Effect of vitamin B6 on lenses of diabetic rats

Vitamin B6 is essential for the metabolism of fat, carbohydrate and protein. In this study the effect of vitamin B6 on diabetes induced impairments in rat lenses was investigated. Although macroscopic examination revealed no opacification of rat lenses in any groups, uncontrolled induced diabetes caused significant decreases in lens glutathione and increases in lens protein nonenzymatic glycosylation and blood glucose. Administration of vitamin B6 did not inhibit these diabetes induced alterations significantly. SDS-polyacrylamide gel electrophoresis revealed some significant differences in some protein bands between groups.     

Effect of vitamin B6 deficiency on pancreatic acpinar cell function

The present study was designed to determine the effect of vitamin B₆ deficiency on pancreatic acinar cell function. Rats were either fed $\text{ad}$$\text{lib}$ or rendered B₆-deficient by a purified B₆-deficient diet; half of the latter being replenished with IP pyridoxine before sacrifice. Body weight, pancreatic weight, RNA and DNA content were decreased in B₆-deficient animals. These changes were considered to be due to inanition resulting from decreased food intake. Amylase content of pancreas in B₆-deficient animals was less compared with B₆-replenished animals. Although slightly higher in B₆-deficient animals, the incorporation of L-phenylalanine¹⁴C into total tissue proteins was not significantly different in the three groups of animals. On B₆-replenishment, incorporation of L-phenylalanine¹⁴C into nascent proteins was diminished in spite of higher tissue amylase and protein content. Vitamin B₆ deficiency decreased total RNA content and adenine-8-¹⁴C incorporation into RNA. DNA content was diminished but incorporation of thymidine-2-¹⁴C into DNA was increased. On replenishment with B₆, thymidine-2-¹⁴C incorporation decreased significantly compared to control animals. Secretion of amylase was diminished commensurate with decreased content. It is concluded from these studies that B₆-deficiency induced DNA injury, decreased RNA turnover and increased protein turnover resulting in diminished amylase content. These data indicate that B₆-deficiency so frequently encountered in alcoholism may contribute to the pancreatic injury in this clinical condition.     

Effect of antibody on interaction between vitamin B2 and riboflavin apoprotein.

1. Dissociation of riboflavin from flavoprotein and from the flavoprotein-antibody complex occurs under the same conditions. 2. The precipitated apoprotein-antibody complex retains 15% of the apoprotein capacity to bind riboflavin. After solubilization of the complex in 0.3 M-KCl or 1 M-urea, the binding of riboflavin amounts to 80 - 90% of its capacity. 3. The apoprotein modified by oxidation of 50% of tryptophan residues loses the ability to bind riboflavin but its immunological reactivity with the anti-flavoprotein antibody is similar to that of native apoprotein. The apoprotein with all tryptophan residues oxidized shows much lower immunoreactivity. 4. The obtained results suggest that in riboflavin flavoprotein the region around the riboflavin-binding site does not show the properties of an antigenic determinant.     

The effect of dietary vitamin B6 on tissue fat contents and lipid composition in livers and gills of Atlantic salmon (Salmo salar)

Atlantic salmon (9 g) were fed a basal experimental diet supplemented with vitamin B₆ at 0, 5 and 10 mg/kg for 10 weeks. Vitamin b₆ unsupplemented fish showed reduced lipid contents in muscle, and reduced levels of 22:6n-3 and sum n-3 fatty acids in the hepatic phospholipids PE and PS. In gills, the fatty acid pattern was not influenced by the dietary vitamin B₆ contents. Desaturation and elongation of [1-¹⁴C]18:3n-3 in liver following intraperitoneal injection was not affected by dietary vitamin b₆. Liver weights, the hepatosomatic index and the activity of aspartate aminotransferase and concentration of vitamin B₆ in white muscle increased with increasing dietary vitamin B₆ levels, and were significantly highest in the highest supplemented fish.     

Microbial production of vitamin B12

One of the most alluring and fascinating molecules in the world of science and medicine is vitamin B12 (cobalamin), which was originally discovered as the anti pernicious anemia factor and whose enigmatic complex structure is matched only by the beguiling chemistry that it mediates. The biosynthesis of this essential nutrient is intricate, involved and, remarkably, confined to certain members of the prokaryotic world, seemingly never have to have made the eukaryotic transition. In humans, the vitamin is required in trace amounts (approximately 1 microg/day) to assist the actions of only two enzymes, methionine synthase and (R)-methylmalonyl-CoA mutase; yet commercially more than 10 t of B12 are produced each year from a number of bacterial species. The rich scientific history of vitamin B12 research, its biological functions and the pathways employed by bacteria for its de novo synthesis are described. Current strategies for the improvement of vitamin B12 production using modern biotechnological techniques are outlined.     

Effect of oral methionine and vitamin E on blood lipid peroxidation in vitamin B6 deficient rats

Lipid peroxidation in blood of vitamin B6 deficient rats was significantly increased when compared to pair-fed controls. The observed increased lipid peroxidation in vitamin B6 deficiency was correlated with high levels of lipids, metal ions and low levels of antioxidants, alpha-tocopherol, ascorbic acid and reduced GSH. Supplementation of methionine or vitamin E along with the vitamin B6 deficient diet restored the levels of antioxidants to near normal and also protected against oxidative stress. However plasma TBARS level as well as total lipids were still elevated in M-B6 diet fed rats and normalized in E-B6-d rats.     

Changes in kinetic properties of pyridoxal-dependent enzymes during dietary vitamin B6 deficiency in rats

The erythrocyte aspartate aminotransferase and renal and intestinal glycogen phosphorylase activities in rats are determined as dependent on their provision with vitamin B6. It has been shown that the aspartate aminotransferase activity decreases and the shape of the aspartate concentration-activity curve changes in the vitamin B6-deficient animals. The B6 insufficiency does not affect the intestinal mucosa glycogen phosphorylase. However the renal phosphorylase activity decreases by 30 percent in the vitamin B6 deficient rats. It occurs due to changes in the affinity of phosphorylase A and B to glucose-1-phosphate but not to AMP. The activation of these investigated enzymes by exogenous pyridoxal phosphate reveals no essential differences between the vitamin B6-deficient and normal rats. The possible causes of the observed changes in the aspartate aminotransferase and phosphorylase activity are discussed.     

Effect of vitamin B6 on gamma-aminobutyric acid level in rat brain.

Vitamin B6 injected intraperitoneally into rats 400 mg/kg body weight, has produced a statistically significant decrease in GABA level concentrations in hippocampus and cerebellum. Cerebral cortex, caudate nucleus and thalamus have shown the decrease in GABA concentrations, but these changes were not statistically significant. No remarkable behavioural changes were noted under such circumstances. The possible functional meaning of these results is discussed in relation to the role of GABA distribution in different brain regions and development of convulsions.     

Effect of vitamin B6 availability on serine hydroxymethyltransferase in MCF-7 cells

Folate-activated one-carbon units are derived from serine through the activity of the pyridoxal-phosphate (PLP)-dependent isozymes of serine hydroxymethyltransferase (SHMT). The effect of vitamin B(6) availability on the activity and expression of the human mitochondrial and cytoplasmic SHMT isozymes was investigated in human MCF-7 cells. Cells were cultured for 6 months in vitamin B(6) replete (4.9 microM pyridoxine) minimal essential medium (alphaMEM) or vitamin B(6)-deficient medium containing 49, 4.9 or 0.49 nM pyridoxine. Total cellular PLP levels and SHMT activity were reduced 72% and 7%, respectively, when medium pyridoxine was decreased from 4.9 microM to 49 nM. Cells cultured in medium containing 4.9 nM pyridoxine exhibited 75%, 27% and 60% reduced levels of PLP, SHMT activity and S-adenosylmethionine, respectively, compared to cells cultured in alphaMEM. Cytoplasmic SHMT activity and protein levels, but not mRNA levels, were decreased in cells cultured in vitamin B(6) deficient medium, whereas mitochondrial SHMT activity and protein levels were less sensitive to vitamin B(6) availability. PLP bound to cytoplasmic SHMT with a K(d)=850 nM, a value two orders of magnitude lower than previously reported for the bovine cytoplasmic SHMT isozyme. Collectively, these data indicate that vitamin B(6) restriction decreases the activity and stability of SHMT, and that the cytoplasmic isozyme is more sensitive to vitamin B(6) deficiency than the mitochondrial isozyme in MCF-7 cells.