Biology subjects

Moritz, W. R.

Publications and source records attributed to Moritz, W. R..

3 recordsLinked to original sources

bioRxiv2022

Kir6.2-containing KATP channels are necessary for glucose dependent increases in amyloid-beta and Alzheimer's-related pathology

Increased neuronal excitability contributes to amyloid-{beta} (A{beta}) production and aggregation in the Alzheimers disease (AD) brain. Previous work from our lab demonstrated that hyperglycemia, or elevated blood glucose levels, increased brain excitability and A{beta} release potentially through inward rectifying, ATP-sensitive potassium (KATP) channels. KATP channels are present on several different cell types and help to maintain excitatory thresholds throughout the brain. KATP channels are sensitive to changes in the metabolic environment, which are coupled to changes in cellular excitability. Therefore, we hypothesized that neuronal KATP channels are necessary for the hyperglycemic-dependent increases in extracellular A{beta} and eliminating KATP channel activity will uncouple the relationship between metabolism, excitability, and A{beta} pathology. First, we demonstrate that Kir6.2/KCNJ11, the pore forming subunits, and SUR1/ABCC8, the sulfonylurea receptors, are predominantly expressed on excitatory and inhibitory neurons in the human brain and that cortical expression of KCNJ11 and ABCC8 change with AD pathology in humans and rodent models. Next, we crossed APP/PS1 mice with Kir6.2 -/- mice, which lack neuronal KATP channel activity, to define the relationship between KATP channels, A{beta}, and hyperglycemia. Using in vivo microdialysis and hyperglycemic clamps, we explored how acute elevations in peripheral blood glucose levels impacted hippocampal interstitial fluid (ISF) glucose, lactate, and A{beta} levels in APP/PS1 mice with or without KATP channels. Kir6.2+/+, APP/PS1 mice and Kir6.2-/-, APP/PS1 mice were exposed to a high sucrose diet for 6 months to determine the effects of chronic hyperglycemia on A{beta} deposition. We found that elevations in blood glucose levels correlate with increased ISF A{beta}, amyloidogenic processing of amyloid precursor protein (APP), and amyloid plaque pathology in APP/PS mice with intact KATP channels. However, neither acute hyperglycemia nor chronic sucrose overconsumption raised ISF A{beta} or increased A{beta} plaque burden in APP/PS1 mice lacking Kir6.2-KATP channel activity. Mechanistic studies demonstrate ISF glucose not only correlates with ISF A{beta} but also ISF lactate. Without KATP channel activity, ISF lactate does not increase during hyperglycemia, which correlates with decreased monocarboxylate transporter 4 (MCT4) expression, a lactate transporter responsible for astrocytic lactate release. This suggests that KATP channel activity regulates ISF lactate during hyperglycemia, which is important for A{beta} release and aggregation. These studies identify a new role for Kir6.2-KATP channels in Alzheimers disease pathology and suggest that pharmacological antagonism of Kir6.2-KATP channels holds therapeutic promise in reducing A{beta} pathology, especially in diabetic and prediabetic patients.

neuroscience↗

bioRxiv2021

Sulfonylureas target the neurovascular response to decrease Alzheimer's pathology

Hyperexcitability is a defining feature of Alzheimers disease (AD), where aberrant neuronal activity is both a cause and consequence of AD. Therefore, identifying novel targets that modulate cellular excitability is an important strategy for treating AD. ATP-sensitive potassium (KATP) channels are metabolic sensors that modulate cellular excitability. Sulfonylureas are KATP channel antagonists traditionally used to combat hyperglycemia in diabetic patients by inhibiting pancreatic KATP channels, thereby stimulating insulin release. However, KATP channels are not limited to the pancreas and systemic modulation of KATP channels has pleotropic physiological effects, including profound effects on vascular function. Here, we demonstrate that human AD patients have higher cortical expression of vascular KATP channels, important modulators of vasoreactivity. We demonstrate that peripheral treatment with the sulfonylurea and KATP channel inhibitor, glyburide, reduced the aggregation and activity-dependent production of amyloid-beta (A{beta}), a hallmark of AD, in mice. Since glyburide does not readily cross the blood brain barrier, our data suggests that glyburide targets vascular KATP channel activity to reduce arterial stiffness, improve vasoreactivity, and normalize pericyte-endothelial cell morphology, offering a novel therapeutic target for AD. Graphical abstractTargeting vascular KATP channel activity for the treatment of Alzheimers disease pathology. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

neuroscience↗

bioRxiv2019

Type-2-diabetes alters CSF but not plasma metabolomic and AD risk profiles in vervet monkeys

Epidemiological studies suggest that individuals with type 2 diabetes (T2D) have a 2-4 fold increased risk for developing Alzheimers disease (AD), however the exact mechanisms linking the two disease is unknown. In both conditions, the majority of pathophysiological changes (including glucose and insulin dysregulation, insulin resistance, and AD-related changes in A{beta} and tau) occur decades before the onset of clinical symptoms and diagnosis. In this study, we investigated the relationship between metabolic biomarkers associated with T2D and AD-related pathology, including A{beta} levels, from cerebrospinal fluid (CSF) and fasting plasma of healthy, prediabetic (PreD), and T2D vervet monkeys (Chlorocebus aethiops sabeus). Consistent with the human disease, T2D monkeys have increased plasma and CSF glucose levels as they transition from normoglycemia to pre-diabetic and diabetic states. Although plasma levels of acylcarnitines and amino acids remained largely unchanged, peripheral hyperglycemia correlated with decreased CSF acylcarnitines and CSF amino acids, including branched chain amino acid (BCAA) concentrations, suggesting profound changes in cerebral metabolism coincident with systemic glucose dysregulation. Moreover, CSF A{beta}40 and CSF A{beta}42 levels decreased in T2D monkeys, a phenomenon observed in the human course of AD which coincides with increased amyloid deposition within the brain. In agreement with our previous studies in mice, CSF A{beta}40 and CSF A{beta}42 were highly correlated with CSF glucose levels, suggesting that glucose levels in the brain are associated with changes in A{beta} metabolism. Interestingly, CSF A{beta}40 and CSF A{beta}42 levels were also highly correlated with plasma but not CSF lactate levels, suggesting that plasma lactate might serve as a potential biomarker of disease progression in AD. Moreover, CSF glucose and plasma lactate levels were correlated with CSF amino acid and acylcarnitine levels, demonstrating alterations in cerebral metabolism occurring with the onset of T2D. Together, these data suggest that peripheral metabolic changes associated with the development of T2D produce alterations in brain metabolism that lead to early changes in the amyloid cascade, similar to those observed in pre-symptomatic AD.

neuroscience↗