Yasuto Takakura

Effects of Trp64Arg mutation in the β3-adrenergic receptor gene on weight loss, body fat distribution, glycemic control, and insulin resistance in obese type 2 diabetic patients

OBJECTIVE To investigate the effects of Trp64Arg mutation in the β3-adrenergic receptor gene on weight loss, body fat distribution, glycemic control, and insulin resistance in obese type 2 diabetic patients. RESEARCH DESIGN AND METHODS We measured body weight, waist-to-hip ratio (WHR), adjusted resting metabolic rate, fasting blood glucose, fasting serum insulin levels, insulin resistance index (fasting glucose × fasting insulin/22.5), and HbA1c levels before and after 12 weeks of obesity treatment in 61 obese women with type 2 diabetes. The Mval polymorphism of the β3-adrenergic receptor gene was determined by polymerase chain reaction-restriction fragment length polymorphism analysis. RESULTS Of obese type 2 diabetic patients, those with the mutation (n = 24) had a higher WHR (P < 0.001), a lower adjusted metabolic rate, and higher blood glucose levels, serum insulin levels, insulin resistance index (P < 0.001), and HbA1c levels (P = 0.016). Furthermore, patients with the mutation had smaller decreases in body weight, WHR, insulin resistance index, and HbA1c levels after the weight-loss program compared with patients without the mutation (n = 37), even though food intake, exercise, and serum thyroid hormone levels were similar in both groups. CONCLUSIONS These present findings show that the Trp64Arg allele of the β3-adrenergic receptor gene may predict difficulty in losing body weight, lowering WHR, and improving glycemic control and insulin resistance in obese patients with type 2 diabetes.

Effects of caffeine on the uncoupling protein family in obese yellow KK mice.

1. The hypothesis that caffeine upregulates uncoupling protein (UCP)‐1, UCP‐2 and UCP‐3 expression, which contribute to thermogenesis, was investigated in obese mice.

Beta 3-adrenoreceptor gene polymorphism: a newly identified risk factor for proliferative retinopathy in NIDDM patients.

Proliferative diabetic retinopathy is an important cause of visual impairment. We investigated whether the polymorphism of the β3-adrenoreceptor (β3-AR) gene, which is associated with insulin resistance and an earlier onset of NIDDM, was associated with proliferative diabetic retinopathy (PDR) in 215 Japanese NIDDM patients with a duration of diabetes of >10 years. The polymorphism of the β3-AR gene was determined by polymerase chain reaction-restriction fragment length polymorphism analysis. The Trp64Arg allele of the β3-AR gene was significantly more frequent in the NIDDM patients with PDR (P = 0.002), but not in those with non-PDR (P = 0.151), than in NIDDM patients without diabetic retinopathy. Those with the mutation had an earlier onset of diabetes, a longer duration of diabetes, and higher current and maximal BMI values, compared with those without the mutation. Moreover, this mutation was also associated with higher serum triglyceride and decreased HDL-cholesterol levels. When adjustment was made for age, age at diagnosis, duration of diabetes, current BMI, systolic blood pressure, HbA1c, and serum lipids in a multiple regression analysis, a significant association was found between the Trp64Arg allele and diabetic retinopathy (P = 0.039). The Arg/Arg or Arg/Trp genotype was significantly associated with PDR, compared with the Trp/Trp genotype, with an odds ratio of 2.55 (95% CI 1.25-5.16). We concluded that the β3-AR gene polymorphism is a newly identified risk factor for PDR.

Genetic Variation in the β3-Adrenergic Receptor in Japanese NIDDM Patients

areas as well, including retroperitoneal and subcutaneous abdominal fat (3), and these properties may be the major determinants of the pathophysiological processes related to increased central adiposity, rather than site itself. CT and MRI are not considered ideal for larger scale investigations or routine screening because of costs, radiation, and availability. However, in small studies there is a weak relationship between anthropometric measures and intraabdominal fat, or insulin resistance, despite significant correlations between waist-to-hip ratio and cardiovascular morbidity and mortality in population studies (4). Using Dual Photon Xray Absorptiometry (DEXA, Lunar DPX-Lunar Radiation Corp., Madison, WI) for measurement of central abdominal fat, we found a strong correlation with hyperinsulinemic-euglycemic clamp-measured insulin sensitivity in women at both high and low risk of diabetes (5), as reported between CT-measured intra-abdominal fat and insulin sensitivity in young men (6). Correlation of insulin sensitivity with abdominal fat was significantly better than with other fat areas, including trunk and total fat (5). DEXA accurately assesses actual fat content of heterogeneous soft tissue and has been validated against other body fatness measures (7). DEXA abdominal fat measurement correlates well with assessment by CT, accounting for 80% of the variation in intra-abdominal fat by CT in postmenopausal women (8), and DEXAmeasured total abdominal fat does not differ significantly from CT (9). We use a window (Fig. 1) from upper L2 vertebra to lower L4 (where the ratio of subcutaneous fat to intra-abdominal fat is least) (10) drawn to exclude subcutaneous fat lateral to the inner costal margins (5). This window has good reproducibility (CV -5%) and excludes 3 0 % subcutaneous fat (crosschecked by MRI, D.G.C., L.V.C., D.J.C., unpublished data). The issue of which abdominal fat domain (if any) is the greatest contributor to the pathophysiological consequences of central adiposity remains unresolved. Further research will clarify the complex interactions of the bodys fat-containing tissues, which are proving to be much more than inert storage depots. Meanwhile, while not yet proposing it for routine clinical use, we recommend DEXA measurement of regional fat as a lowFigure 1—The DEXA areas of fat with the abdominal fat window as marked between 12 and IA and the inner costal margins. • , leg fat; H, arm fat; M, trunk fat; • , central abdominal fat.

Methylenetetrahydrofolate reductase gene polymorphism is not related to diabetic nephropathy in Japanese Type 2 diabetic patients.

The development of diabetic nephropathy varies among individuals, because genetic factors as well as metabolic control contributes to its pathogenesis [1]. Methlenetetrahydrofolate reductase (MTHFR) is an enzyme involved in the re-methylation of homocysteine to methionine [2], and reduced activity can cause hyperhomocysteinemia [3], which in turn promotes atherothrombotic vascular disease [4]. Although a common MTHFR gene (C677T) mutation is associated with hyperhomocysteinemia [5], it does not appear to be a significant, independent risk factor for atherothrombotic vascular disease [6]. The possible association of this mutation and diabetic nephropathy is controversial [7–11]. We therefore examined the association between this MTHFR gene mutation and diabetic nephropathy in Japanese Type 2 diabetic patients. A total of 342 subjects with Type 2 diabetes were enrolled for the study. To avoid the interference of retinopathy, subjects with advanced retinopathy were excluded. Diabetic nephropathy was defined according to the urinary albumin : creatinine ratio and the subjects were subdivided into a normoalbuminuria group (< 30 mg/g.Cr), a microalbuminuria group (30–300 mg/ g.Cr), and a macroalbuminuria group (> 300 mg/g.Cr). The C677T mutation in the MTHFR gene was analysed by real time polymerase chain reaction (PCR) as described previously [12]. As shown in Table 1, the allelic frequency of C677T mutation of MTFHR gene in the total study population was 0.37. Genotype frequencies were in accordance with the Hardy– Weinberg equation (C/C, 39.8%; C/T, 46.5%; T/T, 13.7%). The genotype distribution of C/C allele, C/T allele, and T/T allele in patients with microand macro-albuminuria were not significantly different from those with normoalbuminuria. Allele frequencies for T allele were also similar among the groups. Glycosylated haemoglobin (HbA 1c ), systolic blood pressure, plasma triglyceride were elevated in patients with microalbumiuria compared with those with normoalbuminuria. The patients with macroalbuminuria had longer diabetic duration and higher blood urea and creatinine compared with those with normoalbuminuria. It is hypothesized that individuals homozygous for MTHFR gene mutation (C677T) would be predisposed to develop diabetic nephropathy, as the latter is associated with increased plasma homocysteine levels [13]. Some report an association between this mutation and nephropathy [7–9], whereas others did not [10,11]. In the present study, we found no differences in genotype and allele frequency of MTHFR mutations between patients with and without diabetic nephropathy. Logistic analysis showed significant associations between nephropathy and HbA 1c level or duration of diabetes, but not C677T mutation of MTHRF gene. These conflicting results may be due to differences in ethnic and clinical characteristics. Serum folate concentrations may be another determinate, because high serum folate restores plasma homocysteine levels to normal and so overcomes decreased MTHFR activity accompanied by the MTHFR gene mutation [14]. We have recently reported no association between the C677T MTHFR gene mutation and diabetic retinopathy as another diabetic

Effect of ultrasonic stimulation on mRNA abundance of uncoupling protein (UCP) 2 and UCP 3 in gastrocnemius muscle of rats

1. The hypothesis that ultrasonic stimulation upregulates uncoupling protein (UCP) 2 and UCP3 in gastrocnemius muscle by a different mechanism of exercise was investigated in Wister rats.