Baboon Diet Research Articles

Genetic regulatory effects in response to a high-cholesterol, high-fat diet in baboons

Steady-state expression quantitative trait loci (eQTLs) explain only a fraction of disease-associated loci identified through genome-wide association studies (GWASs), while eQTLs involved in gene-by-environment (GxE) interactions have rarely been characterized in humans due to experimental challenges. Using a baboon model, we found hundreds of eQTLs that emerge in adipose, liver, and muscle after prolonged exposure to high dietary fat and cholesterol. Diet-responsive eQTLs exhibit genomic localization and genic features that are distinct from steady-state eQTLs. Furthermore, the human orthologs associated with diet-responsive eQTLs are enriched for GWAS genes associated with human metabolic traits, suggesting that context-responsive eQTLs with more complex regulatory effects are likely to explain GWAS hits that do not seem to overlap with standard eQTLs. Our results highlight the complexity of genetic regulatory effects and the potential of eQTLs with disease-relevant GxE interactions in enhancing the understanding of GWAS signals for human complex disease using non-human primate models.

Isotopic assessment of marine food consumption by natural-foraging chacma baboons on the Cape Peninsula, South Africa.

Stable isotope analysis has been used to investigate consumption of marine resources in a variety of terrestrial mammals, including humans, but not yet in extant nonhuman primates. We sought to test the efficacy of stable isotope analysis as a tool for such studies by comparing isotope- and observation-based estimates of marine food consumption by a troop of noncommensal, free-ranging chacma baboons. We determined δ13 C and δ15 N values of baboon hair (n = 9) and fecal samples (n = 144), and principal food items (n = 362). These values were used as input for diet models, the outputs of which were compared to observation-based estimates of marine food consumption. Fecal δ13 C values ranged from -29.3‰ to -25.6‰. δ15 N values ranged from 0.9‰ to 6.3‰ and were positively correlated with a measure of marine foraging during the dietary integration period. Mean (± SD) δ13 C values of adult male and female baboon hairs were -21.6‰ (± 0.1) and -21.8‰ (± 0.3) respectively, and corresponding δ15 N values were 5.0‰ (± 0.3) and 3.9‰ (± 0.2). Models indicated that marine contributions were ≤10% of baboon diet within any season, and contributed ≤17% of dietary protein through the year. Model output and observational data were in agreement, both indicating that despite their abundance in the intertidal region, marine foods comprised only a small proportion of baboon diet. This suggests that stable isotope analysis is a viable tool for investigating marine food consumption by natural-foraging primates in temperate regions.

Soil eaten by chacma baboons adsorbs polar plant secondary metabolites representative of those found in their diet.

Geophagy, the deliberate consumption of earth materials, is common among humans and animals. However, its etiology and function(s) remain poorly understood. The major hypotheses about its adaptive functions are the supplementation of essential elements and the protection against temporary and chronic gastrointestinal (GI) distress. Because much less work has been done on the protection hypothesis, we investigated whether soil eaten by baboons protected their GI tract from plant secondary metabolites (PSMs) and described best laboratory practices for doing so. We tested a soil that baboons eat/preferred, a soil that baboons never eat/non-preferred, and two clay minerals, montmorillonite a 2:1 clay and kaolinite a 1:1 clay. These were processed using a technique that simulated physiological digestion. The phytochemical concentration of 10 compounds representative of three biosynthetic classes of compounds found in the baboon diet was then assessed with and without earth materials using high-performance liquid chromatography with diode-array detection (HPLC-DAD). The preferred soil was white, contained 1% halite, 45% illite/mica, 14% kaolinite, and 0.8% sand; the non-preferred soil was pink, contained 1% goethite and 1% hematite but no halite, 40% illite/mica, 19% kaolinite, and 3% sand. Polar phenolics and alkaloids were generally adsorbed at levels 10× higher than less polar terpenes. In terms of PSM adsorption, the montmorillonite was more effective than the kaolinite, which was more effective than the non-preferred soil, which was more effective than the preferred soil. Our findings suggest that HPLC-DAD is best practice for the assessment of PSM adsorption of earth materials due to its reproducibility and accuracy. Further, soil selection was not based on adsorption of PSMs, but on other criteria such as color, mouth feel, and taste. However, the consumption of earth containing clay minerals could be an effective strategy for protecting the GI tract from PSMs.

Abstract 278: Diet-Induced Leukocyte Telomere Shortening Correlates with Extent of Atherosclerosis

Introduction: Cardiovascular disease, the leading cause of death in developed countries, is commonly due to atherosclerosis. Studies have demonstrated association between leukocyte telomere shortening (LTS), extent of atherosclerotic lesions and accelerated cell senescence. Further LTS is associated with dietary intake. However, efforts to link LTS, diet and extent of lesions have been unsuccessful in humans due to difficulties controlling diet in large human population studies. To begin addressing these critical issues, we controlled dietary fat (high-fat, HF) in baboons for 2yrs - a well-developed primate model of human atherosclerosis. This is the first study in primates showing correlation of LTS with both chronic HF diet and atherosclerotic lesions. Hypothesis: We hypothesized that leukocyte telomere length decreased with chronic HF diet in baboons and is correlated with extent of atherosclerotic lesions. Methods and Results: A cohort of pedigreed baboons (n=107; females=46, males=61) was fed a HF diet for 2yrs. Absolute leukocyte telomere lengths (LTL; kb/diploid genome) were quantified by qPCR before and after diet challenge. Total telomere length was calculated by computing the ratio of telomere quantity per single copy gene quantity (baboon LIPG). Mean LTL was significantly shorter after feeding baboons a HF diet for 2 yrs (paired t test, p=0.03). Baboons (n=232) maintained on a low fat diet for 2yrs showed no significant difference in LTL (p=0.47). These findings suggest that a HF diet accelerates LTS. Further we quantified the extent of atherosclerotic lesions in baboons after 2yr HF diet and found that LTL, adjusted for age and sex, were correlated with lesions in descending aorta (Pearson correlation, r=0.19; p=0.03). Interestingly this correlation was significant in females but not in males after adjusting for age (r=0.27, p=0.03). Conclusions: LTS correlates with chronic feeding with a HF diet in baboons, is significantly correlated with arterial lesions and the correlation is sex-specific. These findings suggest that LTS may be a potential biomarker of extent of atherosclerosis.

Increased placental XIAP and caspase 3 is associated with increased placental apoptosis in a baboon model of maternal nutrient reduction

Our objective was to determine signaling molecules and apoptosis rate in the term placenta of a baboon model of maternal nutrient reduction (MNR). Female baboons were fed ad libitum for controls (n = 7) or 70% of control baboon diet (MNR; n = 6) from 30-165 days of gestation with necropsy at 165 days of gestation. Placental tissues were collected and fixed for immunohistochemistry or snap frozen to measure extracellular signal-regulated kinases, protein kinase B, JUN NH(2)-terminal kinase, X-linked inhibitor of apoptosis protein, and caspase 3. Placental villous apoptosis was determined by terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labeling and cytokeratin 18 cleavage. Compared with the control placentas, MNR placentas demonstrated reduced placental weight (P < .02), decreased phospho (p)-ERK (P < .04), increased placental villous apoptosis (P < .001), increased villous cytokeratin 18 cleavage, increased X-linked inhibitor of apoptosis protein (P < .007), and increased active caspase 3 (P < .02). We conclude that placental apoptosis is increased in this baboon model of MNR at term and that the increase in X-linked inhibitor of apoptosis protein may be a protective mechanism against this apoptosis.

Fruit Traits in Baboon Diet: A Comparison with Plant Species Characteristics in West Africa

ABSTRACTPrimate fruit choice among plant species has been attributed to different morphological plant and fruit characteristics. Despite a high abundance of animal‐dispersed plant species in the savanna–forest mosaic of West Africa, few data are available on the interplay between morphological fruit traits and primate fruit consumers in this ecosystem. We tested whether olive baboons (Papio anubis) at Comoé National Park, north‐eastern Ivory Coast, prefer fruit species with particular characteristics relative to the availability of these traits among the woody plant species at the study site. Specifically we were interested in the suites of traits that best predict fruit choice and seed handling by baboons. The baboons ate fruit/seeds from 74 identified plant species, representing 25 percent of the regional pool of woody plant species. They preferred trees to shrubs and lianas as fruit sources. Otherwise, baboons seemed to consume whatever fruit type, color, and size of fruit and seeds available, though they especially included larger fruit into their diet. Against expectations from the African bird–monkey fruit syndrome of brightly colored drupes and berries, baboons ate mostly species having large, dull‐colored fruit. Fruit type and color best described whether baboons included a species into their diet, whereas fruit type and seed size best predicted whether baboons predated upon the seeds of their food plant species. As most plant species at the study site had medium‐sized to large fruits and seeds, large frugivores like baboons might be particularly important for plant fitness and plant community dynamics in West African savanna–forest ecosystems.

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Genetic determination of HDL variation and response to diet in baboons

We fed 634 baboons three diets to assess the separate effects of increasing dietary fat and cholesterol intakes on three independent measures of HDL phenotype: concentrations of HDL cholesterol and apoAI, and size distributions of HDL cholesterol. Increasing dietary fat significantly increased concentrations of HDL cholesterol and apoAI (both, P<0.0001), but did not affect HDL particle sizes, whereas increasing dietary cholesterol increased HDL cholesterol ( P<0.0001) concentrations and HDL particle sizes ( P=0.08), but did not affect apoAI concentrations. A substantial proportion of variation in each of the HDL traits was influenced by genes (heritabilities ranged from 25 to 61%) and a common set of genes influenced HDL variation on each of the diets (genetic correlations ranged from 0.64 to 1.0). However, genes exerted a smaller effect on HDL response to changes of dietary fat and of dietary cholesterol. Therefore, dietary fat and cholesterol alter HDL levels and characteristics, but the dietary responses are not strongly mediated by additive genetic effects.

A major gene influences variation in large HDL particles and their response to diet in baboons

Some baboons accumulate appreciable amounts of large apoE-rich HDLs (HDL 1) which are similar to those reported in humans with several different dyslipoproteinemias. We estimated HDL 1 cholesterol concentrations by gradient gel electrophoresis of serum samples obtained from 634 pedigreed baboons fed with three diets differing in levels of fat and cholesterol. The HDL 1 trait was highly heritable on each diet (0.390≤ h 2≤0.528). Segregation analyses yielded significant evidence that a single major gene plus polygenes affected HDL 1 on a high-fat low-cholesterol diet. The major gene explained approximately 56% of total trait variance and 90% of the additive genetic variance in HDL 1 levels in these baboons. Bivariate one-locus segregation analyses indicated that this major gene exerts significant pleiotropic effects on a number of traditional HDL traits on all three diets, including HDL size distributions, and concentrations of HDL-C, apoAI, and apoE. Linkage analyses showed that this major gene was not located in chromosomal regions that contain six candidate genes whose protein products are important to HDL metabolism ( LCAT, CETP, APOA1, APOE, ABCA1, LIPC). Our results suggest this major gene in baboons plays a pivotal role in HDL metabolism, but is unlikely to code for any of the proteins previously implicated in studies of human HDL 1.

Effect of Protein Diets on the Renal Function of Baboons (Papio hamadryas) With Remnant Kidneys: A 5-Year Follow-up

To assess the progression of renal disease and the effects of protein intake in a species phylogenically close to humans, 14 adolescent baboons (Papio hamadryas) were subjected to infarction of one third of the left kidney and, 2 months later, to right nephrectomy. They were then randomized to a synthetic protein diet containing either 8% or 25% casein. Hemodynamic and metabolic measurements were obtained in awake animals every 4 months. Modest proteinuria developed immediately after left kidney infarction, and hypertension after right nephrectomy. Proteinuria and hypertension, however, were similar in both groups and did not progress for the next 60 months. Inulin clearance markedly increased with implementation of the synthetic diet in baboons given 25% protein, in contrast to animals given 8% protein, averaging 46.6 +/- 4.7 mL/min versus 28.2 +/- 2.6 mL/min, respectively, after 4 months. The glomerular filtration rate (GFR) changed little immediately thereafter and, at 1 year, averaged 43.0 +/- 1.4 mL/min and 28.0 +/- 4.3 mL/min, respectively. During the next 4 years, however, inulin clearance steadily decreased in baboons fed 25% protein. The inverse correlation between inulin clearance and time of follow-up was y = 48.5 - 0.36x (r = -0.879, P < 0.001) in baboons fed 25% protein and y = 29.0 - 0.11x (r = -0.625, P < 0.02) in baboons fed 8% protein. Nevertheless, after 5 years, the mean GFR was still significantly greater in animals given the 25% protein diet than in baboons fed 8% protein, averaging 29.1 +/- 0.6 mL/min and 24.1 +/- 1.0 mL/min, respectively (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Individual behavioral and neuroendocrine changes are correlated with blood-pressure elevations during conflict alone and combined with high-salt diet in baboons

Blood pressure, behavioral, and neuroendocrine measures were obtained from adult male baboons during consecutive experimental phases consisting of daily food reinforcement sessions (baseline, 3 weeks), daily food/shock conflict sessions (2 weeks), and enhanced dietary salt added to the daily conflict protocol (3 weeks). Within-session systolic blood pressure (SBP) increased by an average of 5% ± 1% above baseline during conflict and was accompanied by increases in plasma renin activity, urinary free Cortisol, urinary catecholamines, water intake and body weight, and by decreases in urinary sodium excretion in most animals. Behavioral performances of escape from aversive discriminative stimuli and pausing during danger portions of conflict trials increased, while earned food reinforcers decreased. A strong correspondence was found between the degree of individual BP increase during conflict stress and the degree of change in individual stress indexes. Daily dietary salt further elevated SBP by 10% ± 3% above baseline. Those animals that displayed the greatest changes in physiological and behavioral stress indexes during conflict alone displayed the greatest SBP response during the added high-salt diet. Individuals who are stress-sensitive across a variety of behavioral and physiological systems may be more susceptible to other hypertensinogenic variables.

Baboon diet: a five-year study of stability and variability in the plant feeding and habitat of the yellow baboons (Papio cynocephalus) of Mikumi National Park, Tanzania.

The habitat and plant feeding of 64 well-habituated, individually identified adult male and female yellow baboons was studied for 5 years at Mikumi National Park, Tanzania. Variation across the years showed that a study of only one or two years would have been incomplete and misleading. The list of baboon food species obtained from Mikumi is considerably larger and more diverse than any previously reported. One to six plant parts were eaten from each of more than 180 species. The 25 most common tree genera all contained species used for food. Of the 50 most common grass, shrub and herb genera, 93% included plant foods. Using months in which a species was eaten during at least one year of the study, 21 staple species were eaten during a mean of 8.86 months and 7 were eaten in all 12 months. Although many foods were from commonly available plant species, 15 such species were only rarely eaten. The number of parts of a species eaten per month and an estimate of the amounts eaten per month both varied with temperature and rainfall, being lowest near the end of the cool, dry season. There were substantial differences from year to year in the timing and amount of food production of many species; nevertheless, the same broad feeding pattern was repeated in each of the 5 years of the study. Despite yearly variation in food availability, 14 or more staples and other common foods were eaten in any given month. If crops of many of these foods were to fail, a large number of less commonly eaten species could be substituted. Baboons are eclectic feeders that appear to be optimizing their diet by selective feeding from among a wide array of available foods in an ever-changing floristic environment.