triolein and tyloxapol

Essential fatty acid (EFA) deficiency induces fat malabsorption, but the pathophysiological mechanism is unknown. Bile salts (BS) and EFA-rich biliary phospholipids affect dietary fat solubilization and chylomicron formation, respectively. We investigated whether altered biliary BS and/or phospholipid secretion mediate EFA deficiency-induced fat malabsorption in mice. Free virus breed (FVB) mice received EFA-containing (EFA(+)) or EFA-deficient (EFA(-)) chow for 8 wk. Subsequently, fat absorption, bile flow, and bile composition were determined. Identical dietary experiments were performed in multidrug resistance gene-2-deficient [Mdr2((-/-))] mice, secreting phospholipid-free bile. After 8 wk, EFA(-)-fed wild-type [Mdr2((+/+))] and Mdr2((-/-)) mice were markedly EFA deficient [plasma triene (20:3n-9)-to-tetraene (20:4n-6) ratio >0.2]. Fat absorption decreased (70.1 +/- 4.2 vs. 99.1 +/- 0.3%, P < 0.001), but bile flow and biliary BS secretion increased in EFA(-) mice compared with EFA(+) controls (4.87 +/- 0.36 vs. 2.87 +/- 0.29 microl x min(-1) x 100 g body wt(-1), P < 0.001, and 252 +/- 30 vs. 145 +/- 20 nmol x min(-1) x 100 g body wt(-1), P < 0.001, respectively). BS composition was similar in EFA(+)- and EFA(-)-fed mice. Similar to EFA(-) Mdr2((+/+)) mice, EFA(-) Mdr2((-/-)) mice developed fat malabsorption associated with twofold increase in bile flow and BS secretion. Fat malabsorption in EFA(-) mice is not due to impaired biliary BS or phospholipid secretion. We hypothesize that EFA deficiency affects intracellular processing of dietary fat by enterocytes.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B; ATP-Binding Cassette Transporters; Bile; Bile Acids and Salts; Body Weight; Carbon Radioisotopes; Cholestanetriol 26-Monooxygenase; Cholesterol 7-alpha-Hydroxylase; Cytochrome P-450 Enzyme System; Dietary Fats; Diterpenes; Enterocytes; Fatty Acids; Fatty Acids, Essential; Homozygote; Kinetics; Liver; Malabsorption Syndromes; Mice; Mice, Knockout; Oleic Acid; Phospholipids; Polyethylene Glycols; Retinyl Esters; RNA, Messenger; Steroid Hydroxylases; Triolein; Tritium; Vitamin A

Measurement of the entry rate of an intragastric load of [14C]triolein into the plasma in the presence of Triton WR1339 gave similar values for virgin and weaned rats, but significantly lower values for lactating rats. This decreased entry rate (65%) in lactating compared with virgin rats was due to a failure of Triton WR1339 to inhibit the accumulation of [14C]lipid in the mammary gland. This is further evidence that mammary-gland lipoprotein lipase behaves differently from that in white adipose tissue or muscle.

Topics: Adipose Tissue; Adipose Tissue, Brown; Animals; Carbon Radioisotopes; Detergents; Female; Kinetics; Lactation; Liver; Mammary Glands, Animal; Oxidation-Reduction; Polyethylene Glycols; Pregnancy; Rats; Rats, Inbred Strains; Reference Values; Triolein

To determine the extent to which suckling animals differ from adults in their capacity to absorb fat, we compared the rate of absorption of orally administered [14C]triolein in 11- to 12-day-old suckling rats with that of 10-wk-old adults by three distinct methods. In the first, the rate of [14C]triolein disappearance was determined by quantitating substrate remaining in the gastrointestinal tract after oral administration. In the second, 14CO2 expiration in breath was measured continuously for 6 h after an identical feeding. In the third, intestinal triglyceride output was estimated by the lipoprotein lipase inhibitor, Triton WR-1339. Triolein disappearance, 14CO2 excretion, and intestinal triglyceride output were two- to threefold higher in suckling rats compared with adults (P less than 0.01, P less than 0.0001, and P less than 0.01, respectively). There was also a highly significant linear relationship between 14CO2 excretion and both triolein disappearance and intestinal triglyceride output for both age groups (P less than 0.0001 and P less than 0.003, respectively). These data show that consistent with its high dietary intake, the suckling rat can absorb triolein at rates significantly higher than the adult.

Topics: Absorption; Aging; Animals; Animals, Suckling; Carbon Dioxide; Intestinal Mucosa; Oxidation-Reduction; Polyethylene Glycols; Rats; Rats, Inbred Strains; Respiration; Triglycerides; Triolein