Type 2 diabetes (T2D) is associated with defective insulin secretion, which in turn contributes to worsening glycaemic control and disease progression. The genetic cause(s) associated with impaired insulin secretion in T2D are not well elucidated. Here we used the polygenic New Zealand Obese (NZO) mouse model, which displays all the cardinal features of T2D including hyperglycaemia to identify genes associated with b-cell dysfunction. A genomewide scan identified a major quantitative trait locus (QTL) on chromosome 7 associated with defective glucose-mediated insulin secretion. Using congenic strains, the locus was narrowed to two candidate genes encoding the components of the KATP channel: Abcc8 (SUR1) and Kcnj11 (Kir6.2). The NZO Abcc8 allele was associated with a w211 bp deletion in its transcript and reduced expression of SUR1. Transgenic NZO mice were generated that expressed the WT Abcc8/Kcnj11 genes and displayed significant improvements in early-phase glucosemediated insulin secretion and glucose tolerance, confirming Abcc8 as a causative gene. Importantly, we showed that despite improving b-cell function in the NZO transgenic mice, there was no enhancement of insulin sensitivity or body weight. This study provides evidence for a role of Abcc8 in early-phase glucose-mediated insulin secretion and validates this gene as a contributor to b-cell dysfunction in T2D.
OBJECTIVE:The extent to which leptin protects against obesity is unknown. By intercrossing New Zealand obese mice with lean C57BLa6J mice, we have separated the genes controlling leptin and other weight-related phenotypes. This has allowed us to determine whether hyperleptinaemia is associated with reduced food intake and increased physical activity in mice spanning a large range in body weight. METHODS: Plasma leptin, glucose and insulin, body weight, food intake, running wheel activity, and four adipose depots were measured in 587 adult F2 and backcross mice RESULTS: When mice were categorized by adiposity, a plot of food intake vs leptin illustrated a U-shaped curve. Food intake decreased as leptin levels rose to $15 ngaml, beyond which the relationship reversed. A negative relationship was observed between activity and leptin with a maximal decrease in activity once leptin reached $15 ngaml. CONCLUSION: Leptin has differential responses to food intake and activity, suggesting that it has limited potential to defend against obesity. A genetic defect in leptin sensitivity is unlikely to be the primary cause of obesity in these mice, since hyperleptinaemia was not coinherited with both hyperphagia and inactivity as body weight increased.
e20637 Background: Carboplatin, etoposide, and atezolizumab (PEA) is the most widely used combination for first-line treatment of extensive-stage small cell lung cancer (ES-SCLC). Chemotherapy-induced myelosuppression is a common sequalae that is traditionally managed with lineage-specific supportive care modalities. Studies that evaluated trilaciclib versus placebo in combination with chemotherapy demonstrated statistically significant improvements in the duration of severe neutropenia (SN), defined as ANC < 500 cells/µL, in cycle 1 and incidence of SN as a result of its transient myeloprotective effects. There remains considerable controversy in the adoption of trilaciclib as a supportive medication in clinical practice. The objective of this quality assessment study was to assess utility of trilaciclib in real-world ES-SCLC patients. Methods: This was a single center study with quasi-experimental design comparing patients with confirmed ES-SCLC who received trilaciclib + PEA (PEAT) from April 2021 to July 2022 versus those who received PEA without trilaciclib (PEA) from February 2020 to February 2021. Patients with limited-stage SCLC, prior treatment with immunotherapies, carboplatin dose AUC < 3.5 with cycle 1, and active clinical trial enrollment were excluded. The primary endpoint evaluated was incidence of SN after cycle 1 and during treatment period. Additional measures related to myelopreservation and patient outcomes were assessed as secondary endpoints. Demographic data was analyzed using descriptive statistics. Dichotomous and continuous variables were compared by Mann-Whitney U or one-sided Fisher’s exact test. Progression-free survival (PFS) and overall survival (OS) were evaluated by Kaplan-Meier (KM) estimate. Results: 34 patients received PEAT and 44 patients received PEA. Demographic and baseline clinical characteristics were similar between both cohorts except for older median age of patients (69 years old vs 64 years old) and higher proportion of male patients (65% vs 39%) in the trilaciclib cohort. Even though there was a numerically lower rate of SN (3%) and hospitalization due to febrile neutropenia (FN) or infection (6%) in the PEAT versus the PEA (18%;11%) cohort, statistical significance was not met (p = 0.07;p = 0.065). Likewise, incidence of FN, platelet transfusion requirements, all-cause chemotherapy reductions, and treatment delays were not statistically different. However, the PEAT cohort as compared to PEA experienced a statistically significant reduction in red blood cell transfusion requirements (3% vs 23%; p = 0.02) and grade 3-4 anemia (6% vs 25%; p = 0.03). PFS and OS between the two cohorts were not statistically different. Conclusions: Based on this single center retrospective study, use of trilaciclib appears to confer improvement in the safety profile of PEA without negatively impacting survival outcomes. Therefore, results of this study support the integration of trilaciclib with PEA for ES-SCLC.
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