A cross-sectional ecological analysis of blood pressure and its determinants in eleven Pacific populations

Polymorphisms in the 3'UTR of the human leptin gene and their role in hypertension

Leptin is a protein hormone, mainly synthesized in adipocytes, that regulates the food intake and energy expenditure of the body. Rare mutations in the leptin gene cause obesity. Common polymorphisms of the leptin gene have been associated with obesity, however their association with arterial blood pressure has not been fully elucidated. The aim of the present study was to examine the effect of variants in the 3' flanking region of the leptin gene on blood pressure in hypertensive subjects with high (35.2 ± 5.12) and low (20.13 ± 1.3) body mass index (BMI). Microsatellite polymorphisms and the C538T SNP in the 3'UTR of the leptin gene were screened in 362 subjects, and different biochemical and anthropometric parameters were measured. The levels of serum urea, creatinine, glucose, cholesterol, triglyceride, leptin and angiotensin II were determined in all subjects. A strong association of microsatellite polymorphisms with essential hypertension was found in subjects with a high BMI, but this association was only slight in subjects with a normal BMI. The C538T variant was not found in this population. The frequency of the Class I/Class I and Class I/Class II genotype for tetranucleotide polymorphisms was also significantly higher in the hypertensive compared to the normotensive group (p ≤ 0.0001). In addition, a significant correlation was found between serum leptin and Class I/I and Class I/II genotypes. Linear regression analysis showed an independent correlation of leptinemia with BMI (p=0.019), while a notable correlation was found between serum leptin concentration and angiotensin II. The study confirmed that shorter alleles of microsatellites in the 3' flanking region of leptin are significantly associated with hypertension, however, the underlying mechanism remains unknown.

Blood pressure and the global burden of disease 2000. Part 1: Estimates of blood pressure levels

OBJECTIVE

To provide global estimates of blood pressure by age and sex for adults aged > or = 30 years, by WHO subregion.

DESIGN AND METHODS

Data were obtained from studies identified in a literature review of population-based surveys. These were complemented by data from MONICA and INTERSALT studies. Estimates of the shape of the age-systolic blood pressure (SBP) association were made from survey data utilizing parametric and non-parametric analyses. A linear sex-specific association of SBP with age was demonstrated from 30 to 70 years in females and 20 to 70 years for males in each subregion. Mean age- and sex-specific estimates of SBP were estimated for each WHO subregion separately, based on study and country-weighted SBP data.

RESULTS

Analyses were based on data from about 230 surveys and over 660 000 participants. Age-specific mean SBP values ranged from 114 to 164 mmHg for females, and 117-153 mmHg for males. Females typically had lower SBP levels than males in the 30-44-year age groups, but in all subregions, SBP levels rose more steeply with age for females than males. Therefore, SBP levels in those aged > or = 60 years tended to be higher in females. Subregions with consistently high mean SBP levels included parts of eastern Europe and Africa. Mean SBP levels were lowest in south-east Asia and parts of the western Pacific.

CONCLUSIONS

These global estimates of blood pressure by age, sex and subregion show considerable variation in estimated levels. The lack of data in developing countries is substantial, and this is an important limitation given the role of blood pressure in increasing cardiovascular disease levels.

Salt and hypertension: a phylogenetic perspective

Our hunter-gatherer ancestors appeared to survive on little salt. When today's rural dwellers move to urban environments, they increase their salt intake and the salt-sensitive among them become prone to age-related increase in blood pressure and hypertension. This paper reviews our knowledge of the mechanisms of salt disposal and plasma volume regulation, salt consumption in human evolution, salt intake and prevalence of hypertension, and the results of interventions aimed at modulating both. Finally, it discusses current hypotheses on the mechanisms of selective pressure that may have favored the emergence of a salt-sensitive, hypertensive genotype. Similar to 'thrifty' genes, which supported energy savers in times of scarcity, but may now be causing obesity and type 2 diabetes, 'thirsty' genes, by acting on salt and water retention, might have helped individuals survive the challenge of volume-depleting illnesses, especially when combined with stress-inducing situations, but may now cause high BP and related damage in the post-reproductive age.

Effects of glucose/insulin perturbations on aging and chronic disorders of aging: the evidence

Among changes associated with aging is a decline in glucose tolerance. The reported causes are increased insulin resistance from receptor and/or post receptor disturbances and diminished pancreatic islet B-cell sensitivity to glucose. Many recent reports indicate that insulin resistance with hyperinsulinemia and/or hyperglycemia contribute to or even causes many chronic disorders associated with aging, i.e., chronic metabolic perturbations including noninsulin-dependent diabetes mellitus, obesity, hypertension, lipid abnormalities, and atherosclerosis. How could such disturbances in glucose/insulin metabolism lead to many chronic disorders associated with aging? In aging, similar to diabetes, the elevation in circulating glucose and other reducing sugars secondary to age-induced insulin resistance can react nonenzymatically with proteins and nucleic acids to form products that affect function and diminish tissue elasticity. Also, perturbations in glucose/insulin metabolism are associated with enhanced lipid peroxidation secondary to greater free radical formation. Free radicals of oxygen are important known causes of tissue damage and have been associated with many aspects of aging including inflammatory diseases, cataracts, diabetes, and cardiovascular diseases. Augmented free radical formation and lipid peroxidation are not uncommon in diabetes mellitus, commonly associated with "premature aging". Ingestion of sugars, fats, and sodium have been linked to decreased insulin sensitivity, while caloric restriction, exercise, ingestion of chromium, vanadium, soluble fibers, magnesium, and certain antioxidants are associated with greater insulin sensitivity. Thus, manipulation of diet by influencing the glucose/insulin system may favorably affect lifespan and reduce the incidence of chronic disorders associated with aging.

The Egyptian National Hypertension Project (NHP). Design and rationale. The NHP Investigative Team

Hypertension and its complications appear to be increasingly common in Egypt. The National Hypertension Project (NHP) is a collaborative Egyptian-American effort with the following objectives: (1) to determine the prevalence of hypertension and blood pressure-related preclinical and clinical complications in Egyptian adults, (2) to identify environmental factors associated with high blood pressure, and (3) to build an infrastructure for research and education in cardiovascular disease prevention in Egypt. The NHP surveys were conducted in six of Egypt's 26 governorates, representing distinct geographic regions. In each of these six governorates, a probability sample of 600 households was surveyed. NHP was conducted in two phases. In phase I a team of specially trained physicians conducted household surveys in which all adult residents (age > or = 25 years) were screened for hypertension. In phase II hypertensive adults identified in phase I (ie, those with systolic pressure > or = 140 mm Hg and/or diastolic pressure > or = 90 mm Hg and/or those receiving antihypertensive drug therapy) along with a randomly selected sample of normotensive control subjects were asked to participate in a more extensive evaluation. This included a detailed history and clinical examination, an electrocardiogram, an echocardiogram, laboratory studies, and skin color reflectance (on a subsample). As the first systematic, national survey of hypertension and its complications in an Arab country, NHP should provide data of great interest to the scientific, provider, and public health communities.

Early lead challenge and subsequent hypertension in Sprague-Dawley rats

OBJECTIVE

The consequences of chronic, low grade lead (Pb) burden from earlier exposure on development of hypertension (HT) and cardiovascular disease is, at best, controversial, even though many epidemiological studies suggest the possibility. Accordingly, we examined ability of a short-term Pb challenge to cause later developing HT in rats.

METHODS

We gave 12 newly weaned Sprague-Dawley rats (SD) a 1% Pb acetate solution to drink for 6 weeks, while 12 control rats drank water. The rats were further subdivided into groups consuming high and low amounts of sugar. All rats were followed for 4 months after cessation of the Pb challenge.

RESULTS

Early Pb challenge caused no significant changes in body weight (BW) from controls; however, systolic blood pressures (SBP) of rats initially receiving Pb continued to rise significantly above their respective dietary controls for months after cessation of challenge. While a high sugar diet alone was associated with elevated SBP, high sugar consumers also challenged with Pb had the highest SBP. Protein excretion did not increase, suggesting, along with other evidence, a lack of significant renal damage.

CONCLUSIONS

Previous exposure to Pb can cause subsequent chronic elevations in SBP.

Effects of high sugar diets on renal fluid, electrolyte and mineral handling in rats: relationship to blood pressure

OBJECTIVE

We examined whether sugar-induced systolic blood pressure (SBP) elevations in rats may develop, in part, through a mechanism common to salt-induced hypertension, i.e., renal retention of water and salt.

DESIGN

Spontaneously hypertensive rats (SHR) ate four diets: two high (> 50% of calories) and two low (< 12% of calories) in sugar (sucrose). SBP, various urinary parameters, and the renal angiotensin and prostaglandin systems were assessed.

RESULTS

SHR consuming diets high in sugar showed significantly decreased urinary volume and excretion of electrolytes, which coincided with increasing SBP. When low sugar diets replaced high sugar diets, SBP and urinary parameters rapidly returned to baseline. SHR received captopril while consuming high sugar diets, and both SBP and urinary parameters assumed baseline values, comparable to ones seen in SHR consuming low sugar diets. A direct angiotensin II receptor antagonist (DuPont 753) did not influence SBP. However, we found decreased PGE2 excretion in SHR consuming excess sugar.

CONCLUSIONS

Salt and water retention occur early during sugar-induced hypertension due to reduced renal excretion, consistent with some part in the pathogenesis. The effects of high sugar diets on SBP were not due to angiotensin II inhibition, however, decreased availability of vasodilatory prostaglandins may play a role in the renal events and sugar-induced hypertension in SHR.

Non-communicable diseases in the tropics

The way of life in many developing countries in the tropics is in a state of transition--from traditional to "modern", with its associated industrialisation, urbanisation and cultural readjustment. Infectious diseases are giving way to non-communicable diseases, such as cardiovascular diseases, adult onset diabetes, cancers, trauma and non-infectious respiratory diseases, as major causes of morbidity and premature mortality. The epidemiology, causality, prevention and treatment of these conditions is summarised in the context of developing countries.

A review of persistent, low-grade lead challenge: neurological and cardiovascular consequences

Although acute toxicity following heavy intake of lead (Pb) is a well-established clinical entity, the harmful effects of persistent, low-dose challenge, a situation commonly found among the general population, is uncertain. The major dangers of persistent, low-dose challenge that have been hypothesized are controversial: first, mentation and behavioral perturbations and second, development of hypertension with its consequences on the cardiovascular system. Accordingly, one cannot exclude some contributions from persistent Pb exposure to chronic disease and the aging process. Despite these potential adversities, many sources for Pb contact still remain with us. Current estimates are that 10-50% of American children (over 3-4 million) harbor unsafe levels according to present-day standards. Therefore, it is reasonable to conclude that more work is needed in this area. Clearcut evidence concerning the deleterious influence of Pb on the nervous and/or cardiovascular-renal systems would lead to greater attempt to lessen exposure, to ameliorate symptomatology by providing supplemental agents which obviate the unwanted effects of Pb (iron, calcium, zinc), and to consider therapy with binding agents, like CaNa2EDTA, in the afflicted.

Dietary intake, exercise, obesity and noncommunicable disease in rural and urban populations of three Pacific Island countries

Dietary intake surveys of rural and urban communities in three Pacific Island countries were conducted using an adjusted 24-hour dietary recall method. Dietary survey samples were drawn from noncommunicable disease surveys of Melanesians and Indians in Fiji, Micronesians in Kiribati and Melanesians in Vanuatu. Comparisons of total energy and macronutrient intakes and of obesity, hypertension, diabetes mellitus, serum cholesterol and physical activity levels revealed similar rural/urban trends. Urban subjects were more obese than rural ones, had higher prevalence rates of diabetes and hypertension, and generally had higher cholesterol levels. Rural subjects were leaner, suffered less from diabetes and hypertension, and had greater total energy intakes than urban dwellers. Rural people ate a greater proportion of carbohydrates, while urban subjects ate proportionally more protein and fat, apart from the outer Kiribati atolls with high coconut intakes. Rural subjects in all three studies had higher levels of physical activity. These studies provide persuasive evidence that exercise as well as diet has a significant effect on rural/urban differentials in obesity and noncommunicable disease, and that energy intake reflects energy expenditure.

Prevalence of diabetes, hypertension and obesity at different levels of urbanisation in Vanuatu

OBJECTIVE

To determine the prevalence of non-communicable disease, specifically hypertension, diabetes and obesity, amongst populations at different levels of urbanisation in Vanuatu, and to relate the frequency of these conditions to the modernisation of way of life.

DESIGN

A cross-sectional population-based comparative study of indicative cluster samples.

SETTING

Republic of Vanuatu (south-west Pacific). A relatively undeveloped malarious island country.

PARTICIPANTS

Adult (aged greater than or equal to 20 years) Melanesian ni-Vanuatu of both sexes. An occupation-based (civil servants) urban sample (n = 623) and area-based semi-rural (n = 349) and rural (n = 397) samples were employed. Response rates were 78%-92%.

INTERVENTIONS

Cases detected were referred for assessment and treatment by local medical staff.

MAIN OUTCOME MEASURES

Body mass index, triceps skinfold thickness, blood pressure, plasma glucose (fasting and 2 hours after 75 g glucose), plasma cholesterol and triglyceride levels.

RESULTS

Modernity scores confirmed that the three locations represented different levels of acculturation. Prevalences of non-communicable disease were relatively low compared to other Pacific Island communities and industrialised countries. These conditions were nevertheless more common in the urban sample and least common in the rural sample. Non-communicable disease correlated positively with modernity scores and negatively with physical activity scores. Obesity correlated with blood pressure in the urban sample, and there was indirect evidence (urine sodium concentration) of higher salt intake with modernisation. Mean plasma cholesterol levels were lowest in the rural group.

CONCLUSIONS

Prevalences of non-communicable disease are relatively low in Vanuatu, although rural-urban differentials are present, and likely to increase with continued development. The evidence presented is consistent with non-communicable disease being related to the modernisation of way of life; specifically: decreased exercise, obesity, and dietary change. Preventive activities should commence now.