Insulin resistance and blood pressure circadian variation in an obese hypertensive population

Insulin resistance (IR) is related to arterial hypertension and target organ damage. Hypertensive individuals exhibiting a diminished nocturnal blood pressure (BP) reduction (non-dippers) have an increased incidence of cardiovascular events. The association, however, of IR with BP circadian variation has not been evaluated so far. Therefore, this study examined 226 (116 male and 110 female) overweight and obese subjects (BMI > 27kg/m2) with newly diagnosed essential hypertension who underwent clinical and laboratory evaluation, including an oral glucose tolerance test and ambulatory BP measurement (ABPM). IR was estimated using the homeostasis model assessment (HOMA-IR). The population was grouped according to HOMA-IR values > 2.75 (insulin resistance type) or < 2.75 (insulin sensitive type). Results. No significant differences were observed between dippers (n = 137) and non-dippers (n = 89) with respect to age, gender, BMI, serum cholesterol, triglycerides, LDL-C, and HDL-C levels, nor smoking habits. The proportion of IR subjects among dippers (59.1%) and non-dippers (56.7%) was similar (p = 0.833). Moreover, no significant association was found when the HOMA-IR was examined as a continuous component (p = 0.96). Conclusions. Insulin resistance is not associated with nocturnal blood pressure reduction in obese hypertensives. This may be explained by the notion that insulin secretion does not follow a circadian mode of variation.     

Disturbed circadian blood pressure rhythm and C-reactive protein in essential hypertension

We investigated the effect of the diverse definition criteria of the dipping and non-dipping status on the assessed differences in inflammatory activation between dippers and non-dippers with essential hypertension. 269 consecutive subjects (188 males, aged 50+/-7 years) with untreated stage I-II essential hypertension underwent ambulatory blood pressure (BP) monitoring and high-sensitivity C-reactive protein (hs-CRP) level determination. The population was classified into dippers and non-dippers based on the three following different definitions: true non-dippers (TND): non-dippers (nocturnal fall of systolic and diastolic BP of <10% of the daytime values, n=95) and dippers (the remaining subjects, n=174); true dippers and true non-dippers (TD-TND): non-dippers (nocturnal fall of systolic and diastolic BP<10%, n=95) and dippers (nocturnal fall of systolic and diastolic BP> or =10%, n=75); systolic non-dippers (SND): non-dippers (nocturnal systolic BP fall of <10% of the daytime values, n=145) and dippers (the remaining subjects, n=124). Non-dippers compared to dippers in the TND, TD-TND and SND classification exhibited higher levels of log hs-CRP (by 0.11 mg l(-1), P=0.02; 0.13 mg l(-1), P=0.03 and 0.14 mg l(-1), P=0.02, respectively) and 24 h pulse pressure (PP) (by 4 mm Hg, P=0.006; by 5 mm Hg, P=0.003 and by 5 mm Hg, P<0.0001, respectively). Twenty-four hour PP and nocturnal systolic BP fall were independent predictors of log hs-CRP (P<0.05 for both) in multiple regression analysis. In conclusion, essential hypertensive non-dippers compared to dippers exhibit higher hs-CRP values, irrespective of the dipping status definition. Furthermore, ambulatory PP and nocturnal systolic BP fall interrelate and participate in the inflammatory processes that accompany non-dipping state.     

Circadian variation of blood pressure and endothelial function in patients with essential hypertension:a comparison of dippers and non-dippers

OBJECTIVES: The purpose of this study was to evaluate the relationship between the circadian blood pressure (BP) rhythm and endothelial function in patients with essential hypertension. BACKGROUND: Hypertension is associated with alterations in resistance artery endothelial function. Patients with a non-dipper circadian pattern of BP have a greater risk of cerebrovascular and cardiovascular complications than do patients with a dipper circadian pattern. METHODS: We evaluated the forearm blood flow (FBF) response to intra-arterial acetylcholine (ACh), an endothelium-dependent vasodilator, and isosorbide dinitrate (ISDN), an endothelium-independent vasodilator, infusion in 20 patients with non-dipper hypertension and 20 age- and gender-matched patients with dipper hypertension. The FBF was measured using a mercury-filled Silastic strain-gauge plethysmograph. RESULTS: The 24-h systolic BP, as well as nocturnal systolic and diastolic BPs were higher in non-dipper patients than in dipper patients. The 24-h urinary excretion of nitrite/nitrate and cyclic guanosine monophosphate was lower in non-dippers than in dippers. The response of FBF to ACh was smaller in non-dippers than in dippers (25.1 +/- 3.1 vs. 20.2 +/- 3.0 ml/min/100 ml tissue, p < 0.05). The FBF response to ISDN was similar in dippers and non-dippers. The FBF response to ACh was similar in the two groups following intra-arterial infusion of the nitric oxide (NO) synthase inhibitor N(G)-monomethyl-L-arginine. CONCLUSIONS: These findings suggest that endothelium-dependent vasodilation is blunted through a decrease in NO release in non-dippers compared with patients who have dipper hypertension.     

高血压患者血压节律与靶器官损害的相关性研究

目的 探讨高血压患者血压节律变化与心、脑、肾等靶器官损害的相关性。方法 应用无创性血压监测仪对84例高血压患者进行24小时动态血压监测,对比血压节律正常(勺型组)和异常(非勺型组)患者心、脑、肾靶器官损害程度。结果 非勺型组24小时平均收缩压和舒张压、白昼平均舒张压、夜间平均收缩压和舒张压、收缩压及舒张压负荷值较勺型组升高(P<0.01);左心室重量和重量指数显著增加(P<0.05,0.01),24小时平均动脉压与左心室重量指数呈显著相关性r=0.55,P<0.01;尿微量白蛋白阳性率明显增高(P<0.05);脑梗死发生率明显增加(P<0.05);组间在偶测平均收缩压和舒张压、白昼平均收缩压均无显著性差异(P>0.05)。结论 血压昼夜节律异常较节律正常的高血压患者有更显著的靶器官损害。     

Myocardial ischemia and autonomic activity in dippers and non-dippers with coronary artery disease: assessment of normotensive and hypertensive patients

OBJECTIVES: The aim of this study was to assess the relations between the circadian variations of blood pressure (BP) and the pattern of ischemia and autonomic activity in normotensive and hypertensive patients with coronary artery disease (CAD). PATIENTS AND METHODS: On the basis of the results of ambulatory BP monitoring, 115 patients with stable CAD were divided into Group 1 (with arterial hypertension) and Group 2 (normotensives). Groups were subdivided into dippers and non-dippers. Holter monitoring was performed to assess the occurrence and circadian pattern of ischemic episodes. Time domain and frequency domain HRV analyses were performed to evaluate the autonomic activity. RESULTS: The total number of ischemic episodes was similar in dippers and non-dippers. Non-dippers had a greater number of silent episodes and a different circadian pattern of ischemia with more night episodes. Among the time-domain HRV parameters, only SDNN was similar in dippers and non-dippers. Non-dippers had lower pNN50 and rMSSD-the parameters expressing parasympathetic activity. Differences between diurnal and nocturnal results of spectral HRV analysis were observed in dipper patients only. They presented an elevation of HF power and a decline of LF power at night. All differences between dippers and non-dippers were of similar significance in both hypertensives and normotensives. CONCLUSIONS: A lack of a nocturnal fall in BP is present in normotensive and hypertensive patients with CAD. Non-dippers with CAD had silent and nighttime ischemia more often. They also had an abnormal pattern of autonomic activity with higher sympathetic and lower parasympathetic modulation.     

Circadian blood pressure pattern and cognitive function in newly diagnosed older hypertensives

Hypertensive subjects can be subdivided in two groups, dippers and non-dippers, according to the presence or the lack of a nocturnal fall of blood pressure (BP) of over 10%. Several studies have investigated cardiovascular and cerebrovascular organ damage in the two groups with discordant results, but fewer of them analysed the relationship between circadian BP pattern and cognitive function, and none in the early phases of hypertension. To this purpose, we selected 40 older hypertensives, 23 dippers and 17 non-dippers, with newly diagnosed hypertension, never treated, who underwent to 24-h ambulatory BP monitoring (ABPM), Mini-Mental State Examination (MMSE) and recording of event-related potentials (ERPs). No significant differences between dippers and non-dippers were found in the MMSE scores and P300 latency values, as we expected, and not even in N2 wave latency values, showing that the non-dipping pattern is not associated with lower cognitive function in the early phases of hypertension.     

Replication and meta-analysis of the gene-environment interaction between body mass index and the interleukin-6 promoter polymorphism with higher insulin resistance

Insulin resistance (IR) is a complex disorder caused by an interplay of both genetic and environmental factors. Recent studies identified a significant interaction between body mass index (BMI) and the rs1800795 polymorphism of the interleukin-6 gene that influences both IR and onset of type 2 diabetes mellitus, with obese individuals homozygous for the C allele demonstrating the highest level of IR and greatest risk for type 2 diabetes mellitus. Replication of a gene-environment interaction is important to confirm the validity of the initial finding and extend the generalizability of the results to other populations. Thus, the objective of this study was to replicate this gene-environment interaction on IR in a hypertensive population and perform a meta-analysis with prior published results. The replication analysis was performed using white individuals with hypertension from the Hypertensive Pathotype cohort (N = 311), genotyped for rs1800795. Phenotype studies were conducted after participants consumed 2 diets--high sodium (200 mmol/d) and low sodium (10 mmol/d)--for 7 days each. Measurements for plasma glucose, insulin, and interleukin-6 were obtained after 8 hours of fasting. Insulin resistance was characterized by the homeostatic model assessment (HOMA-IR). In Hypertensive Pathotype, BMI was a significant effect modifier of the relationship between rs1800795 and HOMA-IR; higher BMI was associated with higher HOMA-IR among homozygote CC individuals when compared with major allele G carriers (P = .003). Furthermore, the meta-analysis in 1028 individuals confirmed the result, demonstrating the same significant interaction between rs1800795 and BMI on HOMA-IR (P = 1.05 × 10(-6)). This rare replication of a gene-environment interaction extends the generalizability of the results to hypertension while highlighting this polymorphism as a marker of IR in obese individuals.     

Absence of any significant effects of circadian blood pressure variations on carotid artery elastic properties in essential hypertensive subjects

We sought in this study to examine the effects of diurnal blood pressure variations upon common carotid artery (CCA) elasticity in selected subjects with uncomplicated moderate essential hypertension. Towards this end, 174 non-smoker subjects with stage I-II essential hypertension and without diabetes mellitus, left ventricular hypertrophy and carotid atherosclerosis, were classified as dippers and non-dippers according to the diurnal variation of >10% between mean daytime and night-time systolic and diastolic blood pressure (BP) in 24-h non-invasive ambulatory BP monitoring. CCA distensibility was derived by a combination of surface ultrasonographic data and simultaneous BP measurements at the brachial artery. The dippers and non-dippers were similar with respect to demographic characteristics. Non-dippers had significantly greater office systolic BP, 24-h systolic BP and ambulatory pulse pressure (PP) and significantly less (daytime-night-time) systolic and diastolic BP fall (by 16 mm Hg and 11 mm Hg respectively, P< 0.0001) compared to dippers. CCA distensibility was significantly reduced in non-dippers compared to dippers (by 0.89 dyne(-1)/cm(2/)10(-6), P < 0.05). Multiple linear regression analysis identified patient age and ambulatory PP as significant predictors of the CCA elasticity index. When patient age, 24-h systolic and diastolic BP were used as covariates in an analysis of covariance, the difference of CCA elasticity between dippers and non-dippers ceased to reach statistical significance. In contrast, when patient age, ambulatory PP, systolic (daytime-night-time) BP fall and diastolic (daytime-night-time) BP fall were used as covariates, the difference of CCA distensibility between dippers and non-dippers continued to be statistically significant. In conclusion, the excessive impairment of CCA elastic properties in non-dippers compared to dippers hypertensive seems to be ascribed to the increased of total 24-h haemodynamic load and not to the circadian pattern of BP. Journal of Human Hypertension (2000) 14, 813-818     

Nonalcoholic fatty liver disease, adiponectin and insulin resistance in dipper and nondipper essential hypertensive patients

OBJECTIVE: The pathogenesis of nonalcoholic fatty liver disease (NAFLD) is multifactorial, and the presence of insulin resistance is recognized as the pathophysiological hallmark of this condition. Arterial hypertension is referred as an insulin-resistant state, and insulin resistance may substantially contribute to the cardiovascular risk in this disorder. We examined the inter-relationship between insulin sensitivity, adiponectin levels, and NAFLD in hypertensive patients with different circadian blood pressure profiles. METHODS: Eighty never-treated patients with essential hypertension were selected for having a nocturnal decrement of blood pressure that was at least 10% (dippers, n=47) or less than 10% (nondippers, n=33) of daytime values. No patient had diabetes mellitus, obesity, hyperlipidemia, or other risk factors for hepatic disease. The two groups were similar as to sex, age, and BMI. Abdominal fat distribution and NAFLD were assessed by ultrasonography. RESULTS: Hepatic steatosis was detected in 57.5% of all patients. Nondippers showed a higher prevalence of NAFLD than dippers (81.8 vs. 40.4%, P<0.005). Insulin and the homeostasis model of assessment index were higher (P<0.001) and adiponectin was lower (P<0.001) in nondippers than in dippers, whereas no difference was found in regional fat, liver enzymes, and other metabolic parameters. At multivariate analysis, factors independently associated with nondipping were insulin (P<0.05) and adiponectin (P<0.01) with the homeostasis model of assessment index being of borderline significance. CONCLUSION: In the absence of major risk factors for the development of NAFLD, a high prevalence of liver steatosis was associated with insulin resistance and low adiponectin levels in essential hypertensive patients with a nondipping profile.     

Altered circadian blood pressure profile in patients with active acromegaly. Relationship with left ventricular mass and hormonal values

To determine the relationships between the circadian blood pressure profile and left ventricular mass, hormonal pattern and insulin sensitivity indices in patients with active acromegaly, ambulatory 24-h blood pressure monitoring (ABPM) was recorded in 25 subjects (47.0 +/- 15.1 years, range 23-72). Serum growth hormone (GH) and insulin-like growth factor-1, fasting and mean plasma glucose and insulin during oral glucose tolerance test (OGTT), insulinogenic index, the sum of the plasma insulin levels and the homeostasis model insulin resistance index (Homa's index) were determined. Left ventricular mass index (LVMI) was calculated from two-dimensional guided M-mode echocardiogram. The prevalence of hypertension was 56% (n = 14) and 40% (n = 10) according to sphygmomanometric measurements and ABPM, respectively. Non-dipping profile was observed in six of 10 hypertensives and in six of 15 normotensives. Serum growth hormone, fasting glucose, the area under the serum insulin curve and LVMI were higher for acromegalics with non-dipping profile than for dippers (all of them, P < 0.05). In non-dippers daytime heart rate was higher than night time (P < 0.001). In conclusion, the main observations in the present study suggested that both normotensive and hypertensive acromegalics had a highly prevalent non-dipping profile with a preserved circadian pattern of heart rate, that was associated with higher levels of serum GH. The disturbance in nocturnal blood fall in normotensives was associated with a decreased insulin sensitivity. The role of GH in blood pressure circadian rhythm regulation in essential hypertension deserves further studies.     

Matsuda-DeFronzo insulin sensitivity index is a better predictor than HOMA-IR of hypertension in Japanese: the Tanno-Sobetsu study

Here we examined whether the Matsuda-DeFronzo insulin sensitivity index (ISI-M) is more efficient than the homeostasis model assessment of insulin resistance (HOMA-IR) for assessing risk of hypertension. Cross-sectional and longitudinal analyses were conducted using normotensive subjects who were selected among 1399 subjects in the Tanno-Sobetsu cohort. In the cross-sectional analysis (n=740), blood pressure (BP) level was correlated with HOMA-IR and with ISI-M, but correlation coefficients indicate a tighter correlation with ISI-M. Multiple linear regression analysis adjusted by age, sex, body mass index (BMI) and serum triglyceride level (TG) showed contribution of ISI-M and fasting plasma glucose, but not of HOMA-IR. In the longitudinal analysis (n=607), 241 subjects (39.7%) developed hypertension during a 10-year follow-up period, and multiple logistic regression indicated that age, TG, systolic BP and ISI-M, but not HOMA-IR, were associated with development of hypertension. In subjects <60 years old, odds ratio of new-onset hypertension was higher in the low ISI-M group (ISI-M, less than the median) than in the high ISI-M group for any tertile of BMI. In conclusion, ISI-M is a better predictor of hypertension than is HOMA-IR. Non-hepatic IR may be a determinant, which is independent of TG, BP level and BMI, of the development of hypertension.     

Early signs of left ventricular dysfunction in adolescents with type 1 diabetes mellitus: the importance of impaired circadian modulation of blood pressure and heart rate

Diabetic cardiomyopathy is a well-defined complication of diabetes that occurs in the absence of ischemic heart disease or hypertension. Moreover impaired circadian blood pressure (BP) variation has been associated with autonomic dysfunction. The aim of our study was to evaluate diurnal BP fluctuations and autonomic function and their association with left ventricular function in adolescents with Type 1 diabetes mellitus (T1DM). In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (+/-SD) age of 17.3 (+/-4.1) yr and a mean (+/-SD) diabetes duration of 8.5 (+/-3.3) yr, 24-h ambulatory BP was recorded. Moreover 24-h heart rate (HR) monitoring was performed. Myocardial structural parameters were studied by echocardiogram. Left ventricular end-diastolic (EDDLV) and end-systolic diameters (ESDLV) were estimated and left ventricular mass index (LVMI) was calculated using the Devereux formula. The patients were divided into 2 groups according to the absence of decrease (non-dippers) or the decrease (dippers) of nocturnal diastolic BP (DBP). The non-dippers showed, in comparison with the dippers, reduced mean 24-h HR (79.6 vs 84.0 beats/min, p=0.05) and reduced mean day-time HR (81.3 vs 86.0 beats/min, p=0.05). The nondippers also presented greater ESDLV (28.7 vs 25.9 mm, p=0.001) and EDDLV (47.8 vs 45.1 mm, p=0.040), and LVMI (90.2 vs 78.3 g/m2, p=0.044), in comparison with the dippers. During stepwise multiple regression, the most important variables affecting LVMI were mean HR (day): (b=-0.40, p=0.001), high frequency domain variable of HR variability (b=0.38, p=0.016) and glycosylated hemoglobin (b=0.67, p=0.001). In conclusion, we found that a group of normotensive diabetic adolescents with impaired nocturnal BP reduction, also had autonomic dysfunction, together with impaired left ventricular function. These findings suggest that there is a close relationship between autonomic function and left ventricular remodeling in patients with T1DM, which may be attributed to altered diurnal BP profile, autonomic neuropathy and poor glycemic control.     

Do Obese Individuals With Hypertension Have More Difficult‐to‐Control Blood Pressure and End Organ Damage Than Their Nonobese Counterparts?

The authors assessed whether individuals with elevated body mass index (BMI) and hypertension had more difficult‐to‐control blood pressure (BP) and more evidence of end organ damage using data collected prospectively over 11 years from a secondary care hypertension clinic. A total of 1114 individuals were divided by BMI criteria into normal (n=207), overweight (n=440), and obese (n=467). Mean daytime, nighttime, and 24‐hour systolic BP and diastolic BP were similar in all groups. There was less nocturnal dip in obese compared with overweight groups (P=.025). Individuals with a normal BMI were taking fewer antihypertensive medications than those in the obese group (P=.01). Individuals classified as obese had a higher left ventricular mass index than those with a normal BMI (female, P=.028; male, P<.001); this relationship remained after multivariate linear regression. Obese individuals with hypertension required more medication to achieve similar mean ambulatory BP values, had less nocturnal dip in BP, and had a higher prevalence of left ventricular hypertrophy. As such, obese patients are at potentially increased risk of cardiovascular events.     

Target organ damage and non-dipping pattern defined by two sessions of ambulatory blood pressure monitoring in recently diagnosed essential hypertensive patients

OBJECTIVE : To evaluate in a selected population of patients with a recent diagnosis of hypertension whether a reduced nocturnal fall in blood pressure, confirmed by two 24 h ambulatory blood pressure monitoring (ABPM) sessions is associated with more prominent target organ damage (TOD). METHODS : The study was structured in two phases: in the first, 141 consecutive, recently diagnosed, never-treated essential hypertensives underwent 24 h ABPM twice within 3 weeks; in the second phase, 118 of these patients showing reproducible dipping or non-dipping patterns underwent the following procedures: (1) routine blood chemistry, (2) 24 h urinary collection for microalbuminuria, (3) amydriatic photography of ocular fundi, (4) echocardiography and (5) carotid ultrasonography. RESULTS : The 92 patients with (>10%) night-time fall in systolic blood pressure (SBP) and diastolic blood pressure (DBP) (dippers) in both monitoring sessions were similar for age, gender, body surface area, smoking habit, clinic BP, 24 h and 48 h BP to the 26 patients with a < or = 10% nocturnal fall (non-dippers) in both sessions. The prevalence of left ventricular hypertrophy (LVH) (defined by two criteria: (1) LV mass index > or = 125 g/m2 in both genders; (2) LV mass index > or = 120 and 100 g/m2 in men and women, respectively) and that of carotid intima-media (IM) thickening (IM thickness > or = 0.8 mm) were significantly higher in non-dippers than in dippers (23 versus 5%, P < 0.01; 50 versus 22%, P < 0.05; and 38 versus 18%, P < 0.05, respectively). There were no differences among the two groups in the prevalence of retinal changes and microalbuminuria. The strength of the association of LV mass index with night-time BP was slightly but significantly greater than that with daytime BP. CONCLUSIONS : This study suggests that a blunted reduction in nocturnal BP, persisting over time, may play a pivotal role in the development of some expressions of TOD, such as LVH and IM thickening, during the early phase of essential hypertension, despite similar clinic BP, 24 h and 48 h BP levels observed in non-dippers and dippers.     

Physical activity, dipping and haemodynamics

OBJECTIVE: To determine the effect of physical activity on diurnal blood pressure (BP) and haemodynamic variation. METHODS: Ambulatory measurements were performed during 24 h in 36 subjects (18 hypertensive, 13 male), aged 49.7 +/- 13.5 years. BP was recorded in the brachial artery. Physical activity and posture were measured with five acceleration sensors. RESULTS: Of the subjects 50% were dippers (nocturnal decrease in systolic or diastolic BP >/= 10%). Dippers and non-dippers had similar daytime BP, daytime, night-time, and day-night difference in physical activity, subjective sleep quality, and nocturnal cardiac output decrease (14.9 +/- 9.6 and 16.0 +/- 5.9%). In non-dippers vascular resistance increased from day to night by 9.7 +/- 8.3%, while it remained unchanged (-1.0 +/- 13.9%) in dippers. Day-night changes in heart rate and cardiac output were correlated with day-night changes in physical activity (r = 0.39 and 0.43), whereas day-night changes in systolic BP were correlated with night-time activity (r = -0.34). By selection of the active (i.e. walking) and inactive (i.e. not walking) periods during the day, we showed that physical activity has a large potential effect on dipping status and diurnal haemodynamic variation underlying BP variation. Depending on the BP taken (systolic or diastolic, respectively) the proportion of dippers increased to 81% or decreased to 25% if only the walking period was considered, whereas it decreased to 36% or increased to 53% if only the non-walking period was considered. CONCLUSIONS: Non-dippers differ from dippers by an increase of vascular resistance during the night. The degree of physical activity normally encountered during ambulatory monitoring has little influence on the diurnal BP profile or dipping status, but significantly influences underlying haemodynamics. Related to the different effects of posture and activity on systolic and diastolic BP, dipping classification may vary with the BP index taken.     

Is HOMA index a predictor of nocturnal nondipping in hypertensives with newly diagnosed type 2 diabetes mellitus?

OBJECTIVE: Insulin resistance is involved in glucose intolerance, type 2 diabetes mellitus and hypertension. We aimed to analyze relationship between insulin resistance and nocturnal nondipping. METHODS: Patients underwent physical and biochemical evaluation, clinic and ambulatory blood pressure measurements. The homeostasis model assessment (HOMA) index was calculated. RESULTS: Ninety-six essential hypertensive patients, of whom 42 were dippers, with newly diagnosed type 2 diabetes mellitus were included. Nighttime average heart rate and mean arterial pressure of nondippers were higher than dippers (P<0.0001 and 0.001). Nondippers had higher fasting plasma glucose, serum insulin levels and HOMA indices than dipper patients (P=0.006, <0.0001 and <0.0001). Ten dippers and 36 nondippers were insulin resistant (P<0.0001). Clinic (r=+0.22, P=0.031), daytime average (r=+0.27, P=0.007), nighttime average (r=+0.33, P=0.001), 24-h average systolic (r=+0.25, P=0.015) and nighttime average diastolic blood pressures (r=+0.31, P=0.002) were positively correlated with homeostasis model assessment index. Nighttime mean arterial pressure and heart rates (daytime, nighttime, 24-h average) showed positive correlation with homeostasis model assessment index. In multivariate analysis, high homeostasis model assessment index was associated with increased nondipping risk (odds ratio: 1.85, confidence interval: 1.24-2.76, P=0.003). After adjustment of several factors, average nighttime systolic (P<0.0001), diastolic (P<0.0001) and 24-h diastolic blood pressure (P=0.029) and heart rate (P=0.001) measurements of insulin resistant patients were higher than nonresistant patients. CONCLUSIONS: Insulin resistance is related with diurnal blood pressure variation. The HOMA index may be a predictor of nocturnal nondipping in patients with essential hypertension and newly diagnosed type 2 diabetes mellitus.     

Role of insulin resistance in nondipper essential hypertensive patients.

In hypertensive patients, diminished nocturnal blood pressure (BP) fall is associated with poor prognosis for cardiovascular events. However, the relation of insulin resistance with the etiology of nondipper essential hypertension remains unclear. The aim of the present study was to assess the role of insulin resistance in diminished nocturnal BP fall, left ventricular hypertrophy (LVH), and increased plasma atrial (ANP) and brain natriuretic peptides (BNP) in essential hypertensive patients. One hundred and three patients with essential hypertension were divided into dippers (n = 57; age: 57 +/- 5 years, mean +/- SD) or age-matched nondippers (n = 46; 57 +/- 4 years), based on ambulatory BP (ABP) monitoring. Although the systolic and diastolic ABP values were similar during the day, those at night were higher in nondippers than in dippers ( p < 0.0001 for each). Echocardiographic findings revealed that the left ventricular mass index (LVMI) was higher in nondippers (p < 0.0001). Plasma ANP and BNP were also higher in nondippers (p < 0.0001 for each). Fasting plasma concentrations of glucose and insulin (p < 0.0001 for each) and the homeostasis model assessment (HOMA) index (p < 0.0001) were also higher in nondippers. Multivariate analysis revealed that systolic ABP at night was a significant factor for LVMI, ANP and BNP. In addition, the HOMA index was a significant factor for LVMI and BNP. These observations suggest that diminished nocturnal BP fall is closely related to the development of LVH with concomitant increase in BNP in essential hypertensive patients, and that insulin resistance may play a key role in these processes.     

脉压与胰岛素抵抗的关系

目的评价高血压及正常血压人群脉压与胰岛素抵抗(IR)及其相关危险因素的关系。方法入选原发性高血压病人391例,正常血压者98例,收集如下资料:血压(收缩压、舒张压、脉压)、腹围、体重指数、空腹血糖、空腹胰岛素、HOMA-IR、血脂(甘油三脂、总胆固醇、高密度脂蛋白胆固醇、低密度脂蛋白胆固醇),观察两组不同脉压亚组胰岛素抵抗及其相关危险因素的变化,并分别对两组进行脉压与空腹胰岛素、HOMA-IR、腹围等多因素相关性分析。结果两组随脉压增宽,空腹胰岛素及HOMA-IR显著增高,但高血压组脉压与胰岛素抵抗无独立相关性,脉压与胰岛素抵抗的关系主要依赖于收缩压的变化;正常血压组脉压与胰岛素抵抗独立正相关(r=0.20,P<0.05)。结论脉压可能是反映胰岛素抵抗的较好指标,但在高血压人群的这种作用不如收缩压和腹围。     

高血压合并脂肪肝与胰岛素抵抗的相关分析

目的：探讨高血压合并脂肪肝与胰岛素抵抗（IR）的相关性。方法：根据超声影像学的诊断结果将住院治疗的高血压患者分为高血压合并脂肪肝组（98例）和高血压未合并脂肪肝组（104例），研究两组的体重指数（BMD、血压（BP）、血糖、总胆固醇（TC）、甘油三酯（TG）、高密度脂蛋白胆固醇（HDL-C）、低密度脂蛋白胆固醇（LDL-C）、肝酶和血浆胰岛索，胰岛素抵抗指数（IRI）水平。结果：高血压合并脂肪肝组较高血压未合并脂肪肝组的血糖、胰岛素水平、甘油三酯和胰岛素抵抗指数均明显增高（P〈0．05）。Logistic回归结果表明空腹血糖（FBG）、肥胖、丙氨酸氨基转氨酶（ALT）、葡萄糖负荷试验后3h胰岛素水平、甘油三醋（TG）是脂肪肝形成的独立危险因素（OR=1．980～3．245，P〈0．05）。结论：高血压和脂肪肝均是胰岛素抵抗的重要表现，高血压合并的脂肪肝其发病机制与胰岛素抵抗有关。     

Combined exercise training reduces blood pressure,arterial stiffness,and insulin resistance in obese prehypertensive adolescent girls

Childhood obesity is strongly linked to pathological processes for cardiovascular diseases in later adulthood. Obese adolescent girls with high blood pressure (BP) are reported to have increased arterial stiffness, which is associated with the development of hypertension and atherosclerosis. The present study sought to examine the impact of combined resistance and aerobic exercise (CRAE) training on BP, brachial-ankle pulse wave velocity (baPWV), insulin resistance (IR), and body composition in obese prehypertensive girls. Forty girls (age, 15 ± 1 years; systolic BP, 132 ± 2 mmHg, diastolic BP, 80 ± 5 mmHg) were randomly assigned to either a combined exercise (EX, n = 20) or no exercise group (CON, n = 20). The EX group performed CRAE for 12 weeks, 3 times per week. BP, baPWV, blood nitrite/nitrate, endothelin-1 (ET-1), homeostasis model assessment for insulin resistance (HOMA-IR), and body composition were measured before and after the exercise intervention. BP (?-7.3 ± 2.67 mmHg), baPWV (?-1.23 ± 0.49 m/s), ET-1 (?-14.35 ± 1.76 μmol/mL), nitrite/nitrate (?0.5 ± 0.09 μM), HOMA-IR (?-1.4 ± 0.07), percent body fat (?-1.35 ± 0.9%), and waist circumference were significantly improved (P < 0.05) in the EX group after 12 weeks of training versus the CON group. These findings indicate that 12 weeks of CRAE improves BP, HOMA-IR, and arterial stiffness and reduces central adiposity in obese adolescent girls with prehypertension. Thus, this study provides evidence that CRAE can be a useful therapeutic treatment for high BP, IR, and central adiposity, thereby reducing the likelihood of pathological development for cardiovascular diseases in later adulthood.