Insulin levels during fasting and the glucose tolerance test and Homa's index predict subsequent development of hypertension

Impact of 3-year changes in fasting insulin and insulin resistance indices on incident hypertension: Tehran lipid and glucose study

Background

To examine the association between changes in fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and insulin-glucose ratio (IGR) levels, over approximately 3 years with incident hypertension.

Methods

A total of 2814 Iranian participants (1123 men) without hypertension and known diabetes at baseline and the first examination were followed for a median of 6.32 years. The associations between quartiles of changes in fasting insulin and IR indices with incident hypertension were assessed using multivariate Cox proportional hazard regression analyses with first quartile as reference. The models were adjusted for baseline values of insulin or each IR index, and age, sex, smoking, physical activity, educational levels, marital status, history of cardiovascular diseases, baseline levels of systolic and diastolic blood pressures, estimated glomerular filtration rate, triglycerides, total cholesterol, high-density lipoprotein cholesterol, fasting plasma glucose (only for insulin change) and both body mass index (BMI) per se, and its change. Akaike's information criteria (AIC) was applied as indicator for goodness of fit of each predictive model. The discrimination ability of models was calculated using the Harrell's C statistic.

Results

During the study, 594 incident cases of hypertension (253 men) were identified. The 4th quartile of changes in insulin, HOMA-IR, and IGR showed hazard ratios (95% confidence interval) of 1.31 (1.01-1.69), 1.18 (0.92-1.52), and 1.53 (1.18-1.98) for hypertension, respectively, in fully-adjusted models. Changes in fasting insulin levels and IR indices showed significant increasing trends for incident hypertension, moving from 1st to 4th quartiles (all P-values < 0.05). Focusing on model fitness, no superiority was found between changes in fasting insulin, HOMA-IR, and IGR to predict incident hypertension. The discriminatory powers of changes in fasting insulin and IR indices as assessed by C index were similar (i.e. about 80%).

Conclusion

Changes in fasting insulin and IR indices were significantly associated with developing hypertension among normotensive population even after considering BMI changes.

Clinical features and therapeutic perspectives on hypertension in diabetics

Over 50% of patients with diabetes mellitus, either type 1 or 2, ultimately develop hypertension as a complication. In diabetics, this further increases the incidence of cardiovascular disease (CVD) by 2- to 3-fold and accelerates the progression of diabetic nephropathy. Arteriosclerosis, a clinical feature of hypertension in diabetics, develops and advances from a young age. Therefore, in providing treatment, it is necessary to evaluate the degree of arteriosclerosis. Diabetic patients are encouraged to strictly control their blood glucose levels. Recently developed drugs, such as GLP-1 receptor agonists, DPP-4 inhibitors and SGLT2 inhibitors, also have hypotensive actions, making them ideal for use in diabetics with hypertension. SGLT2 inhibitors and GLP-1 receptor agonists reportedly suppress the onset and progression of CVD, as well as diabetic nephropathy. The possibility of hypoglycemia triggering blood pressure elevation and arrhythmia has been noted, so a key point here is not to cause hypoglycemia. In selecting hypotensive agents, we must choose types that do not aggravate insulin resistance and engage in hypotensive treatment that also considers both nocturnal and morning hypertension. In addition, facing the onset of an aging society, there is a growing need for treatments that do not cause excessive blood pressure reduction or hypoglycemia. Favorable lifelong blood pressure and glucose control are increasingly important for the treatment of diabetes accompanied by hypertension.

Effect of Aerobic Training and Resistance Training on Circulating Irisin Level and Their Association With Change of Body Composition in Overweight/Obese Adults: a Pilot Study

The novel myokine irisin has been reported as a therapeutic target for metabolic disease. The objective of this study is to reveal the effects of aerobic training (AT) and resistance training (RT) on circulating irisin levels and their associations with change of body composition in overweight/obese adults. Twenty eight overweight/obese adults (BMI>23 kg/m2) were included in this study and compared before and after 8 weeks of exercise program (60 min/day, 5 times in a week). The subjects, in both aerobic and resistance training, showed significant improvement in anthropometric parameters and exercise capacities including maximal oxygen uptake and muscle strength. Interestingly, the circulating irisin was significantly increased in resistance training group (p=0.002) but not in aerobic training (p=0.426) compared to control group. In addition, we found the positive correlation between change of the circulating irisin and muscle mass (r=0.432, p=0.022) and the negative correlation between change of the circulating irisin and fat mass (r=−0.407, p=0.031). In the present pilot study, we found that circulating irisin level was increased by 8 weeks of resistance training in overweight/obese adults, suggesting that resistance training could be the efficient exercise type in overweight/obese considering positive change of body composition concomitant with increase of irisin levels.

Euglycemic Clamp Insulin Sensitivity and Longitudinal Systolic Blood Pressure

Insulin resistance may be an independent risk factor for the development of hypertension, but change in blood pressure (BP) over time has not been adequately studied in healthy individuals fully characterized for insulin sensitivity. In the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study, we measured insulin sensitivity (M/I) using the euglycemic clamp technique in 1073 healthy European adults (587 women, 486 men) aged 30 to 60 years followed up 3 years later. Systolic BP (SBP) at baseline was higher in insulin-resistant women (ie, those in the low sex-specific M/I tertile) compared with those in the intermediate ( P <0.001) or high tertiles ( P =0.06; mean±SD: 117±13, 111±12, 114±12 mm Hg, respectively). It did not differ across M/I tertiles in men. After adjustment for age, body mass index, baseline SBP, and other covariates, low insulin sensitivity (M/I) predicted a longitudinal rise in SBP in women but not in men; M/I was not associated with change in diastolic BP. SBP rose over time in both sexes and within all M/I tertiles ( P <0.05), except in women with high insulin sensitivity. Therefore, in women (but not in men), low insulin sensitivity was associated with higher SBP at 3 years, and high insulin sensitivity was associated with a lower rise in SBP over time.

Effect of acacia polyphenol on glucose homeostasis in subjects with impaired glucose tolerance: A randomized multicenter feeding trial

Numerous in vitro and animal studies, as well as clinical trials have indicated that plant-derived polyphenols exert beneficial effects on glucose intolerance or type 2 diabetes. This clinical study aimed to investigate the effects of acacia polyphenol (AP) on glucose and insulin responses to an oral glucose tolerance test (OGTT) in non-diabetic subjects with impaired glucose tolerance (IGT). A randomized, double-blind, placebo-controlled trial was conducted in a total of 34 enrolled subjects. The subjects were randomly assigned to the AP-containing dietary supplement (AP supplement; in a daily dose of 250 mg as AP; n=17) or placebo (n=17) and the intervention was continued for 8 weeks. Prior to the start of the intervention (baseline) and after 4 and 8 weeks of intervention, plasma glucose and insulin were measured during a two-hour OGTT. Compared with the baseline, plasma glucose and insulin levels at 90 and/or 120 min, as well as the total area under the curve values during the OGTT (AUC_0→2h) for glucose and insulin, were significantly reduced in the AP group, but not in the placebo group after intervention for 8 weeks. The decline from baseline in plasma glucose and insulin at 90 or 120 min of the OGTT for the AP group was significantly greater compared with that of the placebo group after 8 weeks of intervention. No AP supplement-related adverse side-effects nor any abnormal changes in routine laboratory tests and anthropometric parameters were observed throughout the study period. The AP supplement may have the potential to improve glucose homeostasis in subjects with IGT.

Elevated glucose level at 30 minutes during an oral glucose tolerance test in obese adolescents: a new disorder of glucose tolerance

We observed glucose levels >140 mg/dL measured at 30 minutes (min) during an oral glucose tolerance test (OGTT) in some obese patients. We aimed to investigate the significance of this finding by comparing lipid profiles, insulin resistance indices, and systemic inflammatory mediators between obese adolescents with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and elevated glucose levels at 30 min. The study involved 80 obese (body mass index >95(th) percentile for age and sex) adolescents (48 female, 32 male) between 11 and 16 years of age. Depending on OGTT results, patients were divided into NGT and IGT groups. The third group was recruited from the NGT group as having glucose levels > 140 mg/dL at 30 minutes. Lipid profiles, [interleukin-6 (IL-6)], neopterin, and lipoprotein associated phospholipase A₂ (Lp-PLA₂)] were assessed. Neopterin and Lp-PLA₂ levels were significantly higher in obese adolescents with elevated glucose levels at 30 min. compared with those in both NGT and IGT groups (p=0.013, and 0.004, respectively). In these adolescents, IL-6 levels were significantly higher only than the NGT group (p=0.01). In logistic regression analysis, IL-6, neopterin and Lp-PLA₂ levels were detected to be related to high blood glucose levels at 30 min (OR 1.11, p=0.01; OR 9.03, p=0.013; OR 1.01, p=0.004 respectively). Obese adolescents with elevated glucose levels at 30 min. demonstrated higher inflammatory mediators levels, which were atherosclerotic indicators, than obese adolescents with NGT and IGT. These results suggest that glucose levels >140 mg/dL measured at 30 min during an OGTT may be a new disorder of glucose tolerance in obesity.

Insulin resistance and risk of incident hypertension among men

J Clin Hypertens (Greenwich). 2009;11:483-490. (c) 2009 Wiley Periodicals, Inc.The independent association between insulin resistance and the development of hypertension remains in doubt because insulin resistance correlates with other metabolic factors also proposed to be associated with hypertension. The authors examined the association between the insulin sensitivity index and incident hypertension in a prospective nested case-control study among 1453 men (mean age, 61 years) who participated in the Health Professionals' Follow-up Study. The authors computed the insulin sensitivity index for each man in the study based on fasting insulin and triglyceride levels. Logistic regression was performed conditioned on age and adjusted for standard hypertension risk factors as well as renal function, cholesterol, and uric acid. The insulin sensitivity index was 6% lower in the cases compared with the controls (P<.001). The multivariable odds ratio for hypertension comparing the lowest with highest quartile of insulin sensitivity index was 1.09 (0.71-1.65) among the entire sample. However, the association between the insulin sensitivity index and incident hypertension differed significantly by age (P interaction <.001). Among men younger than 60 years, the multivariable odds ratio for the lowest compared with highest quartile was 1.93 (1.01-3.71) but was 0.67 (0.37-1.24) among older men. Insulin resistance is independently associated with incident hypertension among younger men.

Insulin resistance predicts future deterioration of glucose tolerance in nondiabetic young African Americans

Insulin resistance has been linked to the development of type 2 diabetes mellitus and increased cardiovascular risk in several high-risk populations. The purpose of this study was to determine if insulin resistance measured by insulin clamp can predict deterioration of glucose metabolism and increased cardiovascular risk in nondiabetic young adult African Americans. Nondiabetic young African American men (n = 60) and women (n = 114) were enrolled. Measurements obtained included blood pressure, anthropometrics, plasma lipids, oral glucose tolerance test, and insulin sensitivity by insulin clamp. Participants were reexamined 8 years later. The relationship between insulin sensitivity and glucose metabolism was analyzed using a 2-way analysis of variance with body mass index at the initial examination as a covariate. After adjusting for the significant difference of body mass index between the insulin-resistant and insulin-sensitive groups, insulin resistance predicted statistically significant worsening glucose metabolism, developing diabetes, and increasing risk factors for cardiovascular disease.

Classical cardiovascular risk factors according to fasting plasma glucose levels

BACKGROUND

To compare the prevalence of classical cardiovascular risk factors (CVRF) and metabolic syndrome (MetS) in our population according to fasting plasma glucose levels (FPG).

METHODS

We have studied 344 subjects between 20-70 years of age, recruited in a Primary Care Clinic. Subjects were divided into four groups according to their fasting plasma glucose (FPG) values: normal plasma glucose (NG) when FPG < 5.6 mmol/L; FPG between 5.6 and 6.0 mmol/L (FPG1); FPG between 6.1-6.9 mmol/L (FPG2); and diabetes (DM) FPG > or = 7 mmol/L or previous diagnosis of diabetes. Cardiovascular risk factors (hypertension, TC/HDL-C index and Apo B values), presence of the MetS and indirect measure of insulin resistance (HOMA) were analyzed.

RESULTS

Subjects with FPG2 have a prevalence of classic CVRF and MetS similar to that observed in subjects with type 2 diabetes mellitus (T2DM). The TC:HDL-C index > or = 5 in 56% and 57%, Apo B > or = 1.2 g/L in 59% and 57%, hypertension in 60% and 54% of FPG2 and T2DM subjects, respectively. MetS was diagnosed in 79% of FPG2 and 80% of T2DM. We found significant differences with FPG1 group who presented low CVRF and MetS proportion.

CONCLUSION

In our population FPG2 and T2DM subjects show a similar cardiovascular risk profile. On the other hand, such risk is significantly lower in subjects with FPG between 5.6-6.0 mmol/L. These results might have practical implications.

Microvascular impairment is associated with insulin resistance in euglycemic mild hypertensives

BACKGROUND

Hypertension and diabetes are significantly associated with insulin resistance (IR), which could affect the vasodilatory capacity and microcirculation. The aim of the study was to verify whether IR is associated with a reduced microvascular blood flow in normoglycemic mild hypertensives.

METHODS

Eighty-four untreated grade-1 hypertensives were equally divided, according to the IR homeostasis model assessment (HOMA) index, into three groups: IR-Low = 2.16 +/- 0.09 vs. IR-Medium = 3.77 +/- 0.09 vs. IR-High = 7.08 +/- 0.68 (P < 0.001) with similar sex distribution, office systolic blood pressure (SBP)/diastolic blood pressure (DBP) and history of hypertension. They underwent ambulatory blood pressure monitoring (ABPM) and a laboratory stress session, during which blood pressure (BP), heart rate (HR), and skin blood flow (Laser Doppler) were taken on the forehead (LDF) and the hand (LDH), where the neuroadrenergic control of the microvascular blood flow is higher. Reactivity was calculated as "area-under-the-curve" (AUC) during arithmetic and cold pressor tests. Postischemic LDH served as the index of endothelial microcirculatory damage.

RESULTS

ABPM confirmed the diagnosis of hypertension, but IR-High patients showed a reduced nighttime BP fall. They also demonstrated reduced LDH-AUC and LDF-AUC although BP-AUC and HR-AUC reactivity were similar. Postischemic LDH was lower in the IR-High group (P < 0.05), and the postischemic LDH change was progressively impaired in both IR-Medium and IR-High patients (P < 0.001). LDH-AUC (-0.305, P = 0.007) and postischemic LDH at 30 s (-0.217, P = 0.059) and 60 s (-0.248, P = 0.030) during hyperemia were associated with HOMA. Multiple regression analysis, with HOMA as the dependent variable, showed that BMI (beta = 0.336, P < 0.001) and LDH (beta = -0.239, P < 0.001), LDH-AUC (beta = -0.296, P < 0.01) and postischemic LDH change (beta = -0.321, P < 0.001) entered the equation.

CONCLUSIONS

The findings suggest that IR is associated with functional microvascular constrictive impairment in normoglycemic mild hypertensives.

[The HOMA and QUICKI indexes, and insulin and C-peptide levels in healthy children. Cut off points to identify metabolic syndrome in healthy children]

OBJECTIVE

The aim of this study was to establish the reference values of the Homeostasis Model Assessment (HOMA) and Quantitative Insulin Sensitivity Check (QUICKI) indexes, as well as those of insulin and C-peptide levels in healthy children and adolescents with a view to determining reference percentiles to detect those at cardiovascular risk.

MATERIAL AND METHODS

A total of 372 children boys and girls of different ages and at distinct pubertal stages with normal body mass index participated in the study. Fasting glucose, insulin and C-peptide values were measured by chemiluminescence and the HOMA and QUICKI indexes were calculated.

RESULTS

Fasting glucose levels were normal in all children. The mean values obtained for each variable were (mean (SD)): fasting glucose 87(7.75) mg/dL, insulin 7.74 (5.35) microU/mL, C-peptide: 1.76 (0.79) ng/mL, HOMA index 1.72 (1.27) and QUICKI index 0.72 (0.29). All the variables progressively increased with age, with statistically significant differences between prepubertal and pubertal children. The QUICKI index showed an inverse relationship. In addition, significant differences were found between sexes. The 90th percentile for all the variables was as follows: insulin 15.05 microU/mL, C-peptide: 2.85 ng/mL, HOMA index 3.43 and QUICKI index 1.10.

CONCLUSIONS

Values of fasting glucose, insulin, C-peptide and the HOMA index significantly increased with age and pubertal stage, while the QUICKI index decreased. We defined the 90th percentile for all the parameters studied as the cut-off point to identify children at cardiovascular risk in our population.

Insulin resistance, hyperinsulinemia, and hypertension: an epidemiologic approach

During the past 2 decades, numerous experimental studies have provided solid evidence for the existence of several mechanisms connecting insulin resistance and hyperinsulinemia with blood pressure elevation, within the context of the cardiometabolic syndrome. In parallel, several groups have attempted to examine these associations from an epidemiologic perspective, but relevant findings were less consistent and not extensively discussed. Hyperinsulinemia has been associated with high blood pressure levels and hypertension development in cross-sectional, case-control, and prospective cohort studies. An association between insulin resistance and hypertension is also evident in existing studies, but prospective data on this relation are limited. Moreover, most of the evidence supporting close associations between these factors derives from Caucasian and Japanese populations, whereas data in other populations are not in agreement. This review summarizes and evaluates the relevant epidemiologic evidence to elucidate an important aspect of the relationship between hypertension and the cardiometabolic syndrome.

Randomized controlled trial for an effect of green tea-extract powder supplementation on glucose abnormalities

OBJECTIVE

We examined whether green tea-extract powder supplementation improves glucose abnormality.

METHODS

The study was conducted for volunteers who resided in eastern communities of Shizuoka Prefecture and who had fasting blood glucose levels of >or=6.1 mmol/l or nonfasting blood glucose levels of >or=7.8 mmol/l in a recent health check-up. Sixty subjects aged 32-73 years (49 males and 11 females) participated in the trial. The Early intervention group consumed a packet of green tea-extract powder containing 544 mg polyphenols (456 mg catechins) daily for the first 2 months and then entered the 2-month nonintervention period. The Later intervention group was observed for the first 2 months and then consumed green tea-extract powder as described above for the subsequent 2 months. Using the two-period crossover design, we analyzed the changes in fasting hemoglobin A1c level and other biomarkers in blood samples collected at baseline, 2 months and 4 months.

RESULTS

A significant reduction in hemoglobin A1c level and a borderline significant reduction in diastolic blood pressure were associated with the intervention. The intervention caused no significant changes in weight, body mass index, body fat, systolic blood pressure, fasting serum glucose level, homeostasis model assessment index, serum lipid level or hypersensitive C-reactive protein.

CONCLUSION

Daily supplementary intake of green tea-extract powder lowered the hemoglobin A1c level in individuals with borderline diabetes.

Validity and reproducibility of HOMA-IR, 1/HOMA-IR, QUICKI and McAuley's indices in patients with hypertension and type II diabetes

The aim of this study was to evaluate the validity and reliability of homeostasis model assessment-insulin resistance (HOMA-IR) index, its reciprocal (1/HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and McAuley's index in hypertensive diabetic patients. In 78 patients with hypertension and type II diabetes glucose, insulin and triglyceride levels were determined after a 12-h fast to calculate these indices, and insulin sensitivity (IS) was measured with the hyperinsulinemic euglycemic clamp technique. Two weeks later, subjects had again their glucose, insulin and triglycerides measured. Simple and multiple linear regression analysis were applied to assess the validity of these indices compared to clamp IS and coefficients of variation between the two visits were estimated to assess their reproducibility. HOMA-IR index was strongly and inversely correlated with the basic IS clamp index, the M-value (r=-0.572, P<0.001), M-value normalized with subjects' body weight or fat-free mass and every other clamp-derived index. 1/HOMA-IR and QUICKI indices were positively correlated with the M-value (r=0.342, P<0.05 and r=0.456, P<0.01, respectively) and the rest clamp indices. McAuley's index generally presented less strong correlations (r=0.317, P<0.05 with M-value). In multivariate analysis, HOMA-IR was the best fit of clamp-derived IS. Coefficients of variation between the two visits were 23.5% for HOMA-IR, 19.2% for 1/HOMA-IR, 7.8% for QUICKI and 15.1% for McAuley's index. In conclusion, HOMA-IR, 1/HOMA-IR and QUICKI are valid estimates of clamp-derived IS in patients with hypertension and type II diabetes, whereas the validity of McAuley's index needs further evaluation. QUICKI displayed better reproducibility than the other indices.

Neuroprotective potential of the Bahadori leanness program: A “mini-fast with exercise” strategy

The Bahadori Leanness Program (BLP) is a multi-step strategy for weight control, the most innovative feature of which is "mini-fast with exercise" - every 24h includes a fast of 12-14 h duration within which is nested a session of aerobic exercise. Low-fat, low-glycemic-index foods choices help to insure that diurnal levels of glucose and insulin remain relatively low. Clinical experience demonstrates that clients can achieve good compliance with this protocol, and the long term impact on body weight is gratifying. Rodent studies demonstrate that alternate-day feeding is even more effective than caloric restriction for promoting neuroprotection, suggesting that intermittent periods of mild metabolic stress induce protective adaptations in the brain; exercise training is also neuroprotective in these models. Mattson has raised the possibility that regular meal-skipping might be a feasible strategy for achieving similar - though perhaps less potent - protection in humans. Thus, it is suggested that exercise superimposed on regular short-term fasts, as in the BLP, might provide meaningful neuroprotection. Studies assessing CSF levels of brain neurotrophic hormones might be useful for evaluating the impact of such a strategy on brain neurochemistry. It should not be overlooked that leanness, good insulin sensitivity, and regular exercise are likely to be neuroprotective in their own right. The episodic metabolic stress associated with BLP may also have potential for prevention and therapy of cancer, inasmuch as down-regulation of systemic IGF-I activity during the mini-fasts would be expected to boost the rate of apoptosis in IGF-I-responsive neoplastic or pre-neoplastic tissues. Moreover, the relatively low-diurnal insulin levels and exercise training associated with BLP would be expected to down-regulate sympathetic activity while boosting cardiac parasympathetic tone - effects that should decrease risk for hypertension and sudden-death arrhythmias. Thus, it is conceivable that BLP will provide a range of health benefits extending beyond those attributable to its favorable impact on body composition.

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.

QUICKI is a useful index of insulin sensitivity in subjects with hypertension

Insulin resistance may link disorders of metabolic homeostasis such as diabetes and obesity with disorders of hemodynamic homeostasis such as hypertension. Thus it is of interest to validate simple methods for quantifying insulin sensitivity in hypertensive patients. The quantitative insulin-sensitivity check index (QUICKI) is a novel mathematical transformation of fasting blood glucose and insulin levels. In obese and diabetic subjects, QUICKI has a significantly better linear correlation with glucose clamp determinations of insulin sensitivity than minimal-model estimates. To determine whether QUICKI is also useful in hypertensive subjects, we performed glucose clamps and frequently sampled intravenous glucose tolerance tests (FSIVGTT) on 27 hypertensive subjects taken off antihypertensive medication. Indexes of insulin sensitivity derived from glucose clamp studies (SIClamp) were compared with QUICKI, minimal-model analysis of FSIVGTTs (SIMM), and homeostasis model assessment (HOMA). The correlation between QUICKI and SIClamp ( r = 0.84) was significantly better than that between SIMM and SIClamp( r = 0.65; P < 0.028). The correlation between QUICKI and SIClamp was comparable to that between 1/HOMA and SIClamp ( r = 0.82). When studies were repeated in 14 subjects who had resumed antihypertensive medications, the percent changes in SIClamp for each of these patients were significantly correlated with percent changes in QUICKI ( r = 0.61) and HOMA ( r = −0.54) but not SIMM ( r = −0.18). We conclude that QUICKI is a simple, robust index of insulin sensitivity that is useful for evaluating and following the insulin resistance of hypertensive subjects in both research studies and clinical practice.

Postprandial lipemia in hypertension

OBJECTIVE

Many studies have shown that patients with coronary artery disease have an exaggerated rise and a delayed fall of plasma triglyceride (TG) concentration postprandially. We examined whether patients with essential hypertension have the same response to a fatty meal.

METHODS

A fatty meal (350g per 2 m(2) body surface with 83.5% fat) was given to 25 patients with essential hypertension (H) and to 25 normotensives (N). The two groups were matched for age, body mass index, lipid profile, basal glucose and insulin concentrations, and an index of homeostasis model of insulin resistance (HOMA-IR). A quantitative insulin sensitivity check index (QUICKI) was calculated. Blood samples were taken at 0, 4, 6, and 8 hours after the fatty meal. Lipid variables were measured in all samples. Blood glucose and insulin levels were measured in the fasting state.

RESULTS

Total and high density lipoprotein cholesterol, apolipoprotein A1 and B, lipoprotein (a), HOMA-IR and QUICKI did not differ significantly over time between the groups. The plasma TG concentration (mg/dL) increased significantly after fat loading in H (from 118 +/- 31 to 284 +/- 137 at 4 hours, 327 +/- 93 at 6 hours and 285 +/- 71 at 8 hours) compared to N group (from 105 +/- 29 to 150 +/- 38 at 4 hours, 148 +/- 40 at 6 hours and 115 +/- 34 at 8 hours), p = 0.001, p < 0.001 and p < 0.001, respectively.

CONCLUSION

This study suggests that patients with hypertension have an exaggerated response and delayed clearance of plasma TG concentration after fat loading.

Insulin Resistance and Hypertension: Seven-Year Follow-Up Study in Middle-Aged Japanese Men (the KEIO Study)

Only a few longitudinal studies in Asians have shown a close association between hyperinsulinemia and the incidence of hypertension. In the present study, we used the insulin resistance index, HOMA-IR [fasting plasma glucose (FPG) (mmol/l) X insulin (microUl/ml) / 22.5], and tried to elucidate longitudinally the relationship among insulin resistance, blood pressure, body mass index (BMI), FPG, and lipid profile in middle-aged Japanese men. Three hundred and ten male non-hypertensive subjects aged 30 to 58 years in 1993 (44.5 +/- 7.8 (SD) years; BMI, 22.6 +/- 2.5 kg/m2) were divided into three groups according to HOMA-IR (A: lowest; B: middle; and C: highest). Their BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, FPG and lipid profile were followed up for 7 years. The percentage of high normal blood pressure in 1993 and 2000 did not differ among the three groups. However, in 2000 hypertensive subjects made up 11.7% of group A (12/103), 15.4% of group B (16/104), and 29.1% of group C (30/103) (chi2 = 11.50, p = 0.003). SBP, DBP, and many other metabolic parameters in 2000 were significantly higher in group C than in the other groups. Furthermore, both SBP and DBP in 2000 were positively correlated with HOMA-IR in 1993 (r = 0.17 and p < 0.01 for both). The correlation between HOMA-IR in 1993 and DBP in 2000 was significant, even after adjustment for age and BMI in 1993. These findings suggest an important role of insulin resistance in predicting the future incidence of hypertension in middle-aged Japanese men.

Indices of insulin action, disposal, and secretion derived from fasting samples and clamps in normal glucose-tolerant black and white children

OBJECTIVE

To validate fasting indices of insulin sensitivity and secretion in a diverse pediatric population against gold standard estimates from euglycemic and hyperglycemic clamps.

RESEARCH DESIGN AND METHODS

A total of 31 children (mean BMI 25.1 +/- 4.9 kg/m(2), mean age 8.7 +/- 1.4 years, 15 girls and 16 boys, 12 black and 19 white) underwent euglycemic and hyperglycemic clamps 2-6 weeks apart to derive insulin sensitivity indices (SI (Eug clamp) and SI (Hyper clamp)). Fasting samples were used to derive the homeostasis model assessment of insulin resistance index (HOMA-IR), HOMA of percent beta-cell function (HOMA-B%), quantitative insulin sensitivity check index (QUICKI), insulinogenic index, antilipolytic insulin sensitivity index (ISI-FFA), and C-peptide-to-insulin ratio.

RESULTS

The QUICKI correlated best with SI (Eug clamp) (r = 0.69, P < 0.05) and had greater correlations to SI (Eug clamp) than did either SI (Hyper clamp) (r = 0.45, P < 0.05) or the HOMA-IR (r = -0.51, P < 0.05). Both fasting insulin and the insulinogenic index correlated well with first- and steady-phase insulin secretion (r's from 0.79 to 0.86, P < 0.05). HOMA-B% was not as highly correlated (r = 0.69-0.72, P < 0.05). Fasting C-peptide-to-insulin ratio was not significantly correlated with clamp-derived metabolic clearance rate of insulin. ISI-FFA was not correlated with the degree of free fatty acid suppression obtained from the clamps.

CONCLUSIONS

The QUICKI, fasting insulin, and the insulinogenic index all closely correlate with corresponding clamp-derived indices of insulin sensitivity and secretion in this diverse pediatric cohort. These results, if replicated in similarly diverse populations, suggest that estimates based on fasting samples can be used to rank order insulin secretion and sensitivity in pediatric cohorts.

Insulin resistance and hypertension in postmenopausal women

The aim of the study was to elucidate the role of hyperinsulinaemia/insulin resistance in hypertension of lean postmenopausal women. Twenty-four women with essential hypertension (systolic/diastolic > or =140/90 mm Hg) and a body mass index (BMI) less than 26 kg/m(2) not receiving antihypertensive treatment or who had been without treatment for a 4-week washout period, and 10 normotensive postmenopausal weight- and aged-matched controls were compared. Both groups were not receiving hormone replacement therapy. Hip and waist circumferences were measured and waist/hip ratios were calculated. Casual blood pressure was measured in triplicate. Neither the fasting plasma glucose nor serum insulin levels in hypertensive women and normotensives differed significantly. During 2 h oral glucose (75 g)-tolerance test the mean plasma glucose levels after 30 min (172.5 +/- 40.24 mg/dl vs. 143.67 +/- 20.16 mg/dl), 60 min (134.88 +/- 38.78 mg/dl vs. 112.33 +/- 5.44 mg/dl) and 120 min (116.08 +/- 26.65 mg/dl vs. 95.56 +/- 20.17 mg/dl) were significantly higher in hypertensives than that for normotensives (P < 0.05 for all three comparisons). The mean serum insulin levels of hypertensive women were significantly higher than that in normotensives after 15 min (92.04 +/- 59.90 microU/ml vs. 54.89 +/- 33.67 microU/ml) and 120 min (49.63 +/- 44.45 microU/ml vs. 19.22 +/- 24.10 microU/ml; P< 0.05 for both comparisons). The mean serum insulin: plasma glucose ratio for hypertensive women was significantly higher than that for normotensives after 15 min (0.596 +/- 0.46 vs. 0.359 +/- 0.20 microU/mg), 60 min (0.406 +/- 0.30 vs. 0.329 +/- 0.25 microU/mg) and 120 min (0.436 +/- 0.35 vs. 0.205 +/- 0.26 microU/mg) (P < 0.05 for all three comparisons). Significant correlations were observed between the daytime period and 24-h average ambulatory systolic blood pressure and the area under the serum insulin curve (r = 0.41 and 0.36, respectively). For non-dippers we found higher fasting insulinaemias but the AUC(insulin) did not differ. Plasma glucose levels did not differ either during fasting or during OGTT (AUC(glucose)). Insulinogenic index was higher in dippers than in non-dippers. We conclude that in lean, postmenopausal hypertensive women insulin resistance is increased compared with age- and weight-matched normotensive women. Also, hyperinsulinaemia correlates with ambulatory systolic blood pressure. Thus, insulin resistance may possibly be involved as a pathogenetic factor in lean, postmenopausal hypertensive women.

Insulin inhibits acetylcholine responses in rat isolated mesenteric arteries via a non-nitric oxide nonprostanoid pathway

Hyperinsulinemia is a risk factor for hypertension and arteriosclerosis. The mechanism by which it contributes to disease progression is not known. The present study examines the effects of insulin on endothelium-derived relaxing factors. Segments of rat mesenteric arterioles and aorta were set up for isometric recordings. The effect of insulin (1 mU/mL) on acetylcholine responses was examined with and without nitro-L-arginine, indomethacin, KCl (40 mmol/L), and apamin+charybdotoxin. Incubation with insulin (maximum response to acetylcholine 90.9+/-8.7% versus 90.7+/-4.5% for before versus after insulin, respectively), nitro-L-arginine, indomethacin, or high K(+) alone had no effect on these responses in mesenteric arterioles. Apamin+charybdotoxin significantly blunted responses to acetylcholine. When coincubated with nitro-L-arginine but not with indomethacin or high K(+), insulin blunted the maximum response to acetylcholine (from 84.8+/-8.2% to 40.7+/-10.2% for before versus after insulin, respectively; P<0.01). When coincubated with apamin+charybdotoxin, insulin had no further effect. Coadministration of indomethacin with nitro-L-arginine had no greater effect than did nitro-L-arginine alone. The addition of insulin, together with nitro-L-arginine and indomethacin, significantly decreased the maximal response to acetylcholine from 96.6+/-5.3% to 52.9+/-10.8% (P<0.01). In the aorta, nitro-L-arginine abolished acetylcholine responses. Coadministration with insulin had no further effect. We conclude that insulin attenuates acetylcholine responses mediated by endothelium-derived hyperpolarizing factor in small but not large arteries. This effect of insulin is apparent only when NO is blocked and may be important in the development of hypertension or arteriosclerosis when reduced NO function has been reported.

Association of multiple risk factors and insulin resistance with increased prevalence of asymptomatic coronary artery disease by an electron-beam computed tomographic study

The insulin resistance syndrome, consisting of resistance to insulin and several metabolic abnormalities, is associated with an increased risk of symptomatic coronary artery disease. Asymptomatic persons with increased coronary calcification have increased coronary plaque and an increased likelihood of future cardiovascular events. Electron-beam computed tomography-derived coronary artery calcium scores, metabolic and anthropometric parameters, and fasting and stimulated concentrations of glucose and insulin were measured in 1160 asymptomatic men and women. Coronary artery calcium scores were positively correlated with glucose, insulin, and homeostasis model assessment (HOMA) insulin resistance. Calcium scores were positively correlated with intra-abdominal adiposity, age, total cholesterol/high density lipoprotein (HDL) ratio, low density lipoprotein, triglycerides, blood pressure, and HOMA beta cell function and inversely correlated with HDL and peripheral fat. These correlations, except for 2-hour glucose, remained significant for all subjects with fasting serum glucose <126 mg/dL or all subjects with fasting serum glucose 110 mg/dL. In a multivariate analysis, age, sex, family history of premature coronary artery disease, intra-abdominal adiposity, low density lipoprotein, and smoking independently predicted calcium scores. Blood pressure, HDL, triglycerides, glucose, insulin, and HOMA insulin resistance or beta cell function were not independently correlated with coronary artery calcium scores. Asymptomatic individuals with insulin resistance have elevated coronary calcium scores. The association between insulin resistance and coronary calcification persists with impaired glucose tolerance and normal fasting serum glucose. Central/visceral adiposity may be a determinant of insulin resistance and atherosclerosis even in asymptomatic nondiabetic persons.

[Insulin resistance quantification by fasting insulin plasma values and HOMA index in a non-diabetic population]

BACKGROUND

Our goal was to determine the prevalence of insulin resistance (IR) by means of fasting insulin plasma values and the HOMA index,and to analyse the relation of these parameters with other components of the metabolic syndrome.

SUBJECTS AND METHOD

We studied 292 non-diabetic individuals, aged between 20 and 65 years, randomly selected from subjects attending an outpatient care center (Valencia-Spain-metropolitan area). 97 subjects who lacked clinical and biological criteria of IR were selected. In addition to calculating the HOMA index, anthropometric parameters, plasma lipids values, fasting glucose and insulin plasma levels were measured by standard methods in all subjects.

RESULTS

In the subgroup of 97 subjects without clinical and biological criteria of IR, we established a diagnosis of IR when the fasting plasma insulin value was >= 16.7 mU/l or the HOMA index was >= 3.8. Cut-off points of the percentil 90th of this subgroup were taken into account. In the whole group,the prevalence of IR (HOMA >= 3.8) was 31.8%, with a higher frequency in men compared to women.

CONCLUSIONS

In addition to fasting plasma insulin values and HOMA index, the best clinical and biochemical indicators of IR were fasting plasma glucose levels, BMI and triglycerides (TG) plasma values. Thus, the odds ratio for insulin resistance was 5.9 for a glycemia >= 110 mg/dl, 2.6% for BMI >= 25 kg/m(2) and 2.2 for triglycerides >= 150 mg/dl.

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.