Mechanistic Link between Vitamin B12 and Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of dementia in the elderly population, affecting over 55 million people worldwide. Histopathological hallmarks of this multifactorial disease are an increased plaque burden and tangles in the brains of affected individuals. Several lines of evidence indicate that B12 hypovitaminosis is linked to AD. In this review, the biochemical pathways involved in AD that are affected by vitamin B12, focusing on APP processing, Aβ fibrillization, Aβ-induced oxidative damage as well as tau hyperphosphorylation and tau aggregation, are summarized. Besides the mechanistic link, an overview of clinical studies utilizing vitamin B supplementation are given, and a potential link between diseases and medication resulting in a reduced vitamin B12 level and AD are discussed. Besides the disease-mediated B12 hypovitaminosis, the reduction in vitamin B12 levels caused by an increasing change in dietary preferences has been gaining in relevance. In particular, vegetarian and vegan diets are associated with vitamin B12 deficiency, and therefore might have potential implications for AD. In conclusion, our review emphasizes the important role of vitamin B12 in AD, which is particularly important, as even in industrialized countries a large proportion of the population might not be sufficiently supplied with vitamin B12.

Dietary Intake and Status of Vitamin B12 in Slovenian Population

Vitamin B12 deficiency poses a health concern, especially in vulnerable populations. Dietary vitamin B12 intake was obtained by two 24 h dietary recalls and food propensity questionnaires in a representative Slovenian cross-sectional food consumption survey, SI.Menu (n = 1248 subjects; 10–74 years). For a subgroup of 280 participants, data on serum vitamin B12 were available through the Nutrihealth study. The estimated usual population-weighted mean daily vitamin B12 intakes were 6.2 µg (adults), 5.4. µg (adolescents), and 5.0 µg (elderly). Lower intakes were observed in females. Inadequate daily vitamin B12 intake (<4 µg) was detected in 37.3% of adolescents, 31.7% of adults, and 58.3% elderlies. The significant predictors for inadequate daily vitamin B12 intake were physical activity score in all age groups, sex in adolescents and adults, financial status and smoking in elderly, and employment in adults. Meat (products), followed by milk (products), made the highest vitamin B12 contribution in all age groups. In adolescents, another important vitamin B12 contributor was cereals. The mean population-weighted serum vitamin B12 levels were 322.1 pmol/L (adults) and 287.3 pmol/L (elderly). Low serum vitamin B12 concentration (<148 nmol/L) and high serum homocysteine (>15 µmol/L) were used as criteria for vitamin B12 deficiency. The highest deficiency prevalence was found in elderlies (7.0%), particularly in males (7.9%). Factors associated with high serum homocysteine were also investigated. In conclusion, although vitamin B12 status was generally not critical, additional attention should be focused particularly to the elderly.

Genetic Bases of VitaminB12 Deficiency: Impact of MTHFR, TCN-II and GIF Polymorphisms on Vitamin B12 Level

Vitamin B12 deficiency is associated with serious health problems such as neurological disorders. In Jordan, few studies have evaluated the level of vitamin B21 in the Jordanian population with different prevalence. Genetic predisposition, lifestyle, environment, socioeconomic status, and geographic have been linked to vitamin B12 deficiency. Polymorphisms in the GIF, MTHFR, and Transcobalamins, have been proposed to be associated with the level of vitamin B12. The aim of the current study was to evaluate the impact of certain polymorphisms in MTHFR, TCN-II and GIF genes on the level of vitamin B12 in the Jordanian population. Polymorphic sites of the MTHFR (c.677 C>T, rs1801133 and c.1286A>C, rs1801131), TCN2-776C>G (Arg259Pro) (rs1801198) and GIF-68 A>G (Q5R) genes were analyzed by RFLP and DNA sequencing in a group of vitamin B12 deficient individuals (n = 100). The control group included 100 matching individuals with a normal level of vitamin B12 (>200 ng/mL). Our results showed a significant association between the homologous variant of the TCN2 gene (G776G) and MTHFR c.677C>T genes and vitamin B12 deficiency. On the other hand, The MTHFR c.1286A>C variant and GIF variants did not show significant association with vitamin B12 deficiency. This study expounds the association of TCN2 and MTHFR polymorphisms with cobalamin levels in a Jordanian population and highlights the necessity of further studies to elucidate the molecular basis and impact of TCN2, GIF, and MTHFR gene polymorphisms on vitamin B12 deficiency and associated disorders.

VITAMIN DEFICIENCY AND FOOD SUPPLEMENTS

Vitamins are a heterogeneous group of organic compounds that help ensure the human bodys wellbeing and function. This paper introduces the importance of all vitamins, both water-soluble and fat-soluble, as well as problems deriving from their deficiency. Additionally, vitamin supplements as part of treating vitamin deficiency, and possible harmful effects on the human body areshowcased. The main focus of the paper is on the vitamin B complex, and vitamin B12 specifically. The benefits of vitamin B12, as well as its action in the human body and the noxious effects of any lack of vitamin B12 in the human body, are also discussed. Some of the health conditionsan individual may need to face when they have vitamin B12 deficiency include neural tube defects, Alzheimers disease, depression, and megaloblastic anaemia, which are also introduced and further discussed, in terms of symptomatology, causes and suggested treatment. The toxicity of vitamin B12 is also introduced, and possible causes for vitamin B12 deficiency are showcased.

Vitamin B12 deficiency is linked with dyslipidemia in gestational diabetes mellitus.

Objective: To determine the vitamin B12 deficiency and dyslipidemia in Gestational Diabetes mellitus (GDM) diagnosed pregnant women. Study Design: Observational study. Setting: Department of Biochemistry and Gynecology/Obstetrics LUMHS Hospital Jamshoro. Period: January 2018 to December 2018. Material & Methods: A sample of 216 diagnosed GDM pregnant women was selected according to study criteria. Venous blood samples were centrifuged to separate sera; that were used for the estimation of (hexokinase method), blood lipids and Vitamin B12 (ECLIA assay method) by Cobas chemistry analyzer. Statistical SPSS software 21.0 (IBM, Inc USA) was used for study research variables at 95% CI (P ≤ 0.05). Results: Age of GDM cases was 36.12±9.5 years. Mean+/-SD vitamin B12 level was noted 154.7±81.7 ng/mL (P=0.0001). Serum cholesterol, triglycerides and LDLc were elevated and HDLc was low in GDM cases (P=0.0001). Of 216 GDM cases, vitamin B12 deficiency was present in 152 (70.3%) (P=0.0001) and dyslipidemia in 50 (23.1%) (X2=452.0) (P=0.0001). Vitamin B12 shows inverse correlation with RBG (r= -0.41, P=0.005), CHOL (r= -0.25, P=0.024), TAG (r= -0.81, P=0.0001), LDLc (r= -0.797, P=0.0001) and positive correlation with HDLc (r= 0.76, P=0.0001). Conclusion: The present study finds vitamin B12 deficiency in 152 (70.3%) and dyslipidemia in 50 (23.1%). Vitamin B12 deficient GDM women show high cholesterol, triglycerides, LDLc and low HDLc. Hence, it is concluded, the vitamin B12 deficiency is linked with dyslipidemia in Gestational Diabetes mellitus.