Project description:Reactive oxygen species have been established to play a critical role in pancreatic carcinogenesis. One of the main antioxidant enzymes is mitochondrial superoxide dismutase (Sod2). Sod2 has been shown to affect tumor initiation and metastatic progression in various cancer types. The impact of Sod2 deletion on pancreatic cancer biology and metabolism has so far not been investigated. We therefore generated three individual Sod2 deficient cell lines from murine pancreatic cancer cell lines isolated from KrasG12D mutant mice and analyzed control and knockout lines with RNA-seq.
Project description:Transfer RNA (tRNA) modifications play a critical role in regulating codon-specific mRNA translation and enabling tumor cell adaptation. The RNA methyltransferase METTL1 installs N7-methylguanosine (m⁷G) modifications on tRNAs, thereby shaping codon usage and translational output. However, the function and mechanistic contribution of the METTL1–tRNA axis in pancreatic ductal adenocarcinoma (PDAC) remain poorly defined. Here, we show that METTL1 is overexpressed in PDAC tissues and that elevated METTL1 expression is associated with poor patient survival. Genetic ablation of METTL1 markedly suppresses PDAC cell proliferation, migration, and tumor growth in vitro and in vivo. Mechanistically, METTL1 loss selectively reduces m⁷G-modified valine tRNAs – particularly, Val-AAC, Val-CAC, and Val-TAC – leading to impaired translation of valine-enriched oxidative phosphorylation transcripts. As a consequence, METTL1 deficiency disrupts mitochondrial respiration and energy production in PDAC cells. Consistent with this model, valine tRNA levels are elevated in PDAC tissues, and their selective depletion phenocopies METTL1 loss by impairing mitochondrial bioenergetics and tumor cell fitness. Thus, the METTL1–valine tRNA axis promotes PDAC progression through codon-dependent translational control of mitochondrial complex I and oxidative metabolism. Together, our findings identify a METTL1–tRNA–mitochondrial signaling axis as a previously unrecognized metabolic vulnerability and a promising therapeutic target in pancreatic cancer.
Project description:It remains unknown whether ER stress response signaling has a metabolic regulatory role in ECs. Here, in mice with high-fat diet-induced obesity, we found that EC-specific ablation of IRE1α selectively impaired the compensatory adaptation of pancreatic islet function in response to metabolic stress. Loss of IRE1α in ECs resulted in significantly lower intra-islet angiogenesis, accompanied by defects in the compensatory growth of pancreatic islets and their capacity of glucose-stimulated insulin secretion, consequently leading to hyperglycemia. Mechanistically, IRE1α could downregulate the intra-islet EC expression of the mRNA encoding thrombospondin-1 (THBS1/TSP1), an endogenous anti-angiogenic factor implicated in islet function regulation and prediabetes, through its RIDD activity. Importantly, EC-specific depletion of THBS1 completely corrected these islet dysfunctions arising from IRE1α deficiency in ECs. Together, our findings demonstrate a critical role of the endothelial IRE1α suppression of THBS1 in governing the vascular support that enables the homeostatic adaptation of pancreatic islets to cope with overnutrition-associated metabolic stress.
Project description:Reduced estrogen action is associated with obesity and insulin resistance. However, the cell and tissue-specific actions of estradiol in maintaining metabolic health remain inadequately understood especially in men. We observed that skeletal muscle ESR1/Esr1 (encodes estrogen receptor a), including expression of specific ESR1 variants is positively correlated with insulin sensitivity and metabolic health in humans and mice. Because skeletal muscle is a primary tissue involved in oxidative metabolism and insulin sensitivity, we generated muscle-selective Esr1 loss- and gain of-expression mouse models. We determined that Esr1 links mitochondrial DNA replication and cristae-nucleoid architecture with metabolic function and insulin action in skeletal muscle of male mice. Overexpression of human ERα in muscle protected male mice from diet-induced disruption of metabolic health and enhanced mitochondrial adaptation to exercise training intervention. Our findings indicate that muscle expression of Esr1 is critical for the maintenance of mitochondrial function and metabolic health in males, and that tissue-selective activation of ERα can be leveraged to combat metabolic-related diseases in both sexes.
Project description:Fibroblast growth factor 21 (FGF21) is a key metabolic regulator which was recently discovered as stress-induced myokine and common denominator of muscle mitochondrial disease. However, its precise function and pathophysiological relevance remains unknown. Here we demonstrate that white adipose tissue (WAT) is the major target of muscle mitochondrial stress-induced FGF21. Strikingly, substantial browning and metabolic remodeling of subcutaneous WAT, together with the reduction of circulating triglycerides and cholesterol are fully FGF21 dependent. Unexpectedly and in contrast to prior expectations, we found a negligible role of FGF21 in muscle stress-related improved glycemic control, obesity resistance and hepatic lipid homeostasis. Furthermore, we show that the protective muscle mitohormesis and metabolic stress adaptation does not require FGF21 action. Taken together, our data imply that although FGF21 drives WAT remodeling, this effect and FGF21 as stress hormone per se may not be essential for the adaptive response under muscle mitochondrial stress conditions. Wildtype male mice and FGF21-knockout male mice, together with muscle specific UCP1-transgenic male animals, and double cross of FGF21-KO with UCP1-Tg male mice, were kept on a standardized low fat diet for 40 weeks. After sacrifice, subcutaneous white adipose tisseu (scWAT) was rapidly removed, weighed, and snap frozen in liquid nitrogen and used for RNA isolation and whole genome gene expression microarray hybridisation using Agilent arrays.