Assay of stearoyl-CoA synthesis in microsomes from normal and Trembler mouse sciatic nerves

Dietary oleic acid not used during brain development and in adult in rat, in contrast with sciatic nerve

In order to determine exactly the effect on the nervous system of concentration of dietary oleic acid on the fatty acid composition of different part of the nervous system, triglycerides were synthesized using chemical and enzymological methods. The dose-effect was determined using an experimental protocol with seven groups of rats who received a diet in which the oleic acid level varied from 0 to 6000 mg per 100 g diet, but the other ingredients were identical (in particular the essential fatty acids, linoleic and alpha-linolenic acid). Rats were fed the diets from two weeks before mating, and their pups were sacrificed aged either 21 or 60 days. When the level of oleic acid in the diet was increased, the main modifications observed in 21-day-old deficient animals were as follows. (i). For 18:1(n-9), in liver, plateau was reached at about 4 g oleic acid per 100 g diet. Below this level, the higher the dose the greater the response. In whole brain, brain myelin, and nerve endings (but not sciatic nerve) the oleic acid level remained optimal and constant whatever the level of oleic acid in the diet. (ii). 16:1(n-7) concentration decreased in liver and in sciatic nerve, but not in nervous tissue. (iii). In 60-day-old animals, results were generally similar to those in 21-day-old animals.

Pathways of incorporation of fatty acid into glycerolipids of the murine peripheral nervous system in vivo: alterations in the dysmyelinating mutant trembler mouse

In vivo glycerolipid metabolism was studied in sciatic nerves of normal and Trembler mice. The results showed that two kinetically independent pathways were implicated in the labeling of diacylglycerophospholipids from [3H]palmitate: the Kennedy pathway and a 'direct acylation' pathway. In normal nerves, 45% of the glycerophospholipids were labeled, with a rate constant k3 = 3.9 x 10(-3) min-1, from phosphatidic acid and diacylglycerol intermediates, themselves formed with a rate constant of k1 = 0.24 min-1 from a free 3H-fatty acid pool, FFA1, that represents 45% of the total injected label. The remaining 55% of the glycerophospholipids were labeled from a kinetically distinct free 3H-fatty acid pool, FFA2, with a rate constant of k4 = 9.8 x 10(-2) min-1, via a process that does not implicate a detectably labeled metabolic intermediate ('direct acylation'). Glycerophospholipid labeling via the Kennedy pathway in the Trembler mouse sciatic nerves was reduced to 75% of the normal level, while labeling via the 'direct acylation' pathway was increased 1.4-fold. The values of the rate constants for free 3H-fatty acid utilisation (k1 and k4) were both increased about 2.5-fold, while that of glycerophospholipid formation from diacylglycerol (k3) was close to normal.