1
|
Dienel GA. Hypothesis: A Novel Neuroprotective Role for Glucose-6-phosphatase (G6PC3) in Brain-To Maintain Energy-Dependent Functions Including Cognitive Processes. Neurochem Res 2020; 45:2529-2552. [PMID: 32815045 DOI: 10.1007/s11064-020-03113-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/10/2020] [Accepted: 08/13/2020] [Indexed: 12/11/2022]
Abstract
The isoform of glucose-6-phosphatase in liver, G6PC1, has a major role in whole-body glucose homeostasis, whereas G6PC3 is widely distributed among organs but has poorly-understood functions. A recent, elegant analysis of neutrophil dysfunction in G6PC3-deficient patients revealed G6PC3 is a neutrophil metabolite repair enzyme that hydrolyzes 1,5-anhydroglucitol-6-phosphate, a toxic metabolite derived from a glucose analog present in food. These patients exhibit a spectrum of phenotypic characteristics and some have learning disabilities, revealing a potential linkage between cognitive processes and G6PC3 activity. Previously-debated and discounted functions for brain G6PC3 include causing an ATP-consuming futile cycle that interferes with metabolic brain imaging assays and a nutritional role involving astrocyte-neuron glucose-lactate trafficking. Detailed analysis of the anhydroglucitol literature reveals that it competes with glucose for transport into brain, is present in human cerebrospinal fluid, and is phosphorylated by hexokinase. Anhydroglucitol-6-phosphate is present in rodent brain and other organs where its accumulation can inhibit hexokinase by competition with ATP. Calculated hexokinase inhibition indicates that energetics of brain and erythrocytes would be more adversely affected by anhydroglucitol-6-phosphate accumulation than heart. These findings strongly support the paradigm-shifting hypothesis that brain G6PC3 removes a toxic metabolite, thereby maintaining brain glucose metabolism- and ATP-dependent functions, including cognitive processes.
Collapse
Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, 4301 W. Markham St., Mail Slot 500, Little Rock, AR, 72205, USA.
- Department of Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA.
| |
Collapse
|
2
|
Ying L, Ma X, Yin J, Wang Y, He X, Peng J, Bao Y, Zhou J, Jia W. The metabolism and transport of 1,5-anhydroglucitol in cells. Acta Diabetol 2018; 55:279-286. [PMID: 29318370 DOI: 10.1007/s00592-017-1093-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 12/19/2017] [Indexed: 11/30/2022]
Abstract
AIMS Our previous studies demonstrated that serum 1,5-anhydroglucitol (1,5-AG) levels increased slightly rather than declined after an acute glucose load. Therefore, the current study aims at exploring the transport and metabolic characteristics of 1,5-AG, as well as the effect of glucose on 1,5-AG transport. METHODS Km and Vmax were determined to measure the affinity of glucose oxidase (GOD) and hexokinase (HK) for 1,5-AG and glucose. HepG2, C2C12, and primary mouse hepatocytes were incubated for 2 h with 1,5-AG at concentrations of 0, 80, and 160 μg/mL. Then, intracellular and extracellular concentrations of 1,5-AG were measured before and after washing with PBS to evaluate the transport and metabolic rates of 1,5-AG. In addition, the influence of an acute glucose load on the transport of 1,5-AG was studied. RESULTS The affinity of GOD and HK for 1,5-AG is 5 and 42.5% of that for glucose, respectively. Moreover, there is no de novo synthesis of 1,5-AG, and its metabolic rate is < 3%. After a 2 h incubation with additional 1,5-AG, the intracellular levels of 1,5-AG were 50-80% of extracellular levels. Moreover, intracellular 1,5-AG concentrations decreased rapidly and reached zero following the removal of 1,5-AG from the external medium. In addition, an acute glucose load can affect the dynamic balance of 1,5-AG, causing the intracellular 1,5-AG levels to decline significantly and the extracellular levels to increase slightly in HepG2 cells. CONCLUSIONS Unlike glucose, 1,5-AG is hard to be metabolized in vivo, and its transport is influenced by an acute glucose load in hepatocytes.
Collapse
Affiliation(s)
- Lingwen Ying
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Xiaojing Ma
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Jun Yin
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China.
| | - Yufei Wang
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Xingxing He
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Jiahui Peng
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Yuqian Bao
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| | - Jian Zhou
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China.
| | - Weiping Jia
- Department of Endocrinology and Metabolism, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Clinical Center for Diabetes, Shanghai Diabetes Institute, Shanghai Key Laboratory of Diabetes Mellitus, 600 Yishan Road, Shanghai, 200233, China
| |
Collapse
|
3
|
Zhang F, Wang L, Zhang C, Zhao Y. Novel regio- and stereoselective phosphonyl radical addition to glycals promoted by Mn(ii)–air: syntheses of 1,2-dideoxy 2-C-diphenylphosphinylglycopyranosides. Chem Commun (Camb) 2014; 50:2046-8. [DOI: 10.1039/c3cc48806c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The novel Mn(ii)–air promoted radical reaction of diphenylphosphine oxide with various glycals in excellent regio- and stereoselectivities generated 1,2-dideoxy-2-C-diphenylphosphinylglycopyranosides.
Collapse
Affiliation(s)
- Fuyi Zhang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Liming Wang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Cui Zhang
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
| | - Yufen Zhao
- The College of Chemistry and Molecular Engineering
- The Key Lab of Chemical Biology and Organic Chemistry
- Zhengzhou University
- Zhengzhou 450052, China
- College of Chemistry and Chemical Engineering
| |
Collapse
|
6
|
Abstract
Concentrations of 1,5-anhydroglucitol (1,5-AG), which is a major circulating polyol, decrease in patients with diabetes mellitus. In both insulinoma-derived RINr and MIN6 cells, 1,5-AG stimulated insulin release within the range of 0.03-0.61 mM in a dose-dependent manner. Insulin release was maximally stimulated by 1,5-AG to levels that reached 25% and 100% greater than that of control (1,5-AG-free group) in RINr and MIN6 cells, respectively. A physiological concentration of 1,5-AG stimulated insulin release after a 5-min incubation and this action was maintained for 60 min. In addition, at approximately 1/200 the concentration of glucose, 1,5-AG had additive action with 20 mM glucose. The action of 1,5-AG on insulin secretion with other types of saccharides and polyol was similarly additive. Mannnoheptulose and diazoxide suppressed the stimulative action of 1,5-AG on insulin release. The secretagogue action of 1,5-AG seemed to be independent on an increase in the intracellular content of cAMP and ATP. These results suggest that 1,5-AG can stimulate insulin secretion through a mechanism that completely differs from that of glucose.
Collapse
Affiliation(s)
- Toshikazu Yamanouchi
- Department of Internal Medicine, University of Teikyo, Kaga, Tokyo 173-0003, Itabashi, Japan.
| | | | | | | | | |
Collapse
|