Periodic Reporting for period 4 - PAPA (Pathophysiology of Primary Aldosteronism)
Berichtszeitraum: 2021-07-01 bis 2022-12-31
Arterial hypertension is classified as the leading preventable cause of premature death worldwide and it affects 20 to 40% of Western societies in an age dependent manner, amounting to more than 1.1 billion hypertensive individuals in the year 2017. Primary aldosteronism (PA) is the most common curable form of hypertension with a prevalence of 6-12% in the general population with hypertension. It is caused by the excessive, autonomous production of aldosterone from the adrenal glands resulting in refractory hypertension. If remaining undiagnosed, PA is a fatal disease leading to decreased quality of life, disabling cardiovascular morbidity and premature death by chronic heart failure, myocardial infarction, stroke and renal insufficiency. This ERC Advanced Grant PAPA has elucidated the humoral and molecular mechanisms underlying aldosterone excess and hypertension in PA to develop a pathophysiology-based classification for targeted treatments.
It was the first hypothesis of this proposal that the pathophysiology of PA is a process based on two ‘hits’: agonistic angiotensin II type 1 receptor (AT1R) autoantibodies and somatic mutations. Whereas agonistic autoantibodies induce proliferation and grossly changes adrenal cortex architecture towards diffuse or nodular hyperplasia, somatic mutations result in adenoma formation. In the past years we have analyzed prevalence and binding characteristics of AT1R autoantibodies as a pathophysiologic basis of PA. These data demonstrate that patients with PA displayed different levels of AT1R activation with different responses to inhibition by losartan, supporting my first hypothesis that agonistic AT1R antibodies may have a functional role in a subgroup of patients with PA. We also found compelling evidence for the second part of hypothesis, identifying new hotspot driver mutations in PA. It was the second hypothesis, that both factors, agonistic AT1R antibodies and somatic driver mutations together induce not only aldosterone but also marked glucocorticoid excess. To this end we have build-up a liquid chromatography–mass spectrometry (LCMS) platform to quantify aldosterone and glucocorticoid excess as disease effectors of PA. This resulted in multiple manuscripts demonstrating that mineralocorticoid and glucocorticoid signatures can be found in plasma and urine of PA patients, and that these signatures are predictive for underlying somatic driver mutations. In conclusion, we found compelling evidence in support of the two main hypotheses of our grant during this action.
It was the first hypothesis of this proposal that the pathophysiology of PA is a process based on two ‘hits’: agonistic angiotensin II type 1 receptor (AT1R) autoantibodies and somatic mutations. Whereas agonistic autoantibodies induce proliferation and grossly changes adrenal cortex architecture towards diffuse or nodular hyperplasia, somatic mutations result in adenoma formation. In the past years we have analyzed prevalence and binding characteristics of AT1R autoantibodies as a pathophysiologic basis of PA. These data demonstrate that patients with PA displayed different levels of AT1R activation with different responses to inhibition by losartan, supporting my first hypothesis that agonistic AT1R antibodies may have a functional role in a subgroup of patients with PA. We also found compelling evidence for the second part of hypothesis, identifying new hotspot driver mutations in PA. It was the second hypothesis, that both factors, agonistic AT1R antibodies and somatic driver mutations together induce not only aldosterone but also marked glucocorticoid excess. To this end we have build-up a liquid chromatography–mass spectrometry (LCMS) platform to quantify aldosterone and glucocorticoid excess as disease effectors of PA. This resulted in multiple manuscripts demonstrating that mineralocorticoid and glucocorticoid signatures can be found in plasma and urine of PA patients, and that these signatures are predictive for underlying somatic driver mutations. In conclusion, we found compelling evidence in support of the two main hypotheses of our grant during this action.
During the ERC project PAPA we gained insights in the classification of PA treatment as we were the lead researchers in an international study to develop consensus criteria for outcomes after unilateral adrenalectomy for unilateral PA and for the histological classification of aldosterone-producing adrenal lesion, the HISTALDO consensus. This is endorsed by the 2022 WHO classification of adrenal cortical tumors. We established a scoring system which allows preoperatively to identify patients with a high probability of clinical remission after surgery. We showed, that agonistic AT1R antibodies in PA plays a role in patients with bilateral adrenal hyperplasia more than in unilateral PA. Studies related to glucocorticoid co-secretion in PA identified significant glucocorticoid co-secretion as a major phenotype of PA, associated with metabolic co-morbidities, cardiac remodeling and impaired glucose metabolism. We were the first to report adrenal insufficiency postoperatively in a significant fraction of patients. We also identified major problems with currently used immunoassays in routine diagnostics for PA. We identified new molecular mechanism for pathophysiology of APAs, multiple aldosterone-producing micronodules (APMs), identified TSPAN12 as a negative regulator of aldosterone production in PA, and BEX1 as promoter of cell survival in adrenal cells by mediating the inhibition of ferroptosis. To gain further insight into genotype-related tumorigenesis, we investigated the transcriptomic and metabolomic divergence of APA from adjacent adrenal tissue using special transcriptomics in combination with MALDI metabolomics. Using Maldi imaging, we demonstrated specific subgroups of multiple APMs with strikingly divergent distribution patterns of metabolites. In collaborative research projects we identified first-in-field zinc transporter ZnT1 mutations using next-generation sequencing. We discovered mutations in the neuronal cell-adhesion gene CADM1. We identified also risk loci for PA in genome-wide association studies on chromosomes 1 and 13. In an international multicentre proof-of-principle study we showed, that adrenal sparing bilateral resections can bring PA into remission, challenging the current dogma of the routine medical management of bilateral aldosterone excess. We found evidence for major dysfunction of salt perception, consumption and handling and found strong evidence for a beneficial effect of moderate dietary salt restriction on blood pressure control and mental well-being in patients with PA in the Salt CONNtrol trial. Finally, we developed a pig model providing mechanistic insights into the physiologic adaptations to salt excess and salt withdrawal in a species closely related to humans. In summary, within the six years of the ERC action we have made significant advances in basic and translational research to elucidate the humoral and molecular mechanisms underlying aldosterone. Dissemination of our main findings have been achieved by 60 publications in international journals, congress presentations, international symposia and press releases.
The overall new concept of PA has shifted during recent years and the ERC PAPA grant has substantially contributed to this paradigm shift. It is nowadays firmly established, that PA is not a binary disease of unilateral and bilateral aldosterone excess. Instead, we have developed a PA model, which is based on the gradual increase in autonomously APMs and nodules over time. This cellular autonomy starts always bilaterally, probably through mutational events, but may develop into a lateralized phenotype, depending on additional mutations or endocrine, para- and autocrine stimulation (including agonistic AT1R autoantibodies). The overall concept has been published in multiple review articles, most recently in Lancet D&E 2021 Reincke et al. and TEM 2022 Williams&Reincke. Several ERC PAPA work packages have developed beyond state of the art the expectation of the 5 year funding period. In short these are: 1) Application of MALDI imaging to aldosterone producing adrenal tumor tissue has shed light on the origin of APMs; 2) Transcriptomic and metabolomic divergence of APA from adjacent adrenal tissue using special transcriptomics in combination with MALDI metabolomics will generate further insight into genotype-related tumorigenesis; 3) Development of a pig large animal model based on a KCNJ5 germline mutation to study the effects of the mutation on clinical phenotype, steroidome, adrenal morphology and remodelling, and long-term outcome. The first pups were born in Dec 2022, and the study is in an early phase; 4) Demonstration that PA is causing impaired salt perception and increased salt consumption accelerating cardiovascular and metabolic morbidity; 5) Recently, we were able, in a collaborative effort together with colleagues from France, UK and US, to identify new driver genes in PA.