Yuri Tanioka

Biologically active vitamin B12 compounds in foods for preventing deficiency among vegetarians and elderly subjects.

The usual dietary sources of vitamin B12 are animal-source based foods, including meat, milk, eggs, fish, and shellfish, although a few plant-based foods such as certain types of dried lavers (nori) and mushrooms contain substantial and considerable amounts of vitamin B12, respectively. Unexpectedly, detailed characterization of vitamin B12 compounds in foods reveals the presence of various corrinoids that are inactive in humans. The majority of edible blue-green algae (cyanobacteria) and certain edible shellfish predominately contain an inactive corrinoid known as pseudovitamin B12. Various factors affect the bioactivity of vitamin B12 in foods. For example, vitamin B12 is partially degraded and loses its biological activity during cooking and storage of foods. The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B12 from naturally occurring vitamin B12 compounds, including its degradation products and inactive corrinoids that are present in daily meal foods. The objective of this review is to present up-to-date information on various factors that can affect the bioactivity of vitamin B12 in foods. To prevent vitamin B12 deficiency in high-risk populations such as vegetarians and elderly subjects, it is necessary to identify plant-source foods that contain high levels of bioactive vitamin B12 and, in conjunction, to prepare the use of crystalline vitamin B12-fortified foods.

Analysis of Vitamin B12 in Food by Silica Gel 60 TLC and Bioautography with Vitamin B12-Dependent Escherichia coli 215

Abstract To evaluate whether certain foods contain vitamin B12 or inactive corrinoids, a simple technique, bioautography with vitamin B12-dependent Escherichia coli mutant after separation of the sample by silica gel 60 thin-layer chromatography, is available. By using the method, vitamin B12-compounds found in some edible cyanobacteria are readily identified. This bioautography has great advantages (simplicity, speed, and inexpensiveness) for the analysis of vitamin B12-compounds in food.

Characterization of a Corrinoid Compound in the Edible (Blue-Green) Alga, Suizenji-nori

The edible blue-green alga (cyanobacterium), Suizenji-nori, contained 143.8±22.4 μg of vitamin B12 per 100 g dry weight of the alga (mean±SE, n=4). A corrinoid compound was purified from the dried Suizenji-nori, and partially characterized. The silica gel 60 TLC and reversed-phase HPLC patterns of the purified corrinoid compound were not identical to those of true vitamin B12, but to those of pseudovitamin B12 which is inactive for humans.

Methyladeninylcobamide functions as the cofactor of methionine synthase in a Cyanobacterium, Spirulina platensis NIES-39

To clarify the physiological function of pseudovitamin B12 (or adeninylcobamide; AdeCba) in Spirulina platensis NIES‐39, cobalamin‐dependent methionine synthase (MS) was characterized. We cloned the full‐length Spirulina MS. The clone contained an open reading frame encoding a protein of 1183 amino acids with a molecular mass of 132 kDa. Deduced amino acid sequences of the Spirulina MS contained critical residues identical to cobalamin‐, zinc‐, S‐adenosylmethionine‐, and homocysteine‐binding motifs. The recombinant Spirulina enzyme showed higher affinity for methyladeninylcobamide than methylcobalamin as a cofactor. These results indicate that Spirulina cells can utilize AdeCba synthesized as the cofactor for MS.

TLC Analysis of a Corrinoid Compound from Dark Muscle of the Yellowfin Tuna (Thunnus albacares)

Abstract A significant amount of vitamin B12 (52.9±8.9 µg/100 g) was found in the dark muscle of the yellowfin tuna (Thunnus albacares), in comparison to that of the light muscle. A corrinoid compound was purified to homogeneity from the dark muscle and partially characterized. TLC and HPLC patterns of the purified corrinoid compound were identical to those of authentic vitamin B12. These results indicate that dark muscle of the yellowfin tuna would be an excellent source of vitamin B12 for humans and aminals.

High dietary fat-induced obesity in Wistar rats and type 2 diabetes in nonobese Goto-Kakizaki rats differentially affect retinol binding protein 4 expression and vitamin A metabolism

Obesity is a major risk factor for type 2 diabetes, which is caused mainly by insulin resistance. Retinol binding protein 4 (RBP4) is the only specific transport protein for retinol in the serum. RBP4 level is increased in the diabetic state and high-fat condition, indicating that retinol metabolism may be affected under these conditions. However, the precise effect of diabetes and high fat-induced obesity on retinol metabolism is unknown. In this study, we examined differences in retinol metabolite levels in rat models of diet-induced obesity and type 2 diabetes (Goto-Kakizaki [GK] rat). Four-week-old male Wistar and GK rats were given either a control diet (AIN-93G) or a high-fat diet (HFD, 40% fat kJ). After 15 weeks of feeding, the RBP4 levels increased by 2-fold in the serum of GK rats but not HFD-fed rats. The hepatic retinol concentration of HFD-fed rats was approximately 50% that of the controls (P < .01). In contrast, the renal retinol concentrations of GK rats increased by 70% (P < .01). However, expression of RARβ in the kidney, which was induced in a retinoic acid-dependent manner, was downregulated by 90% (P < .01) in GK rats. In conclusion, diabetes and obesity affected retinol metabolism differently, and the effects were different in different peripheral tissues. The impact of HFD may be limited to the storage of hepatic vitamin A as retinyl palmitate. In particular, our data indicate that renal retinoic acid production might represent an important target for the treatment of type 2 diabetes mellitus.

Characterization of vitamin B 12 compounds from marine foods

Vitamin B12 is synthesized by only certain bacteria and archaea but not by animals or plants. In marine environments, bacterial vitamin B12 is transferred and concentrated into fish and shellfish bodies by plankton in the marine food chain. Moreover, marine macrophytic red algae, Porphyra spp. specifically contain substantial amounts of vitamin B12, due to microbial interaction. Although some meats or viscera of edible fish and shellfish are excellent sources of biologically active vitamin B12, an inactive corrinoid, pseudovitamin B12, was found in some edible shellfish using liquid chromatography/electrospray ionization–tandem mass spectrometry. To prevent elderly people from developing vitamin B12 deficiency due to food protein-bound vitamin B12 malabsorption, we present a survey of marine foods containing free vitamin B12. The results of our study suggest that bonito and clam extracts (or soup stocks), which contain considerable amounts of free vitamin B12 are useful not only as seasonings and flavorings but also as excellent sources of free vitamin B12.

A Nuclear Factor Involved in Transcriptional Regulation of the AREBP Gene

The AICAR responsive element binding protein (AREBP) suppresses transcription of the gluconeogenic enzyme genes in response to AICAR treatment. Moreover, overexpression of AREBP also suppresses gluconeogenic gene expressions in animals, indicating that AREBP plays an important role in gluconeogenesis. Through a combination of systematic analyses of the AREBP gene promoter and assays for DNA-protein interaction, we identified a nuclear factor involved in tissue-specific expression of AREBP. By targeting this nuclear factor, pharmacological or nutraceutical induction of AREBP gene expression is expected to reduce blood glucose levels in patient with insulin resistance.

TLC Analysis of Corrinoid Compounds in the Halophilic Lactic Acid Bacterium Tetragenococcus halophilus

Abstract Vitamin B12 content (3.1±0.8 µg/100 g wet weight) of the lactic acid bacterium Tetragenococcus halophilus IAC‐ks6, isolated from a fermented skipjack viscera, was determined using the microbiological vitamin B12 assay method with Lactobacillus delbrueckii subsp. lactis ATCC 7830. On the basis of silica gel 60 TLC and C18 reversed‐phase HPLC, true vitamin B12 predominated in the bacterial cells and functioned as each cofactor of the vitamin B12‐dependent enzymes, methionine synthase and ribonucleotide reductase.