Biology subjects

Drummond, M. J.

Publications and source records attributed to Drummond, M. J..

8 recordsLinked to original sources

bioRxiv2026

Females are protected from semaglutide-induced muscle loss in ob/ob mice

Obesity is a major contributor to cardiometabolic disease, and pharmacological therapies such as semaglutide are increasingly used to induce weight loss. However, the commonly used diet-induced obesity model in C57BL/6J mice is limited by relative resistance to weight gain in females, complicating the study of sex-specific effects. Here, we used leptin-deficient ob/ob mice, which develop severe early-onset obesity in both sexes, to investigate sex-specific responses to semaglutide on skeletal muscle mass, function, and mitochondrial metabolism. The ob/ob mice were treated daily with semaglutide or vehicle for three weeks, followed by assessments of body composition, muscle and organ mass, muscle contractile function, and mitochondrial efficiency. Semaglutide induced comparable reductions in body weight and food intake in both sexes but elicited distinct sex-specific changes in body composition. Male mice exhibited losses in both skeletal muscle and organ mass, whereas female mice preferentially lost fat and organ mass while preserving skeletal muscle. Despite these divergent structural adaptations, muscle force generation remained intact in both sexes. Collectively, these findings reveal pronounced sexual dimorphism in skeletal muscle and metabolic remodeling during pharmacologically induced weight loss, highlighting the importance of considering biological sex when evaluating the metabolic and therapeutic effects of anti-obesity interventions. Article HighlightO_LIC57BL/6J mice are limited by relative resistance to weight gain in females, complicating the study of sex-specific effects. So, we wanted to determine the sex-specific effect of semaglutide on skeletal muscle function, and mitochondrial metabolism in ob/ob mice. C_LIO_LIWe assessed body composition and ex-vivo muscle force following the treatment and found that the female ob/ob mice are protected from semaglutide-induced skeletal muscle mass loss. C_LIO_LIThese findings demonstrate sex-specific effects of semaglutide, highlighting the need to consider biological sex in GLP-1RA-based therapies. C_LI

physiology↗

bioRxiv2025

N-acetylcarnosine attenuates age-associated declines in multi-organ systems to improve survival

Histidine containing dipeptides (HCDs) such as N-acetylcarnosine are endogenous metabolites that are ergogenic and mitigate metabolic dysfunction. We previously demonstrated that short-term N-acetylcarnosine treatment is highly efficacious in protecting muscle atrophy induced by disuse. Here we demonstrate that a 6-months treatment of N-acetylcarnosine attenuates a broad spectrum of age-associated maladies and improved survival by [~]50% in female mice. A comprehensive survey of organ systems revealed that N-acetylcarnosine prevents decline in adiposity, diastolic function, vasodilation, muscle strength, and bone density. Together, N-acetylcarnosine substantially delays the onset of system-wide end-stage pathology to prolong lifespan. As an endogenously present metabolite, treatment with N-acetylcarnosine may be a safe and promising intervention to promote healthy aging in humans.

physiology↗

bioRxiv2024

Muscle-specific Keap1 deletion enhances force production but does not prevent inactivity-induced muscle atrophy in mice

Immobilization-associated muscle atrophy and weakness appear to be driven in part by oxidative stress. Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) is a critical redox rheostat that regulates oxidative stress responses, and its deletion is known to accelerate muscle atrophy and weakness during aging (sarcopenia) or denervation. Conversely, pharmacologic activation of NRF2 extends mouse lifespan and attenuates sarcopenia. Similarly, deletion of Kelch-like ECH-associated Protein 1 (Keap1), negative regulator of NRF2, enhances exercise capacity. The purpose of this study was to determine whether muscle-specific Keap1 deletion is sufficient to prevent muscle atrophy and weakness in mice following 7-days of hindlimb unloading (HU). To test this hypothesis, control (Ctrl) and tamoxifen inducible, muscle-specific Keap1 knockout (mKO) mice were subjected to either normal housing (Sham) or HU for 7 days. Activation of NRF2 in muscle was confirmed by increased mRNA of NRF2 targets thioredoxin 1 (Txn1) and NAD(P)H quinone dehydrogenase 1 (NQO1) in mKO mice. Keap1 deletion had an effect to increase force-generating capacity at baseline. However, muscle masses, cross sectional area, and ex vivo force were not different between mKO and Ctrl HU mice. In addition, muscle 4-hydroxynonenal-modified proteins and protein carbonyls were unaffected by Keap1 deletion. These data suggest NRF2 activation improves muscle force production during ambulatory conditions but is not sufficient prevent muscle atrophy or weakness following 7-days of HU. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/616570v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@433d1eorg.highwire.dtl.DTLVardef@61996dorg.highwire.dtl.DTLVardef@19fe734org.highwire.dtl.DTLVardef@104205f_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

Six months of physical inactivity is insufficient to cause chronic kidney disease in C57BL/6J mice

Chronic kidney disease (CKD) is a progressive disorder marked by a decline in kidney function. Obesity and sedentary behavior contribute to the development of CKD, though mechanisms by which this occurs are poorly understood. This knowledge gap is worsened by the lack of a reliable murine CKD model that does not rely on injury, toxin, or gene deletion to induce a reduction in kidney function. High-fat diet (HFD) feeding alone is insufficient to cause reduced kidney function until later in life. Here, we employed a small mouse cage (SMC), a recently developed mouse model of sedentariness, to study its effect on kidney function. Wildtype C57BL/6J male mice were housed in sham or SMC housing for six months with HFD in room (22{degrees}C) or thermoneutral (30{degrees}C) conditions. Despite hyperinsulinemia induced by the SMC+HFD intervention, kidneys from these mice displayed normal glomerular filtration rate (GFR). However, the kidneys showed early signs of kidney injury, including increases in Col1a1 and NGAL transcripts, as well as fibrosis by histology, primarily in the inner medullary/papilla region. High-resolution respirometry and fluorometry experiments showed no statistically significant changes in the capacities for respiration, ATP synthesis, or electron leak. These data confirm the technical challenge in modeling human CKD. They further support the notion that obesity and a sedentary lifestyle make the kidneys more vulnerable, but additional insults are likely required for the pathogenesis of CKD.

physiology↗

bioRxiv2023

Inhibition of skeletal muscle Lands cycle ameliorates weakness induced by physical inactivity

BackgroundLipid hydroperoxides (LOOH) have been implicated in skeletal muscle atrophy with age and disuse. Lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme of Lands cycle, conjugates a polyunsaturated fatty acyl chain to a lysophospholipid (PUFA-PL) molecule, providing substrates for LOOH propagation. Previous studies suggest that inhibition of Lands cycle is an effective strategy to suppress LOOH. Mice with skeletal muscle-specific tamoxifen-inducible knockout of LPCAT3 (LPCAT3-MKO) were utilized to determine if muscle-specific attenuation of LOOH may alleviate muscle atrophy and weakness with disuse. MethodsLPCAT3-MKO and control mice underwent 7 days of sham or hindlimb unloading (HU model) to study muscle mass and force-generating capacity. LOOH was assessed by quantifying 4-hydroxynonenal (4-HNE)-conjugated peptides. Quantitative PCR and lipid mass spectrometry were used to validate LPCAT3 deletion. Results7 days of HU was sufficient to induce muscle atrophy and weakness concomitant to an increase in 4-HNE. Deletion of LPCAT3 reversed HU-induced increase in muscle 4HNE. No difference was found in body mass, body composition, or caloric intake between genotypes. The soleus (SOL) and plantaris (PLANT) muscles of the LPCAT3-MKO mice were partially protected from atrophy compared to controls, concomitant to attenuated decrease in cross-sectional areas in type I and IIa fibers. Strikingly, SOL and extensor digitorum longus (EDL) were robustly protected from HU-induced reduction in force-generating capacity in the LPCAT3-MKO mice compared to controls. ConclusionOur findings demonstrate that attenuation of muscle LOOH is sufficient to restore skeletal muscle function, in particular a protection from reduction in muscle specific force. Thus, muscle LOOH contributes to atrophy and weakness induced by HU in mice.

physiology↗

bioRxiv2022

Phosphatidylethanolamine facilitates mitochondrial pyruvate entry to regulate metabolic flexibility

Carbohydrates and lipids provide the majority of substrates to fuel mitochondrial oxidative phosphorylation (OXPHOS). Metabolic inflexibility, defined as an impaired ability to switch between these fuels, is implicated in a number of metabolic diseases. Here we explore the mechanism by which physical inactivity promotes metabolic inflexibility in skeletal muscle. We developed a mouse model of sedentariness by small mouse cage (SMC) that, unlike other classic models of disuse in mice, faithfully recapitulates metabolic responses that occur in humans. Bioenergetic phenotyping of mitochondria displayed metabolic inflexibility induced by physical inactivity, demonstrated by a reduction in pyruvate-stimulated respiration (JO2) in absence of a change in palmitate-stimulated JO2. Pyruvate resistance in these mitochondria was likely driven by a decrease in phosphatidylethanolamine (PE) abundance in the mitochondrial membrane. Reduction in mitochondrial PE by deletion of phosphatidylserine decarboxylase (PSD) was sufficient to induce metabolic inflexibility measured at the whole-body level, as well as at the level of skeletal muscle mitochondria. Low mitochondrial PE was sufficient to increase glucose flux towards lactate. We further implicate that resistance to pyruvate metabolism is due to attenuated mitochondrial entry via mitochondrial pyruvate carrier (MPC). These findings suggest a novel mechanism by which mitochondrial PE directly regulates MPC activity to modulate metabolic flexibility.

physiology↗

bioRxiv2021

Lipid hydroperoxides promote muscle atrophy through lysosomal amplification

Reactive oxygen species (ROS) accumulation is a cardinal feature of skeletal muscle atrophy. ROS refers to a collection of radical molecules whose cellular signals are vast, and it is unclear which downstream consequences of ROS are responsible for the loss of muscle mass and strength. Here we show that lipid hydroperoxides (LOOH) are increased with age and disuse, and the accumulation of LOOH by deletion of glutathione peroxidase 4 (GPx4) is sufficient to augment muscle atrophy. LOOH promoted atrophy in a lysosomal-dependent, proteasomal-independent manner. In young and old mice, genetic and pharmacologic neutralization of LOOH or their secondary reactive lipid aldehydes robustly prevented muscle atrophy and weakness, indicating that LOOH-derived carbonyl stress mediate age- and disuse-induced muscle dysfunction. Our findings provide novel insights for the role of LOOH in sarcopenia including a therapeutic implication by pharmacologic suppression.

physiology↗

bioRxiv2019

Mitochondrial PE potentiates respiratory enzymes to amplify skeletal muscle aerobic capacity

Exercise capacity is a strong predictor of all-cause mortality. Skeletal muscle mitochondrial respiratory capacity, its biggest contributor, adapts robustly to changes in energy demands induced by contractile activity. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are regulated. Herein, we show that exercise training or muscle disuse alters mitochondrial membrane phospholipids including phosphatidylethanolamine (PE). Addition of PE promoted, whereas removal of PE diminished, mitochondrial respiratory capacity. Surprisingly, skeletal muscle-specific inhibition of mitochondrial-autonomous synthesis of PE caused a respiratory failure due to metabolic insults in the diaphragm muscle. While mitochondrial PE deficiency coincided with increased oxidative stress, neutralization of the latter did not rescue lethality. These findings highlight the previously underappreciated role of mitochondrial membrane phospholipids in dynamically controlling skeletal muscle energetics and function.

physiology↗