Kinetics of cellular and humoral immunogenicity and effectiveness of SARS-CoV-2 booster vaccination in hematologic neoplasms.

Data on the effect of booster SARS-CoV-2 vaccination are mainly focused on humoral immunogenicity, while the kinetics of vaccine-induced cellular response and its correlation with effectiveness in hematologic patients are less explored. Our aim was to evaluate the longitudinal cellular and humoral immunogenicity induced by two and three doses of the mRNA-1273 SARS-CoV-2 vaccine in 270 patients with hematologic malignancies, and its relationship with the severity of breakthrough SARS-CoV-2 infection. Results indicate that at 23 weeks after the second dose, the seroconversion rate declined from 68.5% to 59.3%, with a reduction in median anti-S titers from 1577 to 456 BAU/mL, mainly in patients over 65 years of age or chronic lymphocytic leukemia (CLL) patients undergoing active therapy. Cellular immunogenicity, however, remained positive in 84.4% of cases. A third vaccine dose seroconverted 42.7% (41/96) and triggered cellular response in 36.7% (11/30) of previously negative patients. Notably, only 7.2% (15/209) of patients failed to develop both humoral and cellular response. Active therapy, anti-CD20 antibodies, lymphopenia, hypogammaglobulinemia, and low CD19+ cell count were associated with poor humoral response, while active disease, GvHD immunosuppressive therapy, lymphopenia, and low CD3+ , CD4+ , CD56+ cell count determined an impaired cellular response. After 13.8 months of follow-up, the incidence of SARS-CoV-2 infection was 24.8% (67/270), including 6 (9%) severe/critical cases associated with a weaker cellular (median interferon gamma (IFN-γ) 0.19 vs. 0.35 IU/mL) and humoral response (median anti-S titer <4.81 vs. 788 BAU/mL) than asymptomatic/mild cases. In conclusion, SARS-CoV-2 booster vaccination improves humoral response and COVID-19 severity is associated with impaired vaccine-induced immunogenicity.

Genetic disruption of the Gipr in Apoe-/- mice promotes atherosclerosis.

OBJECTIVE: The gut hormone glucose-dependent insulinotropic polypeptide (GIP) stimulates beta cell function and improves glycemia through its incretin actions. GIP also regulates endothelial function and suppresses adipose tissue inflammation through control of macrophage activity. Activation of the GIP receptor (GIPR) attenuates experimental atherosclerosis and inflammation in mice, however whether loss of GIPR signaling impacts the development of atherosclerosis is uncertain. METHODS: Atherosclerosis and related metabolic phenotypes were studied in Apoe-/-:Gipr-/- mice and in Gipr+/+ and Gipr-/- mice treated with an adeno-associated virus expressing PCSK9 (AAV-PCSK9). Bone marrow transplantation (BMT) studies were carried out using donor marrow from Apoe-/-:Gipr-/-and Apoe-/-:Gipr+/+mice transplanted into Apoe-/-:Gipr-/- recipient mice. Experimental endpoints included the extent of aortic atherosclerosis and inflammation, body weight, glucose tolerance, and circulating lipid levels, the proportions and subsets of circulating leukocytes, and tissue gene expression profiles informing lipid and glucose metabolism, and inflammation. RESULTS: Body weight was lower, circulating myeloid cells were reduced, and glucose tolerance was not different, however, aortic atherosclerosis was increased in Apoe-/-:Gipr-/- mice and trended higher in Gipr-/- mice with atherosclerosis induced by AAV-PCSK9. Levels of mRNA transcripts for genes contributing to inflammation were increased in the aortae of Apoe-/-:Gipr-/- mice and expression of a subset of inflammation-related hepatic genes were increased in Gipr-/- mice treated with AAV-PCSK9. BMT experiments did not reveal marked atherosclerosis, failing to implicate bone marrow derived GIPR + cells in the control of atherosclerosis or aortic inflammation. CONCLUSIONS: Loss of the Gipr in mice results in increased aortic atherosclerosis and enhanced inflammation in aorta and liver, despite reduced weight gain and preserved glucose homeostasis. These findings extend concepts of GIPR in the suppression of inflammation-related pathophysiology beyond its classical incretin role in the control of metabolism.

Cellular and humoral immunogenicity of the mRNA-1273 SARS-CoV-2 vaccine in patients with hematologic malignancies.

Recent studies have shown a suboptimal humoral response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines in patients diagnosed with hematologic malignancies; however, data about cellular immunogenicity are scarce. The aim of this study was to evaluate both the humoral and cellular immunogenicity 1 month after the second dose of the mRNA-1273 vaccine. Antibody titers were measured by using the Elecsys and LIAISON anti-SARS-CoV-2 S assays, and T-cell response was assessed by using interferon-γ release immunoassay technology. Overall, 76.3% (184 of 241) of patients developed humoral immunity, and the cellular response rate was 79% (184 of 233). Hypogammaglobulinemia, lymphopenia, active hematologic treatment, and anti-CD20 therapy during the previous 6 months were associated with an inferior humoral response. Conversely, age >65 years, active disease, lymphopenia, and immunosuppressive treatment of graft-versus-host disease (GVHD) were associated with an impaired cellular response. A significant dissociation between the humoral and cellular responses was observed in patients treated with anti-CD20 therapy (the humoral response was 17.5%, whereas the cellular response was 71.1%). In these patients, B-cell aplasia was confirmed while T-cell counts were preserved. In contrast, humoral response was observed in 77.3% of patients undergoing immunosuppressive treatment of GVHD, whereas only 52.4% had a cellular response. The cellular and humoral responses to the SARS-CoV-2 mRNA-1273 vaccine in patients with hematologic malignancies are highly influenced by the presence of treatments such as anti-CD20 therapy and immunosuppressive agents. This observation has implications for the further management of these patients.

The gut hormone receptor GIPR links energy availability to the control of hematopoiesis.

OBJECTIVE: Glucose-dependent insulinotropic polypeptide (GIP) conveys information from ingested nutrients to peripheral tissues, signaling energy availability. The GIP Receptor (GIPR) is also expressed in the bone marrow, notably in cells of the myeloid lineage. However, the importance of gain and loss of GIPR signaling for diverse hematopoietic responses remains unclear. METHODS: We assessed the expression of the Gipr in bone marrow (BM) lineages and examined functional roles for the GIPR in control of hematopoiesis. Bone marrow responses were studied in (i) mice fed regular or energy-rich diets, (ii) mice treated with hematopoietic stressors including acute 5-fluorouracil (5-FU), pamsaccharide (LPS), and Pam3CysSerLys4 (Pam3CSK4), with or without pharmacological administration of a GIPR agonist, and (iii) mice with global (Gipr-/-) or selective deletion of the GIPR (GiprTie2-/-) with and without bone marrow transplantation (BMT). RESULTS: Gipr is expressed within T cells, myeloid cells, and myeloid precursors; however, these cell populations were not different in peripheral blood, spleen, or BM of Gipr-/- and GiprTie2-/- mice. Nevertheless, gain and loss of function studies revealed that GIPR signaling controls the expression of BM Toll-like receptor (TLR) and Notch-related genes regulating hematopoiesis. Loss of the BM GIPR attenuates the extent of adipose tissue inflammation and dysregulates the hematopoietic response to BMT. GIPR agonism modified BM gene expression profiles following 5-FU and Pam3CSK4 whereas loss of the Gipr altered the hematopoietic responses to energy excess, two TLR ligands, and 5-FU. However, the magnitude of the cellular changes in hematopoiesis in response to gain or loss of GIPR signaling was relatively modest. CONCLUSION: These studies identify a functional gut hormone-BM axis positioned for the transduction of signals linking nutrient availability to the control of TLR and Notch genes regulating hematopoiesis. Nevertheless, stimulation or loss of GIPR signaling has minimal impact on basal hematopoiesis or the physiological response to hematopoietic stress.

Localization of Glucagon-Like Peptide-2 Receptor Expression in the Mouse.

Glucagon-like peptide-2 (GLP-2), secreted from enteroendocrine cells, attenuates gut motility, enhances barrier function, and augments nutrient absorption, actions mediated by a single GLP-2 receptor (GLP-2R). Despite extensive analyses, the precise distribution and cellular localization of GLP-2R expression remains controversial, confounded by the lack of suitable GLP-2R antisera. Here, we reassessed murine Glp2r expression using regular and real-time quantitative PCR (qPCR), in situ hybridization (ISH), and a Glp2rLacZ reporter mouse. Glp2r mRNA expression was detected from the stomach to the rectum and most abundant in the jejunum. Glp2r transcripts were also detected in cerebral cortex, mesenteric lymph nodes, gallbladder, urinary bladder, and mesenteric fat. Surprisingly, Glp2r mRNA was found in testis by qPCR at levels similar to jejunum. However, the testis Glp2r transcripts, detected by different primer pairs and qPCR, lacked 5' mRNA coding sequences, and only a minute proportion of them corresponded to full-length Glp2r mRNA. Within the gut, Glp2r-driven LacZ expression was localized to enteric neurons and lamina propria stromal cells, findings confirmed by ISH analysis of the endogenous Glp2r mRNA. Unexpectedly, vascular Glp2rLacZ expression was localized to mesenteric veins and not arteries. Moreover, mesenteric fat Glp2rLacZ expression was detected within blood vessels and not adipocytes. Reporter LacZ expression was not detected in all tissues expressing an endogenous Glp2r transcript, such as gallbladder, urinary bladder, and mesenteric lymph nodes. Collectively, these findings extend our understanding of the cellular domains of Glp2r expression and highlight limitations inherent in application of commonly used technologies to infer analysis of gene expression.

Circulating Levels of Soluble Dipeptidyl Peptidase-4 Are Dissociated from Inflammation and Induced by Enzymatic DPP4 Inhibition.

Dipeptidyl peptidase-4 (DPP-4) controls glucose homeostasis through enzymatic termination of incretin action. We report that plasma DPP-4 activity correlates with body weight and fat mass, but not glucose control, in mice. Genetic disruption of adipocyte Dpp4 expression reduced plasma DPP-4 activity in older mice but did not perturb incretin levels or glucose homeostasis. Knockdown of hepatocyte Dpp4 completely abrogated the obesity-associated increase in plasma DPP-4 activity, reduced liver cytokine expression, and partially attenuated inflammation in adipose tissue without changes in incretin levels or glucose homeostasis. In contrast, circulating levels of soluble DPP4 (sDPP4) were dissociated from inflammation in mice with endothelial-selective or global genetic inactivation of Dpp4. Remarkably, inhibition of DPP-4 enzymatic activity upregulated circulating levels of sDPP4 originating from endothelial or hematopoietic cells without inducing systemic or localized inflammation. Collectively, these findings reveal unexpected complexity in regulation of soluble versus enzymatic DPP-4 and control of inflammation and glucose homeostasis.

Teneligliptin enhances the beneficial effects of GLP-1 in endothelial cells exposed to hyperglycemic conditions.

High-glucose-induced oxidative stress contributes to cardiovascular endothelial damage in diabetes. Glucagon-like peptide 1 (GLP-1) is beneficial to endothelial cells, but its effects are diminished when cells are continuously exposed to high glucose. Teneligliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor that prevents oxidative stress, apoptosis and the metabolic memory effect. We explored the potential additive effects of Teneligliptin and GLP-1 in hyperglycemia-damaged endothelial cells. Human umbilical vein endothelial cells (HUVECs) were exposed to normal-glucose (5 mmol/L) or high-glucose (HG, 25 mmol/L) for 21 days, or to HG for 14 days followed by normal-glucose for 7 days (HM). These cells were continually treated with Teneligliptin 3.0 µmol/L, alone or in combination with an acute dose of GLP-1 50 nmol/L. DPP-4 was upregulated under hyperglycemic conditions, but Teneligliptin reduced DPP-4 expression and activity. Simultaneous Teneligliptin and GLP-1 synergistically increased the antioxidant response and reduced ROS levels in HG- and HM-exposed HUVECs. Concurrent treatment also enhanced cell proliferation, reduced apoptotic gene expression and ameliorated endoplasmic reticulum stress in HG- and HM-exposed HUVECs. Thus, long-term Teneligliptin treatment reduced DPP-4 levels and activity in HUVECs exposed to chronic hyperglycemia. Moreover, Teneligliptin enhanced the beneficial effects of GLP-1 on oxidative stress, proliferation, apoptosis and endoplasmic reticulum homeostasis.

The dipeptidyl peptidase-4 (DPP-4) inhibitor teneligliptin functions as antioxidant on human endothelial cells exposed to chronic hyperglycemia and metabolic high-glucose memory.

Dipeptidyl peptidase-4 inhibitors are widely used in type 2 diabetes. Endothelium plays a crucial role maintaining vascular integrity and function. Chronic exposure to high glucose drives to endothelial dysfunction generating oxidative stress. Teneligliptin is a novel dipeptidyl peptidase-4 inhibitor with antioxidant properties. This study is aimed to verify a potential protective action of teneligliptin in endothelial cells exposed to high glucose. Human umbilical vein endothelial cells were cultured under normal (5 mmol/L) or high glucose (25 mmol/L) during 21 days, or at high glucose during 14 days followed by 7 days at normal glucose, to reproduce the high-metabolic memory state. During this period, different concentrations of teneligliptin (0.1, 1.0 and 3.0 µmol/L) or sitagliptin (0.5 µmol/L) were added to cells. Ribonucleic acid and protein expression were assessed for antioxidant response, proliferation, apoptosis and endoplasmic reticulum stress markers. Teneligliptin promotes the antioxidant response in human umbilical vein endothelial cells, reducing ROS levels and inducing Nrf2-target genes messenger ribonucleic acid expression. Teneligliptin, but not sitagliptin, reduces the expression of the nicotine amide adenine dinucleotide phosphate oxidase regulatory subunit P22 -phox , however, both blunt the high glucose-induced increase of TXNIP. Teneligliptin improves proliferation rates in human umbilical vein endothelial cells exposed to high glucose, regulating the expression of cell-cycle inhibitors markers (P53, P21 and P27), and reducing proapoptotic genes (BAX and CASP3), while promotes BCL2 expression. Teneligliptin ameliorates high glucose-induced endoplasmic reticulum stress reducing the expression of several markers (BIP, PERK, ATF4, CHOP, IRE1a and ATF6). Teneligliptin has antioxidant properties, ameliorates oxidative stress and apoptotic phenotype and it can overcome the metabolic memory effect, induced by chronic exposure to high glucose in human endothelial cells.

Vascular Biology of Glucagon Receptor Superfamily Peptides: Mechanistic and Clinical Relevance.

Regulatory peptides produced in islet and gut endocrine cells, including glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, and glucose-dependent insulinotropic polypeptide, exert actions with considerable metabolic importance and translational relevance. Although the clinical development of GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors has fostered research into how these hormones act on the normal and diseased heart, less is known about the actions of these peptides on blood vessels. Here we review the effects of these peptide hormones on normal blood vessels and highlight their vascular actions in the setting of experimental and clinical vascular injury. The cellular localization and signal transduction properties of the receptors for glucagon, GLP-1, GLP-2, and glucose-dependent insulinotropic polypeptide are discussed, with emphasis on endothelial cells and vascular smooth muscle cells. The actions of these peptides on the control of blood flow, blood pressure, angiogenesis, atherosclerosis, and vascular inflammation are reviewed with a focus on elucidating direct and indirect mechanisms of action. How these peptides traverse the blood-brain barrier is highlighted, with relevance to the use of GLP-1 receptor agonists to treat obesity and neurodegenerative disorders. Wherever possible, we compare actions identified in cell lines and primary cell culture with data from preclinical studies and, when available, results of human investigation, including studies in subjects with diabetes, obesity, and cardiovascular disease. Throughout the review, we discuss pitfalls, limitations, and challenges of the existing literature and highlight areas of controversy and uncertainty. The increasing use of peptide-based therapies for the treatment of diabetes and obesity underscores the importance of understanding the vascular biology of peptide hormone action.

Oscillating glucose induces microRNA-185 and impairs an efficient antioxidant response in human endothelial cells.

BACKGROUND: Intracellular antioxidant response to high glucose is mediated by Cu/Mn-superoxide dismutases (SOD-1/SOD-2), catalase (CAT) and glutathione peroxidases (GPx), particularly glutathione peroxidase-1 (GPx-1). Although oscillating glucose can induce a more deleterious effect than high glucose on endothelial cells, the mechanism by which oscillating glucose exerts its dangerous effects is incompletely understood; however, the involvement of oxidative damage has been generally accepted. In this study we sought to determine whether oscillating glucose differentially modulates antioxidant response, and to elucidate the potential regulatory mechanisms exerted by the microRNA-185 (miR-185). METHODS: Human endothelial cells were exposed for 1 week to constant and oscillating high glucose. SOD-1, SOD-2, CAT and GPx-1, as well as two markers of oxidative stress [8-hydroxy-2'-deoxyguanosine (8-OHdG) and the phosphorylated form of H2AX (γ-H2AX)] were measured at the end of the experiment. Intracellular miR-185 was measured and loss-of function assays were performed in HUVEC. Bioinformatic tool was used to predict the link between miR-185 on 3'UTR of GPx-1 gene. Luciferase assay was performed to confirm the binding on HUVEC. RESULTS: After exposure to constant high glucose SOD-1 and GPx-1 increased, while in oscillating glucose SOD-1 increased and GPx-1 did not. SOD-2 and CAT remained unchanged under both conditions. A critical involvement of oscillating glucose-induced miR-185 in the dysregulation of endogenous GPx-1 was found. Computational analyses predict GPx-1 as miR-185's target. HUVEC cultures were used to confirm glucose's causal role on the expression of miR-185, its target mRNA and protein and finally the activation of antioxidant response. In vitro luciferase assays confirmed computational predictions targeting of miR-185 on 3'-UTR of GPx-1 mRNA. Knockdown of miR-185, using anti-miR-185 inhibitor, was accompanied by a significant upregulation of GPx-1 in oscillating glucose. 8-OHdG and γ-H2AX increased more in oscillating glucose than in constant high glucose. CONCLUSIONS: Glucose oscillations may exert more deleterious effects on the endothelium than high glucose, likely due to an impaired response of GPx-1, coupled by the upregulation of miR-185.

The simultaneous control of hyperglycemia and GLP-1 infusion normalize endothelial function in type 1 diabetes.

BACKGROUND: To test the effect of normoglycemia and glucagon-like peptide-1 (GLP-1), alone or in combination, on the possible normalization of endothelial function in type 1 diabetes. METHODS: Fifteen people with type 1 diabetes participated in three experiments: reaching and maintaining normoglycemia for 4h; reaching and maintaining hyperglycemia plus GLP-1 infusion for 4h; and reaching and maintaining normoglycemia for 4h with simultaneous infusion of GLP-1. RESULTS: Both normoglycemia and GLP-1 infusion restored endothelial function and decreased and plasma 8-iso prostaglandin F2α levels. However, only the combination of normoglycemia and GLP-1 was able to normalize endothelial function. CONCLUSIONS: This study confirms that long-lasting hyperglycemia in type 1 diabetes induces a permanent alteration which contributes to maintaining endothelial dysfunction even when glycemia is normalized, and that in the presence of normoglycemia, GLP-1 can contribute to normalizing endothelial function.

The pivotal role of high glucose-induced overexpression of PKCß in the appearance of glucagon-like peptide-1 resistance in endothelial cells.

Recently, it has been demonstrated that Glucagon-like peptide-1 (GLP-1) has a protective effect on endothelial cells. Our hypothesis is that this GLP-1 protective effect is partly lost when the cells are exposed to sustained high glucose concentrations. Human umbilical vein endothelial cells (HUVECs) were cultured for 21 days in normal glucose (5 mmol/L, NG) or high glucose (25 mmol/L glucose, HG). GLP-1 (7-37) and Ruboxistaurin were added at 50 and 500 nM, respectively, alone or in combination, 1 h before cell harvesting. Analysis of GLP-1 receptor protein levels, as well as of the gene expression of different ER stress-related genes, proliferation markers, antioxidant cell response-related genes, and PKA subunits, was performed. ROS production was also measured in HUVECs exposed to mentioned treatments. GLP-1 receptor expression was reduced in HUVECs exposed to chronic high glucose concentrations but was partially restored by a chemical PKCß-specific inhibitor. GLP-1, added as an acute treatment in endothelial cells, had the capacity to induce the expression of Nrf2-detoxifying enzyme targets, to increase transcription levels of scavenger genes, to attenuate the expression of high glucose-induced PKA subunits, ER stress and also the apoptotic phenotype of HUVECs; these effects occured only when high glucose-induced PKCß overexpression was reduced by Ruboxistaurin. In a similar manner, ROS production induced by high glucose was reduced by GLP-1 in the presence of PKCß inhibitor. This study suggests that an increase in PKCß, induced by high glucose, could have a role in endothelial GLP-1 resistance, reducing GLP-1 receptor levels and disrupting the GLP-1 canonical pathway.

Short-term high glucose exposure impairs insulin signaling in endothelial cells.

BACKGROUND: Hyperglycemia is the hallmark of diabetes and its cardiovascular complications. Insulin plays an important role in the regulation of vascular homeostasis and maintenance of endothelial function. Insulin signaling occurs after binding to the insulin receptor, causing activation of two separate and parallel pathways: PI3K/AKT/eNOS and Ras/Raf/MAPK pathways. AKT phosphorylates eNOS at Ser1177, resulting in increased nitric oxide production and vasodilation. The MAPK pathway results in endothelin-1 production and vasoconstriction and mitogenic effects. METHODS: We studied the effects of physiological insulin treatment in human umbilical vein endothelial cells (HUVECs) on the two pathways under high glucose conditions, which mimic the in vivo condition of hyperglycemia. HUVECs were incubated with insulin at different physiological concentrations (from 10(-10) to 10(-8) M) for 30 min after 24 h of exposition to normal (5 mmol/L, NG) or high glucose (25 mmol/L, HG). Phosphorylated forms of AKT, eNOS, ERK1/2, p38, JNK and insulin receptor-ß subunit (IRß) were evaluated. RESULTS: In normal glucose, the active phosphorylated forms of AKT, eNOS, ERK1/2, p38 and JNK were increased in insulin treated cells, in a dose-dependent manner. In high glucose, insulin was not able to activate the PI3K/AKT/eNOS pathway, with the phosphorylated form of eNOS reduced with respect to the control. However, insulin was able to induce the up-regulation of phospho-ERK1/2, -p38 and -JNK. Moreover, we found reduced levels of IRß phosphorylated form in high glucose as compared to the control. Insulin was able to increase phospho-IRß in normal glucose but not in high glucose, in which the total protein levels remained reduced. CONCLUSIONS: Exposure to short-term high glucose negatively affects insulin signaling even when physiological insulin concentrations are added. The impairment of the PI3K/AKT/eNOS pathway after physiological insulin treatment could contribute to detrimental effects on cardiovascular homeostasis under high glucose conditions, and might shift toward the activation of certain mitogenic effectors, such as ERK1/2, p38 and JNK, the only ones that respond to physiological insulin treatment in high glucose.

Oscillating glucose and constant high glucose induce endoglin expression in endothelial cells: the role of oxidative stress.

AIM: High glucose-induced oxidative stress has been suggested as one of the mediators of endothelial damage in diabetes. The major endothelial protein, endoglin, has been found overexpressed in the vessels during pathological situations, but little is known about its relation to diabetic vascular complications. To clarify the role of endoglin in endothelial injury, we sought to determine the effects of high and oscillating glucose on its expression. MATERIALS: Furthermore, the activation of the Krüppel-like factor 6 (KLF-6) and the hypoxia-inducible factor-1α (HIF-1α) as possible regulators of endoglin expression has been evaluated. The possible role of the oxidative stress has been studied evaluating the effects of the antioxidant alpha-lipoic acid (ALA) and the cellular antioxidant response mediated by NAD(P)H: quinine-oxido-reductase-1 (NQO-1) and heme oxygenase-1 (HO-1). RESULTS: Primary HUVECs were cultured for 21 days in normal, high and oscillating glucose (5, 25 and 5/25 mmol/l every 24 h, respectively) with/without ALA. In oscillating and high glucose total endoglin, its soluble form (sEng), KLF-6 and HIF-1α were significantly increased. Simultaneously, the oxidative DNA stress markers 8-OHdG and H2A.X were elevated. Moreover, ENG gene transcriptional rate increased during glucose exposures concomitantly with increased KLF-6 nuclear translocations. ALA significantly reduced all these phenomena. Interestingly, during oscillating and chronic high glucose, NQO-1 and HO-1 did not increase, but ALA induced their overexpression. CONCLUSIONS: Together, these findings provide novel clue about endoglin in the regulation of high glucose-mediated vascular damage in HUVECs and the role of oxidative stress in this regulation.

The protective effect of the Mediterranean diet on endothelial resistance to GLP-1 in type 2 diabetes: a preliminary report.

BACKGROUND: In type 2 diabetes, acute hyperglycemia worsens endothelial function and inflammation,while resistance to GLP-1 action occurs. All these phenomena seem to be related to the generation of oxidative stress. A Mediterranean diet, supplemented with olive oil, increases plasma antioxidant capacity, suggesting that its implementation can have a favorable effect on the aforementioned phenomena. In the present study, we test the hypothesis that a Mediterranean diet using olive oil can counteract the effects of acute hyperglycemia and can improve the resistance of the endothelium to GLP-1 action. METHODS: Two groups of type 2 diabetic patients, each consisting of twelve subjects, participated in a randomized trial for three months, following a Mediterranean diet using olive oil or a control low-fat diet. Plasma antioxidant capacity, endothelial function, nitrotyrosine, 8-iso-PGF2a, IL-6 and ICAM-1 levels were evaluated at baseline and at the end of the study. The effect of GLP-1 during a hyperglycemic clamp, was also studied at baseline and at the end of the study. RESULTS: Compared to the control diet, the Mediterranean diet increased plasma antioxidant capacity and improved basal endothelial function, nitrotyrosine, 8-iso-PGF2a, IL-6 and ICAM-1 levels. The Mediterranean diet also reduced the negative effects of acute hyperglycemia, induced by a hyperglycemic clamp, on endothelial function, nitrotyrosine, 8-iso-PGF2a, IL-6 and ICAM-1 levels. Furthermore, the Mediterranean diet improved the protective action of GLP-1 on endothelial function, nitrotyrosine, 8-iso-PGF2a, IL-6 and ICAM-1 levels, also increasing GLP-1-induced insulin secretion. CONCLUSIONS: These data suggest that the Mediterranean diet, using olive oil, prevents the acute hyperglycemia effect on endothelial function, inflammation and oxidative stress, and improves the action of GLP-1, which may have a favorable effect on the management of type 2 diabetes, particularly for the prevention of cardiovascular disease.

Simultaneous GLP-1 and insulin administration acutely enhances their vasodilatory, antiinflammatory, and antioxidant action in type 2 diabetes.

OBJECTIVE: To test the hypothesis that the simultaneous administration of GLP-1 and insulin may increase their vasodilatory, antiinflammatory, and antioxidant action in type 2 diabetes. RESEARCH DESIGN AND METHODS: In two groups of persons with type 2 diabetes, two sets of experiments were performed. The first group had two normoglycemic-normoinsulinemic clamps with or without GLP-1 and two normoglycemic-hyperinsulinemic clamps with or without GLP-1. The second group had two hyperglycemic-normoinsulinemic clamps and two hyperglycemic-hyperinsulinemic clamps with or without GLP-1. RESULTS: During the normoglycemic-hyperinsulinemic clamp, flow-mediated dilatation (FMD) increased, while soluble intercellular adhesion molecule (sICAM-1), plasma 8-iso-prostaglandin F2α (8-iso-PGF2α), nitrotyrosine, and interleukin (IL)-6 decreased compared with normoglycemic-normoinsulinemic clamp. Similar results were obtained with the infusion of GLP-1 during the normoglycemic-normoinsulinemic clamp. The combination of hyperinsulinemia and GLP-1 in normoglycemia was accompanied by a further FMD increase and sICAM-1, 8-iso-PGF2α, nitrotyrosine, and IL-6 decrease. During the hyperglycemic-normoinsulinemic clamp, FMD significantly decreased, while sICAM-1, 8-iso-PGF2α, nitrotyrosine, and IL-6 significantly increased. When hyperglycemia was accompanied by hyperinsulinemia or by the simultaneous infusion of GLP-1, these phenomena were attenuated. The simultaneous presence of hyperinsulinemia and GLP-1 had an increased beneficial effect. CONCLUSIONS: Our results show that the combination of insulin and GLP-1 is more effective than insulin or GLP-1 alone in improving endothelial dysfunction, inflammation, and oxidative stress in type 2 diabetes.

Vitamin C further improves the protective effect of glucagon-like peptide-1 on acute hypoglycemia-induced oxidative stress, inflammation, and endothelial dysfunction in type 1 diabetes.

OBJECTIVE: To test the hypothesis that acute hypoglycemia induces endothelial dysfunction and inflammation through the generation of an oxidative stress. Moreover, to test if the antioxidant vitamin C can further improve the protective effects of glucagon-like peptide 1 (GLP-1) on endothelial dysfunction and inflammation during hypoglycemia in type 1 diabetes. RESEARCH DESIGN AND METHODS: A total of 20 type 1 diabetic patients underwent four experiments: a period of 2 h of acute hypoglycemia with or without infusion of GLP-1 or vitamin C or both. At baseline, after 1 and 2 h, glycemia, plasma nitrotyrosine, plasma 8-iso prostaglandin F2a (PGF2a), soluble intracellular adhesion molecule-1a (sICAM-1a), interleukin-6 (IL-6), and flow-mediated vasodilation were measured. At 2 h of hypoglycemia, flow-mediated vasodilation significantly decreased, while sICAM-1, 8-iso-PGF2a, nitrotyrosine, and IL-6 significantly increased. The simultaneous infusion of GLP-1 or vitamin C significantly attenuated all of these phenomena. Vitamin C was more effective. When GLP-1 and vitamin C were infused simultaneously, the deleterious effect of hypoglycemia was almost completely counterbalanced. RESULTS: At 2 h of hypoglycemia, flow-mediated vasodilation significantly decreased, while sICAM-1, 8-iso-PGF2a, nitrotyrosine, and IL-6 significantly increased. The simultaneous infusion of GLP-1 or vitamin C significantly attenuated all of these phenomena. Vitamin C was more effective. When GLP-1 and vitamin C were infused simultaneously, the deleterious effect of hypoglycemia was almost completely counterbalanced. CONCLUSIONS: This study shows that vitamin C infusion, during induced acute hypoglycemia, reduces the generation of oxidative stress and inflammation, improving endothelial dysfunction, in type 1 diabetes. Furthermore, the data support a protective effect of GLP-1 during acute hypoglycemia, but also suggest the presence of an endothelial resistance to the action of GLP-1, reasonably mediated by oxidative stress.

Vitamin C further improves the protective effect of GLP-1 on the ischemia-reperfusion-like effect induced by hyperglycemia post-hypoglycemia in type 1 diabetes.

BACKGROUND: It has been reported that hyperglycemia following hypoglycemia produces an ischemia-reperfusion-like effect in type 1 diabetes. In this study the possibility that GLP-1 has a protective effect on this phenomenon has been tested. METHODS: 15 type 1 diabetic patients underwent to five experiments: a period of two hours of hypoglycemia followed by two hours of normo-glycemia or hyperglycemia with the concomitant infusion of GLP-1 or vitamin C or both. At baseline, after 2 and 4 hours, glycemia, plasma nitrotyrosine, plasma 8-iso prostaglandin F2alpha, sCAM-1a, IL-6 and flow mediated vasodilation were measured. RESULTS: After 2 h of hypoglycemia, flow mediated vasodilation significantly decreased, while sICAM-1, 8-iso-PGF2a, nitrotyrosine and IL-6 significantly increased. While recovering with normoglycemia was accompanied by a significant improvement of endothelial dysfunction, oxidative stress and inflammation, a period of hyperglycemia after hypoglycemia worsens all these parameters. These effects were counterbalanced by GLP-1 and better by vitamin C, while the simultaneous infusion of both almost completely abolished the effect of hyperglycemia post hypoglycemia. CONCLUSIONS: This study shows that GLP-1 infusion, during induced hyperglycemia post hypoglycemia, reduces the generation of oxidative stress and inflammation, improving the endothelial dysfunction, in type 1 diabetes. Furthermore, the data support that vitamin C and GLP-1 may have an additive protective effect in such condition.