Tissue mineral distributions are differentially modified by dietary protein deficiency and a murine nematode infection

This study was designed to investigate whether mineral concentrations in the spleen, serum, and liver were modified by challenge infection with a gastrointestinal nematode, by infection dose, or by protein deficiency despite adequate dietary intakes of minerals. BALB/c mice fed protein-sufficient (PS, 24%) or protein-deficient (PD, 3%) diets were infected with 100 L3 of Heligmosomoides bakeri, drug-treated, and then re-infected with either 0, 100, or 200 L3. Protein deficiency and infection, but not dose, independently modified tissue mineral distributions. H. bakeri infection lowered serum iron concentrations in both diet groups. Despite this, PD mice had elevated iron and calcium concentrations and Ca/Zn ratio in the spleen as well as Fe/Zn ratio in liver, but they had reduced calcium, zinc, copper, and sulfur concentrations, and Cu/Zn ratio in the liver. Infection reduced calcium and iron concentrations and the Ca/Zn ratio in the spleen. We suggest that tissue mineral distribution is a consequence of Th2 immune and inflammatory responses induced by infection in PS mice and the switch to predominant Th1 inflammation in PD, nematode-infected mice.

Acute phase nematode infection reduces resting metabolic rate in both protein-sufficient and protein-deficient mice

The objective of this study was to investigate whether protein deficiency concurrent with the acute phase of infection with the murine nematode Heligmosomoides bakeri (Durette-Desset, Kinsella and Forrester, 1972; Tenora and Barus, 2001) affected the resting metabolic rate (RMR) in BALB/c mice, and whether deworming caused RMR to return to normal. Mice fed either a protein-sufficient (PS, 24%) or protein-deficient (PD, 3%) diet were infected with 100 larvae, and then treated with an anthelmintic drug on 9 and 14 days postinfection (dpi). RMR was measured on –2, 2, 7, and 19 dpi. The results showed that protein deficiency did not affect RMR at any of these times. RMR was unchanged immediately following infection (2 vs. –2 dpi) at the time when larvae are first embedded in the serosal musculture. Surprisingly, at 7 dpi when larvae migrate from the serosal musculture into the intestinal lumen, RMR was significantly lower in both diet groups compared with earlier time points. This reduced RMR persisted even after deworming. Possible reasons for these results are discussed.

Mechanisms underlying reduced expulsion of a murine nematode infection during protein deficiency

Balb/c mice infected with the gastrointestinal nematode Heligmosomoides bakeri were fed protein sufficient (PS, 24%) or deficient (PD, 3%) diets to investigate whether diet, infection or dose of larval challenge (0, 100 or 200 larvae) influenced gut pathophysiology and inflammation. Among the PS mice, worms were more posteriorad in the intestine of mice infected with 200 compared with 100 larvae, suggesting active expulsion in the more heavily infected mice. This was consistent with the positive correlation between worm numbers and fluid leakage in PS mice; similar patterns were not detected in the PD mice. Infection also induced villus atrophy, which was more pronounced in PS than in PD mice. Our cytokine screening array indicated that infection in PD mice elevated a wide range of pro-inflammatory cytokines and chemokines. Whereas serum leptin concentrations were higher in PD mice, monocyte chemotactic protein-5 (MCP-5) in serum increased with increasing larval dose and concentrations were lower in PD than PS mice. We suggest that elevated MCP-5 together with villus atrophy may contribute to the apparent dose-dependent expulsion of H. bakeri from PS mice but that delayed expulsion in PD mice appeared related to a predominant Th1 cytokine profile that may be driven by leptin.

Oral polyamine administration modifies the ontogeny of hexose transporter gene expression in the postnatal rat intestine

Gastrointestinal mucosal polyamines influence enterocyte proliferation and differentiation during small intestinal maturation in the rat. Studies in postnatal rats have shown that ornithine decarboxylase (ODC) protein and mRNA peak before the maximal expression of brush-border membrane (BBM) sucrase-isomaltase (SI) and the sugar transporters sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2). This study was undertaken to test the hypothesis that the oral administration of spermidine in postnatal rats upregulates the expression of ODC, thereby enhancing the expression of SI and SGLT1 in the brush-border membrane as well as basolateral membrane-facilitative GLUT2 and Na(+)-K(+)-ATPase. Northern and Western blot analyses were performed with antibodies and cDNA probes specific for SI, SGLT1, GLUT2, alpha(1)- and beta(1)-subunits of Na(+)-K(+)-ATPase, and ODC. Postnatal rats fed 6 mumol spermidine daily for 3 days from days 7 to 9 were killed either on postnatal day 10 (Sp10) or day 13 following a 3-day washout period (Sp13). Sp10 rats showed a precocious increase in the abundance of mRNAs for SI, SGLT1, and GLUT2 and Na(+)-K(+)-ATPase activity and alpha(1)- and beta(1)-isoform gene expression compared with controls. ODC activity and protein and mRNA abundance were also increased in Sp10 animals. The increased expression of these genes was not sustained in Sp13 rats, suggesting that these effects were transient. Thus, 3 days of oral polyamine administration induces the precocious maturation of glucose transporters in the postnatal rat small intestine, which may be mediated by alterations in ODC expression.

Re-feeding rapidly restores protection againstHeligmosomoides bakeri(Nematoda) in protein-deficient mice

This study determined whether the timing of re-feeding of protein-deficient mice restored functional protection against the gastrointestinal nematode,Heligmosomoides bakeri. Balb/c mice were fed a 3% protein-deficient (PD) diet and then transferred to 24% protein-sufficient (PS) diet either on the day of primary infection, 10 days after the primary infection, on the day of challenge infection, or 7 days after the challenge infection. Control mice were fed either the PD or PS diet. Onset of challenge, but not primary, infection caused short-term body weight loss, anorexia and reduced feed efficiency. Weight gain was delayed in mice when re-feeding commenced on the day of challenge infection; alkaline phosphatase (ALP) was also elevated in these mice on day 28 post-challenge. In contrast, other re-feeding groups attained similar body weights to PS mice within 4 days and had similar ALP at day 28. Serum leptin was higher in PD than PS mice and positively associated with food intake. As expected, worm survival was prolonged in mice fed the PD diet. However, egg production and worm burdens were similar in all re-feeding groups to the PS mice, indicating that protein re-feeding during either the primary or challenge infection rapidly restored normal parasite clearance.

Mild energy restriction alters mouse–nematode transmission dynamics in free-running indoor arenas

Energy restriction reduces Heligmosomoides polygyrus (Dujardin, 1845) (Nematoda) infection by reducing transmission-related behaviours but prolongs parasite survival by suppressing immune responses in individually housed mice. To determine the relative importance of these two processes in accumulation of worms in mouse populations, 10 female CD1 mice were housed in each of eight indoor arenas with ad libitum access to either an energy-sufficient (ES) diet or an energy-restricted (ER) diet with 20% less metabolizable energy (four arenas per diet). After 3 weeks, H. polygyrus transmission was initiated by introducing larvae onto damp peat trays. Mice adapted to the ER diet through increased food intake and nesting and reduced overall activity; after 6 weeks, nutritional and immunological measures were comparable between diet groups. With continuing exposure to parasite larvae, mice in both ER and ES arenas developed resistance to the incoming larvae; however, mice in the ER arenas accumulated lower worm burdens than mice in the ES arenas despite their increased contact with peat. We suggest that the comparable immunocompetence of mice in the ER and ES arenas enabled the ER mice exposed to higher transmission rates to more rapidly reject the parasites, leading to lower final worm numbers, a pattern frequently observed in other helminth infections.

Energy deficiency alters behaviours involved in transmission ofHeligmosomoides polygyrus(Nematoda) in mice

Independent studies have shown that animal behaviour is affected by nutritional deficiency and that host behaviour influences parasite transmission. The objectives of this study were to determine whether energy deficiency alters the behaviour profile of mice and the rate of exposure of mice to naturally acquired Heligmosomoides polygyrus (Nematoda) larvae. Outbred CF-1 and CD-1 female mice were fed either a control or an energy-deficient (65% of control) diet for 7 days, after which time, the mice fed the deficient diet had consumed signficantly less energy, had lower rectal temperatures, and lower masses (CD-1 mice only) compared with control mice. On day 7, mice were placed individually in natural transmission arenas containing damp peat moss and parasite larvae for 6 h, during which time, each mouse was observed 60 times and her behaviour recorded. All mice were then returned to standard caging and fed the energy-sufficient diets to eliminate confounding effects of energy deficiency on the host immune response over the following 8 days. At necropsy, parasite numbers were significantly lower in the energy-deficient mice of both strains. The behaviour profile differed significantly between diet groups and between strains; deficient mice of both strains groomed less and dug in the peat substrate less than control mice. The frequency of grooming was positively correlated with worm burden in both strains, the frequency of mouthing the peat moss and of sleeping were positively associated with worm burden in CD-1 mice, and the frequency of standing and walking low was positively associated with worm burden in CF-1 mice. These results indicate that grooming and contact with the peat moss are important behaviours in transmission of H. polygyrus, that energy deficiency causes a decrease in the frequency of these behaviours, and that these behavioural changes may contribute to reduced parasite transmission in mice fed the energy-restricted diet.

Dietary pectin, but not cellulose, influences Heligmosomoides polygyrus (Nematoda) reproduction and intestinal morphology in the mouse

Dietary texture has been reported to influence parasite establishment and survival, but to what degree this relationship is modified by either the type or quantity of dietary fibre is unknown. Using a 2 x 4 factorial design, we explored the relationship between fibre type (soluble pectin vs insoluble = cellulose) and fibre quantity (0, 5, 10 and 20% by dry weight) on parasitic outcomes in BALB/c mice infected with 100 Heligmosomoides polygyrus (Nematoda) larvae. Pectin, but not cellulose, exerted a significant effect on parasite egg production. Following in vitro culture of female worms, increasing levels of dietary pectin were associated with increasing release of eggs. Yet this pattern was not observed in vivo, where per capita egg production peaked at the 10% pectin concentration, but was very low in mice fed 20% pectin. Parasite establishment was elevated in mice fed 20% pectin, but was unaffected by cellulose concentration. Neither type nor quantity of fibre affected H. polygyrus survival or spatial distribution along the gastrointestinal tract. To what degree differences in parasite establishment and reproduction could be attributed to the marked effects of pectin on gut morphology (increased intestinal length, villus length, mucosa thickness and villus/crypt ratio) requires further exploration. Our data indicate that cellulose is preferable to pectin as the source of fibre for experimental diets as cellulose did not affect H. polygyrus establishment, reproduction or survival during a 4-week primary infection.

Gastrointestinal nematodes, nutrition and immunity: breaking the negative spiral

Nutritionists have long understood that intestinal nematode parasites have deleterious effects on host nutritional status, but only recently has the importance of malnutrition as a predisposing factor to intestinal nematodes been recognized. Here we review experimental and field studies on the effects of protein, energy, zinc, vitamin A, and iron deficiencies on gastrointestinal (GI) nematodes of humans, livestock, and laboratory rodents, and draw certain conclusions about the state of our current understanding. In general, malnutrition promotes the establishment, survival, and fecundity of these parasites, but the magnitude of the effect depends on factors such as host species, parasite species, particular infection protocol used, magnitude of the infection, severity of the nutritional deficiency, and presence of single or multiple infections and single or multiple nutritional deficiencies. We highlight the Th2 arm of the immune system as a component of primary importance in the association between malnutrition and GI nematode infections. We summarize what is known about underlying mechanisms that may account for the observed patterns. Finally, we suggest future research directions.

Teaching subjects with type 2 diabetes how to incorporate sugar choices into their daily meal plan promotes dietary compliance and does not deteriorate metabolic profile

OBJECTIVE

To determine whether teaching free-living subjects with type 2 diabetes how to incorporate added sugars or sweets into their daily meal plan results in a greater consumption of calories (fat or sugar) and deteriorates their glycemic or lipid profiles but improves their perceived quality of life.

RESEARCH DESIGN AND METHODS

In an 8-month randomized controlled trial, 48 free-living subjects with type 2 diabetes were taught either a conventional (C) meal plan (no concentrated sweets) or one permitting as much as 10% of total energy as added sugars or sweets (S). Mean individual nutrient intake was determined using the average of six 24-h telephone recalls per 4 months. Metabolic control and quality of life were evaluated every 2 months. Quality of life was assessed using the Medical Outcome Survey and the Diabetes Quality of Life questionnaire.

RESULTS

The S group did not consume more calories (fat or sugar) and in fact ate significantly less carbohydrate (-15 vs. 10 g) and less starch (-7 vs. 8 g) and had a tendency to eat fewer calories (-77 vs. 81 kcal) than the C group. Weight remained stable, and there was no evidence that consuming more sugar worsened metabolic profile or improved their perceived quality of life.

CONCLUSIONS

Giving individuals with type 2 diabetes the freedom to include sugar in their daily meal plan had no negative impact on dietary habits or metabolic control. Health professionals can be reassured and encouraged to teach the new "sugar guidelines," because doing so may result in a more conscientious carbohydrate consumption.

Suppressed T helper 2 immunity and prolonged survival of a nematode parasite in protein-malnourished mice

Protein malnutrition may increase susceptibility to gastrointestinal parasitic infections, possibly as a result of impaired intestinal and/or systemic T helper 2 (Th2) effector responses induced by down-regulation of Th2 cytokines and/or up-regulation of Th1 cytokines. To test this hypothesis, female BALB/c mice (n = 18/diet) were fed a control (24%), marginal (7%), or deficient (3%) protein diet and given a challenge infection with Heligmosomoides polygyrus. The 3% mice had higher worm burdens at 1, 2, and 4 weeks postchallenge infection (pci), lower increases in serum IgE, reduced intestinal eosinophilia, and depressed mucosal mast cell proliferation and activation at 1-2 weeks pci. To determine whether these suppressed effector responses resulted from altered spleen and mesenteric lymph node (MLN) cytokine production, cells were restimulated in vitro with parasite antigen and cytokine concentrations were measured. Deficient MLN cells secreted significantly less IL-4 and more IFN-gamma at 1-2 weeks pci than did control MLN cells. Deficient spleen cells also secreted more IFN-gamma at 2 weeks pci compared with control spleen cells. From reverse transcription-PCR analyses, the 3% mice also had lower IL-4 mRNA level in spleen and MLN at 1-2 weeks pci. Our study supports the hypothesis that protein malnutrition increases the survival of a nematode parasite by decreasing gut-associated IL-4 (Th2) and increasing IFN-gamma (Th1) within 2 weeks pci, leading to reduced intestinal and systemic Th2 effector responses.

Zinc deficiency impairs immune responses against parasitic nematode infections at intestinal and systemic sites

Research on the complex interactions among host nutritional status, parasitic infection and immune responsiveness has focused on the detrimental consequences of parasitic infections on host nutritional status and on mechanisms by which malnutrition impairs immunocompetence. Curiously, relatively few studies have examined the effects of malnutrition on the immune response in the parasite-infected host, and even fewer have considered the events occurring at the intestinal level, where absorption of nutrients occurs, intestinal parasites reside, and the gastrointestinal-associated lymphoid tissues play a role in directing both the local and the more systemic immune responses. Our work using a zinc-deficient nematode-infected mouse model reveals that parasites are better able to survive in the zinc-deficient hosts than in well-nourished hosts; that the production of interleukin-4 in the spleen of zinc-deficient mice is depressed, leading to depressed levels of IgE, IgG(1) and eosinophils; and that the function of T cells and antigen-presenting cells is impaired by zinc deficiency as well as by energy restriction. Given the paramount role of the gastrointestinal-associated lymphoid tissues in inducing and regulating immune responses to intestinal parasites and in orchestrating responses in the spleen and peripheral circulation, we conclude that zinc deficiency (in association with energy restriction) exerts profound effects on the gut mucosal immune system, leading to changes in systemically disseminated immune responses and, importantly, to prolonged parasite survival.

Energy deficits suppress both systemic and gut immunity during infection

Protein-energy malnutrition and gastrointestinal nematode infections widely coexist in developing countries. Evidence is provided demonstrating the profound impact of dietary energy deficiency on immune function. Energy-restricted (ER) mice infected with a gastrointestinal nematode showed impaired lymphocyte proliferation and reduced production of Th2 cytokines and lower levels of IgE, parasite-specific IgG1, and eosinophils, which led to higher worm burdens and fecundity. We conclude that mild ER, without concurrent protein malnutrition, can modulate protective immunity from (a) activation early during a primary infection to (b) the expression of acquired immunity during reinfection in both systemic and gut-associated lymphoid tissues.

Diet and waist-to-hip ratio: important predictors of lipoprotein levels in sedentary and active young men with no evidence of cardiovascular disease

OBJECTIVE

Healthy, young men were studied to determine the relationship of energy and nutrient intake and physical activity to concentrations of plasma lipoprotein and cholesteryl ester transfer protein.

DESIGN

A cross-sectional study compared active and sedentary male subjects (17 to 35 years old) with no personal or family history of coronary heart disease. Participants kept 20-day food and activity journals. Individual intakes of energy, protein, carbohydrate, fat, saturated fat, monounsaturated fatty acids, polyunsaturated fatty acids, dietary fiber, and alcohol were evaluated. Measurements of blood lipids (total cholesterol and triglycerides, high- and low-density lipoprotein cholesterol); apolipoproteins; cholesteryl ester transfer protein; anthropometric variables (body mass index, waist-to-hip ratio, percentage of body fat); and aerobic capacity were taken during fall and spring data collection periods. SUBJECT SELECTION: Subjects were selected on the basis of normal blood lipid levels, absence of underlying disease, and willingness to comply with their current level of physical activity for the duration of the study. Minimal sample size for statistical power was 12 men per group: 12 of 15 subjects who exercised and 13 of 15 subjects who were sedentary completed all phases of the study.

STATISTICAL ANALYSES

Statistical analyses consisted of 2-way analysis of variance (activity level and season). Pearson product moment correlations and multiple regression analyses were conducted to assess whether energy and nutrient intakes, physical activity status, and/or anthropometric variables predicted plasma concentrations of lipids and apolipoproteins.

RESULTS

Lower waist-to-hip ratio, and not specifically activity level, was associated with higher levels of high-density lipoprotein cholesterol (HDL-C) and lower levels of low-density lipoprotein cholesterol (LDL-C). Dietary intake of saturated and monounsaturated fats and alcohol predicted changes in some apolipoprotein and lipoprotein levels.

APPLICATIONS

Use of waist-to-hip ratio in the primary prevention of coronary heart disease is a simple and cost-effective measure to predict development of abnormal lipoprotein profiles in young men. Specific dietary recommendations include adoption of a heart-healthy diet with emphasis on monounsaturated fatty acids (10% to 12% of energy or one third of total fat intake) and the suggestion that small amounts of alcohol (< 3 drinks per week) may, indeed, be beneficial. Because alcohol and waist-to-hip ratio were both important predictors of LDL-C level, even in active young men, the consumption of low levels of alcohol may be beneficial only if waist-to-hip ratio is maintained within the healthful range by achieving an appropriate balance of physical activity and macronutrient intake.

Diet texture modifies outcome of a primary infection with Heligmosomoides polygyrus (nematoda) in mice

To determine if dietary texture altered the establishment, survival and reproduction of Heligmosomoides polygyrus during a primary infection, commercial mouse chow (Purina Chow) was fed in either pelleted or powdered form to 2 groups of infected BALB/c mice, and a semipurified, biotin-fortified, egg-white-based diet was provided in powdered form to a third group of mice. Diet texture (powdered vs. pelleted) modified parasite establishment, as evidenced by higher worm recovery 6 days postinfection (PI) in both groups of mice fed powdered diets compared with the group fed the pelleted diet, but diet texture had no detectable effect on net or per capita egg production or on day 30 worm survival. However, almost twice as many worms were recovered from mice fed the semipurified, powdered diet than those fed either textural formulation of the commercial mouse chow on day 30 PI, indicating that a dietary component in the semipurified diet, such as the single fiber source cellulose, facilitated parasite survival, or that other ingredients in the commercial mouse chow, perhaps the more complex fiber components, reduced worm survival, or both. We conclude that dietary texture influences parasite establishment and that specific fibers that change texture can individually and independently modify H. polygyrus survival.

Low intensity exercise and varying proportions of dietary glucose and fat modify milk and mammary gland compositions and pup growth

Exercise during pregnancy or lactation may create a competition for glucose between the exercising muscle and either the developing fetus or the lactating mammary gland. To test these two hypotheses, pregnant rats were randomly assigned to isoenergetic diets with varying levels of glucose (20, 40 or 60% by weight) and fat (30, 22 or 14%, respectively, by weight) and were rested (R) or exercised (E) on a motorized treadmill at 20 m/min, 60 min/d (low intensity), 7 d/wk throughout pregnancy and lactation. Main effects and selected interactions of diet and exercise during pregnancy and diet, exercise and litter size during lactation were tested using 3 x 2 and 3 x 2 x 2 factorial designs, respectively. Neither diet nor exercise affected pregnancy outcomes. In contrast, during lactation, milk and mammary gland compositions and pup growth were altered. Exercise produced higher milk protein concentrations (40% glucose diet) and lower milk lactose concentrations (20% glucose diet). Exercise also lowered mammary gland fat content and produced higher milk fat concentrations. The 60% glucose diet resulted in the highest milk fat concentrations, but pups of dams fed the 40% diet were heavier on lactation d 15 than pups of dams fed the 60% diet. Taken together, these results support the claim of decreased availability of glucose to the mammary gland for lactose synthesis during chronic low intensity exercise. Additionally, the best lactation performance was not supported by a high carbohydrate (60% glucose), lower fat (14%) intake. A more moderate carbohydrate (40% glucose), higher fat (22%) intake promoted greater pup weights at weaning, suggesting an overlooked role for macronutrient composition in optimizing lactation performance.

Postnatal profiles of glycogenolysis and gluconeogenesis are modified in rat pups by maternal dietary glucose restriction

Because glucose is an important metabolic fuel during perinatal development, the effect of restriction of maternal dietary glucose on the developmental profile of neonatal glucoregulatory pathways was investigated. Pregnant rats were fed isoenergetic diets (0, 12, 24 or 60% glucose) and offspring were killed at seven postpartum time periods: 0-2, 4-6, 12-16 and 24 h, and 3, 6 and 15 d. Failure of the most restricted pups (0%) to survive 24 h was explained by persistent hypoglycemia resulting from the following: 1) insufficient tissue glycogen reserves at birth; 2) lower liver glycogen mobilization; 3) delayed phosphorylase a induction; and 4) low phosphoenolpyruvate carboxykinase (PEPCK) gene expression, all of which occurred despite the lower insulin:glucagon ratio. Differences in liver glycogen stores, which had been exhausted in all dietary groups by 16 h, could not account for the high d 1 pup mortality in the moderately restricted (12 and 24% glucose) groups. However, a certain metabolic distress was suggested because these moderately restricted neonates had significantly higher liver PEPCK gene expression at 12-16 h but significantly lower plasma glucose at 24 h. The high d 3 mortality, confirmed by analysis of deviance, was not supported by significant differences in any of the measured glucoregulatory indices. We conclude that dietary glucose during pregnancy is required for neonatal survival; its restriction not only lowers tissue glycogen reserves, but can disrupt the normal gene expression of liver PEPCK and the neonatal profile of phosphorylase a activity. Importantly, these observations show that the development of neonatal glucoregulatory mechanisms is modified by the availability of maternal dietary glucose.

Increased fat intake during lactation modifies hypothalamic-pituitary-adrenal responsiveness in developing rat pups: a possible role for leptin

High fat feeding reportedly enhances hypothalamus-pituitary-adrenal (HPA) responses to stress in adult rats. The present study tested whether elevated fat intake during suckling could have short and/or long lasting consequences on HPA regulation in the offspring. Mothers were fed either a control (C; 5% fat) or high fat (HF; 20% fat) diet during the last week of gestation and throughout lactation. After weaning (day 21), pups from C and HF mothers were fed a chow diet. Offspring from both C- and HF-fed mothers were tested for ACTH and corticosterone responses to stress on postnatal days 10 and 35. We found that HF feeding produced higher lipid levels in the milk of HF compared with C lactating rat dams and that offspring of these mothers had significantly increased retroperitoneal fat pad weight and relative adipose mass on day 21 as well as elevated plasma leptin levels on days 10 and 21 of age. After weaning, pups from the HF mothers had lower plasma leptin levels than those from C mothers. Maternal dietary fat affected HPA responsiveness in the offspring in an age-related manner. Neonatal pups (day 10) from the HF mothers exhibited a reduction in the ACTH and corticosterone responses to ether stress. However, in 35-day-old offspring from HF-fed dams, stress-induced ACTH secretion was increased compared with that in pups from the C-fed mothers. These results demonstrate that maternal diet and increased fat intake through the milk are important regulators of HPA responsiveness in neonates and prepubertal rats. During neonatal life, the blunted stress responsiveness seen with elevated fat intake and the resulting high leptin levels might protect the pups from excessive HPA activation. After removal of the maternal dietary influence and reduced leptin levels, enhanced ACTH stress responses are observed as in adult rats fed a HF diet. Because of the inverse relationship between plasma levels of leptin and HPA responses in pups, the possibility exists that the effects of the HF diet on stress responsiveness are mediated by changes in leptin exposure during development.

Food diversity versus breastfeeding choice in determining anthropometric status in rural Kenyan toddlers

BACKGROUND

Prolonged breastfeeding in developing countries is routinely recommended as a valuable and cost-effective public health measure to promote early childhood growth. However, the effects of breastfeeding beyond 12 months are unclear, with some studies showing positive, and some showing negative effects. The role of complementary foods for children 1-3 years has been less studied.

METHODS

We examined feeding behaviour and illness data in relation to anthropometric status among 154 rural western Kenyan children, aged 12-36 months.

RESULTS

There was little difference in anthropometric status between partially breastfed and fully weaned children. Rather, dietary diversity (number of different foods consumed) was strongly and consistently related to anthropometric status in this age group. In addition, early complementation with starchy gruels was associated with stunting.

CONCLUSIONS

Public health efforts which focus only on prolonged breastfeeding (>12 months) in developing countries will not ensure adequate early childhood growth. Important complementary feeding recommendations that promote diet diversity, through the inclusion of a variety of foods in the diets of children in the 1-3 year age group, are needed.

Dietary protein and zinc restrictions independently modify a Heligmosomoides polygyrus (Nematoda) infection in mice

The effects of dietary protein and zinc restrictions on Heligmosomoides polygyrus were compared following primary and challenge infection in female BALB/c mice fed either control (24%), marginal (7%) or low (3%) protein combined with either high or low zinc (60 or 3 mg Zn/kg diet). Dietary protein restriction (3%) resulted in significantly lower body weight gain. As well, blood urea nitrogen (BUN) significantly decreased with decreasing dietary protein level. However, neither plasma albumin concentration nor relative thymus or spleen weights were reduced. Marginal zinc deficiency was confirmed by significantly lower tibia and liver zinc concentration, but food intake, body weight gain, relative thymus and spleen weights, and alkaline phosphatase activity were not altered. On day 29 post-primary infection, worm burdens were significantly higher in mice fed either marginal or low protein and in mice fed a low zinc diet, while parasite egg output was significantly higher in mice fed both low protein and low zinc diet. Immune status was compromised in mice fed low protein (significantly lower serum IgG1 and lower eosinophilia), and in mice fed low zinc diet (significantly lower eosinophilia). Early in the infection, IgE titres were elevated in mice fed low protein or low zinc, but IgE titres declined to levels lower that the control diet groups after 14-21 days. On day 29 post-challenge infection, worm burdens and parasite egg output were significantly higher in mice fed low protein, whereas the other group had expelled almost all parasites. Dietary restriction had no effect on IgE. Significantly reduced serum IgG1 titres and eosinophilia in mice fed 3% protein supported the view that low dietary protein but not low zinc increased host susceptibility to H. polygyrus by compromising host immune function following reinfection in immunized mice.

Energy restriction and zinc deficiency impair the functions of murine T cells and antigen-presenting cells during gastrointestinal nematode infection

This study examined whether the impaired immune responses in zinc deficient- and/or energy-restricted mice exposed to a challenge infection of Heligmosomoides polygyrus might be associated with reduced numbers of spleen cells, altered proportions of spleen cell subpopulations and/or altered function of the T cells or antigen-presenting cells (APC). Female BALB/c mice were given free access to either a zinc-sufficient (60 mg zinc/kg diet, Zn+) or a zinc-deficient diet (0.75 mg zinc/kg diet, Zn-) or were pair-fed (PF) the zinc-sufficient diet. Significant differences in parasite burdens were observed. Worm numbers were lowest in Zn+ mice, intermediate in the PF mice and highest in the Zn- mice, showing that both zinc deficiency and energy restriction reduced protective immunity against the gastrointestinal nematode H. polygyrus. Although the absolute numbers of spleen cells were reduced in both Zn- and energy-restricted (PF) mice, neither deficiency altered the phenotypic distribution of the subpopulations of positive marker cells in the spleen. In vitro functional assays using a 1:1 ratio of APC:T cells showed that T-cell proliferation in response to parasite antigen (Ag) was impaired by a dietary effect of zinc deficiency on T cells and of energy restriction and zinc deficiency on APC function. Consequences of the nutritional deficiencies on cytokine production in response to parasite antigen were more complex: zinc deficiency reduced T-cell function [interleukin-4 and interleukin-5 (IL-4 and IL-5) production], and both nutritional deficits depressed APC functions [IL-4, IL-5, and interferon-gamma (IFN-gamma) production] and T-cell function (IFN-gamma production). Thus, this study showed that zinc deficiency and energy restriction played identifiably distinct roles in regulating host immune responses against the gastrointestinal nematode H. polygyrus.

High prevalence of obesity in low income and multiethnic schoolchildren: a diet and physical activity assessment

The objective of the study was to assess the prevalence of obesity and/or undernutrition and evaluate diet and activity patterns among schoolchildren from an ethnically diverse low income urban population. A cross-sectional survey of 498 children aged 9-12 y from 24 schools in low income multiethnic neighborhoods in Montreal, Canada was undertaken. Height, weight, dietary intake, physical activity record, and lifestyle and demographic characteristics were measured. There was no evidence of undernutrition because linear growth was appropriate for age, but 39.4% of children were overweight (>85th percentile NHANES II). Dietary fat intake was higher in children from single-parent families (P < 0.001) and those with mothers born in Canada. Intake of vitamins A, C, iron and folate was directly related to income sufficiency. Children who did more physical activity had significantly higher intakes of energy, calcium, iron, zinc and fiber but were not heavier. Dietary intake was systematically underreported among overweight children, i.e., their reported intakes did not meet calculated energy needs. This underreporting makes it difficult to attribute the accumulated energy imbalance to either energy intake or expenditure.

Zinc deficiency and energy restriction modify immune responses in mice during both primary and challenge infection with Heligmosomoides polygyrus (Nematoda)

This study characterized the consequences of zinc-sufficient (Zn+, 60 mg zinc/kg diet, ad libitum), zinc-deficient (Zn-075 mg zinc/kg diet, ad libitum) and energy-restricted (ER, 60 mg zinc/kg diet which was restricted to match food intake of Zn- mice) diets on the in vivo and in vitro immune response of BALB/c mice during both primary and challenge infection with Heligmosomoides polygyrus. In Zn+ mice, both primary and challenge infection with H. polygyrus induced not only a strong Th2 response (IgE, IgG1, eosinophilia, IL-4, IL-5, IL-10), but also elements of a TH1 response (IgG3, IFN-gamma). Zinc deficiency significantly depressed Th2-dependent antibody production during both primary and challenge infection, and reduced mitogen and antigen-induced T cell proliferation during the challenge infection. Th2 cytokine production was reduced by zinc deficiency (IL-4), energy restriction (IL-5) and by zinc deficiency possibly in combination with energy restriction (IL-10) during the primary infection whereas TH1 cytokine production (IFN-gamma) was depressed during the challenge infection by zinc deficiency, possibly together with energy restriction. Both zinc deficiency and energy restriction reduced eosinophilia with the more profound effect being exerted by zinc deficiency. Thus, both zinc deficiency and its concurrent energy restriction modify immune responses in the mice during primary and challenge infection with H. polygyrus.

Maternal dietary glucose modifies phosphoenolpyruvate carboxykinase (PEPCK) gene expression in the kidney of newborn rats

The consequence of low maternal dietary glucose on perinatal phosphoenolpyruvate carboxykinase (PEPCK EC 4.1.32) gene expression was investigated. Pregnant rats were fed isoenergetic diets containing graded levels of glucose (0, 12, 24, and 60%) from gestation day 2 to lactation day 15. The postnatal developmental profile of PEPCK mRNA in the neonatal kidney was analysed by Northern blot and presented as PEPCK/GAPDH mRNA ratios. In comparison with the 24 and 60% dietary groups, maternal dietary glucose restriction (0 or 12%) during pregnancy resulted in a significant delay in postnatal renal PEPCK gene expression. In these glucose restricted pups, renal PEPCK mRNA was barely detected at birth and was fully visualized only at 4-6 hr; it peaked 24 hr after birth, which was 12 hr later than pups born to dams fed 24 or 60% glucose diets. These results demonstrate for the first time that maternal dietary glucose can modify postnatal renal PEPCK gene expression during perinatal development when glucose homeostasis via gluconeogenesis is critical for neonatal survival.

Increased energy intake in pregnant smokers does not prevent human fetal growth retardation

A retrospective cohort study of 729 smoking and 610 nonsmoking pregnant women participating in the Prince Edward Island Prenatal Nutritional Counselling Program (1979-1989) was undertaken to study whether lower energy intake results in lower maternal weight gain and/or a higher rate of small-for-gestational-age infants (SGA) among smokers. A second objective was to quantify, using etiological fractions, the independent contributions of cigarette smoking, maternal pregravid underweight and low pregnancy weight gain to the risk of SGA. Measurements of maternal pregravid weight, height, pregnancy weight gain, smoking status, physical activity, energy intake by a series of 3-d food records throughout the duration of pregnancy, and infant birth weight were collected for women with uncomplicated pregnancies resulting in full-term singleton infants. Multiple linear regression analyses were performed to predict the effect of smoking on maternal energy intake, weight gain and infant birth weight. The independent contributions of smoking, pregravid underweight and low pregnancy weight gain to the risk of SGA were determined using logistic regression analysis. Smoking was independently associated with a higher energy intake [+702 kJ/d (+168 kcal/d)] but with lower maternal weight gain (-2.16 kg) and infant birth weight (-205 g). Dietary energy intake was positively associated with only a small increment in birth weight [5.9 g per 418 kJ (100 kcal)]. The etiologic fraction for SGA attributable to smoking was 30.8%, pregravid underweight 16.7%, and low gestational weight gain 15.3%. We conclude that the important negative effect of smoking on retarding fetal growth cannot be adequately mitigated by simply increasing energy intake.

Vitamin E inhibits fish oil-induced hyperlipidemia and tissue lipid peroxidation in hamsters

Previous research has linked hyperlipidemia with increased serum concentrations of lipid peroxidation products; however, a specific association between diet-induced oxidative stress and hyperlipidemia has not been studied. In the present study, the relationship between tissue lipid peroxidation and hyperlipidemia induced by ingestion of fish oil was examined. In Experiment 1, male Golden Syrian hamsters were fed semipurified diets composed of 1.6 wt% safflower oil plus 15.0 wt% of either butterfat (BF), safflower oil (SAFF), or high-cholesterol menhaden oil [MHO(H-CHOL)] semipurified diets for 27 d. The cholesterol contents of the diets were adjusted to 0.088%. The MHO(H-CHOL)-fed hamsters exhibited higher serum concentrations of total cholesterol, triglycerides, apolipoprotein B, and lipid peroxides when compared to the BF and SAFF diet groups. In a further study (Experiment 2), hamsters were fed for 27 d three dietary treatments: (i) MHO(H-CHOL) with no vitamin E content; (ii) a low-cholesterol menhaden oil containing high concentrations of vitamin E (2.5 mg tocopherol/g oil or dietary concentrations of 375 mg/kg) [MHO(L-CHOL) + E]; and (iii) the MHO(L-CHOL + E) with added cholesterol (595 mg/kg) [MHO(L-CHOL) + CHOL + E] to match the cholesterol content of the MHO(H-CHOL). The MHO(L-CHOL) + E and MHO(L-CHOL) + CHOL + E diet groups showed lower concentrations of serum cholesterol, triglycerides, and hepatic lipid peroxides than the MHO(H-CHOL)-treated group. Moreover, in contrast to the hypercholesterolemia caused by the MHO(H-CHOL) feeding, the MHO(L-CHOL)+ E and MHO(L-CHOL) + CHOL + E diets did not show a serum cholesterol-elevating action. This study supports the hypothesis that oxidative stress in the Syrian hamster could play a causal role in dietary-induced hyperlipidemia which can be inhibited by high vitamin E intake.

Timing of weight gain during pregnancy: promoting fetal growth and minimizing maternal weight retention

OBJECTIVE

To examine the association of the extent and timing of pregnancy weight gain with infant birth weight (IBW) and postpartum weight retention (PPWR).

DESIGN

Retrospective cohort study of pregnant women followed through 6 weeks postpartum.

MEASUREMENTS

Birth weight and maternal weight gain before 20 weeks, 21-30 weeks, 31 weeks to term and postpartum weight retention were measured.

SUBJECTS

A total of 371 healthy white nonsmoking pregnant women followed by the Prenatal Nutrition Counselling Program of the Department of Health and Social Services of the province of Prince Edward Island, Canada, between 1979 and 1989 who had uncomplicated pregnancies resulting in full term singleton infants.

RESULTS

Weight gain during pregnancy (> 12 kg) was associated with PPWR (> 2.5 kg) in underweight, normal and overweight women. Pregnancy weight gain explained 65.2% of the variability in PPWR, but very little of the variability (4.7%) in IBW. Predictors of IBW (gestational age, pregravid weight and infant gender) were not related to PPWR. Early maternal weight gain (< or = 20 weeks) was a strong predictor of PPWR. Comparisons of mothers with PPWR above and below the median of the group indicated important differences in early weight gain (< or = 20 weeks) for underweight (3.3 kg), normal weight (3.3 kg), and overweight (6.2 kg) mothers.

CONCLUSION

The results emphasize the importance of the timing of gestational weight gain and show an advantage in deferring a larger portion of required weight gain to late pregnancy (particularly in well-nourished overweight women) in order to promote fetal growth while reducing the risk of high weight retention and its potential adverse health consequences.

Energy restriction and severe zinc deficiency influence growth, survival and reproduction of Heligmosomoides polygyrus (Nematoda) during primary and challenge infections in mice

The objectives of this study were (1) to determine the impact of severe zinc deficiency on the establishment, growth, survival and reproduction of Heligmosomoides polygyrus in the laboratory mouse, during both primary and challenge infection protocols, and (2) to determine whether the observed effects resulted from zinc deficiency per se, or from the accompanying energy restriction. Three diet groups were used: zinc-sufficient (Zn+:60 mg zinc/kg diet), zinc-deficient (Zn-:0.75 mg zinc/kg diet) and energy restricted (ER:60 mg zinc/kg diet pair fed to Zn- mice). Neither Zn- nor ER influenced the establishment of the parasite during a primary infection. However, both significantly influenced the early development of the parasite. The proportion of adult worms recovered 9 days post-infection (p.i.) was highest in Zn- mice, intermediate in ER mice and lowest in Zn+ mice. Worms were also distributed more distally in the intestine of the Zn- mice and worm survival was highest in Zn- mice, intermediate in ER mice and lowest in Zn+ mice at both 4 and 5 weeks p.i. Although the length of female worms was reduced in Zn- mice, neither per capita fecundity nor egg viability was affected by zinc deficiency. Energy restriction, on the other hand, significantly reduced worm fecundity at 5 weeks post-primary infection, but had no effect on egg viability. Zinc concentration of adult H. polygyrus was similar among dietary groups. The effects of zinc deficiency and energy restriction were also investigated 4 and 5 weeks after a challenge infection. Whereas strong host resistance was evident in Zn+ and ER mice, based on comparison of worm numbers between challenged mice and primary infection controls, no evidence of resistance was detected in Zn- mice. As in the primary infection, female worms were shorter in Zn- mice than in ER and Zn+ mice, and energy restriction but not zinc deficiency significantly affected per capita fecundity. However, in contrast to the primary infection, ER mice had elevated rather than reduced fecundity. This study demonstrates a complex interaction between H. polygyrus and zinc and energy restriction, and highlights the importance of controlling for reduced food intake in nutrition-infection studies.

Maternal dietary carbohydrate restriction and mild-to-moderate exercise during pregnancy modify aspects of fetal development in rats

To determine whether acute bouts of exercise during pregnancy would predispose the fetus to increased risk if maternal dietary carbohydrate were restricted, untrained pregnant rats were randomly assigned to a 0% (low), 12% (moderate) or 60% (high) glucose diet, and either rested or exercised daily for 20 min from d 16 to term on a rodent treadmill at a mild (15.5 m/min) or moderate (24.3 m/min) intensity. A 3 x 3 nested factorial model with and without food intake as a covariate was employed. Both greater exercise intensity and the lower levels of dietary carbohydrate independently decreased term maternal liver and plantaris glycogen concentrations and increased plasma lactate concentrations. However, significant differences due to exercise disappeared (except for plasma lactate) with food intake controlled for in the model, indicating that energy deficits modulated these exercise effects. In contrast, for the offspring, when food intake was controlled for, a restricted level of maternal dietary carbohydrate significantly lowered fetal weight, plasma glucose and insulin concentrations and liver glycogen concentrations measured at term. Exercise alone did not reduce mean fetal weight if nested weights within a litter were used in the statistical analysis. Mild to moderate maternal exercise lowered only fetal plasma glucose concentrations and only if maternal food intake was not controlled for. These results indicate that acute exercise during pregnancy can have detrimental effects on fetal development only if dietary glucose is severely restricted. Otherwise, adequate glucose and energy in the maternal diet in untrained pregnant rats during repeated bouts of acute exercise seem to protect the fetus.

Maternal dietary carbohydrate restriction influences the developmental profile of postnatal rat brain indoleamine metabolism

Dietary glucose restriction during pregnancy can retard fetal brain development, lower term brain glycogen levels and adversely affect the serotonergic neurotransmitter system in the fetus. To study if the postnatal profile of brain indoles continues to respond to these diet-induced changes, pregnant rats were fed graded levels (0, 12, 24, 60%) of glucose from impregnation to day 15 postpartum, and neonatal brain measurements were made. A steady decrease in tryptophan levels, a steady increase in 5-hydroxytryptamine (5-HT) levels and a U-shaped change in 5-hydroxyindoleacetic acid (5-HIAA) were observed during the first 15 postpartum days. Superimposed on these development profiles was a temporary surge in the concentrations of all three indoles 24 h after birth, which was dramatic for tryptophan and more modest for 5-HT and 5-HIAA. The level of carbohydrate in the maternal diet significantly influenced the magnitude of this increase in tryptophan, 5-HT and 5-HIAA at 24 h: the values were significantly higher in the carbohydrate-restricted (12 or 24%) rat pups when compared with control or carbohydrate-free (0% glucose) offspring. No effects of dietary treatment were apparent by day 6. However, the reemergence of a significant difference in brain 5-HT content at day 15 postpartum indicates that even when energy intake is adequate the level of carbohydrate in the maternal diet may continue to play a role in modulating serotonergic neurotransmitter levels later in development.

Maternal dietary glucose-lipid interactions modulate embryological development in vivo and in embryo culture

To examine the dietary interrelationships of glucose and lipid on embryological growth and development, two levels of glucose (0% and 24%) and two types of lipid--soybean oil (SBO; 44.5% 18:2[n-6]) or oleic acid (OL; 6.7% 18:2[n-6])--were fed to pregnant rat dams until Day 12.5 of gestation, when developing embryos and maternal tissues were collected for analysis. In addition, Day 9.5 embryos were obtained from the dietary treatment groups and cultured in vitro until Day 12.5 to ascertain whether or not the embryos showed developmental changes in response to dietary treatment in the absence of maternal and placental factors. Differences in energy intake and macronutrient composition explained differences in early placental weight; macronutrient composition, but not energy intake, accounted for differences in weight of in vivo embryos and in morphological scores of cultured embryos. With food intake as a covariate in the statistical analysis, the results showed that only the level of maternal dietary glucose influenced the number of live embryos and resorptions per litter. Both the level of carbohydrate and the type of lipid in the maternal diet, however, independently and interactively affected both embryonic growth and development in vivo and in culture. To evaluate the biological significance of this dietary interaction, concentrations of essential fatty acids in the embryonic and maternal tissues were measured. A striking result of this study was the rapidity of the diet-induced changes in tissue fatty acid composition. By gestational Day 12.5, the lack of glucose in the OL-based diet was associated with a raised 18:2 (n-6)/20:4 (n-6) ratio and a lowered 20:4 (n-6) content in the embryo and the maternal liver. We suggest that a carbohydrate-free maternal diet with apparently adequate levels of essential fatty acid can contribute to embryonic growth retardation both in vivo and in vitro by perturbing embryonic essential fatty acid metabolism.

Zinc deficiency impairs T cell function in mice with primary infection of Heligmosomoides polygyrus (Nematoda)

This study was designed to determine whether severe zinc deficiency would prolong the course of a primary Heligmosomoides polygyrus infection in mice, and whether this could be related to impaired T cell function. Female BALB/c mice were fed a zinc-sufficient (Zn+; 60 mg/kg), a zinc-deficient (Zn-; 0.75 mg/kg) or an energy restricted (PF; 60 mg zinc/kg) diet. After four weeks, some mice in each dietary group were given a primary infection with 100 larvae; nutritional, parasitological and immunological parameters were assayed over the following five weeks. Liver zinc concentrations were significantly reduced in Zn- mice compared with Zn+ mice. In certain cases, PF mice also had reduced liver zinc concentrations, showing the negative effects of restricted food intake on zinc status. Zinc deficiency prolonged the course of a primary infection, with the effects being most evident five weeks post-infection when Zn+ mice had only 40% as many worms as Zn- mice. Parasite infection induced strong immunological responses in Zn+ mice in contrast to Zn- mice. The reduced production of IL-4 and IFN-gamma, the reduced peripheral eosinophilia and reduced serum levels of IgE and IgG1 in Zn- mice were attributed to the zinc deficiency, whereas the reduced delayed type hypersensitivity response to parasite antigen and reduced production of IL-5 were in certain instances attributed to reduced energy intake rather than zinc deficiency. These results show that zinc deficiency significantly impairs functions normally attributed to both Th1 and Th2 cell populations, and that these alterations are associated with elevated worm numbers in zinc-deficient mice.

Predictors of infant birth weight in gestational diabetes

The objectives were to characterize and determine the predictors of birth weight among women with gestational diabetes mellitus (GDM), and to establish whether these predictors vary by prepregnancy body mass index (BMI). A cohort of 353 women with GDM was examined by using data from clinic charts and the McGill Obstetrical and Neonatal Database. Dietary treatment decreased the rate of weight gain (from 0.35 to 0.16 kg/wk, P < 0.0001) and fasting serum glucose (from 4.8 to 4.2 mmol/L, P < 0.001). Positive predictors of infant birth weight among the underweight and normal-weight women (BMI < or = 26) included prepregnancy BMI, height, parity, prediagnostic rate of weight gain, postprandial serum glucose, and gestational duration. Among the overweight and obese women (BMI > 26) the only variables that predicted increased birth weight were prediagnostic rate of weight gain, and fasting or postprandial serum glucose. Hence, prepregnancy body mass index exerts a strong effect on predictors of infant birth weight in GDM, indicating the need to consider prepregnancy weight in the treatment approach.

Glucose-restricted diets alter milk composition and mammary gland development in lactating rat dams

To examine the effects of chronic restriction of maternal dietary glucose on lactational performance, pregnant dams were fed one of four isoenergetic diets containing graded levels of glucose (0, 12, 24 and 60%) from d 2 of pregnancy to d 15 of lactation. Dams fed the 0% glucose diet produced colostrum with higher protein and lower lactose and fat concentrations than normal, but all pups born to these dams failed to survive more than 24 h postpartum. Dams fed glucose-restricted diets (12 and 24%) had significantly lower d 15 milk fat concentration than dams fed the control diet, but there were no differences in milk protein, lactose and glucose concentrations. On d 15, pups suckling dams fed the 12% glucose diet had significantly lower body weights than pups of dams fed 24 and 60% glucose diets. Restriction of dietary glucose to 12% resulted in significantly smaller mammary gland cell size but failed to produce any significant differences in mammary gland composition (protein, fat and glycogen). The results indicate that the level of glucose in the maternal diet is an important determinant of milk composition and that > 24% glucose is needed for optimal milk fat concentration, whereas 12% dietary glucose is sufficient to sustain normal milk lactose concentration. The altered lactational performance in response to dietary glucose restriction was not mediated through changes in mammary gland composition, but in part by the reduced mammary gland size.

Restriction of maternal dietary carbohydrate decreases fetal brain indoles and glycogen in rats

In spite of evidence that dietary carbohydrate can increase brain tryptophan and 5-hydroxytryptamine in adult rats, the possible influence of maternal dietary carbohydrate on fetal brain indoles has received little attention. We studied the effect of graded levels (0, 4, 12 and 60%) of maternal dietary fructose or glucose fed throughout pregnancy on fetal brain glycogen and indoles. The diets were isoenergetic and met the NRC energy requirements for pregnant rats. The results demonstrated that low maternal dietary carbohydrate, with adequate energy intake, reduced fetal brain weight and concentrations of glycogen, tryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid. There were no significant differences between glucose and fructose feeding at any dietary carbohydrate level for any fetal brain measurements, showing that it was the level and not the type of dietary carbohydrate that was important. Significant correlations between fetal brain 5-hydroxytryptamine and brain glycogen, and between fetal brain 5-hydroxytryptamine and brain weight, suggested that lowered brain 5-hydroxytryptamine was only one symptom of disrupted brain development in fetuses of dams fed low levels of carbohydrate. The results show that dietary carbohydrate restriction during pregnancy can have adverse effects on fetal brain development, glycogen levels, and neurotransmitter synthesis even when maternal dietary protein and energy intake are adequate.

Placental composition does not respond to changes in maternal dietary carbohydrate intake in rats

In this study we investigated whether placental glycogen reserves and protein and DNA content could be manipulated by altering the level of glucose in the maternal diet. Pregnant rat dams were fed isocaloric diets containing graded levels of glucose (0, 12, 24 and 60%), and placentas were analyzed for glycogen, protein and DNA content on gestational days 18.5 to 21.5. Regardless of the level of glucose in the maternal diet, there was a significant increase in placental size with advancing age, which was characterized by protein accretion but not by an increase in cell number of glycogen content. Restriction of glucose in the diets of pregnant dams failed to produce statistically significant reductions in placental protein, DNA and glycogen and did not retard placental growth, even though intrauterine growth retardation was observed. Fetal weight, plasma glucose, and liver and heart glycogen were positively correlated with placental weight and inversely correlated with placental glycogen and DNA concentrations; by contrast, no significant correlations were calculated between maternal and placental variables. Our study indicates that the placenta is not affected by a specific dietary glucose restriction and that changes in placental weight or glycogen content do not account for the growth retardation observed in fetuses of dams fed glucose-restricted diets.

Varied protein intake alters glutathione metabolism in rats

We tested the possibility that protein consumption greater than needed for optimum growth of young adult rats might increase either their hepatic glutathione (GSH) content or plasma GSH turnover. Additional aims were to characterize the relationship between hepatic GSH content and plasma turnover under physiologic conditions and to evaluate the ability of values obtained by noninvasive blood sampling to accurately predict hepatic GSH content. Male Sprague-Dawley rats (300 g) were adapted to purified diets containing 0, 5, 10, 20 or 40% casein. Plasma GSH and amino acid concentrations, hepatic GSH content and [35S]GSH-determined plasma GSH turnover were measured in the anesthetized, intact animals. As dietary protein increased from 0 to 20% casein, liver weight and liver GSH concentration (mumol/g wet wt) both increased. In rats fed the 40% casein diet, liver weight increased even further while liver GSH concentration decreased, with the net result that total liver GSH content of the 40% casein-fed group was not significantly different from that of the 20% casein-fed group. Plasma urea, cysteine, methionine and GSH concentrations increased with increasing protein intake, but with the exception of plasma urea, which increased by 60%, there was no further increase at the 40% casein level. Plasma GSH turnover also increased as dietary casein increased from 0 to 20% but was not significantly increased further by the 40% casein diet. A sigmoid function best described the relationship between plasma GSH turnover and hepatic GSH content (r = 0.80, P less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Marginal zinc deficiency has no effect on primary or challenge infections in mice with Heligmosomoides polygyrus (Nematoda)

The effect of low dietary zinc on the survival of an intestinal nematode (Heligmosomoides polygyrus) was investigated in two experiments. In experiment 1 (primary infection), outbred CD1 mice were infected once only with 100 H. polygyrus larvae. In Experiment 2 (challenge infection), mice were given a primary infection that was terminated after 9 d using an anthelmintic drug; the mice were reinfected 5 d later. This protocol stimulates host immunity to the second parasitic infection. Three dietary treatments (control, 60 mg Zn/kg diet; zinc-restricted, 5 mg Zn/kg diet; and energy-restricted, 60 mg Zn/kg diet) were used for both experiments. Both infected and uninfected mice were included within each dietary treatment to control for the effect of parasitic infection on host nutritional status. Plasma zinc concentrations were significantly lower in mice fed the zinc-restricted diet, compared with mice fed the control or energy-restricted diets in both experiments; there were no significant differences in plasma alkaline phosphatase activity or tissue zinc concentration. The significant reduction in plasma zinc had no significant effect on worm burden or egg production of H. polygyrus in either experiment, indicating that the 30-40% reduction in plasma zinc was not sufficient to modify parasite numbers. However, the parasite did affect host nutritional status. Spleen weight was significantly higher in infected mice in both experiments. Following the challenge infection, both liver and spleen copper concentrations were significantly higher, and spleen iron concentration significantly lower, in the infected compared with the noninfected mice.

Amniotic fluid composition responds to changes in maternal dietary carbohydrate and is related to metabolic status in term fetal rats

The objective of this study was twofold: 1) to determine whether amniotic fluid composition responded to differences in the level or source (glucose vs. fructose) of maternal dietary carbohydrate, and 2) to establish whether any dietary-induced changes in amniotic fluid composition correlated with maternal or fetal metabolic status at term. Pregnant rat dams were fed graded levels (0, 4, 12 and 60%) of glucose or fructose in a triglyceride-based diet (Experiment 1) or isoenergetic low carbohydrate diets having 4% glucose equivalents as glucose, fructose, or lipid-glycerol (Experiment 2) throughout pregnancy. Amniotic fluid and maternal and fetal samples were collected at term (d21). Results demonstrated a significant increase in amniotic fluid glucose and a significant decrease in amniotic fluid uric acid as the level of carbohydrate increased in the maternal diet. Pearson correlation coefficients showed amniotic fluid glucose to be positively associated with maternal and fetal liver glycogen and fetal weight; amniotic fluid uric acid and urea nitrogen were negatively correlated with these same measures. Regression analysis indicated that amniotic fluid glucose was predictive of fetal body weight and fetal liver glycogen at term. The findings show that amniotic fluid can be modified by maternal diet and suggest that composition of amniotic fluid might be used as an accessible nutritional indicator of carbohydrate status in the developing fetus.

Comparison of effects of dietary glucose versus fructose during pregnancy on fetal growth and development in rats

Dietary carbohydrate during pregnancy is essential. Whether this requirement is specific to glucose was investigated. We examined whether fructose at low, intermediate and high levels can substitute for an isoenergetic amount of glucose by feeding graded levels of both carbohydrates (0, 4, 12, 60%) in a triglyceride-based diet throughout pregnancy. It was concluded that the carbohydrate requirement for the rat during pregnancy is not specific to glucose and that the level, not the type, of carbohydrate was critical (experiment 1). A second aspect of the study (experiment 2) was the comparison of isoenergetic, low carbohydrate diets containing different sources of 4% glucose equivalents: glucose, fructose or lipid-glycerol. Fructose and lipid-glycerol were not equivalent substitutes for glucose in the pregnant rat dam at these very low intakes.

Altered lactational performance in rats fed low carbohydrate diets and its effect on growth of neonatal rat pups

The possibility that low carbohydrate diets fed to nursing rat dams altered milk composition and impaired neonatal growth and development was explored. Pregnant control dams fed a 62% glucose diet were paired at parturition with experimental dams fed diets with either severe (0% glucose) or moderate (6% glucose) carbohydrate restriction. At birth half of the littermates of each pair were cross-fostered so that each dam nursed a litter consisting of one-half deficient and one-half control pups. All pups born to dams fed the 0% glucose diet died within 24 h of birth whether they were nursed by control or deficient dams. Control pups cross-fostered to these deficient dams died by the second day; the 0% glucose diet failed to support milk production. In contrast, the dams fed the 6% glucose diet produced milk, but its composition was significantly lower in carbohydrate and lipid than was milk of control dams. This altered milk composition was associated with retarded postnatal growth and development. Control pups cross-fostered to 6% glucose dams showed decreased survival (83% vs. 97%) and significantly reduced body weight (10 g vs. 12 g) at d 7. Conversely, 6% glucose pups cross-fostered to control dams showed improved survival (54% vs. 29%) and significantly increased body weight (9 g vs. 7 g) at d 7. These data showed that carbohydrate-restricted diets altered milk production and/or composition, which, in turn, reduced growth and increased mortality in the pups nursed by dams fed these diets. The results demonstrate that an adequate source of dietary carbohydrate is important for optimal lactational performance.

Evidence for a critical period during late gestation when maternal dietary carbohydrate is essential for survival of newborn rats

Two experiments were designed to test the hypotheses that 1) maternal dietary carbohydrate is required on d 20-21 of gestation (gd 20-21), when fetal liver glycogen is accumulating, to ensure the postnatal survival of the newborn rat pup and that 2) the lack of maternal dietary carbohydrate during this critical 2-d period will cause high neonatal mortality. Pregnant dams were fed one of two lipid-based, carbohydrate-restricted experimental diets. In experiment 1, the primary energy source was soybean oil; the diets contained no added glucose but contained 4% glucose-equivalents as lipid-glycerol. In experiment 2, the major lipid component was food-grade oleic acid; this diet was supplemented with 4% glucose. A crossover design was used. For gd 0-19, dams were fed either the high carbohydrate diet (62% glucose) or one of the carbohydrate-restricted diets (4% glucose or 4% lipid-glycerol); beginning on gd 19 and through neonatal d 7 (nd 7), the opposite diet was fed. For controls in each experiment, a high carbohydrate diet (62% glucose) and the respective carbohydrate-restricted diets were fed throughout pregnancy. The results showed that restriction to 4% glucose equivalents beginning on gd 20 resulted in high first-day neonatal mortality that was comparable in magnitude to nd-1 mortality rates in dams fed the carbohydrate-restricted diets throughout pregnancy. Repletion with the high carbohydrate, control diet after gd 19 significantly reduced mortality. These experiments demonstrate that maternal dietary carbohydrate beginning in late gestation is essential for the postnatal survival of rat pups.

Effect of low carbohydrate diets during pregnancy on embryogenesis and fetal growth and development in rats

Effects in pregnant rats of feeding diets specifically deficient in carbohydrate were studied. The dietary nonprotein energy source was lipid, provided as intact fat (soybean oil) or a fatty acid mixture (edible oleic acid) or a combination of these. These diets provided 9.5% casein protein, which was shown to be minimally adequate in both the lipid-based experimental diets and the high carbohydrate control diet. The diets were fed from mating through d 21 of pregnancy, and pups were delivered by cesarean section. The soybean oil-based zero-carbohydrate diet supported embryogenesis and produced at term normal numbers of normal appearing pups of body weight lower than that of pups from the high carbohydrate control diet. In contrast, the oleic acid-based zero-carbohydrate diet failed to maintain pregnancy, indicating a requirement for carbohydrate or intact fat or both. To maintain pregnancy to term required both 5-10% intact fat and 4% carbohydrate as glucose or its equivalent amount of glycerol from lipid. From feeding graded levels of glucose in fatty acid based diets containing 5-10% intact fat as soybean oil, the carbohydrate requirement was found to be 6-8% glucose to sustain maternal food intake and weight gain and to produce normal fetal weight at term, and 12% glucose to provide approximately half the fetal liver glycogen levels in controls fed a high carbohydrate diet. These experiments have produced the first evidence of the quantitative requirement for carbohydrate for embryogenesis and fetal growth and development in the pregnant rat dam.

Effect of low carbohydrate diets during pregnancy on parturition and postnatal survival of the newborn rat pup

To test the hypothesis that maternal dietary carbohydrate is essential for the postnatal survival of the newborn rat pup, two experiments were designed. Pregnant dams were fed one of two basal carbohydrate-free diets. In experiment 1, the primary energy source was edible oleic acid; in experiment 2, it was soybean oil. Supplemental glucose was substituted for lipid. In experiment 1, pregnant dams were fed 4% dietary glucose for d 0-8 to allow successful implantation, as shown previously. Beginning on d 9 the dams were fed 0, 2, 4, 8, 12 or 62% glucose. Control dams (62% glucose) normally delivered pups weighing 5.6 g on d 21. Dams fed zero glucose delivered pups, weighing 3.1 g, 2 d late. The survivability of the litters increased with maternal dietary carbohydrate. All pups from dams fed 0-4% glucose died within 48 h. Pup survival to d 7 was 10% at 8% glucose, 23% at 12% glucose and 82% at 62% glucose. In experiment 2 soybean oil-based diets (basal supplied ca. 4% glycerol) with 0, 4, 12 and 62% glucose were fed from d 0. At zero glucose, fewer dams delivered late and birth weights were greater than in experiment 1. However, all pups born to zero-glucose dams died by d 4. Pup survival to d 7 was 48% at 4% glucose and 84% at 12% glucose. The data demonstrate that maternal dietary carbohydrate is required for fetal growth, normal parturition and postnatal survival of rat pups. The results indicate that late gestation, parturition and the neonatal period may be especially vulnerable to maternal carbohydrate deprivation.

Maternal and embryonic response to a "carbohydrate-free" diet fed to rats

The effects of a carbohydrate-free, fatty acid (CF) diet on pregnant rats and their progeny were examined. A pregnant pair-fed group was included to compensate for the 40% reduction in food intake of the CF dams. Control and CF dams were killed on days 6, 8, 10, 12, or 14 of gestation. Pair-fed dams were killed on day 14. Maternal CF rats were hypoglycemic and hyperketonemic as compared to pair-fed or control dams. Both CF and pair-fed dams had significantly reduced liver glycogen. Diet had no effect on the number of implantation sites. Conceptuses were classified histologically as normal, retarded, malformed, degenerating or resorbed. Numbers of normal CF embryos were significantly reduced from day 6 and, by day 12, all CF embryos had been resorbed. Control and pair-fed dams showed 5.2% and 43.8% resorptions, respectively, on day 14. These data suggest that approximately half of the embryonic loss can be attributed to the reduction in food intake whereas the remaining embryos succumbed to embryolethal conditions more directly related to the metabolic consequences of carbohydrate deprivation.