Brain α-Tocopherol Concentration and Stereoisomer Profile Alter Hippocampal Gene Expression in Weanling Mice

Interneurons in the CA1 stratum oriens expressing αTTP may play a role in the delayed-ageing Pol μ mouse model

Neurodegeneration associated with ageing is closely linked to oxidative stress (OS) and disrupted calcium homeostasis. Some areas of the brain, like the hippocampus - particularly the CA1 region - have shown a high susceptibility to age-related changes, displaying early signs of pathology and neuronal loss. Antioxidants such as α-tocopherol (αT) have been effective in mitigating the impact of OS during ageing. αT homeostasis is primarily regulated by the α-tocopherol transfer protein (αTTP), which is widely distributed throughout the brain - where it plays a crucial role in maintaining αT levels within neuronal cells. This study investigates the distribution of αTTP in the hippocampus of 4- and 24-month-old Pol μ knockout mice (Pol μ-/-), a delayed-ageing model, and the wild type (Pol μ+/+). We also examine the colocalisation in the stratum oriens (st.or) of CA1 region with the primary interneuron populations expressing calcium-binding proteins (CBPs) (calbindin (CB), parvalbumin (PV), and calretinin (CR)). Our findings reveal that αTTP immunoreactivity (-IR) in the st.or of Pol μ mice is significantly reduced. The density of PV-expressing interneurons (INs) increased in aged mice in both Pol μ genotypes (Pol μ-/- and Pol μ+/+), although the density of PV-positive INs was lower in the aged Pol μ-/- mice compared to wild-type mice. By contrast, CR- and CB-positive INs in Pol μ mice remained unchanged during ageing. Furthermore, double immunohistochemistry reveals the colocalisation of αTTP with CBPs in INs of the CA1 st.or. Our study also shows that the PV/αTTP-positive IN population remains unchanged in all groups. A significant decrease of CB/αTTP-positive INs in young Pol μ-/- mice has been detected, as well as a significant increase in CR/αTTP-IR in older Pol μ-/- animals. These results suggest that the differential expression of αTTP and CBPs could have a crucial effect in aiding the survival and maintenance of the different IN populations in the CA1 st.or, and their coexpression could contribute to the enhancement of their resistance to OS-related damage and neurodegeneration associated with ageing.

Associations between Brain Alpha-Tocopherol Stereoisomer Profile and Hallmarks of Brain Aging in Centenarians

Brain alpha-tocopherol (αT) concentration was previously reported to be inversely associated with neurofibrillary tangle (NFT) counts in specific brain structures from centenarians. However, the contribution of natural or synthetic αT stereoisomers to this relationship is unknown. In this study, αT stereoisomers were quantified in the temporal cortex (TC) of 47 centenarians in the Georgia Centenarian Study (age: 102.2 ± 2.5 years, BMI: 22.1 ± 3.9 kg/m2) and then correlated with amyloid plaques (diffuse and neuritic plaques; DPs, NPs) and NFTs in seven brain regions. The natural stereoisomer, RRR-αT, was the primary stereoisomer in all subjects, accounting for >50% of total αT in all but five subjects. %RRR was inversely correlated with DPs in the frontal cortex (FC) (ρ = -0.35, p = 0.032) and TC (ρ = -0.34, p = 0.038). %RSS (a synthetic αT stereoisomer) was positively correlated with DPs in the TC (ρ = 0.39, p = 0.017) and with NFTs in the FC (ρ = 0.37, p = 0.024), TC (ρ = 0.42, p = 0.009), and amygdala (ρ = 0.43, p = 0.008) after controlling for covariates. Neither RRR- nor RSS-αT were associated with premortem global cognition. Even with the narrow and normal range of BMIs, BMI was correlated with %RRR-αT (ρ = 0.34, p = 0.021) and %RSS-αT (ρ = -0.45, p = 0.002). These results providing the first characterization of TC αT stereoisomer profiles in centenarians suggest that DP and NFT counts, but not premortem global cognition, are influenced by the brain accumulation of specific αT stereoisomers. Further study is needed to confirm these findings and to determine the potential role of BMI in mediating this relationship.

Spatiotemporal biodistribution of α-tocopherol is impacted by the source of 13C-labeled α-tocopherol in mice following a single oral dose

Natural (RRR-) α-tocopherol (αT) is more bioactive than synthetic (all racemic, all rac-) αT, but not enough is known about the tissue kinetics of the 2 αT sources. We examined the time-course bioaccumulation of natural versus synthetic αT in tissues of young, marginally vitamin E-deficient mice using ¹³C-RRR-αT or ¹³C-all rac-αT tracers. In experiment 1, 3-week old male wild-type mice were fed a vitamin E-deficient diet for 0, 1, 2, or 3 weeks (n = 5/time point). Tissue αT levels were analyzed by HPLC-PDA. Feeding a vitamin E-deficient diet for up to 3 weeks decreased total αT concentrations in all analyzed tissues except the brain, which maintained its αT level. In experiment 2, a 2-week αT-depletion period was followed by administration of a single oral dose of 0.5 mg of ¹³C-RRR-αT or ¹³C-all rac-αT. At 12 hr, 1, 2, and 4 days post-dose, serum and multiple tissues were collected (n = 3/time point). αT was quantified by HPLC-PDA, and ¹³C-αT enrichment was determined by LC-MS. Both sources of ¹³C-αT reached maximum serum levels at 12 hr post-dose. ¹³C-RRR-αT levels were significantly higher than ¹³C-all rac-αT in serum at 1 d post-dose, and in heart, lungs, and kidney at 2d post-dose. In brain, ¹³C-RRR-αT concentrations were significantly higher than ¹³C-all rac-αT at 2 and 4 d post-dose. At 4 d post-dose, ¹³C-αT levels were similar between the 2 sources in examined tissues except for brain and adipose tissue where ¹³C-RRR-αT was higher. In conclusion, αT bioaccumulation over time varied substantially depending on αT source and tissue type.

Dietary share of ultra-processed foods and its association with vitamin E biomarkers in Brazilian lactating women

Despite evidence showing that the intake of ultra-processed food has a negative impact on health, diet quality and dietary vitamin E, its impact on vitamin E nutritional status and breast milk remains unknown. This study aimed to assess the influence of the consumption of ultra-processed foods on vitamin E biomarkers of lactating women. A cross-sectional study was performed with 294 lactating women. Food consumption was obtained by 24-h dietary recall, and foods were grouped according to the NOVA classification. Levels of α-tocopherol were analysed by HPLC. Breast milk vitamin E (BMVE) adequacy was based on the quantity of the vitamin in the estimated intake volume. The Kruskal–Wallis test was used to compare the tertiles and linear regression to association between ultra-processed food consumption and biomarkers. Ultra-processed foods accounted for 16 % of energy intake and vitamin E intakes by all women were considered low. Serum α-tocopherol was 26·55 (sd 7·98) µmol/l, 5 % (n 11) showed inadequate vitamin E (< 12 µmol/l) and 78 % had an inadequate BMVE content (< 4 mg/780 ml). The regression showed that a higher dietary share of ultra-processed foods was associated with lower concentrations of serum α-tocopherol (β = –0·168, 95 % CI –0·047, 0·010, P = 0·003) and inadequate BMVE content (β = –0·144, 95 % CI = –0·505, 0·063, P = 0·012) (adjustment for income and maternal age). Thus, higher dietary shares of ultra-processed foods had an impact on vitamin E biomarkers, suggesting that inadequate dietary intake practices during lactation may reduce the supply of vitamin E to women and breast milk.

α-Tocopherol Stereoisomer Profiles in Matched Human Maternal and Umbilical Cord Plasma

BACKGROUND

α-Tocopherol (αT) is essential for fetal development. One study has shown that the human placenta preferentially transfers the natural stereoisomer, RRR-αT. But prenatal supplements generally contain synthetic αT (S-αT).

OBJECTIVES

We aimed to determine if umbilical cord plasma is enriched for RRR-αT in racially diverse neonates from both uncomplicated and complicated pregnancies and if cord RRR-αT enrichment is impacted by maternal αT stereoisomer profile.

METHODS

We measured αT and αT stereoisomers in plasma from a randomly selected subset of 66 predominantly black and Hispanic maternal-fetal pairs from the Camden Study involving control (n = 28) and complicated pregnancies (n = 38). We collected maternal plasma at study entry (week 16 gestation; w16) and week 28 gestation (w28) and cord plasma at birth.

RESULTS

RRR-αT was the predominant stereoisomer in all maternal and cord plasma samples, but S-αT stereoisomers were found in most samples and comprised a high percentage of αT in some maternal-neonate pairs. Cord plasma had a higher percentage RRR-αT (P < 0.05) and lower percentage S-αT (P < 0.0001) than w28 plasma. Pregnancy status did not impact maternal or cord plasma concentrations of αT, RRR-αT, or S-αT; except plasma from complicated pregnancies was higher in S-αT at w28 than at w16 (P < 0.05). Maternal w28 αT did not correlate with cord αT. However, both maternal w28 αT and S-αT positively correlated with both cord S-αT (r = 0.340, P = 0.0049; r = 0.538, P < 0.00001) and percentage S-αT (r = 0.399, P = 0.001; r = 0.786, P < 0.00001) but negatively correlated with cord percentage RRR-αT (r = -0.399, P = 0.0009; r = -0.786, P < 0.00001).

CONCLUSIONS

The proportion of RRR-αT was higher in cord compared with maternal plasma in both uncomplicated and complicated pregnancies. Our data suggest that maternal S-αT raises cord S-αT and decreases the proportion of RRR-αT in the neonatal circulation. Because the bioactivities of RRR-αT and S-αT differ, this warrants future research to determine the importance of our observations to neonatal αT status.

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

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

The aim was to assess the effects of dietary α-T source and dose on oxidative stress and myelination in adult α-tocopherol transfer protein-null (Ttpa- / - ) mouse cerebellum and spinal cord.

METHODS

Three-week-old male Ttpa- / - mice (n = 56) were fed 1 of 4 AIN-93G-based diets for 37 wk: 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); or 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 wk of age, total and stereoisomer α-T concentrations 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 subset of animals (n = 7/group).

RESULTS

Cerebral cortex α-T concentrations were undetectable in Ttpa- / - mice fed the VED diet. α-T concentrations 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) mice, but were significantly lower than in 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-mo-old Ttpa- / - mice. α-T prevents tissue-specific molecular abnormalities, which may prevent severe morphological changes during late adulthood.