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 0–10 d, mean TDP = 110·6 ng/ml; age 11–20 d, mean TDP = 95·4 ng/ml; age 21–103 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.

The gene thiI encodes a protein (ThiI) that plays a role in the transfer of sulfur from cysteine to both thiamin and 4-thiouridine, but the reaction catalyzed by ThiI remains undetermined. Based upon sequence alignments, ThiI shares a unique “P-loop” motif with the PPi synthetase family, four enzymes that catalyze adenylation and subsequent substitution of carbonyl oxygens. To test whether or not this motif is critical for ThiI function, the Asp in the motif was converted to Ala (D189A), and a screen for in vivo 4-thiouridine production revealed the altered enzyme to be inactive. Further scrutiny of sequence data and the crystal structures of two members of the PPi synthetase family implicated Lys321 in the proposed adenylation function of ThiI, and the critical nature of Lys321 has been demonstrated by site-directed mutagenesis and genetic screening. Our results, then, indicate that ThiI catalyzes the adenylation of a substrate at the expense of ATP, a narrowing of possible reactions that provides a strong new basis for deducing the early steps in the transfer of sulfur from cysteine to both thiamin and 4-thiouridine.

The effects of acidogenic conditions, a high S level and the addition of thiamin on the rumen microbial metabolism of thiamin were investigated in vitro in a semi-continuous fermenter (RUSITEC), using a factorial design. Acidogenic conditions were obtained by simultaneously increasing the starch: cellulose ratio and the amount of solid substrate fed, and by decreasing the buffering capacity of the liquid phase of the fermenter. S in the form of sulfate was supplied at two levels, one corresponding to a control amount of S (2 g/kg dietary DM), the second to an excess (5 g/ kg DM) which is sufficient to trigger cerebrocortical necrosis (CCN) when used in vivo. Acidogenic conditions decreased the pH of the fermenters, CH4 production and cellulose digestibility, increased the short-chain fatty acid production, but had no effect on thiamin production. The high S level enhanced the production of sulfide considerably, had no effect on the microbial metabolism of energy and N, and decreased thiamin production (326 ν. 266 nmol/d). The added thiamin was rapidly converted into phosphorylated compounds which largely decreased the apparent synthesis of this vitamin by the rumen microflora. The total thiamin flow was increased by added thiamin. In no case was thiaminase activity in the fermenter liquid phase significantly modified. The high level of S induced only a limited decrease of total thiamin flow. Consequently, it is unlikely that the investigated factors could be considered to be high risk factors for the thiamin-dependent CCN.

The purpose of the present experiments was to extend previous data on the strategy used by adult rats to select feed appropriately when faced with diets devoid of protein or an essential amino acid (EAA), and to compare this strategy with that used when facing vitamin (thiamin) deficiency. Rats fed on either balanced or deficient (EAA or protein) diets were offered a choice between a novel deficient and a familiar (deficient or corrected) diet and their choice was monitored. It was shown that protein- and EAA-deficient rats acquired an aversion for their corresponding familiar devoid diet, which by itself promoted a neophilia for the novel diet. This neophilia was not non-specific because protein-deficient rats facing a choice between a protein-devoid and an EAA-devoid diet did exhibit neophilia but only in the short term (less than 5h), and then switched to a preference for the familiar protein-devoid diet. These results show that, in contrast to the case of vitamin deficiency, the protein- or EAA-devoid diet-induced neophilia can be rapidly reversed if the novel feed happens to be more deleterious than the familiar, inappropriate one. This behaviour suggests the existence of sensitive mechanisms able to reveal within a short time the EAA inadequacy of the ingested feed and to adapt the choice for the most appropriate feeds more promptly than in the face of thiamin deficiency. Thus it appears that balancing EAA is more urgent than balancing thiamin.

On the basis of their respective metabolizable energy contents, supplemental marine oil was partially replaced with a maize starch/dextrin mixture in diets containing approximately 500 g crude protein per kg food thus lowering the total dietary lipid concentration from 141·6 to 100·9 g/kg. The basal diets were then supplemented with thiamin hydrochloride at 0·5, 5·0 and 10·0 mg/kg food to produce six test diets in all. After 182 days of feeding, the fish given the diets containing the higher lipid content with a thiamin supplement of 10·0 mg/kg had shown significantly better growth and food utilization (food conversion efficiency and apparent net protein utilization) than the fish presented with the remaining five diets. Thiamin supplements of 5 mg/kg or less resulted in poorer performance amongst the fish given the high lipid diets. The fish given all three of the low oil diets performed poorly by comparison with those given the high lipid, high thiamin diet and performance was comparable with that of the fish given the high lipid diets containing thiamin at 5 mg/kg or less. Proximate carcass composition in terms of moisture, protein and lipid was unaffected in response to diet. Glycogen accumulation in the liver was significantly elevated amongst the fish given the low lipid diet where the thiamin supplement was 5·0 mg/kg or more. The haematology of the fish was not significantly altered in response to diet although elevated haematocrit was associated with decreasing thiamin supplementation. It would appear that for the seabream, lipid and carbohydrate are not exchangeable on the basis of their metabolizable energy content. When given high lipid diets the thiamin requirement of the seabream is in excess of 5·0 mg/kg and increasing the thiamin supplement to 10 mg/kg in high carbohydrate diets made no impact on performance.

The relationships between thiamin intake, erythrocyte transketolase (EC 2.2.1.1) activity coefficient (ETK-AC) and total erythrocyte thiamin were investigated in a group of adolescents (13 to 14 years old; nineteen boys, thirty-five girls). Thiamin intakes were calculated from 7 d weighed records, using food composition tables, and compared with those obtained by direct analysis of duplicate diets. Average 7 d calculated thiamin intakes were significantly lower than analysed intakes for both sexes. On an individual basis, calculated intakes ranged from 30 to 143 % of corresponding analysed values. Analysed and calculated intakes were significantly correlated when expressed as mg/d; however, when expressed in terms of energy intake, the correlation was significant for males only. Thiamin intake appeared largely adequate when compared with current UK dietary recommendations (Department of Health, 1991), but the limitations of such comparisons are considered. The major food groups contributing to thiamin intake were examined and showed breakfast cereals to contribute more than 25% of dietary thiamin. A proportion of the subjects had ETK-AC values in ranges usually associated with marginal or severe thiamin deficiency. There was, however, no statistically significant relationship between erythrocyte thiamin and basal or stimulated transketolase activity, or between thiamin intake and either of the methods used to assess status. The need to re-evaluate indices of thiamin status is discussed.