Arginase deficiency is a rare autosomal recessive disorder resulting from a loss of the liver arginase isoform, arginase 1 (ARG1), which is the final step in the urea cycle for detoxifying ammonia. ARG1 deficiency leads to hyperargininemia, characterized by progressive neurological impairment, persistent growth retardation and infrequent episodes of hyperammonemia. Using the Cre/loxP-directed conditional gene knockout system, we generated an inducible Arg1-deficient mouse model by crossing “floxed” Arg1 mice with CreERT2 mice. The resulting mice (Arg-Cre) die about two weeks after tamoxifen administration regardless of the starting age of inducing the knockout. These treated mice were nearly devoid of Arg1 mRNA, protein and liver arginase activity, and exhibited symptoms of hyperammonemia. Plasma amino acid analysis revealed pronounced hyperargininemia and significant alterations in amino acid and guanidino compound metabolism, including increased citrulline and guanidinoacetic acid. Despite no alteration in ornithine levels, concentrations of other amino acids such as proline and the branched-chain amino acids were reduced. In summary, we have generated and characterized an inducible Arg1-deficient mouse model exhibiting several pathologic manifestations of hyperargininemia. This model should prove useful for exploring potential treatment options of ARG1 deficiency.

Exercise is beneficial for a variety of age-related disorders. However, the molecular mechanisms mediating the beneficial adaptations to exercise in older adults are not well understood. The aim of the current study was to utilize a dual approach to characterize the genetic and metabolic adaptive pathways altered by exercise in veteran athletes and age-matched untrained individuals. Two groups of 50–60 year old males: competitive cyclists (athletes, n = 9; VO2peak 59.1±5.2 ml·kg−1·min−1; peak aerobic power 383±39 W) and untrained, minimally active individuals (controls, n = 8; VO2peak 35.9±9.7 ml·kg−1·min−1; peak aerobic power 230±57 W) were examined. All participants completed an acute bout of submaximal endurance exercise, and blood and urine samples pre- and post-exercise were analyzed for gene expression and metabolic changes utilizing genome-wide DNA microarray analysis and NMR spectroscopy-based metabolomics, respectively. Our results indicate distinct differences in gene and metabolite expression involving energy metabolism, lipids, insulin signaling and cardiovascular function between the two groups. These findings may lead to new insights into beneficial signaling pathways of healthy aging and help identify surrogate markers for monitoring exercise and training load.

Abdominal aortic aneurysms (AAAs) are a chronic condition that often progress over years to produce a weakened aorta with increased susceptibility for rupture, and currently, there are no pharmacological treatments available to slow disease progression. AAA development has been characterized by increased expression of cyclooxygenase-2 (COX-2), and inactivation of COX-2 before disease initiation reduces AAA incidence in a mouse model of the disease. The current study determined the effectiveness of COX-2 inhibition on AAA progression when treatment was begun after initiation of the disease. COX-2 inhibitor treatment with celecoxib was initiated after angiotensin II-induced AAA formation in a strain of nonhyperlipidemic mice that we have previously identified as highly susceptible to AAA development. When analyzed at different time points during progression of the disease, celecoxib treatment significantly reduced the incidence and severity of AAAs. The celecoxib treatment also protected the mice from aortic rupture and death. The aneurysmal lesion displayed an altered smooth muscle cell (SMC) phenotype, whereas celecoxib treatment was associated with increased expression of differentiated SMC markers and reduced dedifferentiation marker expression during AAA progression. Maintenance of a differentiated SMC phenotype is associated with the effectiveness of COX-2 inhibition for limiting AAA progression in nonhyperlipidemic mice.

Abcg2/Bcrp and Abcb1a/Pgp are xenobiotic efflux transporters limiting substrate permeability in the gastrointestinal system and brain, and increasing renal and hepatic drug clearance. The systemic impact of Bcrp and Pgp ablation on metabolic homeostasis of endogenous substrates is incompletely understood. We performed untargeted metabolomics of cerebrospinal fluid (CSF) and plasma, transcriptomics of brain, liver and kidney from male Sprague Dawley rats (WT) and Bcrp/Pgp double knock-out (dKO) rats, and integrated metabolomic/transcriptomic analysis to identify putative substrates and perturbations in canonical metabolic pathways. A predictive Bayesian machine learning model was used to predict in silico those metabolites with greater substrate-like features for either transporters. The CSF and plasma levels of 169 metabolites, nutrients, signaling molecules, antioxidants and lipids were significantly altered in dKO rats, compared to WT rats. These metabolite changes suggested alterations in histidine, branched chain amino acid, purine and pyrimidine metabolism in the dKO rats. Levels of methylated and sulfated metabolites and some primary bile acids were increased in dKO CSF or plasma. Elevated uric acid levels appeared to be a primary driver of changes in purine and pyrimidine biosynthesis. Alterations in Bcrp/Pgp dKO CSF levels of antioxidants, precursors of neurotransmitters, and uric acid suggests the transporters may contribute to the regulation of a healthy central nervous system in rats. Microbiome-generated metabolites were found to be elevated in dKO rat plasma and CSF. The altered dKO metabolome appeared to cause compensatory transcriptional change in urate biosynthesis and response to lipopolysaccharide in brain, oxidation-reduction processes and response to oxidative stress and porphyrin biosynthesis in kidney, and circadian rhythm genes in liver. These findings present insight into endogenous functions of Bcrp and Pgp, the impact that transporter substrates, inhibitors or polymorphisms may have on metabolism, how transporter inhibition could rewire drug sensitivity indirectly through metabolic changes, and identify functional Bcrp biomarkers.

The effects of vitamin A and/or vitamin D deficiency were studied in an Arf −/− BcR-ABL acute lymphoblastic leukemia murine model. Vitamin D sufficient mice died earlier (p = 0.003) compared to vitamin D deficient (VDD) mice. Vitamin A deficient (VAD) mice fared worst with more rapid disease progression and decreased survival. Mice deficient for vitamins A and D (VADD) had disease progression similar to VAD mice. Regulatory T cells, previously shown to associate with poor BCR-ABL leukemia control, were present at higher frequencies among CD4 + splenocytes of vitamin A deficient vs. sufficient mice. In vitro studies demonstrated 1,25-dihydroxyvitamin D (1,25(OH) 2 VD 3) increased the number of BCR-ABL ALL cells only when co-cultured with bone marrow stroma. 1,25(OH) 2 VD 3 induced CXCL12 expression in vivo and in vitro in stromal cells and CXCL12 increased stromal migration and the number of BCR-ABL blasts. Vitamin D plus leukemia reprogrammed the marrow increasing production of collagens, potentially trapping ALL blasts. Vitamin A (all trans retinoic acid, ATRA) treated leukemic cells had increased apoptosis, decreased cells in S-phase, and increased cells in G 0 /G 1. ATRA signaled through the retinoid X receptor to decrease BCR-ABL leukemic cell viability. In conclusion, vitamin A and D deficiencies have opposing effects on mouse survival from BCR-ABL ALL. Vitamin D deficiency (VDD) affects an estimated 1 billion people in the world across all ethnicities and age groups 1-3. VDD is an independent risk factor for mortality in the general population 4 and almost 60% of children with malignant diseases have suboptimal vitamin D (VD 3) levels 5. Likewise, the world health organization (WHO) estimated 250 million preschool children are vitamin A deficient (VAD), and this increases the risk of disease and death from severe infections. VAD and VDD are not limited to developing countries. Rather, a recent study found that among 45 people tested in Memphis, TN for vitamin A and vitamin D levels, only two individuals had sufficient levels of both vitamins 6. Vitamin D is a fat-soluble vitamin that not only regulates calcium absorption and bone metabolism, but can also regulate cell proliferation, differentiation and the immune response. The biologically active form of vitamin D, 1,25(OH) 2 VD 3 , binds to the vitamin D receptor (VDR) that heterodimerizes with the retinoid X receptor (RXR). This complex then binds to VDR-RXR response elements in target genes to regulate transcription. VDR is highly expressed in intestine, kidney and bone, but also in normal and neoplastic hematopoietic cells and mesenchymal stem cells in bone marrow 7. 1,25(OH) 2 VD 3 can modify embryonic hematopoietic stem and progenitor cell production 8. 1,25(OH) 2 VD 3 inhibits proliferation of mouse and human myeloid leukemia cells 9 and stimulates myeloid cell differentiation into mature macrophages. Indeed, mice with acute myeloid leukemia (AML) when treated with analogs of 1,25(OH) 2 VD 3 survived longer than the untreated mice 10. Moreover, vitam...

Background: Previously, we showed that 6β-hydroxytestosterone (6β-OHT), a cytochrome P450 1B1 (CYP1B1)derived metabolite of testosterone, contributes to angiotensin II (Ang II)-induced hypertension in male mice. This study was conducted to test the hypothesis that 6β-OHT contributes to increased vascular reactivity, endothelial dysfunction, vascular hypertrophy, and reactive oxygen species production associated with Ang II-induced hypertension. Methods: Eight-to 10-week-old intact or castrated C57BL/6 J (Cyp1b1 +/+ and Cyp1b1 −/−) mice were anesthetized for implantation of a micro-osmotic pump which delivered Ang II (700 ng/kg/day) or saline for 14 days. Mice were injected with 6β-OHT (15 μg/g b.w every third day), flutamide (8 mg/kg every day), or its vehicle. Blood pressure was measured via tail-cuff. Vascular reactivity, endothelial-dependent and endothelial-independent vasodilation, media to lumen ratio, fibrosis by collagen deposition, and reactive oxygen species production by dihydroethidium staining were determined in the isolated thoracic aorta. Results: The response of thoracic aorta to phenylephrine and endothelin-1 was increased in Ang II-infused Cyp1b1 +/+ mice compared to intact Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice; these effects of Ang II were restored by treatment with 6β-OHT. Ang II infusion caused endothelial dysfunction, as indicated by decreased relaxation of the aorta to acetylcholine in Cyp1b1 +/+ but not Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice. 6β-OHT did not alter Ang II-induced endothelial dysfunction in Cyp1b1 +/+ mice but restored it in Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice. Ang II infusion increased media to lumen ratio and caused fibrosis and reactive oxygen species production in the aorta of Cyp1b1 +/+ mice. These effects were minimized in the aorta of Cyp1b1 −/− or castrated Cyp1b1 +/+ and Cyp1b1 −/− mice and restored by treatment with 6β-OHT. Treatment with the androgen receptor antagonist flutamide reduced blood pressure and vascular hypertrophy in castrated Ang IIinfused mice injected with 6β-OHT.

Background Sex is a prominent risk factor for abdominal aortic aneurysms (AAAs), and angiotensin II (Ang II) induces AAA formation to a greater degree in male than in female mice. We previously reported that cytochrome P450 1B1 contributes to the development of hypertension, as well as AAAs, in male mice. We also found that a cytochrome P450 1B1‐generated metabolite of testosterone, 6β‐hydroxytestosterone (6β‐OHT), contributes to Ang II‐induced hypertension and associated cardiovascular and renal pathogenesis in male mice. The current study was conducted to determine the contribution of 6β‐OHT to Ang II‐induced AAA development in Apoe –/– male mice. Methods and Results Intact or castrated Apoe –/– /Cyp1b1 +/+ and Apoe –/– /Cyp1b1 –/– male mice were infused with Ang II or its vehicle for 28 days, and administered 6β‐OHT every third day for the duration of the experiment. Abdominal aortas were then evaluated for development of AAAs. We observed a significant increase in the incidence and severity of AAAs in intact Ang II‐infused Apoe –/– /Cyp1b1 +/+ mice, compared with vehicle‐treated mice, which were minimized in castrated Apoe –/– /Cyp1b1 +/+ and intact Apoe –/– /Cyp1b1 –/– mice infused with Ang II. Treatment with 6β‐OHT significantly restored the incidence and severity of AAAs in Ang II‐infused castrated Apoe –/– /Cyp1b1 +/+ and intact Apoe –/– /Cyp1b1 –/– mice. However, administration of testosterone failed to increase AAA incidence and severity in Ang II‐infused intact Apoe –/– /Cyp1b1 –/– mice. Conclusions Our results indicate that the testosterone‐cytochrome P450 1B1‐generated metabolite 6β‐OHT contributes to Ang II‐induced AAA development in Apoe –/– male mice.

BackgroundWe have reported that cytochrome P450 1B1 (CYP1B1), expressed in cardiovascular tissues, contributes to angiotensin II–induced vascular smooth muscle cell (VSMC) migration and proliferation and development of hypertension in various experimental animal models via generation of reactive oxygen species. This study was conducted to determine the contribution of CYP1B1 to platelet‐derived growth factor‐BB–induced VSMC migration and proliferation in vitro and to neointimal growth in vivo.Methods and Results VSMCs isolated from aortas of male Cyp1b1 +/+ and Cyp1b1 −/− mice were used for in vitro experiments. Moreover, carotid arteries of Cyp1b1 +/+ and Cyp1b1 −/− mice were injured with a metal wire to assess neointimal growth after 14 days. Platelet‐derived growth factor‐BB–induced migration and proliferation and H2O2 production were found to be attenuated in VSMCs from Cyp1b1 −/− mice and in VSMCs of Cyp1b1 +/+ mice treated with 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl, a superoxide dismutase and catalase mimetic. In addition, wire injury resulted in neointimal growth, as indicated by increased intimal area, intima/media ratio, and percentage area of restenosis, as well as elastin disorganization and adventitial collagen deposition in carotid arteries of Cyp1b1 +/+ mice, which were minimized in Cyp1b1 −/− mice. Wire injury also increased infiltration of inflammatory and immune cells, as indicated by expression of CD68+ macrophages and CD3+ T cells, respectively, in the injured arteries of Cyp1b1 +/+ mice, but not Cyp1b1 −/− mice. Administration of 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl attenuated neointimal growth in wire‐injured carotid arteries of Cyp1b1 +/+ mice.ConclusionsThese data suggest that CYP1B1‐dependent oxidative stress contributes to the neointimal growth caused by wire injury of carotid arteries of male mice.