Brown fat and obesity: the next big thing?

Brown adipose tissue (BAT) is well recognised to have an important role in the maintenance of body temperature in animals and human neonates, its thermogenic action affected by a tissue-specific uncoupling protein; fatty acid oxidation within the numerous brown adipocyte mitochondria is rendered inefficient leading to heat, rather than adenosine triphosphate (ATP), production. BAT was believed to show rapid involution in early childhood, leaving only vestigial amounts in adults. However, recent evidence suggests that its expression in adults is far more common than previously appreciated, with a higher likelihood of detection in women and leaner individuals. It is conceivable that BAT activity might reduce the risk of developing obesity since fat stores are used for thermogenesis, and a directed enhancement of adipocyte metabolism might have value in weight reduction. However, it is as yet unclear how such manipulation of BAT might be achieved; even in animal models, the control of thermogenic activity is incompletely understood. Even so, there is still much to interest the endocrinologist in BAT, with a range of hormones affecting adipocyte activity. This may either contribute to normal physiological function, or the phenotypical presentation of states of pathological hormone excess or deficiency. Thus, the gender differences in BAT distribution may be attributable to the differential effects of male and female sex hormones, whilst BAT expansion may drive the weight loss associated with catecholamine-producing phaeochromocytomas. These observations support an important influence of the endocrine system on BAT activity and offer new potential targets in the treatment of obesity.     

Do coronary heart disease risk factors change over time?

The stability over a 12-year period of several coronary heart disease (CHD) risk factors was evaluated in 348 individuals who had remained healthy following baseline measurements made of the same variables in 1981. CHD risk factors evaluated were fasting and post-glucose challenge (120-minute) plasma glucose and insulin concentrations, plasma triglyceride (TG), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) concentrations, and the ratio of LDL/HDL cholesterol concentrations. Approximately 40% to 60% of individuals in the highest CHD risk quartile (or lowest in the case of HDL cholesterol concentrations) in 1981 were still at highest risk in 1993. A similar proportion of individuals at lowest risk in 1981 were still in that category in 1993. At least 50% of the participants in this prospective analysis experienced a change by 1 quartile or more in each of the metabolic CHD risk factors measured, and these differences were highly statistically significant for all variables measured with the exception of the TG and HDL cholesterol concentrations. These results demonstrate that the implicit assumption in epidemiological studies that CHD risk factors at baseline remain stable may require examination.     

Is alcohol anti-inflammatory in the context of coronary heart disease?

Although the cardioprotective effect of alcohol has been primarily explained by its effect on blood lipids and platelets, could an anti-inflammatory mechanism be involved?     

Is the prevalence of coronary heart disease falling in British men?

OBJECTIVE—To assess whether long term trends over time in acute coronary heart disease (CHD) event rates have influenced the burden of prevalent CHD in British men.
DESIGN—Longitudinal cohort study.
PARTICIPANTS—7735 men, aged 40-59 at entry (1978-80), selected from 24 British towns.
METHODS—The prevalences of current angina symptoms and history of diagnosed CHD were ascertained by questionnaire in 1978-80, 1983-85, 1992, and 1996. New major CHD events (fatal and non-fatal) were ascertained throughout the study from National Health Service central registers and general practice record reviews. Age adjusted trends in CHD prevalence were compared with trends in major CHD event rates.
RESULTS—From 1978-1996 there was a clear decline in the prevalence of current angina symptoms: the age adjusted annual percentage change in odds was -1.8% (95% confidence interval (CI) -2.8% to -0.8%). However, there was no evidence of a trend in the prevalence of history of diagnosed CHD (annual change in odds 0.1%, 95% CI -1.0% to 1.2%). Over the same period, the CHD mortality rate fell substantially (annual change -4.1%, 95% CI -6.5% to -1.6%); rates of non-fatal myocardial infarction, all major CHD events, and first major CHD event fell by -1.7% (95% CI -3.9% to 0.5%), -2.5% (95% CI -4.1% to -0.8%), and -2.4% (95% CI% -4.3 to -0.4%), respectively.
CONCLUSIONS—These results suggest that middle aged British men are less likely to experience symptoms of angina than in previous decades but are just as likely to have a history of diagnosed CHD. Despite falling rates of new major events and falling symptom prevalence, the need for secondary prevention among middle aged men with established CHD is as great as ever.


Keywords: coronary heart disease; angina; prevalence; trends     

Coronary heart disease in women: Why the disproportionate risk?

Women with diabetes experience much greater relative risks of coronary heart disease (CHD) compared with the nondiabetic population than do men with diabetes. In type 2 diabetes, much of the greater elevation in risk in women is explained by a more adverse pattern of known CHD risk factors. In type 1 diabetes the picture is less clear, but current evidence suggests that a cardioprotective lipid profile is found in type 1 diabetic men, thus reducing the effect of diabetes on CHD, but that in women this is not the case. Also, in type 1 diabetic women there is some evidence of altered body fat distribution and a greater elevation in blood pressure. Whether these reflect a greater degree of insulin resistance in type 1 women, and what the origin of this might be, remains controversial. The practical consequence is that clinicians need to be aware that the usual cardioprotective effect of sex does not apply in diabetic women and that risk factor intervention is needed at an early age.     

Is coronary heart disease rising in India? A systematic review based on ECG defined coronary heart disease

The aim of this study was to investigate whether coronary heart disease (CHD) is rising in India and assess the quality of the evidence. Thirty one studies were reviewed. The sample sizes of the studies varied from approximately 500 to 14,000, with response rates generally over 90%. Many did not fulfil basic requirements for epidemiological research and most studies were in or around Delhi. The three incidence studies used different diagnostic criteria; however, the incidence of myocardial infarction (MI) in urban India in the 14 years to 1991 remained similar at about 6/1000 in males and 2/1000 in females. Prevalence range was higher in urban than rural areas in men (35-90/1000 v 17-45/1000) and women (28-93/1000 v 13-43/1000). There was no clear rise in age specific rates in men over a 27 year period, whereas a rise was seen in women. In conclusion, using a relatively objective measure of CHD it was found that CHD is more common in urban than rural areas of India, but there was little evidence of a rise in CHD over time, especially in men.