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Bu J, Guo Y, Wu Y, Zhang R, Zhuang J, Zhao J, Sun L, Quantock AJ, Liu Z, Li W. Models for Meibomian gland dysfunction: In vivo and in vitro. Ocul Surf 2024; 32:154-165. [PMID: 38490475 DOI: 10.1016/j.jtos.2024.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 02/29/2024] [Accepted: 03/12/2024] [Indexed: 03/17/2024]
Abstract
Meibomian gland dysfunction (MGD) is a chronic abnormality of the Meibomian glands (MGs) that is recognized as the leading cause of evaporative dry eye worldwide. Despite its prevalence, however, the pathophysiology of MGD remains elusive, and effective disease management continues to be a challenge. In the past 50 years, different models have been developed to illustrate the pathophysiological nature of MGD and the underlying disease mechanisms. An understanding of these models is crucial if researchers are to select an appropriate model to address specific questions related to MGD and to develop new treatments. Here, we summarize the various models of MGD, discuss their applications and limitations, and provide perspectives for future studies in the field.
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Affiliation(s)
- Jinghua Bu
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China.
| | - Yuli Guo
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Yang Wu
- Zhongshan Hospital (Xiamen), Fudan University, Xiamen, Fujian, China
| | - Rongrong Zhang
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Jingbin Zhuang
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Jiankai Zhao
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Le Sun
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China
| | - Andrew J Quantock
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom
| | - Zuguo Liu
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China; Xiamen University Affiliated Xiamen Eye Center, Xiamen, Fujian, China
| | - Wei Li
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, Fujian Engineering and Research Center of Eye Regenerative Medicine, School of Medicine, Xiamen University, Xiamen, Fujian, China; Xiamen University Affiliated Xiamen Eye Center, Xiamen, Fujian, China.
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2
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Yang Y, Zhong J, Cui D, Jensen LD. Up-to-date molecular medicine strategies for management of ocular surface neovascularization. Adv Drug Deliv Rev 2023; 201:115084. [PMID: 37689278 DOI: 10.1016/j.addr.2023.115084] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/30/2023] [Accepted: 09/04/2023] [Indexed: 09/11/2023]
Abstract
Ocular surface neovascularization and its resulting pathological changes significantly alter corneal refraction and obstruct the light path to the retina, and hence is a major cause of vision loss. Various factors such as infection, irritation, trauma, dry eye, and ocular surface surgery trigger neovascularization via angiogenesis and lymphangiogenesis dependent on VEGF-related and alternative mechanisms. Recent advances in antiangiogenic drugs, nanotechnology, gene therapy, surgical equipment and techniques, animal models, and drug delivery strategies have provided a range of novel therapeutic options for the treatment of ocular surface neovascularization. In this review article, we comprehensively discuss the etiology and mechanisms of corneal neovascularization and other types of ocular surface neovascularization, as well as emerging animal models and drug delivery strategies that facilitate its management.
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Affiliation(s)
- Yunlong Yang
- Department of Cellular and Genetic Medicine, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
| | - Junmu Zhong
- Department of Ophthalmology, Longyan First Hospital Affiliated to Fujian Medical University, Longyan 364000, Fujian Province, China
| | - Dongmei Cui
- Shenzhen Eye Hospital, Jinan University, Shenzhen Eye Institute, Shenzhen 518040, Guangdong Province, China
| | - Lasse D Jensen
- Department of Health, Medicine and Caring Sciences, Division of Diagnostics and Specialist Medicine, Unit of Cardiovascular Medicine, Linköping University, Linköping, Sweden.
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3
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Butovich IA, Wilkerson A, Goggans KR, Belyaeva OV, Kedishvili NY, Yuksel S. Sdr16c5 and Sdr16c6 control a dormant pathway at a bifurcation point between meibogenesis and sebogenesis. J Biol Chem 2023; 299:104725. [PMID: 37075844 PMCID: PMC10206187 DOI: 10.1016/j.jbc.2023.104725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/23/2023] [Accepted: 04/13/2023] [Indexed: 04/21/2023] Open
Abstract
Genes Sdr16c5 and Sdr16c6 encode proteins that belong to a superfamily of short-chain dehydrogenases/reductases (SDR16C5 and SDR16C6). Simultaneous inactivation of these genes in double-KO (DKO) mice was previously shown to result in a marked enlargement of the mouse Meibomian glands (MGs) and sebaceous glands, respectively. However, the exact roles of SDRs in physiology and biochemistry of MGs and sebaceous glands have not been established yet. Therefore, we characterized, for the first time, meibum and sebum of Sdr16c5/Sdr16c6-null (DKO) mice using high-resolution MS and LC. In this study, we demonstrated that the mutation upregulated the overall production of MG secretions (also known as meibogenesis) and noticeably altered their lipidomic profile, but had a more subtle effect on sebogenesis. The major changes in meibum of DKO mice included abnormal accumulation of shorter chain, sebaceous-type cholesteryl esters and wax esters (WEs), and a marked increase in the biosynthesis of monounsaturated and diunsaturated Meibomian-type WEs. Importantly, the MGs of DKO mice maintained their ability to produce typical extremely long chain Meibomian-type lipids at seemingly normal levels. These observations indicated preferential activation of a previously dormant biosynthetic pathway that produce shorter chain, and more unsaturated, sebaceous-type WEs in the MGs of DKO mice, without altering the elongation patterns of their extremely long chain Meibomian-type counterparts. We conclude that the Sdr16c5/Sdr16c6 pair may control a point of bifurcation in one of the meibogenesis subpathways at which biosynthesis of lipids can be redirected toward either abnormal sebaceous-type lipidome or normal Meibomian-type lipidome in WT mice.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA; Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kelli R Goggans
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Olga V Belyaeva
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Natalia Y Kedishvili
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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4
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Qin Z, Wang P, Chen W, Wang JR, Ma X, Zhang H, Zhang WJ, Wei C. Hepatic ELOVL3 is dispensable for lipid metabolism in mice. Biochem Biophys Res Commun 2023; 658:128-135. [PMID: 37030067 DOI: 10.1016/j.bbrc.2023.03.075] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 03/24/2023] [Accepted: 03/29/2023] [Indexed: 04/04/2023]
Abstract
Very long-chain fatty acid elongase 3 (ELOVL3) catalyzes the synthesis of C20-C24 fatty acids and is highly expressed in the liver and adipose tissues. The deficiency of Elovl3 exhibits an anti-obesity effect in mice, but the specific role of hepatic ELOVL3 in lipid metabolism remains unclear. Here we demonstrate that hepatic Elovl3 is not required for lipid homeostasis or the pathogenesis of diet-induced obesity and hepatic steatosis. We generated Elovl3 liver-specific knockout mice via Cre/LoxP approach, which maintained normal expression of ELOVL1 or ELOVL7 in the liver. Unexpectedly, the mutant mice did not show significant abnormalities in body weight, liver mass and morphology, liver triglyceride content, or glucose tolerance when fed normal chow or even a low-fat diet. Moreover, deletion of hepatic Elovl3 did not significantly affect body weight gain or hepatic steatosis induced by high-fat diet. Lipidomic analysis revealed that the lipid profiles were not significantly altered by the loss of hepatic Elovl3. Unlike its global knockouts, the mice lacking Elovl3 specifically in liver displayed normal expression of genes involved in hepatic de novo lipogenesis, lipid uptake, or beta-oxidation at the mRNA and protein levels. Collectively, our data indicate that hepatic ELOVL3 is dispensable for metabolic homeostasis or diet-induced metabolic disease.
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Siddiqui AJ, Jahan S, Chaturvedi S, Siddiqui MA, Alshahrani MM, Abdelgadir A, Hamadou WS, Saxena J, Sundararaj BK, Snoussi M, Badraoui R, Adnan M. Therapeutic Role of ELOVL in Neurological Diseases. ACS OMEGA 2023; 8:9764-9774. [PMID: 36969404 PMCID: PMC10034982 DOI: 10.1021/acsomega.3c00056] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 02/23/2023] [Indexed: 06/18/2023]
Abstract
Fatty acids play an important role in controlling the energy balance of mammals. De novo lipogenesis also generates a significant amount of lipids that are endogenously produced in addition to their ingestion. Fatty acid elongation beyond 16 carbons (palmitic acid), which can lead to the production of very long chain fatty acids (VLCFA), can be caused by the rate-limiting condensation process. Seven elongases, ELOVL1-7, have been identified in mammals and each has a unique substrate specificity. Researchers have recently developed a keen interest in the elongation of very long chain fatty acids protein 1 (ELOVL1) enzyme as a potential treatment for a variety of diseases. A number of neurological disorders directly or indirectly related to ELOVL1 involve the elongation of monounsaturated (C20:1 and C22:1) and saturated (C18:0-C26:0) acyl-CoAs. VLCFAs and ELOVL1 have a direct impact on the neurological disease. Other neurological symptoms such as ichthyotic keratoderma, spasticity, and hypomyelination have also been linked to the major enzyme (ELOVL1). Recently, ELOVL1 has also been heavily used to treat a number of diseases. The current review focuses on in-depth unique insights regarding the role of ELOVL1 as a therapeutic target and associated neurological disorders.
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Affiliation(s)
- Arif Jamal Siddiqui
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
| | - Sadaf Jahan
- Department
of Medical Laboratory Sciences, College of Applied Medical Sciences, Majmaah University, Al Majmaah 11952, Saudi Arabia
| | - Swati Chaturvedi
- Department
of Pharmaceutics and Pharmacokinetics, Pre-Clinical North, Lab-106, CSIR-Central Drug Research Institute, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India
| | - Maqsood Ahmed Siddiqui
- Department
of Zoology, College of Science, King Saud
University, P.O. Box 2455, Riyadh 11451, Kingdom of Saudi Arabia
| | - Mohammed Merae Alshahrani
- Department
of Clinical Laboratory Sciences, Faculty of Applied Medial Sciences, Najran University, P.O. Box 1988, Najran 61441, Saudi Arabia
| | - Abdelmushin Abdelgadir
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
| | - Walid Sabri Hamadou
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
| | - Juhi Saxena
- Department
of Biotechnology, University Institute of Biotechnology, Chandigarh University, Gharuan, NH-95, Chandigarh State Hwy, Ludhiana, Punjab 140413, India
| | - Bharath K. Sundararaj
- School
of Dental Medicine, Department of Cellular and Molecular Biology, Boston University, Medical Campus Boston, Boston, Massachusetts 02215, United States
| | - Mejdi Snoussi
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
| | - Riadh Badraoui
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
| | - Mohd Adnan
- Department
of Biology, College of Science, University
of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
- Molecular
Diagnostics and Personalized Therapeutics Unit, University of Ha’il, P.O. Box 2440, Ha’il 81451, Saudi Arabia
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6
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Portal C, Lin Y, Rastogi V, Peterson C, Yiu SCH, Foster JW, Wilkerson A, Butovich IA, Iomini C. Primary cilia control cellular patterning of Meibomian glands during morphogenesis but not lipid composition. Commun Biol 2023; 6:282. [PMID: 36932132 PMCID: PMC10023665 DOI: 10.1038/s42003-023-04632-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 02/27/2023] [Indexed: 03/19/2023] Open
Abstract
Meibomian glands (MGs) are modified sebaceous glands producing the tear film's lipids. Despite their critical role in maintaining clear vision, the mechanisms underlying MG morphogenesis in development and disease remain obscure. Cilia-mediate signals are critical for the development of skin adnexa, including sebaceous glands. Thus, we investigated the role of cilia in MG morphogenesis during development. Most cells were ciliated during early MG development, followed by cilia disassembly during differentiation. In mature glands, ciliated cells were primarily restricted to the basal layer of the proximal gland central duct. Cilia ablation in keratine14-expressing tissue disrupted the accumulation of proliferative cells at the distal tip but did not affect the overall rate of proliferation or apoptosis. Moreover, impaired cellular patterning during elongation resulted in hypertrophy of mature MGs with increased meibum volume without altering its lipid composition. Thus, cilia signaling networks provide a new platform to design therapeutic treatments for MG dysfunction.
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Affiliation(s)
- Céline Portal
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA
- Sorbonne Université, INSERM, CNRS, Institut de la Vision, 17 rue Moreau, F-75012, Paris, France
| | - Yvonne Lin
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA
| | - Varuni Rastogi
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA
| | - Cornelia Peterson
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Samuel Chi-Hung Yiu
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA
| | - James W Foster
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
- Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Carlo Iomini
- Department of Ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA.
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, 21231, USA.
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7
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Butovich I, Yuksel S, Wilkerson A. Probing dietary triacylglycerol metabolism and meibogenesis in mice: A stable isotope-labeled tracer LC-MS/MS study. J Biol Chem 2023; 299:103046. [PMID: 36822324 PMCID: PMC10070659 DOI: 10.1016/j.jbc.2023.103046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/10/2023] [Accepted: 02/12/2023] [Indexed: 02/25/2023] Open
Abstract
Exocrine Meibomian glands (MGs) play a central role in the ocular physiology and biochemistry by producing in situ and, mostly, de novo, a secretion (meibum), which is composed of a complex mixture of homologous lipids of various classes, in a metabolic pathway termed meibogenesis. Recent in vivo experiments with a number of mouse models demonstrated that inactivation of any of the major genes of meibogenesis led to alterations in the lipid composition of meibum and severe ocular and MG abnormalities that replicated various human ocular pathologies. However, the role of dietary lipids in meibogenesis, and in the onset and/or alleviation of these diseases, remains controversial. To uncover the role of dietary lipids, the metabolic transformations of a dietary lipid tracer - stable isotope-labeled glyceryl tri(oleate-1,2,3,7,8-13C5) (13C15-TO) - were investigated using LC-high-resolution TOF-MS/MS. We demonstrated that major metabolic transformations of the tracer occurred in the stomach and small intestines where 13C15-TO underwent immediate and extensive transesterification into 13C5- and 13C10-substituted triacylglycerols of various lengths, giving a mixture of 13C-labeled compounds that remain virtually unchanged in the mouse plasma, liver, and white adipose tissue, but were almost undetectable in the feces. Importantly, the tracer and its metabolites were virtually undetectable in MGs, even after 4 weeks of daily supplementation. Notably, unbiased Principal Component Analysis of the data revealed no measurable changes in the overall chemical composition of meibum after the treatment, which implies no direct effect of dietary triacylglycerols on meibogenesis, and left their systemic effects as the most likely mechanism.
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Affiliation(s)
- IgorA Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA; The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Wang D, Li X, Zhang P, Cao Y, Zhang K, Qin P, Guo Y, Li Z, Tian Y, Kang X, Liu X, Li H. ELOVL gene family plays a virtual role in response to breeding selection and lipid deposition in different tissues in chicken (Gallus gallus). BMC Genomics 2022; 23:705. [PMID: 36253734 PMCID: PMC9575239 DOI: 10.1186/s12864-022-08932-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 10/10/2022] [Indexed: 11/11/2022] Open
Abstract
Background Elongases of very long chain fatty acids (ELOVLs), a family of first rate-limiting enzymes in the synthesis of long-chain fatty acids, play an essential role in the biosynthesis of complex lipids. Disrupting any of ELOVLs affects normal growth and development in mammals. Genetic variations in ELOVLs are associated with backfat or intramuscular fatty acid composition in livestock. However, the effects of ELOVL gene family on breeding selection and lipid deposition in different tissues are still unknown in chickens. Results Genetic variation patterns and genetic associations analysis showed that the genetic variations of ELOVL genes were contributed to breeding selection of commercial varieties in chicken, and 14 SNPs in ELOVL2-6 were associated with body weight, carcass or fat deposition traits. Especially, one SNP rs17631638T > C in the promoter of ELOVL3 was associated with intramuscular fat content (IMF), and its allele frequency was significantly higher in native and layer breeds compared to that in commercial broiler breeds. Quantitative real-time PCR (qRT-PCR) determined that the ELOVL3 expressions in pectoralis were affected by the genotypes of rs17631638T > C. In addition, the transcription levels of ELOVL genes except ELOVL5 were regulated by estrogen in chicken liver and hypothalamus with different regulatory pathways. The expression levels of ELOVL1-6 in hypothalamus, liver, abdominal fat and pectoralis were correlated with abdominal fat weight, abdominal fat percentage, liver lipid content and IMF. Noteworthily, expression of ELOVL3 in pectoralis was highly positively correlated with IMF and glycerophospholipid molecules, including phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol and phospholipids inositol, rich in ω-3 and ω-6 long-chain unsaturated fatty acids, suggesting ELOVL3 could contribute to intramuscular fat deposition by increasing the proportion of long-chain unsaturated glycerophospholipid molecules in pectoralis. Conclusions In summary, we demonstrated the genetic contribution of ELOVL gene family to breeding selection for specialized varieties, and revealed the expression regulation of ELOVL genes and their potential roles in regulating lipid deposition in different tissues. This study provides new insights into understanding the functions of ELOVL family on avian growth and lipid deposition in different tissues and the genetic variation in ELOVL3 may aid the marker-assisted selection of meat quality in chicken. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08932-8.
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Affiliation(s)
- Dandan Wang
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Xinyan Li
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Panpan Zhang
- Henan Institute of Veterinary Drug and Feed Control, Zhengzhou, 450002, China
| | - Yuzhu Cao
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Ke Zhang
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Panpan Qin
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Yulong Guo
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China
| | - Zhuanjian Li
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China.,Henan Key Laboratory for Innovation and Utilization of Chicken Germplasm Resources, Zhengzhou, 450046, China.,International Joint Research Laboratory for Poultry Breeding of Henan, Zhengzhou, 450046, China
| | - Yadong Tian
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China.,Henan Key Laboratory for Innovation and Utilization of Chicken Germplasm Resources, Zhengzhou, 450046, China.,International Joint Research Laboratory for Poultry Breeding of Henan, Zhengzhou, 450046, China
| | - Xiangtao Kang
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China.,Henan Key Laboratory for Innovation and Utilization of Chicken Germplasm Resources, Zhengzhou, 450046, China.,International Joint Research Laboratory for Poultry Breeding of Henan, Zhengzhou, 450046, China
| | - Xiaojun Liu
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China. .,Henan Key Laboratory for Innovation and Utilization of Chicken Germplasm Resources, Zhengzhou, 450046, China. .,International Joint Research Laboratory for Poultry Breeding of Henan, Zhengzhou, 450046, China.
| | - Hong Li
- College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, China. .,Henan Key Laboratory for Innovation and Utilization of Chicken Germplasm Resources, Zhengzhou, 450046, China. .,International Joint Research Laboratory for Poultry Breeding of Henan, Zhengzhou, 450046, China.
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9
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Butovich IA, Wilkerson A. Dynamic Changes in the Gene Expression Patterns and Lipid Profiles in the Developing and Maturing Meibomian Glands. Int J Mol Sci 2022; 23:7884. [PMID: 35887230 PMCID: PMC9321132 DOI: 10.3390/ijms23147884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 11/30/2022] Open
Abstract
Meibomian glands (MGs) and their holocrine secretion-meibum-play crucial roles in the physiology of the eye, providing protection from environmental factors and desiccation, among other functions. Importantly, aging was implicated in the deterioration of the morphology and functions of MGs, and the quantity and quality of meibum they produce, leading to a loss of its protective properties, while the meibum of young individuals and experimental animals provide ample protection to the eye. Currently, the molecular mechanisms of meibum biosynthesis (termed meibogenesis) are not fully understood. To characterize the physiological changes in developing and maturing MGs, we studied the lipidomes and transcriptomes of mouse MGs ranging from newborns to adults. The results revealed a gradual increase in the critical genes of meibogenesis (such as Elovl3, Elovl4, Awat2, and Soat1, among others) that positively correlated with the biosynthesis of their respective lipid products. The MG transcriptomes of young and adult mice were also analyzed using single-cell RNA sequencing. These experiments revealed the existence of multiple unique populations of MG cells (meibocytes, epithelial cells, and others) with specific combinations of genes that encode meibogenesis-related proteins, and identified clusters and subclusters of cells that were tentatively classified as meibocytes at different stages of differentiation/maturation, or their progenitor cells. A hypothesis was formulated that these cells may produce different types of lipids, and contribute differentially to the Meibomian lipidome.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA;
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10
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Association of Serum Lipid Level with Meibum Biosynthesis and Meibomian Gland Dysfunction: A Review. J Clin Med 2022; 11:jcm11144010. [PMID: 35887773 PMCID: PMC9323051 DOI: 10.3390/jcm11144010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/27/2022] [Accepted: 07/05/2022] [Indexed: 11/16/2022] Open
Abstract
The primary role of meibomian glands (MGs) is to actively synthesize and secret lipids and proteins spread onto the tear film, and the glandular lipids promote tear stability, prevent evaporation, and reduce friction. Meibomian gland dysfunction (MGD) is the leading cause of dry eye disease and one of the most common ophthalmic problems worldwide. MGs are densely innervated and regulated by hormones and growth factors. However, since the polar and nonpolar lipids are produced through processes in MGs that are not completely understood, a relevant question has been raised: Would the altered systemic lipids metabolism affect the physiology and structure of MGs? This review introduces the recent update regarding the relationships between serum lipid and MGD in clinical and basic research while providing answers to this question. A causal relationship remains to be established; however, serum lipid level or dyslipidemia may be related to MGD directly or indirectly, or both. Further studies are warranted to establish the role of serum lipid level and meibocyte differentiation/maturation and lipid synthesis.
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Widjaja-Adhi MAK, Chao K, Golczak M. Mouse models in studies on the etiology of evaporative dry eye disease. Exp Eye Res 2022; 219:109072. [DOI: 10.1016/j.exer.2022.109072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 03/28/2022] [Accepted: 04/05/2022] [Indexed: 11/26/2022]
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Guo Y, Zhang H, Zhao Z, Luo X, Zhang M, Bu J, Liang M, Wu H, Yu J, He H, Zong R, Chen Y, Liu Z, Li W. Hyperglycemia Induces Meibomian Gland Dysfunction. Invest Ophthalmol Vis Sci 2022; 63:30. [PMID: 35072689 PMCID: PMC8802017 DOI: 10.1167/iovs.63.1.30] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 12/26/2021] [Indexed: 12/12/2022] Open
Abstract
Purpose Patients diagnosed with diabetes are inclined to have abnormalities on stability of tear film and disorder of meibomian gland (MG). This study aims to explore the pathological change of MG induced by diabetes in a rat model. Methods Sprague-Dawley (SD) rats were intraperitoneally injected with streptozotocin (STZ) to establish a diabetic animal model. Lipid accumulation in MG was detected by Oil Red O staining and LipidTox staining. Cell proliferation status was determined by Ki67 and P63 immunostaining, whereas cell apoptosis was confirmed by TUNEL assay. Gene expression of inflammatory cytokines and adhesion molecules IL-1α, IL-1β, ELAM1, ICAM1, and VCAM1 were detected by RT-PCR. Activation of ERK, NF-κB, and AMPK signaling pathways was determined by Western Blot analysis. Oxidative stress-related factors NOX4, 4HNE, Nrf2, HO-1, and SOD2 were detected by immunostaining or Western Blot analysis. Tom20 and Tim23 immunostaining and transmission electron microscopy were performed to evaluate the mitochondria functional and structure change. Results Four months after STZ injection, there was acini dropout in MG of diabetic rats. Evident infiltration of inflammatory cells, increased expression of inflammatory factors, and adhesion molecules, as well as activated ERK and NF-κB signaling pathways were identified. Oxidative stress of MG was evident in 4-month diabetic rats. Phospho-AMPK was downregulated in MG of 2-month diabetic rats and more prominent in 4-month rats. After metformin treatment, phospho-AMPK was upregulated and the morphology of MG was well maintained. Moreover, inflammation and oxidative stress of MG were alleviated after metformin intervention. Conclusions Long-term diabetes may lead to Meibomian gland dysfunction (MGD). AMPK may be a therapeutic target of MGD induced by diabetes.
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Affiliation(s)
- Yuli Guo
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Houjian Zhang
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Zhongyang Zhao
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Xin Luo
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Minjie Zhang
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Jinghua Bu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Minghui Liang
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Han Wu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Jingwen Yu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Hui He
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Rongrong Zong
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Yongxiong Chen
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Zuguo Liu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
| | - Wei Li
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen, China
- Department of Ophthalmology, Xiang'an Hospital of Xiamen University, Xiamen, China
- Xiamen University affiliated Xiamen Eye Center, Xiamen, Fujian, China
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Human meibum and tear film derived cholesteryl and wax esters in meibomian gland dysfunction and tear film structure. Ocul Surf 2022; 23:12-23. [PMID: 34774809 PMCID: PMC9875797 DOI: 10.1016/j.jtos.2021.10.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 10/27/2021] [Accepted: 10/29/2021] [Indexed: 02/07/2023]
Abstract
PURPOSE This study evaluated the presence and roles of cholesteryl esters (CEs) and wax esters (WEs) from human tear film and meibum in meibomian gland dysfunction (MGD). METHODS Out of 195 enrolled subjects, 164 and 179 subjects provided tear and meibum samples, respectively. Subjects were classified into normal, asymptomatic MGD, MGD, and mixed (MGD & aqueous deficient). The precorneal tear film (PCTF) thinning rate (evaporation) was measured using optical coherence tomography. Lipids extracted from tear and meibum samples were infused into a SCIEX 5600 TripleTOF mass spectrometer. CE and WE intensities quantified with Analyst 1.7 TF and LipidView 1.3 were compared across disease groups in MetaboAnalyst 5.0 and correlated with PCTF thinning rates. RESULTS The numbers of unique CEs and WEs identified in the samples were 125 and 86, respectively. Unsupervised Principal Component (PC) analysis and supervised Partial Least Square Discriminant analysis exhibited little separation among groups for both CEs and WEs in tears and meibum. Spearman's correlation analyses showed no association between either the first or second PC scores with PCTF thinning rates. CONCLUSION The abundances of human PCTF and meibum-derived CEs and WEs were independent of MGD disease status and PCTF thinning (evaporation). CEs and WEs alterations do not contribute to alterations in tear film dynamics in MGD, such as has been demonstrated by the (O-acyl) ω-hydroxy fatty acids (OAHFAs).
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Butovich IA, Yuksel S, Leonard B, Gadek T, Polans AS, Albert DM. Novel Lipids of the Rabbit Harderian Gland Improve Tear Stability in an Animal Model of Dry Eye Disease. J Ocul Pharmacol Ther 2021; 37:545-555. [PMID: 34590914 PMCID: PMC8713569 DOI: 10.1089/jop.2021.0015] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
Purpose: Instability of the tear film leads to evaporative dry eye disease (EDED), but the Harderian gland in some terrestrial vertebrates may produce novel lipids that stabilize the tear film and protect against dry eye. Here, the nonpolar lipids in the Harderian gland and tears of the rabbit but absent in human tears were identified and tested in preclinical studies to determine whether they could treat severe EDED. Methods: Lipids were identified primarily by atmospheric pressure chemical ionization mass spectrometry (MS) and fragmentation MS/MS. An identified lipid was synthesized and formulated as an emulsion and as a cyclodextrin (CD) clathrate. Following doses with test agents and controls, tear film breakup time (TBUT), tear production, corneal fluorescein staining, macrophage infiltration, and goblet cell survival were measured using standard tests at 0, 2 and 4 weeks in an animal model of EDED. Results: The lipid emulsion increased TBUT (P < 0.01) and tear production (P < 0.05), while it decreased corneal staining (P < 0.01) compared to controls. The lipid CD formulation increased TBUT (P < 0.05) and tear production (P < 0.05) but had no significant effect on the remaining test parameters. There were no differences in macrophage infiltration and conjunctival impression cytology scores between the formulations and their vehicle controls. Conclusions: Lipids in the rabbit Harderian gland and tears differ from those identified in human meibum and tears. These unique rabbit lipids may confer a protective effect against EDED and, as supplements to human tears, fulfill a similar role.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Brian Leonard
- Department of Surgical & Radiological Sciences, School of Veterinary Medicine, University of California, Davis, Davis, California, USA
| | - Tom Gadek
- MCAL Therapeutics, Inc., Park City, Utah, USA
| | - Arthur S. Polans
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin, USA
| | - Daniel M. Albert
- Casey Eye Institute, School of Medicine, Oregon Health & Science University, Portland, Oregon, USA
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Suzuki T, Kitazawa K, Cho Y, Yoshida M, Okumura T, Sato A, Kinoshita S. Alteration in meibum lipid composition and subjective symptoms due to aging and meibomian gland dysfunction. Ocul Surf 2021; 26:310-317. [PMID: 34666148 DOI: 10.1016/j.jtos.2021.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 10/06/2021] [Accepted: 10/15/2021] [Indexed: 12/14/2022]
Abstract
PURPOSE To investigate the alteration in lipid composition of meibum, objective clinical signs, and subjective symptoms associated with aging and meibomian gland (MG) dysfunction (MGD). METHODS In 10 MGD patients [4 males/6 females, mean age: 65.6 ± 7.9 years (range: 50-79 years)] and 24 healthy volunteer subjects [young subjects: 6 males/6 females, mean age: 25.7 ± 3.8 years (range: 20-35 years), elderly subjects: 6 males/6 females, mean age: 58.4 ± 7.5 years (range: 50-79 years)], three objective clinical signs were evaluated: MG orifice obstruction, meibum score, and tear film lipid layer interference pattern. Subjective symptoms were analyzed via a 15-item questionnaire. After careful collection of meibum samples, comprehensive lipid analysis was performed via liquid chromatography-mass spectrometry. Data was analyzed via JMP® ver. 13 (SAS Institute, Inc., Cary, NC) statistical analysis software. RESULTS In the MGD patients and elderly subjects, there was a significant decrease in non-polar lipids such as cholesterol esters (ChEs), while a significant increase in polar lipids [cholesterol (Ch), (O-acyl)-ω-hydroxy fatty acid (OAHFA), and free fatty acid (FA)] in total lipids (Tukey-Kramer test: p < 0.05). Triglyceride was significantly increased only in MGD patients (p < 0.05). Symptom scores representative of vision quality (i.e., blurred vision/haziness) were significantly negatively-correlated with the ratio of the non-polar lipid ChE, while significantly positively correlated with the polar lipids Ch, OAHFA, and FA (Spearman's rank correlation coefficient: p < 0.05). CONCLUSIONS Our findings revealed that both MGD and aging affect the composition ratio of major meibum lipids, resulting in the appearance of subjective symptoms.
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Affiliation(s)
- Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan; Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan.
| | - Koji Kitazawa
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yuko Cho
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan; Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
| | - Masataka Yoshida
- Research and Development Headquarters, Lion Corporation, Tokyo, Japan
| | - Takashi Okumura
- Research and Development Headquarters, Lion Corporation, Tokyo, Japan
| | - Atsushi Sato
- Research and Development Headquarters, Lion Corporation, Tokyo, Japan
| | - Shigeru Kinoshita
- Department of Frontier Medical Science and Technology for Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan
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Viitaja T, Moilanen J, Svedström KJ, Ekholm FS, Paananen RO. Tear Film Lipid Layer Structure: Self-Assembly of O-Acyl-ω-hydroxy Fatty Acids and Wax Esters into Evaporation-Resistant Monolayers. NANO LETTERS 2021; 21:7676-7683. [PMID: 34468151 DOI: 10.1021/acs.nanolett.1c02475] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In healthy eyes, the tear film lipid layer (TFLL) is considered to act as an evaporation resistant barrier, which prevents eyes from drying. Seeking to understand the mechanisms behind the evaporation resistance of the TFLL, we studied mixtures of lipid layer wax esters and O-acyl-ω-hydroxy fatty acids. Analyzing their self-assembly and biophysical properties led to new discoveries concerning the structure and function of the TFLL. We discovered how these lipids self-assemble at the air-water interface and form an efficient antievaporative barrier, demonstrating for the first time how the interaction of different tear film lipid species can improve the evaporation resistance compared with individual lipid classes on their own. These results provide a potential mechanism for the evaporation resistance of the lipid layer. In addition, the results serve as a base for the future development of improved dry eye treatments and other applications where the evaporation of water represents a significant challenge.
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Affiliation(s)
- Tuomo Viitaja
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Jukka Moilanen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
| | | | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
| | - Riku O Paananen
- Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290 Helsinki, Finland
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki, Finland
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Zwara A, Wertheim-Tysarowska K, Mika A. Alterations of Ultra Long-Chain Fatty Acids in Hereditary Skin Diseases-Review Article. Front Med (Lausanne) 2021; 8:730855. [PMID: 34497816 PMCID: PMC8420999 DOI: 10.3389/fmed.2021.730855] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 07/30/2021] [Indexed: 11/27/2022] Open
Abstract
The skin is a flexible organ that forms a barrier between the environment and the body's interior; it is involved in the immune response, in protection and regulation, and is a dynamic environment in which skin lipids play an important role in maintaining homeostasis. The different layers of the skin differ in both the composition and amount of lipids. The epidermis displays the best characteristics in this respect. The main lipids in this layer are cholesterol, fatty acids (FAs) and ceramides. FAs can occur in free form and as components of complex molecules. The most poorly characterized FAs are very long-chain fatty acids (VLCFAs) and ultra long-chain fatty acids (ULCFAs). VLCFAs and ULCFAs are among the main components of ceramides and are part of the free fatty acid (FFA) fraction. They are most abundant in the brain, liver, kidneys, and skin. VLCFAs and ULCFAs are responsible for the rigidity and impermeability of membranes, forming the mechanically and chemically strong outer layer of cell membranes. Any changes in the composition and length of the carbon chains of FAs result in a change in their melting point and therefore a change in membrane permeability. One of the factors causing a decrease in the amount of VLCFAs and ULCFAs is an improper diet. Another much more important factor is mutations in the genes which code proteins involved in the metabolism of VLCFAs and ULCFAs—regarding their elongation, their attachment to ceramides and their transformation. These mutations have their clinical consequences in the form of inborn errors in metabolism and neurodegenerative disorders, among others. Some of them are accompanied by skin symptoms such as ichthyosis and ichthyosiform erythroderma. In the following review, the structure of the skin is briefly characterized and the most important lipid components of the skin are presented. The focus is also on providing an overview of selected proteins involved in the metabolism of VLCFAs and ULCFAs in the skin.
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Affiliation(s)
- Agata Zwara
- Department of Environmental Analysis, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | | | - Adriana Mika
- Department of Pharmaceutical Biochemistry, Faculty of Pharmacy, Medical University of Gdansk, Gdansk, Poland
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Butovich IA, Wilkerson A, Yuksel S. Differential effects of dietary cholesterol and triglycerides on the lipid homeostasis in Meibomian glands. J Steroid Biochem Mol Biol 2021; 211:105894. [PMID: 33819631 PMCID: PMC8217181 DOI: 10.1016/j.jsbmb.2021.105894] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2020] [Revised: 03/21/2021] [Accepted: 03/31/2021] [Indexed: 12/20/2022]
Abstract
Exocrine Meibomian glands (MG) play a central role in the ocular surface physiology by producing meibum - a lipid secretion composed of cholesteryl esters (CE), cholesterol (Chl), triacylgycerols (TAG), waxes and other types of lipids. MG were previously shown to synthesize Meibomian lipids (ML) in situ via a complex array of reactions termed meibogenesis. However, questions remain about the role of dietary lipids in meibogenesis. To establish if dietary Chl (DC) and TAG (DT) can participate in meibogenesis, we studied mice whose diet was supplemented with trace amounts of deuterated Chl (2H-Chl) and 13C-labeled triolein (13C-TO), and the products of their biosynthetic transformations were analyzed using LC/MS. We demonstrated that 2H-Chl, but not 13C-TO, could be directly incorporated into meibum. Furthermore, 2H-Chl was esterified into MG-specific ultra long 2H-CE, which were vastly different from plasma CE and 2H-CE. The measured 2H-Chl/Chl and 2H-CE/CE ratios in meibum increased in a time-dependent manner reaching ∼5% and ∼1.2 %, respectively. The 2H-Chl/2H-CE ratio was about 3.5x higher than that for endogenous unlabeled Chl and CE, indicating accumulation of 2H-Chl in meibum. The elongation pattern of Meibomian 2H-CE closely replicated that of unlabeled CE. On the other hand, 13C-TO was not detected in any of the ML samples as an intact lipid or its metabolized/hydrolyzed products. We conclude that DC can be directly esterified into MG-specific CE, while DT undergo extensive catabolic transformations before reaching MG. These findings demonstrate that DC can have a direct impact on MG and ocular surface lipid homeostasis and pathophysiology.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA; The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA.
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9057, USA
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Sawai M, Watanabe K, Tanaka K, Kinoshita W, Otsuka K, Miyamoto M, Sassa T, Kihara A. Diverse meibum lipids produced by Awat1 and Awat2 are important for stabilizing tear film and protecting the ocular surface. iScience 2021; 24:102478. [PMID: 34113821 PMCID: PMC8169949 DOI: 10.1016/j.isci.2021.102478] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/17/2021] [Accepted: 04/23/2021] [Indexed: 12/16/2022] Open
Abstract
A lipid layer consisting of meibum lipids exists in the tear film and functions in preventing dry eye disease. Although the meibum lipids include diverse lipid classes, the synthesis pathway and role of each class remain largely unknown. Here, we created single and double knockout (KO and DKO, respectively) mice for the two acyl-CoA wax alcohol acyltransferases (Awat1 and Awat2) and investigated their dry eye phenotypes and meibum lipid composition. Awat2 KO and DKO mice exhibited severe dry eye with meibomian gland dysfunction, whereas Awat1 KO mice had mild dry eye. In these mice, specific meibum lipid classes were reduced: (O-acyl)-ω-hydroxy fatty acids and type 1ω wax diesters in Awat1 KO mice, wax monoesters and types 1ω and 2ω wax diesters in Awat2 KO mice, and most of these in DKO mice. Our findings reveal that Awat1 and Awat2 show characteristic substrate specificity and together produce diverse meibum lipids.
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Affiliation(s)
- Megumi Sawai
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Keisuke Watanabe
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Kana Tanaka
- Pharmaceutical Research Laboratories, Research and Development Headquarters, Lion Corporation, Odawara 256-0811, Japan
| | - Wataru Kinoshita
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Kento Otsuka
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Masatoshi Miyamoto
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Kita 12-jo, Nishi 6-chome, Kita-ku 060-0812, Japan
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Butovich IA, Wilkerson A, Yuksel S. Depletion of Cholesteryl Esters Causes Meibomian Gland Dysfunction-Like Symptoms in a Soat1-Null Mouse Model. Int J Mol Sci 2021; 22:1583. [PMID: 33557318 PMCID: PMC7915537 DOI: 10.3390/ijms22041583] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 02/01/2021] [Accepted: 02/01/2021] [Indexed: 02/08/2023] Open
Abstract
Previous studies on ablation of several key genes of meibogenesis related to fatty acid elongation, omega oxidation, and esterification into wax esters have demonstrated that inactivation of any of them led to predicted changes in the meibum lipid profiles and caused severe abnormalities in the ocular surface and Meibomian gland (MG) physiology and morphology. In this study, we evaluated the effects of Soat1 ablation that were expected to cause depletion of the second largest class of Meibomian lipids (ML)-cholesteryl esters (CE)-in a mouse model. ML of the Soat1-null mice were examined using liquid chromatography high-resolution mass spectrometry and compared with those of Soat1+/- and wild-type mice. Complete suppression of CE biosynthesis and simultaneous accumulation of free cholesterol (Chl) were observed in Soat1-null mice, while Soat1+/- mutants had normal Chl and CE profiles. The total arrest of the CE biosynthesis in response to Soat1 ablation transformed Chl into the dominant lipid in meibum accounting for at least 30% of all ML. The Soat1-null mice had clear manifestations of dry eye and MG dysfunction. Enrichment of meibum with Chl and depletion of CE caused plugging of MG orifices, increased meibum rigidity and melting temperature, and led to a massive accumulation of lipid deposits around the eyes of Soat1-null mice. These findings illustrate the role of Soat1/SOAT1 in the lipid homeostasis and pathophysiology of MG.
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Affiliation(s)
- Igor A. Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA
| | - Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9057, USA; (A.W.); (S.Y.)
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21
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Wilkerson A, Bhat N, Pham HQH, Yuksel S, Butovich I. Physiological effects of inactivation and the roles of Elovl3/ELOVL3 in maintaining ocular homeostasis. FASEB J 2021; 35:e21327. [PMID: 33455016 PMCID: PMC7891900 DOI: 10.1096/fj.202002323r] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 12/22/2022]
Abstract
Recently, elongase of very long chain fatty acids-3 (ELOVL3) was demonstrated to play a pivotal role in physiology and biochemistry of the ocular surface by maintaining a proper balance in the lipid composition of meibum. The goal of this study was to further investigate the effects of ELOVL3 ablation in homozygous Elovl3-knockout mice (E3hom) in comparison with age and sex matched wild-type controls (E3wt). Slit lamp examination of the ocular surface of mice, and histological examination of their ocular tissues, highlighted a severe negative impact of Elovl3 inactivating mutation on the Meibomian glands (MG) and conjunctiva of mice. MG transcriptomes of the E3hom and E3wt mice were assessed and revealed a range of up- and downregulated genes related to lipid biosynthesis, inflammation, and stress response, compared with E3wt mice. Heat stage polarized light microscopy was used to assess melting characteristics of normal and abnormal meibum. The loss of Elovl3 led to a 8°C drop in the melting temperature of meibum in E3hom mice, and increased its fluidity. Also noted were the excessive accumulation of lipid material and tears around the eye and severe ocular inflammation, among other abnormalities.
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Affiliation(s)
- Amber Wilkerson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Hoang Quoc Hai Pham
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Seher Yuksel
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Igor Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- The Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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22
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Fatty Acyl Esters of Hydroxy Fatty Acid (FAHFA) Lipid Families. Metabolites 2020; 10:metabo10120512. [PMID: 33348554 PMCID: PMC7766670 DOI: 10.3390/metabo10120512] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 12/10/2020] [Accepted: 12/16/2020] [Indexed: 01/03/2023] Open
Abstract
Fatty Acyl esters of Hydroxy Fatty Acids (FAHFA) encompass three different lipid families which have incorrectly been classified as wax esters. These families include (i) Branched-chain FAHFAs, involved in the regulation of glucose metabolism and inflammation, with acylation of an internal branched-chain hydroxy-palmitic or -stearic acid; (ii) ω-FAHFAs, which function as biosurfactants in a number of biofluids, are formed via acylation of the ω-hydroxyl group of very-long-chain fatty acids (these lipids have also been designated as o-acyl hydroxy fatty acids; OAHFA); and (iii) Ornithine-FAHFAs are bacterial lipids formed by the acylation of short-chain 3-hydroxy fatty acids and the addition of ornithine to the free carboxy group of the hydroxy fatty acid. The differences in biosynthetic pathways and cellular functions of these lipid families will be reviewed and compared to wax esters, which are formed by the acylation of a fatty alcohol, not a hydroxy fatty acid. In summary, FAHFA lipid families are both unique and complex in their biosynthesis and their biological actions. We have only evaluated the tip of the iceberg and much more exciting research is required to understand these lipids in health and disease.
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23
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Meibomian Gland Dysfunction: What Have Animal Models Taught Us? Int J Mol Sci 2020; 21:ijms21228822. [PMID: 33233466 PMCID: PMC7700490 DOI: 10.3390/ijms21228822] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 11/17/2020] [Accepted: 11/19/2020] [Indexed: 12/16/2022] Open
Abstract
Studies have estimated that currently 344 million people worldwide and 16.4 million adults in the US have some form of dry eye disease (DED). It is believed that approximately 70% of DED cases are due to some form of evaporative dry eye, for which Meibomian gland dysfunction (MGD) is the major cause. Unfortunately, currently there is no effective treatment for MGD, and solely palliative care is available. Given the importance of MGD in DED, there has been a growing interest in studying Meibomian gland development, homeostasis and pathology, and, also, in developing therapies for treating and/or preventing MGD. For such, animal models have shown to be a vital tool. Much of what is known today about the Meibomian gland and MGD was learnt from these important animal models. In particular, canine and rabbit models have been essential for studying the physiopathology and progression of DED, and the mouse model, which includes different knockout strains, has enabled the identification of specific pathways potentially involved in MGD. Herein, we provide a bibliographic review on the various animal models that have been used to study Meibomian gland development, Meibomian gland homeostasis and MGD, primarily focusing on publications between 2000 and 2020.
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24
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Tanno H, Sassa T, Sawai M, Kihara A. Production of branched-chain very-long-chain fatty acids by fatty acid elongases and their tissue distribution in mammals. Biochim Biophys Acta Mol Cell Biol Lipids 2020; 1866:158842. [PMID: 33069870 DOI: 10.1016/j.bbalip.2020.158842] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 09/28/2020] [Accepted: 10/09/2020] [Indexed: 01/12/2023]
Abstract
Although most mammalian fatty acids (FAs) are straight-chain, there also exist branched-chain FAs such as iso- and anteiso-FAs, especially in the meibomian glands. Meibum lipids, which are secreted from the meibomian glands and are important for dry eye prevention, contain abundant branched-chain lipids, such as cholesteryl esters and wax esters with chain-lengths of ≥C21 (very-long-chain; VLC). However, the exact tissue distribution of branched-chain lipids or the enzymes involved in the production of branched-chain VLCFAs has remained poorly understood. Here, we revealed that FA elongases ELOVL1, ELOVL3, and ELOVL7, of the seven mammalian ELOVL isozymes, elongated saturated branched-chain acyl-CoAs. ELOVL3 was highly active toward iso-C17:0 and anteiso-C17:0 acyl-CoAs and elongated them up to iso-C23:0 and anteiso-C25:0 acyl-CoAs, respectively. ELOVL1 elongated both iso- and anteiso-C23:0 acyl-CoAs to C25:0 acyl-CoAs. By establishing a liquid chromatography-tandem mass spectrometry method capable of separating branched- and straight-chain lipids, we showed that essentially all of the cholesteryl esters and 88% of the wax esters in the mouse meibomian glands are branched. In Elovl1 mutant mice, the levels of ≥C24:0 branched-chain cholesteryl esters and ≥C25:0 branched-chain wax esters were decreased, indicating that ELOVL1 indeed elongates branched-chain VLC acyl-CoAs in vivo. In addition, substantial amounts of ceramides containing branched-chain FAs were present in the skin, meibomian glands, and liver. Our findings provide new insights into the molecular mechanisms that create FA and lipid diversity.
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Affiliation(s)
- Honoka Tanno
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
| | - Takayuki Sassa
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
| | - Megumi Sawai
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan
| | - Akio Kihara
- Laboratory of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
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25
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Widjaja-Adhi MAK, Silvaroli JA, Chelstowska S, Trischman T, Bederman I, Sayegh R, Golczak M. Deficiency in Acyl-CoA:Wax Alcohol Acyltransferase 2 causes evaporative dry eye disease by abolishing biosynthesis of wax esters. FASEB J 2020; 34:13792-13808. [PMID: 32851726 PMCID: PMC7722226 DOI: 10.1096/fj.202001191r] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/21/2020] [Accepted: 08/05/2020] [Indexed: 01/16/2023]
Abstract
Lipids secreted by the meibomian glands (MGs) of the eyelids are essential to the protection of the eye's surface. An altered meibum composition represents the primary cause of evaporative dry eye disease (DED). Despite the critical importance of the meibum, its biosynthetic pathways and the roles of individual lipid components remain understudied. Here, we report that the genetic deletion of Acyl-CoA:wax alcohol acyltransferase 2 (AWAT2) causes the obstruction of MGs and symptoms of evaporative DED in mice. The lipid composition of the meibum isolated from Awat2-/- mice revealed the absence of wax esters, which was accompanied by a compensatory overproduction of cholesteryl esters. The resulting increased viscosity of meibum led to the dilation of the meibomian ducts, and the progressive degeneration of the MGs. Overall, we provide evidence for the main physiological role of AWAT2 and establish Awat2-/- mice as a model for DED syndrome that can be used in studies on tear film-oriented therapies.
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Affiliation(s)
| | - Josie A. Silvaroli
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Sylwia Chelstowska
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Thomas Trischman
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Ilya Bederman
- Department of Genetics and Genome Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Rony Sayegh
- Department of Ophthalmology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Marcin Golczak
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA,Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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26
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Butovich IA, Suzuki T. Delineating a novel metabolic high triglycerides-low waxes syndrome that affects lipid homeostasis in meibomian and sebaceous glands. Exp Eye Res 2020; 199:108189. [PMID: 32805264 DOI: 10.1016/j.exer.2020.108189] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 07/12/2020] [Accepted: 08/07/2020] [Indexed: 10/23/2022]
Abstract
Meibomian glands that are embedded in tarsal plates of human eyelids, and sebaceous glands found in the skin, including that of eyelids, are two related types of holocrine glands that produce lipid-rich secretions called meibum and sebum. Pervasive ocular disorders, such as Meibomian gland dysfunction and dry eye, have been linked to changes in the lipid composition of meibum. However, in most described cases the changes were either small, or random, or insufficiently characterized on the molecular level. Here, we present results of comprehensive lipidomic analyses of meibum, tears and sebum of a patient whose secretions were highly abnormal (abnormal meibum, tears and sebum, or AMTS, patient). The lipidomes were characterized on the level of individual lipid species using ultra-high performance liquid chromatography and high resolution mass spectrometry. The major differences between the AMTS patient and normal age- and gender-matched subjects included, among others, severely diminished pools of normal meibomian lipids such as wax esters and cholesteryl esters in meibum and tears, a 2x increase in total cholesteryl esters to wax esters ratio, their skewed molecular profiles, a ~3x increase in free cholesterol to cholesteryl esters ratio, and, most importantly, a 20x to 30x increase in the triglicerides fraction over the norm. Sebum of the AMTS patient was also highly abnormal lacking major wax esters. Notably, the routine blood lipid panel test of the AMTS patient showed no abnormalities. The data imply that the AMTS patient had a severe, previously unreported, metabolic disorder that affected meibogenesis in Meibomian glands and sebogenesis in sebaceous glands. This is, to the best of our knowledge, a first observation of the condition that we have termed High Triglycerides/Low Waxes (HTLW) syndrome.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA; Graduate School of Biomedical Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Tomo Suzuki
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan; Department of Ophthalmology, Kyoto City Hospital Organization, Kyoto, Japan
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27
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Paananen RO, Viitaja T, Olżyńska A, Ekholm FS, Moilanen J, Cwiklik L. Interactions of polar lipids with cholesteryl ester multilayers elucidate tear film lipid layer structure. Ocul Surf 2020; 18:545-553. [PMID: 32562857 DOI: 10.1016/j.jtos.2020.06.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/31/2020] [Accepted: 06/04/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE The tear film lipid layer (TFLL) covers the tear film, stabilizing it and providing a protective barrier against the environment. The TFLL is divided into polar and non-polar sublayers, but the interplay between lipid classes in these sublayers and the structure-function relationship of the TFLL remains poorly characterized. This study aims to provide insight into TFLL function by elucidating the interactions between polar and non-polar TFLL lipids at the molecular level. METHODS Mixed films of polar O-acyl-ω-hydroxy fatty acids (OAHFA) or phospholipids and non-polar cholesteryl esters (CE) were used as a model of the TFLL. The organization of the films was studied by using a combination of Brewster angle and fluorescence microscopy in a Langmuir trough system. In addition, the evaporation resistance of the lipid films was evaluated. RESULTS Phospholipids and OAHFAs induced the formation of a stable multilamellar CE film. The formation of this film was driven by the interdigitation of acyl chains between the monolayer of polar lipids and the CE multilayer lamellae. Surprisingly, the multilayer structure was destabilized by both low and high concentrations of polar lipids. In addition, the CE multilayer was no more effective in resisting the evaporation of water than a polar lipid monolayer. CONCLUSIONS Formation of multilamellar films by major tear film lipids suggest that the TFLL may have a similar structure. Moreover, in contrast to the current understanding, polar TFLL lipids may not mainly act by stabilizing the non-polar TFLL sublayer, but through a direct evaporation resistant effect.
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Affiliation(s)
- Riku O Paananen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland.
| | - Tuomo Viitaja
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland; Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014, Helsinki, Finland
| | - Agnieszka Olżyńska
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 182 23, Prague, Czech Republic
| | - Filip S Ekholm
- Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014, Helsinki, Finland
| | - Jukka Moilanen
- Helsinki Eye Lab, Ophthalmology, University of Helsinki and Helsinki University Hospital, Haartmaninkatu 8, FI-00290, Helsinki, Finland
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 182 23, Prague, Czech Republic
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28
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Butovich IA, Bhat N, Wojtowicz JC. Comparative Transcriptomic and Lipidomic Analyses of Human Male and Female Meibomian Glands Reveal Common Signature Genes of Meibogenesis. Int J Mol Sci 2019; 20:ijms20184539. [PMID: 31540257 PMCID: PMC6769918 DOI: 10.3390/ijms20184539] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 09/09/2019] [Accepted: 09/11/2019] [Indexed: 01/18/2023] Open
Abstract
Meibum is a lipid secretion that is produced by holocrine Meibomian glands (MGs). MGs are a specialized type of sebaceous glands that are embedded in the human eyelids. Chemically, meibum and sebum are different. A detailed characterization of lipidome and transcriptome of MG is required to deconvolute a complex and poorly characterized array of biosynthetic reactions (termed meibogenesis) that lead to formation of meibum. Changes in the composition and quality of meibum have been linked to various ocular disorders, some of which are more prevalent in males, while others in females. To establish the role of gender in meibogenesis in humans, we characterized MG transcriptomes and lipidomes of females and males, and identified signature genes of meibogenesis in both genders. Specimens of MG tissues were subjected to mRNA microarray analyses. Chemical composition of meibum samples was assessed chromatographically and mass spectrometrically. Both targeted and untargeted approaches were used. About 290 signature genes of meibogenesis were identified. The analyses of their expression patterns demonstrated no major differences between the genders. Lipid profiling of major classes of meibomian lipids, such as wax esters, cholesteryl esters, free cholesterol, (O)-acylated omega-hydroxy fatty acids (OAHFA), cholesteryl esters of OAHFA, and triacylglycerols, also demonstrated only minor (and random) differences in these lipids. The results of transcriptomic analyses correlated well with lipidomic data. Taken together, our data imply that in males and females, meibogenesis proceeds in a similar fashion, yielding secretions with similar, highly conserved, compositions. This finding is important for designing novel, gender-independent diagnostic and therapeutic approaches to various MG-related diseases and pathological conditions.
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Affiliation(s)
- Igor A Butovich
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Nita Bhat
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Jadwiga C Wojtowicz
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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