A population model of folate-mediated one-carbon metabolism.

BACKGROUND: Previous mathematical models for hepatic and tissue one-carbon metabolism have been combined and extended to include a blood plasma compartment. We use this model to study how the concentrations of metabolites that can be measured in the plasma are related to their respective intracellular concentrations. METHODS: The model consists of a set of ordinary differential equations, one for each metabolite in each compartment, and kinetic equations for metabolism and for transport between compartments. The model was validated by comparison to a variety of experimental data such as the methionine load test and variation in folate intake. We further extended this model by introducing random and systematic variation in enzyme activity. OUTCOMES AND CONCLUSIONS: A database of 10,000 virtual individuals was generated, each with a quantitatively different one-carbon metabolism. Our population has distributions of folate and homocysteine in the plasma and tissues that are similar to those found in the NHANES data. The model reproduces many other sets of clinical data. We show that tissue and plasma folate is highly correlated, but liver and plasma folate much less so. Oxidative stress increases the plasma S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) ratio. We show that many relationships among variables are nonlinear and in many cases we provide explanations. Sampling of subpopulations produces dramatically different apparent associations among variables. The model can be used to simulate populations with polymorphisms in genes for folate metabolism and variations in dietary input.

The effects of sleep hypoxia on coagulant factors and hepatic inflammation in emphysematous rats.

OBJECTIVES: To develop a sleep hypoxia (SH) in emphysema (SHE) rat model and to explore whether SHE results in more severe hepatic inflammation than emphysema alone and whether the inflammation changes levels of coagulant/anticoagulant factors synthesized in the liver. METHODS: Seventy-five rats were put into 5 groups: SH control (SHCtrl), treated with sham smoke exposure (16 weeks) and SH exposure (12.5% O(2), 3 h/d, latter 8 weeks); emphysema control (ECtrl), smoke exposure and sham SH exposure (21% O(2)); short SHE (SHEShort), smoke exposure and short SH exposure (1.5 h/d); mild SHE (SHEMild), smoke exposure and mild SH exposure (15% O(2)); standard SHE (SHEStand), smoke exposure and SH exposure. Therefore, ECtrl, SHEShort, SHEMild and SHEStand group were among emphysematous groups. Arterial blood gas (ABG) data was obtained during preliminary tests. After exposure, hepatic inflammation (interleukin -6 [IL-6] mRNA and protein, tumor necrosis factor α [TNFα] mRNA and protein) and liver coagulant/anticoagulant factors (antithrombin [AT], fibrinogen [FIB] and Factor VIII [F VIII]) were evaluated. SPSS 11.5 software was used for statistical analysis. RESULTS: Characteristics of emphysema were obvious in emphysematous groups and ABGs reached SH criteria on hypoxia exposure. Hepatic inflammation parameters and coagulant factors are the lowest in SHCtrl and the highest in SHEStand while AT is the highest in SHCtrl and the lowest in SHEStand. Inflammatory cytokines of liver correlate well with coagulant factors positively and with AT negatively. CONCLUSIONS: When SH is combined with emphysema, hepatic inflammation and coagulability enhance each other synergistically and produce a more significant liver-derivative inflammatory and prothrombotic status.

Phorbol esters promote alpha 1-adrenergic receptor phosphorylation and receptor uncoupling from inositol phospholipid metabolism.

DDT1 MF-2 cells, which are derived from hamster vas deferens smooth muscle, contain alpha 1-adrenergic receptors (54,800 +/- 2700 sites per cell) that are coupled to stimulation of inositol phospholipid metabolism. Incubation of these cells with tumor-promoting phorbol esters, which stimulate calcium- and phospholipid-dependent protein kinase, leads to a marked attenuation of the ability of alpha 1-receptor agonists such as norepinephrine to stimulate the turnover of inositol phospholipids. This turnover was measured by determining the 32P content of phosphatidylinositol and phosphatidic acid after prelabeling of the cellular ATP pool with 32Pi. These phorbol ester-treated cells also displayed a decrease in binding affinity of cellular alpha 1 receptors for agonists with no change in antagonist affinity. By using affinity chromatography on the affinity resin Affi-Gel-A55414, the alpha 1 receptors were purified approximately equal to 300-fold from control and phorbol ester-treated 32Pi-prelabeled cells. As assessed by NaDodSO4/polyacrylamide gel electrophoresis, the Mr 80,000 alpha 1-receptor ligand-binding subunit is a phosphopeptide containing 1.2 mol of phosphate per mol of alpha 1 receptor. After phorbol ester treatment this increased to 3.6 mol of phosphate per mol of alpha 1 receptor. The effect of phorbol esters on norepinephrine-stimulated inositol phospholipid turnover and alpha 1-receptor phosphorylation showed the same rapid time course with a t1/2 less than 2 min. These results indicate that calcium- and phospholipid-dependent protein kinase may play an important role in regulating the function of receptors that are coupled to the inositol phospholipid cycle by phosphorylating and deactivating them.

The influence of hepatic function on prostate cancer outcomes after radical prostatectomy.

Prostate growth is dependent on circulating androgens, which can be influenced by hepatic function. Liver disease has been suggested to influence prostate cancer (CaP) incidence. However, the effect of hepatic function on CaP outcomes has not been investigated. A total of 1181 patients who underwent radical prostatectomy (RP) between 1988 and 2008 at four Veterans Affairs hospitals that comprise the Shared Equal Access Regional Cancer Hospital database and had available liver function test (LFT) data were included in the study. Independent associations of LFTs with unfavorable pathological features and biochemical recurrence were determined using logistic and Cox regression analyses. Serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) levels were elevated in 8.2 and 4.4% of patients, respectively. After controlling for CaP features, logistic regression revealed a significant association between SGOT levels and pathological Gleason sum > or =7(4+3) cancer (odds ratio=2.12; 95% confidence interval=1.11-4.05; P=0.02). Mild hepatic dysfunction was significantly associated with adverse CaP grade, but was not significantly associated with other adverse pathological features or biochemical recurrence in a cohort of men undergoing RP. The effect of moderate-to-severe liver disease on disease outcomes in CaP patients managed non-surgically remains to be investigated.

The liver kinase B1 is a central regulator of T cell development, activation, and metabolism.

T cell activation leads to engagement of cellular metabolic pathways necessary to support cell proliferation and function. However, our understanding of the signal transduction pathways that regulate metabolism and their impact on T cell function remains limited. The liver kinase B1 (LKB1) is a serine/threonine kinase that links cellular metabolism with cell growth and proliferation. In this study, we demonstrate that LKB1 is a critical regulator of T cell development, viability, activation, and metabolism. T cell-specific ablation of the gene that encodes LKB1 resulted in blocked thymocyte development and a reduction in peripheral T cells. LKB1-deficient T cells exhibited defects in cell proliferation and viability and altered glycolytic and lipid metabolism. Interestingly, loss of LKB1 promoted increased T cell activation and inflammatory cytokine production by both CD4(+) and CD8(+) T cells. Activation of the AMP-activated protein kinase (AMPK) was decreased in LKB1-deficient T cells. AMPK was found to mediate a subset of LKB1 functions in T lymphocytes, as mice lacking the α1 subunit of AMPK displayed similar defects in T cell activation, metabolism, and inflammatory cytokine production, but normal T cell development and peripheral T cell homeostasis. LKB1- and AMPKα1-deficient T cells each displayed elevated mammalian target of rapamycin complex 1 signaling and IFN-γ production that could be reversed by rapamycin treatment. Our data highlight a central role for LKB1 in T cell activation, viability, and metabolism and suggest that LKB1-AMPK signaling negatively regulates T cell effector function through regulation of mammalian target of rapamycin activity.

EAE cerebrospinal fluid augments in vitro phagocytosis and metabolism of CNS myelin by macrophages.

Previous studies from this laboratory have shown that CNS myelin is phagocytized and metabolized by cultured rat macrophages to a much larger extent when myelin is pretreated with serum containing antibodies to myelin constituents than when it is left untreated or pretreated with non-specific serum. In this study the effect of cerebrospinal fluid (CSF) from rabbits with experimental allergic encephalomyelitis (EAE) in promoting myelin phagocytosis was examined. Fourteen rabbits were immunized with purified myelin in Freund's complete adjuvant, seven of which developed clinical EAE symptoms. Serum and CSF were collected from EAE and control rabbits, and the CSF was centrifuged to remove cells. Sera and CSF from these rabbits and from Freund's adjuvant-immunized controls and untreated controls were measured for IgG content by radial diffusion assay, their myelin antibody characteristics were analyzed by immunoblots, and the ability of these serum and CSF samples to promote myelin phagocytosis when used for myelin opsonization was examined. The ability of a CSF sample to enhance radioactive myelin uptake and phagocytosis by cultured macrophages as measured by the appearance of radioactive cholesterol ester was linearly proportional to its total IgG titer, and correlated approximately both with clinical symptoms of the animal and the presence of antibody against the myelin constituents myelin basic protein, proteolipid protein, and galactocerebroside. The cholesterol esterification activities of EAE sera correlated to a lesser extent with IgG levels and clinical symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)