Branched-chain amino acid levels are associated with improvement in insulin resistance with weight loss

AIMS/HYPOTHESIS

Insulin resistance (IR) improves with weight loss, but this response is heterogeneous. We hypothesised that metabolomic profiling would identify biomarkers predicting changes in IR with weight loss.

METHODS

Targeted mass spectrometry-based profiling of 60 metabolites, plus biochemical assays of NEFA, β-hydroxybutyrate, ketones, insulin and glucose were performed in baseline and 6 month plasma samples from 500 participants who had lost ≥4 kg during Phase I of the Weight Loss Maintenance (WLM) trial. Homeostatic model assessment of insulin resistance (HOMA-IR) and change in HOMA-IR with weight loss (∆HOMA-IR) were calculated. Principal components analysis (PCA) and mixed models adjusted for race, sex, baseline weight, and amount of weight loss were used; findings were validated in an independent cohort of patients (n = 22).

RESULTS

Mean weight loss was 8.67 ± 4.28 kg; mean ∆HOMA-IR was -0.80 ± 1.73, range -28.9 to 4.82). Baseline PCA-derived factor 3 (branched chain amino acids [BCAAs] and associated catabolites) correlated with baseline HOMA-IR (r = 0.50, p < 0.0001) and independently associated with ∆HOMA-IR (p < 0.0001). ∆HOMA-IR increased in a linear fashion with increasing baseline factor 3 quartiles. Amount of weight loss was only modestly correlated with ∆HOMA-IR (r = 0.24). These findings were validated in the independent cohort, with a factor composed of BCAAs and related metabolites predicting ∆HOMA-IR (p = 0.007).

CONCLUSIONS/INTERPRETATION

A cluster of metabolites comprising BCAAs and related analytes predicts improvement in HOMA-IR independent of the amount of weight lost. These results may help identify individuals most likely to benefit from moderate weight loss and elucidate novel mechanisms of IR in obesity.

Modulation of the BP response to diet by genes in the renin-angiotensin system and the adrenergic nervous system

BACKGROUND

Essential hypertension results from the interaction of several genetic and environmental factors. Identification of genetic factors that modulate blood pressure (BP) response to interventions can lead to improved strategies for prevention and control. The purpose of this study was to identify genes that modulate BP response to dietary interventions.

METHODS

We used data and samples collected in two randomized feeding studies to determine the extent to which genetic architecture is associated with the effect on BP of sodium intake and the Dietary Approaches to Stop Hypertension (DASH) dietary pattern. Participants in both trials were adults with above-optimal BP or unmedicated stage 1 hypertension. Genomic DNA was typed for several candidate genes.

RESULTS

The effect of sodium intake on BP differed by genotype at the angiotensinogen, β2-adrenergic receptor, and kallikrein loci. The effect of DASH dietary pattern on BP differed by genotype at the β2-adrenergic receptor locus.

CONCLUSIONS

These findings have implications for understanding the mechanism(s) through which diet affects BP, the heterogeneity of these effects, and the extent to which dietary interventions can modulate genetic predisposition.

Microalbuminuria predicts overt proteinuria among patients with HIV infection

BACKGROUND

This study examines the association between microalbuminuria and the development of proteinuria among HIV-infected persons.

METHODS

A total of 948 subjects provided urine samples for albumin, protein and creatinine measurements semiannually. Microalbuminuria was defined as an albumin-to-creatinine ratio of >30 mg/g. Proteinuria was defined as a protein-to-creatinine ratio of > or =0.350 mg/mg. The progression from microalbuminuria to proteinuria was described.

RESULTS

At baseline, 69.4% of the subjects had no detectable proteinuria, 20.2% had microalbuminuria, and 10.4% had proteinuria. Subjects with microalbuminuria and proteinuria were more likely to be black (P=0.02), have lower CD4 cell counts (P=0.02 comparing subjects without abnormal urine protein excretion to subjects with microalbuminuria; P=0.0001 comparing subjects with microalbuminuria to subjects with proteinuria), and have a higher HIV RNA level (P=0.08 and 0.04, respectively). Among 658 subjects with normal urine protein, 82.7% continued to have no abnormality, 14.3% developed microalbuminuria, and 3.0% developed proteinuria. Subjects without baseline proteinuria (i.e. either normal protein excretion or microalbuminuria) who developed proteinuria were more likely to have microalbuminuria (P=0.001), a lower CD4 cell count (P=0.06), and a higher plasma HIV RNA (P=0.03) than those who did not progress to proteinuria. In multivariate analysis, only microalbuminuria remained associated with the development of proteinuria (odds ratio 2.9; 95% confidence interval 1.5, 5.5; P=0.001).

CONCLUSION

Microalbuminuria predicts the development of proteinuria among HIV-infected persons. Because proteinuria has been linked to poorer outcomes, strategies to affect microalbuminuria should be tested.

Effect of lifestyle modifications on blood pressure by race, sex, hypertension status, and age

Recommendations for control of high blood pressure (BP) emphasize lifestyle modification, including weight loss, reduced sodium intake, increased physical activity, and limited alcohol consumption. The Dietary Approaches to Stop Hypertension (DASH) dietary pattern also lowers BP. The PREMIER randomized trial tested multicomponent lifestyle interventions on BP in demographic and clinical subgroups. Participants with above-optimal BP through stage 1 hypertension were randomized to an Advice Only group or one of two behavioural interventions that implement established recommendations (Est) or established recommendations plus DASH diet (Est plus DASH). The primary outcome was change in systolic BP at 6 months. The study population was 810 individuals with an average age of 50 years, 62% women, 34% African American (AA), 95% overweight/obese, and 38% hypertensive. Participants in all the three groups made lifestyle changes. Mean net reductions in systolic (S) BP in the Est intervention were 1.2 mmHg in AA women, 6.0 in AA men, 4.5 in non-AA women, and 4.2 in non-AA men. The mean effects of the Est Plus DASH intervention were 2.1, 4.6, 4.2, and 5.7 mmHg in the four race-sex subgroups, respectively. BP changes were consistently greater in hypertensives than in nonhypertensives, although interaction tests were nonsignificant. The Est intervention caused statistically significant BP reductions in individuals over and under age 50. The Est Plus DASH intervention lowered BP in both age groups, and significantly more so in older individuals. In conclusion, diverse groups of people can adopt multiple lifestyle changes that can lead to improved BP control and reduced CVD risk.

Comparing office-based and ambulatory blood pressure monitoring in clinical trials

Ambulatory blood pressure monitoring (ABPM) is commonly used in clinical trials. Yet, its ability to detect blood pressure (BP) change in comparison to multiple office-based measurements has received limited attention. We recorded ambulatory and five daily pairs of random zero (RZ) BPs pre- and post-intervention on 321 adult participants in the multicentre Dietary Approaches to Stop Hypertension trial. Treatment effect estimates measured by ambulatory monitoring were similar to those measured by RZ and did not differ significantly for waking vs 24-h ambulatory measurements. For systolic BP, the standard deviations of change in mean 24-h ambulatory BP (8.0 mmHg among hypertensives and 6.0 mmHg among nonhypertensives) were comparable to or lower than the corresponding standard deviations of change in RZ-BP based on five daily readings (8.9 and 5.9 mmHg). The standard deviations of change for mean waking ambulatory BP (8.7 and 6.7 mmHg) were comparable to those obtained using three to four daily RZ readings. Results for diastolic BP were qualitatively similar. Ambulatory monitoring was more efficient (ie, a smaller sample size could detect a given BP change) than three to four sets of daily RZ readings and required fewer clinic visits. The average of 33 ambulatory BP readings during the waking hours had an efficiency comparable to that from the mean of four daily pairs of RZ-BPs. Participants readily accepted the ABPM devices, and their use requires less staff training. ABPM provides a useful alternative to RZ-BP measurements in clinical trials.

The impact of angiotensin II receptor blockade and the DASH diet on markers of endogenous fibrinolysis

Hypertension is associated with impaired fibrinolysis. Both angiotensin receptor blockers (ARB) and the DASH (Dietary Approaches to Stop Hypertension) diet effectively lower blood pressure in hypertensive patients. Some evidence suggests that treatment with ARBs could increase fibrinolysis, however, data is conflicting. The impact of the DASH diet on fibrinolytic parameters is not known. Fifty-five hypertensive participants (35 African-American, 20 white) were randomly assigned to receive 8 weeks of either a control diet or the DASH diet. The diets did not differ in sodium content (approximately 3 g/day). Within each diet, individuals were randomly assigned to receive losartan or placebo for 4 weeks in double-blind, cross-over fashion. Tissue plasminogen activator (t-PA) antigen, t-PA activity, plasminogen activator inhibitor-1 (PAI-1) activity and plasma renin activity (PRA) were measured at the end of a 2-week run-in period on the control diet and after each treatment period. The DASH diet did not affect markers of fibrinolysis. Losartan significantly lowered t-PA antigen levels (-1.8 ng/mL, P = 0.045), but had no effect on t-PA or PAI-1 activities. This effect was more pronounced in whites (-4.1 ng/mL (P = 0.003)) compared with African-Americans (-0.3 ng/mL (P = 0.7), P-interaction = 0.03). Results were not materially affected by adjustment for basline values or changes in blood pressure. This study demonstrates that losartan reduces t-PA antigen levels in white, but not African-American hypertensive individuals. In contrast, the DASH diet had no significant effect on markers of fibrinolysis in whites or African-Americans.

Protease inhibitors are associated with a slowed progression of HIV-related renal diseases

AIMS

While angiotensin-con-verting enzyme inhibitors and zidovudine may improve the course of the most common HIV-related renal disease, HIV-associated nephropathy (HIVAN), the effect of anti-retroviral combination therapy on this and other HIV-related renal diseases has not been assessed. This study describes the clinical course of HIV-related renal diseases and the effect of protease inhibitors on their progression.

METHODS

This retrospective cohort study reviews the clinical course of 19 patients with a clinical or biopsy-proven diagnosis of HIVAN or other HIV-related renal diseases. Groups progressing and not progressing to ESRD were compared using longitudinal analyses to assess the association between creatinine clearance and clinical and therapeutic factors.

RESULTS

The cohort consisted of 16 African-Americans, 2 Caucasians and 1 Native American. Their modes of HIV infection were intravenous drug use (7), a history of men having sex with men (3) and heterosexual behavior (5). Patients were followed for a median of 16.6 months. Seven patients reached ESRD. Loss of creatinine clearance over time did not differ among genders, races, or patients with different modes of HIV infection. Longitudinal analyses demonstrated an association between protease inhibitors and prednisone and a slower decline in creatinine clearance in multivariable models (p = 0.04 and 0.003, respectively).

CONCLUSIONS

The epidemiology and clinical course of HIV-related renal diseases is more heterogeneous than previously described. This study suggests a benefit to the use of protease inhibitors and prednisone on the progression of these nephropathies.

Effects of diet and sodium intake on blood pressure: subgroup analysis of the DASH-sodium trial

BACKGROUND

Initial findings from the Dietary Approaches to Stop Hypertension (DASH)-Sodium Trial demonstrated that reduction of sodium intake in two different diets decreased blood pressure in participants with and without hypertension.

OBJECTIVE

To determine effects on blood pressure of reduced sodium intake and the DASH diet in additional subgroups.

DESIGN

Randomized feeding study.

SETTING

Four clinical centers and a coordinating center.

PARTICIPANTS

412 adults with untreated systolic blood pressure of 120 to 160 mm Hg and diastolic blood pressure of 80 to 95 mm Hg.

INTERVENTION

Participants followed the DASH diet or a control (typical U.S.) diet for three consecutive 30-day feeding periods, during which sodium intake (50, 100, and 150 mmol/d at 2100 kcal) varied according to a randomly assigned sequence. Body weight was maintained.

MEASUREMENTS

Systolic and diastolic blood pressure.

RESULTS

In all subgroups, the DASH diet and reduced sodium intake were each associated with significant decreases in blood pressure; these two factors combined produced the greatest reductions. Among nonhypertensive participants who received the control diet, lower (vs. higher) sodium intake decreased blood pressure by 7.0/3.8 mm Hg in those older than 45 years of age (P < 0.001) and by 3.7/1.5 mm Hg in those 45 years of age or younger (P < 0.05).

CONCLUSION

The DASH diet plus reduced sodium intake is recommended to control blood pressure in diverse subgroups.

Angiotensinogen genotype and blood pressure response in the Dietary Approaches to Stop Hypertension (DASH) study

OBJECTIVE

To determine the relationship between angiotensinogen (ANG) genotype and blood pressure response to the dietary patterns of the Dietary Approaches to Stop Hypertension (DASH) trial. The angiotensin converting enzyme (ACE) gene was also tested.

DESIGN

The DASH trial was a randomized outpatient feeding study comparing the effects on blood pressure (BP) of three dietary patterns: a control diet, similar to typical American intake; a 'fruits and vegetables' diet (F/V) that is rich in fruits and vegetables but otherwise resembles the control diet; and the DASH diet that is reduced in fats and that emphasizes fruits, vegetables and low-fat dairy products. Participants' genotype was also determined.

SETTING

Four clinical sites.

PARTICIPANTS

Adults with above-optimal BP or stage 1 hypertension.

INTERVENTION

Participants ate one of the three dietary patterns for 8 weeks. Sodium intake and weight were held constant. In 355 of 459 DASH participants, DNA was extracted from leukocytes and genotyped for the G-6A ANG polymorphism and the D/I ACE polymorphism, by the polymerase chain reaction.

MAIN OUTCOMES

Genotype at ANG and ACE loci; BP after 8 weeks of intervention diet.

RESULTS

There was no association between ACE genotype and BP response. Associations with ANG polymorphism were significant: net systolic and diastolic BP response to the DASH diet was greatest in individuals with the AA genotype (-6.93/-3.68 mmHg) and least in those with the GG genotype (-2.80/0.20 mmHg). A similar relationship existed for the F/V diet.

CONCLUSIONS

ANG genotype is associated with BP response to the DASH diet. The AA genotype confers excess risk of hypertension and is associated with increased responsiveness to diet.

DASH (Dietary Approaches to Stop Hypertension) diet is effective treatment for stage 1 isolated systolic hypertension

Use of the DASH (Dietary Approaches to Stop Hypertension) diet, which is rich in fruits, vegetables, and low-fat dairy foods, significantly lowers blood pressure. Among the 459 participants in the DASH Trial, 72 had stage 1 isolated systolic hypertension (ISH) (systolic blood pressure, 140 to 159 mm Hg; diastolic blood pressure, <90 mm Hg). We examined the blood pressure response in these 72 participants to determine whether the DASH diet is an effective treatment for stage 1 ISH. After a 3-week run-in period on a typical American (control) diet, participants were randomly assigned for 8 weeks to 1 of 3 diets: a continuation of the control diet (n=25), a diet rich in fruits and vegetables (n=24), or the DASH diet (n=23). Sodium content was the same in the 3 diets, and caloric intake was adjusted during the trial to prevent weight change. Blood pressure was measured at baseline and at the end of the 8-week intervention period with standard sphygmomanometry. Use of the DASH diet significantly lowered systolic blood pressure compared with the control diet (-11.2 mm Hg; 95% confidence interval, -6.1 to -16.2 mm Hg; P<0.001) and the fruits/vegetables diet (-8.0 mm Hg; 95% confidence interval, -2.5 to -13.4 mm Hg; P<0.01). Overall, blood pressure in the DASH group fell from 146/85 to 134/82 mm Hg. Similar results were observed with 24-hour ambulatory blood pressure measurements. In the DASH diet group, 18 of 23 participants (78%) reduced their systolic blood pressure to <140 mm Hg, compared with 24% and 50% in the control and fruits/vegetables groups, respectively. Our results indicate that the DASH diet, which is rich in fruits, vegetables, and low-fat dairy foods, is effective as first-line therapy in stage 1 ISH.

Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group

BACKGROUND

The effect of dietary composition on blood pressure is a subject of public health importance. We studied the effect of different levels of dietary sodium, in conjunction with the Dietary Approaches to Stop Hypertension (DASH) diet, which is rich in vegetables, fruits, and low-fat dairy products, in persons with and in those without hypertension.

METHODS

A total of 412 participants were randomly assigned to eat either a control diet typical of intake in the United States or the DASH diet. Within the assigned diet, participants ate foods with high, intermediate, and low levels of sodium for 30 consecutive days each, in random order.

RESULTS

Reducing the sodium intake from the high to the intermediate level reduced the systolic blood pressure by 2.1 mm Hg (P<0.001) during the control diet and by 1.3 mm Hg (P=0.03) during the DASH diet. Reducing the sodium intake from the intermediate to the low level caused additional reductions of 4.6 mm Hg during the control diet (P<0.001) and 1.7 mm Hg during the DASH diet (P<0.01). The effects of sodium were observed in participants with and in those without hypertension, blacks and those of other races, and women and men. The DASH diet was associated with a significantly lower systolic blood pressure at each sodium level; and the difference was greater with high sodium levels than with low ones. As compared with the control diet with a high sodium level, the DASH diet with a low sodium level led to a mean systolic blood pressure that was 7.1 mm Hg lower in participants without hypertension, and 11.5 mm Hg lower in participants with hypertension.

CONCLUSIONS

The reduction of sodium intake to levels below the current recommendation of 100 mmol per day and the DASH diet both lower blood pressure substantially, with greater effects in combination than singly. Long-term health benefits will depend on the ability of people to make long-lasting dietary changes and the increased availability of lower-sodium foods.

The effect of dietary patterns on blood pressure control in hypertensive patients: results from the Dietary Approaches to Stop Hypertension (DASH) trial

To determine the impact of dietary patterns on the control of hypertension we studied the subgroup of 133 participants with systolic blood pressure (BP) of 140 to 159 mm Hg and/or diastolic BP of 90 to 95 mm Hg enrolled in the Dietary Approaches to Stop Hypertension (DASH) study. Participants were fed a control diet for a 3-week period and were then randomized to receive for 8 weeks either the control diet; a diet rich in fruits and vegetables, but otherwise similar to control; or a combination diet rich in fruits, vegetables, and low-fat dairy products, including whole grains, fish, poultry, and nuts, and reduced in fats, red meats, sweets, and sugar-containing beverages. Sodium intake and body weight were held constant throughout the study. The combination diet significantly reduced systolic BP (-11.4 mm Hg, P < .001) and diastolic BP (-5.5 mm Hg, P < .001). The fruits-and-vegetables diet also significantly reduced systolic BP (-7.2 mm Hg, P < .001) and diastolic BP (-2.8 mm Hg, P = .013). The combination diet produced significantly greater BP effects (P < .05) than the fruits-and-vegetables diet. Blood pressure changes were evident within 2 weeks of starting the intervention feeding. After the 8-week intervention period, 70% of participants eating the combination diet had a normal BP (systolic BP < 140 and diastolic BP < 90 mm Hg) compared with 45% on the fruits-and-vegetables diet and 23% on the control diet. In patients with hypertension, the DASH combination diet effectively lowers BP and may be useful in achieving control of Stage 1 hypertension.

Diagnosis and management of renovascular hypertension

Renovascular hypertension caused by renal artery stenosis accounts for a small portion of overall hypertension but remains important as the most common potentially curable form of high blood pressure. Diagnosis depends on developing an index of suspicion for renovascular hypertension based on the history and physical exam, as well as judicious use of noninvasive and invasive testing. Determining which noninvasive diagnostic test to use remains a persistent dilemma. Treatment options include renal artery angioplasty, arterial stenting, surgery, and medical therapy. The goals of therapy are reduction of blood pressure and protection of renal function. This review discusses the pathophysiology and epidemiology of renovascular hypertension, various noninvasive tests used in diagnosis, and results offered by different treatment modalities. A diagnostic and therapeutic algorithm is offered based on a review of the literature and the experience at our institution.

Effect of dietary patterns on ambulatory blood pressure : results from the Dietary Approaches to Stop Hypertension (DASH) Trial. DASH Collaborative Research Group

We measured ambulatory blood pressure (ABP) in 354 participants in the Dietary Approaches to Stop Hypertension (DASH) Trial to determine the effect of dietary treatment on ABP (24-hour, day and night) and to assess participants' acceptance of and compliance with the ABP monitoring (ABPM) technique. After a 3-week run-in period on a control "typical" American diet, subjects (diastolic blood pressure [BP], 80 to 95 mm Hg; systolic BP, <160 mm Hg; mean age, 45 years) were randomly assigned to 1 of 3 diets for an 8-week intervention period: a continuation of the control diet; a diet rich in fruits and vegetables; and a "combination" diet that emphasized fruits, vegetables, and low-fat dairy products. We measured ABP at the end of the run-in and intervention periods. Both the fruit/vegetable and combination diets lowered 24-hour ABP significantly compared with the control diet (P<0. 0001 for systolic and diastolic pressures on both diets: control diet, -0.2/+0.1 mm Hg; fruit/vegetable diet, -3.2/-1.9 mm Hg; combination diet, -4.6/-2. 6 mm Hg). The combination diet lowered pressure during both day and night. Hypertensive subjects had a significantly greater response than normotensives to the combination diet (24-hour ABP, -10.1/-5.5 versus -2.3/-1.6 mm Hg, respectively). After correction for the control diet responses, the magnitude of BP lowering was not significantly different whether measured by ABPM or random-zero sphygmomanometry. Participant acceptance of ABPM was excellent: only 1 participant refused to wear the ABP monitor, and 7 subjects (2%) provided incomplete recordings. These results demonstrate that the DASH combination diet provides significant round-the-clock reduction in BP, especially in hypertensive participants.

Dietary Approaches to Stop Hypertension: rationale, design, and methods. DASH Collaborative Research Group

Epidemiologic studies across societies have shown consistent differences in blood pressure that appear to be related to diet. Vegetarian diets are consistently associated with reduced blood pressure in observational and interventional studies, but clinical trials of individual nutrient supplements have had an inconsistent pattern of results. Dietary Approaches to Stop Hypertension (DASH) was a multicenter, randomized feeding study, designed to compare the impact on blood pressure of 3 dietary patterns. DASH was designed as a test of eating patterns rather than of individual nutrients in an effort to identify practical, palatable dietary approaches that might have a meaningful impact on reducing morbidity and mortality related to blood pressure in the general population. The objectives of this article are to present the scientific rationale for this trial, review the methods used, and discuss important design considerations and implications.

The effects of dietary patterns on quality of life: a substudy of the Dietary Approaches to Stop Hypertension trial

Few studies have examined the effects of dietary changes, particularly modifications of whole dietary patterns, on quality of life. The Dietary Approaches to Stop Hypertension (DASH) trial compared the effects of 3 dietary patterns on blood pressure. In this substudy, we examined the effect of these diets on health-related quality of life. All DASH participants ate a control diet for 3 weeks and then were randomly assigned to continue the control diet, to a fruits and vegetables diet or to a combination diet for 8 weeks. The combination diet emphasized fruits, vegetables, and low-fat dairy products. It included whole grains, poultry, fish, and nuts, and was reduced in fats, red meat, sweets, and sugar-containing beverages. The control diet was similar to typical American intake; the fruits and vegetables diet was rich in fruits and vegetables but was otherwise similar to the control diet. Both the fruits and vegetables diet (P < .001) and the combination diet (P < .001) significantly lowered blood pressure. At the Duke University Medical Center, Durham, NC, site, participants completed the Medical Outcomes Study Short Form-36 questionnaire to assess their health-related quality of life at baseline and at the end of the dietary intervention. Eighty-three participants completed the questionnaires at both time points. In general, health-related quality of life improved in all treatment groups except for the control group in perceptions of change in health, which diminished. In the combination diet group all the subscales were improved or unchanged compared with baseline values. However, only the change in health score improved significantly (P < .05) as compared with that of the control diet group. When all the subscales were summed into a total score, the control diet was associated with mean improvement of 4.0%, the fruits and vegetables diet with 5.0%, and the combination diet with 5.9% from baseline. These data suggest that the fruits and vegetables diet and particularly the combination diet cannot only lower blood pressure, but may also improve the perception of health-related quality of life.

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-sodium): rationale and design. DASH-Sodium Collaborative Research Group

The DASH Diet, Sodium Intake and Blood Pressure Trial (DASH-Sodium) is a multicenter, randomized trial comparing the effects of 3 levels of sodium intake and 2 dietary patterns on blood pressure among adults with higher than optimal blood pressure or with stage 1 hypertension (120-159/80-95 mm Hg). The 2 dietary patterns are a control diet typical of what many Americans eat, and the DASH diet, which, by comparison, emphasizes fruits, vegetables, and low-fat dairy foods, includes whole grains, poultry, fish, and nuts, and is reduced in fats, red meat, sweets, and sugar-containing beverages. The 3 sodium levels are defined as higher (typical of current US consumption), intermediate (reflecting the upper limit of current US recommendations), and lower (reflecting potentially optimal levels). Participants are randomly assigned to 1 of the 2 dietary patterns using a parallel group design and are fed each of the 3 sodium levels using a randomized crossover design. The study provides participants with all of their food during a 2-week run-in feeding period and three 30-day intervention feeding periods. Participants attend the clinic for 1 meal per day, 5 days per week, and take home food for other meals. Weight is monitored and individual energy intake adjusted to maintain baseline weight. The primary outcome is systolic blood pressure measured at the end of each intervention feeding period. Systolic blood pressure is compared across the 3 sodium levels within each diet and across the 2 diets within each sodium level. If effects previously observed in clinical trials are additive, sodium reduction and the DASH diet together may lower blood pressure to an extent not as yet demonstrated for nonpharmacologic treatment. The DASH-Sodium results will have important implications for the prevention and treatment of high blood pressure.

A dietary approach to prevent hypertension: a review of the Dietary Approaches to Stop Hypertension (DASH) Study

BACKGROUND

Populations eating mainly vegetarian diets have lower blood pressure levels than those eating omnivorous diets. Epidemiologic findings suggest that eating fruits and vegetables lowers blood pressure.

HYPOTHESIS

Two hypotheses were tested: (1) that high intake of fruits and vegetables lowers blood pressure, and (2) that an overall dietary pattern (known as the DASH diet, or DASH combination diet) that is high in fruits, vegetables, nuts, and low-fat dairy products, emphasizes fish and chicken rather than red meat, and is low in saturated fat, cholesterol, sugar, and refined carbohydrate lowers blood pressure.

METHODS

Participants were 459 adults with untreated systolic blood pressure < 160 mmHg and diastolic blood pressure 80-95 mmHg. After a 3-week run-in on a control diet typical of Americans, they were randomized to 8 weeks receiving either the control diet, or a diet rich in fruits and vegetables, or the DASH diet. The participants were given all of their foods to eat, and body weight and sodium intake were held constant. Blood pressure was measured at the clinic and by 24-h ambulatory monitoring.

RESULTS

The DASH diet lowered systolic blood pressure significantly in the total group by 5.5/3.0 mmHg, in African Americans by 6.9/3.7 mmHg, in Caucasians by 3.3/2.4 mmHg, in hypertensives by 11.6/5.3 mmHg, and in nonhypertensives by 3.5/2.2 mmHg. The fruits and vegetables diet also reduced blood pressure in the same subgroups, but to a lesser extent. The DASH diet lowered blood pressure similarly throughout the day and night.

CONCLUSIONS

The DASH diet may offer an alternative to drug therapy in hypertensives and, as a population approach, may prevent hypertension, particularly in African Americans.

Effects of dietary patterns on blood pressure: subgroup analysis of the Dietary Approaches to Stop Hypertension (DASH) randomized clinical trial

OBJECTIVE

To determine the effects of dietary patterns on blood pressure in subgroups.

METHODS

Dietary Approaches to Stop Hypertension (DASH) was a randomized controlled feeding study conducted at 4 academic medical centers. Participants were 459 adults with untreated systolic blood pressure less than 160 mm Hg and diastolic blood pressure 80 to 95 mm Hg. For 3 weeks, participants were fed a "control" diet. They were then randomized to 8 weeks of (1) control diet; (2) a diet rich in fruits and vegetables; or (3) a combination diet rich in fruits, vegetables, and low-fat dairy foods, and reduced in saturated fat, total fat, and cholesterol (the DASH combination diet). Weight and salt intake were held constant. Change in diastolic blood pressure was the primary outcome variable, and systolic blood pressure a secondary outcome. Subgroups analyzed included race, sex, age, body mass index, years of education, income, physical activity, alcohol intake, and hypertension status.

RESULTS

The combination diet significantly lowered systolic blood pressure in all subgroups (P<.008), and significantly lowered diastolic blood pressure (P<.01) in all but 2 subgroups. The fruits-and-vegetables diet also reduced blood pressure in the same subgroups, but to a lesser extent. The combination diet lowered systolic blood pressure significantly more in African Americans (6.8 mm Hg) than in whites (3.0 mm Hg), and in hypertensive subjects (11.4 mm Hg) than in nonhypertensive subjects (3.4 mm Hg) (P<.05 for both interactions).

CONCLUSIONS

The DASH combination diet, without sodium reduction or weight loss, significantly lowered blood pressure in virtually all subgroups examined, and was particularly effective in African Americans and those with hypertension. The DASH combination diet may be an effective strategy for preventing and treating hypertension in a broad cross section of the population, including segments of the population at highest risk for blood pressure-related cardiovascular disease.

Knowledge of diet and blood pressure among African Americans: use of focus groups for questionnaire development

Though focus groups are widely used for development of interventions, little is known about their utility in questionnaire construction, particularly for health surveys in a south-eastern African-American population. In this study, focus groups aided in the development of questions, question sub-components, and response options identifying factors that may influence dietary behavior. Information was used for a survey of dietary knowledge, blood pressure knowledge, and measured blood pressure in a church-based, stratified random sample of middle-class African Americans in North Carolina. Each session, conducted in six churches, lasted 1-1 1/2 hours and had four to nine participants; thirty-four individuals participated. Recorded responses were reviewed and summarized by trained personnel. Results indicate that participants had a general understanding of hypertension, its risk factors, and modes of prevention. However, some misconceptions existed regarding blood pressure and sources of sodium. Television was the most common source of health information. Cost and Southern cultural traditions were deemed the major influences on dietary behavior. Many believed stress was strongly related to blood pressure. The focus group process generated useful information for developing questions about nutrition knowledge, blood pressure knowledge, and health attitudes and beliefs of the target population for the epidemiologic survey that followed.

Recruitment and retention of minority participants in the DASH controlled feeding trial. DASH Collaborative Research Group. Dietary Approaches to Stop Hypertension

The Dietary Approaches to Stop Hypertension (DASH) study was a National Heart, Lung, and Blood Institute multicenter trial that compared the impact of three dietary patterns on blood pressure (BP) among adults with high normal blood pressure or mild (Stage I) hypertension. DASH's high minority representation (two-thirds of the 459 randomized participants came from minority populations, and 60% of the cohort were African American) offered a valuable opportunity to assess factors affecting minority enrollment and retention in clinical trials of lifestyle modification. Recruitment strategies included targeted mailings to specific groups, mass mailings, community and worksite screenings, and mass media advertising; the four DASH clinical centers also reimbursed participants from $150 to $160. The most productive recruitment strategies tended to be mass mailings directed at a broad audience that was weighted toward, but not limited to, minority participants. DASH's African-American participants overwhelmingly (89%) cited health and dietary factors, such as learning more about blood pressure and healthy eating habits, as their primary reason for participating, while only six percent listed the financial incentives as their primary reason for participating. Eighty-eight percent of African-American respondents reported they would participate again in a similar study. The insights from DASH should help inform future efforts to recruit minority participants.

Renal TGF-beta in HIV-associated kidney diseases

Human immunodeficiency virus (HIV)-1 infection may be complicated by progressive renal glomerular disease, including focal segmental glomerulosclerosis (FSGS) and proliferative glomerulonephritis. We examined renal tissue from 71 patients, including biopsies and autopsies from patients in the presence and absence of HIV-1 infection. We assessed the extent of TGF-beta, interstitial fibrosis, and interstitial CD45-positive cellular infiltrate using immunohistochemistry. Extracellular TGF-beta 1/beta 3 was largely confined to the renal interstitium, with the highest scores in HIV-seropositive renal disease and crescentic nephritis. Among all biopsies, the TGF-beta 1/beta 3 score correlated with the fibrosis score (r = 0.79, P < 0.0001) and with the CD45 score (r = 0.60, P < 0.0001). Biopsies from HIV-infected patients, taken together, showed marginally more TGF-beta 1/beta 3 compared to biopsies from HIV-uninfected patients (P = 0.05); similarly, HIV-associated FSGS showed marginally more TGF-beta 1/beta 3 compared to FSGS biopsies obtained from HIV-uninfected patients (P = 0.05). Intracellular TGF-beta 1 and TGF-beta 3 were both expressed by renal tubular epithelial cells and in extraglomerular crescents, whereas TGF-beta 3 was also present within interstitial mononuclear cells and eosinophils, and, exclusively in HIV-infected patients, within glomerular cells. In conclusion, TGF-beta expression was increased in several progressive glomerular diseases, and was particularly but not uniquely elevated in HIV-associated renal diseases.

A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group

BACKGROUND

It is known that obesity, sodium intake, and alcohol consumption factors influence blood pressure. In this clinical trial, Dietary Approaches to Stop Hypertension, we assessed the effects of dietary patterns on blood pressure.

METHODS

We enrolled 459 adults with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80 to 95 mm Hg. For three weeks, the subjects were fed a control diet that was low in fruits, vegetables, and dairy products, with a fat content typical of the average diet in the United States. They were then randomly assigned to receive for eight weeks the control diet, a diet rich in fruits and vegetables, or a "combination" diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat. Sodium intake and body weight were maintained at constant levels.

RESULTS

At base line, the mean (+/-SD) systolic and diastolic blood pressures were 131.3+/-10.8 mm Hg and 84.7+/-4.7 mm Hg, respectively. The combination diet reduced systolic and diastolic blood pressure by 5.5 and 3.0 mm Hg more, respectively, than the control diet (P<0.001 for each); the fruits-and-vegetables diet reduced systolic blood pressure by 2.8 mm Hg more (P<0.001) and diastolic blood pressure by 1.1 mm Hg more than the control diet (P=0.07). Among the 133 subjects with hypertension (systolic pressure, > or =140 mm Hg; diastolic pressure, > or =90 mm Hg; or both), the combination diet reduced systolic and diastolic blood pressure by 11.4 and 5.5 mm Hg more, respectively, than the control diet (P<0.001 for each); among the 326 subjects without hypertension, the corresponding reductions were 3.5 mm Hg (P<0.001) and 2.1 mm Hg (P=0.003).

CONCLUSIONS

A diet rich in fruits, vegetables, and low-fat dairy foods and with reduced saturated and total fat can substantially lower blood pressure. This diet offers an additional nutritional approach to preventing and treating hypertension.

Preliminary evidence of linkage of salt sensitivity in black Americans at the beta 2-adrenergic receptor locus

Salt sensitivity is a heritable trait that is a hallmark of hypertension in black Americans. Genes encoding adrenergic receptors are candidate loci for the inheritance of this hypertension-related trait because of the role of these receptors in the regulation of renal sodium excretion and vascular tone. We performed this study to determine whether these loci are responsible for some of the phenotypic variation in salt sensitivity. Hypertensive black American probands were ascertained, followed by sequential ascertainment of adult sib pairs among the first-, second- and third-degree relatives of the proband. Both hypertensive and normotensive siblings were tested for salt sensitivity by an intravenous sodium-loading, lasix volume-depletion protocol. Genotyping was performed with restriction fragment length polymorphisms in genomic DNA probed with clones containing the beta 2- and alpha 2c10-adrenergic receptor genes. A total of 109 sib pairs was evaluated. Salt sensitivity was defined as the change in blood pressure in each individual, comparing the sodium-loaded with the volume-depleted state. Systolic pressure decreased by an average of 9.0 +/- 9%, diastolic pressure by 1.5 +/- 11%, and mean arterial pressure by 5.0 +/- 9%. Neither blood pressure nor salt sensitivity was linked at the alpha 2c10-adrenergic receptor locus. No evidence suggested that systolic salt sensitivity and baseline blood pressure were linked at the beta 2-adrenergic receptor locus. Model-independent sib pair linkage analysis suggested that diastolic blood pressure response to sodium loading/volume depletion is linked at the beta 2-adrenergic receptor locus (P < .006). Evidence for linkage was significant at the .05 level after adjustment for the number of phenotypic traits examined.

Heritability of salt sensitivity in black Americans

Salt sensitivity is defined as a change in blood pressure in response to changes in salt and water homeostasis. Found in 73% of hypertensive and 36% of normotensive blacks, it is generally considered a hallmark of hypertension in blacks. The higher prevalence of salt sensitivity in blacks compared with whites suggests a genetic influence on this trait, but there is little direct evidence of heritability. We determined the extent to which salt sensitivity is correlated in black families and estimated the heritability of this phenotype. Black families were recruited through a hypertensive proband. Both hypertensive and normotensive adults were phenotyped with respect to salt sensitivity with an intravenous sodium-loading, furosemide volume-depletion protocol. Salt sensitivity was defined as the difference between sodium-loaded and volume-depleted blood pressure. We enrolled 20 families, comprising 30 parent-offspring pairs and 115 adult sibling pairs. Age-adjusted familial correlations ranged from .33 to .44, .19 to .37, and .12 to .21 for mean arterial and systolic and diastolic pressure responses to the salt sensitivity maneuver, respectively. Corresponding heritability estimates were 0.26 to 0.84, 0.26 to 0.74, and 0.004 to 0.24, respectively. These data strongly suggest a heritable component of salt sensitivity.

Effects of gender and ethnic group on blood pressure control in the elderly

In order to determine the adequacy of blood pressure treatment in black and white elderly men and women, the authors performed a cross-sectional population survey in Central North Carolina in 1986-1987. Participants included a random sample of noninstitutionalized individuals age 65 years or older. Blacks were oversampled. A health questionnaire was administered, and blood pressure was measured. Of 5,223 eligible persons, 4,162 (80%) participated. Fifty-four percent of subjects were black and 65% were women. Sixteen percent of the study subjects were white men, 30% white women, 19% black men, and 35% black women. The mean age was 73 years. Fifty-three percent had hypertension. Among hypertensives, 80.8% were taking blood pressure medication. Among treated hypertensives, blood pressure was adequately controlled, (measured diastolic blood pressure of 90 mm Hg or lower) in 85.6%. Women were 52% more likely than men and blacks were 40% less likely than whites to exhibit adequate blood pressure control. Older age and smoking were also associated with better blood pressure control. The authors conclude that hypertension is more likely to be controlled in elderly women than men and less likely to be well-controlled in elderly blacks than whites. The choice of antihypertensive agent may also be important. Further investigation is needed into the mechanisms accounting for the observed sex and race differences.

Association of hypertension with beta2- and alpha2c10-adrenergic receptor genotype

The adrenergic receptors have been implicated in the pathogenesis of essential hypertension. We hypothesized that hypertension is associated with variants at the beta2-adrenergic receptor locus and at one of the alpha2-adrenergic receptor loci. In unrelated individuals, we measured untreated blood pressure and characterized each subject as hypertensive or normotensive. We then used genomic DNA to identify beta2- and alpha2c10-adrenergic receptor restriction fragment length polymorphisms. In 175 subjects (49 percent with hypertension, 55 percent black), both hypertension and race were associated with genotype at the beta2 locus (chi2 for hypertension = 11, P = .004, chi2 for race = 8.8, P = .012). The association with hypertension persisted in each race group separately (blacks only: chi2 = 9.6, P = .008; whites only; chi2 = 14.2, P = .001). This association persisted in a logistic model that controlled for race (P = .01). Genotype was also significantly associated with baseline systolic, diastolic, and mean arterial blood pressures (P = .05, .01, and .02, respectively). These data suggest that the beta2-adrenergic receptor gene is a candidate gene for hypertension in blacks and whites. We also genotyped subjects at the alpha2-adrenergic receptor coded on chromosome 10. There was no association between hypertension and genotype at the alpah2c10 locus in the total group or in blacks, but there was significant association in whites (chi2 = 6.7, P = .03). These data suggest that the beta2- and alph2c10-adrenergic receptor genes may contribute, in a race-specific manner, to the inheritance of essential hypertension. Linkage studies in related individuals are needed to confirm these findings.

Renovascular hypertension in blacks

To define the clinical characteristics of renovascular hypertension (RVH) and determine the clinical usefulness of captopril stimulated peripheral renin and postcaptopril renography in blacks at risk for RVH, 79 clinically selected hypertensive blacks were evaluated. Unstimulated (U-PRA), captopril stimulated (S-PRA) peripheral renin, and postcaptopril renography (PC-RENO) were obtained. All subjects underwent conventional renal arteriography. Renal artery stenosis (RAS) was present in 14 of 79 (18%) patients. Renovascular hypertension (RVH) was found in 7 of 79 (9%) patients. S-PRA had a sensitivity and specificity of 38% and 86% respectively to detect RAS; and a sensitivity and a specificity of 17% and 85% respectively to detect RVH. PC-RENO had a sensitivity and a specificity of 64% and 58% respectively to detect RAS; and a sensitivity and a specificity of 67% and 58% respectively to detect RVH. This study suggests that RAS occurs in 18% of clinically selected hypertensive blacks. RVH was present in 9% of this population. Captopril stimulated peripheral renin and postcaptopril renography are not useful as screening tools for the diagnosis of renovascular disease in blacks. Blacks at high risk should be evaluated with angiography.

Rationale and design of the Dietary Approaches to Stop Hypertension trial (DASH). A multicenter controlled-feeding study of dietary patterns to lower blood pressure

Epidemiologic studies have found that dietary patterns characterized by high intakes of certain minerals and fiber are associated with low blood pressure. Dietary Approaches to Stop Hypertension (DASH) is a multicenter, randomized, controlled-feeding trial designed to test the effects on blood pressure of two such dietary patterns consumed for 8 weeks. The two experimental diets will be compared with each other and with a control dietary pattern that is relatively low in potassium, magnesium, calcium, and fiber, and has a fat and protein profile mirroring current consumption. The first experimental diet, arguably termed "ideal," is high in fruits, vegetables, whole cereal products, low-fat dairy products, fish, chicken, and lean meats designed to be low in saturated fat and cholesterol; moderately high in protein; and high in minerals and fiber. The second experimental diet tests the effect of fruits and vegetables alone. Its potassium, magnesium, and dietary fiber content will be at the same high levels as the ideal dietary pattern, while its fat, protein, and calcium content will resemble that of the control dietary pattern. The study population will consist of 456 healthy men and women, aged 22 years or older, with systolic blood pressure less than 160 mm Hg and diastolic blood pressure 80 to 95 mm Hg. African-American and other minority groups will comprise 67% of the population. Participants will eat one of the three dietary patterns. The DASH trial has unique features. First, dietary patterns rather than single nutrients are being tested. Second, all food for the experimental diets is provided to the participants using a standardized multicenter protocol. Because the dietary patterns are constructed with commonly consumed food items, the results, if positive, may be conveniently implemented in dietary recommendations to the general public.

Doppler evaluation of renal artery stenosis: interobserver agreement in the interpretation of waveform morphology

OBJECTIVE

Analysis of Doppler waveform morphology for features of the tardus-parvus phenomenon has been promoted as a useful and accurate means for detecting renal artery stenosis. The purpose of this study was to examine and quantify the interobserver agreement of such an analysis and to determine if interobserver differences limit the value of this approach for predicting renal artery stenosis.

SUBJECTS AND METHODS

Four observers independently categorized renal artery waveforms of 47 patients (94 kidneys) clinically selected for renovascular hypertension. Waveforms were classified into five categories based on the presence and severity of tardus-parvus changes in the systolic upstroke and early systolic peak. This categorization was then compared with angiographic findings, and the results were analyzed with receiver-operating-characteristic curves. Kappa statistics and agreement tables were computed to evaluate interobserver agreement.

RESULTS

Interobserver agreement in the waveform analysis for the four interpreters was statistically significant (p < 0.001). The receiver-operating-characteristic areas produced by the observers indicated, however, that such waveform classification was not strongly predictive of renal artery stenosis.

CONCLUSION

We conclude that substantial agreement in the interpretation of waveform morphology can be obtained between independent observers, and that such differences that do exist do not preclude the use of the pattern-recognition approach to waveform analysis. Even so, the specific application of this strategy to the waveform contours of early systole was not successful in predicting the presence or severity of renal artery stenosis.

Renal artery stenosis: analysis of Doppler waveform parameters and tardus-parvus pattern

PURPOSE

The utility of Doppler parameters and waveform contour analysis for diagnosis of renal artery stenosis was studied in a hypertensive population screened for renovascular hypertension.

MATERIALS AND METHODS

The Doppler results were compared with those obtained with angiography in a prospective double-blind study involving 118 kidneys in 46 patients with hypertension and 11 potential renal donors with normal blood pressure. Doppler parameters measured in the distal renal artery included systolic acceleration, acceleration time, peak systolic velocity, deceleration in late systole, pulsatility and resistivity indexes, and waveform features in early systole.

RESULTS

Angiograms demonstrated 28 stenotic renal arteries. There was no significant difference between stenotic (> 50% diameter narrowing) and nonstenotic renal arteries for any parameters studied. When stenosis was further categorized as moderate (50%-79%) or severe (80%-95%), significant (P < .05) differences for acceleration time and systolic acceleration were found between nonstenotic and severely stenotic arteries.

CONCLUSION

Doppler characterization of the tardus-parvus phenomenon in the distal renal artery is not an adequate screening method for detection of renal artery stenosis.

Effect of low-dose aspirin on thromboxane production and the antihypertensive effect of captopril

Some of the antihypertensive effects of angiotensin-converting enzyme (ACE) inhibitors occur through nonangiotensin II-mediated mechanisms. One of these is through decreased kinin degradation, leading to enhanced production of vasodilator arachidonic acid metabolites. It was reasoned that if ACE inhibition also leads to an increase in the production of the potent vasoconstrictor thromboxane A2, then maneuvers that selectively inhibit thromboxane production without reducing prostaglandins (PG) E2 + PGI2 might enhance the antihypertensive effect of ACE inhibition. This double-blinded, randomized, crossover study was therefore undertaken to determine: (1) if captopril increases platelet and/or renal thromboxane production; and (2) if low-dose aspirin enhances the antihypertensive effect of captopril. Patients with mild essential hypertension and no other significant medical problems were studied. In a double-blinded, random order, patients took captopril alone (25 mg every 12 h) for 2 wk and captopril plus aspirin (75 mg/day) for another 2 wk. Active treatment periods were preceded by 2 wk of single-blind placebo. Fifteen patients with a mean age of 53 yr and an average mean arterial pressure (MAP) of 114 +/- 8 (+/- SD) mm Hg were studied. Serum thromboxane B2 was higher (P < 0.05) during treatment with captopril/placebo (600 +/- 46 (+/- SE) pg/mL) than during the two washout periods combined (420 +/- 57 and 553 +/- 78) and was lowest (P < 0.0005) during treatment with captopril/aspirin (302 +/- 36). Captopril treatment significantly increased the urinary excretion of PGE2 (P = 0.038). Captopril/placebo significantly lowered MAP (P < 0.05) to 105.0 +/- 3.7 mm Hg compared with the washout period. However, the addition of aspirin to captopril caused no additional lowering of MAP (105.2 +/- 2.8 mm Hg). It was concluded that treatment with captopril does increase platelet thromboxane production. However, lowering platelet thromboxane with low doses of aspirin may not enhance the antihypertensive effect of captopril.

Black/white differences in hypertension in the elderly: an epidemiologic analysis in central North Carolina

Hypertension in blacks, compared with whites, occurs at higher prevalence rates, is more severe, and carries a worse prognosis for cardiovascular morbidity and mortality. The authors examined the degree to which black/white differences in hypertension in the elderly are explained by demographic variables, income, health behavior (smoking, obesity), health service use, and comorbid diabetes. The study population consisted of subjects participating in the Duke site of the Established Populations for Epidemiologic Studies of the Elderly, initiated in 1984. Cross-sectional data reported here were collected between January 1986 and July 1987. Subjects were aged 65 years or older and were not institutionalized. Blacks were oversampled. Of 5,223 eligible persons, 4,163 (80%) agreed to be interviewed; 16% of the study subjects were white men, 30% white women, 19% black men, and 35% black women. The mean age for all groups was approximately 73 years. Forty-four percent of white men, 52% of white women, 50% of black men, and 66% of black women had hypertension. Eighty percent of hypertensives were receiving pharmacologic therapy. Older age, female sex, lower socioeconomic status, obesity, and diabetes mellitus were associated with hypertension. After adjusting for covariables, black race/ethnicity remained an independent risk factor for high blood pressure in the elderly, with an adjusted odds ratio of 1.30.

Potassium chloride lowers blood pressure and causes natriuresis in older patients with hypertension

Epidemiologic surveys, experimental studies in animals, and clinical trials in young and middle-aged patients with hypertension indicate that dietary potassium lowers blood pressure. The mechanism of the antihypertensive effect is not well defined. Variations in serum potassium within the physiologic range may directly affect vascular smooth muscle tone. Potassium may also influence the regulation of blood pressure through effects on sodium handling, aldosterone secretion, the renin/angiotensin system, renal kallikrein, eicosanoids, and atrial natriuretic peptide. This study was undertaken to confirm the blood pressure-lowering effect of potassium in older patients and to determine the mechanism of the antihypertensive effect. Twenty-two patients greater than or equal to 60 yr of age were admitted to a Clinical Research Unit for 8 days after a 2-wk period free of antihypertensive medication. Patients were placed on an isocaloric diet containing 200 mmol/day of Na+, 70 mmol/day of K+, and 500 mg/day of Ca2+ and were treated in a randomized, double-blinded manner with either potassium chloride (120 mmol/day) or placebo. After 4 days, patients were crossed over to the alternate treatment. Systolic blood pressure decreased 8.6 mm Hg (95% confidence interval -14.6, -2.6), and diastolic blood pressure decreased 4.0 mm Hg (-6.9, -1.0) during potassium chloride supplementation. There was no significant change in blood pressure during treatment with placebo. Serum K+ was 3.9 +/- 0.1 mmol/L after 3 days of placebo and 4.3 +/- 0.1 after 4 days of potassium chloride (P less than 0.002). Urinary sodium excretion averaged 192 +/- 11 mmol/day after placebo and 221 +/- 8 after potassium treatment (P less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril renography in the diagnosis of renovascular disease

Several investigators have reported methods for the use of renal scintigraphy in the diagnosis of renal artery stenosis. We report the experience of Duke University Medical Center, and offer some suggestions for standardizing and optimizing the use of this potential screening tool. We evaluated 140 clinically selected hypertensive adults with postcaptopril renal scintigraphy (renography), pre- and postcaptopril peripheral renin activity, and conventional renal arteriography. Postcaptopril renography (using 99mTc-diethylenetriaminepentaacetic acid (DTPA) to measure glomerular filtration and [131I]iodohippurate to measure renal plasma flow) was considered abnormal if one kidney contributed 47% or less of total activity. Postcaptopril renin was considered elevated if it was at least 4 ng/mL/h. Renovascular disease was defined as 50% or greater main renal artery stenosis. Of 140 subjects, 31 (22%) had significant renovascular disease. Captopril-stimulated DTPA renography suggested asymmetric function in 24 (74%) of these, but was also abnormal in 61 of 109 (56%) with normal renal arteries. Captopril-stimulated hippuran renography performed in a similar manner. Captopril-stimulated renin activity was elevated in only 58% of subjects with renal artery stenosis, and had a false positive rate of 24%. These data differ from reports from other centers, perhaps due to differences in renography methods, criteria for interpretation of renography, and/or patient selection criteria.

Imaging of the renal arteries: value of MR angiography

We compared the efficacy of MR angiography with that of conventional angiography for visualizing the renal arteries and detecting renovascular disease. Thirty-three MR angiographic studies, consisting of axial two-dimensional (2-D) phase-contrast, coronal 2-D phase-contrast, and coronal 2-D time-of-flight acquisitions, were performed within 48 hr of conventional arteriography. The studies were done to evaluate possible renovascular hypertension (n = 25) or potential donor nephrectomy (n = 8). The three MR image sets were interpreted independently, in random order by three observers, with regard to the number of renal arteries, degree of vessel visualization, arteriovenous overlap, and presence of renovascular disease. A fourth interpretation was based on the combined axial and coronal phase-contrast image sets. Evaluation was limited to the proximal 35 mm of each renal artery. Renal artery visualization and detection of renovascular disease were more complete with coronal phase-contrast (80% sensitivity, 91% specificity) than with time-of-flight (53% sensitivity, 97% specificity) images. Combined axial and coronal phase-contrast images permitted visualization of the proximal 35 mm of all dominant renal arteries and detection of 13 of 15 stenoses (87% sensitivity, 97% specificity). Our data suggest that biplanar MR angiography has considerable potential as a noninvasive screening technique for the evaluation of renovascular disease.

Racial differences in the incidence and progression of renal diseases

There is an excess incidence of ESRD treatment among non-White North Americans that is not completely explained by the racial prevalences of the underlying diseases, including hypertension, which can potentially cause renal disease. The racial difference is particularly striking for presumed nephrosclerosis from hypertension and for nephropathy from Type II diabetes, but is not yet substantiated for ESRD attributed to polycystic kidney disease or Type I diabetes. The existing data are insufficient to support the notion that poorer blood pressure control alone is responsible for the racial differences in incident ESRD. Black race (and possibly Mexican or Native American heritage) may be a specific risk factor for ESRD, independent of hypertension and its treatment.

Similar prevalence of renovascular hypertension in selected blacks and whites

Renovascular hypertension is a potentially curable form of high blood pressure that is thought to be extremely rare among blacks. We demonstrate, however, that in a clinically selected population, the prevalence of renovascular hypertension is similar in blacks and whites. We prospectively evaluated 167 hypertensive subjects who had one or more clinical features known to be associated with renovascular hypertension. All subjects had captopril-stimulated peripheral renin measurements and conventional renal arteriography. All significant renal artery stenoses (greater than 50% luminal narrowing) were treated with percutaneous transluminal angioplasty or surgery. Renovascular hypertension was diagnosed if there was a blood pressure response to interventional therapy, according to the criteria established by the Cooperative Study of Renovascular Hypertension. Of the total group evaluated, 24% (39 of 167) had renal artery stenosis and 14% (23 of 167) had renovascular hypertension. Renal artery stenosis or occlusion was found in 27% (26 of 97) of whites and 19% (13 of 67) of blacks (p = 0.27). Renovascular hypertension was diagnosed in 18% (17 of 97) of whites and 9% (6 of 67) of blacks evaluated (p = 0.25). Renovascular hypertension was associated with severe or refractory hypertension and with smoking, but there were no racial differences in these associations. Blacks with renovascular hypertension tended to have low captopril-stimulated peripheral renin activity. We conclude that blacks with clinical features suggestive of renovascular hypertension should be evaluated with angiography. Captopril-stimulated plasma renin may not be useful in detecting blacks with renovascular hypertension, but this and other potential screening tests require further evaluation.

Renal vein renins: inability to predict response to revascularization in patients with hypertension

To determine whether the captopril-stimulated renal vein renin ratio (CSRVRR) could enable identification of patients with hemodynamically significant renovascular lesions who would respond to revascularization, the authors measured CSRVRRs in 143 consecutive patients with hypertension who had been selected because of clinical features suggestive of renovascular hypertension. All patients underwent conventional renal arteriography. Renovascular hypertension was the final diagnosis if revascularization resulted in cure or improvement in blood pressure. Complete data were available for 133 patients. Twenty patients had renovascular hypertension; CSRVRR was greater than 1.5 in 13 of these 20 patients (sensitivity, 65%). However, it was also greater than 1.5 in 54 of the 113 patients without renovascular hypertension (false-positive rate, 47.8%). The positive predictive value of CSRVRR was 18.6%; the negative predictive value, 89.3%. It is concluded that CSRVRR is not sufficiently sensitive to enable prediction of which patients will respond to revascularization and is not specific enough to exclude patients who do not have renovascular hypertension.

Clinical characteristics useful in screening for renovascular disease

In an effort to detect renovascular hypertension, clinical characteristics are used to select patients likely to have renal artery stenosis. We prospectively evaluated the ability of commonly used clinical features to predict the presence of renal artery stenosis in 100 hypertensive adults. All subjects had conventional renal arteriography. Renal artery stenosis was diagnosed if there was 50% or more stenosis of a main renal artery. Eighteen of the 100 had renal artery stenosis. The presence of a bruit was strongly associated with renal artery stenosis (P less than .0005). In patients without a bruit, only refractory hypertension was associated with the presence of renal artery stenosis (P = .051). These data suggest that a bruit and refractory hypertension are associated with renal artery stenosis, but that other clinical features investigated may not be and that other means of screening for renovascular disease are needed.

Evaluation of the clinical pharmacology of nilvadipine in patients with mild to moderate essential hypertension

Eighty-four patients with diastolic blood pressure ranging from 100-115 mm Hg were randomized into a multicenter, parallel, double-blind, placebo-controlled, dose response study with nilvadipine (6 mg, 8 mg, 10 mg tid for 28 days). The hypotensive response pattern to nilvadipine was similar with all three doses although duration of response was dose dependent. Maximal decreases in diastolic blood pressure occurred at 1 hour when assessed on days 1 and 15 (16.0, 17.4, and 15.8 mm Hg, vs 17.2, 18.7, and 17.5 mm Hg, respectively). The hypotensive effect remained significant compared to placebo for at least 4 hours after dosing. The increase in heart rate associated with the maximal hypotensive response was minimal and not clinically significant (day 1: 7.6, 5.2, and 4.0 beats/min with 6, 8, and 10 mg; day 15: 4.0, 5.1, 2.6 beats/min with 6, 8, 9, and 10 mg, respectively). Finally, a correlation between plasma drug concentrations and nilvadipine-induced hypotensive response was observed (r = 0.48). Black and white hypertensive patients had similar hypotensive responses. Plasma nilvadipine concentrations on day 15 were similar to those on day 1 suggesting no accumulation of drug with a tid regimen. The most common drug related side effect was headache; less frequently seen were dizziness, edema, palpitations, and abdominal pain. Nilvadipine was well tolerated (only three patients were discontinued due to side effects). The efficacy, lack of tachycardia, and side effect profile observed in this study suggest that nilvadipine may be an important addition to the treatment of hypertension.

Prospective analysis of strategies for diagnosing renovascular hypertension

Renovascular hypertension is a potentially curable form of high blood pressure. However, it is unclear how best to select patients who are likely to have renovascular hypertension, what diagnostic strategy to use in these selected patients, and how to predict the hemodynamic significance of a renal artery stenosis. We determined the prevalence of renovascular hypertension in adults who exhibited suggestive clinical features. In these clinically selected patients, we then determined the test characteristics of various diagnostic and potential screening tests. Renovascular hypertension was diagnosed if correction of renal artery stenosis resulted in decreased blood pressure. Of the 66 hypertensive adults evaluated, 11 (16.7%) had renovascular hypertension. Captopril-stimulated peripheral renin activity detected renovascular hypertension with 73% sensitivity, 72% specificity, 38% positive predictive value, and 92% negative predictive value. Less optimal combinations of sensitivity and specificity were found for differential glomerular filtration rate renography, differential effective renal plasma flow renography, and selective renal vein renin ratios, each performed after a single dose of captopril. Intravenous digital subtraction renal angiography detected all patients with renovascular hypertension and was normal in 71% of patients with essential hypertension. To evaluate potential screening tests for renovascular hypertension, we calculated predictive values applied to a low prevalence population. If the observed sensitivities and specificities apply to a population with 5% prevalence of renovascular hypertension, captopril-stimulated peripheral renin would have a positive predictive value of 12% and a negative predictive value of 98%. In 16 patients with known renal artery stenosis, neither the captopril-stimulated renal vein renin ratio nor captopril-stimulated differential renography accurately predicted blood pressure response to correction of the stenosis. We conclude that clinical criteria can identify a subgroup with 16.7% prevalence of renovascular hypertension. In this high prevalence group, intravenous digital subtraction renal angiography will identify virtually all patients with renovascular hypertension, and a normal study will be sufficient to exclude renovascular hypertension. In unselected hypertensive patients, screening with captopril-stimulated peripheral renin activity may be the most useful and efficient procedure for identification of patients with renovascular hypertension. Functional tests do not accurately predict the hemodynamic significance of a renal artery stenosis.

Intravenous digital subtraction renal angiography: use in screening for renovascular hypertension

Intravenous digital subtraction renal angiography (DSRA) has been compared with conventional angiography only in small, selected series of hypertensive patients. The authors prospectively examined with intravenous DSRA 94 patients at increased risk for renovascular hypertension and compared these studies with conventional angiography. A stenosis of at least one main renal artery was identified with intravenous DSRA in 22 patients and confirmed in 20 patients. No significant stenoses were seen with conventional angiography in any of the 64 patients in whom lesions were not seen with intravenous DSRA. Since inadequate DSRA studies were considered positive for renal artery stenosis, the sensitivity of intravenous DSRA was 100% (25 of 25); specificity, 93% (64 of 69); positive predictive value, 83% (25 of 30); and negative predictive value, 100% (64 of 64). The authors conclude that intravenous DSRA is a sensitive test for identifying stenosis of the main renal arteries and is appropriate to use as a screening test among patients at increased risk for renovascular hypertension.

Comparison of intravenous digital subtraction angiography and conventional arteriography in defining renal anatomy

Intravenous digital subtraction renal angiography (IV-DSRA) is frequently used in the preoperative evaluation of living-related (LR) kidney donors. However, the true accuracy of IV-DSRA in the donor population is difficult to assess since abnormalities of the kidney and its circulation are uncommon in this group. Therefore, we evaluated IV-DSRA in a group of patients more likely to have anomalies and abnormalities that would affect LR donor selection, donor nephrectomy, and subsequent transplantation. Hypertensive adults being evaluated for renovascular hypertension had IV-DSRA and conventional renal arteriograms, which were interpreted independently. We determined the accuracy of IV-DSRA, compared with conventional arteriography, in detecting multiple renal arteries, renal artery stenosis, fibromuscular dysplasia, and abnormal renal parenchyma. Technically unsatisfactory studies were excluded from analysis. Of 59 patients evaluated, 37 had abnormalities or anomalies. IV-DSRA failed to detect 28 of 50 findings in these 37 patients. In 21 patients with multiple renal arteries, IV-DSRA underestimated the number of main renal arteries in 8. Significant renal artery stenosis, present in 16 patients, was undetected by IV-DSRA in 3 of these patients. Mild fibromuscular dysplasia was not detected by IV-DSRA in any of the 5 patients with this condition, and abnormalities of renal parenchyma were not detected in 6 of the 8 patients with scarred or cystic kidneys. When compared with conventional renal arteriography in a hypertensive population, the IV-DSRA does not accurately detect abnormalities of the kidney and its circulation. If these data are confirmed in nonhypertensive subjects, preoperative evaluation of LR kidney donors using IV-DSRA alone may fail to detect potentially important anatomic abnormalities.

Double-blind, placebo-controlled trial of twice-daily nifedipine as a step-2 agent in mild essential hypertension

Nifedipine is a calcium-channel blocker that produces vasodilatation and decreased peripheral resistance in humans. Several clinical reports document blood-pressure-lowering effects of nifedipine with either acute or chronic administration. Little data are available to evaluate sustained-release nifedipine as a step-2 agent. We performed a multicenter double-blind, placebo-controlled trial of twice-daily nifedipine in the treatment of mild essential hypertension not controlled by diuretic alone. Seventy-one subjects completed 8 weeks of treatment with nifedipine or placebo in combination with a stable dose of diuretic. Treatment groups were comparable with respect to age, sex, race, duration of hypertension, and pretreatment weight. Baseline supine blood pressure was no different in the two treatment groups (144 +/- 15/98 +/- 6 mmHg in the nifedipine/diuretic-treated group and 145 +/- 16/98 +/- 6 mmHg in the placebo/diuretic-treated group). After 8 weeks of treatment, supine blood pressure was 132 +/- 11/88 +/- 6 mmHg in the nifedipine/diuretic-treated group and 140 +/- 16/92 +/- 8 mmHg in the placebo/diuretic-treated subjects (p less than 0.01 for both systolic and diastolic blood pressure when compared to placebo/diuretic). Nifedipine with diuretic had similar effects on standing blood pressure. Nifedipine/diuretic decreased blood pressure from baseline values within 1 week of treatment, and the effect persisted for 8 weeks. Heart rate increased in nifedipine/diuretic-treated subjects during the first 2 weeks of treatment but returned to baseline by 4 weeks. No laboratory abnormalities could be attributed to nifedipine/diuretic treatment. Side effects were mild and infrequent. In summary, nifedipine/diuretic is effective and well tolerated in the treatment of uncomplicated essential hypertension inadequately controlled with diuretic therapy alone.

Double-blind, placebo-controlled trial of potassium chloride in the treatment of mild hypertension

Epidemiological and experimental data suggest blood pressure-lowering effects of dietary potassium. A randomized, double-blind clinical trial was used to assess blood pressure response to orally administered potassium, 120 mEq/day, and to placebo in 101 adults with mild hypertension. Blood pressure was measured with a random-zero sphygmomanometer every 2 weeks of this 8-week trial. Systolic blood pressure in the potassium-treated group decreased by 6.4 +/- 13.7 (SD) mm Hg (p less than or equal to 0.025) compared with 0.11 +/- 13.0 mm Hg in the placebo-treated group (p = 0.96). Diastolic blood pressure in the potassium-treated group decreased by 4.1 +/- 8.3 mm Hg (p less than or equal to 0.05) compared with a 1.6 +/- 6.5 mm Hg decrease in placebo-treated subjects (p = 0.09). Baseline blood pressure of potassium-treated subjects was unexpectedly higher than that of controls. After correcting for baseline variation, blood pressure still decreased 3.4/1.8 mm Hg more in potassium recipients than in placebo recipients (p = 0.14 and 0.24, respectively). Blood pressure decreased by 19/13 mm Hg in five blacks taking potassium versus a 1/0 mm Hg increase in seven blacks taking placebo. Compliance with the potassium regimen was 91.5% by pill count; only one subject discontinued treatment because of side effects. In conclusion, 120 mEq/day of microencapsulated potassium chloride was well tolerated in adults with mild hypertension. An antihypertensive effect of potassium cannot be ruled out despite the fact that there was no statistically significant difference between potassium-treated and placebo-treated subjects after adjustment for differences in baseline blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Observer variability in the pulmonary examination

Observer variability in the pulmonary examination was assessed by having four blindfolded observers (two medical students and two pulmonary physicians) twice examine 31 patients with abnormal pulmonary findings. Examiners were consistent in the repetitive detection of pulmonary abnormalities in 74-89% of the examinations; conversely, 11-26% of the time they disagreed with themselves. Although pulmonary specialists recorded fewer (55% of observations) abnormal findings than did medical students (74%), they were significantly (p = 0.008) less self-consistent than were the students. There was no clear trend in agreement between examiners (kappa = 0.20-0.49). Each examiner's findings were compared with those of physicians specially trained in pulmonary examination. Dichotomous variables (wheezes, crackles, rubs) were more reliably detected (kappa = 0.30-0.70) than graded variables (tympany, dullness, breath sound intensity), where kappa = 0.16-0.43. The authors suggest that dichotomous variables deserve greatest clinical reliance; that time in training, alone, does not improve clinical performance; and that there is a disconcertingly large amount of inter- and intraobserver disagreement in this fundamental clinical task.