Frameshift Variant in AMPD2 in Cirneco dell'Etna Dogs with Retinopathy and Tremors.

While the manifestations of many inherited retinal disorders are limited to loss of vision, others are part of a syndrome that affects multiple tissues, particularly the nervous system. Most syndromic retinal disorders are thought to be recessively inherited. Two dogs out of a litter of Cirneco dell' Etna dogs, both males, showed signs of retinal degeneration, along with tremors and signs described as either atypical seizures or paroxysmal dyskinesias, while the other two male littermates were normal. We named this oculo-neurological syndrome CONS (Cirneco oculo-neurological syndrome), and undertook homozygosity mapping and whole-genome sequencing to determine its potential genetic etiology. Notably, we detected a 1-bp deletion in chromosome 6 that was predicted to cause a frameshift and premature stop codon within the canine AMPD2 gene, which encodes adenosine monophosphate deaminase, an enzyme that converts adenosine 5'-monophosphate (AMP) to inosine 5'-monophosphate (IMP). Genotyping of the available Cirneco population suggested perfect segregation between cases and controls for the variant. Moreover, this variant was absent in canine genomic databases comprised of thousands of unaffected dogs. The AMPD2 genetic variant we identified in dogs presents with retinal manifestations, adding to the spectrum of neurological manifestations associated with AMPD2 variants in humans.

AMP deaminase: A crucial regulator in nitrogen stress and lipid metabolism in Mucor circinelloides.

Lipid biosynthesis is a significant metabolic response to nitrogen starvation in oleaginous fungi. The oleaginous fungus Mucor circinelloides copes with nitrogen stress by degrading AMP through AMP deaminase (AMPD). However, the mechanism of AMPD in regulating lipogenesis remains largely unclear. To elucidate the mechanism of AMPD in lipid synthesis in this M. circinelloides, we identified two genes (ampd1 and ampd2) encoding AMPD and constructed an ampd double knockout mutant. The engineered M. circinelloides strain elevated cell growth and lipid accumulation, as well as the content of oleic acid (OA) and gamma-linolenic acid (GLA). In addition to the expected increase in transcription levels of genes associated with lipid and TAG synthesis, we observed suppression of lipid degradation and reduced amino acid biosynthesis. This suggested that the deletion of AMPD genes induces the redirection of carbon towards lipid synthesis pathways. Moreover, the pathways related to nitrogen metabolism, including nitrogen assimilation and purine metabolism (especially energy level), were also affected in order to maintain homeostasis. Further analysis discovered that the transcription factors (TFs) related to lipid accumulation were also regulated. This study provides new insights into lipid biosynthesis in M. circinelloides, indicating that the trigger for lipid accumulation is not entirely AMPD-dependent and suggest that there may be additional mechanisms involved in the initiation of lipogenesis.

Role of AMP Deaminase in Mucor circinelloides: Implications for Nitrogen Utilization and Lipid Biosynthesis.

Lipid accumulation in oleaginous organisms is initiated by AMP deaminase (AMPD) after nitrogen depletion because it mediates the concentration of intracellular adenosine monophosphate (AMP). However, the role of AMPD in lipogenesis in the oleaginous fungus Mucor circinelloides is largely unknown. Therefore, we identified the genes (ampd1 and ampd2) encoding AMPD and investigated the role of AMPD in lipid synthesis in this fungus by overexpressing and deleting ampd genes. Deletion of ampd1 and ampd2 caused 21 and 28% increments in lipid contents under N-limited conditions, respectively. These increases were correlated with the activation of enzymes involved in lipogenesis and the alteration of energy balance. Unexpectedly, overexpression of ampd genes affected nitrogen consumption in both N-limited and N-excess media, which resulted in an increase in cell growth and lipid accumulation compared with the control strain when nitrogen was available. Furthermore, the increased lipid accumulation in the ampd-overexpressing mutants in N-excess media was accompanied by enhanced activities of lipid biosynthetic enzymes. These data suggested that nitrogen metabolism and energy metabolism are affected by AMPD, and overexpression of ampd genes induced lipid accumulation under nitrogen-rich conditions by mimicking the nitrogen limitation response. This highlights an intriguing function of AMPD in M. circinelloides.

Erythrocyte ENT1-AMPD3 Axis is an Essential Purinergic Hypoxia Sensor and Energy Regulator Combating CKD in a Mouse Model.

SIGNIFICANCE STATEMENT: Hypoxia drives kidney damage and progression of CKD. Although erythrocytes respond rapidly to hypoxia, their role and the specific molecules sensing and responding to hypoxia in CKD remain unclear. In this study, we demonstrated in a mouse model that erythrocyte ENT1-AMPD3 is a master energy regulator of the intracellular purinergic hypoxic compensatory response that promotes rapid energy supply from extracellular adenosine, eAMPK-dependent metabolic reprogramming, and O 2 delivery, which combat renal hypoxia and progression of CKD. ENT1-AMPD3-AMPK-BPGM comprise a group of circulating erythroid-specific biomarkers, providing early diagnostic and novel therapeutic targets for CKD. BACKGROUND: Hypoxia drives kidney damage and progression of CKD. Although erythrocytes respond rapidly to hypoxia, their role and the specific molecules sensing and responding to hypoxia in CKD remain unclear. METHODS: Mice with an erythrocyte-specific deficiency in equilibrative nucleoside transporter 1 ( eEnt1-/- ) and a global deficiency in AMP deaminase 3 ( Ampd3-/- ) were generated to define their function in two independent CKD models, including angiotensin II (Ang II) infusion and unilateral ureteral obstruction (UUO). Unbiased metabolomics, isotopic adenosine flux, and various biochemical and cell culture analyses coupled with genetic studies were performed. Translational studies in patients with CKD and cultured human erythrocytes examined the role of ENT1 and AMPD3 in erythrocyte function and metabolism. RESULTS: eEnt1-/- mice display severe renal hypoxia, kidney damage, and fibrosis in both CKD models. The loss of eENT1-mediated adenosine uptake reduces intracellular AMP and thus abolishes the activation of AMPK α and bisphosphoglycerate mutase (BPGM). This results in reduced 2,3-bisphosphoglycerate and glutathione, leading to overwhelming oxidative stress in eEnt1-/- mice. Excess reactive oxygen species (ROS) activates AMPD3, resulting in metabolic reprogramming and reduced O 2 delivery, leading to severe renal hypoxia in eEnt1-/- mice. By contrast, genetic ablation of AMPD3 preserves the erythrocyte adenine nucleotide pool, inducing AMPK-BPGM activation, O 2 delivery, and antioxidative stress capacity, which protect against Ang II-induced renal hypoxia, damage, and CKD progression. Translational studies recapitulated the findings in mice. CONCLUSION: eENT1-AMPD3, two highly enriched erythrocyte purinergic components that sense hypoxia, promote eAMPK-BPGM-dependent metabolic reprogramming, O 2 delivery, energy supply, and antioxidative stress capacity, which mitigates renal hypoxia and CKD progression.

AMPD2 plays important roles in regulating hepatic glucose and lipid metabolism.

Dysregulation of hepatic glucose and lipid metabolism can instigate the onset of various metabolic disorders including obesity, dyslipidemia, insulin resistance, type 2 diabetes, and fatty liver disease. Adenosine monophosphate (AMP) deaminase (AMPD), which converts AMP to inosine monophosphate, plays a key role in maintaining adenylate energy charge. AMPD2 is the major isoform present in the liver. However, the mechanistic link between AMPD2 and hepatic glucose and lipid metabolism remains elusive. In this study, we probed into the hepatic glucose and lipid metabolism in AMPD2-deficient (A2-/-) mice. These mice exhibited reduced body weight, fat accumulation, and blood glucose levels, coupled with enhanced insulin sensitivity while maintaining consistent calorie intake and spontaneous motor activity compared with wild type mice. Furthermore, A2-/- mice showed mitigated obesity and hyper-insulinemia induced by high-fat diet (HFD) but elevated levels of the serum triglyceride and cholesterol. The hepatic mRNA levels of several fatty acid and cholesterol metabolism-related genes were altered in A2-/- mice. RNA sequencing unveiled multiple alterations in lipid metabolic pathways due to AMPD2 deficiency. These mice were also more susceptible to fasting or HFD-induced hepatic lipid accumulation. The liver exhibited elevated AMP levels but unaltered AMP/ATP ratio. In addition, AMPD2 deficiency is not associated with the adenosine production. In summary, this study established a link between purine metabolism and hepatic glucose and lipid metabolism via AMPD2, providing novel insights into these metabolic pathways.

Downregulation of extramitochondrial BCKDH and its uncoupling from AMP deaminase in type 2 diabetic OLETF rat hearts.

Systemic branched-chain amino acid (BCAA) metabolism is dysregulated in cardiometabolic diseases. We previously demonstrated that upregulated AMP deaminase 3 (AMPD3) impairs cardiac energetics in a rat model of obese type 2 diabetes, Otsuka Long-Evans-Tokushima fatty (OLETF). Here, we hypothesized that the cardiac BCAA levels and the activity of branched-chain α-keto acid dehydrogenase (BCKDH), a rate-limiting enzyme in BCAA metabolism, are altered by type 2 diabetes (T2DM), and that upregulated AMPD3 expression is involved in the alteration. Performing proteomic analysis combined with immunoblotting, we discovered that BCKDH localizes not only to mitochondria but also to the endoplasmic reticulum (ER), where it interacts with AMPD3. Knocking down AMPD3 in neonatal rat cardiomyocytes (NRCMs) increased BCKDH activity, suggesting that AMPD3 negatively regulates BCKDH. Compared with control rats (Long-Evans Tokushima Otsuka [LETO] rats), OLETF rats exhibited 49% higher cardiac BCAA levels and 49% lower BCKDH activity. In the cardiac ER of the OLETF rats, BCKDH-E1α subunit expression was downregulated, while AMPD3 expression was upregulated, resulting in an 80% lower AMPD3-E1α interaction compared to LETO rats. Knocking down E1α expression in NRCMs upregulated AMPD3 expression and recapitulated the imbalanced AMPD3-BCKDH expressions observed in OLETF rat hearts. E1α knockdown in NRCMs inhibited glucose oxidation in response to insulin, palmitate oxidation, and lipid droplet biogenesis under oleate loading. Collectively, these data revealed previously unrecognized extramitochondrial localization of BCKDH in the heart and its reciprocal regulation with AMPD3 and imbalanced AMPD3-BCKDH interactions in OLETF. Downregulation of BCKDH in cardiomyocytes induced profound metabolic changes that are observed in OLETF hearts, providing insight into mechanisms contributing to the development of diabetic cardiomyopathy.

Delineating the phenotype and genetic basis of AMPD2-related pontocerebellar hypoplasia.

Pontocerebellar hypoplasia is a group of disorders with a wide range of presentations. We describe here the genetic and phenotypic features of PCH type 9 due to mutations in AMPD2. All patients have severe intellectual disability, and the vast majority manifest abnormal tone, cortical blindness, and microcephaly. Almost all have agenesis of the corpus callosum and severe cerebellar hypoplasia. The course is not progressive, however, few die in the first decade of life. Mutations are spread throughout the gene, and no hot spot can be identified. One of the mutations we report here is the most distal truncating variant known in this gene and is predicted to result in a truncated protein. The phenotype is severe in all cases; thus, no clear genotype-phenotype correlation can be established.

Skeletal muscle contraction kinetics and AMPK responses are modulated by the adenine nucleotide degrading enzyme AMPD1.

AMP deaminase 1 (AMPD1; AMP → IMP + NH3) deficiency in skeletal muscle results in an inordinate accumulation of AMP during strenuous exercise, with some but not all studies reporting premature fatigue and reduced work capacity. To further explore these inconsistencies, we investigated the extent to which AMPD1 deficiency impacts skeletal muscle contractile function of different muscles and the [AMP]/AMPK responses to different intensities of fatiguing contractions. To reduce AMPD1 protein, we electroporated either an inhibitory AMPD1-specific miRNA encoding plasmid or a control plasmid, into contralateral EDL and SOL muscles of C57BL/6J mice (n = 48 males, 24 females). After 10 days, isolated muscles were assessed for isometric twitch, tetanic, and repeated fatiguing contraction characteristics using one of four (None, LOW, MOD, and HIGH) duty cycles. AMPD1 knockdown (∼35%) had no effect on twitch force or twitch contraction/relaxation kinetics. However, during maximal tetanic contractions, AMPD1 knockdown impaired both time-to-peak tension (TPT) and half-relaxation time (½ RT) in EDL, but not SOL muscle. In addition, AMPD1 knockdown in EDL exaggerated the AMP response to contractions at LOW (+100%) and MOD (+54%) duty cycles, but not at HIGH duty cycle. This accumulation of AMP was accompanied by increased AMPK phosphorylation (Thr-172; LOW +25%, MOD +34%) and downstream substrate phosphorylation (LOW +15%, MOD +17%). These responses to AMPD1 knockdown were not different between males and females. Our findings demonstrate that AMPD1 plays a role in maintaining skeletal muscle contractile function and regulating the energetic responses associated with repeated contractions in a muscle- but not sex-specific manner.NEW & NOTEWORTHY AMP deaminase 1 (AMPD1) deficiency has been associated with premature muscle fatigue and reduced work capacity, but this finding has been inconsistent. Herein, we report that although AMPD1 knockdown in mouse skeletal muscle does not change maximal isometric force, it negatively impacts muscle function by slowing contraction and relaxation kinetics in EDL muscle but not SOL muscle. Furthermore, AMPD1 knockdown differentially affects the [AMP]/AMPK responses to fatiguing contractions in an intensity-dependent manner in EDL muscle.

Down-regulation of AMPD3 Is Associated With Poor Survival in Head and Neck Squamous Cell Carcinoma.

BACKGROUND: Adenosine monophosphate deaminase 3 (AMPD3) is an isoenzyme involved in the regulation of the energetic metabolism of mammalian cells. Cancer cells have a high demand for their energy supply. This experimental study aimed to illustrate the role of AMPD3 in human head and neck squamous cell carcinoma (HNSCC). MATERIALS AND METHODS: Real-time quantitative reverse transcription-polymerase chain reaction was used to investigate the expression of the AMPD3 gene in human HNSCC tissues to assess the changes in cancerous and noncancerous parts and the correlation with different tumor behavior. The functions of AMPD3 were investigated using wound-healing and migration assays. RESULTS: AMPD3 was significantly down-regulated in cancerous tissues of HNSCC (p=0.001) and this was correlated with more advanced tumor and clinical stages. Patients with high expression had better 5-year survival. AMPD3 knock-down in SCC-4 and SCC-25 cells demonstrated reduction of proliferation but increased migration and invasion. CONCLUSION: To our knowledge, this is the first report evidencing the expression pattern of AMPD3 in HNSCC and demonstrated that high AMPD3 expression might represent a good prognostic biomarker. AMPD3 may have an antiproliferative potential but its down-regulation may not contribute to reducing the migration and invasion of HNSCC cells.

Rare variants in previously identified linkage regions associated with carotid plaque in Dominican Republic families.

Carotid plaque is a subclinical measure of atherosclerosis. We have previously shown measures of carotid plaque to be heritable in a sample of 100 Dominican families and found evidence for linkage and association of common variants (CVs) on 7q36, 11p15, 14q32 and 15q23 with plaque presence. Our current study aimed to refine these regions further and identify rare variants (RVs) influencing plaque presence. Therefore, we performed targeted sequencing of the one LOD unit down region on 7q36, 11p15, 14q32 and 15q23 in 12 Dominican families with evidence for linkage to plaque presence. Gene-based RV analyses were performed using the Sequence Association Test for familial data (F-SKAT) under two filtering algorithms; 1. all exonic RVs and 2. non-synonymous RVs. Replication analyses were performed using a sample of 22 Dominican families and 556 unrelated Dominicans with Exome Array data. To identify additional non-synonymous RVs influencing plaque, we looked for co-segregation of RVs with plaque in each of the sequenced families. Our most strongly associated gene with evidence for replication was AMPD3 which showed suggestive association with plaque presence in the sequenced families (exonic RV p = 0.003, nonsynonymous RV p = 0.005) and replication families (exonic RV p = 0.04, nonsynonymous RV p = 0.02). Examination of the sequenced family pedigrees revealed two missense variants on chromosome 11 which co-segregated with plaque presence in one of our families; rs61751342 (located in DENND2B), and rs61760882 (located in RNF141). The rs61751342 missense variant is an eQTL for SCUBE2 in the atrial appendage. Notably, SCUBE2 encodes a protein which interacts with vascular endothelial growth factor (VEGF) receptor 2 to regulate VEGF-induced angiogenesis, thus providing biologic plausibility for this gene in atherosclerosis. In conclusion, using targeted sequencing of previously-identified linkage regions, we have identified suggestive evidence for the role of RVs in carotid plaque pathogenesis.

AMP deamination is sufficient to replicate an atrophy-like metabolic phenotype in skeletal muscle.

BACKGROUND: Skeletal muscle atrophy, whether caused by chronic disease, acute critical illness, disuse or aging, is characterized by tissue-specific decrease in oxidative capacity and broad alterations in metabolism that contribute to functional decline. However, the underlying mechanisms responsible for these metabolic changes are largely unknown. One of the most highly upregulated genes in atrophic muscle is AMP deaminase 3 (AMPD3: AMP → IMP + NH3), which controls the content of intracellular adenine nucleotides (AdN; ATP + ADP + AMP). Given the central role of AdN in signaling mitochondrial gene expression and directly regulating metabolism, we hypothesized that overexpressing AMPD3 in muscle cells would be sufficient to alter their metabolic phenotype similar to that of atrophic muscle. METHODS: AMPD3 and GFP (control) were overexpressed in mouse tibialis anterior (TA) muscles via plasmid electroporation and in C2C12 myotubes using adenovirus vectors. TA muscles were excised one week later, and AdN were quantified by UPLC. In myotubes, targeted measures of AdN, AMPK/PGC-1α/mitochondrial protein synthesis rates, unbiased metabolomics, and transcriptomics by RNA sequencing were measured after 24 h of AMPD3 overexpression. Media metabolites were measured as an indicator of net metabolic flux. At 48 h, the AMPK/PGC-1α/mitochondrial protein synthesis rates, and myotube respiratory function/capacity were measured. RESULTS: TA muscles overexpressing AMPD3 had significantly less ATP than contralateral controls (-25%). In myotubes, increasing AMPD3 expression for 24 h was sufficient to significantly decrease ATP concentrations (-16%), increase IMP, and increase efflux of IMP catabolites into the culture media, without decreasing the ATP/ADP or ATP/AMP ratios. When myotubes were treated with dinitrophenol (mitochondrial uncoupler), AMPD3 overexpression blunted decreases in ATP/ADP and ATP/AMP ratios but exacerbated AdN degradation. As such, pAMPK/AMPK, pACC/ACC, and phosphorylation of AMPK substrates, were unchanged by AMPD3 at this timepoint. AMPD3 significantly altered 191 out of 639 detected intracellular metabolites, but only 30 transcripts, none of which encoded metabolic enzymes. The most altered metabolites were those within purine nucleotide, BCAA, glycolysis, and ceramide metabolic pathways. After 48 h, AMPD3 overexpression significantly reduced pAMPK/AMPK (-24%), phosphorylation of AMPK substrates (-14%), and PGC-1α protein (-22%). Moreover, AMPD3 significantly reduced myotube mitochondrial protein synthesis rates (-55%), basal ATP synthase-dependent (-13%), and maximal uncoupled oxygen consumption (-15%). CONCLUSIONS: Increased expression of AMPD3 significantly decreased mitochondrial protein synthesis rates and broadly altered cellular metabolites in a manner similar to that of atrophic muscle. Importantly, the changes in metabolites occurred prior to reductions in AMPK signaling, gene expression, and mitochondrial protein synthesis, suggesting metabolism is not dependent on reductions in oxidative capacity, but may be consequence of increased AMP deamination. Therefore, AMP deamination in skeletal muscle may be a mechanism that alters the metabolic phenotype of skeletal muscle during atrophy and could be a target to improve muscle function during muscle wasting.

Multiple gene integration to promote erythritol production on glycerol in Yarrowia lipolytica.

OBJECTIVE: Erythritol (1,2,3,4-butanetetrol) is a 4-carbon sugar alcohol that occurs in nature as a metabolite or storage compound. In this study, a multiple gene integration strategy was employed to enhance erythritol production in Y. lipolytica. RESULTS: The effects on the production of erythritol in Y. lipolytica of seven key genes involved in the erythritol synthesis pathway were evaluated individually, among which transketolase (TKL1) and transaldolase (TAL1) showed important roles in enhancing erythritol production. The combined overexpression of four genes (GUT1, TPI1, TKL1, TAL1) and disruption of the EYD1 gene (encoding erythritol dehydrogenase), resulted in produce approximately 40 g/L erythritol production from glycerol. Further enhanced erythritol synthesis was obtained by overexpressing the RKI1 gene (encoding ribose 5-phosphate isomerase) and the AMPD gene (encoding AMP deaminase), indicating for the first time that these two genes are also related to the enhancement of erythritol production in Y. lipolytica. CONCLUSIONS: A combined gene overexpression strategy was developed to efficiently improve the production of erythritol in Y. lipolytica, suggesting a great capacity and promising potential of this non-conventional yeast in converting glycerol into erythritol.

A functional mutation in the AMPD1 promoter region affects promoter activity and breast meat freshness in chicken.

Freshness is an important index to determine the quality deterioration (protein degradation and changes in appearance) of chilled chicken meat and is a primary consideration of consumers. Adenosine monophosphate deaminase 1 (AMPD1) catalyzes the deamination of adenosine monophosphate to inosine monophosphate in skeletal muscle and is the rate-limiting step in the purine nucleotide cycle. Inosine monophosphate is regarded as an important indicator of meat freshness in chicken. This study investigated the association of polymorphisms in the chicken AMPD1 promoter region with meat freshness during freezing storage. An SNP (c. -905G>A) was found to be associated with the freshness (K-value) of chicken breast meat. Chickens with the AA genotype had significantly lower K-values than those with GG and AG genotypes (P < 0.01). Individuals with the AA genotype also had higher breast meat AMPD1 mRNA levels than did those with the GG and AG genotypes (P < 0.01, P < 0.05). A luciferase assay revealed that genotype AA had greater transcriptional activity than genotype GG. Transcription factor binding site analysis identified distinct putative transcription factor binding sites in the two alleles of mutation site c. -905. In summary, we identified an SNP (c. -905G>A) in the promoter region of the AMPD1 gene that may modulate the binding affinity of different transcription factors to control AMPD1 expression and affect the freshness K-value of chicken meat.

Adenosine monophosphate deaminase 3 null mutation causes reduction of naive T cells in mouse peripheral blood.

Adenosine monophosphate deaminase 3 (Ampd3) encodes the erythrocyte isoform of the adenosine monophosphate (AMP) deaminase gene family. Mutations in this gene have been reported in humans, leading to autosomal-recessive erythrocyte AMP deaminase deficiency. However, the mutation is considered clinically asymptomatic. Using N-ethyl-N-nitrosourea mutagenesis to find mutations that affect peripheral lymphocyte populations, we identified 5 Ampd3 mutations (Ampd3guangdong, Ampd3carson, Ampd3penasco, Ampd3taos, and Ampd3commanche) that strongly correlated with a reduction in naive CD4+ T and naive CD8+ T-cell populations. Causation was confirmed by targeted ablation of Ampd3. Knockout mice had reduced frequencies of CD62LhiCD44lo CD4+ naive and CD8+ naive T cells. Interestingly, these phenotypes were restricted to T cells circulating in peripheral blood and were not seen in T cells from secondary lymphoid organs (lymph nodes and spleen). We found that reduction of naive T cells in the peripheral blood of Ampd3-/- mice was caused by T-cell-extrinsic factor(s), which we hypothesize to be elevated levels of adenosine triphosphate released by Ampd3-deficient erythrocytes. These findings provide an example in which disruption of an erythrocyte-specific protein can affect the physiological status of lymphocytes in peripheral blood.

Genetic investigation of purine nucleotide imbalance in Saccharomyces cerevisiae.

Because metabolism is a complex balanced process involving multiple enzymes, understanding how organisms compensate for transient or permanent metabolic imbalance is a challenging task that can be more easily achieved in simpler unicellular organisms. The metabolic balance results not only from the combination of individual enzymatic properties, regulation of enzyme abundance, but also from the architecture of the metabolic network offering multiple interconversion alternatives. Although metabolic networks are generally highly resilient to perturbations, metabolic imbalance resulting from enzymatic defect and specific environmental conditions can be designed experimentally and studied. Starting with a double amd1 aah1 mutant that severely and conditionally affects yeast growth, we carefully characterized the metabolic shuffle associated with this defect. We established that the GTP decrease resulting in an adenylic/guanylic nucleotide imbalance was responsible for the growth defect. Identification of several gene dosage suppressors revealed that TAT1, encoding an amino acid transporter, is a robust suppressor of the amd1 aah1 growth defect. We show that TAT1 suppression occurs through replenishment of the GTP pool in a process requiring the histidine biosynthesis pathway. Importantly, we establish that a tat1 mutant exhibits synthetic sickness when combined with an amd1 mutant and that both components of this synthetic phenotype can be suppressed by specific gene dosage suppressors. Together our data point to a strong phenotypic connection between amino acid uptake and GTP synthesis, a connection that could open perspectives for future treatment of related human defects, previously reported as etiologically highly conserved.

Valine acts as a nutritional signal in brain to activate TORC1 and attenuate postprandial ammonia-N excretion in Chinese perch (Siniperca chuatsi).

An emerging concept is that the hypothalamic nutrient sensor can regulate peripheral energy metabolism via a brain-liver circuit. Valine is an essential branched-chain amino acid (BCAA) that drives intracellular signaling cascades by the activation of target of rapamycin complex 1 (TORC1) which is critical to protein metabolism in mammals. However, in teleost fish, it remains scarce in this area especially about how the intraventricular (ICV) injection of valine can mediate the protein metabolism in peripheral organs. This study would tentatively explore the effects of ICV injection of valine on protein metabolism in peripheral organs through evaluating the postprandial ammonia-N excretion rate in Chinese perch. The control group was injected with 5-µL PBS, and the Val group was injected with 20-µg L valine dissolved into 5-µL PBS. The ammonia-N excretion rate of Val group was lower than control group at 4-, 12-, and 24-h postinjection, while the concertation of plasma glucose was increased sharply at 0.5-, 4-, 12-, and 24-h postinjection. We further checked both mRNA level and the enzyme activity of glutamate dehydrogenase (GDH) in the liver and adenosine monophosphate deaminase (AMPD) in muscle, and we found that they were obviously decreased in Val group at 4-, 12-, and 24-h postinjection. The phosphorylation level of ribosomal protein S6, a downstream target protein of TORC1, was markedly enhanced in the liver of Val group at 4-, 12-, and 24-h postinjection. Collectively, these results illustrated that ICV injection of valine can attenuate protein degradation in peripheral organs by depressing the GDH and AMPD enzyme activity; on the other hand, the injected valine can trigger the activation of TORC1 in the liver via a brain-liver circuit and then interdict proteolysis.

Super-enhancer-driven metabolic reprogramming promotes cystogenesis in autosomal dominant polycystic kidney disease.

Metabolic reprogramming is emerging as a key pathological contributor to the progression of autosomal dominant polycystic kidney disease (ADPKD), but the molecular mechanisms underlying dysregulated cellular metabolism in cystic cells remain elusive. Super-enhancers (SEs) are large clusters of transcriptional enhancers that drive robust expression of cell identity and disease genes. Here, we show that SEs undergo extensive remodelling during cystogenesis and that SE-associated transcripts are most enriched for metabolic processes in cystic cells. Inhibition of cyclin-dependent kinase 7 (CDK7), a transcriptional kinase required for assembly and maintenance of SEs, or AMP deaminase 3 (AMPD3), one of the SE-driven and CDK7-controlled metabolic target genes, delays cyst growth in ADPKD mouse models. In a cohort of people with ADPKD, CDK7 expression was frequently elevated, and its expression was correlated with AMPD3 expression and disease severity. Together, our findings elucidate a mechanism by which SE controls transcription of metabolic genes during cystogenesis, and identify SE-driven metabolic reprogramming as a promising therapeutic target for ADPKD treatment.

Genotype scores in energy and iron-metabolising genes are higher in elite endurance athletes than in nonathlete controls.

Information about the association of energy and iron-metabolising genes with endurance performance is scarce. The objective of this investigation was to compare the frequencies of polymorphic variations of genes involved in energy generation and iron metabolism in elite endurance athletes versus nonathlete controls. Genotype frequencies in 123 male elite endurance athletes (75 professional road cyclists and 48 elite endurance runners) and 122 male nonathlete participants were compared by assessing 4 genetic polymorphisms: AMPD1 c.34C/T (rs17602729), PPARGC1A c.1444G/A (rs8192678) HFEH63D c.187C/G (rs1799945) and HFEC282Y c.845G/A (rs1800562). A weighted genotype score (w-TGS; from 0 to 100 arbitrary units (a.u.)) was calculated by assigning a corresponding weight to each polymorphism. In the nonathlete population, the mean w-TGS value was lower (39.962 ± 14.654 a.u.) than in the group of elite endurance athletes (53.344 ± 17.053 a.u). The binary logistic regression analysis showed that participants with a w-TGS > 38.975 a.u had an odds ratio of 1.481 (95% confidence interval: 1.244-1.762; p < 0.001) for achieving elite athlete status. The genotypic distribution of polymorphic variations involved in energy generation and iron metabolism was different in elite endurance athletes vs. controls. Thus, an optimal genetic profile in these genes might contribute to physical endurance in athlete status. Novelty Genetic profile in energy generation and iron-metabolising genes in elite endurance athletes is different than that of nonathletes. There is an implication of an "optimal" genetic profile in the selected genes favouring endurance sporting performance.

AMPD1 C34T Polymorphism (rs17602729) Is Not Associated with Post-Exercise Changes of Body Weight, Body Composition, and Biochemical Parameters in Caucasian Females.

Background: The C34T polymorphism (rs 17602729) in adenosine monophosphate deaminase 1 gene (AMPD1) is associated with muscular energy metabolism in exercise. However, the role of its potential modifying impact on exercise-induced changes in obesity related parameters is unknown. The aim of the study was to determine if the C34T polymorphism influences the effects of an exercise training. METHODS: This study examines a group of one hundred and sixty-eight, young, non-obese Caucasian women in Poland who took part in a 12-week aerobic training program to determine the impact of allele and genotype distribution on training outcomes. RESULTS: A two-way analysis of variance ANOVA was conducted assuming a dominant model by pooling rare homozygotes and heterozygotes (TT + CT, n = 79) and comparing against common homozygotes (CC, n = 89). Our results showed that the AMPD1 C34T polymorphism was not related with selected parameters in study group. After completing the 12-week training program, a wide array of parameters (body mass, body mass index, fat mass, free fat mass, total body water) were significantly changed in the study participants with the exception of AMPD1 genotypes, among whom no significant changes were observed. CONCLUSIONS: The results did not confirm that harboring the rs 17602729 T allele influences the effects of the training program.