INTRODUCTION: The gene-environment interaction of the REarranged during Transfection (RET) gene with vitamin A in the etiopathogenesis of Hirschsprung disease (HSCR) has been suggested in rodents. The aim of this study was to evaluate vitamin A status in mothers of children with HSCR and to assess its association with pathogenic variants of the RET gene in affected children. METHODS: This was a case-control study of stable isotope–based vitamin A measurement stores of mothers of children diagnosed with HSCR (within 8 months from birth, n = 7) and age-matched mothers of normal children (n = 6). Next-generation sequencing of RET exons, along with their upstream promoter region, was performed in the 7 HSCR proband-parent triads to evaluate pathogenic variants. RESULTS: Maternal vitamin A stores in the HSCR group was almost 50% that of those in controls, tending toward significance (0.50 ± 0.17 vs 0.89 ± 0.51 μmol/g respectively, P = 0.079). Two novel pathogenic de novo mutations were identified in 2 cases, and a rare single-nucleotide deletion was detected in the 3.5-kb RET upstream region, in a heterozygous state, in all 7 proband-parent triads. Low-penetrance RET haplotypes associated with HSCR were detected in 5 cases. DISCUSSION: Mothers with children with HSCR had lower vitamin A liver stores than mothers with normal children, and the children who were affected had HSCR despite having no established pathogenic RET variants. Lower maternal vitamin A status may increase the penetrance of genetic mutations in RET, and vitamin-A mediated gene-environment interactions may underpin some of the etiology of HSCR.

Background/Objectives: The bioavailability of crystalline vitamin B₁₂ (B₁₂) through active absorption is reported to have a maximum capacity of 1.5–2.5 µg per dose. A small passive bioavailability has also been suggested at high doses. The present study aimed to determine the dose-dependency of active B₁₂ absorption and to quantify its passive absorption at higher doses. Methods: The dose-dependency of crystalline B₁₂ bioavailability was determined in nine healthy adults, using oral [¹³C]-cyanocobalamin, in a cross-over design at doses of 2.5, 5, and 10 µg. The dose order was randomised, with a washout of one month. Literature data from was added to the present study data in a meta-analysis of the relation between B₁₂ bioavailability and dose, to evaluate its pattern at different doses. Results: Bioavailability, as a function of dose, was significantly different between 2.5, 5, and 10 µg doses of [¹³C]-cyanocobalamin at 50.9 ± 32.5%, 26.7 ± 22.3%, 15.4 ± 13.6%, respectively, (p < 0.01), while the absolute bioavailability trended upward, at 1.16 ± 0.74 µg, 1.22 ± 1.02 µg, and 1.39 ± 1.23 µg (p = 0.46). The meta-analysis showed two distinct phases of bioavailability. Up to a dose of 2.6 µg, there was a significant steep positive correlation, with a slope (bioavailability) of 43%/µg suggesting an active process with a maximum of 1.2 µg. At higher doses, the slope was 1%/µg, not significantly different from zero, possibly a passive process. Conclusions: The active bioavailability of crystalline B₁₂ is not dose-dependent, saturating at ~1.2 µg.

Background. Indians have a poor protein intake in terms of quantity as well as quality because of their predominantly cereal-based diet. However, there is limited information on circulatory amino acid levels in healthy Indians. Herein, we evaluated the acute effect of a protein supplement on the plasma levels of essential amino acids (EAAs) in healthy Indian adults, using targeted EAA analysis. Methods. In this double-blind, randomized, crossover study, 20 healthy Indian adults were randomized to receive the test protein supplement (treatment arm, n = 10) or placebo (control arm, n = 10) with milk, after overnight fasting. After 7 days, the participants returned for the crossover treatment. Blood samples were collected at baseline and at 60 and 120 min after protein/placebo consumption. Plasma EAA levels were estimated using liquid chromatography-tandem mass spectrometry. Repeated measures ANOVA was performed to assess the effect of treatment on EAA levels. values < 0.05 were considered statistically significant. Results. At baseline, mean plasma levels did not differ significantly between the two arms for any of the EAAs. In the treatment arm, the mean levels of all EAAs increased significantly from baseline to 60 min ( ), with no significant change from 60 to 120 min. There was no significant change in amino acid levels in the control arm. The magnitude as well as percentage of increase from baseline to 60 min was significantly greater in the treatment arm than in the control arm for all EAAs. Conclusion. Compared to placebo, protein supplement increased circulatory amino acid levels in healthy Indians. The observed increase in EAA levels and its role in conjunction with exercise in both healthy and diseased states need to be further evaluated. This is the first dataset exploring targeted EAA profiles and the effect of a protein supplement among healthy Indians. The clinical trial is registered with CTRI/2018/12/016777.