Interplay between energy-storing white adipose cells and thermogenic beige adipocytes contributes to obesity and insulin resistance. Irrespective of specialized niche, adipocytes require the activity of the nuclear receptor PPARγ for proper function. Exposure to cold or adrenergic signaling enriches thermogenic cells though multiple pathways that act synergistically with PPARγ; however, the molecular mechanisms by which PPARγ licenses white adipose tissue to preferentially adopt a thermogenic or white adipose fate in response to dietary cues or thermoneutral conditions are not fully elucidated. Here, we show that a PPARγ/long noncoding RNA (lncRNA) axis integrates canonical and noncanonical thermogenesis to restrain white adipose tissue heat dissipation during thermoneutrality and diet-induced obesity. Pharmacologic inhibition or genetic deletion of the lncRNA Lexis enhances uncoupling protein 1–dependent (UCP1-dependent) and -independent thermogenesis. Adipose-specific deletion of Lexis counteracted diet-induced obesity, improved insulin sensitivity, and enhanced energy expenditure. Single-nuclei transcriptomics revealed that Lexis regulates a distinct population of thermogenic adipocytes. We systematically map Lexis motif preferences and show that it regulates the thermogenic program through the activity of the metabolic GWAS gene and WNT modulator TCF7L2. Collectively, our studies uncover a new mode of crosstalk between PPARγ and WNT that preserves white adipose tissue plasticity.
Zhengyi Zhang, Ya Cui, Vivien Su, Dan Wang, Marcus J. Tol, Lijing Cheng, Xiaohui Wu, Jason Kim, Prashant Rajbhandari, Sicheng Zhang, Wei Li, Peter Tontonoz, Claudio J. Villanueva, Tamer Sallam
The G protein-coupled receptor 84 (GPR84), a medium-chain fatty acid receptor, has garnered attention because of its potential involvement in a range of metabolic conditions. However, the precise mechanisms underlying this effect remain elusive. Our study has shed light on the pivotal role of GPR84, revealing its robust expression and functional significance within the brown adipose tissue (BAT). Mice lacking GPR84 exhibited increased lipid accumulation in BAT, rendering them more susceptible to cold exposure, and displaying reduced BAT activity compared to their wild-type counterparts. Our in vitro experiments with primary brown adipocytes from GPR84 knockout mice revealed diminished expression of thermogenic genes and reduced O2 consumption. Furthermore, the application of the GPR84 agonist 6-OAU counteracted these effects, effectively reinstating the brown adipocyte activity. These compelling in vivo and in vitro findings converge to highlight mitochondrial dysfunction as the primary cause of BAT anomalies in GPR84 knockout mice. The activation of GPR84 induced an increase in intracellular Ca2+ levels, which intricately influences mitochondrial respiration. By modulating mitochondrial Ca2+ levels and respiration, GPR84 has emerged as a potent molecule involved in BAT activity. These findings suggested that GPR84 is a potential therapeutic target for invigorating BAT and ameliorating metabolic disorders.
Xuenan Sun, Yu A. An, Vivian A. Paschoal, Camila O. De Souza, May-yun Wang, Lavanya Vishvanath, Lorena M.A. Bueno, Ayanna S. Cobb, Joseph A. Nieto Carrion, Madison E. Ibe, Chao Li, Harrison A. Kidd, Shiuhwei Chen, Wenhong Li, Rana K. Gupta, Da Young Oh
Why apolipoprotein AV (APOA5) deficiency causes hypertriglyceridemia has remained unclear, but we suspected that the underlying cause was reduced amounts of lipoprotein lipase (LPL) in capillaries. By routine immunohistochemistry, we observed reduced LPL staining of heart and brown adipose tissue (BAT) capillaries in Apoa5–/– mice. Also, after an intravenous injection of LPL-, CD31-, and GPIHBP1-specific monoclonal antibodies, the binding of LPL antibodies to heart and BAT capillaries (relative to CD31 or GPIHBP1 antibodies) was reduced in Apoa5–/– mice. LPL levels in the postheparin plasma were also lower in Apoa5–/– mice. We suspected that a recent biochemical observation—that APOA5 binds to the ANGPTL3/8 complex and suppresses its capacity to inhibit LPL catalytic activity—could be related to the low intracapillary LPL levels in Apoa5–/– mice. We showed that an ANGPTL3/8-specific monoclonal antibody (IBA490) and APOA5 normalize plasma triglyceride levels and intracapillary LPL levels in Apoa5–/– mice. We also showed that ANGPTL3/8 detaches LPL from HSPGs and GPIHBP1 on the surface of cells and that the LPL detachment is blocked by IBA490 and APOA5. Our studies explain the hypertriglyceridemia in Apoa5–/– mice and further illuminate the molecular mechanisms that regulate plasma triglyceride metabolism.
Ye Yang, Anne P. Beigneux, Wenxin Song, Le Phuong Nguyen, Hyesoo Jung, Yiping Tu, Thomas A. Weston, Caitlyn M. Tran, Katherine Xie, Rachel G. Yu, Anh P. Tran, Kazuya Miyashita, Katsuyuki Nakajima, Masami Murakami, Yan Q. Chen, Eugene Y. Zhen, Joonyoung R. Kim, Paul H. Kim, Gabriel Birrane, Peter Tontonoz, Michael Ploug, Robert J. Konrad, Loren G. Fong, Stephen G. Young
Glycogen storage disease type 1a (GSD1a) is caused by a congenital deficiency of glucose-6-phosphatase-alpha (G6Pase-α, encoded by G6PC), primarily associated with life-threatening hypoglycemia. Although strict dietary management substantially improves the life expectancy, patients still suffer from intermittent hypoglycemia and develop hepatic complications. Emerging therapies utilizing new modalities such as adeno-associated virus and mRNA with lipid nanoparticles are under development for GSD1a, but potentially require complicated glycemic management throughout life. Here, we present a oligonucleotide-based therapy to produce intact G6Pase-α from a pathogenic human variant, G6PC c.648G>T, the most prevalent variant in East Asia causing aberrant splicing of G6PC. DS-4108b, a splice-switching oligonucleotide, was designed to correct this aberrant splicing, especially in liver. A generated mouse strain with homozygous knock-in of this variant well reflected the pathophysiology of GSD1a patients. DS-4108b recovered hepatic G6Pase activity through splicing correction and prevented hypoglycemia and various hepatic abnormalities in the mice. Moreover, DS-4108b exhibited long-lasting efficacy for more than 12 weeks in the mice with a single dose and favorable pharmacokinetics and tolerability in mice and monkeys. Taking these findings together, this oligonucleotide-based therapy could provide a sustainable and curative therapeutic option under easy disease management for GSD1a patients with G6PC c.648G>T.
Kentaro Ito, Go Tajima, Chikako Kamisato, Miyuki Tsumura, Mitsuhiro Iwamoto, Yukiko Sekiguchi, Yukinobu Numata, Kyoko Watanabe, Yoshiyuki Yabe, Satomi Kanki, Yusuke Fujieda, Koichi Goto, Yoshitaka Sogawa, Masataka Oitate, Hiroyuki Nagase, Shinnosuke Tsuji, Tomohiro Nishizawa, Masayo Kakuta, Takeshi Masuda, Yoshiyuki Onishi, Makoto Koizumi, Hidefumi Nakamura, Satoshi Okada, Masafumi Matsuo, Kiyosumi Takaishi
The comprehensive assessment of long-term effects of reducing intake of energy (CALERIE-II; NCT00427193) clinical trial established that caloric restriction (CR) in humans lowers inflammation. The identity and mechanism of endogenous CR-mimetics that can be deployed to control obesity-associated inflammation and diseases are not well understood. Our studies have found that 2 years of 14% sustained CR in humans inhibits the expression of the matricellular protein, secreted protein acidic and rich in cysteine (SPARC), in adipose tissue. In mice, adipose tissue remodeling caused by weight loss through CR and low-protein diet feeding decreased, while high-fat diet–induced (HFD-induced) obesity increased SPARC expression in adipose tissue. Inducible SPARC downregulation in adult mice mimicked CR’s effects on lowering adiposity by regulating energy expenditure. Deletion of SPARC in adipocytes was sufficient to protect mice against HFD-induced adiposity, chronic inflammation, and metabolic dysfunction. Mechanistically, SPARC activates the NLRP3 inflammasome at the priming step and downregulation of SPARC lowers macrophage inflammation in adipose tissue, while excess SPARC activated macrophages via JNK signaling. Collectively, reduction of adipocyte-derived SPARC confers CR-like metabolic and antiinflammatory benefits in obesity by serving as an immunometabolic checkpoint of inflammation.
Seungjin Ryu, Olga Spadaro, Sviatoslav Sidorov, Aileen H. Lee, Sonia Caprio, Christopher Morrison, Steven R. Smith, Eric Ravussin, Irina Shchukina, Maxim N. Artyomov, Yun-Hee Youm, Vishwa Deep Dixit
Background: Proglucagon can be processed to Glucagon-Like Peptide-1 (GLP-1) within the islet but its contribution to islet function in humans remains unknown. We sought to understand whether ‘pancreatic’ GLP-1 alters islet function in humans and whether this is affected by type 2 diabetes.Methods: We therefore studied individuals with and without type 2 diabetes on 2 occasions in random order. On one occasion exendin 9-39, a competitive antagonist of the GLP-1 Receptor (GLP1R), was infused, while on the other saline was infused. The tracer dilution technique ([3-3H] glucose) was used to measure glucose turnover during fasting and during a hyperglycemic clamp.Results: Exendin 9-39 increased fasting glucose concentrations; fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed. In people with type 2 diabetes fasting glucagon concentrations were markedly elevated and persisted despite hyperglycemia. This impaired suppression of endogenous glucose production by hyperglycemia. These data show that GLP1R blockade impairs islet function, implying that intra-islet GLP1R activation alters islet responses to glucose and does so to a greater degree in people with type 2 diabetes.
Andrew A. Welch, Rahele A. Farahani, Aoife M. Egan, Marcello C. Laurenti, Maya Zeini, Max Vella, Kent R. Bailey, Claudio Cobelli, Chiara Dalla Dalla Man, Aleksey Matveyenko, Adrian Vella
Expanding β cell mass is a critical goal in the fight against diabetes. CDK4, an extensively characterized cell cycle activator, is required to establish and maintain β cell number. β cell failure in the IRS2-deletion mouse type 2 diabetes model is, in part, due to loss of CDK4 regulator cyclin D2. We set out to determine whether replacement of endogenous CDK4 with the inhibitor-resistant mutant CDK4-R24C rescued the loss of β cell mass in IRS2-deficient mice. Surprisingly, not only β cell mass but also β cell dedifferentiation was effectively rescued, despite no improvement in whole body insulin sensitivity. Ex vivo studies in primary islet cells revealed a mechanism in which CDK4 intervened downstream in the insulin signaling pathway to prevent FOXO1-mediated transcriptional repression of critical β cell transcription factor Pdx1. FOXO1 inhibition was not related to E2F1 activity, to FOXO1 phosphorylation, or even to FOXO1 subcellular localization, but rather was related to deacetylation and reduced FOXO1 abundance. Taken together, these results demonstrate a differentiation-promoting activity of the classical cell cycle activator CDK4 and support the concept that β cell mass can be expanded without compromising function.
Rachel E. Stamateris, Huguet V. Landa-Galvan, Rohit B. Sharma, Christine Darko, David Redmond, Sushil G. Rane, Laura C. Alonso
Circadian rhythms govern glucose homeostasis, and their dysregulation leads to complex metabolic diseases. Gut microbes exhibit diurnal rhythms that influence host circadian networks and metabolic processes, yet underlying mechanisms remain elusive. Here, we showed hierarchical, bidirectional communication among the liver circadian clock, gut microbes, and glucose homeostasis in mice. To assess this relationship, we utilized mice with liver-specific deletion of the core circadian clock gene Bmal1 via Albumin-cre maintained in either conventional or germ-free housing conditions. The liver clock, but not the forebrain clock, required gut microbes to drive glucose clearance and gluconeogenesis. Liver clock dysfunctionality expanded proportions and abundances of oscillating microbial features by 2-fold relative to that in controls. The liver clock was the primary driver of differential and rhythmic hepatic expression of glucose and fatty acid metabolic pathways. Absent the liver clock, gut microbes provided secondary cues that dampened these rhythms, resulting in reduced lipid fuel utilization relative to carbohydrates. All together, the liver clock transduced signals from gut microbes that were necessary for regulating glucose and lipid metabolism and meeting energy demands over 24 hours.
Katya Frazier, Sumeed Manzoor, Katherine Carroll, Orlando DeLeon, Sawako Miyoshi, Jun Miyoshi, Marissa St. George, Alan Tan, Evan A. Chrisler, Mariko Izumo, Joseph S. Takahashi, Mrinalini C. Rao, Vanessa A. Leone, Eugene B. Chang
Identifying branched-chain amino acid (BCAA) oxidation enzymes in the nucleus led us to predict that they are a source of propionyl-CoA that are utilized for histone propionylation and, thereby, regulate gene expression. To investigate the effects of BCAA on the development of cardiac hypertrophy and failure, we applied pressure overload on the heart in mice maintained on a diet with standard levels of BCAA (BCAA-control) versus a BCAA-free diet. The former was associated with an increase in histone H3K23-propionyl (H3K23Pr) at the promoters of upregulated genes [e.g., cell signaling and extracellular matrix genes] and a decrease at the promoters of downregulated genes [e.g., electron transfer complex (ETC I-V) and metabolic genes]. Intriguingly, the BCAA-free diet tempered the increases in promoter-H3K23Pr, thus, reducing collagen gene expression and fibrosis during cardiac hypertrophy. Conversely, the BCAA-free diet inhibited the reductions in promoter-H3K23Pr and abolished the downregulation of ETC I-V subunits, enhanced mitochondrial respiration, and curbed progression of cardiac hypertrophy. Thus, lowering the intake of BCAA reduces pressure overload-induced changes in histone propionylation-dependent gene expression in the heart, which retards the development of cardiomyopathy.
Zhi Yang, Minzhen He, Julianne Austin, Danish Sayed, Maha Abdellatif
Stimulation of adipocyte beta-adrenergic receptors (beta-ARs) induces expression of uncoupling protein 1 (UCP1), promoting non-shivering thermogenesis. Association of beta-ARs with a lysine myristoylated form of A-kinase anchoring protein 12 (AKAP12)/gravin-alpha is required for downstream signaling that culminates in UCP1 induction. Conversely, demyristoylation of gravin-alpha by histone deacetylase 11 (HDAC11) suppresses this pathway. Whether inhibition of HDAC11 in adipocytes is sufficient to drive UCP1 expression independently of beta-ARs is not known. Here, we demonstrate that adipocyte-specific deletion of HDAC11 in mice leads to robust induction of UCP1 in adipose tissue (AT), resulting in increased body temperature. These effects are mimicked by treating mice in vivo or human AT ex vivo with an HDAC11-selective inhibitor, FT895. FT895 triggers biphasic, gravin-alpha myristoylation-dependent induction of UCP1 protein expression, with a non-canonical acute response that is post-transcriptional and independent of protein kinase A (PKA), and a delayed response requiring PKA activity and new Ucp1 mRNA synthesis. Remarkably, HDAC11 inhibition promotes UCP1 expression even in models of adipocyte catecholamine resistance where beta-AR signaling is blocked. These findings define cell autonomous, multi-modal roles for HDAC11 as a suppressor of thermogenesis, and highlight the potential of inhibiting HDAC11 to therapeutically alter AT phenotype independently of beta-AR stimulation.
Emma L. Robinson, Rushita Bagchi, Jennifer L. Major, Bryan C. Bergman, Jennifer L. Matsuda, Timothy A. McKinsey