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N. Acar, J. Chardigny, A.M. Bron, C.P. Creuzot-Garcher, J. Sebedio; Impairment of the Wave-amplitudes of the Scotopic ERG in Rats Fed for 21 Months with Small Amounts of trans Alpha-linolenic Acid . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1866.
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Purpose: Among retinal lipids, docosahexaenoic acid (DHA: 22:6 n-3) is the major PUFA (polyunsaturated fatty acid). DHA has usually its double bonds under the cis configuration. However, DHA with a trans double bond can be found in retinal phospholipids of animals fed with trans alpha-linolenic acid (ALA: 18:3 n-3). The aim of this work was to investigate the long-term effects of the isomerization of dietary ALA on the scotopic ERG. Since the isomerization of cis ALA into trans ALA reduces the dietary levels of cis ALA, the effect of dietary supplementation in cis ALA was also studied. Methods: Wistar rats (n=18) were fed for 21 months with diets containing 2.0% of cis ALA (control), 1.3% of cis ALA plus 0.7% of trans ALA ("low cis" group) or 2.0% of cis ALA plus 0.7% of trans ALA ("high cis" group). The scotopic ERG was recorded in vivo and the fatty acid composition of retinal phospholipids was determined by gas chromatography. Results: Trans DHA was incorporated in retinal phospholipids of animals fed with trans ALA and represented until 1.2% of total fatty acids. In the "low cis" group, the retinal level of DHA was lowered and was associated with a decrease of 29% of the a-, b- and P III-wave amplitudes, suggesting a partial deficiency in n-3 PUFA. In the "high cis" group, increasing the levels of dietary cis ALA resulted in having control levels of DHA but not of arachidonic acid (20:4 n-6). ERG amplitudes were 29% lower than controls, suggesting an effect of trans DHA. Conclusions: These results showed that isomerizing a part of dietary ALA may result in an impairment of the scotopic ERG by inducing a deficiency in cis n-3 PUFA. Moreover, these results suggest an effect of trans PUFA on light transduction, showing that it would be better to prevent the intake of trans ALA rather than supplementing the diet in cis ALA.
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