Metabolomics and neuroanatomical evaluation of post-mortem changes in the hippocampus

Understanding the human brain is the ultimate goal in neuroscience, but this is extremely challenging in part due to the fact that brain tissue obtained from autopsy is practically the only source of normal brain tissue and also since changes at different levels of biological organization (genetic, molecular, biochemical, anatomical) occur after death due to multiple mechanisms. Here we used metabolomic and anatomical techniques to study the possible relationship between post-mortem time (PT)-induced changes that may occur at both the metabolomics and anatomical levels in the same brains. Our experiments have mainly focused on the hippocampus of the mouse. We found significant metabolomic changes at 2 h PT, whereas the integrity of neurons and glia, at the anatomical/ neurochemical level, was not significantly altered during the first 5 h PT for the majority of histological markers.

Metabolomics studies in brain tissue: A review

Brain is still an organ with a composition to be discovered but beyond that, mental disorders and especially all diseases that curse with dementia are devastating for the patient, the family and the society. Metabolomics can offer an alternative tool for unveiling new insights in the discovery of new treatments and biomarkers of mental disorders. Until now, most of metabolomic studies have been based on biofluids: serum/plasma or urine, because brain tissue accessibility is limited to animal models or post mortem studies, but even so it is crucial for understanding the pathological processes. Metabolomics studies of brain tissue imply several challenges due to sample extraction, along with brain heterogeneity, sample storage, and sample treatment for a wide coverage of metabolites with a wide range of concentrations of many lipophilic and some polar compounds. In this review, the current analytical practices for target and non-targeted metabolomics are described and discussed with emphasis on critical aspects: sample treatment (quenching, homogenization, filtration, centrifugation and extraction), analytical methods, as well as findings considering the used strategies. Besides that, the altered analytes in the different brain regions have been associated with their corresponding pathways to obtain a global overview of their dysregulation, trying to establish the link between altered biological pathways and pathophysiological conditions.

Comparative Study of EPA-enriched Phosphatidylcholine and EPA-enriched Phosphatidylserine on Lipid Metabolism in Mice

Recent studies have shown that EPA enriched PLs have beneficial effects on lipid metabolism. Our previous study has demonstrated that the anti-obesity and hypolipidemic effects of EPA-PL were superior to DHA-PL. In the present study, we comparatively evaluated the effects of EPA-enriched phosphatidylcholine (EPA-PC) and EPA-enriched phosphatidylserine (EPA-PS) on lipid metabolism in mice. Both 2% dietary EPA-PC and EPA-PS significantly improved serum and hepatic lipid levels in mice. The HDL-c level in mice on EPA-PC diet was significantly higher than the other two groups. The level of DHA in hepatic TG and PL were significantly increased in both EPA-PC and EPA-PS fed groups (98.3 and 117.8%, respectively; p < 0.05). Notably, the proportion of DHA in EPA-PS group was significantly higher than the EPA-PC group. EPA-PC and EPA-PS suppressed hepatic SREBP-1c mediated lipogenesis and activated PPARα mediated fatty acid β-oxidation in the liver. These data are the first to indicate that EPA-PS has beneficial effects on lipid metabolism.

Oral administration of squid lecithin-transphosphatidylated phosphatidylserine improves memory impairment in aged rats

Recently, lecithin-derived phosphatidylserine (PS), which originates from marine life, has received much attention as a viable alternative to bovine cerebral cortex PS. In this study, the use of squid phosphatidylcholine-transphosphatidylated PS (SQ-PS) was evaluated through examination of its ameliorating effects on age-associated learning and memory deficits in rats. Aged rats were orally administered SQ-PS (10, 20, or 50 mg/kg per day) once a day for seven days 30 min prior to behavioral assessment in a Morris water maze. SQ-PS administration produced significant dose-dependent improvements in escape latency for finding the platform in the Morris water maze in the aged rats even though Soy-PS administration also exhibited comparable improvements with SQ-PS. Biochemical alterations in the hippocampal cholinergic system, including changes in choline acetyltransferase and acetylcholinesterase immunoreactivity, were consistent with the behavioral results. In addition, SQ-PS treatment significantly restored age-associated decreases of choline transporter and muscarinic acetylcholine receptor type 1 mRNA expression in the hippocampus. These results demonstrate that orally administered SQ-PS dose-dependently aids in the improvement of memory deficits that occur during normal aging in rats. This suggests that SQ-PS may be a useful therapeutic agent in the treatment of diminished memory function in elderly people.

Phosphatidylserine increases IKBKAP levels in a humanized knock-in IKBKAP mouse model

Familial dysautonomia (FD) is a severe neurodegenerative genetic disorder restricted to the Ashkenazi Jewish population. The most common mutation in FD patients is a T-to-C transition at position 6 of intron 20 of the IKBKAP gene. This mutation causes aberrant skipping of exon 20 in a tissue-specific manner, leading to reduction of the IκB kinase complex-associated protein (IKAP) protein in the nervous system. We established a homozygous humanized mouse strain carrying human exon 20 and its two flanking introns; the 3' intron has the transition observed in the IKBKAP gene of FD patients. Although our FD humanized mouse does not display FD symptoms, the unique, tissue-specific splicing pattern of the IKBKAP in these mice allowed us to evaluate the effect of therapies on gene expression and exon 20 splicing. The FD mice were supplemented with phosphatidylserine (PS), a safe food supplement that increases mRNA and protein levels of IKBKAP in cell lines generated from FD patients. Here we demonstrated that PS treatment increases IKBAKP mRNA and IKAP protein levels in various tissues of FD mice without affecting exon 20 inclusion levels. We also observed that genes associated with transcription regulation and developmental processes were up-regulated in the cerebrum of PS-treated mice. Thus, PS holds promise for the treatment of FD.

Structural elucidation of molecular species of pacific oyster ether amino phospholipids by normal-phase liquid chromatography/negative-ion electrospray ionization and quadrupole/multiple-stage linear ion-trap mass spectrometry

Although marine oysters contain abundant amounts of ether-linked aminophospholipids, the structural identification of the various molecular species has not been reported. We developed a normal-phase silica liquid chromatography/negative-ion electrospray ionization/quadrupole multiple-stage linear ion-trap mass spectrometric (NPLC-NI-ESI/Q-TRAP-MS(3)) method for the structural elucidation of ether molecular species of serine and ethanolamine phospholipids from marine oysters. The major advantages of the approach are (i) to avoid incorrect selection of isobaric precursor ions derived from different phospholipid classes in a lipid mixture, and to generate informative and clear MS(n) product ion mass spectra of the species for the identification of the sn-1 plasmanyl or plasmenyl linkages, and (ii) to increase precursor ion intensities by "concentrating" lipid molecules of each phospholipid class for further structural determination of minor molecular species. Employing a combination of NPLC-NI-ESI/MS(3) and NPLC-NI-ESI/MS(2), we elucidated, for the first time, the chemical structures of docosahexaenoyl and eicosapentaenoyl plasmenyl phosphatidylserine (PS) species and differentiated up to six isobaric species of diacyl/alkylacyl/alkenylacyl phosphatidylethanolamine (PE) in the US pacific oysters. The presence of a high content of both omega-3 plasmenyl PS/plasmenyl PE species and multiple isobaric molecular species isomers is the noteworthy characteristic of the marine oyster. The simple and robust NPLC-NI-ESI/MS(n)-based methodology should be particularly valuable in the detailed characterization of marine lipid dietary supplements with respect to omega-3 aminophospholipids.

Phosphatidylserine increases IKBKAP levels in familial dysautonomia cells

Familial Dysautonomia (FD) is an autosomal recessive congenital neuropathy that results from abnormal development and progressive degeneration of the sensory and autonomic nervous system. The mutation observed in almost all FD patients is a point mutation at position 6 of intron 20 of the IKBKAP gene; this gene encodes the IκB kinase complex-associated protein (IKAP). The mutation results in a tissue-specific splicing defect: Exon 20 is skipped, leading to reduced IKAP protein expression. Here we show that phosphatidylserine (PS), an FDA-approved food supplement, increased IKAP mRNA levels in cells derived from FD patients. Long-term treatment with PS led to a significant increase in IKAP protein levels in these cells. A conjugate of PS and an omega-3 fatty acid also increased IKAP mRNA levels. Furthermore, PS treatment released FD cells from cell cycle arrest and up-regulated a significant number of genes involved in cell cycle regulation. Our results suggest that PS has potential for use as a therapeutic agent for FD. Understanding its mechanism of action may reveal the mechanism underlying the FD disease.