blood supply was derived from the jejunal artery. Ileal segments were taken from the area 10 cm proximal to the cecum. Colonic segments were taken from the area immediately distal to the cecum. In the 10-day-old rat, segments ofjejunum were collected from the small intestine from the area whose blood supply was derived from the jejunal artery.Gut sections were removed and placed in ice-cold KRB containing 10 mM glucose. They were cut longitudinally, rinsed with KRB, and trimmed to a length of 2 cm. These tissue slices were supported on filter paper (Whatman no. 3) and placed in a prewarmed (3r C), modified~Ussing chamber containing KRB in the bottom portion of the chamber (11,18). The top of the chamber was positioned over the gut slice and clamped down. KRB containing choline, 14C-choline, 3H-inulin, and nonradiolabeled inulin (or 3H-D-glucose and D-glucose) was added to this upper chamber. A gas containing 95% oxygen and 5% carbon dioxide was bubbled through the medium throughout the 15-min incubatinn period. 768 Abbreviations KRB, Krebs' Ringer buffer containing 10 mM glucose TLC, thin-layer chromatography

Trimethylamine: Metabolic, Pharmacokinetic and Safety Aspects

“…Other studies conducted in animals, including the rat and mouse, confirm the role of carrier-mediated transport systems involved in the oral absorption of compounds such as choline from the gastrointestinal tract [57][58][59][60]. Similar studies have also reinforced that dietary constituents such as choline, L-carnitine and betaine are precursors to TMA [7,10,14,56,71,72].…”

“…The study by Zhang et al has revealed that there may be increased formation of TMA when the pure chemical form of these precursors is administered to humans as compared to the ingestion as a component of whole food [6]. Studies have also confirmed that choline and L-carnitine undergo carrier mediated absorption [57][58][59][60][61][62][63], meaning that the administration of higher oral doses of these precursors would result in increased generation of TMA [10]. However, Gas chromatography (solid-phase microextraction) Urine Aqueous 0.8 µM to 157 µM Mills et al [39] Gas chromatography (derivitization with 2,2,2-trichloroethylchloroformate) Urine Blood 1pmol to 250 pmol Da Costa et al [41] Fast atom bombardment-mass spectrometry Urine 7 µM to 135 µM Mamer et al [46] Proton nuclear magnetic resonance spectroscopy Urine Abeling et al [44] HPLC (conductimetric detection) Urine Marzo et al [43] HPLC (refractive index) Urine Marzo et al [43] differences in gastrointestinal physiology between animals and humans [64] (for instance the human small intestine is reported to have a lower absorptive capacity for L-carnitine than the rat [52]) could mean that the fate of these chemical precursors may also be dissimilar.…”

“…Similar studies have also reinforced that dietary constituents such as choline, L-carnitine and betaine are precursors to TMA [7,10,14,56,71,72]. Importantly, large oral doses of these compounds including L-carnitine in humans would result in increased amounts reaching the lower segments of the gastrointestinal tract [10,[57][58][59][60][61][62][63] (cecum and colon) where bacteria could convert these dietary constituents to TMA [9,[11][12][13]. Consequently, the amount of the orally administered dose and the form in which it is given (pure chemical or food component) should be considered when examining the formation of TMA from compounds such as choline and Lcarnitine [6].…”

TMAO: A small molecule of great expectations

“…Choline is absorbed from the small intestine via mediated transport which is half saturated at choline concentrations in the intestines of 200-300 µM [39][40][41]. If choline-rich food is ingested, and the concentration of choline in the small intestine exceeds the transport capacity, choline reaches the large bowel.…”

Effect of egg ingestion on trimethylamine-N-oxide production in humans: a randomized, controlled, dose-response study , , ,

“…Choline is present as free choline and choline esters in the diet (5), and these forms of choline are absorbed differently in the intestines. Free choline is absorbed in the small intestine via mediated transport (6), whereas phosphatidylcholine is not converted to choline within the intestinal lumen [it is absorbed intact via the lymphatic system or is hydrolyzed by pancreatic lipases and absorbed as glycerophosphocholine (7)]. On the basis of these differences, dietary free choline (the substrate for trimethylamine formation by bacteria) but not dietary phosphatidylcholine should result in TMAO formation.…”