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No description available.

No description available.

No description available.

A growing body of literature has linked atypical antipsychotics (AAPs) to an increased propensity for weight gain and metabolic disturbances, including type 2 diabetes. While weight gain is a leading risk factor for diabetes, evidence suggests that AAPs may influence glucose homeostasis independently of changes in adiposity. These ‘direct’ drug effects have been consistently supported by animal models, where following even a single dose of certain AAPs immediate effects are observed with noted perturbations on insulin sensitivity, and insulin secretion. However, the mechanisms underlying these effects remain poorly understood. Also, the translational value of the acute dosing rodent model has not been established in humans. As such, we set out to first elucidate mechanisms of these ‘direct’ effects by deconstructing antipsychotic receptor binding profiles using selective antagonists and gold standard clamping techniques to examine effects on glucose metabolism. We also investigated antipsychotic administration directly into the brain in rodents to tease out central vs. peripheral effects on glucose metabolism. Finally, we examined whether the effects of a single dose of olanzapine on glucose metabolism could be replicated in healthy humans, independently of adiposity or the confounding effects of the illness of schizophrenia. Our findings suggest that cholinergic, serotonergic, and dopaminergic pathways may be involved in antipsychotic-induced glucose dysregulation. We also suggest that such effects may be mediated in part through the central nervous system. Our results in humans suggest that acute drug effects may be less pronounced than in rodents, failing to note an effect on insulin sensitivity or secretion, but observing other early perturbations in lipid and glucose metabolism. Taken together, the work here begins to elucidate mechanisms underlying the diabetogenic risk associated with AAPs, findings which have important implications given the widespread use of these drugs, as well as the increased mortality attributable to cardiovascular disease that defines those with schizophrenia.

Nutrient sensing pathways in both the brain and gut decrease hepatic glucose production. Hypothalamic activation of lactate metabolism decreases glucose production, but it is unknown whether the hypothalamus detects circulating lactate to maintain glucose homeostasis. In the gut, lipids decrease glucose production via a neuronal network but the downstream signaling mechanisms are unknown. We tested whether circulating lactate activates central lactate metabolism to decrease glucose production and postulated that duodenal protein kinase C (PKC) acts downstream of lipids to decrease glucose production through a neuronal network. We report that central lactate metabolism is required for the maintenance of glucose homeostasis in the presence of circulating lactate and that activation of duodenal PKC is required for lipids to decrease glucose production. This shows the importance of the brain and gut in the regulation of glucose production, and could pave the way for restoration of glucose homeostasis in disease.

Diabetic nephropathy is the leading cause of end-stage renal disease, yet the mechanisms responsible for hyperglycemia-induced kidney injury have not been fully elucidated. Activation of the renin-angiotensin system and NADPH oxidase-dependent generation of reactive oxygen species are important mediators of chronic kidney disease. I first studied the effect of ACE2, an important enzyme in the renin-angiotensin system, in diabetic kidney injury in the Akita mouse and related the effect to angiotensin peptide and NADPH oxidase. I then demonstrated the interaction between Angiotensin II, the main substrate, and angiotensin-(1-7), the main product of ACE2, respectively, on cell signaling in mesangial cells to better understand the in vitro effect of ACE2. Finally I studied the effect of deletion of p47phox, a regulatory subunit of the NADPH oxidase, on initiation and progression of diabetic nephropathy in the Akita mouse and mesangial cell. Administration of human recombinant ACE2 decreased angiotensin II levels, increased angiotensin-(1-7) levels, normalized NADPH oxidase activity in the Akita mice, and ameliorated diabetes-induced kidney injury. In vitro, hrACE2 attenuated both high glucose and ANG II–induced oxidative stress and NADPH oxidase activity in mesangial cells. Ang-(1–7)-induced ERK1/2 phosphorylation in mesangial cells in a mas receptor-cAMP-PKA-dependent manner. This effect of ang-(1-7) on ERK1/2 phosphorylation is not mediated by AT1R, AT2R, epidermal growth factor or NADPH oxidase. Pre-treatment with Ang-(1-7) attenuated Ang II-induced NADPH oxidase activity and ERK1/2 activation also in a cAMP-PKA-dependent manner. Deletion of p47phox not only reduced diabetes-induced kidney injury but also reduced hyperglycemia by increasing pancreatic and circulating insulin concentrations. p47phox-/- mice exhibited improved glucose tolerance but modestly decreased insulin sensitivity. Deletion of p47phox attenuated high glucose-induced activation of NADPH oxidase and pro-fibrotic gene expression in mesangial cells. There was a positive correlation between p47phox and collagen Iα1 mRNA levels in renal biopsy samples from control subjects and subjects with diabetic nephropathy. The data generated in this thesis strongly suggest a protective role of ACE2, via Ang-(1-7), and a deleterious role of p47phox in diabetic nephropathy. Future therapeutic strategies should include enhancing ACE2 activity in the kidney and inhibiting p47phox-dependent activation of NADPH oxidase in both the kidney and the pancreas.

A growing body of literature has linked atypical antipsychotics (AAPs) to an increased propensity for weight gain and metabolic disturbances, including type 2 diabetes. While weight gain is a leading risk factor for diabetes, evidence suggests that AAPs may influence glucose homeostasis independently of changes in adiposity. These ‘direct’ drug effects have been consistently supported by animal models, where following even a single dose of certain AAPs immediate effects are observed with noted perturbations on insulin sensitivity, and insulin secretion. However, the mechanisms underlying these effects remain poorly understood. Also, the translational value of the acute dosing rodent model has not been established in humans. As such, we set out to first elucidate mechanisms of these ‘direct’ effects by deconstructing antipsychotic receptor binding profiles using selective antagonists and gold standard clamping techniques to examine effects on glucose metabolism. We also investigated antipsychotic administration directly into the brain in rodents to tease out central vs. peripheral effects on glucose metabolism. Finally, we examined whether the effects of a single dose of olanzapine on glucose metabolism could be replicated in healthy humans, independently of adiposity or the confounding effects of the illness of schizophrenia. Our findings suggest that cholinergic, serotonergic, and dopaminergic pathways may be involved in antipsychotic-induced glucose dysregulation. We also suggest that such effects may be mediated in part through the central nervous system. Our results in humans suggest that acute drug effects may be less pronounced than in rodents, failing to note an effect on insulin sensitivity or secretion, but observing other early perturbations in lipid and glucose metabolism. Taken together, the work here begins to elucidate mechanisms underlying the diabetogenic risk associated with AAPs, findings which have important implications given the widespread use of these drugs, as well as the increased mortality attributable to cardiovascular disease that defines those with schizophrenia.

Nutrient sensing pathways in both the brain and gut decrease hepatic glucose production. Hypothalamic activation of lactate metabolism decreases glucose production, but it is unknown whether the hypothalamus detects circulating lactate to maintain glucose homeostasis. In the gut, lipids decrease glucose production via a neuronal network but the downstream signaling mechanisms are unknown. We tested whether circulating lactate activates central lactate metabolism to decrease glucose production and postulated that duodenal protein kinase C (PKC) acts downstream of lipids to decrease glucose production through a neuronal network. We report that central lactate metabolism is required for the maintenance of glucose homeostasis in the presence of circulating lactate and that activation of duodenal PKC is required for lipids to decrease glucose production. This shows the importance of the brain and gut in the regulation of glucose production, and could pave the way for restoration of glucose homeostasis in disease.

Diabetes Mellitus is a common chronic disease that is an ever-increasing public health issue. Continuous glucose monitoring has been shown to help diabetes mellitus patients stabilize their glucose levels, leading to improved patient health. Hence, a glucose sensor, capable of continuous real-time monitoring, has been a topic of research for three decades. Current methods of glucose monitoring, however, require taking blood samples several times a day, hence patient compliance is an issue. Optical methods are one of the painless and promising methods that can be used for blood glucose predictions. However, having accuracies lower than what is acceptable clinically has been a major concern. To improve on the accuracy of the predictions, the signal-to-noise ratio in the spectrum can be increased, for which the use of thermally tunable vertical cavity surface emitting lasers (VCSELs) as the light source to obtain blood absorption spectra, along with a multivariate technique (Partial Least Square (PLS) techniques) for analysis, is proposed. VCSELs are semiconductor lasers with small dimensions and low power consumption, which makes them suitable for implants. VCSELs provide higher signal-to-noise ratio as they have high power spectral density and operate within a small spectrum. In the current research, experiments were run for the preliminary investigations to demonstrate the feasibility of the proposed technique for glucose monitoring. This research involves preliminary investigations for developing a novel optical system for accurate measurement of glucose concentration. Experiments in aqueous glucose solutions were designed to demonstrate the feasibility of the proposed technique for glucose monitoring. In addition, multivariate techniques, such as PLS, were customized for various specific purposes of this project and its preliminary investigation. This research will lead to the development of a small, low power, implantable optical sensor for diabetes patients, which will be a major breakthrough in the area of treating diabetes patients, upon successful completion of this research and development of the device.