Genetic and environmental influences on skeletal muscle phenotypes as a function of age and sex in large, multigenerational families of African heritage

The aim of this study was to estimate the heritability of and environmental contributions to skeletal muscle phenotypes (appendicular lean mass and calf muscle cross-sectional area) in subjects of African descent and to determine whether heritability estimates are impacted by sex or age. Body composition was measured by dual-energy X-ray absorptiometry and computed tomography in 444 men and women aged 18 yr and older (mean: 43 yr) from eight large, multigenerational Afro-Caribbean families (family size range: 21-112). Using quantitative genetic methods, we estimated heritability and the association of anthropometric, lifestyle, and medical variables with skeletal muscle phenotypes. In the overall group, we estimated the heritability of lean mass and calf muscle cross-sectional area (h(2) = 0.18-0.23, P < 0.01) and contribution of environmental factors to these phenotypes (r(2) = 0.27-0.55, P < 0.05). In our age-specific analysis, the heritability of leg lean mass was lower in older vs. younger individuals (h(2) = 0.05 vs. 0.23, respectively, P = 0.1). Sex was a significant covariate in our models (P < 0.001), although sex-specific differences in heritability varied depending on the lean mass phenotype analyzed. High genetic correlations (rho(G) = 0.69-0.81; P < 0.01) between different lean mass measures suggest these traits share a large proportion of genetic components. Our results demonstrate the heritability of skeletal muscle traits in individuals of African heritage and that heritability may differ as a function of sex and age. As the loss of skeletal muscle mass is related to metabolic abnormalities, disability, and mortality in older individuals, further research is warranted to identify specific genetic loci that contribute to these traits in general and in a sex- and age-specific manner.

Possible role of female discrimination against 'redundant' males in the evolution of colour pattern polymorphism in guppies

Multiple paternity of offspring can result from active preferences on the part of females or sexual harassment by males. We examined sexual responses of female guppies to a previous mate versus a novel male (experiment 1) or to a male with a colour pattern similar to that of the previous mate versus a novel male (experiment 2). Females showed significantly more sexual responses to courtship by novel males than to previous mates in experiment 1 or to males that resembled previous mates in experiment 2. These results suggest that females discriminate actively against previous mates, and extend this discrimination to males with similar colour patterns to previous mates. This could lead to negative frequency-dependent sexual selection against common colour patterns (a 'redundant male effect'), which could contribute to the maintenance of the extraordinarily high levels of genetic polymorphism in guppy colour patterns.

Studies on plasma lipids in industrial workers in central Trinidad and Tobago

We assessed the plasma lipid profiles and other cardiovascular disease (CVD) risk factors in 187 (147 men, 47 women) apparently healthy employees of the Caribbean ISPAT industry in Trinidad and Tobago. Anthropometric indices and fasting plasma levels of total cholesterol (T-chol), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were measured. The results indicate that: there was increased body mass and relative hyperlipidemia in the population studied, these CVD risk factors (increased body mass, increased blood T-chol, TG, and LDL) were more prevalent in men than women (p < 0.05), and these parameters did not differ significantly (p < 0.05) when compared among the three ethnic groups (African and Indian descendants and mixed descents). These features suggest a greater risk of CVD in men than in women. It is likely that this observation in the industrial workers might reflect the situation in the general population especially in men. Although further confirmatory studies are necessary across societal socioeconomic strata within Trinidad, we suggest that efforts should be directed at reducing excess body weight among the workers, and providing advice on increased complex carbohydrate diet in place of saturated fat.

Relationships of fasting and postload glucose levels to sex and biased against detection of diabetes in women?

OBJECTIVE: To compare, in men and women, the prevalence of undiagnosed type 2 diabetes assessed using criteria from the American Diabetes Association (ADA) and the World Health Organization (WHO) and to investigate risk factors associated with fasting and 2-h postload plasma glucose. RESEARCH DESIGN AND METHOD: Data from two companion surveys of Europeans, South Asians, and Afro-Caribbean in west London were used. A total of 4,367 men and women aged 40-64 years who were not known to have diabetes underwent an oral glucose tolerance test after an overnight fast. The prevalence of undiagnosed diabetes was estimated using the ADA (fasting plasma glucose > or = 7.0 mmol/l) and WHO (2-h postload glucose > or = 11.1 mmol/l) criteria for epidemiologic studies. The association of body fat and usual alcohol intake with plasma glucose and diabetes prevalence was assessed. RESULTS: Compared with the WHO criterion, the ADA criterion gave a higher prevalence of diabetes in men (6.4 vs 4.7 percent) but a lower prevalence in women (3.3 vs. 4.2 percent). In Afro-Caribbeans, the sex difference in diabetes prevalence was reversed. Women had significantly lower fasting glucose than men despite higher 2-h glucose levels. Alcohol intake was positively associated with fasting glucose in men and women but not with 2-h glucose levels. CONCLUSIONS: The new ADA criterion, based on fasting glucose alone, does not take account of sex differences in metabolic response to fasting or possible artifactual effects on fasting glucose. With ADA criterion, alcohol intake was significant risk factor for diabetes in our study population; this was not the case with the WHO criterion.(AU)

UK prospective diabetes study xii: differences between Asian, Afro-Caribbean and White Caucasian type 2 diabetic patients at diagnosis of diabetes

Clinical and biochemical variables and prevalence of complications at diagnosis of diabetes were assessed in 5098 Type 2 diabetic patients in the UK Prospective Diabetes Study of Whom 82 percent were white Caucasian, 10 percent Asian of Indian origin, and 8 percent Afro-Caribbean. The Asian patient were (p<0.001) younger (mean age 52.3, 47.0, 51.0 years), less obese (BMI 29.3, 26.7, 27.9 Kg m-2), had a greater waist-hip ratio, lower blood pressure (systolic 145, 139,144 diastolic 87, 86, 89 mmHg) and prevalence of hypertension. They were more often sedentary (19, 39, 15 percent), more often abstained from alcohol (21, 55, 25 percent) and had a greater prevalence of first degree relatives with known diabetes (36, 44, 34 percent). The Afro-Caribbean patients had (p<0.001) higher fasting plasma glucose (11.9, 11.3, 12.5, mmol -1), more severely impaired á-cell function (45, 35, 28 percent normal) and less impaired insulin sensitivity(23,19,27 percent normal) by homeostasis model assessment, lower triglyceride (1.8, 1.8, 1.3 mmol-1), and higher HDL-cholesterol (1.05, 1.03, 1.17 mmol 1-1). Prevalence of a history of myocardial infarction, stroke or intermittent claudication at diagnosis was similar. The prevalence of ischaemic ECG (minnesota code), microabuminuria (urine albumin >50 mgl-1), retinopathy ('191' grading of retinal photographs), and neuropathy (abnormal vibration perception threshold or absent leg reflexes) was also similar. At diagnosis of Type 2 diabetes there were no differences in prevalence of complications between white Caucasian, Asian, and Afro-Caribbean patients although differences were found in other clinical and biochemical variables (AU)

Adolescent blood pressure in a cohort study of sickle cell disease

BACKGROUND: Previous studies on low blood pressure in patients with homozygous sickle cell (SS) disease have sought new hypothesis on the mechanism of low blood pressure but have not analyzed the role of known determinants such as weight. METHODS: Blood pressure has been measured by an automated oscillometric method in 220 patients with SS disease, 144 with sickle cell-hemoglobin C disease (both groups aged, 9.5 to 18.5 years) and 122 control subjects with a normal hemoglobin genotype (aged 16.0 to 18.5 years) participating in a cohort study from birth. RESULTS: Significant age-related increases in systolic and mean arterial pressure occurred in sickle cell-hemoglobin C disease but not in SS disease. Further analysis were confined to a subgroup of 51 patients with SS, 41 patients with sickle cell-hemoglobin C, and 97 subjects with normal hemoglobin, aged 16.0 to 18.5 years in whom simultaneous measurements of height, weight, arm circumference, and hematologic test results were also available. Crude analysis showed significantly lower systolic, diastolic, and mean arterial pressure in SS disease compared with control subjects with normal hemaglobin, but further analysis showed the systolic difference to be confined to males and all differences disapperared after ajustment for weight. No difference occurred in sickle cell-hemoglobin C disease. CONCLUSIONS: These results suggest that the lower blood pressure in SS disease is attributable to low weight and that no further mechanisms need be postulated (AU)

Feminizing mesenchymal tumour of the ovary

The clinical and pathological features of 17 cases of feminizing mesenchymal tumours of the ovary observed over a 14-year period have been reviewed. (1) This group of neoplasms accounts for 3.4 percent of all primary ovarian tumours. (2) One case was observed before puberty and the others equally divided between women in the reproductive and the post-menopausal age groups. Most of the thecomas were observed in the reproductive period. (3) The tumours occurred in nulliparous patients and in those of low parity. (4) Vaginal bleeding and swelling of the abdomen were the most frequent presenting symptoms. The former symptom was, however, notably absent in the cases with pure granulosa cell growths. (5) All cases were treated surgically, the extent of the operation depending on the age of the patient and the presence of association uterine pathology. (6) The very large tumours were almost entirely cystic and all these cases died within 5 years. The thecomas were all benign. (7) Follow-up of these patients for life is essential as late recurrences of the tumours are a prominent feature (AU)