Natural and Synthetic α-Tocopherol Modulate the Neuroinflammatory Response in the Spinal Cord of Adult Ttpa-null Mice

Abstract

Background Vitamin E (α-tocopherol, α-T) deficiency causes neurological pathologies. α-T supplementation improves outcomes, but the relative bioactivities of dietary natural and synthetic α-T in neural tissues are unknown. Objective To assess the effects of dietary α-T source and dose on oxidative stress and myelination in adult Ttpa−/− mice cerebellum and spinal cord. Methods Three week old male Ttpa−/- mice (n = 56) were fed 1 of 4 AIN-93G-based diets for 37 weeks: vitamin E-deficient (VED; below α-T limit of detection); natural α-T, 600 mg/kg diet (NAT); synthetic α-T, 816 mg/kg diet (SYN); high synthetic α-T, 1200 mg/kg diet (HSYN). Male Ttpa+/+littermates (n = 14) fed AIN-93G (75 mg synthetic α-T/kg diet, CON) served as controls. At 40 weeks of age, total and stereoisomer α-T levels and oxidative stress markers were determined (n = 7/group). Cerebellar Purkinje neuron morphology and white matter areas in cerebellum and spinal cord were assessed in a second sub-set of animals (n = 7/group). Results Cerebral cortex α-T levels were undetectable in Ttpa−/- mice fed VED. α-T levels were increased in NAT (4.6 ± 0.3 nmol/g), SYN (8.0 ± 0.7 nmol/g), and HSYN (8.5 ± 0.3 nmol/g) animals, but were significantly lower than Ttpa+/+ mice fed CON (27.8 ± 1.9 nmol/g) (P < 0.001). 2R stereoisomers constituted the majority of α-T in brains of Ttpa+/+ mice (91%) and Ttpa−/- mice fed NAT (100%), but were substantially lower in the SYN and HSYN groups (∼53%). Neuroinflammatory genes were increased in the spinal cord, but not cerebellum, of VED-fed animals; NAT, SYN, and HSYN normalized their expression. Cerebellar Purkinje neuron atrophy and myelin pathologies were not visible in Ttpa−/- mice. Conclusions Natural and synthetic α-T supplementation normalized neuroinflammatory markers in neural tissues of 10-month old Ttpa−/- mice. α-T prevents tissue-specific molecular abnormalities, which may prevent severe morphological changes during late adulthood.

α-Tocopherol Transfer Protein-Null Mice with Very Low α-Tocopherol Status Do Not Have an Enhanced Lipopolysaccharide-Induced Acute Inflammatory Response

“…We chose to focus on the brain and heart for our analyses, as an abundance of research supports vitamin E’s antioxidant role in these tissues [ 3 , 31 , 35 , 38 ]. The correlation between cardiovascular disease/immune systems and αT has been examined in epidemiological, animal, and human studies [ 39 ].…”

“…In the current study, genotype groups were fed a VED diet, and study results showed that Ttpa +/+ mice maintained some αT in tissues and serum over this time period [ 33 , 35 ]. In Ttpa −/− mice, serum and some peripheral tissues, such as liver and adipose tissue, were not completely devoid of vitamin E whereas in other tissues vitamin E was depleted.…”

“…All animal diets were customized, and diet preparation procedures were followed as in a previous study [ 33 ]. Briefly, the VED and LOW diets were purchased from Research Diets, Inc. Modified-AIN-93G formulation, including replacing most of the soybean oil with hydrogenated coconut oil to minimize dietary concentrations of vitamin E, was used for these experiments and was based on the diets used in previous studies [ 33 , 35 ]. RRR -αTA [Novatol 6-92 (oil); Archer Daniels Midland] was added to the LOW diet.…”

“…Total RNA was isolated and RT-qPCR analysis was conducted using previously described procedures [ 35 , 37 ]. Briefly, hippocampal and heart total RNA was isolated using RNeasy Lipid Tissue Mini Kit (Qiagen) via the manufacturer’s protocol.…”

“…Actin B1 ( Actb1 ) was used as a reference gene. Genes associated with inflammation and oxidative stress were selected based on previous research [ 27 , 35 ]. Primers were obtained from Integrated DNA Technologies and primer sequences are listed in Supplemental Table 2 .…”