Applicability of the UK DCD risk score in the modern era of liver transplantation: A U.S. update.

BACKGROUND: Careful graft and recipient selection have resulted in improved outcomes in liver transplantation (LT) using donation after cardiac death (DCD) organs. The UK DCD Risk Score was established as a risk stratification tool to guide selection. METHODS: We evaluated the applicability of the UK DCD Risk Score in a contemporary US cohort of adult DCD LT recipients using the United Network for Organ Sharing registry (2011-2020). RESULTS: A total of 3,899 DCD LTs were included in our study (UK DCD Risk Score 0-5 points: 1,438 [36.9%], 6-10 points: 2,034 [52.2%]; 11-20 points: 427 [11.0%]). Compared to a score of 6-10 points, a score of 0-5 points was associated with decreased risk of graft loss (HR = .79, 95%CI: .68-.93, p = .004), while a score of 11-20 points was associated with increased risk of graft loss (HR = 1.26, 95%CI: 1.01-1.56, p = .04). The 5-year graft survival for patients with risk scores of 0-5, 6-10, and 11-20 were 75.9%, 71.8%, and 66.5%, respectively. The C-statistic for the UK DCD Risk Score in our contemporary cohort was .611. CONCLUSIONS: The UK DCD Risk Score demonstrates a more limited ability to differentiate recipient outcomes in the modern era of DCD LT in the US. Acceptable long-term outcomes are achievable for patients stratified to the highest-risk group.

Waitlist mortality and post-liver transplant outcomes of pediatric patients with hepatocellular carcinoma and hepatoblastoma in the United States.

BACKGROUND: Liver transplantation (LT) is offered in cases of advanced disease for both pediatric patients with hepatoblastoma (HBL) and those with hepatocellular carcinoma (HCC). Current United States organ allocation priorities differ between the two groups. METHODS: We retrospectively examined the waitlist and posttransplant outcomes of pediatric LT candidates with HBL and HCC using the United Network for Organ Sharing registry (February 2002 to September 2020). RESULTS: Six hundred sixty-eight children with HBL and 95 children with HCC listed for first LT were identified. Patients with HBL were younger (p < .001), had lower laboratory Model for End-stage Liver Disease (MELD)/Pediatric End-stage Liver Disease (PELD) scores (p < .001), and had lesser proportion with encephalopathy (p = .01). Patients with HCC had an increased risk of waitlist mortality in univariable (unadjusted subdistribution hazard ratio [sHR] = 4.37, 95% confidence interval [CI], 2.01-9.51, p < .001) and multivariable competing risk regression (adjusted sHR = 3.08, 95% CI 1.13-8.37, p = .03) accounting for age and laboratory MELD/PELD score. Five hundred ninety-five children underwent LT for HBL and 76 for HCC. Patients transplanted for HBL had a significantly higher proportion with status 1B exception (71.3% vs. 7.9%, p < .001). No difference was observed in patient (unadjusted log-rank test, p = .52; adjusted hazard ratio [HR] = 0.77, 95% CI, 0.40-1.48, p = .43) or graft survival (unadjusted log-rank test, p = .93; adjusted HR = 0.74, 95% CI 0.42-1.33, p = .32) between HCC and HBL recipients. CONCLUSION: Waitlist mortality for pediatric LT candidates with HCC is significantly higher than for HBL, while posttransplant patient and graft survival are similar. This highlights an opportunity to improve equitable prioritization for children with HCC who may have reduced access to size-appropriate deceased donor organs and less effective bridge-to-transplant therapies.

Liver Transplantation for Langerhans Cell Histiocytosis: A US Population-Based Analysis and Systematic Review of the Literature.

Langerhans cell histiocytosis (LCH) is the most common histiocytic disorder. Liver involvement is seen in 10.1% to 19.8% of patients with LCH and can lead to secondary sclerosing cholangitis requiring liver transplantation (LT). We describe the characteristics and outcomes of patients undergoing LT for LCH. All patients undergoing a first LT for LCH in the United States were identified in the Scientific Registry of Transplant Recipients (SRTR) database (1987-2018). The Kaplan-Meier curve method and log-rank tests evaluated post-LT survival. A systematic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement. A total of 60 LCH LT recipients were identified in the SRTR, and 55 patients (91.7%) were children with median total bilirubin levels at LT of 5.8 mg/dL (interquartile range [IQR], 2.7-12.9). A total of 49 patients (81.7%) underwent deceased donor LT (DDLT). The 1-year, 3-year, and 5-year patient survival rates were 86.6%, 82.4%, and 82.4%, respectively. The systematic review yielded 26 articles reporting on 50 patients. Of the patients, 41 were children (82.0%), 90.0% had multisystem LCH, and most patients underwent DDLT (91.9%; n = 34/37). Pre-LT chemotherapy was administered in 74.0% and steroids in 71.7% (n = 33/46) of the patients, and a recurrence of LCH to the liver was reported in 8.0% of the patients. Of the 50 patients, 11 (22.0%) died during a median follow-up of 25.2 months (IQR, 9.0-51.6), and the 1-year patient survival rate was 79.4%. LT can be considered as a feasible life-saving option for the management of liver failure secondary to LCH in well-selected patients.

Liver Transplantation in Children with Urea Cycle Disorders: The Importance of Minimizing Waiting Time.

Liver transplantation (LT) for children with urea cycle disorders (UCDs) is capable of correcting the enzymatic defect and preventing progressive neurologic injury. We describe the characteristics and outcomes of pediatric LT recipients with UCDs. We identified all pediatric (<18 years) LT candidates with UCDs in the United Network for Organ Sharing (UNOS) database (February 2002 to September 2020). Multivariable Cox and logistic regression were used to determine risk factors for graft loss and cognitive delay, respectively. Of 424 patients, 1.9% (8/424) experienced waitlist mortality and 95.0% underwent LT (403/424). The most frequently encountered UCDs in our cohort were ornithine transcarbamylase deficiency (46.2%), citrullinemia (20.3%), and argininosuccinic aciduria (ASA; 12.9%). The 1-, 3-, and 5-year graft survival rates were 90.4%, 86.3%, and 85.2%, respectively. Multivariable analysis showed a decreased risk of graft loss with increasing weight at LT (adjusted hazard ratio [aHR], 0.96; 95% confidence interval [CI], 0.94-0.99; P = 0.02), male sex (aHR, 0.49; 95% CI, 0.28-0.85; P = 0.01), and ASA diagnosis (aHR, 0.29; 95% CI, 0.09-0.98; P = 0.047), when adjusting for location (intensive care/hospital/home) and graft type (both P ≥ 0.65). In multivariable logistic regression, waitlist time (adjusted odds ratio [aOR], 1.10; 95% CI, 1.02-1.17; P = 0.009) and male sex (aOR, 1.71; 95% CI, 1.02-2.88; P = 0.04) were associated with increased odds of long-term cognitive delay. Waitlist duration is associated with a long-term risk of cognitive delay. Given excellent long-term outcomes, early LT evaluation should be considered in all children with UCDs to prevent progressive neurologic injury and optimize cognitive outcomes.

Adult Combined Heart-Liver Transplantation: The United States Experience.

Background: We aimed to review the indications and outcomes of adults undergoing combined heart-liver transplantation (CHLT) in the US using national registry data. Methods: Adult (≥18 years) CHLT recipients in the United Network for Organ Sharing database were included (09/1987-09/2020; era 1 = 1989-2000, era 2 = 2001-2010, era 3 = 2011-2020). Survival analysis was conducted by means of Kaplan-Meier method, log-rank test, and Cox regression. Results: We identified 369 adults receiving CHLT between 12/1989-08/2020. The number of adult CHLT recipients (R2 = 0.75, p < 0.001) and centers performing CHLT (R2 = 0.80, p < 0.001) have increased over the study period. The most common cardiac diagnosis in the first two eras was restrictive/infiltrative cardiomyopathy, while the most common in era 3 was congenital heart disease (p = 0.03). The 1-, 3-, and 5-years patient survival was 86.8, 80.1, and 77.9%, respectively. In multivariable analysis, recipient diabetes [adjusted hazard ratio (aHR) = 2.35, 95% CI: 1.23-4.48], CHLT between 1989-2000 compared with 2011-2020 (aHR = 5.00, 95% CI: 1.13-22.26), and sequential-liver first CHLT compared with sequential-heart first CHLT (aHR = 2.44, 95% CI: 1.15-5.18) were associated with increased risk of mortality. Higher left ventricular ejection fraction was associated with decreased risk of mortality (aHR = 0.96, 95% CI: 0.92-0.99). Conclusion: CHLT is being increasingly performed with evolving indications. Excellent outcomes can be achieved with multidisciplinary patient and donor selection and surgical planning.

Abdominal Aortic Aneurysm Repair Requiring Left-Sided Inferior Vena Cava Interposition.

BACKGROUND: Left-sided inferior vena cava (IVC) is a rare congenital venous anomaly. We describe a case of open repair of a nonruptured abdominal aortic aneurysm (AAA) in a patient with left-sided inferior vena cava requiring IVC transection and reconstruction with interposition graft. CASE REPORT: A 56-year-old man presented for elective repair of a 6.2-cm AAA with preoperative imaging demonstrating a left-sided IVC. Intraoperatively, IVC crossing at the aneurysm neck conferred inadequate exposure for arterial anastomosis. After transection of the IVC, the AAA was repaired, and the IVC was reconstructed with a 24-mm Dacron tube graft. His recovery was uneventful, and grafts were patent at 3-month follow-up. CONCLUSIONS: Left-sided IVC is a rare anomaly encountered during abdominal aortic surgery that presents technical challenges. Division of the IVC and reconstruction with interposition graft is a possible solution if other techniques fail to provide adequate exposure.

Documentation of HEART score discordance between emergency physician and cardiologist evaluations of ED patients with chest pain.

INTRODUCTION: A triage cardiology program, in which cardiologists provide consultation to the Emergency Department (ED), may safely reduce admissions. For patients with chest pain, the HEART Pathway may obviate the need for cardiology involvement, unless there is a difference between ED and cardiology assessments. Therefore, in a cohort concurrently evaluated by both specialties, we analyzed discordance between ED and cardiology HEART scores. METHODS: We performed a single-center, cross-sectional, retrospective study of adults presenting to the ED with chest pain who had a documented bedside evaluation by a triage cardiologist. Separate ED and cardiology HEART scores were computed based on documentation by the respective physicians. Discrepancies in HEART score between ED physicians and cardiologists were quantified using Cohen κ coefficient. RESULTS: Thirty-three patients underwent concurrent ED physician and cardiologist evaluation. Twenty-three patients (70%) had discordant HEART scores (κ = 0.13; 95% confidence interval, -0.02 to 0.32). Discrepancies in the description of patients' chest pain were the most common source of discordance and were present in more than 50% of cases. HEART scores calculated by ED physicians tended to overestimate the scores calculated by cardiologists. When categorized into low-risk or high-risk by the HEART Pathway, more than 25% of patients were classified as high risk by the ED physician, but low risk by the cardiologist. CONCLUSION: There is substantial discordance in HEART scores between ED physicians and cardiologists. A triage cardiology system may help refine risk stratification of patients presenting to the ED with chest pain, even when the HEART Pathway tool is used.

Delayed graft function and the risk of acute rejection in the modern era of kidney transplantation.

Delayed graft function (DGF) is commonly considered a risk factor for acute rejection, although this finding has not been uniformly observed across all studies. The link between DGF and acute rejection may have changed over time due to advances in immunosuppression and medical management. Here we conducted a cohort study of 645 patients over 12 years to evaluate the association of DGF and biopsy-proven acute rejection (BPAR) in a modern cohort of kidney transplant recipients. DGF was defined as the need for at least one dialysis session in the first week after kidney transplantation. The 1-, 3-, and 5-year cumulative probabilities of BPAR were 16.0, 21.8, and 22.6% in the DGF group, significantly different from the 10.1, 12.4, and 15.7% in the non-DGF group. In multivariable Cox proportional hazards model, the adjusted relative hazard for BPAR in DGF (vs. no DGF) was 1.55 (95% confidence interval (CI): 1.03, 2.32). This association was generally robust to different definitions of DGF. The relative hazard was also similarly elevated for T-cell- or antibody-mediated BPAR (1.52 (0.92, 2.51) and 1.54 (0.85, 2.77), respectively). Finally, the association was consistent across clinically relevant subgroups. Thus DGF remains an important risk factor for BPAR in a contemporary cohort of kidney transplant recipients. Interventions to reduce the risk of DGF and/or its aftereffects remain of paramount importance to improve kidney transplant outcomes.

Risk-benefit analysis of lumbar puncture to evaluate for nontraumatic subarachnoid hemorrhage in adult ED patients.

OBJECTIVE: The objective of the study is to compare the risks and benefits of lumbar puncture (LP) to evaluate for subarachnoid hemorrhage (SAH) after a normal head computed tomographic (CT) scan. METHODS: This was an observational study of adult emergency department patients at a single hospital who presented with headache and underwent LP after a normal head CT to evaluate for SAH. Lumbar puncture results classified as indicating a SAH included xanthochromia in cerebrospinal fluid (CSF) or red blood cells in the final tube of CSF with an aneurysm or arteriovenous malformation on cerebral angiography. An LP-related complication was defined as hospitalization or a return visit due to symptoms attributed to the LP. Proportions of the study patients who had SAH diagnosed by LP and who experienced an LP-related complication were compared. RESULTS: The study included 302 patients, including 2 (0.66%) who were diagnosed with SAH based on LP (number needed to diagnose, 151); both of these patients had a known intracranial aneurysm. Eighteen (5.96%) patients experienced an LP-related complication (P < .01 compared with number with SAH diagnosed; number needed to harm, 17). Complications included 12 patients with low-pressure headaches, 4 with pain at the LP site, and 2 with contaminated CSF cultures. CONCLUSION: The yield of LP for diagnosing SAH in adults with nontraumatic headache after a normal head CT was very low. The severity of LP-related complications was low, but complications were more common than SAH diagnoses. Lumbar puncture may not be advisable after a normal head CT to evaluate for SAH, particularly in patients with low-risk clinical features for SAH.

Large animal preclinical investigation into the optimal extracorporeal life support configuration for pulmonary hypertension and right ventricular failure.

INTRODUCTION: Right ventricular failure (RVF) is a major cause of mortality in pulmonary hypertension (PH). Mechanical circulatory support holds promise for patients with medically refractory PH, but there are no clinical devices for long-term right ventricular (RV) support. Investigations into optimal device parameters and circuit configurations for PH-induced RVF (PH-RVF) are needed. METHODS: Eleven sheep underwent previously published chronic PH model. We then evaluated a low-profile, ventricular assist device (VAD)-quality pump combined with a novel low-resistance membrane oxygenator (Pulmonary Assist Device, PAD) under one of four central cannulation strategies: right atrium-to-left atrium (RA-LA, N = 3), RA-to-pulmonary artery (RA-PA, N=3), pumpless pulmonary artery-to-left atrium (PA-LA, N = 2), and RA-to-ascending aorta (RA-Ao, N = 3). Acute-on-chronic RVF (AoC RVF) was induced, and mechanical support was provided for up to 6 hours at blood flow rates of 1 to 3 liter/min. Circuit parameters, physiologic, hemodynamic, and echocardiography data were collected. RESULTS: The RA-LA configuration achieved blood flow of 3 liter/min. Meanwhile, RA-PA and RA-Ao faced challenges maintaining 3 liter/min of flow due to higher circuit afterload. Pumpless PA-LA was flow-limited due to anatomical limitations inherent to this animal model. RA-LA and RA-Ao demonstrated serial RV unloading with increasing circuit flow, while RA-PA did not. RA-LA also improved left ventricular (LV) and septal geometry by echocardiographic assessment and had the lowest inotropic dependence. CONCLUSION: RA-LA and RA-Ao configurations unload the RV, while RA-LA also lowers pump speed and inotropic requirements, and improves LV mechanics. RA-PA provide inferior support for PH-RVF, while an alternate animal model is needed to evaluate PA-LA.

Extracorporeal membrane oxygenation in patients with hepatopulmonary syndrome undergoing liver transplantation: A systematic review of the literature.

BACKGROUND: Isolated cases of extracorporeal membrane oxygenation (ECMO) in patients with hepatopulmonary syndrome (HPS) undergoing liver transplantation (LT) have been reported with increasing frequency. We aimed to systemically review and synthesize the available literature on ECMO use in this population. METHODS: A systematic literature review of the PubMed, Web of Science, Cochrane Library, and Embase databases (end-of-search date: November 14, 2021) was conducted in accordance with the PRISMA statement. Eligible studies presented clinical parameters and outcomes of adult or pediatric patients with HPS receiving ECMO support at the time of, or following, LT. RESULTS: Sixteen studies from 4 continents reporting on 17 patients who were initiated on ECMO prior to (n = 2), during (n = 1) or after LT (n = 14) were included. Nine of the 16 studies were published between 2019 and 2021. The median pre-LT PaO2 was 38.0 mmHg (IQR 35.0-52.0). The median time from LT to ECMO initiation was 7 days (IQR, 3-12). Six patients (50%, n = 6 of 12) were extubated post-LT, before deterioration, development of refractory hypoxemia, and initiation of ECMO. Most patients were cannulated with a venovenous configuration (75%, n = 12 of 16). Most patients cannulated with a venoarterial or veno-arterial-venous strategy (75%, n = 3 of 4) had concurrent hemodynamic instability. The median total time on ECMO was 13 days (IQR 10-29). Using linear regression, for patients cannulated postoperatively, each day between LT and ECMO initiation was associated with a 3.5-day increase in total ECMO duration (95%CI: 2.23-4.73, p < 0.001, R2 = 73.7%). The median postoperative intensive care unit length of stay was 40 days (IQR, 37-61) and hospital length of stay was 59.5 days (IQR 42-77). 82.4% of patients (14 of 17) survived to discharge. CONCLUSIONS: ECMO is feasible in patients with HPS undergoing LT and appears to be associated with better outcomes compared to other causes of cardiopulmonary failure in LT patients. As the volume of experience grows, ECMO may become a central part of perioperative support in LT patients with severe HPS.

Acute Normovolemic Hemodilution-assisted Terminal Blood Procurement in Swine for Ex Vivo Organ Perfusion.

Swine (Sus scrofa domesticus) are commonly used large animal subjects for the study of disease and preclinical therapies. Organ machine perfusion is a therapy that has gained momentum as a research platform for the study of ex vivo organ preservation and therapeutics. However, complex perfusion circuits and research protocols often require large volumes of blood as perfusate. Here, we report a technique for increasing terminal blood yield during swine organ and blood procurement; our method involves acute normovolemic hemodilution and exsanguination via the femoral artery. We collected a total of 47 ± 4 mL/kg of blood and 4.3 ± 0.6 g/kg of hemoglobin, representing 73% ± 6% of the estimated blood volume and 64% ± 8% of the total estimated intravascular hemoglobin (n = 4). Neither pH, lactate, nor pO2 levels changed significantly during blood procurement. Acute normovolemic hemodilution is an effective method for increasing RBC and hemoglobin yield during blood procurement in swine.

Progression Toward Decompensated Right Ventricular Failure in the Ovine Pulmonary Hypertension Model.

Decompensated right ventricular failure (RVF) in patients with pulmonary hypertension (PH) is fatal, with limited treatment options. Novel mechanical circulatory support systems have therapeutic potential for RVF, but the development of these devices requires a large animal disease model that replicates the pathophysiology observed in humans. We previously reported an effective disease model of PH in sheep through ligation of the left pulmonary artery (PA) and progressive occlusion of the main PA. Herein, we report a case of acute decompensation with this model of chronic RVF. Gradual PA banding raised the RV pressure (maximum RV systolic/mean pressure = 95 mmHg/56 mmHg). Clinical findings and laboratory serum parameters suggested appropriate physiologic compensation for 7 weeks. However, mixed venous saturation declined precipitously on week 7, and creatinine increased markedly on week 9. By the 10th week, the animal developed dependent, subcutaneous edema. Subsequently, the animal expired during the induction of general anesthesia. Post-mortem evaluation revealed several liters of pleural effusion and ascites, RV dilatation, eccentric RV hypertrophy, and myocardial fibrosis. The presented case supports this model's relevance to the human pathophysiology of RVF secondary to PH and its value in the development of novel devices, therapeutics, and interventions.

A Large Animal Model for Pulmonary Hypertension and Right Ventricular Failure: Left Pulmonary Artery Ligation and Progressive Main Pulmonary Artery Banding in Sheep.

Decompensated right ventricular failure (RVF) in pulmonary hypertension (PH) is fatal, with limited medical treatment options. Developing and testing novel therapeutics for PH requires a clinically relevant large animal model of increased pulmonary vascular resistance and RVF. This manuscript discusses the latest development of the previously published ovine PH-RVF model that utilizes left pulmonary artery (PA) ligation and main PA occlusion. This model of PH-RVF is a versatile platform to control not only the disease severity but also the RV's phenotypic response. Adult sheep (60-80 kg) underwent left PA (LPA) ligation, placement of main PA cuff, and insertion of RV pressure monitor. PA cuff and RV pressure monitor were connected to subcutaneous ports. Subjects underwent progressive PA banding twice per week for 9 weeks with sequential measures of RV pressure, PA cuff pressures, and mixed venous blood gas (SvO2). At the initiation and endpoint of this model, ventricular function and dimensions were assessed using echocardiography. In a representative group of 12 animal subjects, RV mean and systolic pressure increased from 28 ± 5 and 57 ± 7 mmHg at week 1, respectively, to 44 ± 7 and 93 ± 18 mmHg (mean ± standard deviation) by week 9. Echocardiography demonstrated characteristic findings of PH-RVF, notably RV dilation, increased wall thickness, and septal bowing. The longitudinal trend of SvO2 and PA cuff pressure demonstrates that the rate of PA banding can be titrated to elicit varying RV phenotypes. A faster PA banding strategy led to a precipitous decline in SvO2 < 65%, indicating RV decompensation, whereas a slower, more paced strategy led to the maintenance of physiologic SvO2 at 70%-80%. One animal that experienced the accelerated strategy developed several liters of pleural effusion and ascites by week 9. This chronic PH-RVF model provides a valuable tool for studying molecular mechanisms, developing diagnostic biomarkers, and enabling therapeutic innovation to manage RV adaptation and maladaptation from PH.

Management of hepatoblastoma in the United States: Can we do better?

BACKGROUND: Hepatoblastoma is the most common type of liver cancer in children. Refined therapeutic approaches combining risk-adapted chemotherapy along with complete tumor resection has led to improved survival. We aimed to evaluate the current state of management and outcomes for hepatoblastoma in the United States. METHODS: We retrospectively reviewed 794 children (<18 years) with hepatoblastoma from the National Cancer Database (2004-2015). We assessed overall survival by means of Kaplan-Meier method, log-rank tests, and multivariable Cox regression. RESULTS: Median age was 1 year (interquartile range: 0-2) and 170 (21.4%) presented with metastatic disease. Surgical resection was included in the treatment of 614 (77.3%) children (resection in 66.8% and liver transplantation in 10.6%). In the entire cohort, 95.1% of children received chemotherapy. In the surgical cohort, 575 (93.6%) received chemotherapy (34.5% neoadjuvant, 28.7% adjuvant, 30.5% both neoadjuvant and adjuvant). The 5-year overall survival was 76.6% for the entire cohort (no-surgery group: 55.3% vs surgery group: 82.8%). In multivariable analysis for all children, age ≥8 years (P = .009), metastasis (P < .001), surgery only (P = .009), and chemotherapy only (P < .001) were risk factors for mortality. In multivariable analysis for the surgical cohort, metastasis (P = .001), multifocality (P = .02), no chemotherapy (P = .03), and margin-positive resection (P = .02) were risk factors for mortality. CONCLUSION: Excellent long-term overall survival is achievable with a combination of chemotherapy and surgical resection when a negative resection margin is achieved. However, nearly a quarter of children never received surgical treatment, representing a potential opportunity for improvement in care.

High-Fat Diet and Palmitate Alter the Rhythmic Secretion of Glucagon-Like Peptide-1 by the Rodent L-cell.

Secretion of the incretin hormone, glucagon-like peptide-1 (GLP-1), by the intestinal L-cell is rhythmically regulated by an independent molecular clock. However, the impact of factors known to affect the activity of similar cell-autonomous clocks, such as circulating glucocorticoids and high-fat feeding, on GLP-1 secretory patterns remains to be elucidated. Herein the role of the endogenous corticosterone rhythm on the pattern of GLP-1 and insulin nutrient-induced responses was examined in corticosterone pellet-implanted rats. Moreover, the impact of nutrient excess on the time-dependent secretion of both hormones was assessed in rats fed a high-fat, high-sucrose diet. Finally, the effects of the saturated fatty acid, palmitate, on the L-cell molecular clock and GLP-1 secretion were investigated in vitro using murine GLUTag L-cells. Diurnal variations in GLP-1 and insulin nutrient-induced responses were maintained in animals lacking an endogenous corticosterone rhythm, suggesting that glucocorticoids are not the predominant entrainment factor for L-cell rhythmic activity. In addition to hyperglycemia, hyperinsulinemia, insulin resistance, and disorganization of feeding behavior, high-fat high-sucrose-fed rats showed a total abrogation of the diurnal variation in GLP-1 and insulin nutrient-induced responses, with comparable levels of both hormones at the normal peak (5:00 pm) and trough (5:00 am) of their daily pattern. Finally, palmitate incubation induced profound derangements in the rhythmic expression of circadian oscillators in GLUTag L-cells and severely impaired the secretory activity of these cells. Collectively our findings demonstrate that obesogenic diets disrupt the rhythmic activity of the L-cell, partially through a direct effect of specific nutritional components.

Circadian secretion of the intestinal hormone GLP-1 by the rodent L cell.

Peripheral clocks are known to modulate circadian patterns of insulin secretion. GLP-1 is an incretin hormone produced by the intestinal L cell that acts as a link between the gut and pancreatic ß-cell. Herein, we demonstrate the existence of a diurnal rhythm in GLP-1 secretory responses to an oral glucose load in rats, with increased release immediately preceding the normal feeding period. This profile of GLP-1 release correlated with the pattern in insulin secretion, and both rhythms were completely inverted in animals subjected to a 12-h feeding cycle disruption and abolished in rats maintained under constant light conditions. A daily variation in the insulin response to exogenous GLP-1 was also found. Consistent with these in vivo findings, we demonstrated a circadian pattern in the GLP-1 secretory response to different secretagogues in murine GLUTag L cells, as well as in the mRNA levels of several canonical clock genes. Furthermore, significant changes in the expression of several genes were demonstrated by microarray and knockdown of two of them, thyrotroph embryonic factor and protein tyrosine phosphatase 4a1, resulted in altered GLP-1 secretion. Collectively, these results indicate that an independent peripheral clock in the L cell drives a circadian rhythm in GLP-1 secretory responses.