Genetic inheritance of body mass index in African-American and African families

Body Mass Index, Self-Esteem, and Suicide Risk in Clinically Depressed African American and White American Females

Self-esteem and depression, as well as depression and body mass index (BMI), have consistently been found to be significantly associated for African American and White American females. The results are dissimilar when BMI and self-esteem are studied. Historically, the relationship between BMI and self-esteem is weak or nonexistent for African American females; however, for White American females, the relationship is usually significant. The goal of this study was to determine whether clinically depressed, healthy-weight, overweight, and obese females would differ significantly on self-esteem and suicide risk measures. In a voluntary hospital-based inpatient psychiatric unit, 165 clinically depressed females completed the self-esteem rating scale and the suicide risk scale. Healthy-weight, overweight, and obese African American females did not differ significantly on measures of self-esteem and suicide risk. However, depressed, obese White American females had significantly lower self-esteem and increased suicide risk than depressed healthy-weight and overweight White American females. Implications of the current results are discussed.

Sleep in America: role of racial/ethnic differences

Sleep duration in America has gradually declined over the last four decades and appears to have reached a plateau for the last six years, with recent studies reporting that the population's current average sleep duration is approximately 6 h. In this paper, we examine epidemiologic and community-based data on sleep complaints reported by American adults, specifically addressing the role of race/ethnicity in the subjective report of sleep problems. Subjective and objective findings indicate that black (throughout the text, we use the term black in lieu of African American for there are instances where we refer to individuals with self-ascribed race/ethnicity as black, African American, African, or Caribbean American; the term white is used to denote individuals of European descent). Americans have higher rates of long (≥9 h) and short (≤5 h) sleep than their white counterparts, and this may mediate a higher risk of cardiovascular disease, obesity and diabetes among blacks. In addition, studies show mixed results on sleep complaints among blacks compared to those among other ethnicities. This paper explores factors that may contribute to racial/ethnic differences in sleep including intra-ethnic variation, cultural biases, genetics and psychosocial factors.

New insights into the genetics of body weight

PURPOSE OF REVIEW

These last months, the wave of genome-wide association scans finally reached the shores of body weight and obesity complex trait. In parallel, thanks to the increasing sequencing and genotyping capacities, large studies on rare mutations can now be carried out.

RECENT FINDINGS

In this review, I tried to cover the most recent findings in genome-wide association analyses, the outcome of conclusions subsequently not replicated, and the weight of rare mutations with strong effects on common obesity. The strongest predictor of obesity, FTO, is responsible for 1% of the total heritability, and results from other genome-wide scans do not provide, so far, any clue of other variants of this effect size. Thus, monogenic obesity studies might well reinstall the importance of rare nonsynonymous mutations of already known genes, especially melanocortin-4 receptor gene, in the general population. Nevertheless, additional genome-wide association analyses and replication are expected to confirm these first intuitions.

SUMMARY

Initial results both support the common variant-common disease hypothesis because at least one such variant exists in FTO, and also tone down its importance because such variants may be fewer than expected. Moreover, having a polymorphism associated with body weight is clearly not the end but rather the beginning of a long search for the gene function and pathway.

Inheritance of six anthropometric traits in Vaidyas of West Bengal, India

BACKGROUND

Anthropometric traits are important quantitative traits used by biological anthropologists. Surprisingly little is known about their pattern of inter-generational transmission, probably due to lack of use of developed statistical analysis in previous studies.

AIM

The present study is an attempt to approach the problem of the inheritance of anthropometric traits through advanced statistical applications.

SUBJECTS AND METHODS

Measurements of 824 individuals from 200 families including two generations were collected from Barasat, West Bengal. The study includes age correction by regression, familial correlation, heritability estimation and segregation analyses.

RESULTS

Results showed that there is strong involvement of the familial component in variation of anthropometric traits. The magnitude of heritability (h2= 57-83%) also supports their strong genetic basis. The results indicated that additive genes are not the only contributing factor; the effect of environment is considerable and that of dominant genes not negligible. Due to genetic interaction with the local environment (specific for each trait), heritabilities vary from one trait to another. Length measurements have higher heritability than breadth measurements. Segregation analysis revealed that either the additive or dominant major gene (MG) is responsible for this effect, which follows simple Mendelian transmission. Beside this, the possibility of the existence of an additional minor gene cannot be discarded.

CONCLUSION

Anthropometric traits have a genetic basis but their mode of inheritance is quite complex in nature. There is evidence of major gene effect (along with polygenes) with Mendelian transmission.

Loci contributing to adult height and body mass index in African American families ascertained for type 2 diabetes

Height and body mass index (BMI) have high heritability in most studies. High BMI and reduced height are well-recognized as important risk factors for a number of cardiovascular diseases. We investigated these phenotypes in African American families originally ascertained for studies of linkage with type 2 diabetes using self-reported height and weight. We conducted a genome wide scan in 221 families containing 580 individuals and 672 relative pairs of African American descent. Estimates of heritability and support for linkage were assessed by genetic variance component analyses using SOLAR software. The estimated heritabilities for height and BMI were 0.43 and 0.64, respectively. We have identified major loci contributing to variation in height on chromosomes 15 (LOD = 2.61 at 35 cM, p = 0.0004), 3 (LOD = 1.82 at 84 cM, p = 0.0029), 8 (LOD = 1.92 at 135 cM, p = 0.0024) and 17 (LOD = 1.70 at 110 cM, p = 0.0044). A broad region on chromosome 4 supported evidence of linkage to variation in BMI, with the highest LOD = 2.66 at 168 cM (p = 0.0005). Two height loci and two BMI loci appear to confirm the existence of quantitative trait loci previously identified by other studies, providing important replicative data to allow further resolution of linkage regions suitable for positional cloning of these cardiovascular disease risk loci.

Lack of evidence for a major gene in the Mendelian transmission of BMI in Chinese

OBJECTIVES

To determine the heritability of BMI and to examine the mode of inheritance of BMI variation in Chinese.

RESEARCH METHODS AND PROCEDURES

Familial correlation and complex segregation analyses for BMI were undertaken in a Chinese sample composed of 392 nuclear families, with 1190 total individuals.

RESULTS

A moderate heritability was found for BMI (h2 = 0.419-0.492). The obtained results do not support a major gene for BMI in our samples. BMI may be inherited in a complex and non-Mendelian manner in Chinese.

DISCUSSION

The findings of this study suggest that identification of specific genes for BMI in Chinese, at least within the same data set, is a serious challenge because of the lack of evidence of a major gene for BMI in our Chinese sample.

Sleep-disordered breathing and hypertension among African Americans

This study investigated differences in sleep-disordered breathing (SDB) between hypertensives without a family history of hypertension and hypertensives with a family history. Furthermore, it examined whether these two groups differed in the severity of SDB. Patients were African Americans (n=162, mean age=51.19+/-13.77 years; mean body mass index (BMI)=37.85+/-9.51 kg/m2, male=57%), who were referred to the clinic because of a sleep complaint. Sleep was recorded in the laboratory using standard physiological parameters; all parameters were analysed by a trained scorer. Altogether, 91% of the patients received an SDB diagnosis. Of these patients, 25% were hypertensives without a family history, 20% were hypertensives with a family history, and 55% were normotensives. We found a significant difference between these patient groups regarding the severity of SDB (F14,158=1.823, P<0.05), but no significant group difference was observed in the rate of SDB. Increasing weight was accompanied by increasing severity of SDB. The finding that hypertensive patients with or without a positive family history showed worse oxygenation and respiratory characteristics than did normotensives is consistent with previous research. Of note, hypertensives reporting a family history were characterized by a greater number of oxygen desaturations and apnoea hypopnoea index than those typified only by a current diagnosis of hypertension. Hypertensives with a family history are likely to show a profile of greater blood pressure, higher BMI, and more severe SDB, which by all accounts are more common among African Americans.

Genetic and environmental influences on body-fat measures among African-American twins

OBJECTIVE

To investigate the genetic and environmental influences on body-fat measures including waist circumference (WC), waist-to-hip ratio (WHR), and body mass index (BMI) among African-American men and women.

RESEARCH METHODS AND PROCEDURES

Measurements were taken as part of the Carolina African American Twin Study of Aging. This sample currently comprises 146 same-sex African-American twins with an average age of 50 years (range, 22 to 88 years). This analysis included 26 monozygotic and 29 dizygotic men and 45 monozygotic and 46 dizygotic women. Maximum likelihood quantitative genetic analysis was used.

RESULTS

In men, additive genetic effects accounted for 77% of the variance in WC, 59% in WHR, and 89% in BMI. In women, additive genetic effects accounted for 76% of the variance in WC, 56% in WHR, and 73% in BMI. The remaining variance in both men and women was attributed to unique environmental effects (WC, 21%; WHR, 36%; BMI, 11% in men and WC, 22%; WHR, 38%; BMI, 27% in women) and age (WC, 2%; WHR, 5% in men and WC, 2%; WHR, 6% in women). When BMI was controlled in the analysis of WC and WHR, it accounted for a portion of the genetic and environmental variance in WHR and over one-half of the genetic and environmental variance in WC.

DISCUSSION

There are both genetic and environmental influences on WC, WHR, and BMI, and independent of BMI, there are genetic and environmental effects on WC and WHR among both genders. The results from this African-American twin sample are similar to findings among white twin samples.