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Home , Plasmalogen

Effects of Myo- Treatment on Plasmalogen Levels and Biosynthesis in Rat Brain

B. Kuczynski1, N. V. Reo1 1Wright State University, Dayton, OH, United States Synopsis NMR in conjunction with 13C labeling was used to examine the effects of myo-Insitol (myo-Ins) administration on the profile and plasmalogen content in rat brain. Several protocols were investigated. Acute myo-Ins + 13C-ethanolamine (13C-Etn) increased the biosynthesis of Etn and produced the greatest elevation in brain myo-Ins and plasmalogen content. These data suggest that brain myo-Ins content is correlated with biosynthesis of Etn plasmalogen. This protocol may provide a unique means to investigate the role of brain plasmalogen in vivo. Introduction plasmalogen (PlsEtn) is a glycerolphospholipid containing a vinyl ether linkage at the -sn-1 carbon and an ester-linked sn-2 acyl chain (1-alkyl-1′-enyl-2-acyl-glycerophosphoethanolamine). This is most abundant in neurological tissues. Studies in vitro suggest that it may act as an antioxidant, but this has never been demonstrated in vivo. Therefore, a means to elevate brain PlsEtn levels may have beneficial effects. Recently, Pettegrew, et al. (Biol. Psychiatry, 49, 444, 2001) reported an increase in brain PlsEtn in rats following chronic administration of myo-Ins. Our laboratory has further examined this phenomenon by using 13C-labeled Etn (13C-Etn) and NMR to monitor the effects of various myo-Ins protocols on Etn- phospholipid biosynthesis in rat brain. Methods Myo-Ins was given to rats by acute dose (5.0 g/Kg, ip) or chronic dose (1.2 g/Kg ip once daily for 10 days). [2-13C]Etn was given as a single dose (92 mg/Kg, ip). Three protocols were used: (1) Acute co-administration of myo-Ins + 13C-Etn {Acute(+)}; (2) Acute myo-Ins alone {Acute(-)}; and (3) Chronic myo-Ins followed by 13C-Etn on day 11 {Chronic(+)}. Corresponding controls received saline rather than myo-Ins. Rats were decapitated 6 h after the final dose. Lipid and aqueous extracts of whole brain were analyzed by 31P and 13C NMR for the levels of phospholipids, particularly phosphatidylethanolamine (PtdE) and PlsEtn, and the incorporation of 13C-Etn into total brain Etn-phospholipids. Results and Discussion The Acute(+) group showed a 47% increase in newly synthesized 13C-Etn-phospholipids, and increases in the brain concentrations of myo-Ins (68%) and PlsEtn (30%) (Fig. 1, p ≤ 0.05). The PlsEtn content (expressed as a percentage of the total phospholipid pool) was increased from 22% to 26% (p ≤ 0.01). The brain PlsEtn/PtdE ratio was increased by 24% in the Acute(+) group (p < 0.01), and was unchanged for the other protocols. Various changes observed in other phospholipids for the Acute(-) protocol will also be presented. Chronic myo-Ins did not influence the amount of 13C incorporation into brain phospholipids nor did it affect the levels of PtdE or PlsEtn. The brain myo-Ins and PlsEtn concentrations appear to be positively correlated as illustrated for the Acute(+) protocol in Fig. 2 (r2 = 0.88). Conclusions Acute co-administration of myo-Ins + Etn produced the most significant change in brain phospholipids, particularly PlsEtn. The increase in brain PlsEtn is greater than that observed by Pettegrew, et al. (30% vs 10%). Our data suggest that the exogenous 13C-Etn was directed to the biosynthesis of brain PlsEtn. The mechanism by which myo-Ins upregulates the biosynthesis of PlsEtn is unknown. This protocol, however, may provide a unique animal model to test the therapeutic antioxidant role of PlsEtn in vivo.

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Acute 14 Acute (-) 25 * (+) Acute Acute 12 (+) (-) 20 * 10 Acute (-) 15 Acute 8 (+) * Acute Acute (+) (-) 6 10 myo-Ins (µmol/g) Acute (+) 4 5 Acute (+) Control 2 12 14 16 18 20 22 0 PlsEtn (µmo/g) PtdE PlsEtn PtdS PtdC

Figure 1. Brain phospholipid concentrations (µmol/g; Mean ± SE) Figure 2. Linear regression analysis for brain [myo-Ins] vs. for Acute(+) and Acute(-) treated (hatched bars) and control (open [PlsEtn] (µmol/g) for the Acute(+) and corresponding control bars) groups. Asterisks denote a difference from control (p<0.05). groups (r2= 0.88).

Proc. Intl. Soc. Mag. Reson. Med. 11 (2003) 1966