Insulin resistance in offspring of hypertensive subjects

How family history and risk factors for hypertension relate to ambulatory blood pressure in healthy adults

BACKGROUND

Although family history is a major predictor of hypertension, other risk factors have been linked to elevated blood pressure (BP). This study explored the relationship of norepinephrine (NE), insulin resistance and lipids to family history of hypertension, and attempted to determine the combined effects of family history and these factors on BP.

METHODS

A total of 220 healthy men and women, aged 22-50 years, completed two 24 h ambulatory BP sessions. Based on family history information obtained from parents, three groups were formed: subjects with two hypertensive parents, one hypertensive parent or normotensive parents. Plasma samples were obtained to derive fasting catecholamine levels, insulin, glucose and lipids.

RESULTS

Individuals with two hypertensive parents had high insulin, insulin resistance and low-density lipoprotein cholesterol. Although NE was not directly linked to family history, high NE levels were associated with increased BP, after controlling for family history and body mass index. Women with two hypertensive parents and elevated NE levels had higher systolic BP and diastolic BP during waking and sleep periods. In men the combination of two hypertensive parents and high NE was related only to diastolic BP during waking.

CONCLUSIONS

NE results provide evidence of sympathetic activation in the identification of individuals at risk for hypertension. Studying family history of hypertension and other risk factors in healthy individuals provides a unique opportunity to explore factors leading to elevated BP long before a diagnosis of hypertension is made.

Prematurity – Another Example of Perinatal Metabolic Programming?

Low birth weight is associated with both later adult diseases such as type 2 diabetes mellitus and a number of metabolic abnormalities, the foremost of which is insulin resistance. Indeed the link between an adverse perinatal environment, manifested by low birth weight, and adult life pathology may be an early, permanent reduction in insulin sensitivity. A reduction in insulin sensitivity has been demonstrated in small for gestational age (SGA), term subjects from childhood through to adulthood. Less is known about children born premature into an adverse neonatal environment. We present data demonstrating that premature infants also have metabolic abnormalities similar to those observed in term, SGA children and that these occur irrespective of whether they are SGA or appropriate for gestational age (AGA).

Insulin secretion, sensitivity, and metabolic profile of young healthy offspring of hypertensive parents

Hyperinsulinemia and insulin resistance are commonly observed in essential hypertension, which is part of the metabolic syndrome. The aim of this study was to examine whether insulin secretion abnormalities or alterations in insulin sensitivity and glucose tolerance are also present in healthy men, offspring of patients with essential hypertension. Twelve young (27 +/- 3.6 years), lean normotensive offspring were compared with 14 age-, sex-, and body mass index (BMI)-matched controls without a family history of hypertension, diabetes mellitus, and coronary heart disease. We studied glucose tolerance, insulin secretion, and sensitivity using 10-hour hyperglycemic and 10-hour hyperinsulinemic-euglycemic clamps (HIC). Glucose tolerance was comparable in the offspring and controls. However, the offspring had higher insulin and C-peptide levels during the hyperglycemic clamp (HGC) compared with controls (P <.05). There was no difference in the early phase of insulin secretion between the groups. The insulin sensitivity index (glucose infusion rate/serum insulin) was significantly lower in the offspring during both clamps. Moreover, the offspring had higher systolic (P <.001) and diastolic (P <.001) blood pressure and had higher serum cholesterol (P <.01) and triglyceride (P <.05) levels. Apparently healthy, young, lean individuals with a genetic predisposition to essential hypertension and with normal glucose tolerance had higher insulin secretion and lower insulin sensitivity than controls. These abnormalities, together with higher blood pressure and altered lipid metabolism, may play a role in the development of hypertension and an increased risk of cardiovascular morbidity and mortality in these individuals.

Relationship of insulin resistance and overweight with cortisol and dehydroepiandrosterone-sulfate levels

BACKGROUND

Our objective was to assess the relationship of hormones such as cortisol and dehydroepiandrosterone-sulfate (DHEA-S) with insulin resistance and overweight.

METHODS

We designed and conducted a cross-sectional, observational survey consisting of home visits within a previously defined area of Mexico City. The study included 303 apparently healthy volunteers from a middle-class socioeconomic urban community. We measured glucose, cholesterol, triglycerides, insulin, cortisol, and DHEA-S. Insulin resistance (IR) was defined as belonging to the first quartile of fasting glucose/insulin ratio (G/IR) distribution or fourth quartile of IR (HOMA). Overweight was defined as body mass index (BMI) > or =25 kg/m(2).

RESULTS

To predict IR in women < or =35 years of age, principal component analysis (PCA) disclosed three components: 1) cholesterol, BMI, and diastolic blood pressure (DBP); 2) cholesterol, triglycerides, and cortisol, and 3) dehydroepiandrosterone-sulfate [DHEA-S]. Solely the latter (DHEA-S) was significantly associated with IR (odds ratio [OR] = 1.80, confidence interval 95% [CI 95%] 1.11-2.91, p = 0.015). For men < or =35 years of age, there were two components: 1) cholesterol, triglycerides, BMI, and DBP, and 2) DHEA-S, cholesterol, and cortisol. Component 1 was significantly associated with IR (OR = 5.65; CI 95% 1.62-19.65, p = 0.006). To predict overweight in women >35 years of age, there were three components, including 1) cholesterol and triglycerides, 2) cortisol, and 3) DHEA-S and G/IR. Component 2 was significantly associated with overweight (OR = 0.38, CI 95% 0.23-0.64, p = 0.000).

CONCLUSIONS

In women < or =35 years of age, high DHEA-S levels were associated with insulin resistance, which suggests that in young women DHEA-S exerts anti-estrogenic action, perhaps caused by its competitive binding with the estrogen receptor. Additionally, in women >35 years of age, low cortisol levels were associated with overweight. These associations were not identified for the male subgroup.

Insulin resistance adds to endothelial dysfunction in hypertensive patients and in normotensive offspring of subjects with essential hypertension

OBJECTIVES

To evaluate whether endothelium-dependent (nitric oxide-mediated) dilation of the brachial artery (BA) is impaired in patients being treated for essential hypertension (EH), and whether this abnormality can be detected in normotensive offspring of subjects with EH (familial trait, FT); and to investigate the interrelationship between flow-mediated vasodilation (FMD) and hyperinsulinaemia/insulin resistance.

DESIGN

Cross-sectional study.

SETTING

Angiology department at a teaching hospital.

SUBJECTS

The study encompassed 172 subjects, of whom 46 were treated hypertonics aged 40-55 (49) years, and 44 age-matched, normotensive volunteers as controls. We also investigated 41 normotonics with FT aged 20-30 (25) years and 41 age-and sex-matched controls without FT.

MAIN OUTCOME MEASURES

Using high-resolution ultrasound, BA diameters at rest, during reactive hyperaemia (endothelium-dependent dilation) and after sublingual glyceryl trinitrate (GTN) application (endothelium-independent dilation) were measured.

RESULTS

In hypertonics FMD was significantly lower than in controls [2.4 (2.9) vs. 7.4 (2.5)%; P < 0.00005], as was GTN-induced dilation [12.1 (4.3) vs. 16.1 (4.6)%; P=0.0007]. In subjects with FT, FMD was also decreased compared with the control group [5.8 (4.1) vs. 10.0 (3.0)%; P < 0.00005]. The response to GTN was comparable in both groups of young subjects. FMD was negatively related to insulin concentration in all subjects studied (P < 0.00005).

CONCLUSIONS

In treated patients with EH, flow-mediated dilation of the BA as well as endothelium-independent dilation are decreased. In individuals with FT the endothelial function of the peripheral arteries is also altered in the absence of elevated blood pressure. Endothelial dysfunction is related to hyperinsulinaemia/insulin resistance, which could be one of the pathogenetic determinants of EH and its complications.

Hyperinsulinemia and abdominal obesity are more prevalent in non-diabetic subjects with family history of type 2 diabetes

BACKGROUND

This study was undertaken in order to identify the relationships between family history of type 2 diabetes and cardiovascular risk factors in non-diabetic Mexican individuals.

METHODS

The design was a cross-sectional, population-based study stratified by age and sex. Participants consisted of 189 non-diabetic volunteers 30-64 years of age, both males and non-pregnant females randomly selected from a middle income neighborhood in Durango, Mexico and distributed into two groups, with and without family history of type 2 diabetes mellitus. Hypertensive subjects were excluded. Body mass index (BMI) and waist-to-hip ratio (WHR) were assessed. Hematocrit, both fasting and 2-h post 75-g glucose load insulin, and glucose levels, lipid profile, serum albumin, and proteinuria were measured.

RESULTS

Ninety-four (49.7%) individuals with family history of type 2 diabetes, and 95 (50.3%) in the control group were included. The prevalence of obesity was greater among women with family history of diabetes, 39 (73.6%) vs. 27 (50.0%) of the control group, p = 0.02. Adiposity tended to be centrally distributed in 86 subjects, of whom 22 (25. 6%) males and 54 (62.8%) females were in the group with family history of diabetes and four (4.6%) males and six (7.0%) females in the control group, p <0.000. Multivariate logistic regression analysis showed a strong relationship between family history of type 2 diabetes with both abdominal obesity (odds ratio [OR] 4.2, CI 95% 1.9-10.1, p <0.05) and fasting hyperinsulinemia (OR 3.1, CI 95% 1. 4-11.2, p <0.05).

CONCLUSION

In the absence of additional risk factors such as diabetes and hypertension, there is a strong relationship between family history of diabetes with hyperinsulinemia and abdominal obesity in middle-aged Mexican individuals.

Insulin resistance, exercise capacity and body composition in subjects with two hypertensive parents

OBJECTIVE

To study insulin resistance in subjects with strong genetic predisposition to essential hypertension, compared with non-disposed subjects.

SUBJECTS

Thirty normotensive subjects aged 18-35 years whose parents both had essential hypertension, and 30 age- and sex matched subjects whose parents were both normotensive, were studied. Subjects or parents with diabetes and morbid obesity were excluded.

METHODS

The study comprised (1) a frequent sampling oral glucose tolerance test; (2) an isoglycemic hyperinsulinemic clamp study; (3) an analysis of body composition by dual-energy X-ray absorptiometry; (4) an exercise test with gas exchange analysis; and (5) investigation of composition of usual diet by diet registration for 5 days.

RESULTS

The 24-h diastolic blood pressure was higher in subjects predisposed to hypertension compared with the controls: 78.1 versus 74.0 mmHg (confidence interval for the difference between the means; -0.5; -7.9), but the insulin sensitivity index was similar: 312 versus 362 I(2) min(-1) pmol(-1) kg(-1) (28; -129). The two groups were similar in terms of body composition, exercise capacity and composition of usual diet. Resting and 24-h diastolic blood pressures were correlated to abdominal fat mass but not to insulin sensitivity.

CONCLUSION

Subjects with a strong genetic predisposition to essential hypertension had increased diastolic blood pressure compared with subjects with normotensive parents, but they were not insulin resistant. This may be due to the subjects being highly selected as to confounding factors. The increased blood pressure in the hypertension prone subjects could not be attributed to differences in body composition, exercise capacity or dietary habits.

Familial hypertension, insulin, sympathetic activity, and blood pressure elevation

This study evaluated the effects of a positive family history of hypertension (FH+) on the contributions of sympathetic nervous system (SNS) activity and insulin to blood pressure elevation (BPE). The study design was longitudinal and evaluated BP, body mass index (BMI), and fasting plasma insulin and norepinephrine (NE) levels for 10 years in 557 young, nonobese Japanese men who were normotensive at entry. FH+ was defined as hypertension in first-degree relatives as verified by historical records or direct determination. BPE was defined as a > or = 10% rise in systolic and diastolic BP over entry levels during the 10-year period. In the total group FH+ was noted in 16%, and BPE occurred in 18% of normotensive subjects. When evaluated by FH, the prevalence of BPE was 33% in FH+ compared with 16% in FH- (P<0.05). BP levels were greater both at entry and at year 10 in the FH+ group. The absolute increment in plasma NE over 10 years was greater in the BPE group than in those without BPE (P<0.01). Of note, the rise in plasma NE levels in BPE individuals was identical in FH+ and FH- subjects. Plasma insulin increments were also greater in normotensive subjects with BPE than in normotensive subjects without BPE. However, compared with NE, development of hyperinsulinemia was more pronounced in the FH+ subjects. The results indicate that SNS hyperactivity may be a less genetically determined predictor of hypertension than is hyperinsulinemia. Because SNS changes in this initially normotensive population appeared more closely related to the development of hypertension than to hyperinsulinemia, environmental rather than genetic factors may be the main determinant of early BPE in nonobese normotensive subjects.

Hypertension and insulin resistance in a native unindustrialised rural population of India

A cross-sectional survey of 2964 individuals aged 16-70 years from a rural area of North India was carried out to test the hypothesis that a rural unindustrialised hypertensive population of North India has central obesity and hyperinsulinemia. Oral glucose tolerance test was carried out on 68 newly detected hypertensives, 82 age- and sex-matched community controls and 58 genetically related members of hypertensives (family controls). Fasting blood samples were examined for plasma glucose, serum insulin and lipids. Postglucose-load blood samples were examined for plasma glucose and serum insulin. Three blood pressure readings were recorded using Random Zero Sphygmomanometer. Anthropometric measurements (waist-hip ratio, subscapular and triceps skinfold thickness) of all three groups of individuals (hypertensives, community controls and family controls) were also recorded. The hypertensives had significantly higher fasting and postglucose-load serum insulin levels (P<0.05), body mass index (21.3 vs. 19 kg/m2: P<0.05), waist-hip ratio (0.89 vs. 0.85: P<0.001), subscapular (18.5 mm vs. 12.7 mm: P<0.001) and triceps fold thickness (17.6 mm vs. 12.9 mm: P<0.05) than community controls. The family controls had significantly higher systolic blood pressure than community controls (P<0.05). The lipids were not significantly different in all the three groups. Multiple logistic regression showed that both fasting and postglucose-load serum insulin were significantly associated with hypertension independent of waist-hip ratio and body mass index. The results of the present study suggest that hyperinsulinemia is related to hypertension in a rural unindustrialised population of North India.