Benfluorex metabolism complemented by electrochemistry-mass spectrometry

The hypolipidemic and hypoglycemic drug benfluorex was widely applied to treat type 2 diabetes mellitus and metabolic syndrome in overweight patients since 1976. However, benfluorex was connected to multiple cases of valvular heart disease and pulmonary arterial hypertension later on. Similar adverse drug reactions were previously found to be associated to the structurally related drug fenfluramine, which was attributed to the formation of its N-deethylated metabolite norfenfluramine. Even though norfenfluramine was known to be a common metabolite of fenfluramine and benfluorex, only fenfluramine was withdrawn from European and United States markets in 1997 while benfluorex remained available until 2009. In this work, the metabolism of benfluorex is simulated by an online hyphenation of electrochemistry and mass spectrometry and the observed transformation products are further characterized using liquid chromatography and high-resolution tandem mass spectrometry. Using this approach, norfenfluramine is found to be the main electrochemical transformation product of benfluorex. Considering the knowledge about norfenfluramine toxicity, rapid metabolite screening using electrochemistry hyphenated to mass spectrometry could have been used to predict the potential of benfluorex for adverse drug reactions early on, showcasing the value of electrochemical metabolism mimicry for rapid drug safety evaluation.

Trichloroethylene perturbs HNF4a expression and activity in the developing chick heart

Exposure to trichloroethylene (TCE) is linked to formation of congenital heart defects in humans and animals. Prior interactome analysis identified the transcription factor, Hepatocyte Nuclear Factor 4 alpha (HNF4a), as a potential target of TCE exposure. As a role for HNF4a is unknown in the heart, we examined developing avian hearts for HNF4a expression and for sensitivity to TCE and the HNF4a agonist, Benfluorex. In vitro analysis using a HNF4a reporter construct showed both TCE and HFN4a to be antagonists of HNF4a-mediated transcription at the concentrations tested. HNF4a mRNA is expressed transiently in the embryonic heart during valve formation and cardiac development. Embryos were examined for altered gene expression in the presence of TCE or Benfluorex. TCE altered expression of selected mRNAs including HNF4a, TRAF6 and CYP2C45. There was a transition between inhibition and induction of marker gene expression in embryos as TCE concentration increased. Benfluorex was largely inhibitory to selected markers. Echocardiography of exposed embryos showed reduced cardiac function with both TCE and Benfluorex. Cardiac contraction was reduced by 29% and 23%, respectively at 10 ppb. The effects of TCE and Benfluorex on autocrine regulation of HNF4a, selected markers and cardiac function argue for a functional interaction of TCE and HNF4a. Further, the dose-sensitive shift between inhibition and induction of marker expression may explain the nonmonotonic-like dose response observed with TCE exposure in the heart.

Drug-induced aortic valve stenosis: An under recognized entity

BACKGROUND

We have been intrigued by the observation that aortic stenosis (AS) may be associated with characteristic features of mitral drug-induced valvular heart disease (DI-VHD) in patients exposed to valvulopathic drugs, thus suggesting that beyond restrictive heart valve regurgitation, valvulopathic drugs may be involved in the pathogenesis of AS.

METHODS

Herein are reported echocardiographic features, and pathological findings encountered in a series of patients suffering from both AS (mean gradient >15mmHg) and mitral DI-VHD after valvulopathic drugs exposure. History of rheumatic fever, chest radiation therapy, systemic disease or bicuspid aortic valve disease were exclusion criteria.

RESULTS

Twenty-five (19 females, mean age 62years) patients having both AS and typical features of mitral DI-VHD were identified. Mean transaortic pressure gradient was 32+/-13mmHg. Aortic regurgitation was ≥ mild in 24 (96%) but trivial in one. Known history of aortic valve regurgitation following drug initiation prior the development of AS was previously diagnosed in 17 patients (68%). Six patients underwent aortic valve replacement and 3 both aortic and mitral valve replacement. In the 9 patients with pathology analysis, aortic valvular endocardium was markedly thickened by dense non-inflammatory fibrosis, a characteristic feature of DI-VHD.

CONCLUSION

The association between AS and typical mitral DI-VHD after valvulopathic drug exposure may not be fortuitous. Aortic regurgitation was usually associated to AS and preceded AS in most cases but may be lacking. Pathology demonstrated the potential role of valvulopathic drugs in the development of AS.

Frequency of drug-induced valvular heart disease in patients previously exposd to benfluorex: a multicentre prospective study

AIMS

The epidemiologic link between benfluorex use and an increased global frequency of left heart valve regurgitation has been well documented. However, no data linking previous drug exposure to the frequency of diagnosis of drug-induced valvular heart disease (DI-VHD) are available. The present study was conducted to address this issue.

METHODS AND RESULTS

This echocardiography reader-blinded, controlled study conducted in 10 centres between February 2010 and February 2012 prospectively included 835 subjects previously exposed to benfluorex referred by primary care physicians for echocardiography. Based on blinded off-line analysis, echocardiography findings were classified as: (i) DI-VHD⁺ for patients with an echocardiographic diagnosis of DI-VHD, (ii) inconclusive, and (iii) DI-VHD⁻ for patients without signs of DI-VHD. Fifty-seven (6.8%) patients exposed to benfluorex were classified as DI-VHD⁺, 733 (87.8%) patients were classified as DI-VHD⁻, and 45 (5.4%) were classified as inconclusive. Mitral and aortic DI-VHD were reported in 43 patients (5.1%) and 30 (3.6%) patients, respectively. Longer duration of exposure, female gender, smoking, and lower BMI were independently associated with a diagnosis of DI-VHD. Good inter-observer reproducibility was observed for the echocardiography classification (Kappa = 0.83, P < 0.00001).

CONCLUSIONS

About 7% of patients without a history of heart valve disease previously exposed to benfluorex present echocardiography features of DI-VHD. Further studies are needed to study the natural history of DI-VHD and to identify risk factors for the development of drug-induced valve lesions.

Impact of selective serotonin reuptake inhibitor therapy on heart valves in patients exposed to benfluorex: a multicentre study

BACKGROUND

Given the association between valvular heart disease and drugs that alter serotonin metabolism, concerns have been raised about the possibility of an association between selective serotonin reuptake inhibitor (SSRI) use and drug-induced valvular disease. In France, SSRI use has been suggested to be an important confounding factor in the development of heart valve lesions in patients exposed to benfluorex in the context of the 'Médiator scandal'.

AIMS

To address the relationship between SSRI use and valve regurgitation and morphology in a large cohort of patients exposed to benfluorex.

METHODS

Overall, 832 consecutive patients exposed to benfluorex prospectively referred to 10 centres underwent complete echocardiography examinations according to a standardized protocol. Echocardiograms were independently and blindly read off-line by two experts.

RESULTS

Ninety patients had been exposed to SSRIs for 3 months or more. The proportions of patients with no or trivial, mild, moderate or severe mitral regurgitation (MR) or aortic regurgitation (AR) were not different between SSRI patients and non-SSRI patients (P=0.63 and 0.58, respectively). The frequencies of AR ≥ mild (20 [22.2%] vs 145 [19.5%]; P=0.55) and MR ≥ mild (14 [15.6%] vs 118 [15.9%]; P=0.93) were similar in SSRI patients and non-SSRI patients. The frequencies of aortic and mitral valve abnormalities suggestive of drug-induced toxicity were also similar in the two patient groups. Multivariable logistic regression analysis confirmed the absence of any identifiable relationship between AR or MR and morphological abnormalities and SSRI use in the present cohort.

CONCLUSION

Exposure to SSRIs was not associated with an increased risk of heart valve regurgitation or morphological abnormalities suggestive of drug-induced toxicity in this large cohort of patients exposed to benfluorex.