Type of obesity and blood pressure

'Get Healthy!' physical activity and healthy eating intervention for adults with intellectual disability: results from the feasibility pilot

BACKGROUND

People with intellectual disabilities (ID) experience high rates of lifestyle related morbidities, in part due to lack of access to tailored health promotion programmes. This study aimed to assess the feasibility and preliminary efficacy of a tailored healthy lifestyle intervention, Get Healthy!

METHODS

Get Healthy! is a 12-week physical activity and healthy eating programme designed to address lifestyle-related risks for adults with mild-moderate ID. The feasibility pilot was designed to assess subjective participant experience and programme feasibility across: recruitment and screening, retention, session attendance and engagement, adverse events, and practicality and reliability of outcome procedures. Exploratory programme efficacy was assessed across the following measures: anthropometry (body mass index, weight, waist circumference), cardiovascular fitness, physical strength, dietary intake, healthy literacy, and quality of life.

RESULTS

Six participants with moderate ID and two carer participants completed the feasibility trial, representing a 100% retention rate. Qualitative data indicated the programme was well received. Participants with ID attended 75% of sessions offered and displayed a high level of engagement in sessions attended (91% mean engagement score). While most data collection procedures were feasible to implement, several measures were either not feasible for our participants, or required a higher level of support to implement than was provided in the existing trial protocol. Participants with ID displayed decreases in mean waist circumference between baseline and endpoint (95% CI: - 3.20, - 0.17 cm) and some improvements in measures of cardiovascular fitness and physical strength. No changes in weight, body mass index, or objectively measured knowledge of nutrition and exercise or quality of life were detected from baseline to programme endpoint. Dietary intake results were mixed.

DISCUSSION

The Get Healthy! programme was feasible to implement and well received by participants with moderate ID and their carers. Exploratory efficacy data indicates the programme has potential to positively impact important cardiometabolic risk factors such as waist circumference, cardiovascular fitness, and physical strength. Several of the proposed data collection instruments will require modification or replacement prior to use in a sufficiently powered efficacy trial.

TRIAL REGISTRATION

ACTRN: ACTRN12618000349246. Registered March 8th 2018-retrospectively registered, https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374497 UTN: U1111-1209-3132.

Urban-rural-specific trend in prevalence of general and central obesity, and association with hypertension in Chinese adults, aged 18-65 years

BACKGROUND

China has the largest obese population in the world, and the prevalence of central obesity is increasing dramatically in China. Moreover, the rapid economic growth of China in recent decades has led to rapid urbanization in rural China. However, studies comparing the prevalence trends of different types of obesity and the association of obesity with hypertension between urban and rural areas in China are very scarce, and most studies have focused only on the difference in the prevalence of overweight and general obesity or hypertension among rural and urban populations. Therefore, the focus of this study was to examine the shifts in the overall distribution of the prevalence of different types of obesity and to estimate the risk of hypertension in different types of obesity among urban and rural adults aged 18-65 years.

METHODS

Seven iterations of the China Health and Nutrition Survey (CHNS), conducted in 1993, 1997, 2000, 2004, 2006, 2009 and 2011, were used in this study. A total of 53,636 participants aged 18-65 years were included. Obesity was classified into three types based on body mass index (BMI) and waist circumference (WC). A log-binomial model was constructed to estimate the prevalence ratio (PR) of hypertension with three types of obesity.

RESULTS

The age-standardized prevalence of central obesity only, general obesity only, and both central and general obesity increased from 15.8, 0.2 and 2.9% in 1993 to 30.3, 0.9 and 10.3% in 2011, respectively. The prevalence of central obesity only (urban vs. rural: 20.8% vs. 13.4% in 1993, 29.6% vs. 30.6% in 2011) and both central and general obesity (urban vs. rural: 3.5% vs. 2.5% in 1993, 10.0% vs. 10.6% in 2011) in rural adults exceeded that in urban adults in 2011. Participants with both central and general obesity had the highest risk for incident hypertension compared with those with normal body measurements (adjusted PR, urban: 2.30 (95% CI, 2.01-2.63), rural: 2.50 (95% CI, 2.25-2.77)).

CONCLUSIONS

Both WC and BMI should be considered measures of obesity and targeted in hypertension prevention. More attention should be paid to the incidence of central obesity in adults in rural China.

Is waist circumference ≥102/88cm better than body mass index ≥30 to predict hypertension and diabetes development regardless of gender, age group, and race/ethnicity? Meta-analysis

Between body mass index (BMI) ≥30 and waist circumference (WC) ≥102/88cm, we investigated which of the two measures is a better predictor of two of the most common chronic diseases - diabetes mellitus and hypertension while also examining differential association by gender, age group, and race/ethnicity. Meta-analysis was conducted for all longitudinal studies with at least 12months of follow-up published up to April 2015. Ratio of relative risk (rRR) and relative risk of diseases were computed and compared by baseline obesity measurement. The final sample included 23 longitudinal observation studies involving 62 study arms with 259,200 individuals. WC≥102/88cm was a better predictor than BMI≥30 for development of diabetes (rRR=0.81, 95% CI=0.68-0.96), but not for hypertension (rRR=0.92, 95% CI=0.80-1.06). Subgroup analyses showed WC≥102/88cm was a better predictor for diabetes in women than men, and for ages 60 and older than other ages. Only WC≥102/88cm, not BMI≥30, predicted development of hypertension among Hispanic/Latinos. Neither BMI≥30 nor WC≥102/88cm were significant predictors of hypertension when age group was controlled. Central obesity may be a more serious risk factor for diabetes development in women and for older ages. The predictive power of BMI≥30 or WC≥102/88cm in hypertension development should not be emphasized as either could mask the effect of age.

Evaluation of Internet-Based Interventions on Waist Circumference Reduction: A Meta-Analysis

Background

Internet-based interventions are more cost-effective than conventional interventions and can provide immediate, easy-to-access, and individually tailored support for behavior change. Waist circumference is a strong predictor of an increased risk for a host of diseases, such as hypertension, diabetes, and dyslipidemia, independent of body mass index. To date, no study has examined the effect of Internet-based lifestyle interventions on waist circumference change.

Objective

This study aimed to systematically review the effect of Internet-based interventions on waist circumference change among adults.

Methods

This meta-analysis reviewed randomized controlled trials (N=31 trials and 8442 participants) that used the Internet as a main intervention approach and reported changes in waist circumference.

Results

Internet-based interventions showed a significant reduction in waist circumference (mean change –2.99 cm, 95% CI −3.68 to −2.30, I²=93.3%) and significantly better effects on waist circumference loss (mean loss 2.38 cm, 95% CI 1.61-3.25, I²=97.2%) than minimal interventions such as information-only groups. Meta-regression results showed that baseline waist circumference, gender, and the presence of social support in the intervention were significantly associated with waist circumference reduction.

Conclusions

Internet-based interventions have a significant and promising effect on waist circumference change. Incorporating social support into an Internet-based intervention appears to be useful in reducing waist circumference. Considerable heterogeneity exists among the effects of Internet-based interventions. The design of an intervention may have a significant impact on the effectiveness of the intervention.

Central obesity and hypertension in Chinese adults: a 12-year longitudinal examination

OBJECTIVE

In Chinese adults, the trend of central obesity and its longitudinal association with hypertension, independent of general obesity, was examined.

METHODS

A 12-year longitudinal analysis was conducted using data retrieved from the China Health and Nutrition Survey. This study examined 6096 individuals (normotensive in 1997) who were followed up with in 2000, 2004, 2006, and 2009. Prevalence of hypertension in 2009 was predicted by baseline central obesity and waist circumference changes during a 12-year follow-up period along with confounding covariates using multiple logistic regressions.

RESULTS

Between 1997 and 2009, the prevalence of central obesity increased from 17.3% to 39.4% and was highest among individuals ≥60 years of age in 1997. By 2009, 26.8% of the participants developed hypertension. The odds ratio of developing hypertension during the 12-year study period for Chinese adults with central obesity at baseline was 1.79 (95% confidence interval=1.36-2.35) compared to those without central obesity, controlling for general obesity, demographics, smoking/drinking behavior, and fat intake.

CONCLUSIONS

Among Chinese adults, central obesity increases the risk for developing hypertension later in life, even after controlling for general obesity, smoking, drinking, and high fat intake among other factors. Waist circumference should be targeted in the efforts of hypertension prevention.

Pathogenic obesity and nutraceuticals

Over a decade of intense research in the field of obesity has led to the knowledge that chronic, excessive adipose tissue expansion leads to an increase in the risk for CVD, type 2 diabetes mellitus and cancer. This is primarily thought to stem from the low-grade, systemic inflammatory response syndrome that characterises adipose tissue in obesity, and this itself is thought to arise from the complex interplay of factors including metabolic endotoxaemia, increased plasma NEFA, hypertrophic adipocytes and localised hypoxia. Plasma concentrations of vitamins and antioxidants are lower in obese individuals than in the non-obese, which is hypothesised to negatively affect the development of inflammation and disease in obesity. This paper provides a review of the current literature investigating the potential of nutraceuticals to ameliorate the development of oxidative stress and inflammation in obesity, thereby limiting the onset of obesity complications. Research has found nutraceuticals able to positively modulate the activity of adipocyte cell lines and further positive effects have been found in other aspects of pathogenic obesity. While their ability to affect weight loss is still controversial, it is clear that they have a great potential to reverse the development of overweight and obesity-related comorbidities; this, however, still requires much research especially that utilising well-structured randomised controlled trials.

Abdominal obesity and the metabolic syndrome: contribution to global cardiometabolic risk

There is currently substantial confusion between the conceptual definition of the metabolic syndrome and the clinical screening parameters and cut-off values proposed by various organizations (NCEP-ATP III, IDF, WHO, etc) to identify individuals with the metabolic syndrome. Although it is clear that in vivo insulin resistance is a key abnormality associated with an atherogenic, prothrombotic, and inflammatory profile which has been named by some the "metabolic syndrome" or by others "syndrome X" or "insulin resistance syndrome", it is more and more recognized that the most prevalent form of this constellation of metabolic abnormalities linked to insulin resistance is found in patients with abdominal obesity, especially with an excess of intra-abdominal or visceral adipose tissue. We have previously proposed that visceral obesity may represent a clinical intermediate phenotype reflecting the relative inability of subcutaneous adipose tissue to act as a protective metabolic sink for the clearance and storage of the extra energy derived from dietary triglycerides, leading to ectopic fat deposition in visceral adipose depots, skeletal muscle, liver, heart, etc. Thus, visceral obesity may partly be a marker of a dysmetabolic state and partly a cause of the metabolic syndrome. Although waist circumference is a better marker of abdominal fat accumulation than the body mass index, an elevated waistline alone is not sufficient to diagnose visceral obesity and we have proposed that an elevated fasting triglyceride concentration could represent, when waist circumference is increased, a simple clinical marker of excess visceral/ectopic fat. Finally, a clinical diagnosis of visceral obesity, insulin resistance, or of the metabolic syndrome is not sufficient to assess global risk of cardiovascular disease. To achieve this goal, physicians should first pay attention to the classical risk factors while also considering the additional risk resulting from the presence of abdominal obesity and the metabolic syndrome, such global risk being defined as cardiometabolic risk.

Association between body composition and blood pressure in a contemporary cohort of 9-year-old children

Elevated blood pressure (BP) in children is an early risk factor for cardiovascular disease and is positively associated with body mass index (BMI). However, BMI does not distinguish between fat and lean masses, and the relationship of BP in children to different elements of body composition is not well established. BP, BMI and body composition were measured in 6863 children enrolled in the Avon Longitudinal Study of Parents and Children. Fat mass, lean mass and trunk fat were assessed using dual-energy X-ray absorptiometry. After full adjustment for confounders, total body fat and BMI were positively associated with systolic blood pressure (SBP) (beta=3.29, 95% confidence interval CI 3.02, 3.57 mm Hg/standard deviation (s.d.) and beta=3.97, 95% CI 3.73, 4.21 mm Hg/s.d., respectively) and diastolic blood pressure (DBP) (beta=1.26, 95% CI 1.05, 1.46 mm Hg/s.d. and beta=1.37, 95% CI 1.19, 1.54 mm Hg/s.d., respectively). SBP was also positively associated with lean mass (beta=3.38, 95% CI 2.95, 3.81 mm Hg/s.d.), and weakly associated with trunk fat (beta=1.42, 95% CI -0.06, 2.90 mm Hg/s.d., independent of total fat mass), which was robust in girls only. The association between lean mass and SBP remained even after accounting for fat mass. SBP in 9-year-old children is independently associated with fat mass and lean mass and, to a lesser extent, trunk fat in girls. In this analysis, because both fat and lean masses are associated with BP, BMI predicts BP at least as well as these components of body composition.

Contributions of the sympathetic nervous system, glutathione, body mass and gender to blood pressure increase with normal aging: influence of heredity

Body mass and sympathetic activity increase with aging and might underlie blood pressure (BP) elevation. Increased body mass index (BMI) may elevate BP by increasing sympathetic activity. Glutathione (GSH) can decrease BP, and declines with aging. We measured systolic (SBP) and diastolic BP, BMI, plasma (NE(pl)) and urine norepinephrine (NEu), and plasma GSH in n=204 twins across the age spectrum. BP correlated directly with BMI, NEpl, and NEu, but inversely with GSH. Age correlated with BP, BMI, NEpl, and NEu. BP, BMI, NEpl, and NEu were higher in older subjects than younger subjects, whereas GSH was lower with aging. In older subjects with high (above median) NEpl, SBP was 8 mmHg higher than in those of comparable age with low NE. In younger subjects with high GSH, BP was significantly lower than in younger subjects having low GSH. NEu was significantly reduced in young high-BMI subjects vs young low-BMI subjects. The heritability (h2) of NEpl, NEu, and GSH ranged from approximately 50 to approximately 70%, and these biochemical quantities were considerably more heritable than BP. We conclude that increases in sympathetic activity contribute to aging-induced SBP elevations, especially in older females. GSH reductions apparently participate in aging-induced BP elevations, most strongly in males. BMI increases contribute to BP elevations, particularly in younger subjects. BMI elevations apparently raise BP mainly by peripheral mechanisms, with generally little sympathetic activation. Substantial h(2) for plasma GSH, NE, and urine NE suggests that such traits may be useful 'intermediate phenotypes' in the search for genetic determinants of BP.

Impact of Waist Circumference on the Relationship Between Blood Pressure and Insulin

Hyperinsulinemia has been suggested to be involved in the etiology of obesity-associated hypertension. The objective of the present study was to quantify, in a population-based study, the respective contributions of excess adiposity (body mass index [BMI]), waist circumference (WC), fasting insulin levels, and insulin sensitivity to the variation of resting blood pressure. The Quebec Health Survey was used to obtain fasting plasma insulin and glucose levels and resting blood pressure as well as anthropometric measurements in a representative sample of 907 men and 937 women. When the sample was divided into tertiles of BMI and further stratified on the basis of the 50th percentile of WC (88 cm in men), nonobese men in the first BMI tertile (<23.2 kg/m 2 ) but with abdominal obesity were characterized by an increased systolic blood pressure (SBP) compared with nonobese men with low WC (130±18 versus 120±11 mm Hg; mean±SD; P =0.075). The SBP was comparable to SBP values measured among men in the top BMI tertile (129±14 mm Hg for BMI ≥26.6 kg/m 2 ). When subjects were classified into tertiles of fasting insulin and WC, no association between insulin levels and blood pressure was noted, once the variation in WC was considered. Insulin sensitivity (estimated with homeostasis model assessment [HOMA]) did not explain variation in blood pressure in men, whereas the contribution of HOMA in women was of marginal clinical significance ( R 2 of <1.3%; P <0.0001). These results suggest that the documented association between obesity, fasting insulin, insulin sensitivity, and blood pressure is largely explained by concomitant variation in WC.

Hyperinsulinemia for the development of hypertension: data from the Hawaii-Los Angeles-Hiroshima Study

The present study was to assess the association of metabolic factors including hyperinsulinemia, with the development of hypertension in Japanese-Americans. One hundred forty normotensive (<140/90 mmHg) subjects aged 40 to 69 years old from the Hawaii-Los Angeles-Hiroshima study were followed for 15 years. Patients with cardiovascular disease were excluded. Body mass index (BMI), blood pressure (BP), serum total cholesterol (TC), triglycerides (TG), uric acid (UA), and glucose and insulin responses at baseline, 1 h, and 2 h after a glucose load were analyzed. Seventeen subjects became hypertensive (systolic BP > or = 160 mmHg, diastolic BP > or = 95 mmHg, or received drug treatment) during follow-up. Age- and sex-adjusted BMI, BP, serum UA, TG, insulin, and changes in fasting glucose during follow-up were higher in subjects who later became hypertensive than in those who did not. There was no difference in the change in BMI. Age- and sex-adjusted relative risks for the development of hypertension by quartiles of BMI, serum UA, TG, and the sum of insulin values (sigmainsulin) during a glucose load were highest in highest quartile of the distribution. When age, sex, systolic BP, BMI, serum UA, TC, TG, fasting glucose, sigmainsulin, and the change in BMI were used in a proportional hazard analysis, hyperinsulinemia, hyperuricemia, and systolic BP were found to be significant risk factors for hypertension. In conclusion, hyperinsulinemia, as well as obesity, hyperuricemia, and hypertriglyceridemia were associated with hypertension in Japanese-Americans. Hyperinsulinemia and hyperuricemia were independent predictors of the development of hypertension.

The relationship between heart rate variability and measures of body habitus

There is a well-recognized relationship between autonomic nervous system function and body habitus although few studies have addressed the role of the parasympathetic nervous system. A decrease in parasympathetic nervous-system-mediated heart rate variability in obesity may in part explain the mortality and morbidity that are associated with the obese state. We used multiple linear regression techniques to explore the relationship between measures of heart rate variability and anthropometric indices in 597 male participants in the Normative Aging Study. After adjustment for age and log10 heart rate, weight and body mass index were significant predictors of both the expiratory to inspiratory ratio (E/I ratio) and the difference between maximum and minimum heart rate (HRMax-Min). The abdomen-to-hip ratio and percentage body fat were not significant predictors of measures of heart rate variability. A one standard deviation change in the anthropometric index (weight, body mass index) resulted in a decrease in the E/I ratio of 0.010-0.014 and a decrease in the HRMax-Min of 0.486-0.715 beats/min. A change in the anthropometric index across the distribution (5-95 percentile) resulted in a decrease in the E/I ratio of 0.032-0.037 and a decrease in the HRMax-Min of 1.56-2.39 beats/min. These results indicate that heart rate variability and overall body size are correlated. This association could in part explain the mortality and morbidity that is associated with the obese state.

Hemodynamic and renal responses to chronic hyperinsulinemia in obese, insulin-resistant dogs

We previously reported that chronic hyperinsulinemia does not cause hypertension in normal insulin-sensitive dogs. However, resistance to the metabolic and vasodilator effects of insulin may be a prerequisite for hyperinsulinemia to elevate blood pressure. The present study tested this hypothesis by comparing the control of systemic hemodynamics and renal function during chronic hyperinsulinemia in instrumented normal conscious dogs (n = 6) and in dogs made obese and insulin resistant by feeding them a high-fat diet for 6 weeks (n = 6). After 6 weeks of the high-fat diet, body weight increased from 24.0 +/- 1.2 to 40.9 +/- 1.2 kg, arterial pressure rose from 83 +/- 5 to 106 +/- 4 mm Hg, and cardiac output rose from 2.98 +/- 0.29 to 5.27 +/- 0.54 L/min. Insulin sensitivity, assessed by fasting hyperinsulinemia and by the hyperinsulinemic euglycemic clamp technique, was markedly reduced in obese dogs. Insulin infusion (1.0 mU/kg per minute for 7 days) in obese dogs elevated plasma insulin from 42 +/- 12 microU/mL to 95 to 219 microU/mL but failed to increase arterial pressure, which averaged 106 +/- 4 mm Hg during control and 102 +/- 4 mm Hg during 7 days of insulin infusion. Hyperinsulinemia for 7 days in obese dogs elevated heart rate from 116 +/- 8 to 135 +/- 7 beats per minute but caused no significant changes in cardiac output, in contrast to normal dogs (n = 6), in which marked increases in cardiac output (31 +/- 5% after 7 days) and decreases in total peripheral resistance occurred during chronic insulin infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Body weight and fat cell size in young men with mild blood pressure elevation

The aim of the study was to assess the relationship between body fat distribution and blood pressure. Forty-four men, aged 19-22 years, with mild blood pressure elevation (MBPE) and 29 normotensive controls (NC) were investigated. Body fat distribution was assessed by calculating fat cell size in biopsy samples of adipose tissue from different subcutaneous depots. The subjects in MBPE group were heavier than those in NC group (79.7 +/- 2.7 and 71.5 +/- 1.6 kg, p < 0.05). Total body fat was also significantly higher in the MBPE group (12.5 +/- 1.6 and 8.1 +/- 1.3 kg, p < 0.05) but not the lean body cell mass (36.8 +/- 1.1 and 34.7 +/- 0.9 kg, n.s.). Fat cell size (microgram/cell) in the lower abdominal area were significantly bigger in MBPE than in NC (respectively 40.9 +/- 4.4 and 28.0 +/- 3.1, p < 0.05). The same differences applied for fat cell size in the upper abdominal (respectively 43.1 +/- 3.0 and 26.8 +/- 3.0, p < 0.001) and averaged abdominal areas (respectively 40.1 +/- 3.4 and 26.8 +/- 2.8; p < 0.05). Fat cell size in gluteal, femoral and averaged gluteofemoral areas did not differ between MBPE and NC. Therefore, the abdominal/gluteofemoral ratio was significantly higher in MBPE than in NC (respectively 1.1 +/- 0.1 and 0.7 +/- 0.1; p < 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance in hypertension: a focused review

The associations between insulin resistance, hyperinsulinemia, and hypertension are well recognized. The insulin resistance and hyperinsulinemia associated with hypertension is the result of increased renal tubular sodium reabsorption, increased sympathetic nervous system activity, and increased arterial wall smooth muscle reactivity. In insulin resistant states, intracellular calcium and sodium accumulation is thought to be the fundamental underlying abnormality. These is evidence that hyperinsulinemia is an independent risk factor for coronary artery disease. Therefore, therapeutic considerations in patients with insulin resistance should include nonpharmacologic methods for increasing insulin sensitivity as well as avoiding the deleterious effects on insulin action and lipid metabolism of various antihypertensive medications. Of the currently available antihypertensives therapies, the angiotensin-converting enzyme inhibitors, the alpha antagonists, and the calcium channel blockers are the most rational choices for treating patients with hypertension with evidence of coexisting insulin resistance.

Obesity-induced hypertension. Renal function and systemic hemodynamics

This study examined the control of renal hemodynamics and tubular function, as well as systemic hemodynamics, during obesity-induced hypertension in chronically instrumented conscious dogs. Mean arterial pressure, cardiac output, and heart rate were monitored 24 hours a day using computerized methods, water and electrolyte balances were measured daily, and renal hemodynamics were measured each week during the control period and 5 weeks of a high-fat diet. After 7 to 10 days of control measurements, 0.5 to 0.9 kg of cooked beef fat was added to the regular diet, and sodium intake was maintained constant at 76 mmol/d throughout the study. After 5 weeks of the high-fat diet, body weight increased from 24.0 +/- 1.0 to 35.9 +/- 4.9 kg, mean arterial pressure increased from 83 +/- 5 to 100 +/- 4 mm Hg, cardiac output increased from 2.86 +/- 0.27 to 4.45 +/- 0.55 L/min, and heart rate rose from 68 +/- 5 to 107 +/- 9 beats per minute. Associated with the hypertension was an increase in cumulative sodium balance to 507 +/- 107 mmol after 35 days and a rise in sodium iothalamate space, an index of extracellular fluid volume, to 131 +/- 4% of control. Sodium retention was due to increased tubular reabsorption, because glomerular filtration rate and effective renal plasma flow increased throughout the 5 weeks of the high-fat diet, averaging 135 +/- 4% and 149 +/- 19% of control, respectively, during the fifth week of the high-fat diet.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of diet in the genesis and treatment of hypertension

In this brief review, we have not been able to address all of the various dietary factors which have been implicated as causal in hypertension. Because of the heterogeneity of hypertension, it is quite difficult to find a simple answer to the question of how important dietary factors are in causing hypertension and even more difficult to answer the question of how diet should be therapeutically altered in treating a hypertensive patient. Given the difficulties in achieving good compliance to almost any dietary prescription and the lifestyle changes these therapies often require, significant benefit must be demonstrated to justify the efforts. It is worth emphasizing that many of the dietary alterations which have been proposed for treating hypertension have even better established preventative health rationales which justify their use. Although salt intake is a factor in the genesis of hypertension, the effectiveness of salt restriction varies between patients. Despite the absence of good predictors of response, moderate sodium reduction is a reasonable first step when dealing with a hypertensive patient. In obese hypertensive patients, weight loss provides a modest but significant BP reduction. Added benefit may be obtained by lowering total fat content and increasing the ratio of polyunsaturated to saturated fats. The reduction in cardiovascular risk with these changes in dietary fat, over and above the lowering of BP, make this approach appropriate in all hypertensive patients. Potassium supplementation, while sometimes effective, is more difficult to recommend broadly. Calcium supplementation is certainly reasonable in women, for whom such therapy should be seen as good dietary advice for the prevention of osteoporosis. Moderate alcohol intake probably has little deleterious effect, whereas heavy alcoholism does contribute to increased BP. Again, reduction of alcohol intake is important for reasons other than the modest BP reduction attained.

Obesity, hyperlipidemia and non-insulin-dependent diabetes: a unified theory

Obesity, hyperlipidemia, and non-insulin-dependent diabetes seem to share common causative factors, chemical abnormalities, and clinical complications. A positive energy balance requiring storage of excess nutrients as triglyceride appears to be an underlying factor in all. It is postulated that everyone has a defined capacity to store triglyceride. Filling the storage space from plasma glucose and triglyceride is insulin dependent. When storage areas are full, the effectiveness of insulin is reduced, and excess nutrients stay in circulation, producing the clinical picture of hyperlipidemia, non-insulin-dependent diabetes, and the shared findings. Comments about the implications of the model for the treatment of hypercholesterolemia, hypertriglyceridemia, and non-insulin-dependent diabetes are also incorporated.

Insulin resistance, hyperinsulinemia, dyslipidemia, hypertension, and accelerated atherosclerosis

Hypertension is only one component of a multifaceted metabolic-hemodynamic complex that also includes obesity, subtle and overt glucose intolerance, dyslipidemia, enhanced vascular resistance and accelerated atherosclerosis. Results of a number of studies in the past 5 years have shown that even nonobese, nondiabetic individuals with hypertension display insulin resistance, which is located in peripheral tissues (primarily skeletal muscle), is limited to nonoxidative pathways of glucose disposal, and appears to be directly correlated with the severity of hypertension. Insulin resistance and associated hyperinsulinemia in hypertensive individuals are also associated with increased plasma triglyceride levels and decreased high-density lipoprotein concentrations, which likely contributes to enhanced atherosclerosis. Hyperinsulinemia may directly promote atherosclerosis by enhancing LDL-cholesterol accumulation in vessel walls, vascular smooth muscle migration, and proliferation, augmenting connective tissue synthesis in the vascular wall, and decreasing the regression of lipid plaques. The enhanced peripheral vascular resistance that characterizes insulin resistance/hyperinsulinemic states may be related to decreased vascular smooth muscle responses to insulin, which normally modulates (attenuates) vascular contractile responses to vasoactive agents.

Relation of central hemodynamics to obesity and body fat distribution

Central obesity increases the risk for cardiovascular disease, but little is known about its hemodynamic effects. The aims were to investigate the influence of obesity (as defined by body mass index) and abdominal fat accumulation (as defined by the waist/hip ratio) on hemodynamics at rest and during mental stress. Invasive hemodynamic studies were performed in 20 healthy, normotensive young men (aged 18-22 years) recruited from an unbiased population sample. Their body mass index and waist/hip ratio ranged between 18.5 and 30.2 (mean 24.1) and 0.77 and 0.98 (mean 0.87), respectively. Hemodynamics were related to the two anthropometric indexes by bivariate regression analyses. Cardiac output and stroke volume were positively correlated to body mass index (p = 0.05 and p = 0.005), but inversely to waist/hip ratio (p = 0.01 and p = 0.01). Mental stress augmented the hemodynamic patterns. Total peripheral resistance during stress correlated inversely to body mass index (p = 0.02), whereas high waist/hip ratio was associated with higher systemic vascular resistance p = 0.002). The delta CO/delta MAP ratio, i.e., relative contribution of cardiac output for the stress-induced increase in mean arterial pressure, showed a strong positive association with body mass index (p = 0.004), but was inversely related to the waist/hip ratio (p = 0.002). Serum insulin correlated significantly to the stress-induced change in total peripheral resistance (r = 0.54; p = 0.02), whereas the increase in cardiac output was inversely related to insulin (r = -0.59; p = 0.007). Thus, central obesity is associated with a specific hemodynamic pattern characterized by higher total peripheral resistance, lower cardiac output, and a vasoconstrictor response to psychosocial stress.

Diabetes mellitus and hypertension

Diabetes mellitus and hypertension are common diseases that coexist at a greater frequency than chance alone would predict. Hypertension in the diabetic individual markedly increases the risk and accelerates the course of cardiac disease, peripheral vascular disease, stroke, retinopathy, and nephropathy. Our understanding of the factors that markedly increase the frequency of hypertension in the diabetic individual remains incomplete. Diabetic nephropathy is an important factor involved in the development of hypertension in diabetics, particularly type I patients. However, the etiology of hypertension in the majority of diabetic patients cannot be explained by underlying renal disease and remains "essential" in nature. The hallmark of hypertension in type I and type II diabetics appears to be increased peripheral vascular resistance. Increased exchangeable sodium may also play a role in the pathogenesis of blood pressure in diabetics. There is increasing evidence that insulin resistance/hyperinsulinemia may play a key role in the pathogenesis of hypertension in both subtle and overt abnormalities of carbohydrate metabolism. Population studies suggest that elevated insulin levels, which often occurs in type II diabetes mellitus, is an independent risk factor for cardiovascular disease. Other cardiovascular risk factors in diabetic individuals include abnormalities of lipid metabolism, platelet function, and clotting factors. The goal of antihypertensive therapy in the patient with coexistent diabetes is to reduce the inordinate cardiovascular risk as well as lowering blood pressure.

Sex-dependence of body fat distribution in patients with obesity and hypertension

The relationship of body fat distribution with blood pressure, fat cell weight and extracellular fluid volume was studied and compared in 20 obese hypertensive men and 20 obese hypertensive women of similar age, degree of overweight and blood pressure level. Body fat distribution, as reflected by the ratio between waist and hip circumference (W/H ratio), was significantly higher in male than in female obese patients. The W/H ratio was positively and independently correlated with systolic arterial pressure both in males and females. However, for the same W/H ratio, systolic arterial pressure was higher in females. The W/H ratio was positively correlated with gluteal fat cell weight only in males and not in females. Both in males and females, the W/H ratio was positively correlated with extracellular fluid volume, independently of the level of blood pressure level and/or the degree of obesity. The study provided evidence that the relationship between body weight and blood pressure in obese hypertensives is affected by the sex-dependence of body fat distribution with possible interferences on fat cell weight and extracellular fluid volume. Several epidemiological studies have emphasized the positive correlation observed between body weight and blood pressure in many. Many investigations have documented the association of blood pressure with body weight, weight to height, overweight or other indices of fatness such as skinfold thickness. However, the correlation coefficients of these different relationships were found constantly small, indicating that the relationship between overweight and blood pressure is somewhat complex. In patients with hypertension, body weight was shown to be strongly related with the levels of both blood pressure and extracellular fluid volume. On the other hand, patients with overweight and hypertension were found to be principally affected by hypertrophic obesity, as shown by the evaluation of fat cell weight. However these findings were exclusively observed in males. No solid data were reported in females. The relationships between body weight and extracellular fluid on one hand, and between body weight and fat cell weight on the other hand, are certainly different in males and in females. First, in females, extracellular fluid volume is submitted to cyclic changes in sodium balance involving the effect of sex steroid hormones. Second, body fat distribution, a parameter which is weakly correlated to blood pressure, is different in males and females. In males, body fat predominates in the upper part of the body while, in females, adiposity is mainly observed in the lower part of the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Mineral homeostasis in obesity: effects of euglycemic hyperinsulinemia

We explored the effects of insulin on mineral homeostasis in five lean and six moderately obese nondiabetic premenopausal women. Serum and urine minerals were measured before and during the steady-state phase of a euglycemic insulin clamp. Each subject participated in two insulin clamp studies on separate days at insulin infusion rates of 10 and 40 mU/m2/min. Euglycemic hyperinsulinemia was associated with (1) a significant increase in urinary calcium excretion when expressed per minute with no change in total serum calcium; (2) a decrease in urine and serum phosphate; (3) a decrease in serum potassium with no change in urine potassium; and (4) no measurable effects on urine or serum sodium. At any given insulin level, the obese individuals excreted significantly more calcium, phosphate, and potassium per minute than lean controls. While insulin administration had no effect on serum parathyroid hormone (PTH) or vitamin D levels, baseline serum 1,25(OH)2D concentration was significantly higher and serum ultrafilterable calcium was significantly lower in obese subjects than in lean controls.

Close correlation of intra-abdominal fat accumulation to hypertension in obese women

The relation between intra-abdominal visceral fat accumulation and blood pressure was investigated in 67 obese women (mean body mass index, 33.6 +/- 3.1; average age, 50 +/- 11 years). As an index of intra-abdominal fat accumulation, the ratio of the intra-abdominal visceral fat area to subcutaneous fat area was determined using a computed tomographic section at the level of the umbilicus. When the obese subjects were divided into a hypertensive group and a normotensive group, the ratio of the intra-abdominal visceral fat area to subcutaneous fat area in the hypertensive group was significantly higher (0.53 +/- 0.33 versus 0.29 +/- 0.12, p less than 0.01). Significant correlations between the ratio of intra-abdominal visceral fat area to subcutaneous fat area and systolic blood pressure (r = 0.62, p less than 0.001) and diastolic blood pressure (r = 0.53, p less than 0.001) also were found. However, no significant difference existed in either the body mass index or the waist-to-hip circumference ratio between the hypertensive and normotensive groups. Plasma renin activity, aldosterone, epinephrine, and norepinephrine levels were not significantly different between the two groups. Moreover, the correlation between the ratio of the intra-abdominal visceral fat area to subcutaneous fat area ratio and blood pressure was found independent of age and body mass index by multiple regression analyses. We conclude that intra-abdominal fat accumulation itself may play an important role in the pathogenesis of hypertension in obesity.

Chronic hyperinsulinemia and blood pressure. Interaction with catecholamines?

Although hyperinsulinemia and increased adrenergic activity have been postulated to be important factors in obesity-associated hypertension, a cause and effect relation between insulin, catecholamines, and hypertension has not been established. The aim of this study was to determine whether chronic hyperinsulinemia, comparable with that found in obese hypertensive patients, causes hypertension in normal dogs, increases plasma catecholamines, or potentiates the blood pressure effects of norepinephrine. In six normal dogs, insulin infusion (1.0 milliunits/kg/min) for 7 days, with euglycemia maintained, increased fasting insulin fourfold to sixfold. However, mean arterial pressure did not increase, averaging 99 +/- 2 mm Hg during the control period and 91 +/- 3 mm Hg during the 7 days of insulin infusion. Insulin did not alter plasma norepinephrine or epinephrine, which averaged 171 +/- 27 and 71 +/- 14 pg/ml, respectively, during the control period and 188 +/- 29 and 45 +/- 12 pg/ml during the 7 days of insulin infusion. In six dogs, norepinephrine was infused (0.2 microgram/kg/min) for 7 days to raise plasma norepinephrine to 2,940 +/- 103 pg/ml. Insulin infusion (1.0 milliunits/kg/min) for 7 days during simultaneous infusion of norepinephrine did not further increase mean arterial pressure, which averaged 101 +/- 3 during norepinephrine and 98 +/- 2 mm Hg during insulin plus norepinephrine infusion. Thus, chronic hyperinsulinemia did not increase mean arterial pressure or plasma catecholamines and did not potentiate the blood pressure actions of norepinephrine. These observations provide no evidence that chronic hyperinsulinemia or interactions between insulin and plasma catecholamines cause hypertension in normal dogs.

Body fat and its distribution in relation to casual and ambulatory blood pressure

This study was undertaken to evaluate the associations of body fat and its distribution with casual and ambulatory blood pressure in nonobese men. One hundred and thirty-five normotensive or mildly hypertensive (but untreated) men employed at three work sites were studied. Casual blood pressure was measured at the work site at initial screening and on a second occasion by a nurse. Ambulatory blood pressure was measured noninvasively for 24 hours on a workday and analyzed as work, home, and sleep blood pressure measurements. Anthropometric measurements included height, weight, and waist and hip circumferences. Blood pressure was highest while at work; home blood pressure was higher than screening blood pressure or nurse blood pressure, and sleep blood pressure was lowest. Weight and both waist and hip circumferences (but not their ratio) were all significantly correlated with screening, nurse, and sleep blood pressures but not with work or home blood pressures. Stepwise regression analysis showed that waist circumference was the best overall predictor of blood pressure. We suggest that in situations where blood pressure is the dependent variable, correlations with other variables may be closest for "basal" measures of blood pressure and may be obscured by the effects of daily activities on blood pressure.

Obesity, hypertension and stroke

Central fat distribution may be more closely associated with stroke risk than relative weight or body mass index, although both are associated with hypertension. Some of this association may reflect the fact that central obesity reflects adult weight gain, which may be more relevant to stroke risk than weight in old age. Three attributes associated with central obesity, hypertension and stroke risk deserve further exploration as a possible explanatory variables for the central obesity-stroke risk association. They are cigarette smoking, heavy alcohol intake and diabetes. Prevention of smoking and excess alcohol intake would be consistent with general public health guidelines and might be more relevant to stroke prevention than caloric reduction and management of general overweight.

Relationship of fat mass and fat distribution to blood pressure

The relationship of fat mass, lean body mass (LBM), and fat distribution to blood pressure was examined in Japanese adult men and women. Percent body fat was estimated using two skinfold thicknesses, and fat mass and LBM were then calculated. Correlation coefficients showed that fat mass, fat distribution, and age were weakly associated with blood pressure levels, and that the correlation coefficients of LBM to blood pressure levels were nearly zero. Stepwise regression analysis revealed that fat mass and age contributed significantly to the variations in blood pressure levels. In addition, only in the case of men, trunk-extremity skinfolds ratio was also entered into the model for diastolic and mean arterial blood pressure. It thus has been concluded that fat mass may be the more predictive determinant of blood pressure level than LBM in the Japanese population, and that the independent correlation of fat distribution to blood pressure is rather small.

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

A cross-sectional interpopulation analysis of blood pressure and its determinants was conducted with the data collected during epidemiologic surveys in 11 Pacific island populations from 1975 to 1981. In each of these populations, the mean arterial blood pressure increased with age; the overall blood pressure levels differed among the populations. The multivariate analyses suggest that dietary factors that result in differences in body mass, plasma cholesterol, and glucose intolerance contribute considerably to interpopulation differences in blood pressure. The impact of these differences in effects of dietary factors on interpopulation blood pressure seemed to be uniform, even though the overall levels of each of these three variables differed significantly among the populations. This study of blood pressure data, accrued from 6224 men and 7029 women aged 20-79 years, supports the hypothesis that dietary factors strongly contribute to high blood pressure as well as to interpopulation differences in the prevalence of hypertension. We propose using these data in planning programs for prevention and control of hypertension in the Pacific countries.

The enigma of insulin resistance and hypertension. Insulin resistance, blood pressure, and the circulation

The epidemiologic link between obesity and hypertension is more clearly emerging to be one between insulin resistance and hypertension. Relative insulin resistance occurs not only in obese hypertensive patients but also in non-obese lean essential hypertensive patients. Although insulin has complex actions on the circulation, plausible mechanisms by which insulin might raise blood pressure include renal sodium retention and stimulation of the sympathetic nervous system. However, the evidence that insulin can actually raise blood pressure in the long-term is lacking. Since hypertension does not develop in all obese or insulin-resistant subjects, the relationship must be modulated by other genetic or environmental factors. Obesity, diminished physical conditioning, aging, and diabetes are ubiquitous contributors to relative insulin resistance and all are associated with a tendency for blood pressure to rise. Conditions and agents associated with acquired insulin resistance and secondary forms of hypertension include pregnancy, oral contraceptives, acromegaly, and glucocorticoids. Although type 2 non-insulin-dependent diabetes is a state of increased insulin resistance, hypertension is partly sustained by secondary renal mechanisms. Future research should identify the genetic and environmental determinants of insulin resistance in hypertension and utilize these in therapy.

Incidence and precursors of hypertension in young adults: the Framingham Offspring Study

The occurrence of hypertension and its precursors is examined in the Framingham Offspring Study of 2,027 men and 2,267 women ages 20-49 years followed for 8 years. The age-specific prevalence of hypertension was similar at both the first (1971-1975) and the second (1979-1983) examination for both men and women. Prevalence rates were higher among men than among women, and there was a higher rate of hypertension treatment at the second exam, particularly among women, 75% of whom reported being treated for hypertension. The incidence of hypertension in participants free from hypertension at the first examination increased threefold from the second to the fifth age decades in men and eight-fold in women. Under age 40, men were twice as likely as women to develop hypertension, but after age 40, 8-year incidence rates were similar in men (14.2%) and women (12.9%). Adiposity, relative weight, heart rate, alcohol intake, hematocrit, blood sugar, serum protein, triglyceride, and phosphorous were all related to hypertension occurrence in one or both sexes, controlling for age. In multivariate analysis, adiposity (P less than 0.01), heart rate (P less than 0.01), and triglyceride (P less than 0.05) were all significant independent predictors of hypertension in men. In women, adiposity (P less than 0.001), heart rate (P less than 0.01), hematocrit (P less than 0.05), and alcohol consumption (P less than 0.05) were independent contributors. When controlling for blood pressure measured at the first examination, the best single predictor of hypertension incidence, the multivariate assessment changed very little. Adiposity stands out as a major controllable contributor to hypertension. Changes in body fat over 8 years were related to changes in both systolic and diastolic blood pressure. Markedly obese women in their fourth decade were seven times more likely to develop hypertension than were lean women of the same age. Weight control deserves a high priority in efforts to prevent hypertension in the general population.

Insulin as a potential factor influencing blood pressure in amputees

War-injured, bilateral above-knee amputees are known to be at increased risk for cardiovascular mortality. To evaluate possible risk factors, we compared blood pressures and plasma glucose and insulin responses to orally administered glucose in 19 above-knee amputees from the Vietnam War (mean age, 36 +/- 1 years) with those of 12 age-matched unilateral below-elbow amputees. Body composition by densitometry and maximal oxygen consumption during arm or leg exercise were also determined. Nine of 19 leg amputees were hypertensive compared with one of 12 arm amputees. Their 3-hour average insulin responses were markedly increased (260 +/- 60 microU/ml) compared with those of normotensive leg (125 +/- 24 microU/ml) and arm amputees (101 +/- 20 microU/ml), and their mean body fat content (37.2%) also was elevated compared with that in both of these groups (23.2 and 22.6%, respectively). A unique finding was that both insulin response and body fat content were strongly and independently correlated with diastolic blood pressure (r = 0.55, p less than 0.01, and r = 0.62, p less than 0.01, respectively). We conclude that insulin may be a major factor in blood pressure regulation in the maturity-onset obesity that develops following traumatic leg amputation in young, healthy men.

Insulin and blood pressure in obesity

To assess factors in overweight persons that account for a tendency toward hypertension, 33 very obese women, 26 to 77 years of age, were studied. Blood pressures in these 33 women varied from low normal to mildly hypertensive. None of them had taken medication for high blood pressure, and none had diabetes mellitus. The effect of independent variables--age, body mass index (weight/height2), fasting serum glucose levels, fasting serum insulin levels, and 24-hour urinary sodium excretion--on systolic and diastolic blood pressure was assessed. There was no correlation between sodium excretion and blood pressure. Age did not correlate with diastolic blood pressure but did correlate with systolic blood pressure when body mass index, serum glucose level, and insulin level were controlled. Diastolic blood pressure correlated with body mass index and serum glucose level, but only the latter remained significant when all independent variables were considered together. Both systolic and diastolic blood pressure were found to be significantly related to fasting serum insulin level (r = 0.47, p = 0.005 and r = 0.68, p less than 0.001) even when age, weight, and serum glucose level were controlled (r = 0.41, p = 0.025 and r = 0.62, p less than 0.001 respectively). The relation between serum insulin and blood pressure was more pronounced in those women with a family history of hypertension. These data indicate that insulin may play a major role in the regulation of blood pressure in obesity and that the previously accepted relation of weight to blood pressure may depend on blood levels of insulin.

The relative contribution of body fat and fat pattern to blood pressure level

Although the association between body weight and blood pressure is irrefutable, body fat mass and blood pressure level may not necessarily be directly related. To clarify the relative contribution of fat mass to blood pressure level, we analyzed data on 399 adults consecutively entering a weight control program. Although most subjects were notably overweight (mean ideal body weight 177%), the population represented a wide spectrum of body weights and blood pressure levels. Study parameters included body fat mass (by total body water, 40K, and Steinkamp formula), lean body mass, body build (chest to height ratio), fat cell number and size from bilateral buttock biopsy specimens, upper fat pattern by arm to thigh circumference ratio, and central fat pattern by subscapular to triceps skinfold ratio. Our results concurred with previously noted correlations between obesity and blood pressure (as mean arterial pressure): weight (r = 0.44), percentage of body fat (r = 0.19), and absolute fat mass (r = 0.38; all p less than 0.01); however, lean body mass, age, and body build correlated highly with both fat mass and mean arterial pressure, thereby confounding this relationship. Multivariate analysis was performed to evaluate the relative contribution of fat mass to mean arterial pressure in the presence of these and other potentially confounding variables. Lean body mass, age, body build, and an upper body fat pattern were found to contribute significantly to the variation in mean arterial pressure (p less than 0.01). In their presence, percentage of body fat, absolute fat mass, central fat pattern, fat cell characteristics, and age of onset of obesity did not significantly improve the predictability of mean arterial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Diastolic function of the heart in untreated primary hypertension

To study left ventricular (LV) diastolic function of the heart in relation to blood pressure (BP) and other signs of hypertensive cardiac and peripheral vascular changes, isovolumic relaxation time and early diastolic filling were determined in four BP groups of untreated 49-year-old men: normotensive subjects (n = 20), men with borderline hypertension (n = 30), mild hypertension (n = 45), and moderate to severe hypertension (n = 24). Isovolumic relaxation time, measured as the distance between aortic closure (A2, phonocardiography) and mitral valve opening (echocardiography), and early diastolic filling, measured as the distance between mitral valve opening and the O point of the apexcardiogram, tended to increase with BP level, and the total interval from aortic closure to the O point (A2O interval) was significantly prolonged in the two groups with mild and moderate to severe hypertension. A prolonged A2O interval (greater than or equal to 117% of expected value at observed heart rate) was seen in several hypertensives, who had no obvious increase in LV wall thickness on M mode echocardiography. This suggests that a prolonged LV relaxation time may be an early sign of cardiac involvement in primary hypertension. In the group with moderate to severe hypertension, an increase in LV wall thickness was seen together with an increase in resistance at maximal dilation in the calf. This supports the theory that when changes in cardiac structure develop they occur in parallel with structural changes also in the periphery.

Disparate cardiovascular effects of obesity and arterial hypertension

Since obesity and essential hypertension frequently coexist, a study was designed to analyze some of their cardiovascular effects. Twenty-eight obese patients, half of whom were normotensive and half with established hypertension, were matched for mean arterial pressure with 28 corresponding lean subjects. Systemic and renal hemodynamics, intravascular volume, plasma renin activity, and circulating catecholamine levels were measured. Obese patients had increased cardiac output (p less than 0.001), stroke volume (p less than 0.001), central blood volume (p less than 0.02), plasma and total blood volume (p less than 0.01), and decreased total peripheral resistance (p less than 0.001). In contrast, cardiac output, central blood volume, and stroke volume of hypertensive patients were normal, but they had increased total peripheral (p less than 0.001) and renal vascular resistance (p less than 0.001) and a contracted intravascular volume. Left ventricular stroke work was elevated to a similar level in obesity (p less than 0.001) and hypertension (p less than 0.02), but the increase was caused by an expanded stroke volume in the former and by an increase in systolic pressure in the latter. It is concluded that the disparate effects of obesity and hypertension on total peripheral resistance and intravascular volume counteract and may even offset each other. Thus, obesity may mitigate the effects of chronically elevated total peripheral resistance (and therefore end-organ damage) in essential hypertension. Since both entities affect the heart through different mechanisms, their presence in the same patient results in a double burden to the left ventricle, thereby gently enhancing the long-term risk of congestive failure.