Shannon P. O'Grady

Hydrogen and oxygen stable isotope ratios of milk in the United States.

Models of hydrogen and oxygen incorporation in human tissues recognize the impact of geographic location on the isotopic composition of fluid intake, but inputs can include nonlocal beverages, such as milk. Milk and cow drinking water were collected from dairies, and commercially available milk was purchased from supermarkets and fast food restaurants. It was hypothesized that milk water delta(2)H and delta(18)O values record geographic location information. Correlations between milk water isotope ratios and purchase location tap water were significant. However, the amount of variation in milk delta(2)H and delta(18)O values explained by tap water was low, suggesting a single estimation of fluid input isotope ratios may not always be adequate in studies. The delta(2)H and delta(18)O values of paired milk and cow drinking water were related, suggesting potential for geographical origin assignment using stable isotope analysis. As an application example, milk water delta(18)O values were used to predict possible regions of origin for restaurant samples.

Aberrant water homeostasis detected by stable isotope analysis

While isotopes are frequently used as tracers in investigations of disease physiology (i.e., 14C labeled glucose), few studies have examined the impact that disease, and disease-related alterations in metabolism, may have on stable isotope ratios at natural abundance levels. The isotopic composition of body water is heavily influenced by water metabolism and dietary patterns and may provide a platform for disease detection. By utilizing a model of streptozotocin (STZ)-induced diabetes as an index case of aberrant water homeostasis, we demonstrate that untreated diabetes mellitus results in distinct combinations, or signatures, of the hydrogen (δ2H) and oxygen (δ18O) isotope ratios in body water. Additionally, we show that the δ2H and δ18O values of body water are correlated with increased water flux, suggesting altered blood osmolality, due to hyperglycemia, as the mechanism behind this correlation. Further, we present a mathematical model describing the impact of water flux on the isotopic composition of body water and compare model predicted values with actual values. These data highlight the importance of factors such as water flux and energy expenditure on predictive models of body water and additionally provide a framework for using naturally occurring stable isotope ratios to monitor diseases that impact water homeostasis.

Hydrogen and Oxygen Isotope Ratios in Body Water and Hair: Modeling Isotope Dynamics in Nonhuman Primates

The stable isotopic composition of drinking water, diet, and atmospheric oxygen influence the isotopic composition of body water (2H/1H, 18O/16O expressed as δ2H and δ18O). In turn, body water influences the isotopic composition of organic matter in tissues, such as hair and teeth, which are often used to reconstruct historical dietary and movement patterns of animals and humans. Here, we used a nonhuman primate system (Macaca fascicularis) to test the robustness of two different mechanistic stable isotope models: a model to predict the δ2H and δ18O values of body water and a second model to predict the δ2H and δ18O values of hair. In contrast to previous human‐based studies, use of nonhuman primates fed controlled diets allowed us to further constrain model parameter values and evaluate model predictions. Both models reliably predicted the δ2H and δ18O values of body water and of hair. Moreover, the isotope data allowed us to better quantify values for two critical variables in the models: the δ2H and δ18O values of gut water and the 18O isotope fractionation associated with a carbonyl oxygen–water interaction in the gut (αow). Our modeling efforts indicated that better predictions for body water and hair isotope values were achieved by making the isotopic composition of gut water approached that of body water. Additionally, the value of αow was 1.0164, in close agreement with the only other previously measured observation (microbial spore cell walls), suggesting robustness of this fractionation factor across different biological systems. Am. J. Primatol. 74:651–660, 2012.

δ2H and δ18O of human body water: a GIS model to distinguish residents from non-residents in the contiguous USA.

An understanding of the factors influencing the isotopic composition of body water is important to determine the isotopic composition of tissues that are used to reconstruct movement patterns of humans. The δ2H and δ18O values of body water (δ2Hbw and δ18Obw) are related to the δ2H and δ18O values of drinking water (δ2Hdw and δ18Odw), but clearly distinct because of other factors including the composition of food. Here, we develop a mechanistic geographical information system (GIS) model to produce spatial projections of δ2Hbw and δ18Obw values for the USA. We investigate the influence of gender, food, and drinking water on the predicted values by comparing them with the published values. The strongest influence on the predicted values was related to the source of δ2Hdw and δ18Odw values. We combine the model with equations that describe the rate of turnover to produce estimates for the time required for a non-resident to reach an isotopic equilibrium with a resident population.

Isotopic insight into host–endosymbiont relationships in Liolaemid lizards

Nitrogen isotopes have been widely used to investigate trophic levels in ecological systems. Isotopic enrichment of 2–5‰ occurs with trophic level increases in food webs. Host–parasite relationships deviate from traditional food webs in that parasites are minimally enriched relative to their hosts. Although this host–parasite enrichment pattern has been shown in multiple systems, few studies have used isotopic relationships to examine other potential symbioses. We examined the relationship between two gut-nematodes and their lizard hosts. One species, Physaloptera retusa, is a documented parasite in the stomach, whereas the relationship of the other species, Parapharyngodon riojensis (pinworms), to the host is putatively commensalistic or mutualistic. Based on the established trophic enrichments, we predicted that, relative to host tissue, parasitic nematodes would be minimally enriched (0–1‰), whereas pinworms, either as commensals or mutualists, would be significantly enriched by 2–5‰. We measured the 15N values of food, digesta, gut tissue, and nematodes of eight lizard species in the family Liolaemidae. Parasitic worms were enriched 1±0.2‰ relative to host tissue, while the average enrichment value for pinworms relative to gut tissue was 6.7±0.2‰. The results support previous findings that isotopic fractionation in a host–parasite system is lower than traditional food webs. Additionally, the larger enrichment of pinworms relative to known parasites suggests that they are not parasitic and may be several trophic levels beyond the host.

Altered expression and chromatin structure of the hippocampal IGF1r gene is associated with impaired hippocampal function in the adult IUGR male rat.

Exposure to intrauterine growth restriction (IUGR) is an important risk factor for impaired learning and memory, particularly in males. Although the basis of IUGR-associated learning and memory dysfunction is unknown, potential molecular participants may be insulin-like growth factor 1 (Igf1) and its receptor, IGF1r. We hypothesized that transcript levels and protein abundance of Igf1 and IGF1r in the hippocampus, a brain region critical for learning and memory, would be lower in IUGR male rats than in age-matched male controls at birth (postnatal day 0, P0), at weaning (P21) and adulthood (P120). We also hypothesized that changes in messenger Ribonucleic acid (mRNA) transcript levels and protein abundance would be associated with specific histone marks in IUGR male rats. Lastly, we hypothesized that IUGR male rats would perform poorer on tests of hippocampal function at P120. IUGR was induced by bilateral ligation of the uterine arteries in pregnant dams at embryonic day 19 (term is 21 days). Hippocampal Igf1 mRNA transcript levels and protein abundance were unchanged in IUGR male rats at P0, P21 or P120. At P0 and P120, IGF1r expression was increased in IUGR male rats. At P21, IGF1r expression was decreased in IUGR male rats. Increased IGF1r expression was associated with more histone 3 lysine 4 dimethylation (H3K4Me2) in the promoter region. In addition, IUGR male rats performed poorer on intermediate-term spatial working memory testing at P120. We speculate that altered IGF1r expression in the hippocampus of IUGR male rats may play a role in learning and memory dysfunction later in life.

Intrauterine Growth Restriction Alters Hippocampal Expression and Chromatin Structure of Cyp19a1 Variants

We evaluated the impact of uteroplacental insufficiency (UPI), and subsequent intrauterine growth restriction (IUGR), on serum testosterone and hippocampal expression of Cyp19a1 variants and aromatase in rats. Additionally, we determined UPI induced histone modification of the promoter regions of Cyp19a1 variants using chromatin immunoprecipitation. Cyp19a1 is the gene encoding the protein aromatase, that catalyzes the biosynthesis of estrogens from androgens and is necessary for masculinization of the brain. IUGR was induced via bilateral uterine artery. UPI increased serum testosterone in day of life 0 (D0) and day of life 21 (D21) IUGR males to 224% and 299% of control values, respectively. While there was no significant impact of UPI on testosterone in D0 females, testosterone in D21 IUGR females was 187% of controls. Cyp19a1 variant 1.f and variant II are expressed in the rat hippocampus at D0 and D21. UPI significantly reduced expression of Cyp19a1 variant 1.f in D0 males, with no impact in females. Similarly at D0, UPI reduced expression of aromatase, the protein encoded by Cyp19a1, in males. Dimethylation of H3K4 was increased in the promoter region of variant 1.f (P1.f) and trimethylation of H3K4 was decreased in the promoter region of variant II (PII). At D21, dimethylation of H3K4 is significantly reduced in PII of IUGR males. We conclude that UPI increases serum testosterone and reduces Cyp19a1 variant 1.f expression in the hippocampus of D0 IUGR males. Additionally, UPI alters the chromatin structure of CYP19a1 at both D0 and D21.

Accuracy and precision of a laser-spectroscopy approach to the analysis of δ2H and δ18O in human urine

The isotope ratio analysis of body water often involves large sample numbers and lengthy sample processing. Here we demonstrate the ability of isotope ratio infrared spectroscopy (IRIS) to rapidly and accurately analyse the isotope ratios of water in urine. We analysed water extracted from human urine using traditional isotope ratio mass spectrometry (IRMS) and compared those values with IRIS-analysed extracted water and un-extracted urine. Regression analyses for δ2H and δ18O values between (1) extracted water analysed via IRMS and IRIS and (2) urine and extracted water analysed via IRIS were significant (R 2=0.99). These results indicate that cryogenic distillation of urine was not required for an accurate estimate of the isotopic composition of urine when using IRIS.

Evaluation of childhood nutrition by dietary survey and stable isotope analyses of hair and breath

The natural abundances of carbon, nitrogen, and sulfur stable isotopes in hair, and of carbon isotopes in breath serve as quantitative biomarkers of protein and carbohydrate sources, but applicability of isotopes for evaluating childrens diet has not been demonstrated. In this study, we sought to describe the stable isotope patterns observed in the hair and breath of children and to assess dietary variations in relation to age and ethnicity, hypothesizing that these would reflect dietary differences across age and ethnic groups and would correlate with intake variables derived from a Food Frequency Questionnaire.

441 INTRAUTERINE GROWTH RETARDATION MODULATES SIRT1 DEACETYLASE, FOXO3 TRANSCRIPTION FACTOR, AND SUPEROXIDE DISMUTASE 2 EXPRESSION IN THE POSTNATAL CEREBRAL CORTEX.

Background Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) alter cerebral postnatal gene expression and increase the risk for neurodevelopmental morbidities. IUGR causes histone hyperacetylatilation in d0 and d21 hippocampus of IUGR male rats. SIRT1, a NAD-dependent histone-deacetylase, has an important role in chromatin silencing, genome stability, neuronal protection, and longevity. SIRT1deacetylates the FOXO3 transcription factor and as a result prevents FOXO3-mediated apoptosis and stimulates FOXO3-mediated resistance to oxidative stress. Deacetylated FOXO3 up-regulates SOD2 expression. Objective We hypothesize that IUGR decreases postnatal SIRT1 mRNA and protein levels and as a result decreases SOD2 gene expression. In this study, we analyzed SIRT1, FOXO3, and SOD2 mRNA expression and protein levels in cerebral cortex of IUGR rats. Methods To test our hypothesis, we used term pups from an IUGR model obtained by bilateral uterine artery ligation. Pups from sham surgeries were used as controls. Protein and mRNA levels were measured on d0 and d21 by performing real-time RT-PCR and Western blot analysis, respectively. Results SIRT1 protein levels decreased to 73.33% of controls in IUGR d0 males (p = .023), followed by SIRT1 decreased mRNA levels (84% of controls) on d21. This is associated with a significant decrease in SOD2 mRNA levels (p = .013, 62.66% of controls) in IUGR d21 brains with a predominant effect in males (p = .01, 61.2% of controls). On day 21, there is also a decrease in IUGR FOXO3 mRNA levels (p = .012, 86.8% of controls) without a significant difference between genders. Conclusion We conclude that IUGR decreases SIRT1 gene expression in male rats, which subsequently decreases SOD2 mRNA levels. This finding may explain the neurologic morbidities and the hippocampal hyperacetylation in d0 and d21 IUGR males, which does not persist in the females. We speculate that alterations in SIRT1 gene expression early in life may contribute to changes in histone acetylation, oxidative stress resistance, and apoptosis that contribute to the long-term neurologic morbidities of the IUGR fetus.