Gene Essentiality Profiling Reveals Gene Networks and Synthetic Lethal Interactions with Oncogenic Ras.

The genetic dependencies of human cancers widely vary. Here, we catalog this heterogeneity and use it to identify functional gene interactions and genotype-dependent liabilities in cancer. By using genome-wide CRISPR-based screens, we generate a gene essentiality dataset across 14 human acute myeloid leukemia (AML) cell lines. Sets of genes with correlated patterns of essentiality across the lines reveal new gene relationships, the essential substrates of enzymes, and the molecular functions of uncharacterized proteins. Comparisons of differentially essential genes between Ras-dependent and -independent lines uncover synthetic lethal partners of oncogenic Ras. Screens in both human AML and engineered mouse pro-B cells converge on a surprisingly small number of genes in the Ras processing and MAPK pathways and pinpoint PREX1 as an AML-specific activator of MAPK signaling. Our findings suggest general strategies for defining mammalian gene networks and synthetic lethal interactions by exploiting the natural genetic and epigenetic diversity of human cancer cells.

A lineage-specific STAT5BN642H mouse model to study NK-cell leukemia.

ABSTRACT: Patients with T- and natural killer (NK)-cell neoplasms frequently have somatic STAT5B gain-of-function mutations. The most frequent STAT5B mutation is STAT5BN642H, which is known to drive murine T-cell leukemia, although its role in NK-cell malignancies is unclear. Introduction of the STAT5BN642H mutation into human NK-cell lines enhances their potential to induce leukemia in mice. We have generated a mouse model that enables tissue-specific expression of STAT5BN642H and have selectively expressed the mutated STAT5B in hematopoietic cells (N642Hvav/+) or exclusively in NK cells (N642HNK/NK). All N642Hvav/+ mice rapidly develop an aggressive T/NKT-cell leukemia, whereas N642HNK/NK mice display an indolent NK-large granular lymphocytic leukemia (NK-LGLL) that progresses to an aggressive leukemia with age. Samples from patients with NK-cell leukemia have a distinctive transcriptional signature driven by mutant STAT5B, which overlaps with that of murine leukemic N642HNK/NK NK cells. To our knowledge, we have generated the first reliable STAT5BN642H-driven preclinical mouse model that displays an indolent NK-LGLL progressing to aggressive NK-cell leukemia. This novel in vivo tool will enable us to explore the transition from an indolent to an aggressive disease and will thus permit the study of prevention and treatment options for NK-cell malignancies.

Tumor necrosis factor α promotes clonal dominance of KIT D816V+ cells in mastocytosis: role of survivin and impact on prognosis.

ABSTRACT: Systemic mastocytosis (SM) is defined by the expansion and accumulation of neoplastic mast cells (MCs) in the bone marrow (BM) and extracutaneous organs. Most patients harbor a somatic KIT D816V mutation, which leads to growth factor-independent KIT activation and accumulation of MC. Tumor necrosis factor α (TNF) is a proapoptotic and inflammatory cytokine that has been implicated in the clonal selection of neoplastic cells. We found that KIT D816V increases the expression and secretion of TNF. TNF expression in neoplastic MCs is reduced by KIT-targeting drugs. Similarly, knockdown of KIT or targeting the downstream signaling cascade of MAPK and NF-κB signaling reduced TNF expression levels. TNF reduces colony formation in human BM cells, whereas KIT D816V+ cells are less susceptible to the cytokine, potentially contributing to clonal selection. In line, knockout of TNF in neoplastic MC prolonged survival and reduced myelosuppression in a murine xenotransplantation model. Mechanistic studies revealed that the relative resistance of KIT D816V+ cells to TNF is mediated by the apoptosis-regulator BIRC5 (survivin). Expression of BIRC5 in neoplastic MC was confirmed by immunohistochemistry of samples from patients with SM. TNF serum levels are significantly elevated in patients with SM and high TNF levels were identified as a biomarker associated with inferior survival. We here characterized TNF as a KIT D816V-dependent cytokine that promotes clonal dominance. We propose TNF and apoptosis-associated proteins as potential therapeutic targets in SM.

Impact of the hepatoselective glucokinase activator TTP399 on ketoacidosis during insulin withdrawal in people with type 1 diabetes.

AIMS: To determine the effect of TTP399, a hepatoselective glucokinase activator, on the risk of ketoacidosis during insulin withdrawal in individuals with type 1 diabetes (T1D). MATERIALS AND METHODS: Twenty-three participants with T1D using insulin pump therapy were randomized to 800 mg TTP399 (n = 12) or placebo (n = 11) for 7 to 10 days. After the treatment period, an insulin withdrawal test (IWT) was performed, during which insulin pumps were removed to induce ketogenesis. The IWT was stopped after 10 hours or if blood glucose reached >399 mg/dL [22.1 mmol/L], if beta-hydroxybutyrate (BHB) was >3.0 mmol/L, or for patient discomfort. The primary endpoint was the proportion of participants who reached BHB concentrations of 1 mmol/L or greater. RESULTS: During the 7- to 10-day treatment period, mean fasting plasma glucose was significantly reduced ( -27.6 vs. -4.4 mg/dL [-1.5 vs. -0.2 mmol/L]; P = 0.03) and there were fewer adverse events, including hypoglycaemia, in the TTP399-treated arm. During the IWT, no differences were observed between TTP399 and placebo in mean serum BHB concentration, mean duration of IWT, or BHB at termination of IWT. However, serum bicarbonate was numerically higher and urine acetoacetate was quantitatively lower in the TTP399-treated participants. As a result of higher bicarbonate values, none of the TTP399-treated participants met the prespecified criteria for diabetic ketoacidosis (DKA), defined as BHB >3 mmol/L and serum bicarbonate <18 mEq/L, compared to 42% of placebo-treated participants. CONCLUSIONS: When used as an adjunctive therapy to insulin, TTP399 improves glycaemia without increasing hypoglycaemia in individuals with T1D. During acute insulin withdrawal, TTP399 did not increase BHB concentrations and decreased the incidence of DKA.

Loss of NKG2D in murine NK cells leads to increased perforin production upon long-term stimulation with IL-2.

NK cells are innate lymphocytes responsible for lysis of pathogen-infected and transformed cells. One of the major activating receptors required for target cell recognition is the NK group 2D (NKG2D) receptor. Numerous reports show the necessity of NKG2D for effective tumor immune surveillance. Further studies identified NKG2D as a key element allowing tumor immune escape. We here use a mouse model with restricted deletion of NKG2D in mature NKp46+ cells (NKG2DΔNK ). NKG2DΔNK NK cells develop normally, have an unaltered IFN-γ production but kill tumor cell lines expressing NKG2D ligands (NKG2DLs) less efficiently. However, upon long-term stimulation with IL-2, NKG2D-deficient NK cells show increased levels of the lytic molecule perforin. Thus, our findings demonstrate a dual function of NKG2D for NK cell cytotoxicity; while NKG2D is a crucial trigger for cytotoxicity of tumor cells expressing activating ligands it is also capable to limit perforin production in IL-2 activated NK cells.

Human signal transducer and activator of transcription 5b (STAT5b) mutation causes dysregulated human natural killer cell maturation and impaired lytic function.

BACKGROUND: Patients with signal transducer and activator of transcription 5b (STAT5b) deficiency have impairment in T-cell homeostasis and natural killer (NK) cells which leads to autoimmunity, recurrent infections, and combined immune deficiency. OBJECTIVE: In this study we characterized the NK cell defect in STAT5b-deficient human NK cells, as well as Stat5b-/- mice. METHODS: We used multiparametric flow cytometry, functional NK cell assays, microscopy, and a Stat5b-/- mouse model to elucidate the effect of impaired and/or absent STAT5b on NK cell development and function. RESULTS: This alteration generated a nonfunctional CD56bright NK cell subset characterized by low cytokine production. The CD56dim NK cell subset had decreased expression of perforin and CD16 and a greater frequency of cells expressing markers of immature NK cells. We observed low NK cell numbers and impaired NK cell maturation, suggesting that STAT5b is involved in terminal NK cell maturation in Stat5b-/- mice. Furthermore, human STAT5b-deficient NK cells had low cytolytic capacity, and fixed-cell microscopy showed poor convergence of lytic granules. This was accompanied by decreased expression of costimulatory and activating receptors. Interestingly, granule convergence and cytolytic function were restored after IL-2 stimulation. CONCLUSIONS: Our results show that in addition to the impaired terminal maturation of NK cells, human STAT5b mutation leads to impairments in early activation events in NK cell lytic synapse formation. Our data provide further insight into NK cell defects caused by STAT5b deficiency.

Validation of distinct type 2 diabetes clusters and their association with diabetes complications in the DEVOTE, LEADER and SUSTAIN-6 cardiovascular outcomes trials.

AIMS: To validate the clusters of Swedish individuals with recent-onset diabetes at differential risk of complications, which were identified in a previous study, in three global populations with long-standing type 2 diabetes (T2D) who were at high cardiovascular risk, and to test for differences in the risk of major diabetes complications and survival endpoints. MATERIALS AND METHODS: We assigned participants from recent global outcomes trials (DEVOTE [n = 7637], LEADER [n = 9340] and SUSTAIN-6 [n = 3297]) to the previously defined clusters according to age at diabetes diagnosis, baseline glycated haemoglobin (HbA1c) and body mass index (BMI). Outcomes were assessed using Kaplan-Meier analysis and log-rank tests. RESULTS: The T2D clusters were consistently replicated across the three trial cohorts. The risk of major adverse cardiovascular events and cardiovascular death differed significantly, in all trials, across clusters over a median follow-up duration of 2.0, 3.8 and 2.1 years, respectively, and was highest for the cluster of participants with high HbA1c and low BMI (P < 0.05 in DEVOTE and LEADER). In LEADER and SUSTAIN-6, the risk of nephropathy differed across clusters (P < 0.0001 and P = 0.003, respectively). The risk of severe hypoglycaemia differed in DEVOTE (P = 0.006). CONCLUSIONS: Previously identified clusters can be replicated in three geographically diverse cohorts of long-standing T2D and are associated with cluster-specific risk profiles for additional clinical and survival outcomes, providing further validation of the clustering methodology. The external validity and stability of clusters across cohorts provides a premise for future work to optimize the clustering approach to yield T2D subgroups with maximum predictive validity who may benefit from subtype-specific treatment paradigms.

The expanding repertoire of receptor activity modifying protein (RAMP) function.

Receptor activity modifying proteins (RAMPs) associate with G-protein-coupled receptors (GPCRs) at the plasma membrane and together bind a variety of peptide ligands, serving as a communication interface between the extracellular and intracellular environments. The collection of RAMP-interacting GPCRs continues to expand and now consists of GPCRs from families A, B and C, suggesting that RAMP activity is extremely prevalent. RAMP association with GPCRs can regulate GPCR function by altering ligand binding, receptor trafficking and desensitization, and downstream signaling pathways. Here, we elaborate on these RAMP-dependent mechanisms of GPCR regulation, which provide opportunities for pharmacological intervention.

Adrenomedullin in lymphangiogenesis: from development to disease.

Over the past decade, we have begun to appreciate that the lymphatic vascular system does more than simply return plasma back into the circulatory system and, in fact, contributes to a wide variety of normal and disease states. For this reason, much research has been devoted to understanding how lymphatic vessels form and function, with a particular interest in which molecules contribute to lymphatic vessel growth and maintenance. In the following review, we focus on a potent lymphangiogenic factor, adrenomedullin, and its known roles in lymphangiogenesis, lymphatic function, and human lymphatic disease. As one of the first, pharmacologically tractable G protein-coupled receptor pathways characterized in lymphatic endothelial cells, the continued study of adrenomedullin effects on the lymphatic system may open new avenues for the modulation of lymphatic growth and function in a variety of lymphatic-related diseases that currently have few treatments.

Epicardial-derived adrenomedullin drives cardiac hyperplasia during embryogenesis.

BACKGROUND: Growth promoting signals from the epicardium are essential for driving myocardial proliferation during embryogenesis. In adults, these signals become reactivated following injury and promote angiogenesis and myocardial repair. Therefore, identification of such paracrine factors could lead to novel therapeutic strategies. The multi-functional peptide adrenomedullin (Adm 5 gene, AM 5 protein) is required for normal heart development. Moreover, elevated plasma AM following myocardial infarction offers beneficial cardioprotection and serves as a powerful diagnostic and prognostic indication of disease severity. RESULTS: Here, we developed a new model of Adm overexpression by stabilizing the Adm mRNA through gene-targeted replacement of the endogenous 30 untranslated region. As expected, Admhi/hi mice express three-times more AM than controls in multiple tissues, including the heart. Despite normal blood pressures, Admhi/hi mice unexpectedly showed significantly enlarged hearts due to increased cardiac hyperplasia during development. The targeting vector was designed to allow for reversion to wild-type levels by means of Cre-mediated modification. Using this approach, we demonstrate that AM derived from the epicardium, but not the myocardium or cardiac fibroblast, is responsible for driving cardiomyocyte hyperplasia. CONCLUSIONS: AM is produced by the epicardium and drives myocyte proliferation during development, thus representing a novel and clinically relevant factor potentially related to mechanisms of cardiac repair after injury.

Occurrence of Gastrointestinal Adverse Events Upon GLP-1 Receptor Agonist Initiation With Concomitant Metformin Use: A Post Hoc Analysis of LEADER, STEP 2, SUSTAIN-6, and PIONEER 6.

OBJECTIVE: To assess the impact of concomitant metformin use on gastrointestinal adverse events during the initiation and titration of a glucagon-like peptide 1 receptor agonist (GLP-1RA). RESEARCH DESIGN AND METHODS: Using data from four clinical trials of liraglutide and semaglutide (Liraglutide Effect and Action in Diabetes: Evaluation of Cardiovascular Outcome Results [LEADER], Semaglutide Treatment Effect in People with Obesity [STEP 2], Trial to Evaluate Cardiovascular and Other Long-Term Outcomes With Semaglutide in Subjects With Type 2 Diabetes [SUSTAIN-6], and Peptide Innovation for Early Diabetes Treatment [PIONEER] 6), we compared the incidence of gastrointestinal adverse events during GLP-1RA initiation and titration in participants with and without concomitant metformin use. RESULTS: Of 16,996 participants, 12,928 (76%) were treated with metformin. Concomitant metformin use did not increase the percentage of participants who developed gastrointestinal adverse events or their severity during the observation window. Among participants experiencing gastrointestinal adverse events, metformin use did not increase study product discontinuation. Within treatment arms (GLP-1RA and placebo), a numerically higher percentage of metformin nonusers experienced gastrointestinal adverse events and discontinued the study product compared with metformin users. CONCLUSIONS: Concomitant metformin use does not increase occurrence of gastrointestinal symptoms during GLP-1RA initiation or impact GLP-1RA discontinuation.

Delayed Diagnosis of Ectopic Cushing Syndrome.

Here, we present the case of a 40-year-old man in whom the diagnosis of ectopic adrenocorticotropin (ACTH) syndrome went unrecognized despite evaluation by multiple providers until it was ultimately suspected by a nephrologist evaluating the patient for edema and weight gain. On urgent referral to endocrinology, screening for hypercortisolism was positive by both low-dose overnight dexamethasone suppression testing and 24-hour urinary free cortisol measurement. Plasma ACTH values confirmed ACTH-dependent Cushing syndrome. High-dose dexamethasone suppression testing was suggestive of ectopic ACTH syndrome. Inferior petrosal sinus sampling demonstrated no central-to-peripheral gradient, and 68Ga-DOTATATE scanning revealed an avid 1.2-cm left lung lesion. The suspected source of ectopic ACTH was resected and confirmed by histopathology, resulting in surgical cure. While many patients with Cushing syndrome have a delayed diagnosis, this case highlights the critical need to increase awareness of the signs and symptoms of hypercortisolism and to improve the understanding of appropriate screening tests among nonendocrine providers.

Association of Premorbid GLP-1RA and SGLT-2i Prescription Alone and in Combination with COVID-19 Severity.

INTRODUCTION: People with type 2 diabetes are at heightened risk for severe outcomes related to COVID-19 infection, including hospitalization, intensive care unit admission, and mortality. This study was designed to examine the impact of premorbid use of glucagon-like peptide-1 receptor agonist (GLP-1RA) monotherapy, sodium-glucose cotransporter-2 inhibitor (SGLT-2i) monotherapy, and concomitant GLP1-RA/SGLT-2i therapy on the severity of outcomes in individuals with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. METHODS: Utilizing observational data from the National COVID Cohort Collaborative through September 2022, we compared outcomes in 78,806 individuals with a prescription of GLP-1RA and SGLT-2i versus a prescription of dipeptidyl peptidase 4 inhibitors (DPP-4i) within 24 months of a positive SARS-CoV-2 PCR test. We also compared concomitant GLP-1RA/SGLT-2i therapy to GLP-1RA and SGLT-2i monotherapy. The primary outcome was 60-day mortality, measured from the positive test date. Secondary outcomes included emergency room (ER) visits, hospitalization, and mechanical ventilation within 14 days. Using a super learner approach and accounting for baseline characteristics, associations were quantified with odds ratios (OR) estimated with targeted maximum likelihood estimation (TMLE). RESULTS: Use of GLP-1RA (OR 0.64, 95% confidence interval [CI] 0.56-0.72) and SGLT-2i (OR 0.62, 95% CI 0.57-0.68) were associated with lower odds of 60-day mortality compared to DPP-4i use. Additionally, the OR of ER visits and hospitalizations were similarly reduced with GLP1-RA and SGLT-2i use. Concomitant GLP-1RA/SGLT-2i use showed similar odds of 60-day mortality when compared to GLP-1RA or SGLT-2i use alone (OR 0.92, 95% CI 0.81-1.05 and OR 0.88, 95% CI 0.76-1.01, respectively). However, lower OR of all secondary outcomes were associated with concomitant GLP-1RA/SGLT-2i use when compared to SGLT-2i use alone. CONCLUSION: Among adults who tested positive for SARS-CoV-2, premorbid use of either GLP-1RA or SGLT-2i is associated with lower odds of mortality compared to DPP-4i. Furthermore, concomitant use of GLP-1RA and SGLT-2i is linked to lower odds of other severe COVID-19 outcomes, including ER visits, hospitalizations, and mechanical ventilation, compared to SGLT-2i use alone. Graphical abstract available for this article.

The Multifaceted Role of STAT3 in NK-Cell Tumor Surveillance.

Signal transducer and activator of transcription 3 (STAT3) is a member of the Janus kinase (JAK)-STAT pathway, which is one of the key pathways contributing to cancer. STAT3 regulates transcription downstream of many cytokines including interleukin (IL)-6 and IL-10. In cancer, STAT3 is mainly described as a tumor promoter driving tumor cell proliferation, resistance to apoptosis, angiogenesis and metastasis and aberrant activation of STAT3 is associated with poor prognosis. STAT3 is also an important driver of immune evasion. Among many other immunosuppressive mechanisms, STAT3 aids tumor cells to escape natural killer (NK) cell-mediated immune surveillance. NK cells are innate lymphocytes, which can directly kill malignant cells but also regulate adaptive immune responses and contribute to the composition of the tumor microenvironment. The inborn ability to lyse transformed cells renders NK cells an attractive tool for cancer immunotherapy. Here, we provide an overview of the role of STAT3 in the dynamic interplay between NK cells and tumor cells. On the one hand, we summarize the current knowledge on how tumor cell-intrinsic STAT3 drives the evasion from NK cells. On the other hand, we describe the multiple functions of STAT3 in regulating NK-cell cytotoxicity, cytokine production and their anti-tumor responses in vivo. In light of the ongoing research on STAT3 inhibitors, we also discuss how targeting STAT3 would affect the two arms of STAT3-dependent regulation of NK cell-mediated anti-tumor immunity. Understanding the complexity of this interplay in the tumor microenvironment is crucial for future implementation of NK cell-based immunotherapies.

Untwining Anti-Tumor and Immunosuppressive Effects of JAK Inhibitors-A Strategy for Hematological Malignancies?

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway propagates signals from a variety of cytokines, contributing to cellular responses in health and disease. Gain of function mutations in JAKs or STATs are associated with malignancies, with JAK2V617F being the main driver mutation in myeloproliferative neoplasms (MPN). Therefore, inhibition of this pathway is an attractive therapeutic strategy for different types of cancer. Numerous JAK inhibitors (JAKinibs) have entered clinical trials, including the JAK1/2 inhibitor Ruxolitinib approved for the treatment of MPN. Importantly, loss of function mutations in JAK-STAT members are a cause of immune suppression or deficiencies. MPN patients undergoing Ruxolitinib treatment are more susceptible to infections and secondary malignancies. This highlights the suppressive effects of JAKinibs on immune responses, which renders them successful in the treatment of autoimmune diseases but potentially detrimental for cancer patients. Here, we review the current knowledge on the effects of JAKinibs on immune cells in the context of hematological malignancies. Furthermore, we discuss the potential use of JAKinibs for the treatment of diseases in which lymphocytes are the source of malignancies. In summary, this review underlines the necessity of a robust immune profiling to provide the best benefit for JAKinib-treated patients.

T Cell-Intrinsic CDK6 Is Dispensable for Anti-Viral and Anti-Tumor Responses In Vivo.

The cyclin-dependent kinase 6 (CDK6) regulates the transition through the G1-phase of the cell cycle, but also acts as a transcriptional regulator. As such CDK6 regulates cell survival or cytokine secretion together with STATs, AP-1 or NF-κB. In the hematopoietic system, CDK6 regulates T cell development and promotes leukemia and lymphoma. CDK4/6 kinase inhibitors are FDA approved for treatment of breast cancer patients and have been reported to enhance T cell-mediated anti-tumor immunity. The involvement of CDK6 in T cell functions remains enigmatic. We here investigated the role of CDK6 in CD8+ T cells, using previously generated CDK6 knockout (Cdk6-/-) and kinase-dead mutant CDK6 (Cdk6K43M) knock-in mice. RNA-seq analysis indicated a role of CDK6 in T cell metabolism and interferon (IFN) signaling. To investigate whether these CDK6 functions are T cell-intrinsic, we generated a T cell-specific CDK6 knockout mouse model (Cdk6fl/fl CD4-Cre). T cell-intrinsic loss of CDK6 enhanced mitochondrial respiration in CD8+ T cells, but did not impact on cytotoxicity and production of the effector cytokines IFN-γ and TNF-α by CD8+ T cells in vitro. Loss of CDK6 in peripheral T cells did not affect tumor surveillance of MC38 tumors in vivo. Similarly, while we observed an impaired induction of early responses to type I IFN in CDK6-deficient CD8+ T cells, we failed to observe any differences in the response to LCMV infection upon T cell-intrinsic loss of CDK6 in vivo. This apparent contradiction might at least partially be explained by the reduced expression of Socs1, a negative regulator of IFN signaling, in CDK6-deficient CD8+ T cells. Therefore, our data are in line with a dual role of CDK6 in IFN signaling; while CDK6 promotes early IFN responses, it is also involved in the induction of a negative feedback loop. These data assign CDK6 a role in the fine-tuning of cytokine responses.

A Genome-Wide CRISPR/Cas9-Based Screen Identifies Heparan Sulfate Proteoglycans as Ligands of Killer-Cell Immunoglobulin-Like Receptors.

While human leukocyte antigen (HLA) and HLA-like proteins comprise an overwhelming majority of known ligands for NK-cell receptors, the interactions of NK-cell receptors with non-conventional ligands, particularly carbohydrate antigens, is less well described. We previously found through a bead-based HLA screen that KIR3DS1, a formerly orphan member of the killer-cell immunoglobulin-like receptor (KIR) family, binds to HLA-F. In this study, we assessed the ligand binding profile of KIR3DS1 to cell lines using Fc fusion constructs, and discovered that KIR3DS1-Fc exhibited binding to several human cell lines including ones devoid of HLA. To identify these non-HLA ligands, we developed a magnetic enrichment-based genome-wide CRISPR/Cas9 knock-out screen approach, and identified enzymes involved in the biosynthesis of heparan sulfate as crucial for the binding of KIR3DS1-Fc to K562 cells. This interaction between KIR3DS1 and heparan sulfate was confirmed via surface plasmon resonance, and removal of heparan sulfate proteoglycans from cell surfaces abolished KIR3DS1-Fc binding. Testing of additional KIR-Fc constructs demonstrated that KIR family members containing a D0 domain (KIR3DS1, KIR3DL1, KIR3DL2, KIR2DL4, and KIR2DL5) bound to heparan sulfate, while those without a D0 domain (KIR2DL1, KIR2DL2, KIR2DL3, and KIR2DS4) did not. Overall, this study demonstrates the use of a genome-wide CRISPR/Cas9 knock-out strategy to unbiasedly identify unconventional ligands of NK-cell receptors. Furthermore, we uncover a previously underrecognized binding of various activating and inhibitory KIRs to heparan sulfate proteoglycans that may play a role in NK-cell receptor signaling and target-cell recognition.

Hemoglobin glycation index, calculated from a single fasting glucose value, as a prediction tool for severe hypoglycemia and major adverse cardiovascular events in DEVOTE.

INTRODUCTION: Hemoglobin glycation index (HGI) is the difference between observed and predicted glycated hemoglobin A1c (HbA1c), derived from mean or fasting plasma glucose (FPG). In this secondary, exploratory analysis of data from DEVOTE, we examined: whether insulin initiation/titration affected the HGI; the relationship between baseline HGI tertile and cardiovascular and hypoglycemia risk; and the relative strengths of HGI and HbA1c in predicting these risks. RESEARCH DESIGN AND METHODS: In DEVOTE, a randomized, double-blind, cardiovascular outcomes trial, people with type 2 diabetes received once per day insulin degludec or insulin glargine 100 units/mL. The primary outcome was time to first occurrence of a major adverse cardiovascular event (MACE), comprising cardiovascular death, myocardial infarction or stroke; severe hypoglycemia was a secondary outcome. In these analyses, predicted HbA1c was calculated using a linear regression equation based on DEVOTE data (HbA1c=0.01313 FPG (mg/dL) (single value)+6.17514), and the population data were grouped into HGI tertiles based on the calculated HGI values. The distributions of time to first event were compared using Kaplan-Meier curves; HRs and 95% CIs were determined by Cox regression models comparing risk of MACE and severe hypoglycemia between tertiles. RESULTS: Changes in HGI were observed at 12 months after insulin initiation and stabilized by 24 months for the whole cohort and insulin-naive patients. There were significant differences in MACE risk between baseline HGI tertiles; participants with high HGI were at highest risk (low vs high, HR: 0.73 (0.61 to 0.87)95% CI; moderate vs high, HR: 0.67 (0.56 to 0.81)95% CI; p<0.0001). No significant differences between HGI tertiles were observed in the risk of severe hypoglycemia (p=0.0911). With HbA1c included within the model, HGI no longer significantly predicted MACE. CONCLUSIONS: High HGI was associated with a higher risk of MACE; this finding is of uncertain significance given the association of HGI with insulin initiation and HbA1c. TRIAL REGISTRATION NUMBER: NCT01959529.

Carbohydrate Intake Prior to Oral Glucose Tolerance Testing.

With the emergence of glycated hemoglobin as a diagnostic test for diabetes, oral glucose tolerance tests (OGTTs) have become rare in endocrinology practice. As they have moved out of favor, the importance of patient instructions on preparation prior to OGTT has faded from memory. Decades-old literature, well-known to endocrinologists a generation ago, emphasized the importance of carbohydrate intake prior to OGTT. In this expert endocrine consult, we discuss an OGTT performed in a research setting without adequate carbohydrate intake at the evening meal prior to the OGTT. The resultant elevated plasma glucose levels at 1-hour and 2-hours mimicked the loss of first-phase insulin release seen in early type 1 and type 2 diabetes. With clinical concern that the research participant had evolving type 1 or type 2 diabetes, the volunteer was subjected to additional testing and experienced anxiety. Repeat OGTT was normal after adequate carbohydrate intake (>150 grams/day and >50 grams the evening prior to overnight fast for the study). The physiology of this phenomenon is explored and is likely mediated through beta cell adaptation and alteration in peripheral glucose uptake in response to nutrient exposure. The learnings of decades ago have clearly faded, and this literature should be revisited to ensure that OGTT results are not compromised when ordered for clinical or research purposes.

The SimpliciT1 Study: A Randomized, Double-Blind, Placebo-Controlled Phase 1b/2 Adaptive Study of TTP399, a Hepatoselective Glucokinase Activator, for Adjunctive Treatment of Type 1 Diabetes.

OBJECTIVE: Despite advances in exogenous insulin therapy, many patients with type 1 diabetes do not achieve acceptable glycemic control and remain at risk for ketosis and insulin-induced hypoglycemia. We conducted a randomized controlled trial to determine whether TTP399, a novel hepatoselective glucokinase activator, improved glycemic control in people with type 1 diabetes without increasing hypoglycemia or ketosis. RESEARCH DESIGN AND METHODS: SimpliciT1 was a phase 1b/2 adaptive study. Phase 2 activities were conducted in two parts. Part 1 randomly assigned 20 participants using continuous glucose monitors and continuous subcutaneous insulin infusion (CSII). Part 2 randomly assigned 85 participants receiving multiple daily injections of insulin or CSII. In both parts 1 and 2, participants were randomly assigned to 800 mg TTP399 or matched placebo (fully blinded) and treated for 12 weeks. The primary end point was change in HbA1c from baseline to week 12. RESULTS: The difference in change in HbA1c from baseline to week 12 between TTP399 and placebo was -0.7% (95% CI -1.3, -0.07) in part 1 and -0.21% (95% CI -0.39, -0.04) in part 2. Despite a greater decrease in HbA1c with TTP399, the frequency of severe or symptomatic hypoglycemia decreased by 40% relative to placebo in part 2. In both parts 1 and 2, plasma ß-hydroxybutyrate and urinary ketones were lower during treatment with TTP399 than placebo. CONCLUSIONS: TTP399 lowers HbA1c and reduces hypoglycemia without increasing the risk of ketosis and should be further evaluated as an adjunctive therapy for the treatment of type 1 diabetes.