The epidemic of type 2 diabetes mellitus in the Asia-Pacific region

Pediatric Type 2 Diabetes in Japan: Similarities and Differences from Type 2 Diabetes in Other Pediatric Populations

PURPOSE OF REVIEW

To review clinical characteristics of pediatric type 2 diabetes in Japan.

RECENT FINDINGS

It is well recognized that Asian populations, particularly the Japanese, have a higher incidence of childhood type 2 diabetes. Of note, most Asian populations show a higher incidence of pediatric type 2 diabetes than that of type 1 diabetes. However, a current report in the USA demonstrated a dramatic increase in the incidence of young people with type 2 diabetes in recent years. The USA could have a much higher incidence of type 2 diabetes than Japan, possibly due to environmental and behavioral factors. The clinical features of Japanese young people with type 2 diabetes might have some differences from type 2 diabetes in other pediatric populations. Japanese children with type 2 diabetes are likely to be thinner than Caucasian children. Approximately 10-15% Japanese patients with type 2 diabetes exhibit normal weight with milder insulin resistance and substantial insulin secretion failure. Autoimmunity is not associated with the etiology of type 2 diabetes. Some genetic background and environmental factors, different from those in Caucasians, could play a role in the development of type 2 diabetes in Japanese children. Considering these characteristics, we must consider adequate therapy and management for young people with type 2 diabetes.

α-Amylase Modulation: Discovery of Inhibitors Using a Multi-Pharmacophore Approach for Virtual Screening

Better control of postprandial hyperglycemia can be achieved by delaying the absorption of glucose resulting from carbohydrate digestion. Because α-amylase initiates the hydrolysis of polysaccharides, the design of α-amylase inhibitors can lead to the development of new treatments for metabolic disorders such as type II diabetes and obesity. In this study, a rational computer-aided approach was developed to identify novel α-amylase inhibitors. Three-dimensional pharmacophores were developed based on the binding mode analysis of six different families of compounds that bind to this enzyme. In a stepwise virtual screening workflow, seven molecules were selected from a library of 1.4 million. Five out of seven biologically tested compounds showed α-amylase inhibition, and the two most potent compounds inhibited α-amylase with IC₅₀ values of 17 and 27 μm. The scaffold benzylideneacetohydrazide was shared by four of the discovered inhibitors, emerging as a novel drug-like non-carbohydrate fragment and constituting a promising lead scaffold for α-amylase inhibition.

Evaluating arterial stiffness in type 2 diabetes patients using ultrasonic radiofrequency

Differences in arterial stiffness between the two sides of the carotid arteries were investigated using ultrasonic radiofrequency in 88 patients with type 2 diabetes and 70 controls. The compliance coefficient (CC), pulse wave velocity (PWV), intima-media thickness (CIMT) and diameter (CCAD) of the common carotid arteries (CCAs) were measured. The ratio of the left to right CCAs was calculated to provide four indexes: CC ratio, PWV ratio, CIMT ratio and CCAD ratio. In the diabetes group, the PWV on the left side was significantly higher than that on the right side, while the CC on the left side was significantly lower than that on the right side. The bilateral CIMT was thicker and CCAD was wider, the left PWV traveled faster, and the right CC was higher in the diabetes group than in the control group. The PWV ratio between the two groups was significantly different and correlated positively with duration of diabetes and systolic blood pressure (SBP). The differences between the two sides of CCAs in patients with diabetes suggested that disease duration and SBP were important risk factors for arterial stiffness. Identifying the difference could potentially lead to the much earlier diagnosis of arteriosclerosis.

Clinical characteristics of non-obese children with type 2 diabetes mellitus without involvement of β-cell autoimmunity

AIMS

We examined the clinical characteristics of non-obese Japanese children with type 2 diabetes mellitus (T2DM) not associated with β-cell autoimmunity.

METHODS

Of 218 children who were diagnosed as having T2DM by a school urine glucose screening program in Tokyo, 24 were identified as being non-obese and were enrolled in this study. None of the children had any evidence of β-cell autoimmunity or genetic disorders.

RESULTS

The mean ages at diagnosis and at the study were 12.5 ± 1.7 and 22.4 ± 5.7 years, respectively. Females were predominant (M/F ratio: 4/20). Family history of T2DM, mostly of the non-obese type, was present in 62.5% of the cases. In regard to the birth weight, 20.8% had a history of low birth weight, and 8.3% were large for gestational age. The mean fasting insulin level, HOMA-R, HOMA-β, and an insulinogenic index on the OGTT at the time of diagnosis were 11.8 ± 7.8 μU/ml, 5.4 ± 3.8, 96.1 ± 55.0 and 0.16 ± 0.14, respectively. Most patients were treated by either oral hypoglycemic drug (45.8%) or insulin (50.0%) therapy at the study, with the mean interval to the start of pharmacological treatment of 3.1 ± 2.3 years.

CONCLUSIONS

Non-obese children with T2DM seemed to show lower insulin secretory capacities with mild, but evident, insulin resistance even from the time of diagnosis, and also earlier requirement of pharmacological therapies during the clinical course. Some genetic factors not associated with autoimmunity may play a role in the etiology of T2DM in non-obese children.

Insulin resistance at diagnosis in Japanese children with type 2 diabetes mellitus

BACKGROUND

Insulin resistance at diagnosis was investigated in Japanese children with type 2 diabetes mellitus (T2DM).

METHODS

A total of 160 children with T2DM were divided into groups on the basis of percent overweight at time of diagnosis: group A (n = 28), <20%; group B (n = 55), 20-39%; group C (n = 37), 40-59%; group D (n = 40), ≥ 60%. Indicators of insulin resistance at diagnosis were compared among the four patient groups, and also between the children with T2DM and the 201 age-matched normal Japanese children.

RESULTS

There were no significant differences in plasma glucose (PG) levels among the four patient groups. The mean concentration of fasting plasma immunoreactive insulin (IRI) was significantly higher in group D than in groups A and B (39.2 µU/mL vs 16.2 µU/mL and 24.1 µU/mL, P < 0.05, respectively). The mean homeostasis model assessment (HOMA-R) was significantly higher in group D than in all the other three groups (17.6 vs 7.8, 10.8 and 12.7, P < 0.05, respectively). The indicators HOMA-R and fasting IRI were significantly higher in each diabetes group, even in non-obese group A, than in normal children (P < 0.01, respectively).

CONCLUSIONS

Japanese children with T2DM had insulin resistance at diagnosis regardless of percent overweight, and the degree of insulin resistance gradually increased with rise in percent overweight.

Structural insight into substrate specificity of human intestinal maltase-glucoamylase

Human maltase-glucoamylase (MGAM) hydrolyzes linear alpha-1,4-linked oligosaccharide substrates, playing a crucial role in the production of glucose in the human lumen and acting as an efficient drug target for type 2 diabetes and obesity. The amino- and carboxyl-terminal portions of MGAM (MGAM-N and MGAM-C) carry out the same catalytic reaction but have different substrate specificities. In this study, we report crystal structures of MGAM-C alone at a resolution of 3.1 Å, and in complex with its inhibitor acarbose at a resolution of 2.9 Å. Structural studies, combined with biochemical analysis, revealed that a segment of 21 amino acids in the active site of MGAM-C forms additional sugar subsites (+ 2 and + 3 subsites), accounting for the preference for longer substrates of MAGM-C compared with that of MGAM-N. Moreover, we discovered that a single mutation of Trp1251 to tyrosine in MGAM-C imparts a novel catalytic ability to digest branched alpha-1,6-linked oligosaccharides. These results provide important information for understanding the substrate specificity of alpha-glucosidases during the process of terminal starch digestion, and for designing more efficient drugs to control type 2 diabetes or obesity.

Structures of human pancreatic α-amylase in complex with acarviostatins: Implications for drug design against type II diabetes

Human pancreatic α-amylase (HPA) catalyzes the hydrolysis of α-d-(1,4) glycosidic linkages in starch and is one of the major therapeutic targets for type II diabetes. Several acarviostatins isolated from Streptomyces coelicoflavus var. nankaiensis previously showed more potent inhibition of HPA than acarbose, which has been successfully used in clinical therapy. However, the molecular mechanisms by which acarviostatins inhibit HPA remains elusive. Here we determined crystal structures of HPA in complexes with a series of acarviostatin inhibitors (I03, II03, III03, and IV03). Structural analyses showed that acarviostatin I03 undergoes a series of hydrolysis and condensation reactions in the HPA active site, similar to acarbose, while acarviostatins II03, III03, and IV03 likely undergo only hydrolysis reactions. On the basis of structural analysis combined with kinetic assays, we demonstrate that the final modified product with seven sugar rings is best suited for occupying the full active site and shows the most efficient inhibition of HPA. Our high resolution structures reported here identify first time an interaction between an inhibitor and subsite-4 of the HPA active site, which we show makes a significant contribution to the inhibitory effect. Our results provide important information for the design of new drugs for the treatment of type II diabetes or obesity.