Identification of glucokinase mutation in subjects with post-renal transplantation diabetes mellitus

Importance of glucokinase -258G/A polymorphism in Asian Indians with post-transplant and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) and post-transplant diabetes mellitus (PTDM) are non-synonymous forms of diabetes. Glucokinase (GCK) plays a key role in glucose metabolism. The relationship between the GCK promoter and specific types of diabetes, such as PTDM and T2DM, in the Asian Indian population is unknown. We examined the occurrence of a specific GCK promoter variant (-258G/A) in patients with T2DM and PTDM. The case-control study enrolled 640 Asian Indian subjects, including controls (n = 250) and T2DM (n = 250), PTDM (n = 42), and non-post-transplant diabetes mellitus (non-PTDM) (n = 98) patients. Purified Deoxyribonucleic acid (DNA) was genotyped with the polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis. The digested PCR products were analyzed on 12% polyacrylamide gels. The anthropometric, biochemical, and clinical details of each group were documented. GCK -258G/A alleles and genotypes were not associated with T2DM. However, among PTDM subjects, we detected a higher frequency of heterozygotes (52.4%) and a positive association with alleles/genotypes. The results suggest that the promoter region (-258G/A) of GCK plays an important role in PTDM in Asian Indians.

Structural Variations of Human Glucokinase Glu256Lys in MODY2 Condition Using Molecular Dynamics Study

Glucokinase (GK) is the predominant hexokinase that acts as glucose sensor and catalyses the formation of Glucose-6-phosphate. The mutations in GK gene influence the affinity for glucose and lead to altered glucose levels in blood causing maturity onset diabetes of the young type 2 (MODY2) condition, which is one of the prominent reasons of type 2 diabetic condition. In view of the importance of mutated GK resulting in hyperglycemic condition, in the present study, molecular dynamics simulations were carried out in intact and 256 E-K mutated GK structures and their energy values and conformational variations were correlated. Energy variations were observed in mutated GK (3500 Kcal/mol) structure with respect to intact GK (5000 Kcal/mol), and it showed increased γ-turns, decreased β-turns, and more helix-helix interactions that affected substrate binding region where its volume increased from 1089.152 Ų to 1246.353 Ų. Molecular docking study revealed variation in docking scores (intact = −12.199 and mutated = −8.383) and binding mode of glucose in the active site of mutated GK where the involvement of A53, S54, K56, K256, D262 and Q286 has resulted in poor glucose binding which probably explains the loss of catalytic activity and the consequent prevailing of high glucose levels in MODY2 condition.

Update on mutations in glucokinase (GCK), which cause maturity-onset diabetes of the young, permanent neonatal diabetes, and hyperinsulinemic hypoglycemia

Glucokinase is a key regulatory enzyme in the pancreatic beta-cell. It plays a crucial role in the regulation of insulin secretion and has been termed the glucose sensor in pancreatic beta-cells. Given its central role in the regulation of insulin release it is understandable that mutations in the gene encoding glucokinase (GCK) can cause both hyper- and hypoglycemia. Heterozygous inactivating mutations in GCK cause maturity-onset diabetes of the young (MODY) subtype glucokinase (GCK), characterized by mild fasting hyperglycemia, which is present at birth but often only detected later in life during screening for other purposes. Homozygous inactivating GCK mutations result in a more severe phenotype presenting at birth as permanent neonatal diabetes mellitus (PNDM). A growing number of heterozygous activating GCK mutations that cause hypoglycemia have also been reported. A total of 620 mutations in the GCK gene have been described in a total of 1,441 families. There are no common mutations, and the mutations are distributed throughout the gene. The majority of activating mutations cluster in a discrete region of the protein termed the allosteric activator site. The identification of a GCK mutation in patients with both hyper- and hypoglycemia has implications for the clinical course and clinical management of their disorder.

Post-Transplant Diabetes Mellitus

New-onset diabetes mellitus in a previously non-diabetic transplant recipient is a serious adverse event that confers significant morbidity and mortality. The most significant consequences of post-transplant diabetes mellitus (PTDM) in solid organ transplant recipients include decreased patient and graft survival, an increased risk of infectious complications, and morbid cardiovascular events. The development of PTDM in the elderly is of particular concern because this group is already at increased risk of progression of cardiovascular disease. Because the elderly, especially those aged >65 years, are the fastest-growing segment of the renal transplant population, attention needs to be given to PTDM risk reduction and post-transplant management. PTDM develops as a consequence of both impaired insulin production and enhanced peripheral insulin resistance. A number of non-modifiable factors such as age, race, family history, hepatitis C, polycystic kidney disease and emerging genetic causes have been identified as risk factors for PTDM. However, a number of modifiable factors can be targets for intervention in high-risk patients, including bodyweight (through dietary restriction and exercise), hypertension, hyperlipidaemia and the effects of certain immunosuppressive agents. The two agents most responsible for PTDM are tacrolimus and corticosteroids, especially when used in combination. Attempts to modify doses and regimens designed to eliminate or avoid these drugs should be considered. Use of HMG-CoA reductase inhibitors ('statins') and ACE inhibitors is particularly helpful in controlling hypertension and hyperlipidaemia in the elderly because these agents confer protection against future adverse cardiovascular events. Bisphosphonates are also advantageous in controlling the progression of osteoporosis and possible increased risk of bone fractures. Future trials in the elderly should focus on such endpoints as PTDM, post-transplant neoplasia, cardiovascular events and bone fracture events in order to identify the safest regimens that provide the optimal control of rejection while limiting the morbidity from these secondary events.

Glucokinase (GCK) mutations in hyper- and hypoglycemia: maturity-onset diabetes of the young, permanent neonatal diabetes, and hyperinsulinemia of infancy

Glucokinase is a key regulatory enzyme in the pancreatic beta-cell. It plays a crucial role in the regulation of insulin secretion and has been termed the pancreatic beta-cell sensor. Given its central role in the regulation of insulin release, it is understandable that mutations in the gene encoding glucokinase (GCK) can cause both hyperglycemia and hypoglycemia. Heterozygous inactivating mutations in GCK cause maturity-onset diabetes of the young (MODY), characterized by mild hyperglycemia, which is present at birth, but is often only detected later in life during screening for other purposes. Homozygous inactivating GCK mutations result in a more severe phenotype, presenting at birth as permanent neonatal diabetes mellitus (PNDM). Several heterozygous activating GCK mutations that cause hypoglycemia have also been reported. A total of 195 mutations in the GCK gene have been described, in a total of 285 families. There are no common mutations and the mutations are distributed throughout the gene. Mutations that cause hypoglycemia are located in various exons in a discrete region of the protein termed the heterotropic allosteric activator site. The identification of a GCK mutation in hyper- and hypoglycemia has implications for the clinical course and clinical management of the disorder.