Fig. 4. MAT1A deletion decreases the mobilization of triglycerides for VLDL secretion in 3-month-old mice.

For enzymatic assays, liver microsomes were prepared from 3-month-old (3m) and 8-month-old (8m) wild type (WT) (□) and MAT1A-knockout (MAT1A-KO) () mice. (A) diacylglycerol acyltransferase (DGAT) and (B) triglyceride (TG) lipase activities were determined by radiometric assays, and the (C) MTP TG transfer activity was measured using a fluorescence assay; all as described in materials and methods. (D–F) 3-month-old mice hepatocytes were incubated 4 hours with 0.4 mM [³H]oleic acid (5 μCi/dish) complexed with 0.5% fatty acid-free BSA and [¹⁴C]glycerol (0.5 μCi/dish) (pulse). After a wash of 1 hour in DMEM, cells were incubated for 4 hours (chase). (D) The percentage of the total [³H]-TG and [¹⁴C]-TG secreted to the media after both the pulse and chase periods, and the TG content in (E) cells and (F) media after the chase period were calculated. Values are means ± SEM of 4–8 animals per group. Statistical differences between MAT1A-KO and WT mice are denoted by *p<0.05, **p<0.01 and ***p<0.001 (Student's t test).