Deoxysphingolipids and ether-linked diacylglycerols accumulate in the tissues of aged mice.

BACKGROUND: Senescence is a well-known risk factor for several diseases, such as neurodegenerative disorders. Therefore, studies exploring the mechanisms underlying aging are expected to guide the discovery of novel drug targets and biomarkers for these diseases. However, a comprehensive overview of the metabolic and lipidomic changes in healthy aging mammals is lacking. To understand the changes of metabolism with aging, especially lipid metabolism, we analyzed the metabolomes and lipidomes of the cerebral cortex, liver, femoral muscle, and epididymal fat in young and aged mice. RESULTS: Two-dimensional cluster analysis revealed clear separation between the metabolite profiles of the aged and young groups. Deoxydihydroceramide (doxDHCer), deoxyceramide (doxCer), and ether-linked diacylglycerol (DAG) levels were elevated during aging. CONCLUSION: This is the first report of age-related variations in deoxysphingolipid and ether-linked DAG levels in mice. DoxCer, doxDHCer, and ether-linked DAGs may be associated with senescence in mammalian tissues.

Inhibition of GCN2 sensitizes ASNS-low cancer cells to asparaginase by disrupting the amino acid response.

General control nonderepressible 2 (GCN2) plays a major role in the cellular response to amino acid limitation. Although maintenance of amino acid homeostasis is critical for tumor growth, the contribution of GCN2 to cancer cell survival and proliferation is poorly understood. In this study, we generated GCN2 inhibitors and demonstrated that inhibition of GCN2 sensitizes cancer cells with low basal-level expression of asparagine synthetase (ASNS) to the antileukemic agent l-asparaginase (ASNase) in vitro and in vivo. We first tested acute lymphoblastic leukemia (ALL) cells and showed that treatment with GCN2 inhibitors rendered ALL cells sensitive to ASNase by preventing the induction of ASNS, resulting in reduced levels of de novo protein synthesis. Comprehensive gene-expression profiling revealed that combined treatment with ASNase and GCN2 inhibitors induced the stress-activated MAPK pathway, thereby triggering apoptosis. By using cell-panel analyses, we also showed that acute myelogenous leukemia and pancreatic cancer cells were highly sensitive to the combined treatment. Notably, basal ASNS expression at protein levels was significantly correlated with sensitivity to combined treatment. These results provide mechanistic insights into the role of GCN2 in the amino acid response and a rationale for further investigation of GCN2 inhibitors for the treatment of cancer.

Intratumor Heterogeneity in Primary Kidney Cancer Revealed by Metabolic Profiling of Multiple Spatially Separated Samples within Tumors.

Metabolic alteration constitutes a hallmark of cancer. Glycolysis and antioxidant pathways in kidney cancer are elevated, with frequent mutation of the VHL gene. Intratumor genetic heterogeneity has been recently demonstrated in kidney cancer. However, intratumor metabolic heterogeneity has not been investigated. Here, we used global metabolomics analysis and tissue slice tracer studies to demonstrate that different portions of a human primary kidney tumor possess different metabolic characteristics and drug sensitivity. Pyruvate levels were elevated and pyruvate metabolism was altered in some tumor sections. These observations indicated that pyruvate metabolism may constitute a possible vulnerability of kidney cancer; indeed, pyruvate stimulated the growth of primary kidney cancer cells and pharmacological inhibition of pyruvate transporters slowed the growth of patient-derived kidney tumors in mice. These findings deepen our understanding of the intratumor metabolic heterogeneity of kidney cancer and may inform novel therapeutic approaches in human kidney cancer.

Succinate dehydrogenase B-deficient cancer cells are highly sensitive to bromodomain and extra-terminal inhibitors.

Mutations in succinate dehydrogenase B (SDHB) gene are frequently observed in several tumors and associated with poor prognosis in these tumors. Therefore, drugs effective for SDHB-deficient tumors could fulfill an unmet medical need. In addition, such drugs would have an advantage in that selection of patients with SDHB-mutant cancer could increase the probability of success in clinical trials. Currently, however, the characteristics of SDHB-deficient cancers are not completely understood. Here, we established SDHB knockout cancer cell lines from human colon cancer HCT116 cells using the clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 knockout system, and clarified its metabolic characteristics.In the SDHB knockout cells, succinate was accumulated and fumarate was decreased. The oxygen consumption rate was decreased while the extracellular acidification rate was increased in the SDHB knockout cells. Accordingly, an enhanced glycolysis pathway in the SDHB knockout cells was demonstrated by metabolomics analysis. Tracer experiments showed bidirectional metabolic flow in the tricarboxylic acid (TCA) cycle, possibly to maintain the necessary amounts of metabolites in the SDHB knockout cells. The proliferation of SDHB knockout cells was suppressed by a glycolysis inhibitor but not by a mitochondrial inhibitor. Additionally, partial dependence on glutaminolysis was observed in the SDHB knockout cells. Compound screening revealed that a bromodomain and extra-terminal (BET) inhibitor, which downregulated c-Myc, suppressed the growth of the SDHB knockout cells more potently than that of control cells. These findings provide an understanding of the metabolic characteristics of SDHB-deficient cancer and its vulnerabilities, which may lead to new therapeutic options.

Associations of number of teeth with risks for all-cause mortality and cause-specific mortality in middle-aged and elderly men in the northern part of Japan: the Iwate-KENCO study.

OBJECTIVES: The objective of this study was to determine the associations of number of teeth with all-cause mortality and cause-specific mortality among middle-aged and elderly Japanese men. METHODS: A total of 7779 men aged 40-79 years who were free from cardiovascular disease (CVD) were followed up prospectively for 5.6 years. Participants were categorized into four groups (no teeth, 1-9 teeth, 10-19 teeth, and ≥20 teeth) by a self-administered questionnaire. Using Cox's proportional hazard model, multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for mortality from all causes, CVD, cancer, and noncancer, non-CVD according to number of teeth were estimated with adjustments for age, body mass index, systolic blood pressure, total- and HDL-cholesterol, HbA1c, current smoking, current alcohol drinking, and low level of education. RESULTS: The numbers (proportions) of participants with no teeth, 1-9 teeth, 10-19 teeth, and ≥20 teeth were 1613 (20.7%), 1650 (21.2%), 1721 (22.1%), and 2795 (35.9%), respectively. During follow-up, a total of 455 deaths (including 175 deaths from cancer, 98 deaths from CVD, and 130 deaths from noncancer, non-CVD) were recorded. In total participants, an inverse relationship between number of teeth and all-cause mortality was found (P for trend = 0.049). Among men aged 40-64 years, inverse relationships were also found in risks for mortality from all causes, CVD, and cancer: multivariate-adjusted HRs (95% CI) for all-cause mortality in men with no teeth, 1-9 teeth, and 10-19 teeth relative to men with ≥20 teeth were 2.75 (1.37-5.49), 1.89 (0.99-3.63), and 1.94 (1.09-3.43), respectively. However, there were no associations of number of teeth with all-cause mortality and cause-specific mortality among men aged 65-79 years. CONCLUSIONS: The number of teeth is an important predictive factor for mortality among middle-aged Japanese men.

Factors related to tooth loss among community-dwelling middle-aged and elderly Japanese men.

BACKGROUND: Using data from a large-scale community-based Japanese population, we attempted to identify factors associated with tooth loss in middle-aged and elderly men. METHODS: A total of 8352 men aged 40 to 79 years who lived in the north of the main island of Japan and underwent health checkups were enrolled between 2002 and 2005. Number of teeth was assessed by the question, "How many teeth do you have (0, 1-9, 10-19, or ≥20)?". On the basis of the answer to this question, participants were classified into 2 groups (≤19 teeth or ≥20 teeth). Using multivariate logistic regression, factors related to having 19 or fewer teeth were estimated. RESULTS: The numbers (percentages) of participants who had 0, 1 to 9, 10 to 19, and 20 or more teeth were 1764 (21.1%), 1779 (21.3%), 1836 (22.0%), and 2973 (35.6%), respectively. Among the participants overall and those aged 65 to 79 years, having 19 or fewer teeth was significantly associated with older age, smoking status (current smoking and ex-smoking), and low education level. In addition, men with 19 or fewer teeth were more likely to have a low body mass index and low serum albumin level and less likely to be current alcohol drinkers. Among men aged 40 to 64 years, but not men aged 65 to 79 years, those with 19 or fewer teeth were more likely to have a low serum high-density lipoprotein cholesterol level and high glycosylated hemoglobin (HbA1c) level. CONCLUSIONS: Smoking, low education level, and poor nutritional status were associated with tooth loss among middle-aged and elderly Japanese men.