Thiocyanate Metabolism in Human Vitamin B12 Deficiency

Patients with subacute combined degeneration who smoked had significantly lowered plasma thiocyanate levels than control smokers, but plasma thiocyanate levels in non-smoking patients with neurological disease due to vitamin B₁₂ deficiency were not significantly different from control values. The results provide no support for the hypothesis that chronic cyanide intoxication is responsible for the occurrence of neurological disease in a minority of patients with vitamin B₁₂ deficiency, although they do not conclusively exclude this possibility. The association between smoking and subacute combined degeneration of the cord has been confirmed in this study but it remains unexplained.     

Differential Proteomics of Helicobacter pylori Associated with Autoimmune Atrophic Gastritis

Atrophic autoimmune gastritis (AAG) is a condition of chronic inflammation and atrophy of stomach mucosa, for which development can be partially triggered by the bacterial pathogen Helicobacter pylori (HP). HP can cause a variety of gastric diseases, such as duodenal ulcer (DU) or gastric cancer (GC). In this study, a comparative proteomic approach was used by two-dimensional fluorescence difference gel electrophoresis (DIGE) to identify differentially expressed proteins of HP strains isolated from patients with AAG, to identify markers of HP strain associated with AAG. Proteome profiles of HP isolated from GC or DU were used as a reference to compare proteomic levels. Proteomics analyses revealed 27 differentially expressed spots in AAG-associated HP in comparison with GC, whereas only 9 differential spots were found in AAG-associated HP profiles compared with DU. Proteins were identified after matrix-assisted laser desorption ionization (MALDI)-TOF and peptide mass fingerprinting. Some AAG-HP differential proteins were common between DU- and GC-HP (peroxiredoxin, heat shock protein 70 [HSP70], adenosine 5′-triphosphate [ATP] synthase subunit α, flagellin A). Our results presented here may suggest that comparative proteomes of HP isolated from AAG and DU share more common protein expression than GC and provide subsets of putative AAG-specific upregulated or downregulated proteins that could be proposed as putative markers of AAG-associated HP. Other comparative studies by two-dimensional maps integrated with functional genomics of candidate proteins will undoubtedly contribute to better decipher the biology of AAG-associated HP strains.     

Hashimoto Thyroiditis not Associated with Vitamin D Deficiency

Objective: Vitamin D deficiency is associated with several autoimmune diseases. This study assessed whether vitamin D deficiency is associated with Hashimoto thyroiditis (HT).Methods: Two groups of patients were selected for which serum 25-hydroxyvitamin D (25(OH)D) levels had been measured: (1) a study group of patients diagnosed with HT as indicated by thyroid antibodies, and (2) a healthy control group. Each group was separated by sex and then controlled for age and body mass index (BMI). Groups' mean 25(OH)D levels were compared by analysis of variance (ANOVA), and percent frequencies of vitamin D sufficiency, insufficiency, and deficiency were compared with a Z-test. The correlations between 25(OH)D levels and thyroid antibodies and thyroid-stimulating hormone (TSH) levels were also tested.Results: The mean 25(OH)D levels for the HT and control groups were significantly different in females (30.75 vs. 27.56 ng/mL, respectively) but not in males (14.24 vs. 13.26 ng/mL). HT females had a higher rate of vitamin D sufficiency (51.7% vs. 31.1%) and a lower rate of insufficiency (48.3% vs. 68.9%) relative to control females. No such differences were found in the male groups. None of the females were vitamin D deficient, but almost all males were. A significant (P = .016) positive correlation (r_s = 0.436) between 25(OH)D and TPOAb was observed in males.Conclusion: HT is not associated with higher rates of vitamin D deficiency relative to a control group.Abbreviations:BMI = body mass indexHT = Hashimoto thyroiditis25(OH)D = 25-hydroxyvitamin DTgAb = thyroglobulin antibodyTSH = thyroid-stimulating hormoneTPOAb = thyroid-peroxidase antibodyVDR = Vitamin D receptor     

Structural Insights into the MMACHC-MMADHC Protein Complex Involved in Vitamin B12 Trafficking

Conversion of vitamin B₁₂ (cobalamin, Cbl) into the cofactor forms methyl-Cbl (MeCbl) and adenosyl-Cbl (AdoCbl) is required for the function of two crucial enzymes, mitochondrial methylmalonyl-CoA mutase and cytosolic methionine synthase, respectively. The intracellular proteins MMACHC and MMADHC play important roles in processing and targeting the Cbl cofactor to its destination enzymes, and recent evidence suggests that they may interact while performing these essential trafficking functions. To better understand the molecular basis of this interaction, we have mapped the crucial protein regions required, indicate that Cbl is likely processed by MMACHC prior to interaction with MMADHC, and identify patient mutations on both proteins that interfere with complex formation, via different mechanisms. We further report the crystal structure of the MMADHC C-terminal region at 2.2 Å resolution, revealing a modified nitroreductase fold with surprising homology to MMACHC despite their poor sequence conservation. Because MMADHC demonstrates no known enzymatic activity, we propose it as the first protein known to repurpose the nitroreductase fold solely for protein-protein interaction. Using small angle x-ray scattering, we reveal the MMACHC-MMADHC complex as a 1:1 heterodimer and provide a structural model of this interaction, where the interaction region overlaps with the MMACHC-Cbl binding site. Together, our findings provide novel structural evidence and mechanistic insight into an essential biological process, whereby an intracellular “trafficking chaperone” highly specific for a trace element cofactor functions via protein-protein interaction, which is disrupted by inherited disease mutations.     

Gene Polymorphisms of Micrornas in Helicobacter pylori-Induced High Risk Atrophic Gastritis and Gastric Cancer

Background and aims

MicroRNAs (miRNAs) are known for their function as translational regulators of tumor suppressor or oncogenes. Single nucleotide polymorphisms (SNPs) in miRNAs related genes have been shown to affect the regulatory capacity of miRNAs and were linked with gastric cancer (GC) and premalignant gastric conditions. The purpose of this study was to evaluate potential associations between miRNA-related gene polymorphisms (miR-27a, miR-146a, miR-196a-2, miR-492 and miR-608) and the presence of GC or high risk atrophic gastritis (HRAG) in European population.

Methods

Gene polymorphisms were analyzed in 995 subjects (controls: n = 351; GC: n = 363; HRAG: n = 281) of European descent. MiR-27a T>C (rs895819), miR-146a G>C (rs2910164), miR-196a-2 C>T (rs11614913), miR-492 G>C (rs2289030) and miR-608 C>G (rs4919510) SNPs were genotyped by RT-PCR.

Results

Overall, SNPs of miRNAs were not associated with the presence of GC or HRAG. We observed a tendency for miR-196a-2 CT genotype to be associated with higher risk of GC when compared to CC genotype, however, the difference did not reach the adjusted P-value (odds ratio (OR) - 1.46, 95% confidence interval (CI) 1.03-2.07, P = 0.032). MiR-608 GG genotype was more frequent in GC when compared to controls (OR −2.34, 95% CI 1.08–5.04), but significance remained marginal (P = 0.029). A similar tendency was observed in a recessive model for miR-608, where CC + CG vs GG genotype comparison showed a tendency for increased risk of GC with OR of 2.44 (95% CI 1.14–5.22, P = 0.021). The genotypes and alleles of miR-27a, miR-146a, miR-196a-2, miR-492 and miR-608 SNPs had similar distribution between histological subtypes of GC and were not linked with the presence of diffuse or intestinal-type GC.

Conclusions

Gene polymorphisms of miR-27a, miR-146a, miR-196a-2, miR-492, miR-492a and miR-608 were not associated with the presence of HRAG, GC or different histological subtypes of GC in European subjects.     

Nutrition-Related Vitamin B12 Deficiency in Patients in Pakistan with Type 2 Diabetes Mellitus not Taking Metformin

ObjectiveTo estimate the frequency of undiagnosed vitamin B₁₂ deficiency among patients with type 2 diabetes mellitus who had not taken metformin during at least the prior 5 years and to ascertain whether vitamin B₁₂ deficiency among the patients with type 2 diabetes was due to nutritional deficiency or malabsorption.MethodsSerum vitamin B₁₂ levels were measured in 44 subjects with diabetes and a mean age of 51 years (range, 40 to 70), 21 (48%) of whom had low levels (< 200 pg/mL). Of those 21 patients, 10 agreed to enroll in an intervention phase consisting of oral supplementation with mecobalamin, 1,500 μg daily for 3 months. Those patients in whom vitamin B₁₂ levels failed to normalize after oral supplementation alone would be presumed to have vitamin B₁₂ deficiency attributable to malabsorption.ResultsAlmost half of the subjects with type 2 diabetes not taking metformin had biochemically proven vitamin B₁₂ deficiency. All 10 subjects who enrolled in the intervention phase had normalization of their vitamin B₁₂ levels after 3 months of oral supplementation with mecobalamin.ConclusionWe conclude that vitamin B₁₂ deficiency is common among patients with type 2 diabetes and was related to nutrition in our study group. In addition to intensive glycemic control, vitamin B₁₂ supplementation should be considered for treatment of diabetic neuropathy. In almost 50% of patients with low vitamin B₁₂ levels, the deficiency was corrected with oral supplementation only. This, indeed, is an important finding, inasmuch as oralvitamin B₁₂ supplementation is easy, convenient, and readily accepted by patients. This finding highlights the need for aggressive and early diagnosis and treatment to avoid complications of vitamin B₁₂ deficiency. (Endocr Pract. 2010;16:205-208)     

Assessment of Deoxyuridine Suppression Test in Diagnosis of Vitamin B12 or Folate Deficiency

Deoxyuridine (dU) suppression tests have been performed on virtually all marrow samples aspirated at this hospital over the past 12 months. Of the 110 samples studied 26 gave abnormal results, and these 26 samples came from patients deficient in either vitamin B₁₂ or folate. The dU suppression test was found to be of particular value in the diagnosis of vitamin B₁₂ or folate deficiency in non-anaemic patients with macrocytosis and equivocal changes in marrow morphology and in patients in whom the serum vitamin B₁₂ or red cell folate levels were within the normal range.     

Role of Third Serum Vitamin B12 Binding Protein in Vitamin B12 Transport

A third vitamin B₁₂ binding protein present in normal serum has been shown to participate in transport of labelled vitamin B₁₂ absorbed from the gut. All three vitamin B₁₂ binding proteins in serum were labelled at the same time after oral administration of vitamin B₁₂, implying that “free” vitamin B₁₂ reached the portal blood from the gut mucosa.