Endocrinology
Abstract
Type 2 diabetes affects more than 38 million people in the US, and a major complication is kidney disease. During the analysis of lipotoxicity in diabetic kidney disease, global fatty acid transport protein-2 (FATP2) gene deletion was noted to markedly reduce plasma glucose in db/db mice due to sustained insulin secretion. To identify the mechanism, we observed that islet FATP2 expression was restricted to α-cells, and α-cell FATP2 was functional. Basal glucagon and alanine-stimulated gluconeogenesis were reduced in FATP2KO db/db compared to db/db mice. Direct evidence of FATP2KO-induced α-cell-mediated glucagon-like peptide-1 (GLP-1) secretion included increased GLP-1-positive α-cell mass in FATP2KO db/db mice, small molecule FATP2 inhibitor enhancement of GLP-1 secretion in αTC1-6 cells and human islets, and exendin[9-39]-inhibitable insulin secretion in FATP2 inhibitor-treated human islets. FATP2-dependent enteroendocrine GLP-1 secretion was excluded by demonstration of similar glucose tolerance and plasma GLP-1 concentrations in db/db FATP2KO mice following oral versus intraperitoneal glucose loading, non-overlapping FATP2 and preproglucagon mRNA expression, and lack of FATP2/GLP-1 co-immunolocalization in intestine. We conclude that FATP2 deletion or inhibition exerts glucose-lowering effects through α-cell-mediated GLP-1 secretion and paracrine ß-cell insulin release.
Authors
Shenaz Khan, Robert J. Gaivin, Zhiyu Liu, Vincent Li, Ivy Samuels, Jinsook Son, Patrick Osei-Owusu, Jeffrey L. Garvin, Domenico Accili, Jeffrey R. Schelling
Abstract
Understanding the genetic causes of diseases affecting pancreatic β cells and neurons can give insights into pathways essential for both cell types. Microcephaly, epilepsy and diabetes syndrome (MEDS) is a congenital disorder with two known aetiological genes, IER3IP1 and YIPF5. Both genes encode proteins involved in endoplasmic reticulum (ER) to Golgi trafficking. We used genome sequencing to identify 6 individuals with MEDS caused by biallelic variants in the novel disease gene, TMEM167A. All had neonatal diabetes (diagnosed <6 months) and severe microcephaly, five also had epilepsy. TMEM167A is highly expressed in developing and adult human pancreas and brain. To gain insights into the mechanisms leading to diabetes, we silenced TMEM167A in EndoC-βH1 cells and knocked-in one patient’s variant, p.Val59Glu, in induced pluripotent stem cells (iPSCs). Both TMEM167A depletion in EndoC-βH1 cells and the p.Val59Glu variant in iPSC-derived β cells sensitized β cells to ER stress. The p.Val59Glu variant impaired proinsulin trafficking to the Golgi and induced iPSC-β cell dysfunction. The discovery of TMEM167A variants as a new genetic cause of MEDS highlights a critical role of TMEM167A in the ER to Golgi pathway in β cells and neurons.
Authors
Enrico Virgilio, Sylvia Tielens, Georgia Bonfield, Fang-Shin Nian, Toshiaki Sawatani, Chiara Vinci, Molly Govier, Hossam Montaser, Romane Lartigue, Anoop Arunagiri, Alexandrine Liboz, Flavia Natividade da Silva, Maria Lytrivi, Theodora Papadopoulou, Matthew N. Wakeling, James Russ-Silsby, Pamela Bowman, Matthew B. Johnson, Thomas W. Laver, Anthony Piron, Xiaoyan Yi, Federica Fantuzzi, Sirine Hendrickx, Mariana Igoillo-Esteve, Bruno J. Santacreu, Jananie Suntharesan, Radha Ghildiyal, Darshan G. Hegde, Nikhil Avnish Shah, Sezer Acar, Beyhan Özkaya Dönmez, Behzat Özkan, Fauzia Mohsin, Iman M. Talaat, Mohamed Tarek Abbas, Omar Saied Abbas, Hamed Ali Alghamdi, Nurgun Kandemir, Sarah E. Flanagan, Raphael Scharfmann, Peter Arvan, Matthieu Raoux, Laurent Nguyen, Andrew T. Hattersley, Miriam Cnop, Elisa De Franco
Abstract
The incretin receptor agonists semaglutide and tirzepatide have transformed the medical management of obesity. The neural mechanisms by which incretin analogs regulate appetite remain incompletely understood, and dissecting this process is critical for the development of next-generation anti-obesity drugs that are more targeted and tolerable. Moreover, the physiologic functions of incretins in appetite regulation and gut-brain communication have remained elusive. Using in vivo fiber photometry, we discovered distinct pharmacologic and physiologic roles for the incretin hormones glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1). We showed that GIP, but not GLP-1, was required for normal nutrient-mediated inhibition of hunger-promoting AgRP neurons. By contrast, both GIP and GLP-1 analogs at pharmacologic doses were sufficient to inhibit AgRP neurons. The magnitude of neural inhibition was proportional to the effect of each incretin on food intake, and dual GIP and GLP-1 receptor agonism more potently inhibited AgRP neurons and suppressed food intake than either agonist alone. Our results have revealed a role for endogenous GIP in gut-brain appetite regulation and indicate that incretin analogs act in part via AgRP neurons to mediate their anorectic effects.
Authors
Hayley E. McMorrow, Andrew B. Cohen, Carolyn M. Lorch, Nikolas W. Hayes, Stefan W. Fleps, Joshua A. Frydman, Jessica L. Xia, Ricardo J. Samms, Lisa R. Beutler
Abstract
Cancer cells present neoantigens dominantly through MHC class I (MHCI) to drive tumor rejection through cytotoxic CD8+ T-cells. There is growing recognition that a subset of tumors express MHC class II (MHCII), causing recognition of antigens by TCRs of CD4+ T-cells that contribute to the anti-tumor response. We find that mouse BrafV600E-driven anaplastic thyroid cancers (ATC) respond markedly to the RAF + MEK inhibitors dabrafenib and trametinib (dab/tram) and that this is associated with upregulation of MhcII in cancer cells and increased CD4+ T-cell infiltration. A subset of recurrent tumors lose MhcII expression due to silencing of Ciita, the master transcriptional regulator of MhcII, despite preserved interferon gamma signal transduction, which can be rescued by EZH2 inhibition. Orthotopically-implanted Ciita–/– and H2-Ab1–/– ATC cells into immune competent mice become unresponsive to the MAPK inhibitors. Moreover, depletion of CD4+, but not CD8+ T-cells, also abrogates response to dab/tram. These findings implicate MHCII-driven CD4+ T cell activation as a key determinant of the response of Braf-mutant ATCs to MAPK inhibition.
Authors
Vera Tiedje, Jillian Greenberg, Tianyue Qin, Soo-Yeon Im, Gnana P. Krishnamoorthy, Laura Boucai, Bin Xu, Jena D. French, Eric J. Sherman, Alan L. Ho, Elisa de Stanchina, Nicholas D. Socci, Jian Jin, Ronald A. Ghossein, Jeffrey A. Knauf, Richard P. Koche, James A. Fagin
Abstract
Selective and controlled expansion of endogenous β-cells has been pursued as a potential therapy for diabetes. Ideally, such therapies would preserve feedback control of β-cell proliferation to avoid excessive β-cell expansion. Here, we identified a regulator of β-cell proliferation whose inactivation results in controlled β-cell expansion: the protein deacetylase Sirtuin 2 (SIRT2). Sirt2 deletion in β-cells of mice increased β-cell proliferation during hyperglycemia with little effect in homeostatic conditions, indicating preservation of feedback control of β-cell mass. SIRT2 restrains proliferation of human islet β-cells, demonstrating conserved SIRT2 function. Analysis of acetylated proteins in islets treated with a SIRT2 inhibitor revealed that SIRT2 deacetylates enzymes involved in oxidative phosphorylation, dampening the adaptive increase in oxygen consumption during hyperglycemia. At the transcriptomic level, Sirt2 inactivation has context-dependent effects on β-cells, with Sirt2 controlling how β-cells interpret hyperglycemia as a stress. Finally, we provide proof-of-principle that systemic administration of a GLP1-coupled Sirt2-targeting antisense oligonucleotide achieves β-cell Sirt2 inactivation and stimulates β-cell proliferation during hyperglycemia. Overall, these studies identify a therapeutic strategy for increasing β-cell mass in diabetes without circumventing feedback control of β-cell proliferation. Future work should test the extent that these findings translate to human β-cells from individuals with and without diabetes.
Authors
Matthew Wortham, Bastian Ramms, Chun Zeng, Jacqueline R. Benthuysen, Somesh Sai, Dennis P. Pollow, Fenfen Liu, Michael Schlichting, Austin R. Harrington, Bradley Liu, Thazha P. Prakash, Elaine C. Pirie, Han Zhu, Siyouneh Baghdasarian, Sean T. Lee, Victor A. Ruthig, Kristen L. Wells, Johan Auwerx, Orian S. Shirihai, Maike Sander
Abstract
There is growing evidence for direct actions of follicle–stimulating hormone (FSH) on tissues other than the ovaries and testes. Blocking FSH action, either genetically or pharmacologically, protects against bone loss, fat gain, and memory loss in mice. We thus developed a humanized FSH–blocking antibody––MS-Hu6––as a lead therapeutic for three diseases of public health magnitude––osteoporosis, obesity and Alzheimer’s disease (AD) that track together in post–menopausal women. Here, we report the crystal structure of MS-Hu6 and its interaction with FSH in atomistic detail. Using our Good–Laboratory–Practice–Compliant platform (21CFR58), we formulated MS-Hu6 and the murine equivalent Hf2 at an ultra–high concentration; both formulated antibodies displayed enhanced thermal and colloidal stability. A single injection of 89Zr–labelled MS-Hu6 revealed a beta–phase t½ of 89 and 131 hours for female and male mice, respectively, with retention in regions of interest. Female mice injected subcutaneously with Hf2 displayed a dose–dependent reduction in body weight and body fat. Hf2 also rescued recognition memory and spatial learning loss in a context– and time–dependent manner in AD–prone 3xTg and APP/PS1 mice. MS-Hu6 injected into African green monkeys (8 mg/kg) intravenously, and then subcutaneously at monthly intervals, was safe, and without effects on vitals, blood chemistries or blood counts. There was a notable ~4% weight loss in all four monkeys after the first injection, which continued in two of four monkeys. We thus provide IND–enabling data towards an upcoming first–in–human study.
Authors
Anusha R. Pallapati, Funda Korkmaz, Satish Rojekar, Steven Sims, Anurag Misra, Judit Gimenez–Roig, Aishwarya Gangadhar, Victoria Laurencin, Anissa Gumerova, Uliana Cheliadinova, Farhath Sultana, Darya Vasilyeva, Liam Cullen, Jonathan Schuermann, Jazz Munitz, Hasni Kannangara, Surabhi Parte, Georgii Pevnev, Guzel Burganova, Zehra Tumoglu, Ronit Witztum, Soleil Wizman, Natan Kramskiy, Liah Igel, Fazilet Sen, Anna Ranzenigo, Anne Macdonald, Susan Hutchison, Abraham J.P. Teunissen, Heather Burkart, Mansi Saxena, Yelena Ginzburg, Ki Goosens, Weibin Zhou, Vitaly Ryu, Ofer Moldavski, Orly Barak, Michael Pazianas, John Caminis, Shalender Bhasin, Richard Fitzgerald, Se-Min Kim, Matthew Quinn, Shozeb Haider, Susan Appt, Tal Frolinger, Clifford J. Rosen, Daria Lizneva, Yogesh K. Gupta, Tony Yuen, Mone Zaidi
Abstract
Elevated cholesterol poses cardiovascular risks. The glucocorticoid receptor (GR) harbors a still undefined role in cholesterol regulation. Here, we report that a coding single nucleotide polymorphism (SNP) in the gene en-coding the GR, rs6190, associated with increased cholesterol in women according to UK Biobank and All Of Us datasets. In SNP-genocopying mice, we found that the SNP enhanced hepatic GR activity to transactivate Pcsk9 and Bhlhe40, negative regulators of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) re-ceptors respectively. In mice, the SNP was sufficient to elevate circulating cholesterol across all lipoprotein frac-tions and the risk and severity of atherosclerotic lesions on the pro-atherogenic hAPOE*2/*2 background. The SNP effect on atherosclerosis was blocked by in vivo liver knockdown of Pcsk9 and Bhlhe40. Also, corti-costerone and testosterone were protective against the mutant GR program in cholesterol and atherosclerosis in male mice, while the SNP effect was additive to estrogen loss in females. Remarkably, we found that the mu-tant GR program was conserved in human hepatocyte-like cells using CRISPR-engineered, SNP-genocopying human induced pluripotent stem cells (hiPSCs). Taken together, our study leverages a non-rare human variant to uncover a novel GR-dependent mechanism contributing to atherogenic risk, particularly in women.
Authors
Hima Bindu Durumutla, April Haller, Greta Noble, Ashok Daniel Prabakaran, Kevin McFarland, Hannah Latimer, Akanksha Rajput, Olukunle Akinborewa, Bahram Namjou-Khales, David Y. Hui, Mattia Quattrocelli
Abstract
The incretin peptides glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors coordinate β-cell secretion that is proportional to nutrient intake. This effect permits consistent and restricted glucose excursions across a range of carbohydrate intake. The canonical signaling downstream of ligand-activated incretin receptors involves coupling to Gɑs protein and generation of intracellular cyclic adenosine monophosphate (cAMP). However, recent reports have highlighted the importance of additional signaling nodes engaged by incretin receptors, including other G-proteins and β-arrestin proteins. Here, the importance of Gɑs signaling was tested in mice with conditional, post-developmental β-cell deletion of Gnas (encoding Gɑs) under physiological and pharmacological conditions. Deletion of Gɑs/cAMP signaling induced immediate and profound hyperglycemia that responded minimally to incretin receptor agonists, a sulfonylurea, or bethanechol. While islet area and insulin content were not affected in Gnasβcell-/-, perifusion of isolated islets demonstrated impaired responses to glucose, incretins, acetylcholine and IBMX. In the absence of Gɑs, incretin-stimulated insulin secretion was impaired but not absent, with some contribution from Gɑq signaling. Collectively, these findings validate a central role for cAMP to mediate incretin signaling, but also demonstrate broad impairment of insulin secretion in the absence of Gɑs that causes both fasting hyperglycemia and glucose intolerance.
Authors
Megan E. Capozzi, David Bouslov, Ashot Sargsyan, Michelle Y. Chan, Sarah M. Gray, Katrina Viloria, Akshay Bareja, Jonathan D. Douros, Sophie L. Lewandowski, Jason C.L. Tong, Annie Hasib, Federica Cuozzo, Elizabeth C. Ross, Matthew W. Foster, Lee S. Weinstein, Mehboob A. Hussain, Matthew J. Merrins, Francis S. Willard, Mark O. Huising, Kyle W. Sloop, David J. Hodson, David A. D'Alessio, Jonathan E. Campbell
Abstract
Castration-resistant prostate cancer (CRPC) marks the advanced and lethal stage of prostate cancer (PCa). TRIM28, also known as KAP1, is a transcriptional regulator recently shown to promote CRPC cell proliferation and xenograft tumor growth. Nonetheless, knowledge gaps persist regarding the mechanisms underlying TRIM28 upregulation in CRPC as well as the genomic targets regulated by TRIM28. Here, we report that TRIM28 is a E2F1 target in CRPC. Using an integrated genomic approach, we have demonstrated that TRIM28 forms a positive feedback loop to promote the transcriptional activation and genomic function of E2F1 independent of retinoblastoma (Rb) status. Furthermore, we identified RSK1 as a kinase that directly phosphorylates TRIM28 at S473, and, as such, RSK1 drives the TRIM28/E2F1 feedback loop. Accordingly, pS473-TRIM28 promotes CRPC progression, which is mitigated by RSK inhibition. In summary, our study reveals a critical role of the RSK1–TRIM28–E2F1 axis in CRPC progression, which may be exploited as a vulnerability in treating Rb-deficient CRPC.
Authors
Miyeong Kim, Jinpeng Liu, Yanquan Zhang, Ruixin Wang, Ryan Goettl, Jennifer Grasso, Derek B. Allison, Chi Wang, Tianyan Gao, Xiaoqi Liu, Ka-Wing Fong
Abstract
Pancreatic islet microvasculature is essential for optimal islet function and glucose homeostasis. However, islet vessel pathogenesis in obesity and its role in the manifestation of metabolic disorders remain understudied. Here, we depict the time-resolved decline of intra-islet endothelial cell responsiveness to vascular endothelial cell growth factor A (VEGF-A) and islet vessel function in a mouse model of diet-induced obesity. Longitudinal imaging of sentinel islets transplanted into mouse eyes revealed substantial vascular remodeling and diminished VEGF-A response in islet endothelial cells after 12 weeks of western diet (WD) feeding. This led to islet vessel barrier dysfunction and hemodynamic dysregulation, delaying transportation of secreted insulin into the blood. Notably, islet vessels exhibited a metabolic memory of previous WD feeding. Neither VEGF-A sensitivity nor the other vascular alterations was fully restored by control diet (CD) refeeding, resulting in modest yet significant impairment in glucose clearance despite normalized insulin sensitivity. Mechanistic analysis implicated hyperactivation of atypical protein kinase C (aPKC) under both WD and recovery conditions, which inhibited VEGF receptor 2 (VEGFR2) internalization and blunted VEGF-A triggered signal transduction in endothelial cells. In summary, prolonged WD feeding causes irreversible islet endothelial cell desensitization to VEGF-A and islet vessel dysfunction, directly undermining glucose homeostasis.
Authors
Yan Xiong, Andrea Dicker, Montse Visa, Erwin Ilegems, Per-Olof Berggren
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)