Circulating leptin levels are not associated with cardiovascular morbidity and mortality in women with diabetes: a prospective cohort study

CHANGES IN THE SERUM LEVEL OF LEPTIN AND TRANSFORMING GROWTH FACTOR-Β1 IN PATIENTS WITH ARTERIAL HYPERTENSION ON A BACKGROUND OF ABDOMINAL OBESITY

OBJECTIVE

The aim: Study of the levels of leptin and the growth modulator TGF-β1 in the blood serum of patients with hypertension, which occurs on the background of AO and without it.

PATIENTS AND METHODS

Materials and methods: Carbohydrate metabolism was studied by the enzymatic method, the level of insulin in the blood (by the enzyme immunoassay method), the oral glucose tolerance test and the calculation of the NOMA index.

RESULTS

Results: The data obtained in the work indicate a significant role of leptin in the formation of hypertension itself and the development of obesity, carbohydrate and lipid metabolism disorders. The increased level of transforming growth factor-β1 in the blood of such patients can be used as a fairly informative marker of the unfavorable prognosis of these diseases.

CONCLUSION

Conclusions: 1. In the control group, there was a significant increase in the initial values of heart rate, average levels of SBP and DBP, the frequency of hy-percholesterolemia and insulin resistance was established. 2. Significant disorders of lipid and carbohydrate metabolism and leptin synthesis were found in patients with hypertension, which occurs against the background of AO. 3. When analyzing the level of leptin depending on gender, a statistically significant increase in the level of blood leptin was found in the group of women with AH with AO compared to women with AH without AO and the control group. 4. A significant increase in the level of transforming growth factor-β1 in blood serum of patients with hypertension was established.

Association of Low Leptin with Poor 3-Month Prognosis in Ischemic Stroke Patients with Type 2 Diabetes

Background

Leptin, an adipokine, has effects on the cardiovascular system with both protective and harmful role. This study aimed to assess the relationship between leptin and 3-month prognosis in ischemic stroke patients with type 2 diabetes.

Patients and Methods

As a prospective single-center observational study, we collected consecutive first-ever acute ischemia stroke with type 2 diabetes mellitus from February 2019 to February 2020. Serum samples were obtained at admission, and leptin serum levels were tested by the ELISA method. Logistic regression models were used to assess leptin's prognostic value to predict the functional outcome and mortality within three months.

Results

Finally, two hundred and eleven patients were included, and the mean leptin serum level was 16.8 (SD. 6.9) ng/mL. At admission, 53.6% of those included patients (N=113) were defined as severe stroke (NIH Stroke Scale [NIHSS]>5). In multivariable models adjusted for other factors, leptin levels<11.6ng/mL (lowest quartile, Q1) related to severe stroke and the risk increased 175% (odds ratios [OR] =2.75; 95% confidence interval [CI]=2.13-3.38; P=0.002). Serum leptin levels on admission in patients with poor outcomes and nonsurvivors were significantly reduced (P<0.001 and P<0.001). Leptin levels <11.6ng/mL (lowest quartile, Q1) related to a higher risk of poor functional impairment (OR=5.13; 95% CI =3.25-6.86; P<0.001) and mortality (OR=3.19; 95% CI =2.03-4.25; P<0.001).

Conclusion

The data shows that leptin serum level is a useful prognostic biomarker in ischemic stroke patients with type 2 diabetes, and this relationship is negative.

Irisin and leptin concentrations in relation to obesity, and developing type 2 diabetes: A cross sectional and a prospective case-control study nested in the Normative Aging Study

OBJECTIVE

To investigate the associations between irisin and leptin levels in obesity and insulin resistance in a cross sectional study. To assess the potential role of irisin and leptin as a predictive marker of T2DM using a nested case-control study.

METHODS

Both studies were designed within the longitudinal VA NAS cohort. The cross sectional study involved 111 non obese and 105 obese subjects who were subdivided into two groups based on their fasting glucose tolerance. In the nested 1:3 case-control study, 47 subjects with T2DM and 140 non-diabetic controls were selected. Serum samples collected 3-5 years before the diagnosis of T2DM were analyzed. Irisin and leptin concentrations were measured using a validated ELISA and radioimmunoassay respectively.

RESULTS

In the cross-sectional study, irisin did not differ between groups based on their fasting glucose tolerance. When subjects were grouped based on obesity status, both irisin and leptin concentrations were significantly higher in obese compared to the non-obese group (p=0.03 and <0.001, respectively). Irisin concentrations positively correlated with leptin concentrations (r= 0.392, P < 0.001). In the nested case control study, leptin concentrations were a significant predictor of developing diabetes (p=0.005) in unadjusted models, but not after correcting for BMI, whereas irisin concentrations did not play a role of comparable significance.

CONCLUSIONS

Leptin concentrations are higher in the obese group irrespective of their glucose tolerance. Obese individuals with impaired fasting glucose have higher concentrations of circulating irisin compared to non-obese subjects with normal glucose tolerance. Irisin concentrations do not predict risk of developing diabetes prospectively.

The role of adipokines as prognostic factors of one-year mortality in hip fracture patients

This study investigated the impact of anthropometric parameters, adiponectin, leptin, homeostatic model assessment for insulin resistance (HOMA-IR), beta-isomerised C-terminal telopeptide of collagen type I (β-CTX), and routine biochemical tests on one-year mortality in hip fracture patients. We found that male patients with high adiponectin, leptin, and β-CTX levels had a 5-fold increase in all-cause one-year mortality.

INTRODUCTION

Several predictors of one-year hip fracture mortality have been identified including advanced age, male sex, low bone mineral density, and preexisting comorbidities. However, the impact of metabolic parameters on hip fracture mortality remains unknown. The aim of this study was to examine the effect of serum leptin and adiponectin levels, as well as other metabolic parameters on all-cause one-year hip fracture mortality.

METHODS

This prospective study included 236 patients of all ages with non-traumatic hip fractures. Anthropometric parameters, adiponectin, leptin, HOMA-IR, β-CTX, and routine biochemical tests were recorded at admission and correlated with one-year mortality by using multivariate Cox proportional hazard models.

RESULTS

The median patient age was 82 (75-87) years, and one-year mortality rate was 28.4%. In univariate analysis, adiponectin, age, β-CTX, and renal function were associated with mortality. However, in a multivariate model, male gender, high β-CTX, adiponectin, and leptin were independently associated with increased mortality. Thus, we constructed a nomogram that included all the latter variables in addition to age. The nomogram predicted mortality with a sensitivity of 74.8% (66.0-82.3) and specificity of 74.4% (57.9-87.0), and had an area under the curve of 0.784. Patients that scored <9.2 had a mortality of 10.1%, while those with >9.2 had a mortality of 49.2% (relative risk 5.4, 95% CI 2.8-10.2, P < 0.001).

CONCLUSION

Male patients with high adiponectin, leptin, and β-CTX levels have a 5-fold increase in all-cause one-year mortality after hip fracture.

Beneficial effects of leptin treatment in a setting of cardiac dysfunction induced by transverse aortic constriction in mouse

KEY POINTS

Leptin, is a 16 kDa pleiotropic peptide not only primarily secreted by adipocytes, but also produced by other tissues, including the heart. Controversy exists regarding the adverse and beneficial effects of leptin on the heart We analysed the effect of a non-hypertensive dose of leptin on cardiac function, [Ca²⁺ ]_i handling and cellular electrophysiology, which participate in the genesis of pump failure and related arrhythmias, both in control mice and in mice subjected to chronic pressure-overload by transverse aorta constriction. We find that leptin activates mechanisms that contribute to cardiac dysfunction under physiological conditions. However, after the establishment of pressure overload, an increase in leptin levels has protective cardiac effects with respect to rescuing the cellular heart failure phenotype. These beneficial effects of leptin involve restoration of action potential duration via normalization of transient outward potassium current and sarcoplasmic reticulum Ca²⁺ content via rescue of control sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase levels and ryanodine receptor function modulation, leading to normalization of Ca²⁺ handling parameters.

ABSTRACT

Leptin, is a 16 kDa pleiotropic peptide not only primary secreted by adipocytes, but also produced by other tissues, including the heart. Evidence indicates that leptin may have either adverse or beneficial effects on the heart. To obtain further insights, in the present study, we analysed the effect of leptin treatment on cardiac function, [Ca²⁺ ]_i handling and cellular electrophysiology, which participate in the genesis of pump failure and related arrhythmias, both in control mice and in mice subjected to chronic pressure-overload by transverse aorta constriction (TAC). Three weeks after surgery, animals received either leptin (0.36 mg kg^-1  day^-1 ) or vehicle via osmotic minipumps for 3 weeks. Echocardiographic measurements showed that, although leptin treatment was deleterious on cardiac function in sham, leptin had a cardioprotective effect following TAC. [Ca²⁺ ]_i transient in cardiomyocytes followed similar pattern. Patch clamp experiments showed prolongation of action potential duration (APD) in TAC and leptin-treated sham animals, whereas, following TAC, leptin reduced the APD towards control values. APD variations were associated with decreased transient outward potassium current and Kv4.2 and KChIP2 protein expression. TAC myocytes showed a higher incidence of triggered activities and spontaneous Ca²⁺ waves. These proarrhythmic manifestations, related to Ca²⁺ /calmodulin-dependent protein kinase II and ryanodine receptor phosphorylation, were reduced by leptin. The results of the present study demonstrate that, although leptin treatment was deleterious on cardiac function in control animals, leptin had a cardioprotective effect following TAC, normalizing cardiac function and reducing arrhythmogeneity at the cellular level.

Role of leptin as a link between metabolism and the immune system

Leptin is an adipocyte-derived hormone not only with an important role in the central control of energy metabolism, but also with many pleiotropic effects in different physiological systems. One of these peripheral functions of leptin is a regulatory role in the interplay between energy metabolism and the immune system, being a cornerstone of the new field of immunometabolism. Leptin receptor is expressed throughout the immune system and the regulatory effects of leptin include cells from both the innate and adaptive immune system. Leptin is one of the adipokines responsible for the inflammatory state found in obesity that predisposes not only to type 2 diabetes, metabolic syndrome and cardiovascular disease, but also to autoimmune and allergic diseases. Leptin is an important mediator of the immunosuppressive state in undernutrition status. Placenta is the second source of leptin and it may play a role in the immunomodulation during pregnancy. Finally, recent work has pointed to the participation of leptin and leptin receptor in the pathophysiology of inflammation in oral biology. Therefore, leptin and leptin receptor should be considered for investigation as a marker of inflammation and immune activation in the frontier of innate-adaptive system, and as possible targets for intervention in the immunometabolic mediated pathophysiology.

Adiponectin, leptin, nitric oxide, and C-reactive protein levels in kidney transplant recipients: comparison with the hemodialysis and chronic renal failure

BACKGROUND

Cardiovascular disease (CVD) is the leading cause of mortality and morbidity in patients with chronic kidney disease (CKD) including kidney transplant recipients (KTR). Secondary lipid metabolism disorders, endothelial dysfunction, and inflammation enhance the risk of CVD development in these patients. The aim of the present study was to investigate the lipid profile, adiponectin, leptin, nitric oxide (NO), and high sensitivity C-reactive protein (hs-CRP) levels in KTR and to compare these parameters with those of the patients with chronic renal failure (CRF), hemodialysis (HD) patients, and healthy controls.

METHODS

Serum adiponectin and leptin levels were measured by radioimmunoassay; hs-CRP was determined immunoturbidimetrically. Determination of NO was based on the Griess reaction.

RESULTS

Compared with the control group, serum NO and adiponectin levels were significantly higher in the KTR, CRF, and HD groups; hs-CRP levels were significantly higher in the KTR and HD groups; leptin levels were significantly higher in the KTR. In addition, serum NO level was significantly higher in the KTR compared to CRF cases. Adiponectin correlated positively with high density lipoprotein-cholesterol in the control and patient groups. A positive correlation was observed between hs-CRP and NO in the KTR and the patients with CRF. Serum adiponectin levels were inversely correlated with hs-CRP and leptin in the HD group.

CONCLUSION

KTR suffer from inflammation and accompanying changes in levels of adipocytokines and NO which contribute to the increased risk of CVD in these patients.

Predictors of leptin concentration and association with cardiovascular risk in patients with coronary artery disease: results from the AtheroGene study

CONTEXT

Leptin is produced in white adipose tissue, but also in human coronary atherosclerotic lesions.

OBJECTIVE

The aim of this study is to assess the prognostic value of leptin in patients with proven coronary artery disease (CAD) (N = 1907).

METHODS

AtheroGene is a contemporary CAD cohort study (N = 3229). Median follow-up time was 3.8 (Quartile 1/3 with 2.8/4.9) years.

RESULTS

Leptin concentration was associated with a hazard ratio (HR) for the fully adjusted model of HR = 1.32 in women but was not significant in men. The endpoint cardiovascular death and non-fatal myocardial infarction was observed in 167 patients.

CONCLUSION

In women with known CAD, increased leptin concentration is useful for predicting cardiovascular death and non-fatal myocardial infarction.

The Association of Serum Leptin with Mortality in Older Adults

Objective

Elevated levels of serum leptin are associated with increased adiposity and production of pro-inflammatory cytokines. Both cytokines and body adiposity have been shown to predict cardiovascular events and mortality. The primary objective of the present study is to explore the associations between serum leptin and all-cause mortality and mortality from cardiovascular disease (CVD) over a span of 10 years, controlling for body adiposity and proinflammatory cytokines.

Methods

The Health, Aging and Body Composition (Health ABC) study is a prospective cohort of 3,075 older adults aged 70 to 79 years. This analysis includes 2,919 men and women with complete serum leptin and vital status data. Data on all-cause mortality and incident cardiovascular events (including Coronary Heart Disease and Congestive Heart Failure) were collected over 10 years of follow-up (mean 8.4 years).

Results

Women with leptin in quartile 2 and 3 were at lower risk of all-cause mortality, and those with leptin in quartile 2 were at lower risk of mortality from CVD as compared to women with lowest leptin values when adjusted for age, race, site, years of education, alcohol use, smoking, and physical activity. When these associations were additionally adjusted for body fat, C-reactive protein and pro-inflammatory cytokines, women with leptin values in quartile 3 were at lower risk of all-cause mortality and women with leptin in quartile 2 and 3 were at lower risk of mortality from CVD than women with lowest leptin values. These associations were not significant among men after adjusting for body fat and cytokines.

Conclusions

The present study suggests that moderately elevated concentrations of serum leptin are independently associated with lower risk of all-cause mortality and CVD-related mortality among older women. Among men, serum leptin is not associated with reduced risk of all-cause and CVD mortality after controlling for body fat and cytokines.

Serum Leptin Levels and the Risk of Stroke: The Framingham Study

BACKGROUND AND PURPOSE

Leptin is a major adipokine that regulates weight balance and energy homeostasis. There is inconsistent evidence linking circulating leptin levels to risk of stroke. We tested the hypothesis that leptin levels are associated with risk of incident stroke in an elderly community based sample.

METHODS

Serum leptin levels were assayed in 757 stroke free individuals (mean age, 79 years; 62% women) from the Framingham Original Cohort at the 22nd examination cycle (1990-1994). Incidence of all -stroke and ischemic stroke were prospectively ascertained.

RESULTS

During a mean follow up of 10 years, 119 individuals developed stroke (99 ischemic strokes). In multivariable Cox regression models, log leptin levels were not associated with incidence of all -stroke or ischemic stroke (hazard ratios per SD increment in log leptin 0.90 [0.73-1.09] and 0.89 [0.72-1.11], respectively). The results were suggestive for potential effect modification by waist/hip ratio for the association between leptin and stroke (P=0.03). Adjusting for age, sex, and established stroke risk factors, analysis stratified by waist/hip ratio quartiles revealed a lower incidence of first-ever all-stroke and ischemic stroke associated with higher leptin levels among only subjects in the top waist/hip ratio quartile (hazard ratio, 0.64 [0.43, 0.95] versus 0.98 [0.77, 1.25] for incident all-stroke and 0.61 [0.39, 0.95] versus 0.96 [0.74, 1.26] for ischemic stroke).

CONCLUSIONS

Leptin levels were not directly related to the risk of incident stroke overall but there was an inverse association with stroke in the top waist/hip ratio quartile. Further investigations are required to confirm these findings and explore possible mechanisms for the observed association.

Serum leptin levels are independently related to the incidence of ischemic heart disease in a prospective study of patients with type 2 diabetes

Background

New and clinically useful markers of cardiovascular risk are of essence in type 2 diabetes since ischemic heart disease is a major cause of death in these patients.

Methods

We analyzed baseline data from 476 men and 244 women who participated in “Cardiovascular Risk factors in Patients with Diabetes -a Prospective study in Primary care” study. All participants had type 2 diabetes and were 55-66 years old at recruitment during year 2005 to 2008. Except for established traditional risk markers for vascular disease, we also estimated vascular complications non-invasively by performance of carotid-femoral pulse-wave velocity (PWV, with applanation-tonometry) and intima-media thickness of carotid arteries (IMT, with B-mode ultrasound). Patients were followed for incidence of ischemic heart disease mortality and morbidity until end of the year 2012, using the national Swedish Cause of Death and Hospitalization Registries.

Results

During the follow-up period of a median of 6 years 47 men and 10 women died or were hospitalized for ischemic heart disease including myocardial infarction. Leptin levels were positively related to the hazard ratio (HR) in men (HR for each log 10 unit 4.9, CI 1.99 to 11.8) and women (HR 11.5, CI 1.47 to 89.7). Leptin predicted ischemic heart disease independently of age, HbA1c, BMI, systolic blood pressure and LDL-cholesterol/HDL-cholesterol ratio (men: HR 12.9 CI 3.2-53, women: HR 19.9, CI 1.2-327) This finding of increased risk related to high leptin levels was also statistically significant when carotid-femoral PWV and IMT were both added to the equations in men (hazard ratio 9.2 CI 2.1-41).

Conclusions

Our data support the use of serum leptin in type 2 diabetes to add independent prognostic information in terms of ischemic heart disease when compared with traditional cardiovascular risk factors. In the men of the cohort this prognostic information was in addition also to data on IMT and PWV, two non-invasive measurements of the extent of vascular disease. The power to detect a similar relationship in women was less strong due to lower incidence of cardiovascular disease.

Trial registration

ClinicalTrials.gov: NCT01049737.

Leptin Reference Values and Cutoffs for Identifying Cardiometabolic Abnormalities in the Spanish Population

INTRODUCTION AND OBJECTIVES

Estimate leptin reference values and calculate leptinemia cutoff values for identifying cardiometabolic abnormalities in Spain.

METHODS

Cross-sectional study carried out between 2008 and 2010 in 11 540 individuals representing the Spanish population aged ≥ 18 years. Data were obtained by standardized physical examination and analyses were performed at a central laboratory. Leptinemia was measured using ELISA. Cardiometabolic abnormality was defined as the presence of at least two of the following: high blood pressure, high triglycerides, reduced high density lipoprotein cholesterol, high insulin resistance values, and elevated C-reactive protein and glucose.

RESULTS

Leptin values were higher in women than men (geometric mean, 21.9 and 6.6 ng/mL; P<.001). The median [interquartile range] was 24.5 [14.1-37.0] ng/mL in women, and 7.2 [3.3-14.3] ng/mL in men. In the multivariate analysis, leptin was significantly associated with anthropometric measures, insulin, and C-reactive protein, and inversely associated with age, smoking, and physical activity in women (r(2)=0.53; P<.001) and in men (r(2)=0.61; P<.001). The leptin values that identified cardiometabolic abnormality were 23.75 ng/mL in women (area under the curve, 0.722; sensitivity, 72.3%; specificity, 58.7%) and 6.45 ng/mL in men (area under the curve, 0.716; sensitivity, 71.4%; specificity, 60.2%).

CONCLUSIONS

These results facilitate the interpretation of leptin values in clinical and population studies. Leptin has moderate sensitivity and specificity for identifying cardiometabolic abnormalities.

From leptin to other adipokines in health and disease: facts and expectations at the beginning of the 21st century

This year marks the 20th anniversary of the discovery of leptin, which has tremendously stimulated translational obesity research. The discovery of leptin has led to realizations that have established adipose tissue as an endocrine organ, secreting bioactive molecules including hormones now termed adipokines. Through adipokines, the adipose tissue influences the regulation of several important physiological functions including but not limited to appetite, satiety, energy expenditure, activity, insulin sensitivity and secretion, glucose and lipid metabolism, fat distribution, endothelial function, hemostasis, blood pressure, neuroendocrine regulation, and function of the immune system. Adipokines have a great potential for clinical use as potential therapeutics for obesity, obesity related metabolic, cardiovascular and other diseases. After 20 years of intense research efforts, recombinant leptin and the leptin analog metreleptin are already available for the treatment of congenital leptin deficiency and lipodystrophy. Other adipokines are also emerging as promising candidates for urgently needed novel pharmacological treatment strategies not only in obesity but also other disease states associated with and influenced by adipose tissue size and activity. In addition, prediction of reduced type 2 diabetes risk by high circulating adiponectin concentrations suggests that adipokines have the potential to be used as biomarkers for individual treatment success and disease progression, to monitor clinical responses and to identify non-responders to anti-obesity interventions. With the growing number of adipokines there is an increasing need to define their function, molecular targets and translational potential for the treatment of obesity and other diseases. In this review we present research data on adipose tissue secreted hormones, the discovery of which followed the discovery of leptin 20 years ago pointing to future research directions to unravel mechanisms of action for adipokines.

Association of plasma leptin, homocysteine and nitric oxide levels with the presence and unstability of coronary artery disease

AIM

Leptin and total homocysteine (tHcy) may participate in the pathogenesis of coronary artery disease (CAD) through nitric oxide (NO) depletion. We sought to investigate whether leptin, tHcy and NO are suitable predictors of CAD.

PATIENTS & METHODS

This study contained 50 control subjects and 50 stable and 50 unstable angina patients. Plasma leptin, tHcy and NO levels were determined using enzyme immunoassay, HPLC fluorescence and spectrophotometric methods, respectively. Other conventional risk factors were also determined.

RESULTS

Leptin and tHcy levels were highest in unstable angina patients, followed by stable angina patients and then controls (p < 0.001). Controls had significantly higher NO than patients (p <0.001). Leptin and tHcy had a positive and NO a negative association with the presence of CAD.

CONCLUSIONS

Some athrogenic effects of leptin may be mediated by affecting tHcy and NO levels. Plasma leptin, tHcy and NO levels showed significant contribution to CAD prediction and discrimination.

Hyperleptinemia: implications on the inflammatory state and vascular protection in obese adolescents submitted to an interdisciplinary therapy

The low-grade systemic inflammation seen in obesity may affect the actions of some adipose tissue-derived adipokines that are involved in the regulation of vascular function. We sought to verify whether hyperleptinemia may influence the inflammatory and atherogenic responses in obese adolescents undergoing interdisciplinary therapy. Thirty-four obese adolescents underwent interdisciplinary therapy for 1 year. Subjects were considered hyperleptinemic if they had baseline values of leptin above 20 ng/mL for boys and 24 ng/mL for girls. Both groups showed an improvement in body composition and a reduction in carotid intima-media thickness. However, only subjects in the non-hyperleptinemic group showed an increase in adiponectin concentration after therapy. Moreover, leptin concentration was positively correlated with adiponectin and inversely correlated with PAI-1 in this group. Hyperleptinemic state may impair the attenuation of inflammation in obese adolescents undergoing interdisciplinary therapy, particularly by impeding the increase in adiponectin concentration, which is directly involved in vascular protection.

Effect of increased leptin and C-reactive protein levels on mortality: results from the National Health and Nutrition Examination Survey

OBJECTIVE

Leptin and C-reactive protein (CRP) have each been linked to adverse cardiovascular events, and prior cross-sectional research suggests that increased levels of both biomarkers pose an even greater risk. The effect of increased levels of both leptin and CRP on mortality has not, however, been previously assessed.

METHODS

We used data from the third National Health and Nutrition Examination Survey (NHANES III) to estimate the mortality effect of high leptin and high CRP levels. Outcomes were compared with the use of inverse-probability-weighting adjustment. Among 6259 participants included in the analysis, 766 were in their sex-specific, population-weighted highest quartiles of both leptin and CRP. Median follow-up time was 14.3 years.

RESULTS

There was no significant difference in adjusted all-cause mortality between the groups (risk ratio 1.22, 95% confidence interval [CI], 0.97-1.54). Similar results were noted with the use of several different analytic methods and in many subgroups, though high leptin and CRP levels may increase all-cause mortality in males (hazard ratio, 1.80, 95% CI, 1.32-2.46; P for interaction, 0.011). A significant difference in cardiovascular mortality was also noted (risk ratio, 1.54, 95% CI, 1.08-2.18), though that finding was not confirmed in all sensitivity analyses..

CONCLUSIONS

In this observational study, no significant difference in overall all-cause mortality rates in those with high leptin and high CRP levels was found, though high leptin and CRP levels appear associated with increased mortality in males. High leptin and CRP levels also likely increase risk for cardiovascular death..

Relationship between obesity, adipocytokines and inflammatory markers in type 2 diabetes: relevance for cardiovascular risk prevention

This study aimed to analyse the impact of obesity in type 2 diabetes (T2D) on adipocytokines (adiponectin, leptin and resistin) and inflammatory markers (TNF-α, IL-6 and hsCRP) as cardiovascular risk factors. A cross-sectional study comparing the basal levels of adipocytokines and inflammatory markers was done in 18 obese (BMI ≥ 30 kg/m²) (group A), 21 overweight (25 kg/m² ≤ BMI < 30 kg/m²) (group B), 25 non-obese T2D patients (group C) and 15 non-obese controls (group D). The lowest levels of adiponectin and the highest levels of leptin, resistin, TNF-α, IL-6 and hsCRP were found in group A. Adiponectin levels were significantly lower, and resistin, TNF-α, and hsCRP levels were elevated in group C vs. D. However, leptin and IL-6 levels differed significantly between groups A and B, but not between groups C and D. Moreover, we found a significant negative correlation between adiponectin and TNF-α, but not with other markers, which was independent of the presence of obesity. In contrast, leptin and resistin correlated with the inflammatory markers, and this correlation was obesity-dependent. Our results suggest that obesity influences cardiovascular risk primarily through changes in leptin and resistin and less efficiently at the level of adiponectin.

Association of serum adiponectin, leptin, and resistin concentrations with the severity of liver dysfunction and the disease complications in alcoholic liver disease

Background and aims. There is growing evidence that white adipose tissue is an important contributor in the pathogenesis of alcoholic liver disease (ALD). We investigated serum concentrations of total adiponectin (Acrp30), leptin, and resistin in patients with chronic alcohol abuse and different grades of liver dysfunction, as well as ALD complications. Materials and Methods. One hundred forty-seven consecutive inpatients with ALD were prospectively recruited. The evaluation of plasma adipokine levels was performed using immunoenzymatic ELISA tests. Multivariable logistic regression was applied in order to select independent predictors of advanced liver dysfunction and the disease complications. Results. Acrp30 and resistin levels were significantly higher in patients with ALD than in controls. Lower leptin levels in females with ALD compared to controls, but no significant differences in leptin concentrations in males, were found. High serum Acrp30 level revealed an independent association with advanced liver dysfunction, as well as the development of ALD complications, that is, ascites and hepatic encephalopathy. Conclusion. Gender-related differences in serum leptin concentrations may influence the ALD course, different in females compared with males. Serum Acrp30 level may serve as a potential prognostic indicator for patients with ALD.

The effect of weight loss magnitude on pro-/anti-inflammatory adipokines and carotid intima-media thickness in obese adolescents engaged in interdisciplinary weight loss therapy

BACKGROUND

Obesity is a chronic disease defined by an excess amount of adipose tissue and presents a low-grade inflammatory state, increasing cardiovascular risk.

OBJECTIVE

To assess the effect of weight loss magnitude on the inflammatory profile and carotid intima-media thickness (cIMT) in obese adolescents engaged in interdisciplinary therapy.

DESIGN AND PATIENTS

Seventy-seven postpubertal obese adolescents with a BMI greater than the 95th percentile (37·18 ± 5·14), of both genders and between the ages of 14 and 19 years (16·74 ± 1·59) were subjected to a 1-year period of interdisciplinary intervention (nutrition, psychology, physical exercise and clinical support).

MEASUREMENTS

Blood samples were collected to analyse glucose, lipid and adipokine concentrations. Body composition, anthropometric profiles and cIMT were measured. The results are presented according to quartiles of weight loss: 1st (≤5·80 kg) = low; 2nd (5·80-10·90 kg) = low to moderate; 3rd (10·90-15·90 kg) = moderate; and 4th (>15·90 kg) = massive.

RESULTS

Leptin, the leptin/adiponectin ratio and plasminogen activator inhibitor 1 (PAI-1) were decreased significantly in the low-to-moderate weight loss. The cIMT was reduced in the moderate weight loss. Moreover, adiponectin was increased only in the massive weight loss. Additionally, weight loss was an independent predictor of changes in leptin level, the adiponectin/leptin ratio (A/L ratio) and PAI-1 when the data were adjusted for age and gender. BMI changes were predictors of changes in leptin and PAI-1 levels. A/L ratio was associated with lean body mass (%), independent of gender and age. In addition, changes in A/L ratio were independent predictors of cIMT alterations.

CONCLUSIONS

Interdisciplinary therapy may reduce cardiovascular risk factors among adolescents depending on their degree of weight loss (moderate to massive) and when correlated with their inflammatory profile, metabolic state and cIMT.

Leptin and cardiovascular diseases

1. Leptin is a 16-kDa hormone, synthesized primarily by adipocyte, which acts as a key factor for maintenance of energy homeostasis in central and peripheral tissues. In most obese individuals, serum leptin levels are increased and correlate with the individual's body mass index. 2. Abundant investigations ranging from clinical and animal model studies to in vitro analyses show that leptin plays a pivotal role in obesity-related cardiovascular diseases (CVD). Hyperleptinaemia has been confirmed to be a predictor of acute cardiovascular events. However, some studies have shown that leptin has a cardioprotective effect in leptin-deficient models. These data suggest the influences of leptin on the pathophysiology of cardiovascular diseases are complex and not completely understood. 3. In the present review, we summarize the major leptin signalling pathways, including Janus-activated kinase/signal transducers and activators of transcription (Jak/STAT), mitogen-activated protein kinases (MAPK), and phosphatidylinositol 3-kinase (PI-3K) signalling pathways, and analyse the probable mechanisms of selective leptin resistance. We then provide a detailed review of the effects of leptin on the cardiovascular system, including sympathoactivation, oxidative stress, vascular inflammation, endothelial dysfunction, vascular cell proliferation, cardiomyocytes hypertrophy, as well as fatty acid metabolism, all of which contribute to the pathogenesis of cardiovascular diseases (e.g. ischaemic heart disease). The central premise of this review is to elucidate the mechanisms by which leptin affects the cardiovascular function and provide insight into obesity-related CVD.

Obesity and endoplasmic reticulum (ER) stresses

In obesity, the adipose cells behave as inflammatory source and result to low grade inflammation. This systemic inflammation along with oxidative stress is a silent killer and damages other vital organs also. High metabolic process, induced due to high nutritional intake, results to endoplasmic reticulum (ER) stress and mitochondrial stress. This review describes the triggering factor and basic mechanism behind the obesity mediated these stresses in relation to inflammation. Efforts have been made to describe the effect-response cycle between adipocytes and non-adipocyte cells with reference to metabolic syndrome (MS).

Inflammation and metabolic dysfunction: links to cardiovascular diseases

Abdominal obesity is a major risk factor for cardiovascular disease, and recent studies highlight a key role of adipose tissue dysfunction, inflammation, and aberrant adipokine release in this process. An increased demand for lipid storage results in both hyperplasia and hypertrophy, finally leading to chronic inflammation, hypoxia, and a phenotypic change of the cellular components of adipose tissue, collectively leading to a substantially altered secretory output of adipose tissue. In this review we have assessed the adipo-vascular axis, and an overview of adipokines associated with cardiovascular disease is provided. This resulted in a first list of more than 30 adipokines. A deeper analysis only considered adipokines that have been reported to impact on inflammation and NF-κB activation in the vasculature. Out of these, the most prominent link to cardiovascular disease was found for leptin, TNF-α, adipocyte fatty acid-binding protein, interleukins, and several novel adipokines such as lipocalin-2 and pigment epithelium-derived factor. Future work will need to address the potential role of these molecules as biomarkers and/or drug targets.

Association of low leptin with cardiovascular events and mortality in patients with stable coronary artery disease: the Heart and Soul Study

OBJECTIVE

Leptin is an adipokine with both protective and harmful effects on the cardiovascular (CV) system. Prior studies evaluating the association between leptin and CV outcomes have yielded conflicting results. Thus, we sought to investigate the relationship between leptin and CV events and mortality in patients with chronic stable coronary artery disease (CAD).

METHODS

We performed a prospective cohort study of 981 outpatients with stable CAD. Leptin levels were measured in fasting venous samples at baseline. We used proportional hazards models to evaluate the association of baseline leptin with subsequent CV events (myocardial infarction, stroke, transient ischemic attack) and death.

RESULTS

During a mean follow-up of 6.2±2.1 years, there were 304 deaths, 112 myocardial infarctions, and 52 strokes/TIAs. In models adjusted for age, sex, and race, low leptin was associated with a 30% increased risk of the combined outcome (HR 1.30, CI 1.05-1.59, p=0.01). After further adjustment for obesity, traditional CV risk factors and biomarkers, low leptin remained associated with a 37% increased risk of events (HR 1.37, CI 1.06-1.76, p=0.02).

CONCLUSIONS

Low leptin is associated with increased CV events and mortality in patients with stable coronary artery disease. This association is independent of known factors affecting leptin levels, including gender and obesity.

Inflammation, a link between obesity and cardiovascular disease

Obesity, the most common nutritional disorder in industrialized countries, is associated with an increased mortality and morbidity of cardiovascular disease (CVD). Obesity is primarily considered to be a disorder of energy balance, and it has recently been suggested that some forms of obesity are associated with chronic low-grade inflammation. The present paper focuses on the current status of our knowledge regarding chronic inflammation, a link between obesity and CVDs, including heart diseases, vascular disease and atherosclerosis. The paper discusses the methods of body fat evaluation in humans, the endocrinology and distribution of adipose tissue in the genders, the pathophysiology of obesity, the relationship among obesity, inflammation, and CVD, and the adipose tissue-derived cytokines known to affect inflammation. Due to space limitations, this paper focuses on C-reactive protein, serum amyloid A, leptin, adiponectin, resistin, visfatin, chemerin, omentin, vaspin, apelin, and retinol binding protein 4 as adipokines.

Decrease in leptin production by the adipose tissue in obesity associated with severe metabolic syndrome

OBJECTIVE: To evaluate the associations between leptinemia and the components of metabolic syndrome (MetS). METHODS: Fifty-one obese adults (9 men; 36.7 ± 10.0 years; body mass index (BMI) 46.2 ± 10.0 kg/m²) were submitted to clinical examination, determinations of body fat mass (BF, bioimpedance) and resting energy expenditure (REE, indirect calorimetry), and to hormonal and biochemical analysis. Patients were categorized into three groups, according to the number of criteria for MetS: Group I: none or 1; Group II: 2; and Group III: 3 or 4 criteria. RESULTS: Absolute leptinemia (LepA; 37.5 ± 16.9 ng/mL) was directly correlated with BMI (r = 0.48; p = 0.0004), waist circumference (r = 0.31; p = 0.028) and BF (r = 0.52; p = 0.0001). Leptinemia adjusted for BF (LepBF) was inversely correlated with weight (r = -0.41; p=0.027), REE (r = -0.34; p = 0.01) and number of MetS criteria (r = -0.32; p = 0.02). There was no difference in LepA among the groups. LepBF in Group III (0.58 ± 0.27 ng/mL/kg) was significantly lower compared to Group I (0.81 ± 0.22 ng/mL/kg; p = 0.03) and Group II (0.79 ± 0.30 ng/mL/kg; p = 0.02). CONCLUSIONS: Leptin production by the adipose tissue is decreased in obese subjects fulfilling three or more criteria of MetS, suggesting a state of relative leptin deficiency in obesity associated with advanced stages of MetS.

Altered plasma adipokines and markers of oxidative stress suggest increased risk of cardiovascular disease in First Nation youth with obesity or type 2 diabetes mellitus

OBJECTIVE

To evaluate cardiovascular disease risk in First Nation youth with and without type 2 diabetes mellitus (T2DM) or obesity by comparing pro- and anti-inflammatory adipokines, markers of oxidative stress and the plasma phospholipid fatty acid profile.

METHOD

Self-declared First Nation youth (12-15 yr) with T2DM (n = 24) as well as age-, gender-, and body mass index-matched controls (obese group; n = 19) and unmatched controls (control group; n = 34) were recruited from a pediatric diabetes clinic.

RESULTS

Plasma tumor necrosis factor-alpha, ultrasensitive C-reactive protein, resistin, and total antioxidant status were not different among the three groups. Plasma total leptin, soluble leptin receptor, and free leptin were significantly higher in the T2DM group than the control group (p < 0.001, p = 0.019, p < 0.001, respectively) but did not differ from the obese group. Similarly, oxidized low-density lipoprotein was higher in the T2DM group compared with controls (p = 0.002) but not in the obese group. However, interleukin-6 was significantly higher (p < 0.001) in the T2DM group compared with both the control and the obese groups, suggesting that T2DM, but not an increase in adiposity, was responsible for this elevation. Adiponectin was significantly lower in the T2DM group compared with the control group only (p = 0.035).

CONCLUSIONS

Changes in plasma adipokines and oxidative stress can already be detected in youth with T2DM; however, many of the changes are mirrored in obese youth, suggesting that both these populations are at an increased risk for future cardiovascular complications.

Leptin in humans: lessons from translational research

Leptin has emerged over the past decade as a key hormone in not only the regulation of food intake and energy expenditure but also in the regulation of neuroendocrine and immune function as well as the modulation of glucose and fat metabolism as shown by numerous observational and interventional studies in humans with (complete) congenital or relative leptin deficiency. These results have led to proof-of-concept studies that have investigated the effect of leptin administration in subjects with complete (congenital) leptin deficiency caused by mutations in the leptin gene as well as in humans with relative leptin deficiency, including states of lipoatrophy or negative energy balance and neuroendocrine dysfunction, as for instance seen with hypothalamic amenorrhea in states of exercise-induced weight loss. In those conditions, most neuroendocrine, metabolic, or immune disturbances can be restored by leptin administration. Leptin replacement therapy is thus a promising approach in several disease states, including congenital complete leptin deficiency, states of energy deprivation, including anorexia nervosa or milder forms of hypothalamic amenorrhea, as well as syndromes of insulin resistance seen in conditions such as congenital or acquired lipodystrophy. In contrast, states of energy excess such as garden-variety obesity are associated with hyperleptinemia that reflects either leptin tolerance or leptin resistance. For those conditions, development of leptin sensitizers is currently a focus of pharmaceutical research. This article summarizes our current understanding of leptin's role in human physiology and its potential role as a novel therapeutic option in human disease states associated with a new hormone deficiency, ie, leptin deficiency.

Leptin predicts diabetes but not cardiovascular disease: results from a large prospective study in an elderly population

OBJECTIVE

To clarify the association of circulating levels of leptin with risk for cardiovascular disease (CVD) events and new-onset diabetes in men and women.

RESEARCH DESIGN AND METHODS

We related baseline leptin levels to CVD events (n = 864) and incident diabetes (n = 289) in an elderly population (n = 5,672) over 3.2 years of follow-up.

RESULTS

In treatment-, age-, and country-adjusted models, leptin was not associated with risk of CVD in men (hazard ratio 1.02 [95% CI 0.90-1.16] per unit log-leptin increase) or women (1.05 [0.91-1.20]) but was associated with risk of diabetes in men (2.75 [2.14-3.52]) and women (1.54 [1.22-1.94]). After adjusting for classic risk factors and BMI, C-reactive protein, and glucose, the diabetes association retained significance in men (1.85 [1.30-2.63]) but not in women (0.89 [0.64-1.26]).

CONCLUSIONS

Leptin, similar to other markers of adiposity in general, is more strongly related to risk of diabetes than CVD in the elderly.

Adipose tissue dysfunction in obesity, diabetes, and vascular diseases

The classical perception of adipose tissue as a storage place of fatty acids has been replaced over the last years by the notion that adipose tissue has a central role in lipid and glucose metabolism and produces a large number of hormones and cytokines, e.g. tumour necrosis factor-alpha, interleukin-6, adiponectin, leptin, and plasminogen activator inhibitor-1. The increased prevalence of excessive visceral obesity and obesity-related cardiovascular risk factors is closely associated with the rising incidence of cardiovascular diseases and type 2 diabetes mellitus. This clustering of vascular risk factors in (visceral) obesity is often referred to as metabolic syndrome. The close relationship between an increased quantity of visceral fat, metabolic disturbances, including low-grade inflammation, and cardiovascular diseases and the unique anatomical relation to the hepatic portal circulation has led to an intense endeavour to unravel the specific endocrine functions of this visceral fat depot. The objective of this paper is to describe adipose tissue dysfunction, delineate the relation between adipose tissue dysfunction and obesity and to describe how adipose tissue dysfunction is involved in the development of diabetes mellitus type 2 and atherosclerotic vascular diseases. First, normal physiology of adipocytes and adipose tissue will be described.

Leptin: a predictor of abnormal glucose tolerance and prognosis in patients with myocardial infarction and without previously known Type 2 diabetes

AIMS

High levels of leptin and low adiponectin are associated with Type 2 diabetes mellitus (T2DM) and cardiovascular (CV) disease. We studied the prognostic implications of leptin and adiponectin in patients with acute myocardial infarction (AMI) without previously known Type 2 DM.

METHODS

One hundred and eighty-one patients were included. Based on an oral glucose tolerance test at hospital discharge (day 4-5), 168 (67% men) had normal or abnormal glucose tolerance (AGT), defined as impaired glucose tolerance or T2DM. Sex- and age-matched healthy persons served as control subjects (n = 185). The associations between fasting serum leptin and adiponectin (day 2) and newly discovered AGT and CV events (CV mortality, non-fatal stroke, reinfarction or severe heart failure) during a median follow-up of 34 months were investigated.

RESULTS

Compared with control subjects, patients of both genders had significantly higher levels of leptin 2 days after an AMI. These levels were higher than those obtained at hospital discharge and 3 months later. Circulating levels of (ln) leptin 2 days after the AMI predicted AGT at discharge (odds ratio 2.03, P = 0.042). Ln leptin at day 2 was the only biochemical variable that significantly predicted CV events both on univariate [hazard ratio (HR) 1.60, P = 0.018] and on multivariate analysis (HR 1.75, P = 0.045). Adiponectin levels did not differ between patients and control subjects and did not relate to AGT or CV events.

CONCLUSIONS

Elevated circulating levels of leptin on the first morning after an AMI are associated with the presence of AGT at discharge and with a poorer long-term prognosis.

Short-term treatment with ezetimibe, simvastatin or their combination does not alter circulating adiponectin, resistin or leptin levels in healthy men

OBJECTIVE

Statin therapy decreases cardiovascular morbidity and mortality, and ezetimibe, a novel cholesterol absorption inhibitor has both lipid-lowering and anti-atherosclerotic effects in animal models. As several adipokines, that is, adiponectin, high molecular weight (HMW) adiponectin, leptin and/or possibly resistin are involved in the pathogenesis of insulin resistance (IR), dyslipidaemia and atherosclerosis, we investigated whether ezetimibe and/or statin treatment may modulate serum concentrations of these four major adipokines.

RESEARCH DESIGN AND METHODS

One-centre, randomized, parallel three-group study in 72 healthy men [mean age 32 +/- 9 years, mean body mass index (BMI) 25.7 +/- 3.2 kg/m(2)].

PATIENTS

Seventy-two healthy men. Each group of 24 subjects received a 14-day treatment with either ezetimibe (10 mg/day), simvastatin (40 mg/day) or their combination. Blood was drawn before and after the 14-day treatment period.

MEASUREMENTS

Lipid levels, IR indices, serum leptin, adiponectin, HMW adiponectin and resistin concentrations. Results Neither ezetimibe nor simvastatin or their combination had any effect on serum leptin, adiponectin, HMW adiponectin and resistin concentrations. Baseline leptin levels correlated positively, while adiponectin and HMW adiponectin negatively, with BMI. Leptin concentrations correlated negatively while adiponectin and HMW adiponectin positively with plasma high-density lipoprotein-cholesterol concentrations. Resistin concentrations were not associated with BMI, lipid levels or indicators of IR.

CONCLUSIONS

Treatment with ezetimibe, simvastatin or their combination does not alter circulating levels of adiponectin, leptin or resistin in adult healthy men.

Relationship between leptin and C-reactive protein in young Finnish adults

CONTEXT

Leptin and C-reactive protein (CRP) concentrations are increased in inflammation, and both have been linked to increased risk for cardiovascular diseases.

OBJECTIVE

The objective of the study was to explore in a population-based sample whether the relation between leptin and CRP is independent of obesity level and whether genetic causes of CRP elevation contribute to leptin levels.

DESIGN

This was a population-based study including 1862 young adults (971 women; 891 men) aged 24-39 yr.

SETTING

The study was conducted at five centers in Finland.

MAIN OUTCOME MEASURES

Associations between leptin and CRP adjusted for obesity indices, risk factors, genetic variables, and lifestyle variables were measured.

RESULTS

Women had 3.0-fold higher median concentrations of leptin (12.5 vs. 4.1 ng/ml) and 1.3-fold higher median concentrations of CRP (0.75 vs. 0.56 mg/liter) than men (P < 0.0001 in both comparisons). In univariate analyses, CRP and leptin were significantly intercorrelated (r = 0.47, P < 0.0001 for women; r = 0.46, P < 0.0001 for men). In multiple regression analysis including age, body mass index, waist circumference, insulin, lipids, systolic and diastolic blood pressures, smoking status, and use of oral contraceptives in women, leptin was the main determinant of CRP in men (P < 0.0001) and the second most important determinant in women (P < 0.0001). A Mendelian randomization test based on genetic variants in the CRP gene (five single nucleotide polymorphisms) provided no support for CRP as a causal agent for leptin.

CONCLUSIONS

Leptin, obesity, and oral contraceptive use in women were the main factors related to CRP. The relation between leptin and CRP was independent of obesity and cardiovascular risk factors.