Detection and treatment of hypertension in rural Australia

Background: The inequity of cardiac health outcomes between metropolitan and rural areas is well documented. As hypertension is a major cardiovascular risk factor, we need to have a better understanding of how well it is detected and managed rural areas. This study reports on the prevalence, detection and treatment of hypertension in rural Australia.

Method: Three population stratified surveys were undertaken in the Greater Green Triangle. Three thousand three hundred and twenty adults aged 25–74 years were randomly selected, stratified by gender and 10-year age groups. Anthropometric, clinical and self-administered questionnaire data relating to chronic disease risk were collected in accordance with the WHO MONICA protocol. Blood pressure (BP) was measured by trained nurses and the questionnaire collected information on the history of hypertension and medications used for treatment.

Results: Information on BP measurement, medication and awareness was available on 1506 (45%) participants. Study found that one-third of participants had hypertension. Only 54% (95% CI 47–60) of male and 71% (65–77) of female participants with hypertension were aware of their condition. While only half of the participants with hypertension were treated, only half of these treated participants had their hypertension under control. Treatment and control of hypertension was more common in women (60%, 54–67 and 55%, 47–64) compared with men (42%, 36–49 and 35%, 26–44).

Conclusion: Results of our study suggest that detection and treatment of hypertension in rural is suboptimal, particularly in men. If cardiovascular outcomes are to improve in rural Australia, people need to be encouraged to have their blood pressure measured regularly and better systems for the management of hypertension in primary care are needed.

Prevalence, awareness, treatment, and control of hypertension in China data from the China National Nutrition and Health Survey 2002

Background— The present article aims to provide accurate estimates of the prevalence, awareness, treatment, and control of hypertension in adults in China.

Methods and Results— Data were obtained from sphygmomanometer measurements and an administered questionnaire from 141 892 Chinese adults 18 years of age who participated in the 2002 China National Nutrition and Health Survey. In 2002, 153 million Chinese adults were hypertensive. The prevalence was higher among men than women (20% versus 17%; P<0.001) and was higher in successive age groups. Overall, the prevalence of hypertension was higher in urban compared with rural areas in men (23% versus 18%; P<0.01) and women (18% versus 16%; P<0.001). Of the 24% affected individuals who were aware of their condition, 78% were treated and 19% were adequately controlled. Despite evidence to suggest improved levels of treatment in individuals with hypertension over the past decade, compared with estimates from 1991, the ratio of controlled to treated hypertension has remained largely unchanged at 1:4.

Conclusions— One in 6 Chinese adults is hypertensive, but only one quarter are aware of their condition. Despite increased rates of blood pressure–lowering treatment, few have their hypertension effectively controlled. National hypertension programs must focus on improving awareness in the wider community, as well as treatment and control, to prevent many tens of thousands of cardiovascular-related deaths.

Dietary protein level interacts with ω-3 polyunsaturated fatty acid deficiency to induce hypertension

Background : Dietary ω-3 fatty acid deficiency can lead to hypertension in later life; however, hypertension is affected by numerous other dietary factors. We examined the effect of altering the dietary protein level on blood pressure in animals deficient or sufficient in ω-3 fatty acids.

Methods : Female rats were placed on one of four experimental diets 1 week prior to mating. Diets were either deficient (10% safflower oil; DEF) or sufficient (7% safflower oil, 3% flaxseed oil; SUF) in ω-3 fatty acids and contained 20 or 30% casein (DEF20, SUF20, DEF30, SUF30). Offspring were maintained on the maternal diet for the duration of the experiment. At 12, 18, 24, and 30 weeks, blood pressure was assessed by tail cuff plethysmography.

Results : At both 12 and 18 weeks of age, no differences in blood pressure were observed based on diet, however, by 24 weeks hypertension was evident in DEF30 animals; there were no blood pressure differences between the other groups. This hypertension in DEF30 group was increased at 30 weeks, with systolic, diastolic, and mean arterial pressure all elevated.

Conclusions : These results indicate that the hypertension previously attributed to ω-3 fatty acid deficiency is dependent on additional dietary factors, including protein content. Furthermore, this study is the first to plot the establishment of ω-3 fatty acid deficiency hypertension over time.

Studies on dietary fibre : analysis, epidemiological and physiological aspects

This thesis involves an investigation in three areas; first, a study of an enzymatic-gravimetric method for the analysis of dietary fibre; second, a survey of dietary fibre intake in an area of a developing country, and finally, some observations on the functional aspects of gel-forming dietary fibre in the rat. A simple and rapid enzymatic-gravimetric assay for both soluble and insoluble dietary fibre has been critically investigated. Reference samples were also analysed by a more comprehensive, enzymatic gas chromatographic method to allow testing of the relative accuracy of the enzymatic-gravimetric method. The enzymatic-gravimetric method was found to be highly reproducible but gave a slightly higher value for total dietary fibre than the more comprehensive method. This discrepancy is probably due to the presence of small quantities of resistant starch and protein residue which are recovered in the enzymatic-gravimetric method. In the enzymatic-gas chromatographic method, protein residue is not measured, and resistant starch is estimated, but not counted as dietary fibre. The enzymatic-gravimetric method was applied to the analysis of foods commonly consumed in the Padang region of West Sumatra in Indonesia, in order to estimate dietary fibre intake in the region. Daily intakes of usual foods were estimated by use of a 24-hour recall procedure aided by food photographs to assist in the estimation of portion size. Samples of approximately 60 of the most commonly consumed foods were collected and analysed for dietary fibre. These appear to be the first data which report values for dietary fibre in Indonesion foods and they represent a significant improvement upon the existing data on crude fibre content. Knowledge of the amounts of foods usually consumed and their dietary fibre content allowed an estimation of usual intakes of dietary fibre. Fibre intake was found to be lower than in the developing countries of Africa and was comparable to intakes measured in the U.K. This is the first study to show that in this part of South East Asia, a developing country area using polished rice as a staple food, dietary fibre intakes are as low as in Western countries. Low intakes of fibre are believed to be related to the prevalence of a range of diseases and, in this study, preliminary data on the rates of non-infective, chronic diseases were collected from the two main hospitals in West Sumatra. Chronic, non-infectious diseases such as inguinal hernia, appendicitis, haemorrhoids, diabetes mellitus, hypertension and malignant neoplasms of the rectum are relatively frequent in West Sumatra. While no firm conclusions can be drawn from these data, they do show the possibility of a relationship between low intakes of dietary fibre and the prevalence of these diseases, and suggest that further investigation is necessary. Some observations were made of the effect of gel-forming dietary fibre on stomach emptying and intestinal transit rate in the rat. Xanthan gum was added to iso-osmotic solutions to produce increased viscosity and phenol sulphonphthalein (phenol red) was used as a non-absorbable marker. Gavage feeding of solutions with a range of viscosities was used to study the effect of viscosity on the rate of stomach emptying and intestinal transit. Increased viscosity was observed to slow gastro-intestinal transit and this provides one mechanism by which dietary fibre of the gel-forming type ray improve glucose tolerance.

Alterations in renal and myocardial adrenoceptors associated with ethynyloestradiol- and levonorgestrel-induced hypertension in the rat

Hypertension is one of many side effects of oral contraceptive use in a small percentage of women. Although the underlying pathology has yet to be fully resolved, alterations in the renin-angiotensin-aldosterone axis, sympathetic nervous system/ renal and cardiac function have been implicated. In the thesis to be presented, the possible involvement of alterations in renal and myocardial adrenoceptor characteristics in the pathogenesis of steroid contraceptive-induced hypertension in rats was examined by radioligand binding techniques. In Chapter 2, a rat model of OC hypertension is described. Chronic low-dose administration of ethynyloestradiol (EE2), levonorgestrel (NG) or a combination of both steroids (EE2/NG) to female Sprague-Dawley rats was shown to significantly increase systolic blood pressure (SBP). Renal and cardiac hypertrophy developed in association with EE2-, EE2/NG- but not NG-induced hypertension. Moreover, whereas administration of NG alone attenuated body weight gain, combined EE2/NG administration increased body weight gain from the second week of treatment onwards. Based on the above observations, it is proposed that EE2 and NG induce hypertension in rats via different mechanisms. Although SBP was elevated to a similar maximum in all steroid-treated groups (+ 20 mmHg compared to controls), only with EE2 administration did SBP remain elevated for the duration of the 17 week treatment regimen. NG may therefore have a protective effect on blood pressure with long-term combined steroid contraceptive treatment. In Chapter 4, renal adrenoceptors were characterized using radioactively labelled adrenocephor antagonists. Under appropriate conditions, binding of [3H]-prazosin and [3H]-rauwolscine to membrane preparations of whole rat kidney displayed the kinetics, saturability and specificity of α1- and α2 -adrenoceptors respectively, which were present in a ratio 3:1. In contrast, [3H]-dihydroergocryptine ([3H]-DHE) apparently bound to both α1 and α2-adrenoceptors. Binding sites identified by [125I] –iodocyanopindolol (ICYP) had the recognition characteristics of β-adrenoceptors. In drug competition studies using the subtype-selective antagonists practolol (β1) and ICI 118,551 (β2)/ the ratio of β1- to β2 -adrenoceptors was found to be approximately 2:1. Subsequently, renal adrenoceptors were investigated at various stages during the development of hypertension with the different steroid contraceptive treatments (Chapters 5 and 6). Preliminary binding studies with [3H]-DHE and [3H]-prazosin suggested that the number of renal α2 - but not α1-adrenoceptors was reduced in rats with established EE2-induced hypertension (17 weeks treatment). This was subsequently confirmed using [3H]-rauwolscine, which in addition showed that the reduction in renal α2 -adrenoceptor number occurred during the developmental stage of EE2/NG~induced hypertension (6 weeks treatment) and established EE2-induced hypertension (12 weeks treatment). NG induced hypertension was unassociated with changes in renal α1- and α2-adrenoceptor characteristics. Renal β-adrenoceptor affinity was reduced in established EE2-, but not NG- or EE2/NG- induced hypertension. Moreover, the β-adrenoceptor agonist (-)-isoprenaline bound to renal β-adrenoceptors with reduced affinity following EE2 administration. Several endogenous and synthetic steroids were found to be ineffective inhibitors of [3H] –prazosin, [3H] –rauwolscine and ICYP binding excluding a direct interaction of these steroids with renal α1-, α2- and β -adrenoceptors. In Chapter 7, myocardial adrenoceptors were characterized and investigated in steroid-treated rats. In membrane preparations of whole myocardium, [3H]-prazosin binding was characteristically to α1- adrenoceptors, whereas there was a notable absence of [3H]-rauwolscine binding. Using ICYP, β-adrenoceptors were also detected, the ratio of β1- to β2~adrenoceptors being 3:1. Steroid contraceptive-induced hypertension was not associated with myocardial α1-adrenoceptor changes. Similarly, myocardial β-adrenoceptors were unchanged in established EE2-, NG- and EE2/NG-induced hypertension (12 weeks treatment). The affinity of (-)-isoprenaline for myocardial β-adrenoceptors was unaffected by EE2 aditiinistration. These studies suggest that established EE2- but not NG-induced hypertension in rats is associated with selective alterations in renal α2- and (β-adrenoceptors. These adrenoceptor changes may help to maintain elevated blood pressure by affecting the control of renal function by the sympathetic nervous system, catecholamines and several hormones which affect renin release and the transport of fluid and electrolytes in the nephron.

Dietary resistant starch interacts with non-starch polysaccharide and protein to influence colonic protein fermentation, with possible implications for colon cancer risk in humans

Resistant starch is dietary starch that passes undigested into the colon where it can have effects similar to non-starch polysaccharide (dietary fibre). The results support the potential health benefits of incorporating foods containing high levels of both resistant starch and non-starch polysaccharide, such as whole grain breads and legumes, as part of well balanced diets containing fruit, vegetables, cereals, meat/alternatives and dairy foods.