Lipid synthesis in isolated intestinal cells

Since the small intestine contributes significantly to serum cholesterol and very low density lipoprotein levels, acute regulation of lipid synthesis was investigated in isolated rat intestinal cells incubated in Krebs-Ringer bicarbonate buffer with 5 mM glucose and [¹⁴C]acetate or ³H₂O. Incorporation of [¹⁴C]acetate into cellular lipids was 6- to 8-fold greater in crypt than in villus cells. In both cell types the distribution of ¹⁴C among the various lipid classes was as follows: 52.5% in triglycerides, diglycerides, and monoglycerides; 22.3% in cholesterol; 8.3% in cholesteryl esters; 1.9% in fatty acids; and 15.0% in phospholipids. In contrast, the medium lipids contained significantly higher amounts of tri-, di- and monoglycerides (61.1%) and lower amounts of cholesteryl esters (2.3%) and phospholipids (11.9%). After saponification 2/3 of the recovered ³H₂O was in fatty acids and 1/3 in cholesterol. Ethanol (10 mM) tripled ³H₂O incorporation into cellular lipids but had no effect on [¹⁴C]acetate incorporation. Epinephrine and norepinephrine (10 μM), glucagon (10 μM), dibutyryl cyclic AMP (1 mM), dexamethasone (1 mM and 1 μM), and cholera toxin (1 μg/ml) did not affect [¹⁴C]acetate incorporation. The authors conclude that ethanol stimulates intestinal lipid synthesis; however, in sharp contrast to their inhibition of lipid synthesis in hepatocytes and adipocytes, catecholamines, glucagon, and dibutyryl cyclic AMP do not inhibit lipid synthesis in intestinal cells.