Bioavailability and daily requirement of vitamin B12 in adult humans: an observational study of its colonic absorption and daily excretion as measured by [13C]-cyanocobalamin kinetics

BACKGROUND

Clinical and biochemical vitamin B12 (B12) deficiency is lower than anticipated in vegetarians. Extraileal absorption, such as from the colon, as well as reduced daily excretion, may be adaptive mechanisms to maintain B12 homeostasis with marginal intakes.

OBJECTIVE

To measure the absorption of B12 from the small and large intestine, and its daily rate of excretion from the body, using a [13C]-cyanocobalamin tracer.

METHODS

Oral B12 bioavailability was measured over 12 h after administration of [13C]-cyanocobalamin tracer (2.5 μg) in normal participants. The colonic B12 bioavailability was evaluated by direct instillation of [13C]-cyanocobalamin (5 μg) into the ascending colon. Bioavailability was calculated from 2-compartmental modeling of the tracer appearance in plasma. The excretion rate of B12 was measured from [13C]-cyanocobalamin elimination from the body over 4 wk after oral dosing (5 μg).

RESULTS

The oral B12 bioavailability (n = 11) was 63% ± 10% measured over 12 h. A late absorption peak, accounting for 12% of the absorption, was observed after an average lag time of 8.7 h from dosing. The colonic B12 bioavailability (n = 10) was 7% ± 5% over 4 h. The daily B12 excretion rate (n = 4) was 0.7 ± 0.2 μg/d. The minimum daily requirement of B12 in these participants was derived at 1 μg /d.

CONCLUSIONS

B12 is absorbed in the human colon. This observation confirms the potential contribution of the colon in daily B12 nutriture, and along with a possible lower requirement, could explain the absence of clinical deficiency in populations with marginal B12 intakes.

TRIAL REGISTRATION NUMBER

This study was registered in Clinical Trials Registry of India (CTRI) with the registration number CTRI/2018/04/012957, available from https://ctri.nic.in/Clinicaltrials/showallp.php?mid1=49319&EncHid=&userName=029108.

The Thin But Fat Phenotype is Uncommon at Birth in Indian Babies

BACKGROUND

Indian babies are hypothesized to be born thin but fat. This has not been confirmed with precise measurements at birth. If it is true, it could track into later life and confer risk of noncommunicable diseases (NCDs).

OBJECTIVES

Primarily, to accurately measure percentage of body fat (%BF) and body cell mass (BCM) in Indian babies with normal birth weight, compare them across different gestational ages and sex, and test the hypothesis of the thin but fat phenotype in Indian babies. Secondarily, to examine the relation between body weight and body fat in Indian babies.

METHODS

Term newborns (n = 156) weighing ≥2500 g, from middle socioeconomic status mothers were recruited in Bengaluru, India, and their anthropometry, %BF (air displacement plethysmography), and BCM (whole-body potassium counter) were measured. Maternal demography and anthropometry were recorded. The mean %BF and its dispersion were compared with earlier studies. The relation between newborn %BF and body weight was explored by regression analysis.

RESULTS

Mean birth weight was 3.0 ± 0.3 kg, with mean %BF 9.8 ± 3.5%, which was comparable to pooled estimates of %BF from published studies (9.8%; 95% CI: 9.7, 10.0; P > 0.05). Appropriate-for-gestational age (AGA) babies had higher %BF (1.8%) compared to small-for-gestational age (SGA) babies (P < 0.01). Mean %BCM of all babies at birth was 35.4 ± 10.5%; AGA babies had higher %BCM compared to SGA babies (7.0%, P < 0.05). Girls in comparison to boys had significantly higher %BF and lower %BCM. Body weight was positively associated with %BF.

CONCLUSION

Indian babies with normal birth weight did not demonstrate the thin but fat phenotype. Body weight and fat had positive correlation, such that SGA babies did not show a preservation of their %BF. These findings will have relevance in planning optimal interventions during early childhood to prevent NCDs risk in adult life.

Estimation of protein requirements in Indian pregnant women using a whole-body potassium counter

BACKGROUND

The 2007 World Health Organization/Food and Agriculture Organization/United Nations University (WHO/FAO/UNU) recommendation for the Estimated Average Requirement (EAR) of additional protein during pregnancy for a gestational weight gain (GWG) of 12 kg (recalculated from a GWG of 13.8 kg) is 6.7 and 21.7 g/d in the second and the third trimester, respectively. This EAR is based on measurements of potassium accretion in high-income country (HIC) pregnant women. It is not known if low- to middle-income country, but well-nourished, pregnant women have comparable requirements.

OBJECTIVE

We aimed to estimate total body potassium (TBK) accretion during pregnancy in Indian pregnant women, using a whole-body potassium counter (WBKC), to measure their additional protein EAR.

METHODS

Well-nourished pregnant women (20-40 y, n = 38, middle socioeconomic stratum) were recruited in the first trimester of pregnancy. Anthropometric, dietary, and physical activity measurements, and measurements of TBK using a WBKC, were performed at each trimester and at birth.

RESULTS

The mid-trimester weight gain was 2.7 kg and 8.0 kg in the second and the third trimester, respectively, for an average 37-wk GWG of 10.7 kg and a mean birth weight of 3.0 kg. Protein accretion was 2.7 and 5.7 g/d, for an EAR of 8.2 and 18.9 g/d in the second and the third trimester, respectively. The additional protein EAR, calculated for a GWG of 12 kg, was 9.1 and 21.2 g/d in the second and the third trimester, respectively.

CONCLUSION

The additional protein requirements of well-nourished Indian pregnant women for a GWG of 12 kg in the second and third trimesters were similar to the recalculated 2007 WHO/FAO/UNU requirements for 12 kg.

The development of a whole-body potassium counter for the measurement of body cell mass in adult humans

BACKGROUND AND OBJECTIVES

Total body potassium (TBK), has a natural radioactive isotope, which can be measured to derive body cell mass (BCM), making it useful in clinical conditions, early growth and pregnancy. The objective was to build a whole-body potassium counter (WBKC), to accurately measure TBK in the body.

METHODS AND STUDY DESIGN

A WBKC was designed and constructed using a shadow shield. A cellular four compartment (4C) model of fat free mass (FFM), using estimates of TBK along with total body water (TBW), was compared with a molecular 4C model of the body in twenty healthy adults (10 men and 10 women). The molecular 4C model used measurements of TBW, bone mineral content (BMC), and body volume from deuterium dilution (DD), dual energy x-ray absorptiometry (DXA) and air displacement plethysmography (ADP) respectively.

RESULTS

The accuracy and precision of the WBKC were 2.8% and 1.9% with TBK phantoms. The mean estimate of FFM by the molecular 4C model was 40.4±6.8 kg, while it was 41.2±7.3 kg using the cellular 4C model.

CONCLUSIONS

A WBKC constructed from base principles, was relatively low cost, efficient, safe and noninvasive, but requires some design considerations. Its measurement of FFM compared well with the molecular 4C model. Once constructed, it offers a relatively costless, accurate and repeatable method to measure body composition in conditions with uncertain hydration status, at all life stages.

Assessment of peripheral neutrophil functions in patients with localized aggressive periodontitis in the Indian population

Background:

Localized aggressive periodontitis (LAP) patients exhibit abnormal neutrophil functions to a variety of environmental and host stimuli. The aim of the present study was to evaluate neutrophils chemotaxis, phagocytosis, microbicidal activity and superoxide generation in LAP patients of Indian origin.

Materials and Methods:

Eleven LAP patients and nine healthy subjects were included in the study. Neutrophil chemotaxis was evaluated against an alkali-soluble casein solution using Wilkinson's method. Phagocytosis and microbicidal activity assay were performed using Candida albicans as an indicator organism. Nitrobluetetrazolium (NBT) test was used to assess superoxide generation by neutrophils using E. coli endotoxin.

Results:

The chemotactic activity and phagocytic and microbicidal activity were observed to be significantly reduced (P < 0.01) in LAP neutrophils. On the contrary, superoxide generation was observed to be significantly increased (P < 0.01) in LAP neutrophils compared with healthy individuals.

Conclusion:

The results of the present study suggest that neutrophil functions, namely chemotaxis, phagocytosis and microbicidal activity, are deficient LAP patients. However, superoxide generation was significantly increased when stimulated by endotoxins, which may explain the tissue damage seen in LAP. These abnormal neutrophil functions may predispose to increased susceptibility for LAP. Further large-scale studies are required in the Indian population to ascertain the cause-and-effect relationship of defective host factors and aggressive periodontitis and to develop treatment strategies for more predictable periodontal treatment outcome.

Effect of the probiotic Lactobacilli reuteri (Prodentis) in the management of periodontal disease: a preliminary randomized clinical trial

Objectives

The aim of this study was to evaluate the effects of Lactobacilli reuteri (Prodentis) alone and in combination with scaling and root planing (SRP) in a double blind, randomized, placebo-controlled clinical trial of volunteers with chronic periodontitis.

Methods

Thirty, otherwise systemically healthy, chronic periodontitis patients (19 males and 11 females, aged between 34 and 50 years) were included. The study period was 42 days. ‘Split-mouth’ design was used for the SRP, which was performed on day 0; two quadrants (either right or left) were treated with SRP whereas the remaining two quadrants were left untreated. The participants received a toothbrush, toothpaste, and brushing instructions. L. reuteri Prodentis lozenges (1×10⁸ CFU DSM17938+1×10⁸ CFU ATCC PTA 5289) or the corresponding placebo lozenges were taken twice daily from day 21 to day 42. Statistical analysis was done for comparisons of clinical parameters (Plaque Index (PI), Gingival Index (GI), Gingival Bleeding Index (GBI), probing pocket depth (PPD), clinical attachment level (CAL)) and microbiological levels of the pathogens Aggregibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), and Prevotella intermedia (Pi). All p-values less than 0.05 were considered significant. Assessments were made on day 0 before SRP treatment, on day 21 before administration of the lozenges, and on day 42.

Results

At day 42, the PI, GI, and GBI were significantly reduced by all treatment modalities. When ranked, the amount of PI, GI and GBI reduction by the different treatments was SRP + Prodentis Prodentis SRP + placebo placebo; all differences were statistically significant. For PPD and CAL, the best result was obtained with the SRP+Prodentis treatment. PPD was reduced from 5.08±0.75 to 3.78±0.61 mm (p<0.001) and CAL from 3.93±0.93 to 2.85±0.74 mm (p<0.001). Prodentis, either alone or following SRP, reduced Aa, Pi, and Pg by 1 log₁₀ unit (p<0.01). The SRP+placebo combination did not significantly affect the levels of the pathogens.

Conclusion

The present randomized controlled trial confirms the plaque inhibition, anti-inflammatory, and antimicrobial effects of L. reuteri Prodentis. L. reuteri Prodentis probiotic can be recommended during non-surgical therapy and the maintenance phase of periodontal treatment. Considering the beneficial effects of probiotics, this therapy could serve as a useful adjunct or alternative to periodontal treatment when SRP might be contraindicated. Further studies are required in this direction.

Effect of iron on the survival of Vibrio cholerae in water

Effect of iron in the form of ferric oxide (Fe2O3) on the survival of V. cholerae O1 was studied. V. cholerae O1 survived for 8 days in plain water whereas in presence of Fe2O3 it survived up to 15 days. Presence of organic material in the water further promoted the bacterial survival by at least 4 days. There was no difference between the behaviour of El Tor and classical biotype. These results indicate that the presence of iron in water could promote the survival of V. cholerae O1 in water and may play a significant role in the epidemiology of cholera.

Copper resistance & its correlation to multiple drug resistance in Salmonella typhi isolates from south Karnataka

A study was conducted to ascertain the prevalence of copper resistant Salmonella typhi isolates in south Karnataka. Of the 186 strains studied, 26 (13.97%) were found to be copper resistant. Among the copper resistant strains 19 (73.08%) were found multi drug resistant. All copper resistant strains remained uniformly sensitive to ceftriaxone, ciprofloxacin and norfloxacin. Multiple drug resistance was exclusively associated with E1 phage types.

Antimicrobial susceptibility of Salmonella typhi to quinolones & cephalosporins

Antimicrobial sensitivity testing was carried out for 85 isolates of S. typhi by disc diffusion and microbroth dilution for estimation of minimum inhibitory concentration (MIC). The drugs used included amoxycillin, chloramphenicol, ciprofloxacin, ofloxacin, gentamicin, netilmicin, cefuroxime, ceftizoxime, cefoperazone and ceftazidime. Ninety three per cent of our isolates were resistant to amoxycillin and chloramphenicol but total susceptibility was seen to quinolones and aminoglycosides. We also found that 3 per cent of our isolates were resistant to cephalosporins and 23 per cent were in the intermediate range with an MIC of 12.5 or 25 micrograms/ml to these drugs. In spite of decreased efficacy, the strains continued to be fully susceptible to ciprofloxacin as could be seen from the extended dilutions in microbroth dilution tests. The study also revealed that there was lack of correlation between the two methods of sensitivity testing for cephalosporins. We feel that the development of resistance of S. typhi to third generation cephalosporins is a finding worth consideration for further studies.

Evaluation of laboratory techniques for diagnosis of amoebiasis

Evaluation of 82 cases of amoebiasis including 4 of liver abscess was done. Microscopy of 62 stool samples revealed trophozoites in 19 (30.6%) and cysts in 8 (12.9%). PVA preserved samples were stained by iron-hamatoxylin and trichrome. Twenty-nine samples (46.7%) were positive by culture on Endamoeba, NIH and Charcoal agar. Additional two culture positive cases were negative by direct microscopy. Three (75%) samples of liver abscess pus were culture positive. Of the sera screened for amoebic antibodies by ELISA, 13 (17.3%) were positive. Stool and blood of healthy controls and 25 gastroenteritis cases were similarly analysed. Of healthy controls one had a high ELISA titre.

Neonatal bacteremia due to high level aminoglycoside resistant (HLAR) enterococci

A study was conducted to determine the drug resistance pattern of enterococci isolated from cases of neonatal bacteremia. A total of 41 strains of enterococci were isolated of which 35 (85.4%) were Enterococcus faecalis and 6 (14.6%) were Enterococcus faecium. A total of 3 (8.6%) strains of E. faecalis and 2 (33.3%) E. faecium strains showed high level aminoglycoside resistance (HLAR). None of the enterococci tested were vancomycin resistant. Drug resistance was more common among E. faecium strains. All clinically significant isolates of enterococci should be tested for their antibiotic sensitivity pattern including HLAR, and for treatment, antibiotics are selected based on in vitro antibiotic sensitivity test results.

High level aminoglycoside resistance in enterococci isolated from hospitalized patients

Drug resistance in enterococci isolated from hospitalized patients is reported. Out of 421 strains tested, 45 (10.7%) showed high level aminoglycoside resistance (HLAR). At the species level, 8.2 per cent of Enterococcus faecalis and 33.3 per cent of E. faecium were HLAR. While all the strains of E. faecalis were sensitive to vancomycin, one strain of E. faecium was vancomycin resistant.

Effect of trace metals on synthesis of exoproteins and exotoxins by Staphylococcus aureus

Staphylococcus aureus did not grow in chemically defined medium completely free of trace metals. At low concentrations all the trace metals showed stimulating effect on growth and exoprotein production. Increasing concentrations of Ca2+ and Mg2+ were growth stimulatory whereas Co2+, Cu2+, Fe3+, Mn2+, Ni2+ and Zn2+ were inhibitory. The amount of exoprotein and haemolytic exotoxins produced in relation to final viable count increased with increasing concentrations of growth inhibitory trace metals whereas it decreased with increasing concentrations of Ca2+ and Mg2+. Trace metals did not show significant influence on amount of haemolytic exotoxins produced in relation to total exoproteins. The results indicate presence of a common regulatory mechanism for all types of exoproteins produced by S. aureus.

Immunohistochemical localization of riboflavin carrier protein in testicular cells of mammals

Using specific polyclonal antibodies against chicken riboflavin carrier protein (cRCP), immunocytochemical localization of riboflavin carrier protein was carried out in testicular sections and isolated cells of mammals. A positive reaction was observed in the developing germ cells of rat testis, especially in meiotic and post-meiotic germ cells such as pachytene spermatocytes, round spermatids and spermatozoa. In addition both the somatic cells of the testis, viz. Leydig and Sertoli cells with vital function in germ cell proliferation and differentiation, displayed a moderate to strong staining reaction. This was further confirmed using in utero X-irradiated rat testis devoid of germ cells. Different types of cells isolated from testis when subjected to immunostaining showed similar patterns of reaction as in the intact tissue. Mature spermatozoa from different mammals (rat, bull and monkey) exhibited strong staining reaction in their head regions localized mainly in acrosomal caps. It is suggested that the testicular riboflavin carrier protein has a role in cell to cell communication and may be crucial during development of germ cells especially at the meiotic and post-meiotic stages.

Effect of trace metals on production of exoprotein and beta-lactamase by Staphylococcus aureus

A minimum concentration of 0.01 mM of Mg2+ was essential for any growth of S. aureus. Of the trace metals, Mg2+ and Ca2+ were highly stimulatory for growth. All trace metals except Ni2+ in small concentrations were stimulatory for growth and exoprotein production. Amounts of exoprotein and beta-lactamase produced relative to the number of viable cells were maximum during the period of suboptimal proliferation of bacteria. Trace metals did not significantly influence the amount of beta-lactamase produced relative to exoprotein.

Effect of magnesium on the physiology of Staphylococcus aureus

The role of magnesium (Mg2+) in the metabolism of Staphylococcus aureus was studied using a chemically defined medium. At least 0.01 mM Mg2+ was required for any growth of S. aureus. Increasing concentration of Mg2+ up to 1.6mM steadily increased the bacterial growth. Glucose utilisation and acid production were also influenced by Mg2+. Excessive cobalt (Co2+) and zinc (Zn2+) were inhibitory to S. aureus growth and Mg2+ could reverse the inhibitory effect.

A modified chemically defined medium for Staphylococcus aureus

A chemically defined medium has been described which supported good growth of S. aureus. Optimal production of different exoproteins, viz. coagulase, acid phosphatase, proteinase, lipase, beta-lactamase and alpha-toxin was recorded in the medium.

New microbiological method for the detection of staphylococcal beta-lactamase

The method has been designed as such to include the induction and testing of beta-lactamase in a single procedure. This method compares favourably with the existing method.