51
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McFie PJ, Izzard S, Vu H, Jin Y, Beauchamp E, Berthiaume LG, Stone SJ. Membrane topology of human monoacylglycerol acyltransferase-2 and identification of regions important for its localization to the endoplasmic reticulum. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1192-1204. [PMID: 27373844 DOI: 10.1016/j.bbalip.2016.06.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 11/16/2022]
Abstract
Acyl CoA:2-monoacylglycerol acyltransferase (MGAT)-2 has an important role in dietary fat absorption in the intestine. MGAT2 resides in the endoplasmic reticulum and catalyzes the synthesis of diacylglycerol which is then utilized as a substrate for triacylglycerol synthesis. This triacylglycerol is then incorporated into chylomicrons which are released into the circulation. In this study, we determined the membrane topology of human MGAT2. Protease protection experiments showed that the C-terminus is exposed to the cytosol, while the N-terminus is partially buried in the ER membrane. MGAT2, like murine DGAT2, was found to have two transmembrane domains. We also identified a region of MGAT2 associated with the ER membrane that contains the histidine-proline-histidine-glycine sequence present in all DGAT2 family members that is thought to comprise the active site. Proteolysis experiments demonstrated that digestion of total cellular membranes from cells expressing MGAT2 with trypsin abolished MGAT activity, indicating that domains that are important for catalysis face the cytosol. We also explored the role that the five cysteines residues present in MGAT2 have in catalysis. MGAT activity was sensitive to two thiol modifiers, N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid). Furthermore, mutation of four cysteines resulted in a reduction in MGAT activity. However, when the C-terminal cysteine (C334) was mutated, MGAT activity was actually higher than that of wild-type FL-MGAT2. Lastly, we determined that both transmembrane domains of MGAT2 are important for its ER localization, and that MGAT2 is present in mitochondrial-associated membranes.
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Affiliation(s)
- Pamela J McFie
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Sabrina Izzard
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Huyen Vu
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Youzhi Jin
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada
| | - Erwan Beauchamp
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Luc G Berthiaume
- Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
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52
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Sachdev V, Leopold C, Bauer R, Patankar JV, Iqbal J, Obrowsky S, Boverhof R, Doktorova M, Scheicher B, Goeritzer M, Kolb D, Turnbull AV, Zimmer A, Hoefler G, Hussain MM, Groen AK, Kratky D. Novel role of a triglyceride-synthesizing enzyme: DGAT1 at the crossroad between triglyceride and cholesterol metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1132-1141. [PMID: 27344248 PMCID: PMC4948681 DOI: 10.1016/j.bbalip.2016.06.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 06/13/2016] [Accepted: 06/22/2016] [Indexed: 12/13/2022]
Abstract
Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in triacylglycerol (TG) biosynthesis. Here we show that genetic deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1−/−) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1−/− and DGAT1 inhibitor-treated mice. We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects whole-body cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for treating hypercholesterolemia.
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Affiliation(s)
- Vinay Sachdev
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Christina Leopold
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Raimund Bauer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Jay V Patankar
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Jahangir Iqbal
- Department of Cell Biology, SUNY Downstate Medical Center, 11203 New York, United States
| | - Sascha Obrowsky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Renze Boverhof
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Marcela Doktorova
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Bernhard Scheicher
- Institute of Pharmaceutical Sciences, University of Graz, 8010 Graz, Austria
| | - Madeleine Goeritzer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Dagmar Kolb
- Institute of Cell Biology, Histology, and Embryology, Medical University of Graz, 8010 Graz, Austria
| | | | - Andreas Zimmer
- Institute of Pharmaceutical Sciences, University of Graz, 8010 Graz, Austria
| | - Gerald Hoefler
- Institute of Pathology, Medical University of Graz, 8010 Graz, Austria
| | - M Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, 11203 New York, United States
| | - Albert K Groen
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Dagmar Kratky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria.
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53
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Acyl-CoA:Diacylglycerol Acyltransferase 1 Expression Level in the Hematopoietic Compartment Impacts Inflammation in the Vascular Plaques of Atherosclerotic Mice. PLoS One 2016; 11:e0156364. [PMID: 27223895 PMCID: PMC4880185 DOI: 10.1371/journal.pone.0156364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 05/12/2016] [Indexed: 01/09/2023] Open
Abstract
The final step of triacylglycerol synthesis is catalyzed by acyl-CoA:diacylglycerol acyltransferases (DGATs). We have previously shown that ApoE-/-Dgat1-/- mice are protected from developing atherosclerosis in association with reduced foam cell formation. However, the role of DGAT1, specifically in myeloid and other hematopoietic cell types, in determining this protective phenotype is unknown. To address this question, we reconstituted the bone marrow of irradiated Ldlr–/–mice with that from wild-type (WT→ Ldlr–/–) and Dgat1–/–(Dgat1–/–→ Ldlr–/–) donor mice. We noted that DGAT1 in the hematopoietic compartment exerts a sex-specific effect on systemic cholesterol homeostasis. However, both male and female Dgat1–/–→ Ldlr–/–mice had higher circulating neutrophil and lower lymphocyte counts than control mice, suggestive of a classical inflammatory phenotype. Moreover, specifically examining the aortae of these mice revealed that Dgat1–/–→ Ldlr–/–mice have atherosclerotic plaques with increased macrophage content. This increase was coupled to a reduced plaque collagen content, leading to a reduced collagen-to-macrophage ratio. Together, these findings point to a difference in the inflammatory contribution to plaque composition between Dgat1–/–→ Ldlr–/–and control mice. By contrast, DGAT1 deficiency did not affect the transcriptional responses of cultured macrophages to lipoprotein treatment in vitro, suggesting that the alterations seen in the plaques of Dgat1–/–→ Ldlr–/–mice in vivo do not reflect a cell intrinsic effect of DGAT1 in macrophages. We conclude that although DGAT1 in the hematopoietic compartment does not impact the overall lipid content of atherosclerotic plaques, it exerts reciprocal effects on inflammation and fibrosis, two processes that control plaque vulnerability.
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54
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Anderson JL, Carten JD, Farber SA. Using fluorescent lipids in live zebrafish larvae: From imaging whole animal physiology to subcellular lipid trafficking. Methods Cell Biol 2016; 133:165-78. [PMID: 27263413 DOI: 10.1016/bs.mcb.2016.04.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Lipids serve essential functions in cells as signaling molecules, membrane components, and sources of energy. Defects in lipid metabolism are implicated in a number of pandemic human diseases, including diabetes, obesity, and hypercholesterolemia. Many aspects of how fatty acids and cholesterol are absorbed and processed by intestinal cells remain unclear and present a hurdle to developing approaches for disease prevention and treatment. Numerous studies have shown that the zebrafish is an excellent model for vertebrate lipid metabolism. In this chapter, we review commercially available fluorescent lipids that can be deployed in live zebrafish to better understand lipid signaling and metabolism. In this chapter, we present criteria one should consider when selecting specific fluorescent lipids for the study of digestive physiology or lipid metabolism in larval zebrafish.
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Affiliation(s)
- J L Anderson
- Carnegie Institution for Science, Baltimore, MD, United States
| | - J D Carten
- Carnegie Institution for Science, Baltimore, MD, United States
| | - S A Farber
- Carnegie Institution for Science, Baltimore, MD, United States
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55
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Mansbach CM, Siddiqi S. Control of chylomicron export from the intestine. Am J Physiol Gastrointest Liver Physiol 2016; 310:G659-68. [PMID: 26950854 DOI: 10.1152/ajpgi.00228.2015] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 02/22/2016] [Indexed: 01/31/2023]
Abstract
The control of chylomicron output by the intestine is a complex process whose outlines have only recently come into focus. In this review we will cover aspects of chylomicron formation and prechylomicron vesicle generation that elucidate potential control points. Substrate (dietary fatty acids and monoacylglycerols) availability is directly related to the output rate of chylomicrons. These substrates must be converted to triacylglycerol before packaging in prechylomicrons by a series of endoplasmic reticulum (ER)-localized acylating enzymes that rapidly convert fatty acids and monoacylglycerols to triacylglycerol. The packaging of the prechylomicron with triacylglycerol is controlled by the microsomal triglyceride transport protein, another potential limiting step. The prechylomicrons, once loaded with triacylglycerol, are ready to be incorporated into the prechylomicron transport vesicle that transports the prechylomicron from the ER to the Golgi. Control of this exit step from the ER, the rate-limiting step in the transcellular movement of the triacylglycerol, is a multistep process involving the activation of PKCζ, the phosphorylation of Sar1b, releasing the liver fatty acid binding protein from a heteroquatromeric complex, which enables it to bind to the ER and organize the prechylomicron transport vesicle budding complex. We propose that control of PKCζ activation is the major physiological regulator of chylomicron output.
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Affiliation(s)
- Charles M Mansbach
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
| | - Shahzad Siddiqi
- Department of Medicine, Division of Gastroenterology, University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Medicine, Veterans Affairs Medical Center, Memphis, Tennessee
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56
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D'Aquila T, Hung YH, Carreiro A, Buhman KK. Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:730-47. [PMID: 27108063 DOI: 10.1016/j.bbalip.2016.04.012] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/16/2016] [Accepted: 04/16/2016] [Indexed: 02/07/2023]
Abstract
Dietary fat provides essential nutrients, contributes to energy balance, and regulates blood lipid concentrations. These functions are important to health, but can also become dysregulated and contribute to diseases such as obesity, diabetes, cardiovascular disease, and cancer. Within enterocytes, the digestive products of dietary fat are re-synthesized into triacylglycerol, which is either secreted on chylomicrons or stored within cytoplasmic lipid droplets (CLDs). CLDs were originally thought to be inert stores of neutral lipids, but are now recognized as dynamic organelles that function in multiple cellular processes in addition to lipid metabolism. This review will highlight recent discoveries related to dietary fat absorption with an emphasis on the presence, synthesis, and metabolism of CLDs within this process.
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Affiliation(s)
- Theresa D'Aquila
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Alicia Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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57
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Zhu JJ, Luo J, Xu HF, Wang H, Loor JJ. Short communication: Altered expression of specificity protein 1 impairs milk fat synthesis in goat mammary epithelial cells. J Dairy Sci 2016; 99:4893-4898. [PMID: 26995134 DOI: 10.3168/jds.2015-10733] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 02/05/2016] [Indexed: 11/19/2022]
Abstract
Specificity protein 1 (encoded by SP1) is a novel transcription factor important for the regulation of lipid metabolism and the normal function of various hormones in model organisms. Its potential role, if any, on ruminant milk fat is unknown. Despite the lower expression of the lipolysis-related gene ATGL (by 44 and 37% respectively), both the adenoviral overexpression and the silencing of SP1 [via short interfering (si)RNA] markedly reduced cellular triacylglycerol (TAG) content (by 28 and 25%, respectively), at least in part by decreasing the expression of DGAT1 (-36% in adenovirus treatment) and DGAT2 (-81 and -87%, respectively) that are involved in TAG synthesis. Consistent with the markedly lower expression of genes related to lipid droplet formation and secretion (TIP47 by 19 and 32%, and ADFP by 25 and 25%, respectively), cellular lipid droplet content was also decreased sharply, by 9 and 8.5%, respectively, after adenoviral overexpression of SP1 or its silencing via siRNA. Overall, the results underscored a potentially important role of SP1 in maintaining milk-fat droplet synthesis in goat mammary epithelial cells.
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Affiliation(s)
- J J Zhu
- Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Reservation and Exploitation, Southwest University for Nationalities, Chengdu, Sichuan, 610041, P. R. China; Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, 712100, P. R. China
| | - J Luo
- Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Reservation and Exploitation, Southwest University for Nationalities, Chengdu, Sichuan, 610041, P. R. China.
| | - H F Xu
- Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Reservation and Exploitation, Southwest University for Nationalities, Chengdu, Sichuan, 610041, P. R. China
| | - H Wang
- Key Laboratory of Sichuan Province for Qinghai-Tibetan Plateau Animal Genetic Reservation and Exploitation, Southwest University for Nationalities, Chengdu, Sichuan, 610041, P. R. China
| | - J J Loor
- Mammalian NutriPhysioGenomics, Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801.
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58
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Khatun I, Clark RW, Vera NB, Kou K, Erion DM, Coskran T, Bobrowski WF, Okerberg C, Goodwin B. Characterization of a Novel Intestinal Glycerol-3-phosphate Acyltransferase Pathway and Its Role in Lipid Homeostasis. J Biol Chem 2015; 291:2602-15. [PMID: 26644473 DOI: 10.1074/jbc.m115.683359] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Indexed: 01/01/2023] Open
Abstract
Dietary triglycerides (TG) are absorbed by the enterocytes of the small intestine after luminal hydrolysis into monacylglycerol and fatty acids. Before secretion on chylomicrons, these lipids are reesterified into TG, primarily through the monoacylglycerol pathway. However, targeted deletion of the primary murine monoacylglycerol acyltransferase does not quantitatively affect lipid absorption, suggesting the existence of alternative pathways. Therefore, we investigated the role of the glycerol 3-phosphate pathway in dietary lipid absorption. The expression of glycerol-3-phosphate acyltransferase (GPAT3) was examined throughout the small intestine. To evaluate the role for GPAT3 in lipid absorption, mice harboring a disrupted GPAT3 gene (Gpat3(-/-)) were subjected to an oral lipid challenge and fed a Western-type diet to characterize the role in lipid and cholesterol homeostasis. Additional mechanistic studies were performed in primary enterocytes. GPAT3 was abundantly expressed in the apical surface of enterocytes in the small intestine. After an oral lipid bolus, Gpat3(-/-) mice exhibited attenuated plasma TG excursion and accumulated lipid in the enterocytes. Electron microscopy studies revealed a lack of lipids in the lamina propria and intercellular space in Gpat3(-/-) mice. Gpat3(-/-) enterocytes displayed a compensatory increase in the synthesis of phospholipid and cholesteryl ester. When fed a Western-type diet, hepatic TG and cholesteryl ester accumulation was significantly higher in Gpat3(-/-) mice compared with the wild-type mice accompanied by elevated levels of alanine aminotransferase, a marker of liver injury. Dysregulation of bile acid metabolism was also evident in Gpat3-null mice. These studies identify GPAT3 as a novel enzyme involved in intestinal lipid metabolism.
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Affiliation(s)
- Irani Khatun
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Ronald W Clark
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Nicholas B Vera
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Kou Kou
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Derek M Erion
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Timothy Coskran
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Walter F Bobrowski
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Carlin Okerberg
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Bryan Goodwin
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
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59
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Liu J, McLaren DG, Chen D, Kan Y, Stout SJ, Shen X, Murphy BA, Forrest G, Karanam B, Sonatore L, He S, Roddy TP, Pinto S. Potential mechanism of enhanced postprandial glucagon-like peptide-1 release following treatment with a diacylglycerol acyltransferase 1 inhibitor. Pharmacol Res Perspect 2015; 3:e00193. [PMID: 27022467 PMCID: PMC4777249 DOI: 10.1002/prp2.193] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 09/01/2015] [Accepted: 09/05/2015] [Indexed: 01/09/2023] Open
Abstract
Studies have demonstrated that blockade of diacylglycerol acyltransferase 1 (DGAT1) leads to prolonged release of glucagon‐like peptide 1 (GLP‐1) after meal challenge. The current study was undertaken to investigate the mechanism of action underlying the elevated levels of GLP‐1 release following pharmacological inhibition of DGAT1. We utilized a potent, specific DGAT1 inhibitor, compound A, to investigate the changes in intestinal lipid profile in a mouse model after oral administration of the compound and challenge with tracer containing fatty meal. [13C18]‐oleic acid and LC‐MS were employed to trace the fate of dietary fatty acids provided as part of a meal challenge in lean mice. Lipid profiles in plasma, proximal to distal segments of intestine, and feces were evaluated at various times following the meal challenge to study the kinetics of fatty acid absorption, synthesis into complex lipids, and excretion. Pharmacological inhibition of DGAT1 led to reduction of postprandial total and newly synthesized triglyceride (TG) excursion and significant increases in TG and FFA levels in the distal portion of intestine enriched with enteroendocrine L cells. Enhanced levels of FFA and cholesteryl ester were observed via fecal fat profiling. DGAT1 inhibition leads to enhancement of carbon flow to the synthesis of phosphatidylcholine within the intestine. DGAT1 inhibition markedly increases levels of TG and FFA in the distal intestine, which could be the predominant contributor to the prolonged and enhanced postprandial GLP‐1 release. Inactivation of DGAT1 could provide potential benefit in the treatment of dysmetabolic diseases.
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Affiliation(s)
- Jinqi Liu
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - David G McLaren
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Dunlu Chen
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Yanqing Kan
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Steven J Stout
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Xiaolan Shen
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Beth Ann Murphy
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Gail Forrest
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Bindhu Karanam
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Lisa Sonatore
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Shuwen He
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
| | - Thomas P Roddy
- Agios Pharmaceuticals 38 Sidney Street Cambridge Massachusetts 02139
| | - Shirly Pinto
- Merck Research Laboratories 2000 Galloping Hill Road Kenilworth New Jersey 07033
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60
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Mendonza A, Hanna I, Meyers D, Koo P, Neelakantham S, Zhu B, Majumdar T, Rebello S, Sunkara G, Chen J. Assessment of pharmacokinetic drug-drug interaction between pradigastat and atazanavir or probenecid. J Clin Pharmacol 2015; 56:355-64. [PMID: 26189431 DOI: 10.1002/jcph.595] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 07/15/2015] [Indexed: 11/08/2022]
Abstract
Pradigastat, a novel diacylglycerol acyltransferase-1 inhibitor, has activity in common metabolic diseases associated with abnormal accumulation of triglycerides. In vitro studies suggest that glucuronidation is the predominant metabolism pathway for elimination of pradigastat in humans and confirmed the role of uridine 5'-diphosphoglucuronosyltransferase (UGT) enzymes, UGT1A1, -1A3, and -2B7. The in vitro studies using atazanavir as a selective inhibitor of UGT1A1 and -1A3 indicated that these enzymes contribute ∼55% toward the overall glucuronidation pathway. Therefore, a clinical study was conducted to assess the potential for drug interaction between pradigastat and probenecid (purported general UGT inhibitor) or atazanavir (selective UGT1A1, -1A3 inhibitor). The study included 2 parallel cohorts, each with 3 sequential treatment periods and 22 healthy subjects per cohort. The 90%CI of the geometric mean ratios for Cmax,ss and AUCτ,ss of pradigastat were within 0.80-1.25 when administered in combination with probenecid. However, the Cmax,ss and AUCτ,ss of pradigastat decreased by 31% (90%CI: 0.62-0.78) and 26% (0.67-0.82), respectively, when administered in combination with atazanavir. This magnitude of decrease in pradigastat steady-state exposure is not considered clinically relevant. Pradigastat was well tolerated by all subjects, either alone or in combination with atazanavir or probenecid.
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Affiliation(s)
- Anisha Mendonza
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Imad Hanna
- Novartis Institutes for BioMedical Research, East Hanover, NJ, USA
| | - Dan Meyers
- Novartis Institutes for BioMedical Research, Cambridge, MA, USA
| | - Phillip Koo
- Novartis Institutes for BioMedical Research, East Hanover, NJ, USA
| | | | - Bing Zhu
- Novartis Institutes for BioMedical Research, East Hanover, NJ, USA
| | | | - Sam Rebello
- Novartis Institutes for BioMedical Research, East Hanover, NJ, USA
| | | | - Jin Chen
- Novartis Institutes for BioMedical Research, East Hanover, NJ, USA
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61
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Structural characterisation of the acyl CoA: diacylglycerol acyltransferase 1 (DGAT1) gene and association studies with milk traits in Assaf sheep breed. Small Rumin Res 2015. [DOI: 10.1016/j.smallrumres.2015.08.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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62
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Song XS, Zhang J, Chen X, Palyha O, Chung C, Sonatore LM, Wilsie L, Stout S, McLaren DG, Taggart A, Imbriglio JE, Pinto S, Garcia-Calvo M, Addona GH. Identification of DGAT2 Inhibitors Using Mass Spectrometry. ACTA ACUST UNITED AC 2015; 21:117-26. [DOI: 10.1177/1087057115607463] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 08/23/2015] [Indexed: 11/17/2022]
Abstract
Mass spectrometry offers significant advantages over other detection technologies in the areas of hit finding, hit validation, and medicinal chemistry compound optimization. The foremost obvious advantage is the ability to directly measure enzymatic product formation. In addition, the inherent sensitivity of the liquid chromatography/mass spectrometry (LC/MS) approach allows the execution of enzymatic assays at substrate concentrations typically at or below substrate Km. Another advantage of the LC/MS approach is the ability to assay impure enzyme systems that would otherwise be difficult to prosecute with traditional labeled methods. This approach was used to identify inhibitors of diacylglycerol O-acyltransferase-2 (DGAT2), a transmembrane enzyme involved in the triglyceride (TG) production pathway. The LC/MS approach was employed because of its increased assay window (compared with control membranes) of more than sevenfold compared with less than twofold with a conventional fluorogenic assay. The ability to generate thousands of dose-dependent IC50 data was made possible by the use of a staggered parallel LC/MS system with fast elution gradients. From the hit-deconvolution efforts, several structural scaffold series were identified that inhibit DGAT2 activity. Additional profiling of one chemotype in particular identified two promising reversible and selective compounds (compound 15 and compound 16) that effectively inhibit TG production in mouse primary hepatocytes.
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Affiliation(s)
- Xuelei S. Song
- Department of Pharmacology, Merck Research Laboratories, Boston, MA, USA
| | - Jiaping Zhang
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Xun Chen
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Oksana Palyha
- Atherosclerosis, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Christine Chung
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Lisa M. Sonatore
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Larissa Wilsie
- Atherosclerosis, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Steven Stout
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - David G. McLaren
- Department of Pharmacology, Merck Research Laboratories, Kenilworth, NJ, USA
| | - Andrew Taggart
- Atherosclerosis, Merck Research Laboratories, Kenilworth, NJ, USA
| | | | - Shirly Pinto
- Atherosclerosis, Merck Research Laboratories, Kenilworth, NJ, USA
| | | | - George H. Addona
- Department of Pharmacology, Merck Research Laboratories, Boston, MA, USA
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Discovery and optimization of adamantane carboxylic acid derivatives as potent diacylglycerol acyltransferase 1 inhibitors for the potential treatment of obesity and diabetes. Eur J Med Chem 2015. [DOI: 10.1016/j.ejmech.2015.06.043] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Meyers CD, Amer A, Majumdar T, Chen J. Pharmacokinetics, pharmacodynamics, safety, and tolerability of pradigastat, a novel diacylglycerol acyltransferase 1 inhibitor in overweight or obese, but otherwise healthy human subjects. J Clin Pharmacol 2015; 55:1031-41. [PMID: 25854859 DOI: 10.1002/jcph.509] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 03/28/2015] [Indexed: 11/09/2022]
Abstract
Pradigastat is a potent and selective inhibitor of diacylglycerol acyltransferase 1, an enzyme highly expressed in the small intestine that plays a key role in postprandial triglyceride synthesis. This first-in-human study evaluated the pharmacokinetics, pharmacodynamics, safety, and tolerability of pradigastat administered at single and multiple doses in overweight or obese healthy subjects. In single-dose cohorts (n = 72), subjects were randomized sequentially to receive single doses of pradigastat (1, 3, 10, 30, 100, or 300 mg) or placebo under fasted condition and prior to breakfast. In multiple-dose cohorts (n = 106), subjects were randomized to receive pradigastat (1, 5, 10, or 25 mg) or placebo prior to breakfast for 14 days. Following a single oral dosing, pradigastat was absorbed slowly, with a median tmax of ∼10 hours and eliminated slowly with a long half-life. With multiple oral doses, a 10- to 17-fold higher systemic exposure was observed. Pradigastat treatment (single and multiple doses) led to dose-dependent suppression of postprandial triglyceride excursions over 9 hours following a high-fat meal test. In addition, pradigastat suppressed postprandial glucose and insulin and increased plasma glucagon-like peptide-1 levels. Overall, pradigastat was safe and tolerated at single and multiple doses in healthy subjects.
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Affiliation(s)
- Charles D Meyers
- Novartis Institutes for BioMedical Research (NIBR), Cambridge, MA, USA
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65
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Abstract
Dietary lipids are efficiently absorbed by the small intestine, incorporated into triglyceride-rich lipoproteins (chylomicrons), and transported in the circulation to various tissues. Intestinal lipid absorption and mobilization and chylomicron synthesis and secretion are highly regulated processes. Elevated chylomicron production rate contributes to the dyslipidemia seen in common metabolic disorders such as insulin-resistant states and type 2 diabetes and likely increases the risk for atherosclerosis seen in these conditions. An in-depth understanding of the regulation of chylomicron production may provide leads for the development of drugs that could be of therapeutic utility in the prevention of dyslipidemia and atherosclerosis. Chylomicron secretion is subject to regulation by various factors, including diet, body weight, genetic variants, hormones, nutraceuticals, medications, and emerging interventions such as bariatric surgical procedures. In this review we discuss the regulation of chylomicron production, mechanisms that underlie chylomicron dysregulation, and potential avenues for future research.
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Affiliation(s)
- Satya Dash
- Departments of Medicine and Physiology and the Banting & Best Diabetes Centre, University of Toronto, Toronto, Ontario, M5G 2C4 Canada;
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66
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Cooper DE, Grevengoed TJ, Klett EL, Coleman RA. Glycerol-3-phosphate Acyltransferase Isoform-4 (GPAT4) Limits Oxidation of Exogenous Fatty Acids in Brown Adipocytes. J Biol Chem 2015; 290:15112-20. [PMID: 25918168 DOI: 10.1074/jbc.m115.649970] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Indexed: 11/06/2022] Open
Abstract
Glycerol-3-phosphate acyltransferase-4 (GPAT4) null pups grew poorly during the suckling period and, as adults, were protected from high fat diet-induced obesity. To determine why Gpat4(-/-) mice failed to gain weight during these two periods of high fat feeding, we examined energy metabolism. Compared with controls, the metabolic rate of Gpat4(-/-) mice fed a 45% fat diet was 12% higher. Core body temperature was 1 ºC higher after high fat feeding. Food intake, fat absorption, and activity were similar in both genotypes. Impaired weight gain in Gpat4(-/-) mice did not result from increased heat loss, because both cold tolerance and response to a β3-adrenergic agonist were similar in both genotypes. Because GPAT4 comprises 65% of the total GPAT activity in brown adipose tissue (BAT), we characterized BAT function. A 45% fat diet increased the Gpat4(-/-) BAT expression of peroxisome proliferator-activated receptor α (PPAR) target genes, Cpt1α, Pgc1α, and Ucp1, and BAT mitochondria oxidized oleate and pyruvate at higher rates than controls, suggesting that fatty acid signaling and flux through the TCA cycle were enhanced. To assess the role of GPAT4 directly, neonatal BAT preadipocytes were differentiated to adipocytes. Compared with controls, Gpat4(-/-) brown adipocytes incorporated 33% less fatty acid into triacylglycerol and 46% more into the pathway of β-oxidation. The increased oxidation rate was due solely to an increase in the oxidation of exogenous fatty acids. These data suggest that in the absence of cold exposure, GPAT4 limits excessive fatty acid oxidation and the detrimental induction of a hypermetabolic state.
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Affiliation(s)
| | | | - Eric L Klett
- From the Departments of Nutrition and Medicine, University of North Carolina, Chapel Hill, North Carolina 27599
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67
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Douglass JD, Zhou YX, Wu A, Zadroga JA, Gajda AM, Lackey AI, Lang W, Chevalier KM, Sutton SW, Zhang SP, Flores CM, Connelly MA, Storch J. Global deletion of MGL in mice delays lipid absorption and alters energy homeostasis and diet-induced obesity. J Lipid Res 2015; 56:1153-71. [PMID: 25842377 DOI: 10.1194/jlr.m058586] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 11/20/2022] Open
Abstract
Monoacylglycerol lipase (MGL) is a ubiquitously expressed enzyme that catalyzes the hydrolysis of monoacylglycerols (MGs) to yield FFAs and glycerol. MGL contributes to energy homeostasis through the mobilization of fat stores and also via the degradation of the endocannabinoid 2-arachidonoyl glycerol. To further examine the role of MG metabolism in energy homeostasis, MGL(-/-) mice were fed either a 10% (kilocalories) low-fat diet (LFD) or a 45% (kilocalories) high-fat diet (HFD) for 12 weeks. Profound increases of MG species in the MGL(-/-) mice compared with WT control mice were found. Weight gain over the 12 weeks was blunted in both diet groups. MGL(-/-) mice were leaner than WT mice at both baseline and after 12 weeks of LFD feeding. Circulating lipids were decreased in HFD-fed MGL(-/-) mice, as were the levels of several plasma peptides involved in glucose homeostasis and energy balance. Interestingly, MGL(-/-) mice had markedly reduced intestinal TG secretion following an oral fat challenge, suggesting delayed lipid absorption. Overall, the results indicate that global MGL deletion leads to systemic changes that produce a leaner phenotype and an improved serum metabolic profile.
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Affiliation(s)
- John D Douglass
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Yin Xiu Zhou
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Amy Wu
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - John A Zadroga
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Angela M Gajda
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Atreju I Lackey
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901
| | - Wensheng Lang
- Janssen Research & Development, LLC, Spring House, PA 19477
| | | | | | - Sui-Po Zhang
- Janssen Research & Development, LLC, Spring House, PA 19477
| | | | | | - Judith Storch
- Department of Nutritional Sciences Rutgers University, New Brunswick, NJ 08901 Rutgers Center for Lipid Research, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, NJ 08901
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68
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Lactobacillus rhamnosus lowers zebrafish lipid content by changing gut microbiota and host transcription of genes involved in lipid metabolism. Sci Rep 2015; 5:9336. [PMID: 25822072 PMCID: PMC4378510 DOI: 10.1038/srep09336] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 02/09/2015] [Indexed: 12/24/2022] Open
Abstract
The microbiome plays an important role in lipid metabolism but how the introduction of probiotic communities affects host lipid metabolism is poorly understood. Using a multidisciplinary approach we addressed this knowledge gap using the zebrafish model by coupling high-throughput sequencing with biochemical, molecular and morphological analysis to evaluate the changes in the intestine. Analysis of bacterial 16S libraries revealed that Lactobacillus rhamnosus was able to modulate the gut microbiome of zebrafish larvae, elevating the abundance of Firmicutes sequences and reducing the abundance of Actinobacteria. The gut microbiome changes modulated host lipid processing by inducing transcriptional down-regulation of genes involved in cholesterol and triglycerides metabolism (fit2, agpat4, dgat2, mgll, hnf4α, scap, and cck) concomitantly decreasing total body cholesterol and triglyceride content and increasing fatty acid levels. L. rhamnosus treatment also increased microvilli and enterocyte lengths and decreased lipid droplet size in the intestinal epithelium. These changes resulted in elevated zebrafish larval growth. This integrated system investigation demonstrates probiotic modulation of the gut microbiome, highlights a novel gene network involved in lipid metabolism, provides an insight into how the microbiome regulates molecules involved in lipid metabolism, and reveals a new potential role for L. rhamnosus in the treatment of lipid disorders.
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69
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Li C, Li L, Lian J, Watts R, Nelson R, Goodwin B, Lehner R. Roles of Acyl-CoA:Diacylglycerol Acyltransferases 1 and 2 in Triacylglycerol Synthesis and Secretion in Primary Hepatocytes. Arterioscler Thromb Vasc Biol 2015; 35:1080-91. [PMID: 25792450 DOI: 10.1161/atvbaha.114.304584] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 03/04/2015] [Indexed: 02/06/2023]
Abstract
OBJECTIVE Very low-density lipoprotein assembly and secretion are regulated by the availability of triacylglycerol. Although compelling evidence indicates that the majority of triacylglycerol in very low-density lipoprotein is derived from re-esterification of lipolytic products released by endoplasmic reticulum-associated lipases, little is known about roles of acyl-CoA:diacylglycerol acyltransferases (DGATs) in this process. We aimed to investigate the contribution of DGAT1 and DGAT2 in lipid metabolism and lipoprotein secretion in primary mouse and human hepatocytes. APPROACH AND RESULTS We used highly selective small-molecule inhibitors of DGAT1 and DGAT2, and we tracked storage and secretion of lipids synthesized de novo from [(3)H]acetic acid and from exogenously supplied [(3)H]oleic acid. Inactivation of individual DGAT activity did not affect incorporation of either radiolabeled precursor into intracellular triacylglycerol, whereas combined inactivation of both DGATs severely attenuated triacylglycerol synthesis. However, inhibition of DGAT2 augmented fatty acid oxidation, whereas inhibition of DGAT1 increased triacylglycerol secretion, suggesting preferential channeling of separate DGAT-derived triacylglycerol pools to distinct metabolic pathways. Inactivation of DGAT2 impaired cytosolic lipid droplet expansion, whereas DGAT1 inactivation promoted large lipid droplet formation. Moreover, inactivation of DGAT2 attenuated expression of lipogenic genes. Finally, triacylglycerol secretion was significantly reduced on DGAT2 inhibition without altering extracellular apolipoprotein B levels. CONCLUSIONS Our data suggest that DGAT1 and DGAT2 can compensate for each other to synthesize triacylglycerol, but triacylglycerol synthesized by DGAT1 is preferentially channeled to oxidation, whereas DGAT2 synthesizes triacylglycerol destined for very low-density lipoprotein assembly.
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Affiliation(s)
- Chen Li
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Lena Li
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Jihong Lian
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Russell Watts
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Randal Nelson
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Bryan Goodwin
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.)
| | - Richard Lehner
- From the Group on Molecular and Cell Biology of Lipids (C.L., L.L., J.L., R.W., R.N., R.L.), Department of Cell Biology (C.L., R.L.), Department of Pediatrics (L.L., J.L., R.W., R.N., R.L.), Mazankowski Alberta Heart Institute, University of Alberta, Edmonton, Alberta, Canada; and Pfizer Global Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA (B.G.).
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70
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Lehnert K, Ward H, Berry SD, Ankersmit-Udy A, Burrett A, Beattie EM, Thomas NL, Harris B, Ford CA, Browning SR, Rawson P, Verkerk GA, van der Does Y, Adams LF, Davis SR, Jordan TW, MacGibbon AKH, Spelman RJ, Snell RG. Phenotypic population screen identifies a new mutation in bovine DGAT1 responsible for unsaturated milk fat. Sci Rep 2015; 5:8484. [PMID: 25719731 PMCID: PMC4341421 DOI: 10.1038/srep08484] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 12/30/2014] [Indexed: 12/21/2022] Open
Abstract
Selective breeding has strongly reduced the genetic diversity in livestock species, and contemporary breeding practices exclude potentially beneficial rare genetic variation from the future gene pool. Here we test whether important traits arising by new mutations can be identified and rescued in highly selected populations. We screened milks from 2.5 million cows to identify an exceptional individual which produced milk with reduced saturated fat content, and improved unsaturated and omega-3 fatty acid concentrations. The milk traits were transmitted dominantly to her offspring, and genetic mapping and genome sequencing revealed a new mutation in a previously unknown splice enhancer of the DGAT1 gene. Homozygous carriers show features of human diarrheal disorders, and may be useful for the development of therapeutic strategies. Our study demonstrates that high-throughput phenotypic screening can uncover rich genetic diversity even in inbred populations, and introduces a novel strategy to develop novel milks with improved nutritional properties.
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Affiliation(s)
- Klaus Lehnert
- 1] ViaLactia Biosciences (NZ) Ltd., Auckland, New Zealand [2] School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Hamish Ward
- ViaLactia Biosciences (NZ) Ltd., Auckland, New Zealand
| | - Sarah D Berry
- ViaLactia Biosciences (NZ) Ltd., Auckland, New Zealand
| | | | | | | | | | | | | | - Sharon R Browning
- Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
| | - Pisana Rawson
- Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | | | | | - Linda F Adams
- ViaLactia Biosciences (NZ) Ltd., Auckland, New Zealand
| | | | - T William Jordan
- Centre for Biodiscovery, Victoria University of Wellington, Wellington, New Zealand
| | | | | | - Russell G Snell
- 1] ViaLactia Biosciences (NZ) Ltd., Auckland, New Zealand [2] School of Biological Sciences, University of Auckland, Auckland, New Zealand
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71
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Zhu JJ, Luo J, Sun YT, Shi HB, Li J, Wu M, Yu K, Haile AB, Loor JJ. Short communication: Effect of inhibition of fatty acid synthase on triglyceride accumulation and effect on lipid metabolism genes in goat mammary epithelial cells. J Dairy Sci 2015; 98:3485-91. [PMID: 25726120 DOI: 10.3168/jds.2014-8202] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 01/12/2015] [Indexed: 01/12/2023]
Abstract
The role of fatty acid synthase (FASN) on de novo fatty acid synthesis has been well established. In monogastrics, unlike acetyl-coenzyme A carboxylase, FASN is primarily controlled at the transcriptional level. However, no data exist on ruminant mammary cells evaluating effects of FASN knockdown on mRNA expression of lipogenic genes. Inhibition of FASN in mammary cells by C75-mediated interference, a synthetic inhibitor of FASN activity, and short hairpin RNA-mediated interference markedly reduced cellular triglyceride content at least in part by decreasing the expression of genes related to triglyceride synthesis (GPAT, AGPAT6, and DGAT2) and enhancing the expression of lipolysis-related genes (ATGL and HSL). Consistent with the markedly lower expression of genes related to lipid droplet formation and secretion (TIP47, ADFP, BTN1A1, and XDH), cellular lipid droplets also were reduced sharply after incubation with C75 or adenovirus-short-hairpin-RNA. The results underscored the essential role of FASN in the overall process of milk-fat formation in goat mammary epithelial cells.
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Affiliation(s)
- J J Zhu
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - J Luo
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100.
| | - Y T Sun
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - H B Shi
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - J Li
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - M Wu
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - K Yu
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - A B Haile
- Shaanxi Key Laboratory of Molecular Biology for Agriculture, College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi, P. R. China 712100
| | - J J Loor
- Mammalian NutriPhysioGenomics, Department of Animal Sciences and Division of Nutritional Sciences, University of Illinois, Urbana 61801
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Effect of the DGAT1 inhibitor pradigastat on triglyceride and apoB48 levels in patients with familial chylomicronemia syndrome. Lipids Health Dis 2015; 14:8. [PMID: 25889044 PMCID: PMC4337059 DOI: 10.1186/s12944-015-0006-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 01/28/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Familial chylomicronemia syndrome (FCS) is a rare lipid disease caused by complete lipoprotein lipase (LPL) deficiency resulting in fasting chylomicronemia and severe hypertriglyceridemia. Inhibition of diacylglycerol acyltransferase 1 (DGAT1), which mediates chylomicron triglyceride (TG) synthesis, is an attractive strategy to reduce TG levels in FCS. In this study we assessed the safety, tolerability and TG-lowering efficacy of the DGAT1 inhibitor pradigastat in patients with FCS. METHODS Six FCS patients were enrolled in an open-label clinical study. Following a 1-week very low fat diet run-in period patients underwent baseline lipid assessments, including a low fat meal tolerance test. Patients then underwent three consecutive 21 day treatment periods (pradigastat at 20, 40 & 10 mg, respectively). Treatment periods were separated by washout periods of ≥4 weeks. Fasting TG levels were assessed weekly through the treatment periods. Postprandial TGs, ApoB48 and lipoprotein lipid content were also monitored. RESULTS Following once daily oral dosing, steady-state exposure was reached by Day 14. There was an approximately dose proportional increase in pradigastat exposure at studied doses. Pradigastat was associated with a 41% (20 mg) and 70% (40 mg) reduction in fasting triglyceride over 21 days of treatment. The reduction in fasting TG was almost entirely accounted for by a reduction in chylomicron TG. Pradigastat treatment also led to substantial reductions in postprandial TG as well as apo48 (both fasting and postprandial). Pradigastat was safe and well tolerated, with only mild, transient gastrointestinal adverse events. CONCLUSION The novel DGAT1 inhibitor pradigastat substantially reduces plasma TG levels in FCS patients, and may be a promising new treatment for this orphan disease. TRIAL REGISTRATION ClinicalTrials.gov identifier NCT01146522 .
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Abstract
The intestinal production of lipoproteins is one of the key processes by which the body prepares dietary lipid for dissemination to locations throughout the body where they are required. Paramount to this is the relationship between dietary lipid and the enterocytes that line the gut, along with the processes which prepare this lipid for efficient uptake by these cells. These include those which occur in the mouth and stomach along with those which occur within the intestinal lumen itself. Additionally, the interplay between digested lipid, dual avenues for lipid uptake by enterocytes (passive and lipid transporter proteins), a system of intercellular lipid resynthesis and transport, and a complex system of lipoprotein synthesis yield a system open to significant modulation. In this review, we will attempt to outline the processes of lipid digestion, lipoprotein synthesis and the exogenous and endogenous factors which exert their influence.
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Affiliation(s)
- Alan A Hennessy
- Teagasc Food Research Centre, Moorepark, Fermoy, Co. Cork, Ireland,
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74
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Han S, Hu L, Quach T, Simpson JS, Trevaskis NL, Porter CJH. Profiling the Role of Deacylation-Reacylation in the Lymphatic Transport of a Triglyceride-Mimetic Prodrug. Pharm Res 2014; 32:1830-44. [DOI: 10.1007/s11095-014-1579-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 11/13/2014] [Indexed: 01/03/2023]
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75
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Tsuda N, Kumadaki S, Higashi C, Ozawa M, Shinozaki M, Kato Y, Hoshida K, Kikuchi S, Nakano Y, Ogawa Y, Furusako S. Intestine-targeted DGAT1 inhibition improves obesity and insulin resistance without skin aberrations in mice. PLoS One 2014; 9:e112027. [PMID: 25405858 PMCID: PMC4236014 DOI: 10.1371/journal.pone.0112027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 10/10/2014] [Indexed: 11/26/2022] Open
Abstract
Objective Diacylglycerol O-acyltransferase 1 (DGAT1) catalyzes the final committed step in triglyceride biosynthesis. DGAT1 null mice are known to be resistant to diet-induced obesity, and more insulin sensitive relative to the wild-type; however, the mice exhibit abnormalities in the skin. This work determined whether the intestine-targeted DGAT1 inhibitor could improve obesity and insulin resistance without skin aberrations in mice. Design and Methods We synthesized 2 DGAT1 inhibitors: Compound A, described in the patent application from the Japan Tobacco, and Compound B (A-922500), reported by Abbott Laboratories. Both compounds were evaluated for inhibitory activities against DGAT1 enzymes and effects on the skin in mice in vivo. Compound B was further investigated for effects on obesity and insulin resistance in diet-induced-obese (DIO) mice. Results The 2 compounds comparably inhibited the DGAT1 enzyme activity and the cellular triglyceride synthesis in vitro, while they showed different distribution patterns in mice in vivo. Compound A, which distributed systemically, caused skin aberrations, while Compound B, which preferentially distributed to the intestine, improved obesity and insulin resistance without skin aberrations in DIO mice. Conclusions Our results suggest that the intestine is the key tissue in which DGAT1 plays a role in promoting obesity and insulin resistance.
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Affiliation(s)
- Naoto Tsuda
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
- Department of Molecular Endocrinology and Metabolism, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
- * E-mail:
| | - Shin Kumadaki
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Chika Higashi
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Makoto Ozawa
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Mikihiko Shinozaki
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Yutaka Kato
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Koutarou Hoshida
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Satomi Kikuchi
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Yoshihisa Nakano
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
| | - Yoshihiro Ogawa
- Department of Molecular Endocrinology and Metabolism, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Shoji Furusako
- Discovery Research, Mochida Pharmaceutical Company Limited, Shizuoka, Japan
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76
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Yen CLE, Nelson DW, Yen MI. Intestinal triacylglycerol synthesis in fat absorption and systemic energy metabolism. J Lipid Res 2014; 56:489-501. [PMID: 25231105 DOI: 10.1194/jlr.r052902] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The intestine plays a prominent role in the biosynthesis of triacylglycerol (triglyceride; TAG). Digested dietary TAG is repackaged in the intestine to form the hydrophobic core of chylomicrons, which deliver metabolic fuels, essential fatty acids, and other lipid-soluble nutrients to the peripheral tissues. By controlling the flux of dietary fat into the circulation, intestinal TAG synthesis can greatly impact systemic metabolism. Genes encoding many of the enzymes involved in TAG synthesis have been identified. Among TAG synthesis enzymes, acyl-CoA:monoacylglycerol acyltransferase 2 and acyl-CoA:diacylglycerol acyltransferase (DGAT)1 are highly expressed in the intestine. Their physiological functions have been examined in the context of whole organisms using genetically engineered mice and, in the case of DGAT1, specific inhibitors. An emerging theme from recent findings is that limiting the rate of TAG synthesis in the intestine can modulate gut hormone secretion, lipid metabolism, and systemic energy balance. The underlying mechanisms and their implications for humans are yet to be explored. Pharmacological inhibition of TAG hydrolysis in the intestinal lumen has been employed to combat obesity and associated disorders with modest efficacy and unwanted side effects. The therapeutic potential of inhibiting specific enzymes involved in intestinal TAG synthesis warrants further investigation.
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Affiliation(s)
- Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706.
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
| | - Mei-I Yen
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
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77
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Jin Y, McFie PJ, Banman SL, Brandt C, Stone SJ. Diacylglycerol acyltransferase-2 (DGAT2) and monoacylglycerol acyltransferase-2 (MGAT2) interact to promote triacylglycerol synthesis. J Biol Chem 2014; 289:28237-48. [PMID: 25164810 DOI: 10.1074/jbc.m114.571190] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Acyl CoA:1,2-diacylglycerol acyltransferase (DGAT)-2 is an integral membrane protein that catalyzes triacylglycerol (TG) synthesis using diacylglycerol and fatty acyl CoA as substrates. DGAT2 resides in the endoplasmic reticulum (ER), but when cells are incubated with fatty acids, DGAT2 interacts with lipid droplets presumably to catalyze localized TG synthesis for lipid droplet expansion. Previous studies have shown that DGAT2 interacts with proteins that synthesize its fatty acyl CoA substrates. In this study, we provide additional evidence that DGAT2 is present in a protein complex. Using a chemical cross-linker, disuccinimidyl suberate (DSS), we demonstrated that DGAT2 formed a dimer and was also part of a protein complex of ∼ 650 kDa, both in membranes and on lipid droplets. Using co-immunoprecipitation experiments and an in situ proximity ligation assay, we found that DGAT2 interacted with monoacylglycerol acyltransferase (MGAT)-2, an enzyme that catalyzes the synthesis of diacylglycerol. Deletion mutagenesis showed that the interaction with MGAT2 was dependent on the two transmembrane domains of DGAT2. No significant interaction of DGAT2 with lipin1, another enzyme that synthesizes diacylglycerol, could be detected. When co-expressed in cells, DGAT2 and MGAT2 co-localized in the ER and on lipid droplets. Co-expression also resulted in increased TG storage compared with expression of DGAT2 or MGAT2 alone. Incubating McArdle rat hepatoma RH7777 cells with 2-monoacylglycerol caused DGAT2 to translocate to lipid droplets. This also led to the formation of large cytosolic lipid droplets, characteristic of DGAT2, but not DGAT1, and indicated that DGAT2 can utilize monoacylglycerol-derived diacylglycerol. These findings suggest that the interaction of DGAT2 and MGAT2 serves to channel lipid substrates efficiently for TG biosynthesis.
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Affiliation(s)
- Youzhi Jin
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada and
| | - Pamela J McFie
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada and
| | - Shanna L Banman
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4, Canada
| | - Curtis Brandt
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada and
| | - Scot J Stone
- From the Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada and
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78
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Choi PM, Guo J, Erwin CR, Wandu WS, Leinicke JA, Xie Y, Davidson NO, Warner BW. Disruption of retinoblastoma protein expression in the intestinal epithelium impairs lipid absorption. Am J Physiol Gastrointest Liver Physiol 2014; 306:G909-15. [PMID: 24742992 PMCID: PMC4024723 DOI: 10.1152/ajpgi.00067.2014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 04/07/2014] [Indexed: 01/31/2023]
Abstract
We previously demonstrated increased villus height following genetic deletion, or knockout, of retinoblastoma protein (Rb) in the intestinal epithelium (Rb-IKO). Here we determined the functional consequences of augmented mucosal growth on intestinal fat absorption and following a 50% small bowel resection (SBR). Mice with constitutively disrupted Rb expression in the intestinal epithelium (Rb-IKO) along with their floxed (wild-type, WT) littermates were placed on a high-fat diet (HFD, 42% kcal fat) for 54 wk. Mice were weighed weekly, and fat absorption, indirect calorimetry, and MRI body composition were measured. Rb-IKO mice were also subjected to a 50% SBR, followed by HFD feeding for 33 wk. In separate experiments, we examined intestinal fat absorption in mice with conditional (tamoxifen-inducible) intestinal Rb (inducible Rb-IKO) deletion. Microarray revealed that the transcriptional expression of lipid absorption/transport genes was significantly reduced in constitutive Rb-IKO mice. These mice demonstrated greater mucosal surface area yet manifested paradoxically impaired intestinal long-chain triglyceride absorption and decreased cholesterol absorption. Despite attenuated lipid absorption, there were no differences in metabolic rate, body composition, and weight gain in Rb-IKO and WT mice at baseline and following SBR. We also confirmed fat malabsorption in inducible Rb-IKO mice. We concluded that, despite an expanded mucosal surface area, Rb-IKO mice demonstrate impaired lipid absorption without compensatory alterations in energy homeostasis or body composition. These findings underscore the importance of delineating structural/functional relationships in the gut and suggest a previously unknown role for Rb in the regulation of intestinal lipid absorption.
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Affiliation(s)
- Pamela M Choi
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Jun Guo
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Christopher R Erwin
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Wambui S Wandu
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Jennifer A Leinicke
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri
| | - Yan Xie
- Department of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri
| | - Nicholas O Davidson
- Department of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri
| | - Brad W Warner
- Division of Pediatric Surgery, St Louis Children's Hospital, Department of Surgery, Washington University School of Medicine, St. Louis, Missouri;
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79
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Nelson DW, Gao Y, Yen MI, Yen CLE. Intestine-specific deletion of acyl-CoA:monoacylglycerol acyltransferase (MGAT) 2 protects mice from diet-induced obesity and glucose intolerance. J Biol Chem 2014; 289:17338-49. [PMID: 24784138 DOI: 10.1074/jbc.m114.555961] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The absorption of dietary fat involves the re-esterification of digested triacylglycerol in the enterocytes, a process catalyzed by acyl-CoA:monoacylglycerol acyltransferase (MGAT) 2. Mice without a functional gene encoding MGAT2 (Mogat2(-/-)) are protected from diet-induced obesity. Surprisingly, these mice absorb normal amounts of dietary fat but increase their energy expenditure. MGAT2 is expressed in tissues besides intestine, including adipose tissue in both mice and humans. To test the hypothesis that intestinal MGAT2 regulates systemic energy balance, we generated and characterized mice deficient in MGAT2 specifically in the small intestine (Mogat2(IKO)). We found that, like Mogat2(-/-) mice, Mogat2(IKO) mice also showed a delay in fat absorption, a decrease in food intake, and a propensity to use fatty acids as fuel when first exposed to a high fat diet. Mogat2(IKO) mice increased energy expenditure although to a lesser degree than Mogat2(-/-) mice and were protected against diet-induced weight gain and associated comorbidities, including hepatic steatosis, hypercholesterolemia, and glucose intolerance. These findings illustrate that intestinal lipid metabolism plays a crucial role in the regulation of systemic energy balance and may be a feasible intervention target. In addition, they suggest that MGAT activity in extraintestinal tissues may also modulate energy metabolism.
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Affiliation(s)
- David W Nelson
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Yu Gao
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Mei-I Yen
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
| | - Chi-Liang Eric Yen
- From the Department of Nutritional Sciences, University of Wisconsin, Madison, Wisconsin 53706
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80
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Denison H, Nilsson C, Löfgren L, Himmelmann A, Mårtensson G, Knutsson M, Al-Shurbaji A, Tornqvist H, Eriksson JW. Diacylglycerol acyltransferase 1 inhibition with AZD7687 alters lipid handling and hormone secretion in the gut with intolerable side effects: a randomized clinical trial. Diabetes Obes Metab 2014; 16:334-43. [PMID: 24118885 DOI: 10.1111/dom.12221] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Revised: 08/21/2013] [Accepted: 09/30/2013] [Indexed: 02/02/2023]
Abstract
AIM Inhibition of diacylglycerol acyltransferase 1 (DGAT1) is a potential treatment modality for patients with type 2 diabetes mellitus and obesity, based on preclinical data suggesting it is associated with insulin sensitization and weight loss. This randomized, placebo-controlled, phase 1 study in 62 overweight or obese men explored the effects and tolerability of AZD7687, a reversible and selective DGAT1 inhibitor. METHODS Multiple doses of AZD7687 (1, 2.5, 5, 10 and 20 mg/day, n = 6 or n = 12 for each) or placebo (n = 20) were administered for 1 week. Postprandial serum triacylglycerol (TAG) was measured for 8 h after a standardized 45% fat meal. Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) were measured and a paracetamol challenge was performed to assess gastric emptying. RESULTS Dose-dependent reductions in postprandial serum TAG were demonstrated with AZD7687 doses ≥5 mg compared with placebo (p < 0.01). Significant (p < 0.001) increases in plasma GLP-1 and PYY levels were seen at these doses, but no clear effect on gastric emptying was demonstrated at the end of treatment. With AZD7687 doses >5 mg/day, gastrointestinal (GI) side effects increased; 11/18 of these participants discontinued treatment owing to diarrhoea. CONCLUSIONS Altered lipid handling and hormone secretion in the gut were demonstrated during 1-week treatment with the DGAT1 inhibitor AZD7687. However, the apparent lack of therapeutic window owing to GI side effects of AZD7687, particularly diarrhoea, makes the utility of DGAT1 inhibition as a novel treatment for diabetes and obesity questionable.
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81
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Nakamura MT, Yudell BE, Loor JJ. Regulation of energy metabolism by long-chain fatty acids. Prog Lipid Res 2013; 53:124-44. [PMID: 24362249 DOI: 10.1016/j.plipres.2013.12.001] [Citation(s) in RCA: 482] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 12/03/2013] [Accepted: 12/04/2013] [Indexed: 12/12/2022]
Abstract
In mammals, excess energy is stored primarily as triglycerides, which are mobilized when energy demands arise. This review mainly focuses on the role of long chain fatty acids (LCFAs) in regulating energy metabolism as ligands of peroxisome proliferator-activated receptors (PPARs). PPAR-alpha expressed primarily in liver is essential for metabolic adaptation to starvation by inducing genes for beta-oxidation and ketogenesis and by downregulating energy expenditure through fibroblast growth factor 21. PPAR-delta is highly expressed in skeletal muscle and induces genes for LCFA oxidation during fasting and endurance exercise. PPAR-delta also regulates glucose metabolism and mitochondrial biogenesis by inducing FOXO1 and PGC1-alpha. Genes targeted by PPAR-gamma in adipocytes suggest that PPAR-gamma senses incoming non-esterified LCFAs and induces the pathways to store LCFAs as triglycerides. Adiponectin, another important target of PPAR-gamma may act as a spacer between adipocytes to maintain their metabolic activity and insulin sensitivity. Another topic of this review is effects of skin LCFAs on energy metabolism. Specific LCFAs are required for the synthesis of skin lipids, which are essential for water barrier and thermal insulation functions of the skin. Disturbance of skin lipid metabolism often causes apparent resistance to developing obesity at the expense of normal skin function.
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Affiliation(s)
- Manabu T Nakamura
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 905 South Goodwin Avenue, Urbana, IL 61801, USA.
| | - Barbara E Yudell
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 905 South Goodwin Avenue, Urbana, IL 61801, USA
| | - Juan J Loor
- Division of Nutritional Sciences, University of Illinois at Urbana-Champaign, 905 South Goodwin Avenue, Urbana, IL 61801, USA
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82
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Abstract
Diabetes and obesity are both associated with lipotoxic cardiomyopathy exclusive of coronary artery disease and hypertension. Lipotoxicities have become a public health concern and are responsible for a significant portion of clinical cardiac disease. These abnormalities may be the result of a toxic metabolic shift to more fatty acid and less glucose oxidation with concomitant accumulation of toxic lipids. Lipids can directly alter cellular structures and activate downstream pathways leading to toxicity. Recent data have implicated fatty acids and fatty acyl coenzyme A, diacylglycerol, and ceramide in cellular lipotoxicity, which may be caused by apoptosis, defective insulin signaling, endoplasmic reticulum stress, activation of protein kinase C, MAPK activation, or modulation of PPARs.
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83
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Buttet M, Traynard V, Tran TTT, Besnard P, Poirier H, Niot I. From fatty-acid sensing to chylomicron synthesis: role of intestinal lipid-binding proteins. Biochimie 2013; 96:37-47. [PMID: 23958439 DOI: 10.1016/j.biochi.2013.08.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 08/05/2013] [Indexed: 12/31/2022]
Abstract
Today, it is well established that the development of obesity and associated diseases results, in part, from excessive lipid intake associated with a qualitative imbalance. Among the organs involved in lipid homeostasis, the small intestine is the least studied even though it determines lipid bioavailability and largely contributes to the regulation of postprandial hyperlipemia (triacylglycerols (TG) and free fatty acids (FFA)). Several Lipid-Binding Proteins (LBP) are expressed in the small intestine. Their supposed intestinal functions were initially based on what was reported in other tissues, and took no account of the physiological specificity of the small intestine. Progressively, the identification of regulating factors of intestinal LBP and the description of the phenotype of their deletion have provided new insights into cellular and molecular mechanisms involved in fat absorption. This review will discuss the physiological contribution of each LBP in the main steps of intestinal absorption of long-chain fatty acids (LCFA): uptake, trafficking and reassembly into chylomicrons (CM). Moreover, current data indicate that the small intestine is able to adapt its lipid absorption capacity to the fat content of the diet, especially through the coordinated induction of LBP. This adaptation requires the existence of a mechanism of intestinal lipid sensing. Emerging data suggest that the membrane LBP CD36 may operate as a lipid receptor that triggers an intracellular signal leading to the modulation of the expression of LBP involved in CM formation. This event could be the starting point for the optimized synthesis of large CM, which are efficiently degraded in blood. Better understanding of this intestinal lipid sensing might provide new approaches to decrease the prevalence of postprandial hypertriglyceridemia, which is associated with cardiovascular diseases, insulin resistance and obesity.
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Affiliation(s)
- Marjorie Buttet
- Physiologie de la Nutrition et Toxicologie Team (NUTox), UMR U866 INSERM, Université de Bourgogne, AgroSup Dijon, 1 Esplanade Erasme, 21000 Dijon, France
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84
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Kwak HJ, Pyun YM, Kim JY, Pagire HS, Kim KY, Kim KR, Rhee SD, Jung WH, Song JS, Bae MA, Lee DH, Ahn JH. Synthesis and biological evaluation of aminobenzimidazole derivatives with a phenylcyclohexyl acetic acid group as anti-obesity and anti-diabetic agents. Bioorg Med Chem Lett 2013; 23:4713-8. [DOI: 10.1016/j.bmcl.2013.05.081] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 05/21/2013] [Accepted: 05/24/2013] [Indexed: 11/24/2022]
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85
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Liu J, Gorski JN, Gold SJ, Chen D, Chen S, Forrest G, Itoh Y, Marsh DJ, McLaren DG, Shen Z, Sonatore L, Carballo-Jane E, Craw S, Guan X, Karanam B, Sakaki J, Szeto D, Tong X, Xiao J, Yoshimoto R, Yu H, Roddy TP, Balkovec J, Pinto S. Pharmacological inhibition of diacylglycerol acyltransferase 1 reduces body weight and modulates gut peptide release--potential insight into mechanism of action. Obesity (Silver Spring) 2013; 21:1406-15. [PMID: 23671037 DOI: 10.1002/oby.20193] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 11/11/2012] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Investigation was conducted to understand the mechanism of action of diacylglycerol acyltransferase 1 (DGAT1) using small molecules DGAT1 inhibitors, compounds K and L. DESIGN AND METHODS Biochemical and stable-label tracer approaches were applied to interrogate the functional activities of compounds K and L on TG synthesis and changes of carbon flow. Energy homeostasis and gut peptide release upon DGAT1 inhibition was conducted in mouse and dog models. RESULTS Compounds K and L, dose-dependently inhibits post-prandial TG excursion in mouse and dog models. Weight loss studies in WT and Dgat1(-/-) mice, confirmed that the effects of compound K on body weight loss is mechanism-based. Compounds K and L altered incretin peptide release following oral fat challenge. Immunohistochemical studies with intestinal tissues demonstrate lack of detectable DGAT1 immunoreactivity in enteroendocrine cells. Furthermore, (13) C-fatty acid tracing studies indicate that compound K inhibition of DGAT1 increased the production of phosphatidyl choline (PC). CONCLUSION Treatment with DGAT1 inhibitors improves lipid metabolism and body weight. DGAT1 inhibition leads to enhanced PC production via alternative carbon channeling. Immunohistological studies suggest that DGAT1 inhibitor's effects on plasma gut peptide levels are likely via an indirect mechanism. Overall these data indicate a translational potential towards the clinic.
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Affiliation(s)
- Jinqi Liu
- Merck Research Laboratories, Rahway, New Jersey, USA
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86
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Lee KR, Choi SH, Song JS, Seo H, Chae YJ, Cho HE, Ahn JH, Ahn SH, Bae MA. Determination of PF-04620110, a novel inhibitor of diacylglycerol acyltransferase-1, in rat plasma using liquid chromatography-tandem mass spectrometry and its application in pharmacokinetic studies. Biomed Chromatogr 2013; 27:846-52. [DOI: 10.1002/bmc.2869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Revised: 12/18/2012] [Accepted: 12/20/2012] [Indexed: 11/10/2022]
Affiliation(s)
- Kyeong-Ryoon Lee
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
| | - Sung Heum Choi
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
- College of Pharmacy; Chungbuk National University; Cheongju 361-763 Republic of Korea
| | - Jin-Sook Song
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
| | - Hyewon Seo
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
| | - Yoon-Jee Chae
- Department of Neurology; University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School; Piscataway NJ 08954 USA
| | - Hwang Eui Cho
- College of Pharmacy; Chungbuk National University; Cheongju 361-763 Republic of Korea
| | - Jin Hee Ahn
- Medicinal Chemistry Research Center; Korea Research Institute of Chemical Technology; Daejeon 305-600 Republic of Korea
| | - Sung-Hoon Ahn
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
| | - Myung Ae Bae
- Drug Discovery Platform Technology Team; Korea Research Institute of Chemical Technology; Daejon 305-343 Republic of Korea
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87
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Maciejewski BS, LaPerle JL, Chen D, Ghosh A, Zavadoski WJ, McDonald TS, Manion TB, Mather D, Patterson TA, Hanna M, Watkins S, Gibbs EM, Calle RA, Steppan CM. Pharmacological inhibition to examine the role of DGAT1 in dietary lipid absorption in rodents and humans. Am J Physiol Gastrointest Liver Physiol 2013; 304:G958-69. [PMID: 23558010 DOI: 10.1152/ajpgi.00384.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Alterations in fat metabolism, in particular elevated plasma concentrations of free fatty acids and triglycerides (TG), have been implicated in the pathogenesis of Type 2 diabetes, obesity, and cardiovascular disease. Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), a member of the large family of membrane-bound O-acyltransferases, catalyzes the final step in triacylglycerol formation. In the intestine, DGAT1 is one of the acyltransferases responsible for the reesterficiation of dietary TG. Following a single dose of a selective pharmacological inhibitor of DGAT1, PF-04620110, a dose-dependent inhibition of TG and vitamin A absorption postprandially was demonstrated in rodents and human subjects. In C57/BL6J mice, acute DGAT1 inhibition alters the temporal and spatial pattern of dietary lipid absorption. To understand the impact of DGAT1 inhibition on enterocyte lipid metabolism, lipomic profiling was performed in rat intestine and plasma as well as human plasma. DGAT1 inhibition causes an enrichment of polyunsaturated fatty acids within the TG class of lipids. This pharmacological intervention gives us insight as to the role of DGAT1 in human dietary lipid absorption.
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Affiliation(s)
- Benjamin S Maciejewski
- Pfizer Worldwide Research and Development, Cardiovascular and Metabolic Diseases Research Unit, Cambridge, MA, USA
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88
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Hepatic triacylglycerol synthesis and secretion: DGAT2 as the link between glycaemia and triglyceridaemia. Biochem J 2013; 451:1-12. [PMID: 23489367 DOI: 10.1042/bj20121689] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
lThe liver regulates both glycaemia and triglyceridaemia. Hyperglycaemia and hypertriglyceridaemia are both characteristic of (pre)diabetes. Recent observations on the specialised role of DGAT2 (diacylglycerol acyltransferase 2) in catalysing the de novo synthesis of triacylglycerols from newly synthesized fatty acids and nascent diacylglycerols identifies this enzyme as the link between the two. This places DGAT2 at the centre of carbohydrate-induced hypertriglyceridaemia and hepatic steatosis. This function is complemented, but not substituted for, by the ability of DGAT1 to rescue partial glycerides from complete hydrolysis. In peripheral tissues not normally considered to be lipogenic, synthesis of triacylglycerols may largely bypass DGAT2 except in hyperglycaemic/hyperinsulinaemic conditions, when induction of de novo fatty acid synthesis in these tissues may contribute towards increased triacylglycerol secretion (intestine) or insulin resistance (adipose tissue, and cardiac and skeletal muscle).
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89
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Uchida A, Slipchenko MN, Eustaquio T, Leary JF, Cheng JX, Buhman KK. Intestinal acyl-CoA:diacylglycerol acyltransferase 2 overexpression enhances postprandial triglyceridemic response and exacerbates high fat diet-induced hepatic triacylglycerol storage. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1377-85. [PMID: 23643496 DOI: 10.1016/j.bbalip.2013.04.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Revised: 04/24/2013] [Accepted: 04/25/2013] [Indexed: 02/06/2023]
Abstract
Intestinal acyl-CoA:diacylglycerol acyltransferase 2 (DGAT2) is important in the cellular and physiological responses to dietary fat. To determine the effect of increased intestinal DGAT2 on cellular and physiological responses to acute and chronic dietary fat challenges, we generated mice with intestine-specific overexpression of DGAT2 and compared them with intestine-specific overexpression of DGAT1 and wild-type (WT) mice. We found that when intestinal DGAT2 is present in excess, triacylglycerol (TG) secretion from enterocytes is enhanced compared to WT mice; however, TG storage within enterocytes is similar compared to WT mice. We found that when intestinal DGAT2 is present in excess, mRNA levels of genes involved in fatty acid oxidation were reduced. This result suggests that reduced fatty acid oxidation may contribute to increased TG secretion by overexpression of DGAT2 in intestine. Furthermore, this enhanced supply of TG for secretion in Dgat2(Int) mice may be a significant contributing factor to the elevated fasting plasma TG and exacerbated hepatic TG storage in response to a chronic HFD. These results highlight that altering fatty acid and TG metabolism within enterocytes has the capacity to alter systemic delivery of dietary fat and may serve as an effective target for preventing and treating metabolic diseases such as hepatic steatosis.
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Affiliation(s)
- Aki Uchida
- Purdue University, West Lafayette, IN, USA.
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90
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Gao Y, Nelson DW, Banh T, Yen MI, Yen CLE. Intestine-specific expression of MOGAT2 partially restores metabolic efficiency in Mogat2-deficient mice. J Lipid Res 2013; 54:1644-1652. [PMID: 23536640 DOI: 10.1194/jlr.m035493] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acyl CoA:monoacylglycerol acyltransferase (MGAT) catalyzes the resynthesis of triacylglycerol, a crucial step in the absorption of dietary fat. Mice lacking the gene Mogat2, which codes for an MGAT highly expressed in the small intestine, are resistant to obesity and other metabolic disorders induced by high-fat feeding. Interestingly, these Mogat2⁻/⁻ mice absorb normal amounts of dietary fat but exhibit a reduced rate of fat absorption, increased energy expenditure, decreased respiratory exchange ratio, and impaired metabolic efficiency. MGAT2 is expressed in tissues besides intestine. To test the hypothesis that intestinal MGAT2 enhances metabolic efficiency and promotes the storage of metabolic fuels, we introduced the human MOGAT2 gene driven by the intestine-specific villin promoter into Mogat2⁻/⁻ mice. We found that the expression of MOGAT2 in the intestine increased intestinal MGAT activity, restored fat absorption rate, partially corrected energy expenditure, and promoted weight gain upon high-fat feeding. However, the changes in respiratory exchange ratio were not reverted, and the recoveries in metabolic efficiency and weight gain were incomplete. These data indicate that MGAT2 in the intestine plays an indispensable role in enhancing metabolic efficiency but also raise the possibility that MGAT2 in other tissues may contribute to the regulation of energy metabolism.
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Affiliation(s)
- Yu Gao
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI
| | - David W Nelson
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI
| | - Taylor Banh
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI
| | - Mei-I Yen
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI
| | - Chi-Liang Eric Yen
- Department of Nutritional Sciences, University of Wisconsin, Madison, WI.
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91
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Schober G, Arnold M, Birtles S, Buckett LK, Pacheco-López G, Turnbull AV, Langhans W, Mansouri A. Diacylglycerol acyltransferase-1 inhibition enhances intestinal fatty acid oxidation and reduces energy intake in rats. J Lipid Res 2013; 54:1369-84. [PMID: 23449193 DOI: 10.1194/jlr.m035154] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Acyl CoA:diacylglycerol acyltransferase-1 (DGAT-1) catalyzes the final step in triacylglycerol (TAG) synthesis and is highly expressed in the small intestine. Because DGAT-1 knockout mice are resistant to diet-induced obesity, we investigated the acute effects of intragastric (IG) infusion of a small molecule diacylglycerol acyltransferase-1 inhibitor (DGAT-1i) on eating, circulating fat metabolites, indirect calorimetry, and hepatic and intestinal expression of key fat catabolism enzymes in male rats adapted to an 8 h feeding-16 h deprivation schedule. Also, the DGAT-1i effect on fatty acid oxidation (FAO) was investigated in enterocyte cell culture models. IG DGAT-1i infusions reduced energy intake compared with vehicle in high-fat diet (HFD)-fed rats, but scarcely in chow-fed rats. IG DGAT-1i also blunted the postprandial increase in serum TAG and increased β-hydroxybutyrate levels only in HFD-fed rats, in which it lowered the respiratory quotient and increased intestinal, but not hepatic, protein levels of Complex III of the mitochondrial respiratory chain and of mitochondrial hydroxymethylglutaryl-CoA synthase. Finally, the DGAT-1i enhanced FAO in CaCo2 (EC50 = 0.3494) and HuTu80 (EC50 = 0.00762) cells. Thus, pharmacological DGAT-1 inhibition leads to an increase in intestinal FAO and ketogenesis when dietary fat is available. This may contribute to the observed eating-inhibitory effect.
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Affiliation(s)
- Gudrun Schober
- Physiology and Behavior Laboratory, Institute of Food, Nutrition, and Health, Swiss Federal Institute of Technology, Zurich, Switzerland.
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92
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Denison H, Nilsson C, Kujacic M, Löfgren L, Karlsson C, Knutsson M, Eriksson JW. Proof of mechanism for the DGAT1 inhibitor AZD7687: results from a first-time-in-human single-dose study. Diabetes Obes Metab 2013; 15:136-43. [PMID: 22950654 DOI: 10.1111/dom.12002] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 07/30/2012] [Accepted: 09/02/2012] [Indexed: 01/29/2023]
Abstract
AIMS Inhibition of diacylglycerol acyltransferase 1 (DGAT1), which catalyses the final step in triacylglycerol (TAG) assembly, is suggested as a treatment for type 2 diabetes and obesity based on animal data indicating insulin sensitization and weight reduction. This first-time-in-human single ascending dose study explored the safety, tolerability, pharmacokinetics and pharmacodynamics of the selective DGAT1 inhibitor AZD7687. METHODS Eighty healthy male subjects were enrolled. In each of 10 cohorts, six subjects received the same dose of AZD7687 orally (range across cohorts 1-60 mg) and two placebo. Plasma AZD7687 exposure was measured repeatedly. Postprandial serum TAG excursion was measured during 8 h after a standardized mixed meal with fat energy content of 60% (SMM 60%; five cohorts, 1-20 mg), before (baseline) and after dosing, to assess effects on gut DGAT1 activity. RESULTS AZD7687 markedly reduced postprandial TAG excursion with a steep concentration-effect relationship. Incremental TAG AUC (area under the serum concentration vs. time curve) following SMM 60% was decreased >75% from baseline at doses ≥5 mg (p < 0.0001 vs. placebo). Serum levels of diacylglycerol, specifically measured with mass spectrometry, did not increase after AZD7687 administration. Nausea, vomiting and diarrhoea were reported with increasing doses and they limited dose escalation. Lowering of SMM fat content to 45 or 30% in five cohorts gradually reduced the frequency of gastrointestinal symptoms at a given dose of AZD7687. CONCLUSIONS The attenuating effect of AZD7687 on postprandial TAG excursion provides proof of mechanism with respect to gut DGAT1 inhibition. However, dose and diet-related gastrointestinal side effects may impact further development of DGAT1 inhibitors.
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93
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Semova I, Carten JD, Stombaugh J, Mackey LC, Knight R, Farber SA, Rawls JF. Microbiota regulate intestinal absorption and metabolism of fatty acids in the zebrafish. Cell Host Microbe 2013; 12:277-88. [PMID: 22980325 DOI: 10.1016/j.chom.2012.08.003] [Citation(s) in RCA: 561] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 05/01/2012] [Accepted: 08/02/2012] [Indexed: 12/16/2022]
Abstract
Regulation of intestinal dietary fat absorption is critical to maintaining energy balance. While intestinal microbiota clearly impact the host's energy balance, their role in intestinal absorption and extraintestinal metabolism of dietary fat is less clear. Using in vivo imaging of fluorescent fatty acid (FA) analogs delivered to gnotobiotic zebrafish hosts, we reveal that microbiota stimulate FA uptake and lipid droplet (LD) formation in the intestinal epithelium and liver. Microbiota increase epithelial LD number in a diet-dependent manner. The presence of food led to the intestinal enrichment of bacteria from the phylum Firmicutes. Diet-enriched Firmicutes and their products were sufficient to increase epithelial LD number, whereas LD size was increased by other bacterial types. Thus, different members of the intestinal microbiota promote FA absorption via distinct mechanisms. Diet-induced alterations in microbiota composition might influence fat absorption, providing mechanistic insight into how microbiota-diet interactions regulate host energy balance.
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Affiliation(s)
- Ivana Semova
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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94
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Diacylglycerol acyltransferase-1 (DGAT1) inhibition perturbs postprandial gut hormone release. PLoS One 2013; 8:e54480. [PMID: 23336002 PMCID: PMC3545956 DOI: 10.1371/journal.pone.0054480] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Accepted: 12/12/2012] [Indexed: 12/27/2022] Open
Abstract
Diacylglycerol acyltransferase-1 (DGAT1) is a potential therapeutic target for treatment of obesity and related metabolic diseases. However, the degree of DGAT1 inhibition required for metabolic benefits is unclear. Here we show that partial DGAT1 deficiency in mice suppressed postprandial triglyceridemia, led to elevations in glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) only following meals with very high lipid content, and did not protect from diet-induced obesity. Maximal DGAT1 inhibition led to enhanced GLP-1 and PYY secretion following meals with physiologically relevant lipid content. Finally, combination of DGAT1 inhibition with dipeptidyl-peptidase-4 (DPP-4) inhibition led to further enhancements in active GLP-1 in mice and dogs. The current study suggests that targeting DGAT1 to enhance postprandial gut hormone secretion requires maximal inhibition, and suggests combination with DPP-4i as a potential strategy to develop DGAT1 inhibitors for treatment of metabolic diseases.
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95
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Uchida A, Lee HJ, Cheng JX, Buhman KK. Imaging Cytoplasmic Lipid Droplets in Enterocytes and Assessing Dietary Fat Absorption. Methods Cell Biol 2013; 116:151-66. [DOI: 10.1016/b978-0-12-408051-5.00014-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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96
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Waring MJ, Birch AM, Birtles S, Buckett LK, Butlin RJ, Campbell L, Gutierrez PM, Kemmitt PD, Leach AG, MacFaul PA, O'Donnell C, Turnbull AV. Optimisation of biphenyl acetic acid inhibitors of diacylglycerol acetyl transferase 1 – the discovery of AZD2353. MEDCHEMCOMM 2013. [DOI: 10.1039/c2md20190a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Focus on ligand efficiency, ligand lipophilicity efficiency, and conformational restriction led to the discovery of AZD2353.
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Affiliation(s)
- Michael J. Waring
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Alan M. Birch
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Susan Birtles
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Linda K. Buckett
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Roger J. Butlin
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Leonie Campbell
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | | | - Paul D. Kemmitt
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Andrew G. Leach
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Philip A. MacFaul
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Charles O'Donnell
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
| | - Andrew V. Turnbull
- Cardiovascular and Gastrointestinal Innovative Medicines Unit
- AstraZeneca R&D
- Cheshire
- UK
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97
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Schmidt S, Willers J, Stahl F, Mutz KO, Scheper T, Hahn A, Schuchardt JP. Regulation of lipid metabolism-related gene expression in whole blood cells of normo- and dyslipidemic men after fish oil supplementation. Lipids Health Dis 2012; 11:172. [PMID: 23241455 PMCID: PMC3543286 DOI: 10.1186/1476-511x-11-172] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 12/07/2012] [Indexed: 01/19/2023] Open
Abstract
Background Beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) on the lipid levels of dyslipidemic subjects are widely described in the literature. However, the underlying molecular mechanisms are largely unknown. The aim of this study was to investigate the effects of n-3 PUFAs on the expression of lipid metabolism-related genes in normo- and dyslipidemic men to unveil potential genes and pathways affecting lipid metabolism. Methods Ten normo- and ten dyslipidemic men were supplemented for twelve weeks with six fish oil capsules per day, providing 1.14 g docosahexaenoic acid and 1.56 g eicosapentaenoic acid. The gene expression levels were determined by whole genome microarray analysis and quantitative real-time polymerase chain reaction. Results Several transcription factors (peroxisome proliferator-activated receptor α (PPARα), retinoid X receptor (RXR) α, RXRγ, hepatic nuclear factor (HNF) 6, and HNF1ß) as well as other genes related to triacylglycerol (TG) synthesis or high-density lipoprotein (HDL-C) and cholesterol metabolism (phospholipids transfer protein, ATP-binding cassette sub-family G member 5, 2-acylglycerol O-acyltransferase (MOGAT) 3, MOGAT2, diacylglycerol O-acyltransferase 1, sterol O-acyltransferase 1, apolipoprotein CII, and low-density lipoprotein receptor) were regulated after n-3 PUFA supplementation, especially in dyslipidemic men. Conclusion Gene expression analyses revealed several possible molecular pathways by which n-3 PUFAs lower the TG level and increase the HDL-C and low-density lipoprotein level, whereupon the regulation of PPARα appear to play a central role. Trial registration ClinicalTrials.gov (ID: NCT01089231)
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Affiliation(s)
- Simone Schmidt
- Institute of Food Science and Human Nutrition, Faculty of Natural Sciences at the Leibniz University of Hannover, Am Kleinen Felde 30, Hannover, 30167, Germany
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98
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Haas JT, Winter HS, Lim E, Kirby A, Blumenstiel B, DeFelice M, Gabriel S, Jalas C, Branski D, Grueter CA, Toporovski MS, Walther TC, Daly MJ, Farese RV. DGAT1 mutation is linked to a congenital diarrheal disorder. J Clin Invest 2012; 122:4680-4. [PMID: 23114594 DOI: 10.1172/jci64873] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 09/06/2012] [Indexed: 01/06/2023] Open
Abstract
Congenital diarrheal disorders (CDDs) are a collection of rare, heterogeneous enteropathies with early onset and often severe outcomes. Here, we report a family of Ashkenazi Jewish descent, with 2 out of 3 children affected by CDD. Both affected children presented 3 days after birth with severe, intractable diarrhea. One child died from complications at age 17 months. The second child showed marked improvement, with resolution of most symptoms at 10 to 12 months of age. Using exome sequencing, we identified a rare splice site mutation in the DGAT1 gene and found that both affected children were homozygous carriers. Molecular analysis of the mutant allele indicated a total loss of function, with no detectable DGAT1 protein or activity produced. The precise cause of diarrhea is unknown, but we speculate that it relates to abnormal fat absorption and buildup of DGAT substrates in the intestinal mucosa. Our results identify DGAT1 loss-of-function mutations as a rare cause of CDDs. These findings prompt concern for DGAT1 inhibition in humans, which is being assessed for treating metabolic and other diseases.
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Affiliation(s)
- Joel T Haas
- Gladstone Institute of Cardiovascular Disease, San Francisco, California 94158, USA
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99
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Ables GP, Yang KJZ, Vogel S, Hernandez-Ono A, Yu S, Yuen JJ, Birtles S, Buckett LK, Turnbull AV, Goldberg IJ, Blaner WS, Huang LS, Ginsberg HN. Intestinal DGAT1 deficiency reduces postprandial triglyceride and retinyl ester excursions by inhibiting chylomicron secretion and delaying gastric emptying. J Lipid Res 2012; 53:2364-79. [PMID: 22911105 PMCID: PMC3466005 DOI: 10.1194/jlr.m029041] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Acyl CoA:diacylglycerol acyltransferase (DGAT) 1 catalyzes the final step of triglyceride (TG) synthesis. We show that acute administration of a DGAT1 inhibitor (DGAT1i) by oral gavage or genetic deletion of intestinal Dgat1 (intestine-Dgat1(-/-)) markedly reduced postprandial plasma TG and retinyl ester excursions by inhibiting chylomicron secretion in mice. Loss of DGAT1 activity did not affect the efficiency of retinol esterification, but it did reduce TG and retinoid accumulation in the small intestine. In contrast, inhibition of microsomal triglyceride transfer protein (MTP) reduced chylomicron secretion after oral fat/retinol loads, but with accumulation of dietary TG and retinoids in the small intestine. Lack of intestinal accumulation of TG and retinoids in DGAT1i-treated or intestine-Dgat1(-/-) mice resulted, in part, from delayed gastric emptying associated with increased plasma levels of glucagon-like peptide (GLP)-1. However, neither bypassing the stomach through duodenal oil injection nor inhibiting the receptor for GLP-1 normalized postprandial TG or retinyl esters excursions in the absence of DGAT1 activity. In summary, intestinal DGAT1 inhibition or deficiency acutely delayed gastric emptying and inhibited chylomicron secretion; however, the latter occurred when gastric emptying was normal or when lipid was administered directly into the small intestine. Long-term hepatic retinoid metabolism was not impacted by DGAT1 inhibition.
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Affiliation(s)
- Gene P Ables
- Department of Medicine, Columbia University, New York, NY, USA
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100
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Abstract
Intestinal lipid transport plays a central role in fat homeostasis. Here we review the pathways regulating intestinal absorption and delivery of dietary and biliary lipid substrates, principally long-chain fatty acid, cholesterol, and other sterols. We discuss the regulation and functions of CD36 in fatty acid absorption, NPC1L1 in cholesterol absorption, as well as other lipid transporters including FATP4 and SRB1. We discuss the pathways of intestinal sterol efflux via ABCG5/G8 and ABCA1 as well as the role of the small intestine in high-density lipoprotein (HDL) biogenesis and reverse cholesterol transport. We review the pathways and genetic regulation of chylomicron assembly, the role of dominant restriction points such as microsomal triglyceride transfer protein and apolipoprotein B, and the role of CD36, l-FABP, and other proteins in formation of the prechylomicron complex. We will summarize current concepts of regulated lipoprotein secretion (including HDL and chylomicron pathways) and include lessons learned from families with genetic mutations in dominant pathways (i.e., abetalipoproteinemia, chylomicron retention disease, and familial hypobetalipoproteinemia). Finally, we will provide an integrative view of intestinal lipid homeostasis through recent findings on the role of lipid flux and fatty acid signaling via diverse receptor pathways in regulating absorption and production of satiety factors.
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Affiliation(s)
- Nada A Abumrad
- Center for Human Nutrition and Division of Gastroenterology, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA
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