Expression of 5-methylcytosine and 5-hydroxymethylcytosine in bone tissue of rats with different types of skeletal fluorosis / 中华地方病学杂志

Objective:To learn about the levels of 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in bone tissue of rats with different types of skeletal fluorosis and analyze their correlation.Methods:Thirty 4-week-old SPF grade healthy SD rats were selected. After adaptive feeding for 1 week, the rats were divided into control group (4 ml·kg -1·bw deionized water + standard maintenance diet), osteosclerosis group [20 mg·kg -1·bw sodium fluoride (NaF) + standard maintenance diet], and osteoporosis/osteomalacia group (20 mg·kg -1·bw NaF + low-calcium and low-protein partial diet) according to their body weight (100 - 120 g) by random number table method, with 10 rats in each group, half male and half female; gavaged 6 days each week and the experimental period was 5 months. At the end of the experiment, samples of rat heart blood and lower limb femur were collected. The contents of serum methyl donor S-adenosylmethionine (SAM) and its metabolite S-adenosylhomocysteine (SAH) in serum, and the levels of 5-mC and 5-hmC in bone tissue were measured by enzyme-linked immunosorbent assay (ELISA). Western blot was used to determine the expression of DNA methyltransferase (DNMTs) and DNA hydroxymethylase (TETs) in bone tissue of rats. The correlation between serum SAM content, SAM/SAH ratio and bone tissue 5-mC level, and between the bone tissue 5-mC level and 5-hmC level was analyzed. Results:Serum SAM [11.03 (7.06, 18.63), 3.96 (2.32, 9.09), 3.91 (2.35, 4.46) nmol/L], SAH content [(4.69 ± 0.55), (5.41 ± 1.13), (13.90 ± 1.09) ng/L], SAM/SAH ratio [2.58 (1.54, 4.12), 0.62 (0.52, 1.69), 0.14 (0.13, 0.15)] and bone tissue 5-mC [103.39 (97.37, 109.35), 52.50 (50.19, 68.13), 55.03 (49.97, 59.57) ng/L], 5-hmC levels [(32.61 ± 8.84), (56.96 ± 8.48), (20.34 ± 6.22) ng/L] in the control group, osteosclerosis group and osteoporosis/osteomalacia group were compared, and the differences were statistically significant beween three groups ( H/ F = 12.81, 284.24, 21.85, 19.37, 55.23, P < 0.01). Compared with the control group, the content of SAM, the ratio of SAM/SAH, the level of 5-mC in the osteosclerosis group and osteoporosis/osteomalacia group, and the level of 5-hmC in the osteoporosis/osteomalacia group were lower ( P < 0.05), while the content of SAH in the osteoporosis/osteomalacia group and the level of 5-hmC in the osteosclerosis group were higher ( P < 0.05). Compared with the osteosclerosis group, the content of SAH in the osteoporosis/osteomalacia group was higher, while the ratio of SAM/SAH and the level of 5-hmC were lower ( P < 0.05). Western blot showed that there were statistically significant differences in the expression levels of DNMT1, DNMT3A, DNMT3B, TET1 and TET2 protein in bone tissue of rats in the control group, osteosclerosis group, and osteoporosis/osteomalacia group ( F = 285.45, 345.58, 239.83, 311.52, 318.24, P < 0.001). Among them, the expression levels of DNMT1, DNMT3A and DNMT3B protein in the osteosclerosis group and osteoporosis/osteomalacia group were lower than those in the control group, and the expression levels of DNMT1, DNMT3A and DNMT3B protein in the osteosclerosis/osteomalacia group were lower than those in the osteosclerosis group ( P < 0.05); the expression levels of TET1 and TET2 protein in osteosclerosis group were higher than those in the control group and osteoporosis/osteomalacia group, and the expression levels of TET1 and TET2 protein in the osteoporosis/osteomalacia group were lower than those in the control group ( P < 0.05). The results of Spearman rank correlation analysis showed that the content of SAM and the ratio of SAM/SAH in the control group, osteosclerosis group and osteoporosis/osteomalacia group were positively correlated with the level of 5-mC in bone tissue ( rs = 0.89, 0.92, 0.81, 0.73, 0.87, 0.73, P < 0.05). The levels of 5-mC and 5-hmC in bone tissue of rats in each group were negatively correlated ( rs = - 0.69, - 0.68, - 0.72, P < 0.05). Conclusions:The level of 5-mC in bone tissue of osteosclerotic fluorosis rats is low, and the level of 5-hmC is high, while those of osteoporosis/osteomalacia fluorosis rats are lower. The difference of 5-mC level in bone tissue of rats with different types of skeletal fluorosis is not significant, which may be related to the difference of 5-hmC level in bone tissue.

Distribution of 5-methylcytosine and 5-hydroxymethylcytosine in bovine fetal tissue of the placenta / Distribuição de 5-metilcitosina e 5-hidroximetilcitosina em placenta fetal bovina

5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) are modified cytosines found in mammals that are involved in the regulation of gene expression. The aim of this study was to characterize the global patterns of 5-mC and 5-hmC of the fetal placenta of Nellore cattle as well as blood and sperm as controls. 5-mC and 5-hmC levels were determined using MethylFlash Methylated/Hydroxymethylated DNA Quantification Kit, respectively. Placenta tissues showed lower levels of 5-mC and 5-hmC compared to sperm. The male cotyledon showed higher levels of 5-hmC than the female. For the first time, the levels of 5-mC and 5-hmC in Bos taurus indicus were characterized, which may contribute to our understanding of the mechanisms of epigenetic regulation in the placenta. The presence of 5-hmC in somatic tissues suggest that 5-hmC has its own biological function and it is not only a byproduct from the oxidation of 5-mC. These results may be of interest in ARTs, especially in cloning in the diagnosis/prognosis of aberrant placentation and the viability of pregnancies.(AU)

5-metilcitosina (5-mC) e 5-hidroximetilcitosina (5-hmC) são citosinas modificadas encontradas nos mamíferos que estão envolvidas com a regulação da expressão gênica. O objetivo do presente estudo foi caracterizar os padrões globais de 5-mC e 5-hmC em placenta fetal de animais da raça Nelore, assim como em sangue e espermatozoides, usados como controles. Os níveis de 5-mC e 5-hmC foram determinados usando os kits MethylFlash Methylated/Hydroxymethylated DNA Quantification, respectivamente. Tecidos placentários apresentaram menores níveis de 5-mC e 5-hmC quando comparados com espermatozoides. Cotilédones de machos apresentaram maiores níveis de 5-hmC do que os de fêmeas. Os níveis de 5-mC e 5-hmC em animais Bos taurus indicus foram caracterizados pela primeira vez, o que pode contribuir para o nosso conhecimento sobre a regulação dos mecanimos epigenéticos na placenta. A presença de 5-hmC em tecidos somáticos sugerem que essa base pode ter sua própria função biológica, sendo não somente um sub-produto da oxidação da 5-mC. Esses resultados podem ser de interesse nas Tecnologias de Reprodução Assistida, especialmente na clonagem, no diagnóstico/prognóstico de placentação aberrante e viabilidade da progênie.(AU)

Relationship between global DNA methylation and hydroxymethylation levels in peripheral blood of elderly patients with myocardial infarction and the degree of coronary atherosclerosis / 上海交通大学学报（医学版）

Objective • To investigate the relationship between the levels of global DNA methylation and hydroxymethylation in peripheral blood of elderly patients with myocardial infarction (MI) and the degree of coronary atherosclerosis. Methods • Forty-three elderly patients with MI were enrolled as the study group and 53 elderly patients with negative findings in coronary angiograms during the same period were collected as the control group. Peripheral blood samples were collected. The levels of global DNA methylation and hydroxymethylation in peripheral blood and the concentration of plasma TET2 were detected by ELISA. TET2 mRNA expression was determined by real-time qPCR. Results • Compared with the control group, the levels of global DNA methylation and hydroxymethylation in peripheral blood of elderly patients with MI were significantly increased (P=0.014, P=0.000). The concentration of plasma TET2 and its mRNA expression in patients with MI were significantly higher than those in the control group (P=0.004, P=0.028). The levels of global DNA methylation and hydroxymethylation in MI group were significantly correlated with the degree of coronary atherosclerosis (r=0.262, P=0.017; r=0.360, P=0.001). Conclusion • The levels of global DNA methylation and hydroxymethylation in peripheral blood of elderly patients with MI are significantly increased, which are significantly correlated with the degree of coronary atherosclerosis.

Research on DNA Hydroxymethylation Modification in Digestive System Carcinoma / 现代生物医学进展

DNA hydroxymethylation modification is an important part of genome epigenetic regulation.The demethylation process from 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) is catalyzed by Tet protein.Abnormal genomic methylation leads to the occurrence of a variety of tumors.Hydroxymethylation is modified as a kind of demethylation and is inseparable from tumorigenesis.The expression of 5-hmC changes accompanied with the development and progression of digestive system tumors,which may be associated with the TET protein family and IDH mutation.It suggested that DNA hydroxymethylation is involved in the development and progression of digestive system tumors.This paper reviews the relationship between DNA hydroxymethylation and digestive system tumors,and aims to provide a new direction for the study of Hydroxymethylation modification in digestive system tumors.

Iron Supplementation Reverses the Reduction of Hydroxymethylcytosine in Hepatic DNA Associated With Chronic Alcohol Consumption in Rats

BACKGROUND: Alcohol is known to affect two epigenetic phenomena, DNA methylation and DNA hydroxymethylation, and iron is a cofactor of ten-eleven translocation (TET) enzymes that catalyze the conversion from methylcytosine to hydroxymethylcytosine. In the present study we aimed to determine the effects of alcohol on DNA hydroxymethylation and further effects of iron on alcohol associated epigenetic changes. METHODS: Twenty-four male Sprague-Dawley rats were fed either Lieber-DeCarli alcohol diet (36% calories from ethanol) or Lieber-DeCarli control diet along with or without iron supplementation (0.6% carbonyl iron) for 8 weeks. Hepatic non-heme iron concentrations were measured by colorimetric assays. Protein levels of hepatic ferritin and transferrin receptor were determined by Western blotting. Methylcytosine, hydroxymethylcytosine and unmodified cytosine in DNA were simultaneously measured by liquid chromatography/mass spectrometry method. RESULTS: Iron supplementation significantly increased hepatic non-heme iron contents (P < 0.05) but alcohol alone did not. However, both alcohol and iron significantly increased hepatic ferritin levels and decreased hepatic transferrin receptor levels (P < 0.05). Alcohol reduced hepatic DNA hydroxymethylation (0.21% ± 0.04% vs. 0.33% ± 0.04%, P = 0.01) compared to control, while iron supplementation to alcohol diet did not change DNA hydroxymethylation. There was no significant difference in methylcytosine levels, while unmodified cytosine levels were significantly increased in alcohol-fed groups compared to control (95.61% ± 0.08% vs. 95.26% ± 0.12%, P = 0.03), suggesting that alcohol further increases the conversion from hydroxymethylcytosine to unmodified cytosine. CONCLUSIONS: Chronic alcohol consumption alters global DNA hydroxymethylation in the liver but iron supplementation reverses the epigenetic effect of alcohol.

Placental hydroxymethylation vs methylation at the imprinting control region 2 on chromosome 11p15.5

In addition to methylated cytosines (5-mCs), hydroxymethylcytosines (5-hmCs) are present in CpG dinucleotide-enriched regions and some transcription regulator binding sites. Unlike methylation, hydroxymethylation does not result in silencing of gene expression, and the most commonly used methods to study methylation, such as techniques based on restriction enzymatic digestion and/or bisulfite modification, are unable to distinguish between them. Genomic imprinting is a process of gene regulation where only one member of an allelic pair is expressed depending on the parental origin. Chromosome 11p15.5 has an imprinting control region (ICR2) that includes a differentially methylated region (KvDMR1) that guarantees parent-specific gene expression. The objective of the present study was to determine the presence of 5-hmC at the KvDMR1 in human placentas. We analyzed 16 third-trimester normal human placentas (chorionic villi). We compared two different methods based on real-time PCR after enzymatic digestion. The first method distinguished methylation from hydroxymethylation, while the other method did not. Unlike other methylation studies, subtle variations of methylation in ICRs could represent a drastic deregulation of the expression of imprinted genes, leading to important phenotypic consequences, and the presence of hydroxymethylation could interfere with the results of many studies. We observed agreement between the results of both methods, indicating the absence of hydroxymethylation at the KvDMR1 in third-trimester placentas. To the best of our knowledge, this is the first study describing the investigation of hydroxymethylation in human placenta using a genomic imprinting model.