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Atherosclerosis and symptoms of metabolic syndrome such as obesity, high cholesterol, and insulin resistance often coincide and exacerbate one another, but the cellular and molecular events in common with these conditions have not yet been fully elucidated. Low density lipoprotein receptor adaptor protein 1 (LDLRAP1) is an adaptor protein which interacts with the cytoplasmic tail of the LDL receptor, internalizing the receptor when it engages with LDL. Mutations in this gene lead to LDLR malfunction and cause Autosomal Recessive Hypercholesterolemia (ARH) in humans; however, direct causality on atherogenesis or metabolism in a defined pre-clinical model has not been reported. The aim of this study was to test the hypothesis that deletion of LDLRAP1 would lead to hypercholesterolemia and atherosclerosis. LDLRAP1-/- mice fed a high fat, western diet (HFD) for 16 weeks had significantly increased plasma cholesterol and triglyceride concentrations, accompanied with significantly increased plaque burden compared with wild-type controls. Unexpectedly, LDLRAP1-/- mice gained significantly more weight compared to the wild-type, LDLRAP1-/- mice were insulin resistant, and calorimetric studies suggested an altered metabolic profile. We determined that LDLRAP1 is highly expressed in white adipose tissue (WAT), and LDLRAP1-/- adipocytes are significantly larger and have reduced glucose uptake and AKT phosphorylation, but increased CD36 expression. WAT from LDLRAP1-/- mice is hypoxic, and has gene expression signatures of dysregulated lipid storage and energy homeostasis. These data indicate that lack of LDLRAP1 directly leads to atherosclerosis in mice, and also are the first to suggest that LDLRAP1 plays an unanticipated metabolic regulatory role in adipose tissue. LDLRAP1 deletion leads to systemic effects, and may act as a molecular link which regulates dyslipidemia, atherosclerosis, insulin resistance, and obesity. / Biomedical Sciences

INTRODUCTION: Exercise increases insulin stimulated glucose uptake (insulin action) if expended energy (kcal) is withheld following exercise, but the effect is blunted when expended energy is replaced as carbohydrate. Restricting carbohydrate and replacing expended energy as fat maintains increased insulin action in rodents; however, this effect has not been evaluated in humans. In humans, restricting carbohydrate intake following exercise may be a useful strategy to maximize the effect of individual exercise bouts on insulin action and promote gains in metabolic health over time. Therefore, the purpose of this study was to determine if carbohydrate restriction following exercise (carbohydrate deficit) increased insulin action in sedentary, overweight adults as hypothesized. METHODS: Ten healthy, sedentary, men and women, aged 21±2 years, body fat 37.3±3.1%, and VO2peak 34.6±1.2ml×kg-1×min-1 completed three, two-day experimental conditions in random order: 1) a no-exercise baseline condition (BASE), 2) exercise followed by a high-carbohydrate meal (HIGH-CHO= 76.3±2.5% CHO), and 3) exercise followed by a low-carbohydrate meal (LOW-CHO=17.8±0.1% CHO). On DAY 1, subjects came to the laboratory (early evening) and expended 30% of total daily energy expenditure on a cycle ergometer at 70% of VO2peak. Following exercise, an isocaloric meal (HIGH-CHO or LOW-CHO) was consumed to refeed the expended energy during exercise and venous blood samples were taken to record the insulin and glucose responses to the meals. Twelve hours later (Day 2), whole-body insulin action (steady-state glucose uptake per unit insulin) was measured using a continuous infusion of glucose with stable isotope tracers. A paired t-test was used to detect differences between exercise bouts and the glucose and insulin responses to the post-exercise meals. A one-way repeated measures ANOVA was performed to evaluate the effect of experimental condition on insulin action (p<0.05, for all tests). RESULTS: Intensity (VO2peak), duration (minutes) and energy expenditure (kcal) were similar between exercise bouts. After exercise, plasma glucose and insulin concentrations were significantly higher following the HIGH-CHO meal compared to the LOW-CHO meal (p<0.001, respectively). The next morning, insulin action was similar between experimental conditions (p=0.30). Non-oxidative glucose disposal was increased during the glucose infusion in Low-CHO compared to BASE (27.2±3.2 vs. 16.9±3.5µM×kg-1×min-1, p<0.05). Carbohydrate oxidation was reduced in Low-CHO (8.6±1.3µM×kg-1×min-1) compared to High-CHO (12.2±1.2µM×kg-1×min-1), and to BASE (17.1 ± 2.2 µM×kg-1×min-1), p<0.05 respectively. Resting fat oxidation was increased in Low-CHO compared to BASE (109.8 ± 10.5 mg×min-1 vs. 80.7 ± 9.6 mg×min-1, p<0.05) and remained elevated during the glucose infusion. CONCLUSION: Limiting carbohydrate, but not energy intake after exercise (carbohydrate deficit) resulted in increased non-oxidative glucose disposal, decreased carbohydrate oxidation and increased fat oxidation during the glucose infusion, compared to baseline, indicating a favorable shift in energy metabolism. Creating a carbohydrate deficit, by withholding expended carbohydrate but not energy following exercise may be a sensible strategy to promote favorable gains in insulin action that requires further evaluation.

Human white adipose tissue is a metabolically active organ with distinct depot-specific functions. Despite their locations close to the gastrointestinal tract, mesenteric adipose tissue and epiploic adipose tissue have only scarcely been investigated. The aim is to characterise these adipose tissues in-depth and estimate their contribution to alterations in whole-body metabolism. While mesenteric adipose tissue exhibited signatures similar to those found in the omental depot, epiploic adipose tissue was distinct from all other studied fat depots. Multiomics allowed clear discrimination between the insulin sensitive and insulin resistance states in all tissues. The highest discriminatory power between insulin sensitivity and insulin resistance was seen in epiploic adipose tissue, where profound differences in the regulation of developmental, metabolic and inflammatory pathways were observed. Gene expression levels of key molecules involved in adipose tissue function, metabolic homeostasis and inflammation revealed significant depot-specific differences with epiploic adipose tissue showing the highest expression levels. Multi-omics epiploic adipose tissue signatures reflect systemic insulin resistance and obesity subphenotypes distinct from other fat depots. These data suggest a previously unrecognised role of human epiploic fat in the context of obesity, impaired insulin sensitivity and related diseases.:Introduction...................................................................................................................3 Publication..................................................................................................................11 Summary.....................................................................................................................25 Bibliography................................................................................................................28 Supplements...............................................................................................................30

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The burgeoning adoption of modern technologies provides a great opportunity for gathering multiple modalities of comprehensive personalized data on individuals. The thesis aims to address statistical challenges in analyzing these data, including patient-specific biomarkers, digital phenotypes and clinical data available from the electronic health records (EHRs) linked with other data sources to achieve precision medicine. The first part of the thesis introduces a dimension reduction method of microbiome data to facilitate subsequent analysis such as regression and clustering. We adopt the proposed zero-inflated Poisson factor analysis (ZIPFA) model on the Oral Infections, Glucose Intolerance and Insulin Resistance Study (ORIGINS) and provide valuable insights into the relation between subgingival microbiome and periodontal disease. The second part focuses on modeling the intensive longitudinal digital phenotypes collected by mobile devices. We develop a method based on a generalized state-space model to estimate the latent process of patient's health status. The application to the Mobile Parkinson's Observatory for Worldwide Evidence-based Research (mPower) data reveals the low-rank structure of digital phenotypes and infers the short-term and long-term Levodopa treatment effect. The third part proposes a self-matched learning method to learn individualized treatment rule (ITR) from longitudinal EHR data. The medical history data in EHRs provide the opportunity to alleviate unmeasured time-invariant confounding by matching different periods of treatments within the same patient (self-controlled matching). We estimate the ITR for type 2 diabetes patients for reducing the risk of diabetes-related complications using the EHRs data from New York Presbyterian (NYP) hospital. Furthermore, we include an additional example of self-controlled case series (SCCS) study on the side effect of stimulants. Significant associations between the use of stimulants and mortality are found from both FDA Adverse Event Reporting System and the SCCS study, but the latter uses a much smaller sample size which suggests high efficiency of the SCCS design.

BACKGROUND: Type 2 diabetes (T2DM) is a metabolic disease that arises from insulin resistance and facilitates progression to cardiovascular consequences including myocardial infarction, coronary artery disease, and stroke. A contributor to the cardiovascular complications seen in T2DM is endothelial dysfunction. From a molecular standpoint, studies have shown that the pathophysiology of T2DM involves an altered metabolic milieu and increased oxidative stress, which both arise from insulin resistance, and lead to endothelial dysfunction. There is still much to discover on the pathways that are altered in this disease. Proteomics is a rapidly improving technique that can elucidate the differences in serum biomarkers, and their relationship to vascular endothelial health to further understand the pathophysiology of T2DM. OBJECTIVE: To evaluate the proteomic background and the implicated pathways in T2DM, and to understand how these biomarkers are associated with endothelial cell phenotype and systemic vascular function. METHODS: Age and sex similar individuals with T2DM and control individuals without T2DM between the ages of 30 and 80 were enrolled in this study. Blood was obtained for blood glucose and insulin levels and two proteomics panels assessing 192 serum biomarkers. Baseline vascular measures were obtained including blood pressure, heart rate, and flow-mediated dilation. Endothelial cells collected from participants were stimulated with insulin ex vivo and stained with phosphorylated endothelial nitric oxide synthase (p-eNOS) to measure changes in the insulin-mediated eNOS pathway. Associations between biomarker levels and insulin-stimulated p-eNOS levels were evaluated. RESULTS: The present study includes 69 subjects including 37 subjects with T2DM (age 57±8 years, 41% female) and 32 control subjects (age 53±9 years, 38% female). Measures of vascular health showed evidence of impairment in patients with T2DM including higher pulse pressure (56±12 mmHg versus 48±11 mmHg, p=0.02) and lower flow-mediated dilation (6.04±3.41% versus 9.1±4.4%, p=0.01). The proteomic panels revealed 24 serum biomarkers that were significantly upregulated and 2 that were significantly downregulated (adjusted p<0.05) in patients with T2DM compared to nondiabetic controls. These biomarkers are mainly involved in metabolism, vascular and fluid homeostasis, immune response, and apoptosis. Endothelial cell phenotype was abnormal in patients with T2DM compared to controls: mean fold change in insulin-stimulated p-eNOS was 0.34±0.07 for nondiabetic controls and -0.14±0.03 (p=0.01) for patients with T2DM. Renin and Adrenomedullin were significantly associated with lower insulin stimulated p-eNOS activation (r=-0.38, r=-0.27, and p=0.004, p=0.049 respectively). Whereas Chymotrypsin C (r=0.37, p=0.006), Paraoxonase 3 (r=0.35, p=0.009), Lipoprotein Lipase (r=0.34, p=0.01), and Superoxide Dismutase 2 (r=0.31, p=0.02) were significantly associated with higher insulin stimulated p-eNOS activation. CONCLUSIONS: We found associations between serum biomarker levels and insulin-stimulated p-eNOS levels which showed that there is a relationship between altered biomarkers and endothelial cell phenotype. Patients with T2DM had worse vascular endothelial health as shown by measures of endothelial dysfunction and arterial stiffness. Endothelial cell insulin resistance was present in patients with T2DM. In the same group, serum biomarkers showed elevated adiposity, inflammation and oxidative stress, and upregulation of the renin-angiotensin-aldosterone system.

Prediabetes is defined by elevated blood glucose concentrations not high enough to meet criteria for type 2 diabetes. Exercise or metformin, a common “anti-diabetes” medication, may attenuate the progression from prediabetes to type 2 diabetes by improving insulin sensitivity and cardio-metabolic health. Because each treatment has its primary action in different tissues, combining exercise (muscle) with metformin (liver) may further enhance insulin sensitivity and cardio-metabolic health. Purpose: To determine the efficacy of combining exercise training with metformin on insulin sensitivity and cardio-metabolic health in men and women with prediabetes. We hypothesized that the combined treatment would improve insulin sensitivity and cardio-metabolic health more than either treatment alone. Methods: Thirty-two men and women with prediabetes were placed in placebo (P), metformin (M), exercise training and placebo (EP), or exercise training and metformin (EM) groups. Pill distribution was double-blind, and the groups were well-matched for age, weight, and fitness. There were no baseline differences in any characteristic. Subjects were provided P or 2000mg/d of M for 12 weeks and EM and EP underwent a progressive training protocol. Insulin sensitivity was measured 28-30hr post-exercise with a euglycemic hyperinsulinemic clamp. Traditional cardio-metabolic measures were also collected in the fasted state (e.g. blood pressure, blood lipids and inflammation). Group means were compared using a 2-way repeated measures analysis of variance. Results: Relative to baseline, all 3 interventions increased insulin sensitivity (p < 0.05), however, EP increased insulin sensitivity approximately 25-30% more than either EM or M. Compared to control, EP and M both lowered systolic blood pressure and C-reactive protein (p < 0.05, p = 0.06) and these reductions were approximately 15% more than EM. Each treatment raised HDL (p < 0.05). Enhanced insulin sensitivity was associated with increased non-oxidative glucose metabolism (i.e. glucose storage) (r = 0.85; p < 0.01). Conclusions: Despite more weight loss (4 kg), metformin blunted, rather than accentuated the effects of training on enhancing insulin sensitivity and lowering systolic blood pressure and inflammation. Given that metformin and physical activity are widely recommended treatments for prediabetes, it is important to better understand the mechanisms and ramifications of the combined treatment.

Osteoarthritis (OA) is a common and incapacitating joint disease beginning with breakdown of articular cartilage and extending into subchondral bone. At present, the processes through which the disease occurs are poorly understood, and interventions are limited to pain relief and eventual joint replacement. OA is commonly associated with obesity and corresponding pathologies, and as OA is demonstrably not a product of passive erosion of cartilage over time or under increased loads there must needs be some other mechanistic link between the two conditions. We hypothesize that the production of ceramides, a hallmark of the insulin resistance syndrome underlying many obesity-related conditions, acts to induce OA through its pro-inflammatory and pro-apoptotic activities, as well as directly inhibiting intracellular mediators of cartilage production and homeostasis. We demonstrate in Wistar rats that a high-fat, high-sugar (HFHS) diet successfully induces OA and that downregulation of ceramide synthesis through intraperitoneal myriocin administration does not prevent this degradation, and that myriocin in conjunction with a standard chow diet actually induces OA. Alteration in OA biomarkers in this study are discussed. We then tested the efficacy of a topical regimen of wogonin, an anti-inflammatory, anti-oxidative, and potentially analgesic compound in a surgical destabilization model (DMM) of OA in mice and demonstrate its disease modifying anti-OA properties. We further test the efficacy of this compound on the HFHS model previously established and find it successfully ameliorated the morphology and biomarker changes associated with OA; based on this data we hypothesize that inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is the most relevant physiological target of wogonin in a HFHS-induced OA model. Lastly and separately, we seek to clarify conflicting data regarding secondhand smoke (SHS), which observational studies suggest having either deleterious or beneficial effects to preexisting OA. In the first controlled study on the subject we model we demonstrate in a murine DMM model that SHS accelerates cartilage degradation and patterns of biomarker expression characteristic of OA, eliminating the question of any potential benefits of SHS to articular cartilage.