Gender-related differences in the metabolic response to fasting

CONTEXT: Free fatty acids (FFA) may induce insulin resistance via synthesis of intramyocellular ceramide. During fasting, women have lower plasma glucose levels than men despite higher plasma FFA, suggesting protection from FFA-induced insulin resistance. OBJECTIVE: We studied whether the relative protection from FFA-induced insulin resistance during fasting in women is associated with lower muscle ceramide concentrations compared with men. MAIN OUTCOME MEASURES AND DESIGN: After a 38-h fast, measurements of glucose and lipid fluxes and muscle ceramide and fatty acid translocase/CD36 were performed before and after a hyperinsulinemic euglycemic clamp. RESULTS: Plasma glucose levels were significantly lower in women than men with a trend for a lower endogenous glucose production in women, whereas FFA and lipolysis were significantly higher. Insulin-mediated peripheral glucose uptake was not different between sexes. There was no gender difference in muscle ceramide in the basal state, and ceramide did not correlate with peripheral glucose uptake. Muscle fatty acid translocase/CD36 was not different between sexes in the basal state and during the clamp. CONCLUSION: After 38 h of fasting, plasma FFA were higher and plasma glucose was lower in women compared with men. The higher plasma FFA did not result in differences in peripheral insulin sensitivity, possibly because of similar muscle ceramide and fatty acid translocase/CD36 levels in men and women. We suggest that during fasting, women are relatively protected from FFA-induced insulin resistance by preventing myocellular accumulation of ceramide.     

Quantification of myocardial blood flow with <Superscript>82</Superscript>Rb dynamic PET imaging

Purpose The PET tracer ⁸²Rb is commonly used to evaluate regional perfusion defects for the diagnosis of coronary artery disease. There is limited information on the quantification of myocardial blood flow and flow reserve with this tracer. The goal of this study was to investigate the use of a one-compartment model of ⁸²Rb kinetics for the quantification of myocardial blood flow. Methods Fourteen healthy volunteers underwent rest and dipyridamole stress imaging with both ¹³N-ammonia and ⁸²Rb within a 2-week interval. Myocardial blood flow was estimated from the time-activity curves measured with ¹³N-ammonia using a standard two-compartment model. The uptake parameter of the one-compartment model was estimated from the time-activity curves measured with ⁸²Rb. To describe the relationship between myocardial blood flow and the uptake parameter, a nonlinear extraction function was fitted to the data. This function was then used to convert estimates of the uptake parameter to flow estimates. The extraction function was validated with an independent data set obtained from 13 subjects with documented evidence of coronary artery disease (CAD). Results The one-compartment model described ⁸²Rb kinetics very well (median R-square = 0.98). The flow estimates obtained with ⁸²Rb were well correlated with those obtained with ¹³N-ammonia (r = 0.85), and the best-fit line did not differ significantly from the identity line. Data obtained from the subjects with CAD confirmed the validity of the estimated extraction function. Conclusion It is possible to obtain accurate estimates of myocardial blood flow and flow reserve with a one-compartment model of ⁸²Rb kinetics and a nonlinear extraction function.     

PTEN Contributes to Profound PI3K/Akt Signaling Pathway Deregulation in Dystrophin-Deficient Dog Muscle

Duchenne muscular dystrophy is the most common and severe form of muscular dystrophy, and although the genetic basis of this disease is well defined, the overall mechanisms that define its pathogenesis remain obscure. Alterations in individual signaling pathways have been described, but little information is available regarding their putative implications in Duchenne muscular dystrophy pathogenesis. Here, we studied the status of various major signaling pathways in the Golden Retriever muscular dystrophy dog that specifically reproduces the full spectrum of human pathology. Using antibody arrays, we found that Akt1, glycogen synthase kinase-3β (GSK3β), 70-kDa ribosomal protein S6 kinase (p70S6K), extracellular signal-regulated kinases 1/2, and p38δ and p38γ kinases all exhibited decreased phosphorylation in muscle from a 4-month-old animal with Golden Retriever muscular dystrophy, revealing a deep alteration of the phosphatidylinositol 3-kinase (PI3K)/Akt and mitogen-activated protein kinase pathways. Immunohistochemistry analysis revealed the presence of muscle fibers exhibiting a cytosolic accumulation of Akt1, GSK3β, and phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN), an enzyme counteracting PI3K-mediated Akt activation. Enzymatic assays established that these alterations in phosphorylation and expression levels were associated with decreased Akt and increased GSK3β and PTEN activities. PTEN/GSK3β-positive fibers were also observed in muscle sections from 3- and 36-month-old animals, indicating long-term PI3K/Akt pathway alteration. Collectively, our data suggest that increased PTEN expression and activity play a central role in PI3K/Akt/GSK3β and p70S6K pathway modulation, which could exacerbate the consequences of dystrophin deficiency.Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects 1 newborn boy in 3500. This recessive disease is caused by mutations in the dystrophin gene, resulting in total lack of the protein,^1,2,3 and is characterized by severe degeneration of muscle fibers, progressive paralysis, and death. Dystrophin is located under the sarcolemma of muscle fibers, and is associated with a complex comprising several integral, peripheral membrane and cytoplasmic proteins: the dystrophin-glycoprotein complex (DGC).^4,5,6,7 By providing a strong physical link between the cytoskeleton network and the extracellular matrix, the DGC ensures the integrity of skeletal muscle fibers. In the absence of dystrophin, the complex is destabilized and this integrity is lost.^5,8 However, the impaired structural role of the DGC alone may not be sufficient to account for the massive degenerative process observed in DMD muscles. Numerous observations suggest that signaling pathway alterations may also participate in DMD pathogenesis.Dystrophin and various DGC proteins have been demonstrated to interact with a number of signaling proteins, including growth factor receptor-bound protein 2,⁹ neuronal nitric oxide synthase,¹⁰ calmodulin,¹¹ focal adhesion kinase,¹² and caveolin-3.^13,14,15 Moreover, studies of the X chromosome-linked muscular dystrophy (mdx) mouse¹⁶ revealed modulations in mitogen-activated protein kinase (MAPK) signaling cascades, as dystrophic animals exhibited increased phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2)^17,18 and c-jun N-terminal kinases 1 and 2 (JNK1/2),^19,20,21 and decreased phosphorylation of p38.¹⁸ Also, the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway has been shown to be affected in the mdx mouse, with increased synthesis and phosphorylation of Akt.^22,23In addition to the limited information related to the origin of signal perturbations in dystrophic muscle, almost no information is available regarding signaling pathways in clinically relevant animal models or human tissue samples.²³ It is noteworthy that the mdx mouse model of DMD is characterized by successive degeneration/regeneration processes, but does not exhibit the progressive muscle wasting and accumulation of connective tissue observed during the development of the human disease.^24,25,26 The Golden Retriever muscular dystrophy (GRMD) dog, characterized by rapidly progressive clinical dysfunction, severe muscle weakness, and abundant fiber necrosis, displays a disease progression that is far more similar to human DMD.^27,28In this study, we used antibody arrays to assess the global phosphorylation status of key proteins of the PI3K/Akt and MAPK signaling pathways in skeletal muscles of 4-month-old healthy and GRMD dogs. Our data indicated that Akt1, glycogen synthase kinase-3β (GSK3β) and p70S6K, as well as ERK1/2 and p38δ and γ kinases all displayed a decreased phosphorylation level in GRMD muscle. Western immunoblot, immunohistochemistry analysis, and enzymatic assays allowed us to confirm these results and demonstrated that they were associated with a reduction in Akt activity and with enhanced GSK3β expression and activity. Analysis of key enzymes involved in Akt regulation revealed that phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase (PTEN) was present at a much higher level and was more active in GRMD muscle. Moreover, immunohistochemistry analysis showed that all of the GSK3β-positive fibers observed in GRMD muscle sections exhibited a strong cytosolic labeling of PTEN, suggesting that the accumulation of the phosphatase could play a central role in PI3K/Akt signaling pathway deregulation. The observation of PTEN/GSK3β-positive fibers in muscle sections from 3- and 36-month-old GRMD dogs further demonstrated that both the early and late stages of the disease share deregulation of the pathway. Collectively, our findings highly suggest that alterations in PTEN exist in GRMD muscle, which leads to long-term and deep modulation of the PI3K/Akt signaling pathway.     

DNAX accessory molecule‐1 (CD226) promotes human hepatocellular carcinoma cell lysis by Vγ9Vδ2 T cells

Human Vγ9Vδ2 T lymphocytes can be activated by nonpeptidic antigens such as the mevalonate pathway‐derived isopentenyl pyrophosphate or synthetic phosphoantigen such as bromohydrin pyrophosphate. They display a strong cytotoxic activity against several tumor types, including hepatocellular carcinoma (HCC). Little is known about the mechanisms underlying Vγ9Vδ2 T‐cell recognition of tumor cells, but there is strong evidence that activating NK receptors play a role in γδ T‐cell cytotoxicity. In this study, we showed that the two NK receptors DNAX accessory molecule‐1 (DNAM‐1) and CD96 were expressed by Vγ9Vδ2 T cells. The ligands Nectin‐like‐5 specific of both DNAM‐1 and CD96, and also Nectin‐2, an additional ligand of DNAM‐1, were present on all HCC cell lines analyzed. Furthermore, we demonstrated by mAb‐mediated masking experiments that cytotoxicity against HCC cells as well as IFN‐γ production in γδ T cells were dependent on DNAM‐1. Our experiments indicated that Nectin‐like‐5 but not Nectin‐2 was involved in DNAM‐1‐dependent γδ T‐cell functions. We did not reveal a role for CD96 in the killing of HCC cells. Finally, we showed by combined mAb‐mediated blockade that DNAM‐1 and NKG2D could cooperate in the cell lysis of HCC.     

Comparison of the 1996 and 2001 census data for Aboriginal and non-Aboriginal workers in health care occupations

To meet the unique health needs of Aboriginal peoples (First Nations, Inuit and Métis), it is important to increase and encourage Aboriginal representation in health care. One Federal initiative, the Aboriginal Health Human Resource Initiative (AHHRI) at Health Canada, focuses on: (1) increasing the number of Aboriginal people working in health careers; (2) adapting health care educational curricula to support the development of cultural competencies; and (3) improving the retention of health care workers in Aboriginal communities. A health care system that focuses on understanding the unique challenges, concerns, and needs of Aboriginal people can better respond to this specific population, which suffers disproportionately from ill health in comparison to their non-Aboriginal counterparts. This report examines the supply of Aboriginal health care providers in Canada, based on geographic region, area of residence, Aboriginal identity, and occupation. Findings are drawn from the 1996 and 2001 censuses from Statistics Canada. Quantitative results provide a greater understanding of labour force characteristics of First Nation, Inuit, Métis, and non-Aboriginal health providers.     

Cost-effectiveness of pneumococcal polysaccharide vaccination in adults: A systematic review of conclusions and assumptions

Streptococcus pneumoniae infections in adults are associated with substantial morbidity, mortality, and costs. A literature review was conducted to identify strengths and limitations of the cost-effectiveness of pneumococcal polysaccharide vaccine studies. A comparative analysis of the impact of model parameters on cost-effectiveness ratios was complemented by systematic assessment of the studies. We identified 11 economic evaluations of pneumococcal polysaccharide vaccine (PPV-23) in adults. In general, all 11 studies found that vaccination with PPV-23 is a cost-effective, and in some cases a cost-saving strategy for the prevention of invasive pneumococcal disease (IPD). The systematic assessment indicated that the results of the cost-effectiveness studies of PPV-23 are influenced by the values applied to vaccine efficacy, IPD incidence and case-fatality.     

Dihydropyrimidine dehydrogenase activity and the IVS14+1G>A mutation in patients developing 5FU-related toxicity

AIMS: To examine retrospectively the relationship between DPD phenotype/genotype and the intensity of 5FU toxicity. METHODS: One hundred and thirty-one case-reports (81 women, 50 men) with 5FU-related toxicity were analyzed. RESULTS: The lower the DPD activity (10-504 pmol min(-1) mg(-1)), the higher the toxicity grade was scored (P < 0.01). Toxicity-related deaths occurred in nine patients (eight women) who significantly expressed lower DPD activity than other patients. Two of the deceased patients had normal DPD activity. The IVS14+1G>A mutation, analyzed in 93 patients, was detected in two patients (nonlethal toxicity). CONCLUSIONS: The IVS14+1G>A mutation may not help prevent toxicity and patients with normal DPD activity may develop life-threatening 5FU toxicity.     

Unmet needs and health care utilization in young adults with cerebral palsy

PURPOSE: To gain insight into the unmet needs and utilization of health care of young adults with cerebral palsy (CP) and to explore relations between unmet needs, health care utilization and subject characteristics. METHOD: A cross-sectional study was performed in 29 young adults with CP without severe learning disabilities (IQ > 70). Subject characteristics such as age, gender, limb distribution, level of gross motor functioning, level of education and perceived participation and autonomy were measured. Outcome measures were the Southampton Needs Assessment Questionnaire, Impact on Participation and Autonomy and a questionnaire on health care utilization. RESULTS: Young adults with CP reported unmet needs mostly on information (79%), mobility (66%) and health care (66%). About half of the participants visited a rehabilitation physician (52%) or a physical therapist (55%) in the past year. Participants with lower levels of gross motor functioning were found to have more unmet needs and visited various health care professionals more often than young adults with higher levels of gross motor functioning. However, participants with higher levels of gross motor functioning still reported several unmet needs. CONCLUSIONS: Although young adults with CP frequently receive treatment from health care professionals, they indicate unmet needs with respect to several areas such as information on diagnosis, functional mobility and formal health care. In the treatment of young adults with CP, attention should be paid to these aspects.