Perinatal galactose metabolism

Comparative evaluation of enriched formula milk powder with OPO and MFGM vs. breastfeeding and regular formula milk powder in full-term infants: a comprehensive study on gut microbiota, neurodevelopment, and growth

This study investigated the non-inferiority of feeding term healthy infants with enriched formula milk powder containing 1,3-dioleoyl-2-palmitoylglycerol (OPO) and milk fat globular membrane (MFGM), compared to breast milk, in terms of the formation of gut microbiota, neurodevelopment and growth. Infants were divided into three groups: breast milk group (BMG, N = 50), fortified formula group (FFG, N = 17), and regular formula group (RFG, N = 12), based on the feeding pattern. Growth and development information was collected from the infants at one month, four months, and six months after the intervention. Fecal samples were collected from infants and analyzed for gut microbiota using 16S ribosomal DNA identification. The study found that at the three time points, the predominant bacterial phyla in FFG and BMG were Proteobacteria, Firmicutes, and Bacteroidetes, which differed from RFG. The abundance of Bifidobacterium in the RFG was lower than the FFG (one month, p = 0.019) and BMG (four months, p = 0.007). The abundance of Methanoprebacteria and so on (genus level) are positively correlated with bone mineral density (BMD) of term infants, and have the potential to be biomarkers for predicting BMD. The abundance of beta-galactosidase, a protein that regulates lactose metabolism and sphingoid metabolism, was higher in FFG (six months, p = 0.0033) and BMG (one month, p = 0.0089; four months, p = 0.0005; six months, p = 0.0005) than in the RFG group, which may be related to the superior bone mineral density and neurodevelopment of infants in the FFG and BMG groups than in the RFG group. Our findings suggest that formula milk powder supplemented with OPO and MFGM is a viable alternative to breastfeeding, providing a practical alternative for infants who cannot be breastfed for various reasons.

Proteomics identifies the developmental regulation of HKDC1 in liver of pigs and mice

During the perinatal period, unique metabolic adaptations support energetic requirements for rapid growth. To gain insight into perinatal adaptations, quantitative proteomics was performed comparing the livers of Yorkshire pigs at postnatal day 7 and adult. These data revealed differences in the metabolic control of liver function including significant changes in lipid and carbohydrate metabolic pathways. Newborn livers showed an enrichment of proteins in lipid catabolism and gluconeogenesis concomitant with elevated liver carnitine and acylcarnitines levels. Sugar kinases were some of the most dramatically differentially enriched proteins compared with neonatal and adult pigs including galactokinase 1 (Galk1), ketohexokinase (KHK), hexokinase 1 (HK1), and hexokinase 4 (GCK). Interestingly, hexokinase domain containing 1 (HKDC1), a newly identified fifth hexokinase associated with glucose disturbances in pregnant women, was highly enriched in the liver during the prenatal and perinatal periods and continuously declined throughout postnatal development in pigs and mice. These changes were confirmed via Western blot and mRNA expression. These data provide new insights into the developmental and metabolic adaptations in the liver during the transition from the perinatal period to adulthood in multiple mammalian species.

Experimental non-alcoholic fatty liver disease causes regional liver functional deficits as measured by the capacity for galactose metabolism while whole liver function is preserved

BACKGROUND

Increasing incidence of non-alcoholic fatty liver disease (NAFLD) calls for improved understanding of how the disease affects metabolic liver function.

AIMS

To investigate in vivo effects of different NAFLD stages on metabolic liver function, quantified as regional and total capacity for galactose metabolism in a NAFLD model.

METHODS

Male Sprague Dawley rats were fed a high-fat, high-cholesterol diet for 1 or 12 weeks, modelling early or late NAFLD, respectively. Each NAFLD group (n = 8 each) had a control group on standard chow (n = 8 each). Metabolic liver function was assessed by 2-[¹⁸F]fluoro-2-deoxy-D-galactose positron emission tomography; regional galactose metabolism was assessed as standardised uptake value (SUV). Liver tissue was harvested for histology and fat quantification.

RESULTS

Early NAFLD had median 18% fat by liver volume. Late NAFLD had median 32% fat and varying features of non-alcoholic steatohepatitis (NASH). Median SUV reflecting regional galactose metabolism was reduced in early NAFLD (9.8) and more so in late NAFLD (7.4; p = 0.02), both significantly lower than in controls (12.5). In early NAFLD, lower SUV was quantitatively explained by fat infiltration. In late NAFLD, the SUV decrease was beyond that attributable to fat; probably related to structural NASH features. Total capacity for galactose elimination was intact in both groups, which in late NAFLD was attained by increased fat-free liver mass to 21 g, versus 15 g in early NAFLD and controls (both p ≤ 0.002).

CONCLUSION

Regional metabolic liver function was compromised in NAFLD by fat infiltration and structural changes. Still, whole liver metabolic function was preserved in late NAFLD by a marked increase in the fat-free liver mass.

Lactose and Digestible Maltodextrin in Milk Replacers Differently Affect Energy Metabolism and Substrate Oxidation: A Calorimetric Study in Piglets

BACKGROUND

In recent years, lactose-free infant formulas have been increasingly used. Digestible maltodextrins are commonly used as a substitute for lactose in these formulas, but the effects on energy metabolism are unknown.

OBJECTIVE

We aimed to evaluate the differences in energy metabolism and substrate oxidation in piglets fed milk replacers containing lactose compared with maltodextrin as the only source of carbohydrates.

METHODS

Piglets (Tempo × Topigs 20) from 8 litters were fed milk replacers containing lactose or maltodextrin (28% w/w, milk powder basis) from 1 to 9 wk of age (n =  4 litters/milk replacer). At 5 wk of age, 4 females and 4 entire males (mean ± SEM bodyweight, 10 ± 0.3 kg) were selected per litter, and housed in 16 groups of 4 littermates, with 2 females and 2 males per pen (n = 8 groups/milk replacer). Between 7 and 9 wk of age, groups were housed for 72 h in climate respiration chambers, and fed their experimental milk replacer in 2 meals per day, at 08:30 and 16:30. Heat production data were calculated from the continuous measurement of gaseous exchanges and analyzed using general linear models in SAS.

RESULTS

Resting metabolic rate was 6% less in maltodextrin- than in lactose-fed piglets, notably before the morning meal. The postprandial respiratory quotient was 13% greater in maltodextrin- than in lactose-fed piglets after both meals. Net rates of carbohydrate oxidation were on average 5% greater in maltodextrin- than in lactose-fed piglets, particularly after the afternoon meal, whereas net rates of fat oxidation were 9% less in maltodextrin- than in lactose-fed piglets, particularly after the morning meal.

CONCLUSIONS

Compared with lactose, maltodextrin in milk replacers reduced resting metabolic rate in the fasting state, and induced a shift in postprandial substrate oxidation profiles in pigs. Further research is warranted to evaluate the consequences of these metabolic changes for body composition.

Non-alcoholic fatty liver disease causes dissociated changes in metabolic liver functions

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a major health concern affecting 25% of the world's population. It is generally held that a fatty liver does not influence liver function, but quantitative measurements of metabolic liver functions have not been systematically performed. We aimed to study selected hepatocellular metabolic functions in patients with different stages of NAFLD.

METHODS

Twenty-five non-diabetic, biopsy-proven NAFLD patients [12 with simple steatosis; 13 with non-alcoholic steatohepatitis (NASH)] and ten healthy controls were included in a cross-sectional study. Hepatocyte cytosolic function was assessed by the galactose elimination capacity (GEC), mitochondrial-cytosolic metabolic capacity by the functional hepatic nitrogen clearance (FHNC), microsomal function by the aminopyrine breath test, and excretory liver function by indocyanine green (ICG) elimination.

RESULTS

GEC was 20% higher in NAFLD than in controls [3.15 mmol/min (2.9-3.41) vs. 2.62 (2.32-2.93); P = 0.02]. FHNC was 30% lower in NAFLD [23.3 L/h (18.7-28.9) vs. 33.1 (28.9-37.9); P = 0.04], more so in simple steatosis [19.1 L/h (13.9-26.2); P = 0.003] and non-significantly in NASH [27.9 L/h (20.6-37.8); P = 0.19]. Aminopyrine metabolism was 25% lower in simple steatosis [8.9% (7.0-10.7)] and 50% lower in NASH [6.0% (4.5-7.5)] than in controls [11.9% (9.3-12.8)] (P < 0.001). ICG elimination was intact.

CONCLUSIONS

The hepatocellular metabolic functions were altered in a manner that was dissociated both by different effects on different liver functions and by different effects of different stages of NAFLD. Thus, NAFLD has widespread consequences for metabolic liver function, even in simple steatosis.

Non-alcoholic steatohepatitis, but not simple steatosis, disturbs the functional homogeneity of the liver - a human galactose positron emission tomography study

BACKGROUND

The disease severity of non-alcoholic fatty liver disease (NAFLD) and the distinction between simple steatosis and non-alcoholic steatohepatitis (NASH) are based on the pathohistological presence of steatosis, inflammation, ballooning and fibrosis. However, little is known about the relation between such structural changes and the function of the afflicted liver.

AIMS

To investigate in vivo effects of hepatic fat fraction, ballooning and fibrosis on regional and whole liver metabolic function assessed by galactose elimination in NASH and simple steatosis.

METHODS

Twenty-five biopsy-proven, nondiabetic patients with NAFLD (13 NASH with low-grade fibrosis, 12 simple steatosis with no fibrosis) underwent 2-[¹⁸ F]fluoro-2-deoxy-d-galactose positron emission tomography and magnetic resonance imaging-derived proton density fat fraction of the liver. Nine healthy persons were included as controls.

RESULTS

In the NASH patients, the standardised hepatic uptake of 2-[¹⁸ F]fluoro-2-deoxy-d-galactose was reduced to 13.5 (95% confidence interval, 12.1-14.9) as compared with both simple steatosis and controls (16.4 (15.6-17.1), P < 0.001). Thus, the NASH patients had reduced regional metabolic liver function. The liver fat fraction diluted the standardised uptake equally in NASH and simple steatosis but the fibrosis and ballooning of NASH were associated with a further decrease. Moreover, the NASH livers exhibited increased variation in their standardised uptake values (coefficient of variation 13.8% vs 11.6% in simple steatosis and 10.2% in controls, P = 0.02), reflecting an increased functional heterogeneity.

CONCLUSIONS

In NASH, the regional metabolic liver function was lower and more heterogeneous than in both simple steatosis and healthy controls. Thus, NASH disturbs the normal homogeneous metabolic function of the liver.

Continued Enteral Feeding Is Beneficial in Hypoglycemic Infants Admitted to Intensive Care for Parenteral Dextrose Therapy

There is variability in practice among care providers on feeding infants admitted with neonatal hypoglycemia (NH) for parenteral dextrose. We compared clinical outcomes in infants who were fed (NH-Fed) and hypoglycemic infants who were kept nothing per os (NPO) (NH-NPO) at the time of initiation of intravenous (IV) dextrose. We performed a retrospective review of all newborn infants admitted to the neonatal intensive care unit with NH for IV dextrose. Infants were grouped as per the feeding approach at initiation of IV dextrose: NH-Fed or NH-NPO infants. We found that infants in the NH-Fed group had lower maximum glucose infusion rate, less duration of glucose infusion therapy compared with the NH-NPO group, and significantly less number of days of hospital stay compared with the NH-NPO group (5.87 ± 1.4 days vs 4.9 ± 1.4 days, P < .006). In conclusion, feeding infants with hypoglycemia who require IV dextrose offers tangible benefits of shorter duration of parenteral dextrose and shorter length of hospitalization.

Postprandial metabolic response of breast-fed infants and infants fed lactose-free vs regular infant formula: A randomized controlled trial

Lactose intolerance is a major concern driving the growth of lactose-free foods including lactose-free infant formula. It is unknown what the metabolic consequence is of consumption of a formula where lactose has been replaced with corn syrup solids (CSS). Here, a randomized double-blinded intervention study was conducted where exclusively formula-fed infants were fed formula containing either lactose or CSS-based infant formula and compared with an equal number of exclusively breast-fed infants. Plasma metabolites and insulin were measured at baseline, 15, 30, 60, 90 and 120 min after feeding. Differences in plasma metabolite profiles for formula-fed infants included a rapid increase in circulating amino acids, creatinine and urea compared with breast-fed infants. At 120 min post-feeding, insulin was significantly elevated in formula-fed compared with breast-fed infants. Infants fed lactose-based formula had the highest levels of glucose at 120 min, and leucine, isoleucine, valine and proline at 90 and 120 min, whereas infants fed CSS-based formula had the lowest levels of non-esterified fatty acids at all time points, and glucose at 120 min. Overall, these differences highlight that changes in infant formula composition impact infant metabolism, and show that metabolomics is a powerful tool to help with development of improved infant formulas.

Metabolite profiles of formula milk compared to breast milk

Breast milk (BM) feeding is the gold standard in neonate nutrition. When BM is not available it can be substituted or integrated with commercial formula milk (FM) usually sold under different brands and formulations. In this work, the low-molecular-weight hydrophilic compounds in milk were studied by gas chromatography electronic impact mass spectrometry (GC-MS), comparing eight different FM brands with BM samples. With the aid of multivariate statistical data analysis, a marked variability among FM brands, especially driven by the presence of prebiotics in their formulation, was highlighted. Quali-quantitative differences were found between FM and BM. Orotic acid and isomaltulose were found exclusively in FM, while phenylalanine and tyrosine levels were high in two FM brands. Moreover, higher levels of malic acid, sugars (glucose, fructose and galactose), and mannitol were detected in FM. On the other hand, BM showed a higher amino acid content. In conclusion, GC-MS proved to be a very sensitive analytical technique for the study of FM, highlighting metabolite differences among FM brands, and between FM and BM, that may have a possible strong impact on neonatal nutrition.

Locust bean gum safety in neonates and young infants: an integrated review of the toxicological database and clinical evidence

Locust bean gum (LBG) is a galactomannan polysaccharide used as thickener in infant formulas with the therapeutic aim to treat uncomplicated gastroesophageal reflux (GER). Since its use in young infants below 12weeks of age is not explicitly covered by the current scientific concept of the derivation of health based guidance values, the present integrated safety review aimed to compile all the relevant preclinical toxicological studies and to combine them with substantial evidence gathered from the clinical paediatric use as part of the weight of evidence supporting the safety in young infants below 12weeks of age. LBG was demonstrated to have very low toxicity in preclinical studies mainly resulting from its indigestible nature leading to negligible systemic bioavailability and only possibly influencing tolerance. A standard therapeutic level of 0.5g/100mL in thickened infant formula is shown to confer a sufficiently protective Margin of Safety. LBG was not associated with any adverse toxic or nutritional effects in healthy term infants, while there are limited case-reports of possible adverse effects in preterms receiving the thickener inappropriately. Altogether, it can be concluded that LBG is safe for its intended therapeutic use in term-born infants to treat uncomplicated regurgitation from birth onwards.

Impact of selected inborn errors of metabolism on prenatal and neonatal development

In general, data regarding maturational processes of different metabolic pathways in the very vulnerable fetal and neonatal period are rare. This review is to substantiate the impact of selected inborn errors of metabolism on this critical period of life and their clinical manifestation. Significant adaptation of mitochondrial/energy-, carbohydrate-, lysosomal-, and amino acid-metabolism occurs during early prenatal and neonatal development. In utero, metabolic environment has an impact on the development of the fetus as well as fetal organ maturation. Defects of distinct metabolic pathways could therefore already be of significant relevance in utero and for clinical manifestations in the early fetal and neonatal period. Disturbances of these pathways may influence intrauterine growth and health. Production of a toxic intrauterine milieu, energy-deficiency, modification of membrane function, or disturbance of the normal intrauterine expression of genes may be responsible for fetal compromise and developmental disorders. Three categories of metabolic disorders will be discussed: the "intoxication type" (classical galactosemia, ornithine transcarbamylase deficiency, and "maternal phenylketonuria"), the "storage type" (Morbus Niemann Pick type C), and the "energy deficient type" (including long-chain fatty acid oxidation disorders, pyruvate dehydrogenase deficiency, and respiratory chain defects). For these disorders, the pathophysiology of early manifestation, special aspects regarding the prenatal and neonatal period, and diagnostic as well as therapeutic options are presented.

Plasma concentrations of carbohydrates and sugar alcohols in term newborns after milk feeding

Nonglucose carbohydrates such as galactose, mannose, and inositol play a clinically important role in fetal and neonatal nutrition, though little is known about their metabolism in the neonate. The aim of this study was to determine whether postprandial changes in plasma carbohydrate and sugar alcohol concentrations are affected by clinical variables such as postnatal age (PNA), milk type, feeding volume, or feeding duration in term newborns. Neonates (n = 26) taking intermittent enteral feedings were enrolled. Blood samples were obtained at baseline (immediately before the start of a feeding) and at 2-3 subsequent time points up to 110 min. Postprandial rise was only observed for plasma glucose concentrations [Glu] and plasma galactose concentrations [Gal] and clinical variables did not predict this change. Despite equimolar delivery in milk, the median of [Glu] rise minus [Gal] rise from baseline to second postprandial plasma sample was 674 microM (-38, 3333 microM; p < 0.0001), reflecting efficient hepatic first-pass metabolism of galactose. A significant PNA effect on [Gal] was observed such that for each day PNA there was an 18% decrease in [Gal] (p = 0.03). [Gal] are a function of PNA, suggesting maintenance of a significant ductus venosus shunt in term infants.

The synthesis of 2-, 3-, 4- and 6-O-α-d-glucopyranosyl-d-galactopyranose, and their evaluation as nutritional supplements for pre-term infants

Four methods have been screened for the synthesis of some alpha-D-glucopyranosides, with the recently reported (Mukaiyama) combination of 2,3,4,6-tetra-O-benzyl-alpha-D-glucopyranosyl iodide and triphenylphosphine oxide being the most successful, especially in the diastereoselectivity exhibited. The alpha-D-glucopyranosides so obtained have been deprotected to yield 2-, 3-, 4- and 6-O-alpha-D-glucopyranosyl-D-galactopyranose. Only the last disaccharide showed any hydrolysis by alpha-glycosidases but this success was not emulated by mucosal extracts from the small intestine of the pig.

Dietary galactose inhibits GDF-9 mediated follicular development in the rat ovary

Clinical evidence suggests an association between galactosemia and premature ovarian failure, but the mechanism is still not fully understood. Growth differentiation factor-9 (GDF-9) is thought to be an obligatory growth factor during the gonadotropin-independent phase of folliculogenesis. The objective of this study was to examine the effects of galactose on initiation of folliculogenesis in the peripubertal interval and the connection between galactose toxicity and GDF-9 expression in the ovary. After immature Long-Evans rats (n = 10) were fed a diet consisting of 20% galactose for 19 days, whole body, ovary and uterine weights were measured. Serum estradiol and progesterone concentrations were measured by radioimmunoassay. Ovarian follicles were counted by morphometric analysis and GDF-9 expression was investigated by immunohistochemistry and immunoblot assay. Galactose treatment did not affect the onset of puberty as marked by the time of vaginal opening. The galactose diet significantly decreased the number of healthy growing follicles. The results of immunoblot assay showed that both bands corresponding to propeptide and mature forms of GDF-9 decreased with the galactose diet about 90 and 70%, respectively. The results of immunohistochemical staining showed that the GDF-9 positive follicle number and the ratio of GDF-9 positive to GDF negative (primordial/non-growing) follicles significantly decreased with this high galactose diet. The present study suggests that a high galactose diet inhibits follicular development, possibly through down-regulation of GDF-9 in the rat ovary, implying that GDF-9 may be involved in galactose-related ovarian toxicity.

Insights into the pathogenesis of galactosemia

In humans, the absence of galactose-1-phosphate uridyltransferase (GALT) leads to significant neonatal morbidity and mortality which are dependent on galactose ingestion, as well as long-term complications of primary ovarian failure and cognitive dysfunction, which are diet independent. The creation of a knockout mouse model for GALT deficiency was aimed at providing an organism in which metabolic challenges and gene manipulation could address the enigmatic pathophysiologic questions raised by humans with galactosemia. Instead, the mouse represents a biochemical phenotype without evidence of clinical morbidity. The similarities and differences between mice and humans with galactosemia are explored from metabolite, enzyme, and process points of view. The mouse both produces and oxidizes galactose in a manner similar to humans. It differs in brain accumulation of galactitol. Future directions for exploration of this enigmatic condition are discussed.

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Determination of blood sugars by high pressure liquid chromatography with fluorescent detection

In this study, a high pressure liquid chromatography method with fluorescent detector was developed to analyze blood galactose, lactose and glucose simultaneously. Plasma sugars were prepared as fluorescent derivatives to react with FMOC-hydrazine (9-fluorenyl methyl chloroformate). A C18 reversed phase column and a fluorescent detector were used and run in ambient. The resolution index of galactose and glucose derivatives in the analytical method was 1.15. The coefficients of variation of the analysis were less than 7.5%. The concentration of FMOC-hydrazine did not significantly influence the analytical results for determination of the concentration of galactose. However, the ratios of acetonitrile in the mobile phase significantly affected the analysis of the fluorescent derivatives of sugars. The sensitivity of this method for galactose detection was 5 micrograms ml-1, and the required plasma volume for testing was only 25 microliters each. This analytical method was successfully applied to study the pharmacokinetics of galactose in vivo in a rabbit model.

Assessing the effect of disease on nutrition of the preterm infant

OBJECTIVE

To review existing data on nutritional requirements of extremely low birth weight (ELBW) and very low birth weight (VLBW) preterm infants (those who weigh < 1000 g and 1000-1500 g at birth, respectively), and the effects of diseases on these nutritional requirements.

DATA SOURCES

A literature search was conducted on applicable articles related to nutritional requirements of preterm ELBW and VLBW infants and the effects of diseases in these infants on their nutritional and metabolic requirements.

DATA SYNTHESIS

The literature was analyzed to determine nutritional requirements of preterm ELBW and VLBW infants, to select the most common diseases that have significant and important effects on nutrition and metabolism in these infants, and to make recommendations about diagnostic and therapeutic approaches to nutritional problems as affected by diseases in ELBW and VLBW infants.

CONCLUSIONS

Many diseases unique to preterm infants, either directly or by enhancing the effects of stress on the metabolism of such infants, provide important changes in the nutrient requirements. The overriding observation from all studies, however, is that ELBW and VLBW preterm infants are underfed during the early postnatal period and that this condition, combined with additional stresses from various diseases, increases the risk of long-term neurological sequelae. The value of achieving a specific body composition and growth weight is less certain. There remains a critical need for determining the right quality as well as quantity of nutrients for these infants.

Maintenance of villus height and crypt depth, and enhancement of disaccharide digestion and monosaccharide absorption, in piglets fed on cows' whole milk after weaning

The aims of the present study were (a) to maintain the structure and function of the small intestine of the piglet after weaning, and (b) to compare the capacity in vivo of sucking and weaned piglets to digest oral boluses of lactose and sucrose and absorb their monosaccharide products. Piglets were fed on cows' whole milk ad libitum every 2 h for 5 d after weaning. Physiological doses of lactose plus fructose (treatment LAC+FRU) and sucrose plus galactose (treatment SUC+GAL) were administered on day 27 of lactation and on the fifth day after weaning, after which time piglets were killed. Villus height and crypt depth were maintained (P > 0.05) by feeding cows' milk after weaning. The areas under the curves (AUC) for galactose and glucose, adjusted for live weight and plasma volume, increased (P < 0.05) after weaning. Despite the enhancement of gut function after weaning, the galactose index (GalI:AUC for galactose ingested as lactose divided by the AUC for the same dose of galactose ingested as the monosaccharide) and fructose index (FruI: AUC for fructose ingested as sucrose divided by the AUC for the same dose of fructose ingested as the monosaccharide), which are indices of digestive and absorptive efficiency, both decreased after weaning. This apparent anomaly may be reconciled by increased growth, and hence surface area, of the small intestine between weaning and slaughter such that 'total' digestion and absorption most probably increased despite apparent decreases in GalI and FruI. Positive correlations (P < 0.05) between villus height and GalI are consistent with the maximum activity of lactase occurring more apically along the villus. Significant linear relationships (P < 0.05) were recorded between villus height at the proximal jejunum and adjusted AUC for galactose and glucose following treatment LAC+FRU, and between villus height at the proximal jejunum and adjusted glucose AUC following treatment SUC+GAL. These relationships suggest that maximum digestion and absorption occurs at increasing distances along the crypt:villus axis in the weaned pig.

Hepatic glycogen accurately reflected by acetaminophen glucuronide in dogs refed after fasting

To validate a method to "biochemically biopsy" the immediate precursor of intrahepatic glycogen [uridyl diphosphate (UDP)-glucose] using acetaminophen and to assess how fasting affects the direct and indirect pathways of glycogen synthesis, dogs were fasted overnight (group 1, n = 5) or for 2.5 days (group 2, n = 5) and then given a 4-h duodenal infusion of unlabeled glucose, [3-3H]glucose, and [U-14C]lactate to label hepatic glycogen via the direct and indirect pathways, respectively, and [1-13C]galactose to measure intrahepatic UDP-glucose flux. After 3 h for equilibration, acetaminophen was given and urine was collected for acetaminophen glucuronide. Multiple liver biopsies were obtained. The mean 3H/14C ratios of glucose derived from glycogen (10.4 +/- 4.1 and 1.1 +/- 0.3 for groups 1 and 2, respectively) and glucose derived from acetaminophen glucuronide (11.5 +/- 4.0 and 1.0 +/- 0.1 for groups 1 and 2, respectively) were similar. Fasting significantly increased UDP-glucose flux, the rate of glycogen synthesis, and the contribution of the indirect pathway. We conclude that, in dogs, 1) no functional hepatic zonation exists with regard to acetaminophen glucuronidation and liver glycogen synthesis and 2) with appropriate choice of isotopic tracers and study design, UDP-glucose flux can accurately reflect rates of hepatic glycogen synthesis.

The response in the blood of piglets to oral doses of galactose and glucose and intravenous administration of galactose

The kinetics of the response in the blood of piglets to physiological oral intakes of galactose and glucose, and intravenous administration of galactose are described. Following the intravenous administration of galactose to 2- and 10-d-old piglets (n 7), the half-life was 7.98 (SD 0.75) and 7.99 (SD 1.89) min respectively, and efficient elimination rate was 9.09 (SD 2.15) and 8.75 (SD 0.79)% per min respectively. The turnover of galactose in the piglets was 100.3 micrograms/min per kg body weight. These observations demonstrate that galactose was rapidly removed from the blood of the piglets. While the dosing and sampling procedures stimulated hyperglycaemia, they had no effect on the concentration of galactose in the peripheral plasma. The galactose area under the curve (adjusted to the plasma volume of the animal) following a dose of either galactose or galactose plus glucose was 1.75 (SD 0.15) and 1.95 (SD 0.14) arbitrary units respectively in 2-d-old piglets and 1.96 (SD 0.26) and 1.98 (SD 0.10) arbitrary units respectively in 10-d-old piglets. Since the presence of glucose did not lower the adjusted area under the curve for galactose in the peripheral blood, the effect of glucose on the metabolism of galactose in piglets was more like that reported for rats than that for man, guinea-pigs or mice. It is suggested that the galactose moiety of lactose may make an important contribution to the replenishment of liver glycogen in the neonatal piglet.

Hepatic metabolism of glucose, galactose, and lactate after milk feeding in newborn lambs

The purpose of this study was to test the ability of the liver to efficiently clear substrates absorbed from the gastrointestinal tract after a feeding before entry into the systemic circulation. We placed a hepatic vein (HV) catheter in utero at 135-140 days gestation. The lamb was then allowed to deliver spontaneously, and additional catheters were placed in the portal vein (PV) and femoral artery (FA) at 1-3 days postnatal age. After at least 2 days recovery, lambs were fasted overnight at 4-10 days of age and then allowed to nurse ad libitum. There was significant hepatic glucose release during fasting and after 80 min postprandially. No net hepatic uptake of glucose was observed before or after feeding. PV galactose was significantly greater than FA and HV from 40 to 160 min after feeding (P less than 0.005). Hepatic glucose extraction was negligible in the fasted state (1 +/- 3%) and increased after feeding to 75 +/- 2% when PV galactose was less than 1.0 mM. There was a significant hepatic arteriovenous concentration difference of lactate (0.23 +/- 0.03 mM) and of oxygen (0.27 +/- 0.01 mM), which did not change significantly after feeding. The metabolic quotient for galactose increased significantly after feeding, such that galactose was the largest carbon contributor for postprandial hepatic carbon accretion. After a milk feeding, the newborn liver efficiently extracts galactose, lactate, and oxygen, but not glucose.

Lactose and cataract in humans: a review

In this review, the relationship between lactose and human cataract is examined from the presently available biochemical, metabolic, and epidemiological data. The exceptional cases of homozygous enzyme deficiency being excluded, fragmentary data give reason to believe that a risk of cataract secondary to lactose and galactose ingestion is present in certain subpopulations. In these population groups, the size of which is unknown, the lens could be exposed to intermittent episodes of hypergalactosemia due to the presence of a partial enzyme deficiency in the galactose metabolic pathway, and/or the persistence of a high adult jejunal lactase activity, and/or to a large and repeated consumption of either whole lactose or easily absorbed lactose (hydrolyzed forms and nonpasteurized yogurt).

Changes in the concentrations of glucose and galactose in the peripheral blood of sucking piglets

Changes in the concentrations of glucose and galactose were measured in the peripheral blood of ten piglets after they had ingested milk during a natural sucking. In addition, the mild stress associated with the experimental procedure was determined by sampling nine fasted piglets over a period of 9 to 12 min. During this period there was a significant increase in the concentration of glucose in the blood of the piglets but no change in the concentration of galactose. After milk ingestion during a natural sucking the concentrations of both glucose and galactose increased from 5.7 mM and 19 microM to reach peak values of 7.7 mM and 122 microM, respectively, by 30 to 35 min. The concentrations of glucose and galactose returned to initial values in 60-80 min and 80-100 min, respectively, after sucking. Since the change in the concentration of galactose in the peripheral blood was much lower than the change in the concentration of glucose, we conclude that galactose was rapidly removed by the livers of sucking piglets. However, after the ingestion of milk the percentage increase (from initial to peak values) in the concentration of galactose in the blood was much larger (650%) than the increase in the concentration of glucose (43%). Thus, we propose that the determination of galactose in the peripheral blood may provide a qualitative method for monitoring the digestion and absorption of milk lactose in sucking piglets.

The glucose-galactose paradox in neonatal murine hepatic glycogen synthesis

In adults glucose incorporation to glycogen is indirect after recycling from lactate. In neonates galactose entry to glycogen exceeds that for glucose, but the pathway is unknown. The pathway of hexose incorporation to glycogen was studied in 5-7-day-old rats and 6-h-old rats injected intraperitoneally (IP) with either double-labeled [6-3H]glucose (nonrecycling), [U-14C]glucose (recycling), or [6-3H]glucose and [U-14C]galactose in saline. In another group of pups, 1 g/kg of glucose or galactose was administered in addition to tracers to determine glycemia and net glycogen synthesis between 15 and 180 min after injection. Blood glucose increased from 3.4 +/- 0.4 to 8.5 +/- 1.5 mM in 5-7-day-old pups in response to IP glucose; there was no glycemic response to galactose, although galactose levels increased from 0.5 to 6.3 mM at 15 min. Hepatic glycogen increased after IP glucose from 14 +/- 2 at 15 min to 30 +/- 3 at 120 min (P less than 0.01), whereas after IP galactose glycogen was 44 +/- 6 mumol/g at 120 min (P less than 0.05). After IP glucose, 3H and 14C disintegration per minute in glycogen increased slowly with 14C exceeding 3H at 120 and 180 min. In contrast IP [14C]galactose resulted in a much greater peak of 14C incorporation into glycogen. The ratio of 3H to 14C in glycogen relative to the injectate after IP glucose decreased from 0.69 +/- 0.12 to 0.36 +/- 0.03 (P less than 0.01) between 15 to 180 min, whereas the ratio after galactose was 0.20 +/- 0.007 to 0.15 +/- 0.02 at these times. The 6-h-old pups also demonstrated augmented incorporation of [14C]galactose in glycogen relative to [3H-14C]glucose. In contrast to 5-7-day-old pups there was no evidence of glucose recycling in 6-h-old pups. In conclusion galactose entry into glycogen exceeds that for glucose and is not dependent on recycling. Direct incorporation of galactose exceeds that for direct incorporation from [3H]glucose, suggesting a preferential utilization of galactose for neonatal glycogen synthesis.

Compared roles of glucose, galactose and fructose as glycogen precursors during the acute response to insulin in cultured rat foetal hepatocytes

1. The efficiency of the contribution of hexoses to basal- and stimulated-glycogenesis, when studied in cultured 18 day-old rat foetal hepatocytes in the presence of glucose, was as follows: galactose greater than glucose greater than fructose. 2. Glucose deprivation had opposite effects on the contributions of [14C]galactose (decreased) and [14C]fructose (increased) to glycogenesis, which occurred independently of insulin and were reversed by glucose concentrations as low as 30-100 microM. 3. The stimulation of glycogenesis by insulin measured with [14C]glucose (3.2-fold) was superior to that obtained with either [14C]galactose or [14C]fructose (2.7-fold in both cases), which revealed a specific beneficial effect of insulin on glucose contribution.