High plasma leptin concentrations in hypertensive men but not in hypertensive women

Lower body mass index is associated with orthostatic hypotension in Parkinson's disease

INTRODUCTION

Lower body mass index (BMI) is associated with orthostatic hypotension (OH) in the general population, especially in the elderly; however, no studies have addressed this issue in Parkinson's disease (PD).

METHODS

We investigated the results of the head-up tilt test and BMI of patients with PD, and evaluated whether BMI is related to orthostatic systolic blood pressure (SBP) change during the head-up tilt test. PD patients were divided into male and female groups, and further divided into middle-aged (age<65years) and elderly (age≥65years) subgroups in each sex.

RESULTS

OH was observed in 13 of 64 male and 12 of 75 female patients with PD. BMI was lower in patients with OH than in those without, in both men and women. In the elderly group, a significant correlation between BMI and orthostatic SBP change was found (men, r=0.47, p=0.006; women, r=0.43, p=0.005), and a BMI below mean-0.5 standard deviation increased OH odds (men: BMI<20.5; odds ratio, 6.79; 95% CI, 1.06-43.36; women: BMI<18.5; odds ratio, 5.11; 95% CI, 1.05-24.96).

CONCLUSION

Lower BMI is a predisposing factor of OH in elderly patients with PD.

Obesity-induced increases in sympathetic nerve activity: sex matters

Abundant evidence obtained largely from male human and animal subjects indicates that obesity increases sympathetic nerve activity (SNA), which contributes to hypertension development. However, recent studies that included women reported that the strong relationships between muscle SNA and waist circumference or body mass index (BMI) found in men are not present in overweight and obese women. A similar sex difference in the association between adiposity and hypertension development has been identified in animal models of obesity. In this brief review, we consider two possible mechanisms for this sex difference. First, visceral adiposity, leptin, insulin, and angiotensin II have been identified as potential culprits in obesity-induced sympathoexcitation in males. We explore if these factors wield the same impact in females. Second, we consider if sex differences in vascular reactivity to sympathetic activation contribute. Our survey of the literature suggests that premenopausal females may be able to resist obesity-induced sympathoexcitation and hypertension in part due to differences in adipose disposition as well as its muted inflammatory response and reduced production of pressor versus depressor components of the renin-angiotensin system. In addition, vascular responsiveness to increased SNA may be reduced. However, more importantly, we identify the urgent need for further study, not only of sex differences per se, but also of the mechanisms that may mediate these differences. This information is required not only to refine treatment options for obese premenopausal women but also to potentially reveal new therapeutic avenues in obese men and women.

The association of leptin with dyslipidemia, arterial hypertension and obesity in Kyrgyz (Central Asian nation) population

BACKGROUND

Leptin, an adipocytokine produced by adipose tissue, along with the traditional cardiometabolic risk factors, contributes to the development of cardiovascular complications. At the same time, ethnic features of adipocytokines have been insufficiently investigated, especially among Asians, who have an increased risk of cardiovascular complications compared with Europeans. Aim of study was to investigate the relationship between leptin levels and age, gender, anthropometric parameters, lipid parameters, arterial hypertension (AH), and obesity in the adult population of ethnic Kyrgyz people living in Central Asia.

RESULTS

In total, 322 ethnic Kyrgyz (145 men, 177 women) aged ≥ 30 years were studied. Waist and hip circumference, body mass index, blood glucose, lipids, leptin, and homeostatic model assessment were measured. Patients in the upper quartile of leptin levels had high values of BMI, WC, systolic and diastolic blood pressure, glucose, and HOMA index compared with patients with lower leptin levels. The prevalence of metabolic syndrome and AH increased with higher levels of leptin. Leptin positively correlated with BMI, WC, triglycerides, and glucose concentrations in patients of both sexes. According to the multivariate logistic regression analysis, elevated leptin levels increased by 30 times the risk of obesity in men, regardless of the presence of type 2 diabetes, and 17.7 times in women.

CONCLUSION

Leptin is associated with general and abdominal obesity, dyslipidemia, and insulin resistance in Kyrgyz patients.

Association between adipocytokines and insulin resistance in Indian hypertensive patients

OBJECTIVE

Although the relationship between obesity, hypertension (HT), and insulin resistance is well-recognised, the pathophysiological mechanism involved is relatively poorly understood. The present study aims in examining the relationship between adipocytokines and insulin resistance in Indian hypertensive patients to better understand the pathogenesis of HT.

METHODS

A total of 124 subjects including 41 controls, 41 obese, and 42 hypertensive patients were recruited in this cross-sectional study. Fasting adipocytokines (leptin, adiponectin, resistin) and highly sensitive C-reactive protein (hsCRP) levels were measured by enzyme-linked immunosorbent assay (ELISA). Insulin resistance (IR) index was calculated by the homeostasis model assessment (HOMA). The relation between these variables was studied by univariate and multiple logistic regression analysis.

RESULTS

Among the hypertensive patients, obese hypertensive patients exhibited significantly increased HOMA-IR and altered adipocytokine profile compared to the non-obese control subjects. In a stepwise multiple linear regression analysis with IR as a dependant variable, the study shows leptin as a significant predictor in hypertensive patients. Multiple logistic regression analysis revealed that among the adipocytokines, leptin had a strong association with HT in our population.

CONCLUSION

Among the adipocytokine, serum leptin levels were significantly increased in hypertensive patients and were also associated with IR and HT. Thus, our findings suggest that leptin may be playing an important role in the development of HT in our population.

Contribution of serum leptin to metabolic syndrome in obese and nonobese subjects

BACKGROUND AND AIMS

Little evidence exists regarding the association of leptin with metabolic syndrome (MetS) as defined by conventional criteria. Moreover, the contribution of obesity to this relationship is not well understood. This study aimed to evaluate the association between leptin concentrations with MetS in obese and nonobese subjects.

METHODS

Data from the Third National Surveillance of Risk Factors of Non-Communicable Diseases (SuRFNCD) in Iran was used. In a cross-sectional study of 3045 adults (48.2% men) aged 25-64 years, anthropometric indices, blood pressure, fasting plasma glucose, fasting insulin, lipid profile [triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides], and fasting leptin were measured. Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) was also calculated.

RESULTS

Leptin concentrations were 2.6 fold higher in women compared with men. Subjects with MetS had significantly higher leptin concentrations. Leptin concentrations increased steadily with an increment in the number of MetS components (p <0.001). Leptin was significantly associated with MetS after adjustment for age, cigarette smoking, medication use, physical activity, HOMA-IR, and LDL-C. The significant association between leptin and MetS persisted after adjustment for body mass index (OR: 1.31, 95% CI: 1.09-1.58 in males and 1.17, 95% CI: 1.01-1.38 in females) and waist circumference (OR: 1.24 95% CI: 1.01-1.51 in men and 1.22, 95% CI: 1.04-1.43 in women). After dividing subjects into obese and nonobese, leptin concentrations were again significantly higher in subjects with MetS in both groups.

CONCLUSIONS

We demonstrated that leptin concentrations are significantly associated with International Diabetes Federation (IDF)-defined MetS, independent of overall and central obesity. Our findings point to an independent role for leptin in development of MetS.

Leptinemia and its association with stroke and coronary heart disease in the Jackson Heart Study

BACKGROUND

To examine the association of increased plasma leptin concentration with prevalent stroke and coronary heart disease (CHD) and to examine the genetic contributions of leptin to this association in the Jackson Heart Study cohort.

METHODS

A cohort of 5170 participants aged 21-84 years who underwent Exam I during 2000-2004 was analysed. Odds ratios (OR) of prevalent stroke and CHD were calculated using a logistic regression model adjusted for age, smoking, hypertension and waist circumference (WC). Variance component analysis was used to partition the phenotypic variance of leptin into the polygenic and environmental components.

RESULTS

The prevalence of stroke and CHD was 4.04% and 5.85% in women, and 4.88% and 8.92% in men, respectively. Body mass index (BMI) and WC were highly correlated with leptin both in men and women. In multivariate analysis stratified by sex, leptin was significantly associated with stroke (OR = 1.97, 95% CI = 1.21-3.21) in women after adjustment for age, smoking, systolic blood pressure, BMI and WC (P = 0.0079). No significant association was observed in men. Heritability of sex-, age-adjusted log-transformed leptin for this cohort was 38.0% and 37.8% after further adjustment for WC and hypertension, respectively. In addition, a sibship effect was also found to be significant and explained 12.2% of the total variance of leptin (P = 0.007).

CONCLUSION

There is a significant association of leptin with stroke in women, which is partly influenced by the genetic factor. The findings suggest that leptinemia is an independent risk factor for stroke in African American women.

Leptin and high-sensitivity C-reactive protein and their interaction in the metabolic syndrome in middle-aged subjects

High-sensitivity C-reactive protein (hsCRP) and leptin, known to interact at the molecular level, have been associated with the metabolic syndrome (MS). We examined the independent and joint effects of high leptin and hsCRP levels on the development of MS in a population-based cohort of middle-aged subjects (N = 1035). Leptin and hsCRP levels increased with an increase in the number of metabolic abnormalities (P < .001). However, additional adjustment for body mass index diluted the association of leptin with MS in women. In men, the association of high leptin with insulin resistance and waist circumference (P < .001), and in women, the association of high hsCRP with insulin resistance (P = .029) and waist circumference (P = .009) persisted in the multivariate logistic regression models. High leptin in men and high hsCRP in women were significant predictors of MS in logistic regression analysis (P < .001). The highest prevalence of MS (86% in men and 71% in women) was observed in the subjects who belonged to the highest quartile in both leptin and hsCRP. MS is associated independently with high leptin in men and with hsCRP in women, whereas individuals with both of these markers belong to the highest risk of metabolic cluster. The study suggests sex-specific interplay between metabolic and inflammatory markers in the pathogenesis of MS.

Plasma Leptin and its Relationship with Lipid Peroxidation and Nitric Oxide in Obese Female Patients with or without Hypertension

BACKGROUND

Recent evidence suggested that leptin-induced oxidative stress in human endothelial cells in vivo and increased oxidative stress in human essential hypertension may further contribute to both the development of atherosclerosis and other cardiovascular diseases. We investigated the association of plasma leptin levels with plasma lipid peroxidation and nitric oxide metabolites (NOx) in obese hypertensive atherosclerosis model.

METHODS

Plasma leptin, lipid peroxidation and NOx levels were determined in age-matched non-obese normotensive female subjects (n = 30), obese normotensive female subjects (n = 45), and obese hypertensive female subjects (n = 50). Plasma leptin levels were determined by immunoradiometric method. Lipid peroxidation was determined as thiobarbituric acid reactive substances (TBARS) using spectrophotometric method. NOx levels were determined using enzymatic method.

RESULTS

We found that plasma leptin and TBARS levels were increased in obesity, and obese hypertensives have significantly higher plasma leptin and TBARS levels than obese normotensives (p <0.001 and p <0.001). Obese hypertensives have significantly lower plasma NOx levels than obese normotensives (p <0.001). In univariate and multivariate regression analysis, plasma leptin levels were significantly correlated with TBARS (p <0.01 and p <0.01) in obese subjects. Plasma TBARS were also inversely correlated with NOx in hypertensive obese subjects (r = -0.412, p <0.01).

CONCLUSIONS

Our results have shown that elevated leptin levels may be associated with increased oxidative stress and free-radical-induced decreased NOx levels. Therefore, hyperleptinemia may be an important contributor to the generation of hypertension in obesity.

Role of leptin in blood pressure regulation and arterial hypertension

Leptin is a 16-kDa protein secreted by white adipose tissue that is primarily involved in the regulation of food intake and energy expenditure. Plasma leptin concentration is proportional to the amount of adipose tissue and is markedly increased in obese individuals. Recent studies suggest that leptin is involved in cardiovascular complications of obesity, including arterial hypertension. Acutely administered leptin has no effect on blood pressure, probably because it concomitantly stimulates the sympathetic nervous system and counteracting depressor mechanisms such as natriuresis and nitric oxide (NO)-dependent vasorelaxation. By contrast, chronic hyperleptinemia increases blood pressure because these acute depressor effects are impaired and/or additional sympathetic nervous system-independent pressor effects appear, such as oxidative stress, NO deficiency, enhanced renal Na reabsorption and overproduction of endothelin. Although the cause-effect relationship between leptin and high blood pressure in humans has not been demonstrated directly, many clinical studies have shown elevated plasma leptin in patients with essential hypertension and a significant positive correlation between leptin and blood pressure independent of body adiposity both in normotensive and in hypertensive individuals. In addition, leptin may contribute to end-organ damage in hypertensive individuals such as left ventricular hypertrophy, retinopathy and nephropathy, independent of regulating blood pressure. Here, current knowledge about the role of leptin in the regulation of blood pressure and in the pathogenesis of arterial hypertension is presented.

A Positive Association between Leptin and Blood Pressure of Normal Range in Japanese Men

The results of previous studies on the relationship between leptin and blood pressure are discordant. We investigated to what extent the serum leptin level was related to blood pressure independent of the degree of insulin resistance. The subjects were 1916 men aged 34-69 years whose mean body mass index (BMI) was 23.0 kg/m2. Blood pressure was regressed by leptin concentrations with adjustments for age, BMI, insulin resistance, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol, physical activity, drinking habits and smoking status. Leptin was associated with diastolic blood pressure (DBP) (standardized beta: 0.092, p = 0.003), but not with systolic blood pressure (SBP) (standardized beta: 0.035, p = 0.25), although insulin resistance was positively associated with both SBP and DBP (standardized beta: 0.175 for SBP, p < 0.001 and 0.114 for DBP, p < 0.001) among all subjects. After subjects were divided into those with normal blood pressure (SBP <130 mmHg and DBP <85 mmHg) and those with higher blood pressure, leptin was positively and significantly associated with DBP (standardized beta: 0.106, p = 0.012) independent of the degree of insulin resistance, but not with SBP (standardized beta: 0.064, p = 0.13) among subjects in the normal blood pressure range. Among the subjects with higher blood pressure, however, neither the association of leptin with SBP nor that of leptin with DBP was statistically significant. These findings suggest that leptin may maintain and increase arterial tone, resulting in the elevation of DBP only within normal blood pressure range. It is also likely that leptin is a physiological mediator--or at least a marker--of some degree of DBP elevation in obesity.

Leptin: sympathetic and cardiovascular effects

Shortly after leptin was first discovered, it was hailed as the key to understanding obesity. However, it didn't take long for investigators to realize that the hormone was more than a feedback signal to inhibit further food intake. Since those early days, leptin has been well characterized in rodents. It exerts an influence in many physiologic processes, including food intake, thermoregulation, fertility, thyroid function, adrenal function, sympathetic nerve activation, renal function, blood vessel tone, and blood pressure. No longer a satiety hormone, it is being looked at from many different perspectives. One such perspective is its influence on the cardiovascular system. This review highlights some of the work in this area.

Comparative analysis of plasma leptin levels in both genders of patients with essential hypertension and healthy subjects

While pathogenesis of hypertension is not clearly deciphered yet, increase in body weight, most of the time, is associated with hypertension. There are reports indicating that leptin, product of the Ob gene mainly synthesized in adipocytes, may have role(s) in hypertension, but contribution of the gender is rather contradictive. In the present study, plasma leptin levels in patients of both genders with hypertension and normotensive controls were measured and the relationship between plasma leptin levels and BMI were evaluated in both sexes. Total of 62 patients (31 M/31 F) diagnosed with essential hypertension who were not under any antihypertensive medication were admitted into the study. The control group was composed of 56 (25 M/31 F) age-, BMI- and sex-matched healthy normotensive volunteers. Plasma leptin levels were determined by a commercial ELISA kit. Plasma leptin and leptin/BMI levels (Mean +/- SEM) of women (n:62) were significantly higher than men (n:56) (20.10 +/- 1.47 ng/ml versus 4.72 +/- 0.50 ng/ml; p < 0.0001). Plasma leptin and leptin/BMI levels of patients of both genders with hypertension were significantly higher than in normotensive subjects (p < 0.05). Leptin and leptin/BMI levels in obese hypertensives were higher than obese normotensives (p < 0.05). Obese hypertensive women had higher leptin and leptin/BMI levels than obese normotensive women (p < 0.05). In conclusion, these results support the hypothesis that a possible link exists between leptin and hypertension. Further studies are needed to clarify how increased levels of leptin affects the pathophysiology of hypertension.

Insulin and insulin resistance: impact on blood pressure and cardiovascular disease

Cardiovascular disease is a major cause of mortality in individuals with diabetes. Many factors, including hypertension, contribute to the high prevalence of CVD in this population. Hypertension occurs approximately twice as frequently in patients with diabetes compared with patients without diabetes. Conversely, recent data suggest that hypertensive persons are more likely to develop diabetes than normotensive persons. In addition, up to 75% of CVD in patients with diabetes may be attributed to hypertension, leading to recommendations for more aggressive blood pressure control (ie, < 130/85 mm Hg) in persons with coexistent diabetes and hypertension. Increasing obesity further contributes to both diabetes and hypertension and significantly increases CVD morbidity and mortality. Other important risk factors for CVD in these patients include atherosclerosis, dyslipidemia, microalbuminuria, endothelial dysfunction, platelet hyperaggregability, coagulation abnormalities, and diabetic cardiomyopathy. The current knowledge regarding these risk factors has been reviewed, placing special emphasis on the metabolic syndrome, hypertension, microalbuminuria, and the role of obesity in these disorders. Although not discussed in detail, it is acknowledged that both hygienic measures (weight loss and aerobic exercise) and treatment strategies that include aspirin, statins, INS sensitizers, and antihypertensive agents that reduce renin-angiotensin-aldosterone system activity have been shown to reduce inflammation, coagulation abnormalities, endothelial function, proteinuria, and in some cases reduce CVD and renal disease progression. Additional therapeutic agents are currently being developed specifically to improve INS sensitivity and other CVD risk factors that are components of the cardiometabolic syndrome.

Serum leptin is elevated in Saudi Arabian patients with metabolic syndrome and coronary artery disease

AIMS

To compare plasma leptin in Saudi subjects with Type 2 diabetes and coronary heart disease (CHD) with non-diabetic control subjects and to examine the relationship of plasma leptin to other CHD risk factors.

RESEARCH DESIGN AND METHOD

Serum leptin concentrations were measured in 144 Saudi men. Subjects studied included 59 with Type 2 diabetes mellitus [BMI 27.5 (3.7) kg/m2 mean (sd)], 34 with coronary heart disease [BMI 29.6 (1.8) kg/m2], and 51 non-diabetic controls [BMI 28.0 (3.5) kg/m2]. There was no significant difference in BMI between the groups. Fasting serum leptin, lipids, insulin, apolipoproteins and glucose were measured. BMI, blood pressure; smoking habit and age were also recorded. Insulin resistance was assessed using the HOMA model.

RESULTS

Leptin concentrations were significantly higher in diabetic and CHD patients than in controls (P = 0.024 and 0.016, respectively). Multiple regression analysis showed that body weight (P < 0.0006), serum triglyceride concentration (P = 0.046) and systolic blood pressure (P = 0.013) were all significantly related to the logarithm of the serum leptin concentration (R2 = 0.549) in CHD patients. A subgroup analysis, comparing those patients who had the metabolic syndrome, as defined by WHO, with controls, showed higher serum leptin in those with metabolic syndrome (P = 0.05).

CONCLUSIONS

Serum leptin is increased in Saudi subjects with diabetes mellitus, metabolic syndrome and CHD. Leptin may be a marker of risk of CHD, at least in men, and contribute to the CHD risk profile in subjects with insulin resistance. Further studies are needed to evaluate this relationship prospectively.

Hypertension and obstructive sleep apnea

Obstructive sleep apnea is a common disorder that is often unrecognized and underappreciated. Emerging evidence suggests that there is a causal link between obstructive sleep apnea and hypertension. This relationship appears to be independent of other comorbidities that have been previously linked to hypertension, such as obesity. The majority of studies support the contention that alleviation of sleep disordered breathing has a clinically significant beneficial impact on decreasing both nighttime and daytime blood pressure. A pathophysiologic basis for patients with sleep apnea having an increased risk for hypertension is not fully elucidated. However, there is consistent evidence that autonomic mechanisms are implicated. Sympathetic activation along with humoral responses to repetitive episodes of hypoxemia and apnea over the longer term may cause vasoconstriction, endothelial dysfunction, and possibly hypertension. Patients with sleep apnea are often obese and may be predisposed to weight gain. Hence, obesity may further contribute to hypertension in this patient population.

Association between serum leptin levels and 24-hour blood pressure in obese women

OBJECTIVE

To assess the relationship between serum leptin and 24-hour blood pressure (BP) in obese women, according to body fat distribution.

RESEARCH METHODS AND PROCEDURES

A cross-sectional study was carried out in a population of 70 nondiabetic, normotensive, obese women (40 with android and 30 with gynoid type of obesity) and 20 nonobese healthy women as a control group. All subjects underwent 24-hour ambulatory BP monitoring. Blood samples were collected for serum leptin and plasma insulin measurements. Total cholesterol and high-density lipoprotein cholesterol were also measured.

RESULTS

Serum leptin levels were significantly higher in obese subjects than in controls, and they were more elevated in android obese women than in gynoid ones. Leptin levels were positively related to body mass index (BMI), insulin, and waist and hip circumferences in the android group. Among gynoid subjects, leptin levels showed positive associations with BMI and insulin. In women with android obesity, strong positive correlations (p < 0.001) were found between leptin levels and 24-hour systolic BP (SBP), daytime SBP, nighttime SBP, 24-hour diastolic BP (DBP), and daytime DBP. Multiple regression analyses, including age, insulin and leptin concentrations, BMI, and waist and hip circumferences on 24-hour and daytime SBP and DBP, showed that only leptin levels contributed to the variability of BP.

CONCLUSIONS

Our study shows that serum leptin levels are directly related to 24-hour BP levels in normotensive women with android fat distribution, independently of BMI.

Gender, ethnicity and genetics in cardiovascular disease: part 1: Basic principles

Prior to 1993, most drug efficacy and safety trials were conducted in white males, although gender and racial differences in pharmacodynamics and pharmacokinetics have been documented since the early 1900s. Over the last 2 decades, supported by the FDA and legislation, attempts to include more women and minorities in clinical drug trials have been made, with limited success. Yet, there are important differences in pathophysiology and pharmacogenetics, as well as pharmacotherapeutic effectiveness. This is the first of 2 articles that review the basic scientific principles of such differences. In particular, genetic polymorphisms of cardiovascular candidate genes and drug metabolism are described. The pharmacodynamic and pharmacokinetic variations among genders and ethnicities are summarized.

Plasma leptin and blood pressure in men: graded association independent of body mass and fat pattern

OBJECTIVE

The role of leptin in the association between body mass, central adiposity, and blood pressure (BP) is controversial. This study evaluated the relationship between leptin and BP in relation to body mass index (BMI) and fat distribution in a large sample of untreated male adults.

RESEARCH METHODS AND PROCEDURES

The study population was made up of 457 untreated male employees of the Olivetti factory in Naples. Plasma leptin, complete anthropometry, BP, and relevant biochemical variables were measured.

RESULTS

Log-transformed plasma leptin levels were directly associated with BMI (r = 0.661, p < 0.001) and waist circumference (r = 0.630; p < 0.001). Leptin also correlated with systolic (r = 0.258) and diastolic (r = 0.277) BP (p < 0.001). The association between leptin and BP was maintained after accounting for age, BMI (or waist circumference), log-insulin, and serum creatinine (p < 0.01); this association was stronger than that with BMI. Logistic regression analysis showed that an increased prevalence of hypertension (BP >or= 140 and/or 90 mm Hg) was associated with high plasma leptin levels when controlling for age and waist circumference (odds ratio, 1.99; 95%CI, 1.06 to 3.72) or for age and BMI (odds ratio, 1.92; 95%CI, 1.02 to 3.61).

DISCUSSION

A graded positive relationship between plasma leptin levels and BP was observed in this sample of untreated male adults. This association was independent of age, BMI, abdominal adiposity, and fasting plasma insulin. Moreover, elevated plasma leptin concentrations were associated with greater probability of hypertension, again independently of potential confounders.

Relationship between high plasma leptin concentrations and metabolic syndrome in obese pre-pubertal children

OBJECTIVE

To evaluate the relationship between serum leptin levels and metabolic syndrome, fasting insulin level and anthropometric index in obese pre-pubertal children.

DESIGN

A cross-sectional study was carried out on obese children.

SUBJECTS

A study was made of 41 obese children (aged 6-9 y) and the same number of non-obese children (control group), matched by age and sex.

METHODS

Body mass index (BMI), waist/hip ratio (WHR) and blood pressure were determined in each child. Serum leptin, glucose, insulin, lipid profile, sex hormone binding globulin (SHBG), plasminogen activator inhibitor-1 (PAI-1), tissue-plasminogen activator (t-PA) and fibrinogen were all measured.

RESULTS

The serum leptin level was significantly higher in obese children (15.47 vs 4.73 ng/ml). In the obese group, leptin showed a positive correlation with BMI (P<0.001), insulin (P<0.001), triglycerides (P<0.05), PAI-1 (P<0.05) and t-PA (P<0.05), and correlated negatively with SHBG (P<0.01), apolipoprotein A-I (P<0.05) and high-density lipoproteins cholesterol (HDL-C) (P<0.05). Corrected for BMI and WHR, leptin (P partial=0.002) is only an independent predictive factor for basal insulin. Using multivariant regression analysis, only insulin (P partial=0.003) and BMI (P partial=0.018) were independent predictive factors for leptin.

CONCLUSION

For this age group, high leptin resistance may be another component of metabolic syndrome, and may be involved in its etiopathogenesis. The involvement of leptin in this syndrome may be indirect, modulating the insulin's action.

Sleep disordered breathing and risk factors for cardiovascular disease

Patients with sleep disordered breathing (SDB) are at increased risk for cardiovascular disease including hypertension, angina, myocardial infarction, and stroke. Neurohumoral and hemodynamic responses to untreated sleep apnea are likely mechanisms that produce functional and structural changes within the cardiovascular system. Obesity, higher blood pressure, and advancing age, which are common characteristics of patients with SDB, contribute to the overall risk for cardiovascular disease. Recent studies indicate that OSA is associated with or aggravates other risk markers for cardiovascular disease. These factors include leptin, C-reactive protein, homocysteine, and insulin resistance syndrome. Elevations in C-reactive protein and glucose intolerance may be correlated with the severity of SDB. The impact of alleviating SDB on these cardiovascular risk factors has not been fully elucidated. Regardless, assessment of overall cardiovascular risk in patients with sleep apnea is warranted to identify those individuals that are high-risk who require immediate attention and intervention or in those that should be treated more aggressively.

Relationship between changes in serum leptin levels and blood pressure after weight loss

Insulin resistance is thought to raise blood pressure. Recently, a significant positive relationship between mean blood pressure and plasma leptin levels, but there have been no reports dealing with the relationship between blood pressure and either insulin resistance or serum leptin levels after weight loss. In the present work, we attempted to clarify the relationship between changes in blood pressure and either the serum leptin level or the insulin level in 102 moderately obese females (mean body mass index (BMI), 29.5 +/- 0.5 kg/m2; age, 47.0 +/- 0.9) during a 3 month period. No differences in age, fat-mass, homeostasis model assessment (HOMA), the summation of insulin (sigmaIRI), plasma renin activity (PRA) or 24 h norepinephrine excretion (24hU-NE) were observed between the hypertensive (HT) group (n = 31) and normotensive (NT) group (n = 71) before weight loss, but the basal serum leptin was significantly higher in the HT (16.8 +/- 1.1 ng/ml) than in the NT group (15.2 +/- 0.8 ng/ml), after adjusting for abdominal total fat. After a 3 month weight reduction program, the total abdominal fat, serum leptin and sigmaIRI significantly decreased in both groups. The systolic blood pressure (SBP)/diastolic blood pressure (DBP) significantly decreased from 144/84 to 130/77 mmHg only in the HT but not in the NT group. The PRA decreased in both groups, while the 24hU-NE significantly decreased only in the HT group. The changes in the leptin level were significantly correlated with the changes in both sigmaIRI and HOMA after weight loss in the two groups, respectively. Finally, a statistically significant positive correlation was observed between the changes in the leptin and the changes in the mean blood pressure (MBP) (r = 0.412, p < 0.05) only in the HT group. Multiple regression analysis revealed that the changes in MBP were independently associated with the changes in 24hU-NE and the changes in either sigmaIRI or HOMA in all subjects. However, a statistically significant positive correlation was observed between the changes in MBP and the changes in leptin levels even after adjusting for the total abdominal fat, 24hU-NE and either sigmaIRI or HOMA (both expressed as a percentage of the baseline value) in a multiple regression analysis only in the HT group. These results suggest that leptin may play a role in the pathophysiology of obese hypertension.

Leptin gene polymorphism is associated with hypertension independent of obesity

Leptin is an adipocyte-derived hormone that regulates food intake and energy expenditure. Recent functional studies have suggested a direct effect of leptin on blood pressure. In this study we examined the genetic association of the leptin gene polymorphism with obesity, insulin resistance, and hypertension. A highly polymorphic tetranucleotide repeat polymorphism in the 3'-flanking region of the leptin gene was examined. The alleles of the polymorphism consisted of two groups with different size distributions: a shorter one (class I) and a longer one (class II). The frequency of class I/class I genotype was much higher in hypertensive subjects than in control subjects (13.5% vs. 3.4%; P = 0.0027). No significant difference in body mass index was observed with different genotypes in either patients with hypertension or control subjects. Insulin responses to glucose and insulin sensitivity were not different among patients with different genotypes. The leptin gene polymorphism was associated with hypertension independent of obesity. These data together with recent functional data on the direct effect of leptin on blood pressure suggest that the leptin gene and its product, leptin, are an attractive target for studies on the mechanisms of hypertension and for the development of methods for the prediction, prevention, and therapy for hypertension.

Hypertension and obesity

Obesity, as defined by bodily weight (body weight) and by bodily conformation-derived variables, accompanies hypertension in many patients. Both conditions are independent cardiovascular risk factors. In a formal survey carried out in the adult general population of Uruguay (LATIR Study, 575 adult and elderly subjects of whom 41.6% were males), we found the prevalence of hypertension to be 28.5% (95% CI: 24.9-32.4%) and that 74.4% of hypertensive individuals had a body mass index (BMI) higher than 25 kg/m(2) (95% CI: 67.0-80.8%). This association between obesity and hypertension forms part of a broader relationship between body weight and blood pressure (BP). In the general population, BP bears a positive linear correlation with BMI and waist-to-hip ratio over the continuous ranges of normal and unfavourable values of these three variables (r = 0.42, P < 0.001 for the correlation between BMI and mean BP, LATIR Study). Patients who present hypertension and obesity usually present other unfavourable conditions for cardiovascular prognosis, including changes in carbohydrate and lipid metabolism, hyperuricaemia, left ventricular hypertrophy, and/or the obstructive sleep apnoea syndrome. On average, hypertension is salt-sensitive in obese patients, and plasma volume and cardiac index are increased. Adequate control of body weight results in substantial reductions in total blood volume, cardiac output, BP and left ventricular mass, and in an amelioration or the disappearance of sleep apnoea. Adequate sodium intake restriction must form part of any diet prescribed to obese hypertensive patients. Various drug classes may be used to treat hypertension efficaciously in patients who also present obesity.

Elevated serum leptin concentrations in women with components of multiple risk factor clustering syndrome

This cross sectional study was undertaken to determine whether serum leptin levels were associated with multiple risk factor (MRF) clustering syndrome. We examined the relationship between serum leptin concentrations and blood pressure (BP), serum lipids levels, calculated insulin resistance (HOMA-ratio) and adiposity among 581 Japanese adult women. The serum leptin was increased in female subjects with systolic (> or =160 mmHg) and diastolic > or =90 mmHg) hypertension compared with the normotensive females (mean+/-SE; 9.3+/-0.5 vs 7.7+/-0.3; 10.2+/-0.6 vs 7.1+/-0.3 ng/ml, both p<0.001). Serum leptin was elevated in those with hyper-cholesterolemia (C; > or =220 mg/dl) and triglyceridemia (TG; > or =150 mg/dl) compared with the normolipidemia (9.4+/-0.4 vs 7.8+/-0.3; 11.7+/-0.6 vs 7.5+/-0.2 ng/ml, both p <0.001). Serum leptin was also elevated in those with adiposity (BMI > or =26.4 kg/m2) and insulin resistance (HOMA-ratio > or =2.5) compared with the normal females (14.8+/-0.7 vs 5.2+/-0.2; 11.3+/-1.1 vs 7.1+/-0.4ng/ml, both p<0.001). Even after adjusting for BMI or percent body fat mass (BFM), leptin levels remained to be elevated significantly in all these diseases. There was a positive correlation between serum leptin and systolic, diastolic BP, TC, TG, BMI, BFM, IRI and HOMA-ratio (r=0.12, p=0.005; r=0.24, p<0.0001; r=0.19, p<0.0001; r=0.35, p<0.0001; r=0.72, p<0.0001; r=0.73, p<0.0001; r=0.47, p< 0.0001; r=0.44, p<0.0001), and a negative correlation with HDL-C levels (r= -0.20, p< 0.0001). These correlations were also observed in leptin levels after adjusting for the BMI or BFM. Multiple regression analysis showed that BFM, HOMA-ratio and TG were significant determinants of leptin concentration before (t=12.6, p<0.0001; t=3.33, p=0.001; t=3.22, p=0.001) and after adjusting for BMI or BFM. These results suggest that because serum leptin levels were elevated in components of MRF clustering syndrome, leptin may have a pathophysiological role in MRF clustering syndrome.

Serum leptin levels in patients with primary hyperaldosteronism before and after treatment: relationships to insulin sensitivity

BACKGROUND

Leptin is a protein hormone produced predominantly by adipocytes that plays a role in food intake regulation and a series of other physiological processes including blood pressure regulation.

OBJECTIVES

The aim of our study was to compare serum leptin levels in patients with primary hyperaldosteronism (PA) with those of healthy subjects and to explore the relationship of serum leptin levels and the parameters of insulin action in these patients before and after surgical or pharmacological treatment.

METHODS

Serum potassium, leptin, aldosterone, insulin levels and plasma renin activity were measured and hyperinsulinaemic euglycaemic clamp was performed in 11 patients with PA and 11 healthy age-, gender- and body mass index (BMI)-matched subjects. In eight of 11 patients the same measurements were repeated at least 6 months after surgical or pharmacological treatment.

RESULTS

The basal serum leptin levels in PA patients did not significantly differ from those of healthy subjects (mean+/-s.e.m. 8.4+/-1.9 vs 11.2+/-1.8 ng/ml, P=0.30), although their insulin sensitivity was significantly impaired (PA patients vs control subjects: glucose disposal rate in the last 20 min of clamp (M) 18.7+/-1.8 vs 30.6+/-3.3 micromol/kg/min, metabolic clearance rate of glucose (MCR(g)) 3.9+/-0.5 vs 7.2+/-1.1 ml/kg/min, P<0.05). The surgical or pharmacological treatment of PA patients increased significantly their serum leptin levels (10.9+/-3.7 vs 8.4+/-1.9 ng/ml, P<0.05) and simultaneously improved their insulin sensitivity. Basal serum leptin levels in both groups correlated positively with BMI and serum insulin levels. The inverse relationship between serum leptin levels and the insulin sensitivity parameters was found in both PA patients before treatment and healthy subjects. These relationships disappeared after treatment of PA patients except for those between serum leptin levels and MCR(g).

CONCLUSION

Basal serum leptin levels in untreated patients with PA do not significantly differ from those of healthy subjects, but increase significantly after surgical or pharmacological treatment. The increase in serum leptin levels is paradoxically accompanied by the improvement of insulin sensitivity in these patients.