Handbook of Functional Lipids

phospholipids showed that increased levels of AA in type 2 diabetes patients compared
with the age-matched controls and the levels were disproportionately high compared
with those in plasma total lipids [178]. Diabetic subjects with proliferative retinopathy
showed significantly higher AA uptake activity than those with little or no background
retinopathy; however, no difference was found for LA uptake activity in platelets
between the two groups [179]. Positive results obtained from several clinical studies
have evidenced that providing GLA to bypass blocked

∆

6-desaturase activity can

favorably alter platelet fatty acid composition and prostonoic metabolism [180–182].
Poisson and co-workers [183] provided a good review on this aspect of GLA.

Diabetic neuropathy is a characteristic of diabetes that affects sensory nerves and

also of neuropathy affecting autonomic nerves. Lack of GLA metabolites is also a
considered factor for normal neuronal structure, function, and microcirculation; thus
impaired membrane function and nerve damage are observed in diabetic neuropathy
[184,185]. Several observations made on diabetic animals suggest that the neuropathy
may relate to changes in the phospholipid structure of the neuronal membrane and/or
to abnormal neuronal microvascular function. Low levels of AA have been found in
neuronal phospholipids (PLs) from diabetic animals with neuropathy [186].

TAGs containing GLA have been shown to normalize nerve conduction velocity

and sciatic endoneurial blood flow [187,188]. GLA is able to correct nerve conduc-
tion abnormalities by enhancing the synthesis of the cyclooxygenase-derived vasodi-
lator prostanoid, PGE

, which is capable of increasing vasa nervorum perfusion

[189]. Studies carried out on diabetic rats showed that ascorbate combined with
GLA has therapeutic advantage over GLA alone; thus ascorbyl GLA may be suitable
in clinical trials for diabetic neuropathy [62].

REFERENCES

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(Oenothera biennis) and a new linolenic acid, Arch. Pharm., 257, 33, 1919.

2. Eibner, A. and Schild, E., Quantitative analysis and technical evaluation of a

Oenothera oil, Chem. Umschau Fette, Oele, Wachse Harze, 34, 339, 1927.

3. Riley, J.P., Seed fat of Oenothera biennis L., J. Chem. Soc., 4, 2728, 1949.
4. Wolf, R.B., Kleiman, R., and England, R.E., New sources of

-linolenic acid, J. Am.

Oil Chem. Soc., 60, 1858, 1983.

5. Gunstone, F.D., Gamma linolenic acid: occurrence and physical and chemical prop-

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6. Guil-Guerrero, J.L. et al., Occurrence and characterization of oils rich in

-linolenic

acid Part I: Echium seeds from Macaronesia, Phytochemistry, 53, 451, 2000.

7. Guil-Guerrero, J.L. et al.,

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seed oil of 4 accessions from several Ribes species, J. Agric. Food Chem., 49, 349, 2001.

9. Traitler, H. et al., Characterization of

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