REPTOR and CREBRF encode key regulators of muscle energy metabolism

Hepatic gluconeogenesis and PDK3 upregulation drive cancer cachexia in flies and mice

Cachexia, a severe wasting syndrome characterized by tumour-induced metabolic dysregulation, is a leading cause of death in people with cancer, yet its underlying mechanisms remain poorly understood. Here we show that a longitudinal full-body single-nuclei-resolution transcriptome analysis in a Drosophila model of cancer cachexia captures interorgan dysregulations. Our study reveals that the tumour-secreted interleukin-like cytokine Upd3 induces fat-body expression of Pepck1 and Pdk, key regulators of gluconeogenesis, disrupting glucose metabolism and contributing to cachexia. Similarly, in mouse cancer cachexia models, we observe IL-6-JAK-STAT-signalling-mediated induction of Pck1 and Pdk3 expression in the liver. Increased expression of these genes in fly, mouse, and human correlates with poor prognosis, and hepatic expression of Pdk3 emerges as a previously unknown mechanism contributing to metabolic dysfunction in cancer cachexia. This study highlights the conserved nature of tumour-induced metabolic disruptions and identifies potential therapeutic targets to mitigate cachexia in people with cancer.

Dissection of type 2 diabetes: a genetic perspective

Diabetes is a leading cause of global mortality and disability, and its economic burden is substantial. This Review focuses on type 2 diabetes, which makes up 90-95% of all diabetes cases. Type 2 diabetes involves a progressive loss of insulin secretion often alongside insulin resistance and metabolic syndrome. Although obesity and a sedentary lifestyle are considerable contributors, research over the last 25 years has shown that type 2 diabetes develops on a predisposing genetic background, with family and twin studies indicating considerable heritability (ie, 31-72%). This Review explores type 2 diabetes from a genetic perspective, highlighting insights into its pathophysiology and the implications for precision medicine. More specifically, the traditional understanding of type 2 diabetes genetics has focused on a dichotomy between monogenic and polygenic forms. However, emerging evidence suggests a continuum that includes monogenic, oligogenic, and polygenic contributions, revealing their complementary roles in type 2 diabetes pathophysiology. Recent genetic studies provide deeper insights into disease mechanisms and pave the way for precision medicine approaches that could transform type 2 diabetes management. Additionally, the effect of environmental factors on type 2 diabetes, particularly from epigenetic modifications, adds another layer of complexity to understanding and addressing this multifaceted disease.

FlyRNAi.org 2025 update-expanded resources for new technologies and species

The design, analysis and mining of large-scale 'omics studies with the goal of advancing biological and biomedical understanding require use of a range of bioinformatics tools, including approaches tailored to needs specific to a given species and/or technology. The FlyRNAi database at the Drosophila RNAi Screening Center and Transgenic RNAi Project (DRSC/TRiP) Functional Genomics Resources (https://fgr.hms.harvard.edu/tools) supports an increasingly broad group of technologies and species. Recently, for example, we expanded the database to include additional new data-centric resources that facilitate mining and analysis of single-cell transcriptomics. In addition, we have applied our approaches to CRISPR reagent and gene-centric bioinformatics approaches in Drosophila to arthropod vectors of infectious diseases. Building on our previous comprehensive reports on the FlyRNAi database, here we focus on new and updated resources with a primary focus on data-centric tools. Altogether, our suite of online resources supports various stages of functional genomics studies for Drosophila and other arthropods, and facilitate a wide range of reagent design, analysis, data mining and analysis approaches by biologists and biomedical experts studying Drosophila, other common genetic model species, arthropod vectors and/or human biology.

Selpercatinib mitigates cancer cachexia independent of anti-tumor activity in the HT1080 tumor model

Anorexia is a major cause of cancer cachexia and is induced by growth differentiation factor-15 (GDF15), which activates the rearranged during transfection (RET) protein tyrosine kinase in the hindbrain through GDF family receptor α-like (GFRAL), raising the possibility of targeting RET for cancer cachexia treatment. RET-altered cancer patients treated with RET-selective kinase inhibitors gain weight, however, it is unclear whether this results from tumor regression that improves the overall health of patients. Thus, the potential of using a RET inhibitor to address cancer cachexia remains unknown. Using a RET-negative tumor model, we evaluated the activity of the RET-selective inhibitor selpercatinib (LOXO-292) against cancer cachexia. In tumor-bearing animals, selpercatinib significantly increased food consumption, skeletal muscle mass and strength, adipose tissues, and body temperature, as well as reducing body weight loss, without significantly affecting tumor growth. Transcriptomes of skeletal muscle from mock-treated tumor-bearing mice were enriched in starvation and muscle atrophy genes, whereas those from selpercatinib-treated mice were enriched in myoblast proliferation, gluconeogenesis, and insulin receptor signaling genes. In parallel, retrospective analysis of weight gain in selpercatinib-treated patients showed that weight gain was not correlated with tumor response to selpercatinib. Our data demonstrate that selpercatinib could alleviate anorexia and cancer cachexia in an animal model and that weight gain in selpercatinib-treated patients is not dependent on tumor regression. These results identify a RET inhibitor as the first protein tyrosine kinase inhibitor for mitigating cancer cachexia.

Fat body glycolysis defects inhibit mTOR and promote distant muscle disorganization through TNF-α/egr and ImpL2 signaling in Drosophila larvae

The fat body in Drosophila larvae functions as a reserve tissue and participates in the regulation of organismal growth and homeostasis through its endocrine activity. To better understand its role in growth coordination, we induced fat body atrophy by knocking down several key enzymes of the glycolytic pathway in adipose cells. Our results show that impairing the last steps of glycolysis leads to a drastic drop in adipose cell size and lipid droplet content, and downregulation of the mTOR pathway and REPTOR transcriptional activity. Strikingly, fat body atrophy results in the distant disorganization of body wall muscles and the release of muscle-specific proteins in the hemolymph. Furthermore, we showed that REPTOR activity is required for fat body atrophy downstream of glycolysis inhibition, and that the effect of fat body atrophy on muscles depends on the production of TNF-α/egr and of the insulin pathway inhibitor ImpL2.

High sugar diet promotes tumor progression paradoxically through aberrant upregulation of pepck1

High dietary sugar (HDS), a contemporary dietary concern due to excessive intake of added sugars and carbohydrates, escalates the risk of metabolic disorders and concomitant cancers. However, the molecular mechanisms underlying HDS-induced cancer progression are not completely understood. We found that phosphoenolpyruvate carboxykinase 1 (PEPCK1), a pivotal enzyme in gluconeogenesis, is paradoxically upregulated in tumors by HDS, but not by normal dietary sugar (NDS), during tumor progression. Targeted knockdown of pepck1, but not pepck2, specifically in tumor tissue in Drosophila in vivo, not only attenuates HDS-induced tumor growth but also significantly improves the survival of Ras/Src tumor-bearing animals fed HDS. Interestingly, HP1a-mediated heterochromatin interacts directly with the pepck1 gene and downregulates pepck1 gene expression in wild-type Drosophila. Mechanistically, we demonstrated that, under HDS conditions, pepck1 knockdown reduces both wingless and TOR signaling, decreases evasion of apoptosis, reduces genome instability, and suppresses glucose uptake and trehalose levels in tumor cells in vivo. Moreover, rational pharmacological inhibition of PEPCK1, using hydrazinium sulfate, greatly improves the survival of tumor-bearing animals with pepck1 knockdown under HDS. This study is the first to show that elevated levels of dietary sugar induce aberrant upregulation of PEPCK1, which promotes tumor progression through altered cell signaling, evasion of apoptosis, genome instability, and reprogramming of carbohydrate metabolism. These findings contribute to our understanding of the complex relationship between diet and cancer at the molecular, cellular, and organismal levels and reveal PEPCK1 as a potential target for the prevention and treatment of cancers associated with metabolic disorders.

Identification of high sugar diet-induced dysregulated metabolic pathways in muscle using tissue-specific metabolic models in Drosophila

Individual tissues perform highly specialized metabolic functions to maintain whole-body homeostasis. Although Drosophila serves as a powerful model for studying human metabolic diseases, a lack of tissue-specific metabolic models makes it challenging to quantitatively assess the metabolic processes of individual tissues and disease models in this organism. To address this issue, we reconstructed 32 tissue-specific genome-scale metabolic models (GEMs) using pseudo-bulk single cell transcriptomics data, revealing distinct metabolic network structures across tissues. Leveraging enzyme kinetics and flux analyses, we predicted tissue-dependent metabolic pathway activities, recapitulating known tissue functions and identifying tissue-specific metabolic signatures, as supported by metabolite profiling. Moreover, to demonstrate the utility of tissue-specific GEMs in a disease context, we examined the effect of a high sugar diet (HSD) on muscle metabolism. Together with 13C-glucose isotopic tracer studies, we identified glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as a rate-limiting enzyme in response to HSD. Mechanistically, the decreased GAPDH activity was linked to elevated NADH/NAD+ ratio, caused by disturbed NAD+ regeneration rates, and oxidation of GAPDH. Furthermore, we introduced a pathway flux index to predict and validate additionally perturbed pathways, including fructose and butanoate metabolism. Altogether, our results represent a significant advance in generating quantitative tissue-specific GEMs and flux analyses in Drosophila, highlighting their use for identifying dysregulated metabolic pathways and their regulation in a human disease model.

The impact of CREBRF rs373863828 Pacific-variant on infant body composition

In Māori and Pacific adults, the CREBRF rs373863828 minor (A) allele is associated with increased body mass index (BMI) but reduced incidence of type-2 and gestational diabetes mellitus. In this prospective cohort study of Māori and Pacific infants, nested within a nutritional intervention trial for pregnant women with obesity and without pregestational diabetes, we investigated whether the rs373863828 A allele is associated with differences in growth and body composition from birth to 12-18 months' corrected age. Infants with and without the variant allele were compared using generalised linear models adjusted for potential confounding by gestation length, sex, ethnicity and parity, and in a secondary analysis, additionally adjusted for gestational diabetes. Carriage of the rs373863828 A allele was not associated with altered growth and body composition from birth to 6 months. At 12-18 months, infants with the rs373863828 A allele had lower whole-body fat mass [FM 1.4 (0.7) vs. 1.7 (0.7) kg, aMD -0.4, 95% CI -0.7, 0.0, P = 0.05; FM index 2.2 (1.1) vs. 2.6 (1.0) kg/m2 aMD -0.6, 95% CI -1.2,0.0, P = 0.04]. However, this association was not significant after adjustment for gestational diabetes, suggesting that it may be mediated, at least in part, by the beneficial effect of CREBRF rs373863828 A allele on maternal glycemic status.