Sirtuin 3 (SIRT3), an important regulator of energy metabolism and lipid oxidation, is induced in fasted liver mitochondria and implicated in metabolic syndrome. In fasted liver, SIRT3-mediated increases in substrate flux depend on oxidative phosphorylation (OXPHOS), but precisely how OXPHOS meets the challenge of increased substrate oxidation in fasted liver remains unclear. Here, we show that liver mitochondria in fasting mice adapt to the demand of increased substrate oxidation by increasing their OXPHOS efficiency. In response to cAMP signaling, SIRT3 deacetylated and activated leucine-rich protein 130 (LRP130; official symbol, LRPPRC), promoting a mitochondrial transcriptional program that enhanced hepatic OXPHOS. Using mass spectrometry, we identified SIRT3-regulated lysine residues in LRP130 that generated a lysine-to-arginine (KR) mutant of LRP130 that mimics deacetylated protein. Compared with wild-type LRP130 protein, expression of the KR mutant increased mitochondrial transcription and OXPHOS in vitro. Indeed, even when SIRT3 activity was abolished, activation of mitochondrial transcription and OXPHOS by the KR mutant remained robust, further highlighting the contribution of LRP130 deacetylation to increased OXPHOS in fasted liver. These data establish a link between nutrient sensing and mitochondrial transcription that regulates OXPHOS in fasted liver and may explain how fasted liver adapts to increased substrate oxidation.
Lijun Liu, Minwoo Nam, Wei Fan, Thomas E. Akie, David C. Hoaglin, Guangping Gao, John F. Keaney Jr., Marcus P. Cooper
How glucose sensing by the nervous system impacts the regulation of β cell mass and function during postnatal development and throughout adulthood is incompletely understood. Here, we studied mice with inactivation of glucose transporter 2 (
David Tarussio, Salima Metref, Pascal Seyer, Lourdes Mounien, David Vallois, Christophe Magnan, Marc Foretz, Bernard Thorens
Energy and glucose homeostasis are regulated by central serotonin 2C receptors. These receptors are attractive pharmacological targets for the treatment of obesity; however, the identity of the serotonin 2C receptor–expressing neurons that mediate the effects of serotonin and serotonin 2C receptor agonists on energy and glucose homeostasis are unknown. Here, we show that mice lacking serotonin 2C receptors (
Eric D. Berglund, Chen Liu, Jong-Woo Sohn, Tiemin Liu, Mi Hwa Kim, Charlotte E. Lee, Claudia R. Vianna, Kevin W. Williams, Yong Xu, Joel K. Elmquist
Inadequate functional β cell mass underlies both type 1 and type 2 diabetes. β Cell growth and regeneration also decrease with age through mechanisms that are not fully understood. Age-dependent loss of enhancer of zeste homolog 2 (EZH2) prevents adult β cell replication through derepression of the gene encoding cyclin-dependent kinase inhibitor 2a (
Josie X. Zhou, Sangeeta Dhawan, Hualin Fu, Emily Snyder, Rita Bottino, Sharmistha Kundu, Seung K. Kim, Anil Bhushan
Type 2 diabetes is characterized by insulin resistance and mitochondrial dysfunction in classical target tissues such as muscle, fat, and liver. Using a murine model of type 2 diabetes, we show that there is hypothalamic insulin resistance and mitochondrial dysfunction due to downregulation of the mitochondrial chaperone HSP60. HSP60 reduction in obese, diabetic mice was due to a lack of proper leptin signaling and was restored by leptin treatment. Knockdown of
André Kleinridders, Hans P.M.M. Lauritzen, Siegfried Ussar, Jane H. Christensen, Marcelo A. Mori, Peter Bross, C. Ronald Kahn
Insulin-independent glucose disposal (referred to as glucose effectiveness [GE]) is crucial for glucose homeostasis and, until recently, was thought to be invariable. However, GE is reduced in type 2 diabetes and markedly decreased in leptin-deficient
Gregory J. Morton, Miles E. Matsen, Deanna P. Bracy, Thomas H. Meek, Hong T. Nguyen, Darko Stefanovski, Richard N. Bergman, David H. Wasserman, Michael W. Schwartz
Circulating pancreatic glucagon is increased during fasting and maintains glucose balance by stimulating hepatic gluconeogenesis. Glucagon triggering of the cAMP pathway upregulates the gluconeogenic program through the phosphorylation of cAMP response element–binding protein (CREB) and the dephosphorylation of the CREB coactivator CRTC2. Hormonal and nutrient signals are also thought to modulate gluconeogenic gene expression by promoting epigenetic changes that facilitate assembly of the transcriptional machinery. However, the nature of these modifications is unclear. Using mouse models and in vitro assays, we show that histone H3 acetylation at Lys 9 (H3K9Ac) was elevated over gluconeogenic genes and contributed to increased hepatic glucose production during fasting and in diabetes. Dephosphorylation of CRTC2 promoted increased H3K9Ac through recruitment of the lysine acetyltransferase 2B (KAT2B) and WD repeat–containing protein 5 (WDR5), a core subunit of histone methyltransferase (HMT) complexes. KAT2B and WDR5 stimulated the gluconeogenic program through a self-reinforcing cycle, whereby increases in H3K9Ac further potentiated CRTC2 occupancy at CREB binding sites. Depletion of KAT2B or WDR5 decreased gluconeogenic gene expression, consequently breaking the cycle. Administration of a small-molecule KAT2B antagonist lowered circulating blood glucose concentrations in insulin resistance, suggesting that this enzyme may be a useful target for diabetes treatment.
Kim Ravnskjaer, Meghan F. Hogan, Denise Lackey, Laszlo Tora, Sharon Y.R. Dent, Jerrold Olefsky, Marc Montminy
Improvements in metabolite-profiling techniques are providing increased breadth of coverage of the human metabolome and may highlight biomarkers and pathways in common diseases such as diabetes. Using a metabolomics platform that analyzes intermediary organic acids, purines, pyrimidines, and other compounds, we performed a nested case-control study of 188 individuals who developed diabetes and 188 propensity-matched controls from 2,422 normoglycemic participants followed for 12 years in the Framingham Heart Study. The metabolite 2-aminoadipic acid (2-AAA) was most strongly associated with the risk of developing diabetes. Individuals with 2-AAA concentrations in the top quartile had greater than a 4-fold risk of developing diabetes. Levels of 2-AAA were not well correlated with other metabolite biomarkers of diabetes, such as branched chain amino acids and aromatic amino acids, suggesting they report on a distinct pathophysiological pathway. In experimental studies, administration of 2-AAA lowered fasting plasma glucose levels in mice fed both standard chow and high-fat diets. Further, 2-AAA treatment enhanced insulin secretion from a pancreatic β cell line as well as murine and human islets. These data highlight a metabolite not previously associated with diabetes risk that is increased up to 12 years before the onset of overt disease. Our findings suggest that 2-AAA is a marker of diabetes risk and a potential modulator of glucose homeostasis in humans.
Thomas J. Wang, Debby Ngo, Nikolaos Psychogios, Andre Dejam, Martin G. Larson, Ramachandran S. Vasan, Anahita Ghorbani, John O’Sullivan, Susan Cheng, Eugene P. Rhee, Sumita Sinha, Elizabeth McCabe, Caroline S. Fox, Christopher J. O’Donnell, Jennifer E. Ho, Jose C. Florez, Martin Magnusson, Kerry A. Pierce, Amanda L. Souza, Yi Yu, Christian Carter, Peter E. Light, Olle Melander, Clary B. Clish, Robert E. Gerszten
Polymorphisms in the fat mass and obesity-associated gene (
Efthimia Karra, Owen G. O’Daly, Agharul I. Choudhury, Ahmed Yousseif, Steven Millership, Marianne T. Neary, William R. Scott, Keval Chandarana, Sean Manning, Martin E. Hess, Hiroshi Iwakura, Takashi Akamizu, Queensta Millet, Cigdem Gelegen, Megan E. Drew, Sofia Rahman, Julian J. Emmanuel, Steven C.R. Williams, Ulrich U. Rüther, Jens C. Brüning, Dominic J. Withers, Fernando O. Zelaya, Rachel L. Batterham
Type 2 diabetes (T2DM) commonly arises from islet β cell failure and insulin resistance. Here, we examined the sensitivity of key islet-enriched transcription factors to oxidative stress, a condition associated with β cell dysfunction in both type 1 diabetes (T1DM) and T2DM. Hydrogen peroxide treatment of β cell lines induced cytoplasmic translocation of MAFA and NKX6.1. In parallel, the ability of nuclear PDX1 to bind endogenous target gene promoters was also dramatically reduced, whereas the activity of other key β cell transcriptional regulators was unaffected. MAFA levels were reduced, followed by a reduction in NKX6.1 upon development of hyperglycemia in
Shuangli Guo, Chunhua Dai, Min Guo, Brandon Taylor, Jamie S. Harmon, Maike Sander, R. Paul Robertson, Alvin C. Powers, Roland Stein