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Bayne M, Alvarsson A, Devarakonda K, Li R, Jimenez-Gonzalez M, Garibay D, Conner K, Varghese M, Serasinghe MN, Chipuk JE, Hof PR, Stanley SA. Repeated hypoglycemia remodels neural inputs and disrupts mitochondrial function to blunt glucose-inhibited GHRH neuron responsiveness. JCI Insight 2020; 5:133488. [PMID: 33148883 PMCID: PMC7710320 DOI: 10.1172/jci.insight.133488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 09/24/2020] [Indexed: 11/29/2022] Open
Abstract
Hypoglycemia is a frequent complication of diabetes, limiting therapy and increasing morbidity and mortality. With recurrent hypoglycemia, the counterregulatory response (CRR) to decreased blood glucose is blunted, resulting in hypoglycemia-associated autonomic failure (HAAF). The mechanisms leading to these blunted effects are only poorly understood. Here, we report, with ISH, IHC, and the tissue-clearing capability of iDISCO+, that growth hormone releasing hormone (GHRH) neurons represent a unique population of arcuate nucleus neurons activated by glucose deprivation in vivo. Repeated glucose deprivation reduces GHRH neuron activation and remodels excitatory and inhibitory inputs to GHRH neurons. We show that low glucose sensing is coupled to GHRH neuron depolarization, decreased ATP production, and mitochondrial fusion. Repeated hypoglycemia attenuates these responses during low glucose. By maintaining mitochondrial length with the small molecule mitochondrial division inhibitor-1, we preserved hypoglycemia sensitivity in vitro and in vivo. Our findings present possible mechanisms for the blunting of the CRR, significantly broaden our understanding of the structure of GHRH neurons, and reveal that mitochondrial dynamics play an important role in HAAF. We conclude that interventions targeting mitochondrial fission in GHRH neurons may offer a new pathway to prevent HAAF in patients with diabetes. GHRH neurons in the arcuate nucleus are activated by glucose deprivation; however, repeated hypoglycemia blunts activation, remodels inputs, and disrupts mitochondrial fusion.
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Affiliation(s)
| | | | | | | | | | | | | | - Merina Varghese
- Nash Family Department of Neuroscience and Friedman Brain Institute, and
| | - Madhavika N Serasinghe
- Tisch Cancer Institute and Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Jerry E Chipuk
- Tisch Cancer Institute and Department of Oncological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Patrick R Hof
- Nash Family Department of Neuroscience and Friedman Brain Institute, and
| | - Sarah A Stanley
- Diabetes, Obesity and Metabolism Institute.,Nash Family Department of Neuroscience and Friedman Brain Institute, and
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Gurzov EN, Tran M, Fernandez-Rojo MA, Merry TL, Zhang X, Xu Y, Fukushima A, Waters MJ, Watt MJ, Andrikopoulos S, Neel BG, Tiganis T. Hepatic oxidative stress promotes insulin-STAT-5 signaling and obesity by inactivating protein tyrosine phosphatase N2. Cell Metab 2014; 20:85-102. [PMID: 24954415 PMCID: PMC4335267 DOI: 10.1016/j.cmet.2014.05.011] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 03/23/2014] [Accepted: 04/28/2014] [Indexed: 12/18/2022]
Abstract
Hepatic insulin resistance is a key contributor to the pathogenesis of obesity and type 2 diabetes (T2D). Paradoxically, the development of insulin resistance in the liver is not universal, but pathway selective, such that insulin fails to suppress gluconeogenesis but promotes lipogenesis, contributing to the hyperglycemia, steatosis, and hypertriglyceridemia that underpin the deteriorating glucose control and microvascular complications in T2D. The molecular basis for the pathway-specific insulin resistance remains unknown. Here we report that oxidative stress accompanying obesity inactivates protein-tyrosine phosphatases (PTPs) in the liver to activate select signaling pathways that exacerbate disease progression. In obese mice, hepatic PTPN2 (TCPTP) inactivation promoted lipogenesis and steatosis and insulin-STAT-5 signaling. The enhanced STAT-5 signaling increased hepatic IGF-1 production, which suppressed central growth hormone release and exacerbated the development of obesity and T2D. Our studies define a mechanism for the development of selective insulin resistance with wide-ranging implications for diseases characterized by oxidative stress.
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Affiliation(s)
- Esteban N Gurzov
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Melanie Tran
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Manuel A Fernandez-Rojo
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Troy L Merry
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Xinmei Zhang
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Yang Xu
- Princess Margaret Cancer Center, University Health Network, 101 College Street, Toronto Medical Discovery Tower, University of Toronto, Toronto, ON M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Atsushi Fukushima
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Michael J Waters
- Institute for Molecular Bioscience, Services Road, University of Queensland, St. Lucia, QLD 4072, Australia
| | - Matthew J Watt
- Department of Physiology, Monash University, Wellington Road, Clayton, VIC 3800, Australia
| | - Sofianos Andrikopoulos
- Department of Medicine Heidelberg Repatriation Hospital, 300 Waterdale Road, Heidelberg West, The University of Melbourne, VIC 3081, Australia
| | - Benjamin G Neel
- Princess Margaret Cancer Center, University Health Network, 101 College Street, Toronto Medical Discovery Tower, University of Toronto, Toronto, ON M5G 1L7, Canada; Department of Medical Biophysics, University of Toronto, 1 King's College Circle, Toronto, ON M5S 1A8, Canada
| | - Tony Tiganis
- Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, VIC 3800, Australia.
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