Biology subjects

McGuinness, O. P.

Publications and source records attributed to McGuinness, O. P..

6 recordsLinked to original sources

bioRxiv2026

A high-resolution mass spectrometry-based method for quantifying insulin-stimulated glucose uptake in mice following an intraperitoneal injection of tracer

ObjectiveA catheter-free, non-radiolabeled method that permits in vivo measurement of tissue-specific glucose uptake does not exist. To address this gap, we sought to develop and validate a new, higher throughput mass spectrometry (MS)-based method that combines an injection of insulin with a non-radiolabeled glucose tracer, 2-fluoro-2-deoxyglucose (2FDG), to determine insulin-stimulated tissue-specific glucose clearance in conscious, unrestrained mice. MethodsInjections of saline or insulin with 2FDG were coupled with LC-Q Exactive Hybrid Quadrupole-Orbitrap (LC) MS-based measures of plasma 2FDG and tissue (2-fluoro-2-deoxyglucose-6-phosphate) 2FDGP to determine glucose clearance in mice under several different conditions. ResultsThe newly developed method was first applied to a dose response experiment in mice. Next, the ability of this method to quantify changes in glucose clearance in response to an insulin stimulus was assessed, and glucose clearance was compared between chow and high fat fed mice. Results from these studies showed that insulin-stimulated skeletal muscle and heart glucose clearance can be estimated following a bolus injection of tracer, and these fluxes are blunted in diet-induced obese mice. The broad applicability of this approach was then demonstrated by assessing glucose clearance in a mouse model with anticipated changes in insulin-stimulated skeletal muscle glucose metabolism. ConclusionsThe results validated a new LC-MS method to quantify insulin-stimulated tissue-specific glucose clearance in vivo without the use of catheters or radiolabeled tracers. The method offers great potential because it is designed for application to pre-clinical studies seeking high throughput tests and/or assays that can be coupled with discovery technologies such as genomics, proteomics and metabolomics. HIGHLIGHTSO_LIIn vivo glucose clearance can be estimated by a new non-radiolabeled method. C_LIO_LIThe plasma tracer to tracee ratio is required to determine tissue tracer phosphorylation. C_LIO_LIMeasures of plasma glucose and tracer kinetics are critical for data interpretation. C_LIO_LIThe new method can be combined with omics technologies such as metabolomics. C_LI

physiology↗

bioRxiv2025

Alpha Parvin Promotes Glucose Uptake and Metabolism in Skeletal Muscle with Minimal Influence on Hepatic Insulin Sensitivity

Skeletal muscle and liver insulin resistance are early features in the sequelae of type 2 diabetes. Integrins are extracellular matrix receptors expressed on skeletal muscle cells and hepatocytes and have been implicated in modulating obesity-associated insulin resistance. Integrins regulate cell function through intracellular proteins including the ILK-PINCH-Parvin (IPP) complex. ILK promotes skeletal muscle and liver insulin resistance in diet-induced obesity in mice but the role of Parvin is unexplored. Here we demonstrate that hepatocyte specific deletion of -Parvin had only minimal influence on endogenous glucose production or whole-body insulin sensitivity. In contrast, deletion of -Parvin in skeletal muscle caused a striking reduction in muscle glucose uptake during an insulin clamp in lean mice which was not exacerbated by diet-induced obesity. Insulin-mediated GLUT4 membrane recruitment was impaired in mutant muscles which displayed significant morphological abnormalities due to actin cytoskeleton dysfunction. Consistent with severe muscular dysfunction, mitochondrial oxidative capacity and aerobic exercise capacity were blunted in muscle -Parvin-null mice. Thus, -Parvin has a minor role in liver insulin action but is required for insulin-stimulated glucose uptake in skeletal muscle due to its role in actin cytoskeleton regulation. These data suggest that individual IPP complex proteins link cell structure to metabolism via distinct mechanisms in a tissue-specific fashion.

physiology↗

bioRxiv2023

Insulin at the Intersection of Thermoregulation and Glucose Homeostasis

Mammals are protected from changes in environmental temperature by altering energetic processes that modify heat production. Insulin is the dominant stimulus of glucose uptake and metabolism, which are fundamental for thermogenic processes. The purpose of this work was to determine the interaction of ambient temperature induced changes in energy expenditure (EE) on the insulin sensitivity of glucose fluxes. Short-term and adaptive responses to thermoneutral temperature (TN, [~]28{degrees}C) and room (laboratory) temperature (RT, [~]22{degrees}C) were studied in mice. This range of temperature does not cause detectable changes in circulating catecholamines or shivering and postabsorptive glucose homeostasis is maintained. We tested the hypothesis that a decrease in EE that occurs with TN causes insulin resistance and that this reduction in insulin action and EE is reversed upon short term (<12h) transition to RT. Insulin-stimulated glucose disposal (Rd) and tissue specific glucose uptake were assessed combining isotopic tracers with hyperinsulinemic-euglycemic clamps. EE and insulin-stimulated Rd are both decreased ([~]50%) in TN-adapted vs RT-adapted mice. When RT-adapted mice are switched to TN, EE rapidly decreases and Rd is reduced by [~]50%. TN-adapted mice switched to RT exhibit a rapid increase in EE, but whole body insulin-stimulated Rd remains at the low rates of TN-adapted mice. In contrast, whole body glycolytic flux rose with EE. This higher EE occurs without increasing glucose uptake from the blood, but rather by diverting glucose from glucose storage to glycolysis. In addition to adaptations in insulin action, insulin-independent glucose uptake in brown fat is exquisitely sensitive to thermoregulation. These results show that insulin action adjusts to non-stressful changes in ambient temperature to contribute to the support of body temperature homeostasis without compromising glucose homeostasis. HighlightsO_LIEnergy expenditure and insulin-mediated glucose fluxes are reduced in thermoneutral (TN)-adapted mice versus room laboratory temperature (RT)-adapted mice. C_LIO_LIReduced insulin sensitivity manifests in TN mice regardless of whether they are TN-adapted or short-term transitioned from RT-adapted to TN. C_LIO_LITN-adapted mice are resistant to the RT-induced increase in whole-body insulin sensitivity even though metabolic rate is increased. C_LIO_LITN-adapted mice switched to RT meets increased thermogenic needs, not by increasing glucose uptake, but by partitioning a greater fraction of glucose from glycogen storage to glycolysis. C_LIO_LIBrown fat glucose uptake sensitively increases with RT and decreases with TN by an insulin-independent mechanism. C_LI

physiology↗

bioRxiv2020

Impairment of the Gβγ-SNAP25 brake on exocytosis enhances insulin action, protects against diet-induced obesity, and promotes adipocyte browning

Negative regulation of exocytosis from secretory cells throughout the body is accomplished through inhibitory signals from Gi/o G protein-coupled receptors by G{beta}{gamma} subunit inhibition of two common mechanisms: (i) decreased calcium entry and (ii) direct interaction of G{beta}{gamma} with the Soluble N-ethylmaleimide-sensitive factor Attachment Protein (SNAP) Receptor (SNARE) plasma membrane fusion machinery. We have previously shown that disabling the second mechanism with a truncation of SNAP25 (SNAP25{Delta}3/{Delta}3) decreases the affinity of G{beta}{gamma} for the SNARE complex, leaving exocytotic fusion as well as modulation of calcium entry intact but disabling GPCR inhibition of exocytosis. Here we report significant beneficial metabolic remodeling in mice carrying this mutation. Chow-fed SNAP25{Delta}3/{Delta}3 mice exhibit enhanced insulin sensitivity and increased beiging of white fat. In response to a high fat diet, the metabolic protection was amplified in SNAP25{Delta}3/{Delta}3 mice. Glucose homeostasis, whole body insulin action, and insulin-mediated glucose uptake into white adipose tissue were improved along with resistance to diet-induced obesity. This metabolic protection in SNAP25{Delta}3/{Delta}3 mice occurred without compromising the physiological response to fasting or cold. All metabolic phenotypes were reversed at thermoneutrality, suggesting basal autonomic activity is required. Direct electrode stimulation of sympathetic neurons exocytosis from SNAP25{Delta}3/{Delta}3 inguinal adipose depot resulted in enhanced and prolonged norepinephrine release. Thus, the G{beta}{gamma}-SNARE interaction represents a cellular mechanism that deserves further exploration as a new avenue for combatting metabolic disease. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/069138v4_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@2c1fa0org.highwire.dtl.DTLVardef@d076ceorg.highwire.dtl.DTLVardef@27e351org.highwire.dtl.DTLVardef@bce219_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2020

Eating breakfast and avoiding the evening snack sustains lipid oxidation

Circadian (daily) regulation of metabolic pathways implies that food may be metabolized differentially over the daily cycle. To test that hypothesis, we monitored the metabolism of older subjects in a whole-room respiratory chamber over two separate 56-h sessions in a random crossover design. In one session, one of the three daily meals was presented as breakfast whereas in the other session, a nutritionally equivalent meal was presented as a late-evening snack. The duration of the overnight fast was the same for both sessions. Whereas the two sessions did not differ in overall energy expenditure, the respiratory exchange ratio (RER) was different during sleep between the two sessions. Unexpectedly, this difference in RER due to daily meal timing was not due to daily differences in physical activity, sleep disruption, or core body temperature. Rather, we found that the daily timing of nutrient availability coupled with daily/circadian control of metabolism drives a switch in substrate preference such that the late-evening snack session resulted in significantly lower lipid oxidation compared to the breakfast session. Therefore, the timing of meals during the day/night cycle affects how ingested food is oxidized or stored in humans with important implications for optimal eating habits.

animal behavior and cognition↗

bioRxiv2019

A big-data approach to understanding metabolic rate and response to obesity in laboratory mice

Maintaining a healthy body weight requires an exquisite balance between energy intake and energy expenditure. In humans and in laboratory mice these factors are experimentally measured by powerful and sensitive indirect calorimetry devices. To understand the genetic and environmental factors that contribute to the regulation of body weight, an important first step is to establish the normal range of metabolic values and primary sources contributing to variability in results. Here we examine indirect calorimetry results from two experimental mouse projects, the Mouse Metabolic Phenotyping Centers and International Mouse Phenotyping Consortium to develop insights into large-scale trends in mammalian metabolism. Analysis of nearly 10,000 wildtype mice revealed that the largest experimental variances are consequences of institutional site. This institutional effect on variation eclipsed those of housing temperature, body mass, locomotor activity, sex, or season. We do not find support for the claim that female mice have greater metabolic variation than male mice. An analysis of these factors shows a normal distribution for energy expenditure in the phenotypic analysis of 2,246 knockout strains and establishes a reference for the magnitude of metabolic changes. Using this framework, we examine knockout strains with known metabolic phenotypes. We compare these effects with common environmental challenges including age, and exercise. We further examine the distribution of metabolic phenotypes exhibited by knockout strains of genes corresponding to GWAS obesity susceptibility loci. Based on these findings, we provide suggestions for how best to design and conduct energy balance experiments in rodents, as well as how to analyze and report data from these studies. These recommendations will move us closer to the goal of a centralized physiological repository to foster transparency, rigor and reproducibility in metabolic physiology experimentation.

physiology↗