Thiamine deficiency in diabetes mellitus and the impact of thiamine replacement on glucose metabolism and vascular disease

Mechanisms of Non-coenzyme Action of Thiamine: Protein Targets and Medical Significance

Thiamine (vitamin B1) is a precursor of the well-known coenzyme of central metabolic pathways thiamine diphosphate (ThDP). Highly intense glucose oxidation in the brain requires ThDP-dependent enzymes, which determines the critical significance of thiamine for neuronal functions. However, thiamine can also act through the non-coenzyme mechanisms. The well-known facilitation of acetylcholinergic neurotransmission upon the thiamine and acetylcholine co-release into the synaptic cleft has been supported by the discovery of thiamine triphosphate (ThTP)-dependent phosphorylation of the acetylcholine receptor-associated protein rapsyn, and thiamine interaction with the TAS2R1 receptor, resulting in the activation of synaptic ion currents. The non-coenzyme regulatory binding of thiamine compounds has been demonstrated for the transcriptional regulator p53, poly(ADP-ribose) polymerase, prion protein PRNP, and a number of key metabolic enzymes that do not use ThDP as a coenzyme. The accumulated data indicate that the molecular mechanisms of the neurotropic action of thiamine are far broader than it has been originally believed, and closely linked to the metabolism of thiamine and its derivatives in animals. The significance of this topic has been illustrated by the recently established competition between thiamine and the antidiabetic drug metformin for common transporters, which can be the reason for the thiamine deficiency underlying metformin side effects. Here, we also discuss the medical implications of the research on thiamine, including the role of thiaminases in thiamine reutilization and biosynthesis of thiamine antagonists; molecular mechanisms of action of natural and synthetic thiamine antagonists, and biotransformation of pharmacological forms of thiamine. Given the wide medical application of thiamine and its synthetic forms, these aspects are of high importance for medicine and pharmacology, including the therapy of neurodegenerative diseases.

The Catalytic Mechanism of Human Transketolase

We have computationally determined the catalytic mechanism of human transketolase (hTK) using a cluster model approach and density functional theory calculations. We were able to determine all the relevant structures, bringing solid evidences to the proposed experimental mechanism, and to add important detail to the structure of the transition states and the energy profile associated with catalysis. Furthermore, we have established the existence of a crucial intermediate of the catalytic cycle, in agreement with experiments. The calculated data brought new insights to hTK's catalytic mechanism, providing free-energy values for the chemical reaction, as well as adding atomistic detail to the experimental mechanism.

B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin

Background

Neurotropic B vitamins play crucial roles as coenzymes and beyond in the nervous system. Particularly vitamin B1 (thiamine), B6 (pyridoxine), and B12 (cobalamin) contribute essentially to the maintenance of a healthy nervous system. Their importance is highlighted by many neurological diseases related to deficiencies in one or more of these vitamins, but they can improve certain neurological conditions even without a (proven) deficiency.

Aim

This review focuses on the most important biochemical mechanisms, how they are linked with neurological functions and what deficits arise from malfunctioning of these pathways.

Discussion

We discussed the main role of B Vitamins on several functions in the peripheral and central nervous system (PNS and CNS) including cellular energetic processes, antioxidative and neuroprotective effects, and both myelin and neurotransmitter synthesis. We also provide an overview of possible biochemical synergies between thiamine, pyridoxine, and cobalamin and discuss by which major roles each of them may contribute to the synergy and how these functions are inter‐related and complement each other.

Conclusion

Taking into account the current knowledge on the neurotropic vitamins B1, B6, and B12, we conclude that a biochemical synergy becomes apparent in many different pathways in the nervous system, particularly in the PNS as exemplified by their combined use in the treatment of peripheral neuropathy.

Vitamins in diet of patients with metabolic syndrome

Aim - analysis of data on the role of vitamin and carotenoid deficiency in the development of metabolic syndrome (MS), the consumption of individual vitamins and vitamin supplements, as well as estimation of the effectiveness of the use of vitamins in patients with MS. A review of the existing literature has been carried out in the databases of RINC, CyberLeninka, Google Scholar, Pubmed. The lack of vitamins is a risk factor for MS and its components. The diet of people with MS is characterized by excessive caloric content and at the same time contains an inadequate amount of most vitamins. The most frequent in patients with MS is the deficiency (blood level) of vitamin D, E, B vitamins, carotenoids. Among patients with MS, individuals with a reduced concentration of vitamins in the blood plasma are often found. In turn, among those with a deficiency of vitamins, MS is more often found. Low concentrations of 25(OH)D in the serum are associated with an increased risk of MS. An inverse association between the concentration of the hormonal form of vitamin 1.25(OH)2D3 in the serum and the development of MC has been found. In patients with MS, the α-tocopherol concentration associated with lipids is lower than in healthy individuals, and γ-tocopherol, on the contrary, is higher. Taking high doses of one of the vitamin E homologues shifts the balance between tocopherols in the blood plasma. Sufficient supply of the body with all vitamins involved in the formation of metabolically active forms of vitamins (D, B6, PP) is a necessary condition for the exercise of these biological functions by these vitamins. The lack of vitamins is a risk factor for MS and its components. Enrichment of the diet of patients with MS should be considered as a necessary favorable background for its treatment. Since the body has functional connections between vitamins, it is advisable to use not individual vitamins, but their complexes.

Myocardial dysfunction in relation to serum thiamine levels in children with diabetic ketoacidosis

Background Thiamine deficiency is commonly reported in patients with diabetes especially during diabetic ketoacidosis (DKA) that could attribute to myocardial dysfunction in those patients. However, there is limited data regarding its relation to myocardial function among those patients. This study aimed to explore the association between myocardial function and serum thiamine levels in children with type 1 diabetes mellitus (DM). Methods This cross-sectional comparative study included 25 patients with DKA. Clinical data assessment, echocardiographic examination and measurement of serum high-sensitive troponin T (hs-cTnT) and thiamine levels were done. We also assessed the association between troponin levels, echocardiographic ventricular systolic and diastolic function and serum thiamine. Results Twenty-four percent of children with DKA had thiamine deficiency. DKA children with thiamine deficiency had significant acidosis and higher serum troponin levels and significant impairment of diastolic function than those without thiamine deficiency. The serum thiamine level had a significant positive correlation with the echocardiographic indices of diastolic function but negative correlation with troponin levels. Conclusions Thiamine deficiency is a common finding during the treatment of children with DKA, and this deficiency may be associated with myocardial dysfunction.

[Increasing lactate levels during treatment of diabetic ketoacidosis]

A young woman with type 1 diabetes mellitus and severe diabetic ketoacidosis was treated in an intensive care unit according to the guidelines. Only a few hours after starting the therapy, rising lactate values were diagnosed in the arterial blood gas analysis. Since there were no indications for other reasons of lactatemia, an acute refeeding syndrome caused by the insulin therapy was suspected. Thiamine and phosphate were thus replaced. With this treatment, lactate values fell, supporting the hypothesis of lactatemia due to substrate deficiency.

Blood Thiamine Level and Cognitive Function in Older Hospitalized Patients

AIM

We sought to identify any association between whole blood thiamine level and functional status in older hospitalized patients.

METHODS

This cross-sectional study retrospectively analyzed the results of routine measurements of whole blood thiamine levels of 233 older patients who were consecutively hospitalized to a geriatric acute care ward. Nutritional status, depression, and the participants' cognitive impairment were evaluated using the Mini Nutritional Assessment-Short Form, Depression in Old Age Scale, and Montreal Cognitive Assessment, respectively. Activities of daily living were determined using Barthel Index (BI) on admission and at the time of discharge. Diagnoses of dementia and delirium were derived from the patients' medical records.

RESULTS

Of 233 participants (mean age 82.1 [7.1]), 47.0% and 39.0% were at risk of malnutrition and malnourished, respectively. There was no thiamine deficiency (<20 ng/mL) in total population. Nearly all patients (95%) were screened with impaired cognitive function, in which 36% and 9% had the diagnosis of dementia and delirium, respectively. Patients with dementia (P = .040) and delirium (P = .002) demonstrated lower mean thiamine blood levels compared to patients without. Mean blood vitamin B₁ was higher in patients with functional recovery (change in BI ≥5 points during hospitalization; P = .018). In a binary logistic regression analysis, blood vitamin B₁, weight loss, and female gender were the major independent risk factors for delirium but not for dementia.

CONCLUSION

Despite the absence of thiamine deficiency, whole blood thiamine was lower in patients with dementia and delirium compared to those without. Higher thiamine levels were significantly associated with functional recovery during hospitalization.

Modified Diet Supplementation With Group B Vitamins Changes Antioxidant Defense Activity Of Brain

The research aimed at effect of modified diet and supplementation with synthetic B vitamins on brain antioxidant status evaluation. Forty male Wistar rats were divided into 4 groups (n = 10); group I - fed Basic Diet (BD), groups II-IV - Modified Diet (MD), where wheat flour replaced 83.5 % wheat and sucrose replaced 50 % maize. Groups I-II received only water, while group III (MD + AS) was given an aqueous vitamins solution supplementing deficiency from diet modification (MD + Adequate Supplementation: B₁-0.94, B₂-0.48, B₆-0.5, niacin-1.9 mg); group IV (MD + ES) received a solution in order to supplement deficiency resulting from the change in diet and recommended prophylactic dose of vitamins (MD + Excessive Supplementation: B₁-3.1, B₂-2.3, B₆-2.4, niacin-6.65 mg). The experimental phase lasted 6 weeks. Blood serum was examined, to determine glucose and iron concentration; determination of FRAP in plasma, in brain tissue the activities of GST, GPx, CAT, SOD, SH content, and FRAP. It was found that MD and MD + AS did not influence cereal antioxidant status. In brain tissue, MD + ES group exhibited an increased glycaemia (7.49 mmol×l^-1 p = 0.038) and increased activity of antioxidant enzymes activity (GST 0,099 U/mg protein p = 0.005; GPx 0,039 U/mg protein p = 0.007). Brain tissue of rats also exhibited larger content of protein bond SH in comparison to BD, MD and MD + AS groups (SH 414.6 mmol/g wet weight p < 0.001; p < 0.005). These findings suggest that, an excessive supplementation with vitamins B and niacin, in sucrose rich diet, may lead to enhancing activity of cellular antioxidant defense in brain tissue of rats.

A Machine-Learning-Based Drug Repurposing Approach Using Baseline Regularization

We present the baseline regularization model for computational drug repurposing using electronic health records (EHRs). In EHRs, drug prescriptions of various drugs are recorded throughout time for various patients. In the same time, numeric physical measurements (e.g., fasting blood glucose level) are also recorded. Baseline regularization uses statistical relationships between the occurrences of prescriptions of some particular drugs and the increase or the decrease in the values of some particular numeric physical measurements to identify potential repurposing opportunities.

Reuniting overnutrition and undernutrition, macronutrients, and micronutrients

Over-nutrition and its late consequences are a dominant theme in medicine today. In addition to the health hazards brought on by over-nutrition, the medical community has recently accumulated a roster of health benefits with obesity, grouped under "obesity paradox." Throughout the world and throughout history until the 20^th century, under-nutrition was a dominant evolutionary force. Under-nutrition brings with it a mix of benefits and detriments that are opposite to and continuous with those of over-nutrition. This continuum yields J-shaped or U-shaped curves relating body mass index to mortality. The overweight have an elevated risk of dying in middle age of degenerative diseases while the underweight are at increased risk of premature death from infectious conditions. Micronutrient deficiencies, major concerns of nutritional science in the 20^th century, are being neglected. This "hidden hunger" is now surprisingly prevalent in all weight groups, even among the overweight. Because micronutrient replacement is safe, inexpensive, and predictably effective, it is now an exceptionally attractive target for therapy across the spectrum of weight and age. Nutrition-related conditions worthy of special attention from caregivers include excess vitamin A, excess vitamin D, and deficiency of magnesium.

Effects of α-Lipoic Acid, Carnosine, and Thiamine Supplementation in Obese Patients with Type 2 Diabetes Mellitus: A Randomized, Double-Blind Study

Type 2 diabetes mellitus (T2DM) is evolving to an epidemic of the modern world. T2DM is associated with a number of pathological complications, including cardiovascular disease that is mostly promoted by the increased oxidative stress in type 2 diabetic patients. We performed a randomized double-blind placebo-controlled trial to investigate the effectiveness of an individualized oral supplementation with α-lipoic acid (ALA), carnosine, and thiamine. For that purpose, 82 obese type 2 diabetic patients were randomly assigned to 2 groups, and were either supplemented daily with 7 mg ALA/kg body weight, 6 mg carnosine/kg body weight, and 1 mg thiamine/kg body weight or placebo for 8 weeks. An array of biochemical tests including the estimation of oxidative stress and platelet aggregation were performed at baseline and at follow-up. Moreover, the antiplatelet activity of each of the supplement's components was determined ex vivo at human and washed rabbit platelets. Glucose and HbA_1c levels were significantly reduced after supplementation (135.7 ± 19.5 mg/dL vs. 126.5 ± 16.8 mg/dL and 8.3% ± 0.3% vs. 6.03% ± 0.58%, respectively, P < .05); however, insulin was significantly increased (3.6 ± 0.7 μIU/mL vs. 6.8 ± 0.2 μIU/mL, P < .05). The patients treated with the supplement recorded higher follow-up values for HOMA-IR and HOMA-β, and a significant drop in serum hydroperoxide level. Only ALA inhibited platelets aggregation ex vivo through ADP, platelet activating factor, arachidonic acid, epinephrine, collagen, and thrombin pathways. Daily supplementation with an individualized ALA, carnosine, and thiamine supplement effectively reduced glucose concentration in type 2 diabetic patients, probably by increasing insulin production from the pancreas. In addition to that, the reduction of oxidative stress and inhibition of platelet aggregation could potentially provide greater cardiovascular protection. Further studies are needed to fine-tune the supplementation dose-response effects in T2DM patients.

A single-step method for simultaneous quantification of thiamine and its phosphate esters in whole blood sample by ultra-performance liquid chromatography-mass spectrometry

Thiamine and its phosphate esters play vital physiological roles and thiamine deficiency causes deleterious effects on human body. It is important to quantify accurately the thiamine metabolites in body fluids. However, due to the lack of appropriate internal standards, poor inter-laboratory standardization and time-consuming pretreatment procedure, the existing methods are limited in clinical applications. Hence, we developed a single-step HPLC-MS/MS method for accurate and precise measurement of thiamine and its phosphate esters in human whole blood. Whole blood samples were deproteinized and the supernatants were collected. The levels of thiamine diphosphate (TDP), thiamine monophosphate (TMP), and thiamine were determined by HPLC-MS/MS method after adding isotopic internal standards. The method was linear from 15.625-3.125-1.563 nmol/L to 1000-200-100 nmol/L for TDP-TMP-thiamine. The lower limit of quantification was 15.625-3.125-1.563 nmol/L. The intra-day and inter-day precisions and accuracy for all QCs samples were ≤15.9% and ≤11.1%, respectively. The matrix effect was not significant. Recoveries were 103.7% for TDP, 102.7% for TMP, and 105.3% for thiamine. All QCs were stable for three freeze-thaw cycles, or at room temperature for 3 h, or at -80 °C for 15 days. We compared this new method with an established HPLC method based on derivatization of thiamine metabolites. It is found that this method correlated well with HPLC method for TDP determination (R² = 0.93). However, the correlation was not ideal for TMP (R² = 0.40) or thiamine (R² = 0.72) determination. Subject's diet was shown to have no significant effect on the concentrations of thiamine metabolites in their blood samples. To conclude, we developed a single-step, non-derivatization HPLC-MS/MS method that can detect thiamine and its phosphate esters in human whole blood accurately and quickly.

Stabilization of the hypoxia-inducible transcription Factor-1 alpha (HIF-1α) in thiamine deficiency is mediated by pyruvate accumulation

Vitamin B1, or thiamine is a critical enzyme cofactor required for metabolic function and energy production. Thiamine deficiency (TD) is common in various diseases, and results in severe neurological complications due to diminished mitochondrial function, oxidative stress, excitotoxicity and inflammation. These pathological sequelae result in apoptotic cell death in both neurons and astrocytes in distinct regions, in particular the thalamus and mammillary bodies. Comparable histological injuries in patients with hypoxia/ischemia (H/I) have also been described, suggesting a congruency between the cellular responses to these stresses. Analogous to H/I, TD stabilizes and activates Hypoxia Inducible Factor-1α (HIF-1α) even without changes in physiological oxygen levels. However, the mechanism of HIF-1α stabilization in TD is currently unknown. Using a pyruvate assay, we have demonstrated that TD induces pyruvate accumulation in mouse primary astrocytes which correlates to an increase in HIF-1α expression. Additionally, we utilized an enzymatic assay for pyruvate dehydrogenase to demonstrate a reduction in catalytic activity during TD due to lack of available thiamine pyrophosphate cofactor, resulting in the observed pyruvate accumulation. Finally, a pyruvate kinase inhibitor which limited pyruvate accumulation was utilized to demonstrate the role of pyruvate accumulation in HIF-1α stabilization during TD. These results reveal that stabilization of HIF-1α protein in TD centralizes on pyruvate accumulation in mouse primary astrocytes due to metabolic disruption of PDH.

Biomarkers for In Vivo Assessment of Transporter Function

Drug-drug interactions are a major concern not only during clinical practice, but also in drug development. Due to limitations of in vitro-in vivo predictions of transporter-mediated drug-drug interactions, multiple clinical Phase I drug-drug interaction studies may become necessary for a new molecular entity to assess potential drug interaction liabilities. This is a resource-intensive process and exposes study participants, who frequently are healthy volunteers without benefit from study treatment, to the potential risks of a new drug in development. Therefore, there is currently a major interest in new approaches for better prediction of transporter-mediated drug-drug interactions. In particular, researchers in the field attempt to identify endogenous compounds as biomarkers for transporter function, such as hexadecanedioate, tetradecanedioate, coproporphyrins I and III, or glycochenodeoxycholate sulfate for hepatic uptake via organic anion transporting polypeptide 1B or N1-methylnicotinamide for multidrug and toxin extrusion protein-mediated renal secretion. We summarize in this review the currently proposed biomarkers and potential limitations of the substances identified to date. Moreover, we suggest criteria based on current experiences, which may be used to assess the suitability of a biomarker for transporter function. Finally, further alternatives and supplemental approaches to classic drug-drug interaction studies are discussed.

Dietary B Vitamin Intake Is Associated with Lower Urinary Monomethyl Arsenic and Oxidative Stress Marker 15-F2t-Isoprostane among New Hampshire Adults

Background: Arsenic exposure has been associated with an increased risk of cardiovascular disease (CVD). Growing evidence suggests that B vitamins facilitate arsenic metabolism and may protect against arsenic toxicity. However, to our knowledge, few studies have evaluated this in US populations.Objective: Our objective was to examine whether higher B vitamin intake is associated with enhanced arsenic metabolism and lower concentrations of preclinical markers of CVD among New Hampshire adults.Methods: We used weighted quantile sum (WQS) regression to evaluate the collective impact of 6 dietary B vitamins (thiamin, riboflavin, folate, niacin, and vitamins B-6 and B-12) on 1) the proportion of arsenic metabolites in urine and 2) 6 CVD-related markers [including urinary 15-F_2t-isoprostane (15-F_2t-IsoP)] among 418 participants (26-75 y of age) from the New Hampshire Health Study. Contributions of arsenic metabolites to B vitamin-CVD marker associations were also explored in structural equation models.Results: In WQS models, the weighted sum of B vitamin intakes from food sources was inversely associated with the proportion of monomethyl arsenic species in urine (uMMA) (β: -1.03; 95% CI: -1.91, -0.15; P = 0.02). Thiamin and vitamins B-6 and B-12 contributed the most to this association, whereas riboflavin had a negligible effect. Higher overall B vitamin intake was also inversely associated with 15-F_2t-IsoP (β: -0.21; 95% CI: -0.32, -0.11; P < 0.01), with equal contributions from the 6 B vitamins, which was partially explained by differences in the proportion of uMMA (indirect effect β: -0.01; 95% CI: -0.04, -0.00).Conclusions: Among New Hampshire adults, higher intakes of certain B vitamins (particularly thiamin and vitamins B-6 and B-12 from food sources) may reduce the proportion of uMMA, an intermediate of arsenic metabolism that has been associated with an increased risk of CVD. Higher overall B vitamin intake may also reduce urinary 15-F_2t-IsoP, a marker of oxidative stress and potential risk factor for CVD, in part by reducing the proportion of uMMA.

Vitamin supplements in type 2 diabetes mellitus management: A review

Type 2 diabetes mellitus (T2DM) is a major public health challenge that affects countries across the world. The use of pharmacological therapy is often limited in some patients due to a loss of effect over time or development of adverse effects such as weight gain or hypoglycaemia. This has prompted searches into the role of non-pharmacological therapies in T2DM. The availability and use of vitamin supplements in developed countries have increased significantly and there is evidence that certain vitamins may have roles in the management of T2DM. This review examines the literature assessing the use of vitamins A, C, E, D, K and the B group vitamins (B1, B3, B7, B6, B9, B12) in the management of T2DM. No clear evidence supporting the beneficial role of any specific vitamin in the treatment of T2DM was found. Thus, it is recommended that until further studies are conducted to clarify the role of such vitamins in T2DM management, they should not be routinely recommended in clinical practice.

Thiamine Assays-Advances, Challenges, and Caveats

Thiamine (vitamin B1) is essential to the health of all living organisms and deficiency has long been associated with diseases in animals such as fish, birds, alligators, and domesticated ruminant mammals. Thiamine is also implicated in several human diseases including Alzheimer's, diabetes, dementia, depression and, most notably, Wernicke-Korsakoff syndrome and Beriberi disease. Yet, highly sensitive and specific detection of thiamine remains an analytical challenge, as pM to nm levels of thiamine need to be detected in environmental and human samples, respectively, various phosphorylated variants need to be discriminated, and rapid on-site detection would be highly desirable. Furthermore, appropriate sample preparation is mandatory, owing to the complexity of the relevant sample matrices including fish tissues, ocean water, and body fluids. This Review has two objectives. First, it provides a thorough overview of analytical techniques published for thiamine detection over the last 15 years. Second, it describes the principles of analytical approaches that are based on biorecognition and may open up new avenues for rapid and high-throughput thiamine analysis. Most notably, periplasmic binding proteins, ribozymes, and aptamers are of particular interest, as they function as bioaffinity recognition elements that can fill an important assay technology gap, owing to the unavailability of thiamine-specific commercial antibodies. Finally, the authors provide brief evaluations of key outcomes of the major assay concepts and suggest how innovative techniques could help develop sensitive and specific thiamine analytical test systems.

Computational Drug Repositioning Using Continuous Self-Controlled Case Series

Computational Drug Repositioning (CDR) is the task of discovering potential new indications for existing drugs by mining large-scale heterogeneous drug-related data sources. Leveraging the patient-level temporal ordering information between numeric physiological measurements and various drug prescriptions provided in Electronic Health Records (EHRs), we propose a Continuous Self-controlled Case Series (CSCCS) model for CDR. As an initial evaluation, we look for drugs that can control Fasting Blood Glucose (FBG) level in our experiments. Applying CSCCS to the Marshfield Clinic EHR, well-known drugs that are indicated for controlling blood glucose level are rediscovered. Furthermore, some drugs with recent literature support for the potential effect of blood glucose level control are also identified.

Comparison of endpoints relevant to toxicity assessments in 3 generations of CD-1 mice fed irradiated natural and purified ingredient diets with varying soy protein and isoflavone contents

Diet is an important variable in toxicology. There are mixed reports on the impact of soy components on energy utilization, fat deposition, and reproductive parameters. Three generations of CD-1 mice were fed irradiated natural ingredient diets with varying levels of soy (NIH-41, 5K96, or 5008/5001), purified irradiated AIN-93 diet, or the AIN-93 formulation modified with ethanol-washed soy protein concentrate (SPC) or SPC with isoflavones (SPC-IF). NIH-41 was the control for pairwise comparisons. Minimal differences were observed among natural ingredient diet groups. F0 males fed AIN-93, SPC, and SPC-IF diets had elevated glucose levels and lower insulin levels compared with the NIH-41 group. In both sexes of the F1 and F2 generations, the SPC and SPC-IF groups had lower body weight gains than the NIH-41 controls and the AIN-93 group had an increased percent body fat at postnatal day 21. AIN-93 F1 pups had higher baseline glucose than NIH-41 controls, but diet did not significantly affect breeding performance or responses to glucose or uterotrophic challenges. Reduced testes weight and sperm in the AIN-93 group may be related to low thiamine levels. Our observations underline the importance of careful selection, manufacturing procedures, and nutritional characterization of diets used in toxicological studies.

Inhibition of α-glucosidase by vitamin D3 and the effect of vitamins B1 and B2

Vitamin D₃ occupies the active site of α-glucosidase to avoid the entry of the substrate and causes the inhibition of α-glucosidase.

Immunocapture and microplate-based activity and quantity measurement of pyruvate dehydrogenase in human peripheral blood mononuclear cells

BACKGROUND

Pyruvate dehydrogenase (PDH) activity is altered in many human disorders. Current methods require tissue samples and yield inconsistent results. We describe a modified method for measuring PDH activity from isolated human peripheral blood mononuclear cells (PBMCs). RESULTS/METHODOLOGY: We found that PDH activity and quantity can be successfully measured in human PBMCs. Freeze-thaw cycles cannot efficiently disrupt the mitochondrial membrane. Processing time of up to 20 h does not affect PDH activity with proteinase inhibitor addition and a detergent concentration of 3.3% showed maximum yield. Sample protein concentration is correlated to PDH activity and quantity in human PBMCs from healthy subjects.

CONCLUSION

Measuring PDH activity from PBMCs is a novel, easy and less invasive way to further understand the role of PDH in human disease.

Evidence for altered thiamine metabolism in diabetes: Is there a potential to oppose gluco- and lipotoxicity by rational supplementation?

Growing prevalence of diabetes (type 2 as well as type 1) and its related morbidity due to vascular complications creates a large burden on medical care worldwide. Understanding the molecular pathogenesis of chronic micro-, macro- and avascular complications mediated by hyperglycemia is of crucial importance since novel therapeutic targets can be identified and tested. Thiamine (vitamin B1) is an essential cofactor of several enzymes involved in carbohydrate metabolism and published data suggest that thiamine metabolism in diabetes is deficient. This review aims to point out the physiological role of thiamine in metabolism of glucose and amino acids, to present overview of thiamine metabolism and to describe the consequences of thiamine deficiency (either clinically manifest or latent). Furthermore, we want to explain why thiamine demands are increased in diabetes and to summarise data indicating thiamine mishandling in diabetics (by review of the studies mapping the prevalence and the degree of thiamine deficiency in diabetics). Finally, we would like to summarise the evidence for the beneficial effect of thiamine supplementation in progression of hyperglycemia-related pathology and, therefore, to justify its importance in determining the harmful impact of hyperglycemia in diabetes. Based on the data presented it could be concluded that although experimental studies mostly resulted in beneficial effects, clinical studies of appropriate size and duration focusing on the effect of thiamine supplementation/therapy on hard endpoints are missing at present. Moreover, it is not currently clear which mechanisms contribute to the deficient action of thiamine in diabetes most. Experimental studies on the molecular mechanisms of thiamine deficiency in diabetes are critically needed before clear answer to diabetes community could be given.

Micronutrient status in type 2 diabetes: a review

Type 2 diabetes is characterized by significant losses of important micronutrients due to metabolic basis of the disease and its complications. Evidence of changes in trace mineral and vitamin metabolism as a consequence of type 2 diabetes is reviewed in this chapter. This review is not a meta-analysis but an overview of the micronutrient status, metabolic needs, and potential micronutrient requirements in type 2 diabetics. This chapter will not concentrate on vitamin D and type 2 diabetes as this is a topic that has been extensively reviewed before. The less well-known micronutrients notably zinc, magnesium, chromium, copper, manganese, iron, selenium, vanadium, B-group vitamins, and certain antioxidants are assessed. While some evidence is available to demonstrate the positive influence of micronutrient supplementation on glycemic control, much remains to be investigated. Additional research is necessary to characterize better biomarkers of micronutrient status and requirements in type 2 diabetics. The optimal level of micronutrient supplementation to achieve glucose homeostasis in type 2 diabetics remains a challenge.

Thiamine and its phosphate esters in relation to cardiometabolic risk factors in Saudi Arabs

Background

Thiamine deficiency has suggested to be linked to several insulin-resistance complications. In this study, we aim to associate circulating thiamine levels among cardiometabolic parameters in an Arab cohort using a simple, sensitive, rapid and selective high-performance liquid chromatography (HPLC) method that has recently been developed.

Methods

A total of 236 randomly selected, consenting Saudi adult participants (166 males and 70 females) were recruited and screened for the presence of the metabolic syndrome (MetS) using the modified National Cholesterol Education Program–Adult Treatment Panel III definition. Blood thiamine and its derivatives were quantified using HPLC.

Results

A total of 140 participants (53.9%) had MetS. The levels of thiamine and its derivatives of those with MetS were not significantly different from those without. However, hypertensive subjects had significantly higher urinary thiamine (P = 0.03) as well as significantly lower levels of thiamine diphosphate (TDP) (P = 0.01) and total thiamine (P = 0.02) than the normotensive subjects, even after adjusting for age and body mass index (BMI). Furthermore, age- and BMI-matched participants with elevated blood glucose levels had significantly lower levels of thiamine monophosphate (P = 0.020), TDP (P < 0.001) and total thiamine (P < 0.001) and significantly elevated levels of urinary thiamine (P = 0.005) compared to normoglycemic participants.

Conclusions

Low thiamine levels are associated with elevated blood glucose and hypertension in Saudi adults. Determination of thiamine status may be considered and corrected among patients with, or at high risk for, MetS, but the question whether thiamine deficiency correction translates to improved cardiometabolic status needs further longitudinal investigation.

The relationship between lactate and thiamine levels in patients with diabetic ketoacidosis

PURPOSE

Thiamine functions as an important cofactor in aerobic metabolism and thiamine deficiency can contribute to lactic acidosis. Although increased rates of thiamine deficiency have been described in diabetic outpatients, this phenomenon has not been studied in relation to diabetic ketoacidosis (DKA). In the present study, we hypothesize that thiamine deficiency is associated with elevated lactate in patients with DKA.

MATERIALS AND METHODS

This was a prospective observational study of patients presenting to a tertiary care center with DKA. Patient demographics, laboratory results, and outcomes were recorded. A one-time blood draw was performed and analyzed for plasma thiamine levels.

RESULTS

Thirty-two patients were enrolled. Eight patients (25%) were thiamine deficient, with levels lower than 9 nmol/L. A negative correlation between lactic acid and plasma thiamine levels was found (r = -0.56, P = .002). This relationship remained significant after adjustment for APACHE II scores (P = .009). Thiamine levels were directly related to admission serum bicarbonate (r = 0.44, P = .019), and patients with thiamine deficiency maintained lower bicarbonate levels over the first 24 hours (slopes parallel with a difference of 4.083, P = .002).

CONCLUSIONS

Patients with DKA had a high prevalence of thiamine deficiency. Thiamine levels were inversely related to lactate levels among patients with DKA. A study of thiamine supplementation in DKA is warranted.

Dietary nutrient intake and metabolic syndrome risk in Chinese adults: a case-control study

Background

Because human diets are composed of a wide variety of nutrients that may work synergistically to prevent or promote disease, assessing dietary nutrient intake status may be informative. The purpose of this study was to assess the dietary nutrient intake status of Chinese adults with metabolic syndrome (MetS) and to evaluate its possible role in MetS.

Methods

This case–control study was conducted from March 2010 to January 2011. A total of 123 patients with MetS and 135 controls participated in this study at the Health Examination Center of Heping District in Tianjin, China. Dietary intake was estimated by 24-h dietary recalls. We used principal component factor analysis to derive nutrient groups from 17 major nutrients. We examined the odds ratios and 95% confidence intervals using logistic regression models to test the relationship between tertiles of dietary nutrient pattern and MetS.

Results

There were 4 major dietary nutrient patterns in this study: “vitamin B group”, “protein and lipids”, “vitamin E and minerals”, and “antioxidant vitamins”. After adjustment for potential confounders, the highest tertile of the nutrient pattern factor score for the “vitamin B group” (odds ratio: 0.16; 95% confidence interval: 0.05–0.47) was negatively associated with MetS compared with the lowest tertiles. No relationships were found between other dietary nutrient patterns and MetS.

Conclusions

The “vitamin B group” pattern was inversely associated with MetS in Chinese adults. This finding supports the hypothesis that the “vitamin B group” pattern may have a potentially beneficial effect on the prevention of MetS.

Regulation of Phosphatidylethanolamine Homeostasis&#8212;The Critical Role of CTP:Phosphoethanolamine Cytidylyltransferase (Pcyt2)

Phosphatidylethanolamine (PE) is the most abundant lipid on the protoplasmatic leaflet of cellular membranes. It has a pivotal role in cellular processes such as membrane fusion, cell cycle regulation, autophagy, and apoptosis. CTP:phosphoethanolamine cytidylyltransferase (Pcyt2) is the main regulatory enzyme in de novo biosynthesis of PE from ethanolamine and diacylglycerol by the CDP-ethanolamine Kennedy pathway. The following is a summary of the current state of knowledge on Pcyt2 and how splicing and isoform specific differences could lead to variations in functional properties in this family of enzymes. Results from the most recent studies on Pcyt2 transcriptional regulation, promoter function, autophagy, and cell growth regulation are highlighted. Recent data obtained from Pcyt2 knockout mouse models is also presented, demonstrating the essentiality of this gene in embryonic development as well as the major physiological consequences of deletion of one Pcyt2 allele. Those include development of symptoms of the metabolic syndrome such as elevated lipogenesis and lipoprotein secretion, hypertriglyceridemia, liver steatosis, obesity, and insulin resistance. The objective of this review is to elucidate the nature of Pcyt2 regulation by linking its catalytic function with the regulation of lipid and energy homeostasis.

Glucose-induced down regulation of thiamine transporters in the kidney proximal tubular epithelium produces thiamine insufficiency in diabetes

Increased renal clearance of thiamine (vitamin B(1)) occurs in experimental and clinical diabetes producing thiamine insufficiency mediated by impaired tubular re-uptake and linked to the development of diabetic nephropathy. We studied the mechanism of impaired renal re-uptake of thiamine in diabetes. Expression of thiamine transporter proteins THTR-1 and THTR-2 in normal human kidney sections examined by immunohistochemistry showed intense polarised staining of the apical, luminal membranes in proximal tubules for THTR-1 and THTR-2 of the cortex and uniform, diffuse staining throughout cells of the collecting duct for THTR-1 and THTR-2 of the medulla. Human primary proximal tubule epithelial cells were incubated with low and high glucose concentration, 5 and 26 mmol/l, respectively. In high glucose concentration there was decreased expression of THTR-1 and THTR-2 (transporter mRNA: -76% and -53% respectively, p<0.001; transporter protein -77% and -83% respectively, p<0.05), concomitant with decreased expression of transcription factor specificity protein-1. High glucose concentration also produced a 37% decrease in apical to basolateral transport of thiamine transport across cell monolayers. Intensification of glycemic control corrected increased fractional excretion of thiamine in experimental diabetes. We conclude that glucose-induced decreased expression of thiamine transporters in the tubular epithelium may mediate renal mishandling of thiamine in diabetes. This is a novel mechanism of thiamine insufficiency linked to diabetic nephropathy.

Effects of combined dietary chromium(III) propionate complex and thiamine supplementation on insulin sensitivity, blood biochemical indices, and mineral levels in high-fructose-fed rats

Insulin resistance is the first step in glucose intolerance and the development of type 2 diabetes mellitus, thus effective prevention strategies should also include dietary interventions to enhance insulin sensitivity. Nutrients, such as microelement chromium(III) and thiamine, play regulatory roles in carbohydrate metabolism. The objective of this study was to evaluate the insulin-sensitizing potential of the combined supplementary chromium(III) propionate complex (CrProp) and thiamine in insulin resistance animal model (rats fed a high-fructose diet). The experiment was carried out on 40 nine-week-old male Wistar rats divided into five groups (eight animals each). Animals were fed ad libitum: the control diet (AIN-93 M) and high-fructose diets with and without a combination of two levels of CrProp (0.1 and 1 mg Cr/kg body mass/day) and two levels of thiamine (0.5 and 10 mg/kg body mass/day) for 8 weeks. At the end of the experiment rats were sacrificed to collect blood and internal organs for analyses of blood biochemical and hematologic indices as well as tissular microelement levels that were measured using appropriate methods. It was found that both supplementary CrProp and thiamine (given alone) have significant insulin-sensitizing and moderate blood-lipid-lowering properties, while the combined supplementation with these agents does not give synergistic effects in insulin-resistant rats. CrProp given separately increased kidney Cu and Cr levels, while thiamine alone increased hepatic Cu contents and decreased renal Zn and Cu contents.

The malnutrition of obesity: micronutrient deficiencies that promote diabetes

Obesity and diabetes are increasing in prevalence worldwide. Despite excessive dietary consumption, obese individuals have high rates of micronutrient deficiencies. Deficiencies of specific vitamins and minerals that play important roles in glucose metabolism and insulin signaling pathways may contribute to the development of diabetes in the obese population. This paper reviews the current evidence supporting this hypothesis.