Indian women of childbearing age do not metabolically conserve arginine as do American and Jamaican women

Ethnic Minority Participation in Clinical Trials from Latin America and the Caribbean: A Scoping Review

We summarize the clinical trials (CTs) main characteristics, including members of ethnic minorities from Latin America. We carried out a systematic search in six databases. We made a descriptive synthesis of CTs, summarizing the characteristics, interventions, main findings, results, and conclusions reported. 4411 studies were acquired in search strategy, leaving 24 CTs in the final selection. Of these, ten were randomized, four were non-randomized, and the remainder had other designs. Most of the studies were carried out in the population of infants and children (08), ten of the studies included only women, and two studies included men. Nine studies were conducted in Mexico, with the Mayan ethnic minority being mostly evaluated (05). In only 15 it was mentioned that their research was approved by a research ethics committee. Finally, half of the CTs reported funding from international agencies and third reported funding from government agencies. Our results show that that CTs in ethnic minorities are limited and reduced to a few native peoples of the continent.

Tryptophan oxidation in young children with environmental enteric dysfunction classified by the lactulose rhamnose ratio

BACKGROUND

In young children, associations between linear growth faltering, environmental enteric dysfunction (EED), and the plasma kynurenine (Kyn)/tryptophan (Trp) ratio (KTR) have led to the proposal that higher Trp catabolism in response to intestinal/systemic inflammation limits Trp availability for protein synthesis, resulting in impaired growth.

OBJECTIVES

We sought to estimate the Trp oxidation rate and the Trp conversion rate to Kyn in young children with and without EED.

METHODS

Children aged 18-24 mo, from urban slums, were assigned to EED (n = 19) or no-EED (n = 26) groups on the basis of a urinary lactulose/rhamnose ratio (LRR) cutoff based on mean + 2 SDs of LRR (≥0.068) in normal age- and sex-matched, high-socioeconomic status children. Plasma KTR and fecal biomarkers of EED were measured. Trp oxidation in the fed state was measured using 13C1-Trp in an oral plateau feeding protocol.

RESULTS

The median (quartile 1, quartile 3) fasted KTR was 0.089 (0.066, 0.110) in children with EED compared with 0.070 (0.050, 0.093) in children with no EED (P = 0.077). However, there was no difference in fed-state Trp oxidation [median (quartile 1, quartile 3) 3.1 (1.3, 5.8) compared with 3.9 (1.8, 6.0) µmol/kg FFM/h, respectively, P = 0.617] or Trp availability for protein synthesis [42.6 (36.5, 45.7) compared with 42.5 (37.9, 46.9) µmol/kg FFM/h, respectively, P = 0.868] between the groups. In contrast, the median (quartile 1, quartile 3) fractional synthesis rates of Kyn [12.5 (5.4, 20.0) compared with 21.3 (16.1, 24.7) %pool/h, P = 0.005] and the fraction of Ala derived from Trp [0.007 (0.005, 0.015) compared with 0.012 (0.008, 0.018), P = 0.037], respectively, in the plasma compartment were significantly slower in the EED group. Fecal biomarkers of EED did not differ between the groups.

CONCLUSIONS

The static plasma KTR value is not a good indicator of the dynamic Trp flux down its oxidative pathway. In a poor sanitary environment, children without EED actually have a faster Kyn synthesis rate, which might be beneficial, because of the cytoprotective and anti-inflammatory functions of downstream metabolites. This study was registered in the Clinical Trials Registry of India as CTRI/2017/02/007921.

Perspective: L-arginine and L-citrulline Supplementation in Pregnancy: A Potential Strategy to Improve Birth Outcomes in Low-Resource Settings

The available data support the hypothesis that L-arginine or L-citrulline supplementation would be suitable for implementation in resource-constrained settings and will enhance placental vascular development and improve birth outcomes. In resource-constrained settings, the rates of adverse birth outcomes, including fetal growth restriction, preterm birth, and low birth weight, are disproportionately high. Complications resulting from preterm birth are now the leading cause of mortality in children <5 y of age worldwide. Despite the global health burden of adverse birth outcomes, few effective interventions are currently available and new strategies are urgently needed, especially for low-resource settings. L-arginine is a nutritionally essential amino acid in pregnancy and an immediate precursor of nitric oxide. During pregnancy, placental and embryonic growth increases the demand for L-arginine, which can exceed endogenous synthesis of L-arginine from L-citrulline, necessitating increased dietary intake. In many low-resource settings, dietary intake of L-arginine in pregnancy is inadequate owing to widespread protein malnutrition and depletion of endogenous L-arginine due to maternal infections, in particular malaria. Here we examine the role of the L-arginine-nitric oxide biosynthetic pathway in pregnancy including placental vascular development and fetal growth. We review the evidence for the relations between altered L-arginine bioavailability and pregnancy outcomes, and strategies for arginine supplementation in pregnancy. Existing studies of L-arginine supplementation in pregnancy in high-resource settings have shown improved maternal and fetal hemodynamics, prevention of pre-eclampsia, and improved birth outcomes including higher birth weight and longer gestation. Arginine supplementation studies now need to be extended to pregnant women in low-resource settings, especially those at risk of malaria.

Geography, Ethnicity or Subsistence-Specific Variations in Human Microbiome Composition and Diversity

One of the fundamental issues in the microbiome research is characterization of the healthy human microbiota. Recent studies have elucidated substantial divergences in the microbiome structure between healthy individuals from different race and ethnicity. This review provides a comprehensive account of such geography, ethnicity or life-style-specific variations in healthy microbiome at five major body habitats—Gut, Oral-cavity, Respiratory Tract, Skin, and Urogenital Tract (UGT). The review focuses on the general trend in the human microbiome evolution—a gradual transition in the gross compositional structure along with a continual decrease in diversity of the microbiome, especially of the gut microbiome, as the human populations passed through three stages of subsistence like foraging, rural farming and industrialized urban western life. In general, gut microbiome of the hunter-gatherer populations is highly abundant with Prevotella, Proteobacteria, Spirochaetes, Clostridiales, Ruminobacter etc., while those of the urban communities are often enriched in Bacteroides, Bifidobacterium, and Firmicutes. The oral and skin microbiome are the next most diverse among different populations, while respiratory tract and UGT microbiome show lesser variations. Higher microbiome diversity is observed for oral-cavity in hunter-gatherer group with higher prevalence of Haemophilus than agricultural group. In case of skin microbiome, rural and urban Chinese populations show variation in abundance of Trabulsiella and Propionibacterium. On the basis of published data, we have characterized the core microbiota—the set of genera commonly found in all populations, irrespective of their geographic locations, ethnicity or mode of subsistence. We have also identified the major factors responsible for geography-based alterations in microbiota; though it is not yet clear which factor plays a dominant role in shaping the microbiome—nature or nurture, host genetics or his environment. Some of the geographical/racial variations in microbiome structure have been attributed to differences in host genetics and innate/adaptive immunity, while in many other cases, cultural/behavioral features like diet, hygiene, parasitic load, environmental exposure etc. overshadow genetics. The ethnicity or population-specific variations in human microbiome composition, as reviewed in this report, question the universality of the microbiome-based therapeutic strategies and recommend for geographically tailored community-scale approaches to microbiome engineering.

The Microbiome, Intestinal Function, and Arginine Metabolism of Healthy Indian Women Are Different from Those of American and Jamaican Women

BACKGROUND

Indian women have slower arginine flux during pregnancy compared with American and Jamaican women. Arginine is a semi-essential amino acid that becomes essential during periods of rapid lean tissue deposition. It is synthesized only from citrulline, a nondietary amino acid produced mainly in the gut. The gut is therefore a key site of arginine and citrulline metabolism, and gut microbiota may affect their metabolism.

OBJECTIVE

The objective of this study was to identify differences in the gut microbiota of nonpregnant American, Indian, and Jamaican women and characterize the relations between the gut microbiota, gut function, and citrulline and arginine metabolism.

METHODS

Thirty healthy American, Indian, and Jamaican women (n = 10/group), aged 28.3 ± 0.8 y, were infused intravenously with [guanidino-15N2]arginine, [5,5-2H2]citrulline, and [15N2]ornithine and given oral [U-13C6]arginine in the fasting and postprandial states. Fecal bacterial communities were characterized by 16S rRNA gene sequencing.

RESULTS

In the fasting state, Indian women had lower citrulline flux than did American and Jamaican women [7.0 ± 0.4 compared with 9.1 ± 0.4 and 8.9 ± 0.2 μmol ⋅ kg fat-free mass (FFM)-1 ⋅ h-1, P = 0.01] and greater enteral arginine conversion to ornithine than did American women (1.4 ± 0.11 compared with 1.0 ± 0.08 μmol ⋅ kg FFM-1 ⋅ h-1, P = 0.04). They also had lower mannitol excretion than American and Jamaican women (154 ± 37.1 compared with 372 ± 51.8 and 410 ± 39.6 mg/6 h, P < 0.01). Three dominant stool community types characterized by increased abundances of the genera Prevotella, Bacteroides, and Bacteroides with Clostridium were identified. Indian women had increased mean relative abundances of Prevotella (42%) compared to American and Jamaican women (7% and < 1%, P = 0.03) which were associated with diet, impaired intestinal absorptive capacity, and arginine flux.

CONCLUSIONS

These findings suggest that dysregulated intestinal function and a unique gut microbiome may contribute to altered arginine metabolism in Indian women.