Blood ACE Phenotyping for Personalized Medicine: Revelation of Patients with Conformationally Altered ACE.

Background: The angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated blood ACE is a marker for granulomatous diseases and elevated ACE expression in tissues is associated with increased risk of cardiovascular diseases. Objective and Methodology: We applied a novel approach -ACE phenotyping-to find a reason for conformationally impaired ACE in the blood of one particular donor. Similar conformationally altered ACEs were detected previously in 2-4% of the healthy population and in up to 20% of patients with uremia, and were characterized by significant increase in the rate of angiotensin I hydrolysis. Principal findings: This donor has (1) significantly increased level of endogenous ACE inhibitor in plasma with MW less than 1000; (2) increased activity toward angiotensin I; (3) M71V mutation in ABCG2 (membrane transporter for more than 200 compounds, including bilirubin). We hypothesize that this patient may also have the decreased level of free bilirubin in plasma, which normally binds to the N domain of ACE. Analysis of the local conformation of ACE in plasma of patients with Gilbert and Crigler-Najjar syndromes allowed us to speculate that binding of mAbs 1G12 and 6A12 to plasma ACE could be a natural sensor for estimation of free bilirubin level in plasma. Totally, 235 human plasma/sera samples were screened for conformational changes in soluble ACE. Conclusions/Significance: ACE phenotyping of plasma samples allows us to identify individuals with conformationally altered ACE. This type of screening has clinical significance because this conformationally altered ACE could not only result in the enhancement of the level of angiotensin II but could also serve as an indicator of free bilirubin levels.

Predictive potential of ACE phenotyping in extrapulmonary sarcoidosis.

Elevated ACE expression in tissues (reflected by blood ACE levels) is associated with increased risk of cardiovascular diseases and is also a marker for granulomatous diseases. We developed a new approach for characterization of ACE status in the blood-ACE phenotyping and established normal values of ACE levels 50-150% of control pooled plasma. ACE phenotyping was performed in citrated plasma of 120 patients with known interstitial lung diseases. In the 1st set of 100 patients we found 22 patients with ACE levels > 150%; ACE phenotyping also objectively identified the presence of ACE inhibitors in the plasma of 15 patients. After excluding these patients and patient with ACE mutation that increases ACE shedding, 17 patients were identified as a suspicious for systemic sarcoidosis based on elevation of blood ACE (> 150% of mean). A new parameter that we have established-ACE immunoreactivity (with mAb 9B9)-allowed us to detect 22 patients with decreased values (< 80%) of this parameter, which may indicate the presence of ACE in the blood that originates from macrophages/dendritic cells of granulomas. In the remaining 20 patients, this new parameter (mAbs binding/activity ratio) was calculated using 3 mAbs (9B9, 3A5 and i1A8-having overlapping epitopes), and 8 patients were identified as having decreases in this parameter, thus increasing dramatically the sensitivity for detection of patients with systemic sarcoidosis. Whole body PET scan confirmed extrapulmonary granulomas in some patients with lower immunoreactivity towards anti-ACE mAbs. ACE phenotyping has novel potential to noninvasively detect patients with systemic sarcoidosis.

Targeted Sequencing of 242 Clinically Important Genes in the Russian Population From the Ivanovo Region.

We performed a targeted sequencing of 242 clinically important genes mostly associated with cardiovascular diseases in a representative population sample of 1,658 individuals from the Ivanovo region northeast of Moscow. Approximately 11% of 11,876 detected variants were not found in the Single Nucleotide Polymorphism Database (dbSNP) or reported earlier in the Russian population. Most novel variants were singletons and doubletons in our sample, and virtually no novel alleles presumably specific for the Russian population were able to reach the frequencies above 0.1-0.2%. The overwhelming majority (99.3%) of variants detected in this study in three or more copies were shared with other populations. We found two dominant and seven recessive known pathogenic variants with allele frequencies significantly increased compared to those in the gnomAD non-Finnish Europeans. Of the 242 targeted genes, 28 were in the list of 59 genes for which the American College of Medical Genetics and Genomics (ACMG) recommended the reporting of incidental findings. Based on the number of variants detected in the sequenced subset of ACMG59 genes, we approximated the prevalence of known pathogenic and novel or rare protein-truncating variants in the complete set of ACMG59 genes in the Ivanovo population at 1.4 and 2.8%, respectively. We analyzed the available clinical data and observed the incomplete penetrance of known pathogenic variants in the 28 ACMG59 genes: only 1 individual out of 12 with such variants had the phenotype most likely related to the variant. When known pathogenic and novel or rare protein-truncating variants were considered together, the overall rate of confirmed phenotypes was about 19%, with maximum in the subset of novel protein-truncating variants. We report three novel protein truncating variants in APOB and one in MYH7 observed in individuals with hypobetalipoproteinemia and hypertrophic cardiomyopathy, respectively. Our results provide a valuable reference for the clinical interpretation of gene sequencing in Russian and other populations.

Phenotyping Angiotensin-Converting Enzyme in Blood: A Necessary Approach for Precision Medicine.

BACKGROUND: Angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated ACE expression in tissues (which is generally reflected by ACE in blood) is associated with increased risk of cardiovascular diseases. Elevated ACE in blood is also a marker for granulomatous diseases. METHODS: We applied our novel approach-ACE phenotyping-to characterize serum ACE in 300 unrelated patients and to establish normal values for ACE levels. ACE phenotyping includes (a) determination of ACE activity with 2 substrates (Z-Phe-His-Leu [ZPHL] and Hip-His-Leu [HHL]), (b) calculation of a ratio for hydrolysis of ZPHL and HHL, and (c) quantification of ACE immunoreactive protein levels and ACE conformation with a set of monoclonal antibodies (mAbs) to ACE. RESULTS: Only a combination of ACE activity determination with 2 substrates and quantification of the amount of ACE immunoreactive protein with mAbs 1G12 and 9B9 allows for the unequivocal detection of the presence of ACE inhibitors in the blood. After excluding such subjects, we were able to establish normal values of ACE in healthy populations: 50%-150% from control pooled serum. This ACE phenotyping approach in screening format with special attention to outliers can also identify patients with various mutations in ACE and may help to identify the as yet unknown ACE secretase or other mechanistic details of precise regulation of ACE expression. CONCLUSIONS: ACE phenotyping is a promising new approach with potential clinical significance to advance precision medicine screening techniques by establishing different risk groups based on ACE phenotype.

A Data-Driven Approach to Carrier Screening for Common Recessive Diseases.

Genetic screening is an advanced tool for reducing recessive disease burden. Nowadays, it is still unclear as to the number of genes or their variants that are necessary for effective screening. This paper describes the development of a carrier screening custom panel for cystic fibrosis, phenylketonuria, alpha-1 antitrypsin deficiency, and sensorineural hearing loss consisting of 116 variants in the CFTR, PAH, SERPINA1, and GJB2 genes. The approach is based on the cheapest and fastest method, on using a small number of genes, and on the estimation of the effectiveness of carriers' detection. The custom panel was tested on a population-based cohort that included 1244 participants. Genotypes were determined by the TaqMan OpenArray Genotyping platform on the QuantStudio 12K Flex Real-Time PCR System. The frequency of heterozygotes in the Russian population was 16.87% or 1:6 (CI95%: 14.76-19.00% by Clopper-Pearson exact method): in CFTR-2.81% (1:36), PAH-2.33% (1:43), SERPINA1-4.90% (1:20), and GJB2-6.83% (1:15). The data on allele frequencies were obtained for the first time on a Russian population. The panel allows us to identify the vast majority of carriers of recessive diseases in the population. It is an effective approach to carrier screening for common recessive diseases.

Tissue ACE phenotyping in prostate cancer.

Epithelial cells of prostate express significant level of ACE and, as a result, seminal fluid has 50-fold more ACE than plasma. The substitution of highly specialized prostate epithelial cells by tumor cells results in dramatic decrease in ACE production in prostate tissues. We performed detailed characterization of ACE status in prostate tissues from patients with benign prostate hyperplasia (BPH) and prostate cancer (PC) using new approach- ACE phenotyping, that includes evaluation of: 1) ACE activity with two substrates (HHL and ZPHL); 2) the ratio of the rates of their hydrolysis (ZPHL/HHL ratio); 3) the ratio of immunoreactive ACE protein to ACE activity; 4) the pattern of mAbs binding to different epitopes on ACE - ACE conformational fingerprint - to reveal conformational changes in prostate ACE due to prostate pathology. ACE activity dramatically decreased and the ratio of immunoreactive ACE protein to ACE activity increased in PC tissues. The catalytic parameter, ZPHL/HHL ratio, increased in prostate tissues from all patients with PC, but was did not change for most |BPH patients. Nevertheless, prostate tissues of several patients diagnosed with BPH based on histology, also demonstrated decreased ACE activity and increased immunoreactive ACE protein/ACE activity and ZPHL/HHL ratios, that could be considered as more early indicators of prostate cancer development than routine histology. Thus, ACE phenotyping of prostate biopsies has a potential to be an effective approach for early diagnostics of prostate cancer or at least for differential diagnostics of BPH and PC.