Gillian R. Bentley

Mitochondrial DNA analysis reveals diverse histories of tribal populations from India

We analyzed 370 bp of the first hypervariable region of the mitochondrial DNA (mtDNA) control region in 752 individuals from 17 tribal and four nontribal groups from the Indian subcontinent, to address questions concerning the origins, genetic structure and relationships of these groups. Southern Indian tribes showed reduced diversity and large genetic distances, both among themselves and when compared with other groups, and no signal of prehistoric demographic expansions. These results probably reflect enhanced genetic drift because of small population sizes and/or bottlenecks in these groups. By contrast, northern groups exhibited more diversity and signals of prehistoric demographic expansions. Phylogenetic analyses revealed that southern and northern groups (except northeastern ones) have related mtDNA sequences albeit at different frequencies, further supporting the larger impact of drift on the genetic structure of southern groups. The Indian mtDNA gene pool appears to be more closely related to the east Eurasian gene pool (including central, east and southeast Asian populations) than the west Eurasian one (including European and Caucasian populations). Within India, northeastern tribes are quite distinct from other groups; they are more closely related to east Asians than to other Indians. This is consistent with linguistic evidence in that these populations speak Tibeto-Burman languages of east Asian origin. Otherwise, analyses of molecular variance suggested that caste and tribal groups are genetically similar with respect to mtDNA variation.

Independent origins of Indian caste and tribal paternal lineages

The origins of the nearly one billion people inhabiting the Indian subcontinent and following the customs of the Hindu caste system are controversial: are they largely derived from Indian local populations (i.e. tribal groups) or from recent immigrants to India? Archaeological and linguistic evidence support the latter hypothesis, whereas recent genetic data seem to favor the former hypothesis. Here, we analyze the most extensive dataset of Indian caste and tribal Y chromosomes to date. We find that caste and tribal groups differ significantly in their haplogroup frequency distributions; caste groups are homogeneous for Y chromosome variation and more closely related to each other and to central Asian groups than to Indian tribal or any other Eurasian groups. We conclude that paternal lineages of Indian caste groups are primarily descended from Indo-European speakers who migrated from central Asia approximately 3,500 years ago. Conversely, paternal lineages of tribal groups are predominantly derived from the original Indian gene pool. We also provide evidence for bidirectional male gene flow between caste and tribal groups. In comparison, caste and tribal groups are homogeneous with respect to mitochondrial DNA variation, which may reflect the sociocultural characteristics of the Indian caste society.

Childhood Conditions Influence Adult Progesterone Levels

Background Average profiles of salivary progesterone in women vary significantly at the inter- and intrapopulation level as a function of age and acute energetic conditions related to energy intake, energy expenditure, or a combination of both. In addition to acute stressors, baseline progesterone levels differ among populations. The causes of such chronic differences are not well understood, but it has been hypothesised that they may result from varying tempos of growth and maturation and, by implication, from diverse environmental conditions encountered during childhood and adolescence. Methods and Findings To test this hypothesis, we conducted a migrant study among first- and second-generation Bangladeshi women aged 19–39 who migrated to London, UK at different points in the life-course, women still resident in Bangladesh, and women of European descent living in neighbourhoods similar to those of the migrants in London (total n = 227). Data collected included saliva samples for radioimmunoassay of progesterone, anthropometrics, and information from questionnaires on diet, lifestyle, and health. Results from multiple linear regression, controlled for anthropometric and reproductive variables, show that women who spend their childhood in conditions of low energy expenditure, stable energy intake, good sanitation, low immune challenges, and good health care in the UK have up to 103% higher levels of salivary progesterone and an earlier maturation than women who develop in less optimal conditions in Sylhet, Bangladesh (F 9,178 = 5.05, p < 0.001, standard error of the mean = 0.32; adjusted R 2 = 0.16). Our results point to the period prior to puberty as a sensitive phase when changes in environmental conditions positively impact developmental tempos such as menarcheal age (F 2,81 = 3.21, p = 0.03) and patterns of ovarian function as measured using salivary progesterone (F 2,81 = 3.14, p = 0.04). Conclusions This research demonstrates that human females use an extended period of the life cycle prior to reproductive maturation to monitor their environment and to modulate reproductive steroid levels in accordance with projected conditions they might encounter as adults. Given the prolonged investment of human pregnancy and lactation, such plasticity (extending beyond any intrauterine programming) enables a more flexible and finely tuned adjustment to the potential constraints or opportunities of the later adult environment. This research is the first, to our knowledge, to demonstrate a postuterine developmental component to variation in reproductive steroid levels in women.

Dietary composition and ovarian function among Lese horticulturalist women of the Ituri Forest, Democratic Republic of Congo

Objective: To assess dietary composition in relation to energetic status and ovarian function.Design: An eight-month prospective study undertaken in 1989.Setting: Ituri Forest, northeast Democratic Republic of Congo.Subjects: Sixty-four female volunteers of reproductive age (16–45), with a subsample of 30 for nutritional focal follows, 39 for analysis of salivary progesterone levels, and 18 for analysis of salivary oestradiol.Interventions: Regular anthropometric measurements of heights, weights, and mid-triceps skinfolds, 204 h of nutritional focal follows when all foods prepared and consumed were recorded and weighed, analysis of dietary composition using African food tables, collection of saliva samples every-other day for radioimmunoassay of salivary oestradiol and progesterone.Results: The primary staple in the Lese diet is manioc, consumed at nearly every meal, but the diet is subject to seasonal fluctuations. Important seasonal crops are groundnuts and rice. Carbohydrates comprise 64% of the diet, protein 14% and fat 22%, but seasonal fluctuations in food items create significant differences in protein content (P=0.007). Energy intake falls by 25% in the hunger season. Lese energy balance reflects this lack with women losing a mean 7% of total body weight. The mean BMI for Lese women at the beginning of the study was 22.8 but, during the hunger season, the BMI for 20% of women fell to <18.5, indicative of chronic energy shortage. Mean levels of Lese salivary oestradiol and progesterone are chronically and significantly lower than healthy, Western controls (P=0.0001 for progesterone; P=0.03 for follicular values of oestradiol, P=0.0001 for mid-cycle values, and P=0.0002 for luteal values). Mean salivary progesterone levels were significantly lower for those Lese women losing weight (P=0.03), and significantly lower for weight-loss women when comparing levels at the beginning and end of the hunger season (P=0.03).Discussion: The relatively low-fat, high-fibre diet of the Lese appears healthy, but there are occasional seasonal deficiencies in protein-energy and micronutrient content, especially for pregnant and lactating women. Dietary composition may affect Lese levels of reproductive steroids, partly explaining the chronically low salivary oestradiol profile of this population.Sponsorship: This work was supported by a National Science Foundation Grant (BNS-88-10931) to PT Ellison, and a Royal Society Research Fellowship to GR Bentley.

Patterns of occurrence and concordance between subjective and objective hot flashes among Muslim and Hindu women in Sylhet, Bangladesh

This study examined the pattern of occurrence and the rate of concordance between objective hot flashes measured by sternal skin conductance and the subjective experience of “gorom vap laga” (feeling steaming hot) among Muslim and Hindu women living in Sylhet, Bangladesh. Participants were aged 40–55, not pregnant or lactating, not using hormone therapy, and with no history of hysterectomy. Thirty women wore an ambulatory hot flash monitor for 8 h on average, from mid‐morning to early evening. True positive, false negative, and false positive measures of hot flashes were examined in relation to demographic, reproductive, and lifestyle variables. On body diagrams, women were most likely to indicate hot flashes on the top of their head (64%) and upper chest (68%). The greatest number of objective hot flashes occurred during the hour of 17:00, perhaps due to the heat of the day, and the clothing and activity associated with prayer. Muslim participants demonstrated more objective hot flashes per woman than Hindu participants (1.5 vs. 0.1, P < 0.05), and Muslims had more false positive measures (86%) compared with Hindu participants (0%, P = 0.06). Among all women who reported subjective hot flashes (n = 19), the proportion of true positive scores was 19%. Overall, the frequency of objective hot flashes was low compared with reports from studies in the United States. The pattern of sweating assessed by body diagrams was not associated with variation in hot flash experience. Am. J. Hum. Biol., 2008.

Infertility in the modern world: present and future prospects.

1. Introduction G. R. Bentley and C. G. Nicholas Mascie-Taylor Part I. Biomedical Perspectives on Fertility: 2. Reproductive possibilities for infertile couples: present and future S. Fishel, K. Dowell and S. Thornton 3. Genetic influences on human infertility A. H. Bittles and P. L. Matson Part II. Environmental Influences on Fertility: 4. Environmental pollutants and fertility G. R. Bentley 5. From STD epidemics to AIDS: a socio-demographic and epidemiologic perspective on Sub-Saharan Africa J. C. Caldwell and P. Caldwell Part III. Social Perspectives on Infertility: 6. Voluntary childlessness: trends and implications F. McAllister and L. Clarke 7. Sexual orientation and fertility C. J. Patterson and L. V. Friel.

Life course effects on age at menopause among Bangladeshi sedentees and migrants to the UK

To assess how different variables experienced across the life course, but particularly during early life, might affect age at menopause among 174 Bangladeshi migrants to London by comparing them to 157 nonmigrant sedentees and 154 women of European descent in London.

Betel Nut Use among First and Second Generation Bangladeshi Women in London, UK

This study evaluated the effects of socio-economic variables and migration history on the prevalence of betel nut and smokeless tobacco use in both UK- and Bangladeshi born migrant women resident in London. No significant difference in betel nut use prevalence was found among women of different generations. However, in all groups betel nut users were significantly older and less educated than non-users. Among first generation women there was no effect of either length of time living in the UK or age at migration on use of betel nut, even after controlling for current age. No significant differences in prevalence use due to language spoken, occupation, marital status or borough of residence in London were found. We conclude that, although there are some indications of a change in behavior among younger individuals, betel nut chewing is a practice very much present among Bangladeshi women born and brought up in a bicultural context.

Ethnicity or environment: effects of migration on ovarian reserve among Bangladeshi women in the United Kingdom

OBJECTIVE To assess whether the quality of early childhood environments among different groups of Bangladeshi women, including migrants to the United Kingdom (UK), contributes to variation in ovarian reserve and the rate of reproductive aging in later life. DESIGN Cross-sectional study. SETTING Not applicable. PATIENT(S) A total of 179 healthy women volunteers aged 35-59 years were divided into four groups: [1] 36 Bangladeshis living in Sylhet, Bangladesh; [2] 53 Bangladeshis who migrated to the UK as adults; [3] 40 Bangladeshis who migrated to the UK as children aged 0-16 years; and [4] a reference group of 50 women of European origin living in London. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Levels of serum antimüllerian hormone, inhibin B, FSH, and E2, and anthropometrics derived from biomarkers; reproductive, demographic, and health variables from structured questionnaires. RESULT(S) Bangladeshi migrants who moved to the UK as children and European women had a highly significantly larger, age-related ovarian reserve compared with migrant Bangladeshis who had moved to the UK as adults or Bangladeshi women still living in Bangladesh. There were no other significant covariates in the model aside from age and menopausal status. CONCLUSION(S) The study points to the importance of childhood development in considering variation in ovarian reserve across different ethnic groups. Clinical studies and research in assisted reproductive technology have emphasized the role of genes or race in determining inter-population variation in ovarian reserve. Early life developmental factors should be given due consideration when evaluating inter-group differences in response to assisted reproductive technology.

Childhood Environment Influences Adrenarcheal Timing among First-Generation Bangladeshi Migrant Girls to the UK

Background Adrenarche is a key early life event that marks middle childhood at approximately 7 years of age. Earlier work with British-Bangladeshi migrant women suggested that environmental conditions experienced before adrenarche influence adult reproductive function. We therefore investigated whether Bangladeshi children who migrate to the United Kingdom (UK) reach adrenarche earlier than non-migrants in Bangladesh or the United Kingdom. Methods and Findings Healthy girls, aged 5–16 years, were recruited from schools in Sylhet, Bangladesh and London, England comprising four groups: Sylhetis (n = 165), first-generation migrants to the United Kingdom (n = 42), second-generation girls (n = 162), and British girls of European origin (n = 50). Anthropometric measurements were collected together with questionnaire data for migration and socioeconomic characteristics. Saliva samples were assayed for dehydroepiandrosterone (DHEAS) using enzyme-linked immunosorbent assays. Multiple linear regressions tested for group differences in anthropometric and socioeconomic variables and DHEAS levels. Median ages at adrenarche (DHEAS>400 pg/ml) were estimated using Weibull regression models for parametric survival analysis. Hazard ratios for reaching adrenarche earlier and 95% confidence intervals (CI), both unadjusted and adjusted for anthropometric variables, were estimated from the survival analyses. First-generation migrants had a median age at adrenarche (5.3 years) that was significantly earlier than Sylheti (7.2), second-generation (7.4), and European (7.1) girls. In univariate analyses, first-generation girls reached adrenarche significantly earlier than Sylhetis [HR (CI): 2.8 (1.4–5.5]. In multivariate models, first generation girls still reached adrenarche earlier than Sylhetis after adjusting for height [HR(CI): 1.9 (0.9–4.1)] and weight [HR(CI):1.7 (0.8–3.8)], but these results were attenuated. Conclusions We suggest that rapid catch-up growth experienced by first generation girls during early childhood may explain their advanced adrenarche. The environmental conditions leading to an earlier adrenarche, as well as the health implications of this early transition, merit further exploration.