Effect of neonatal thiamine and vitamin A deficiency on rat brain gangliosides

Dietary Control of Ganglioside Expression in Mammalian Tissues

Gangliosides are series of glycosphingolipids containing sialic acids in the oligosaccharide portion in mammalian cells. Gangliosides are a component of cellular membranes and play roles in modulating membrane function and the activity of membrane proteins. Abnormal expression and metabolism of gangliosides lead to the onset of several conditions in humans, such as neurologic diseases, diabetes, and cancer. A number of studies have been carried out to date to investigate the role of gangliosides in these diseases, and the effect of diet on tissue expression of gangliosides has recently become a topic of interest in this field. As gangliosides are degraded in the intestinal tract, ingested food-derived gangliosides are not directly absorbed into tissues in vivo, but the degradation products can be absorbed and affect ganglioside expression in the tissues. Recent studies have also shown that the expression of gangliosides in tissue cells can be indirectly induced by controlling the expression of ganglioside metabolism-related genes via the diet. These results indicate that dietary control can regulate the expression levels of gangliosides in tissues, which is expected to play a role in preventing and treating ganglioside-related diseases. This review introduces recent studies on the effect of diet on the expression of gangliosides in tissues, with a focus on our findings.

Thiamin deficiency on fetal brain development with and without prenatal alcohol exposure

Adequate thiamin levels are crucial for optimal health through maintenance of homeostasis and viability of metabolic enzymes, which require thiamine as a co-factor. Thiamin deficiency occurs during pregnancy when the dietary intake is inadequate or excessive alcohol is consumed. Thiamin deficiency leads to brain dysfunction because thiamin is involved in the synthesis of myelin and neurotransmitters (e.g., acetylcholine, γ-aminobutyric acid, glutamate), and its deficiency increases oxidative stress by decreasing the production of reducing agents. Thiamin deficiency also leads to neural membrane dysfunction, because thiamin is a structural component of mitochondrial and synaptosomal membranes. Similarly, in-utero exposure to alcohol leads to fetal brain dysfunction, resulting in negative effects such as fetal alcohol spectrum disorder (FASD). Thiamin deficiency and prenatal exposure to alcohol could act synergistically to produce negative effects on fetal development; however, this area of research is currently under-studied. This minireview summarizes the evidence for the potential role of thiamin deficiency in fetal brain development, with or without prenatal exposure to alcohol. Such evidence may influence the development of new nutritional strategies for preventing or mitigating the symptoms of FASD.

Reduction of globotriaosylceramide in Fabry disease mice by substrate deprivation

We used a potent inhibitor of glucosylceramide synthase to test whether substrate deprivation could lower globotriaosylceramide levels in alpha-galactosidase A (alpha-gal A) knockout mice, a model of Fabry disease. C57BL/6 mice treated twice daily for 3 days with D-threo-1-ethylendioxyphenyl-2-palmitoylamino-3-pyrrolidi no-propanol (D-t-EtDO-P4) showed a concentration-dependent decrement in glucosylceramide levels in kidney, liver, and spleen. A single intraperitoneal injection of D-t-EtDO-P4 resulted in a 55% reduction in renal glucosylceramide, consistent with rapid renal glucosylceramide metabolism. A concentration-dependent decrement in renal and hepatic globotriaosylceramide levels was observed in alpha-Gal A(-) males treated for 4 weeks with D-t-EtDO-P4. When 8-week-old alpha-Gal A(-) males were treated for 8 weeks with 10 mg/kg twice daily, renal globotriaosylceramide fell to below starting levels, consistent with an alpha-galactosidase A-independent salvage pathway for globotriaosylceramide degradation. Complications observed with another glucosylceramide synthase inhibitor, N-butyldeoxynojirimycin, including weight loss and acellularity of lymphatic organs, were not observed with D-t-EtDO-P4. These data suggest that Fabry disease may be amenable to substrate deprivation therapy.

Retinoids increase perinatal spinal cord neuronal survival and astroglial differentiation

In this report we demonstrate that retinol and retinoic acid (RA) increase the survival and morphological differentiation of rat spinal cord neurons in vitro. Micromolar amounts of retinol and RA increased the number of surviving neurons by 2- to 3-fold and affected neuritic density resulting in increased secondary and tertiary processes compared to untreated sister cultures. A marked morphological differentiation of the astrocyte population in conjunction with an antiproliferative effect in the presence of retinoids were apparent. These trophic effects occurred mainly after 5 days in vitro, a time that corresponds to the time of birth in vivo. Retinoic acid exerted a direct trophic effect on spinal cord neurons in the absence of glial cells while retinol lost its effectiveness. Metabolic labeling suggested that retinol is converted to the biologically active RA within astrocytes but not in neurons. Taken together, our results have demonstrated direct trophic effects of RA on spinal cord neurons and have suggested another role for astrocytes in the maintenance of normal neural physiology by regulating RA concentrations through the oxidation of retinol.