There is accumulating evidence from epidemiological studies that changes in body weight are associated with Alzheimer’s disease (AD) from mid-life obesity increasing the risk of developing AD to weight loss occurring at the earliest stages of AD. Therefore, factors that regulate body weight are likely to influence the development and progression of AD. The adipocyte-derived hormone leptin has emerged as a major regulator of body weight mainly by activating hypothalamic neural circuits. Leptin also has several pleotropic effects including regulating cognitive function and having neuroprotective effects, suggesting a potential link between leptin and AD. Here, we will examine the relationship between leptin and AD by reviewing the recent evidence from cellular and animal models to human studies. We present a model where leptin has a bidirectional role in AD. Not only can alterations in leptin levels and function worsen cognitive decline and progression of AD pathology, but AD pathology, in of itself, can disrupt leptin signaling, which together would lead to a downward spiral of progressive neurodegeneration and worsening body weight and systemic metabolic deficits. Collectively, these studies serve as a framework to highlight the importance of understanding the molecular mechanisms underlying the body weight and systemic metabolic deficits in AD, which has the potential to open new avenues that may ultimately lead to novel therapeutic targets and diagnostic tools.
Circulating tumor cells (CTC) have been implicated in the hematogenous spread of cancer. To investigate the fluid phase of cancer from a physical sciences perspective, the multi-institutional Physical Sciences-Oncology Center (PS-OC) Network performed multidisciplinary biophysical studies of single CTC and CTC aggregates from a patient with breast cancer. CTCs, ranging from single cells to aggregates comprised of 2-5 cells, were isolated using the high-definition CTC assay and biophysically profiled using quantitative phase microscopy. Single CTCs and aggregates were then modeled in an in vitro system comprised of multiple breast cancer cell lines and microfluidic devices used to model E-selectin mediated rolling in the vasculature. Using a numerical model coupling elastic collisions between red blood cells and CTCs, the dependence of CTC vascular margination on single CTCs and CTC aggregate morphology and stiffness was interrogated. These results provide a multifaceted characterization of single CTC and CTC aggregate dynamics in the vasculature and illustrate a framework to integrate clinical, biophysical, and mathematical approaches to enhance our understanding of the fluid phase of cancer.circulating tumor cell; metastasis; breast cancer; cell lines; fluid dynamics; physics of cancer; hemodynamics; quantitative phase microscopy; microfluidics; immersed finite element method WHILE THE PRESENCE of circulating tumor cells (CTCs) in the vasculature has been implicated in the metastatic cascade of epithelial carcinomas, new evidence has revealed a putative role of CTC aggregates as a potential form of stromal-assisted metastasis across a variety of epithelial tumor types (6). In concert, the presence of homotypic interactions among CTCs leading to aggregation occurring at sites of endothelial attachment suggest the involvement of CTC aggregates in the hematogenous dissemination of cancer. Despite compelling evidence suggesting a role for CTC aggregates in metastatic progression (28), the physics underlying CTC vascular transport including the influence of blood flow, coagulation, intercellular adhesion, and collisions with cells of the vasculature, such as red blood cells (RBCs) and endothelial cells (ECs), remains poorly understood. Better physical understanding of CTC transport and mechanobiology could enable, for example, new strategies to monitor patient response to chemotherapy (22).Here, we demonstrate a multidisciplinary approach (29) that utilizes clinical measurements on single CTCs and CTC aggregates from a patient with breast cancer as a quantitative guide in the rational design of in vitro and in silico models to investigate the dynamics of CTC transport in the vasculature. Using the high-definition (HD) CTC assay to identify circulating tumor cells in the blood, coupled with quantitative phase microscopy (QPM) to quantify the subcellular density organization of CTCs, we profiled the biophysical properties of CTCs in a patient with breast cancer. These metrics, including geometric and density features,...
Weight loss is an early manifestation of Alzheimer's disease that can precede the cognitive decline, raising the possibility that amyloid- (A) disrupts hypothalamic neurons critical for the regulation of body weight. We previously reported that, in young transgenic mice overexpressing mutated amyloid precursor protein (Tg2576), A causes dysfunction in neuropeptide Y (NPY)-expressing hypothalamic arcuate neurons before plaque formation. In this study, we examined whether A causes arcuate NPY neuronal dysfunction by disrupting intracellular Ca 2ϩ homeostasis. Here, we found that the L-type Ca 2ϩ channel blocker nimodipine could hyperpolarize the membrane potential, decrease the spontaneous activity, and reduce the intracellular Ca 2ϩ levels in arcuate NPY neurons from Tg2576 brain slices. In these neurons, there was a shift from high to low voltage-threshold activated L-type Ca 2ϩ currents, resulting in increased Ca 2ϩ influx closer to the resting membrane potential, an effect recapitulated by A 1-42 and reversed by nimodipine. These low voltage-threshold activated L-type Ca 2ϩ currents were dependent in part on calcium/calmodulin-dependent protein kinase II and IP 3 pathways. Furthermore, the effects on intracellular Ca 2ϩ signaling by both a positive (ghrelin) and negative (leptin) modulator were blunted in these neurons. Nimodipine pretreatment restored the response to ghrelin-mediated feeding in young (3-5 months), but not older (10 months), female Tg2576 mice, suggesting that intracellular Ca 2ϩ dysregulation is only reversible early in A pathology. Collectively, these findings provide evidence for a key role for low-threshold activated voltage gated L-type Ca 2ϩ channels in A-mediated neuronal dysfunction and in the regulation of body weight.
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