Functional analysis of yeast gene families involved in metabolism of vitamins B1 and B6

In order to clarify their physiological functions, we have undertaken a characterization of the three-membered gene families SNZ1-3 and SNO1-3. In media lacking vitamin B(6), SNZ1 and SNO1 were both required for growth in certain conditions, but neither SNZ2, SNZ3, SNO2 nor SNO3 were required. Copies 2 and 3 of the gene products have, in spite of their extremely close sequence similarity, slightly different functions in the cell. We have also found that copies 2 and 3 are activated by the lack of thiamine and that the Snz proteins physically interact with the thiamine biosynthesis Thi5 protein family. Whereas copy 1 is required for conditions in which B(6) is essential for growth, copies 2 and 3 seem more related with B(1) biosynthesis during the exponential phase.     

Vitamin D status in growing dairy goats and sheep: Influence of ultraviolet B radiation on bone metabolism and calcium homeostasis

The aim of this study was to investigate how controlled UVB irradiation in combination with reduced nutritional vitamin D (vitD) supply affects vitD status and Ca metabolism of growing goats and sheep. The hypothesis was that, like dairy cows, goats and sheep are able to compensate for the missing nutritional supply of vitD through endogenous production in the skin, with the consequence of a high vitD status and a balanced Ca homeostasis. Sixteen lambs and 14 goat kids aged 3 and a half months were housed in an UVB free environment and fed hay and a vitD-free concentrate over a period of 13 wk. One group of each species was exposed to UVB lamps daily during individual feeding; the other groups served as controls. Serum, urine, and feces samples were taken at the start and at a monthly interval. Serum was analyzed for vitD metabolites, bone markers, growth hormone, insulin-like growth factor I, Ca, and P. Apparent digestibility and urinary excretion of Ca and P were determined. The left metatarsus was analyzed by peripheral quantitative computer tomography for bone mineral density before starting and at the end of the trial. In wk 13, all animals were slaughtered and samples of skin, rumen, duodenum, kidney, and bone (metatarsus) were collected. Content of sterols of vitD synthesis in the skin, Ca flux rates in rumen and duodenum, expression of vitD receptor in duodenum and kidney, renal and intestinal gene expression of Ca transport proteins, and renal enzymes related to vitD metabolism were determined. The UVB exposure led to lower 7-dehydrocholesterol content in the skin and a better vitD status (higher serum 25-hydroxyvitamin D), but no signs of vitD deficiency were seen in the control groups and no effect of irradiation was detected in the analyzed parameters of Ca homeostasis. Differences between the 2 species were detected: lambs had a higher increase of bone mineral density, lower values of bone markers, growth hormone, and insulin-like growth factor I in serum and higher tachysterol and lower lumisterol content in skin compared with goat kids. The results indicated that growing lambs and goat kids are able to compensate for a vitD-reduced diet by cutaneous vitD synthesis when exposed to UVB irradiation and therefore to keep a high vitD status. In contrast, when a reduced vitD diet is combined with missing UVB exposure, the vitD status drops, but the experimental time was probably too short to induce a vitD deficiency or an effect on Ca homeostasis.     

Determination of water-soluble vitamins B1, B2, B6 and B12 in milk using HPLC]

Simple methods of determining the water-soluble vitamins B1, B2, B6 and B12 in milk by HPLC are described. Compared to existing procedures, the following improvements can be realized. The oxidation of vitamin B1 to thiochrome is stopped by the addition of sodium sulphite. This step significantly increases repeatability. Thiochrome is then extracted with butan-1-ol, which results in fewer co-extracts and greater selectivity. After the hydrolysis of the 5-phosphates of the vitamin B6 (pyridoxine, pyridoxal and pyridoxamine), these three vitamers are determined by isocratic HPLC as DDS-ion-pairs and with fluorimetric detection. As only microbiological methods have so far been used for the determination of minute quantities of vitamin B12 in milk, a new HPLC procedure is proposed with a detection limit of 0.2 micrograms vitamin B12/L milk.     

Vitamin D status and glucose metabolism in youth

This study aimed to review and synthesize the available scientific evidence on the relationship between serum 25(OH)D concentrations and glucose metabolism among adolescents. A total of 19 studies were included. Many studies did not find a relation between 25(OH)D concentrations and insulin sensitivity, but most studies have shown that vitamin D status influences glucose dysregulation in youth due to particularities of this life stage. Considering the prevalence of vitamin D deficiency and insufficiency were high among adolescents, the importance for vitamin D status correction in this young group, in which chronic diseases are not expected but getting every day more common, is mandatory.     

Providing with vitamins of different population groups in Sverdlovsk]

The investigation on providing with vitamins of varying population groups: preschool children, schoolchildren, students of trade schools and higher schools, workers and employees was conducted in Sverdlovsk. Low levels of vitamin C were detected in the blood of 40-92%, folic acid--in 10-76%, vitamin A--in 4-28%, carotene--in 8-60%, tocopherol--in 4-50% of the examinees. Vitamin B1 deficiency was noted in 36-68%, vitamin B2--in 17-71%. The highest deficiency of ascorbic acid was recorded in workers and students of trade schools and higher schools, of folic acid--in workers and adolescents of 15-18 years, of vitamins B1, E, A and carotene--in children and adolescents, vitamin B1--in employees. The mass character of vitamin deficiencies and their negative effects on the health of the population have necessitated broad-scale prophylactic measures: production of vitamin-enriched foods, regular use of multivitamins.     

Lack of Vitamin B6 Activity of 6-Hydroxypyridoxine

Hydroxylation of the C-6 position of pyridoxine has been described recently as a mechanism for the degradation of vitamin B6 in foods. The nutritional properties of the resulting 6-hydroxypyridoxine in mammals have not been previously evaluated. 6-Hydroxypyridoxine was synthesized and its structure confirmed by UV and NMR spectroscopy. A rat bioassay with multiple dose levels was conducted to compare the vitamin B6 activity of pyridoxine and 6-hydroxypyridoxine with respect to a variety of indices of vitamin B6 metabolism. By all criteria employed, 6-hydroxypyridoxine exhibited neither vitamin B6 nor antivitamin B6 activity and, thus, is nutritionally inert.     

Measurement of Glycosylated Vitamin B6 in Foods

To examine the levels of glycosylated vitamin B6 in 22 foods, each food was stirred for 2 hr at pH 6.8 and then incubated for 2 hr at pH 5.0 and 37°C with β-glucosidase (60 units per g food). Vitamin B6 content of foods was measured microbiologically before and after enzyme treatment as well as with acid hydrolysis. Animal products contained no measurable amount of glycosylated B6. Grains and legumes generally had a high level of this bound form (6–57% of the total vitamin B6). Of the fruits analyzed, orange juice had the highest level of glycosylated vitamin B6 (47%). Among fresh vegetables studied, raw carrots had the highest level (51%). For broccoli and cauliflower, the glycosylated value was higher for the processed food as compared to the raw food.     

Vitamin B12 and its binding proteins in milk from cow and buffalo in relation to bioavailability of B12

Milk is an important source of highly bioavailable vitamin B₁₂ (cobalamin) in human nutrition. In most animal products, vitamin B₁₂ is strongly bound to various specific protein carriers. The 2 vitamin B₁₂-specific proteins, predominantly transcobalamin (TC) and haptocorrin (HC), were earlier found in milk from Holstein Friesian cows and in human or sow milk, respectively. As the type of vitamin B₁₂ binders may influence bioavailability of the vitamin, we examined vitamin B₁₂ carriers in pooled milk specimens derived from European and Indian cow and buffalo herds. The total endogenous vitamin B₁₂ concentration was comparable in all milk pools (≈3 nM), but the vitamin carriers varied considerably: TC + caseins in Danish cows, TC + HC in Indian cows and buffaloes, and mainly HC in Italian buffaloes. Danish cow milk contained half as much TC as vitamin B₁₂, and the surplus vitamin was all attached via a single coordination bond to abundantly available histidine residues of casein. The specific binding proteins in Indian cow milk (TC + HC) approximately matched the molar content of vitamin B₁₂. Milk from the 2 buffalo breeds contained more specific binders than vitamin B₁₂, and the surplus proteins included the unsaturated TC ≈ 3 nM (Indian stock), or both TC ≈ 4 nM and HC ≈ 23 nM (Italian stock). The abundant HC of the latter sample bound nearly all endogenous vitamin B₁₂. We tested (in vitro) the transfer of vitamin B₁₂ from milk proteins to human carriers, involved in the intestinal uptake. The bovine TC-vitamin B₁₂ complex rapidly dissociated at pH 2 (time of half reaction, τ_1/2 < 1 min, 37°C) and was susceptible to digestion with trypsin + chymotrypsin (pH 7.5). Transfer of vitamin B₁₂ from the precipitated bovine casein (pH 2) to human carriers proceeded with τ_1/2 ≈ 7 min (37°C) and τ_1/2 ≈ 35 min (20°C). Liberation of vitamin B₁₂ from buffalo HC was hampered because of its pH stability and slow proteolysis. Nutritional availability of vitamin B₁₂ is expected to be high in cow milk (with TC-vitamin B₁₂ and casein-vitamin B₁₂ complexes) but potentially constrained in buffalo milk (with HC-vitamin B₁₂). This especially concerns the Italian buffalo milk, where a high excess of HC was found. We speculate whether the isolated stock of Italian buffalo maintained the ancestral secretion of carriers (HC ≫ vitamin B₁₂, TC ≈ 0), whereas intensive crossbreeding of cows and buffaloes from other regions caused a change to TC ≤ vitamin B₁₂, with low or absent HC. The substitution of HC by less sturdy carriers is apparently more beneficial to human consumers as far as vitamin B₁₂ bioavailability is concerned.     

不同剥皮率对面粉B族维生素含量影响

小麦籽粒富含B族维生素,其大部分集中于小麦糊粉层,经加工后B族维生素受到极大损失。通过测定高、中、低筋3种小麦在7个剥皮率梯度下面粉基本指标及B族维生素含量变化,研究小麦剥皮处理对面粉品质及面粉VB族含量影响;结果表明,不同剥皮率对小麦制粉和面粉品质具有明显影响,对面粉VB族含量差异性显著,且4%剥皮率能有效降低小麦B族维生素流失,提高面粉中VB族含量。     

Vitamin D3 and D3 metabolites in young goats fed varying amounts of calcium and vitamin D3

Twenty-four male goats, 2 to 4 wk of age, were allotted to four dietary treatments in a 2 X 2 factorial design and, for 20 wk, were fed a milk diet at 12.5% body weight. Treatments varied in amounts of supplemental calcium and vitamin D3. Daily allowances per kilogram body weight were: 9.4 IU vitamin D3 (basal), 9.4 IU vitamin D3 plus 406 mg calcium carbonate (basal plus Ca), 940 IU vitamin D3 (basal plus D3), and 940 IU vitamin D3 plus 406 mg calcium carbonate (basal plus Ca plus D3). At the end of wk 7, a corn supplement was added to all diets at 1% body weight daily. Addition of vitamin D3 to the diet resulted in a dramatic increase in plasma concentrations of vitamin D3. Goats in the basal plus D3 and basal plus Ca plus D3 groups had nearly 100 X greater concentrations of vitamin D3 than goats in the basal and basal plus Ca groups. When greater amounts of vitamin D3 were fed, dietary calcium interacted to decrease plasma vitamin D3 concentrations. Plasma concentrations of 25-hydroxyvitamin D3 were unaffected by additional dietary calcium but were increased by dietary vitamin D3, increasing sixfold to seven-fold in the basal plus D3 and basal plus Ca plus D3 groups. Supplemental calcium resulted in decreased plasma 1,25-dihydroxyvitamin D3. No signs of vitamin D toxicity were noted. The physiological responses reported implicate the goat as a potential animal model for vitamin D research in dairy cattle.     

Glycolaldehyde-forming route in Bacillus subtilis in relation to vitamin B6 biosynthesis

Glycolaldehyde (GA) was shown to be a precursor of vitamin B6 (B6), and to be formed from glycolate by glycolaldehyde dehydrogenase (GADH) in Escherichia coli. In this study, we show the glycolaldehyde-forming route in B6 biosynthesis in Bacillus subtilis. In the crude extract of B. subtilis, the oxidizing activity of GADH was detected. However, coexisting NADH/NADPH oxidase activity interfered with the determination of the reducing (GA-forming) activity of GADH. NADH/NADPH oxidase was purified and identified as the product of ahpF. In an ahpF disruptant, NADH/NADPH activity was almost eliminated, but the reducing activity of GADH was not detected. We also investigated another possible GA-forming enzyme, glyoxal reductase (GR). GR was partially purified and identified as the product of yvgN. yvgN disruptant did not require B6, and retained the ability to synthesize the same amount of B6 as the wild-type strain. From these results, we concluded that neither GADH nor GR is involved in B6 biosynthesis in B. subtilis.     

Vitamin B 12 metabolism and the status of sulfhydryl groups in protein-choline deficiency in rats. Effects of methyl- and adenosylcobalamins]

The effect of low protein choline-deficient diet on total vitamin B12 content and individual cobalamin level in the blood serum and liver of rats was determined. Moreover the total and non-protein SH-group content and glutathione transferase activity in the liver of rats were studied. Total cobalamin content increased in the blood serum, but it did not change in the liver of rats fed choline-deficient low protein diet. Total and non-protein SH-group level as well as glutathione transferase activity in the liver decreased significantly. The causes of changes revealed are discussed. Methylcobalamin (but not adenosylcobalamin) administration normalized individual cobalamin level in the blood serum. Administration of both methylcobalamin and adenosyl-cobalamin resulted in total SH-group content restoration whereas non-protein SH-group level and glutathione transferase activity were restored only in methylcobalamin-treated rats.     

The results of application of magnesium-bearing medications and different load doses of vitamins B1 and B2 in volunteers

Presently is no consensus of opinion of the size of human optimal daily allowance as for thiamine and riboflavin, so for magnesium, what their content in polyvitamin and mineral preparations testify to. The study was conducted in 60 volunteers, who once took oral dosing of magnesium -bearing preparation "Magnerot" (500 mg of magnesium orotat converting to Mg2+ 32,8 Mg) and "Centrum" (100 mg of magnesium oxide converting to Mg2+ - 60,3 Vg) or vitamins B1 and B2 in 10, 20 and 30 mg doses. The received data testify that during the application of both of these preparations, equal concentration of this element takes place, though in case of magnesium oxide it happens later. As for the used vitamin B1 and B2 doses, it is determined that 10 mg is the optimal dose for treating their hypoavitaminosis.     

产维生素B6乳酸菌的筛选及其鉴定

以源自内蒙古呼和浩特市婴儿粪便选出的10株乳酸杆菌为试验材料,通过微生物分析方法,筛选乳酸菌合成维生素B6能力较强的菌株并对其进行初步鉴定.结果表明,有4株菌株B25、B72、B76和N59-1合成维生素B6的能力较高,其中菌株N59-1合成维生素B6的量可高达32.62 g/100 L,菌株N59-1经鉴定为植物乳杆菌.