Protein requirements of adult cebus monkeys (Cebus albifrons).

Twenty-nine adult cebus monkeys (18 males and 11 females) were used in long-term feeding experiments designed to study the protein requirements of this species. By feeding an otherwise adequate diet containing graded levels of lactalbumin, it was shown that diets containing 7.5% of the calories as protein were necessary for long-term weight maintenance. This estimate is compared to data obtained with young growing cebus monkeys in which 7% of the calories was sufficient for maximum growth, although it must be emphasized that due to its greater caloric intake/kg body weight, the protein intake/kg body weight of the younger animal is higher. Whereas a diet containing 9.34% protein supplied by dried bread crumbs (bread diet) was insufficient for weight maintenance of the adults, additions of 4 g lysine/kg bread crumbs and 1.5 g each methionine and threonine/kg bread crumbs produced a diet indistinguishable from the control diet (4.7% bread protein + 4.7% lactalbumin). When wheat gluten was added to the bread diet elevating the protein content to 16.2% of the calories, the amount of lysine necessary to improve the diet to weight maintenance levels increased when expressed/100 dietary kcal as compared to the bread diet alone, although the amounts in both diets were similar when expressed/g of dietary protein.

Dissociated response of plasma albumin and transferrin to protein-calorie restriction in squirrel monkeys (Saimiri sciureus).

The responses of albumin and transferrin to selective nutritional interventions were assessed in 31 infant monkeys. Diets were restricted in protein, calories, or both from age 2 to 8 wk (study A) or protein alone from age 4 to 24 wk (study B)--in both cases to prevent growth. Transferrin levels in study A were significantly lower than control in all three restricted groups whereas albumin levels were decreased only in both low-protein groups. In study B albumin and transferrin concentrations were significantly decreased during the first 12 wk of intervention. A sharp recovery in the transferrin concentrations, however, was observed when a minimal increase in protein intake was allowed in the latter portion of the study. It appears that the response of albumin is linked to amino acid availability whereas the response of transferrin is influenced by variables such as acute dietary manipulation and rate of growth, among others. The value of these indices as single predictors of nutritional status is questioned.

Protein-calorie malnutrition in squirrel monkeys: adaptive response to calorie deficiency.

Control, low-protein, low-calorie, and low-protein-plus-low-calorie diets were fed to 37, 14, 8, and 16 infant squirrel monkeys, respectively, from ages 2-8 wk. The deficient diets were planned to prevent growth and were designed to examine the short- and long-term effects of defined nutritional restrictions on body weight, food intake, hematocrit, plasma albumin, growth hormone, and cortisol concentrations. During the restriction period, plasma albumin levels were significantly decreased in both groups with a protein restriction component: plasma cortisol levels were significantly increased only in the low protein and low calorie groups. No significant group differences were observed for hematocrit or plasma growth hormone. Results of this study indicate that 1) energy restriction did not seem to modify the protein requirement for weight maintenance and 2) animals fed low-protein diets, even in the face of growth failure, have a mechanism for wasting energy.

Dietary fat and serum lipids: an evaluation of the experimental data.

Regression analysis of the combined published data on the effects of dietary fatty acids and cholesterol on serum cholesterol and lipoprotein cholesterol evaluated with groups of human subjects shows that 1) saturated fatty acids increase and are the primary determinants of serum cholesterol, 2) polyunsaturated fatty acids actively lower serum cholesterol, 3) monounsaturated fatty acids have no independent effect on serum cholesterol and, 4) dietary cholesterol increases serum cholesterol and must be considered when the effects of fatty acids are evaluated. More limited data on low-density-lipoprotein cholesterol (LDL-C) show that changes in LDL-C roughly parallel the changes in serum cholesterol but that changes in high-density-lipoprotein cholesterol cannot be satisfactorily predicted from available data.

Comparative assessment of soy and milk protein quality in infant cebus monkeys.

Protein qualities of lactalbumin (L), casein (C), soy concentrate (SC), soy isolate (SI), and soy isolate plus 15.3 mg methionine/g protein (SIM) were investigated in a slope-ratio assay using 32, 8-wk old cebus monkeys. Growth (28 days) and nitrogen balance (NB) (days 19-28) data were evaluated in a multiple-regression format with nitrogen intake and body weight as the independent variables. Based upon growth, potencies compared to L were: C, 72.1; SC, 52.5; SI, 40.6; and SIM, 72.2. Based upon NB, comparable potencies were: C, 62.2; SC, 69.0; SI, 46.8; and SIM, 90.7. NB data showed that the potency of SC was significantly greater than SI and that methionine supplementation of SI improved it to a potency not distinguishable from the standard. The marked improvement from SI to SIM emphasizes the beneficial effect of sulfur amino acid supplementation of soy protein for an infant primate species.

Experimental maternal and neonatal folate status relationships in nonhuman primates.

The influence of maternal dietary folic acid intake on folate status was studied in Cebus albifrons monkeys by feeding 10 or 250 micrograms/100 kcal dietary folic acid during pregnancy and 4 wk postpartum. Maternal, infant, and nonpregnant hematologic indices; blood and liver folate concentrations; and urinary formiminoglutamic acid excretion all varied with dietary folate intake and pregnancy status as did milk folate concentration in lactating dams. Maternal folate status, determined by plasma, red blood cell, and milk folate concentrations, as well as urinary formiminoglutamic acid excretion, all were correlated significantly with liver folate concentrations in neonates (r = 0.740, r = 0.919, r = 0.936, and r = -0.851, respectively). Results in these primates showed that neonatal folate status was related significantly to the dietary folate intake and folate status of the mother during pregnancy and lactation.

Assessment of the efficiency of protein utilization in young squirrel and macaque monkeys.

The efficiency of protein utilization was assessed in three groups of infant squirrel monkeys fed diets containing restricted amounts of lactalbumin, casein, and soy protein isolate as the sole nitrogen source for 3-week periods. Lactalbumin was fed in similar conditions to a group of macaques for comparison. The regression of weight gain on protein intake was calculated for each dietary protein yielding an estimate of protein needs for weight maintenance and an estimate of the efficiency of utilization of protein for growth (slope X percentage protein in tissue). Mean requirements for weight maintenance of infant squirrel monkeys for lactalbumin, casein and soy protein isolate were 3.43, 3.63, and 7.96 g/kg per day and growth was accomplished with an efficiency of 27.8, 32.1, and 22.2%, respectively. In contrast, the macaques utilized lactalbumin with an efficiency of 65%, similar to that of the infant cebus monkey and adult man. The low efficiency found in young squirrel monkeys was altered neither when the habitual feeding schedule was prolonged from 16 to 24 hr per day in a group of casein-fed animals nor when sulfur amino acids were added to casein.

Acute erythroid hypoplasia in malnourished infant squirrel monkeys fed isolated soy protein.

Infant squirrel monkeys fed low protein diets using an isolated soy protein develop an acute anemia. To investigate this syndrome, four groups of animals fed diets containing adequate or restricted amounts of casein or soy protein were studied from 1 through 16 weeks of age. The low protein groups, in which growth was prevented by adjustment of the protein content between 2 through 8 weeks, showed no difference in caloric intake or plasma albumin concentrations. However, the low soy group developed a severe anemia (hemoglobin 4 to 7 g/dl) after 4 to 6 weeks of dietary treatment. The anemia was characterized as normocytic, normochromic, and was associated with reduced reticulocyte concentrations. Bone marrow specimens showed an increased myeloid/erythroid ratio due primarily to an absolute erythroid hypoplasia. Juvenile animals fed similar low soy diets did not become anemic. The selective effect of this isolated soy protein, demonstrable only during the transitional period of early infancy, was attributed to the interaction of the malnourished animal with a component of the isolated soy protein per se. The potential role of soy glycoproteins is discussed.

Individual variability in lipoprotein cholesterol response to National Cholesterol Education Program Step 2 diets.

The effects of National Cholesterol Education Program (NCEP) Step 2 diets on plasma lipoprotein profiles in 72 men [mean (+/- SD) age: 44 +/- 15 y, range: 19-81 y] and 48 women (mean age: 50 +/- 21 y, range: 21-78 y) participating in five previously published studies were examined. Subjects were placed on a baseline diet similar to an average American diet (35-41% total fat, 13-16% saturated fat, 31-45 mg cholesterol/MJ) and then on an NCEP Step 2 diet (18-29% total fat, 4-7% saturated fat, 11-20 mg cholesterol/MJ) under isoenergetic conditions. All food and drink were provided. Compared with the baseline diet, consumption of the NCEP Step 2 diets was associated with significant decreases in concentrations of low-density-lipoprotein (LDL) cholesterol (-18.9% and -15.6%, respectively) and high-density-lipoprotein (HDL) cholesterol (-17.0% and -11.2%, respectively) in both men and women. Men with the apolipoprotein (apo) E 3,4 phenotype had a significantly greater decrease in LDL cholesterol (-24.2%) with the NCEP Step 2 diets than men with the apo E 3,3 phenotype (-17.7%). Men with the apo A-IV 1,2 phenotype tended to have less LDL cholesterol lowering (-12.8%) than men with the apo A-IV 1,1 phenotype (-19.6%), but this difference was not significant. No differences were seen by apo E and A-IV phenotype in women. A large variability in lipid response to the diet was observed, with changes in LDL cholesterol ranging from +3% to -55% in men and and from +13% to -39% in women. Forty-eight percent of the variability in LDL-cholesterol response (in mmol/L) to the diet could be accounted for by baseline LDL concentrations and age in men, and 13% by age in women.

Rice bran oil lowers serum total and low density lipoprotein cholesterol and apo B levels in nonhuman primates.

The hypolipidemic response of rice bran oil (RBO) was investigated in nonhuman primates fed semi-purified diets containing blends of oils which included RBO at 0-35% Kcals as dietary fat. The studies demonstrated the following: (a) the degree of reduction of serum total cholesterol (TC) and low density lipoprotein cholesterol (LDLC) was highly correlated with initial serum cholesterol levels of the monkey on the stabilization diet; (b) the content of rice bran oil in the diet was the predominant factor influencing serum TC, LDLC and apoB causing up to a 40% reduction in LDLC without affecting high density lipoprotein cholesterol (HDLC) when RBO was the sole dietary oil fed; (c) the cholesterol-lowering capabilities of RBO were not explained by its fatty acid composition. These studies suggest that RBO may be an additional vegetable oil which lowers serum cholesterol levels by unique mechanisms which will require further study.

Dietary cholesterol increases the susceptibility of low density lipoprotein to oxidative modification.

Evidence suggests that oxidative modification of low density lipoprotein (LDL) occurs in vivo, increasing the atherogenecity of the particle. A total of 13 subjects (age range 46-78 years) with an LDL cholesterol concentration >3.36 mmol/l consumed each of four diets for 32-day periods. The diets contained 30% energy as fat of which 2/3 was either corn oil or beef tallow with and without 115 mg/4.2 MJ of supplemental cholesterol in the form of cooked egg yolk. The susceptibility of LDL to oxidation was assessed during a challenge with hemin and hydrogen peroxide, and results are expressed as lag time to oxidation in minutes. Addition of moderate amounts of cholesterol to either the corn oil or beef tallow enriched diet resulted in increased susceptibility of LDL to oxidation (decreased lag time): 69+/-22 min versus 96+/-24 min in the corn oil diet with versus without supplemental cholesterol, respectively, P = 0.006; 82+/-20 min versus 96+/-26 min in the beef tallow diet with versus without supplemental cholesterol, respectively, P = 0.025. A stepwise equation indicated that as plasma oleic acid concentrations increased and/or linoleic acid concentrations decreased, lag time increased (decreased susceptibility to oxidation), whereas as dietary cholesterol concentrations increased, lag time decreased (increased susceptibility to oxidation). In conclusion, these data suggest that addition of a moderate amount of dietary cholesterol to a reduced fat diet rich in polyunsaturated or saturated fatty acids increased the in vitro susceptibility of LDL to oxidation.

Criteria and recommendations for vitamin C intake.

The experimental evidence that forms the basis for setting recommended intake levels of vitamin C for humans is currently undergoing review. A recent study suggests that a vitamin C intake of 100 mg-200 mg/day is needed, which is two to threefold greater than the current Recommended Dietary Allowance. This study also proposes that individuals consume no more than 1 gram of vitamin C per day.

Oryzanol decreases cholesterol absorption and aortic fatty streaks in hamsters.

Oryzanol is a class of nonsaponifiable lipids of rice bran oil (RBO). More specifically, oryzanol is a group of ferulic acid esters of triterpene alcohol and plant sterols. In experiment 1, the mechanisms of the cholesterol-lowering action of oryzanol were investigated in 32 hamsters made hypercholesterolemic by feeding chow-based diets containing 5% coconut oil and 0.1% cholesterol with or without 1% oryzanol for 7 wk. Relative to the control animals, oryzanol treatment resulted in a significant reduction in plasma total cholesterol (TC) (28%, P < 0.01) and the sum of IDL-C, LDL-C, and VLDL-C (NON-HDL-C) (34%, P < 0.01). In addition, the oryzanol-treated animals also exhibited a 25% reduction in percent cholesterol absorption vs. control animals. Endogenous cholesterol synthesis, as measured by the liver and intestinal HMG-CoA reductase activities, showed no difference between the two groups. To determine whether a lower dose of oryzanol was also efficacious and to measure aortic fatty streaks, 19 hamsters in experiment 2 were divided into two groups and fed for 10 wk chow-based diets containing 0.05% cholesterol and 10% coconut oil (w/w) (control) and the control diet plus 0.5% oryzanol (oryzanol). Relative to the control, oryzanol-treated hamsters had reduced plasma TC (44%, P < 0.001), NON-HDL-C (57%, P < 0.01), and triglyceride (TG) (46%, P < 0.05) concentrations. Despite a 12% decrease in high density lipoprotein cholesterol (HDL-C) (P < 0.01), the oryzanol-treated animals maintained a more optimum NON-HDL-C/HDL-C profile (1.1 +/- 0.4) than the control (2.5 +/- 1.4; P < 0.0075). Aortic fatty streak formation, so defined by the degree of accumulation of Oil Red O-stained macrophage-derived foam cells, was reduced 67% (P < 0.01) in the oryzanol-treated animals. From these studies, it is concluded that a constituent of the non-saponifiable lipids of RBO, oryzanol, is at least partially responsible for the cholesterol-lowering action of RBO. In addition, the cholesterol-lowering action of oryzanol was associated with significant reductions in aortic fatty streak formation.

Deuterium uptake and plasma cholesterol precursor levels correspond as methods for measurement of endogenous cholesterol synthesis in hypercholesterolemic women.

To assess the validity of two techniques used to measure human cholesterol synthesis, the rate of uptake of deuterium (D) into plasma free cholesterol (FC), and plasma cholesterol precursor (squalene, lanosterol, desmosterol and lathosterol) levels were compared in 14 women [65-71 yr with low density lipoprotein-cholesterol (LDL-C) > or = 3.36 mmol x L(-1)]. Subjects consumed each of six diets for 5-wk periods according to a randomized crossover design. The experimental diets included a baseline diet (39% energy as fat, 164 mg chol x 4.2 MJ(-1)) and five reduced-fat diets (30% of energy as fat), where two-thirds of the fat was either soybean oil; squeeze, tub or stick margarines; or butter. Fractional and absolute synthesis rates (FSR and ASR) of FC were determined using the deuterium incorporation (DI) method, while cholesterol precursor levels were measured using gas-liquid chromatography. Data were pooled across diets for each variable and correlation coefficients were calculated to determine if associations were present. There was good agreement among levels of the various cholesterol precursors. In addition, FSR in pools/d (p x d(-1)) and ASR in grams/d (g x d(-1)) were strongly associated with lathosterol (r= 0.72 and 0.71, P= 0.0001), desmosterol (r= 0.75 and 0.75, P = 0.0001), lanosterol (r = 0.67 and 0.67), and squalene (r = 0.69 and 0.68) when levels of the precursors were expressed as micromol x mmol(-1) C. Significant but lower correlations were observed between the D uptake and plasma cholesterol precursor levels when the latter were expressed in absolute amounts (micromol x L(-1)). The wide range of fatty acid profiles of the experimental diets did not influence the degree of association between methods. In conclusion, the DI method and levels of some cholesterol precursors correspond as methods for shortterm measurement of cholesterol synthesis.

Campylobacter-induced enteritis and diarrhea in captive cotton-top tamarins (Saguinus oedipus) during the first year of life.

A prospective study of 43 cotton-top tamarins, from infancy to 6 to 17 months of age, was conducted to determine the epidemiology of Campylobacter spp. infection. Nine infants followed for one year in an isolation unit, where attendants wore protective clothing, did not become infected. In the main facility where 32 of 34 animals had repeated infections with C. coli, 6% of the infections developed initially in incubators, 66% in the nursery room, and 28% after transfer to the main colony. Fifteen of these tamarins also were infected with C. jejuni. Twenty percent of the infections developed initially in the nursery room and 80% in the colony. Polyacrylamide gel electrophoresis analysis of C. jejuni cultures revealed multiple reinfections with different strains. Both types of infections were most prevalent between 3 and 9 months of age. Campylobacterjejuni infection developed most frequently between April and June and C. coli infection developed between October and December. In the nursery, diarrhea developed most frequently at times when there was no infection with Campylobacter spp. Forty percent of animals with diarrhea in the nursery had C. coli and none had C. jejuni, whereas, in the colony, 49% had C. jejuni and 11% had C. coli infections. There was no association between these infections and diet or idiopathic colitis.

Effect of long-term feeding of soy-based diets on the pancreas of Cebus monkeys.

Feeding soy-based protein containing trypsin inhibitor causes pancreatic hypertrophy in the rat, and long-term feeding (up to 2 years) has revealed a high incidence of adenoma following hypertrophy. It was therefore of interest to determine whether the ingestion of soy-based protein has any adverse effects on the primate pancreas. A resource of 27 Cebus albifrons monkeys, previously used to evaluate the protein quality of several soy and milk proteins, has been maintained on semi-synthetic diets for 3 to 4 years; the protein sources for the diets were casein, lactalbumin, soy isolate and soy concentrate. In general the monkeys were in good physical health and their weights were appropriate for age and sex. Serum biochemical and hematological profiles were normal and there were no major differences between the groups. A pancreatic biopsy from both the head and tail region of the pancreas was taken from each monkey. Visual observation of the pancreas revealed no overt pathology; two independent histological examinations indicated no diet-related differences between groups, and biochemical analyses of trypsin, chymotrypsin, protein, DNA and RNA revealed no differences. It is concluded that feeding low level trypsin inhibitor-containing diets for up to 4 years caused no adverse effects in the pancreas of the Cebus nonhuman primate.

Assessment of the efficiency of nitrogen utilization in the infant cebus monkey (Cebus albifrons) by nitrogen balance.

Nitrogen (N) balance and growth were utilized to assess the efficiency of N utilization in the infant cebus monkey (Cebus albifrons). The efficiency of N utilization as calculated from N balance data was 35%. The efficiency of N utilization for growth was 37% as determined by weight change over a 28-day trial and by body composition data from the literature. These results indicate, therefore, that growth and N balance are comparable indicators of N utilization in these primates.