We carried out a multistage genome-wide association study of type 2 diabetes mellitus in Japanese individuals, with a total of 1,612 cases and 1,424 controls and 100,000 SNPs. The most significant association was obtained with SNPs in KCNQ1, and dense mapping within the gene revealed that rs2237892 in intron 15 showed the lowest Pvalue (6.7 x 10(-13), odds ratio (OR) = 1.49). The association of KCNQ1 with type 2 diabetes was replicated in populations of Korean, Chinese and European ancestry as well as in two independent Japanese populations, and meta-analysis with a total of 19,930 individuals (9,569 cases and 10,361 controls) yielded a P value of 1.7 x 10(-42) (OR = 1.40; 95% CI = 1.34-1.47) for rs2237892. Among control subjects, the risk allele of this polymorphism was associated with impairment of insulin secretion according to the homeostasis model assessment of beta-cell function or the corrected insulin response. Our data thus implicate KCNQ1 as a diabetes susceptibility gene in groups of different ancestries.

We conducted a genome-wide association study using 207,097 SNP markers in Japanese individuals with type 2 diabetes and unrelated controls, and identified KCNQ1 (potassium voltage-gated channel, KQT-like subfamily, member 1) to be a strong candidate for conferring susceptibility to type 2 diabetes. We detected consistent association of a SNP in KCNQ1 (rs2283228) with the disease in several independent case-control studies (additive model P = 3.1 x 10(-12); OR = 1.26, 95% CI = 1.18-1.34). Several other SNPs in the same linkage disequilibrium (LD) block were strongly associated with type 2 diabetes (additive model: rs2237895, P = 7.3 x 10(-9); OR = 1.32, 95% CI = 1.20-1.45, rs2237897, P = 6.8 x 10(-13); OR = 1.41, 95% CI = 1.29-1.55). The association of these SNPs with type 2 diabetes was replicated in samples from Singaporean (additive model: rs2237895, P = 8.5 x 10(-3); OR = 1.14, rs2237897, P = 2.4 x 10(-4); OR = 1.22) and Danish populations (additive model: rs2237895, P = 3.7 x 10(-11); OR = 1.24, rs2237897, P = 1.2 x 10(-4); OR = 1.36).

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Concept of Diabetes Mellitus: Diabetes mellitus is a group of diseases associated with various metabolic disorders, the main feature of which is chronic hyperglycemia due to insufficient insulin action. Its pathogenesis involves both genetic and environmental factors. The long-term persistence of metabolic disorders can cause susceptibility to specific complications and also foster arteriosclerosis. Diabetes mellitus is associated with a broad range of clinical presentations, from being asymptomatic to ketoacidosis or coma, depending on the degree of metabolic disorder. Classification (Tables 1 and 2, and Figure 1): The classification of glucose metabolism disorders is principally derived from etiology, and includes staging of pathophysiology based on the degree of deficiency of insulin action. These disorders are classified into four groups: (i) type 1 diabetes mellitus; (ii) type 2 diabetes mellitus; (iii) diabetes mellitus due to other specific mechanisms or diseases; and (iv) gestational diabetes mellitus. Type 1 diabetes is characterized by destruction of pancreatic b-cells. Type 2 diabetes is characterized by combinations of decreased insulin secretion and decreased insulin sensitivity (insulin resistance). Glucose metabolism disorders in category (iii) are divided into two subgroups; subgroup A is diabetes in which a genetic abnormality has been identified, and subgroup B is diabetes associated with other pathologic disorders or clinical conditions. The staging of glucose metabolism includes normal, borderline and diabetic stages depending on the degree of hyperglycemia occurring as a result of the lack of insulin action or clinical condition. The diabetic stage is then subdivided into three substages: non-insulin-requiring, insulin-requiring for glycemic control, and insulin-dependent for survival. The two former conditions are called non-insulin-dependent diabetes and the latter is known as insulin-dependent diabetes. In each individual, these stages may vary according to the deterioration or the improvement of the metabolic state, either spontaneously or by treatment. Diagnosis (Tables 3-7 and Figure 2): Categories of the State of Glycemia: Confirmation of chronic hyperglycemia is essential for the diagnosis of diabetes mellitus. When plasma glucose levels are used to determine the categories of glycemia, patients are classified as having a diabetic type if they meet one of the following criteria: (i) fasting plasma glucose level of ‡126 mg/dL ( ‡7.0 mmol/L); (ii) 2-h value of ‡200 mg/dL ( ‡11.1 mmol/L) in 75 g oral glucose tolerance test (OGTT); or (iii) casual plasma glucose level of ‡200 mg/dL ( ‡11.1 mmol/L). Normal type is defined as fasting plasma glucose level of <110 mg/dL (<6.1 mmol/L) and 2-h value of <140 mg/dL (<7.8 mmol/L) in OGTT. Borderline type (neither diabetic nor normal type) is defined as falling between the diabetic and normal values. According to the current revision, in addition to the earlier listed plasma glucose values, hemoglobin A 1c (HbA 1c ) has been given a more p...

Concept of Diabetes Mellitus:Diabetes mellitus is a group of diseases associated with various metabolic disorders, the main feature of which is chronic hyperglycemia due to insufficient insulin action. Its pathogenesis involves both genetic and environmental factors. The long‐term persistence of metabolic disorders can cause susceptibility to specific complications and also foster arteriosclerosis. Diabetes mellitus is associated with a broad range of clinical presentations, from being asymptomatic to ketoacidosis or coma, depending on the degree of metabolic disorder.Classification (Tables 1 and 2, and Figure 1):Table 1 Etiological classification of diabetes mellitus and glucose metabolism disordersI. Type 1 (destruction of pancreatic β‐cells, usually leading to absolute insulin deficiency) A. Autoimmune B. IdiopathicII. Type 2 (ranging from predominantly insulin secretory defect, to predominantly insulin resistance with varying degrees of insulin secretory defect)III. Due to other specific mechanisms or diseases (see Table 2 for details) A. Those in which specific mutations have been identified as a cause  of genetic susceptibility  (1) Genetic abnormalities of pancreatic β‐cell function  (2) Genetic abnormalities of insulin action B. Those associated with other diseases or conditions  (1) Diseases of exocrine pancreas  (2) Endocrine diseases  (3) Liver disease  (4) Drug‐ or chemical‐induced  (5) Infections  (6) Rare forms of immune‐mediated diabetes  (7) Various genetic syndromes often associated with diabetesIV. Gestational diabetes mellitusNote: Those that cannot at present be classified as any of the above are called unclassifiable.The occurrence of diabetes‐specific complications has not been confirmed in some of these conditions.Table 2 Diabetes mellitus and glucose metabolism disorders due to other specific mechanisms and diseasesA. Those in which specific mutations have been identified as a cause of genetic susceptibilityB. Those associated with other diseases or conditions(1) Genetic abnormalities of pancreatic β‐cell function
Insulin gene (abnormal insulinemia, abnormal proinsulinemia, neonatal diabetes mellitus) 
HNF 4α gene (MODY1) 
Glucokinase gene (MODY2) 
HNF 1α gene (MODY3) 
IPF‐1 gene (MODY4) 
HNF 1β gene (MODY5) 
Mitochondria DNA (MIDD) 
NeuroD1 gene (MODY6) 
Kir6.2 gene (neonatal diabetes mellitus) 
SUR1 gene (neonatal diabetes mellitus) 
Amylin
Others
(2) Genetic abnormalities of insulin action
Insulin receptor gene (type A insulin resistance, leprechaunism, Rabson–Mendenhall syndrome etc.) 
Others(1) Diseases of exocrine pancreas
Pancreatitis
Trauma/pancreatectomy
Neoplasm
Hemochromatosis
Others
(2) Endocrine diseases
Cushing’s syndrome
Acromegaly
Pheochromocytoma
Glucagonoma
Aldosteronism
Hyperthyroidism
Somatostatinoma
Others
(3) Liver disease
Chronic hepatitis
Liver cirrhosis 
Others
(4) Drug‐ or chemical‐induced
Glucocorticoids
Interferon
Others
(5) Infections
Congenital rubella
Cytomegalovirus
Others
(6) Rare forms of immune‐mediated diabetes
Anti‐insulin receptor antibodies
St...

Summary Concept of diabetes mellitusDiabetes mellitus is a group of diseases associated with various metabolic disorders, the main feature of which is chronic hyperglycemia due to insufficient insulin action. Its pathogenesis involves both genetic and environmental factors. The long-term persistence of metabolic disorders can cause susceptibility to specific complications and also foster arteriosclerosis. Diabetes mellitus is associated with a broad range of clinical presentations, from being asymptomatic to ketoacidosis or coma, depending on the degree of metabolic disorder.Classification (Tables 1, 2; Fig. 1) The classification of glucose metabolism disorders is principally derived from etiology, and includes staging of pathophysiology based on the degree of deficiency of insulin action. These disorders are classified into four groups: (i) type 1 diabetes mellitus; (ii) type 2 diabetes mellitus; (iii) diabetes mellitus those due to other specific mechanisms or diseases; and (iv) gestational diabetes mellitus. Type 1 diabetes is characterized by destruction of pancreatic b-cells. Type 2 diabetes is characterized by combinations of decreased insulin secretion and decreased insulin sensitivity (insulin resistance). Glucose metabolism disorders in category (iii) are divided into two subgroups; subgroup A is diabetes in which a genetic abnormality has been identified, and subgroup B is diabetes associated with other pathologic disorders or clinical conditions.

The prevalence of NAFLD was 29% in apparently healthy middle-aged Japanese adults and NAFLD was independently associated with impaired glucose metabolism.

BackgroundIn recent years, several oral antidiabetic drugs with new mechanisms of action have become available, expanding the number of treatment options. Sodium/glucose cotransporter-2 (SGLT2) inhibitors are a new class of oral antidiabetic drugs with an insulin-independent mechanism promoting urinary glucose excretion. We report the results of a combined Phase 2 and 3 clinical study (Japic CTI-101349) of the SGLT2 inhibitor tofogliflozin (CSG452, RG7201) in Japanese patients with type 2 diabetes mellitus.MethodsThe efficacy and safety of tofogliflozin were assessed in this multicenter, placebo-controlled, randomized, double-blind parallel-group study involving 230 patients with type 2 diabetes mellitus with inadequate glycemic control on diet/exercise therapy. Between 30 October 2010 and 28 February 2012, patients at 33 centers were randomized to either placebo (n = 56) or tofogliflozin (10, 20, or 40 mg; n = 58 each) orally, once daily for 24 weeks. The primary efficacy endpoint was the change from baseline in HbA1c at week 24.ResultsOverall, 229 patients were included in the full analysis set (placebo: n = 56; tofogliflozin 10 mg: n = 57; tofogliflozin 20 and 40 mg: n = 58 each). The least squares (LS) mean change (95% confidence interval) from baseline in HbA1c at week 24 was −0.028% (−0.192 to 0.137) in the placebo group, compared with −0.797% (−0.960 to −0.634) in the tofogliflozin 10 mg group, −1.017% (−1.178 to −0.856) in the tofogliflozin 20 mg group, and −0.870% (−1.031 to −0.709) in the tofogliflozin 40 mg group (p < 0.0001 for the LS mean differences in all tofogliflozin groups vs placebo). There were also prominent decreases in fasting blood glucose, 2-h postprandial glucose, and body weight in all tofogliflozin groups compared with the placebo group. The main adverse events were hyperketonemia, ketonuria, and pollakiuria. The incidence of hypoglycemia was low. Furthermore, most adverse events were classified as mild or moderate in severity.ConclusionsTofogliflozin 10, 20, or 40 mg administered once daily as monotherapy significantly decreased HbA1c and body weight, and was generally well tolerated in Japanese patients with type 2 diabetes mellitus. Phase 3 studies were recently completed and support the findings of this combined Phase 2 and 3 study.Trial registrationThis study was registered in the JAPIC clinical trials registry (ID: Japic CTI-101349).