Master of Science (MS), Ohio University, 2020, Exercise Physiology-Research (Health Sciences and Professions)

The purpose of this investigation was to determine the acute effects of overfeeding followed by a single bout of exercise on postprandial glycemia and insulinemia. Nine apparently healthy men (24.9  5.0) participated in three experimental trials, each trial consisting of two sessions. The first session included a period of controlled feeding for 24 hours with a single exercise bout, controlling the participants' energy availability at 25 (caloric deficit), 45 (caloric balance) and 65 (caloric surplus) kcal/kg FFM. The single exercise bout consisted of treadmill running at 60% of the participants' VO2max until 10 kcal/kg FFM was expended. These calories were replaced back into their caloric intake. The following morning, the participants returned to the laboratory for a baseline blood sample, consumption of a mixed meal followed by subsequent blood samples over a three-hour period. The results of this study indicated that controlled caloric intake over a 24 hour period with a single bout of exercise did not significantly diminish or improve insulin sensitivity among the calorically restricted, balanced and overfed trials.

Committee: Sharon Perry Ph.D (Advisor); Michael Clevidence M.S (Committee Member); Paul Chase Ph.D (Committee Member) Subjects: Health Sciences; Medicine; Physiology

Bachelor of Science (BS), Ohio University, 2019, Biological Sciences

Diabetes is one of the most devastating and prevalent health conditions worldwide, affecting over 30 million Americans (Centers for Disease Control and Prevention 2017). Of recent interest is the study of insulin resistance and diabetes' contribution to cognitive decline and impairment. A unique aspect this relationship is the study of Rho GTPases, a member of the Ras superfamily of small GTPases, and one of their regulatory proteins, the Rho GTPase Activating Proteins, or RhoGAPs. These Rho GTPases and regulatory RhoGAPs have been shown to alter hippocampal dendritic spine morphology. Dendritic spines, which branch off of a neurons' dendrites, are critical in proper synapse formation, influencing spatial learning and memory. In addition, improper dendritic spine formation has been shown to lead to cognitive disabilities and cognitive decline. One of these RhoGAP proteins, Arhgap39, has shown to be regulated by insulin and insulin-like growth factor-1 (IGF-1). This suggests a possible explanation into how insulin resistance may hasten cognitive decline. However, the mechanism behind insulin and IGF-1's effect on Arhgap39 expression is still unclear. As a result, investigation into the process by which insulin regulates Arhgap39 and its downstream effectors presents a promising avenue in the field of diabetes and cognitive dysfunction research. This project focused on investigating the effects of increasing insulin concentration treatments on wild type and insulin receptor knockdown cells. The aim of this study was to determine how insulin regulates Arhgap39 expression, and through which receptor it exhibits its effects. It was hypothesized that insulin would downregulate the suppressive effect of insulin on Arhgap39, confirming that insulin acts through its own receptor in its regulation of Arhgap39. Results from this study show that treating cells with increasing insulin concentrations results in increased Arhgap39 expression, which is predominantly meditated th (open full item for complete abstract)

Committee: Felicia Nowak M.D./Ph.D. (Advisor); Soichi Tanda D.Sc. (Advisor); Cary Frith (Other) Subjects: Biology; Biomedical Research; Cellular Biology

Master of Sciences, Case Western Reserve University, 0, Biochemical Research

Insulin plays a key role in metabolism. Insulin binds to its insulin receptors on insulin responsive cell surfaces and stimulates cellular uptake of glucose, turns on glycolysis and glycogen synthesis, inhibits gluconeogenesis and glycogenolysis in the liver, and stimulates triglyceride synthesis. Previous research has shown that amino acid substitutions, deletions, or additions on insulin alter insulin function. We have found the single-chain insulin (SCI) 70-01, with a substitution of B10His to Asp (12,16), causes blood glucose to fall as rapidly as KP but remain lower longer when injected in diabetic rats. The focus of this research is to study the mechanism of 70-01's prolonged action, and compare it to control insulins, including 81-01, an identical SCI devoid of the AspB10 substitution. We conclude that 70-01 remains for a longer period in the bloodstream, and continues to stimulate phosphorylation of the insulin receptors in a tissue-specific manner, longer than control insulins.

Committee: Faramarz Ismail-Beigi (Advisor); William Merrick (Committee Chair); Martin Snider (Committee Member) Subjects: Biochemistry

Doctor of Philosophy in Biomedical Sciences (Ph.D.), University of Toledo, 2010, College of Medicine

Impaired hepatic insulin clearance causes hyperinsulinemia and secondary insulin resistance, which may progress to involve various components of metabolic syndrome. The carcinoembryonic-related cell adhesion molecule 1 (CEACAM1) has been shown to promote insulin clearance, downregulate the mitogenic action of insulin, and limit lipogenesis in the early hours of refeeding. Mice with liver-specific Ceacam1 inactivation (L-SACC1) or with global null mutation (Cc1–/–), exhibit impairment of insulin clearance and hyperinsulinemia, which causes insulin resistance. Since the lack of CEACAM1 correlates with insulin resistance, and regulates insulin action in liver, an important diet-responsive organ, we proposed that reduction of CEACAM1 is implicated in the pathogenesis of diet-induced insulin resistance; and that increasing hepatic levels of CEACAM1 would be protective against metabolic abnormalities associated with metabolic syndrome. Therefore we examined CEACAM1 levels in an animal model of metabolic syndrome and non-alcoholic steatohepatitis (NASH), the low aerobic capacity runner (LCR) rats, in comparison to high aerobic capacity runner (HCR) rats. We found that in response to caloric restriction by 30% over a period of 2-3 months profound improvements in insulin sensitivity and reversal of hepatic inflammation, oxidative stress and fibrosis. Caloric restriction exerts these effects along with increases in fasting levels of CEACAM1 in liver. Additionally we examined the effect of high-fat diet on wild-type mice and on a transgenic mouse with liver-specific overexpression of rat CEACAM1 (L-CC1). We found that an early event associated with high-fat feeding is repression of CEACAM1 by a PPARalpha-mediated mechanism, and that this leads to impaired insulin clearance prior to the development of a pro-inflammatory state. Transgenic overexpression of CEACAM1 in liver prevents hyperinsulinemia and insulin resistance, and limits visceral obesity and the metabolic response to (open full item for complete abstract)

Committee: Sonia Najjar PhD (Committee Chair); Maurice Manning PhD (Committee Member); Raymond Bourey MD (Committee Member); Beata Lecka-Czernik PhD (Committee Member); Sandrine Pierre PhD (Committee Member) Subjects: Biomedical Research; Molecular Biology

Doctor of Philosophy in Medical Sciences (Ph.D.), University of Toledo, 2005, Graduate School

CEACAM1 is a transmembrane glycoprotein highly expressed in liver. It downregulates the mitogenic effect of insulin, and contributes to circulating insulin level by regulating hepatic insulin clearance. We have proposed that CEACAM1 exerts its effect by taking part of the insulin endocytosis complex, and have identified Shc as an adaptor between CEACAM1 and IR. In the current studies, we explored the role of Shc/CEACAM1 complex in receptor-mediated insulin endocytosis and insulin-stimulated mitogenesis. Disruption of Shc/CEACAM1 or Shc/Grb2 interaction by overexpression the SH2 domain of Shc or of Grb2, respectively, revealed that CEACAM1 binding to Shc partitions it to the endocytosis rather than mitogenesis pathways. CEACAM1-mediated partitioning of Shc may provide a highly efficient method to regulate insulin signaling. In agreement with the role of CEACAM1 in hepatic insulin clearance, LSACC1 mice with liver-specific overexpression of the dominant-negative phosphorylation-defective CEACAM1 developed hyperinsulinemia primarily due to impaired insulin clearance. Noteworthy, there is a consistent correlation between obesity and loss of function/expression of CEACAM1 in rodent models. Herein we investigated the role of CEACAM1 in fat metabolism, and observed both in vitro and in vivo that CEACAM1 mediates an acute downregulatory effect of insulin on fatty acid synthase. We performed thorough analysis on CEACAM1/FAS interaction, and identified that it requires the phosphorylation of

Committee: Sonia Najjar, Ph.D. (Advisor) Subjects: Health Sciences, Pharmacology

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2024, College of Liberal Arts and Social Sciences

Metabolic syndrome (MetS) is a complex condition characterized by a cluster of metabolic abnormalities including obesity, dyslipidemia, insulin resistance, and hypertension. These abnormalities significantly increase the risk of health disorders such as cardiovascular diseases and type 2 diabetes. However, the molecular mechanisms underlying MetS are not fully understood. Recent evidence shows that Ribonuclease L (RNase L), an antiviral protein, is emerging in MetS. RNase L is an interferon inducible enzyme involved in innate immunity during viral infection. In this study, we investigated the role of RNase L in MetS using RNase L wildtype and knockout mice and cells. The findings revealed that RNase L deficiency did not influence food intake but significantly impacted glucose clearance post-glucose challenge, leading to insulin resistance in KO mice. Subsequent investigation of how RNase L affects insulin signaling unveiled a pronounced decrease in insulin responsiveness in RNase L knockout cells. Additionally, we employed the LC/MS proteomic method to identify a potential target of RNase L, which may elucidate the molecular mechanism underlying the involvement of RNase L in insulin signaling. These results highlight the intricate role of RNase L in MetS and underscore RNase L as a conceivable therapeutic target for this disorder.

Committee: Aimin Zhou (Advisor); Crystal Weyman (Committee Member); Xue-Long Sun (Committee Member); Michael Kalafatis (Committee Member); Bin Su (Committee Member) Subjects: Biochemistry; Cellular Biology; Health Sciences; Molecular Biology

Master of Science (MS), Wright State University, 2021, Pharmacology and Toxicology

Insulin secretion plays a crucial role in energy homeostasis. Accordingly, disrupted insulin secretion has been associated with metabolic disorders such as insulin resistance syndrome and diabetes mellitus. Insulin secretion from pancreatic β-cells is tightly regulated by complex ionic mechanisms usually included in a consensus mechanism involving ATP-sensitive K+ channels as the only key player. However, K+ channels solely do not reflect the whole mechanism. Anionic channels also contribute to the machinery of insulin secretion by initiating electrogenic Cl– fluxes in β-cells. The Na+K+2Cl– cotransporter 1 (Nkcc1) and other Cl– transporters participate in the non-equilibrium distribution of Cl– in β-cells. Recent studies from our laboratory and others have demonstrated a potential role of Nkccs in insulin secretion. However, virtually nothing is known regarding the role of Nkcc1 in energy homeostasis. In this study, we unravel part of the physio-pathological consequences that follow the disruption of insulin secretion upon elimination of Nkcc1 from β-cells in mice. Our results suggest that deficient insulin secretion due to altered β-cells Cl– homeostasis impairs satiation responses to feeding leading to nocturnal hyperphagia before the onset of overweight and metabolic complications including, hyperglycemia, hyperinsulinemia, glucose/insulin resistance, steatohepatitis, fat tissue inflammation and obesity. Everything considered, we conclude that loss of β-cell Nkcc1 impairs insulin secretion in vivo impinging long-term metabolic consequences triggered by an early impairment in the feeding behavior. Altogether, our results suggest that elimination of Nkcc1 from β-cells recapitulates, at least in part, the natural progression of metabolic syndrome, a major risk factor for the development of type-2 diabetes.

Committee: Mauricio Di Fulvio Ph.D. (Advisor); Khalid Elased Pharm.D., Ph.D. (Committee Member); Courtney Sulentic Ph.D. (Committee Member) Subjects: Endocrinology; Pharmacology

Doctor of Philosophy (PhD), University of Toledo, 2019, Biomedical Sciences (Molecular Medicine)

Insulin-like growth factor 1 (IGF-1) and insulin exert biological effects through highly homologous tyrosine kinase receptors, which are ubiquitously expressed in rodents. During the last two decades, substantial progress has been made in understanding the role of IGF-1 and insulin signaling in the brain. Major progress has been made in identifying differences of IGF-1 and insulin signaling in the brain and understanding the phenotypic discrepancies of disruptions of the IGF-1 receptors (IGF1Rs) and insulin receptors (IRs) in the brain. Metabolic diseases such as obesity and diabetes are global public health crises. Moreover, perturbations of metabolism cause various reproductive diseases such as abnormal puberty onset, irregular estrus cycle, altered ovarian function, infertility and reproductive system cancers. Thus, understanding and deciphering brain IGF1R and IR signaling are crucial to current research and crucial for potential therapeutic interventions for metabolic and reproductive diseases. Neurons are the fundamental units of the brain and carry out distinct functions, which raises another challenge -- understanding the role of a given subset of neurons. Two subsets of neurons-leptin receptor (LepRb) neuron and kisspeptin (Kiss1) neuron have drawn my attention due to their distinct activities in metabolism and reproduction respectively. Current technique Cre/loxP system enables conditional suppression of gene expression in distinct subsets of neurons of interest. We used this technique to generate transgenic mice to study the role of IGF1R and IR signaling in LepRb neurons and Kiss1 neurons. Chapter 1 gives a review of metabolic and reproductive function of IGF1R and IR, and a central control of metabolism and reproduction by LepRb neurons and Kiss1 neurons. By characterizing reproductive and metabolic phenotype of mice lacking IGF1Rs and/or IRs exclusively in LepRb neurons (IGF1RLepRb mice and IGF1R/IRLepRb mice), we found that IGF1RLepRb and IGF1R/IR (open full item for complete abstract)

Committee: Jennifer Hill (Committee Chair); Beata Lecka-Czernik (Committee Member); Edwin Sanchez (Committee Member); David Giovannucci (Committee Member); Joshua Park (Committee Member) Subjects: Biomedical Research

Doctor of Philosophy in Clinical-Bioanalytical Chemistry, Cleveland State University, 2018, College of Sciences and Health Professions

Diabetes is characterized by hyperglycemia mainly due to defect in insulin secretion and/or action. Regulation of glucose transport and use by insulin is central to the maintenance of whole-body glucose homeostasis. One of the potential mechanisms associated with insulin sensitivity is the activation of insulin receptor (IR) and subsequently transduces the signal through phosphorylation of insulin receptor substrate (IRS) and activation of the PI-3K/Akt pathway. In contrast, activation of the mammalian target of rapamycin (mTOR) and ribosomal protein S6 kinase (p70S6K) suppresses the signal cascade. RNase L, an interferon (IFN)-inducible enzyme, plays an important role in IFN functions against viral infection and cell proliferation. However, a direct link between RNase L and insulin sensitivity has yet to be clearly established. RNase L+/+ and -/- mouse embryonic fibroblasts (MEFs) and hepatocytes were used to investigate the role of RNase L in insulin signaling and sensitivity. Cells were treated with insulin at various time points and different concentrations. Activation of the insulin signaling pathway was determined by immunoblot analyses for the protein level and phosphorylation status of these components such as IR/p-IR, IRS1/p-IRS1 and AKT/p-AKT in the presence or absence of a chemical inhibitor. Interestingly, we found that RNase L might mediate insulin signaling and glucose homeostasis through impacting insulin receptor (IR) which is a trans-membrane receptor activated by insulin. The phosphorylation status of IR was significantly reduced in the cell deficient RNase L. As a result, activation of downstream components in the insulin signaling pathway and the PI3K/AKT pathway was significantly inhibited in RNase L-/- cells. Further investigation of the molecular mechanism underlying the role of RNase L in mediating the activation of IR revealed that RNase L might regulate cleaving the precursor of IR and activating IRS-1 via the ubiquitin/ proteasome system. (open full item for complete abstract)

Committee: Aimin Zhou (Committee Chair); Michael Kalafatis (Committee Member); Bin Su (Committee Member); Xue-Long Sun (Committee Member); Nolan Holland (Committee Member) Subjects: Biochemistry; Molecular Biology

Doctor of Philosophy (PhD), University of Toledo, 2018, Biomedical Sciences (Molecular Medicine)

Insulin resistance has long been considered to play a crucial role in the pathophysiology of metabolic syndrome that is the leading cause of mortality and morbidity worldwide. Metabolic diseases consist of a group of metabolic abnormalities that increase the risk of health problems, such as type 2 diabetes (T2D) and cardiovascular disease. Nonalcoholic fatty liver disease (NAFLD) is associated with obesity and metabolic syndromes. It is the fastest growing cause of liver dysfunction. Its progressive form nonalcoholic steatohepatitis (NASH) is associated with hepatic fibrosis that can develop into cirrhosis. In addition, there is a growing body of evidence that among risk factors that promote atherosclerosis, metabolic syndrome is a potent predictor of cardiovascular events. Insulin resistance seems to play a major role in the pathophysiology of atherosclerosis in relation with metabolic syndrome. Given that patients with NAFLD/NASH are at a high risk to develop atherosclerosis; these two diseases may share some pathology. However, precise molecular mechanisms underlying the pathogenesis and progression of these diseases are not well understood. Thus studying the molecular link between them would pinpoint sites of more effective pharmacologic interventions. The carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), a protein that is markedly reduced in the liver of patients with NASH, promotes insulin clearance to regulate insulin action. Whether or not CEACAM1 links hyperinsulinemia to NAFLD/NASH and atherosclerosis still needs to be determined. CEACAM1 enhances the rate of uptake of the insulin-receptor complex into the clathrin-coated vesicles of hepatocytes. It also plays a major role in mediating the negative acute effect on fatty acid synthase (Fasn) activity. As such, CEACAM1 regulates insulin and lipid metabolism. Mice with global null mutation of CEACAM1 (Cc1–/–) display hyperinsulinemia resulting from impaired insulin clearance, insulin resist (open full item for complete abstract)

Committee: Sonia Najjar PhD (Committee Chair); Guillermo Vazquez PhD (Committee Member); Jennifer Hill PhD (Committee Member); Rajesh Gupta MD (Committee Member); David Kennedy PhD (Committee Member); Steven Haller PhD (Committee Member) Subjects: Biomedical Research

Doctor of Philosophy, Case Western Reserve University, 2018, Physiology and Biophysics

Single-chain insulin (SCI) analogs have long provided a valuable model for structure-function studies of insulin. Recently, a biologically active SCI containing a six-residue connecting (C) domain (inserted between the B- and A chains of two-chain insulin) demonstrated marked resistance to thermal degradation. Such a design has potential to circumvent the cold-storage requirements of current insulin therapeutic formulations which hinder their distribution, storage, and use in developing regions. An understanding of how this SCI scaffold can be engineered to confer desired biophysical and pharmacological properties would enable rational design, development, and clinical implementation of SCIs. This Thesis leverages principles of protein folding, structure, dynamics, stability and function to modulate SCI properties. Following an introduction of insulin analog design with focus on how SCIs could address a global need for ultra-stable formulations (Chapter 1), a synthetic single-chain [des-B29,des-B30]-insulin platform was utilized to model an oxidative intermediate in the folding of wild-type insulin. This system enabled comparative studies of an unstable TyrB16->Pro variant, which exhibited a severe folding defect (Chapter 2). Chapters 3-4 contain studies of two novel biologically active SCIs: SCI-a and SCI-b. These analogs exhibited remarkable resistance to thermal inactivation; SCI-a had native-like duration of hormone action in diabetic rats. Collaborative X-ray crystallographic studies of SCI-a revealed a novel zinc-free T6 hexamer (Chapter 3) whereas NMR and molecular dynamics studies of SCI-b provided insight into its mechanisms of enhanced stability and receptor binding (Chapter 4). Studies of variant SCIs containing amino-acid substitutions at position A14 (Chapter 5) suggested that the reverse hydrophobic effect, a general biophysical principle uncommonly observed, was operative. This principle could be leveraged to enhance SCI resistance to chemical degrada (open full item for complete abstract)

Committee: Michael Weiss MD, PhD (Advisor); Matthias Buck DPhil (Committee Chair); Faramarz Ismail-Beigi MD, PhD (Committee Member); George Dubyak PhD (Committee Member); Michael Zagorski PhD (Committee Member) Subjects: Biochemistry; Biophysics

Master of Science (MS), Ohio University, 2015, Biological Sciences (Arts and Sciences)

Increasing rates of obesity and associated complications worldwide have increased research interest in the complex interplay of hormones, metabolism, and adiposity. There is much evidence indicating that hormones such as growth hormone (GH), insulin-like growth factor 1 (IGF-1), and insulin affect white adipose tissue (WAT) in a depot-specific manner. This suggests that hormone-induced intracellular signaling is more active in some WAT depots compared to others, as evidenced by hormone receptor expression levels. To add another layer of complexity, WAT is made up of many cell types with distinct functions, including adipocytes and cells of the stromal vascular fraction (SVF), which can differentially express these receptors. The purpose of this thesis is to further develop our understanding of how GH-, IGF-1-, and insulin-induced signaling affect adiposity in a WAT depot-specific manner. The original aims of this thesis were to: 1) use quantitative polymerase chain reaction (qPCR) to compare the expression of the receptors of the above hormones (GH, IGF-1, and insulin) in the SVF and adipocyte portions of the most commonly studied WAT depots in wildtype (WT) mice (subcutaneous, epididymal, retroperitoneal, and mesenteric), and 2) compare the expression of these receptors in the WAT depots of growth hormone antagonist (GHA) and WT mice. Unfortunately, due to low adipocyte RNA concentrations and purity, the first aim was adjusted to examine receptor RNA expression in whole WAT (as opposed to isolated adipocytes) and SVF. No significant differences in receptor expression were observed in the first aim, but a trend toward greater insulin receptor (IR) RNA expression in the SVF of the epididymal depot compared to the SVF of the mesenteric depot was seen. The main significant finding of the second aim was that growth hormone receptor (GHR) was more strongly expressed in GHA mice than in WT mice in the mesenteric depot, a result that could be explained by differences in SV (open full item for complete abstract)

Committee: Darlene Berryman PhD (Advisor); John Kopchick PhD (Committee Member); Shigeru Okada PhD (Committee Member); Karen Coschigano PhD (Committee Member) Subjects: Biology; Molecular Biology

Doctor of Philosophy in Biomedical Sciences (Ph.D.), University of Toledo, 2009, College of Medicine

The pathogenesis of T2DM is complex and is preceeded by the development of insulinresistance. Previous studies have shown CEACAM1 to play a major role in mediating insulin clearance in the liver and that altered CEACAM1 function can cause impaired insulin clearance, hyperinsulinemia, altered fat metabolism, and the development of insulin restance. In this work, three unique strategies were employed in order to gain a better understanding of the physiologic role of CEACAM1 in vivo. First, the metabolic phenotype of Cc1–/– mice which are homozygous for a null mutation of the Ceacam1 gene was characterized. As expected, these mice exhibited an impairment of insulin clearance, hyperinsulinemia, and altered fat metabolism. Moreover, hyperinsulinemiceuglycemic clamp studies revealed that the inbred Cc1–/– mice developed insulin resistance primarily in liver. Finally, despite substantial expression of CEACAM1 in pancreatic β-cells, insulin secretion in response to glucose in vivo and isolated islets was normal in Cc1–/– mice. This undermines the notion CEACAM1 is involved in regulating insulin secretion in the pancreas and suggests the principal role of CEACAM1 in insulin action is to mediate insulin clearance in liver. Next, an alternative approach at investigating the function of CEACAM1 in vivo was taken by generating a transgenic mouse model (Tg(ApoA1-Cc1)7Smn) overexpressing CEACAM1 specifically in the liver. Analysis of Tg(ApoA1-Cc1)7Smn transgenic mice confirmed expression of the CEACAM1 transgene in a liver specific manner. These mice are currently being utilized to perform a gain of function study in Cc1-/- mice. This will allow us to investigate whether or not restitution of CEACAM1 expression in the liver of Cc1-/- mice is sufficient to ameliorate impaired insulin clearance, insulin resistance, and subsequent metabolic abnormalities. Finally, human expression of CEACAM1 mirrors the combined expression of murine CEACAM1 and CEACAM2. Therefore, we attempted to gen (open full item for complete abstract)

Committee: Sonia Najjar Ph.D. (Committee Chair); James Trempe Ph.D. (Committee Member); Joseph Shapiro M.D. (Committee Member); Ray Bourey M.D. (Committee Member); Francisco Moore Ph.D. (Committee Member); Edwin Sanchez Ph.D. (Committee Member) Subjects: Genetics; Molecular Biology; Physiological Psychology

Doctor of Philosophy in Medical Sciences (Ph.D.), University of Toledo, 2008, College of Graduate Studies

Insulin resistance is the hallmark of type 2 diabetes. CEACAM1, a substrate of insulin receptor in liver, regulates insulin action by promoting insulin clearance. Inactivation of CEACAM1 impairs insulin clearance and causes hyperinsulinemia, insulin resistance, dyslipidemia and visceral adiposity in transgenic mice. Moreover, CEACAM1 levels are significantly reduced in spontaneously obese rats. Thus, there is a strong association between visceral obesity, insulin resistance and reduced hepatic CEACAM1 level. Free fatty acids (FFA) that are released from adipose tissue, in particular during fasting and obesity, are transported to liver to activate the transcription factor peroxisome proliferator-activated receptor α (PPARα), which regulates expression of genes involved in fatty acid transport and oxidation. Thus, we investigated whether PPARα downregulates CEACAM1 level and hence mediates insulin resistance in obese mice. We fed normal wild-type male mice with a high-fat diet (HF) (45% of calories from fat), for 9 to 30 d. HF treatment for 9 d caused a loss of hepatic CEACAM1 mRNA and protein content by up to 35% without affecting insulin clearance and insulin action. However, treatment for 21-30 d reduced CEACAM1 mRNA and protein levels by ~≥ and led to impaired insulin clearance and insulin resistance in a reversible manner. On the other hand when we inhibited lipolysis in HF-fed mice by nicotinic acid, we observed normal hepatic CEACAM1 level and insulin action. Increased mobilization of 178 FFA from the adipose tissue, especially during fasting, increases FFA uptake by liver and their conversion into long chain fatty acids (LCFA) and LCFA-CoA. These activate the peroxisome proliferator-activated receptor α (PPARα, a nuclear transcription factor that upregulates transcription of proteins involved in fatty acid transport into mitochondria and oxidation in order to support gluconeogenesis). We have observed that at fasting, when PPARα levels are highest the leve (open full item for complete abstract)

Committee: Sonia Najjar (Advisor) Subjects: Health Sciences, Pharmacology

Doctor of Philosophy in Medical Sciences (Ph.D.), University of Toledo, 2005, College of Graduate Studies

The CEACAM1, a substrate of insulin receptor kinase in hepatocytes, promotes receptor-mediated insulin endocytosis and degradation, as demonstrated in L-SACC1 transgenic mice in which impaired insulin clearance causes hyperinsulinemia and hepatic insulin resistance. By decreasing visceral adiposity and circulating FFAs levels, carnitine normalized insulin levels and glucose tolerance in female L-SACC1 mice. Because carnitine does not affect receptor-mediated insulin internalization directly, the data suggest that altered fat metabolism plays an important role in the pathogenesis of impaired insulin clearance and insulin resistance in L-SACC1 mice. Deletion of Ceacam1 led to decreased insulin clearance, consistent with the predominant expression of CEACAM1 in liver, the major site of insulin clearance. In contrast, deletion of its homolog, Ceacam2, led to hyperinsulinemia without altering insulin clearance, in keeping with the low expression of CEACAM2 in liver. Both in vivo first-phase insulin secretion in response to exogenous glucose and glucose-stimulated insulin secretion from isolated islets were impaired in Ceacam2 null mice, whereas these parameters were unchanged in Ceacam1 null mice. Thus, CEACAM1 modulates hepatic insulin clearance and lipid metabolism, whereas CEACAM2 regulates glucose-induced insulin secretion. This study demonstrates non-redundant functions of these two closely related CEACAM proteins in maintaining insulin sensitivity.

Committee: Sonia Najjar, Ph.D. (Advisor) Subjects: Health Sciences, Pharmacology

Master of Science, The Ohio State University, 1960, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1965, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1962, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2006, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2024, Translational Biomedical Sciences

Studying the early pathophysiology of pancreatic islet dysfunction is key to preventing or reversing type 2 diabetes (T2D). Long before T2D is diagnosed, islets become hyperactive, causing systemic hyperinsulinemia. Pulsatile insulin secretion also becomes disordered, leading to the loss of efficient insulin secretion from the islets and reduced insulin signaling and clearance at the liver. A constantly high demand for insulin can eventually lead to exhaustion and failure of the islets. Preventing these early maladaptations to nutrient excess in islets may prevent the progression of obesity to T2D. To study islet and hepatocyte dysfunction in the context of T2D, innovative in vitro technologies are needed to overcome limitations in current models. Therefore, we created a series of microfluidic chips to investigate the role of pulsatile insulin secretion in islet and hepatocyte function. A syringe pump system was used to force islets to oscillate with alternating stimulatory and inhibitory solutions. Murine islets were treated chronically with high glucose to cause dysfunction followed by forced overnight oscillation treatment or a constant reduction in glycolytic activity with the glucokinase inhibitor mannoheptulose. Glucose-stimulated calcium recordings revealed that islets forced to oscillate had a greater recovery of function compared to islets with constantly reduced glycolytic activity, indicating a role for oscillations in maintaining beta-cell function. Using chips designed to hold hepatocytes or both islets and hepatocytes, we determined that pulsatile insulin delivery to hepatocytes improves nutrient storage compared to continuous insulin delivery. Another new in vitro model has emerged from the advancements in stem-cell-derived islets (SC-islets) that facilitate the study of beta cells that are relevant to human disorders. However, SC-islets are still functionally immature and can benefit from new techniques that augment their insulin secretion. Us (open full item for complete abstract)

Committee: Craig Nunemaker (Advisor); Kevin Lee (Committee Member); Sarah Wyatt (Committee Member); Sonia Najjar (Committee Member); John Kopchick (Committee Member) Subjects: Biomedical Research