Combined genetic deletion of GDF15 and FGF21 has modest effects on body weight, hepatic steatosis and insulin resistance in high fat fed mice

Molecular metabolism

2022 Sep 02

Patel, S;Haider, A;Alvarez-Guaita, A;Bidault, G;El-Sayed Moustafa, JS;Guiu-Jurado, E;Tadross, JA;Warner, J;Harrison, J;Virtue, S;Scurria, F;Zvetkova, I;Blüher, M;Small, KS;O'Rahilly, S;Savage, DB;
PMID: 36064109 | DOI: 10.1016/j.molmet.2022.101589

Obesity in humans and mice is associated with elevated levels of two hormones responsive to cellular stress, namely GDF15 and FGF21. Over-expression of each of these is associated with weight loss and beneficial metabolic changes but where they are secreted from and what they are required for physiologically in the context of overfeeding remains unclear.Here we used tissue selective knockout mouse models and human transcriptomics to determine the source of circulating GDF15 in obesity. We then generated and characterized the metabolic phenotypes of GDF15/FGF21 double knockout mice.Circulating GDF15 and FGF21 are both largely derived from the liver, rather than adipose tissue or skeletal muscle, in obese states. Combined whole body deletion of FGF21 and GDF15 does not result in any additional weight gain in response to high fat feeding but it does result in significantly greater hepatic steatosis and insulin resistance than that seen in GDF15 single knockout mice.Collectively the data suggest that overfeeding activates a stress response in the liver which is the major source of systemic rises in GDF15 and FGF21. These hormones then activate pathways which reduce this metabolic stress.

Prolonged breastfeeding protects from obesity by hypothalamic action of hepatic FGF21

Nature metabolism

2022 Jul 01

Pena-Leon, V;Folgueira, C;Barja-Fernández, S;Pérez-Lois, R;Da Silva Lima, N;Martin, M;Heras, V;Martinez-Martinez, S;Valero, P;Iglesias, C;Duquenne, M;Al-Massadi, O;Beiroa, D;Souto, Y;Fidalgo, M;Sowmyalakshmi, R;Guallar, D;Cunarro, J;Castelao, C;Senra, A;González-Saenz, P;Vázquez-Cobela, R;Leis, R;Sabio, G;Mueller-Fielitz, H;Schwaninger, M;López, M;Tovar, S;Casanueva, FF;Valjent, E;Diéguez, C;Prevot, V;Nogueiras, R;Seoane, LM;
PMID: 35879461 | DOI: 10.1038/s42255-022-00602-z

Early-life determinants are thought to be a major factor in the rapid increase of obesity. However, while maternal nutrition has been extensively studied, the effects of breastfeeding by the infant on the reprogramming of energy balance in childhood and throughout adulthood remain largely unknown. Here we show that delayed weaning in rat pups protects them against diet-induced obesity in adulthood, through enhanced brown adipose tissue thermogenesis and energy expenditure. In-depth metabolic phenotyping in this rat model as well as in transgenic mice reveals that the effects of prolonged suckling are mediated by increased hepatic fibroblast growth factor 21 (FGF21) production and tanycyte-controlled access to the hypothalamus in adulthood. Specifically, FGF21 activates GABA-containing neurons expressing dopamine receptor 2 in the lateral hypothalamic area and zona incerta. Prolonged breastfeeding thus constitutes a protective mechanism against obesity by affecting long-lasting physiological changes in liver-to-hypothalamus communication and hypothalamic metabolic regulation.

Translatomic analysis of regenerating and degenerating spinal motor neurons in injury and ALS

iScience

2021 Jul 01

Shadrach, J;Stansberry, W;Milen, A;Ives, R;Fogarty, E;Antonellis, A;Pierchala, B;
| DOI: 10.1016/j.isci.2021.102700

The neuromuscular junction is a synapse critical for muscle strength and coordinated motor function. Unlike CNS injuries, motor neurons mount robust regenerative responses after peripheral nerve injuries. Conversely, motor neurons selectively degenerate in diseases such as amyotrophic lateral sclerosis (ALS). To assess how these insults affect motor neurons in vivo, we performed ribosomal profiling of mouse motor neurons. Motor neuron-specific transcripts were isolated from spinal cords following sciatic nerve crush, a model of acute injury and regeneration, and in the SOD1G93A ALS model. Of the 267 transcripts upregulated after nerve crush, 38% were also upregulated in SOD1G93A motor neurons. However, most upregulated genes in injured and ALS motor neurons were context specific. Some of the most significantly upregulated transcripts in both paradigms were chemokines such as Ccl2 and Ccl7, suggesting an important role for neuroimmune modulation. Collectively these data will aid in defining pro-regenerative and pro-degenerative mechanisms in motor neurons.

Neuronal Mitochondrial Dysfunction Activates the Integrated Stress Response to Induce Fibroblast Growth Factor 21

Cell Rep.

2018 Aug 07

Restelli LM, Oettinghaus B, Halliday M, Agca C, Licci M, Sironi L, Savoia C, Hench J, Tolnay M, Neutzner A, Schmidt A, Eckert A, Mallucci G, Scorrano L, Frank S.
PMID: 30089252 | DOI: 10.1016/j.celrep.2018.07.023

Stress adaptation is essential for neuronal health. While the fundamental role of mitochondria in neuronal development has been demonstrated, it is still not clear how adult neurons respond to alterations in mitochondrial function and how neurons sense, signal, and respond to dysfunction of mitochondria and their interacting organelles. Here, we show that neuron-specific, inducible in vivo ablation of the mitochondrial fission protein Drp1 causes ER stress, resulting in activation of the integrated stress response to culminate in neuronal expression of the cytokine Fgf21. Neuron-derived Fgf21 induction occurs also in murine models of tauopathy and prion disease, highlighting the potential of this cytokine as an early biomarker for latent neurodegenerative conditions.

Central FGF21 production regulates memory but not peripheral metabolism

Cell reports

2022 Aug 23

Zhou, B;Claflin, KE;Flippo, KH;Sullivan, AI;Asghari, A;Tadinada, SM;Jensen-Cody, SO;Abel, T;Potthoff, MJ;
PMID: 36001982 | DOI: 10.1016/j.celrep.2022.111239

Fibroblast growth factor 21 (FGF21) is a liver-derived endocrine hormone that functions to regulate energy homeostasis and macronutrient intake. Recently, FGF21 was reported to be produced and secreted from hypothalamic tanycytes, to regulate peripheral lipid metabolism; however, rigorous investigation of FGF21 expression in the brain has yet to be accomplished. Using a mouse model that drives CRE recombinase in FGF21-expressing cells, we demonstrate that FGF21 is not expressed in the hypothalamus, but instead is produced from the retrosplenial cortex (RSC), an essential brain region for spatial learning and memory. Furthermore, we find that central FGF21 produced in the RSC enhances spatial memory but does not regulate energy homeostasis or sugar intake. Finally, our data demonstrate that administration of FGF21 prolongs the duration of long-term potentiation in the hippocampus and enhances activation of hippocampal neurons. Thus, endogenous and pharmacological FGF21 appear to function in the hippocampus to enhance spatial memory.

Neuronal metabotropic glutamate receptor 8 protects against neurodegeneration in CNS inflammation

The Journal of experimental medicine

2021 May 03

Woo, MS;Ufer, F;Rothammer, N;Di Liberto, G;Binkle, L;Haferkamp, U;Sonner, JK;Engler, JB;Hornig, S;Bauer, S;Wagner, I;Egervari, K;Raber, J;Duvoisin, RM;Pless, O;Merkler, D;Friese, MA;
PMID: 33661276 | DOI: 10.1084/jem.20201290

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system with continuous neuronal loss. Treatment of clinical progression remains challenging due to lack of insights into inflammation-induced neurodegenerative pathways. Here, we show that an imbalance in the neuronal receptor interactome is driving glutamate excitotoxicity in neurons of MS patients and identify the MS risk-associated metabotropic glutamate receptor 8 (GRM8) as a decisive modulator. Mechanistically, GRM8 activation counteracted neuronal cAMP accumulation, thereby directly desensitizing the inositol 1,4,5-trisphosphate receptor (IP3R). This profoundly limited glutamate-induced calcium release from the endoplasmic reticulum and subsequent cell death. Notably, we found Grm8-deficient neurons to be more prone to glutamate excitotoxicity, whereas pharmacological activation of GRM8 augmented neuroprotection in mouse and human neurons as well as in a preclinical mouse model of MS. Thus, we demonstrate that GRM8 conveys neuronal resilience to CNS inflammation and is a promising neuroprotective target with broad therapeutic implications.

G9a dictates neuronal vulnerability to inflammatory stress via transcriptional control of ferroptosis

Science advances

2022 Aug 05

Rothammer, N;Woo, MS;Bauer, S;Binkle-Ladisch, L;Di Liberto, G;Egervari, K;Wagner, I;Haferkamp, U;Pless, O;Merkler, D;Engler, JB;Friese, MA;
PMID: 35930635 | DOI: 10.1126/sciadv.abm5500

Neuroinflammation leads to neuronal stress responses that contribute to neuronal dysfunction and loss. However, treatments that stabilize neurons and prevent their destruction are still lacking. Here, we identify the histone methyltransferase G9a as a druggable epigenetic regulator of neuronal vulnerability to inflammation. In murine experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS), we found that the G9a-catalyzed repressive epigenetic mark H3K9me2 was robustly induced by neuroinflammation. G9a activity repressed anti-ferroptotic genes, diminished intracellular glutathione levels, and triggered the iron-dependent programmed cell death pathway ferroptosis. Conversely, pharmacological treatment of EAE mice with a G9a inhibitor restored anti-ferroptotic gene expression, reduced inflammation-induced neuronal loss, and improved clinical outcome. Similarly, neuronal anti-ferroptotic gene expression was reduced in MS brain tissue and was boosted by G9a inhibition in human neuronal cultures. This study identifies G9a as a critical transcriptional enhancer of neuronal ferroptosis and potential therapeutic target to counteract inflammation-induced neurodegeneration.

Medial orbitofrontal neurotrophin systems integrate hippocampal input into outcome-specific value representations

Cell reports

2022 Sep 13

Woon, EP;Butkovich, LM;Peluso, AA;Elbasheir, A;Taylor, K;Gourley, SL;
PMID: 36103822 | DOI: 10.1016/j.celrep.2022.111334

In everyday life, we mentally represent possible consequences of our behaviors and integrate specific outcome values into existing knowledge to inform decisions. The medial orbitofrontal cortex (MO) is necessary to adapt behaviors when outcomes are not immediately available-when they and their values need to be envisioned. Nevertheless, neurobiological mechanisms remain unclear. We find that the neuroplasticity-associated neurotrophin receptor tropomyosin receptor kinase B (TrkB) is necessary for mice to integrate outcome-specific value information into choice behavior. This function appears attributable to memory updating (and not retrieval) and the stabilization of dendritic spines on excitatory MO neurons, which led us to investigate inputs to the MO. Ventral hippocampal (vHC)-to-MO projections appear conditionally necessary for value updating, involved in long-term aversion-based value memory updating. Furthermore, vHC-MO-mediated control of choice is TrkB dependent. Altogether, we reveal a vHC-MO connection by which specific value memories are updated, and we position TrkB within this functional circuit.

Tanycytes and hypothalamic FGF21: New players in the metabolic game

Cell reports

2023 Jan 11

Geller, S;Pellerin, L;
PMID: 36640320 | DOI: 10.1016/j.celrep.2022.111954

	Description
sense Example: Hs-LAG3-sense	Standard probes for RNA detection are in antisense. Sense probe is reverse complent to the corresponding antisense probe.
Intron# Example: Mm-Htt-intron2	Probe targets the indicated intron in the target gene, commonly used for pre-mRNA detection
Pool/Pan Example: Hs-CD3-pool (Hs-CD3D, Hs-CD3E, Hs-CD3G)	A mixture of multiple probe sets targeting multiple genes or transcripts
No-XSp Example: Hs-PDGFB-No-XMm	Does not cross detect with the species (Sp)
XSp Example: Rn-Pde9a-XMm	designed to cross detect with the species (Sp)
O# Example: Mm-Islr-O1	Alternative design targeting different regions of the same transcript or isoforms
CDS Example: Hs-SLC31A-CDS	Probe targets the protein-coding sequence only
EnEm	Probe targets exons n and m
En-Em	Probe targets region from exon n to exon m
Retired Nomenclature
tvn Example: Hs-LEPR-tv1	Designed to target transcript variant n
ORF Example: Hs-ACVRL1-ORF	Probe targets open reading frame
UTR Example: Hs-HTT-UTR-C3	Probe targets the untranslated region (non-protein-coding region) only
5UTR Example: Hs-GNRHR-5UTR	Probe targets the 5' untranslated region only
3UTR Example: Rn-Npy1r-3UTR	Probe targets the 3' untranslated region only
Pan Example: Pool	A mixture of multiple probe sets targeting multiple genes or transcripts

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