{"id":58,"date":"2024-03-10T12:19:19","date_gmt":"2024-03-10T12:19:19","guid":{"rendered":"https:\/\/glocentrica.usquaresolutions.com\/?page_id=58"},"modified":"2026-11-01T11:11:00","modified_gmt":"2026-11-01T11:11:00","slug":"hexokinase-linked-glycolytic-overload-and-unscheduled-glycolysis-in-hyperglycemia-induced-pathogenesis-of-insulin-resistance-beta-cell-glucotoxicity-and-diabetic-vascular-complications","status":"publish","type":"page","link":"https:\/\/pjthornalley.com\/index.php\/hexokinase-linked-glycolytic-overload-and-unscheduled-glycolysis-in-hyperglycemia-induced-pathogenesis-of-insulin-resistance-beta-cell-glucotoxicity-and-diabetic-vascular-complications\/","title":{"rendered":"Hexokinase-linked unscheduled glycolysis and glycolytic overload in hyperglycemia-induced impaired incretin effect and pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications"},"content":{"rendered":"\n

Summary<\/strong><\/p>\n\n\n\n

Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased activity of glycolytic enzymes\u2014unscheduled glycolysis\u2014produces increased levels of glycolytic intermediates with overspill into effector pathways of cell dysfunction and pathogenesis. HK1 is saturated with glucose in euglycemia and, where it is the major HK, provides for basal glycolytic flux without glycolytic overload. HK2 has similar saturation characteristics, except that, in persistent hyperglycemia, it is stabilized to proteolysis by high intracellular glucose concentration, increasing HK activity and initiating glycolytic overload and unscheduled glycolysis. This drives the development of vascular complications of diabetes. Similar HK2-linked unscheduled glycolysis in skeletal muscle and adipose tissue in impaired fasting glucose drives the development of peripheral insulin resistance. Glucokinase (GCK or HK4)-linked glycolytic overload and unscheduled glycolysis occurs in persistent hyperglycemia in hepatocytes and beta-cells, contributing to hepatic insulin resistance and beta-cell glucotoxicity, leading to the development of type 2 diabetes. Downstream effector pathways of HK-linked unscheduled glycolysis are mitochondrial dysfunction and increased reactive oxygen species (ROS) formation; activation of hexosamine, protein kinase c, and dicarbonyl stress pathways; and increased Mlx\/Mondo A signaling. Mitochondrial dysfunction and increased ROS was proposed as the initiator of metabolic dysfunction in hyperglycemia, but it is rather one of the multiple downstream effector pathways. Correction of HK2 dysregulation is proposed as a novel therapeutic target. Pharmacotherapy addressing it corrected insulin resistance in overweight and obese subjects in clinical trial. Overall, the damaging effects of hyperglycemia are a consequence of HK-gated increased flux of glucose metabolism without increased glycolytic enzyme activities to accommodate it.<\/p>\n\n\n\n

Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications<\/strong><\/p>\n\n\n\n

\"A<\/p>\n\n\n\n

Figure 1. a. Regulation of glycolytic enzymes by insulin and Mondo A in scheduled glycolysis. <\/strong>Key: blue highlighted text, genes with expression and\/or activity regulated by insulin. Lilac highlighted text, genes with expression regulated by Mondo A\/Mlx. b.<\/strong> Dysregulation of glycolytic enzymes and metabolic dysfunction in hexokinase-2 linked glycolytic overload and unscheduled glycolysis hypothesis.<\/strong> Key: Pink highlighted text \u2013 HK2 and metabolites increased in unscheduled glycolysis.<\/p>\n\n\n\n

Principal publication<\/strong><\/p>\n\n\n\n

Rabbani, N. and Thornalley, P.J. (2024) Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis in insulin resistance, beta-cell glucotoxicity and diabetic vascular complications. Frontiers in Endocrinology 14 doi.org\/10.3389\/fendo.2023.1268308<\/a><\/p>\n\n\n\n

Unraveling the impaired incretin effect in obesity and type 2 diabetes: Key role of hyperglycemia-induced unscheduled glycolysis and glycolytic overload<\/strong><\/p>\n\n\n\n

Glucagon-like peptide-1 (GLP-1) agonists and GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) co-agonists are major treatment options for subjects with obesity and patients with type 2 diabetes mellitus (T2DM). They counter without addressing the mechanistic cause of the impaired incretin effect associated with obesity and T2DM. Incretin effect impairment is characterized by decreased secretion of incretins from enteroendocrine cells and incretin resistance of pancreatic \u03b2-cells. It is linked to hyperglycemia. We present evidence that subversion of the gating of glucose entry into glycolysis, mainly by glucokinase (hexokinase-4), during persistent hyperglycemia in enteroendocrine cells, pancreatic \u03b2- and \u03b1-cells and appetite-regulating neurons contributes to the biochemical mechanism of the impaired incretin effect. Unscheduled glycolysis and glycolytic overload thereby produced decreases cell signalling of incretin secretion to glucose and other secretion stimuli and incretin receptor responses. This mechanism provides a guide for development of alternative therapies targeting recovery of the impaired incretin effect.<\/p>\n\n\n\n

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Figure 2.<\/strong> a.<\/strong> Regulation of glycolytic enzymes by insulin and Mondo A in scheduled glycolysis.<\/strong> Key: blue highlighted text, genes with expression and\/or activity regulated by insulin. Lilac highlighted text, genes with expression regulated by Mondo A\/Mlx. b.<\/strong> Dysregulation of glycolytic enzymes and metabolic dysfunction in GCK and HK2-linked glycolytic overload and unscheduled glycolysis hypothesis. <\/strong>Key: Pink highlighted text \u2013 HK2 and metabolites increased in unscheduled glycolysis. For GCK, detachment from VDAC also promotes oligomerization of Bax, cytochrome c release and apoptosis [120]. Abbreviations: DHAP, dihydroxyacetone-phosphate; F-6-P, fructose-6-phosphate; F-1,6-bis-P, fructose-1,6-bisphosphate; F-2,6-bis-P, fructose-2,6-bisphosphate; G-6-P, glucose-6-phosphate; GA3P, glyceraldehyde-3-phosphate; MCT, monocarboxylate transporter; ROS, reactive oxygen species; VDAC, voltage-dependent anion channel.<\/p>\n\n\n\n

Principal publication<\/strong><\/p>\n\n\n\n

Rabbani, N. and Thornalley, P.J. (2024) Unraveling the impaired incretin effect in obesity and type 2 diabetes: key role of hyperglycemia-induced unscheduled glycolysis and glycolytic overload. Diabetes Res. Clin. Pract., 217, 111905<\/a><\/p>\n\n\n\n

Molecular mechanisms of metabolic dysfunction-associated steatotic liver disease (MASLD): functional analysis of glucose and fructose metabolism pathways<\/strong><\/h2>\n\n\n\n

Metabolic dysfunction\u2013associated steatotic liver disease\u00a0(MASLD) is a major non-communicable disease with global prevalence of 38% and no early-stage treatment. It has risk factors of insulin resistance, impaired glucose tolerance, type 2 diabetes and diets rich in glucose and fructose. In this review, we explore evidence of abnormal increased early-stage glycolytic intermediates, glycolytic overload, in the initiation of MASLD and propose a new strategy for improved therapy. Glucose is mainly metabolized to glucose-6-phosphate by glucokinase (GCK) in the human liver. This is slowed by the competitive inhibitor, glucokinase regulatory protein (GKRP), with inhibition potentiated by fructose-6-phosphate and lifted by fructose-1-phosphate. The in situ<\/em> activity of GCK is predicted to increase up to 3-fold by dietary glucose and over 4-fold with concurrent fructose. Related increased glycolytic intermediates activate carbohydrate response element binding protein (ChREBP), hexosamine pathway, and methylglyoxal-stimulated unfolded protein response (UPR). Activation of ChREBP contributes to enhanced lipogenesis and impaired suppression of hepatic glucose production by down regulation of insulin receptor substrate-2 (IRS-2). IRS-1 signaling is maintained, contributing to enhanced lipogenesis through activation of sterol response element binding protein-1c and down regulation of IRS-2. Hexosamine pathway activity stabilizes GCK and ChREBP to proteolysis and the UPR stimulates inflammation and fibrosis. Hepatocytes then export glucose excessively, increasing fasting plasma glucose and risk of peripheral insulin resistance, type 2 diabetes and vascular complications. Activators of nuclear factor erythroid 2-related factor 2 (Nrf2) provide a novel strategy for therapy. They divert excess glucose metabolism to the pentosephosphate pathway, decreasing activation of ChREBP and hexosamine pathway and formation of methylglyoxal, and decrease lipogenic gene expression. Nrf2 activator, trans<\/em>-resveratrol and hesperetin combination, corrected glycolytic overload and insulin resistance clinically and now merits evaluation for early-stage treatment of MASLD.<\/p>\n\n\n\n

\n

Take home message:<\/strong> MASLD is a disease with hepatic glycolytic overload as contributing initiator where, once developing, stimulates increased fasting plasma glucose and risk of peripheral insulin resistance, beta-cell glucotoxicity and development of type 2 diabetes. <\/h2>\n\n\n\n

<\/p>\n<\/div>\n\n\n\n

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Figure 1: Unscheduled glycolysis and glycolytic overload in the initiation of metabolic dysfunction-associated steatotic liver disease.<\/strong> Key: pink back-filled metabolites, glycolytic intermediates increased in unscheduled glycolysis; red arrows \u2013 pathways of pathogenesis initiated by unscheduled glycolysis in hepatocytes; and blue metabolites and arrows \u2013 metabolism of fructose. Names of enzymes are given in italics. The nuclear translocation of GCK and GKRP is not shown for clarity.<\/p>\n\n\n\n

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Figure 2. Mechanisms of hepatic insulin resistance and de-novo lipogenesis in the development of MASLD.<\/strong> Greyed out pathway of IRS-2 indicates decreased downregulation of gluconeogenesis and yellow highlighted IRS-2 promoter elements involved in down regulation, hexosamine pathway O-GlcNAc modification of GCK and ChREBP and MG-linked activation of the UPR in MASLD.<\/p>\n\n\n\n

Conclusions<\/strong><\/h2>\n\n\n\n

The liver has a unique role in glucose metabolism in the body, providing for glucose storage in the absorptive phase and glucose production and export in the fasting phase whilst exposed to intermittent high glucose and fructose dietary inputs. Abnormal magnitude and persistence of increased early-stage glycolytic intermediates in hepatocytes is likely damaging to glucose and lipid homeostasis \u2013 explaining why hepatocytes uniquely have in situ<\/em> inhibition of glucokinase (GCK) by glucokinase regulatory protein (GKRP). Dietary fructose is particularly damaging because it lifts GKRP inhibition of GCK to enhance glycolytic overload and also induces fructolytic enzyme expression. A cytoprotective response is increasing hepatic export of glucose which extends into the fasting phase to increase fasting plasma glucose. Whilst protective for the liver, this shifts the risk of glycolytic overload also to skeletal muscle, adipose tissue, pancreatic beta-cells, vascular cells and cells of the incretin effect. Long-term this contributes to development of peripheral insulin resistance, impaired incretin effect, type 2 diabetes (T2DM) and related vascular complications<\/a> \u2013 also partly explaining why MASLD is also a risk factor for T2DM and cardiovascular disease. From the glycolytic overload hypothesis, a new and likely effective and safe strategy to counter MASLD has emerged: activation of Nrf2 by GlucoRegulate supplement. Correction of insulin resistance in overweight and obese subjects in clinical trial suggests it may also be effective for treatment of early-stage MASLD which is now deserving of evaluation.<\/p>\n\n\n\n

Principal publication<\/strong><\/h2>\n\n\n\n

Rabbani N, Thornalley PJ. Molecular mechanisms of metabolic dysfunction-associated steatotic liver disease (MASLD): functional analysis of glucose and fructose metabolism pathways. Clin Sci<\/em> 2025;139:<\/strong> 1406 \u2013 29.<\/a><\/p>\n\n\n\n

Hexokinase-2 Glycolytic Overload Axis in Brain Disorders Exacerbated by Diabetes<\/strong><\/h2>\n\n\n\n

Subjects with diabetes have increased risk of dementia, Parkinson\u2019s disease and stroke. In the CNS there is increased inflammation, blood-brain barrier permeability, amyloid-beta and alpha-synuclein deposition and decreased neuronal synaptogenesis and survival. The role of hexokinases controlling glucose metabolism therein is often overlooked. We propose hexokinase-2 dysfunction driven glycolytic overload is critically involved. This increases glycolytic intermediates in astrocytes, microglial cells, microvessel endothelial cells and pericytes, stimulating mitochondrial dysfunction, protein O-GlcNAcylation, protein kinase c phosphorylation, and methylglyoxal-induced unfolded protein response and NLRP3 inflammasome activation. Therapeutic prevention is through activation of transcription factor Nrf2, increasing expression of glucose-6-phosphate dehydrogenase, glyoxalase 1 and antioxidant enzymes. This diverts excess glucose-6-phosphate to pentose phosphate pathway, methylglyoxal to glyoxalase pathway and counters oxidative stress, respectively.
<\/strong><\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Figure 1. Dysregulation of glycolytic enzymes and metabolic dysfunction in hexokinase-2 linked glycolytic overload in cells of the CNS.<\/strong> A.<\/strong> Neurons, OPCs and oligodendrocytes. In sustained hyperglycemia, glycolytic flux is unchanged as HK1 is saturated. Indirect effects producing the glycolytic phenotype are mediated by exposure to increased long range-acting reactive metabolites, hydrogen peroxide and methylglyoxal, inflammatory mediators released from activated astroglial cells and direct interaction with activated microglia cells. B.<\/strong> Astrocytes, microglial cells and microvessel endothelial cells and pericytes. In sustained hyperglycemia, HK2 is stabilized to proteolysis leading to increase in glycolytic flux by 2 – 3 fold producing the glycolytic phenotype.<\/strong> Key: Pink highlighted text \u2013 HK2 and metabolites increased in unscheduled glycolysis. For neurons, increased flow of MG and hydrogen peroxide into neurons from proximate astroglial cells in the interstitial fluid is shown. Normal low level MG formation in glycolysis is omitted for clarity. Also see Box 1 and text. Abbreviations: 13BPG, 1,3-bisphosphoglycerate; DHAP, dihydroxyacetonephosphate; F16BP, fructose-1,6-bisphosphate; F6P, fructose-6-phosphate; G6P, glucose-6-phosphate; GA3PD, glyceraldehyde-3-phosphate dehydrogenase; GPI, glucose-6-phosphate isomerase; HK1, hexokinase-1; HK2, hexokinase-2; MCT1-4,\u00a0 proton-linked monocarboxylate transporter family, isomers 1 \u2013 4; MG, methylglyoxal; OPC, oligodendrocyte precursor cells; PFK-1, phosphofructokinase-1; TPI, triosephosphate isomerase; VDAC, voltage dependent anion channel.<\/p>\n\n\n\n

Take home message<\/strong><\/h2>\n\n\n\n

The damaging effects of increased glucose concentration in the brain starts<\/strong> with glycolytic overload induced in astrocytes, microglial cells, MVECs and pericytes. They are predisposed to hexokinase-2 (HK2) driven glycolytic overload in persistent hyperglycemia with related metabolic dysfunction likely contributing to the increased risk of MCI, vascular dementia, Alzheimer’s disease, Parkinson’s disease and stroke in diabetes. Neurons, oligodendrocyte precursor cells (OPCs) and oligodendrocytes (OLs) suffer mostly indirect impact through increased release of hydrogen peroxide, methylglyoxal and inflammatory mediators from activated astroglial cells and interaction with activated microglial cells. We propose applicability of the glycolytic overload hypothesis beyond patients with diabetes is merited as: (i) subjects with impaired fasting glucose and\/or increased HK2 expression in the brain – as found in the elderly – are susceptible to glycolytic overload even with plasma glucose concentration within the normal range; and (ii) crosstalk with beta-amyloid, \u03b1-synuclein, mitochondrial dysfunction and oxidative stress produces a multifactorial downstream response. With this new approach, safe and effective preventive therapy of these neurological disorders will likely emerge. Supporting evidence suggests the supplement GlucoRegulate may provide safe and enhanced preventive therapy against risk of developing dementia, Parkinson’s disease and stroke. See scheme below.<\/p>\n\n\n\n

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Principal publication<\/strong><\/h2>\n<\/div>\n\n\n\n

Alhujaily M, Rabbani N, Thornalley PJ. Hexokinase-2\u2013glycolytic overload axis in brain disorders exacerbated by diabetes. Trends in Endocrinology & Metabolism<\/em> 2026.<\/a><\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Summary Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"templates\/template-full.php","meta":{"footnotes":""},"class_list":["post-58","page","type-page","status-publish","hentry","post"],"_links":{"self":[{"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/pages\/58","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/comments?post=58"}],"version-history":[{"count":25,"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/pages\/58\/revisions"}],"predecessor-version":[{"id":3159,"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/pages\/58\/revisions\/3159"}],"wp:attachment":[{"href":"https:\/\/pjthornalley.com\/index.php\/wp-json\/wp\/v2\/media?parent=58"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}