Predictors of physical activity energy expenditure in Afro-Caribbean children.

BACKGROUND/OBJECTIVES: We hypothesized that maternal size during pregnancy and birth size are determinants of childhood physical activity energy expenditure (PAEE). Also, childhood PAEE is inversely related to adiposity and levels of cardiovascular risk factors. SUBJECTS/METHODS: The Vulnerable Windows Cohort Study is a longitudinal observational study of 569 Afro-Jamaican mothers recruited from the first trimester and their offspring. Anthropometry, bioelectrical impedance, PAEE (using the Actical monitor) and cardiovascular risk factors (blood pressure, fasting glucose, insulin and lipids) were measured in 124 boys and 160 girls at a mean age of 13.2 years. RESULTS: Boys had more fat-free mass (FFM) and expended more energy than girls (12.3±3.3 vs 9.6±2.8 kcal/kg/day; P<0.001). Maternal weight was associated with child's PAEE (r=0.29; P<0.001). PAEE was not significantly associated with birth weight. Maternal weight, after adjusting for child's age and sex, was positively associated with the child's FFM, fat mass and %fat (P-values 0.01). Age- and sex-adjusted PAEE was positively associated with FFM, fat mass and % fat (P-values <0.001), but not after adjusting for current weight. Age- and sex-adjusted PAEE was positively associated with triglycerides, insulin and systolic blood pressure (P-values <0.05), but not after adjusting for weight and height. PAEE was associated with fasting glucose after controlling for age, sex, weight and height (r=-0.12; P=0.02). CONCLUSIONS: Maternal size, but not birth weight, is a determinant of childhood PAEE. PAEE is not strongly associated with childhood body composition, but is inversely related to fasting glucose concentration.

Relationship between birth weight and urea kinetics in children.

OBJECTIVE: To explore the effect of birth weight on urea kinetics in young healthy children. DESIGN: Observational study. SETTING: Tertiary center for treatment of malnutrition. SUBJECTS: A total of 17 male children, 6-24 months old, who had recovered from malnutrition. INTERVENTIONS: Urea kinetics were measured using stable isotope methodology with [(15)N(15)N]-urea over 36 h. RESULTS: Birth weight was negatively related to urea hydrolysis after controlling for the intake of protein (adjusted R (2 ) = 0.91, P = 0.001) and separately for energy intake (adjusted R (2) = 0.95, P = 0.001), age (adjusted R (2) = 0.90, P = 0.001) and rate of weight gain (adjusted R (2) = 0.91, P = 0.001). There was a tendency for higher urea production in the children with lower birth weight after controlling for nitrogen intake (adjusted R (2) = 0.93, P = 0.099), and separately for age (adjusted R (2) = 0.94, P = 0.06) and rate of weight gain (adjusted (R (2) = 0.92, P = 0.096). Urea excretion was not significantly related to birth weight. CONCLUSIONS: The salvaging of urea nitrogen following urea hydrolysis contributed significantly more to the nitrogen economy in children with lower birth weight compared to those with higher birth weight. This may be as a result of reductive adaptation in the children with lower birth weight as a consequence of inappropriate prenatal nutrition and growth.

Maldigestion and malabsorption of dietary lipid during severe childhood malnutrition.

BACKGROUND: Diets rich in lipid are used to provide energy density in treating children with severe malnutrition, but the extent to which their digestion and absorption can cope with the load effectively is uncertain. AIM: To determine the extent of impaired digestion or absorption, in three groups of eight malnourished children (aged 5-23 months) using isotopic probes of the predominant fatty acids in coconut and corn oil used to fortify the diet. METHODS: Each child received oral doses of one of three (13)C labelled triglycerides (trilaurin, triolein, or trilinolein). The recovery of (13)C label in stool either as triglyceride (TAG) or fatty acid (FA), was used to assess digestion and absorption. In a separate test, the recovery of label in stool following an oral dose of [(13)C]-glycocholate was measured to assess bile salt malabsorption. RESULTS: The median recovery of label in stool was 9% (range 1-29%) of administered dose. Following treatment there was a reduction in stool (13)C excretion for the labelled TAG (<1%). In half the subjects, label was recovered as TAG in stool (median 0.6%, range 0-44%). Most label in stool was recovered as FA (median 30%, range 0-100%). Following [(13)C]-glycocholate, label was recovered in excess in about one third of studies. CONCLUSION: Abnormalities in the gastrointestinal handling of lipid were observed in over 50% of children with severe malnutrition, reflecting problems in absorption, although impaired solubilisation or hydrolysis could also be contributory factors. The underlying lesion improves as treatment progresses, leading to concomitant improvement in function.

The effect of splenectomy for hypersplenism on whole body protein turnover, resting metabolic rate and growth in sickle cell disease.

OBJECTIVE: To determine whether, in the same individual, an observed fall in whole body protein turnover following splenectomy in children with hypersplenism and homozygous sickle cell (SS) disease is associated with a measurable fall in resting metabolic rate (RMR) and an increase in rate of growth. SUBJECTS: Six children (5 SS disease, 1 S beta degree thalassaemia), aged 68 to 126 months, were studied before and after splenectomy for hypersplenism. DESIGN: Protein turnover was measured by the end product method using prime/intermittent oral doses of 15N-glycine and RMR by indirect calorimetry before preoperative transfusion and repeated at least eight weeks after splenectomy. Height and weight velocities were measured over six month periods before and after splenectomy. SETTING: University Hospital of the West Indies in Jamaica and the Medical Research Laboratories (Jamaica). RESULTS: After splenectomy protein turnover fell significantly by 30% and RMR by 34 kJ/kg/d. Mean weight velocity which was below normal before surgery, z = -2.3, improved significantly after surgery, z = 0.7, (P = 0.03). Height velocity increased in two children but the mean height velocity did not change following splenectomy. The reduction in protein turnover was estimated to account for 62% of the fall in RMR. CONCLUSION: This study confirms that there is a significant reduction in energy expenditure following splenectomy for hypersplenism in SS disease. A reduction in protein turnover was a major contributor to the saving in energy, although it is not clear whether it accounted for all. In the present group of children the energy saved was associated with an improvement in the wasting present before splenectomy.

Urea production and salvage during pregnancy in normal Jamaican women.

The pattern of aggregate nitrogen demand during pregnancy and the fetal and maternal components are unclear. Excess demand enhances efficiency of nitrogen utilization. Urea salvage contributes to enhanced efficiency. Dietary protein intake, urea production, and salvage of urea nitrogen were measured in eight nonpregnant control subjects, and trimesterly in nine pregnant women. Production was measured after prime-intermittent intravenous doses of [15N 15N]-urea by dilution of label in urinary urea. Dietary protein intake was greater in trimester 1 than in nonpregnant women (167 +/- 36 vs 224 +/- 60 mg N.kg-1.d-1), and increased further in trimester 2 (266 +/- 59 mg N.kg-1.d-1). Urea production was not higher during pregnancy. Despite higher protein intake, urea salvage was higher in pregnancy (40 +/- 24 nonpregnant vs 77 +/- 23, 61 +/- 31, and 51 +/- 12 mg N.kg-1.d-1). Therefore, the demand-supply gap for nitrogen was greatest early in pregnancy when fetoplacental growth is slowest, and implies heightened maternal demand.

Adaptation to a marginal intake of energy in young children.

Six male children, aged 8-28 months, were studied for three consecutive periods of 1 week each. They were given diets that provided 1.7 g protein/kg per d and supplements of minerals and vitamins, with a metabolizable energy intake during the 1st, 2nd and 3rd week of 419, 293 and 335 kJ (100, 70 and 80 kcal)/kg per d, diets 1, 2 and 3 respectively. All the food offered was consumed. Each child was weighed at the same time each day on an electronic balance. On the 6th and 7th day of each study period urine and stool were collected for 24 h to assess nitrogen balance. Using linear regression analysis it was shown that all children gained weight on diet 1, 2.3 (SD 1.3) g/kg per d, and five of six children gained weight on diet 3, the mean for the whole group being 2.7 (SD 2.3) g/kg per d, not significantly different. On diet 2 all children lost weight, -5.4 (SD 1.3) g/kg per d, highly significantly different from each of the other dietary periods. Using asymptotic regression analysis it could be shown that the rate of weight loss during the first part of the week on diet 2, -11 g/kg per d, was greater than at the end of the week, -2 g/kg per d, with a tendency towards a steady weight by day 7. Apparent N retention (mg/kg per d) was positive at the end of each of the three dietary periods: diet 1, 112 (SD 25); diet 2, 54 (SD 34); diet 3, 82 (SD 20). In five of the six children there was a marked reduction in stool frequency on diet 2 compared with diet 1, that was maintained to the period on diet 3. The findings suggest that during the period on diet 2 there was a saving of energy of the order of 105 kJ (25 kcal)/kg per d, which lasted through into the period on diet 3.

Urinary excretion of 5-oxoproline (pyroglutamic aciduria) as an index of glycine insufficiency in normal man.

1. The evidence is accumulating to suggest that glycine, the simplest amino acid, is conditionally essential in man. Benzoic acid, by conjugation with glycine to form hippuric acid, is known to deplete the free glycine pool of the body. Glycine is one substrate for the enzyme glutathione synthase (EC 6.3.2.3) and in the inborn error of metabolism in which glutathione synthase function is defective, increased quantities of 5-oxoproline are excreted in the urine. 2. An oral dose of 4-10 g sodium benzoate was given to six normal adults to deplete the metabolic pool of glycine, and the urinary excretion of 5-oxoproline was followed for 6 h. In five of the six, a significant increase in the urinary 5-oxoproline was seen within 3 h. 3. These findings show that 5-oxoprolinuria can result from limited glycine availability, and may provide a useful test for assessing glycine sufficiency in a range of physiological and pathological states.