Hyperuricemia is implicated in numerous pathologies but the mechanisms underlying uric acid production are poorly understood. Using a combination of mouse studies, cultured cell studies, and human serum samples, we sought to determine the cellular source of uric acid. In mice, fasting and glucocorticoid treatment increased serum uric acid and uric acid release from ex vivo incubated skeletal muscle. In vitro, glucocorticoids and the transcription factor FoxO3 increased purine nucleotide degradation and purine release from differentiated muscle cells, which coincided with the transcriptional upregulation of AMP deaminase 3, a rate-limiting enzyme in adenine nucleotide degradation. Heavy isotope tracing during co-culture experiments revealed that oxidation of muscle purines to uric acid required their transfer from muscle cells to a cell type that expresses xanthine oxidoreductase, such as endothelial cells. Lastly, in healthy women, matched for age and body composition, serum uric acid was greater in individuals scoring below average on standard physical function assessments. Together, these studies reveal skeletal muscle purine degradation is an underlying driver of uric acid production, with the final step of uric acid production occurring primarily in a non-muscle cell type. This suggests that skeletal muscle fiber purine degradation may represent a therapeutic target to reduce serum uric acid and treat numerous pathologies.
Spencer G. Miller, Catalina Matias, Paul S. Hafen, Andrew S. Law, Carol A. Witczak, Jeffrey J. Brault
Interorgan crosstalk via secreted hormones and metabolites is a fundamental aspect of mammalian metabolic physiology. Beyond the highly specialized endocrine cells, peripheral tissues are emerging as an important source of metabolic hormones that influence energy and nutrient metabolism and contribute to disease pathogenesis. Neuregulin 4 (Nrg4) is a fat-derived hormone that protects mice from nonalcoholic steatohepatitis (NASH) and NASH-associated liver cancer by shaping hepatic lipid metabolism and the liver immune microenvironment. Despite its enriched expression in brown fat, whether NRG4 plays a role in thermogenic response and mediates the metabolic benefits of cold exposure remain unexplored. Here we show that Nrg4 expression in inguinal white adipose tissue (iWAT) is highly responsive to chronic cold exposure. Nrg4 deficiency impairs beige fat induction and renders mice more susceptible to diet-induced metabolic disorders under mild cold conditions. Using mice with adipocyte and hepatocyte-specific Nrg4 deletion, we reveal that adipose tissue-derived NRG4, but not hepatic NRG4, is essential for beige fat induction following cold acclimation. Furthermore, treatment with recombinant NRG4-Fc fusion protein promotes beige fat induction in iWAT and improves metabolic health in diet-induced obese mice. These findings highlight a critical role of NRG4 in mediating beige fat induction and preserving metabolic health under mild cold conditions.
Zhimin Chen, Peng Zhang, Tongyu Liu, Xiaoxue Qiu, Siming Li, Jiandie D. Lin
Increased mitochondrial function may render some cancers vulnerable to mitochondrial inhibitors. Since mitochondrial function is regulated partly by mitochondrial DNA copy number (mtDNAcn), accurate measurements of mtDNAcn could help reveal which cancers are driven by increased mitochondrial function and may be candidates for mitochondrial inhibition. However, prior studies have employed bulk macrodissections that fail to account for cell type-specific or tumor cell heterogeneity in mtDNAcn. These studies have often produced unclear results, particularly in prostate cancer. Herein, we developed a multiplex in situ method to spatially quantify cell type specific mtDNAcn. We show that mtDNAcn is increased in luminal cells of high-grade prostatic intraepithelial neoplasia (HGPIN), is increased in prostatic adenocarcinomas (PCa), and is further elevated in metastatic castration-resistant prostate cancer. Increased PCa mtDNAcn was validated by two orthogonal methods and is accompanied by increases in mtRNAs and enzymatic activity. Mechanistically, MYC inhibition in prostate cancer cells decreases mtDNA replication and expression of several mtDNA replication genes, and MYC activation in the mouse prostate leads to increased mtDNA levels in the neoplastic prostate cells. Our in situ approach also revealed elevated mtDNAcn in precancerous lesions of the pancreas and colon/rectum, demonstrating generalization across cancer types using clinical tissue samples.
Jiayu Chen, Qizhi Zheng, Jessica L. Hicks, Levent Trabzonlu, Busra Ozbek, Tracy Jones, Ajay M. Vaghasia, Tatianna C. Larman, Rulin Wang, Mark C. Markowski, Samuel R. Denmeade, Kenneth J. Pienta, Ralph H. Hruban, Emmanuel S. Antonarakis, Anuj Gupta, Chi V. Dang, Srinivasan Yegnasubramanian, Angelo M. De Marzo
Previous studies have implicated the orexigenic hormone ghrelin as a mediator of exercise endurance and the feeding response post-exercise. Specifically, plasma ghrelin levels nearly double in mice when they are submitted to an hour-long bout of high-intensity interval exercise (HIIE) using treadmills. Also, GHSR (ghrelin receptor)-null mice exhibit decreased food intake following HIIE and a diminished running distance (time until exhaustion) during a longer, step-wise exercise endurance protocol. To investigate whether ghrelin-responsive mediobasal hypothalamus (MBH) neurons mediate these effects, we stereotaxically delivered the inhibitory DREADD virus AAV2-hSyn-DIO-hM4(Gi)-mCherry to the MBH of Ghsr-IRES-Cre mice, which express Cre-recombinase directed by the Ghsr promoter. We found that chemogenetic inhibition of GHSR-expressing MBH neurons [upon delivery of clozapine-N-oxide (CNO)] 1) suppressed food intake following HIIE by 31.3%, 2) reduced maximum running distance by 20.7%-22.7% and raised blood glucose and blood lactate levels by 18.4%-51.5% and 24.6%-39.2%, respectively, during an exercise endurance protocol, 3) reduced food intake following ghrelin administration by 57.2%, but 4) did not affect glucose tolerance. Further, HIIE increased MBH Ghsr expression. These results indicate that activation of ghrelin-responsive MBH neurons is required for the normal feeding response to HIIE and the usual amount of running exhibited during an exercise endurance protocol.
Omprakash Singh, Sean B. Ogden, Salil Varshney, Kripa Shankar, Deepali Gupta, Subhojit Paul, Sherri Osborne-Lawrence, Corine P. Richard, Nathan P. Metzger, Connor Lawrence, Luis León-Mercado, Jeffrey M. Zigman
Fibroblast growth factor 23 (FGF23) is a phosphate (Pi)-regulating hormone produced by bone. Hereditary hypophosphatemic disorders are associated with FGF23 excess, impaired skeletal growth and osteomalacia. Blocking FGF23 became an effective therapeutic strategy in X-linked hypophosphatemia, but testing remains limited in autosomal recessive hypophosphatemic rickets (ARHR). This study investigates the effects of Pi repletion and bone specific deletion of Fgf23 on bone and mineral metabolism in the Dmp1 knockout (Dmp1KO) mouse model of ARHR.At 12 weeks, Dmp1KO mice showed increased serum FGF23 and PTH levels, hypophosphatemia, impaired growth, rickets and osteomalacia. Six weeks of dietary Pi supplementation exacerbated FGF23 production, hyperparathyroidism, renal Pi excretion and osteomalacia. In contrast, osteocyte-specific deletion of Fgf23 resulted in a partial correction of FGF23 excess, which was sufficient to fully restore serum Pi levels, but only partially corrected the bone phenotype. In vitro, we show that FGF23 directly impairs osteoprogenitors differentiation and that DMP1 deficiency contributes to impaired mineralization independently of FGF23 or Pi levels. In conclusion, FGF23-induced hypophosphatemia is only partially responsible for the bone defects observed in Dmp1KO mice. Our data suggest that combined DMP1 repletion and FGF23 blockade could effectively correct ARHR-associated mineral and bone disorders.
Guillaume Courbon, Dominik Kentrup, Jane Joy Thomas, Xueyan Wang, Hao-Hsuan Tsai, Jadeah J. Spindler, John Von Drasek, Laura Mazudie Ndjonko, Marta Martinez-Calle, Sana Lynch, Lauriane Hivert, Xiaofang Wang, Wenhan Chang, Jian Q. Feng, Valentin David, Aline Martin
Emerging evidence shows that KRAS-mutant colorectal cancer (CRC) depends on glutamine (Gln) for survival and progression, indicating that targeting Gln metabolism may be a promising therapeutic strategy for KRAS-mutant CRC. However, the precise mechanism by which Gln metabolism reprogramming promotes and coordinates KRAS-mutant CRC progression remains to be fully investigated. Here, we discovered that solute carrier 25 member 21 (SLC25A21) expression was downregulated in KRAS-mutant CRC, and that SLC25A21 downregulation was correlated with poor survival of KRAS-mutant CRC patients. SLC25A21 depletion selectively accelerated the growth, invasion, migration, and metastasis of KRAS-mutant CRC cells in vitro and in vivo, and inhibited Gln-derived α-ketoglutarate (α-KG) efflux from mitochondria, thereby potentiating Gln replenishment, accompanied by increased GTP availability for persistent KRAS activation in KRAS-mutant CRC. The restoration of SLC25A21 expression impaired the KRAS-mutation-mediated resistance to cetuximab in KRAS-mutant CRC. Moreover, the arrested α-KG efflux that occurred in response to SLC25A21 depletion inhibited the activity of α-KG–dependent DNA demethylases, resulting in a further decrease in SLC25A21 expression. Our studies demonstrate that SLC25A21 plays a significant role as a tumor suppressor in KRAS-mutant CRC by antagonizing Gln-dependent anaplerosis to limit GTP availability for KRAS activation, which suggests potential alternative therapeutic strategies for KRAS-mutant CRC.
Sha-Sha Hu, Yue Han, Tian-Yuan Tan, Hui Chen, Jia-Wen Gao, Lan Wang, Min-Hui Yang, Li Zhao, Yi-Qing Wang, Yan-Qing Ding, Shuang Wang
Diabetes commonly affects cancer patients. We investigated the influence of diabetes on breast cancer biology using a three-pronged approach that included analysis of orthotopic human tumor xenografts, patient tumors, and breast cancer cells exposed to diabetes/hyperglycemia-like conditions. We aimed to identify shared phenotypes and molecular signatures by investigating the metabolome, transcriptome, and tumor mutational burden. Diabetes and hyperglycemia did not enhance cell proliferation but induced mesenchymal and stem cell-like phenotypes linked to increased mobility and odds of metastasis. They also promoted oxyradical formation and both a transcriptome and mutational signatures of DNA repair deficiency. Moreover, food- and microbiome-derived metabolites tended to accumulate in breast tumors in the presence of diabetes, potentially affecting tumor biology. Breast cancer cells cultured under hyperglycemia-like conditions acquired increased DNA damage and sensitivity to DNA repair inhibitors. Based on these observations, we conclude that diabetes-associated breast tumors may show an increased drug response to DNA damage repair inhibitors.
Gatikrushna Panigrahi, Julián Candia, Tiffany H. Dorsey, Wei Tang, Yuuki Ohara, Jung S. Byun, Tsion Z. Minas, Amy L. Zhang, Anuoluwapo Ajao, Ashley Cellini, Harris G. Yfantis, Amy L. Flis, Dean Mann, Olga Ioffe, Xin Wei Wang, Huaitian Liu, Christopher A. Loffredo, Anna Maria Napoles, Stefan Ambs
Albuminuria and podocyte injury are the key cellular events in the progression of diabetic nephropathy (DN). Acetyl-CoA synthetase 2 (ACSS2) is a nucleocytosolic enzyme responsible for the regulation of metabolic homeostasis in mammalian cells. This study aimed to investigate the possible roles of ACSS2 in kidney injury in DN. We constructed an ACSS2-deleted mouse model to investigate the role of ACSS2 in podocyte dysfunction and kidney injury in diabetic mouse models. In vitro, podocytes were chosen and transfected with ACSS2 siRNA and ACSS2 inhibitor and treated with high glucose. We found that ACSS2 expression was significantly elevated in the podocytes of patients with DN and diabetic mice. ACSS2 upregulation promoted phenotype transformation and inflammatory cytokine expression while inhibiting podocytes’ autophagy. Conversely, ACSS2 inhibition improved autophagy and alleviated podocyte injury. Furthermore, ACSS2 epigenetically activated raptor expression by histone H3K9 acetylation, promoting activation of the mammalian target of rapamycin complex 1 (mTORC1) pathway. Pharmacological inhibition or genetic depletion of ACSS2 in the streptozotocin-induced diabetic mouse model greatly ameliorated kidney injury and podocyte dysfunction. To conclude, ACSS2 activation promoted podocyte injury in DN by raptor/mTORC1-mediated autophagy inhibition.
Jian Lu, Xue Qi Li, Pei Pei Chen, Jia Xiu Zhang, Liang Liu, Gui Hua Wang, Xiao Qi Liu, Ting Ting Jiang, Meng Ying Wang, Wen Tao Liu, Xiong Zhong Ruan, Kun Ling Ma
Thyroid hormone (TH) levels are low during development, and the deiodinases control TH signaling through tissue-specific activation or inactivation of TH. Here we studied human iPSC-derived hepatic organoids and identified a robust induction in DIO2 expression (the deiodinase that activates T4 to T3) that occurs in hepatoblasts. The surge in D2-T3 per-sists until the hepatoblasts differentiate into hepatocytes- or cholangiocytes-like cells, nei-ther of which express DIO2. Preventing the induction of the D2-T3 signaling modified the expression of key transcription factors, decreased the number of hepatocyte-like cells by 60%, and increased the number of cholangiocyte-like cells by 55% without affecting the growth or the size of the mature liver organoid. Physiological levels of T3 could not ful-ly restore the transition from hepatoblasts to mature cells. This indicates that the timed surge in D2-T3 signaling critically determines the fate of developing human hepatoblasts and the transcriptome of the maturing hepatocytes, with physiological and clinical implica-tions for how the liver handles energy substrates.
Jorge Hidalgo-Álvarez, Federico Salas-Lucia, Diana Vera Cruz, Tatiana L. Fonseca, Antonio C. Bianco
In youth with obesity, the gut hormone potentiation of insulin secretion - the incretin effect - is blunted. We explored the longitudinal impact of the incretin effect during pubertal transition on beta cell function and insulin sensitivity. Youths with obesity and 2-h glucose≥120mg/dL underwent a 3-h OGTT and an isoglycemic intravenous glucose infusion to quantify the incretin effect. After 2 years, 30/39 participants had a repeated OGTT and were stratified into three tertiles according to the baseline incretin effect. Thirty participants completed the baseline and follow-up tests. The high-incretin effect group demonstrated a longitudinal increase in beta cell function (DIMM) (p=0.034), with greater insulin sensitivity at follow-up (p=0.034) and stable insulin secretion (φtotal) (p=0.077). A lower incretin effect at baseline was associated with a higher 1-h and 2-h glucose at follow-up (r = -0.558, p=0.001 and r = -0.533, p=0.004). The high-incretin effect group displayed a greater increase of GLP-17-36 than the moderate- and low-incretin group at baseline (p=0.008 and p=0.029), while such a difference did not persist after 2 years. Glucagon suppression was reduced at follow-up in those with low-baseline incretin respect to the high-incretin group (p=0.049).
Alfonso Galderisi, Domenico Tricò, Jessica O. Lat, Stephanie L. Samuels, Ram Weiss, Michelle Van Name, Bridget Pierpont, Nicola Santoro, Sonia Caprio
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