Effect of dietary lipids and endocrine changes on polyunsaturated fatty acids in phospholipids of pancreas and brown adipose tissue of obese and lean rats.
Obese (fa/fa) rats fed on control diet have lower proportions of linoleic acid (18:2n-6) and/or arachidonic acid (20:4n6) in IBAT and pancreas phospholipids compared with lean (Fa/-) rats. Lower stearic acid (18:0) to oleic acid (18:1n-9) mean ratios in fa/fa compared with Fa/- suggest enhanced delta 9-desaturase activity in the former. 18:2/20:4 mean ratios in pancreas, but not IBAT, are indicative of a reduced delta 6-desaturase activity in fa/fa rats. Absolute amounts of phospholipids (mg/unit tissue wt) were 2-fold greater in IBAT of fa/fa compared with Fa/- rats, irrespective of their diet. This was reflected in greater absolute amounts of 18:2n-6 and 20:4n-6 only in HSO and HTO fa/fa groups, but not in the control group. Adrenalectomy (Adx) or T3 treatment also modified phospholipid fatty acid composition of IBAT and pancreas phospholipids in animals fed on the control diet with fa/fa rats more sensitive to endocrine induced changes. In fa/fa rats T3 treatment increased docosahexaenoic acid (22:6n-3) in IBAT of both phenotypes compared with the control, but this effect was evident only in fa/fa and not Fa/- pancreas. T3 treatment also increased docosapentaenoic acid (22:5n-3) in IBAT from, both phenotypes, but no 22:5n-3 was evident in the pancreatic tissue of these animals. ADX also increased 22:6n-3 in the IBAT of fa/fa (Fa/- values were less than 1%) but not in the pancreas of fa/fa or Fa/-. ADX modified the relative proportions of 18:0 to 18:1 and 18:2 to 20:4 in IBAT and pancreas of fa/fa in a way that indicated decreased delta 9-desaturase and increased delta 6-desaturase activities; these effects tended toward normal again in pancreas of fa/fa rats on corticosterone replacement (CST).
Lipid Metabolism Unit, Rowett Research Institute, Bucksburn, Aberdeen, U.K.
K W
KW
Wahle
L
L
Milne
J M
JM
Fletcher
G
G
McIntosh
D002001:Adipose Tissue, Brown / Q000187:drug effects* / Q000378:metabolism; D000315:Adrenalectomy; D000818:Animals; D004041:Dietary Fats / Q000494:pharmacology*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D008297:Male; D009765:Obesity / Q000378:metabolism*; D010179:Pancreas / Q000187:drug effects* / Q000378:metabolism; D010641:Phenotype; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011924:Rats, Zucker; D013045:Species Specificity; D014284:Triiodothyronine / Q000378:metabolism
D004041:Dietary Fats; D005231:Fatty Acids, Unsaturated; D010743:Phospholipids; D014284:Triiodothyronine