A single-center review of outcomes between COVID-19 vaccinated and unvaccinated liver transplant recipients.

BACKGROUND: With the availability of vaccines against SARS-COV-2, recommendations for vaccination of transplant candidates are widespread. At our institution, patients may receive liver transplant (LTx) regardless of vaccine status. The purpose of this study is to compare post-LTx outcomes between vaccinated (VAX) and unvaccinated (UNVAX) LTx recipients. METHODS: This is a retrospective, single-center study of LTx from January 1, 2021-March 30, 2022. The primary outcome is incidence of post-LTx COVID-19. Secondary outcomes include graft function, mortality, graft loss, and COVID-19 treatment. RESULTS: One hundred and seventy-seven LTx recipients were included, 57% [101/177] VAX and 43% [76/177] UNVAX. Baseline characteristics were similar between groups. Overall, 28 (36.8%) UNVAX and 34 (33.7%) VAX tested COVID-19 positive during the study period (p = .193) at a mean of 312.6 [255.4-369.8] days for UNVAX versus 254.6 [215.2-293.9] days for VAX (p = .084). COVID-19 treatment was administered in 15 (53.6%) of the UNVAX compared to 22 (64.7%) in the VAX (p = .374), although eight (28.6%) of UNVAX required hospital admission for treatment compared with two (5.9%) of VAX (p = .016). There were no statistically significant differences in death, and no COVID-19 related death or graft loss. There were no statistically significant differences in liver function tests at 3- and 12-months post LTx. CONCLUSION: In a series with a large percentage of UNVAX patients, LTx appears to be safe, with no difference in the rate of COVID-19 or transplant-related outcomes compared to VAX. While we encourage vaccination to prevent severe COVID, based on our results, vaccine status should not be reason to deny lifesaving transplant.

Comparison of outcomes in vaccinated versus unvaccinated COVID-19 kidney transplant recipients, a single center retrospective study-Is the taboo justified?

INTRODUCTION: We assessed differences in the post-transplant outcomes between COVID-19 vaccinated and unvaccinated Kidney transplant (KTx) recipients. METHODS: We conducted a retrospective, single-center study of 400 KTx from 2/1/2021 to 4/30/2022 with 6-21 months follow-up. Primary outcomes included differences in the incidence of post-transplant COVID-19, ICU admission for COVID-19, death, and graft failure between the two groups. Secondary outcomes were inpatient floor admission, outpatient-management, length of hospital stay during COVID-19 admission. We also reported rejection, DGF, CMV needing treatment, and BK PCR >10 000 in baseline characteristics. RESULT: 70.5% (282/400) were fully vaccinated, and 29.5% (118/400) were unvaccinated. 33% (92/282) of vaccinated and 39% (46/118) of unvaccinated patients developed COVID-19 (p-value .03). In both groups, 16% received outpatient treatments for COVID-19. 3% (12/282) of the vaccinated and 8% (11/118) unvaccinated were admitted to the general floors (p-value .06), and 1% (3/282) of the vaccinated and 3.3% (4/118) of the unvaccinated patients needed admission to the ICU (p-value .2). The length of stay was 12 days in both groups. 13/282 (4.6%) vaccinated patients and 7/118 (5.93%) unvaccinated patients died during the follow-up period (p-value = .3). COVID-19 was deemed the etiology of death in 5/13 cases in the vaccinated and 3/7 in the unvaccinated. DGF, rejection, CMV requiring treatment, and BK PCR >10 000 were comparable between groups. CONCLUSION: The incidence of COVID-19 was higher in unvaccinated than in vaccinated KTx. The two groups were not statistically different for other primary outcomes, including the need for hospital admissions (outpatient, general floor, ICU), length of hospital stay, death, and graft failure.

GPR-160 Receptor Signaling in the Dorsal Vagal Complex of Male Rats Modulates Meal Microstructure and CART-Mediated Hypophagia.

The g-protein coupled receptor GPR-160, recently identified as a putative receptor for the cocaine and amphetamine-regulated transcript (CART) peptide, shows abundant expression in the energy-balance control nuclei, including the dorsal vagal complex (DVC). However, its physiological role in the control of food intake has yet to be fully explored. Here, we performed a virally mediated, targeted knockdown (KD) of Gpr160 in the DVC of male rats to evaluate its physiological role in control of feeding. Our results indicate that DVC Gpr160 KD affects meal microstructure. Specifically, DVC Gpr160 KD animals consumed more frequent, but shorter meals during the dark phase and showed decreased caloric intake and duration of meals during the light phase. Cumulatively, however, these bidirectional effects on feeding resulted in no difference in body weight gain. We next tested the role of DVC GPR-160 in mediating the anorexigenic effects of exogenous CART. Our results show that DVC Gpr160 KD partially attenuates CART's anorexigenic effects. To further characterize Gpr160+ cells in the DVC, we utilized single-nucleus RNA sequencing data to uncover abundant GPR-160 expression in DVC microglia and only minimal expression in neurons. Altogether, our results suggest that DVC CART signaling may be mediated by Gpr160+ microglia, which in turn may be modulating DVC neuronal activity to control food intake.

A Single-Center Case Series of Successful Abdominal Organ Transplantation From SARS-CoV-2-infected Donors to Uninfected Recipients-Do We Need Rigorous Monitoring?

There is limited documentation of hematogenous transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in non-lung transplants from infected donors to uninfected recipients. Methods: We analyzed 16 recipients (7 liver, 9 kidney) transplanted from SARS-CoV-2 nucleic acid test+ deceased donors from December 25, 2021, to February 28, 2022, who were followed-up for at least 90 d. Primary outcomes included coronavirus disease 2019-positivity, allograft loss, and all-cause mortality. Secondary outcomes included biopsy-proven rejection (BPAR), donor-specific antibodies, delayed graft function, and opportunistic infections. Unlike previous studies, we followed the recipients clinically with the intent to treat if they developed SARS-CoV-2 symptoms. Results: All donors were SARS-CoV-2 polymerase chain reaction-positive 72 h before donation. No recipients developed SARS-CoV-2 infection. The nadir serum creatinine and estimated glomerular filtration rate were 1.33 mg/dL and 64 mL/min/1.732 m2 for kidney transplantation (KTx) respectively. The median alanine transaminase was 14.5 IU/L, aspartate aminotransferase 13 IU/L, and alkaline phosphatase 74 IU/L. Two KTx patients lost allograft, and 1 liver transplantation patient died with a failed allograft. However, this was unrelated to their SARS-CoV-2-positive donor status. One BPAR in the liver transplantation was treated with steroids. No donor-specific antibodies or BPAR were reported in the KTx. Six KTx patients experienced delayed graft function, and 4 are off dialysis. Two KTx patients developed cytomegalovirus infection because of an error in reporting the cytomegalovirus serostatus by the donor center. We did not do serial testing for SARS-CoV-2 by polymerase chain reaction, imaging, or cycle threshold score pre- or posttransplant for donor/recipient and had comparable outcomes with previous studies. Conclusions: Because of the low risk of transmission, serial testing might not be necessary and, thus, could be reciprocated at small-volume transplant centers.

Kidney transplant from HCV viremic donors to HCV-negative recipients and risk for de novo donor specific antibodies and acute rejection.

BACKGROUND: Kidney transplantation from HCV-viremic donors into uninfected recipients is associated with excellent short-term outcomes. However, concerns regarding an increased risk for the development of de novo donor specific antibodies (DSA) and acute rejection have been raised in single center reports. METHODS: A retrospective study of HCV-negative kidney-only transplant recipients between 2018 and 2020. Patients were grouped based on the donor HCV status into group 1; HCV-viremic donors, and group 2; HCV-negative donors. Inverse probability of treatment weighting (IPTW), with weights derived from the propensity score, were used to estimate the effect of donors' HCV-viremia on the recipients. The primary objective was to compare the 1-year incidence of de novo DSA. Secondary outcomes included group comparison of the incidence of biopsy proven acute rejection (BPAR), 1-year patient and allograft survival, and 1-year renal allograft function. RESULTS: A total of 71 patients were included in the HCV NAT+ group, and 440 in the HCV- negative group. One-year incidence of de novo DSA was higher in the HCV NAT+ group in the IPTW weighted analysis (19% vs. 9%, p = .02). In the unweighted analysis, BPAR occurred in 7% of recipients in the HCV NAT+ group, compared to 3% in the control group (p = .06). However, due to the low event rate in the in the IPTW weighted groups, a statistical significance test could not be performed. Average estimated GFR was higher in the HCV-viremic group at 3 months (61 vs. 53 ml/min/1.73 m2 p = .002), but comparable at 6 (59 vs. 56 ml/min/1.73 m2 , p = .31) and 12 months (60 vs. 55 ml/min/1.73 m2 , p = .07). Patient and allograft survival were comparable between the two groups. CONCLUSION: Kidney transplant from HCV-viremic donors was associated with an increased risk for the development of post-transplant de novo DSA in the first year after transplantation, but no difference in patient and graft survival.

Single nucleus transcriptomic analysis of rat nucleus accumbens reveals cell type-specific patterns of gene expression associated with volitional morphine intake.

Opioid exposure is known to cause transcriptomic changes in the nucleus accumbens (NAc). However, no studies to date have investigated cell type-specific transcriptomic changes associated with volitional opioid taking. Here, we use single nucleus RNA sequencing (snRNAseq) to comprehensively characterize cell type-specific alterations of the NAc transcriptome in rats self-administering morphine. One cohort of male Brown Norway rats was injected with acute morphine (10 mg/kg, i.p.) or saline. A second cohort of rats was allowed to self-administer intravenous morphine (1.0 mg/kg/infusion) for 10 consecutive days. Each morphine-experienced rat was paired with a yoked saline control rat. snRNAseq libraries were generated from NAc punches and used to identify cell type-specific gene expression changes associated with volitional morphine taking. We identified 1106 differentially expressed genes (DEGs) in the acute morphine group, compared to 2453 DEGs in the morphine self-administration group, across 27 distinct cell clusters. Importantly, we identified 1329 DEGs that were specific to morphine self-administration. DEGs were identified in novel clusters of astrocytes, oligodendrocytes, and D1R- and D2R-expressing medium spiny neurons in the NAc. Cell type-specific DEGs included Rgs9, Celf5, Oprm1, and Pde10a. Upregulation of Rgs9 and Celf5 in D2R-expressing neurons was validated by RNAscope. Approximately 85% of all oligodendrocyte DEGs, nearly all of which were associated with morphine taking, were identified in two subtypes. Bioinformatic analyses identified cell type-specific upstream regulatory mechanisms of the observed transcriptome alterations and downstream signaling pathways, including both novel and previously identified molecular pathways. These findings show that volitional morphine taking is associated with distinct cell type-specific transcriptomic changes in the rat NAc and highlight specific striatal cell populations and novel molecular substrates that could be targeted to reduce compulsive opioid taking.

Kidney transplant from hepatitis C viremic donors into aviremic recipients and risk for post-transplant BK and cytomegalovirus infection.

BACKGROUND: kidney transplantation from Hepatitis C virus (HCV) viremic donors to uninfected recipients is associated with excellent short-term outcomes. However, HCV viremia might be associated with an increased risk for post-transplant viral complications. METHODS: We designed a retrospective study of HCV-negative kidney-only transplant recipients between 2018 and 2020. Recipients were grouped into group 1; HCV-negative donors, and group 2; HCV-viremic donors. Patients were matched 1:1 using propensity score. The primary objectives were to compare the incidence of cytomegalovirus (CMV) viremia ≥ 200 ml/IU, and BK viremia ≥1000 copies/ml between the groups. Secondary outcomes included group comparison of CMV disease, BK viremia ≥10 000 copies/ml, and 1-year patient and allograft survival. RESULTS: The study included 634 patients in group 1, and 71 patients in group 2. Sixty-five pairs of patients were matched. Incidence of CMV viremia (33.3% vs. 40.0%, p = .4675), and BK viremia (15.9% vs. 27.7%, p = .1353) did not differ significantly between groups in the matched cohort. Incidence of CMV disease (81.0% vs. 76.9%, p = 1.000), and BK viremia ≥10 000 copies/ml (9.5% vs. 16.9%, p = .2987) were comparable between groups. There was no difference in the 1-year patient or allograft survival between groups. CONCLUSION: kidney transplant from HCV-viremic donors is not associated with increased risk for BK or CMV viremia.

The role of glia in the physiology and pharmacology of glucagon-like peptide-1: implications for obesity, diabetes, neurodegeneration and glaucoma.

The medical applications of glucagon-like peptide-1 receptor (GLP-1R) agonists is evergrowing in scope, highlighting the urgent need for a comprehensive understanding of the mechanisms through which GLP-1R activation impacts physiology and behaviour. A new area of research aims to elucidate the role GLP-1R signalling in glia, which play a role in regulating energy balance, glycemic control, neuroinflammation and oxidative stress. Once controversial, existing evidence now suggests that subsets of glia (e.g. microglia, tanycytes and astrocytes) and infiltrating macrophages express GLP-1Rs. In this review, we discuss the implications of these findings, with particular focus on the effectiveness of both clinically available and novel GLP-1R agonists for treating metabolic and neurodegenerative diseases, enhancing cognition and combating substance abuse. LINKED ARTICLES: This article is part of a themed issue on GLP1 receptor ligands (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.4/issuetoc.

The long-acting amylin/calcitonin receptor agonist ZP5461 suppresses food intake and body weight in male rats.

The peptide hormone amylin reduces food intake and body weight and is an attractive candidate target for novel pharmacotherapies to treat obesity. However, the short half-life of native amylin and amylin analogs like pramlintide limits these compounds' potential utility in promoting sustained negative energy balance. Here, we evaluate the ability of the novel long-acting amylin/calcitonin receptor agonist ZP5461 to reduce feeding and body weight in rats, and also test the role of calcitonin receptors (CTRs) in the dorsal vagal complex (DVC) of the hindbrain in the energy balance effects of chronic ZP5461 administration. Acute dose-response studies indicate that systemic ZP5461 (0.5-3 nmol/kg) robustly suppresses energy intake and body weight gain in chow- and high-fat diet (HFD)-fed rats. When HFD-fed rats received chronic systemic administration of ZP5461 (1-2 nmol/kg), the compound initially produced reductions in energy intake and weight gain but failed to produce sustained suppression of intake and body weight. Using virally mediated knockdown of DVC CTRs, the ability of chronic systemic ZP5461 to promote early reductions in intake and body weight gain was determined to be mediated in part by activation of DVC CTRs, implicating the DVC as a central site of action for ZP5461. Future studies should address other dosing regimens of ZP5461 to determine whether an alternative dose/frequency of administration would produce more sustained body weight suppression.

Modification in induction immunosuppression regimens to safely perform kidney transplants amid the COVID-19 pandemic: A single-center retrospective study.

BACKGROUND: The COVID-19 pandemic has negatively impacted organ donation and transplantation across the globe. METHODS: This study analyzed transplant outcomes during the pre-pandemic [PPE, 1/2019-2/2020] and pandemic era [PE, 3/2020-8/2020] based on changes in induction immunosuppression. During PPE, high immunological risk patients received 4-6 mg/kg, moderate risk 2-4 mg/kg, and low risk 1-2 mg/kg of ATG. During PE, ATG doses were reduced to 3-4 mg/kg for high risk, 1-2 mg/kg for moderate, and low changed to basiliximab. Primary outcomes are as follows: biopsy-proven rejection [BPAR], de-novo donor-specific antibody [DSA], delayed graft function [DGF], infection rates, graft loss, and all-cause of mortality. RESULTS: During PPE, 224 kidney transplants [KTx] and 14 kidney/pancreas transplants [KP] were included, while 180 KTx and 5 KP were included for PE. Basiliximab use increased by 30% in the PE. The odds of DGF were statistically significant between PE vs PPE, OR 1.7 [1.05, 2.8, p-value = .042]. The odds of developing DSAs and BPAR during the PE vs. PPE were 0.34 [0.16, 0.71, p-value = .004] and OR 0.34 (0.1 to 1.1, p-value, .104)], respectively. Cytomegalovirus [19% in PE, 37% in PPE] and BK virus [5.4% PE vs. 16% PPE] incidence reduced during PE vs. PPE. COVID-19, graft loss, and mortality were comparable between groups. CONCLUSION: KTx and KP transplants were performed safely during the COVID-19 pandemic with a reduction of induction immunosuppression.

Past, present and future of cocaine- and amphetamine-regulated transcript peptide.

The existence of the peptide encoded by the cocaine- and amphetamine-regulated transcript (Cartpt) has been recognized since 1981, but it was not until 1995, that the gene encoding CART peptide (CART) was identified. With the availability of the predicted protein sequence of CART investigators were able to identify sites of peptide localization, which then led to numerous approaches attempting to clarify CART's multiple pharmacologic effects and even provide evidence of potential physiologic relevance. Although not without controversy, a picture emerged of the importance of CART in ingestive behaviors, reward behaviors and even pain sensation. Despite the wealth of data hinting at the significance of CART, in the absence of an identified receptor, the full potential for this peptide or its analogs to be developed into therapeutic agents remained unrealized. There was evidence favoring the action of CART via a G protein-coupled receptor (GPCR), but despite multiple attempts the identity of that receptor eluded investigators until recently. Now with the identification of the previously orphaned GPCR, GPR160, as a receptor for CART, focus on this pluripotent neuropeptide will in all likelihood experience a renaissance and the potential for the development of pharmcotherapies targeting GPR160 seems within reach.

Activation of PPG neurons following acute stressors differentially involves hindbrain serotonin in male rats.

Within the hindbrain, serotonin (5-HT) functions as a modulator of the central glucagon-like peptide-1 (GLP-1) system. This interaction between 5-HT and GLP-1 is achieved via 5-HT2C and 5-HT3 receptors and is relevant for GLP-1-mediated feeding behavior. The central GLP-1 system is activated by various stressors, activates the hypothalamic pituitary adrenocortical (HPA) axis, and contributes to stress-related behaviors. Whether 5-HT modulates GLP-1's role in the stress response in unknown. We hypothesized that the serotonergic modulation of GLP-1-producing neurons (i.e., PPG neurons) is stimuli-specific and that stressed-induced PPG activity is one of the modalities in which 5-HT plays a role. In this study, we investigated the roles of 5-HT2C and 5-HT3 receptors in mediating the activation of PPG neurons in the nucleus tractus solitarius (NTS) following exposure to three different acute stressors: lithium chloride (LiCl), noncontingent cocaine (Coc), and novel restraint stress (RES). Results showed that increased c-Fos expression in PPG neurons following LiCl and RES-but not Coc-is dependent on hindbrain 5-HT2C and 5-HT3 receptor signaling. Additionally, stressors that depend on 5-HT signaling to activate PPG neurons (i.e., LiCl and RES) increased c-Fos expression in 5-HT-expressing neurons within the caudal raphe (CR), specifically in the raphe magnus (RMg). Finally, we showed that RMg neurons innervate NTS PPG neurons and that some of these PPG neurons lie in close proximity to 5-HT axons, suggesting RMg 5-HT-expressing neurons are the source of 5-HT input responsible for engaging NTS PPG neurons. Together, these findings identify a direct RMg to NTS pathway responsible for the modulatory effect of 5-HT on the central GLP-1 system-specifically via activation of 5-HT2C and 5-HT3 receptors-in the facilitation of acute stress responses.

Signaling in rat brainstem via Gpr160 is required for the anorexigenic and antidipsogenic actions of cocaine- and amphetamine-regulated transcript peptide.

Recent work identified Gpr160 as a candidate receptor for cocaine- and amphetamine-regulated transcript peptide (CARTp) and described its role in pain modulation. The aims of the present study were to determine if Gpr160 is required for the CARTp's ability to reduce food intake and water intake and to initially identify the distribution of Gpr160-like immunoreactivity (Gpr160ir) in the rat brain. A passive immunoneutralization approach targeting Gpr160 was used to block the behavioral effects of a pharmacological dose of CARTp in the fourth cerebroventricle (4V) of rats and to determine the importance of endogenously produced CARTp in the control of ingestive behaviors. Passive immunoneutralization of Gpr160 in the 4V blocked the actions of CARTp to inhibit food intake and water intake. Blockade of Gpr160 in the 4V, independent of pharmacological CART treatment, caused an increase in both overnight food intake and water intake. The decrease in food intake, but not water intake, caused by central injection of CARTp was demonstrated to be interrupted by prior administration of a glucagon-like peptide 1 (GLP-1) receptor antagonist. Gpr160ir was observed in several, distinct sites throughout the rat brain, where CARTp staining has been described. Importantly, Gpr160ir was observed to be present in both neuronal and nonneuronal cell types. These data support the hypothesis that Gpr160 is required for the anorexigenic actions of central CARTp injection and extend these findings to water drinking. Gpr160ir was observed in both neuronal and nonneuronal cell types in regions known to be important in the multiple pharmacological effects of CARTp, identifying those areas as targets for future compromise of function studies.

Antithymocyte induction dosing and incidence of opportunistic viral infections using steroid-free maintenance immunosuppression.

BACKGROUND: Currently, there is limited literature evaluating rATG induction dosing and incidence of opportunistic viral infections when using steroid-free maintenance immunosuppression. METHODS: This single-center, retrospective, study compared high rATG (>4.5 mg/kg) versus low (<4.5 mg/kg) induction dosing and the overall incidence of early opportunistic viral infection at 180 days in the setting of maintenance immunosuppression consisting of tacrolimus, mycophenolate, rapid steroid withdrawal, and a tiered antiviral prevention strategy based on donor-recipient Cytomegalovirus (CMV) serostatus. RESULTS: A total of 209 patients were included; 76 patients received low-dose and 133 patients received high-dose rATG. Incidence of overall opportunistic viral infection occurred more frequently in patients who received high compared to low dose (29.8% vs 25% p = .030). Incidence of CMV infection was also significantly increased in the high-dose group (31.6% vs 18.4% p = .039). In a multivariable model, rATG dose, as a continuous variable, remained a significant independent predictor of infection along with CMV risk (OR 1.46, 95% CI 1.02-2.09) controlling for age and CMV risk. There were no differences in graft-related outcomes at 180 days. CONCLUSION: Higher cumulative rATG induction dose was associated with increased incidence of opportunistic viral infections, in the setting of a steroid-free maintenance immunosuppression in the early post-transplant period.

Early life overnutrition impairs plasticity of non-neuronal brainstem cells and drives obesity in offspring across development in rats.

BACKGROUND: The prevalence of adolescent obesity has increased dramatically, becoming a serious public health concern. While previous evidence suggests that in utero- and early postnatal overnutrition increases adult-onset obesity risk, the neurobiological mechanisms underlying this outcome are not well understood. Non-neuronal cells play an underestimated role in the physiological responses to metabolic/nutrient signals. Hypothalamic glial-mediated inflammation is now considered a contributing factor in the development and perpetuation of obesity; however, attention on the role of gliosis and microglia activation in other nuclei is still needed. METHODS/RESULTS: Here, we demonstrate that early life consumption of high-fat/sucrose diet (HFSD) is sufficient to increase offspring body weight, hyperleptinemia and potentially maladaptive cytoarchitectural changes in the brainstem dorsal-vagal-complex (DVC), an essential energy balance processing hub, across postnatal development. Our data demonstrate that pre- and postnatal consumption of HFSD result in increased body weight, hyperleptinemia and dramatically affects the non-neuronal landscape, and therefore the plasticity of the DVC in the developing offspring. CONCLUSIONS: Current findings are very provocative, considering the importance of the DVC in appetite regulation, suggesting that HFSD-consumption during early life may contribute to subsequent obesity risk via DVC cytoarchitectural changes.

Corrination of a GLP-1 Receptor Agonist for Glycemic Control without Emesis.

Glucagon-like peptide-1 receptor (GLP-1R) agonists used to treat type 2 diabetes mellitus often produce nausea, vomiting, and in some patients, undesired anorexia. Notably, these behavioral effects are caused by direct central GLP-1R activation. Herein, we describe the creation of a GLP-1R agonist conjugate with modified brain penetrance that enhances GLP-1R-mediated glycemic control without inducing vomiting. Covalent attachment of the GLP-1R agonist exendin-4 (Ex4) to dicyanocobinamide (Cbi), a corrin ring containing precursor of vitamin B12, produces a "corrinated" Ex4 construct (Cbi-Ex4). Data collected in the musk shrew (Suncus murinus), an emetic mammal, reveal beneficial effects of Cbi-Ex4 relative to Ex4, as evidenced by improvements in glycemic responses in glucose tolerance tests and a profound reduction of emetic events. Our findings highlight the potential for clinical use of Cbi-Ex4 for millions of patients seeking improved glycemic control without common side effects (e.g., emesis) characteristic of current GLP-1 therapeutics.

A second-generation glucagon-like peptide-1 receptor agonist mitigates vomiting and anorexia while retaining glucoregulatory potency in lean diabetic and emetic mammalian models.

AIM: To develop a conjugate of vitamin B12 bound to the glucagon-like peptide-1 receptor (GLP-1R) agonist exendin-4 (Ex4) that shows reduced penetrance into the central nervous system while maintaining peripheral glucoregulatory function. METHODS: We evaluated whether a vitamin B12 conjugate of Ex4 (B12-Ex4) improves glucose tolerance without inducing anorexia in Goto-Kakizaki (GK) rats, a lean type 2 diabetes model of an understudied but medically compromised population of patients requiring the glucoregulatory effects of GLP-1R agonists without anorexia. We also utilized the musk shrew (Suncus murinus), a mammalian model capable of emesis, to test B12-Ex4 on glycaemic profile, feeding and emesis. RESULTS: In both models, native Ex4 and B12-Ex4 equivalently blunted the rise in blood glucose levels during a glucose tolerance test. In both GK rats and shrews, acute Ex4 administration decreased food intake, leading to weight loss; by contrast, equimolar administration of B12-Ex4 had no effect on feeding and body weight. There was a near absence of emesis in shrews given systemic B12-Ex4, in contrast to reliable emesis produced by Ex4. When administered centrally, both B12-Ex4 and Ex4 induced similar potency of emesis, suggesting that brain penetrance of B12-Ex4 is required for induction of emesis. CONCLUSIONS: These findings highlight the potential therapeutic value of B12-Ex4 as a novel treatment for type 2 diabetes devoid of weight loss and with reduced adverse effects and better tolerance, but similar glucoregulation to current GLP-1R agonists.

Synthesis and Characterization of a Leucine-Based Block Co-Polypeptide: The Effect of the Leucine Zipper on Self-Assembly.

The self-assembly behavior of an ABC triblock copolypeptide consisting of poly(ethylene oxide-b-(leucine-s-valine)-b-lysine) (PEO-PLV-PK) was examined via dynamic light scattering in dilute aqueous solution. Leucine is a hydrophobic, α-helix forming polypeptide that exhibits a "zipper effect" in coiled-coil dimers. We hypothesize that the specific interaction afforded by the leucine zipper dominates the thermodynamics of self-assembly through the side-by-side ordering of α-helices, which drives vesicle formation in a polymer with only 6 wt % hydrophobic content. Additionally, a multitude of assembly sizes and morphologies were attainable from a single polymer, depending on the solution processing method. Thermodynamic effects of the leucine zipper can be interpreted, in part, from solubility parameters determined from molecular modeling. The combination of synthesis, solvent processing, and computational studies helps to elucidate the thermodynamic effects of this unique assembly motif on classical self-assembly processes.

A novel regulator of thirst behavior: phoenixin.

There are examples of physiological conditions under which thirst is inappropriately exaggerated, and the mechanisms for these paradoxical ingestive behaviors remain unknown. We are interested in thirst mechanisms across the female life cycle and have identified a novel mechanism through which ingestive behavior may be activated. We discovered a previously unrecognized endogenous hypothalamic peptide, phoenixin (PNX), identified physiologically relevant actions of the peptide in brain and pituitary gland to control reproductive hormone secretion in female rodents, and in the process identified the previously orphaned G protein-coupled receptor Gpr173 to be a potential receptor for the peptide. Labeled PNX binding distribution in brain parallels areas known to be important in ingestive behaviors as well in areas where gonadal steroids feedback to control estrous cyclicity (Stein LM, Tullock CW, Mathews SK, Garcia-Galiano D, Elias CF, Samson WK, Yosten GLC, Am J Physiol Regul Integr Comp Physiol 311: R489-R496, 2016). We have demonstrated upregulation of Gpr173 during puberty, fluctuations across the estrous cycle, and, importantly, upregulation during the last third of gestation. It is during this hypervolemic, hyponatremic state that both vasopressin secretion and thirst are inappropriately elevated in humans. Here, we show that central administration of PNX stimulated water drinking in both males and females under ad libitum conditions, increased water drinking after overnight fluid deprivation, and increased both water and 1.5% NaCl ingestion under fed and hydrated conditions. Importantly, losartan pretreatment blocked the effect of PNX on water drinking, and knockdown of Gpr173 by use of short interfering RNA constructs significantly attenuated water drinking in response to overnight fluid deprivation. These actions, together with the stimulatory action of PNX on vasopressin secretion, suggest that this recently discovered neuropeptide may impact the recruitment of critically important neural circuits through which ingestive behaviors and endocrine mechanisms that maintain fluid and electrolyte homeostasis are regulated.

Dorsal vagal complex and hypothalamic glia differentially respond to leptin and energy balance dysregulation.

Previous studies identify a role for hypothalamic glia in energy balance regulation; however, a narrow hypothalamic focus provides an incomplete understanding of how glia throughout the brain respond to and regulate energy homeostasis. We examined the responses of glia in the dorsal vagal complex (DVC) to the adipokine leptin and high fat diet-induced obesity. DVC astrocytes functionally express the leptin receptor; in vivo pharmacological studies suggest that DVC astrocytes partly mediate the anorectic effects of leptin in lean but not diet-induced obese rats. Ex vivo calcium imaging indicated that these changes were related to a lower proportion of leptin-responsive cells in the DVC of obese versus lean animals. Finally, we investigated DVC microglia and astroglia responses to leptin and energy balance dysregulation in vivo: obesity decreased DVC astrogliosis, whereas the absence of leptin signaling in Zucker rats was associated with extensive astrogliosis in the DVC and decreased hypothalamic micro- and astrogliosis. These data uncover a novel functional heterogeneity of astrocytes in different brain nuclei of relevance to leptin signaling and energy balance regulation.