A. Aarsland et Rr. Wolfe, HEPATIC SECRETION OF VLDL FATTY-ACIDS DURING STIMULATED LIPOGENESIS IN MEN, Journal of lipid research, 39(6), 1998, pp. 1280-1286
Fatty acids (FA) that are utilized for triglyceride (TG) synthesis in
the liver and principally from two sources: FA synthesized de novo in
the liver and preformed FA. We have measured the contribution from the
two sources to very low density lipoprotein (VLDL) TG synthesis indiv
idually for palmitate, oleate, stearate, and linoleate (approximate to
98% of the total FA of VLDL TG (VLDL TGFA)) by isotopomer analysis. F
ive healthy men were studied in the basal state, and 1 (day 1) and 4 d
ays (day 4) after the start of a hypercaloric carbohydrate-enriched di
et (approximate to 2.5 times energy expenditure). The secretion of de
novo palmitate was increased 15- and 43-fold after 1 and 4 days of hyp
eralimentation (2.6 +/- 1.2 (basal state), 40.8 +/- 20.0 (day 1), and
113.3 +/- 42.0 mu mol/kg per d (day 4)). Even though 4 days of hyperal
imentation increased the secretion of de novo stearate 43-fold and de
novo oleate 70-fold (stearate; 0.2 +/- 0.2 (basal), 8.6 +/- 3.3 mu mol
/kg per d (day 4), oleate; 0.4 +/- 0.4 (basal), 28.2 +/- 12.7 mu mol/k
g per d (day 4)), palmitate accounted for 75-85% of all the de novo VL
DL TGFA. One day of carbohydrate hyperalimentation tended to decrease
the secretion while 4 days increased the secretion of all preformed FA
in VLDL TG. The rate of secretion of preformed palmitate and oleate w
ere almost identical (palmitate; 80.2 +/- 22.2 (basal), 45.1 +/- 23.8
(day 1), and 256.2 +/- 74.1 mu mol/kg per d (day 4), oleate; 95.2 +/-
22.8 (basal), 46.2 +/- 24.2 (day 1), and 356.8 +/- 74.1 mu mol/kg per
d (day 4)) and collectively these two FA accounted for 80-90% of the s
ecretion from the preformed source. Palmitate is the predominant produ
ct of acute and prolonged carbohydrate mediated lipogenesis in the hum
an liver. The pathway of further elongation and subsequent desaturatio
n of de novo synthesized palmitate to generate stearate and oleate is
inducible but, quantitatively, of minor significance in hepatic lipoge
nesis.