Vitamin B6 Metabolism in Infants and Children

Maternal micronutrient restriction programs the body adiposity, adipocyte function and lipid metabolism in offspring: a review

Fetal growth is a complex process which depends both on the genetic makeup and intrauterine environment. Maternal nutrition during pregnancy is an important determinant of fetal growth. Adequate nutrient supply is required during pregnancy and lactation for the support of fetal/infant growth and development. Macro- and micronutrients are both important to sustain pregnancy and for appropriate growth of the fetus. While macronutrients provide energy and proteins for fetal growth, micronutrients play a major role in the metabolism of macronutrients, structural and cellular metabolism of the fetus. Discrepancies in maternal diet at different stages of foetal growth / offspring development can have pronounced influences on the health and well-being of the offspring. Indeed intrauterine growth restriction induced by nutrient insult can irreversibly modulate the endocrine/metabolic status of the fetus that leads to the development of adiposity and insulin resistance in its later life. Understanding the role of micronutrients during the development of fetus will provide insights into the probable underlying / associated mechanisms in the metabolic pathways of endocrine related complications. Keeping in view the modernized lifestyle and food habits that lead to the development of adiposity and world burden of obesity, this review focuses mainly on the role of maternal micronutrients in the foetal origins of adiposity.

Antenatal treatment in two Dutch families with pyridoxine-dependent seizures

Incidental reports suggest that antenatal treatment of pyridoxine dependent seizures (PDS) may improve neurodevelopmental outcome of affected patients. Two families with PDS are reported, both with two affected siblings. Antenatal treatment with pyridoxine was instituted during the second pregnancy in each family (50 and 60 mg daily from 3 and 10 weeks of gestation, respectively). Perinatal characteristics and neurodevelopmental outcome at 4 (Family A) and 12 (Family B) years of age were compared between the untreated and treated child within each family. Meconium-stained amniotic fluid was present in both first pregnancies and abnormal foetal movements were noticed in one. In the treated infants, pregnancy and birth were uncomplicated. In family A, postnatal pyridoxine supplementation prevented neonatal seizures. Both children in family A were hypotonic and started walking after 2 years of age; both had white matter changes on MRI, and the first child was treated for squint. IQ was 73 and 98 in the antenatally untreated and treated child, respectively. The second child in family B developed seizures on the seventh day, because pyridoxine maintenance therapy had not been instituted after birth. Seizures responded rapidly to pyridoxine supplementation. MRI showed large ventricles and a mega cisterna magna. IQ was 80 and 106 in the antenatally untreated and treated child respectively. Both children had normal motor development. These results suggest that antenatal pyridoxine supplementation may be effective in preventing intrauterine seizures, decreasing the risk of complicated birth and improving neurodevelopmental outcome in PDS.

Pyridoxine-dependent seizures: a clinical and biochemical conundrum

Pyridoxine-dependent seizures have been recognised for 40 years, but the clinical and biochemical features are still not understood. It is a rare recessively inherited condition where classically a baby starts convulsing in utero and continues to do so after birth, until given pyridoxine. Many of these early onset cases also have an acute encephalopathy and other clinical features. Late onset cases are now recognised with a less severe form of the condition. Seizures can break through with intercurrent illness but otherwise remain controlled on pharmacologic doses of pyridoxine. The long-term outcome is affected by several factors including whether onset is early or late and how soon pyridoxine is given. Biochemical studies have been sparse, on very small numbers. There does not appear to be any defect in the uptake or metabolism of pyridoxine or pyridoxal phosphate (PLP). For a long time glutamic acid decarboxylase (GAD), a pyridoxal-dependent enzyme, has been suspected to be the abnormal gene product, but glutamate and gamma-aminobutyric acid (GABA) studies on the cerebrospinal fluid (CSF) have been contradictory and recent genetic studies have not found any linkage to the two brain isoforms. A recent report describes raised pipecolic acid levels in patients but how this ties in is unexplained.

Risk of low vitamin B6 status in infants breast-fed exclusively beyond six months

Our aim was to ascertain the adequacy of human milk as the sole source of vitamin B6 and the associations between maternal and infant status during extended exclusive breast-feeding. Vitamin B6 status was followed in lactating mothers and their exclusively breast-fed infants by determinations of erythrocyte pyridoxal 5'-phosphate concentration and the erythrocyte aspartate transaminase stimulation test at 2 months (n = 118), 4 months (n = 118), 6 months (n = 112), 7.5 months (n = 70), 9 months (n = 36), 10 months (n = 14), 11 months (n = 11), and 12 months (n = 7) postpartum. Of the mothers, 54% had used vitamin B6 supplement during pregnancy, and all received a pyridoxine hydrochloride supplement of 1 mg/day throughout lactation. The infants had a higher vitamin B6 status than their mothers. During the first 4 months, infant vitamin B6 status was generally adequate independently of the actual vitamin status of the nursing mother. Most of the infants with low status at 2 months were those born to mothers who were not supplemented during pregnancy. By 6 months of exclusive breast-feeding, 30% of cases of low vitamin B6 status in nursing mothers were reflected in their infants. Thereafter, the risk of low vitamin B6 status in exclusively breast-fed infants increased even if the mother's status was adequate. Our findings suggest that gestationally accumulated stores are important for the maintenance of adequate vitamin B6 status of infants during the early months and that for some infants, human milk alone, without supplementary foods, may be insufficient to meet vitamin B6 needs after 6 months of age.

Regional changes in the concentrations of glutamate, glycine, taurine, and GABA in the vitamin B-6 deficient developing rat brain: association with neonatal seizures

It is well known that a dietary restriction of vitamin B-6 during gestation and lactation produces spontaneous seizures in neonatal animals. Since pyridoxal phosphate, one of the biologically active forms of vitamin B-6, is the cofactor for GAD the neonatal seizures have been attributed to low levels of brain GABA as a result of cofactor depletion. Although GABA levels are significantly lower in B-6 restricted neonatal rats with spontaneous seizures, seizure activity is not present in B-6 deficient adult rats or 28 day old rats in the present study, despite significantly low levels of brain GABA. These facts suggest that depletion of GABA is not the only biochemical alteration essential for the emergence of seizures. In the present study, the effect of vitamin B-6 undernutrition on the concentrations of the neuroactive amino acids, Glu, Gly, Tau, and GABA was determined in selected regions of the developing rat brain. The results show that the concentrations of Glu, Tau, and GABA were significantly lower and GLY significantly higher in selected brain regions of the B-6 restricted 14 day old rat compared to control tissue. Most of these changes were unique to 14 days of age, the time when spontaneous seizures are observed, and not present at 28 or 56 days of age when seizures are absent. This pattern of amino acid changes in the brain and the magnitude of the changes was consistent with those measured in a variety of chemically-induced animal models of epilepsy and in human epileptic foci.(ABSTRACT TRUNCATED AT 250 WORDS)

Pyridoxine-dependency seizure: report of a rare presentation

A child developed minor motor seizures at the age of 14 months accompanied by an abnormal electroencephalogram showing single spikes and polyspikes over the vertex and frontocentral regions. Seizures continued until the age of 22 months despite administration of several standard anticonvulsants. At age 22 months, pyridoxine, 75 mg daily, was initiated and anticonvulsants were discontinued. Both the seizures and the electroencephalographic abnormality have disappeared over the ensuing 20 months with pyridoxine therapy.

Pyridoxol metabolism in vitamin B6-responsive convulsions of early infancy

As there is uncertainty about the nature of the metabolic defect in vitamin B6-responsive convulsion, certain aspects of pyridoxol metabolism were studied in 3 patients who were believed on clinical grounds to have the condition. The findings were compared with those in healthy children and adults, and in children with mental handicap. The magnitude of the initial rise and the subsequent fall in plasma pyridoxal phosphate (PALP) concentrations after a load of pyridoxol suggested that the vitamin B6-responsive patients were able to synthesise PALP normally but were unable to maintain the prolonged high levels normally found in plasma. The urinary excretion of 4-pyridoxic acid was within normal limits, but the excretion of pyridoxol after the load was raised. It is suggested that there may be an instability of the PALP-albumin complex in this condition. Some of the biochemical features were also observed in an infant presenting with convulsions soon after birth but without evidence of clinical B6-dependency.

Effects of L-dopa and vitamin B6 on electroencephalograms of schizophrenic patients: a preliminary report

1. To assess the therapeutic effect of low-dose L-Dopa therapy and associated EEG changes in chronic schizophrenia, 10 patients with a mean duration of illness of 12.4 years were treated with L-Dopa for a period of eight weeks during which the dosage was increased progressively from an initial level of 300 mg q.d. biweekly up to 600 mg q.d. The treatment was moderately effective in one case and slightly efficacious in one, produced no significant change in the conditions of seven patients while the remaining patient showed exacerbation; hence a noticeably low rate of improvement. There occurred no significant changes in the EEG pattern in the series of 10 patients on the average. The individual patients' responses, nevertheless, could be classified into three groups: one with no observable EEG changes, the second showing a slight degree of increase in alpha activity and the third exhibiting diminution of alpha activity in the EEG. The patients in the latter two groups all had durations of disease less than 10 years. 2. Observations were made primarily of changes in the EEG in 20 chronically schizophrenic patients with a mean duration of disease of 13 years receiving 60 mg of vitamin B6 (as pyridoxal-5'-phosphate) daily over a period of four weeks. Slight increase of alpha activity and decrease of theta activity in the EEG were noted on the average of the 20 cases, in response to the vitamin B6 therapy. The increase of alpha activity was frequently seen among patients with a duration of illness less than 10 years whose pretreatment EEG pattern had been alpha dominant (five out of 10 cases), whereas a slight ameliorative tendency of EEG was observed only in one out of 10 patients whose pretreatment EEG pattern had been slow-wave dominant. Symptomatic improvement was evident only in one of the 20 cases studied. 3. Observations were made of the therapeutic effect and associated EEG changes in eight patients receiving combined medication of 200 mg L-Dopa and 30 mg vitamin B6 (as pyridoxal-5'-phosphate) daily for a period of 12 weeks. Of these eight patients with a mean duration of disease of 18.3 years, two showed excellent response, three good and three fair; hence good to excellent responses attained in five out of the eight cases or 62.5%. A marked increase in alpha activity in the EEG occurred from the 2nd to 4th weeks onward in all eight cases. The EEG changes were likely to precede the symptomatic improvement. 4. To sum up the results of these three clinical trials, administration of L-Dopa alone resulted in practically no symptomatic improvement or EEG changes in patients with chronic schizophrenia whilst vitamin B6 administered singly as pyridoxal-5'-phosphate scarcely produced significant symptomatic improvement but brought about a slight ameliorative tendency in the EEG of such patients. Both symptomatic amelioration and EEG improvement occurred following combined medication of L-Dopa and vitamin B6...