The relation between acute changes in the systemic inflammatory response and circulating thiamine and magnesium concentrations after elective knee arthroplasty.

Thiamine diphosphate (TDP) and magnesium are co-factors for key enzymes in human intermediary metabolism. However, their role in the systemic inflammatory response (SIR) is not clear. Therefore, the aim of the present study was to examine the relation between acute changes in the SIR and thiamine and magnesium dependent enzyme activity in patients undergoing elective knee arthroplasty (a standard reproducible surgical injury in apparently healthy individuals). Patients (n = 35) who underwent elective total knee arthroplasty had venous blood samples collected pre- and post-operatively for 3 days, for measurement of whole blood TDP, serum and erythrocyte magnesium, erythrocyte transketolase activity (ETKA), lactate dehydrogenase (LDH), glucose and lactate concentrations. Pre-operatively, TDP concentrations, erythrocyte magnesium concentrations, ETKA and plasma glucose were within normal limits for all patients. In contrast, 5 patients (14%) had low serum magnesium concentrations (< 0.75 mmol/L). On post-operative day1, both TDP concentrations (p < 0.001) and basal ETKA (p < 0.05) increased and serum magnesium concentrations decreased (p < 0.001). Erythrocyte magnesium concentrations correlated with serum magnesium concentrations (rs = 0.338, p < 0.05) and remained constant during SIR. Post-operatively 14 patients (40%) had low serum magnesium concentrations. On day1 serum magnesium concentrations were directly associated with LDH (p < 0.05), WCC (p < 0.05) and neutrophils (p < 0.01). Whole blood TDP and basal ETKA increased while serum magnesium concentrations decreased, indicating increased requirement for thiamine and magnesium dependent enzyme activity during SIR. Therefore, thiamine and magnesium represent potentially modifiable therapeutic targets that may modulate the host inflammatory response. Erythrocyte magnesium concentrations are likely to be reliable measures of status, whereas serum magnesium concentrations and whole blood TDP may not.ClinicalTrials.gov: NCT03554668.

The Effects of Genetic Mutations and Drugs on the Activity of the Thiamine Transporter, SLC19A2.

A rare cause of megaloblastic anemia (MA) is thiamine-responsive megaloblastic anemia (TRMA), a genetic disorder caused by mutations in SLC19A2 (encoding THTR1), a thiamine transporter. The study objectives were to (1) functionally characterize selected TRMA-associated SLC19A2 variants and (2) determine whether current prescription drugs associated with drug-induced MA (DIMA) may act via inhibition of SLC19A2. Functional characterization of selected SLC19A2 variants was performed by confocal microscopy and isotopic uptake studies of [3H]-thiamine in HEK293 cells. Sixty-three drugs associated with DIMA were screened for SLC19A2 inhibition in isotopic uptake studies. Three previously uncharacterized SLC19A2 variants identified in TRMA patients exhibited disrupted localization to the plasma membrane along with near-complete loss-of-function. Ten of 63 drugs inhibited SLC19A2-mediated thiamine transport ≥ 50% at screening concentrations; however, with the exception of erythromycin, none was predicted to inhibit SLC19A2 at clinically relevant unbound plasma concentrations. Data from electronic health records revealed reduced levels of thiamine pyrophosphate (TPP) in patients prescribed erythromycin, consistent with inhibition of SLC19A2-mediated thiamine transport. Here, we confirmed the role of three SLC19A2 variants in TRMA pathology. Additionally, we report that inhibition of SLC19A2 is a potential, but uncommon mechanism for DIMA.

Comparison of Thiamin Diphosphate High-Performance Liquid Chromatography and Erythrocyte Transketolase Assays for Evaluating Thiamin Status in Malaria Patients without Beriberi.

Thiamin deficiency, or beriberi, is an increasingly re-recognized cause of morbidity and mortality in the developing world. Thiamin status has traditionally been measured through the erythrocyte activation assay (ETKA) or basal transketolase activity (ETK), which indirectly measure thiamin diphosphate (TDP). Thiamin diphosphate can also be measured directly by high-performance liquid chromatography (HPLC), which may allow a more precise estimation of thiamin status. We compared the direct measurement of TDP by HPLC with basal ETK activity and ETKA in 230 patients with Plasmodium falciparum malaria in rural southern Laos without overt clinical beriberi, as part of a trial of thiamin supplementation. Admission thiamin status measured by basal ETK activity and ETKA (α) were compared with thiamin status assessed by the measurement of TDP by HPLC. 55% of 230 included patients were male, and the median age was 10 (range 0.5-73) years. Using α ≥ 25% as the gold standard of thiamin deficiency, the sensitivity of TDP < 275 ng/gHb as a measure of thiamin deficiency was 68.5% (95% CI: 54.4-80.5%), with specificity of 60.8 (95% CI: 53.2-68.1%). There was a significant inverse correlation between the results of the two tests (Kendall's tau = -0.212, P < 0.001). Basal ETK activity was also significantly positively correlated with TDP levels (Kendall's tau = 0.576, P < 0.001). Thiamin diphosphate measurement may have a role in measuring thiamin levels in clinical settings. Further studies evaluating TDP concentration in erythrocytes with basal ETK activity and ETKA (α) in beriberi patients would help establish comparative values of these assays.

Thiamine Deficiency in Adolescents with Eating Disorders: A Prospective Cohort Study.

BACKGROUND: Pediatric eating disorders (PED) patients are prone to nutritional deficiencies. Thiamine deficiency is well described in other malnutrition states but is not routinely screened for in PED. In the current study we evaluated the prevalence of thiamine deficiency among PED patients on their first admission to an outpatient day hospital for eating disorders (DH). METHODS: In this prospective cohort study, we measured whole blood thiamine pyrophosphate concentrations (TPP) in addition to a routine laboratory workup in 69 girls on their first admission to DH. Two subgroup analyses were performed: (I) Patients with a previous dietary intervention ("diet" group, n = 30) or naïve-to-treatment patients ("naïve" group, n = 39) and (II) Type of PED: Restrictive (group R, n = 44) or binge-eating/purging (group BP, n = 25). RESULTS: Thiamine deficiency was identified in four girls (6%), all in the "naïve" group. Three of them had BP, and one had R. Patients in the "diet" group had a significantly higher TPP compared to the "naïve" group (55.5 µg/L vs. 46.7 µg/L, p = 0.004). TPP levels returned to normal after two weeks of the treatment program in all deficient patients. CONCLUSION: Thiamine deficiency was uncommon among PED patients and was easily replenished. Screening for deficiency should be performed among treatment-naïve patients. Keynotes: Whole blood thiamine pyrophosphate concentrations (TPP) are seldom screened for among PED patients. In the current study, we detected thiamine deficiency in only 6% of patients on their first admission to an outpatient day hospital for eating disorders. All deficient patients did not have a recent dietary intervention. We recommend considering screening for thiamine deficiency in treatment-naïve PED patients.

A high performance liquid chromatography fluorescence method for the analysis of both pyridoxal-5-phosphate and thiamine pyrophosphate in whole blood.

BACKGROUND AND AIMS: The active coenzymes of the water soluble vitamins B1 and B6 (thiamine pyrophosphate (TPP) and pyridoxal-5-phosphate (P5P) respectively) play an important role in numerous bodily functions. The simultaneous analysis of both these analytes is limited to either mass spectrometry based methods or commercial kit suppliers. In this study we developed a novel method for analysis of both TPP and P5P by fluorescence detection. METHODS: Briefly, whole blood samples are precipitated by trichloroacetic acid, and P5P and TPP are both derivatised before separation on a C18-PFP column. The new assay's performance was compared against a recent cycle from an external quality assurance program (RCPAQAP) and the current only existing commercial kit (n = 76). RESULTS: Linearity for both analytes was above 0.99 (r2) up to a concentration range of: 4000 nmol/L (P5P) and 2000 nmol/L (TPP). Precision of the method (intra-day and inter-day) compared against commercial quality control material was below 6% (coefficient of variation). Recovery of both compounds exceeded 90%. Accuracy of the protocol displayed satisfactory results in proficiency testing and had an acceptable level of agreement with the existing current kit method. CONCLUSIONS: Overall, this method provides an economical alternative in routine clinical diagnostic laboratories wishing to perform P5P and TPP analysis.

High thiamine diphosphate level as a protective factor for Alzheimer's disease.

Objectives Thiamine diphosphate (TDP) is an indispensable coenzyme for three key enzymes in glucose metabolism. Reduced TDP levels in patients with Alzheimer's disease (AD) has been widely demonstrated and is a diagnostic biomarker for the disease. In this study, we further explored the correlation between altered TDP metabolism and AD along with other risk factors. Methods A 1:1 case-control study was employed with 90 AD patients and 90 control subjects with normal-range cognitive abilities as assayed by the Mini Mental Status Evaluation. Age (≤2 years variation), gender, and educational background were strictly matched. Levels of the main thiamine metabolites in whole blood samples, including TDP, thiamine monophosphate, and thiamine, were assayed using high-performance liquid chromatography. Apolipoprotein E genotypes, haemoglobin, and several metabolic factors (fasting glucose, uric acid, triglyceride, and total cholesterol) associated with AD were also measured. Results The odds ratio of TDP level for AD was 0.95 (with TDP level as a continuous variable) or 0.09 (with TDP level as a dichotomized variable with a cut-off value of 99.48 nmol/L). Blood TDP levels were significantly decreased in female AD patients compared to male AD patients. No correlations were identified between TDP levels and several metabolic factors (fasting glucose, uric acid, triglyceride, and total cholesterol). Conclusions TDP is a protective factor for AD and its protective efficacy may be independent of other metabolic factors. The difference of TDP levels between genders may be another possible explanation for the higher prevalence of AD in females.

Thiamine Diphosphate Status and Dialysis-Related Losses in End-Stage Kidney Disease Patients Treated with Hemodialysis.

AIM: (1) To describe the whole blood content of thiamine diphosphate (TDP), a biologically active form of vitamin B1 in end-stage kidney disease patients treated with hemodialysis (HD); (2) to establish the impact of a single HD procedure on TDP blood concentrations; and (3) to describe potential explanatory variables influencing TDP dialysis related losses, including dialysis prescription, vitamin B1 dietary intake and supplementation. METHODS: Single-center, cross-sectional study in 50 clinically stable maintenance HD patients. The assessment of whole blood TDP with the High Performance Liquid Chromatography method, before and after a single, middle-week dialysis session and analysis of clinical and laboratory parameters potentially influencing TDP status Results: We report a significant difference in TDP levels before and after HD sessions - 42.5 (95% CI 38.7-46.2) µg/L and 23.6 (95% CI 18.9-28.2) µg/L, respectively (p = 0.000). The magnitude of intradialytic TDP changes is highly variable among individuals and is negatively associated only with the body weight of the patients (p < 0.013). Vitamin B1 dietary intake and supplementation do not influence whole blood TDP and dialysis-related loss of TDP. CONCLUSIONS: TDP, a bioactive compound of vitamin B1, is substantially lost during the HD procedure, and the magnitude of its loss is associated with the patient's body weight but it is not influenced by vitamin B1 dietary intake and standard supplementation dose.

Dysfunctional protection against advanced glycation due to thiamine metabolism abnormalities in gestational diabetes.

While the pathogenic role of dicarbonyl stress and accelerated formation of advanced glycation end products (AGEs) to glucose intolerance and to the development of diabetic complications is well established, little is known about these processes in gestational diabetes mellitus (GDM), a condition pathogenically quite similar to type 2 diabetes. The aims of the present study were (i) to determine plasma thiamine and erythrocyte thiamine diphosphate (TDP) and transketolase (TKT) activity in pregnant women with and without GDM, (ii) to assess relationships between thiamine metabolism parameters and selected clinical, biochemical and anthropometric characteristics and, finally, (iii) to analyse relationship between variability in the genes involved in the regulation of transmembrane thiamine transport (i.e. SLC19A2 and SLC19A3) and relevant parameters of thiamine metabolism. We found significantly lower plasma BMI adjusted thiamine in women with GDM (P = 0.002, Mann-Whitney) while levels of erythrocyte TDP (an active TKT cofactor) in mid-trimester were significantly higher in GDM compared to controls (P = 0.04, Mann-Whitney). However, mid-gestational TKT activity - reflecting pentose phosphate pathway activity - did not differ between the two groups (P > 0.05, Mann-Whitney). Furthermore, we ascertained significant associations of postpartum TKT activity with SNPs SLC19A2 rs6656822 and SLC19A3 rs7567984 (P = 0.03 and P = 0.007, resp., Kruskal-Wallis). Our findings of increased thiamine delivery to the cells without concomitant increase of TKT activity in women with GDM therefore indicate possible pathogenic role of thiamine mishandling in GDM. Further studies are needed to determine its contribution to maternal and/or neonatal morbidity.

Correlation of thiamine metabolite levels with cognitive function in the non-demented elderly.

Thiamine metabolism is critical for glucose metabolism and also vital for brain function, which is susceptible to decline in the elderly. This study aimed to investigate whether thiamine metabolites correlate with cognitive function in the non-demented elderly and their impact factors. Volunteers >60 years old were recruited and their blood thiamine metabolites and Mini-Mental State Examination (MMSE) scores were measured. The apolipoprotein E (APOE) genotype, routine blood parameters, liver and kidney function, and levels of fasting blood glucose and triglycerides were also measured. The results showed that the thiamine diphosphate (TDP) level weakly correlated with MMSE score in the non-demented elderly. Participants with high TDP levels performed better in Recall and Attention and Calculation than those with low TDP. TDP levels were associated with the APOE ε2 allele, body mass index, hemoglobin level, fasting blood glucose, and triglycerides. Our results suggest that TDP, which is easily affected by many factors, impacts cognitive function in the elderly.

Poor thiamin and riboflavin status is common among women of childbearing age in rural and urban Cambodia.

BACKGROUND: Thiamin deficiency in infancy is the underlying cause of beriberi, which can be fatal without rapid treatment. Reports of thiamin deficiency are common in Cambodia; however, population representative data are unavailable. Because B-complex vitamin deficiencies commonly occur in combination, riboflavin was also investigated. OBJECTIVE: We determined the biomarker status of thiamin and riboflavin in women of childbearing age in rural and urban Cambodia. METHODS: We measured thiamin (erythrocyte thiamin diphosphate; TDP) and riboflavin (erythrocyte glutathione reductase activity coefficient; EGRac) status in a representative sample of Cambodian women (aged 20-45 y) in urban Phnom Penh (n = 146) and rural Prey Veng (n = 156), Cambodia, and, for comparison purposes, in a convenience sample of women in urban Vancouver, British Columbia, Canada (n = 49). RESULTS: Thiamin insufficiency (TDP ≤ 90 nmol/L) was common among both urban (39%) and rural (59%) Cambodian women (P < 0.001), whereas <20% of Vancouver women were thiamin insufficient (P < 0.001). The prevalence of suboptimal and deficient riboflavin status (EGRac ≥ 1.3) was 89%, 92%, and 70% among women in Phnom Penh, Prey Veng, and Vancouver, respectively (P < 0.001). CONCLUSIONS: Suboptimal status of both thiamin and riboflavin were common in Cambodian women, with substantially higher rates among women living in rural Prey Veng than in urban Phnom Penh. Strategies may be needed to improve the thiamin and riboflavin status of women in Cambodia. The unexpected finding of high riboflavin inadequacy status in Vancouver women warrants further investigation.

Small-fiber degeneration in alcohol-related peripheral neuropathy.

BACKGROUND: Alcohol-related peripheral neuropathy (ALN) is generally characterized as an axonal large-fiber polyneuropathy caused by thiamine deficiency. We hypothesized, based on clinical observations, that ALN is associated with a small-fiber polyneuropathy that can be diagnosed with skin biopsy in heavy alcohol drinking subjects with normal thiamine status. METHODS: Eighteen individuals (9 heavy alcohol drinking subjects and 9 healthy control subjects) were assessed for the potential utility of skin biopsies in detecting ALN-associated small nerve fiber degeneration. Heavy drinking was defined as greater than 4 drinks/d and 5 drinks/d in women and men, respectively, as determined by the Timeline Follow-Back and lifetime drinking history. All subjects underwent neurological examination, nerve conduction studies, and skin biopsies to quantify end nerve fiber densities (ENFD). Other causes of neuropathy were excluded and thiamine status was assessed. RESULTS: Average ENFD were significantly decreased at the calf in the alcohol group as compared with control group (p < 0.0001). Histological sections demonstrated striking attrition and architectural simplification of intraepidermal nerve fibers in the heavy alcohol drinking subjects. There were no significant intergroup differences with respect to clinical assessments of neuropathy or thiamine status. CONCLUSIONS: ALN is associated with a small-fiber neuropathy that can be detected with skin biopsy in heavy alcohol drinking individuals with normal thiamine status. Skin biopsy is a useful, minimally invasive biomarker that could extend studies to understand the effect of alcohol on the peripheral nerves and to evaluate potential therapeutic agents in larger clinical trials.

Thiamine deficiency and cardiac dysfunction in Cambodian infants.

OBJECTIVES: To compare blood thiamine concentrations, echocardiography findings, and plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels in infants with clinically diagnosed beriberi and healthy matched controls, and to evaluate changes after thiamine treatment. STUDY DESIGN: Sixty-two Cambodian infants (20 cases and 42 controls), aged 2-47 weeks, were enrolled in this prospective study. Echocardiography and phlebotomy were performed at baseline and after thiamine treatment. RESULTS: Both cases and controls were thiamine-deficient, with median blood thiamine diphosphate (TDP) concentrations of 47.6 and 55.1 nmol/L, respectively (P = .23). All subjects had normal left ventricular ejection fraction. The median NT-proBNP concentration in cases (340 pg/mL [40.1 pmol/L]) was higher than previously reported normal ranges, but not statistically significantly different from that in controls (175 pg/mL [20.7 pmol/L]) (P = .10), and was not correlated with TDP concentration (P = .13). Two cases with the lowest baseline TDP concentrations (24 and 21 nmol/L) had right ventricular enlargement and elevated NT-proBNP levels that improved dramatically by 48 hours after thiamine administration. CONCLUSION: Only a minority of thiamine-deficient Cambodian infants demonstrate abnormal echocardiography findings. Thiamine deficiency produces echocardiographic evidence of right ventricular dysfunction, but this evidence is not apparent until deficiency is severe. NT-proBNP concentrations are mildly elevated in sick infants with normal echocardiography findings, indicating possible physiological changes not yet associated with echocardiographic abnormalities.

5-Methyltetrahydrofolate and thiamine diphosphate in cord-blood erythrocytes of preterm versus term newborns.

BACKGROUND/OBJECTIVES: A low folate or low thiamine status may be associated with the risk of preterm delivery, small for gestational age (SGA) offspring and adverse pregnancy outcomes. SUBJECTS/METHODS: 5-Methyltetrahydrofolate (5MTHF) and thiamine diphosphate (TDP) were measured directly in cord-blood erythrocytes (CBEs) of early preterm (n=26; <32 weeks gestational age; including 50% multiple births), late preterm (n=38; 32 to <37 weeks; including 24% multiple births) and term newborns (n=60, 37-42 weeks) via high-performance liquid chromatography and fluorescence detection. Associations between 5MTHF and TDP with gestational age, newborn anthropometrics (birth weight, newborn's length and head circumference) and risk of being SGA were explored. RESULTS: Group comparison as well as multivariate linear regression analysis of cord-blood vitamins revealed that 5MTHF was significantly lower in late preterms compared with terms but did not differ between singletons and multiples. TDP tended to be higher in preterms than in terms and lower in multiples than in singletons in both early and late preterms. Multivariate analysis on birth outcomes showed that 5MTHF was significantly positively associated with gestational age, birth weight and newborn's length. 5MTHF, increasing gestational age and parity were associated with a significantly reduced risk for being SGA, while TDP, multiple births and gender were not associated with the risk for being SGA. CONCLUSIONS: Higher CBE concentrations of 5MTHF were associated with improved birth outcomes. Lower TDP concentrations were observed in multiple births. Future studies evaluating cord-blood vitamin concentrations and their associations with birth outcomes should additionally include dietary intakes and maternal blood concentrations at different stages of pregnancy.

Understanding the role of sulfur-thiamine interaction in the pathogenesis of sulfur-induced polioencephalomalacia in beef cattle.

This study examined the role of sulfur (S) in the pathogenesis of S-induced polioencephalomalacia (PEM) in beef cattle in the context of thiamine status and metabolism. Thiamine, thiamine monophosphate (TMP) and thiamine pyrophosphate (TPP) status in rumen fluid, blood and brain tissue were determined in beef heifers fed 2 levels of S [low S (LS) vs. high S (HS)] at 2 forage-to-concentrate ratios (F:C). High S diet did not affect ruminal and blood thiamine status. Interestingly, however, HS diet showed increased brain thiamine levels. No gross or histopathological changes indicative of PEM were detected in the brains of the heifers. Of note, during the course of the present study, we documented an outbreak of S-induced PEM in commercial feedlot steers. Brain thiamine variables in experimental animals fed HS diet were then contrasted with brain thiamine status in PEM affected feedlot steers. Interestingly, in clinically normal animals, exposure to HS diet resulted in increased levels of both TMP and TPP in the brain tissue, in comparison to animals fed LS diet. In contrast, the PEM affected brains showed overall lower levels of thiamine phosphates. It is noteworthy that TPP levels were 36.5% lower, despite 4.9-fold higher free thiamine in PEM brains compared to normal brains. Our results indicate that high dietary S may increase the metabolic demand for TPP, and that animals incapable of maintaining requisite levels of brain TPP are at high risk to develop fulminant cerebrocortical necrosis.

Thiamine pharmacokinetics in Cambodian mothers and their breastfed infants.

BACKGROUND: Thiamine deficiency is common in parts of Asia and causes beriberi. Pharmacokinetics of thiamine in deficient populations are unknown. OBJECTIVE: We characterized thiamine pharmacokinetics in Cambodian mothers and their breastfed infants. DESIGN: Total plasma thiamine, whole-blood thiamine diphosphate (TDP), and breast milk total thiamine were measured in 16 healthy Cambodian mothers and their infants before and after mothers received oral thiamine hydrochloride (100 mg for 5 d). Assays were also performed in 16 healthy American mothers. RESULTS: On day 1, Cambodian mothers were thiamine deficient, with median (range) total plasma thiamine and TDP concentrations of 2.4 nmol/L (0-4.4 nmol/L) and 58.0 nmol/L (27-98 nmol/L), respectively. After a single oral dose, the mean ± SD maximal concentration of thiamine and net area under the thiamine concentration-time curve were 73.4 ± 45.6 nmol/L and 465 ± 241 h · nmol ∙ L⁻¹. Day 6 median maternal total plasma thiamine and TDP concentrations were normal [18.6 nmol/L (13.4-25.3 nmol/L) and 76.5 nmol/L (48-107 nmol/L), respectively; P ≤ 0.001 compared with day 1]. Median Cambodian total breast milk thiamine concentration increased from 180 nmol/L (85-359 nmol/L) on day 1 to 403 nmol/L (314-415 nmol/L) on day 2 and 503 nmol/L (360-808 nmol/L) on day 6; the corresponding American breast milk value was 500 nmol/L (114-622 nmol/L). Median Cambodian infant total plasma thiamine and TDP concentrations increased from 3.0 nmol/L (0-7.3 nmol/L) and 38.5 nmol/L (23-57 nmol/L), respectively, on day 1 to 5.6 nmol/L (0-9.7 nmol/L) and 45.5 nmol/L (32-70 nmol/L), respectively, on day 6. CONCLUSIONS: Thiamine-deficient Cambodian mothers effectively absorb oral thiamine, with sharp increases in breast milk thiamine concentrations, but their breastfed infants remain thiamine deficient after 5 d of maternal supplementation. Longer-term maternal supplementation may be necessary to correct thiamine deficiency in breastfed infants. This trial was registered at clinicaltrials.gov as NCT01864057.

Plasma AGE-peptides and C-peptide in early-stage diabetic nephropathy patients on thiamine and pyridoxine therapy.

AIM: The aim of the study was to evaluate circulatory AGE-peptide levels in diabetic nephropathy and to observe the effects of thiamine (vitamin B1) and pyridoxine (vitamin B6) therapy. METHODS: Type 2 diabetic patients (N.=57) were divided into two groups as "with nephropathy" (N.=27) and "without nephropathy" (N.=30). Diabetic nephropathy patients were treated with either B6 (N.=12) (250 mg/day) or B1+B6 (N.=15) (250 mg/day, each) for five months. At the beginning and the end of the experimentation period, glucose, HbA1c, triglyceride, cholesterol, insulin, C-peptide, thiamine pyrophosphate, pyridoxal phosphate and AGE- peptides were measured. RESULTS: AGE-peptides were higher in the diabetic group with nephropathy than without nephropathy (P=0.005). Within five months AGE-peptides increased in the diabetic group without nephropathy (P=0.042) but not in the group with nephropathy treated either with B1+B6 or B6. In B6 treated group a substantial decrease was observed in HbA1c (P=0.033). B1+B6 or B6 treatment both caused an increase in C-peptide (P=0.006, P=0.004). CONCLUSION: Among the parameters measured, plasma AGE-peptides was the only parameter found to be higher in type 2 diabetes mellitus patients "with nephropathy" than "without nephropathy". However, patients with nephropathy treated with B1+B6 or B6 did not display any further increase in AGE-peptides within five months. Both of the treatments caused an increase in C-peptide.

Thiamin status of premature infants assessed by measurement of thiamin diphosphate in whole blood.

Premature infants constitute a risk group for thiamin deficiency but only little is known about their thiamin status. The aim of the present study was to investigate the thiamin status of premature infants by determination of thiamin diphosphate (TDP) and to identify risk factors for low TDP concentrations. In a prospective, longitudinal study TDP was determined by HPLC in whole blood in the first days of life and approximately every 2 weeks. Demographical data, weight gain, type of nutrition and thiamin intake were recorded. A total of 111 premature infants were included at the Children's Hospital of the University of Cologne, Germany from May 2009 until December 2010 and 222 blood samples were analysed. TDP concentrations showed an age-dependent decline (age 0­10 d, mean TDP = 110.6 ng/ml; age 11­20 d, mean TDP = 95.4 ng/ml; age 21­103 d, mean TDP = 33.6 ng/ml). There was no significant difference between males and females. Young gestational age and low birth weight were associated with low TDP concentrations. No infant was diagnosed with thiamin deficiency. The current nutritional regimen in our hospital did not lead to thiamin deficiency in the study cohort. Further research is required to evaluate how TDP concentrations are regulated in premature infants.

Thiamine nutritional status and depressive symptoms are inversely associated among older Chinese adults.

Thiamine has been hypothesized to play an important role in mental health; however, few studies have investigated the association between thiamine nutritional status and depression in the general population. Concentrations of free thiamine and its phosphate esters [thiamine monophosphate (TMP) and thiamine diphosphate (TDP)] in erythrocytes were measured by HPLC among 1587 Chinese men and women aged 50-70 y. The presence of depressive symptoms was defined as a Center for Epidemiological Studies Depression Scale score of ≥16. The median erythrocyte concentration (nmol/L) was 3.73 for free thiamine, 3.74 for TMP, and 169 for TDP. The overall prevalence of depressive symptoms was 11.3%. Lower concentrations of all 3 erythrocyte thiamine biomarkers were monotonically associated with a higher prevalence of depressive symptoms: the multivariable adjusted ORs comparing the lowest with the highest quartiles were 2.97 (95% CI = 1.87, 4.72; P-trend < 0.001) for free thiamine, 3.46 (95% CI = 1.99, 6.02; P-trend < 0.001) for TMP, and 1.98 (95% CI = 1.22, 3.21; P-trend = 0.002) for TDP. In conclusion, poorer thiamine nutritional status and higher odds of depressive symptoms were associated among older Chinese adults. This finding should be further investigated in prospective or interventional studies.

Increased thiamine intake may be required to maintain thiamine status during weight loss in patients with type 2 diabetes.

During weight loss, erythrocyte thiamine pyrophosphate (TPP) decreased (221±52 to 195±39 nmol/L, P<0.05) on a diet with adequate thiamine (1.1 mg/day) but was unchanged (217±55 vs 218±52 nmol/L, NS) on a high thiamine diet (2.8 mg/day). Attention to thiamine status may be required in patients with diabetes after weight loss.