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Ashayeri Ahmadabad H, Mohammadi Panah S, Ghasemnejad-Berenji H, Ghojavand S, Ghasemnejad-Berenji M, Khezri MR. Metformin and the PI3K/AKT signaling pathway: implications for cancer, cardiovascular, and central nervous system diseases. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2024:10.1007/s00210-024-03358-3. [PMID: 39225830 DOI: 10.1007/s00210-024-03358-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 08/02/2024] [Indexed: 09/04/2024]
Abstract
Recent findings have brought our understanding of diseases at the molecular level, highlighting upstream intracellular pathways as potential therapeutic targets. The PI3K/AKT pathway, a key regulator of cellular responses to environmental changes, is frequently altered in various diseases, making it a promising target for intervention. Metformin is the most known anti-diabetic agent that is known due to its effects on cancer, inflammatory-related diseases, oxidative stress, and other human diseases. It is clearly understood that metformin modulates the activity of the PI3K/AKT pathway leading to a wide variety of outcomes. This interaction has been well-studied in various diseases. Therefore, this review aims to examine PI3K/AKT-modulating properties of metformin in cancer, cardiovascular, and central nervous system diseases. Our findings indicate that metformin is effective in treating cancer and CNS diseases, and plays a role in both the prevention and treatment of cardiovascular diseases. These insights support the potential of metformin in comprehensive strategies for disease management.
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Affiliation(s)
| | | | - Hojat Ghasemnejad-Berenji
- Reproductive Health Research Center, Clinical Research Institute, Urmia University of Medical Sciences, Urmia, Iran
| | - Shabnam Ghojavand
- Faculty of Pharmacy, Islamic Azad University of Tehran, Tehran, Iran
| | - Morteza Ghasemnejad-Berenji
- Department of Pharmacology and Toxicology, School of Pharmacy, Urmia University of Medical Sciences, Urmia, Iran.
- Research Center for Experimental and Applied Pharmaceutical Sciences, Urmia University of Medical Sciences, Urmia, Iran.
| | - Mohammad Rafi Khezri
- Reproductive Health Research Center, Clinical Research Institute, Urmia University of Medical Sciences, Urmia, Iran.
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Chakraborty R, Mukherjee AK, Bala A. Breakthroughs in road mapping IL-35 mediated immunotherapy for type-1 and autoimmune diabetes mellitus. Cytokine 2024; 181:156692. [PMID: 38986251 DOI: 10.1016/j.cyto.2024.156692] [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: 04/05/2024] [Revised: 05/22/2024] [Accepted: 07/05/2024] [Indexed: 07/12/2024]
Abstract
IL-35 is a recently discovered protein made up of IL-12α and IL-27β chains. It is encoded by IL12A and EBI3 genes. Interest in researching IL-35 has significantly increased in recent years, as evidenced by numerous scientific publications. Diabetes is on the rise globally, causing more illness and death in developing countries. The International Diabetes Federation (IDF) reports that diabetes is increasingly affecting children and teenagers, with varying rates across different regions. Therefore, scientists seek new diabetes treatments despite the growth of drug research. Recent research aims to emphasize IL-35 as a critical regulator of diabetes, especially type 1 and autoimmune diabetes. This review provides an overview of recent research on IL-35 and its link to diabetes and its associated complications. Studies suggest that IL-35 can offer protection against type-1 diabetes and autoimmune diabetes by regulating macrophage polarization, T-cell-related cytokines, and regulatory B cells (Bregs). This review will hopefully assist biomedical scientists in exploring the potential role of IL-35-mediated immunotherapy in treating diabetes. However, further research is necessary to determine the exact mechanism and plan clinical trials.
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Affiliation(s)
- Ratul Chakraborty
- Pharmacology and Drug Discovery Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), Vigyan Path, Guwahati 781035, Assam, India; Academy of Scientific and Innovative Research (AcSIR), AcSIR (an Indian Institute of National Importance), Sector 19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh 201002, India
| | - Ashis K Mukherjee
- Microbial Biotechnology and Protein Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), Vigyan Path, Guwahati 781035, Assam, India
| | - Asis Bala
- Pharmacology and Drug Discovery Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), Vigyan Path, Guwahati 781035, Assam, India; Academy of Scientific and Innovative Research (AcSIR), AcSIR (an Indian Institute of National Importance), Sector 19, Kamla Nehru Nagar, Ghaziabad, Uttar Pradesh 201002, India.
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3
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Bejarano E, Domenech-Bendaña A, Avila-Portillo N, Rowan S, Edirisinghe S, Taylor A. Glycative stress as a cause of macular degeneration. Prog Retin Eye Res 2024; 101:101260. [PMID: 38521386 DOI: 10.1016/j.preteyeres.2024.101260] [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: 01/05/2024] [Revised: 03/08/2024] [Accepted: 03/11/2024] [Indexed: 03/25/2024]
Abstract
People are living longer and rates of age-related diseases such as age-related macular degeneration (AMD) are accelerating, placing enormous burdens on patients and health care systems. The quality of carbohydrate foods consumed by an individual impacts health. The glycemic index (GI) is a kinetic measure of the rate at which glucose arrives in the blood stream after consuming various carbohydrates. Consuming diets that favor slowly digested carbohydrates releases sugar into the bloodstream gradually after consuming a meal (low glycemic index). This is associated with reduced risk for major age-related diseases including AMD, cardiovascular disease, and diabetes. In comparison, consuming the same amounts of different carbohydrates in higher GI diets, releases glucose into the blood rapidly, causing glycative stress as well as accumulation of advanced glycation end products (AGEs). Such AGEs are cytotoxic by virtue of their forming abnormal proteins and protein aggregates, as well as inhibiting proteolytic and other protective pathways that might otherwise selectively recognize and remove toxic species. Using in vitro and animal models of glycative stress, we observed that consuming higher GI diets perturbs metabolism and the microbiome, resulting in a shift to more lipid-rich metabolomic profiles. Interactions between aging, diet, eye phenotypes and physiology were observed. A large body of laboratory animal and human clinical epidemiologic data indicates that consuming lower GI diets, or lower glycemia diets, is protective against features of early AMD (AMDf) in mice and AMD prevalence or AMD progression in humans. Drugs may be optimized to diminish the ravages of higher glycemic diets. Human trials are indicated to determine if AMD progression can be retarded using lower GI diets. Here we summarized the current knowledge regarding the pathological role of glycative stress in retinal dysfunction and how dietary strategies might diminish retinal disease.
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Affiliation(s)
- Eloy Bejarano
- Department of Biomedical Sciences, School of Health Sciences and Veterinary School, Universidad Cardenal Herrera-CEU, CEU Universities, Valencia, Spain
| | - Alicia Domenech-Bendaña
- Department of Biomedical Sciences, School of Health Sciences and Veterinary School, Universidad Cardenal Herrera-CEU, CEU Universities, Valencia, Spain
| | | | - Sheldon Rowan
- JM USDA Human Nutrition Research Center on Aging at Tufts University, United States
| | - Sachini Edirisinghe
- Tufts University Friedman School of Nutrition Science and Policy, United States
| | - Allen Taylor
- Tufts University Friedman School of Nutrition Science and Policy, United States.
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Yu MG, Gordin D, Fu J, Park K, Li Q, King GL. Protective Factors and the Pathogenesis of Complications in Diabetes. Endocr Rev 2024; 45:227-252. [PMID: 37638875 PMCID: PMC10911956 DOI: 10.1210/endrev/bnad030] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 06/13/2023] [Accepted: 08/24/2023] [Indexed: 08/29/2023]
Abstract
Chronic complications of diabetes are due to myriad disorders of numerous metabolic pathways that are responsible for most of the morbidity and mortality associated with the disease. Traditionally, diabetes complications are divided into those of microvascular and macrovascular origin. We suggest revising this antiquated classification into diabetes complications of vascular, parenchymal, and hybrid (both vascular and parenchymal) tissue origin, since the profile of diabetes complications ranges from those involving only vascular tissues to those involving mostly parenchymal organs. A major paradigm shift has occurred in recent years regarding the pathogenesis of diabetes complications, in which the focus has shifted from studies on risks to those on the interplay between risk and protective factors. While risk factors are clearly important for the development of chronic complications in diabetes, recent studies have established that protective factors are equally significant in modulating the development and severity of diabetes complications. These protective responses may help explain the differential severity of complications, and even the lack of pathologies, in some tissues. Nevertheless, despite the growing number of studies on this field, comprehensive reviews on protective factors and their mechanisms of action are not available. This review thus focused on the clinical, biochemical, and molecular mechanisms that support the idea of endogenous protective factors, and their roles in the initiation and progression of chronic complications in diabetes. In addition, this review also aimed to identify the main needs of this field for future studies.
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Affiliation(s)
- Marc Gregory Yu
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - Daniel Gordin
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
- Department of Nephrology, University of Helsinki and Helsinki University Central Hospital, Stenbäckinkatu 9, FI-00029 Helsinki, Finland
- Minerva Foundation Institute for Medical Research, Tukholmankatu 8, 00290 Helsinki, Finland
| | - Jialin Fu
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - Kyoungmin Park
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - Qian Li
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
| | - George Liang King
- Research Division, Joslin Diabetes Center, Boston, MA 02215, USA
- Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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Changkakoti L, Das JM, Borah R, Rajabalaya R, David SR, Balaraman AK, Pramanik S, Haldar PK, Bala A. Protein Kinase C (PKC)-mediated TGF-β Regulation in Diabetic Neuropathy: Emphasis on Neuro-inflammation and Allodynia. Endocr Metab Immune Disord Drug Targets 2024; 24:777-788. [PMID: 37937564 DOI: 10.2174/0118715303262824231024104849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 08/08/2023] [Accepted: 09/25/2023] [Indexed: 11/09/2023]
Abstract
According to the World Health Organization (WHO), diabetes has been increasing steadily over the past few decades. In developing countries, it is the cause of increased morbidity and mortality. Diabetes and its complications are associated with education, occupation, and income across all levels of socioeconomic status. Factors, such as hyperglycemia, social ignorance, lack of proper health knowledge, and late access to medical care, can worsen diabetic complications. Amongst the complications, neuropathic pain and inflammation are considered the most common causes of morbidity for common populations. This review is focused on exploring protein kinase C (PKC)-mediated TGF-946; regulation in diabetic complications with particular emphasis on allodynia. The role of PKC-triggered TGF-946; in diabetic neuropathy is not well explored. This review will provide a better understanding of the PKC-mediated TGF-946; regulation in diabetic neuropathy with several schematic illustrations. Neuroinflammation and associated hyperalgesia and allodynia during microvascular complications in diabetes are scientifically illustrated in this review. It is hoped that this review will facilitate biomedical scientists to better understand the etiology and target drugs effectively to manage diabetes and diabetic neuropathy.
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Affiliation(s)
- Liza Changkakoti
- Pharmacology and Drug Discovery Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), An Autonomous Institute Under - Department of Science & Technology (Govt. of India) Vigyan Path, Guwahati, PIN- 781035 Assam, India
| | - Jitu Mani Das
- Pharmacology and Drug Discovery Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), An Autonomous Institute Under - Department of Science & Technology (Govt. of India) Vigyan Path, Guwahati, PIN- 781035 Assam, India
| | - Rajiv Borah
- Department of Mechanical, Manufacturing and Biomedical Engineering, Trinity College Dublin, The University of Dublin, Dublin, Ireland
| | - Rajan Rajabalaya
- PAPRSB Institute of Health Sciences, Universiti Brunei Darussalam, BE 1410 Bandar Seri Begawan, Brunei Darussalam
| | - Sheba Rani David
- School of Pharmacology, University of Wyoming, Laramie, Wyoming, 82071, USA
| | - Ashok Kumar Balaraman
- Faculty of Pharmacy, MAHSA University, Bandar Saujana Putra, 42610, Jenjarom, Selangor, Malaysia
| | - Subrata Pramanik
- Jyoti and Bhupat Mehta School of Health Sciences & Technology, Indian Institute of Technology (IIT), Guwahati, Assam- 781039, India
| | - Pallab Kanti Haldar
- Department of Pharmaceutical Technology, Division of Pharmacology & Toxicology, Jadavpur University, Kolkata, 700032, India
| | - Asis Bala
- Pharmacology and Drug Discovery Research Laboratory, Division of Life Sciences, Institute of Advanced Study in Science and Technology (IASST), An Autonomous Institute Under - Department of Science & Technology (Govt. of India) Vigyan Path, Guwahati, PIN- 781035 Assam, India
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Xue Y, Zhu X, Yan W, Zhang Z, Cui E, Wu Y, Li C, Pan J, Yan Q, Chai X, Zhao S. Dietary Supplementation With Acer truncatum Oil Promotes Remyelination in a Mouse Model of Multiple Sclerosis. Front Neurosci 2022; 16:860280. [PMID: 35585921 PMCID: PMC9109879 DOI: 10.3389/fnins.2022.860280] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
Background Multiple sclerosis is a chronic demyelinating disease of uncertain etiology. Traditional treatment methods produce more adverse effects. Epidemiological and clinical treatment findings showed that unknown environmental factors contribute to the etiology of MS and that diet is a commonly assumed factor. Despite the huge interest in diet expressed by people with MS and the potential role diet plays in MS, very little data is available on the role of diet in MS pathogenesis and MS course, in particular, studies on fats and MS. The oil of Acer truncatum is potential as a resource to be exploited in the treatment of some neurodegenerative diseases. Objective Here, we investigated the underlying influences of Acer truncatum oil on the stimulation of remyelination in a cuprizone mouse model of demyelination. Methods Cuprizone (0.2% in chow) was used to establish a mouse model of demyelination. Acer truncatum oil was administrated to mice during remyelination. Following techniques were used: behavioral test, histochemistry, fluorescent immunohistochemistry, transmission electron microscope. Results Mice exposed to cuprizone for 6 weeks showed schizophrenia-like behavioral changes, the increased exploration of the center in the open field test (OFT), increased entries into the open arms of the elevated plus-maze, as well as demyelination in the corpus callosum. After cuprizone withdrawal, the diet therapy was initiated with supplementation of Acer truncatum oil for 2 weeks. As expected, myelin repair was greatly enhanced in the demyelinated regions with increased mature oligodendrocytes (CC1) and myelin basic protein (MBP). More importantly, the supplementation with Acer truncatum oil in the diet reduced the schizophrenia-like behavior in the open field test (OFT) and the elevated plus-maze compared to the cuprizone recovery group. The results revealed that the diet supplementation with Acer truncatum oil improved behavioral abnormalities, oligodendrocyte maturation, and remyelination in the cuprizone model during recovery. Conclusion Diet supplementation with Acer truncatum oil attenuates demyelination induced by cuprizone, indicating that Acer truncatum oil is a novel therapeutic diet in demyelinating diseases.
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Affiliation(s)
- Yuhuan Xue
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Xiaoyan Zhu
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Wenyong Yan
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Zhihan Zhang
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Enhui Cui
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Yongji Wu
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Cixia Li
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Jiarong Pan
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
| | - Qijiang Yan
- Multiple Sclerosis Research Center of New York, New York, NY, United States
| | - Xuejun Chai
- Department of Basic Medicine, Xi’an Medical University, Xi’an, China
| | - Shanting Zhao
- College of Veterinary Medicine, Northwest A&F University, Yangling, China
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7
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Li D, Zhu Y, Wang Y, Zou Q, Duan J, Sun-Waterhouse D, Sun B. Perspectives on diacylglycerol-induced improvement of insulin sensitivity in type 2 diabetes. FOOD SCIENCE AND HUMAN WELLNESS 2022. [DOI: 10.1016/j.fshw.2021.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Verbascoside Protects Gingival Cells against High Glucose-Induced Oxidative Stress via PKC/HMGB1/RAGE/NFκB Pathway. Antioxidants (Basel) 2021; 10:antiox10091445. [PMID: 34573077 PMCID: PMC8464661 DOI: 10.3390/antiox10091445] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/07/2021] [Accepted: 09/09/2021] [Indexed: 12/28/2022] Open
Abstract
Impaired wound healing often occurs in patients with diabetes and causes great inconvenience to them. Aside from the presence of prolonged inflammation, the accumulation of oxidative stress is also implicated in the delayed wound healing. In the present study, we tested the effect of verbascoside, a caffeoyl phenylethanoid glycoside, on the improvement of cell viability and wound healing capacity of gingival epithelial cells under high glucose condition. We showed that verbascoside attenuated the high glucose-induced cytotoxicity and impaired healing, which may be associated with the downregulation of oxidative stress. Our results demonstrated that verbascoside increased the activity of the antioxidant enzyme SOD and reduced the oxidative stress indicator, 8-OHdG, as well as apoptosis. Moreover, verbascoside upregulated the PGC1-α and NRF1 expression and promoted mitochondrial biogenesis, which was mediated by suppression of PKC/HMGB1/RAGE/NFκB signaling. Likewise, we showed the inhibitory effect of verbascoside on oxidative stress was via repression of PKC/HMGB1/RAGE/NFκB activation. Also, our data suggested that the PKC-mediated oxidative stress may lead to the elevated production of inflammatory cytokines, IL-6 and IL-1β. Collectively, we demonstrated that verbascoside may be beneficial to ameliorate impaired oral wound healing for diabetic patients.
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Nakamizo S, Honda T, Sato T, Al Mamun M, Chow Z, Duan K, Lum J, Tan KJ, Tomari K, Sato R, Kitoh A, Tay ASL, Common JEA, Guan NL, Setou M, Ginhoux F, Kabashima K. High-fat diet induces a predisposition to follicular hyperkeratosis and neutrophilic folliculitis in mice. J Allergy Clin Immunol 2021; 148:473-485.e10. [PMID: 33713763 DOI: 10.1016/j.jaci.2021.02.032] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 02/23/2021] [Accepted: 02/26/2021] [Indexed: 01/22/2023]
Abstract
BACKGROUND Neutrophilic folliculitis is an inflammatory condition of hair follicles. In some neutrophilic folliculitis, such as in patients with acne and hidradenitis suppurativa, follicular hyperkeratosis is also observed. Neutrophilic folliculitis is often induced and/or exacerbated by a high-fat diet (HFD). However, the molecular mechanisms by which an HFD affects neutrophilic folliculitis are not fully understood. OBJECTIVE Our aim was to elucidate how an HFD promotes the development of neutrophilic folliculitis. METHODS Mice were fed an HFD, and their skin was subjected to histologic, RNA sequencing, and imaging mass spectrometry analyses. To examine the effect of an HFD on neutrophil accumulation around the hair follicles, phorbol 12-myristate 13-acetate (PMA) was used as an irritant to the skin. RESULTS Histologic analysis revealed follicular hyperkeratosis in the skin of HFD-fed mice. RNA sequencing analysis showed that genes related to keratinization, especially in upper hair follicular keratinocytes, were significantly upregulated in HFD-fed mice. Application of PMA to the skin induced neutrophilic folliculitis in HFD-fed mice but not in mice fed a normal diet. Accumulation of neutrophils in the skin and around hair follicles was dependent on CXCR2 signaling, and CXCL1 (a CXCR2 ligand) was produced mainly by hair follicular keratinocytes. Imaging mass spectrometry analysis revealed an increase in fatty acids in the skin of HFD-fed mice. Application of these fatty acids to the skin induced follicular hyperkeratosis and caused PMA-induced neutrophilic folliculitis even in mice fed a normal diet. CONCLUSION An HFD can facilitate the development of neutrophilic folliculitis with the induction of hyperkeratosis of hair follicles and increased neutrophil infiltration around the hair follicles via CXCR2 signaling.
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Affiliation(s)
- Satoshi Nakamizo
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore; Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore; Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Tetsuya Honda
- Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan; Department of Dermatology, School of Medicine, Hamamatsu University, Hamamatsu, Shizuoka, Japan.
| | - Tomohito Sato
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Md Al Mamun
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Zachary Chow
- Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Kaibo Duan
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Josephine Lum
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Kahbing Jasmine Tan
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore; Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Kaori Tomari
- Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Reiko Sato
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore; Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Akihiko Kitoh
- Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Angeline S L Tay
- Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore
| | - John E A Common
- Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Ng Lai Guan
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore
| | - Mitsutoshi Setou
- Department of Cellular and Molecular Anatomy, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Florent Ginhoux
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore; Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore.
| | - Kenji Kabashima
- Singapore Immunology Network, Agency for Science, Technology and Research, Biopolis, Singapore; Skin Research Institute of Singapore, Agency for Science, Technology and Research, Biopolis, Singapore; Department of Dermatology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
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Si X, Tian J, Shu C, Wang Y, Gong E, Zhang Y, Zhang W, Cui H, Li B. Serum Ceramide Reduction by Blueberry Anthocyanin-Rich Extract Alleviates Insulin Resistance in Hyperlipidemia Mice. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2020; 68:8185-8194. [PMID: 32692177 DOI: 10.1021/acs.jafc.0c01931] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Blueberry anthocyanin-rich extract (BAE) was supplemented to high-fat diet (HFD)-fed mice to investigate sphingolipid metabolism modulating factors involved in the attenuated hyperinsulinemia and hyperlipidemia. A BAE-containing diet effectively controlled food intake and liver weight and significantly attenuated insulin resistance triggered by a HFD. Higher BAE (200 mg/kg of body weight) administration performed more efficiently in the improvement of hepatic steatosis and adipocyte hypertrophy, together with distinct suppressions in serum triacylglycerol and cholesterol in total and species. Serum lipid compositions revealed 200 mg/kg of BAE supplementation remarkably suppressed ceramide accumulation. Consistently, genes encoding enzymes associated with sphingomyelin conversion and ceramide de novo synthesis were modulated toward a healthy direction for restrained sphingolipid accumulation. Further, the inhibited mRNA expressions of protein phosphatase 2A and protein kinase Cζ involved in blocking Akt phosphorylation connected the controlled ceramides with the restored insulin sensitivity.
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Affiliation(s)
- Xu Si
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Jinlong Tian
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Chi Shu
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Yuehua Wang
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Ersheng Gong
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Ye Zhang
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Weijia Zhang
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Huijun Cui
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
| | - Bin Li
- College of Food Science, Shenyang Agricultural University, Shenyang, Liaoning 110866, People's Republic of China
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11
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Petersen MC, Shulman GI. Roles of Diacylglycerols and Ceramides in Hepatic Insulin Resistance. Trends Pharmacol Sci 2017; 38:649-665. [PMID: 28551355 DOI: 10.1016/j.tips.2017.04.004] [Citation(s) in RCA: 234] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 04/19/2017] [Accepted: 04/20/2017] [Indexed: 12/22/2022]
Abstract
Although ample evidence links hepatic lipid accumulation with hepatic insulin resistance, the mechanistic basis of this association is incompletely understood and controversial. Diacylglycerols (DAGs) and ceramides have emerged as the two best-studied putative mediators of lipid-induced hepatic insulin resistance. Both lipids were first associated with insulin resistance in skeletal muscle and were subsequently hypothesized to mediate insulin resistance in the liver. However, the putative roles for DAGs and ceramides in hepatic insulin resistance have proved more complex than originally imagined, with various genetic and pharmacologic manipulations yielding a vast and occasionally contradictory trove of data to sort. In this review we examine the state of this field, turning a critical eye toward both DAGs and ceramides as putative mediators of lipid-induced hepatic insulin resistance.
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Affiliation(s)
- Max C Petersen
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA
| | - Gerald I Shulman
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520, USA; Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA; Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06520, USA.
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Softic S, Cohen DE, Kahn CR. Role of Dietary Fructose and Hepatic De Novo Lipogenesis in Fatty Liver Disease. Dig Dis Sci 2016; 61:1282-93. [PMID: 26856717 PMCID: PMC4838515 DOI: 10.1007/s10620-016-4054-0] [Citation(s) in RCA: 414] [Impact Index Per Article: 51.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Accepted: 01/21/2016] [Indexed: 12/11/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome. Overconsumption of high-fat diet (HFD) and increased intake of sugar-sweetened beverages are major risk factors for development of NAFLD. Today the most commonly consumed sugar is high fructose corn syrup. Hepatic lipids may be derived from dietary intake, esterification of plasma free fatty acids (FFA) or hepatic de novo lipogenesis (DNL). A central abnormality in NAFLD is enhanced DNL. Hepatic DNL is increased in individuals with NAFLD, while the contribution of dietary fat and plasma FFA to hepatic lipids is not significantly altered. The importance of DNL in NAFLD is further established in mouse studies with knockout of genes involved in this process. Dietary fructose increases levels of enzymes involved in DNL even more strongly than HFD. Several properties of fructose metabolism make it particularly lipogenic. Fructose is absorbed via portal vein and delivered to the liver in much higher concentrations as compared to other tissues. Fructose increases protein levels of all DNL enzymes during its conversion into triglycerides. Additionally, fructose supports lipogenesis in the setting of insulin resistance as fructose does not require insulin for its metabolism, and it directly stimulates SREBP1c, a major transcriptional regulator of DNL. Fructose also leads to ATP depletion and suppression of mitochondrial fatty acid oxidation, resulting in increased production of reactive oxygen species. Furthermore, fructose promotes ER stress and uric acid formation, additional insulin independent pathways leading to DNL. In summary, fructose metabolism supports DNL more strongly than HFD and hepatic DNL is a central abnormality in NAFLD. Disrupting fructose metabolism in the liver may provide a new therapeutic option for the treatment of NAFLD.
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Affiliation(s)
- Samir Softic
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, One Joslin Place, Boston, MA, 02215, USA
- Department of Gastroenterology, Hepatology and Nutrition, Boston Children's Hospital, Boston, MA, USA
| | - David E Cohen
- Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - C Ronald Kahn
- Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, One Joslin Place, Boston, MA, 02215, USA.
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13
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Coelho M, Nunes P, Mendes VM, Manadas B, Heerschap A, Jones JG. Effect of Global ATGL Knockout on Murine Fasting Glucose Kinetics. J Diabetes Res 2015; 2015:542029. [PMID: 26236747 PMCID: PMC4506825 DOI: 10.1155/2015/542029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 06/08/2015] [Indexed: 12/25/2022] Open
Abstract
Mice deficient in adipose triglyceride lipase (ATGL(-/-)) present elevated ectopic lipid levels but are paradoxically glucose-tolerant. Measurement of endogenous glucose production (EGP) and Cori cycle activity provide insights into the maintenance of glycemic control in these animals. These parameters were determined in 7 wild-type (ATGL(+/-)) and 6 ATGL(-/-) mice by a primed-infusion of [U-(13)C6]glucose followed by LC-MS/MS targeted mass-isotopomer analysis of blood glucose. EGP was quantified by isotope dilution of [U-(13)C6]glucose while Cori cycling was estimated by analysis of glucose triose (13)C-isotopomers. Fasting plasma free fatty-acids were significantly lower in ATGL(-/-) versus control mice (0.43 ± 0.05 mM versus 0.73 ± 0.11 mM, P < 0.05). Six-hour fasting EGP rates were identical for both ATGL(-/-) and control mice (79 ± 11 versus 71 ± 7 μmol/kg/min, resp.). Peripheral glucose metabolism was dominated by Cori cycling (80 ± 2% and 82 ± 7% of glucose disposal for ATGL(-/-) and control mice, resp.) indicating that peripheral glucose oxidation was not significantly upregulated in ATGL(-/-) mice under these conditions. The glucose (13)C-isotopomer distributions in both ATGL(-/-) and control mice were consistent with extensive hepatic pyruvate recycling. This suggests that gluconeogenic outflow from the Krebs cycle was also well compensated in ATGL(-/-) mice.
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Affiliation(s)
- Margarida Coelho
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | | | - Vera M. Mendes
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Bruno Manadas
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
| | - Arend Heerschap
- Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands
| | - John G. Jones
- CNC—Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal
- Portuguese Diabetes Association (APDP), Lisbon, Portugal
- *John G. Jones:
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Qu X, Dang L, Seale JP. Inhibitory Effect of Hypocrellin A on Protein Kinase C in Liver and Skeletal Muscle of Obese Zucker Rats. THE AMERICAN JOURNAL OF CHINESE MEDICINE 2012; 31:871-8. [PMID: 14992539 DOI: 10.1142/s0192415x03001624] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this ex vivo study, the inhibitory activity of hypocrellin A (HA), a perylene quinonoid pigment isolated from the Chinese medicinal fungus Hypocrella bambuase, on protein kinase C (PKC) enzyme activity in insulin target tissues of obese Zucker rats was assessed. Pre-incubation with HA for 30 minutes significantly inhibited the activity of partially purified PKC enzyme from liver and soleus skeletal muscle in a dose-dependent manner ( IC 50=0.07 and 0.26 μg/ml, respectively). HA produced a greater inhibitory effect in enzyme prepared from the liver than enzyme prepared from soleus muscle. Since total PKC activity in these two insulin target tissues is the net result of several different isoforms of PKC, and PKC-θ is a major isoform expressed in the soleus skeletal muscle, the present data suggest that the naturally occurring compound, HA, may selectively inhibit certain PKC isoforms other than PKC-θ. Further investigations are required to determine which PKC isoforms are most susceptible to HA and whether changes in PKC signaling during treatment with HA can reverse abnormalities of glucose and lipid metabolism in insulin resistant and diabetic states.
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Affiliation(s)
- Xianqin Qu
- Department of Health Sciences, University of Technology, Sydney, NSW, Australia.
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15
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Ståhlman M, Pham HT, Adiels M, Mitchell TW, Blanksby SJ, Fagerberg B, Ekroos K, Borén J. Clinical dyslipidaemia is associated with changes in the lipid composition and inflammatory properties of apolipoprotein-B-containing lipoproteins from women with type 2 diabetes. Diabetologia 2012; 55:1156-66. [PMID: 22252473 DOI: 10.1007/s00125-011-2444-6] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 12/12/2011] [Indexed: 11/28/2022]
Abstract
AIMS/HYPOTHESIS The aim of this study was to use lipidomics to determine if the lipid composition of apolipoprotein-B-containing lipoproteins is modified by dyslipidaemia in type 2 diabetes and if any of the identified changes potentially have biological relevance in the pathophysiology of type 2 diabetes. METHODS VLDL and LDL from normolipidaemic and dyslipidaemic type 2 diabetic women and controls were isolated and quantified with HPLC and mass spectrometry. A detailed molecular characterisation of VLDL triacylglycerols (TAG) was also performed using the novel ozone-induced dissociation method, which allowed us to distinguish vaccenic acid (C18:1 n-7) from oleic acid (C18:1 n-9) in specific TAG species. RESULTS Lipid class composition was very similar in VLDL and LDL from normolipidaemic type 2 diabetic and control participants. By contrast, dyslipidaemia was associated with significant changes in both lipid classes (e.g. increased diacylglycerols) and lipid species (e.g. increased C16:1 and C20:3 in phosphatidylcholine and cholesteryl ester and increased C16:0 [palmitic acid] and vaccenic acid in TAG). Levels of palmitic acid in VLDL and LDL TAG correlated with insulin resistance, and VLDL TAG enriched in palmitic acid promoted increased secretion of proinflammatory mediators from human smooth muscle cells. CONCLUSIONS We showed that dyslipidaemia is associated with major changes in both lipid class and lipid species composition in VLDL and LDL from women with type 2 diabetes. In addition, we identified specific molecular lipid species that both correlate with clinical variables and are proinflammatory. Our study thus shows the potential of advanced lipidomic methods to further understand the pathophysiology of type 2 diabetes.
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Affiliation(s)
- M Ståhlman
- Department of Molecular and Clinical Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
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Farooqui AA, Farooqui T, Panza F, Frisardi V. Metabolic syndrome as a risk factor for neurological disorders. Cell Mol Life Sci 2012; 69:741-62. [PMID: 21997383 PMCID: PMC11115054 DOI: 10.1007/s00018-011-0840-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 09/08/2011] [Accepted: 09/15/2011] [Indexed: 02/07/2023]
Abstract
The metabolic syndrome is a cluster of common pathologies: abdominal obesity linked to an excess of visceral fat, insulin resistance, dyslipidemia and hypertension. At the molecular level, metabolic syndrome is accompanied not only by dysregulation in the expression of adipokines (cytokines and chemokines), but also by alterations in levels of leptin, a peptide hormone released by white adipose tissue. These changes modulate immune response and inflammation that lead to alterations in the hypothalamic 'bodyweight/appetite/satiety set point,' resulting in the initiation and development of metabolic syndrome. Metabolic syndrome is a risk factor for neurological disorders such as stroke, depression and Alzheimer's disease. The molecular mechanism underlying the mirror relationship between metabolic syndrome and neurological disorders is not fully understood. However, it is becoming increasingly evident that all cellular and biochemical alterations observed in metabolic syndrome like impairment of endothelial cell function, abnormality in essential fatty acid metabolism and alterations in lipid mediators along with abnormal insulin/leptin signaling may represent a pathological bridge between metabolic syndrome and neurological disorders such as stroke, Alzheimer's disease and depression. The purpose of this review is not only to describe the involvement of brain in the pathogenesis of metabolic syndrome, but also to link the pathogenesis of metabolic syndrome with neurochemical changes in stroke, Alzheimer's disease and depression to a wider audience of neuroscientists with the hope that this discussion will initiate more studies on the relationship between metabolic syndrome and neurological disorders.
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Affiliation(s)
- Akhlaq A Farooqui
- Department of Molecular and Cellular Biochemistry, Ohio State University, Columbus, OH 43221, USA.
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17
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Huang W, Bansode RR, Xie Y, Rowland L, Mehta M, Davidson NO, Mehta KD. Disruption of the murine protein kinase Cbeta gene promotes gallstone formation and alters biliary lipid and hepatic cholesterol metabolism. J Biol Chem 2011; 286:22795-805. [PMID: 21550971 PMCID: PMC3123047 DOI: 10.1074/jbc.m111.250282] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 05/04/2011] [Indexed: 12/16/2022] Open
Abstract
The protein kinase C (PKC) family of Ca(2+) and/or lipid-activated serine-threonine protein kinases is implicated in the pathogenesis of obesity and insulin resistance. We recently reported that protein kinase Cβ (PKCβ), a calcium-, diacylglycerol-, and phospholipid-dependent kinase, is critical for maintaining whole body triglyceride homeostasis. We now report that PKCβ deficiency has profound effects on murine hepatic cholesterol metabolism, including hypersensitivity to diet-induced gallstone formation. The incidence of gallstones increased from 9% in control mice to 95% in PKCβ(-/-) mice. Gallstone formation in the mutant mice was accompanied by hyposecretion of bile acids with no alteration in fecal bile acid excretion, increased biliary cholesterol saturation and hydrophobicity indices, as well as hepatic p42/44(MAPK) activation, all of which enhance susceptibility to gallstone formation. Lithogenic diet-fed PKCβ(-/-) mice also displayed decreased expression of hepatic cholesterol-7α-hydroxylase (CYP7A1) and sterol 12α-hydroxylase (CYP8b1). Finally, feeding a modified lithogenic diet supplemented with milk fat, instead of cocoa butter, both increased the severity of and shortened the interval for gallstone formation in PKCβ(-/-) mice and was associated with dramatic increases in cholesterol saturation and hydrophobicity indices. Taken together, the findings reveal a hitherto unrecognized role of PKCβ in fine tuning diet-induced cholesterol and bile acid homeostasis, thus identifying PKCβ as a major physiological regulator of both triglyceride and cholesterol homeostasis.
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Affiliation(s)
- Wei Huang
- From the Department of Molecular and Cellular Biochemistry, The Dorothy M. Davis Heart and Lung Research Institute, and
| | - Rishipal R. Bansode
- From the Department of Molecular and Cellular Biochemistry, The Dorothy M. Davis Heart and Lung Research Institute, and
| | - Yan Xie
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Leslie Rowland
- From the Department of Molecular and Cellular Biochemistry, The Dorothy M. Davis Heart and Lung Research Institute, and
| | - Madhu Mehta
- the Department of Medicine, The Ohio State University College of Medicine, Columbus, Ohio 43210 and
| | - Nicholas O. Davidson
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Kamal D. Mehta
- From the Department of Molecular and Cellular Biochemistry, The Dorothy M. Davis Heart and Lung Research Institute, and
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18
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Li GY, Li CP, Zhong XL, Kang M. Role of PI-3K, DGAT2 and PKC-ε in pathogenesis of non-alcoholic fatty liver disease in rats. Shijie Huaren Xiaohua Zazhi 2011; 19:782-788. [DOI: 10.11569/wcjd.v19.i8.782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the role of phosphatidylinositol 3-kinase (PI-3K), acyl-CoA: diacylgycerol acyltransferase 2 (DGAT2) and protein kinase C-ε (PKC-ε) in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) in rats.
METHODS: Forty-eight Sprague-Dawley rats were randomly divided into normal control group and high-fat diet group. Rats of the high-fat diet group were fed a high-fat diet for 4, 8 or 12 weeks, while the normal control group was fed a normal diet. Liver slices were prepared to grade the degree of fatty change, inflammation and fibrosis. The expression of PKC-ε protein was determined by immunohistochemistry (IHC), while the mRNA levels of PI-3K (p85) and DGAT2 were measured by reverse transcription-polymerase chain reaction (RT-PCR).
RESULTS: Feeding a high-fat diet caused the development of NAFLD in rats. The degree of fatty change and inflammation was significantly more severe in the high-fat die group than in the normal control group. The degree of inflammation, fibrosis and ballooning degeneration was significantly more severe in rats fed a high-fat diet for 8 and 12 wk than for 4 wk. The expression of PKC-ε in rats feeding a high-fat diet for 8 and 12 wk was significantly higher than that in the normal control group (7.68 ± 1.32 vs 6.68 ± 2.16, 8.46 ± 1.19 vs 5.52 ± 1.05, P < 0.05 or 0.01). The expression of PI-3K (p85a) was significantly lower in the high-fat diet group than in the normal control group and in rats fed a high-fat diet for 8 and 12 wk than for 4 wk. In contrast, the expression of DGAT2 was significantly higher in the high-fat diet group than in the normal control group and in rats fed a high-fat diet for 8 and 12 wk than for 4 wk.
CONCLUSION: PI-3K and its associated proteins DGAT2 and PKC-ε may be critically involved in the pathogenesis of NAFLD.
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Gupta J, Gaikwad AB, Tikoo K. Hepatic expression profiling shows involvement of PKC epsilon, DGK eta, Tnfaip, and Rho kinase in type 2 diabetic nephropathy rats. J Cell Biochem 2010; 111:944-54. [DOI: 10.1002/jcb.22783] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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20
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Vanni E, Bugianesi E, Kotronen A, De Minicis S, Yki-Järvinen H, Svegliati-Baroni G. From the metabolic syndrome to NAFLD or vice versa? Dig Liver Dis 2010; 42:320-30. [PMID: 20207596 DOI: 10.1016/j.dld.2010.01.016] [Citation(s) in RCA: 359] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2010] [Accepted: 01/17/2010] [Indexed: 02/07/2023]
Abstract
The metabolic syndrome encompasses metabolic and cardiovascular risk factors which predict diabetes and cardiovascular disease (CVD) better than any of its individual components. Nonalcoholic fatty liver disease (NAFLD) comprises a disease spectrum which includes variable degrees of simple steatosis (nonalcoholic fatty liver, NAFL), nonalcoholic steatohepatitis (NASH) and cirrhosis. NAFLD is the hepatic manifestation of the metabolic syndrome, with insulin resistance as the main pathogenetic mechanism. Recent data indicate that hyperinsulinemia is probably the consequence rather than cause of NAFLD and NAFLD can be considered an independent predictor of cardiovascular disease. Serum free fatty acids derived from lipolysis of visceral adipose tissue are the main source of hepatic triglycerides in NAFLD, although hepatic de novo lipogenesis and dietary fat supply contribute to the pathogenesis of NAFLD. Approximately 10-25% NAFLD patients develop NASH, the evolutive form of hepatic steatosis. Presumably in a genetically predisposed environment, this increased lipid overload overwhelms the oxidative capacity and reactive oxygen species are generated, leading to lipid peroxidation, cytokine induction, chemoattraction of inflammatory cells, hepatic stellate cell activation and finally fibrogenesis with extracellular matrix deposition. No currently available therapies for NAFLD and NASH exist. Recently nuclear receptors have emerged as key regulators of lipid and carbohydrate metabolism for which specific pharmacological ligands are available, making them attractive therapeutic targets for NAFLD and NASH.
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Affiliation(s)
- Ester Vanni
- Division of Gastro-Hepatology, San Giovanni Battista Hospital, University of Turin, C. so Bramante 88, 10126 Turin, Italy
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21
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Li GY, Li CP. Advances in research on the role of phosphatidylinositol-3 kinase in the pathogenesis of nonalcoholic fatty liver disease. Shijie Huaren Xiaohua Zazhi 2009; 17:2277-2282. [DOI: 10.11569/wcjd.v17.i22.2277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Due to improvement in living standards, changes in eating habits, as well as a sharp increase in the incidence of diabetes and metabolic syndrome, the incidence of nonalcoholic fatty liver disease is continuously increasing. Recent studies have shown that the phosphatidylinositol 3-kinase (PI-3K) pathway plays a crucial role in the pathogenesis of nonalcoholic fatty liver disease. In this article, we will review the role of PI-3K in the pathogenesis of nonalcoholic fatty liver disease.
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Huang W, Bansode R, Mehta M, Mehta KD. Loss of protein kinase Cbeta function protects mice against diet-induced obesity and development of hepatic steatosis and insulin resistance. Hepatology 2009; 49:1525-36. [PMID: 19296465 PMCID: PMC2728215 DOI: 10.1002/hep.22815] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Obesity is an energy balance disorder in which intake is greater than expenditure, with most excess calories stored as triglyceride (TG). We previously reported that mice lacking the beta-isoform of protein kinase C (PKCbeta), a diacylglycerol- and phospholipid-dependent kinase, exhibit marked reduction in the whole body TG content, including white adipose tissue (WAT) mass. To investigate the role of this signaling kinase in metabolic adaptations to severe dietary stress, we studied the impact of a high-fat diet (HFD) on PKCbeta expression and the effect of PKCbeta deficiency on profound weight gain. We report herein that HFD selectively increased PKCbeta expression in obesity-prone C57BL/6J mice, specifically in WAT; the expression levels were little or unchanged in the liver, muscle, kidney, and heart. Basal PKCbeta expression was also found to be elevated in WAT of obese ob/ob mice. Remarkably, mice lacking PKCbeta were resistant to HFD-induced obesity, showing significantly reduced WAT and slightly higher core body temperatures. Unlike lean lipodystrophic mouse models, these mice did not have fatty livers, nor did they exhibit insulin resistance. Moreover, PKCbeta(-/-) mice exhibited changes in lipid metabolism gene expression, and such alterations were accompanied by significant changes in serum adipokines. These observations suggest that PKCbeta deficiency induced a unique metabolic state congruous with obesity resistance, thus raising the possibility that dysregulation of PKCbeta expression could contribute to dietary fat-induced obesity and related disorders.
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Affiliation(s)
- Wei Huang
- Department of Molecular and Cellular Biochemistry, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University College of Medicine, 464 Hamilton Hall, Columbus, OH 43210
| | - Rishipal Bansode
- Department of Molecular and Cellular Biochemistry, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University College of Medicine, 464 Hamilton Hall, Columbus, OH 43210
| | - Madhu Mehta
- Department of Internal Medicine, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University College of Medicine, 464 Hamilton Hall, Columbus, OH 43210
| | - Kamal D. Mehta
- Department of Molecular and Cellular Biochemistry, Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University College of Medicine, 464 Hamilton Hall, Columbus, OH 43210,Dr. Kamal D. Mehta, Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, 464 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43016. Tel: 614-688-8451; Fax: 614-292-4118; E-mail:
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Kotronen A, Seppänen-Laakso T, Westerbacka J, Kiviluoto T, Arola J, Ruskeepää AL, Oresic M, Yki-Järvinen H. Hepatic stearoyl-CoA desaturase (SCD)-1 activity and diacylglycerol but not ceramide concentrations are increased in the nonalcoholic human fatty liver. Diabetes 2009; 58:203-8. [PMID: 18952834 PMCID: PMC2606873 DOI: 10.2337/db08-1074] [Citation(s) in RCA: 179] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
OBJECTIVE To determine whether 1) hepatic ceramide and diacylglycerol concentrations, 2) SCD1 activity, and 3) hepatic lipogenic index are increased in the human nonalcoholic fatty liver. RESEARCH DESIGN AND METHODS We studied 16 subjects with (n = 8) and without (n = 8) histologically determined nonalcoholic fatty liver (NAFL(+) and NAFL(-)) matched for age, sex, and BMI. Hepatic concentrations of lipids and fatty acids were quantitated using ultra-performance liquid chromatography coupled to mass spectrometry and gas chromatography. RESULTS The absolute (nmol/mg) hepatic concentrations of diacylglycerols but not ceramides were increased in the NAFL(+) group compared with the NAFL(-) group. The livers of the NAFL(+) group contained proportionally less long-chain polyunsaturated fatty acids as compared with the NAFL(-) group. Liver fat percent was positively related to hepatic stearoyl-CoA desaturase 1 (SCD1) activity index (r = 0.70, P = 0.003) and the hepatic lipogenic index (r = 0.54, P = 0.030). Hepatic SCD1 activity index was positively related to the concentrations of diacylglycerols (r = 0.71, P = 0.002) but not ceramides (r = 0.07, NS). CONCLUSIONS We conclude that diacylglycerols but not ceramides are increased in NAFL. The human fatty liver is also characterized by depletion of long polyunsaturated fatty acids in the liver and increases in hepatic SCD1 and lipogenic activities.
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Affiliation(s)
- Anna Kotronen
- Department of Medicine, Division of Diabetes, Helsinki, Finland.
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24
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Miele C, Paturzo F, Teperino R, Sakane F, Fiory F, Oriente F, Ungaro P, Valentino R, Beguinot F, Formisano P. Glucose regulates diacylglycerol intracellular levels and protein kinase C activity by modulating diacylglycerol kinase subcellular localization. J Biol Chem 2007; 282:31835-43. [PMID: 17675299 DOI: 10.1074/jbc.m702481200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although chronic hyperglycemia reduces insulin sensitivity and leads to impaired glucose utilization, short term exposure to high glucose causes cellular responses positively regulating its own metabolism. We show that exposure of L6 myotubes overexpressing human insulin receptors to 25 mm glucose for 5 min decreased the intracellular levels of diacylglycerol (DAG). This was paralleled by transient activation of diacylglycerol kinase (DGK) and of insulin receptor signaling. Following 30-min exposure, however, both DAG levels and DGK activity returned close to basal levels. Moreover, the acute effect of glucose on DAG removal was inhibited by >85% by the DGK inhibitor R59949. DGK inhibition was also accompanied by increased protein kinase C-alpha (PKCalpha) activity, reduced glucose-induced insulin receptor activation, and GLUT4 translocation. Glucose exposure transiently redistributed DGK isoforms alpha and delta, from the prevalent cytosolic localization to the plasma membrane fraction. However, antisense silencing of DGKdelta, but not of DGKalpha expression, was sufficient to prevent the effect of high glucose on PKCalpha activity, insulin receptor signaling, and glucose uptake. Thus, the short term exposure of skeletal muscle cells to glucose causes a rapid induction of DGK, followed by a reduction of PKCalpha activity and transactivation of the insulin receptor signaling. The latter may mediate, at least in part, glucose induction of its own metabolism.
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Affiliation(s)
- Claudia Miele
- Dipartimento di Biologia e Patologia Cellulare e Molecolare & Istituto di Endocrinologia ed Oncologia Sperimentale del CNR, Federico II University of Naples, Via Pansini 5, Naples 80131, Italy
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Holland WL, Knotts TA, Chavez JA, Wang LP, Hoehn KL, Summers SA. Lipid mediators of insulin resistance. Nutr Rev 2007; 65:S39-46. [PMID: 17605313 DOI: 10.1111/j.1753-4887.2007.tb00327.x] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Lipid abnormalities such as obesity, increased circulating free fatty acid levels, and excess intramyocellular lipid accumulation are frequently associated with insulin resistance. These observations have prompted investigators to speculate that the accumulation of lipids in tissues not suited for fat storage (e.g., skeletal muscle and liver) is an underlying component of insulin resistance and the metabolic syndrome. We review the metabolic fates of lipids in insulin-responsive tissues and discuss the roles of specific lipid metabolites (e.g., ceramides, GM3 ganglioside, and diacylglycerol) as antagonists of insulin signaling and action.
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Affiliation(s)
- William L Holland
- Division of Endocrinology, Metabolism, and Diabetes, Department of Internal Medicine, University of Utah, Salt Lake City, Utah 84132, USA
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26
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Choi CS, Savage DB, Kulkarni A, Yu XX, Liu ZX, Morino K, Kim S, Distefano A, Samuel VT, Neschen S, Zhang D, Wang A, Zhang XM, Kahn M, Cline GW, Pandey SK, Geisler JG, Bhanot S, Monia BP, Shulman GI. Suppression of diacylglycerol acyltransferase-2 (DGAT2), but not DGAT1, with antisense oligonucleotides reverses diet-induced hepatic steatosis and insulin resistance. J Biol Chem 2007; 282:22678-88. [PMID: 17526931 DOI: 10.1074/jbc.m704213200] [Citation(s) in RCA: 294] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Nonalcoholic fatty liver disease (NAFLD) is a major contributing factor to hepatic insulin resistance in type 2 diabetes. Diacylglycerol acyltransferase (Dgat), of which there are two isoforms (Dgat1 and Dgat2), catalyzes the final step in triglyceride synthesis. We evaluated the metabolic impact of pharmacological reduction of DGAT1 and -2 expression in liver and fat using antisense oligonucleotides (ASOs) in rats with diet-induced NAFLD. Dgat1 and Dgat2 ASO treatment selectively reduced DGAT1 and DGAT2 mRNA levels in liver and fat, but only Dgat2 ASO treatment significantly reduced hepatic lipids (diacylglycerol and triglyceride but not long chain acyl CoAs) and improved hepatic insulin sensitivity. Because Dgat catalyzes triglyceride synthesis from diacylglycerol, and because we have hypothesized that diacylglycerol accumulation triggers fat-induced hepatic insulin resistance through protein kinase C epsilon activation, we next sought to understand the paradoxical reduction in diacylglycerol in Dgat2 ASO-treated rats. Within 3 days of starting Dgat2 ASO therapy in high fat-fed rats, plasma fatty acids increased, whereas hepatic lysophosphatidic acid and diacylglycerol levels were similar to those of control rats. These changes were associated with reduced expression of lipogenic genes (SREBP1c, ACC1, SCD1, and mtGPAT) and increased expression of oxidative/thermogenic genes (CPT1 and UCP2). Taken together, these data suggest that knocking down Dgat2 protects against fat-induced hepatic insulin resistance by paradoxically lowering hepatic diacylglycerol content and protein kinase C epsilon activation through decreased SREBP1c-mediated lipogenesis and increased hepatic fatty acid oxidation.
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Affiliation(s)
- Cheol Soo Choi
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Sidiropoulos KG, Zastepa A, Adeli K. Translational control of apolipoprotein B mRNA via insulin and the protein kinase C signaling cascades: Evidence for modulation of RNA–protein interactions at the 5′UTR. Arch Biochem Biophys 2007; 459:10-9. [PMID: 17288985 DOI: 10.1016/j.abb.2006.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Revised: 11/02/2006] [Accepted: 11/03/2006] [Indexed: 11/30/2022]
Abstract
The link between hepatic insulin signaling and apolipoprotein B (apoB) production has important implications in understanding the etiology of metabolic dyslipidemia commonly observed in insulin-resistant states. Recent studies have revealed important translational mechanisms of apoB mRNA involving the 5' untranslated region (5'UTR) and insulin-mediated translational suppression via an insulin-sensitive RNA binding protein. Here, we have investigated the role of the protein kinase C (PKCs) signaling cascade in the regulation of apoB mRNA translation, using a series of chimeric apoB UTR-luciferase constructs, in vitro translation of UTR-luciferase cRNAs, and metabolic labeling of intact HepG2 cells. The PKC activator, phorbol 12-myristate 13-acetate (PMA), increased luciferase expression of constructs containing the apoB 5' UTR whereas treatment with Bis-I, a general PKC inhibitor or Go6976, a more specific PKC alpha/beta inhibitor, decreased expression, under both basal and insulin-treated conditions. These effects were confirmed to be translational in nature based on in vitro translation studies of T7 apoB UTR-luciferase constructs transcribed and translated in vitro in the presence of HepG2 cytosol treated with insulin or signaling modulators. Mobility shift experiments using cytosol treated with either PKC inhibitor (Bis-I) or activator (PMA) showed parallel changes between translation of apoB 5'UTR-luciferase constructs and the binding of a protein(s) complex migrating around 110 kDa to the apoB 5' UTR. ApoB mRNA levels were unaltered under these conditions based on real-time PCR analysis. Bis-I and Go6976 were both able to significantly decrease newly synthesized apoB100 protein in the presence or absence of insulin. Overall, the data suggests that PKC activation may induce increased mRNA translation and synthesis of apoB100 protein through a mechanism involving the interaction of trans-acting factors with the apoB 5'UTR. We postulate potential links between PKC activation as seen in insulin-resistant/diabetic states, enhanced translation of apoB mRNA, and hepatic VLDL-apoB overproduction.
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Affiliation(s)
- Konstantinos Gus Sidiropoulos
- Clinical Biochemistry Division, Department of Laboratory Medicine and Pathobiology, Hospital for Sick Children, University of Toronto, Toronto, Ont., Canada M5G 1X8
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Savage DB, Choi CS, Samuel VT, Liu ZX, Zhang D, Wang A, Zhang XM, Cline GW, Yu XX, Geisler JG, Bhanot S, Monia BP, Shulman GI. Reversal of diet-induced hepatic steatosis and hepatic insulin resistance by antisense oligonucleotide inhibitors of acetyl-CoA carboxylases 1 and 2. J Clin Invest 2006; 116:817-24. [PMID: 16485039 PMCID: PMC1366503 DOI: 10.1172/jci27300] [Citation(s) in RCA: 341] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 12/13/2005] [Indexed: 12/26/2022] Open
Abstract
Hepatic steatosis is a core feature of the metabolic syndrome and type 2 diabetes and leads to hepatic insulin resistance. Malonyl-CoA, generated by acetyl-CoA carboxylases 1 and 2 (Acc1 and Acc2), is a key regulator of both mitochondrial fatty acid oxidation and fat synthesis. We used a diet-induced rat model of nonalcoholic fatty liver disease (NAFLD) and hepatic insulin resistance to explore the impact of suppressing Acc1, Acc2, or both Acc1 and Acc2 on hepatic lipid levels and insulin sensitivity. While suppression of Acc1 or Acc2 expression with antisense oligonucleotides (ASOs) increased fat oxidation in rat hepatocytes, suppression of both enzymes with a single ASO was significantly more effective in promoting fat oxidation. Suppression of Acc1 also inhibited lipogenesis whereas Acc2 reduction had no effect on lipogenesis. In rats with NAFLD, suppression of both enzymes with a single ASO was required to significantly reduce hepatic malonyl-CoA levels in vivo, lower hepatic lipids (long-chain acyl-CoAs, diacylglycerol, and triglycerides), and improve hepatic insulin sensitivity. Plasma ketones were significantly elevated compared with controls in the fed state but not in the fasting state, indicating that lowering Acc1 and -2 expression increases hepatic fat oxidation specifically in the fed state. These studies suggest that pharmacological inhibition of Acc1 and -2 may be a novel approach in the treatment of NAFLD and hepatic insulin resistance.
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Affiliation(s)
- David B Savage
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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McCarty MF. Potential utility of natural polyphenols for reversing fat-induced insulin resistance. Med Hypotheses 2005; 64:628-35. [PMID: 15617879 DOI: 10.1016/j.mehy.2003.11.042] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2003] [Accepted: 11/21/2003] [Indexed: 12/13/2022]
Abstract
There is intriguing recent evidence that the beta subunit of the signalsome--IKKbeta, a crucial catalyst of NF-kappaB activation--is an obligate mediator of the disruption of insulin signaling induced by excessive exposure of tissues to free fatty acids and by hypertrophy of adipocytes. Thus, agents which safely inhibit or suppress the activation of IKKbeta may have utility for reversing insulin resistance syndrome and aiding control of type 2 diabetes. Two natural agents which can achieve this effect in vitro--and which may have clinical potential in this regard--are the polyphenols resveratrol and silibinin. To date, limited absorbability and/or rapid glucuronidation have prevented these agents from achieving full therapeutic utility, but, by administering these agents in optimally absorbable forms, and co-administering inhibitors of glucuronidation such as probenecid, it may prove feasible to make these agents more clinically viable. Oral silibinin, in the guise of the milk thistle extract silymarin, already has documented clinical utility in a range of hepatic disorders, and recent evidence that dietary silibinin can inhibit the growth of certain cancers in rodents suggests that this agent may indeed have clinical potential as an IKKbeta inhibitor. A report that silymarin has a favorable impact on glycemic and lipidemic control in type 2 diabetics with cirrhosis, may or may not be indicative of IKKbeta inhibition in skeletal muscle and adipocytes. In light of the fact that IKKbeta plays a crucial role, not only in the induction of insulin resistance, but also atherogenesis, a host of inflammatory disorders, and the survival and spread of cancer, the development of pharmaceutical agents that could safely and feasibly achieve a down-regulation of IKKbeta activity would have broad therapeutic and preventive implications.
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Affiliation(s)
- Mark F McCarty
- Pantox Laboratories, 4622 Santa Fe St., San Diego, CA 92109, USA.
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Kim JK, Fillmore JJ, Sunshine MJ, Albrecht B, Higashimori T, Kim DW, Liu ZX, Soos TJ, Cline GW, O'Brien WR, Littman DR, Shulman GI. PKC-theta knockout mice are protected from fat-induced insulin resistance. J Clin Invest 2004; 114:823-7. [PMID: 15372106 PMCID: PMC516267 DOI: 10.1172/jci22230] [Citation(s) in RCA: 172] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2004] [Accepted: 07/28/2004] [Indexed: 11/17/2022] Open
Abstract
Insulin resistance plays a primary role in the development of type 2 diabetes and may be related to alterations in fat metabolism. Recent studies have suggested that local accumulation of fat metabolites inside skeletal muscle may activate a serine kinase cascade involving protein kinase C-theta (PKC-theta), leading to defects in insulin signaling and glucose transport in skeletal muscle. To test this hypothesis, we examined whether mice with inactivation of PKC-theta are protected from fat-induced insulin resistance in skeletal muscle. Skeletal muscle and hepatic insulin action as assessed during hyperinsulinemic-euglycemic clamps did not differ between WT and PKC-theta KO mice following saline infusion. A 5-hour lipid infusion decreased insulin-stimulated skeletal muscle glucose uptake in the WT mice that was associated with 40-50% decreases in insulin-stimulated tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) and IRS-1-associated PI3K activity. In contrast, PKC-theta inactivation prevented fat-induced defects in insulin signaling and glucose transport in skeletal muscle. In conclusion, our findings demonstrate that PKC-theta is a crucial component mediating fat-induced insulin resistance in skeletal muscle and suggest that PKC-theta is a potential therapeutic target for the treatment of type 2 diabetes.
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Affiliation(s)
- Jason K Kim
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA.
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McCarty MF. Elevated sympathetic activity may promote insulin resistance syndrome by activating alpha-1 adrenergic receptors on adipocytes. Med Hypotheses 2004; 62:830-8. [PMID: 15082116 DOI: 10.1016/j.mehy.2003.11.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2003] [Accepted: 11/11/2003] [Indexed: 11/19/2022]
Abstract
An excess of free intracellular calcium can reduce the efficiency of insulin-mediated glucose transport by blocking the dephosphorylation of GLUT-4. Classical isoforms of protein kinase C (PKC) can interfere with insulin signalling via serine phosphorylation of IRS-1 and the insulin receptor. Parathyroid hormone (PTH), by activating phospholipase C-beta in adipocytes, can promote a sustained increase in intracellular free calcium in these cells, while also activating classical PKCs. This may rationalize the fact that insulin resistance is a typical feature of hyperparathyroidism, as well as epidemiological evidence that regular ingestion of dairy products or of ethanol--which down-regulates PTH secretion--reduces risk for insulin resistance syndrome and diabetes. Alpha-1 adrenergic receptors of adipocytes--like PTH receptors--also activate phospholipase C-beta, and thus have an effect analogous to PTH on intracellular free calcium and PKC activity in adipocytes. This suggests that, via activation of alpha-1 adrenergic receptors, increased sympathetic activity in adipose tissue may promote insulin resistance syndrome. In fact, measures which provoke increased sympathetic output--such as diuretic use and severe salt restriction--are known to compromise insulin sensitivity, whereas alpha-1 antagonist drugs, as well as drugs that act centrally to suppress sympathetic activity, typically have a favorable effect on insulin function. When insulin resistance syndrome is associated with elevated sympathetic activity--for example, in hypertensives who are obese or on diuretic therapy--measures which down-regulate sympathetic activity, or, more specifically, alpha-1 adrenergic activity, may be warranted. These include centrally acting imidazoline analogs (moxonidine, rilmenidine) and alpha-1 antagonists (doxazosin, prazosin). Taurine and high-dose pyridoxine may represent practical nutritional strategies for moderating elevated sympathetic activity, and exercise training and low-insulin-response diets may be useful in this regard as well.
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Affiliation(s)
- Mark F McCarty
- Pantox Laboratories, 4622 Santa Fe St., San Diego, CA 29109, USA.
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Kim JK, Fillmore JJ, Sunshine MJ, Albrecht B, Higashimori T, Kim DW, Liu ZX, Soos TJ, Cline GW, O’Brien WR, Littman DR, Shulman GI. PKC-θ knockout mice are protected from fat-induced insulin resistance. J Clin Invest 2004. [DOI: 10.1172/jci200422230] [Citation(s) in RCA: 358] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Verrier E, Wang L, Wadham C, Albanese N, Hahn C, Gamble JR, Chatterjee VKK, Vadas MA, Xia P. PPARgamma agonists ameliorate endothelial cell activation via inhibition of diacylglycerol-protein kinase C signaling pathway: role of diacylglycerol kinase. Circ Res 2004; 94:1515-22. [PMID: 15117825 DOI: 10.1161/01.res.0000130527.92537.06] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Subject- Peroxisome proliferator-activated receptor (PPAR)-gamma agonists are emerging as potential protectors against inflammatory cardiovascular diseases including atherosclerosis and diabetic complications. However, their molecular mechanism of action within vasculature remains unclear. We report here that PPARgamma agonists, thiazolidinedione class drugs (TZDs), or 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) were capable of activating diacylglycerol (DAG) kinase (DGK), resulting in attenuation of DAG levels and inhibition of protein kinase C (PKC) activation. The PPARgamma agonist-induced DGK was completely blocked by a dominant-negative mutant of PPARgamma, indicating an essential receptor-dependent action. Importantly, the suppression of DAG-PKC signaling pathway was functional linkage to the anti-inflammatory properties of PPARgamma agonists in endothelial cells (EC), characterized by the inhibition of proinflammatory adhesion molecule expression and adherence of monocytes to the activated EC induced by high glucose. These findings thus demonstrate a novel molecular action of PPARgamma agonists to suppress the DAG-PKC signaling pathway via upregulation of an endogenous attenuator, DGK.
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Affiliation(s)
- Emily Verrier
- Signal Transduction Laboratory, Hanson Institute, Adelaide, SA, Australia
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35
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Hulver MW, Berggren JR, Cortright RN, Dudek RW, Thompson RP, Pories WJ, MacDonald KG, Cline GW, Shulman GI, Dohm GL, Houmard JA. Skeletal muscle lipid metabolism with obesity. Am J Physiol Endocrinol Metab 2003; 284:E741-7. [PMID: 12626325 DOI: 10.1152/ajpendo.00514.2002] [Citation(s) in RCA: 239] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objectives of this study were to 1). examine skeletal muscle fatty acid oxidation in individuals with varying degrees of adiposity and 2). determine the relationship between skeletal muscle fatty acid oxidation and the accumulation of long-chain fatty acyl-CoAs. Muscle was obtained from normal-weight [n = 8; body mass index (BMI) 23.8 +/- 0.58 kg/m(2)], overweight/obese (n = 8; BMI 30.2 +/- 0.81 kg/m(2)), and extremely obese (n = 8; BMI 53.8 +/- 3.5 kg/m(2)) females undergoing abdominal surgery. Skeletal muscle fatty acid oxidation was assessed in intact muscle strips. Long-chain fatty acyl-CoA concentrations were measured in a separate portion of the same muscle tissue in which fatty acid oxidation was determined. Palmitate oxidation was 58 and 83% lower in skeletal muscle from extremely obese (44.9 +/- 5.2 nmol x g(-1) x h(-1)) patients compared with normal-weight (71.0 +/- 5.0 nmol x g(-1) x h(-1)) and overweight/obese (82.2 +/- 8.7 nmol x g(-1) x h(-1)) patients, respectively. Palmitate oxidation was negatively (R = -0.44, P = 0.003) associated with BMI. Long-chain fatty acyl-CoA content was higher in both the overweight/obese and extremely obese patients compared with normal-weight patients, despite significantly lower fatty acid oxidation only in the extremely obese. No associations were observed between long-chain fatty acyl-CoA content and palmitate oxidation. These data suggest that there is a defect in skeletal muscle fatty acid oxidation with extreme obesity but not overweight/obesity and that the accumulation of intramyocellular long-chain fatty acyl-CoAs is not solely a result of reduced fatty acid oxidation.
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Affiliation(s)
- Matthew W Hulver
- Department of Physiology, The Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
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Chavez JA, Knotts TA, Wang LP, Li G, Dobrowsky RT, Florant GL, Summers SA. A role for ceramide, but not diacylglycerol, in the antagonism of insulin signal transduction by saturated fatty acids. J Biol Chem 2003; 278:10297-303. [PMID: 12525490 DOI: 10.1074/jbc.m212307200] [Citation(s) in RCA: 455] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Multiple studies suggest that lipid oversupply to skeletal muscle contributes to the development of insulin resistance, perhaps by promoting the accumulation of lipid metabolites capable of inhibiting signal transduction. Herein we demonstrate that exposing muscle cells to particular saturated free fatty acids (FFAs), but not mono-unsaturated FFAs, inhibits insulin stimulation of Akt/protein kinase B, a serine/threonine kinase that is a central mediator of insulin-stimulated anabolic metabolism. These saturated FFAs concomitantly induced the accumulation of ceramide and diacylglycerol, two products of fatty acyl-CoA that have been shown to accumulate in insulin-resistant tissues and to inhibit early steps in insulin signaling. Preventing de novo ceramide synthesis negated the antagonistic effect of saturated FFAs toward Akt/protein kinase B. Moreover, inducing ceramide buildup recapitulated and augmented the inhibitory effect of saturated FFAs. By contrast, diacylglycerol proved dispensable for these FFA effects. Collectively these results identify ceramide as a necessary and sufficient intermediate linking saturated fats to the inhibition of insulin signaling.
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Affiliation(s)
- Jose Antonio Chavez
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523-1870, USA
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37
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Lin Y, Itani SI, Kurowski TG, Dean DJ, Luo Z, Yaney GC, Ruderman NB. Inhibition of insulin signaling and glycogen synthesis by phorbol dibutyrate in rat skeletal muscle. Am J Physiol Endocrinol Metab 2001; 281:E8-E15. [PMID: 11404218 DOI: 10.1152/ajpendo.2001.281.1.e8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Numerous studies have shown a correlation between changes in protein kinase C (PKC) distribution and/or activity and insulin resistance in skeletal muscle. To investigate which PKC isoforms might be involved and how they affect insulin action and signaling, studies were carried out in rat soleus muscle incubated with phorbol esters. Muscles preincubated for 1 h with 1 microM phorbol 12,13-dibutyrate (PDBu) showed an impaired ability of insulin to stimulate glucose incorporation into glycogen and a translocation of PKC-alpha, -betaI, -theta, and -epsilon, and probably -betaII, from the cytosol to membranes. Preincubation with 1 microM PDBu decreased activation of the insulin receptor tyrosine kinase by insulin and to an even greater extent the phosphorylation of Akt/protein kinase B and glycogen synthase kinase-3. However, it failed to diminish the activation of phosphatidylinositol 3'-kinase by insulin. Despite these changes in signaling, the stimulation by insulin of glucose transport (2-deoxyglucose uptake) and glucose incorporation into lipid and oxidation to CO2 was unaffected. The results indicate that preincubation of skeletal muscle with phorbol ester leads to a translocation of multiple conventional and novel PKC isoforms and to an impairment of several, but not all, events in the insulin-signaling cascade. They also demonstrate that these changes are associated with an inhibition of insulin-stimulated glycogen synthesis but that, at the concentration of PDBu used here, glucose transport, its incorporation into lipid, and its oxidation to CO2 are unaffected.
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Affiliation(s)
- Y Lin
- Diabetes and Metabolism Unit, Boston University Medical Center, Boston, Massachusetts 02118, USA
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38
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Cortright RN, Azevedo JL, Zhou Q, Sinha M, Pories WJ, Itani SI, Dohm GL. Protein kinase C modulates insulin action in human skeletal muscle. Am J Physiol Endocrinol Metab 2000; 278:E553-62. [PMID: 10710511 DOI: 10.1152/ajpendo.2000.278.3.e553] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is good evidence from cell lines and rodents that elevated protein kinase C (PKC) overexpression/activity causes insulin resistance. Therefore, the present study determined the effects of PKC activation/inhibition on insulin-mediated glucose transport in incubated human skeletal muscle and primary adipocytes to discern a potential role for PKC in insulin action. Rectus abdominus muscle strips or adipocytes from obese, insulin-resistant, and insulin-sensitive patients were incubated in vitro under basal and insulin (100 nM)-stimulated conditions in the presence of GF 109203X (GF), a PKC inhibitor, or 12-deoxyphorbol 13-phenylacetate 20-acetate (dPPA), a PKC activator. PKC inhibition had no effect on basal glucose transport. GF increased (P < 0.05) insulin-stimulated 2-deoxyglucose (2-DOG) transport approximately twofold above basal. GF plus insulin also increased (P < 0.05) insulin receptor tyrosine phosphorylation 48% and phosphatidylinositol 3-kinase (PI 3-kinase) activity approximately 50% (P < 0.05) vs. insulin treatment alone. Similar results for GF on glucose uptake were observed in human primary adipocytes. Further support for the hypothesis that elevated PKC activity is related to insulin resistance comes from the finding that PKC activation by dPPA was associated with a 40% decrease (P < 0.05) in insulin-stimulated 2-DOG transport. Incubation of insulin-sensitive muscles with GF also resulted in enhanced insulin action ( approximately 3-fold above basal). These data demonstrate that certain PKC inhibitors augment insulin-mediated glucose uptake and suggest that PKC may modulate insulin action in human skeletal muscle.
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Affiliation(s)
- R N Cortright
- School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA
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Laybutt DR, Schmitz-Peiffer C, Saha AK, Ruderman NB, Biden TJ, Kraegen EW. Muscle lipid accumulation and protein kinase C activation in the insulin-resistant chronically glucose-infused rat. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E1070-6. [PMID: 10600797 DOI: 10.1152/ajpendo.1999.277.6.e1070] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic glucose infusion results in hyperinsulinemia and causes lipid accumulation and insulin resistance in rat muscle. To examine possible mechanisms for the insulin resistance, alterations in malonyl-CoA and long-chain acyl-CoA (LCA-CoA) concentration and the distribution of protein kinase C (PKC) isozymes, putative links between muscle lipids and insulin resistance, were determined. Cannulated rats were infused with glucose (40 mg. kg(-1). min(-1)) for 1 or 4 days. This increased red quadriceps muscle LCA-CoA content (sum of 6 species) by 1.3-fold at 1 day and 1.4-fold at 4 days vs. saline-infused controls (both P < 0.001 vs. control). The concentration of malonyl-CoA was also increased (1.7-fold at 1 day, P < 0.01, and 2.2-fold at 4 days, P < 0.001 vs. control), suggesting an even greater increase in cytosolic LCA-CoA. The ratio of membrane to cytosolic PKC-epsilon was increased twofold in the red gastrocnemius after both 1 and 4 days, suggesting chronic activation. No changes were observed for PKC-alpha, -delta, and -theta. We conclude that LCA-CoAs accumulate in muscle during chronic glucose infusion, consistent with a malonyl-CoA-induced inhibition of fatty acid oxidation (reverse glucose-fatty acid cycle). Accumulation of LCA-CoAs could play a role in the generation of muscle insulin resistance by glucose oversupply, either directly or via chronic activation of PKC-epsilon.
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Affiliation(s)
- D R Laybutt
- Garvan Institute of Medical Research, Sydney, New South Wales 2010, Australia
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40
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Chen MF, Jockusch H. Role of phosphorylation and physiological state in the regulation of the muscular chloride channel ClC-1: a voltage-clamp study on isolated M. interosseus fibers. Biochem Biophys Res Commun 1999; 261:528-33. [PMID: 10425219 DOI: 10.1006/bbrc.1999.1061] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chloride currents (I(Cl)) were investigated with the two-electrode voltage-clamp technique in enzymatically isolated fibers from interosseus muscles of wild-type (WT), denervated WT, and myotonic (ADR, ClC-1-deficient) mice. Characteristics of I(Cl) were consistent with previous observations on rat muscle fibers and cultured nonmuscle cells transfected with hClC-1 cDNA. In the presence of 0.1 mM anthracene-9-carboxylic acid and in ADR fibers, I(Cl) was reduced by >90%. WT interosseus fibers denervated 6-7 days prior to isolation showed approximately 50% I(Cl) compared to control fibers. Addition of 3.3 microM staurosporine, a nonspecific inhibitor of protein kinases, increased I(Cl) in WT interosseus fibers by a factor of approximately two and altered its kinetic characteristics. We conclude that in dissociated fibers cultured for 1-2 days, in contrast to freshly isolated muscles, chloride conductance is downregulated by a mechanism involving protein phosphorylation. In situ, this short-term regulation may complement transcriptional long-term regulation of ClC-1.
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Affiliation(s)
- M F Chen
- Developmental Biology and Molecular Pathology, University of Bielefeld, Germany
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41
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Donnelly R, Qu X. Mechanisms of insulin resistance and new pharmacological approaches to metabolism and diabetic complications. Clin Exp Pharmacol Physiol 1998; 25:79-87. [PMID: 9493493 DOI: 10.1111/j.1440-1681.1998.tb02181.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. Resistance to insulin-mediated glucose transport and metabolism has been identified as a primary mechanism in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) and as a target for drug development. The aetiology of insulin resistance is likely to be multifactorial, but the present review focuses on candidate post-receptor mechanisms of insulin resistance, particularly protein kinase C (PKC), and the metabolic and genetic significance of beta3-adrenoceptors (beta3-AR) in adipose tissue. 2. Multiple lines of evidence suggest that isoform-selective activation of PKC phosphorylates and down-regulates one or more substrates involved in glucose transport and metabolism (e.g. glycogen synthase and the insulin receptor) and recent studies have shown increased expression of calcium-independent isozymes (PKC-epsilon and PKC-theta) in the membrane fraction of skeletal muscle in fructose- and fat-fed rat models of insulin resistance. In addition, there is separate evidence that glucose-induced PKC activation plays an important role in the micro- and macrovascular complications of diabetes. 3. New pharmacological approaches to NIDDM and obesity have focused on insulin-sensitizing agents (e.g. troglitazone), beta3-AR agonists, anti-lipolytic drugs (e.g. the adenosine A1 receptor agonist GR79236) and selective inhibitors of PKC isoforms (e.g. the inhibitor of PKC-beta LY333531). Experimental studies with GR79236 show that this drug ameliorates the hypertriglyceridaemia induced by fructose feeding and that the reduction in fatty acid levels is associated with secondary improvements in glucose tolerance. 4. Recent insights into the pathogenesis of NIDDM and its associated complications have been used to develop a range of new therapeutic agents that are currently showing promise in clinical and preclinical development.
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Affiliation(s)
- R Donnelly
- Department of Pharmacology, University of Sydney, New South Wales, Australia.
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42
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Schmitz-Peiffer C, Oakes ND, Browne CL, Kraegen EW, Biden TJ. Reversal of chronic alterations of skeletal muscle protein kinase C from fat-fed rats by BRL-49653. THE AMERICAN JOURNAL OF PHYSIOLOGY 1997; 273:E915-21. [PMID: 9374677 DOI: 10.1152/ajpendo.1997.273.5.e915] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
We have recently shown that the reduction in insulin sensitivity of rats fed a high-fat diet is associated with the translocation of the novel protein kinase C epsilon (nPKC epsilon) from cytosolic to particulate fractions in red skeletal muscle and also the downregulation of cytosolic nPKC theta. Here we have further investigated the link between insulin resistance and PKC by assessing the effects of the thiazolidinedione insulin-sensitizer BRL-49653 on PKC isoenzymes in muscle. BRL-49653 increased the recovery of nPKC isoenzymes in cytosolic fractions of red muscle from fat-fed rats, reducing their apparent activation and/or downregulation, whereas PKC in control rats was unaffected. Because BRL-49653 also improves insulin-stimulated glucose uptake in fat-fed rats and reduces muscle lipid storage, especially diglyceride content, these results strengthen the association between lipid availability, nPKC activation, and skeletal muscle insulin resistance and support the hypothesis that chronic activation of nPKC isoenzymes is involved in the generation of muscle insulin resistance in fat-fed rats.
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Affiliation(s)
- C Schmitz-Peiffer
- Garvan Institute of Medical Research, Sydney, New South Wales, Australia
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43
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Palmer RM, Thompson MG, Knott RM, Campbell GP, Thom A, Morrison KS. Insulin and insulin-like growth factor-I responsiveness and signalling mechanisms in C2C12 satellite cells: effect of differentiation and fusion. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1355:167-76. [PMID: 9042337 DOI: 10.1016/s0167-4889(96)00127-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In proliferating C2C12 myoblasts, serum and physiological concentrations of insulin and IGF-I stimulated protein synthesis and RNA accretion. After fusion, the multinucleated myotubes remained responsive to serum but not to insulin or IGF-I, even though both insulin and type-I IGF receptor mRNAs increased in abundance. Protein synthetic responses to insulin and IGF-I in myoblasts were not inhibited by dexamethasone, ibuprofen or Ro-31-8220, thus phospholipase A2, cyclo-oxygenase and protein kinase C did not appear to be involved in the signalling mechanisms. Neither apparently were polyphosphoinositide-specific phospholipase C or phospholipase D since neither hormone increased inositol phosphate, phosphatidic acid, choline or phosphatidylbutanol production. Only the phosphatidylinositol-3-kinase inhibitor, wortmannin, and the 70 kDa S6-kinase inhibitor, rapamycin, wholly or partially blocked the effects of insulin and IGF-I on protein synthesis. 2-deoxyglucose uptake remained responsive to insulin and IGF-I after fusion and was also inhibited by wortmannin. The results suggest that the loss of responsiveness after fusion is not due to loss of receptors, but to the uncoupling of a post-receptor pathway, occurring after the divergence of the glucose transport and protein synthesis signalling systems, and that, if wortmannin acts at a single site, this is prior to that point of divergence.
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Affiliation(s)
- R M Palmer
- Rowett Research Institute, Bucksburn, Aberdeen, UK
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44
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deVente JE, Carey JO, Bryant WO, Pettit GJ, Ways DK. Transcriptional regulation of insulin receptor substrate 1 by protein kinase C. J Biol Chem 1996; 271:32276-80. [PMID: 8943287 DOI: 10.1074/jbc.271.50.32276] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Insulin receptor substrate-1 (IRS-1) is involved in insulin signal transduction distal to receptor occupation. Targeted disruption of IRS-1 leads to insulin resistance and hyperglycemia in mice, which suggests that altered IRS-1 expression could contribute to the insulin resistance seen in non-insulin-dependent diabetes mellitus. In vitro studies using phorbol esters have implicated the protein kinase C (PKC) pathway as being involved in the pathogenesis of insulin resistance. Using the MCF-7 breast cancer cell, a role for PKC in regulating IRS-1 expression was examined. In an MCF-7 cell line (MCF-7-PKC-alpha) that exhibits multiple alterations in PKC isoform expression, IRS-1 content was reduced to negligible levels relative to parental MCF-7 cells. This decrease in IRS-1 content was associated with a 30-fold reduction in IRS-1 transcription. In parental MCF-7 cells, PKC inhibitors (GF109203X (bisindolylmaleimide I) and staurosporine) reduced IRS-1 content. Chronic exposure to 12-O-tetradecanoylphorbol-13-acetate (TPA; >8 h) reduced IRS-1 content and down-regulated the novel PKC-delta isoform. Bryostatin 1 inhibited TPA-induced depletion of both IRS-1 and PKC-delta expression in MCF-7 cells. Associated with TPA-induced reduction in IRS-1 content was a reduction in IRS-1 transcription. These data demonstrate that PKC can modulate IRS-1 content and suggest a potential role for PKC-delta in positively regulating IRS-1 expression.
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Affiliation(s)
- J E deVente
- Department of Medicine, East Carolina University School of Medicine, Greenville, North Carolina 27858, USA
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45
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Kellerer M, Coghlan M, Capp E, Mühlhöfer A, Kroder G, Mosthaf L, Galante P, Siddle K, Häring HU. Mechanism of insulin receptor kinase inhibition in non-insulin-dependent diabetes mellitus patients. Phosphorylation of serine 1327 or threonine 1348 is unaltered. J Clin Invest 1995; 96:6-11. [PMID: 7615833 PMCID: PMC185166 DOI: 10.1172/jci118073] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The tyrosine kinase activity of insulin receptor isolated from the skeletal muscle of NIDDM patients has previously been found to be decreased compared with the activity of receptor from nondiabetic subjects but the mechanism underlying this defect is unknown. Phosphorylation of receptor serine/threonine residues has been proposed to exert an inhibitory influence on receptor tyrosine kinase activity and Ser 1327 and Thr 1348 have been identified as specific sites of phosphorylation in the insulin receptor COOH terminal domain. To address the potential negative regulatory role of phosphorylation of these residues in vivo, we assessed the extent of phosphorylation of each site in insulin receptor isolated from the skeletal muscle of 12 NIDDM patients and 13 nondiabetic, control subjects. Phosphorylation of Ser 1327 and Thr 1348 was determined using antibodies that specifically recognize insulin receptor phosphorylated at these sites. In addition, a phosphotyrosine-specific antibody was used to monitor receptor tyrosine phosphorylation. The extent of insulin-induced tyrosine autophosphorylation was decreased in receptor isolated from diabetic versus nondiabetic muscle, thus confirming earlier reports. In contrast, there was no significant difference in the extent of phosphorylation of either Ser 1327 or Thr 1348 in receptor isolated from diabetic or nondiabetic muscle as assessed by immunoprecipitation (Ser 1327: 5.6 +/- 1.6% diabetics vs. 4.7 +/- 2.0% control; Thr 1348: 3.8 +/- 1.0% diabetics vs. 3.2 +/- 1.2% control). Moreover, within each group there was no correlation between the level of tyrosine kinase activity and the extent of serine/threonine phosphorylation. It is concluded that the stoichiometry of serine/threonine phosphorylation of insulin receptor in vivo is low, and that increased phosphorylation of Ser 1327 or Thr 1348 is not responsible for the decreased insulin receptor tyrosine kinase activity observed in the skeletal muscle of NIDDM patients.
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Affiliation(s)
- M Kellerer
- Institut für Diabetesforschung, München, Germany
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46
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Su W, Liu W, Schaffhausen BS, Roberts TM. Association of Polyomavirus middle tumor antigen with phospholipase C-gamma 1. J Biol Chem 1995; 270:12331-4. [PMID: 7759472 DOI: 10.1074/jbc.270.21.12331] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Middle tumor antigen (MT) is the primary transforming protein of murine Polyomavirus. MT transforms by associating with and modulating the activities of cellular proteins involved in control of cell proliferation. MT binds to and is phosphorylated by cellular tyrosine kinases. The phosphorylated tyrosines become docking sites for SH2 (Src homology 2) domain-containing molecules. Tyrosine 322 of MT is known to be phosphorylated but has no known binding protein. We have found that phospholipase C-gamma 1 (PLC-gamma 1), a SH2 domain-containing protein, coimmunoprecipitates with MT. Tyrosine phosphorylation of PLC-gamma 1 is elevated in cells expressing MT, suggesting activation of this enzyme by MT. A Tyr-322-->Phe mutation in MT renders it defective in MT-PLC-gamma 1 interaction and in transformation. From the correlation between transformation and MT-PLC-gamma 1 interaction, we suggest that PLC-gamma 1 may play a role in transformation.
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Affiliation(s)
- W Su
- Division of Cellular and Molecular Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
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47
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Malminiemi K. Association between serum lipids, glucose tolerance, and insulin sensitivity during 12 months of celiprolol treatment. Cardiovasc Drugs Ther 1995; 9:295-304. [PMID: 7662596 DOI: 10.1007/bf00878674] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The study was undertaken to evaluate the development and association of parameters related to the metabolic syndrome during celiprolol treatment. Hyperinsulinemic euglycemic clamp and independent oral glucose tolerance tests (OGTT) were performed on 25 nondiabetic patients with controlled hypertension and dyslipidemia. The tests were carried out during the patients' previous antihypertensive monotherapy (beta- or Ca-blocker, or an ACE inhibitor), and after 6 and 12 months of celiprolol treatment. About one third of patients were randomized to a control group in which treatment was kept unchanged. Insulin sensitivity index (ISI), measured by the euglycemic clamp test, increased 35% in the celiprolol group at 6 months and remained at that level at 12 months, independent of the previous treatment (p = 0.03, compared to the change in the control group). During a 2 hour OGTT, incremental glucose area under the curve (AUC) decreased from 4.5 to 1.9 hr x mmol/l during 6 months of celiprolol treatment, and decreased further to 1.5 hr x mmol/l at 12 months (p < 0.001). Insulin AUC decreased from 113 to 72 hr x mU/l, and decreased further to 68 hr x mU/l (p < 0.01). All insulin parameters in OGTT were highly significant (p < 0.0001) and inversely associated with ISI. Insulin AUC had the best linear correlation with ISI (r = -0.682, p < 0.0001). Glucose parameters in OGTT correlated only weakly and inversely with insulin sensitivity. From the fasting serum lipids, triglycerides showed an inverse (p < 0.001) and HDL a weak (p < 0.05) positive association with ISI. Four out of 20 metabolic, clinical, and demographic parameters proved to be independently significant predictors for ISI in multiple regression analysis. These were insulin AUC, fasting insulin levels, triglyceride values, and age. The coefficient of determination in this four-parameter linear model was 69%. In this preliminary, observer-masked trial with a limited control group, celiprolol improved the impaired insulin sensitivity and glucose tolerance of dyslipidemic hypertensive patients. A fairly predictive model can be formulated to evaluate the peripheral insulin sensitivity of hypertensive patients with suspected metabolic syndrome using OGTT with serum insulin determinations.
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Affiliation(s)
- K Malminiemi
- University of Tampere, Department of Medicine, Finland
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48
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Donnelly R, Chang H, Azhar S, Reaven GM. Tissue-dependent activation of protein kinase C in fructose-induced insulin resistance. Endocrine 1995; 3:129-33. [PMID: 21153149 DOI: 10.1007/bf02990064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/1994] [Accepted: 10/19/1994] [Indexed: 10/21/2022]
Abstract
Rats fed a fructose-enriched diet develop increases in blood pressure and resistance to insulin-mediated glucose disposal, but the underlying biochemical alterations have not been clearly defined. Since protein kinase C (PKC) has been implicated in the pathogenesis of insulin resistance, as well as blood pressure (BP) regulation, the present study was initiated to see whether changes in PKC signaling are present in rats with fructose-induced insulin resistance and hypertension. Consequently, liver, muscle, and adipose tissues were collected from fructose (n = 13) and chow (n = 12) fed Sprague-Dawley rats. PKC enzyme activity, and expression of classical PKC isozymes, were measured in cytosol and membrane fractions, and 1, 2-diacylglycerol (DAG), an endogenous stimulator of PKC, was measured by radio-enzymatic assay. Fructose feeding was associated with significant increases in fasting plasma insulin (140%) and triglyceride (400%) levels, and increased BP (20 mmHg). PKC activity was increased in the membrane fraction of adipose tissue (234 ± 38 (SE)vs 85 ± 30 pmol/min/mg protein,P< 0.007), without evidence of increased translocation or activation by DAG. Thus, fructose-induced insulin resistance has no effect on conventional PKC activity and subcellular distribution in liver and muscle, but the 3-fold increase in membraneassociated kinase activity in fat may be relevant to the mechanism of hypertriglyceridemia associated with fructose feeding.
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Affiliation(s)
- R Donnelly
- Department of Medicine, Stanford University School of Medicine and Geriatric Research, Education and Clinical Center, 94304, Palo Alto, California, USA
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49
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Abstract
A method for the analysis of 1,2-diacylglycerols in biological samples is presented. After tissue extraction and derivatisation with 3,5-dinitrobenzoyl chloride, samples are analysed by normal phase HPLC, using a 3.9 x 300 mm microPorasil column, and ultraviolet detection at 254 nm. The method gives quantitative recovery of 1,2-diacylglycerol, and is of sufficient sensitivity to allow quantitation of 1,2-diacylglycerol in human muscle needle biopsy specimens, from as little as 10 mg muscle. Human skeletal muscle from fasted control subjects was found to have a 1,2-diacylglycerol content of 455 +/- 78 nmol/g wet weight. The method is robust, giving intra- and inter-assay coefficients of variation of 2.9% and 5.9%, respectively, and should prove useful for the analysis of 1,2-diacylglycerol levels in human disease states, such as diabetes, in which no measurements of 1,2-diacylglycerol have yet been undertaken.
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Affiliation(s)
- S Eaton
- Department of Medicine, Medical School, University of Newcastle upon Tyne, UK
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