Metformin Transport Rates Between Plasma and Red Blood Cells in Humans

Background Metformin has been used for the treatment of type 2 diabetes for over 60 years; however, its mechanism of pharmacological action is not fully clear. Different hypotheses exist regarding metformin distribution and redistribution mechanisms between plasma and erythrocytes/red blood cells (RBCs). Objective We aimed to test the hypothesis that the metformin distribution between plasma and RBC occurs via concentration difference-driven passive transport and estimated transport rate coefficient values based on metformin concentration time series in plasma and RBCs from in vivo studies. Methods An ordinary differential equation (ODE) system with two compartments was used to describe diffusion-based passive transport between plasma and RBCs. Metformin concentration time series in plasma and RBCs of 35 individuals were used for metformin transport parametrization. Plasma concentration has been approximated by biexponential decline. Results A single passive transport coefficient, k = 0.044 +/- 0.014 (h(-1)), can be applied, describing the uptake and release transport rate versus the linear equation v = k x (M-pl - M-RBC), where M-pl is the metformin concentration in plasma and M-RBC is the metformin concentration in RBCs. Conclusions Our research suggests that passive transport can explain metformin distribution dynamics between plasma and RBCs because transport speed is proportional to the metformin concentration difference and independent of the transport direction. Concentration difference-driven passive transport can explain the mechanism of faster metformin distribution to RBCs the first few hours after administration, and faster release and domination of the redistribution transport rate after metformin concentration in plasma becomes smaller than in RBCs.Peer reviewe

Case Report : Micro-RNAs in Plasma From Bilateral Inferior Petrosal Sinus Sampling and Peripheral Blood From Corticotroph Pituitary Neuroendocrine Tumors

Funding Information: The authors acknowledge the Latvian Biomedical Research and Study Centre and the Genome Database of the Latvian Population for providing infrastructure, biological material and data. Funding Information: This research was funded by the European Regional Development Fund within the project RNA molecular determinants in development of pituitary adenoma” (1.1.1.1/18/A/089). Publisher Copyright: Copyright © 2022 Niedra, Peculis, Konrade, Balcere, Romanovs, Steina, Stukens, Sokolovska, Klovins and Rovite.Objective: Circulating miRNAs are found in bodily fluids including plasma and can serve as biomarkers for diseases. The aim of this study was to provide the first insight into the landscape of circulating miRNAs in close proximity to the adrenocorticotropic hormone (ACTH) secreting PitNET. To achieve this objective next-generation sequencing of miRNAs in plasma from bilateral inferior petrosal sinus sampling (BIPSS) - a gold standard in diagnosing ACTH-secreting PitNETs was carried out and selected miRNA candidates were further tested by RT-qPCR in independent patient cohorts. Methods: Sinistral (left) and dextral (right) BIPSS blood samples of the patient were collected in three time points: before the administration of corticotropin-releasing hormone, 5 and 15 minutes after stimulation. In differential expression analysis, sinistral plasma was compared with dextral. The selected miRNA candidates were tested in plasma by RT-qPCR in two patient groups: 1) in five ACTH secreting PitNET patients with plasma samples taken before and 24 hours after surgery, 2) in 12 ACTH secreting PitNET patients vs. 9 non-functioning PitNET patients. Results: BIPSS concluded that the highest amount of ACTH was released in the sinistral side at the 5th minute mark indicating a presence of a tumor. The highest amount of differentially expressed miRNAs was observed 5 minutes after stimulation (20 upregulated, 14 downregulated). At the 5th minute mark in sinistral plasma, two miRNAs were identified: hsa-miR-7-5p and hsa-miR-375-3p that were highly upregulated compared to other BIPSS samples and peripheral plasma samples. Further testing by qPCR revealed significant reduction of miR-7-5p in plasma 24 hours after surgery and upregulation in plasma of ACTH secreting PitNET patients compared to non-functioning PitNET patients (P =0.0013). Conclusions: By stimulating the ACTH secreting PitNET with CRH a rapid increase of two miRNAs (hsa-mir-7-5p, hsa-mir-375-3p) and ACTH can be observed in sinistral inferior petrosal (tumor side). A decrease of miR-7-5p in plasma after surgery and upregulation in plasma of ACTH secreting PitNET patients was discovered implying that further studies of this miRNA as diagnostic marker is needed.publishersversionPeer reviewe

Polymorphisms in MEN1 and DRD2 genes are associated with the occurrence and characteristics of pituitary adenomas

Publisher Copyright: © 2016 European Society of Endocrinology Published by Bioscientifica Ltd. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.Objective: Although pituitary adenomas (PAs) affect a significant proportion of the population, only a fraction have the potential to become clinically relevant during an individual's lifetime, causing hormonal imbalance or complications due to mass effect. The overwhelming majority of cases are sporadic and without a clear familial history, and the genotype-phenotype correlation in PA patients is poorly understood. Our aim was to investigate the involvement of genes known for their role in familial cases on drug response and tumor suppression in the development and pathology of PAs in a patient group from Latvia. Design: The study included 143 cases and 354 controls, we investigated the role of single-nucleotide polymorphisms (SNPs) in seven genes (SSTR2, SSTR5, DRD2, MEN1, AIP, GNAS, and PRKAR1A) associated with pituitary tumor occurrence, phenotype, and clinical symptoms. Methods: Genotyping of 96 tag and nonsynonymous SNPs was performed in the genomic regions of interest. Results: We discovered a significant association (OR = 17.8, CI 0.95 = 2.18-145.5, P = 0.0002) between a rare MEN1 mutation (rs2959656) and clinically active adenoma in our patients. Additionally, rs7131056 at DRD2 was associated with a higher occurrence of extrasellar growth in patients with prolactinoma and somatotropinoma (OR = 2.79, CI 0.95 = 1.58-4.95, P = 0.0004). Conclusions: rs2959656, a nonsynonymous variant in MEN1, is associated with the development of clinically active PA. Furthermore, rs7131056 in DRD2 contributes to either faster growth of the adenoma or reduced symptomatic presentation, allowing PAs to become larger before detection.publishersversionPeer reviewe

Whole exome sequencing reveals novel risk genes of pituitary neuroendocrine tumors

Funding Information: This research was supported by the European Regional Development Fund (ERDF), Measure 1.1.1.1 “Industry-Driven Research” project „Molecular markers of pituitary tumour development, progression and therapy response” (Project No. 1.1.1.1/16/A/066, 2017). The authors acknowledge the Latvian Biomedical Research and Study Centre and the Genome Database of the Latvian Population for providing infrastructure, biological material and data. Publisher Copyright: © 2022 Peculis et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Somatic genetic alterations in pituitary neuroendocrine tumors (PitNET) tissues have been identified in several studies, but detection of overlapping somatic PitNET candidate genes is rare. We sequenced and by employing multiple data analysis methods studied the exomes of 15 PitNET patients to improve discovery of novel factors involved in PitNET development. PitNET patients were recruited to the study before PitNET removal surgery. For each patient, two samples for DNA extraction were acquired: venous blood and PitNET tissue. Exome sequencing was performed using Illumina NexSeq 500 sequencer and data analyzed using two separate workflows and variant calling algorithms: GATK and Strelka2. A combination of two data analysis pipelines discovered 144 PitNET specific somatic variants (mean = 9.6, range 0–19 per PitNET) of which all were SNVs. Also, we detected previously known GNAS PitNET mutation and identified somatic variants in 11 genes, which have contained somatic variants in previous WES and WGS studies of PitNETs. Noteworthy, this is the third study detecting somatic variants in gene RYR1 in the exomes of PitNETs. In conclusion, we have identified two novel PitNET candidate genes (AC002519.6 and AHNAK) with recurrent somatic variants in our PitNET cohort and found 13 genes overlapping from previous PitNET studies that contain somatic variants. Our study demonstrated that the use of multiple sequencing data analysis pipelines can provide more accurate identification of somatic variants in PitNETs.publishersversionPeer reviewe

Evaluation of the Possibility to Detect Circulating Tumor DNA From Pituitary Adenoma

Funding Information: The authors acknowledge the Latvian Biomedical Research and Study Center and the Genome Database of the Latvian Population for providing infrastructure, biological material, and data. Funding. This research was supported by the European Regional Development Fund (ERDF), Measure 1.1.1.1 Industry-Driven Research project Molecular markers of pituitary tumor development, progression and therapy response (Project No. 1.1.1.1/16/A/066, 2017), and Roche Academy project Immunohistochemical analysis of pituitary adenoma tissue. Publisher Copyright: © Copyright © 2019 Megnis, Peculis, Rovite, Laksa, Niedra, Balcere, Caune, Breiksa, Nazarovs, Stukens, Konrade, Pirags and Klovins.Objective: Circulating free DNA (cfDNA) in general and circulating tumor DNA (ctDNA) in particular is becoming an increasingly used form of liquid biopsy biomarkers. In this study, we are investigating the ability to detect ctDNA from the plasma of pituitary adenoma (PA) patients. Design: Tumor tissue samples were obtained from planed PA resections, before which blood plasma samples were taken. Somatic variants found in PA tissue samples were evaluated in related cfDNA, isolated from plasma samples. Methods: Sanger sequencing, as well as previously obtained whole-exome sequencing data, were used to evaluate somatic variants composition in tumor tissue samples. cfDNA was isolated from the same PA patients and competitive allele-specific TaqMan PCR and amplicon-based next-generation sequencing (NGS) approach were used for targeted detection of variants found in corresponding tumor tissue samples. Results: Using NGS-based analysis, we detected five out of 17 somatic variants in 40 to 60% of total reads, three variants in 0.50–5.00% of total read count, including GNAS c.601C>T, which was detected using ultra-deep NGS (1.78 million X) in 0.77% of amplicons reads. Nine variants were not detected. We also detected We were not able to detect variant found in PA tissue in cfDNA using cast-PCR, indicating that the portion of variant-containing ctDNA in total isolated cfDNA is too small to be detected with this method. Conclusions: For the first time, we demonstrate the possibility to detect somatic variants of PA in cfDNA isolated from patients' blood plasma. Whether the source of variant detected in cfDNA is PA should be further tested.publishersversionPeer reviewe

Analysis of polymorphisms at the adiponectin gene locus in association with type 2 diabetes, body mass index and cardiovascular traits in Latvian population

Funding Information: The work was supported by the National Research Programme in Medicine 2006–2009 project No. 14, “Creation of the unified and generally accessible data base on the main life expectancy and life quality threatening pathologies and epidemiology of their risk factors in Latvian population”, Latvian Council of Science Grant 01.0023.01. We acknowledge Genome Database of Latvian Population, Latvian Biomedical Research and Study Centre for providing data and DNA samples. Copyright: Copyright 2010 Elsevier B.V., All rights reserved.Despite the number of recently conducted studies seeking to determine the association between genetic variants of adiponectin gene and susceptibility to type 2 diabetes (T2D) and increased body mass index (BMI), the results obtained are often inconsistent. To determine the impact of common polymorphisms in promoter and coding regions of adiponectin gene on these conditions in Latvian population, we selected ten SNPs (rs2241767, rs1501299, rs3777261, rs16861210, rs2241766, rs822396, rs182052, rs17300539, rs16861194, rs266729) based on haploblock structure and previously reported association studies. The selected SNPs were screened in a study group of 835 participants from the Genome Data Base of Latvian Population and mainly consisted of patients with T2D and coronary heart disease. None of the individual polymorphisms were significantly associated with T2D status or BMI when analysed using logistic or linear regression and adjusted for gender, age and other significant covariates. Frequency of rs2241766 T allele homozygotes however was significantly increased in T2D patients compared to controls (uncorrected P = 0.007). When analysed with other traits, the rs182052 G allele was found to be less frequent in patients suffering from myocardial infarction (P = 0.02; OR = 0.76, CI95% [0.61-0.92]) compared to others. Haplotype analysis revealed significant association of one haplotype with atrial fibrillation (uncorrected P = 0.01). In summary, we conclude that SNPs in adiponectin gene are unlikely to represent the risk for T2D, but may be involved in pathogenesis of CHD in the Latvian population.publishersversionPeer reviewe

Functional characterization of two melanocortin (MC) receptors in lamprey showing orthology to the MC1 and MC4 receptor subtypes

<p>Abstract</p> <p>Background</p> <p>The melanocortin (MC) receptors have a key role in regulating body weight and pigmentation. They belong to the rhodopsin family of G protein-coupled receptors (GPCRs). The purpose of this study was to identify ancestral MC receptors in agnathan, river lamprey.</p> <p>Results</p> <p>We report cloning of two MC receptors from river lamprey. The lamprey receptors, designated MCa and MCb, showed orthology to the MC1 and MC4 receptor subtypes, respectively. The molecular clock analysis suggested that lamprey MC receptor genes were not duplicated recently and diverged from each other more than 400 MYR ago. Expression and pharmacological characterization showed that the lamprey MCa receptor was able to bind and be activated by both lamprey and human MSH peptides. The lamprey MCa receptor had relatively high affinity for ACTH derived peptides similarly to the fish MC receptors. We found that both of the lamprey MC receptors were expressed in skin, while the MCb receptor was also found in liver, heart and skeletal muscle.</p> <p>Conclusion</p> <p>This study shows presence of MC receptors in agnathans indicating early signs of specific functions of melanocortin receptor subtypes.</p

Novel susceptibility loci identified in a genome-wide association study of type 2 diabetes complications in population of Latvia

Funding Information: The study was supported by European Regional Development Fund (ERDF) On Implementation of Activity 1.1.1.2 “Post-doctoral Research Aid” of the Specific Aid Objective 1.1.1 “To increase the research and innovative capacity of scientific institutions of Latvia and the ability to attract external financing, investing in human resources and infrastructure” of the Operational Programme “Growth and Employment”. Project No 1.1.1.2/VIAA/2/18/287 “Identification of clinical subgroups of Type 2 diabetes mellitus and application of pharmacogenetics in the development of personalized antidiabetic therapy”. The funding body was not involved in the design of the study, collection, analysis or interpretation of data, or writing the manuscript. Publisher Copyright: © 2021, The Author(s).Background: Type 2 diabetes complications cause a serious emotional and economical burden to patients and healthcare systems globally. Management of both acute and chronic complications of diabetes, which dramatically impair the quality of patients' life, is still an unsolved issue in diabetes care, suggesting a need for early identification of individuals with high risk for developing diabetes complications. Methods: We performed a genome-wide association study in 601 type 2 diabetes patients after stratifying them according to the presence or absence of four types of diabetes complications: diabetic neuropathy, diabetic nephropathy, macrovascular complications, and ophthalmic complications. Results: The analysis revealed ten novel associations showing genome-wide significance, including rs1132787 (GYPA, OR = 2.71; 95% CI = 2.02–3.64) and diabetic neuropathy, rs2477088 (PDE4DIP, OR = 2.50; 95% CI = 1.87–3.34), rs4852954 (NAT8, OR = 2.27; 95% CI = 2.71–3.01), rs6032 (F5, OR = 2.12; 95% CI = 1.63–2.77), rs6935464 (RPS6KA2, OR = 2.25; 95% CI = 6.69–3.01) and macrovascular complications, rs3095447 (CCDC146, OR = 2.18; 95% CI = 1.66–2.87) and ophthalmic complications. By applying the targeted approach of previously reported susceptibility loci we managed to replicate three associations: MAPK14 (rs3761980, rs80028505) and diabetic neuropathy, APOL1 (rs136161) and diabetic nephropathy. Conclusions: Together these results provide further evidence for the implication of genetic factors in the development of type 2 diabetes complications and highlight several potential key loci, able to modify the risk of developing these conditions. Moreover, the candidate variant approach proves a strong and consistent effect for multiple variants across different populations.publishersversionPeer reviewe

Medication for Acromegaly Reduces Expression of MUC16, MACC1 and GRHL2 in Pituitary Neuroendocrine Tumour Tissue

Funding Information: The authors acknowledge the Latvian Biomedical Research and Study Centre and the Genome Database of the Latvian Population for providing the infrastructure, biological material, and data. Publisher Copyright: © Copyright © 2021 Saksis, Silamikelis, Laksa, Megnis, Peculis, Mandrika, Rogoza, Petrovska, Balcere, Konrade, Steina, Stukens, Breiksa, Nazarovs, Sokolovska, Pirags, Klovins and Rovite.Acromegaly is a disease mainly caused by pituitary neuroendocrine tumor (PitNET) overproducing growth hormone. First-line medication for this condition is the use of somatostatin analogs (SSAs), that decrease tumor mass and induce antiproliferative effects on PitNET cells. Dopamine agonists (DAs) can also be used if SSA treatment is not effective. This study aimed to determine differences in transcriptome signatures induced by SSA/DA therapy in PitNET tissue. We selected tumor tissue from twelve patients with somatotropinomas, with half of the patients receiving SSA/DA treatment before surgery and the other half treatment naive. Transcriptome sequencing was then carried out to identify differentially expressed genes (DEGs) and their protein–protein interactions, using pathway analyses. We found 34 upregulated and six downregulated DEGs in patients with SSA/DA treatment. Three tumor development promoting factors MUC16, MACC1, and GRHL2, were significantly downregulated in therapy administered PitNET tissue; this finding was supported by functional studies in GH3 cells. Protein–protein interactions and pathway analyses revealed extracellular matrix involvement in the antiproliferative effects of this type of the drug treatment, with pronounced alterations in collagen regulation. Here, we have demonstrated that somatotropinomas can be distinguished based on their transcriptional profiles following SSA/DA therapy, and SSA/DA treatment does indeed cause changes in gene expression. Treatment with SSA/DA significantly downregulated several factors involved in tumorigenesis, including MUC16, MACC1, and GRHL2. Genes that were upregulated, however, did not have a direct influence on antiproliferative function in the PitNET cells. These findings suggested that SSA/DA treatment acted in a tumor suppressive manner and furthermore, collagen related interactions and pathways were enriched, implicating extracellular matrix involvement in this anti-tumor effect of drug treatment.publishersversionPeer reviewe

Genetic Characteristics of Latvian Patients with Familial Hypercholesterolemia: The First Analysis from Genome-Wide Sequencing

This article belongs to the Special Issue New Possibilities for the Treatment of DyslipidemiasBackground: There is limited data on the genetic characteristics of patients with familial hypercholesterolemia (FH) in Latvia. We aim to describe monogenic variants in patients from the Latvian Registry of FH (LRFH). Methods: Whole genome sequencing with 30 coverage was performed in unrelated index cases from the LRFH and the Genome Database of Latvian Population. LDLR, APOB, PCSK9, LDLRAP1, ABCG5, ABCG8, LIPA, LPA, CYP27A1, and APOE genes were analyzed. Only variants annotated as pathogenic (P) or likely pathogenic (LP) using the FH Variant Curation Expert Panel guidelines for LDLR and adaptations for APOB and PCSK9 were reported. Results: Among 163 patients, the mean highest documented LDL-cholesterol level was 7.47 1.60 mmol/L, and 79.1% of patients had LDL-cholesterol 6.50 mmol/L. A total of 15 P/LP variants were found in 34 patients (diagnostic yield: 20.9%): 14 in the LDLR gene and 1 in the APOB gene. Additionally, 24, 54, and 13 VUS were detected in LDLR, APOB, and PCSK9, respectively. No P/LP variants were identified in the other tested genes. Conclusions: Despite the high clinical likelihood of FH, confirmed P/LP variants were detected in only 20.9% of patients in the Latvian cohort when assessed with genome-wide next generation sequencing.This research is funded by the Latvian Council of Science, project “Low-coverage whole-genome sequencing analysis of polygenic mechanisms of high cholesterol levels in patients with clinically diagnosed or possible familial hypercholesterolemia”, project No. lzp-2020/1-0151.info:eu-repo/semantics/publishedVersio