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Al Madhoun A. Glucokinase regulatory protein rs780094 polymorphism is associated with type 2 diabetes mellitus, dyslipidemia, non-alcoholic fatty liver disease, and nephropathy. World J Diabetes 2024; 15:814-817. [PMID: 38766433 PMCID: PMC11099372 DOI: 10.4239/wjd.v15.i5.814] [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] [Received: 12/04/2023] [Revised: 01/31/2024] [Accepted: 03/11/2024] [Indexed: 05/10/2024] Open
Abstract
In this editorial, we comment on the article by Liu et al published in the recent issue of the World Journal of Diabetes (Relationship between GCKR gene rs780094 polymorphism and type 2 diabetes with albuminuria). Type 2 diabetes mellitus (T2DM) is a chronic disorder characterized by dysregulated glucose homeostasis. The persistent elevated blood glucose level in T2DM significantly increases the risk of developing severe complications, including cardiovascular disease, re-tinopathy, neuropathy, and nephropathy. T2DM arises from a complex interplay between genetic, epigenetic, and environmental factors. Global genomic studies have identified numerous genetic variations associated with an increased risk of T2DM. Specifically, variations within the glucokinase regulatory protein (GCKR) gene have been linked to heightened susceptibility to T2DM and its associated complications. The clinical trial by Liu et al further elucidates the role of the GCKR rs780094 polymorphism in T2DM and nephropathy development. Their findings demonstrate that individuals carrying the CT or TT genotype at the GCKR rs780094 locus are at a higher risk of developing T2DM with albuminuria compared to those with the CC genotype. These findings highlight the importance of genetic testing and risk assessment in T2DM to develop effective preventive strategies and personalized treatment plans.
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Affiliation(s)
- Ashraf Al Madhoun
- Department of Genetics and Bioinformatics, Dasman Diabetes Institute, Dasman 15400, Kuwait
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2
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Kaur U, Pathak BK, Meerashahib TJ, Krishna DVV, Chakrabarti SS. Should Glucokinase be Given a Chance in Diabetes Therapeutics? A Clinical-Pharmacological Review of Dorzagliatin and Lessons Learned So Far. Clin Drug Investig 2024; 44:223-250. [PMID: 38460077 DOI: 10.1007/s40261-024-01351-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2024] [Indexed: 03/11/2024]
Abstract
Despite advances in the management of type 2 diabetes mellitus (T2DM), one-third of patients with diabetes do not achieve the desired glycemic goal. Considering this inadequacy, many agents that activate glucokinase have been investigated over the last two decades but were withdrawn before submission for marketing permission. Dorzagliatin is the first glucokinase activator that has been granted approval for T2DM, only in China. As overstimulation of glucokinase is linked with pathophysiological disturbances such as fatty liver and cardiovascular issues and a loss of therapeutic efficacy with time. This review aims to highlight the benefits of glucokinase activators vis-à-vis the risks associated with chronic enzymatic activation. We discuss the multisystem disturbances expected with chronic activation of the enzyme, the lessons learned with glucokinase activators of the past, the major efficacy and safety findings with dorzagliatin and its pharmacological properties, and the status of other glucokinase activators in the pipeline. The approval of dorzagliatin in China was based on the SEED and the DAWN trials, the major pivotal phase III trials that enrolled patients with T2DM with a mean glycosylated hemoglobin of 8.3-8.4%, and a mean age of 53-54.5 years from multiple sites in China. Patients with uncontrolled diabetes, cardiac diseases, organ dysfunction, and a history of severe hypoglycemia were excluded. Both trials had a randomized double-blind placebo-controlled phase of 24 weeks followed by an open-label phase of 28 weeks with dorzagliatin. Drug-naïve patients with T2DM with a disease duration of 11.7 months were enrolled in the SEED trial while the DAWN trial involved patients with T2DM with a mean duration of 71.5 months and receiving background metformin therapy. Compared with placebo, the decline in glycosylated hemoglobin at 24 weeks was more with dorzagliatin with an estimated treatment difference of - 0.57% in the SEED trial and - 0.66% in the DAWN trial. The desired glycosylated hemoglobin (< 7%) was also attained at more than two times higher rates with dorzagliatin. The glycemic improvement was sustained in the SEED trial but decreased over 52 weeks in the DAWN trial. Hyperlipidemia was observed in 12-14% of patients taking dorzagliatin versus 9-11% of patients receiving a placebo. Additional adverse effects noticed over 52 weeks with dorzagliatin included an elevation in liver enzymes, hyperuricemia, hyperlacticacidemia, renal dysfunction, and cardiovascular disturbances. Considering the statistically significant improvement in glycosylated hemoglobin with dorzagliatin in patients with T2DM, the drug may be given a chance in treatment-naïve patients with a shorter disease history. However, with the waning therapeutic efficacy witnessed in patients with long-standing diabetes, which was also one of the potential concerns with previously tested molecules, extended studies involving patients with chronic and uncontrolled diabetes are needed to comment upon the long-term therapeutic performance of dorzagliatin. Likewise, evidence needs to be generated from other countries, patients with organ dysfunction, a history of severe hypoglycemia, cardiac diseases, and elderly patients before extending the use of dorzagliatin. Apart from monitoring lipid profiles, long-term safety studies of dorzagliatin should involve the assessment of serum uric acid, lactate, renal function, liver function, and cardiovascular parameters.
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Affiliation(s)
- Upinder Kaur
- Department of Pharmacology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, 221005, India.
| | - Bhairav Kumar Pathak
- Department of Pharmacology and Therapeutics, All India Institute of Medical Sciences, Gorakhpur, Uttar Pradesh, India
| | - Tharik Jalal Meerashahib
- Department of Pharmacology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India
| | | | - Sankha Shubhra Chakrabarti
- Department of Geriatric Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, 221005, India.
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3
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Estes SK, Shiota C, O'Brien TP, Printz RL, Shiota M. The impact of glucagon to support postabsorptive glucose flux and glycemia in healthy rats and its attenuation in male Zucker diabetic fatty rats. Am J Physiol Endocrinol Metab 2024; 326:E308-E325. [PMID: 38265288 PMCID: PMC11193518 DOI: 10.1152/ajpendo.00192.2023] [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: 06/26/2023] [Revised: 01/19/2024] [Accepted: 01/19/2024] [Indexed: 01/25/2024]
Abstract
Hyperglucagonemia is a hallmark of type 2 diabetes (T2DM), yet the role of elevated plasma glucagon (P-GCG) to promote excessive postabsorptive glucose production and contribute to hyperglycemia in patients with this disease remains debatable. We investigated the acute action of P-GCG to safeguard/support postabsorptive endogenous glucose production (EGP) and euglycemia in healthy Zucker control lean (ZCL) rats. Using male Zucker diabetic fatty (ZDF) rats that exhibit the typical metabolic disorders of human T2DM, such as excessive EGP, hyperglycemia, hyperinsulinemia, and hyperglucagonemia, we examined the ability of hyperglucagonemia to promote greater rates of postabsorptive EGP and hyperglycemia. Euglycemic or hyperglycemic basal insulin (INS-BC) and glucagon (GCG-BC) clamps were performed in the absence or during an acute setting of glucagon deficiency (GCG-DF, ∼10% of basal), either alone or in combination with insulin deficiency (INS-DF, ∼10% of basal). Glucose appearance, disappearance, and cycling rates were measured using [2-3H] and [3-3H]-glucose. In ZCL rats, GCG-DF reduced the levels of hepatic cyclic AMP, EGP, and plasma glucose (PG) by 50%, 32%, and 50%, respectively. EGP fell in the presence GCG-DF and INS-BC, but under GCG-DF and INS-DF, EGP and PG increased two- and threefold, respectively. GCG-DF revealed the hyperglucagonemia present in ZDF rats lacked the ability to regulate hepatic intracellular cyclic AMP levels and glucose flux, since EGP and PG levels fell by only 10%. We conclude that the liver in T2DM suffers from resistance to all three major regulatory factors, glucagon, insulin, and glucose, thus leading to a loss of metabolic flexibility.NEW & NOTEWORTHY In postabsorptive state, basal plasma insulin (P-INS) and plasma glucose (PG) act dominantly to increase hepatic glucose cycling and reduce endogenous glucose production (EGP) and PG in healthy rats, which is only counteracted by the acute action of basal plasma glucagon (P-GCG) to support EGP and euglycemia. Hyperglucagonemia, a hallmark of type 2 diabetes (T2DM) present in Zucker diabetic fatty (ZDF) rats, is not the primary mediator of hyperglycemia and high EGP as commonly thought; instead, the liver is resistant to glucagon as well as insulin and glucose.
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Affiliation(s)
- Shanea K Estes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Chiyo Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Tracy P O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Richard L Printz
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States
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Haddad D, Dsouza VS, Al-Mulla F, Al Madhoun A. New-Generation Glucokinase Activators: Potential Game-Changers in Type 2 Diabetes Treatment. Int J Mol Sci 2024; 25:571. [PMID: 38203742 PMCID: PMC10779250 DOI: 10.3390/ijms25010571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 12/28/2023] [Accepted: 12/28/2023] [Indexed: 01/12/2024] Open
Abstract
Achieving glycemic control and sustaining functional pancreatic β-cell activity remains an unmet medical need in the treatment of type 2 diabetes mellitus (T2DM). Glucokinase activators (GKAs) constitute a class of anti-diabetic drugs designed to regulate blood sugar levels and enhance β-cell function in patients with diabetes. A significant progression in GKA development is underway to address the limitations of earlier generations. Dorzagliatin, a dual-acting GKA, targets both the liver and pancreas and has successfully completed two phase III trials, demonstrating favorable results in diabetes treatment. The hepato-selective GKA, TTP399, emerges as a strong contender, displaying clinically noteworthy outcomes with minimal adverse effects. This paper seeks to review the current literature, delve into the mechanisms of action of these new-generation GKAs, and assess their efficacy and safety in treating T2DM based on published preclinical studies and recent clinical trials.
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Affiliation(s)
- Dania Haddad
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Vanessa Sybil Dsouza
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Fahd Al-Mulla
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
| | - Ashraf Al Madhoun
- Genetics and Bioinformatics Department, Dasman Diabetes Institute, Dasman 15462, Kuwait; (D.H.); (V.S.D.); (F.A.-M.)
- Animal and Imaging Core Facilities, Dasman Diabetes Institute, Dasman 15462, Kuwait
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5
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O'Brien TP, Jenkins EC, Estes SK, Castaneda AV, Ueta K, Farmer TD, Puglisi AE, Swift LL, Printz RL, Shiota M. Correcting Postprandial Hyperglycemia in Zucker Diabetic Fatty Rats With an SGLT2 Inhibitor Restores Glucose Effectiveness in the Liver and Reduces Insulin Resistance in Skeletal Muscle. Diabetes 2017; 66:1172-1184. [PMID: 28246292 PMCID: PMC5399614 DOI: 10.2337/db16-1410] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 02/17/2017] [Indexed: 12/11/2022]
Abstract
Ten-week-old Zucker diabetic fatty (ZDF) rats at an early stage of diabetes embody metabolic characteristics of obese human patients with type 2 diabetes, such as severe insulin and glucose intolerance in muscle and the liver, excessive postprandial excursion of plasma glucose and insulin, and a loss of metabolic flexibility with decreased lipid oxidation. Metabolic flexibility and glucose flux were examined in ZDF rats during fasting and near-normal postprandial insulinemia and glycemia after correcting excessive postprandial hyperglycemia using treatment with a sodium-glucose cotransporter 2 inhibitor (SGLT2-I) for 7 days. Preprandial lipid oxidation was normalized, and with fasting, endogenous glucose production (EGP) increased by 30% and endogenous glucose disposal (E-Rd) decreased by 40%. During a postprandial hyperglycemic-hyperinsulinemic clamp after SGLT2-I treatment, E-Rd increased by normalizing glucose effectiveness to suppress EGP and stimulate hepatic glucose uptake; activation of glucokinase was restored and insulin action was improved, stimulating muscle glucose uptake in association with decreased intracellular triglyceride content. In conclusion, SGLT2-I treatment improves impaired glucose effectiveness in the liver and insulin sensitivity in muscle by eliminating glucotoxicity, which reinstates metabolic flexibility with restored preprandial lipid oxidation and postprandial glucose flux in ZDF rats.
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Affiliation(s)
- Tracy P O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Erin C Jenkins
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Shanea K Estes
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Antonio V Castaneda
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Kiichiro Ueta
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Tiffany D Farmer
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, TN
| | - Allison E Puglisi
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, TN
| | - Larry L Swift
- Department of Pathology, Vanderbilt University School of Medicine, Nashville, TN
| | - Richard L Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, TN
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Affiliation(s)
- Loranne Agius
- Institutes of Cellular Medicine and Ageing and Health, Medical School, Newcastle University, Newcastle upon Tyne, NE2 4HH United Kingdom;
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Farmer TD, Jenkins EC, O'Brien TP, McCoy GA, Havlik AE, Nass ER, Nicholson WE, Printz RL, Shiota M. Comparison of the physiological relevance of systemic vs. portal insulin delivery to evaluate whole body glucose flux during an insulin clamp. Am J Physiol Endocrinol Metab 2015; 308:E206-22. [PMID: 25516552 PMCID: PMC4312835 DOI: 10.1152/ajpendo.00406.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
To understand the underlying pathology of metabolic diseases, such as diabetes, an accurate determination of whole body glucose flux needs to be made by a method that maintains key physiological features. One such feature is a positive differential in insulin concentration between the portal venous and systemic arterial circulation (P/S-IG). P/S-IG during the determination of the relative contribution of liver and extra-liver tissues/organs to whole body glucose flux during an insulin clamp with either systemic (SID) or portal (PID) insulin delivery was examined with insulin infusion rates of 1, 2, and 5 mU·kg(-1)·min(-1) under either euglycemic or hyperglycemic conditions in 6-h-fasted conscious normal rats. A P/S-IG was initially determined with endogenous insulin secretion to exist with a value of 2.07. During an insulin clamp, while inhibiting endogenous insulin secretion by somatostatin, P/S-IG remained at 2.2 with PID, whereas, P/S-IG disappeared completely with SID, which exhibited higher arterial and lower portal insulin levels compared with PID. Consequently, glucose disappearance rates and muscle glycogen synthetic rates were higher, but suppression of endogenous glucose production and liver glycogen synthetic rates were lower with SID compared with PID. When the insulin clamp was performed with SID at 2 and 5 mU·kg(-1)·min(-1) without managing endogenous insulin secretion under euglycemic but not hyperglycemic conditions, endogenous insulin secretion was completely suppressed with SID, and the P/S-IG disappeared. Thus, compared with PID, an insulin clamp with SID underestimates the contribution of liver in response to insulin to whole body glucose flux.
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Affiliation(s)
- Tiffany D Farmer
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Erin C Jenkins
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Tracy P O'Brien
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Gregory A McCoy
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Allison E Havlik
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Erik R Nass
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Wendell E Nicholson
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Richard L Printz
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Masakazu Shiota
- Diabetes Research Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee; Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; and
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8
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Hale C, Lloyd DJ, Pellacani A, Véniant MM. Molecular targeting of the GK-GKRP pathway in diabetes. Expert Opin Ther Targets 2014; 19:129-39. [DOI: 10.1517/14728222.2014.965681] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
The glucokinase (GK) enzyme (EC 2.7.1.1.) is essential for the use of dietary glucose because it is the first enzyme to phosphorylate glucose in excess in different key tissues such as the pancreas and liver. The objective of the present review is not to fully describe the biochemical characteristics and the genetics of this enzyme but to detail its nutritional regulation in different vertebrates from fish to human. Indeed, the present review will describe the existence of the GK enzyme in different animal species that have naturally different levels of carbohydrate in their diets. Thus, some studies have been performed to analyse the nutritional regulation of the GK enzyme in humans and rodents (having high levels of dietary carbohydrates in their diets), in the chicken (moderate level of carbohydrates in its diet) and rainbow trout (no carbohydrate intake in its diet). All these data illustrate the nutritional importance of the GK enzyme irrespective of feeding habits, even in animals known to poorly use dietary carbohydrates (carnivorous species).
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10
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Cullen KS, Al-Oanzi ZH, O'Harte FPM, Agius L, Arden C. Glucagon induces translocation of glucokinase from the cytoplasm to the nucleus of hepatocytes by transfer between 6-phosphofructo 2-kinase/fructose 2,6-bisphosphatase-2 and the glucokinase regulatory protein. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1843:1123-34. [PMID: 24566088 PMCID: PMC4024195 DOI: 10.1016/j.bbamcr.2014.02.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Revised: 02/07/2014] [Accepted: 02/12/2014] [Indexed: 01/28/2023]
Abstract
Glucokinase activity is a major determinant of hepatic glucose metabolism and blood glucose homeostasis. Liver glucokinase activity is regulated acutely by adaptive translocation between the nucleus and the cytoplasm through binding and dissociation from its regulatory protein (GKRP) in the nucleus. Whilst the effect of glucose on this mechanism is well established, the role of hormones in regulating glucokinase location and its interaction with binding proteins remains unsettled. Here we show that treatment of rat hepatocytes with 25mM glucose caused decreased binding of glucokinase to GKRP, translocation from the nucleus and increased binding to 6-phosphofructo 2-kinase/fructose 2,6 bisphosphatase-2 (PFK2/FBPase2) in the cytoplasm. Glucagon caused dissociation of glucokinase from PFK2/FBPase2, concomitant with phosphorylation of PFK2/FBPase2 on Ser-32, uptake of glucokinase into the nucleus and increased interaction with GKRP. Two novel glucagon receptor antagonists attenuated the action of glucagon. This establishes an unequivocal role for hormonal control of glucokinase translocation. Given that glucagon excess contributes to the pathogenesis of diabetes, glucagon may play a role in the defect in glucokinase translocation and activity evident in animal models and human diabetes.
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Affiliation(s)
- Kirsty S Cullen
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Ziad H Al-Oanzi
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK; Department of Laboratory Medicine, Al-Jouf University, Sakaka, Saudi Arabia
| | - Finbarr P M O'Harte
- The Saad Centre for Pharmacy & Diabetes, School of Biomedical Sciences, University of Ulster, Coleraine, UK
| | - Loranne Agius
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK
| | - Catherine Arden
- Institute of Cellular Medicine, Newcastle University, Newcastle Upon Tyne, UK.
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11
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Ueta K, O'Brien TP, McCoy GA, Kim K, Healey EC, Farmer TD, Donahue EP, Condren AB, Printz RL, Shiota M. Glucotoxicity targets hepatic glucokinase in Zucker diabetic fatty rats, a model of type 2 diabetes associated with obesity. Am J Physiol Endocrinol Metab 2014; 306:E1225-38. [PMID: 24714398 PMCID: PMC4042096 DOI: 10.1152/ajpendo.00507.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A loss of glucose effectiveness to suppress hepatic glucose production as well as increase hepatic glucose uptake and storage as glycogen is associated with a defective increase in glucose phosphorylation catalyzed by glucokinase (GK) in Zucker diabetic fatty (ZDF) rats. We extended these observations by investigating the role of persistent hyperglycemia (glucotoxicity) in the development of impaired hepatic GK activity in ZDF rats. We measured expression and localization of GK and GK regulatory protein (GKRP), translocation of GK, and hepatic glucose flux in response to a gastric mixed meal load (MMT) and hyperglycemic hyperinsulinemic clamp after 1 or 6 wk of treatment with the sodium-glucose transporter 2 inhibitor (canaglifrozin) that was used to correct the persistent hyperglycemia of ZDF rats. Defective augmentation of glucose phosphorylation in response to a rise in plasma glucose in ZDF rats was associated with the coresidency of GKRP with GK in the cytoplasm in the midstage of diabetes, which was followed by a decrease in GK protein levels due to impaired posttranscriptional processing in the late stage of diabetes. Correcting hyperglycemia from the middle diabetic stage normalized the rate of glucose phosphorylation by maintaining GK protein levels, restoring normal nuclear residency of GK and GKRP under basal conditions and normalizing translocation of GK from the nucleus to the cytoplasm, with GKRP remaining in the nucleus in response to a rise in plasma glucose. This improved the liver's metabolic ability to respond to hyperglycemic hyperinsulinemia. Glucotoxicity is responsible for loss of glucose effectiveness and is associated with altered GK regulation in the ZDF rat.
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Affiliation(s)
- Kiichiro Ueta
- Department of Molecular Physiology and Biophysics and
| | | | | | - Kuikwon Kim
- Department of Molecular Physiology and Biophysics and
| | - Erin C Healey
- Department of Molecular Physiology and Biophysics and
| | - Tiffany D Farmer
- Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - E Patrick Donahue
- Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | | | - Richard L Printz
- Department of Molecular Physiology and Biophysics and Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics and Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
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12
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Kaminski MT, Schultz J, Waterstradt R, Tiedge M, Lenzen S, Baltrusch S. Glucose-induced dissociation of glucokinase from its regulatory protein in the nucleus of hepatocytes prior to nuclear export. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:554-64. [DOI: 10.1016/j.bbamcr.2013.12.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 11/18/2013] [Accepted: 12/04/2013] [Indexed: 12/12/2022]
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13
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Antidiabetic effects of glucokinase regulatory protein small-molecule disruptors. Nature 2013; 504:437-40. [PMID: 24226772 DOI: 10.1038/nature12724] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Accepted: 09/30/2013] [Indexed: 11/08/2022]
Abstract
Glucose homeostasis is a vital and complex process, and its disruption can cause hyperglycaemia and type II diabetes mellitus. Glucokinase (GK), a key enzyme that regulates glucose homeostasis, converts glucose to glucose-6-phosphate in pancreatic β-cells, liver hepatocytes, specific hypothalamic neurons, and gut enterocytes. In hepatocytes, GK regulates glucose uptake and glycogen synthesis, suppresses glucose production, and is subject to the endogenous inhibitor GK regulatory protein (GKRP). During fasting, GKRP binds, inactivates and sequesters GK in the nucleus, which removes GK from the gluconeogenic process and prevents a futile cycle of glucose phosphorylation. Compounds that directly hyperactivate GK (GK activators) lower blood glucose levels and are being evaluated clinically as potential therapeutics for the treatment of type II diabetes mellitus. However, initial reports indicate that an increased risk of hypoglycaemia is associated with some GK activators. To mitigate the risk of hypoglycaemia, we sought to increase GK activity by blocking GKRP. Here we describe the identification of two potent small-molecule GK-GKRP disruptors (AMG-1694 and AMG-3969) that normalized blood glucose levels in several rodent models of diabetes. These compounds potently reversed the inhibitory effect of GKRP on GK activity and promoted GK translocation both in vitro (isolated hepatocytes) and in vivo (liver). A co-crystal structure of full-length human GKRP in complex with AMG-1694 revealed a previously unknown binding pocket in GKRP distinct from that of the phosphofructose-binding site. Furthermore, with AMG-1694 and AMG-3969 (but not GK activators), blood glucose lowering was restricted to diabetic and not normoglycaemic animals. These findings exploit a new cellular mechanism for lowering blood glucose levels with reduced potential for hypoglycaemic risk in patients with type II diabetes mellitus.
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14
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Modulation of glucokinase by glucose, small-molecule activator and glucokinase regulatory protein: steady-state kinetic and cell-based analysis. Biochem J 2012; 441:881-7. [PMID: 22044397 DOI: 10.1042/bj20110721] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
GK (glucokinase) is an enzyme central to glucose metabolism that displays positive co-operativity to substrate glucose. Small-molecule GKAs (GK activators) modulate GK catalytic activity and glucose affinity and are currently being pursued as a treatment for Type 2 diabetes. GK progress curves monitoring product formation are linear up to 1 mM glucose, but biphasic at 5 mM, with the transition from the lower initial velocity to the higher steady-state velocity being described by the rate constant kact. In the presence of a liver-specific GKA (compound A), progress curves at 1 mM glucose are similar to those at 5 mM, reflecting activation of GK by compound A. We show that GKRP (GK regulatory protein) is a slow tight-binding inhibitor of GK. Analysis of progress curves indicate that this inhibition is time dependent, with apparent initial and final Ki values being 113 and 12.8 nM respectively. When GK is pre-incubated with glucose and compound A, the inhibition observed by GKRP is time dependent, but independent of GKRP concentration, reflecting the GKA-controlled transition between closed and open GK conformations. These data are supported by cell-based imaging data from primary rat hepatocytes. This work characterizes the modulation of GK by a novel GKA that may enable the design of new and improved GKAs.
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Abstract
Male Zucker diabetic fatty fa/fa (ZDF) rats develop obesity and insulin resistance at a young age, and then with aging, progressively develop hyperglycemia. This hyperglycemia is associated with impaired pancreatic β-cell function, loss of pancreatic β-cell mass, and decreased responsiveness of liver and extrahepatic tissues to the actions of insulin and glucose. Of particular interest are the insights provided by studies of these animals into the mechanism behind the progressive impairment of carbohydrate metabolism. This feature among others, including the development of obesity- and hyperglycemia-related complications, is common between male ZDF rats and humans with type 2 diabetes associated with obesity. We discuss the diabetic features and complications found in ZDF rats and why these animals are widely used as a genetic model for obese type 2 diabetes.
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Affiliation(s)
- Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA.
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Shiota M. Measurement of glucose homeostasis in vivo: combination of tracers and clamp techniques. Methods Mol Biol 2012; 933:229-53. [PMID: 22893411 DOI: 10.1007/978-1-62703-068-7_15] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A tracer technique referred to as "pancreatic-blood glucose clamp" allows assessment in response to a change in blood glucose, insulin, and/or glucagon of whole body glucose disposal, endogenous glucose production, specific tissue/organ glucose uptake and storage, and insulin secretion. This technique is currently considered the optimal method for measurement of insulin sensitivity and glucose effectiveness. We describe here, for use in conscious-unrestrained mice and rats, the pancreatic-blood glucose clamp technique and its associated methods; which include catheterization of blood vessels; a clamp of plasma insulin, glucagon, and glucose; analyses of metabolites and tracers; and calculations.
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Affiliation(s)
- Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN, USA.
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Rees MG, Ng D, Ruppert S, Turner C, Beer NL, Swift AJ, Morken MA, Below JE, Blech I, Mullikin JC, McCarthy MI, Biesecker LG, Gloyn AL, Collins FS. Correlation of rare coding variants in the gene encoding human glucokinase regulatory protein with phenotypic, cellular, and kinetic outcomes. J Clin Invest 2011; 122:205-17. [PMID: 22182842 DOI: 10.1172/jci46425] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 11/09/2011] [Indexed: 01/24/2023] Open
Abstract
Defining the genetic contribution of rare variants to common diseases is a major basic and clinical science challenge that could offer new insights into disease etiology and provide potential for directed gene- and pathway-based prevention and treatment. Common and rare nonsynonymous variants in the GCKR gene are associated with alterations in metabolic traits, most notably serum triglyceride levels. GCKR encodes glucokinase regulatory protein (GKRP), a predominantly nuclear protein that inhibits hepatic glucokinase (GCK) and plays a critical role in glucose homeostasis. The mode of action of rare GCKR variants remains unexplored. We identified 19 nonsynonymous GCKR variants among 800 individuals from the ClinSeq medical sequencing project. Excluding the previously described common missense variant p.Pro446Leu, all variants were rare in the cohort. Accordingly, we functionally characterized all variants to evaluate their potential phenotypic effects. Defects were observed for the majority of the rare variants after assessment of cellular localization, ability to interact with GCK, and kinetic activity of the encoded proteins. Comparing the individuals with functional rare variants to those without such variants showed associations with lipid phenotypes. Our findings suggest that, while nonsynonymous GCKR variants, excluding p.Pro446Leu, are rare in individuals of mixed European descent, the majority do affect protein function. In sum, this study utilizes computational, cell biological, and biochemical methods to present a model for interpreting the clinical significance of rare genetic variants in common disease.
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Affiliation(s)
- Matthew G Rees
- National Human Genome Research Institute, NIH, Bethesda, Maryland 20892, USA
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Hein GJ, Chicco A, Lombardo YB. Fish oil normalizes plasma glucose levels and improves liver carbohydrate metabolism in rats fed a sucrose-rich diet. Lipids 2011; 47:141-50. [PMID: 22045300 DOI: 10.1007/s11745-011-3623-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 10/04/2011] [Indexed: 12/23/2022]
Abstract
A sucrose-rich diet (SRD) induces insulin resistance and dyslipidemia with impaired hepatic glucose production and gluconeogenesis, accompanied by altered post-receptor insulin signaling steps. The aim of this study was to examine the effectiveness of fish oil (FO) to reverse or improve the impaired hepatic glucose metabolism once installed in rats fed 8 months a SRD. In the liver of rats fed SRD in which FO replaced corn-oil during the last 2 months, as dietary fat, several key enzyme activities and metabolites involved in glucose metabolisms (phosphorylation, glycolysis, gluconeogenesis and oxidative and non oxidative glucose pathway) were measured. The protein mass levels of IRS-1 and αp85 PI-3K at basal conditions were also analyzed. FO improved the altered activities of some enzymes involved in the glycolytic and oxidative pathways observed in the liver of SRD fed rats but was unable to restore the impaired capacity of glucose phosphorylation. Moreover, FO reversed the increase in PEPCK and G-6-Pase and reduced the G-6-Pase/GK ratio. Glycogen concentration and GSa activity returned to levels similar to those observed in the liver of the control-fed rats. Besides, FO did not modify the altered protein mass levels of IRS-1 and αp85 PI-3K. Finally, dietary FO was effective in reversing or improving the impaired activities of several key enzymes of hepatic carbohydrate metabolism contributing, at least in part, to the normalization of plasma glucose levels in the SRD-fed rats. However, these positive effects of FO were not observed under basal conditions in the early steps of insulin signaling transduction.
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Affiliation(s)
- Gustavo J Hein
- Department of Biochemistry, School of Biochemistry, University of Litoral, Ciudad Universitaria Paraje El Pozo. CC 242 (3000), Santa Fe, Argentina
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Torres TP, Fujimoto Y, Donahue E, Printz RL, Houseknecht KL, Treadway JL, Shiota M. Defective glycogenesis contributes toward the inability to suppress hepatic glucose production in response to hyperglycemia and hyperinsulinemia in zucker diabetic fatty rats. Diabetes 2011; 60:2225-33. [PMID: 21771972 PMCID: PMC3161317 DOI: 10.2337/db09-1156] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Examine whether normalizing net hepatic glycogenesis restores endogenous glucose production and hepatic glucose phosphorylation in response to diabetic levels of plasma glucose and insulin in Zucker diabetic fatty rats (ZDF). RESEARCH DESIGN AND METHODS Hepatic glucose and intermediate fluxes (µmol · kg(-1) · min(-1)) were measured with and without a glycogen phosphorylase inhibitor (GPI) using [2-(3)H]glucose, [3-(3)H]glucose, and [U-(14)C]alanine in 20 h-fasted conscious ZDF and their lean littermates (ZCL) under clamp conditions designed to maintain diabetic levels of plasma glucose and insulin. RESULTS With infusion of GPI into ZDF (ZDF-GPI+G), compared with vehicle infused ZDF (ZDF-V), high glycogen phosphorylase a activity was decreased and low synthase I activity was increased to that of ZCL. Low net glycogenesis from plasma glucose rose to 75% of ZCL levels (4 ± 1 in ZDF-V, 18 ± 1 in ZDF-GPI+G, and 24 ± 2 in ZCL) and phosphoenolpyruvate 260% (4 ± 2 in ZDF-V, 16 ± 1 in ZDF+GPI-G, and 6 ± 2 in ZCL). High endogenous glucose production was suppressed with GPI infusion but not to that of ZCL (46 ± 4 in ZDF-V, 18 ± 4 in ZDF-GPI+G, and -8 ± 3 in ZCL). This was accompanied by reduction of the higher glucose-6-phosphatase flux (75 ± 4 in ZDF-V, 41 ± 4 in ZDF-GPI+G, and 86 ± 12 in ZCL) and no change in low glucose phosphorylation or total gluconeogenesis. CONCLUSIONS In the presence of hyperglycemic-hyperinsulinemia in ZDF, reduced glycogenic flux partially contributes to a lack of suppression of hepatic glucose production by failing to redirect glucose-6-phosphate flux from production of glucose to glycogen but is not responsible for a lower rate of glucose phosphorylation.
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Affiliation(s)
- Tracy P. Torres
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Yuka Fujimoto
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - E.P. Donahue
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Richard L. Printz
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | | | | | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Corresponding author: Masakazu Shiota,
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Shankaraia P, Narsimha R Y, Venkatesha A, Venkata Ra N, Krishna D. Differential Expression of Glucokinase activity in Indian Type-2 Diabetes Patients. INT J PHARMACOL 2010. [DOI: 10.3923/ijp.2010.500.504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Affiliation(s)
- Loranne Agius
- Institute of Cellular Medicine, The Medical School, Newcastle University, Newcastle upon Tyne, UK.
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Torres TP, Catlin RL, Chan R, Fujimoto Y, Sasaki N, Printz RL, Newgard CB, Shiota M. Restoration of hepatic glucokinase expression corrects hepatic glucose flux and normalizes plasma glucose in zucker diabetic fatty rats. Diabetes 2009; 58:78-86. [PMID: 18952838 PMCID: PMC2606896 DOI: 10.2337/db08-1119] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 10/11/2008] [Indexed: 11/13/2022]
Abstract
OBJECTIVE We examined in 20-week-old Zucker diabetic fatty (ZDF) rats whether restoration of hepatic glucokinase (GK) expression would alter hepatic glucose flux and improve hyperglycemia. RESEARCH DESIGN AND METHODS ZDF rats were treated at various doses with an adenovirus that directs the expression of rat liver GK (AdvCMV-GKL) dose dependently, and various metabolic parameters were compared with those of nondiabetic lean littermates (ZCL rats) before and during a hyperglycemic clamp. Viral infection per se did not affect hepatic GK activity, since expression of a catalytically inactive form of GK did not alter endogenous hepatic GK activity. RESULTS ZDF rats compared with ZCL rats have lower hepatic GK activity (11.6 +/- 1.9 vs. 32.5 +/- 3.2 mU/mg protein), marked hyperglycemia (23.9 +/- 1.2 vs. 7.4 +/- 0.3 mmol/l), higher endogenous glucose production (80 +/- 3 vs. 38 +/- 3 micromol x kg(-1) x min(-1)), increased glucose-6-phosphatase flux (150 +/- 11 vs. 58 +/- 8 micromol x kg(-1) x min(-1)), and during a hyperglycemic clamp, a failure to suppress endogenous glucose production (80 +/- 7 vs. -7 +/- 4 micromol x kg(-1) x min(-1)) and promote glucose incorporation into glycogen (15 +/- 5 vs. 43 +/- 3 micromol/g liver). Treatment of ZDF rats with different doses of AdvCMV-GKL, which restored hepatic GK activity to one to two times that of ZCL rats, normalized plasma glucose levels and endogenous glucose production. During a hyperglycemic clamp, glucose production was suppressed and glucose incorporation into glycogen was normal. CONCLUSIONS Alteration of hepatic GK activity in ZDF rats has profound effects on plasma glucose and hepatic glucose flux.
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Affiliation(s)
- Tracy P Torres
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Anderka O, Boyken J, Aschenbach U, Batzer A, Boscheinen O, Schmoll D. Biophysical characterization of the interaction between hepatic glucokinase and its regulatory protein: impact of physiological and pharmacological effectors. J Biol Chem 2008; 283:31333-40. [PMID: 18809676 DOI: 10.1074/jbc.m805434200] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucokinase (GK) is a key enzyme of glucose metabolism in liver and pancreatic beta-cells, and small molecule activators of GK (GKAs) are under evaluation for the treatment of type 2 diabetes. In liver, GK activity is controlled by the GK regulatory protein (GKRP), which forms an inhibitory complex with the enzyme. Here, we performed isothermal titration calorimetry and surface plasmon resonance experiments to characterize GK-GKRP binding and to study the influence that physiological and pharmacological effectors of GK have on the protein-protein interaction. In the presence of fructose-6-phosphate, GK-GKRP complex formation displayed a strong entropic driving force opposed by a large positive enthalpy; a negative change in heat capacity was observed (Kd = 45 nm, DeltaH = 15.6 kcal/mol, TDeltaS = 25.7 kcal/mol, DeltaCp = -354 cal mol(-1) K(-1)). With k(off) = 1.3 x 10(-2) s(-1), the complex dissociated quickly. The thermodynamic profile suggested a largely hydrophobic interaction. In addition, effects of pH and buffer demonstrated the coupled uptake of one proton and indicated an ionic contribution to binding. Glucose decreased the binding affinity between GK and GKRP. This decrease was potentiated by an ATP analogue. Prototypical GKAs of the amino-heteroaryl-amide type bound to GK in a glucose-dependent manner and impaired the association of GK with GKRP. This mechanism might contribute to the antidiabetic effects of GKAs.
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Affiliation(s)
- Oliver Anderka
- Sanofi Aventis Deutschland GmbH, Research and Development, D-65926 Frankfurt am Main, Germany.
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Abstract
Conversion of glucose into glycogen is a major pathway that contributes to the removal of glucose from the portal vein by the liver in the postprandial state. It is regulated in part by the increase in blood-glucose concentration in the portal vein, which activates glucokinase, the first enzyme in the pathway, causing an increase in the concentration of glucose 6-P (glucose 6-phosphate), which modulates the phosphorylation state of downstream enzymes by acting synergistically with other allosteric effectors. Glucokinase is regulated by a hierarchy of transcriptional and post-transcriptional mechanisms that are only partially understood. In the fasted state, glucokinase is in part sequestered in the nucleus in an inactive state, complexed to a specific regulatory protein, GKRP (glucokinase regulatory protein). This reserve pool is rapidly mobilized to the cytoplasm in the postprandial state in response to an elevated concentration of glucose. The translocation of glucokinase between the nucleus and cytoplasm is modulated by various metabolic and hormonal conditions. The elevated glucose 6-P concentration, consequent to glucokinase activation, has a synergistic effect with glucose in promoting dephosphorylation (inactivation) of glycogen phosphorylase and inducing dephosphorylation (activation) of glycogen synthase. The latter involves both a direct ligand-induced conformational change and depletion of the phosphorylated form of glycogen phosphorylase, which is a potent allosteric inhibitor of glycogen synthase phosphatase activity associated with the glycogen-targeting protein, GL [hepatic glycogen-targeting subunit of PP-1 (protein phosphatase-1) encoded by PPP1R3B]. Defects in both the activation of glucokinase and in the dephosphorylation of glycogen phosphorylase are potential contributing factors to the dysregulation of hepatic glucose metabolism in Type 2 diabetes.
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Lange AJ. For the ZDF rat, “Breaking Up Is Hard To Do”: dissociation of the GK:GKRP complex. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1379-80. [PMID: 17185403 DOI: 10.1152/ajpregu.00867.2006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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