Insulin resistance is a fundamental pathogenic factor that characterizes various metabolic disorders, including obesity and type 2 diabetes. Adipose tissue contributes to the development of obesity-related insulin resistance through increased release of fatty acids, altered adipokine secretion, and/or macrophage infiltration and cytokine release. Here, we aimed to analyze the participation of the cyclin-dependent kinase 4 (CDK4) in adipose tissue biology. We determined that white adipose tissue (WAT) from CDK4-deficient mice exhibits impaired lipogenesis and increased lipolysis. Conversely, lipolysis was decreased and lipogenesis was increased in mice expressing a mutant hyperactive form of CDK4 (CDK4R24C). We performed a global kinome analysis and found that mice lacking Cdk4 had impaired insulin signaling in the adipose tissue. Interestingly, our results demonstrated that insulin activates the cyclin D3-CDK4 complex, which, in turn, phosphorylates the insulin receptor substrate 2 (IRS2) at the Ser 388, likely creating a positive feedback loop to maintain adipocyte insulin signaling. Furthermore, we found that CCND3 expression and IRS2 serine 388 phosphorylation are increased in human obese subjects. Together, our results demonstrate that CDK4 is a major regulator of insulin signaling in WAT.
Sylviane Lagarrigue, Isabel C. Lopez-Mejia, Pierre-Damien Denechaud, Xavier Escoté, Judit Castillo-Armengol, Veronica Jimenez, Carine Chavey, Albert Giralt, Qiuwen Lai, Lianjun Zhang, Laia Martinez-Carreres, Brigitte Delacuisine, Jean-Sébastien Annicotte, Emilie Blanchet, Sébastien Huré, Anna Abella, Francisco J. Tinahones, Joan Vendrell, Pierre Dubus, Fatima Bosch, C. Ronald Kahn, Lluis Fajas
Resistance to regeneration of insulin-producing pancreatic beta cells is a fundamental challenge for Type 1 and Type 2 diabetes. Recently, small molecule inhibitors of the kinase DYRK1A have proven effective in inducing adult human beta cells to proliferate, but their detailed mechanism of action is incompletely understood. We interrogated our human insulinoma and beta cell transcriptomic databases seeking to understand why beta cells in insulinomas proliferate, while normal beta cells do not. This search suggested the DREAM complex as a central regulator of quiescence in human beta cells. DREAM complex consists of a module of transcriptionally repressive proteins that assemble in response to DYRK1A kinase activity, thereby inducing and maintaining cellular quiescence. In the absence of DYRK1A, DREAM subunits reassemble into the pro-proliferative MMB complex. Here we demonstrate that small molecule DYRK1A inhibitors induce human beta cells to replicate by converting the repressive DREAM complex to its pro-proliferative MMB conformation.
Peng Wang, Esra Karakose, Carmen Argmann, Huan Wang, Metodi Balev, Rachel I. Brody, Hembly G. Rivas, Xinyue Liu, Olivia Wood, Hongtao Liu, Lauryn Choleva, Dan Hasson, Emily Bernstein, Joao A. Paulo, Donald K. Scott, Luca Lambertini, James A. DeCaprio, Andrew F. Stewart.
Hepatic inflammation is culpable for the evolution of asymptomatic steatosis to nonalcoholic steatohepatitis (NASH). Hepatic inflammation results from abnormal macrophage activation. We found that FoxO1 links overnutrition to hepatic inflammation by regulating macrophage polarization and activation. FoxO1 was upregulated in hepatic macrophages, correlating with hepatic inflammation, steatosis and fibrosis in mice and patients with NASH. Myeloid cell-conditional FoxO1 knockout skewed macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 phenotypes, accompanied by the reduction of macrophage infiltration in liver. These effects mitigated overnutrition-induced hepatic inflammation and insulin resistance, contributing to improved hepatic metabolism and increased energy expenditure in myeloid cell FoxO1 knockout mice on HFD. When fed a NASH-inducing diet, myeloid cell FoxO1 knockout mice were protected from developing NASH, culminating in the reduction of hepatic inflammation, steatosis and fibrosis. Mechanistically, FoxO1 counteracts Stat6 to skew macrophage polarization from M2 toward M1 signatures to perpetuate hepatic inflammation in NASH. FoxO1 appears as a pivotal mediator of macrophage activation in response to overnutrition and a therapeutic target for ameliorating hepatic inflammation to stem the disease progression from benign steatosis to NASH.
Sojin Lee, Taofeek O. Usman, Jun Yamauchi, Goma Chhetri, Xingchun Wang, Gina M. Coudriet, Cuiling Zhu, Jingyang Gao, Riley McConnell, Kyler Krantz, Dhivyaa Rajasundaram, Sucha Singh, Jon Piganelli, Alina Ostrowska, Alejandro Soto-Gutierrez, Satdarshan P. Monga, Aatur D. Singhi, Radhika H. Muzumdar, Allan Tsung, H. Henry Dong
BACKGROUND Multiple islet autoantibodies (AAbs) predict the development of type 1 diabetes (T1D) and hyperglycemia within 10 years. By contrast, T1D develops in only approximately 15% of individuals who are positive for single AAbs (generally against glutamic acid decarboxylase [GADA]); hence, the single GADA+ state may represent an early stage of T1D.METHODS Here, we functionally, histologically, and molecularly phenotyped human islets from nondiabetic GADA+ and T1D donors.RESULTS Similar to the few remaining β cells in the T1D islets, GADA+ donor islets demonstrated a preserved insulin secretory response. By contrast, α cell glucagon secretion was dysregulated in both GADA+ and T1D islets, with impaired glucose suppression of glucagon secretion. Single-cell RNA-Seq of GADA+ α cells revealed distinct abnormalities in glycolysis and oxidative phosphorylation pathways and a marked downregulation of cAMP-dependent protein kinase inhibitor β (PKIB), providing a molecular basis for the loss of glucose suppression and the increased effect of 3-isobutyl-1-methylxanthine (IBMX) observed in GADA+ donor islets.CONCLUSION We found that α cell dysfunction was present during the early stages of islet autoimmunity at a time when β cell mass was still normal, raising important questions about the role of early α cell dysfunction in the progression of T1D.FUNDING This work was supported by grants from the NIH (3UC4DK112217-01S1, U01DK123594-02, UC4DK112217, UC4DK112232, U01DK123716, and P30 DK019525) and the Vanderbilt Diabetes Research and Training Center (DK20593).
Nicolai M. Doliba, Andrea V. Rozo, Jeffrey Roman, Wei Qin, Daniel Traum, Long Gao, Jinping Liu, Elisabetta Manduchi, Chengyang Liu, Maria L. Golson, Golnaz Vahedi, Ali Naji, Franz M. Matschinsky, Mark A. Atkinson, Alvin C. Powers, Marcela Brissova, Klaus H. Kaestner, Doris A. Stoffers, for the HPAP Consortium
Glucocorticoid steroids are commonly prescribed for many inflammatory conditions, but chronic daily use produces adverse effects including muscle wasting and weakness. In contrast, shorter glucocorticoid pulses may improve athletic performance, although the mechanisms remain unclear. Muscle is sexually dimorphic and comparatively little is known about how male and female muscles respond to glucocorticoid steroids. We investigated the impact of once-weekly glucocorticoid exposure on skeletal muscle performance comparing male and female mice. One month of once-weekly glucocorticoid dosing improved muscle specific force in both males and females. Transcriptomic profiling of isolated myofibers identified a striking sexually dimorphic response to weekly glucocorticoids. Male myofibers had increased expression of genes in the IGF1/PI3K pathway and calcium handling, while female myofibers had profound upregulation of lipid metabolism genes. Muscles from weekly prednisone-treated males had improved calcium handling, while comparably treated female muscles had reduced intramuscular triglycerides. Consistent with altered lipid metabolism, weekly prednisone-treated female mice had greater endurance relative to controls. Using chromatin immunoprecipitation, we defined a sexually dimorphic chromatin landscape after weekly prednisone. These results demonstrate that weekly glucocorticoid exposure elicits distinct pathways in males versus females resulting in enhanced performance.
Isabella M. Salamone, Mattia Quattrocelli, David Y. Barefield, Patrick G. Page, Ibrahim Tahtah, Michele Hadhazy, Garima Tomar, Elizabeth M. McNally
Type 2 diabetes (T2D) is associated with defective insulin secretion and reduced β cell mass. Available treatments provide a temporary reprieve, but secondary failure rates are high, making insulin supplementation necessary. Reversibility of β cell failure is a key translational question. Here, we reverse engineered and interrogated pancreatic islet–specific regulatory networks to discover T2D-specific subpopulations characterized by metabolic inflexibility and endocrine progenitor/stem cell features. Single-cell gain- and loss-of-function and glucose-induced Ca2+ flux analyses of top candidate master regulatory (MR) proteins in islet cells validated transcription factor BACH2 and associated epigenetic effectors as key drivers of T2D cell states. BACH2 knockout in T2D islets reversed cellular features of the disease, restoring a nondiabetic phenotype. BACH2-immunoreactive islet cells increased approximately 4-fold in diabetic patients, confirming the algorithmic prediction of clinically relevant subpopulations. Treatment with a BACH inhibitor lowered glycemia and increased plasma insulin levels in diabetic mice, and restored insulin secretion in diabetic mice and human islets. The findings suggest that T2D-specific populations of failing β cells can be reversed and indicate pathways for pharmacological intervention, including via BACH2 inhibition.
Jinsook Son, Hongxu Ding, Thomas B. Farb, Alexander M. Efanov, Jiajun Sun, Julie L. Gore, Samreen K. Syed, Zhigang Lei, Qidi Wang, Domenico Accili, Andrea Califano
Large-cell calcifying Sertoli cell tumors (LCCSCTs) are among the most frequent lesions occurring in male Carney complex (CNC) patients. Although they constitute a key diagnostic criterion for this rare multiple neoplasia syndrome resulting from inactivating mutations of the tumor suppressor PRKAR1A, leading to unrepressed PKA activity, LCCSCT pathogenesis and origin remain elusive. Mouse models targeting Prkar1a inactivation in all somatic populations or separately in each cell type were generated to decipher the molecular and paracrine networks involved in the induction of CNC testis lesions. We demonstrate that the Prkar1a mutation was required in both stromal and Sertoli cells for the occurrence of LCCSCTs. Integrative analyses comparing transcriptomic, immunohistological data and phenotype of mutant mouse combinations led to the understanding of human LCCSCT pathogenesis and demonstrated PKA-induced paracrine molecular circuits in which the aberrant WNT4 signal production is a limiting step in shaping intratubular lesions and tumor expansion both in a mouse model and in human CNC testes.
Cyril Djari, Isabelle Sahut-Barnola, Amandine Septier, Ingrid Plotton, Nathanaëlle Montanier, Damien Dufour, Adrien Levasseur, James Wilmouth Jr., Jean-Christophe Pointud, Fabio R. Faucz, Crystal Kamilaris, Antoine-Guy Lopez, Florian Guillou, Amanda Swain, Seppo J. Vainio, Igor Tauveron, Pierre Val, Hervé Lefebvre, Constantine A. Stratakis, Antoine Martinez, Anne-Marie Lefrançois-Martinez
Dysregulation in adipokine biosynthesis and function contributes to obesity-induced metabolic diseases. However, the identities and functions of many of the obesity-induced secretory molecules remain unknown. Here, we report the identification of leucine-rich alpha-2-glycoprotein 1 (LRG1) as an obesity-associated adipokine that exacerbates high fat diet-induced hepatosteatosis and insulin resistance. Serum levels of LRG1 were markedly elevated in obese humans and mice compared to their respective controls. LRG1 deficiency in mice greatly alleviated diet-induced hepatosteatosis, obesity, and insulin resistance. Mechanistically, LRG1 bound with high selectivity to the liver and promoted hepatosteatosis by increasing de novo lipogenesis and suppressing fatty acid β-oxidation. LRG1 also inhibited hepatic insulin signaling by down-regulating insulin receptor substrates 1 and 2. Our study identified LRG1 as a key molecule that mediates the crosstalk between adipocytes and hepatocytes in diet-induced hepatosteatosis and insulin resistance. Suppressing LRG1 expression and function may be a promising strategy for the treatment of obesity-related metabolic diseases.
Sijia He, Jiyoon Ryu, Juanhong Liu, Hairong Luo, Ying Lv, Paul R. Langlais, Jie Wen, Feng Dong, Zhe Sun, Wenjuan Xia, Jane L. Lynch, Ravindranath Duggirala, Bruce J. Nicholson, Mengwei Zang, Yuguang Shi, Fang Zhang, Feng Liu, Juli Bai, Lily Q. Dong
The PRDM13 (PR Domain containing 13) putative chromatin modifier and transcriptional regulator functions downstream of the transcription factor PTF1A, which controls GABAergic fate in the spinal cord and neurogenesis in the hypothalamus. Here, we report a novel, recessive syndrome associated with PRDM13 mutation. Patients exhibited intellectual disability, ataxia with cerebellar hypoplasia, scoliosis and delayed puberty with congenital hypogonadotropic hypogonadism (CHH). Expression studies revealed Prdm13/PRDM13 transcripts in the developing hypothalamus and cerebellum in mouse and human. An analysis of hypothalamus and cerebellum development in mice homozygous for a Prdm13 mutant allele revealed a significant reduction in the number of Kisspeptin (Kiss1) neurons in the hypothalamus and PAX2+ progenitors emerging from the cerebellar ventricular zone. The latter was accompanied by ectopic expression of the glutamatergic lineage marker TLX3. Prdm13-deficient mice displayed cerebellar hypoplasia, normal gonadal structure, but delayed pubertal onset. Together, these findings identify PRDM13 as a critical regulator of GABAergic cell fate in the cerebellum and of hypothalamic kisspeptin neuron development, providing a mechanistic explanation for the co-occurrence of CHH and cerebellar hypoplasia in this syndrome. To our knowledge, this is the first evidence linking disrupted PRDM13-mediated regulation of Kiss1 neurons to CHH in humans.
Danielle E. Whittaker, Roberto Oleari, Louise C. Gregory, Polona Le Quesne Stabej, Hywel J. Williams, John G. Torpiano, Nancy Formosa, Mario J. Cachia, Daniel Field, Antonella Lettieri, Louise A. Ocaka, Alyssa J.J. Paganoni, Sakina H. Rajabali, Kimberley L.H. Riegman, Lisa B. De Martini, Taro Chaya, Iain C. Robinson, Takahisa Furukawa, Anna Cariboni, M. Albert Basson, Mehul T. Dattani
Loss-of-function mutations in the transcription factor CREB3L3 (CREBH) associate with severe hypertriglyceridemia in humans. CREBH is believed to lower plasma triglycerides by augmenting the action of lipoprotein lipase (LPL). However, by using a mouse model of type 1 diabetes mellitus (T1DM), we found that greater liver expression of active CREBH normalized both elevated plasma triglycerides and cholesterol. Residual triglyceride-rich lipoprotein (TRL) remnants were enriched in apolipoprotein E (APOE) and impoverished in APOC3, an apolipoprotein composition indicative of increased hepatic clearance. The underlying mechanism was independent of LPL as CREBH reduced both triglycerides and cholesterol in LPL-deficient mice. Instead, APOE was critical for CREBH’s ability to lower circulating remnant lipoproteins because it failed to reduce TRL cholesterol in Apoe-/- mice. Importantly, humans with CREB3L3 loss-of-function mutations exhibited increased levels of remnant lipoproteins that were deprived of APOE. Recent evidence suggests that impaired clearance of TRL remnants promotes cardiovascular disease in patients with T1DM. Consistently, we found that hepatic expression of CREBH prevented the progression of diabetes-accelerated atherosclerosis. Our results support the proposal that CREBH acts through an APOE-dependent pathway to increase hepatic clearance of remnant lipoproteins. They also implicate elevated levels of remnants in the pathogenesis of atherosclerosis in T1DM.
Masami Shimizu-Albergine, Debapriya Basu, Jenny E. Kanter, Farah Kramer, Vishal Kothari, Shelley Barnhart, Carissa Thornock, Adam E. Mullick, Noemie Clouet-Foraison, Tomas Vaisar, Jay W. Heinecke, Robert A. Hegele, Ira J. Goldberg, Karin E. Bornfeldt