Plasma phospholipid-mediated transfer of docosahexaenoic acid from liver to brain phospholipids in type 1 and type 2 diabetic rats

Docosahexaenoic acid (C22:6ω3) generated in the liver from circulating α-linolenic acid (C18:3ω3) was recently proposed as the source of brain C22:6ω3 when the latter fatty acid is absent from the diet. The present study aims at exploring whether a comparable situation prevails in Types 1 and 2 diabetic rats, even when exposed to a normal diet. The fatty acid profile of liver, plasma and brain phospholipids (PL) was examined in 22 rats including 6 streptozotocin-induced diabetic animals (Type 1 diabetes), 8 Goto-Kakizaki rats (Type 2 diabetes) and 8 control animals. Both fed and overnight starved rats of both genders were included in this study. To avoid the interference of any group effect, all individual results were expressed relative to the mean value found in animals of the same gender, same strain, same nutritional situation and same glycemic status, such results being referred to as normalized values. Significant positive correlations were observed between the normalized values for the C22:6ω3 relative weight content of liver and plasma PL and, after exclusion of 2 female control rats with an abnormally high brain/plasma PL C22:6ω3 ratio, plasma and brain PL. Noticeably, the variation coefficients (SD/mean) for the 3 variables did not exceed 7.1±1.8%. A comparable situation prevailed between liver, plasma and brain triglycerides. Our results suggest that circulating PL participate in the transfer of C22:6ω3 from the liver to the brain, even in control and diabetic rats not deprived of a dietary source of long-chain polyunsaturated ω3 fatty acids.