Confirmatory factor analysis of the Japanese Health Locus of Control scales among people with musculoskeletal disorders.

[Purpose] To determine whether the 25-item Japanese Health Locus of Control (25-JHLC) scale satisfies a 5-factor structure among Japanese with musculoskeletal disorders. [Participants and Methods] The primary inclusion criterion was people undergoing physical therapy for musculoskeletal disorders in two medical facilities. The 25-JHLC scale and demographic data were obtained by conducting an anonymous survey. Confirmatory factor analysis was used to analyze data from the 25-JHLC scale in 200 patients with musculoskeletal disorders. Fits for the 5-factor structure (1-internal; 2-family; 3-professional; 4-chance; and 5-supernatural) and the 2-factor structure (1-internal; and 2-external, including family, professional, chance, and supernatural) were studied. The goodness-of-fit criteria included chi-squared/degree of freedom, goodness-of-fit index, adjusted goodness-of-fit index, and root mean square error of approximation. [Results] The mean (standard deviation) age of the participants was 46.3 (18.3) years of age. The 2-factor structure satisfied no criteria; however, the 5-factor structure satisfied two criteria for acceptable fit (chi-squared/degree of freedom, and root mean square error of approximation). [Conclusion] This study found that the 5-factor structure of the 25-JHLC scale can be accepted to some extent among Japanese with musculoskeletal disorders without comorbidities.

Fructose prevents the development of hyperglycaemia in WBN/Kob diabetic fatty rats via maintaining high insulin levels.

Fructose is considered to negatively affect type 2 diabetes mellitus (T2DM); however, there are contradictory reports. The present study aimed to elucidate the effects of fructose-rich diet (FRD) on glucose metabolism of Wistar Bonn Kobori (WBN/Kob) fatty diabetic (WBKDF) rats, a spontaneous T2DM model, and Wistar rats. Wistar Bonn Kobori fatty diabetic and Wistar rats were fed either FRD or standard diet (STD) for 4 weeks. The food intake, body weight, plasma glucose and insulin were measured weekly. After the 4-week challenge, rats were subjected to an intravenous glucose tolerance test (IVGTT). The liver and pancreas were used for histological analysis. The 4-week challenge of FRD in Wistar rats did not cause hyperglycaemia, but increased insulin resistance (Homeostatic Model Assessment for Insulin Resistance [HOMA-IR]). Feeding WBKDF rats with a FRD accelerated obesity, but prevented the onset of severe hyperglycaemia via maintaining high plasma insulin levels. Homeostatic Model Assessment for Insulin Resistance in WBKDF rats was not changed by FRD feeding. Intravenous glucose tolerance test revealed that FRD feeding in Wistar rats did not affect glucose tolerance, but slightly increased the plasma insulin level. In contrast, FRD feeding in WBKDF rats significantly reduced the glucose tolerance, but insulin response was not improved. Fructose-rich diet feeding did not alter the ß cell area in Wistar rats, but significantly increased it in WBKDF rats. In conclusion, FRD caused insulin resistance in Wistar rats, suggesting that fructose overconsumption is a risk factor for T2DM, whereas FRD inhibited severe hyperglycaemia by maintaining high insulin levels in WBKDF rats. Fructose may be a beneficial sugar for T2DM patients with severe obesity-induced insulin resistance.

Further thermo-stabilization of thermophilic rhodopsin from Thermus thermophilus JL-18 through engineering in extramembrane regions.

It is known that a hyperthermostable protein tolerable at temperatures over 100°C can be designed from a soluble globular protein by introducing mutations. To expand the applicability of this technology to membrane proteins, here we report a further thermo-stabilization of the thermophilic rhodopsin from Thermus thermophilus JL-18 as a model membrane protein. Ten single mutations in the extramembrane regions were designed based on a computational prediction of folding free-energy differences upon mutation. Experimental characterizations using the UV-visible spectroscopy and the differential scanning calorimetry revealed that four of ten mutations were thermo-stabilizing: V79K, T114D, A115P, and A116E. The mutation-structure relationship of the TR constructs was analyzed using molecular dynamics simulations at 300 K and at 1800 K that aimed simulating structures in the native and in the random-coil states, respectively. The native-state simulation exhibited an ion-pair formation of the stabilizing V79K mutant as it was designed, and suggested a mutation-induced structural change of the most stabilizing T114D mutant. On the other hand, the random-coil-state simulation revealed a higher structural fluctuation of the destabilizing mutant S8D when compared to the wild type, suggesting that the higher entropy in the random-coil state deteriorated the thermal stability. The present thermo-stabilization design in the extramembrane regions based on the free-energy calculation and the subsequent evaluation by the molecular dynamics may be useful to improve the production of membrane proteins for structural studies.

Methodology for Further Thermostabilization of an Intrinsically Thermostable Membrane Protein Using Amino Acid Mutations with Its Original Function Being Retained.

We develop a new methodology best suited to the identification of thermostabilizing mutations for an intrinsically stable membrane protein. The recently discovered thermophilic rhodopsin, whose apparent midpoint temperature of thermal denaturation Tm is measured to be ∼91.8 °C, is chosen as a paradigmatic target. In the methodology, we first regard the residues whose side chains are missing in the crystal structure of the wild type (WT) as the "residues with disordered side chains," which make no significant contributions to the stability, unlike the other essential residues. We then undertake mutating each of the residues with disordered side chains to another residue except Ala and Pro, and the resultant mutant structure is constructed by modifying only the local structure around the mutated residue. This construction is based on the postulation that the structure formed by the other essential residues, which is nearly optimized in such a highly stable protein, should not be modified. The stability changes arising from the mutations are then evaluated using our physics-based free-energy function (FEF). We choose the mutations for which the FEF is much lower than for the WT and test them by experiments. We successfully find three mutants that are significantly more stable than the WT. A double mutant whose Tm reaches ∼100 °C is also discovered.

Characteristics of WBN/Kob diabetic fatty rats supplemented with a fructose-rich diet as a metabolic syndrome model: response to a GLP-1 receptor agonist.

The incidence of metabolic syndrome is rapidly increasing worldwide, and adequate animal models are crucial for studies on its pathogenesis and therapy. In the search of an adequate experimental model to simulate human metabolic syndrome, the present study was performed to examine the pharmacological response of WBN/Kob-Leprfa (WBKDF) rats supplemented with a fructose-rich diet (FRD) to liraglutide, a GLP-1 receptor agonist. Male WBKDF rats fed FRD at 7 weeks of age were divided into 3 groups, and administered liraglutide (75, 300 µg/kg subcutaneously) or saline (control group), once daily for 4 weeks. All rats in the control group became overweight, and developed hyperglycemia, hypertension and dyslipidemia as they aged. The rats given liraglutide exhibited a dose-dependent reduction in body weight, visceral fat content and food intake compared with control rats. In addition, liraglutide suppressed the development of hyperglycemia, hypertension and dyslipidemia. An intravenous glucose tolerance test revealed that liraglutide improved glucose tolerance, insulin secretion and insulin resistance. On histological examination, decreased hepatic fatty degeneration was observed in the liraglutide groups. The present study demonstrated that liraglutide protected against obesity, hyperglycemia, hypertension, dyslipidemia, and hepatic steatosis in WBKDF rats fed FRD, suggesting that WBKDF rats fed FRD may be a useful model to investigate the etiology of human metabolic syndrome.