Publications by authors named "Roman Iakoubov"

14 Publications

  • Page 1 of 1

Self-sampling versus health care professional-guided swab collection for SARS-CoV-2 testing.

Infection 2021 May 10. Epub 2021 May 10.

Department of Internal Medicine II, School of Medicine, University Hospital Rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Purpose: To evaluate the diagnostic reliability and practicability of self-collected oropharyngeal swab samples for the detection of SARS-CoV-2 infection as self-sampling could enable broader testing availability and reduce both personal protective equipment and potential exposure.

Methods: Hospitalized SARS-CoV-2-infected patients were asked to collect two oropharyngeal swabs (SC-OPS1/2), and an additional oropharyngeal swab was collected by a health care professional (HCP-OPS). SARS-CoV-2 PCR testing for samples from 58 participants was performed, with a 48-h delay in half of the self-collected samples (SC-OPS2). The sensitivity, probability of concordance, and interrater reliability were calculated. Univariate and multivariate analyses were performed to assess predictive factors. Practicability was evaluated through a questionnaire.

Results: The test sensitivity for HCP-OPS, SC-OPS1, and SC-OPS2 was 88%, 78%, and 77%, respectively. Combining both SC-OPS results increased the estimated sensitivity to 88%. The concordance probability between HCP-OPS and SC-OPS1 was 77.6% and 82.5% between SC-OPS1 and SC-OPS2, respectively. Of the participants, 69% affirmed performing future self-sampling at home, and 34% preferred self-sampling over HCP-guided testing. Participants with both positive HCP-OPS1 and SC-OPS1 indicating no challenges during self-sampling had more differences in viral load levels between HCP-OPS1 and SC-OPS1 than those who indicated challenges. Increasing disease duration and the presence of anti-SARS-CoV-2-IgG correlated with negative test results in self-collected samples of previously confirmed SARS-CoV-2 positive individuals.

Conclusion: Oropharyngeal self-sampling is an applicable testing approach for SARS-CoV-2 diagnostics. Self-sampling tends to be more effective in early versus late infection and symptom onset, and the collection of two distinct samples is recommended to maintain high test sensitivity.
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http://dx.doi.org/10.1007/s15010-021-01614-9DOI Listing
May 2021

SARS-CoV-2 serology increases diagnostic accuracy in CT-suspected, PCR-negative COVID-19 patients during pandemic.

Respir Res 2021 Apr 23;22(1):119. Epub 2021 Apr 23.

Department of Internal Medicine II, School of Medicine, Technical University of Munich, Munich, Germany.

Background: In the absence of PCR detection of SARS-CoV-2 RNA, accurate diagnosis of COVID-19 is challenging. Low-dose computed tomography (CT) detects pulmonary infiltrates with high sensitivity, but findings may be non-specific. This study assesses the diagnostic value of SARS-CoV-2 serology for patients with distinct CT features but negative PCR.

Methods: IgM/IgG chemiluminescent immunoassay was performed for 107 patients with confirmed (group A: PCR + ; CT ±) and 46 patients with suspected (group B: repetitive PCR-; CT +) COVID-19, admitted to a German university hospital during the pandemic's first wave. A standardized, in-house CT classification of radiological signs of a viral pneumonia was used to assess the probability of COVID-19.

Results: Seroconversion rates (SR) determined on day 5, 10, 15, 20 and 25 after symptom onset (SO) were 8%, 25%, 65%, 76% and 91% for group A, and 0%, 10%, 19%, 37% and 46% for group B, respectively; (p < 0.01). Compared to hospitalized patients with a non-complicated course (non-ICU patients), seroconversion tended to occur at lower frequency and delayed in patients on intensive care units. SR of patients with CT findings classified as high certainty for COVID-19 were 8%, 22%, 68%, 79% and 93% in group A, compared with 0%, 15%, 28%, 50% and 50% in group B (p < 0.01). SARS-CoV-2 serology established a definite diagnosis in 12/46 group B patients. In 88% (8/9) of patients with negative serology > 14 days after symptom onset (group B), clinico-radiological consensus reassessment revealed probable diagnoses other than COVID-19. Sensitivity of SARS-CoV-2 serology was superior to PCR > 17d after symptom onset.

Conclusions: Approximately one-third of patients with distinct COVID-19 CT findings are tested negative for SARS-CoV-2 RNA by PCR rendering correct diagnosis difficult. Implementation of SARS-CoV-2 serology testing alongside current CT/PCR-based diagnostic algorithms improves discrimination between COVID-19-related and non-related pulmonary infiltrates in PCR negative patients. However, sensitivity of SARS-CoV-2 serology strongly depends on the time of testing and becomes superior to PCR after the 2 week following symptom onset.
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http://dx.doi.org/10.1186/s12931-021-01717-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8062836PMC
April 2021

Mucosal-Associated Invariant T (MAIT) Cells Are Highly Activated and Functionally Impaired in COVID-19 Patients.

Viruses 2021 02 3;13(2). Epub 2021 Feb 3.

Department of Internal Medicine II, University Hospital Rechts der Isar, School of Medicine, Technical University of Munich (TUM), 81675 Munich, Germany.

Coronavirus disease 2019 (COVID-19), caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), comprises mild courses of disease as well as progression to severe disease, characterised by lung and other organ failure. The immune system is considered to play a crucial role for the pathogenesis of COVID-19, although especially the contribution of innate-like T cells remains poorly understood. Here, we analysed the phenotype and function of mucosal-associated invariant T (MAIT) cells, innate-like T cells with potent antimicrobial effector function, in patients with mild and severe COVID-19 by multicolour flow cytometry. Our data indicate that MAIT cells are highly activated in patients with COVID-19, irrespective of the course of disease, and express high levels of proinflammatory cytokines such as IL-17A and TNFα ex vivo. Of note, expression of the activation marker HLA-DR positively correlated with SAPS II score, a measure of disease severity. Upon MAIT cell-specific in vitro stimulation, MAIT cells however failed to upregulate expression of the cytokines IL-17A and TNFα, as well as cytolytic proteins, that is, granzyme B and perforin. Thus, our data point towards an altered cytokine expression profile alongside an impaired antibacterial and antiviral function of MAIT cells in COVID-19 and thereby contribute to the understanding of COVID-19 immunopathogenesis.
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http://dx.doi.org/10.3390/v13020241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7913667PMC
February 2021

Effects of antiretroviral combination therapies F/TAF, E/C/F/TAF and R/F/TAF on insulin resistance in healthy volunteers: the TAF-IR Study.

Antivir Ther 2018 3;23(7):629-632. Epub 2018 Oct 3.

Department of Medicine II, University Hospital Klinikum rechts der Isar, Munich, Germany.

Background: Increased insulin resistance (IR), associated with specific antiretroviral drugs or drug classes, is an established risk factor for type 2 diabetes in HIV patients, ultimately increasing morbidity and mortality. To date, data on the risk of IR in tenofovir alafenamide (TAF)-based protocols are unavailable.

Methods: This prospective randomized, open-label study evaluated the effects of IR on 30 healthy volunteers receiving fixed-dose combinations (FDCs) of emtricitabine/tenofovir alafenamide (F/TAF), elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide (E/C/F/TAF) or rilpivirine/emtricitabine/tenofovir alafenamide (R/F/TAF). IR was measured before and after 14-day treatments using the hyperinsulinemic-euglycaemic clamp technique (HEGC). Changes in IR in each group were evaluated using the mean glucose disposal rate, normalized with body weight (M [mg glucose/(min×kg)]).

Results: A total of 30 subjects underwent randomization: one subject in the F/TAF arm withdrew consent after randomization and one in the R/F/TAF arm had to be excluded because of technical failure during HEGC, resulting in 28 subjects in the per-protocol population (F/TAF, n=9 subjects; E/C/F/TAF, n=10 subjects; R/F/TAF n=9 subjects). No significant differences were detected on the baseline characteristics. IR did not differ among the groups before treatment. None of the studied antiretroviral combinations resulted in a significant change in IR after 14 days compared with baseline values, as measured by M (F/TAF, 11.42 ±3.04 mean [±sd] versus 11.43 ±3.23, P=0.49; E/C/F/TAF, 10.04 ±2.49 versus 10.95 ±4.26, P=0.30; R/F/TAF, 11.03 ±1.96 versus 13.01 ±4.11, P=0.13).

Conclusions: Short-term treatment for F/TAF, E/C/F/TAF or R/F/TAF did not increase IR in healthy male volunteers.
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http://dx.doi.org/10.3851/IMP3271DOI Listing
September 2019

Dynamics of Adrenocorticotropin after Application of Metyrapone.

Exp Clin Endocrinol Diabetes 2017 Jan 17;125(1):53-56. Epub 2016 Oct 17.

II. Medizinische Klinik und Poliklinik, Klinikum rechts der Isar, TU München, Munich.

To investigate the kinetics of adrenocorticotropin (ACTH) following oral metyrapone administration and describe differences between ACTH-deficient and non-ACTH-deficient subjects. Patients from a tertiary endocrine center at a University Hospital in Munich, Germany, were tested for secondary adrenal insufficiency in a regular patient care setting. Metyrapone (Metopirone, HRA Pharma, France) was administered with a dosage of 40 mg/kg bodyweight at 8 a.m. Consecutive levels of ACTH were determined at 0, 60, 120, 180, and 240 min. Patients were categorized according to their need of glucocorticoid substitution in the follow-up phase. A significant rise in ACTH concentration compared to basal values was found at 60 and 120 min following oral metyrapone administration. ACTH concentrations at 60 and 120 min predicted patients without need for glucocorticoid substitution. ACTH concentrations determined later had no additional benefit. In contrast to previous reports, we found a significant rise in ACTH concentration as soon as one hour after oral metyrapone administration. ACTH values seem to estimate the pituitary corticotrophic function when correlating results to the further clinical course of subjects. Further studies are needed to investigate this finding as a potential basis for a ACTH-based metyrapone short test protocol.
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http://dx.doi.org/10.1055/s-0042-117832DOI Listing
January 2017

Neither boosted elvitegravir nor darunavir with emtricitabine/tenofovir disoproxil fumarate increase insulin resistance in healthy volunteers: results from the STRIBILD-IR study.

Antivir Ther 2016 6;21(7):627-631. Epub 2016 Apr 6.

Department of Medicine II, University Hospital Klinikum rechts der Isar, Munich, Germany.

Background: Insulin resistance (IR) was one of the first reported complications in HIV-positive patients who were receiving antiretroviral therapy (ART). However, the metabolic effects of newer fixed-dose ART combinations are unclear.

Methods: This Phase I prospective randomized open-label study evaluated the effects on IR in 30 healthy volunteers who were receiving newer fixed-dose combinations of tenofovir disoproxil fumarate, emtricitabine, elvitegravir and cobicistat (E/C/F/TDF, 10 patients) or the established ART regimens, such as tenofovir disoproxil fumarate/emtricitabine with lopinavir/ritonavir (F/TDF+LPV/r, 9 patients) or darunavir/ritonavir (F/TDF+DRV/r, 9 patients). IR was measured before and after the 14-day treatments using the hyperinsulinemic-euglycemic clamp technique, and changes in IR were evaluated using the mean glucose disposal rate that was normalized to body weight (M) and lipid metabolism.

Results: The groups exhibited similar pretreatment IR, although M was significantly lower after the 14-day F/TDF+LPV/r treatment compared with baseline (12.5 ±3.3 versus 9.2 ±1.8 mg glucose/min×kg; P=0.037). No significant IR changes were observed for E/C/F/TDF (11.2 ±3.2 versus 11.3 ±2.5) or F/TDF+DRV/r (11.6 ±2.5 versus 11.3 ±2.4). Compared with baseline, F/TDF+LPV/r and F/TDF+DRV/r treatments significantly increased day 14 triglyceride levels (62 [54-73] versus 119 [77-147] mg/dl, P=0.0109; 75 [56-95] versus 96 [93-128] mg/dl, P=0.009, respectively).

Conclusions: Short-term treatment using fixed-dose combinations of E/C/F/TDF or F/TDF+DRV/r did not affect IR, although IR significantly increased after treatment using F/TDF+LPV/r.
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http://dx.doi.org/10.3851/IMP3049DOI Listing
February 2018

Clinically relevant lot-to-lot reagent difference in a commercial immunoturbidimetric assay for glycated hemoglobin A1c.

Clin Biochem 2015 Nov 15;48(16-17):1167-70. Epub 2015 Jul 15.

Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Str. 22, 81675 München, Germany. Electronic address:

Objectives: Hemoglobin A1c (HbA1c) is employed for diagnosis and therapy monitoring of diabetes mellitus. The effect of a change of reagent lot on the measured values of a commercial immunoturbidimetric HbA1c assay (A1C3) was investigated.

Design And Methods: Comparison measurements of A1C3 and an automated affinity chromatography method (VIIT) were performed in 15 samples for the initial and in 20 samples for the subsequent A1C3 lot. The results of 27 and 19 measurements of a normal and of 28 and 20 of a pathological control (before and after the switch of the A1C3 reagent lot, respectively) were evaluated. Finally, the results of 6463 patient samples that had been measured with the initial and 434 that had been measured with the subsequent A1C3 lot were investigated.

Results: VIIT yielded significantly higher results than the initial A1C3 lot (bias: 0.41% HbA1c, 4.5mmol/mol) but agreed well with the subsequent lot (bias: -0.01% HbA1c, -0.1mmol/mol). Changing to the subsequent reagent lot resulted in significant increases of the mean of the normal control of 0.316% HbA1c (3.5mmol/mol) and of the pathological control of 0.749% HbA1c (8.2mmol/mol). The median of patient samples measured with the subsequent lot was significantly higher by 0.40% HbA1c (4.4mmol/mol).

Conclusions: The subsequent A1C3 reagent lot yields significantly higher measurement results than the initial by approximately 0.5% HbA1c (5.5mmol/mol). This difference is considered as clinically relevant. A combined effort of manufacturers and notified bodies is necessary to minimize lot-to-lot variation.
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http://dx.doi.org/10.1016/j.clinbiochem.2015.07.018DOI Listing
November 2015

Occurrence of giant focal forms of congenital hyperinsulinism with incorrect visualization by (18) F DOPA-PET/CT scanning.

Clin Endocrinol (Oxf) 2014 Dec 19;81(6):847-54. Epub 2014 May 19.

Institut für experimentelle pädiatrische Endokrinologie, Charité Universitätsmedizin, Berlin, Germany.

Context: Congenital hyperinsulinism (CHI) is a rare disease characterized by severe hypoglycaemic episodes due to pathologically increased insulin secretion from the pancreatic beta cells. When untreated, CHI might result in irreversible brain damage and death. Currently, two major subtypes of CHI are known: a focal form, associated with local distribution of affected beta cells and a nonfocal form, affecting every single beta cell. The identification of focal forms is important, as the patients can be cured by limited surgery. (18) F DOPA-PET/CT is an established non-invasive approach to differentiate focal from nonfocal CHI.

Objective: The purpose of this study was to identify possible limitations of (18) F DOPA-PET/CT scan in patients with focal forms nonfocal CHI.

Design: A retrospective chart review of 32 patients (from 2008 through 2013) who underwent (18) F DOPA-PET/CT and partial pancreatectomy for focal CHI at the reference centres in Berlin, Germany and London, UK.

Results: In most cases (n = 29, 90·7%), (18) F DOPA-PET/CT was sufficient to localize the complete focal lesion. However, in some patients (n = 3, 9·3%), (18) F DOPA-PET/CT wrongly visualized only a small portion of the focal lesion. In this group of patients, a so-called 'giant focus' was detected in histopathological analysis during the surgery.

Conclusions: Our data show that in most patients with focal CHI (18) F DOPA-PET/CT correctly predicts the size and anatomical localisation of the lesion. However, in those patients with a 'giant focal' lesion (18) F DOPA-PET/CT is unreliable for correct identification of 'giant focus' cases.
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http://dx.doi.org/10.1111/cen.12473DOI Listing
December 2014

T1R3: how to indulge the gut's sweet tooth.

Am J Physiol Endocrinol Metab 2012 Oct 14;303(7):E813-4. Epub 2012 Aug 14.

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http://dx.doi.org/10.1152/ajpendo.00418.2012DOI Listing
October 2012

Novel biological action of the dipeptidylpeptidase-IV inhibitor, sitagliptin, as a glucagon-like peptide-1 secretagogue.

Endocrinology 2012 Feb 20;153(2):564-73. Epub 2011 Dec 20.

Department of Physiology, Medical Sciences Building, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8 Canada.

Glucagon-like peptide-1 (GLP-1) is an incretin hormone secreted into the circulation by the intestinal L cell. The dipeptidylpeptidase-IV (DPP-IV) inhibitor, sitagliptin, prevents GLP-1 degradation and is used in the clinic to treat patients with type 2 diabetes mellitus, leading to improved glycated hemoglobin levels. When the effect of sitagliptin on GLP-1 levels was examined in neonatal streptozotocin rats, a model of type 2 diabetes mellitus, a 4.9 ± 0.9-fold increase in basal and 3.6 ± 0.4-fold increase in oral glucose-stimulated plasma levels of active GLP-1 was observed (P < 0.001), in association with a 1.5 ± 0.1-fold increase in the total number of intestinal L cells (P < 0.01). The direct effects of sitagliptin on GLP-1 secretion and L cell signaling were therefore examined in murine GLUTag (mGLUTag) and human hNCI-H716 intestinal L cells in vitro. Sitagliptin (0.1-2 μM) increased total GLP-1 secretion by mGLUTag and hNCI-H716 cells (P < 0.01-0.001). However, MK0626 (1-50 μM), a structurally unrelated inhibitor of DPP-IV, did not affect GLP-1 secretion in either model. Treatment of mGLUTag cells with the GLP-1 receptor agonist, exendin-4, did not modulate GLP-1 release, indicating the absence of feedback effects of GLP-1 on the L cell. Sitagliptin increased cAMP levels (P < 0.01) and ERK1/2 phosphorylation (P < 0.05) in both mGLUTag and hNCI-H716 cells but did not alter either intracellular calcium or phospho-Akt levels. Pretreatment of mGLUTag cells with protein kinase A (H89 and protein kinase inhibitor) or MAPK kinase-ERK1/2 (PD98059 and U0126) inhibitors prevented sitagliptin-induced GLP-1 secretion (P < 0.05-0.01). These studies demonstrate, for the first time, that sitagliptin exerts direct, DPP-IV-independent effects on intestinal L cells, activating cAMP and ERK1/2 signaling and stimulating total GLP-1 secretion.
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http://dx.doi.org/10.1210/en.2011-1732DOI Listing
February 2012

Essential role for protein kinase Cζ in oleic acid-induced glucagon-like peptide-1 secretion in vivo in the rat.

Endocrinology 2011 Apr 15;152(4):1244-52. Epub 2011 Feb 15.

Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.

Luminal monounsaturated long-chain fatty acids [e.g. oleic acid (OA)] increase secretion of the incretin, glucagon-like peptide-1 (GLP-1) from the ileocolonic L cell. However, it is not known whether OA ingestion causes a sufficient increase in distal luminal concentrations to directly enhance GLP-1 secretion. Furthermore, we have demonstrated that protein kinase Cζ (PKCζ) is required for OA-induced GLP-1 secretion in vitro; however, the physiological relevance of this finding remains unknown. Therefore, we have determined luminal OA concentrations in OA-fed rats and examined the effects of direct OA stimulation on GLP-1 secretion using a novel model of intestinal-specific PKCζ knockdown. Murine GLUTag L cells express numerous fatty acid transport proteins and take up OA in a saturable manner. Oral administration of OA increased the ileal chyme content of OA by 140-fold over 60-120 min (P < 0.05-0.01), peaking at 105 ± 50 μmol/g. To evaluate the direct effects of OA on GLP-1 secretion, 125 mm OA was rectally infused into the colon and terminal ileum of rats. Plasma bioactive GLP-1 increased from 20 ± 6 to 102 ± 21 pg/ml at 60 min (P < 0.01). However, pretreatment with ileocolonic adenoviral PKCζ small interfering RNA resulted in a 68 ± 8% reduction in the GLP-1 response to rectal OA (P < 0.001). The results of these studies indicate that OA levels in the rat terminal gut after oral ingestion are sufficient to induce GLP-1 secretion and that PKCζ is necessary for the effects of OA on GLP-1 secretion in vivo. PKCζ may therefore serve as a novel therapeutic target to enhance GLP-1 levels in patients with type 2 diabetes.
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http://dx.doi.org/10.1210/en.2010-1352DOI Listing
April 2011

Carcinogenic effects of exogenous and endogenous glucagon-like peptide-2 in azoxymethane-treated mice.

Endocrinology 2009 Sep 4;150(9):4033-43. Epub 2009 Jun 4.

Departments of Physiology, University of Toronto, Toronto, Ontario, Canada.

Glucagon-like peptide-2 (GLP-2) is a nutrient-dependent intestinotropic hormone that promotes intestinal growth, via increased intestinal proliferation and decreased apoptosis, as well as increases in nutrient absorption and barrier function. The long-acting analog h(Gly(2))GLP-2[1-33] is currently being tested for treatment of short bowel syndrome and Crohn's disease. However, the role of GLP-2 in colon carcinogenesis is controversial. To assess the intestinotropic effects of exogenous and endogenous GLP-2, C57BL6/J mice were injected with 1 microg h(Gly(2))GLP-2[1-33]; 30 or 60 ng hGLP-2[3-33], a GLP-2 receptor antagonist; or PBS (4 wk, twice a day, sc). Chronic h(Gly(2))GLP-2[1-33] increased small intestinal weight/body weight (P < 0.001), villus height (P < 0.001), crypt depth (P < 0.001), and crypt cell proliferation, as measured by expression of the proliferative marker Ki67 (P < 0.05-0.01). In contrast, chronic hGLP-2[3-33] decreased small intestinal weight/body weight (P < 0.05) and colon weight/body weight (P < 0.05). To assess the carcinogenic effects of endogenous and exogenous GLP-2, separate mice were injected with azoxymethane (10 mg/kg, 4 wk, every 7 d, ip), followed by 1.5 microg h(Gly(2))GLP-2[1-33], 30 ng hGLP-2[3-33], or PBS (4 wk, twice a day, sc) 2 or 12 wk thereafter. At 10 or 46 wk after azoxymethane treatment, the numbers of aberrant crypt foci increased with h(Gly(2))GLP-2[1-33] (P < 0.001) and decreased with hGLP-2[3-33] (P < 0.01-0.05) treatment. Furthermore, mucin-depleted aberrant foci, consistent with progressive dysplasia, were almost exclusively present in h(Gly(2))GLP-2[1-33]-treated mice (P < 0.01-0.001). Additionally, adenocarcinomas developed in h(Gly(2))GLP-2[1-33]-treated mice but not in those receiving hGLP-2[3-33] or PBS. Taken together, these studies indicate that chronic treatment with GLP-2 enhances colon carcinogenesis, whereas antagonism of the GLP-2 receptor decreases dysplasia, with possible implications for human therapy.
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http://dx.doi.org/10.1210/en.2009-0295DOI Listing
September 2009

GPR119 is essential for oleoylethanolamide-induced glucagon-like peptide-1 secretion from the intestinal enteroendocrine L-cell.

Diabetes 2009 May 10;58(5):1058-66. Epub 2009 Feb 10.

Department of Physiology, University of Toronto, Toronto, Ontario, Canada.

Objective: Intestinal L-cells secrete the incretin glucagon-like peptide-1 (GLP-1) in response to ingestion of nutrients, especially long-chain fatty acids. The Galphas-coupled receptor GPR119 binds the long-chain fatty acid derivate oleoylethanolamide (OEA), and GPR119 agonists enhance GLP-1 secretion. We therefore hypothesized that OEA stimulates GLP-1 release through a GPR119-dependent mechanism.

Research Design And Methods: Murine (m) GLUTag, human (h) NCI-H716, and primary fetal rat intestinal L-cell models were used for RT-PCR and for cAMP and GLP-1 radioimmunoassay. Anesthetized rats received intravenous or intraileal OEA, and plasma bioactive GLP-1, insulin, and glucose levels were determined by enzyme-linked immunosorbent assay or glucose analyzer.

Results: GPR119 messenger RNA was detected in all L-cell models. OEA treatment (10 micromol/l) of mGLUTag cells increased cAMP levels (P < 0.05) and GLP-1 secretion (P < 0.001) in all models, with desensitization of the secretory response at higher concentrations. GLP-1 secretion was further enhanced by prevention of OEA degradation using the fatty acid amide hydrolase inhibitor, URB597 (P < 0.05-0.001 vs. OEA alone), and was abolished by H89-induced inhibition of protein kinase A. OEA-induced cAMP levels and GLP-1 secretion were significantly reduced in mGLUTag cells transfected with GPR119-specific small interfering RNA (P < 0.05). Application of OEA (10 micromol/l) directly into the rat ileum, but not intravenously, increased plasma bioactive GLP-1 levels in euglycemic animals by 1.5-fold (P < 0.05) and insulin levels by 3.9-fold (P < 0.01) but only in the presence of hyperglycemia.

Conclusions: The results of these studies demonstrate, for the first time, that OEA increases GLP-1 secretion from intestinal L-cells through activation of the novel GPR119 fatty acid derivate receptor in vitro and in vivo.
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http://dx.doi.org/10.2337/db08-1237DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671052PMC
May 2009

Protein kinase Czeta is required for oleic acid-induced secretion of glucagon-like peptide-1 by intestinal endocrine L cells.

Endocrinology 2007 Mar 16;148(3):1089-98. Epub 2006 Nov 16.

Department of Physiology, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.

Long-chain, monounsaturated fatty acids (FAs) stimulate secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1) from the intestinal L cell. Because the atypical protein kinase C (PKC), PKCzeta, is involved in FA signaling in many cells, the role of PKCzeta in FA-induced GLP-1 secretion was investigated, using the murine GLUTag L cell line and primary rat intestinal L cells. GLUTag cells expressed mRNA for several PKC isoforms, including PKCzeta, and PKCzeta protein was localized throughout the cytoplasm in GLUTag and primary L cells as well as normal mouse and rat L cells. Treatment with oleic acid (150-1000 microm) for 2 h increased GLP-1 secretion (P < 0.001), and this was abrogated by the PKCzeta inhibitor ZI (P < 0.05) and PKCzeta small interfering RNA transfection (P < 0.05) but not inhibition of classical/novel PKC isoforms. Although most PKCzeta was localized in the particulate compartment of GLUTag cells, oleate treatment did not alter PKCzeta levels or activity in this cell fraction. GLUTag cells expressed mRNA for the Gq-coupled FA receptor GPR120; however, oleic acid did not induce any changes in Akt, MAPK, or calcium, and pretreatment with LY294002 and PD98059 to inhibit phosphatidylinositol 3-kinase and MAPK, respectively, did not prevent the effects of oleic acid. Finally, GLUTag cells also released GLP-1 in response to arachidonic acid (P < 0.001) but were not affected by other long-chain FAs. These findings demonstrate that PKCzeta is required for oleic acid-induced GLP-1 secretion. This enzyme may therefore serve as a therapeutic target to enhance GLP-1 release in type 2 diabetes.
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http://dx.doi.org/10.1210/en.2006-1403DOI Listing
March 2007