Effect of excessive methionine on the development of the cranial growth plate in newborn rats.

OBJECTIVE: Methionine is an essential amino acid and pivotal for normal growth and development. However, previous animal studies have shown that excessive maternal intake of methionine causes growth restrictions, organ damages, and abnormal growth of the mandible in newborn animals. However, the effect of excessive methionine on the development of the cranial growth plate is unknown. This study investigated histological alterations of the cranial growth plate induced by high methionine administration in newborn rats. DESIGN: Twenty pregnant dams were divided into a control and an experimental group. The controls received a diet for rats and the experimental group was fed from the 18th gestational day with a special manufactured high methionine diet for rats. The high methionine diet was maintained until the end of the lactation phase (day 20). The offspring of both groups were killed at day 10 or 20 postnatally and their spheno-occipital synchondroses were collected for histological analysis. RESULTS: The weight of the high-dose methionine treated experimental group was considerably reduced in comparison to the control group at day 10 and 20 postnatally. The cartilaginous area of the growth plate and the height of the proliferative zone were markedly reduced at postnatal day 10 in the experimental group. CONCLUSIONS: In summary, the diet-induced hypermethioninemia in rat dams resulted in growth retardations and histomorphological changes of the spheno-occipital synchondrosis, an important craniofacial growth centre in newborns. This finding may elucidate facial dysmorphoses reported in patients suffering from hypermethioninemia.

Induction and prevention of cleft lip, alveolus and palate and neural tube defects with special consideration of B vitamins and the methylation cycle.

Previous studies on the development of cleft lip, alveolus, palate, and velum and neural tube defects have revealed several shared multifactorial causes. Both anomalies emerge at different times during embryonic development and are not associated with each other unless there is a genetic component to the etiology. Vitamin deficiency disorders are one of several factors contributing to the etiology of these anomalies.Vitamins B6, folic acid and B12 play an essential role in the methylation cycle. A lack of or deficiency in these vitamins thus has severe consequences for the organism, especially the unborn child. Due to its short half-life, vitamin B6 is particularly important for undisturbed embryogenesis and should be taken along with folic acid as a periconceptional supplement to prevent embryonic deformities. This paper is intended to provide the orthodontist (as a member of the interdisciplinary cleft team) with an overview of the issues and etiological significance of vitamin B deficiencies as possible inducers of these embryopathies. This may encourage comprehensive counselling, particularly of parents of children born with deformities who wish to have more children.