Influence of family history of hypertension on insulin sensitivity in lean and obese hypertensive subjects

Central obesity is important but not essential component of the metabolic syndrome for predicting diabetes mellitus in a hypertensive family-based cohort. Results from the Stanford Asia-pacific program for hypertension and insulin resistance (SAPPHIRe) Taiwan follow-up study

Background

Metabolic abnormalities have a cumulative effect on development of diabetes, but only central obesity has been defined as the essential criterion of metabolic syndrome (MetS) by the International Diabetes Federation. We hypothesized that central obesity contributes to a higher risk of new-onset diabetes than other metabolic abnormalities in the hypertensive families.

Methods

Non-diabetic Chinese were enrolled and MetS components were assessed to establish baseline data in a hypertensive family-based cohort study. Based on medical records and glucose tolerance test (OGTT), the cumulative incidence of diabetes was analyzed in this five-year study by Cox regression models. Contribution of central obesity to development of new-onset diabetes was assessed in subjects with the same number of positive MetS components.

Results

Among the total of 595 subjects who completed the assessment, 125 (21.0%) developed diabetes. Incidence of diabetes increased in direct proportion to the number of positive MetS components (P ≪ 0.001). Although subjects with central obesity had a higher incidence of diabetes than those without (55.7 vs. 30.0 events/1000 person-years, P ≪ 0.001), the difference became non-significant after adjusting of the number of positive MetS components (hazard ratio = 0.72, 95%CI: 0.45-1.13). Furthermore, in all participants with three positive MetS components, there was no difference in the incidence of diabetes between subjects with and without central obesity (hazard ratio = 1.04, 95%CI: 0.50-2.16).

Conclusion

In Chinese hypertensive families, the incidence of diabetes in subjects without central obesity was similar to that in subjects with central obesity when they also had the same number of positive MetS components. We suggest that central obesity is very important, but not the essential component of the metabolic syndrome for predicting of new-onset diabetes. (Trial registration: NCT00260910, ClinicalTrials.gov).

Arterial hypertension in obesity: relationships with hormone and anthropometric parameters

BACKGROUND

Obesity has been recognized as an independent risk factor for arterial hypertension.

DESIGN

This study was addressed to identify parameters predictive of 24-h mean systolic and/or diastolic blood pressure levels in obesity.

METHODS

A cohort of 180 euthyroid overweight and obese patients, 79 women and 101 men, aged 20-63 years, normotensive (n = 62) or with recently developed hypertension (n = 118), and never treated with antihypertensive drugs, was examined. Waist circumference, fasting insulin, thyroid stimulating hormone (TSH), free thyroxine (FT) FT(3), FT(4), glucose, and lipid (cholesterol, high-density lipoprotein cholesterol and triglyceride) serum concentrations, and 24-h urinary aldosterone and catecholamines were measured. Ambulatory blood pressure monitoring (ABPM) was performed and hypertension was confirmed when 24-h mean systolic blood pressure was ≥125 mmHg and/or 24-h mean diastolic blood pressure was ≥80 mmHg, according to the 2007 European Society of Hypertension and European Society of Cardiology Practice Guidelines for the Management of Arterial Hypertension.

RESULTS

24-h noradrenaline (p < 0.01) and adrenaline (p < 0.05) levels were higher in hypertensive than in normotensive subjects. The odds ratio (OR) was determined by several univariate and multivariate logistic regression analyses to evaluate the predictive factors of high 24-h blood pressure mean values. When subjects with high systolic and/or high diastolic blood pressure levels (n = 118) were compared to individuals with normal systolic and diastolic blood pressure levels (n = 62), multivariate analysis showed an independent association of hypertension with male gender and 24-h noradrenaline levels. When subjects with high systolic blood pressure levels (n = 108) were compared with those with normal systolic blood pressure levels (n = 72), multivariate analysis showed an independent association of high systolic blood pressure with noradrenaline levels. Lastly, when subjects with high diastolic blood pressure levels (n = 87) were compared with those with normal diastolic blood pressure levels (n = 93), multivariate analysis showed an independent negative association between high diastolic blood pressure and body mass index.

CONCLUSIONS

the present study shows that diastolic blood pressure is independently and negatively associated with body mass index in normotensive or with recently discovered hypertension overweight and obese subjects, and never treated with antihypertensive drugs. These results suggest that obesity per se is responsible for a decrease in diastolic blood pressure before hypertensive state becomes stable. This study also confirms that male gender and daily noradrenaline production contribute to hypertension, and to higher systolic blood pressure levels in particular.

Family history of hypertension and cardiovascular risk factors in prepubertal children

BACKGROUND

To determine the relationship between family history of hypertension (FHH) and cardiovascular risk factors (CVRF) in healthy prepubertal children.

METHODS

DESIGN

Cross-sectional, population-based study.

SETTING

Elementary schools from San Luis Potosi and Durango, cities in middle and northern Mexico.

PARTICIPANTS

A total of 358 randomly enrolled, healthy boys and girls aged 6-10 years in Tanner stage 1, with and without FHH.

OUTCOME MEASURES

Odds ratio (OR) that estimates the relationship between FHH and CVRF.

RESULTS

FHH was identified in 72 (20.1%) children; 212 (59.2%) children had at least one CVRF, where low high-density lipoprotein (HDL)-cholesterol (36.3%), elevated waist circumference (WC) (29.3%), and hypertriglyceridemia (28.8%) were the most frequent; high-blood pressure (HBP) and hyperglycemia were recognized in 10 (3.3%) and 1 (0.3%) children. Metabolic syndrome and hyperinsulinemia were identified in 36 (10.0%) and 48 (13.4%) children. In all subjects, hyperinsulinemia (OR 2.0; 95% confidence interval (CI) 1.2-8.4), but not other CVRF was significantly associated with FHH. Subsequent analysis stratified by WC showed that FHH was not associated with CVRF in children with elevated WC. Among children with nonelevated WC, FHH in the maternal branch, but not in the paternal branch, was associated with hyperinsulinemia (OR 1.5; 95% CI 1.1-5.5), HBP (OR 4.0; 95% CI 1.3-30.1), hypertriglyceridemia (OR 1.6; 95% CI 1.1-7.2), and low HDL-cholesterol (OR 1.3; 95% CI 1.1-3.0).

CONCLUSION

Results show that FHH in the maternal branch is associated with CVRF in children with nonelevated WC.

Relations of Insulin Sensitivity to Longitudinal Blood Pressure Tracking

Background— The relations of insulin sensitivity (IS) to hypertension incidence may vary according to baseline age, body mass index (BMI), and blood pressure (BP).

Methods and Results— We investigated the relations of IS (insulin sensitivity index, ISI 0,120 ) to 4-year incidence of hypertension and BP progression in 1933 nonhypertensive Framingham Study participants (median age, 51 years; 56% women). Analyses were stratified by age (less than versus greater than or equal to median), BMI (<25 [normal], 25 to <30 [overweight], ≥30 kg/m 2 [obese]), and BP category (systolic BP≥130 or diastolic BP≥85, “high normal” per the sixth report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High BP [JNC-VI] versus BP<130/85 mm Hg). On follow-up, 41% of participants had BP progression (≥1 BP stage increase) and 18% had development of hypertension (systolic BP≥140 or diastolic BP≥90 mm Hg or antihypertensive medication use). In younger (<51 years) people with normal BMI and baseline BP<130/85 mm Hg, the second-to-fourth ISI 0,120 quartiles were associated with lower multivariable-adjusted odds for hypertension incidence (0.27; 95% CI, 0.09 to 0.83; P <0.05) and BP progression (0.37; 95% CI, 0.18 to 0.77; P <0.01) relative to the lowest (most insulin resistant) quartile. IS was not related to BP progression or hypertension incidence in older individuals, in obese participants, or in people with BP≥130/85 mm Hg.

Conclusions— In our large community-based sample, reduced IS predicted BP tracking principally in younger people with normal BMI and BP<130/85 mm Hg. Effect modification by age, BMI, and baseline BP may explain variation in the results of prior clinical investigations relating IS to hypertension incidence.

Clustering and heritability of insulin resistance in Chinese and Japanese hypertensive families: a Stanford-Asian Pacific Program in Hypertension and Insulin Resistance sibling study

The clustering between hypertension and other metabolic abnormalities related to insulin resistance syndrome (IRS) has been investigated in cross-sectional and prospective studies. Offspring studies have revealed that the clustering characteristics of IRS have familial components. However, it is not known whether the clustering also occurs in siblings (sibs) with different levels of blood pressure (BP). In addition, the genetic susceptibility accounting for the clustering in hypertensive families has not been determined. Siblings with Japanese or Chinese ancestry and having either similar BP levels (concordant sibs) or different BP levels (discordant sibs) were recruited. The delta method and variance component model were applied to analyze the differences in metabolic variables between hypertension (HTN) and low BP (LBP) sibs, and to compute the polygenic heritabilities for these metabolic variables and insulin sensitivity. After adjustment for age, gender and body mass index (BMI), HTN (n=393) sibs had higher levels of triglyceride (p < 0.0001), VLDL-cholesterol (p<0.0001), fasting insulin (p < 0.05), and homeostasis model assessment of insulin resistance (HOMAir) (p < 0.05) than LBP sibs (n = 389), but there were no differences in fasting glucose or high density lipoprotein (HDL)-cholesterol. The HTN sibs also had higher plasma glucose and insulin levels at 2 h after 75 g oral glucose loading (p<0.001 and p<0.01, respectively). The heritability estimates for fasting glucose, fasting insulin and HOMAir were 0.58, 0.43 and 0.46, respectively; for triglyceride, HDL-cholesterol, and BMI they were 0.60, 0.63 and 0.54, respectively. In hypertensive families, sibs with extreme levels of BP have significant differences in IRS-associated metabolic variables. The clustering characteristics and the significance of heritability estimation for these metabolic variables indicate that IRS is familial in nature and heritable in Chinese and Japanese hypertensive families.

Elevated blood pressure in subjects with lipodystrophy

OBJECTIVES

To assess the prevalence of elevated blood pressure in patients with lipodystrophy.

DESIGN

Case-control study.

PARTICIPANTS

Forty-two patients with abnormal body fat (100%) and serum lipids (86%) (HIV-positive cohort) were matched by age and sex to 42 HIV-positive controls without previously diagnosed lipodystrophy and to 13 HIV-negative controls.

SETTING

Tertiary care, university-based, fully dedicated HIV clinic.

MAIN OUTCOME MEASURES

Frequency and magnitude of elevated blood pressure during highly active antiretroviral therapy.

RESULTS

There were 23 +/- 16 and 22 +/- 12 blood pressure measurements recorded per subject over 21 +/- 11 and 22 +/- 11 months for the HIV-positive cohort and HIV-positive controls, respectively. Three or more elevated readings occurred in 74% of the cohort and in 48% of the HIV-positive controls (P = 0.01) and accounted for 38 +/- 25% versus 22 +/- 26% (P = 0.01) of the total readings, respectively. The average of the three highest systolic readings (153 +/- 17 versus 144 +/- 15 mmHg; P = 0.01) and diastolic readings (92 +/- 10 versus 87 +/- 9 mmHg; P = 0.01) was greater for the cohort than for the HIV-positive controls. Family history of hypertension was more common in the cohort than in the controls but accounted for only 13% of the log odds ratio value for elevated blood pressure in the cohort. Systolic blood pressure was correlated with waist-to-hip ratios in the cohort (r = 0.45; P = 0.003) but not in the HIV controls (r = 0.06; P = 0.68) and tended to be related to fasting triglycerides (r = 0.34; P = 0.052) in subjects with HIV.

CONCLUSIONS

Elevated blood pressure may be linked to the metabolic disorders occurring in patients with HIV, as in the dysmetabolic syndrome.

Insulin and diastolic dysfunction in lean and obese hypertensives: genetic influence

We investigated the influence of genetic predisposition to hypertension by studying the relation between insulin sensitivity and left ventricular (LV) mass and function in untreated lean and obese hypertensives. We selected 50 lean hypertensives with normotensive parents (negative family history of hypertension [F-]), 64 lean hypertensives with 1 or both parents hypertensive (positive family history of hypertension [F+]), 40 obese F- hypertensives, and 43 obese F+ hypertensives. The 4 groups were comparable regarding age, gender, 24-hour blood pressure profile, and known duration of hypertension. We measured glucose, insulin, and C-peptide during fasting and during an oral glucose tolerance test; LV morphology and function were assessed by digitized M-mode echocardiography. Glucose (fasting and test) levels were normal in all and similar among the 4 groups. Insulin and C-peptide (fasting and stimulated) levels were higher in obese hypertensives than in lean hypertensives; at similar body mass index, insulin and C-peptide levels were higher in F+ than in F- groups. Compared with lean hypertensives, obese hypertensives had greater LV mass index; LV systolic function was normal in all and similar among the groups. The indices of LV diastolic function were significantly lower in F+ than in F- groups. LV mass index did not correlate with metabolic parameters; the indices of LV diastolic function were inversely correlated with insulin area during test in only the 2 F+ groups. In conclusion, genetic predisposition to hypertension is associated with a reduced insulin sensitivity and affects the response of the myocardium to increased insulin levels, inducing a greater impairment of diastolic function. Insulin sensitivity and genetic predisposition to hypertension seem to have no influence on LV mass.