A. Chicco et al., EFFECT OF MODERATE LEVELS OF DIETARY FISH-OIL ON INSULIN-SECRETION AND SENSITIVITY, AND PANCREAS INSULIN CONTENT IN NORMAL RATS, Annals of nutrition & metabolism, 40(2), 1996, pp. 61-70
The effect of omega-3 fatty acids derived from fish and marine mammals
on subjects with normal glucose tolerance is still unclear. The aim o
f the present study was to test whether the hypolipidemia that follows
the chronic administration of cod liver oil, rich in polyunsaturated
fatty acids (omega-3), to normal rats is accompanied by changes in glu
cose metabolism, insulin secretion and sensitivity, and pancreatic ins
ulin content. To achieve this goal, male Wistar rats were fed with a s
emisynthetic diet (w/w): 62.5% cornstarch, 7% cod liver oil plus 1% co
rn oil, and 17% protein (CD + CLO). Control rats were fed with the sam
e semisynthetic diet with the only exception that the source of fat wa
s 8% (w/w) corn oil (CD). Both diets were administered ad libitum for
1 month. At the end of the experimental period, the results obtained w
ere as follows (mean +/- SEM): serum triacylglycerol (mM): CD + CLO 0.
21 +/- 0.04 vs. CD 0.58 +/- 0.05 (p < 0.05); free fatty acids (mu M):
CD + CLO 257 +/- 20 vs. CD 288 +/- 22 (p = NS); total cholesterol (mM)
: CD + CLO 1.13 +/- 0.09 vs. CD 1.82 +/- 0.06 (p < 0.05); high-density
lipoprotein cholesterol (mM): CD + CLO 0.58 +/- 0.08 vs. CD 1.07 +/-
0.04 (p < 0.05); plasma glucose (mM): CD + CLO 6.30 +/- 0.29 vs. CD 6.
28 +/- 0.10 (p = NS); liver triacylglycerol (mu mol/liver): CD + CLO 1
04.1 +/- 11.4 vs. CD 136.8 +/- 4.3 (p < 0.05); glycogen (mu mol/g wet
weight): CD + CLO 298.3 +/- 21.0 vs. CD 297.0 +/- 19.0 (p = NS); gluco
se-6-phosphate dehydrogenase (U/liver): CD + CLO 37.9 +/- 2.2 vs. CD 5
8.8 +/- 5.0 (p < 0.05); triacylglycerol secretion (nmol/min/100 g body
weight): CD + CLO 101.0 +/- 2.0 vs. CD 166.0 +/- 9.7 (p < 0.01); remo
val of fat emulsion (K-2% min(-1)): CD + CLO 15.0 x 10(-2) + 0.8 x 10(
-2) vs. CD 8.2 x 10(-2) +/- 0.2 x 10(-2) (p < 0.01); intravenous gluco
se tolerance (kg 10(-2)): CD + CLO 2.68 +/- 0.37 vs. CD 2.70 +/- 0.14
(p = NS); immunoreactive insulin (mu U/ml/ min): with the area under t
he curve between 0 and 30 min CD + CLO 544 +/- 60 vs. CD 1,050 +/- 38
(p < 0.05), with the area under the curve between 0 and 60 min CD + CL
O 1,188 +/- 150 vs. CD 2,160 +/- 137 (p < 0.05), and pancreas insulin
content (mU/mg pancreas): CD + CLO 1.85 +/- 0.29 vs. CD 2.04 +/- 0.12
(p = NS). In conclusion, the present study shows that the strong hypol
ipidemic effect produced by the administration of low doses of fish oi
l to normal rats is accompanied by a significant reduction of plasma i
nsulin levels without changes in glucose tolerance. Since no changes i
n pancreatic insulin content were observed, lower plasma insulin level
s, both basal and after an intravenous glucose challenge, may be the r
esult of an increased peripheral insulin sensitivity in normoglycemic
animals.