Unconventional metabolites in chromatin regulation

Chromatin, the complex of DNA and histone proteins, serves as a main integrator of cellular signals. Increasing evidence links cellular functional to chromatin state. Indeed, different metabolites are emerging as modulators of chromatin function and structure. Alterations in chromatin state are decisive for regulating all aspects of genome function and ultimately have the potential to produce phenotypic changes. Several metabolites such as acetyl-CoA, S-adenosyl methionine (SAM) or adenosine triphosphate (ATP) have now been well characterized as main substrates or cofactors of chromatin modifying enzymes. However, there are other metabolites that can directly interact with chromatin influencing its state or that modulate the properties of chromatin regulatory factors. Also, there is a growing list of atypical enzymatic and non-enzymatic chromatin modifications that originate from different cellular pathways that have not been in the limelight of chromatin research. Here, we summarize different properties and functions of uncommon regulatory molecules originating from intermediate metabolism of lipids, carbohydrates and amino acids. Based on the various modes of action on chromatin and the plethora of putative, so far not described chromatin regulating metabolites, we propose that there are more links between cellular functional state and chromatin regulation to be discovered. We hypothesize that these connections could provide interesting starting points for interfering with cellular epigenetic states at a molecular level.

CYP2D6 phenotype and ABCB1 haplotypes are associated with antipsychotic safety in adolescents experiencing acute psychotic episodes

Objectives To identify possible associations of CYP2D6, CYP3A4/5, and ABCB1 gene polymorphisms with the efficacy and safety of antipsychotics in adolescents with acute psychotic episodes. Methods We examined the associations of pharmacogenetic factors with the efficacy and safety of antipsychotics in 101 adolescents with acute psychotic episodes. The diagnosis on admission was “Brief psychotic disorder” (F23.0–23.9 by ICD-10). All patients were administered antipsychotics for 14 days. Treatment efficacy and safety were assessed using the PANSS, CGAS, CGI-S(I), UKU SERS, BARS, and SAS scales. Pharmacokinetic genotyping was performed for the CYP2D6*4, *10, ABCB1 1236C>T, 2677G>T, and 3435C>T genes. Results CYP2D6 intermediate metabolisers had “Micturition disturbances” more often than extensive metabolisers (24.2 vs. 7.4%; p=0.026). “Wild” homozygote ABCB1 3435C>T CC was associated with more prominent akathisia. Haplotype analysis of three ABCB1 polymorphisms revealed that the “wild” alleles “C-G-C” (ABCB1 1236-2677-3435) were associated with higher risk of “Reduced salivation” (OR=2.95; 95% CI=1.35–6.45; p=0.0078). Conclusions CYP2D6 intermediate metabolism was associated with the risk of urinary difficulties under treatment with antipsychotics. We found that “wild” homozygotes ABCB1 1236C>T, 2677G>T, and 3435C>T were predictors of adverse drug effects caused by treatment with antipsychotics.

2,3,7,8–Tetrachlorodibenzo-p-dioxin elicited decreases in cobalamin inhibits methylmalonyl–CoA mutase activity redirecting propionyl–CoA metabolism to the β–oxidation–like pathway resulting in hepatic accumulation of the toxic intermediate acrylyl–CoA

2,3,7,8 –Tetrachlorodibenzo –p –dioxin (TCDD) is a persistent environmental contaminant and the prototypical ligand for the aryl hydrocarbon receptor (AhR). AhR mediates the effects of TCDD and related compounds, including the reprograming of intermediate metabolism. Untargeted metabolomics analysis of hepatic extracts prepared from mice orally gavaged with TCDD every 4 days for 28 days identified the dose –dependent induction of acrylyl –CoA, a highly reactive toxic intermediate produced during the metabolism of propionyl –CoA in the cobalamin (Cbl) –independent β –oxidation –like pathway. Acrylyl –CoA is a biomarker of inborn errors of metabolism associated with propionic and methylmalonic acidemia associated with Cbl deficiency, transport and/or defects in Cbl –dependent methylmalonyl –CoA mutase (MUT). Although TCDD repressed gene expression for both the canonical Cbl –dependent carboxylase and the alternate Cbl –independent β –oxidation –like pathways, inhibition occurred only at 30 μg/kg TCDD while acrylyl –CoA levels increased at ~3 μg/kg. In contrast, TCDD decreased serum Cbl and hepatic cobalt levels at ~3 μg/kg TCDD consistent with the dose –dependent increase in acrylyl –CoA levels. TCDD elicited negligible effects on the expression of genes associated with Cbl absorption, transport, trafficking and derivatization to 5 –deoxy –adenosylcobalamin (AdoCbl), the required MUT cofactor. In addition, TCDD induced the decarboxylation of cis –aconitate to itaconate by Acod1. Itaconate can then be activated to itaconyl –CoA, a MUT suicide inactivator that forms an adduct with AdoCbl, blocking MUT activity and reducing Cbl levels. Collectively, these results suggest MUT activity was impaired due to Cbl depletion by TCDD causing propionyl –CoA metabolism to be redirected to the alternate Cbl –independent β –oxidation –like pathway resulting in hepatic acrylyl –CoA accumulation.

Lysine and Methionine Supplementation for Dairy Calves Is More Accurate through the Liquid than the Solid Diet

This study aimed to evaluate the performance and metabolic changes in dairy calves supplemented with lysine and methionine in milk replacer (MR) or starter concentrate (SC). Male Holstein calves (n = 45) were blocked and distributed in Control without supplementation (1) and; Lysine and Methionine supplementation to achieve an intake of 17 and 5.3 g/d in the SC (2) and to achieve of 17 and 5.3 g/d in the MR (3). MR was fed (6 L/d) until the 8th week of life when weaning occurred. Calves were followed until the 10th week of age. Feed intake was measured daily. Weight and body measurements were registered weekly. Blood samples were collected biweekly to evaluate the intermediate metabolism. The AA supplementation resulted in lower body weight at weaning and week 10. Calves fed SC Lys:Met had lower SC intake and lower total feed intake at weaning when compared to control. Calves fed control had higher heart girth, hip-width, and plasma glucose concentration. The supplementation with Lys and Met did not benefit dairy calves’ performance nor metabolism in this study. Supplementation through the MR was more efficient than SC to result in adequate daily intakes of AA. Further studies are needed to understand the negative effects of AA on calf starter intake.

Freedom of assembly: metabolic enzymes come together

Many different enzymes in intermediate metabolism dynamically assemble filamentous polymers in cells, often in response to changes in physiological conditions. Most of the enzyme filaments known to date have only been observed in cells, but in a handful of cases structural and biochemical studies have revealed the mechanisms and consequences of assembly. In general, enzyme polymerization functions as a mechanism to allosterically tune enzyme kinetics, and it may play a physiological role in integrating metabolic signaling. Here, we highlight some principles of metabolic filaments by focusing on two well-studied examples in nucleotide biosynthesis pathways—inosine-5’-monophosphate (IMP) dehydrogenase and cytosine triphosphate (CTP) synthase.

Pharmacogenomics: Personalizing palliative pharmacotherapy.

126 Background: Pharmacogenomics (PGx) is a developing field in individualized medicine concerned with understanding genetic polymorphisms that may explain inter-individual variation in drug efficacy and toxicity. Understanding these polymorphisms is a key tool in guiding clinician’s selection and dosing of specific medications to optimally manage patient symptoms. Common pharmacogenes that impact analgesic prescribing include: CYP2D6, OPRM1, and COMT; for mood disorders: CYP2C19. This cross-sectional study explored the activity of pharmacogenes of clinical significance in palliative medicine with either Level 1 or 2 evidence. Methods: We performed PGx testing on 50 new referrals to the palliative medicine clinic with an active malignancy. Each patient underwent PGx testing with clinical pharmacist review and interpretation prior to their initial office appointment. Results: In our cohort 54% were men and the mean age was 64.7 (24-87). The average number of medications, medication allergies, and creatinine clearance were 10.5 (1-22), 1.3 (0-13), and 78.4 (31-120), respectively. Among the pharmacogenes impacting opiate and antiemetic prescribing, 14% (7/50) of patients were poor metabolizers of CYP2D6 and 8% (4/50) were rapid or ultra-rapid metabolizers. Another 60% (30/50) showed intermediate metabolism which would impact initial dosing. Poor metabolism of COMT or OPRM1 was seen in 8% (4/50) with another 36% (18/50) demonstrating rapid metabolism. Activity for the pharmacogene CYP2C19, which impacts many psychotropics, revealed 32% (16/50) rapid or ultra-rapid metabolizers and no poor metabolizers. Overall, 66% (33/50) of patients had pharmacogene activity suggestive of significant clinical impact necessitating either drug avoidance due to toxicity risks or substantial dose adjustment to be efficacious. Conclusions: Polymorphisms impacting pharmacotherapy were common in our cohort. Patients with difficult-to-control symptoms or multiple medication toxicities can utilize PGx testing as a guide to symptom relief. As PGx technology becomes readily accessible and economical, opportunities for patients to have precision genomic information guide healthcare decisions is expected to increase.