Increased cell wall teichoic acid production and D-alanylation are common phenotypes among daptomycin-resistant methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates

Multiple mechanisms have been correlated with daptomycin-resistance (DAP-R) in Staphylococcus aureus. However, one common phenotype observed in many DAP-R S. Aureus strains is a thickened cell wall (CW). The first evidence for an impact of CW-linked glycopolymers on this phenotype was recently demonstrated in a single, well-characterized DAP-R methicillin-susceptible S. aureus (MSSA) strain. In this isolate the thickened CW phenotype was linked to an increased production and D-alanylation of wall teichoic acids (WTA). In the current report, we extended these observations to methicillin-resistant daptomycin-sensitive/daptomyin-resistant (DAP-S/DAP-R) strain-pairs. These pairs included methicillin-resistant S. aureus (MRSA) isolates with and without single nucleotide polymorphisms (SNPs) in mprF (a genetic locus linked to DAP-R phenotype). We found increased CW dry mass in all DAP-R vs DAP-S isolates. This correlated with an increased expression of the WTA biosynthesis gene tagA, as well as an increased amount of WTA in the DAP-R vs DAP-S isolates. In addition, all DAP-R isolates showed a higher proportion of WTA D-alanylation vs their corresponding DAP-S isolate. We also detected an increased positive surface charge amongst the DAP-R strains (presumably related to the enhanced D-alanylation). In comparing the detailed CW composition of all isolate pairs, substantive differences were only detected in one DAP-S/DAP-R pair. The thickened CW phenotype, together with an increased surface charge most likely contributes to either: i) a charge-dependent repulsion of calcium complexed-DAP; and/or ii) steric-limited access of DAP to the bacterial cell envelope target. Taken together well-defined perturbations of CW structural and functional metrics contribute to the DAP-R phenotype and are common phenotypes in DAP-R S. Aureus isolates, both MSSA and MRSA.

Note: Although “daptomycin-nonsusceptibility” is the generally accepted terminology, we have utilized the term “daptomycin resistance” for ease of presentation in this manuscript

A multicentre, multinational, randomized, placebo-controlled, double-blind, phase 3 trial to evaluate the efficacy and safety of gemigliptin (LC15-0444) in patients with type 2 diabetes

AIM

This study was designed to assess the efficacy and safety of the dipeptidyl peptidase IV inhibitor gemigliptin (LC15-0444) 50 mg versus placebo in patients with type 2 diabetes.

METHODS

We conducted a 24-week, randomized, double-blind, placebo-controlled phase III trial in 182 patients (74 from Korea and 108 from India) with type 2 diabetes. After an initial 2 weeks of a diet and exercise programme followed by 2 weeks of a single-blind placebo run-in period, eligible patients were randomized to gemigliptin 50 mg or placebo, receiving the assigned treatment for 24 weeks. HbA1c and fasting plasma glucose (FPG) were measured periodically, and oral glucose tolerance test was performed at baseline and weeks 12 and 24.

RESULTS

At week 24, gemigliptin treatment led to significant reductions in HbA1c measurements compared to placebo (adjust mean after subtracting the placebo effect size: -0.71%, 95% confidence interval: -1.04 to -0.37%). A significantly greater proportion of patients achieved an HbA1c <7% with gemigliptin than with placebo. The placebo-subtracted FPG change from baseline at week 24 was -19.80 mg/dl. The overall incidence rates for adverse events were similar in the gemigliptin and placebo groups.

CONCLUSIONS

This study showed the efficacy and safety of gemigliptin 50 mg administered once daily as a monotherapy for type 2 diabetes patients.

Virulence of endemic nonpigmented northern Australian Staphylococcus aureus clone (clonal complex 75, S. argenteus) is not augmented by staphyloxanthin

Staphylococcus aureus clonal complex 75 (herein referred to as S. argenteus) lacks the carotenoid pigment operon, crtOPQMN, responsible for production of the putative virulence factor, staphyloxanthin. Although a common cause of community-onset skin infections among Indigenous populations in northern Australia, this clone is infrequently isolated from hospital-based patients with either bacteremic or nonbacteremic infections. We hypothesized that S. argenteus would have attenuated virulence compared to other S. aureus strains due to its staphyloxanthin "deficiency." Compared to prototypical S. aureus strains, S. argenteus was more susceptible to oxidative stress and neutrophil killing in vitro and had reduced virulence in murine sepsis and skin infection models. Transformation with pTX-crtOPQMN resulted in staphyloxanthin expression and increased resistance to oxidative stress in vitro. However, neither resistance to neutrophil killing nor in vivo virulence was increased. Thus, reduced virulence of S. argenteus in these models is due to mechanisms unrelated to lack of staphyloxanthin production.

YM155 induces EGFR suppression in pancreatic cancer cells

YM155, which inhibits the anti-apoptotic protein survivin, is known to exert anti-tumor effects in various cancers, including prostate and lung cancer. However, there are few reports describing the inhibitory effect of YM155 on human pancreatic cancers that highly express survivin. Here, we tested the effects of YM155 on a variety of cancer cell lines, including pancreatic cancer cells. We found that YM155 exerts an anti-proliferative effect in pancreatic cancer cells, inducing cell death through suppression of XIAP (X-linked inhibitor of apoptosis) as well as survivin without affecting the anti-apoptotic proteins Bcl-xL or Mcl-1. YM155 also inhibited tumor growth in vivo, reducing the size of pancreatic cancer cell line MIAPaCa-2 xenografts by 77.1% on day 31. Western blot analyses further showed that YM155 downregulated phosphoinoside 3-kinase (PI3K) expression and reduced the levels of phosphorylated (activated) extracellular signal-regulated kinase (ERK) and STAT3 (signal transducer and activator of transcription 3) in PANC-1 cells. Interestingly, we also found that YM155 downregulated the epidermal growth factor receptor (EGFR) in various cancer cell lines and induced the EGFR phosphorylation and ubiquitination of EGFR in PANC-1 cells. YM155 also modestly promoted the ubiquitination of survivin and XIAP. Therefore, YM155 acts through modulation of EGFR and survivin expression to subsequently reduce survival. We suggest that YM155 has potential as a therapeutic agent in the treatment of pancreatic cancer.

Use of antistaphylococcal beta-lactams to increase daptomycin activity in eradicating persistent bacteremia due to methicillin-resistant Staphylococcus aureus: role of enhanced daptomycin binding

We used daptomycin plus antistaphylococcal β-lactams (ASBL) to clear refractory MRSA bacteremia. In vitro studies showed enhanced daptomycin bactericidal activity, increased membrane daptomycin binding, and decrease in positive surface charge induced by ASBLs against daptomycin nonsusceptible MRSA. Addition of ASBLs to daptomycin may be of benefit in refractory MRSA bacteremia. (Although the official designation is "daptomycin nonsusceptiblity," we will use the term "daptomycin-resistance" in this paper for facility of presentation.).

Serum selenoprotein P levels in patients with type 2 diabetes and prediabetes: implications for insulin resistance, inflammation, and atherosclerosis

CONTEXT AND OBJECTIVE

The dysregulation of hepatokines may be associated with the pathogenesis of insulin resistance and type 2 diabetes. A recent study has suggested that selenoprotein P (SeP), a novel hepatokine, may play a role in the regulation of glucose metabolism and insulin sensitivity. We examined the relationship between circulating SeP levels and clinical parameters associated with insulin resistance in humans.

PARTICIPANTS AND METHODS

We compared serum SeP concentrations in 100 subjects with diverse glucose tolerance statuses. Furthermore, we evaluated the relationship between SeP and cardiometabolic risk factors including insulin resistance, high-sensitivity C-reactive protein, and carotid intima-media thickness.

RESULTS

Serum SeP concentrations were significantly higher in patients with type 2 diabetes or prediabetes than those with normal glucose tolerance (all P < 0.01) and decreased in a stepwise manner [1032.4 (495.9-2149.4) vs. 867.3 (516.3-1582.7) vs. 362.0 (252.5-694.5), P = 0.004]. In addition, overweight and obese subjects had significantly increased SeP levels compared with lean subjects (P = 0.002). Spearman's partial correlation analysis adjusted for age and gender showed a significant relationship between SeP and cardiometabolic factors including body mass index, waist circumference, systolic blood pressure, triglycerides, glucose, hemoglobin A1c, aspartate aminotransferase, and insulin resistance. Furthermore, in multiple regression analyses, SeP showed an independent association with carotid intima-media thickness as well as high-sensitivity C-reactive protein, even after adjustment for other confounding factors.

CONCLUSIONS

Circulating SeP concentrations were elevated in patients with glucose metabolism dysregulation and were related to various cardiometabolic parameters including insulin resistance, inflammation, and atherosclerosis.

Daptomycin resistance mechanisms in clinically derived Staphylococcus aureus strains assessed by a combined transcriptomics and proteomics approach

OBJECTIVES

The development of daptomycin resistance in Staphylococcus aureus is associated with clinical treatment failures. The mechanism(s) of such resistance have not been clearly defined.

METHODS

We studied an isogenic daptomycin-susceptible (DAP(S)) and daptomycin-resistant (DAP(R)) S. aureus strain pair (616; 701) from a patient with relapsing endocarditis during daptomycin treatment, using comparative transcriptomic and proteomic techniques.

RESULTS

Minor differences in the genome content were found between strains by DNA hybridization. Transcriptomic analyses identified a number of genes differentially expressed in important functional categories: cell division; metabolism of bacterial envelopes; and global regulation. Of note, the DAP(R) isolate exhibited reduced expression of the major cell wall autolysis gene coincident with the up-regulation of genes involved in cell wall teichoic acid production. Using quantitative (q)RT-PCR on the gene cadre putatively involved in cationic peptide resistance, we formulated a putative regulatory network compatible with microarray data sets, mainly implicating bacterial envelopes. Of interest, qRT-PCR of this same gene cadre from two distinct isogenic DAP(S)/DAP(R) clinical strain pairs revealed evidence of other strain-dependent networks operative in the DAP(R) phenotype. Comparative proteomics of 616 versus 701 revealed a differential abundance of proteins in various functional categories, including cell wall-associated targets and biofilm formation proteins. Phenotypically, strains 616 and 701 showed major differences in their ability to develop bacterial biofilms in the presence of the antibacterial lipid, oleic acid.

CONCLUSIONS

Compatible with previous in vitro observations, in vivo-acquired DAP(R) in S. aureus is a complex, multistep phenomenon involving: (i) strain-dependent phenotypes; (ii) transcriptome adaptation; and (iii) modification of the lipid and protein contents of cellular envelopes.

Abstract 2539: Antitumor effects of oral paclitaxel DHP107 on gastric cancer xenografts

Oral paclitaxel DHP107 (Daehwa, Seoul Korea), an antineoplastic agent, is effectively absorbed through the gastrointestinal tract via the lipid uptake mechanism, which is currently under clinical investigation. Oral capecitabine generates 5-fluorouracil (5-FU) by thymidine phosphorylase, preferentially in tumor tissue. Taxanes, such as paclitaxel and docetaxel, have the ability to up-regulate levels of thymidine phosphorylase which show the its increased activity in tumors compared with that of normal tissue. Accordingly, combination treatment using taxanes with capecitabine is effective in several tumors, especially in gastric cancer. In this study, we investigated the antitumor effect of DHP107 combined with capecitabine and compared the effects of DHP107 and Taxol in gastric cancer xenografts. DHP107 in combination with capecitabine dramatically inhibited tumor growth without additive toxicity compared with each agent used alone in gastric xenografts. The expression of the level of thymidine phosphorylase in tumor was markedly increased four hours after treatment with DHP107. The apoptotic effects, assessed using TUNEL and soft agar colony-formation assay on xenograft tumors, were greater with combined treatment than with either agent used alone. The antitumor effects of DHP107 were similar to those of Taxol in gastric cancer xenografts. These data indicate that DHP107 combined with capecitabine had enhanced antitumor effects in human gastric tumor xenografts and that DHP107 had antitumor effects in gastric cancer models, both of which provide support for future clinical trials of DHP107.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2539. doi:10.1158/1538-7445.AM2011-2539

Effects of the HDAC inhibitor CG2 in combination with irinotecan, 5-fluorouracil, or oxaliplatin on HCT116 colon cancer cells and xenografts

Chemotherapies for colon cancer have recently advanced. However, there is still a need to develop agents and identify effective regimens for better treatments of colon cancer. Histone deacetylase inhibitors (HDACIs) have shown potential as anti-cancer agents. We investigated the anti-tumor effects of CG2 (an HDACI) in combination with irinotecan, 5-FU, or oxaliplatin. Combinations of CG2 with SN38 (the active form of irinotecan), 5FU, or oxaliplatin were more effective than the agents alone when used to inhibit the growth of HCT116 cells. The protein expressions of acetyl-H3, p21, caspase-3, -8, and -9, PARP, and XIAP were affected in a time- and dose-dependent manner in HCT116 cells treated with the CG2 alone or combined CG2 and SN-38. In HCT116 xenografts, the HDACI CG2 in combination with irinotecan dramatically inhibited tumor growth without showing additive toxicity. These data indicate that CG2 together with irinotecan is a promising combination novel treatment for colon cancer.

Removal and fate of estrogens in an anaerobic-anoxic-oxic activated sludge system

Laboratory-scale experiments were conducted to investigate the removal and fate of estrogens 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) in an anaerobic-anoxic-oxic (AAO) activated sludge system. Estrogen concentrations in the aqueous and solid phases in each reactor of AAO system were analyzed separately. E2 was not detected in the final effluent. The anaerobic, anoxic and oxic reactors accounted for 71%, 7% and 22% of the overall E2 removal, respectively. The overall EE2 removal efficiency was about 80%, and the anaerobic, anoxic and oxic reactors were responsible for 44%, 8% and 48% of the overall EE2 removal, respectively. In anaerobic unit, sorption was the dominant mechanism for the removal of E2 and EE2. While E2 was degraded in all the three units of the AAO system, EE2 was only degraded in the anoxic and aerobic units. Biodegradation is important for the fate of E2 compared to sorption. Of the total influent E2 in the AAO system, 99.99% was biodegraded and 0.01% remained in the waste sludge. Nevertheless, both sorption and biodegradation play important roles in the removal of EE2. Of the total influent EE2, 79.1% was degraded by activated sludge, 19.9% was discharged in the effluent and 1% remained in the waste sludge.

The association between the ratio of visceral fat to thigh muscle area and metabolic syndrome: the Korean Sarcopenic Obesity Study (KSOS)

OBJECTIVE

A relationship between visceral fat accumulation and metabolic syndrome (MetS) has been established. However, the effect of a relative increase in visceral fat and a decrease in muscle mass on metabolic disorders has not been investigated. The aim of the present study was to examine the association between the ratio of visceral fat to thigh muscle area (VMR) and MetS in Korean adults. STUDY SUBJECT/MEASUREMENTS: A total of 264 age-and gender-matched subjects recruited from the Korean Sarcopenic Obesity Study (KSOS), an ongoing prospective observational cohort study, were categorized into four groups based on their body mass index (BMI) and VMR. We measured visceral fat area and thigh muscle area using computed tomography.

RESULTS

Subjects with MetS showed a significantly higher VMR than those without MetS. In both obese and nonobese groups, the subjects with a higher VMR had a higher prevalence of MetS than those in the lower VMR groups. VMR was significantly related to components of the metabolic syndrome, especially in women, and was positively correlated with a number of MetS components in both men and women. In multiple logistic regression analysis, the odds ratio for MetS was 6·72 (highest vs lowest quartile, 95% confidence interval, 1·60-28·14) after an adjustment of potential confounders, including BMI and waist-to-hip ratio.

CONCLUSION

VMR is significantly increased in subjects with MetS and independently associated with MetS. These results suggest that the VMR may be a potential indicator for MetS risk in Korean adults.

Daptomycin-oxacillin combinations in treatment of experimental endocarditis caused by daptomycin-nonsusceptible strains of methicillin-resistant Staphylococcus aureus with evolving oxacillin susceptibility (the "seesaw effect")

In vivo development of daptomycin resistance (DAPr) among Staphylococcus aureus strains, especially methicillin-resistant S. aureus (MRSA) strains, in conjunction with clinical treatment failures, has emerged as a major problem. This has raised the question of DAP-based combination regimens to enhance efficacy against such strains. We studied five recent DAP-susceptible (DAPs)/DAPr clinical MRSA strain pairs obtained from patients who failed DAP monotherapy regimens, as well as one DAPs/DAPr MRSA strain pair in which the resistant strain was generated by in vitro passage in DAP. Of note, we identified a DAP-oxacillin (OX) "seesaw" phenomenon in vitro in which development of DAPr was accompanied by a concomitant fall in OX resistance, as demonstrated by 3- to 4-fold decreases in the OX MIC, a susceptibility shift by population analyses, and enhanced early killing by OX in time-kill assays. In addition, the combination of DAP and OX exerted modest improvement in in vitro bactericidal effects. Using an experimental model of infective endocarditis and two DAPs/DAPr strain pairs, we demonstrated that (i) OX monotherapy was ineffective at clearing DAPr strains from any target tissue in this model (heart valve, kidneys, or spleen) and (ii) DAP-OX combination therapy was highly effective in DAPr strain clearances from these organs. The mechanism(s) of the seesaw effect remains to be defined but does not appear to involve excision of the staphylococcal cassette chromosome mec (SCCmec) that carries mecA.

AMP-activated protein kinase mediates activity-dependent regulation of peroxisome proliferator-activated receptor gamma coactivator-1alpha and nuclear respiratory factor 1 expression in rat visual cortical neurons

Nuclear respiratory factor 1 (NRF-1) is one of the key transcription factors implicated in mitochondrial biogenesis by activating the transcription of mitochondrial transcription factor A (mtTFA) and subunit genes of respiratory enzymes. NRF-1 transactivation activity can be enhanced by interaction with transcription coactivator peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha). The expression of PGC-1alpha, NRF-1 and mtTFA in neurons is known to be tightly regulated by neuronal activity. However, the coupling signaling mechanism is poorly understood. Here, we use primary cultures of rat visual cortical neurons and a rat model of monocular deprivation (MD) to investigate whether AMP-activated protein kinase (AMPK) is implicated in mediating activity-dependent regulation of PGC-1alpha and NRF-1 expression in neurons. We find that KCl depolarization rapidly activates AMPK and significantly increases PGC-1alpha, NRF-1, and mtTFA levels with increased ATP production in neuron cultures. Similarly, pharmacological activation of AMPK with 5'-aminoimidazole-4-carboxamide riboside (AICAR) or resveratrol also markedly increases PGC-1alpha and NRF-1 mRNA levels in neuron cultures. All these effects can be completely blocked by an AMPK inhibitor, Compound C. Conversely, 1 week of MD significantly reduces AMPK phosphorylation and activity, dramatically down-regulates PGC-1alpha and NRF-1 expression in deprived primary visual cortex. Administration of resveratrol in vivo significantly activates AMPK activity and attenuates the effects of MD on mitochondria by significant increase in PGC-1alpha and NRF-1 levels, mitochondria amount, and coupled respiration. These results strongly indicate that AMPK is an essential upstream mediator that couples neuronal activity to mitochondrial energy metabolism by regulation of PGC-1alpha-NRF-1 pathway in neurons.

Enhanced expression of dltABCD is associated with the development of daptomycin nonsusceptibility in a clinical endocarditis isolate of Staphylococcus aureus

Using isogenic clinical bloodstream Staphylococcus aureus strains from a patient with relapsing endocarditis, we investigated the transcriptional profiles of the mprF and dlt genes in the context of cell-surface charge and daptomycin nonsusceptibility. As in prior studies, a point mutation within mprF was observed in the daptomycin-nonsusceptible strain. However, neither the transcriptional profile of mprF nor the membrane phospholipid analyses were compatible with the anticipated mprF gain-in-function phenotype. In contrast, we demonstrated enhanced dlt expression coincident with increased positive surface charge and reduced daptomycin binding.

Disparity in the in vitro versus in vivo regulation of fibronectin-binding proteins by 2 global regulators, saeRS and sigB, in Staphylococcus aureus

Fibronectin-binding protein A plays an important role in Staphylococcus aureus endovascular infections. We characterized the sigB-saeRS-fnbA expression network with fibronectin binding in vitro and in an experimental infective endocarditis (IE) model using parental strains RN6390 and SH1000 and their respective isogenic saeRS mutants. In contrast to the in vitro data, there was no influence of saeRS on fnbA expression in the IE model, yet ex vivo fibronectin binding was reduced in saeRS mutants. Moreover, as opposed to the in vitro findings, sigB appeared to have a positive rather than a negative effect on saeRS expression within cardiac vegetations.

The bacterial defensin resistance protein MprF consists of separable domains for lipid lysinylation and antimicrobial peptide repulsion

Many bacterial pathogens achieve resistance to defensin-like cationic antimicrobial peptides (CAMPs) by the multiple peptide resistance factor (MprF) protein. MprF plays a crucial role in Staphylococcus aureus virulence and it is involved in resistance to the CAMP-like antibiotic daptomycin. MprF is a large membrane protein that modifies the anionic phospholipid phosphatidylglycerol with l-lysine, thereby diminishing the bacterial affinity for CAMPs. Its widespread occurrence recommends MprF as a target for novel antimicrobials, although the mode of action of MprF has remained incompletely understood. We demonstrate that the hydrophilic C-terminal domain and six of the fourteen proposed trans-membrane segments of MprF are sufficient for full-level lysyl-phosphatidylglycerol (Lys-PG) production and that several conserved amino acid positions in MprF are indispensable for Lys-PG production. Notably, Lys-PG production did not lead to efficient CAMP resistance and most of the Lys-PG remained in the inner leaflet of the cytoplasmic membrane when the large N-terminal hydrophobic domain of MprF was absent, indicating a crucial role of this protein part. The N-terminal domain alone did not confer CAMP resistance or repulsion of the cationic test protein cytochrome c. However, when the N-terminal domain was coexpressed with the Lys-PG synthase domain either in one protein or as two separate proteins, full-level CAMP resistance was achieved. Moreover, only coexpression of the two domains led to efficient Lys-PG translocation to the outer leaflet of the membrane and to full-level cytochrome c repulsion, indicating that the N-terminal domain facilitates the flipping of Lys-PG. Thus, MprF represents a new class of lipid-biosynthetic enzymes with two separable functional domains that synthesize Lys-PG and facilitate Lys-PG translocation. Our study unravels crucial details on the molecular basis of an important bacterial immune evasion mechanism and it may help to employ MprF as a target for new anti-virulence drugs.

A Ubiquitous Chronic Disease Care system using cellular phones and the internet

AIMS

The rapidly increasing prevalence of chronic diseases is an important challenge to healthcare systems worldwide. To improve the quality and efficiency of chronic disease care, we investigated the effectiveness and applicability of the Ubiquitous Chronic Disease Care (UCDC) system using cellular phones and the internet for overweight patients with both Type 2 diabetes and hypertension.

METHODS

We conducted a randomized, controlled clinical trial over 3 months that included 123 patients at a university hospital and a community public health centre.

RESULTS

After 12 weeks, there were significant improvements in HbA(1c) in the intervention group (7.6 +/- 0.9% to 7.1 +/- 0.8%, P < 0.001) compared with the control group (7.4 +/- 0.9% to 7.6 +/- 1.0%, P = 0.03). Furthermore, we observed a significant reduction in systolic and diastolic blood pressure, as well as improvements in total cholesterol, low-density lipoprotein-cholesterol and triglyceride levels in the intervention group. Furthermore, there was a significant increase in adiponectin levels in the intervention group compared with the control group, although high-sensitivity C-reactive protein and interleukin-6 levels did not change in either group.

CONCLUSIONS

The novel UCDC system presented in this paper improved multiple metabolic parameters simultaneously in overweight patients with both Type 2 diabetes and hypertension.

Inhibition of the chemokine (C-C motif) ligand 2/chemokine (C-C motif) receptor 2 pathway attenuates hyperglycaemia and inflammation in a mouse model of hepatic steatosis and lipoatrophy

AIMS/HYPOTHESIS

Using a mouse model of lipoatrophic diabetes, we hypothesised that the chemokine (C-C motif) ligand 2 (CCL2)/chemokine (C-C motif) receptor 2 (CCR2) pathway contributes to hepatic macrophage accumulation and insulin resistance through induction of a chronic inflammatory state.

METHODS

Metabolic variables of insulin resistance and inflammation were characterised in wild-type and lipoatrophic A-ZIP/F-1 transgenic (AZIP-Tg) mice. The AZIP-Tg mice were then treated with a CCR2 antagonist (RS504393, 2 mg kg(-1) day(-1)) or vehicle for 28 days via a subcutaneous mini-osmotic pump to examine the role of the CCL2/CCR2 pathway in lipoatrophic diabetes.

RESULTS

The lipoatrophic AZIP-Tg mice were diabetic with high fasting glucose and serum insulin concentrations compared with littermate controls. The livers of AZIP-Tg mice were more than threefold enlarged and exhibited increased triacylglycerol content. CCL2 levels were highly elevated in both liver and serum of the AZIP-Tg mice compared with controls. In addition, the circulating CCL2 concentration was associated with increased macrophage accumulation and inflammation as documented by upregulation of Cd68 gene and Tnf-alpha [also known as Tnf] gene in livers from the AZIP-Tg mice. Treatment of the lipoatrophic AZIP-Tg mice with the CCR2 antagonist ameliorated the hyperglycaemia, hyperinsulinaemia and hepatomegaly in conjunction with a reduction in liver inflammation.

CONCLUSIONS/INTERPRETATION

These findings demonstrate a significant role of the CCL2/CCR2 pathway in lipoatrophy-induced diabetes and provide clear evidence that metabolic improvements resulting from the inhibition of this inflammatory pathway are not adipose tissue-dependent.

Trichinella spiralis--a potential anti-tumor agent

Murine forestomach carcinoma (cell line MFC), ascitic hepatoma (cell line H22) and sarcoma (cell line S180) solid tumor models were used to test the anti-tumor effect of Trichinella spiralis in vivo. Mice previously infected by oral administration of 400 viable T. spiralis larvae per mouse for 7 days were grafted with various solid tumor cell lines. Other groups of tumor-bearing mice were given caudal vein injection of crude extracts of adult and newborn larvae at 17.5, 35.0 or 70.0 mg kg(-1). These treatments to inhibit tumor growth were dose-dependent (p<0.05). The anti-proliferative activity of crude T. spiralis extract was examined in vitro at 0.035, 0.070 or 0.140 mg ml(-1) using MFC, H22, S180, human chronic myeloid leukemia cell line (K562) and hepatoma cell line (H7402), tumor cell proliferation in vitro was measured by methyl thiazolium stain and was inhibited in dose-dependent manner (p<0.05). At the same doses, crude T. spiralis extracts induced apoptosis of K562 and H7402 as detected by DNA fragmentation. Cell cycle analysis indicated that crude T. spiralis extracts, at 0.140 mg ml(-1), arrested the cell cycle of K562 and H7402 in G1 or S phase. It is concluded that T. spiralis contains anti-tumor active agent.

Interaction of leptin and nitric oxide on food intake in broilers and Leghorns

Leptin, which is produced in proportion to adiposity, has been reported to regulate feeding behaviors. Previous researchers reported that inhibition of nitric oxide (NO) synthase (NOS) decreased food intake, while L-arginine attenuated this effect. Recently, studies showed that NO plays an important role as a mediator of feeding behavior induced by a variety of neuropeptides. We investigated whether the anorectic effect of leptin is mediated by nitric oxide in broilers and Leghorns. In the first experiment, leptin was intracerebroventricularly (ICV) administered into the right lateral ventricle of broilers and food intake monitored at 15-min intervals through 180 min postinjection. L-arginine attenuated the decrease in food intake induced by leptin. In the second experiment, leptin was coinjected ICV with NG-nitro-arginine methyl ester HC1 (L-NNA), a NOS inhibitor. In the following study, we investigated whether the decreased feeding induced by leptin (10 microg/l0 microl) is mediated by nitric oxide in chickens. Three week old chickens were administered two levels of leptin (A=aCSF, B=10 microg/l0 microl) into the right lateral ventricle, and nitrate and nitrite (nitric oxide metabolites) were monitored 30-min postinjection. The results showed leptin decreased NO formation significantly compared with the control group. These results suggest that NO interacts with leptin in the central nervous system to modulate feeding behavior in the chicken.

Transcriptional profiling of a Staphylococcus aureus clinical isolate and its isogenic agr and sarA mutants reveals global differences in comparison to the laboratory strain RN6390

The production of Staphylococcus aureus virulence factors is under the control of complex regulatory circuits. Most studies aimed at defining these regulatory networks have focused on derivatives of the strain NCTC 8325, most notably RN6390. However, all NCTC 8325 derivatives, including RN6390, possess an 11 bp deletion in rsbU. This deletion renders NCTC 8325 derivatives naturally sigma-factor-B deficient. Recent studies have shown that RN6390 is also deficient, in comparison to clinical isolates, with respect to biofilm formation, a process which is important for both pathogenesis and antimicrobial resistance. Based on these considerations, the authors carried out genome-scale transcriptional profiling, comparing RN6390 with the virulent rsbU-positive clinical isolate UAMS-1. The results revealed significant genome-wide differences in expression patterns between RN6390 and UAMS-1, and suggested that the overall transcriptional profile of UAMS-1 is geared toward expression of factors that promote colonization and biofilm formation. In contrast, the transcriptional profile of RN6390 was heavily influenced by RNAIII expression, resulting in a phenotype characterized by increased production of exoproteins, and decreased capacity to form a biofilm. The greater influence of agr in RN6390 relative to UAMS-1 was also evident when the transcriptional profile of UAMS-1 was compared with that of its isogenic sarA and agr mutants. Specifically, the results indicate that, in contrast to NCTC 8325 derivatives, agr plays a limited role in overall regulation of gene expression in UAMS-1, when compared with sarA. Furthermore, by defining the sarA regulon in a biofilm-positive clinical isolate, and comparing the results with transcriptional profiling experiments defining biofilm-associated gene expression patterns in the same strain, the authors identified a sarA-regulated operon (alsSD) that is also induced in biofilms, and demonstrated that mutation of alsSD results in reduced capacity to form a biofilm.

Characterization of the Staphylococcus aureus CidR regulon: elucidation of a novel role for acetoin metabolism in cell death and lysis

The Staphylococcus aureus cid and lrg operons encode a novel regulatory system that affects murein hydrolase activity, stationary-phase survival and antibiotic tolerance. Expression of the lrgAB operon is positively regulated by a two-component regulatory system encoded by the lytSR operon located immediately upstream to lrgAB. By comparison, the cidABC operon lies downstream from the cidR gene, encoding a protein homologous to the LysR-type family of transcriptional regulators. Transcription analysis of a cidR mutant revealed that CidR enhances cidABC expression in the presence of acetic acid generated by the metabolism of excess glucose. Microarray studies identified additional CidR-regulated operons including the IrgAB and alsSD encoding proteins involved in acetoin production. Surprisingly, Northern blot analyses revealed that cidABC and lrgAB transcription was uninducible in an alsSD mutant grown in the presence of excess glucose, suggesting that the CidR-mediated upregulation of cidABC and lrgAB transcription is dependent on the presence of intact alsSD genes. Zymographic and quantitative analyses of murein hydrolase activity also revealed that disruption of the alsSD genes results in significantly decreased extracellular murein hydrolase activity compared with that of the parental strain, UAMS-1. Furthermore, the alsSD mutant displayed decreased stationary-phase survival relative to UAMS-1, both in the presence and absence of glucose. The results of this study define the CidR regulon and demonstrate that the generation of acetoin is linked to the control of cell death and lysis in S. aureus.

Activity-dependent transcriptional regulation of nuclear respiratory factor-1 in cultured rat visual cortical neurons

Nuclear respiratory factor 1 is a transcription factor involved in the regulation of mitochondrial biogenesis by activating the transcription of subunit genes of cytochrome oxidase and other respiratory enzymes. Very little is known of its role in neurons. To determine if neuronal activity regulates nuclear respiratory factor 1 expression, cultured primary neurons from postnatal rat visual cortex were subjected to 20 mM KCl depolarizing treatment for 1, 3, 5, and 7 h, or exposed to 7 h of KCl followed by withdrawal for 1, 3, 5, and 7 h. Nuclear respiratory factor 1 expression was analyzed by immunoblots, immunocytochemistry, quantitative electron microscopy, real-time quantitative PCR, and in situ hybridization. Nuclear respiratory factor 1 protein was expressed at relatively low basal levels in both the nucleus, where it was associated primarily with euchromatin, and in the cytoplasm, where it was localized to free ribosomes and occasionally to the Golgi apparatus and the outer nuclear membrane. Depolarizing treatment progressively up-regulated both nuclear respiratory factor 1 protein and mRNA in a time-dependent manner, increasing above controls after 1 h and remaining high at 3, 5, and 7 h. Both nuclear and cytoplasmic mRNA levels increased with stimulation, and there was an apparent cytoplasmic-to-nuclear translocation of protein. Following the withdrawal of KCl, both nuclear respiratory factor 1 message and protein were significantly reduced after 1 h. The message returned to basal levels by 5 h and the protein by 7 h. These results strongly indicate that the expression and compartmental redistribution of nuclear respiratory factor 1 protein and mRNA in visual cortical neurons are dynamic processes tightly controlled by neuronal activity.