BACKGROUND In the Joslin Medalist Study (Medalists), we determined whether significant associations exist between β cell function and pathology and clinical characteristics.METHODS Individuals with type 1 diabetes (T1D) for 50 or more years underwent evaluation including HLA analysis, basal and longitudinal autoantibody (AAb) status, and β cell function by a mixed-meal tolerance test (MMTT) and a hyperglycemia/arginine clamp procedure. Postmortem analysis of pancreases from 68 Medalists was performed. Monogenic diabetes genes were screened for the entire cohort.RESULTS Of the 1019 Medalists, 32.4% retained detectable C-peptide levels (>0.05 ng/mL, median: 0.21 ng/mL). In those who underwent a MMTT (n = 516), 5.8% responded with a doubling of baseline C-peptide levels. Longitudinally (n = 181, median: 4 years), C-peptide levels increased in 12.2% (n = 22) and decreased in 37% (n = 67) of the Medalists. Among those with repeated MMTTs, 5.4% (3 of 56) and 16.1% (9 of 56) had waxing and waning responses, respectively. Thirty Medalists with baseline C-peptide levels of 0.1 ng/mL or higher underwent the clamp procedure, with HLA–/AAb– and HLA+/AAb– Medalists being most responsive. Postmortem examination of pancreases from 68 Medalists showed that all had scattered insulin-positive cells; 59 additionally had few insulin-positive cells within a few islets; and 14 additionally had lobes with multiple islets with numerous insulin-positive cells. Genetic analysis revealed that 280 Medalists (27.5%) had monogenic diabetes variants; in 80 (7.9%) of these Medalists, the variants were classified as “likely pathogenic” (rare exome variant ensemble learner [REVEL] >0.75).CONCLUSION All Medalists retained insulin-positive β cells, with many responding to metabolic stimuli even after 50 years of T1D. The Medalists were heterogeneous with respect to β cell function, and many with HLA+ diabetes risk alleles also had monogenic diabetes variants, indicating the importance of genetic testing for clinically diagnosed T1D.FUNDING Funding for this work was provided by the Dianne Nunnally Hoppes Fund; the Beatson Pledge Fund; the NIH, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK); and the American Diabetes Association (ADA).
Marc Gregory Yu, Hillary A. Keenan, Hetal S. Shah, Scott G. Frodsham, David Pober, Zhiheng He, Emily A. Wolfson, Stephanie D’Eon, Liane J. Tinsley, Susan Bonner-Weir, Marcus G. Pezzolesi, George Liang King
Pancreatic beta cells (β-cells) differentiate during fetal life, but only postnatally acquire the capacity for glucose-stimulated insulin secretion (GSIS). How this happens is not clear. In exploring what molecular mechanisms drive the maturation of β-cell function, we found that the control of cellular signaling in β-cells fundamentally switched from the nutrient sensor target of rapamycin (mTORC1) to the energy sensor 5'-adenosine monophosphate-activated protein kinase (AMPK), and that this was critical for functional maturation. Moreover, AMPK was activated by the dietary transition taking place during weaning, and this in turn inhibited mTORC1 activity to drive the adult β-cell phenotype. While forcing constitutive mTORC1 signaling in adult β-cells relegated them to a functionally immature phenotype with characteristic transcriptional and metabolic profiles, engineering the switch from mTORC1 to AMPK signaling was sufficient to promote β-cell mitochondrial biogenesis, a shift to oxidative metabolism, and functional maturation. We also found that type 2 diabetes, a condition marked by both mitochondrial degeneration and dysregulated GSIS, was associated with a remarkable reversion of the normal AMPK-dependent adult β-cell signature to a more neonatal one characterized by mTORC1 activation. Manipulating the way in which cellular nutrient signaling pathways regulate β-cell metabolism may thus offer new targets to improve β-cell function in diabetes.
Rami Jaafar, Stella Tran, Ajit Shah, Gao Sun, Martin Valdearcos, Piero Marchetti, Matilde Masini, Avital Swisa, Simone Giacometti, Ernesto Bernal-Mizrachi, Aleksey Matveyenko, Matthias Hebrok, Yuval Dor, Guy A. Rutter, Suneil K. Koliwad, Anil Bhushan
Beta-arrestin-1 and -2 (Barr1 and Barr2, respectively) are intracellular signaling molecules that regulate many important metabolic functions. We previously demonstrated that mice lacking Barr2 selectively in pancreatic beta-cells showed pronounced metabolic impairments. Here we investigated whether Barr1 plays a similar role in regulating beta-cell function and whole body glucose homeostasis. Initially, we inactivated the Barr1 gene in beta-cells of adult mice (beta-barr1-KO mice). Beta-barr1-KO mice did not display any obvious phenotypes in a series of in vivo and in vitro metabolic tests. However, glibenclamide and tolbutamide, two widely used antidiabetic drugs of the sulfonylurea (SU) family, showed greatly reduced efficacy in stimulating insulin secretion in the KO mice in vivo and in perifused KO islets in vitro. Additional in vivo and in vitro studies demonstrated that Barr1 enhanced SU-stimulated insulin secretion by promoting SU-mediated activation of Epac2. Pull-down and co-immunoprecipitation experiments showed that Barr1 can directly interact with Epac2 and that SUs such as glibenclamide promote Barr1/Epac2 complex formation, triggering enhanced Rap1 signaling and insulin secretion. These findings suggest that strategies aimed at promoting Barr1 signaling in beta-cells may prove useful for the development of efficacious antidiabetic drugs.
Luiz F. Barella, Mario Rossi, Lu Zhu, Yinghong Cui, Fang C. Mei, Xiaodong Cheng, Wei Chen, Vsevolod V. Gurevich, Jürgen Wess
Lactation induces bone loss to provide sufficient calcium in the milk, a process that involves osteoclastic bone resorption but also osteocytes and perilacunar resorption. The exact mechanisms by which osteocytes contribute to bone loss remain elusive. Osteocytes express genes required in osteoclasts for bone resorption, including cathepsin K (Ctsk), and lactation elevates their expression. We show that Ctsk deletion in osteocytes prevented the increase in osteocyte lacunar area seen during lactation, as well as the effects of lactation to increase osteoclast numbers and decrease trabecular bone volume, cortical thickness and mechanical properties. In addition, Ctsk deletion in osteocytes increased bone Parathyroid Hormone related Peptide (PTHrP), prevented the decrease in serum Parathyroid Hormone (PTH) induced by lactation, but amplified the increase in serum 1,25(OH)2D. The net result of these changes is to maintain serum and milk calcium levels in the normal range, ensuring normal offspring skeletal development. Our studies confirm the fundamental role of osteocytic perilacunar remodeling in physiological states of lactation and provides genetic evidence that osteocyte-derived Ctsk contributes not only to osteocyte perilacunar remodeling, but also to the regulation of PTH, PTHrP, 1,25-Dyhydroxyvitamin D (1,25(OH)2D), osteoclastogenesis and bone loss in response to the high calcium demand associated with lactation.
Sutada Lotinun, Yoshihito Ishihara, Kenichi Nagano, Riku Kiviranta, Vincent Carpentier, Lynn Neff, Virginia Parkman, Noriko Ide, Dorothy Hu, Pamela Dann, Daniel Brooks, Mary L. Bouxsein, John Wysolmerski, Francesca Gori, Roland Baron
Hormone therapy (HT) is reported to be deficient in improving learning and memory in older postmenopausal women according to recent clinical studies; however, the reason for failure is unknown. A “window of opportunity” for estrogen treatment is proposed to explain this deficiency. Here, we found that facilitation of memory extinction and long-term depression by 17β-estradiol (E2) was normal in mice 1 week after ovariectomy (OVXST), but it was impaired in mice 3 months after ovariectomy (OVXLT). High-throughput sequencing revealed a decrease of miR-221-5p, which promoted cannabinoid receptor 1 (CB1) ubiquitination by upregulation of Neurl1a/b in E2-treated OVXLT mice. Blood samples from postmenopausal women aged 56–65 indicated decreases of miR-221-5p and 2-arachidonoylglycerol compared with samples from perimenopausal women aged 46–55. Replenishing of miR-221-5p or treatment with a CB1 agonist rescued the impairment of fear extinction in E2-treated OVXLT mice. The present study demonstrates that an HT time window in mice can be prolonged by cotreatment with a CB1 agonist, implying a potential strategy for HT in long-term menopausal women.
Kun Zhang, Qi Yang, Le Yang, Yan-jiao Li, Xin-shang Wang, Yu-jiao Li, Rui-li Dang, Shao-yu Guan, Yan-yan Guo, Ting Sun, Yu-mei Wu, An Liu, Yan Zhang, Shui-bing Liu, Ming-gao Zhao
Bariatric surgeries are integral to the management of obesity and its metabolic complications. However, these surgeries cause bone loss and increase fracture risk through poorly understood mechanisms. In a mouse model, vertical sleeve gastrectomy (VSG) caused trabecular and cortical bone loss that was independent of sex, body weight, and diet, and this loss was characterized by impaired osteoid mineralization and bone formation. VSG had a profound effect on the bone marrow niche, with rapid loss of marrow adipose tissue, and expansion of myeloid cellularity, leading to increased circulating neutrophils. Following VSG, circulating granulocyte–colony stimulating factor (G-CSF) was increased in mice, and was transiently elevated in a longitudinal study of humans. Elevation of G-CSF was found to recapitulate many effects of VSG on bone and the marrow niche. In addition to stimulatory effects of G-CSF on myelopoiesis, endogenous G-CSF suppressed development of marrow adipocytes and hindered accrual of peak cortical and trabecular bone. Effects of VSG on induction of neutrophils and depletion of marrow adiposity were reduced in mice deficient for G-CSF; however, bone mass was not influenced. Although not a primary mechanism for bone loss with VSG, G-CSF plays an intermediary role for effects of VSG on the bone marrow niche.
Ziru Li, Julie Hardij, Simon S. Evers, Chelsea R. Hutch, Sarah M. Choi, Yikai Shao, Brian S. Learman, Kenneth T. Lewis, Rebecca L. Schill, Hiroyuki Mori, Devika P. Bagchi, Steven M. Romanelli, Ki-Suk Kim, Emily Bowers, Cameron Griffin, Randy J. Seeley, Kanakadurga Singer, Darleen A. Sandoval, Clifford J. Rosen, Ormond A. MacDougald
Chronic glucocorticoid therapy has serious side effects, including diabetes and fatty liver. However, the molecular mechanisms responsible for steroid-induced diabetes remain largely enigmatic. Here, we show that hepatic Krüppel-like factor 9 (Klf9) gene expression is induced by dexamethasone and fasting. The overexpression of Klf9 in primary hepatocytes strongly stimulated Pgc1a gene expression through direct binding to its promoter, thereby activating the gluconeogenic program. However, Klf9 mutation abolished the stimulatory effect of dexamethasone on cellular glucose output. Adenovirus-mediated overexpression of KLF9 in the mouse liver markedly increased blood glucose levels and impaired glucose tolerance. Conversely, both global Klf9-mutant mice and liver-specific Klf9-deleted mice displayed fasting hypoglycemia. Moreover, the knockdown of Klf9 in the liver in diabetic mouse models, including ob/ob and db/db mice, markedly lowered fasting blood glucose levels. Notably, hepatic Klf9 deficiency in mice alleviated hyperglycemia induced by chronic dexamethasone treatment. These results suggest a critical role for KLF9 in the regulation of hepatic glucose metabolism and identify hepatic induction of KLF9 as a mechanism underlying glucocorticoid therapy–induced diabetes.
Anfang Cui, Heng Fan, Yinliang Zhang, Yujie Zhang, Dong Niu, Shuainan Liu, Quan Liu, Wei Ma, Zhufang Shen, Lian Shen, Yanling Liu, Huabing Zhang, Yuan Xue, Ying Cui, Qinghua Wang, Xinhua Xiao, Fude Fang, Jichun Yang, Qinghua Cui, Yongsheng Chang
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.
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
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.
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
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.
Alberto Bartolome, Changyu Zhu, Lori Sussel, Utpal B. Pajvani