Leptin levels are not affected by enalapril treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men

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Eriksson, M A., Söderberg, S., Nilsson, T K., Eriksson, M., Boman, K. et al. (2020) Leptin levels are not affected by enalapril treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men

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Leptin levels are not affected by enalapril

treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men

Maria A. Eriksson, Stefan Söderberg, Torbjörn K. Nilsson, Marie Eriksson, Kurt Boman & Jan-Håkan Jansson

To cite this article: Maria A. Eriksson, Stefan Söderberg, Torbjörn K. Nilsson, Marie Eriksson, Kurt Boman & Jan-Håkan Jansson (2020) Leptin levels are not affected by enalapril treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men, Scandinavian Journal of Clinical and Laboratory Investigation, 80:4, 303-308, DOI: 10.1080/00365513.2020.1731848

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© 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

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ORIGINAL ARTICLE

Leptin levels are not affected by enalapril treatment after an uncomplicated myocardial infarction, but associate strongly with changes in fibrinolytic variables in men

Maria A. Eriksson ^a , Stefan S€oderberg ^a , Torbj€orn K. Nilsson ^b , Marie Eriksson ^c , Kurt Boman ^d and Jan-Håkan Jansson ^d

a

Department of Public Health and Clinical Medicine, Medicine, Umeå University, Umea, Sweden;

Department of Medical Biosciences/

Clinical Chemistry, Umeå University, Umea, Sweden;

Department of Statistics, USBE, Umeå University, Umea, Sweden;

Research Unit Skellefteå, Department of Public Health and Clinical Medicine, Umeå University, Umea, Sweden

ABSTRACT

Leptin, an adipocyte-derived hormone, is involved in the regulation of body weight and is associated with obesity-related complications, notably cardiovascular disease (CVD). A putative link between obesity and CVD could be induction of plasminogen activator inhibitor-1 (PAI-1) synthesis by leptin. In this study, we hypothesized that the beneficial effect of the angiotensin-converting enzyme inhibitor (ACE

) enalapril on PAI-1 levels is mediated by effects on leptin levels. The association between leptin and components of the fibrinolytic system was evaluated in a non-prespecified post hoc analysis of a placebo-controlled random- ized, double-blind trial where the effect of the ACE

enalapril on fibrinolysis was tested. A total of 46 men and 37 women were randomized to treatment with enalapril or placebo after (median 12 months) an uncomplicated myocardial infarction. At baseline, the participants were stable and had no signs of congest- ive heart failure. Leptin and fibrinolytic variables (mass concentrations of PAI-1, tissue plasminogen activa- tor (tPA) and tPA –PAI complex) were measured at baseline, and after 10 days, 6 months and 12 months.

Enalapril treatment did not change leptin levels, which increased significantly during 1 year of follow-up ( p ¼ .007). Changes in leptin levels were strongly associated with changes of tPA mass (p ¼ .001), tPA–PAI complex ( p ¼ .003) and of PAI-1 (p ¼ .006) in men, but not in women. Leptin levels are not influenced by treatment with an ACE

. In contrast, leptin associates strongly with changes in fibrinolytic variables notably with a sex difference, which could be of importance for obesity-related CVD.

ARTICLE HISTORY Received 27 August 2019 Revised 7 February 2020 Accepted 16 February 2020 KEYWORDS

Leptin; ACE inhibitor;

cardiovascular disease;

PAI-1; fibrinolysis

Introduction

Adipose tissue is an endocrine organ with both autocrine and paracrine functions, and several pathways regulating glucose and lipid metabolism have been shown [1]. In add- ition, fat cells express receptors that respond to both neuronal and hormonal signals [2]. Leptin is an adipocyte- derived hormone with sex-related differences in circulating levels and signaling and high levels are associated with obes- ity suggesting leptin resistance [3,4].

Furthermore, hyperleptinemia associated with metabolic dis- ease [5], including dysfibrinolysis [6,7] and the renin –angioten- sin–aldosterone (RAAS) system [8], and sex-related differences have been seen in some of these associations [9]. Notably, high levels of leptin have also been associated with the development of myocardial infarction and stroke with a sex difference [10,11]. Large randomized clinical trials have established that angiotensin-converting enzyme inhibitors (ACE

), such as ena- lapril, are of pivotal importance for reducing mortality in patients with atherosclerotic disease irrespective of blood

pressure-lowering effect [12,13], or with heart failure, with or without a previous acute myocardial infarction (AMI) [14].

The physiological pathways for these beneficial effects of ACEi are not fully understood. However, brain leptin-RAS interac- tions with effect on feeding behavior have been suggested [15].

As reported in our previous paper, treatment with enalapril improved fibrinolytic status [16], and was associated with decreasing circulating levels of plasminogen activator inhibitor- 1 (PAI-1) and tissue plasminogen activator (tPA) mass.

Our primary aim with this post hoc analysis was to explore if enalapril treatment also affected circulating leptin levels.

Furthermore, as a secondary aim, we studied if changes in lep- tin levels were associated with changes in fibrinolytic status.

Methods

Design and subjects

This study is a non-prespecified post hoc analysis of a previ- ously presented randomized controlled trial [16]. Briefly, in a

CONTACT Maria Alice Eriksson maria.a.eriksson@umu.se Department of Public Health and Clinical Medicine, Umeå University Hospital, SE-90185 Umea, Sweden

Supplemental data for this article can be accessed here.

ß 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

SCANDINAVIAN JOURNAL OF CLINICAL AND LABORATORY INVESTIGATION 2020, VOL. 80, NO. 4, 303 –308

https://doi.org/10.1080/00365513.2020.1731848

clinical trial at Skellefteå Hospital, Skellefteå, Sweden, patients with an earlier AMI were randomized to treatment with an ACE

(enalapril) or placebo. To be eligible for the study, the following criteria had to be fulfilled. An age of 18 years or older when admitted for chest pain lasting for more than 20 min and within 24 h of onset, plus electrocardiogram (ECG) changes (ST elevation in two adjacent leads or new Q waves) or elevation of biochemical markers above normal.

Chest X-rays and echocardiography were performed if clinic- ally indicated, and patients were excluded from the study if congestive heart failure emerged (clinical or radiological find- ings or an ejection fraction <40%) in the acute phase or at any time before randomization. Furthermore, patients with any contraindication to an ACE

, or with any severe disorder that affected short-term prognosis were excluded.

Two months or later from the qualifying AMI (median 12 months, interquartile range 8–22 months), men and women were asked to participate in this study. Risk factors for AMI (self- reported smoking, hypertension, and dia- betes), medical treatment, use of thrombolytics, and invasive procedures (by-pass surgery and percutaneous transluminal coronary angioplasty [PTCA]) were registered, and eligible subjects were randomized to enalapril or matching placebo in a blinded fashion. From an initial dose of 2.5 mg daily, the dose was up-titrated to 20 mg given as a single dose.

Subjects were then followed for 1 year and cardiovascular complications (i.e. death, AMI, unstable angina, new stable angina and heart failure) were registered.

The study protocol was approved by the Regional Ethics Review Board, Umeå (dnr 94-181), and written informed consent was obtained from all participants.

Sampling and measurements

Body mass index (BMI) at study start was calculated as total body weight in kilograms divided by the square of height in meters. Blood pressure was recorded with a Mercury sphygmomanometer.

Blood sampling was carried out in the morning (8–10 AM) after an overnight fast, at baseline and after 10 days, 6 months, and 12 months. Subjects rested for at least 10 min in the recumbent position before sampling and a minimum of stasis was used.

Fresh serum samples were used for the analysis of lipids.

Cholesterol and triglycerides were determined by enzymatic methods (Boehringer Mannheim GmbH Diagnostica, Mannheim, DE), and low-density lipoprotein (LDL) choles- terol was calculated according to Friedewald’s formula.

Plasma for the following analyses was collected into sili- conized citrated tubes, and centrifuged at 4 ^ C within 5 min, and was snap-frozen and stored at 70 ^ C until analysis.

The mass concentrations of PAI-1, tPA and tPA –PAI complex were determined by enzyme-linked immunosorbent assays, as previously described [17,18]. The reagents for these assays (Imulyse tPA, Imulyse tPA/PAI-1, and Imulyse PAI-1, respectively) were purchased from Biopool, Umeå, Sweden.

Leptin levels were determined by a double-antibody radioimmunoassay (RIA) with rabbit anti-human leptin antibodies,

I-labeled human leptin as tracer, and human leptin as standard (Linco Res., St. Louis, MO, USA). All leptin samples were analyzed in duplicates as recommended by the manufacturer. Total coefficients of variation (CV) were calculated from these duplicate measurements and total CV was 4.7% at both low (2–4 ng/mL) and high (10–15 ng/mL) levels.

Statistics

The initial study was designed to detect enalapril-induced changes in fibrinolytic variables [16]. In order to show the impact of enalapril, it was calculated that 40–50 patients were needed in each group to show a statistical ( p < .05) and clin- ically significant (15% reduction) result with 80% power.

For this non-prespecified post hoc analysis, we had 80%

power to detect an association between leptin and PAI-1 at p < .05 with a b-coefficient greater than ±0.23 in men, and greater than ±0.27 in women [19].

Analysis was carried out on an intention-to-treat basis and in all patients on drug therapy.

Skewed variables were transformed using a natural loga- rithm in order to achieve an approximately normal distribu- tion. Means (geometric for transformed values) with 95%

confidence intervals (CI) or median with interquartile range are presented. We used Student’s t-tests, or an analysis of variance (ANOVA) with adjustments or Mann –Whitney test when appropriate, for exploring differences between men and women. To analyze changes during the period studied, a repeated measures of variance was used. The transformed variable was used as the response variable whereas treatment allocation, sex, age and BMI were included as independent factors. To avoid assumptions regarding linearity, age and BMI were divided into tertiles using sex-specific cut-off points. Univariate tests were used to test within subjects’

effects, i.e. time and timefactor interaction effects. When the assumption regarding sphericity was rejected according to Mauchly ’s criteria, the degrees of freedom were adjusted by the Greenhouse–Geisser epsilon. Polynomial contrasts were used to test for linear, quadratic and cubic time trends.

Changes in leptin, tPA, PAI-1, tPA –PAI complex were cal- culated (delta values) as the difference between the ln-trans- formed 12 months (or other intervals of interest) and the baseline measurements. This difference equals the ratio between the measurements when back transformed. These delta values were used as dependent (fibrinolytic variables) and independent (leptin) variable in a simple and multiple linear regression analysis for test of associations, adjusted for age, BMI, triglycerides and treatment allocation. As lep- tin measurements were missing at 16 occasions, the analysis was carried out both with missing data and after replace- ment with the mean of two adjacent measurements. Two- tailed tests were used and a value of p < .05 was considered as significant. All calculations were made using Statistical Package for the Social Sciences (SPSS) software program, version 25.0 (Chicago, IL, USA).

304 M. A. ERIKSSON ET AL.

Results

Men and women with a previous myocardial infarction were recruited for a clinical study determining the effect of the ACE inhibitor enalapril on fibrinolytic variables. These men were younger than women and more women suffered from hypertension (Table 1). Furthermore, women had higher sys- tolic blood pressure than men and their levels of total and HDL-cholesterol, tPA mass, and leptin were higher (Table 2).

Differences in blood pressure and total cholesterol between sexes remained during follow -up, whereas the dif- ference in tPA disappeared. Levels of tPA –PAI complex were higher in women at all time points, but significantly only at 12 months (Table 2).

Leptin levels (geometric means) according to treatment allo- cation stratified for sex are shown in Supplementary Table 1.

No differences were observed in measured variables at base- line between treatment allocation groups (data not shown).

In order to explore if changes in leptin levels related to covariates and treatment allocation, a repeated measure assessment was carried out. The univariate test of the within-subject effect showed a statistically significant overall time effect of increased levels of leptin during 1 year ( p ¼ .005). None of the time factor interaction effects were significant. The test for a linear time trend for leptin was statistically significant (p ¼ .007). The leptin levels differed statistically significantly depending on sex ( p < .001) and

Table 1. Subject characteristics at baseline.

Men Range IQR Women Range IQR p-Value

N 46 37

Age (years) 65 43 16 72 27 10 .002

BMI (kg/m

) 26.4 16.1 3.1 25.7 16.2 5.7 .71

Smoker (%) 15.2 8.1 .33

Diabetes (%) 6.5 .0 .08

Hypertension (%) 32.6 56.8 .03

Thrombolytic treatment (%) 50.0 40.5 .40

History of coronary by-pass (%) 37.0 32.4 .67

b-Blocker (%) 71.7 75.7 .69

ASA (%) 89.1 89.2 .99

Statins (%) 17.4 27.0 .30

Active treatment with ACE inhibitor (%) 41.3 56.8 .17

Time-lag between AMI and study-start (months) 10.0 42 8 19.0 44 19 <.001

Numbers shown are proportions and medians with ranges and IQR.

Differences between groups tested with Student ’s t-test or Mann–Whitney tests when appropriate.

IQR: interquartile range.

Table 2. Subject characteristics at baseline and changes during the year.

Variable Time point Men 95% CI p

Women 95% CI p

p

Systolic blood pressure (mmHg) Baseline 145.6 138.4 –152.8 158.9 151 –166.9 .02

10 days 134.1 127.7 –140.4 146.8 139.6 –154 .01

6 months 133.6 127.5 –139.6 149.5 142.6 –156.4 .001

12 months 145.4 138.6 –152.2 <.001 159.2 151.2 –167.1 .001 .01

Diastolic blood pressure (mmHg) Baseline 84.3 81.3 –87.4 85.1 81.7 –88.5 .74

10 days 76.4 73.3 –79.6 77.1 73.5 –80.6 .79

6 months 77.2 74 –80.5 76.1 72.4 –79.8 .64

12 months 82.8 80 –85.6 <.001 82.6 79.4 –85.9 <.001 .96

Total cholesterol (mmol/L) Baseline 6.5 6.1 –6.8 7.2 6.8 –7.7 .01

12 months 5.9 5.5 –6.2 <.001 6.5 6.1 –6.9 .002 .03

HDL cholesterol (mmol/L) Baseline 1.1 1.01 –1.18 1.27 1.17 –1.36 .008

12 months 1.2 1.02 –1.39 <.001 1.47 1.26 –1.69 .15 .06

Triglycerides (mmol/L) Baseline 1.6 1.5 –1.8 1.7 1.5 –1.9 .5

12 months 1.9 1.6 –2.1 .007 1.9 1.6 –2.2 .04 .82

Leptin (ng/mL) Baseline 5.8 5.1 –6.5 17.6 15.2 –20.4 <.001

10 days 5.8 5 –6.6 16.9 14.5 –19.8 <.001

6 months 5.9 5.2 –6.9 17.6 14.9 –20.8 <.001

12 months 6.5 5.5 –7.6 .04 19.6 16.2 –23.7 .09 <.001

tPA mass ( mg/L) Baseline 11.2 10 –12.5 13.3 11.7 –15.1 .05

10 days 10.3 9.2 –11.5 12.3 10.9 –13.9 .03

6 months 10.8 9.7 –12 11.7 10.3 –13.2 .34

12 months 11.7 10.6 –13 .005 12.8 11.4 –14.4 .12 .26

PAI-1 mass ( mg/L) Baseline 26.1 22.1 –30.8 25.4 21.2 –30.5 .83

10 days 21 17.7 –24.9 23.2 19.3 –27.9 .43

6 months 17 13.9 –20.8 18 14.2 –22.7 .73

12 months 21.5 18 –25.7 <.001 19.1 15.5 –23.5 .02 .4

tPA –PAI complex (mg/L) Baseline 4.2 3.6 –5 5.4 4.4 –6.6 .08

10 days 3.9 3.3 –4.7 4.7 3.8 –5.8 .2

6 months 3.9 3.2 –4.6 4.9 4 –6 .07

12 months 4.5 3.9 –5.3 .02 5.9 4.9 –7.1 .03 .04

Adjusted (treatment allocation, and age and BMI at baseline) means (geometric) with 95% confidence intervals (CI).

Differences between men and women at each time point tested with an ANOVA ( p

), and overall time effects between baseline and 12 months with a repeated assessment analysis ( p

), all adjusted for age, BMI and treatment allocation.

SCANDINAVIAN JOURNAL OF CLINICAL AND LABORATORY INVESTIGATION 305

BMI (p < .001). After adjustment for BMI, sex and age, ena- lapril treatment had no statistically significant effect on lep- tin levels at any time point of the trial.

An increasing trend over time for leptin was seen in both men and women randomized to either placebo or to active treatment, although not significant, which could be due to small groups (data not shown).

After 1 year, changes in leptin levels associated independ- ently (adjusted for age and BMI at baseline and for treatment allocation) with changes of tPA mass concentration (p ¼ .001), PAI-1 mass concentration (p ¼ .006), and tPA–PAI complex (p ¼ .003) in men. After stratification for treatment allocation, changes in leptin associated with changes in tPA (p < .001) and tPA –PAI complex (p ¼ .02) in men on placebo. In women, changes in leptin did not associate with any changes in fibrinolytic variables at any time point, neither in univariate nor in multivariate analysis (Table 3).

Further adjustment for time from AMI to blood sam- pling did not attenuate these associations (data not shown).

Enalapril treatment was associated with decreasing tPA mass and PAI-1 levels after 1 year in men ( p ¼ .04 and p ¼ .002, respectively), even after adjustment for changes of leptin (Table 3). Enalapril treatment was not associated with any changes in fibrinolysis, once adjusted for changes in leptin levels after 1 year in women.

Further adjustments for circulating levels of triglycerides did not alter the results (data not shown)

Finally, these results were similar after replacement of missing leptin data (16 occasions) with the mean of two adjacent measurements (data not shown).

Discussion

In this non-prespecified post hoc analysis, we show that ena- lapril treatment did not associate with circulating leptin lev- els. However, even though a causal relationship cannot be concluded by this post hoc analysis, we show that changes in leptin levels strongly associated with changes in fibrinolytic variables, notably with a clear sex difference.

We have previously reported that treatment with enalap- ril improved fibrinolysis as measured by decreasing circulat- ing levels of PAI-1, tPA mass and tPA–PAI complex [16]

and the effect was remaining for PAI-1 after 1 year whereas the effect was transient for tPA and tPA –PAI complex. We hypothesized that this effect could be mediated by decreas- ing leptin levels, which was thus not seen. However, leptin levels increased during the study presumably due to weight gain, and changes in leptin levels were independent of ena- lapril treatment.

We acknowledge that BMI was only measured at baseline in our study and it was thus not possible to adjust for weight changes (presumably weight gain). We conclude that our negative findings between leptin and enalapril treatment cannot exclude an interaction that has to be studied in a specifically designed study with rigorous control of con- founding variables such as anthropometry. However, the association between leptin and dysfibrinolysis was independ- ent of both general and central obesity in our previous study [9]. Furthermore, we have earlier shown that leptin levels and anthropometric measurements are not only two ways of measure obesity, associations differ in various physiological conditions [20]. Women have more than three times higher levels of circulating leptin as compared to men despite similar general and central obesity, and differences in numbers and size of adipocytes, amount of subcutaneous versus visceral adipose tissue and androgenicity may con- tribute to this effect [21,22].

Sex-related differences in leptin signaling and sensitivity have also been shown, as the brains of male and female rats are differentially sensitive to the catabolic actions of leptin with higher sensitivity in females, and estrogens can alter the hypothalamic sensitivity for leptin by inducing produc- tion of the leptin receptor [23,24].

We and others have shown that hyperleptinemia inde- pendently predicts atherosclerotic disease [5,11,25] and interestingly, this association has mainly been seen in men but not in women.

These data extend our previous findings with further associations with hyperleptinemia and tPA and PAI –tPA

Table 3. Multivariate linear regression models testing associations between changes in leptin and fibrinolytic variables.

tPA mass change PAI-1 mass change tPA –PAI complex change

b SE St b p b SE St b p b SE St b p

All men

Leptin change 0.435 0.122 0.542 .001 0.747 0.250 0.433 .006 0.550 0.170 0.491 .003

Treatment 0.172 0.082 0.324 .044 0.585 0.168 0.513 .002 0.100 0.114 0.136 .386

Men on placebo

Leptin change 0.709 0.147 0.896 <.001 0.764 0.367 0.511 .053 0.698 0.277 0.592 .021

Men on enalapril

Leptin change 0.348 0.279 0.425 .241 0.907 0.554 0.520 .136 0.583 0.322 0.555 .103

All women

Leptin change 0.166 0.184 0.179 .377 0.125 0.396 0.072 .755 0.175 0.292 0.125 .554

Treatment 0.118 0.123 0.195 .346 0.057 0.265 0.050 .831 0.113 0.195 0.123 .568

Women on placebo

Leptin change 0.096 0.261 0.199 .726 0.627 0.440 0.669 .203 0.326 0.400 0.389 .446

Women on enalapril

Leptin change 0.325 0.365 0.217 .394 0.557 0.746 0.202 .474 0.218 0.507 0.108 .676

Multivariate linear regression with fibrinolytic variables as dependent variables, and stratified for sex and treatment allocation.

Delta-values of ln-transformed variables (over 1 year) used for leptin, tPA mass, PAI-1 mass and tPA –PAI complex.

Treatment: 1 ¼ placebo and 2 ¼ enalapril. BMI and age tested as tertiles with sex-specific cut-off.

Cut-off points (men;women): BMI <25.4;<24.2, 25.4–27.1; 24.2–28.4; and 27.1þ;28.4þ, and for age <59;<68, 59–70;68–74, and 70þ;74þ.

b: regression coefficients; SE(b): standard error of b; St b: standardized regression coefficients.

306 M. A. ERIKSSON ET AL.

complex. We have previously reported independent associa- tions between hyperleptinemia and abnormal fibrinolysis (high PAI-1 activity and low tPA activity) in men and post- menopausal women, but not in pre-menopausal women [9], findings that have been confirmed by others [6,7].

Mechanistically, there are several mechanisms by which lep- tin could cause atherosclerosis [26]. Our study provides fur- ther evidence that high leptin levels may induce increased risk for cardiovascular disease in men, possibly by effects on the fibrinolytic system.

The vascular damage affected by high levels of leptin could be mediated by the fibrinolytic system in different pathways related to thrombotic vascular disease. Leptin may have both stimulatory [27,28] and no effects [29] (in vitro experiments) on PAI-1 production. Differential effects upon different cells may explain this conundrum, as leptin stimu- lated PAI-1 production in vascular smooth muscle cells [27,28], but not in adipocytes [29].

In metabolic deranged patients with diabetes mellitus, high levels of leptin associated with a procoagulant state probably by inducing expression of tissue factor mRNA and protein [30], and furthermore, by an up-regulated PAI and tPA expression.

tPA activates the fibrinolytic system, and most of circu- lating tPA is released from the vascular endothelium [31].

We found an association between tPA mass and leptin which is noteworthy as previous studies have not shown any stimulation of tPA release after administration of leptin [27]. tPA mass includes both active tPA and tPA bound to PAI and the positive association found probably reflects the association with PAI-1. Notably, leptin was associated with tPA mass and tPA–PAI complex in men on placebo, but not in men on enalapril. If this is a play of chance or an indication that enalapril may alter the association between leptin and the atherosclerotic process is an important ques- tion that remains to be addressed.

An association between dyslipidemia and dysfibrinolysis has been shown as triglycerides increase the production of PAI-1 in cultured adipocytes, suggesting pro-atherogenic mechanisms [32]. Furthermore, it has been shown that lep- tins ability to regulate lipid and carbohydrate metabolism in obesity is attenuated [29,33–36]. The mechanism is most certain post receptor then there is no finding of decreased levels of hepatic leptin receptor expression [33]. In addition, ACE inhibitors are found to have a preventive effect of hypertriglyceridemia [37].

Even though we could not detect any associations between changes in blood pressure and changes in leptin levels in this study, leptin is suggested to induce obesity- related hypertension via several mechanisms, including sym- pathetic activation, NO-production and release and natri- uresis [38] and leptin interacts with intracellular effects of angiotensin II [39]. Further results indicate interactions between the leptinergic and angiotensinergic systems (acute leptin infusion restored ACE activity in leptin-deficient mice) with possible influence developing the metabolic syn- drome [8] and treatment with an ACE inhibitor in

hypertensive patients give an improved adipokine profile with higher levels of adiponectin and lower levels of lep- tin [40].

Our study has limited power, and smaller b-coefficients than ±0.23 in men and ±0.27 in women (calculated for PAI- 1) could not be detected, given the number of participants [19]. We can thus not exclude weaker associations in men and in women. Lack of repeated measurements of BMI and waist circumference is another limitation.

Notably, this randomized placebo-controlled trial will not be possible to repeat in the modern era where ACEi is man- datory after a myocardial infarction, and the study is thus a unique resource to study the effect of ACEi on leptin in a controlled fashion despite the limitations listed above.

In conclusion, enalapril treatment after a myocardial infarction was not associated with changes in leptin levels.

However, changes in leptin levels strongly associated with changes in fibrinolytic status. Further studies exploring the mechanisms linking the adipocyte-derived leptin with increased risk for cardiovascular disease are highly warranted.

Acknowledgements

We are indebted to Eva Jonsson for dedicated care of the patients, Bengt Norrfors for nursing and valuable assistance, Karin Hjertqvist for technical assistance, and to Gunilla Journath, MSD, Sweden for valuable administrative support. MSD was not involved in the acquisi- tion or analysis of data, or manuscript preparation of this study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Funding

This work was supported in part by a medical school grant from MSD, Inc.

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