type 2 diabetes

A novel MRI method for noninvasive imaging of bone quality in type 2 diabetes

ABSTRACT: Type 2 diabetes mellitus (T2DM) affects 500 million of the global population, which is expected to increase to 800 million in 20 years. One of the multiple complications involved with T2DM is the significantly increased bone fracture risk and post-fracture mortality. Dual-energy X-ray absorptiometry (DXA) scans are routinely performed to measure bone mineral density (BMD) and associated fracture risk. However, T2DM patients often show preserved or even elevated BMD despite the significantly increased fracture risk. This mismatch between the BMD measurement and actual fracture risk hampers the accurate assessment of fracture risk and the appropriate treatment of T2DM that considers patient bone health. The lack of an accurate fracture risk assessment tool also confounds the evaluation of the bone health effect of antidiabetic drugs, including recently highlighted glucagon-like peptide-1 receptor agonists (e.g., semaglutide) and sodium-glucose cotransporter-2 inhibitors. Previous studies have suggested that bone quality, rather than bone quantity, as represented by BMD, is a crucial factor contributing to fracture risk in T2DM settings. Collagen crosslinking via advanced glycation end-products (AGEs) in cortical bone has been identified as a distinctive bone quality characteristic of T2DM patients, which explains the increased bone fragility. Although this finding is highly promising for improving the bone health management of T2DM patients, currently, no non-invasive method can monitor collagen crosslinking in the bones. This proposal aims to develop an ultrashort echo time (UTE) MRI-based method for measuring the degree of bone collagen crosslinking by quantifying magnetization transfer between water and collagen in the bone. This method, termed UTE-quantitative magnetization transfer (UTE-qMT) MRI, measures not only the quantity of macromolecules (e.g., collagen) in the bone but also the rates of exchange between water and macromolecular protons, which are related to the degree of collagen crosslinking. The proposal will develop and optimize the accelerated UTE-qMT method for reliably measuring the exchange rate in Aim 1. The optimized technique will be validated by correlating exchange rates with AGE-driven collagen crosslinking and subsequent compromise of bone mechanical properties in Aim 2. Finally, the optimized UTE-qMT MRI method will be translated to animal and human studies to demonstrate its clinical feasibility for investigating the effect of antidiabetic drugs on bone health in patients with T2DM in Aim 3. The successful completion of these aims will enable rapid and accurate assessment of bone fracture risk in patients with T2DM. Furthermore, noninvasively probing bone quality can also accurately assess the effect of antidiabetic drugs on bone health and aid in screening novel T2DM therapeutics for their impact on bone health.

Characterizing adipocyte heterogeneity in response to metabolic stress

Project Summary Adipose tissue is a central player in metabolism, storing energy healthily under normal conditions but becoming dysfunctional when overloaded. This can lead to the development of metabolic disease, most notably insulin resistance and type 2 diabetes (T2D). Understanding the contribution of adipose tissue to these complications requires knowledge of the individual cell types within adipose tissue and how they respond to different metabolic conditions. My previous work used single nucleus RNA sequencing to profile the cell types in adipose tissue and identified a number of subpopulations of white adipocytes that are differentially associated with clinical characteristics such as body mass index. In this grant, I now aim to better understand how a diverse array of stimuli influences adipocyte development and specification, the role that intra-individual variation plays in the response to these stimuli, and a better understanding of the relationship of adipocyte state to the development of metabolic disease. To do this, I propose using a model in which I can study human adipocyte development and function in mice to perform experiments such as high fat diet and cold exposure that are well-characterized in mice but not in humans. By performing experiments using cells from humans with a range of starting clinical characteristics, I can determine what changes will happen in response to a stimuli in all individuals verses those that only occur in specific populations. The experience that I have in characterizing adipocytes and adipose tissue both at the bench and computationally make me uniquely positioned to answer these questions. Taken together, these studies can test the behavior of adipocyte subpopulations from different people and under different conditions, ultimately leading to a better understanding of how subpopulations develop and, eventually, how we can target these populations to treat metabolic disease.

A Novel Mitochondrial-Targeted Inhibitor of NLRP3 Inflammasome Activation

PROJECT ABSTRACT Inflammasomes are multiprotein complexes of the innate immune system that assemble upon detecting specific molecular patterns associated with pathogens and cellular damage. Once assembled, activated inflammasomes trigger a cascade of downstream events that culminate in cell death and inflammation. Aberrant activation of the NLRP3 inflammasome contributes to the pathogenesis of numerous inflammatory and degenerative diseases, including gout, atherosclerosis, type 2 diabetes, and Alzheimer’s disease. Despite its central role in innate immunity and inflammation, there are no FDA-approved therapies that directly target the NLRP3 inflammasome. Current strategies rely on biologics that inhibit downstream pro-inflammatory cytokines produced from inflammasome activation, such as interleukin-1β (IL-1β), but do not block upstream inflammasome assembly or pyroptotic cell death, highlighting a critical unmet need for selective small-molecule inhibitors with novel mechanisms of action. To address this gap, we identified a covalent small molecule, Compound-2 (C-2), that robustly inhibits NLRP3 inflammasome activation in murine and human immune cells. C-2 suppresses multiple downstream events triggered by inflammasome activation, including IL-1β secretion and pyroptosis, with no apparent toxicity. Chemoproteomic profiling revealed that C-2 interacts with SLC25A3, a mitochondrial phosphate and copper transporter, suggesting a previously unrecognized regulatory node in inflammasome signaling. This R21 project aims to (1) elucidate the mechanism by which C-2 suppresses NLRP3 activation and (2) define the molecular interaction between C-2 and SLC25A3 and its functional consequences. Our studies will integrate biochemical, cellular, and in vivo approaches to uncover a novel mitochondrial mechanism of inflammasome regulation and validate C-2 as a first-in-class inflammasome inhibitor. Successful completion of this project will lay the foundation for future therapeutic development targeting mitochondrial- inflammasome crosstalk in inflammatory disease.

Targeting the brain to improve obesity and type 2 diabetes

The increasing prevalence of obesity and type 2 diabetes (T2D) and associated morbidity and mortality emphasizes the need for a more complete understanding of the mechanisms mediating energy homeostasis to accelerate the identification of new medications. Recent reports indicate that obesity medication, 5-hydroxytryptamine (5-HT, serotonin)2C receptor (5-HT2CR) agonist lorcaserin improves glycemic control in association with weight loss in obese patients with T2D. We examined whether lorcaserin has a direct effect on insulin sensitivity and how this effect is achieved. We clarify that lorcaserin dose-dependently improves glycemic control in a mouse model of T2D without altering body weight. Examining the mechanism of this effect, we reveal a necessary and sufficient neurochemical mediator of lorcaserin’s glucoregulatory effects, via activation of brain pro-opiomelanocortin (POMC) peptides. We observed that lorcaserin reduces hepatic glucose production and improves insulin sensitivity. These data suggest that lorcaserin’s action within the brain represents a mechanistically novel treatment for T2D: findings of significance to a prevalent global disease.

A metabolic function of the hippocampal sharp wave-ripple

The hippocampal formation has been implicated in both cognitive functions as well as the sensing and control of endocrine states. To identify a candidate activity pattern which may link such disparate functions, we simultaneously measured electrophysiological activity from the hippocampus and interstitial glucose concentrations in the body of freely behaving rats. We found that clusters of sharp wave-ripples (SPW-Rs) recorded from both dorsal and ventral hippocampus reliably predicted a decrease in peripheral glucose concentrations within ~10 minutes. This correlation was less dependent on circadian, ultradian, and meal-triggered fluctuations, it could be mimicked with optogenetically induced ripples, and was attenuated by pharmacogenetically suppressing activity of the lateral septum, the major conduit between the hippocampus and subcortical structures. Our findings demonstrate that a novel function of the SPW-R is to modulate peripheral glucose homeostasis and offer a mechanism for the link between sleep disruption and blood glucose dysregulation seen in type 2 diabetes and obesity.

Hippocampal neurovascular coupling and spatial working memory impairment in a rodent model of type 2 diabetes: impact of dietary nitrate intervention

Regulation of the apoptosis/autophagy switch by propionic acid in ventromedial hypothalamus of rats with type 2 diabetes mellitus

Aggression control by type 2 diabetes risk gene Dusp8

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Antioxidant effect of combined administration of metformin and propionate in a rat model of type 2 diabetes mellitus

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Impact of type 2 diabetes and high-intensity interval exercise on neurogenesis, angiogenesis, and the accumulation of lipid droplets in the hippocampus

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Non-canonical anti-inflammatory effects of sitagliptin, a drug for type 2 diabetes, in microglia

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Prediabetes and type 2 diabetes affect tau phosphorylation patterns in murine models of Alzheimer’s disease

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Structural and functional alterations in the retina of a model of Alzheimer’s disease and type 2 diabetes

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Subchronic administration of the antidiabetic drug metformin mitigates cognitive impairments in a mouse model of type 2 diabetes mellitus

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