Retrograde mitochondrial signaling governs the identity and maturity of metabolic tissues
Ontology highlight
ABSTRACT: Mitochondrial damage is a hallmark of metabolic diseases, including diabetes and metabolic dysfunction-associated steatotic liver disease, yet the consequences of impaired mitochondria in metabolic tissues are often unclear. Here, we report that dysfunctional mitochondrial quality control engages a retrograde (mitonuclear) signaling program that impairs cellular identity and maturity across multiple metabolic tissues. Surprisingly, we demonstrate that defects in the mitochondrial quality control machinery, which we observe in pancreatic β cells of humans with diabetes, cause reductions of β cell mass due to dedifferentiation, rather than apoptosis. Utilizing transcriptomic profiling, lineage tracing, and assessments of chromatin accessibility, we find that targeted deficiency anywhere in the mitochondrial quality control pathway (e.g., genome integrity, dynamics, or turnover) activate the mitochondrial integrated stress response and promote cellular immaturity in β cells, hepatocytes, and brown adipocytes. Intriguingly, pharmacologic blockade of mitochondrial retrograde signaling in vivo restores β cell mass and identity to ameliorate hyperglycemia following mitochondrial damage. Thus, we observe that a shared mitochondrial retrograde response controls cellular identity across metabolic tissues and may be a promising target to treat or prevent metabolic disorders.
Project description:Pluripotent stem cell-derived (SC) islets offer a renewable source for β cell replacement for type 1 diabetes, yet functional and metabolic immaturity may limit their long-term therapeutic efficacy. Here, we describe that limitations in mitochondrial transcriptional programming prevent the maturation of SC-β cells. We observe several alterations in SC-islet mitochondria compared to human islets, including reductions in mitochondrial respiration, expression of OXPHOS machinery, and mitochondrial lipid metabolism. Surprisingly, these effects were not related to reductions in mitochondrial mass, genome integrity, or structure. Transcriptomic profiling throughout differentiation to SC-islets revealed several unstudied candidates in β cell maturation that regulate programming of mitochondrial oxidative and fatty acid metabolism, including the nuclear receptors PPAR⍺ and PPARγ. Indeed, treatment of SC-islets with WY14643, a potent PPAR⍺ agonist with PPARγ activity, promoted expression of mitochondrial targets, improved insulin secretion, and increased the presence of β cells both in vitro and upon transplantation into immunodeficient mice. Mitochondria are vital to fuel β cell insulin release; however, our studies here revealed the potential for targeting mitochondrial programming to enhance the differentiation and metabolic maturation of SC-β cells.
2025-01-15 | GSE270220 | GEO
Project description:Single cell RNAseq for Retrograde mitochondrial signaling governs the identity and maturity of metabolic tissues
Project description:Mitochondrial fusion and fission proteins regulate mitochondrial quality control and mitochondrial metabolism. In turn, mitochondrial dysfunction is associated with aging, although its causes are still under debate. Here, we show that aging is characterized by a progressive reduction of Mitofusin 2 (Mfn2) in mouse skeletal muscle and that skeletal muscle Mfn2 ablation in mice generates a gene signature linked to aging. Furthermore, muscle Mfn2-deficient mice show unhealthy aging characterized by altered metabolic homeostasis and sarcopenia. Mfn2 deficiency impairs mitochondrial quality control, which contributes to an exacerbated age-related mitochondrial dysfunction. Surprisingly, aging-induced Mfn2 deficiency triggers a ROS-dependent retrograde signaling pathway through induction of HIF1 transcription factor and BNIP3. This pathway ameliorates mitochondrial autophagy and minimizes mitochondrial damage. Our findings reveal that repression of Mfn2 in skeletal muscle during aging is determinant for the loss of mitochondrial quality, contributing to age-associated metabolic alterations and loss of muscle fitness. Quadriceps muscle from four mice per genotype were used (Control young (6 month-old), Mfn2KO young (6-month-old), control old (22-month-old) and Mfn2KO old (22-month-old)
Project description:Progressive reductions in β-cell mass and function comprise the core of the pathogenesis mechanism leading to type 2 diabetes (T2D). To understand the molecular events in this process, we quantified the temporal transcriptome and proteome of pancreatic islets from Goto-Kakizaki (GK) rats at different stages of diabetes. Integrated omics analysis allowed us to unravel the chronological order of T2D-related molecular events during GK islet deterioration. Two major events occur early in the disease, specifically, a reduction in β-cell mass caused by defective neogenesis and senescence-related low proliferation, and metabolic shift caused by mitochondrial dysfunction. Furthermore, our data revealed the evolution of compensation failure in GK islets and two distinct stages of islet inflammation: priming and amplification. Our study offers a valuable resource for the diabetes research community and will facilitate further studies aimed at protecting β-cell mass and function.
Project description:Imbalances in glucose and energy homeostasis are at the core of the worldwide epidemic of obesity and diabetes. Here, we illustrate an important role of the TGF-beta/Smad3 signaling pathway in regulating glucose and energy homeostasis. Smad3 deficient mice are protected from diet-induced obesity and diabetes. Interestingly, the metabolic protection is accompanied by Smad3-/- white adipose tissue acquiring the bioenergetic and gene expression profile of brown fat/skeletal muscle. Smad3-/- adipocytes demonstrate a marked increase in mitochondrial biogenesis, with a corresponding increase in basal respiration, and Smad3 acts as a repressor of PGC-alpha1 expression. We observe significant correlation between TGF-beta1 levels and adiposity in rodents and humans. Further, systemic blockade of TGF-beta1 signaling protects mice from obesity, diabetes and hepatic steatosis. Together, these results demonstrate that TGF-beta signaling regulates glucose tolerance and energy homeostasis and suggest that modulation of TGF-beta1 activity might be an effective treatment strategy for obesity and diabetes. Smad3-/- and WT mice were fed with regular diet (RD) and high fat diet (HFD), and diet induced obese (DIO) mice were treated with IgG and anti-TGF-b1 antibody
Project description:Diabetes mellitus results from an inadequately functioning beta-cell mass. In the adult pancreas, beta-cell mass is dynamic, increasing to meet metabolic demands and decreasing with metabolic or injury insults. Exendin-4 (Ex-4) is a glucagon-like peptide-1 receptor agonist that augments beta-cell mass by increasing beta-cell neogenesis and proliferation and by reducing apoptosis. We utilized a cDNA microarray approach to identify genes that are differentially regulated during islet growth after Ex-4 treatment or a partial pancreatectomy (Ppx). Mice underwent 50% Ppx or sham operation and received Ex-4 or vehicle every 24 hours. cDNA prepared from total pancreatic RNA isolated at 12, 24 and 48 hrs after surgery was hybridized to the PancChip 4.0 microarray.
Project description:The inability of the beta-cell to meet the demand for insulin brought about by insulin resistance leads to type 2 diabetes. In adults, beta-cell replication is one of the mechanisms thought to cause the expansion of beta-cell mass. Efforts to treat diabetes require knowledge of the pathways that drive facultative beta-cell proliferation in vivo. A robust physiological stimulus of beta-cell expansion is pregnancy, and identifying the mechanisms underlying this stimulus may provide therapeutic leads for the treatment of type 2 diabetes. The peak in beta-cell proliferation during pregnancy occurs on day 14.5 of gestation in mice. Using advanced genomic approaches, we globally characterize the gene expression signature of pancreatic islets on day 14.5 of gestation during pregnancy. We identify a total of 1,907 genes as differentially expressed in the islet during pregnancy. We demonstrate that the islet's ability to compensate for relative insulin deficiency during metabolic stress is associated with the induction of both proliferative and survival pathways. A comparison of the genes induced in three different models of islet expansion suggests that diverse mechanisms can be recruited to expand islet mass. The identification of many novel genes involved in islet expansion during pregnancy provides an important resource for diabetes researchers to further investigate how these factors contribute to the maintenance of not only islet mass, but ultimately beta-cell mass.
Project description:Mitochondrial fusion and fission proteins regulate mitochondrial quality control and mitochondrial metabolism. In turn, mitochondrial dysfunction is associated with aging, although its causes are still under debate. Here, we show that aging is characterized by a progressive reduction of Mitofusin 2 (Mfn2) in mouse skeletal muscle and that skeletal muscle Mfn2 ablation in mice generates a gene signature linked to aging. Furthermore, muscle Mfn2-deficient mice show unhealthy aging characterized by altered metabolic homeostasis and sarcopenia. Mfn2 deficiency impairs mitochondrial quality control, which contributes to an exacerbated age-related mitochondrial dysfunction. Surprisingly, aging-induced Mfn2 deficiency triggers a ROS-dependent retrograde signaling pathway through induction of HIF1 transcription factor and BNIP3. This pathway ameliorates mitochondrial autophagy and minimizes mitochondrial damage. Our findings reveal that repression of Mfn2 in skeletal muscle during aging is determinant for the loss of mitochondrial quality, contributing to age-associated metabolic alterations and loss of muscle fitness.