孕期缺少维生素B12可致后代胰岛素抵抗

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Low Vitamin B12 in Pregnancy Linked to Insulin Resistance in Offspring

By C. Vidyashankar, MD

CHENNAI, India (Reuters Health) Feb 15 - Low plasma vitamin B12 in the first trimester and high folate levels in the second trimester of pregnancy predispose offspring to insulin resistance, according to the results of a study conducted in India, published in the January issue of Diabetologia.

As a part of the Pune Maternal Nutrition Study, Dr. Chittaranjan S. Yajnik from the King Edward Memorial Hospital, Pune, in western India, and his multinational colleagues evaluated the dietary intake, vitamin B12, folate, total homocysteine and methylmalonic acid levels of 700 women at 18 weeks' and 28 weeks' gestation.

Six hundred fifty-three offspring of these mothers were followed-up at 6 years of age with physical and biochemical measurements, body composition using X-ray absorptiometry, and insulin resistance using homeostatic models.

The plasma B12 levels were low (<150 pmol/L) in a majority of the women at 18 weeks and 28 weeks gestation, but were significantly higher among mothers whose diet included dairy products and non-vegetarian foods, the researchers report. The median red cell folate was significantly elevated at 28 weeks gestation, they note.

Insulin resistance at 6 years of age was significantly more common in the offspring of mothers who had low B12 levels at 18 weeks and high folate levels at 28 weeks of pregnancy, and was highest among those with a combination of both, Dr. Yajnik&#39;s team reports.

Adiposity was greater among the offspring of mothers with higher folate levels, they add.

Increased plasma levels of homocysteine and methylmalonic acid as a consequence of low plasma B12 results in lipogenesis, reduced protein synthesis and reduced lean body mass, and may be the precursor of insulin resistance, the researchers postulate. \"Epigenetic regulation, involving DNA methylation, may be another mechanism of nutritional programming,\" they add.

An imbalance in the vitamin B12 and folic acid levels produces the \"undesirable effects,\" Dr. Yajnik told Reuters Health in an email communication.

\"Multigenerational vegetarianism means that vitamin B12 deficiency is common in Indians, but folate deficiency is relatively rare,\" Dr. Yajnik explained. \"High folate intakes in vitamin B12-deficient mothers could increase the risk of type 2 diabetes in the offspring.\"

\"The National Anemia Program recommends use of iron and folic acid in pregnancy but ignores vitamin B12. This needs to be reconsidered and due attention needs to be given to vitamin B12,\" Dr. Yajnik concluded.

Diabetologia 2008; 51:29-38.

Low Vitamin B12 in Pregnancy Linked to Insulin Resistance in Offspring
孕期缺少维生素B12可致后代胰岛素抵抗。
CHENNAI，印度（路透社，健康版）二月15----根据在印度完成的发表在一月份的Diabetologia上一项研究结果，孕期前三月血浆维生素B12低水平和中三个月叶酸高水平预示后代的胰岛素抵抗。作为Pune产妇营养研究的一部分，Dr. Chittaranjan S. Yajnik（来自King Edward Memorial医院），Pune（印度西部），以及他的多国同仁评估700女性在孕18周和孕28周饮食摄入、维生素B12、叶酸、总同型半胱氨酸和甲基丙二酸水平。653名这些妈妈的后代被随访到6岁，进行物理和生物化学检查，身体成分用x-ray吸光测定法，胰岛素抵抗采用稳态模式。B12水平在大部分女性孕18周和28周血浆均低（<150 pmol/L），但在饮食中含牛奶制品及非素食者中水平很高。中位红细胞叶酸研主要是在孕28周检测，他们注明道。Dr. Yajnik的团队报道：孕18周B12水平低或28周叶酸高的妈妈的孩子6岁时胰岛素抵抗很普遍，两者都有时的比例更高。
Adiposity was greater among the offspring of mothers with higher folate levels, they add.
高叶酸水平妈妈的孩子肥胖比例很高，他们补充道。血浆同型半胱氨酸和甲基丙二酸水平增高作为血浆B12低水平results in lipogenesis，减少蛋白质合成和减少瘦体重，且可能预示胰岛素抵抗，研究者们推测道。“表观遗传调控，包括DNA甲基化，可能是另一种营养机制”。在一次email交流中Dr. Yajnik告诉路透社健康版：维生素B12和叶酸水平的不平衡导致“不良后果。” “多代素食，意味着维生素B12缺乏症印度人常见，但叶酸缺乏是比较罕见的”。“维生素B12缺乏的母亲摄入高叶酸可以增加患2型糖尿病的后代。” “国家贫血计划建议孕期使用的铁和叶酸，但忽略了维生素B12，这需要重新考虑并予维生素B12以应有的重视，”Dr. Yajnik总结道。

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孕期要平衡补充叶酸和维生素B12。从孕前3个月到孕3个月。