| Research Abstract |
The interaction of dietary fish oil, soybean phospholipid and soybean oil, and conjugated linoleic acid (CLA) in affecting the activity of hepatic lipogenic enzymes and gene expression in liver and adipose tissue was examined in mice. A diet containing 1.0% CLA mainly composed of 9c, 11t- and 10t,12c-octadecadienoic acids at equivalent amounts greatly decreased adipose tissue weight and serum concentrations of leptin and adiponectin accompanying a down-regulation of the expression of various adipocyte-abundant genes in epididymal adipose tissue. But CLA increased the serum insulin concentration 4-fold, and caused hepatomegaly accompanying huge increases in the triacylglycerol level and the activity and mRNA levels of hepatic lipogenic enzymes. Different amounts (1.5, 3 and 6%) of fish oil added to CLA-containing diets dose-dependently down-regulated parameters of lipogenesis accompanying a parallel decrease in the triacylglycerol level in the liver. The supplementation of CLA-containin
… More
g diets with fish oil was also associated with an increase in fat pad mass and mRNA levels of many adipocyte-abundant genes in epididymal adipose tissue accompanying a normalization of serum concentrations of leptin and adiponectin in a dose-dependent manner. However, in mice fed a diet containing 1.5% fish oil and CLA in whom fat pad mass was still low and comparable to that in the animals fed CLA alone, the serum insulin concentration much exceeded (2-fold) the value observed in mice fed CLA alone indicating an aggravation of insulin resistance. This hyperinsulinemia was ameliorated with increasing amounts of fish oil in the diets. Different amounts (1.5, 3 and 6% as fatty acid) of soybean phospholipid added to CLA-containing diets also dose-dependently down-regulated parameters of lipogenesis accompanying a parallel decrease in the triacylglycerol level in the liver. However, this dietary lipid failed to increase adipose tissue weight despite the increase in gene expression of may genes in this tissue. Also, this dietary lipid was totally ineffective in ameliorating hyperinsulinemia caused by CLA, and it rather aggravated the this metabolic disorder. Soybean oil compared to fish oil and soybean phospholipid was much less effective in counteracting augmented lipogenesis as well as lipid accumulation induced by CLA. Soybean oil was not effective in restoring the adipose tissue weight that was depleted by CLA. Also, soybean oil rather aggravated hyperinsulinemia caused by CLA. t10, c12-octadecadienoic acid can mimic the physiological activity of CLA mixture containing both 9c,11t- and 10t, 12c-octadecadienoic acids in affecting hepatic lipogenesis, hepatic lipid content, adipose tissue weight and serum concentration of insullin. Fish oil added effectively counteracted the metabolic disorder caused by this CLA isomer. 9c, 11t-octadecadienoic acid in contrast to 10t, 12c-octadecadienoic acid did not affect hepatic lipogenesis and hepatic lipid content, adipose tissue weight and serum insulin concentration. But, it was revealed the combination of 9c, 11t-octadecadienoic acid and fish oil was effective in decreasing hepatic lipogenesis, serum lipid concentrations and hepatic triacylglycerol level in a synergistic manner. Apparently, many of the physiological effects of CLA can be reversed by fish oil. Combination with fish oil will provide the effective and safe way to adopt CLA as a dietary factor to prevent obesity. Less
|
