Biology subjects

Karsenty, G.

Publications and source records attributed to Karsenty, G..

6 recordsLinked to original sources

bioRxiv2026

Bone regulates locomotion by sustaining motoneuronal mitochondrial function

Body-brain communication is crucial for optimal neuronal performance across the lifespan, yet whether peripheral organs regulate spinal cord motoneuron (MN) function through circulating molecules remains unknown. The expression of hormone receptors by spinal MNs raises the possibility that circulating cues allow the spinal cord to sense the body's energetic state and sustain motor activity. Here, we show that the bone-derived hormones osteocalcin (OCN) signals on spinal MNs via its receptor GPR158. GPR158 is selectively enriched in spinal cholinergic MNs, and its loss, globally or specifically in spinal MNs, or the one of OCN, impairs locomotor function and reduces choline acetyltransferase (ChAT) levels. Mechanistically, OCN signaling through GPR158 fine-tunes autophagy, mitophagy and mitochondrial activity in spinal MNs. Restoring any of these processes, by pharmacologically inducing mitophagy or chemogenetically activating mitochondria, is sufficient to rescue the locomotor deficits of Gpr158-deficient mice. Finally, OCN restoration in aged mice reverses age-related locomotor decline through a mechanism that requires MN autophagy and mitophagy. This study reveals that through OCN, the skeleton influences motor functions by fine-tuning motoneuronal mitochondria, and suggests that age-related motor decline is, at least in part, reversible.

neuroscience↗

bioRxiv2025

A skeletal muscle-sympathetic nerve-intestine network underlies muscle inflammation and atrophy induced by immobilization

Immobility is a common cause of muscle atrophy, but the underlying mechanisms have remained unclear. Here we show that limb immobilization in mice elicits inflammation and atrophy of skeletal muscle that are preventable by neutralizing antibodies to the chemokine CXCL10. Limb immobilization also induced changes to the gut microbiota and intestinal inflammation, and either sterilization of the intestine with antibiotics or administration of 10-hydroxy-cis-12-octadecenoic acid--a linoleic acid-derived gut microbial metabolite--prevented intestinal and muscle inflammation as well as muscle atrophy induced by immobilization, implicating intestinal inflammation in muscle inflammation and atrophy. Limb immobilization activated sympathetic nerves and increased {beta}2-adrenergic receptor gene (Adrb2) expression in the intestine. Single-cell RNA-sequencing analysis revealed that, among cells expressing Adrb2 in the intestine, immobilization increased only the population of macrophages. Pharmacological inhibition or macrophage-specific ablation of Adrb2 prevented immobilization-induced intestinal and muscle inflammation. Our results thus implicate a previously unrecognized muscle-nerve-intestine network in immobilization-induced muscle atrophy.

molecular biology↗

bioRxiv2023

Osteocalcin of maternal and embryonic origins synergize to establish homeostasis in offspring

Many physiological functions regulated by osteocalcin are affected in adult offspring of mothers experiencing an unhealthy pregnancy. Furthermore, osteocalcin signaling during gestation influences cognition and adrenal steroidogenesis in adult mice. Together these observations suggest that osteocalcin functions during pregnancy may be a broader determinant of organismal homeostasis in adult mammals than previously thought. To test this hypothesis, we analyzed in unchallenged wildtype and Osteocalcin-deficient, newborn, and adult mice of various genotypes and origin, and that were maintained on different genetic backgrounds, the functions of osteocalcin in the pancreas, liver and testes and their molecular underpinnings. This analysis revealed that providing mothers are themselves Osteocalcin-deficient, Osteocalcin haploinsufficiency in embryos hampers insulin secretion, liver gluconeogenesis, glucose homeostasis, testes steroidogenesis in adult offspring; inhibits cell proliferation in developing pancreatic islets and testes; and disrupts distinct programs of gene expression in these organs and in the brain. This study indicates that through their synergistic regulation of multiple physiological functions, osteocalcin ofmaternal and embryonic origins contributes to the establishment and maintenance of organismal homeostasis in newborn and adult offspring.

physiology↗

bioRxiv2022

GLUT1 ablation in astrocytes paradoxically improves central and peripheral glucose metabolism via enhanced insulin-stimulated ATP release

Astrocytes are considered an essential source of blood-borne glucose or its metabolites to neurons. Nonetheless, the necessity of the main astrocyte glucose transporter, i.e. GLUT1, for brain glucose metabolism has not been defined. Unexpectedly, we found that brain glucose metabolism was paradoxically augmented in mice with astrocytic GLUT1 ablation (GLUT11'GFAP mice). These mice also exhibited improved peripheral glucose metabolism especially in obesity, rendering them metabolically healthier. Importantly, GLUT11'GFAP mice did not present cognitive alterations. Mechanistically, we observed that GLUT1-ablated astrocytes exhibited increased insulin receptor-dependent ATP release, and both astrocyte insulin signalling and brain purinergic signalling are essential for improved brain function and systemic glucose metabolism. Collectively, we demonstrate that astrocytic GLUT1 is central to the regulation of brain energetics, yet its ablation triggers a reprogramming of brain metabolism sufficient to sustain energy requirements, peripheral glucose homeostasis and cognitive function.

neuroscience↗

bioRxiv2020

PHOSPHO1, a novel skeletal regulator of insulin resistance and obesity

The skeleton is recognised as a key endocrine regulator of metabolism. Here we show that mice lacking the bone mineralization enzyme PHOSPHO1 (Phospho1-/-) exhibited improved basal glucose homeostasis and resisted high-fat-diet induced weight gain and diabetes. The metabolic protection in Phospho1-/- mice was manifested in the absence of altered levels of osteocalcin. Osteoblasts isolated from Phospho1-/- mice were enriched for genes associated with energy metabolism and diabetes; Phospho1 both directly and indirectly interacted with genes associated with glucose transport and insulin receptor signalling. Canonical thermogenesis via brown adipose tissue did not underlie the metabolic protection observed in adult Phospho1-/- mice. However, the decreased serum choline levels in Phospho1-/- mice were normalized by feeding a 2% choline rich diet resulting in a normalization in insulin sensitivity and fat mass. This study identifies PHOSPHO1 as a potential therapeutic target for the treatment of obesity and diabetes.

physiology↗

bioRxiv2019

Protein Tyrosine Phosphatase 1B Regulates MicroRNA-208b-Argonaute 2 Association and Thyroid Hormone Responsiveness in Cardiac Hypertrophy

Elevated reactive oxygen species (ROS) production plays an important role in the pathogenesis of several diseases, including cardiac hypertrophy. While the regulation of diverse sources of ROS is well characterized in the heart, the redox-sensitive targets that contribute to redox signaling remain largely undefined. We now report that protein tyrosine phosphatase 1B (PTP1B) is reversibly oxidized and inactivated in hearts undergoing hypertrophy and that gene deletion of PTP1B in mouse hearts cause an hypertrophic phenotype that is critically exacerbated in mice subjected to pressure overload. Furthermore, we show that PTP1B dephosphorylates Tyr393 on argonaute 2, a key component of the RNA-induced silencing complex, and sustains gene silencing in the heart. Our results indicate that PTP1B inactivation and argonaute 2 Tyr393 phosphorylation specifically prevents argonaute 2 from interacting with miR-208b. Phosphorylation and inactivation of argonaute 2 in PTP1B cKO mice revealed a mechanism by which defective miR-208b-mediated repression of thyroid hormone receptor-associated protein 1 (THRAP1/MED13) contributes to thyroid hormone-mediated cardiac hypertrophy. In support of this conclusion, inhibiting the synthesis of triiodothyronine (T3), using propylthiouracil, rescued TAC-induced hypertrophy and improved myocardial contractility and systolic function in PTP1B cKO mice. Together, our data illustrate that PTP1B activity exerts a cardioprotective effect in the heart and that redox signaling is tightly linked to thyroid hormone responsiveness and to microRNA-mediated gene silencing in pathological hypertrophy.

cell biology↗