The SMILE transcriptional corepressor inhibits cAMP response element–binding protein (CREB)–mediated transactivation of gluconeogenic genes

Lee, Ji-Min,Han, Hye-Sook,Jung, Yoon Seok,Harris, Robert A.,Koo, Seung-Hoi,Choi, Hueng-Sik American Society for Biochemistry and Molecular Bi 2018 The Journal of biological chemistry Vol.293 No.34

<P>Under fasting conditions, activation of several hepatic genes sets the stage for gluconeogenesis in the liver. cAMP response element-binding protein (CREB), CREB-regulated transcription coactivator 2 (CRTC2), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha) are essential for this transcriptional induction of gluconeogenic genes. PGC-1insight that may help inform potential therapeutic approaches targeting PGC-l alpha-mediated regulation of hepatic glucose metabolism. induction is mediated by activation of a CREB/CRTC2 signaling complex, and recent findings have revealed that small heterodimer partner-interacting leucine zipper protein (SMILE), a member of the CREB/ATF family of basic region-leucine zipper (bZIP) transcription factors, is an insulin-inducible corepressor that decreases PGC-1 alpha expression and abrogates its stimulatory effect on hepatic gluconeogenesis. However, the molecular mechanism whereby SMILE suppresses PGC-1a expression is unknown. Here, we investigated SMII.E's effects on the CREB/CRTC2 signaling pathway and glucose metabolism. We found that SMILE significantly inhibits CREB/ CRTC2-induced PGC-1 alpha expression by interacting with and disrupting the CREB/CRTC2 complex. Consequently, SMILE decreased PGC-1 alpha-induced hepatic gluconeogenic gene expression. Furthermore, SMILE inhibited CREB/CRTC2-induced phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) gene expression by directly repressing the expression of these genes and by indirectly inhibiting the expression of PGC-1 alpha via CREB/CRTC2 repression. Indeed, enhanced gluconeogenesis and circulating blood glucose levels in mice injected with an adenovirus construct containing a constitutively active CRTC2 variant (CRTC2-S171A) were significantly reduced by WT SMILE, but not by leucine zipper-mutated SMILE. These results reveal that SMILE represses CREB/CRTC2-induced PGC-1 alpha expression, an insight that may help inform potential therapeutic approaches targeting PGC-1 alpha-mediated regulation of hepatic glucose metabolism.</P>

Metabolic Connection of Inflammatory Pain: Pivotal Role of a Pyruvate Dehydrogenase Kinase-Pyruvate Dehydrogenase-Lactic Acid Axis

Jha, Mithilesh Kumar,Song, Gyun Jee,Lee, Maan Gee,Jeoung, Nam Ho,Go, Younghoon,Harris, Robert A.,Park, Dong Ho,Kook, Hyun,Lee, In-Kyu,Suk, Kyoungho Society for Neuroscience 2015 The Journal of neuroscience Vol.35 No.42

<P>Pyruvate dehydrogenase kinases (PDK1–4) are mitochondrial metabolic regulators that serve as decision makers via modulation of pyruvate dehydrogenase (PDH) activity to convert pyruvate either aerobically to acetyl-CoA or anaerobically to lactate. Metabolic dysregulation and inflammatory processes are two sides of the same coin in several pathophysiological conditions. The lactic acid surge associated with the metabolic shift has been implicated in diverse painful states. In this study, we investigated the role of PDK-PDH-lactic acid axis in the pathogenesis of chronic inflammatory pain. Deficiency of <I>Pdk2</I> and/or <I>Pdk4</I> in mice attenuated complete Freund's adjuvant (CFA)-induced pain hypersensitivities. Likewise, <I>Pdk2/4</I> deficiency attenuated the localized lactic acid surge along with hallmarks of peripheral and central inflammation following intraplantar administration of CFA. <I>In vitro</I> studies supported the role of PDK2/4 as promoters of classical proinflammatory activation of macrophages. Moreover, the pharmacological inhibition of PDKs or lactic acid production diminished CFA-induced inflammation and pain hypersensitivities. Thus, a PDK-PDH-lactic acid axis seems to mediate inflammation-driven chronic pain, establishing a connection between metabolism and inflammatory pain.</P><P><B>SIGNIFICANCE STATEMENT</B> The mitochondrial pyruvate dehydrogenase (PDH) kinases (PDKs) and their substrate PDH orchestrate the conversion of pyruvate either aerobically to acetyl-CoA or anaerobically to lactate. Lactate, the predominant end product of glycolysis, has recently been identified as a signaling molecule for neuron-glia interactions and neuronal plasticity. Pathological metabolic shift and subsequent lactic acid production are thought to play an important role in diverse painful states; however, their contribution to inflammation-driven pain is still to be comprehended. Here, we report that the PDK-PDH-lactic acid axis constitutes a key component of inflammatory pain pathogenesis. Our findings establish an unanticipated link between metabolism and inflammatory pain. This study unlocks a previously ill-explored research avenue for the metabolic control of inflammatory pain pathogenesis.</P>

Role of Pyruvate Dehydrogenase Kinase 4 in Regulation of Blood Glucose Levels

정남호,Robert A. Harris 대한당뇨병학회 2010 Diabetes and Metabolism Journal Vol.34 No.5

In the well-fed state a relatively high activity of the pyruvate dehydrogenase complex (PDC) reduces blood glucose levels by directing the carbon of pyruvate into the citric acid cycle. In the fasted state a relatively low activity of the PDC helps maintain blood glucose levels by conserving pyruvate and other three carbon compounds for gluconeogenesis. The relative activities of the pyruvate dehydrogenase kinases (PDKs) and the opposing pyruvate dehydrogenase phosphatases determine the activity of PDC in the fed and fasted states. Up regulation of PDK4 is largely responsible for inactivation of PDC in the fasted state. PDK4 knockout mice have lower fasting blood glucose levels than wild type mice, proving that up regulation of PDK4 is important for normal glucose homeostasis. In type 2 diabetes, up regulation of PDK4 also inactivates PDC, which promotes gluconeogenesis and thereby contributes to the hyperglycemia characteristic of this disease. When fed a high fat diet, wild type mice develop fasting hyperglycemia but PDK4 knockout mice remain euglycemic, proving that up regulation of PDK4 contributes to hyperglycemia in diabetes. These finding suggest PDK4 inhibitors might prove useful in the treatment of type 2 diabetes.

The Role of Pyruvate Metabolism in Mitochondrial Quality Control and Inflammation

이인규,Min-Ji Kim,Hoyul Lee,Dipanjan Chanda,Themis Thoudam,Hyeon-Ji Kang,Robert A. Harris 한국분자세포생물학회 2023 Molecules and cells Vol.46 No.5

Pyruvate metabolism, a key pathway in glycolysis and oxidative phosphorylation, is crucial for energy homeostasis and mitochondrial quality control (MQC), including fusion/fission dynamics and mitophagy. Alterations in pyruvate flux and MQC are associated with reactive oxygen species accumulation and Ca2+ flux into the mitochondria, which can induce mitochondrial ultrastructural changes, mitochondrial dysfunction and metabolic dysregulation. Perturbations in MQC are emerging as a central mechanism for the pathogenesis of various metabolic diseases, such as neurodegenerative diseases, diabetes and insulin resistance-related diseases. Mitochondrial Ca2+ regulates the pyruvate dehydrogenase complex (PDC), which is central to pyruvate metabolism, by promoting its dephosphorylation. Increase of pyruvate dehydrogenase kinase (PDK) is associated with perturbation of mitochondria-associated membranes (MAMs) function and Ca2+ flux. Pyruvate metabolism also plays an important role in immune cell activation and function, dysregulation of which also leads to insulin resistance and inflammatory disease. Pyruvate metabolism affects macrophage polarization, mitochondrial dynamics and MAM formation, which are critical in determining macrophage function and immune response. MAMs and MQCs have also been intensively studied in macrophage and T cell immunity. Metabolic reprogramming connected with pyruvate metabolism, mitochondrial dynamics and MAM formation are important to macrophages polarization (M1/M2) and function. T cell differentiation is also directly linked to pyruvate metabolism, with inhibition of pyruvate oxidation by PDKs promoting proinflammatory T cell polarization. This article provides a brief review on the emerging role of pyruvate metabolism in MQC and MAM function, and how dysfunction in these processes leads to metabolic and inflammatory diseases.

Role of pyruvate dehydrogenase kinase 4 in regulating PDH activation during acute muscle contraction

Herbst, Eric A.F.,Dunford, Emily C.E.,Harris, Robert A.,Vandenboom, Rene,LeBlanc, Paul J.,Roy, Brian D.,Jeoung, Nam Ho,Peters, Sandra J. Canadian Science Publishing 2012 APPLIED PHYSIOLOGY NUTRITION AND METABOLISM Vol.37 No.1

<P> The oxidation of carbohydrates in mammals is regulated by the pyruvate dehydrogenase (PDH) complex, which is covalently regulated by four PDH kinases (PDK1-4) and two PDH phosphatases (PDP1-2) unique to the PDH complex. To investigate the role that PDK4 plays in regulating PDH activation (PDHa) during muscle contraction, mouse extensor digitorum muscle was removed from wild type (WT) and PDK4-knockout (PDK4-KO) mice after a 24 h fast and stimulated for 3 min either at 10 Hz (low-intensity contraction), 40 Hz (moderate-intensity contraction), or allowed to rest. Force was recorded and muscle PDHa activity and metabolite concentrations were measured. PDHa activity was ∼2.5-fold higher at rest in PDK4-KO mice than WT mice (P = 0.009) and ∼2-fold higher in PDK4-KO mice at both 10 Hz (P @@<@@ 0.001) and 40 Hz (P @@<@@ 0.001). Force relative to muscle weight was similar at 10 Hz, but was 5.8 ± 0.7 mN·g<SUP>-1</SUP> in PDK4-KO mice and 3.5 ± 0.7 mN·g<SUP>-1</SUP> in WT mice at 40 Hz (P @@<@@ 0.001), with a similar rate of fatigue in both genotypes. From these results it was concluded that PDK4 plays a role in reducing PDHa activity during low to moderate-intensity muscle stimulation, and that absence of PDK4 and the subsequent changes in carbohydrate utilization may alter force production. </P>

Role of Pyruvate Dehydrogenase Kinase 4 in Regulation of Blood Glucose Levels

Jeoung, Nam Ho,Harris, Robert A. Korean Diabetes Association 2010 Korean diabetes journal Vol.34 No.5

<P>In the well-fed state a relatively high activity of the pyruvate dehydrogenase complex (PDC) reduces blood glucose levels by directing the carbon of pyruvate into the citric acid cycle. In the fasted state a relatively low activity of the PDC helps maintain blood glucose levels by conserving pyruvate and other three carbon compounds for gluconeogenesis. The relative activities of the pyruvate dehydrogenase kinases (PDKs) and the opposing pyruvate dehydrogenase phosphatases determine the activity of PDC in the fed and fasted states. Up regulation of PDK4 is largely responsible for inactivation of PDC in the fasted state. PDK4 knockout mice have lower fasting blood glucose levels than wild type mice, proving that up regulation of PDK4 is important for normal glucose homeostasis. In type 2 diabetes, up regulation of PDK4 also inactivates PDC, which promotes gluconeogenesis and thereby contributes to the hyperglycemia characteristic of this disease. When fed a high fat diet, wild type mice develop fasting hyperglycemia but PDK4 knockout mice remain euglycemic, proving that up regulation of PDK4 contributes to hyperglycemia in diabetes. These finding suggest PDK4 inhibitors might prove useful in the treatment of type 2 diabetes.</P>

Metformin Inhibits Growth Hormone–Mediated Hepatic <i>PDK4</i> Gene Expression Through Induction of Orphan Nuclear Receptor Small Heterodimer Partner

Kim, Yong Deuk,Kim, Yong-Hoon,Tadi, Surendar,Yu, Ji Hoon,Yim, Yong-Hyeon,Jeoung, Nam Ho,Shong, Minho,Hennighausen, Lothar,Harris, Robert A.,Lee, In-Kyu,Lee, Chul-Ho,Choi, Hueng-Sik American Diabetes Association 2012 Diabetes Vol.61 No.10

<P><B/></P><P>Growth hormone (GH) is a counter-regulatory hormone that plays an important role in preventing hypoglycemia during fasting. Because inhibition of the pyruvate dehydrogenase complex (PDC) by pyruvate dehydrogenase kinase 4 (PDK4) conserves substrates for gluconeogenesis, we tested whether GH increases PDK4 expression in liver by a signaling pathway sensitive to inhibition by metformin. The effects of GH and metformin were determined in the liver of wild-type, small heterodimer partner (SHP)-, PDK4-, and signal transducer and activator of transcription 5 (STAT5)-null mice. Administration of GH in vivo increased PDK4 expression via a pathway dependent on STAT5 phosphorylation. Metformin inhibited the induction of PDK4 expression by GH via a pathway dependent on AMP-activated protein kinase (AMPK) and SHP induction. The increase in PDK4 expression and PDC phosphorylation by GH was reduced in STAT5-null mice. Metformin decreased GH-mediated induction of PDK4 expression and metabolites in wild-type but not in SHP-null mice. In primary hepatocytes, dominant-negative mutant-AMPK and SHP knockdown prevented the inhibitory effect of metformin on GH-stimulated PDK4 expression. SHP directly inhibited STAT5 association on the <I>PDK4</I> gene promoter. Metformin inhibits GH-induced PDK4 expression and metabolites via an AMPK-SHP–dependent pathway. The metformin-AMPK-SHP network may provide a novel therapeutic approach for the treatment of hepatic metabolic disorders induced by the GH-mediated pathway.</P>

Insulin-Inducible SMILE Inhibits Hepatic Gluconeogenesis

Lee, Ji-Min,Seo, Woo-Young,Han, Hye-Sook,Oh, Kyoung-Jin,Lee, Yong-Soo,Kim, Don-Kyu,Choi, Seri,Choi, Byeong Hun,Harris, Robert A.,Lee, Chul-Ho,Koo, Seung-Hoi,Choi, Hueng-Sik American Diabetes Association 2016 Diabetes Vol.65 No.1

<P>The role of a glucagon/cAMP-dependent protein kinase-inducible coactivator PGC-1 signaling pathway is well characterized in hepatic gluconeogenesis. However, an opposing protein kinase B (PKB)/Akt-inducible corepressor signaling pathway is unknown. A previous report has demonstrated that small heterodimer partner-interacting leucine zipper protein (SMILE) regulates the nuclear receptors and transcriptional factors that control hepatic gluconeogenesis. Here, we show that hepatic SMILE expression was induced by feeding in normal mice but not in db/db and high-fat diet (HFD)-fed mice. Interestingly, SMILE expression was induced by insulin in mouse primary hepatocyte and liver. Hepatic SMILE expression was not altered by refeeding in liver-specific insulin receptor knockout (LIRKO) or PKB beta-deficient (PKB beta(-/-)) mice. At the molecular level, SMILE inhibited hepatocyte nuclear factor 4-mediated transcriptional activity via direct competition with PGC-1 alpha. Moreover, ablation of SMILE augmented gluconeogenesis and increased blood glucose levels in mice. Conversely, overexpression of SMILE reduced hepatic gluconeogenic gene expression and ameliorated hyperglycemia and glucose intolerance in db/db and HFD-fed mice. Therefore, SMILE is an insulin-inducible corepressor that suppresses hepatic gluconeogenesis. Small molecules that enhance SMILE expression would have potential for treating hyperglycemia in diabetes.</P>

O-GlcNAcylation of Orphan Nuclear Receptor Estrogen-Related Receptor γ Promotes Hepatic Gluconeogenesis

Misra, Jagannath,Kim, Don-Kyu,Jung, Yoon Seok,Kim, Han Byeol,Kim, Yong-Hoon,Yoo, Eun-Kyung,Kim, Byung Gyu,Kim, Sunghoon,Lee, In-Kyu,Harris, Robert A.,Kim, Jeong-Sun,Lee, Chul-Ho,Cho, Jin Won,Choi, Hue American Diabetes Association 2016 Diabetes Vol.65 No.10

<P>Estrogen-related receptor gamma (ERR gamma) is a major positive regulator of hepatic gluconeogenesis. Its transcriptional activity is suppressed by phosphorylation signaled by insulin in the fed state, but whether posttranslational modification alters its gluconeogenic activity in the fasted state is not known. Metabolically active hepatocytes direct a small amount of glucose into the hexosamine biosynthetic pathway, leading to protein O-GlcNAcylation. In this study, we demonstrate that ERR gamma is O-GlcNAcylated by O-GlcNAc transferase in the fasted state. This stabilizes the protein by inhibiting proteasome-mediated protein degradation, increasing ERR gamma recruitment to gluconeogenic gene promoters. Mass spectrometry identifies two serine residues (S317, S319) present in the ERR gamma ligand-binding domain that are O-GlcNAcylated. Mutation of these residues destabilizes ERR gamma protein and blocks the ability of ERR gamma to induce gluconeogenesis in vivo. The impact of this pathway on gluconeogenesis in vivo was confirmed by the observation that decreasing the amount of O-GlcNAcylated ERR gamma by overexpressing the deglycosylating enzyme O-GlcNAcase decreases ERR gamma-dependent glucose production in fasted mice. We conclude that O-GlcNAcylation of ERR gamma serves as a major signal to promote hepatic gluconeogenesis.</P>

Pyruvate dehydrogenase kinase 1 and 2 deficiency reduces high-fat diet-induced hypertrophic obesity and inhibits the differentiation of preadipocytes into mature adipocytes

강현지,Min Byong-Keol,최원일,Jeon Jae-Han,Kim Dong Wook,박성미,Lee Yun-Kyung,Kim Hwa-jin,Byeon Ju-Eun,고영훈,Ham Hye Jin,전용현,Kim Mi-Jin,Lee Jung Yi,Wende Adam R.,Choi Sung Hee,Harris Robert A.,이인규 생화학분자생물학회 2021 Experimental and molecular medicine Vol.53 No.-

Obesity is now recognized as a disease. This study revealed a novel role for pyruvate dehydrogenase kinase (PDK) in diet-induced hypertrophic obesity. Mice with global or adipose tissue-specific PDK2 deficiency were protected against diet-induced obesity. The weight of adipose tissues and the size of adipocytes were reduced. Adipocyte-specific PDK2 deficiency slightly increased insulin sensitivity in HFD-fed mice. In studies with 3T3-L1 preadipocytes, PDK2 and PDK1 expression was strongly increased during adipogenesis. Evidence was found for epigenetic induction of both PDK1 and PDK2. Gain- and loss-of-function studies with 3T3-L1 cells revealed a critical role for PDK1/2 in adipocyte differentiation and lipid accumulation. PDK1/2 induction during differentiation was also accompanied by increased expression of hypoxia-inducible factor-1α (HIF1α) and enhanced lactate production, both of which were absent in the context of PDK1/2 deficiency. Exogenous lactate supplementation increased the stability of HIF1α and promoted adipogenesis. PDK1/2 overexpression-mediated adipogenesis was abolished by HIF1α inhibition, suggesting a role for the PDK-lactate-HIF1α axis during adipogenesis. In human adipose tissue, the expression of PDK1/2 was positively correlated with that of the adipogenic marker PPARγ and inversely correlated with obesity. Similarly, PDK1/2 expression in mouse adipose tissue was decreased by chronic high-fat diet feeding. We conclude that PDK1 and 2 are novel regulators of adipogenesis that play critical roles in obesity.