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<<   作成日時 : 2009/07/07 00:39   >>

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 帝王切開で生まれた新生児は白血球のDNAに変化が起こり、糖尿病や喘息と言った免疫が関係する病気のリスクが高くなるとのスウェーデンからの報告。
 ストックホルムのKarolinska研究所の小児科専門医ノーマン博士によれば、帝王切開は、アレルギー、糖尿病、白血病のリスク増大と関連していると言う。
 37人の新生児の出生直後と3-5日後の血液サンプルをとり、免疫システムのキーとなる白血球のDNAメチル化の程度を評価した。DNAメチル化により、DNAは、外部環境における変化に呼応して遺伝子を活性化するか、不活化するか化学的に修正される。
 帝王切開で生まれた新生児16人では経腟分娩21人に比べて出生直後に高いDNAメチル化率が見られた。生後3-5日後には両グループに差はなかった。
 動物での研究で、誕生時のネガティブなストレスが遺伝子のメチル化に影響することがわかっており、同様のことが起きていると考えられる。
 帝王切開による出生では、彼らは出生について準備がなく、出生後のストレスが大きくなる。呼吸など急速な環境変化に順応するためのストレスが、正常な経腟分娩での徐々に起こるストレスと異なる。
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C-Section Stress Could Alter Baby's Immune Cells
http://health.msn.com/pregnancy/articlepage.aspx?cp-documentid=100241418
And that might raise odds for diabetes, asthma later on, researchers say
-- Robert Preidt

画像THURSDAY, July 2 (HealthDay News) -- Babies delivered by cesarean section experience changes to the DNA of white blood cells, which might explain why they're at increased risk for immunological diseases such as diabetes and asthma later in life, Swedish researchers say.

"Delivery by C-section has been associated with increased allergy, diabetes and leukemia risks," Dr. Mikael Norman, a pediatric specialist at the Karolinska Institute in Stockholm, said in a news release from Wiley-Blackwell publishers. "Although the underlying cause is unknown, our theory is that altered birth conditions could cause a genetic imprint in the immune cells that could play a role later in life."

Norman and his colleagues analyzed blood samples from 37 infants taken just after delivery and samples taken three to five days after birth. The blood was analyzed to assess the degree of DNA-methylation in the white blood cells, which are a key part of the immune system. In DNA-methylation, DNA is chemically modified to activate or turn off genes in response to changes in the external environment.

The 16 infants born by C-section had higher DNA-methylation rates immediately after delivery than the 21 infants born by vaginal delivery, according to the report, in the July issue of Acta Paediatrica. Three to five days after birth, both groups of infants had similar levels of DNA-methylation.

Further research is needed to determine why infants born by C-section have higher DNA-methylation rates after delivery, the researchers said.

"Animal studies have shown that negative stress around birth affects methylation of the genes, and therefore it is reasonable to believe that the differences in DNA-methylation that we found in human infants are linked to differences in birth stress," the researchers wrote.

"We know that the stress of being born is fundamentally different after planned C-section compared to normal vaginal delivery," they explained. "When babies are delivered by C-section, they are unprepared for the birth and can become more stressed after delivery than before. This is different [from] a normal vaginal delivery, where the stress gradually builds up before the actual birth, helping the baby to start breathing and quickly adapt to the new environment outside the womb."

More information

The Nemours Foundation has more about cesarean delivery.
SOURCE: Wiley-Blackwell, news release, June 29, 2009

Copyright (c) 2009 ScoutNews, LLC. All rights reserved.
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Epigenetic modulation at birth -- altered DNA-methylation in white blood cells after Caesarean section

T Schlinzig 1 , S Johansson 2 , A Gunnar 3 , TJ Ekstro"m 3 , M Norman 1
1. Department of Clinical Science, Intervention and Technology, Karolinska Institute, Stockholm, Sweden
2. Department of Woman & Child Health, Karolinska Institute, Stockholm, Sweden
3. Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
Correspondence to M Norman, Division of Pediatrics, Department of Clinical Science, Intervention and Technology, Karolinska Institute & University Hospital -- Huddinge B57, S-141 86 Stockholm, Sweden.
Tel: +46-736-204596 |
Fax: +46-8-58587545 |
Email: mikael.norman@ki.se
Copyright Journal Compilation (c) 2009 Foundation Acta P?diatrica
KEYWORDS
Developmental biology . Gene expression regulation . Mode of delivery . Newborn infant . Programming
ABSTRACT

Aim: Delivery by C-section (CS) has been associated with increased risk for allergy, diabetes and leukaemia. Whereas the underlying cause is unknown, epigenetic change of the genome has been suggested as a candidate molecular mechanism for perinatal contributions to later disease risk. We hypothesized that mode of delivery affects epigenetic activity in newborn infants.

Methods: A total of 37 newborn infants were included. Spontaneous vaginal delivery (VD) occurred in 21, and 16 infants were delivered by elective CS. Blood was sampled from the umbilical cord and 3--5 days after birth. DNA-methylation was analyzed in leucocytes.

Results: Infants born by CS exhibited higher DNA-methylation in leucocytes compared with that of those born by VD (p < 0.001). After VD, newborn infants exhibited stable levels of DNA-methylation, as evidenced by comparing cord blood values with those 3--5 days after birth (p = 0.55). On postnatal days 3--5, DNA-methylation had decreased in the CS group (p = 0.01) and was no longer significantly different from that of VD (p = 0.10).

Conclusion: DNA-methylation is higher in infants delivered by CS than in infants vaginally born. Although currently unknown how gene expression is affected, or whether epigenetic differences related to mode of delivery are long-lasting, our findings open a new area of clinical research with potentially important public health implications.

Received 15 April 2009; revised 30 April 2009; accepted 4 May 2009.
DIGITAL OBJECT IDENTIFIER (DOI)
10.1111/j.1651-2227.2009.01371.x About DOI

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