Molecular and enzymatic characterization of a unique carnitine palmitoyltransferase 1A mutation in the Hutterite community.

Hepatic carnitine palmitoyltransferase 1 (CPT1A) deficiency is a rare disorder of mitochondrial fatty acid oxidation inherited as an autosomal recessive trait. Symptomatology comprises attacks of hypoketotic hypoglycemia with risk of sudden death or neurological sequelae. Only one CPT1A mutation has been reported so far. Identification of the disease-causing mutations allows both insights into the structure-function relationships of CPT1A and management of the patients and their relatives. The molecular analysis of CPT1A deficiency in a large Hutterite kindred illustrates this point. Both cDNA and genomic DNA analysis demonstrate that the affected patients are homozygous for a 2129G>A mutation predicting a G710E substitution. Studies in fibroblasts from one patient as well as heterologous expression of the mutagenized CPT1A in yeast show that the G710E mutation alters neither mitochondrial targeting nor stability of the CPT1A protein. By contrast, kinetic studies conclusively establish that the mutant CPT1A is totally inactive, indicating that the G710E mutation dramatically impairs the catalytic function of CPT1A. Finally, due to a strongly suspected founder effect for the origin of CPT1A deficiency in this Hutterite kindred, identification of this disease-causing mutation allows the setup of a targeted DNA-based newborn screening in this at-risk population.

Vitamin D deficiency in a Manitoba community.

OBJECTIVE: Using a cross-sectional survey, to investigate the vitamin D status of a random sample of 80 mother-child pairs (child age 3-24 months) in a Manitoba community with a high incidence of rickets. METHOD: A questionnaire on feeding habits, gestational history, maternal diet and vitamin supplements was administered to mothers in their homes with the assistance of a local interpreter. Venous blood was collected from both mother and child for serum 25-hydroxyvitamin D levels. RESULTS: Of 91% babies initially breastfed, 36% received no formula or milk after weaning and 40% received no vitamin supplements. 24% of mothers took no vitamin supplements during pregnancy and lactation. Knowledge about rickets was poor. In 43% of children and 76% of mothers, serum 25-hydroxyvitamin D levels were below normal range. CONCLUSIONS: Vitamin D levels are low in this population due to lack of fortified dairy products and vitamin D supplements. A public health program should include counseling on rickets and vitamin D supplementation for all infants and pregnant or lactating women.

PIP: In the isolated Island Lake area of northern Manitoba, which has a high incidence of rickets, interviews were conducted with 80 mothers, each with a child at least 2 years old, living in St. Theresa Point and Garden Hill in their homes during June-July 1987 to determine their knowledge and attitudes towards rickets. Nurses obtained blood samples from the women and their young children so the researchers could determine the vitamin D status of both. The mother-child pairs were native Canadians from the Ojibway linguistic group that speaks its own dialect of Ojibway-Cree. Mothers initially breast fed 91% of the children. After weaning, 1/3 of infants received neither infant formula nor milk. No vitamin supplements were given to 40%. Many of the children who did receive vitamin supplements did not receive them regularly. 70% of the mothers did not drink any milk. 24% were milk-intolerant. 24% took no vitamin supplements during pregnancy and lactation. Mothers who did take supplements did not do so regularly. 17% claimed that their skin was sensitive to sunlight. 84% of mothers in one community had never heard of rickets. Most did not know its cause. Neither mothers nor the children were exposed to the sunlight in the summer. When outside, almost all small infants were completely covered to protect them from the elements. The mean 25-hydroxy-vitamin D level was 26.2 nmol/l for the children and 19.8 nmol/l for the mothers. 43% of children and 76% of mothers had a 25-hydroxy-vitamin D level below the normal range. These high levels of vitamin D insufficiency were even more troublesome given that the blood was taken in late June and July when vitamin D levels would be likely to be at their highest. The dearth of vitamin D fortified dairy products and vitamin supplements greatly contributed to the low level of vitamin D status in this area. The findings show a need for public health officials to include education on rickets and vitamin D supplementation for all infants and pregnant or lactating women.

Vitamin-D-deficient rickets in Manitoba, 1972-84.

Vitamin-D-deficient rickets still exists in children in Manitoba and adjacent areas. Between 1972 and 1984, 48 cases were documented at Winnipeg Children's Hospital. The patients ranged in age from 1 to 49 months; 40 were Canadian natives (38 Indians and 2 Inuit), most of whom lived in the Island Lake area of northern Manitoba. Of the 48, 16 had clinical signs of rickets, 12 had tetany due to hypocalcemia and 38 had radiologic evidence of rickets. Hypocalcemia was found in 27, and hypophosphatemia in 19; hyperaminoaciduria was found in 7 of 20. All 48 had elevated serum alkaline phosphatase levels. In addition to rickets, 16 patients aged 12 months or more had evidence of malnutrition. Climate and lifestyle in northern areas of the Canadian midwest result in little or no biosynthesis of vitamin D by solar radiation; therefore, adequate dietary vitamin D intake is essential to prevent deficiency. The diets of pregnant women and infants in these areas are deficient in vitamin D. The authors recommend vitamin D supplements for all pregnant women and infants in areas of risk to eradicate this preventable disease.

Disaccharide consumption and malabsorption in Canadian Indians.

Twenty-eight Sioux and 29 Saluteaux Indians from a southern and an isolated northern Manitoban community were screened for lactose malabsorption; 55 were also screened for sucrose tolerance. Sixty percent of the subjects were lactose malabsorbers; the incidence increased with age. Lactase deficiency appeared, on the average, between 8 and 15 years of age. About 45% of the subjects were lactose intolerant. Malabsorbers who did not regularly drink milk had the highest symptom scores. The northern subjects consumed significantly more lactose and sucrose than the southern subjects. Two Sioux children were sucrose malabsorbers. It was hypothesized that the significantly greater sucrose consumption by the Saulteaux subjects were responsible for their markedly higher blood glucose curve following the sucrose tolerance tests. Dietary sucrose increases jejunal sucrase activity and the intestinal transport of glucose and fructose. Three of eight children less than 4 years were lactose malabsorbers; hence, medical personnel treating noninjective diarrhea in Indian children should examine for lactase deficiency. It was recommended that vitamin D fortified milk supplements to Indian school children be continued and that the milk be treated so as to reduce abdominal symptoms in the intolerant individuals.

Serum 25-hydroxyvitamin D in infantile rickets.

In small children with nutritional vitamin D deficiency, the serum concentration of 25-hydroxyvitamin D (25-OH-D), the major circulating metabolite of vitamin D, was correlated with the stage of clinical disease. It was low (16 to 20 ng/ml) but within the normal range in the earliest (hypocalcemic) stage of the deficiency syndrome and decreased (less than 15 ng/ml) in the more advanced stages. In patients with familial hypophosphatemia (X-linked dominant), mean serum 25-OH-D concentration was the same as in age-matched normal controls. Evidence is presented that endogenous parathyroid hormone may have a role in the depletion of serum 25-OH0D in deficiency states.