Modification of liver fatty acid metabolism in mice by n-3 and n-6 delta 6-desaturase substrates and products.
The effects of dietary supplementation of either alpha-linolenic acid (18:3(n-3)) or stearidonic acid (18:4(n-3)) in combination with either linoleic acid (18:2(n-6)) or gamma-linolenic acid (18:3(n-6)) on liver fatty acid composition in mice were examined. Essential fatty acid deficient male C57BL/6 mice were separated into four groups of seven each and were fed a fat-free semi-purified diet supplemented with 1% (w/w) fatty acid methyl ester mixture (1:1), 18:2(n-6)/18:3(n-3), 18:2(n-6)/18:4(n-3), 18:3(n-6)/18:3(n-3), or 18:3(n-6)/18:4(n-3). After 7 days on the diets, fatty acid compositions in liver phosphatidylcholine and phosphatidylethanolamine fractions were analyzed. In groups fed 18:4(n-3) (18:2(n-6)/18:4(n-3) or 18:3(n-6)/18:4(n-3)) as compared to those fed 18:3(n-3) (18:2(n-6)/18:3(n-3) or 18:3(n-6)/18:3(n-3)), the levels of 20:4(n-3), 20:5(n-3) and 22:5(n-3) were increased, whereas those of 20:3(n-6) and 20:4(n-6) were decreased. When 18:3(n-6) replaced 18:2(n-6) as the source of n-6 acids, the levels of 18:3(n-6), 20:3(n-6), 20:4(n-6) and 22:5(n-6) were increased, whereas those of 20:4(n-3) and 20:5(n-3) were reduced. Replacing 18:3(n-3) by 18:4(n-3) reduced the (n-6)/(n-3) ratio by approx. 30%, whereas replacing 18:2(n-6) by 18:3(n-6) increased the (n-6)/(n-3) ratio by approx. 2-fold. These findings indicated that delta 6-desaturase products were metabolized more readily than their precursors. Both products also competed for the subsequent metabolic enzymes. However, the n-6 fatty acids derived from 18:3(n-6) were incorporated more favourably into liver phospholipids than n-3 fatty acids derived from 18:4(n-3).
Huang
Y S
YS
Efamol Research Institute, Kentville, Nova Scotia, Canada.
Smith
R S
RS
Redden
P R
PR
Cantrill
R C
RC
Horrobin
D F
DF
D000818:Animals; D001835:Body Weight; D002788:Cholesterol Esters / Q000737:chemistry / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D050602:Linoleoyl-CoA Desaturase; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009929:Organ Size; D014280:Triglycerides / Q000737:chemistry / Q000378:metabolism; D015430:Weight Gain
D002788:Cholesterol Esters; D005227:Fatty Acids; D014280:Triglycerides; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase