Endocrinology
Abstract
Using an integrated approach to characterize the pancreatic tissue and isolated islets from a 33-year-old with 17 years of type 1 diabetes (T1D), we found that donor islets contained β cells without insulitis and lacked glucose-stimulated insulin secretion despite a normal insulin response to cAMP-evoked stimulation. With these unexpected findings for T1D, we sequenced the donor DNA and found a pathogenic heterozygous variant in the gene encoding hepatocyte nuclear factor-1α (HNF1A). In one of the first studies of human pancreatic islets with a disease-causing HNF1A variant associated with the most common form of monogenic diabetes, we found that HNF1A dysfunction leads to insulin-insufficient diabetes reminiscent of T1D by impacting the regulatory processes critical for glucose-stimulated insulin secretion and suggest a rationale for a therapeutic alternative to current treatment.
Authors
Rachana Haliyur, Xin Tong, May Sanyoura, Shristi Shrestha, Jill Lindner, Diane C. Saunders, Radhika Aramandla, Greg Poffenberger, Sambra D. Redick, Rita Bottino, Nripesh Prasad, Shawn E. Levy, Raymond D. Blind, David M. Harlan, Louis H. Philipson, Roland W. Stein, Marcela Brissova, Alvin C. Powers
Abstract
The agonistic/antagonistic biocharacter of selective estrogen receptor modulators (SERMs) can have therapeutic advantages, particularly in the case of premenopausal breast cancers. Although the contradictory effects of these modulators have been studied in terms of crosstalk between the estrogen receptor α (ER) and coactivator dynamics and growth factor signaling, the molecular basis of these mechanisms is still obscure. We identify a series of regulatory mechanisms controlling cofactor dynamics on ER and SERM function, whose activities require F-box protein 22 (Fbxo22). Skp1, Cullin1, F-box–containing complex (SCFFbxo22) ubiquitylated lysine demethylase 4B (KDM4B) complexed with tamoxifen-bound (TAM-bound) ER, whose degradation released steroid receptor coactivator (SRC) from ER. Depletion of Fbxo22 resulted in ER-dependent transcriptional activation via transactivation function 1 (AF1) function, even in the presence of SERMs. In living cells, TAM released SRC and KDM4B from ER in a Fbxo22-dependent manner. SRC release by TAM required Fbxo22 on almost all ER-SRC–bound enhancers and promoters. TAM failed to prevent the growth of Fbxo22-depleted, ER-positive breast cancers both in vitro and in vivo. Clinically, a low level of Fbxo22 in tumor tissues predicted a poorer outcome in ER-positive/human epidermal growth factor receptor type 2–negative (HER2-negative) breast cancers with high hazard ratios, independently of other markers such as Ki-67 and node status. We propose that the level of Fbxo22 in tumor tissues defines a new subclass of ER-positive breast cancers for which SCFFbxo22-mediated KDM4B degradation in patients can be a therapeutic target for the next generation of SERMs.
Authors
Yoshikazu Johmura, Ichiro Maeda, Narumi Suzuki, Wenwen Wu, Atsushi Goda, Mariko Morita, Kiyoshi Yamaguchi, Mizuki Yamamoto, Satoi Nagasawa, Yasuyuki Kojima, Koichiro Tsugawa, Natsuko Inoue, Yasuo Miyoshi, Tomo Osako, Futoshi Akiyama, Reo Maruyama, Jun-ichiro Inoue, Yoichi Furukawa, Tomohiko Ohta, Makoto Nakanishi
Abstract
Notch signaling regulates differentiation of the pancreatic endocrine lineage during embryogenesis, but the role of Notch in mature β cells is unclear. We found that islets derived from lean mice show modest β cell Notch activity, which increases in obesity and in response to high glucose. This response appeared maladaptive, as mice with β cell-specific deficient Notch transcriptional activity (β-Rbpj, β-DNMAML) showed improved glucose tolerance when subjected to high-fat diet feeding. Conversely, mice with β cell-specific expression of constitutively-active Notch1 (β-NICD) had a progressive loss of β cell maturity, due to proteasomal degradation of MafA, leading to impaired glucose-stimulated insulin secretion and glucose intolerance with aging or obesity. Surprisingly, Notch-active β cells had increased proliferative capacity, leading to increased but dysfunctional β cell mass. These studies demonstrate a dynamic role for Notch in developed β cells to simultaneously regulate β cell function and proliferation.
Authors
Alberto Bartolome, Changyu Zhu, Lori Sussel, Utpal B. Pajvani
Abstract
Levothyroxine (LT4) is a form of thyroid hormone used to treat hypothyroidism. In the brain, T4 is converted to the active form T3 by the type 2 deiodinase (D2). Thus, it is intriguing that carriers of the Thr92Ala polymorphism in the D2 gene (DIO2) exhibit clinical improvement when liothyronine (LT3) is added to LT4 therapy. Here we report that D2 is a cargo protein in endoplasmic reticulum Golgi intermediary compartment (ERGIC) vesicles, recycling between ER and Golgi. The Thr92 to Ala substitution (Ala92-D2) caused ER stress and activated the unfolded protein response (UPR); Ala92-D2 accumulated in the trans-Golgi and generated less T3, all of which was restored by eliminating ER stress with the chemical chaperone 4-phenyl butyric acid (4-PBA). An Ala92-Dio2 polymorphism-carrying mouse exhibited UPR and hypothyroidism in distinct brain areas. The mouse refrained from physical activity, slept more and required additional time to memorize objects. Enhancing T3 signaling in the brain with LT3 improved cognition, whereas restoring proteostasis with 4-PBA eliminated the Ala92-Dio2 phenotype. In contrast, primary hypothyroidism intensified the Ala92-Dio2 phenotype, with only partial response to LT4 therapy. Disruption of cellular proteostasis and reduced Ala92-D2 activity may explain the failure of LT4 therapy in carriers of Thr92Ala-DIO2.
Authors
Sungro Jo, Tatiana L. Fonseca, Barbara M.L. Da Costa Bocco, Gustavo W. Fernandes, Elizabeth A. McAninch, Anaysa P. Bolin, Rodrigo R. Da Conceição, Joao Pedro W.S. De Castro, Daniele L. Ignacio, Péter Egri, Dorottya Németh, Csaba Fekete, Maria Martha Bernardi, Victoria D. Leitch, Naila S. Mannan, Katharine F. Curry, Natalie C. Butterfield, J.H. Duncan Bassett, Graham R. Williams, Balázs Gereben, Miriam O. Ribeiro, Antonio C. Bianco
Abstract
The loss of insulin-secreting β cells is characteristic among Type I and Type II diabetes. Stimulating proliferation to expand sources of β cells for transplantation remains a challenge because adult β cells do not proliferate readily. The cell cycle inhibitor p57 has been shown to control cell division in human β cells. Expression of p57 is regulated by the DNA methylation status of the Imprinting Control Region 2 (ICR2), which is commonly hypomethylated in Beckwith Wiedemann-Syndrome patients who exhibit massive β cell proliferation. We hypothesized that targeted demethylation of the ICR2 using a transcription activator-like effector protein fused to the catalytic domain of TET1 (ICR2-TET1) would repress p57 expression and promote cell proliferation. We report here that overexpression of ICR2-TET1 in human fibroblasts reduces p57 expression levels and increases proliferation. Furthermore, human islets overexpressing ICR2-TET1 exhibit repression of p57 with concomitant upregulation of Ki-67 while maintaining glucose-sensing functionality. When transplanted into diabetic, immunodeficient mice, the epigenetically edited islets show increased β cell replication compared to control islets. These findings demonstrate that epigenetic editing is a promising tool for inducing β cell proliferation, which may one day alleviate the scarcity of transplantable β cells for the treatment of diabetes.
Authors
Kristy Ou, Ming Yu, Nicholas G. Moss, Yue J. Wang, Amber W. Wang, Son C. Nguyen, Connie Jiang, Eseye Feleke, Vasumathi Kameswaran, Eric F. Joyce, Ali Naji, Benjamin Glaser, Dana Avrahami, Klaus H. Kaestner
Abstract
Bone marrow mesenchymal stem cells (BMSCs) exhibit an age-related lineage switch between osteogenic and adipogenic fates, which contributes to bone loss and adiposity. Here we identified a long noncoding RNA, Bmncr, which regulated the fate of BMSCs during aging. Mice depleted of Bmncr (Bmncr-KO) showed decreased bone mass and increased bone marrow adiposity, whereas transgenic overexpression of Bmncr (Bmncr-Tg) alleviated bone loss and bone marrow fat accumulation. Bmncr regulated the osteogenic niche of BMSCs by maintaining extracellular matrix protein fibromodulin (FMOD) and activation of the BMP2 pathway. Bmncr affected local 3D chromatin structure and transcription of Fmod. The absence of Fmod modified the bone phenotype of Bmncr-Tg mice. Further analysis revealed that Bmncr would serve as a scaffold to facilitate the interaction of TAZ and ABL, and thus facilitate the assembly of the TAZ and RUNX2/PPARG transcriptional complex, promoting osteogenesis and inhibiting adipogenesis. Adeno-associated viral-mediated overexpression of Taz in osteoprogenitors alleviated bone loss and marrow fat accumulation in Bmncr-KO mice. Furthermore, restoring BMNCR levels in human BMSCs reversed the age-related switch between osteoblast and adipocyte differentiation. Our findings indicate that Bmncr is a key regulator of the age-related osteogenic niche alteration and cell fate switch of BMSCs.
Authors
Chang-Jun Li, Ye Xiao, Mi Yang, Tian Su, Xi Sun, Qi Guo, Yan Huang, Xiang-Hang Luo
Abstract
Obesity is a major risk factor for developing nonalcoholic fatty-liver disease (NAFLD). NAFLD is the most common form of chronic liver disease and closely associated with insulin resistance, ultimately leading to cirrhosis and hepatocellular carcinoma. However, knowledge of the intracellular regulators of obesity-linked fatty-liver disease remains incomplete. Here we showed that hepatic Rho-kinase 1 (ROCK1) drives obesity-induced steatosis in mice through stimulation of de novo lipogenesis. Mice lacking ROCK1 in the liver were resistant to diet-induced obesity due to increased energy expenditure and thermogenic gene expression. Constitutive expression of hepatic ROCK1 was sufficient to promote adiposity, insulin resistance, and hepatic lipid accumulation in mice fed a high-fat diet. Correspondingly, liver-specific ROCK1 deletion prevented the development of severe hepatic steatosis and reduced hyperglycemia in obese diabetic (ob/ob) mice. Of pathophysiologic significance, hepatic ROCK1 was markedly up-regulated in humans with fatty-liver disease and correlated with risk factors clustering around NAFLD and insulin resistance. Mechanistically, we found that hepatic ROCK1 suppresses AMPK activity and a ROCK1-AMPK pathway is necessary to mediate cannabinoid-induced lipogenesis in the liver. Furthermore, treatment with metformin, the most widely used anti-diabetes drug, reduced hepatic lipid accumulation by inactivating ROCK1, resulting in activation of AMPK downstream signaling. Taken together, our findings establish a ROCK1-AMPK signaling axis that regulates de novo lipogenesis, providing a unique target for treating obesity-related metabolic disorders such as NAFLD.
Authors
Hu Huang, Seung-Hwan Lee, Inês Sousa-Lima, Sang Soo Kim, Won Min Hwang, Yossi Dagon, Won-Mo Yang, Sungman Cho, Min-Cheol Kang, Ji A Seo, Munehiko Shibata, Hyunsoo Cho, Getachew Debas Belew, Jinhyuk Bhin, Bhavna N. Desai, Min Jeong Ryu, Minho Shong, Peixin Li, Hua Meng, Byung-Hong Chung, Daehee Hwang, Min Seon Kim, Kyong Soo Park, Paula Macedo, Morris White, John Jones, Young-Bum Kim
Abstract
Sugar- and lipid-derived aldehydes are reactive carbonyl species (RCS) frequently used as surrogate markers of oxidative stress in obesity. A pathogenic role for RCS in metabolic diseases of obesity remains controversial, however, due in part to their highly diffuse and broad reactivity, and to lack of specific RCS-scavenging therapies. Naturally occurring histidine dipeptides (e.g., anserine and carnosine) possess RCS reactivity, but their therapeutic potential in humans is limited by serum carnosinases. Here we present the rational design, characterization and pharmacological evaluation of ‘carnosinol’ (i.e. (2S)-2-(3-amino propanoylamino)-3-(1H-imidazol-5-yl)propanol) a derivative of carnosine with high oral bioavailability that is resistant to carnosinases. Carnosinol displayed a suitable ADMET profile and was determined to have the greatest potency and selectivity toward α,β-unsaturated aldehydes (e.g. 4-hydroxynonenal, HNE, acrolein) among all others so far reported. In rodent models of diet-induced obesity and metabolic syndrome, carnosinol dose-dependently attenuated HNE-adduct formation in liver and skeletal muscle while simultaneously mitigating inflammation, dyslipidemia, insulin resistance, and steatohepatitis. These improvements in metabolic parameters with carnosinol were not due to changes in energy expenditure, physical activity, adiposity or body weight. Collectively, our findings illustrate a pathogenic role for RCS in obesity-related metabolic disorders, and provide validation for a promising new class of carbonyl-scavenging therapeutic compounds rationally derived from carnosine.
Authors
Ethan J. Anderson, Giulio Vistoli, Lalage A. Katunga, Katsuhiko Funai, Luca Regazzoni, T. Blake Monroe, Ettore Gilardoni, Luca Cannizzaro, Mara Colzani, Danilo De Maddis, Giuseppe Rossoni, Renato Canevotti, Stefania Gagliardi, Marina Carini, Giancarlo Aldini
Abstract
Hyperphosphatemic familial tumoral calcinosis (HFTC)/hyperostosis-hyperphosphatemia syndrome (HHS) is an autosomal recessive disorder of ectopic calcification due to deficiency of or resistance to intact fibroblast growth factor 23 (iFGF23). Inactivating mutations in FGF23, N-acetylgalactosaminyltransferase 3 (GALNT3), or KLOTHO have been reported to cause HFTC/HHS. We present the first identified case of autoimmune hyperphosphatemic tumoral calcinosis in an 8-year-old boy. In addition to the classical clinical and biochemical features of hyperphosphatemic tumoral calcinosis, the patient exhibited markedly elevated intact and C-terminal FGF23 levels suggestive of FGF23 resistance. However, no mutations in FGF23, KLOTHO, or fibroblast growth factor receptor 1 (FGFR1) were identified. He subsequently developed type 1 diabetes mellitus, which raised the possibility of an autoimmune cause for hyperphosphatemic tumoral calcinosis. Luciferase immunoprecipitation systems revealed significantly elevated FGF23 autoantibodies without detectable FGFR1 or KLOTHO autoantibodies. Using an in vitro FGF23 functional assay, the FGF23 autoantibodies in the patient’s plasma blocked downstream signaling via the MAPK/ERK signaling pathway in a dose-dependent manner. Thus, this report describes the first case of autoimmune hyperphosphatemic tumoral calcinosis with pathogenic autoantibodies targeting FGF23. Identification of this pathophysiology extends the etiologic spectrum of hyperphosphatemic tumoral calcinosis and suggests that immunomodulatory therapy may be an effective treatment.
Authors
Mary Scott Roberts, Peter D. Burbelo, Daniela Egli-Spichtig, Farzana Perwad, Christopher J. Romero, Shoji Ichikawa, Emily G. Farrow, Michael J. Econs, Lori C. Guthrie, Michael T. Collins, Rachel I. Gafni
Abstract
The glucocorticoid receptor (GR) is a major drug target in inflammatory disease. However, chronic glucocorticoid (GC) treatment leads to disordered energy metabolism, including increased weight gain, adiposity, and hepatosteatosis — all programs modulated by the circadian clock. We demonstrated that while antiinflammatory GC actions were maintained irrespective of dosing time, the liver was significantly more GC sensitive during the day. Temporal segregation of GC action was underpinned by a physical interaction of GR with the circadian transcription factor REVERBa and co-binding with liver-specific hepatocyte nuclear transcription factors (HNFs) on chromatin. REVERBa promoted efficient GR recruitment to chromatin during the day, acting in part by maintaining histone acetylation, with REVERBa-dependent GC responses providing segregation of carbohydrate and lipid metabolism. Importantly, deletion of Reverba inverted circadian liver GC sensitivity and protected mice from hepatosteatosis induced by chronic GC administration. Our results reveal a mechanism by which the circadian clock acts through REVERBa in liver on elements bound by HNF4A/HNF6 to direct GR action on energy metabolism.
Authors
Giorgio Caratti, Mudassar Iqbal, Louise Hunter, Donghwan Kim, Ping Wang, Ryan M. Vonslow, Nicola Begley, Abigail J. Tetley, Joanna L. Woodburn, Marie Pariollaud, Robert Maidstone, Ian J. Donaldson, Zhenguang Zhang, Louise M. Ince, Gareth Kitchen, Matthew Baxter, Toryn M. Poolman, Dion A. Daniels, David R. Stirling, Chad Brocker, Frank Gonzalez, Andrew S.I. Loudon, David A. Bechtold, Magnus Rattray, Laura C. Matthews, David W. Ray
Copyright © 2019 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)