College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item EVALUATING THE EFFECTS OF MODIFIABLE LIFESTYLE AND CARDIOVASCULAR HEALTH FACTORS ON DIABETES LIFE EXPECTANCY IN NHANES AND BRAIN AGING IN UK BIOBANK(2024) Feng, Li; Lei, David K.Y. DL; Ma, Tianzhou TM; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation explored the impact of lifestyle and cardiovascular health factors on aging, particularly focusing on individuals with diabetes, the effects of blood pressure on brain aging, and the influence of cardiovascular health and genetic predispositions on brain white matter aging.The first study examined the trends in lifestyle quality among US adults with type 2 diabetes from 1999 to 2018 using NHANES data, involving 7,410 participants. A healthy lifestyle score encompassing smoking, drinking, physical activity, and diet showed a slight increased over the years. Notably, disparities remained significant by socioeconomic groups. The study found that adherence to low-risk lifestyle factors was associated with a 55%-57% lower risk of all-cause mortality, emphasizing the importance of lifestyle modification in diabetes management, and it was independent of cardiovascular risk control. The second study investigated the causal effect of elevated blood pressure on white matter brain aging in a cohort of 228,473 European ancestries aged 40-69 from the UK Biobank by using two-sample Mendelian randomization. Our result revealed that high blood pressure, particularly diastolic, accelerated the machine-learning-derived white matter brain age gap, based on white matter microstructure integrity measured by fractional anisotropy derived from diffusion tensor imaging data, with a causal effect evidence found in late middle-aged women. This underscores the importance of blood pressure control in preventing brain aging, especially in post-menopausal women. Lastly, the impact of Life's Essential 8 (LE8), a comprehensive measure of cardiovascular health (lifestyle part: diet, smoke, physical activity, sleep; health part: BMI, blood sugar, blood pressure, blood lipid), on white matter brain aging was assessed, with a particular focus on how the APOE4 genotype modifies the relationship. Analyzing data from 18,817 European ancestries aged 40-60 from the UK Biobank, the study revealed that higher LE8 scores correlated with a younger brain age. Interestingly, the effect varied significantly with APOE4 status, highlighting the need for personalized health strategies based on genetic profiles. In conclusion, these studies collectively highlight the crucial role of modifiable lifestyle and health factors in managing chronic diseases, controlling blood pressure, and maintaining brain health, with an emphasis on the integration of genetic profiles for personalized healthcare.Item Development of a Multilocus Sequence Typing Scheme for Avibacterium paragallinarum(2023) Harris, Alyssa Meihua; Ghanem, Mostafa; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Avibacterium paragallinarum (A. paragallinarum), the causative agent of the respiratory disease Infectious Coryza (IC) in chickens, has seen a rising incidence in the United States. Current strain differentiation is inadequate for detailed epidemiological analysis. The objective of this study was to develop a Multilocus sequence typing (MLST) scheme for A. paragallinarum for outbreak investigations and to offer a better tool for strain differentiation. By evaluating whole genome sequences and clinical samples, we designed PCR amplicons for eighteen gene segments, selected six genes for their nucleotide diversity and discrimination potential. The MLST was used to differentiate seventy-five samples. Our MLST showed greater discriminatory power than existing HPG2-based methods, aligning closely with adhoc core genome MLST in 75 tested sample. Our newly developed MLST scheme enables more accurate strain differentiation, allowing for better understanding of A. paragallinarum epidemiology and population structure to help prevention and control efforts worldwide.Item Flavonoids, Cardiovascular Disease, and Diabetes(2019) Gahche, Jaime; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Flavonoids have been shown to have anti-inflammatory, antioxidant, and vasodilatory properties; mechanisms that may lead to cardio-protective benefits. Results from observational studies assessing the associations between flavonoid intake and cardiovascular disease (CVD) and type 2 diabetes mellitus have been largely equivocal. Earlier studies were limited due to lack of complete flavonoid composition databases. With the development of more complete databases, total flavonoid intake can be more accurately estimated, but the associations between them and CVD and diabetes have not been assessed in a nationally representative sample of the U.S. population. Aims: The objective of this study was to assess the relationship between dietary intake of flavonoids and risk of: 1) CVD outcomes, and 2) diabetes. Methods: Baseline data from the Third National Health and Nutrition Examination Survey (NHANES III) were collected from participants in 1988-1994 and linked with administrative records to identify CVD and diabetes outcomes. The National Death Index was used for mortality and CMS Medicare Claims and Medicare enrollment data to identify initial events. Flavonoid intake was assessed with up to four 24-hour dietary recalls and the USDA’s flavonoid databases were used to assign flavonoid values to reported food and beverage consumption. Usual intakes of flavonoids and flavonoid sub-classes were estimated using the NCI method. Hazard ratios and 95% confidence intervals were estimated using Cox proportional hazards regression modeling. Results: In this nationally representative sample of adults, from a 1988-1994 constructed cohort and followed passively for over 20 years, significant inverse associations between total flavonoids or sub-classes and CVD outcomes or diabetes were not evident. However, there was a marginal association between flavanones and CVD mortality, for males only (HR =0.93, 95 % CI 0.87, 1.00, p-value<0.04). Conclusions: In this population-based sample of individuals, associations between intakes of flavonoid and CVD mortality (with the exception of flavanone intake for men only), CVD morbidity or diabetes were not evident after 20 years of follow-up. This may be due to their low levels of usual intake, to errors in measurement of flavonoid intake, or misclassification over time of flavonoid intakes, or relatively small sample sizes.Item ASSOCIATIONS OF HEALTH MARKERS, PERCEPTIONS, AND LIFESTYLE BEHAVIORS WITH DIET QUALITY INDICES AND TYPE 2 DIABETES STATUS IN U.S. ADULTS(2018) Al-Ibrahim, Afnan Abdul Hamid; Jackson, Robert T; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There is growing evidence that adherence to healthful dietary patterns reduces the risk of type 2 diabetes (T2DM). The Healthy Eating Index 2010 (HEI-2010) and the Alternate Healthy Eating Index 2010 (AHEI-2010) are recognized as assessment tools for measuring dietary quality. This research had three main objectives: 1) Determine whether the AHEI-2010 provides a more accurate assessment of dietary quality than the HEI-2010 in relation to diabetes status; 2) Examine the relationship between diabetes status and discrepancies between perceived diet quality (PDQ) and measured diet quality (MDQ) (using total HEI-2010 and AHEI-2010 scores, respectively); 3) Examine the relationships between selected lifestyle behaviors independently, and in combination with other lifestyle behaviors, and dietary quality (using total HEI-2010 and AHEI-2010 scores) by diabetes status. Data from the National Health and Nutrition Examination Survey (NHANES) 2007-2010 were used to analyze participants age 20 years and older (n = 4097). Overall, the total HEI-2010 and AHEI-2010 scores for the sample indicate that U.S. adults need dietary improvement (mean total HEI-2010 score = 47.3 ± 0.4; mean total AHEI-2010 score = 38.2 ± 0.4). Diabetics had higher total HEI-2010 and AHEI-2010 scores compared to prediabetics and non diabetics, but did not have better health markers. Results indicate no predictive value of total HEI-2010 and AHEI-2010 scores (OR = 1.00, p > 0.05) in relation to diabetes status. In addition, the associations between diabetes status and discrepancy scores (for both HEI-2010 and AHEI-2010) were not significant after adjusting for perceived health status (p > 0.05). However, there were significant associations between individual lifestyle behaviors and total HEI-2010 and AHEI-2010 scores by diabetes status (p < 0.05). In addition, the combined Lifestyle Behaviors score was a significant predictor of total HEI-2010 and AHEI-2010 scores (p < 0.05) by diabetes status. In conclusion, these findings suggest that dietary quality, measured with HEI-2010 or AHEI-2010 is associated with health markers, perceptions, and lifestyle behaviors, all of which can influence the development of T2DM. Findings of this research have implications for developing more successful strategies to improve compliance with dietary guidelines and evidence-based recommendations for disease management and prevention.Item INVESTIGATING THE ASSOCIATION OF PHTHALATE EXPOSURES AND ADVERSE REPRODUCTIVE HEALTH OUTCOMES IN A REPRESENTATIVE SAMPLE OF U.S. WOMEN(2017) Bibb, Katrina Alexandra; Alcala, Lesliam Q; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Phthalates are endocrine disrupting chemicals present in a large variety of consumer goods. There is supporting evidence from animal studies that exposure to phthalates affect the female reproductive system by disrupting the epigenome and folliculogenesis/oogenesis. Although women of reproductive age experience higher phthalate exposures versus males due to frequent use of cosmetics and personal care products (PCP), studies investigating reproductive health effects of these chemicals are scarce. In this study, a nationally representative sample was used to investigate the association between exposure to phthalates (primarily in PCPs and cosmetics) and subfertility in women aged 18-44. We observed significantly higher phthalate levels among minority women and positive associations between DBP exposure and subfertility in regressions when adjusted for important covariates This is the first study to use such a sample of women to study the effects of phthalates on subfertility. More epidemiological studies are needed to investigate phthalate levels among minorities.Item FACTORS ASSOCIATED WITH OBESITY AND PERCEIVED BARRIERS TO WEIGHT MAINTENANCE AMONG SAUDI WOMEN OF REPRODUCTIVE AGE IN JEDDAH CITY.(2016) Alharbi, Muneera MohammedRashed; Jackson, Robert T; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The prevalence of obesity is significantly higher in Saudi women (33.5%) than men (24.1%), however, the information surrounding the risk factors of obesity and barriers to maintaining a healthy weight among Saudi women of reproductive age is deficient due to the limited number of studies that assessed obesity among them. Using a representative sample of 15-49 years old Saudi women attending Jeddah Public Health Care Centers (JPHCCs), this study aims to (1) identify obesity risk factors, (2) explore the barriers to maintaining a healthy weight, and (3) explore the obesity rates and physical activity (PA) levels. A cross-sectional study was conducted in 2014 using a stratified two-stage cluster sampling design comprising 408 Saudi women attending 12 JPHCCs. Body mass index (BMI) and waist circumference (WC) data also were obtained. Data were collected using a structured questionnaire consisting of socio-demographic factors, eating habits (EHs), PA, and perceived barriers to weight maintenance. Of the 408 women evaluated, 33.8% were obese (BMI ≥ 30 kg/m2), 25.1% were abdominally obese (WC ≥ 88 cm), and 31.2% were physically inactive. Age, family history of obesity, and EHs were significant risk factors for both general and abdominal obesity. A high proportion of women faced great barriers in maintaining their weight related to healthy eating (HE) or PA (49.2% versus 50.7%). The most common barriers to HE and PA in the study group were a lack of willpower, skills, knowledge, enjoyment, time, resources, and social influence. Social norms and hot weather had a great impact on the women’s PA level. There was a positive significant association between EHs and PA level and between HE and PA barriers, but no significant associations were found between barriers to maintaining weight and either type of obesity. An intervention program to combat obesity is thus greatly needed, especially one that focuses on eliminating the identified obesity risk factors, and barriers to maintaining a healthy weight.Item NECK CIRCUMFERENCE AS A NEW ANTHROPOMETRIC INDICATOR FOR PREDICTION OF CARDIOMETABOLIC RISKS IN SAUDI POPULATION(2016) Albassam, Reem Sulaiman; Lei, David; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Recent studies have associated neck circumference (NC) with metabolic and cardiovascular disease risk factors. No studies designed to examine NC as a measure of cardiometabolic risks have been performed in Saudi Arabia (KSA). Objective: This study aimed to analyze the association between NC and several cardiometabolic risk factors, and to determine the cut-off point value of NC for predicting women at increased risk of metabolic syndrome (MetS). Methods: This cross-sectional study comprised of 700 participants (623 women and 77 men aged 18–70). Study performed in Riyadh city, KSA. International Diabetes Federation (IDF) guidelines were used to diagnose MetS among the subjects. The main indicators studied were NC, waist circumference (WC), body mass index (BMI), body fat %, blood pressure, plasma glucose, total cholesterol, lipoproteins, triglycerides, and homeostasis model assessment-estimated insulin resistance (HOMA-IR) levels. Covariance, and logistic regression analyses were used to evaluate the association of NC to cardiometabolic risk factors separately by genders. Receivers operating characteristic (ROC) curves analyses were used to determine the optimal cutoffs. Results: NC is associated with BMI and WC in men and women. In women, it is associated with cardiometabolic risk factors beyond other anthropometric indices. NC is independently associated with all cardiometabolic risk factors except LDL (P < 0.001). Fully adjusted OR (95% CI) values for incremental increases in NC for women were 1.70 (1.48–2.94) for raised fasting glucose; 1.29 (1.15–1.45) for raised blood pressure; 1.25 (1.13–1.38) for high triglycerides; 1.20 (1.02–1.40) for insulin resistance; and 1.14 (1.02–1.40) for low HDLc. Women in the largest NC quartile were 13 times more likely [OR (95% CI): 13.39 (6.35 - 28.23)] to have MetS compared to the lowest NC quartile after adjustments for possible confounders (all P < 0.01). Finally, our results indicated that the appropriate NC to predict three or more metabolic risk factors in Saudi women is 35.5 cm. This cutoff value was associated with a much greater risk of MetS in participants with both high and normal BMI and WC values. Conclusion: NC is significantly and independently associated with cardiometabolic risk factors in adult Saudi women.Item Epidemiology and population structure of Xylella fastidiosa, the causal agent of bacterial leaf scorch, among urban trees in the District of Columbia(2014) Harris, Jordan Lee; Balci, Yilmaz; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A survey of urban trees affected by bacterial leaf scorch caused by Xylella fastidiosa was conducted in the District of Columbia during 2012 and 2013. Disease occurred most frequently with Quercus palustris, Q. rubra, Ulmus americana, and Platanus occidentalis. Eight other symptomatic and five asymptomatic tree species were found infected. The bacterium was also detected on asymptomatic portion of seven tree species. The occurrence of crown dieback was found significantly associated with X. fastidiosa-infection on Q. palustris, Q. rubra, U. americana, and P. occidentalis. A multi-locus sequence typing analysis using 10 housekeeping loci for X. fastidiosa revealed five clonal strains among the urban trees. These strains were host specific, with only one clone being associated with members of the red oak family, American elm, American sycamore, and two clones being associated with mulberry. Long-term management strategies aimed at mitigating the occurrence of bacterial leaf scorch disease are discussed.Item Epidemiological Analysis of Biosecurity Practices and Associated Prevalence of Diseases in Non-Commercial Poultry Flocks(2012) Madsen, Jennifer Marie; Tablante, Nathaniel L.; Veterinary Medical Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A cross-sectional study was conducted in backyard poultry flocks among nine counties of Maryland from May 2011 to August 2011. The objective of this study was to obtain baseline data from a survey on biosecurity practices and investigate risk factors associated with positive findings of avian influenza (AI), Newcastle disease (ND), infectious laryngotracheitis (ILT), Mycoplasma gallisepticum (MG), and Salmonella Enteritidis (SE). Serum, tracheal, and cloacal swabs were randomly collected from 262 birds among 39 registered premises. Analysis revealed flock prevalence and seroprevalence respectively for the following: AI (0%, 23%), ND (0%, 23%), ILT (26%, 49%), MG (3%, 13%), SE (0%, ND). Vaccine status could not be confirmed for ND, ILT, or MG. Premises positives were identified by partial nucleotide sequencing. No statistically significant associations were identified, however, AI seroprevalence was positively associated with exposure to waterfowl (Relative Risk [RR] = 3.14, 95% confidence interval [CI] 1.1-8.9) and absence of pest control (RR=2.5; 95% CI, 0.6-10.4).Item Folate intake and biomarkers and risk of chronic disease(2014) Hu, Jing; Sahyoun, Nadine R; Nutrition; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Background: Folate status of the U.S. population significantly improved after folic acid fortification of enriched cereal-grain products in 1998. Recent evidence suggests that the increased folate levels may have impacts on the risk of chronic disease. The kidneys are known to be highly involved in folate metabolism. Reduced renal function may affect folate metabolism and play a role in the associations between folate and chronic disease. Objectives: The purpose of this study was to review key events regulating folate homeostasis along folate metabolic pathway. In addition, we examined the associations between folate intake and biomarker levels and the incidence of cancer, stroke and cardiovascular disease (CVD) and between folate biomarker levels and renal function among older adults in post-fortification years. Design: The Key Events Dose-Response Framework was used to review key steps of folate metabolism. Data of adult participants of the National Health and Nutrition Examination Survey 1999-2002 were used as the baseline data. Incidence of cancer, stroke and CVD were obtained from the linked Medicare and mortality files. The associations between folate intake and biomarker levels and incidence of cancer, stroke and CVD, and the associations between estimated glomerular filtration rate (eGFR) and folate biomarkers, serum unmetabolized folic acid (UMFA) and plasma homocysteine levels were assessed using Cox proportional hazards regression models and multivariable regression models, respectively. Results: The saturation of dihydrofolate reductase in the liver is the determining point regulating the release of UMFA in circulation. Lower red blood cell (RBC) folate levels and intake of dietary folate equivalents were associated with a higher cancer incidence. Lower RBC folate and serum folate levels were associated with a higher stroke incidence. No significant associations between folate and CVD were observed. In addition, reduced renal function was associated with higher RBC folate and plasma homocysteine levels among men and women, and higher prevalence of UMFA in blood among women. Conclusion: High intake of folate may disturb folate metabolism by overwhelming folate regulation mechanisms. Folate may play a protective role against cancer and stroke even at high levels in post-fortification years. Reduced renal function may be implicated in the increased blood folate concentrations.