FOXO1 delays skeletal muscle regeneration and suppresses myoblast proliferation

Unloading stress, such as bed rest, inhibits the regenerative potential of skeletal muscles; however, the underlying mechanisms remain largely unknown. FOXO1 expression, which induces the upregulated expression of the cell cycle inhibitors p57 and Gadd45α, is known to be increased in the skeletal muscle under unloading conditions. However, there is no report addressing FOXO1-induced inhibition of myoblast proliferation. Therefore, we induced muscle injury by cardiotoxin in transgenic mice overexpressing FOXO1 in the skeletal muscle (FOXO1-Tg mice) and observed regeneration delay in skeletal muscle mass and cross-sectional area in FOXO1-Tg mice. Increased p57 and Gadd45α mRNA levels, and decreased proliferation capacity were observed in C2C12 myoblasts expressing a tamoxifen-inducible active form of FOXO1. These results suggest that decreased proliferation capacity of myoblasts by FOXO1 disrupts skeletal muscle regeneration under FOXO1-increased conditions, such as unloading.     

Uptake and accumulation of exogenous docosahexaenoic acid by Chlorella

Tuna oil or its hydrolysate was added to a culture of Chlorella for its nutritional fortification as a feed for rotifer. Exogenous docosahexaenoic acid (DHA) in its free form was taken up by the cells of Chlorella vulgaris strain K-22 and by other strains, but tuna oil was not taken up by the cells. Accumulated DHA was found by electron microscopy in the cells in oil droplets. All strains of Chlorella used in these experiments took up exogenous DHA into the cells. It seems that the structure of the cell wall did not affect the uptake of DHA into the Chlorella cells.     

ER-60 domains responsible for interaction with calnexin and calreticulin

ER-60 is a thiol oxidoreductase family protein of the endoplasmic reticulum that facilitates the oxidative folding of glycoproteins via interaction with calnexin (CNX) and calreticulin (CRT). In this study, we tried to identify the site of interaction with CNX and CRT in the ER-60 molecule. ER-60 was shown to be composed of at least four domains, named a, b, b', and a', by limited proteolysis. Recombinant fragments of ER-60, a, b', and a'c, were each expressed in Escherichia coli as an individual soluble folded protein that underwent a cooperative unfolding transition along a urea gradient. These fragments each gave the circular dichroism (CD) spectrum of the folded protein. On the other hand, fragment b, which did not undergo the cooperative unfolding transition along a urea gradient gel, did not show any sign of the folded structure on the CD measurement. However, subtraction of the spectra showed that the b domain was folded in wild-type ER-60 or abb'. Both a and a'c, which have a catalytic center CGHC motif, showed activity almost equivalent to half of that of wild-type ER-60. Extension from a or a'c to ab and abb' or b'a'c had little effect on their isomerase activity, suggesting that the b and b' domains hardly contribute to the catalytic activity of ER-60. The contribution of both the b and b' domains to the binding with CNX and CRT was revealed by surface plasmon resonance analysis and oxidative-refolding experiments of monoglucosylated RNase B with addition of the luminal domain of CNX.     

Location of the Bombyx mori 175kDa cadherin-like protein-binding site on Bacillus thuringiensis Cry1Aa toxin

To identify and gain a better understanding of the cadherin-like receptor-binding site on Bacillus thuringiensis Cry toxins, it is advantageous to use Cry1Aa toxin, because its 3D structure is known. Therefore, Cry1Aa toxin was used to examine the locations of cadherin-like protein-binding sites. Initial experiments examining the binding compatibility for Cry1Aa toxin of partial fragments of recombinant proteins of a 175kDa cadherin-like protein from Bombyx mori (BtR175) and another putative receptor for Cry1Aa toxin, amino peptidaseN1, from Bo.mori (BmAPN1), suggested that their binding sites are close to each other. Of the seven mAbs against Cry1Aa toxin, two mAbs were selected that block the binding site for BtR175 on Cry1Aa toxin: 2A11 and 2F9. Immunoblotting and alignment analyses of four Cry toxins revealed amino acids that included the epitope of mAb 2A11, and suggested that the area on Cry1Aa toxin blocked by the binding of mAb 2A11 is located in the region consisting of loops2 and 3. Two Cry1Aa toxin mutants were constructed by substituting a Cys on the area blocked by the binding of mAb 2A11, and the small blocking molecule, N-(9-acridinyl)maleimide, was introduced at each Cys substitution to determine the BtR175-binding site. Substitution of Tyr445 for Cys had a crippling effect on binding of Cry1Aa toxin to BtR175, suggesting that Tyr445 may be in or close to the BtR175-binding site. Monoclonal antibodies that blocked the binding site for BtR175 on Cry1Aa toxin inhibited the toxicity of Cry1Aa toxin against Bo.mori, indicating that binding of Cry1Aa toxin to BtR175 is essential for the action of Cry1Aa toxin on the insect.     

Formation of lipid droplets induced by 2,3-dihydrogeranylgeranoic acid distinct from geranylgeranoic acid

Geranylgeranoic acid (GGA) and 2,3-dihydrogeranylgeranoic acid (2,3-diGGA) are geranylgeraniol-derived metabolites (Kodaira et al. (2002) J Biochem 132: 327-334). In the present study, we examined the effects of these acids on HL-60 cells. The cells were differentiated into neutrophils by GGA stimulation like retinoic acid stimulation. In the case of cells stimulated with 2,3-diGGA, neutrophils were not detected, but the formation of lipid droplets was induced. On the other hand, when the cells were cultured in the presence of 0.1% FBS instead of 10% FBS, apoptotic cells were induced not only by GGA stimulation but also with 2,3-diGGA. In the latter case, when the cells were cultured in the co-presence of a caspase-3 inhibitor (Ac-DMQD-CHO), the lipid droplets formation was observed in the cells. These results suggest that GGA and 2,3-diGGA are extremely different from each other with respect to their effects on HL-60 cells.     

Impact of overweight on left ventricular function in type 2 diabetes mellitus

Background

Coexistence of left ventricular (LV) longitudinal myocardial systolic dysfunction with LV diastolic dysfunction could lead to heart failure with preserved ejection fraction (HFpEF). Diabetes mellitus (DM) is known as a significant factor associated with HFpEF. Although the mechanisms of DM-related LV myocardial injury are complex, it has been postulated that overweight contributes to the development of LV myocardial injury in type 2 diabetes mellitus (T2DM) patients. However, the precise impact of overweight on LV longitudinal myocardial systolic function in T2DM patients remains unclear.

Methods

We studied 145 asymptomatic T2DM patients with preserved LV ejection fraction (LVEF) without coronary artery disease. LV longitudinal myocardial systolic function was assessed by global longitudinal strain (GLS), which was defined as the average peak strain of 18-segments obtained from standard apical views. Overweight was defined as body mass index (BMI) ≥ 25 kg/m². Ninety age-, gender- and LVEF-matched healthy volunteers served as controls.

Results

GLS of overweight T2DM patients was significantly lower than that of non-overweight patients (17.9 ± 2.4% vs. 18.9 ± 2.6%, p < 0.05), whereas GLS of both overweight and non-overweight controls was similar (19.8 ± 1.3% vs. 20.4 ± 2.1%, p = 0.38). Furthermore, multiple regression analysis revealed that for T2DM patients, BMI was the independent determinant parameters for GLS as well as LV mass index.

Conclusions

Overweight has a greater effect on LV longitudinal myocardial systolic function in T2DM patients than on that in non-DM healthy subjects. Our finding further suggests that the strict control of overweight in T2DM patients may be associated with prevention of the development of HFpEF.

     

Molecular epidemiology of Salmonella enterica serovar typhimurium isolates from cattle in hokkaido, Japan: evidence of clonal replacement and characterization of the disseminated clone

The molecular epidemiology of 545 Salmonella enterica serovar Typhimurium isolates collected between 1977 and 2009 from cattle in Hokkaido, Japan, was investigated using pulsed-field gel electrophoresis (PFGE). Nine main clusters were identified from 116 PFGE patterns. Cluster I comprised 248 isolates, 243 of which possessed a sequence specific to definitive phage type 104 (DT104) or U302. The cluster I isolates were dominant in 1993 to 2003, but their numbers declined beginning in 2004. Beginning in 2002, an increase was observed in the number of cluster VII isolates, consisting of 21 PFGE patterns comprising 165 isolates. A total of 116 isolates representative of the 116 PFGE profiles were analyzed by multilocus variable-number tandem-repeat analysis (MLVA). Other than two drug-sensitive isolates, 19 isolates within cluster VII were classified in the same cluster by MLVA. Among the cluster VII isolates, an antibiotic resistance type showing resistance to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracycline, kanamycin, cefazolin, and sulfamethoxazole-trimethoprim and a resistance type showing resistance to ampicillin, streptomycin, sulfonamides, tetracycline, and kanamycin were found in 23 and 125 isolates, respectively. In the 19 isolates representative of cluster VII, the bla(TEM-1) gene was found on a Salmonella serotype Typhimurium virulence plasmid, which was transferred to Escherichia coli by electroporation along with resistance to two to four other antimicrobials. Genomic analysis by subtractive hybridization and plasmid analysis suggested that the bla(TEM-1)-carrying virulence plasmid has a mosaic structure composed of elements of different origin. These results indicate an emerging multidrug-resistant S. Typhimurium clone carrying a virulence-resistance plasmid among cattle in Hokkaido, Japan.     

Comparison of testosterone and insulin-like peptide 3 secretions in response to human chorionic gonadotropin in cultured interstitial cells from scrotal and retained testes in dogs

Levels of testosterone and insulin-like peptide 3 (INSL3) secretions in response to different doses of human chorionic gonadotropin (hCG) in cultured interstitial cells were compared between retained and scrotal testes in dogs. Retained (n=10) and scrotal (n=9) testes were obtained from small-breed dogs. The testicular tissues were dispersed in Dulbecco's Modified Eagle Medium with Ham's nutrient mixture containing 2000 PU/ml dispase II and 10% fetal bovine serum. The cells were plated with differing concentrations (0-10 IU/ml) of hCG for 18 h in multiwell-plates. Testosterone and INSL3 in the same spent medium were measured by enzyme-immunoassays (EIA). A new EIA with a reliable detection range of 0.025-5 ng/ml was developed in order to measure canine INSL3 in culture medium. Dose-dependent stimulation of testosterone by hCG was observed in the cells of both retained and scrotal testes. The incremental rate of testosterone secretion was significantly lower at 0.1, 1 and 10 IU/ml hCG in the cells of retained testes than in scrotal testes, however. INSL3 secretion was significantly stimulated at 10 IU/ml hCG relative to unstimulated controls comprising cells of scrotal testes; no such stimulation was observed in the cells of retained testes. At 10 IU/ml hCG, the incremental rate of INSL3 was significantly lower in the cells of retained testes than scrotal testes. These results suggest that LH-induced secretory testosterone and INSL3 responses are lower in the interstitial cells of retained testes than of scrotal testes. Furthermore, the high concentrations of LH may acutely stimulate INSL3 release in scrotal testes of dogs, but not in retained testes.