The clinical therapy for treating acute myocardial infarction is primary percutaneous coronary intervention (PPCI). PPCI is effective at reperfusing the heart, however the rapid re-introduction of blood can cause ischemia-reperfusion (I/R). Reperfusion injury is responsible for up to half of the final myocardial damage, but there are no pharmacological interventions to reduce I/R. We previously demonstrated that inhibiting monocarboxylate transporter 4 (MCT4) and re-directing pyruvate towards oxidation can blunt hypertrophy. We hypothesized this pathway might be important during I/R. Here, we establish that the pyruvate-lactate axis plays a role in determining myocardial salvage following injury. Post-I/R, the mitochondrial pyruvate carrier (MPC), required for pyruvate oxidation, is upregulated in the surviving myocardium. In cardiomyocytes lacking the MPC, there was increased cell death and less salvage after I/R, which was associated with an upregulation of MCT4. To determine the importance of pyruvate oxidation, we inhibited MCT4 with a small-molecule drug (VB124) at reperfusion. This strategy normalized reactive oxygen species (ROS), mitochondrial membrane potential (∆Ψ), and Ca2+, increased pyruvate entry to TCA cycle, increased oxygen consumption, improved myocardial salvage and functional outcomes following I/R. Our data suggests normalizing pyruvate-lactate metabolism by inhibiting MCT4 is a promising therapy to mitigate I/R injury.
Joseph R. Visker, Ahmad A. Cluntun, Jesse N. Velasco-Silva, David R. Eberhardt, Luis Cedeno-Rosario, Thirupura S. Shankar, Rana Hamouche, Jing Ling, Hyoin Kwak, J. Yanni Hillas, Ian Aist, Eleni Tseliou, Sutip Navankasattusas, Dipayan Chaudhuri, Gregory S. Ducker, Stavros G. Drakos, Jared Rutter
Clarifying multifactorial musculoskeletal disorder etiologies supports risk analysis and development of targeted prevention and treatment modalities. Deep learning enables comprehensive risk factor identification through systematic analysis of disease datasets but does not provide sufficient context for mechanistic understanding, limiting clinical applicability for etiological investigations. Conversely, multiscale biomechanical modeling can evaluate mechanistic etiology within the relevant biomechanical and physiological context. We propose a hybrid approach combining 3D explainable deep learning and multiscale biomechanical modeling; we applied this approach to investigate temporomandibular joint (TMJ) disorder etiology by systematically identifying risk factors and elucidating mechanistic relationships between risk factors and TMJ biomechanics and mechanobiology. Our 3D convolutional neural network recognized TMJ disorder patients through subject-specific morphological features in condylar, ramus, and chin. Driven by deep learning model outputs, biomechanical modeling revealed that small mandibular size and flat condylar shape were associated with increased TMJ disorder risk through increased joint force, decreased tissue nutrient availability and cell ATP production, and increased TMJ disc strain energy density. Combining explainable deep learning and multiscale biomechanical modeling addresses the “mechanism unknown” limitation undermining translational confidence in clinical applications of deep learning and increases methodological accessibility for smaller clinical datasets by providing the crucial biomechanical context.
Shuchun Sun, Pei Xu, Nathan Buchweitz, Cherice N. Hill, Farhad Ahmadi, Marshall B. Wilson, Angela Mei, Xin She, Benedikt Sagl, Elizabeth H. Slate, Janice S. Lee, Yongren Wu, Hai Yao
Lipoprotein lipase (LPL) hydrolyzes circulating triglycerides (TGs), releasing fatty acids (FA) and promoting lipid storage in white adipose tissue (WAT). However, the mechanisms regulating adipose LPL and its relationship with the development of hypertriglyceridemia are largely unknown. WAT from obese humans exhibited high PAR2 expression, which was inversely correlated with the LPL gene. Decreased LPL expression was also inversely correlated with elevated plasma TG levels, suggesting that adipose PAR2 might regulate hypertriglyceridemia by downregulating LPL. In mice, aging and high palmitic acid diet (PD) increased PAR2 expression in WAT, which was associated with a high level of macrophage migration inhibitory factor (MIF). MIF downregulated LPL expression and activity in adipocytes by binding with CXCR2/4 receptors and inhibiting Akt phosphorylation. In a MIF overexpression model, high-circulating MIF levels suppressed adipose LPL, and this suppression was associated with increased plasma TGs but not FA. Following PD feeding, adipose LPL expression and activity were significantly reduced, and this reduction was reversed in Par2–/– mice. Recombinant MIF infusion restored high plasma MIF levels in Par2–/– mice, and the levels decreased LPL and attenuated adipocyte lipid storage, leading to hypertriglyceridemia. These data collectively suggest that downregulation of adipose LPL by PAR2/MIF may contribute to the development of hypertriglyceridemia.
Yiheng Huang, Liujun Chen, Lisha Li, Yadan Qi, Haibin Tong, Hong Wu, Jinjie Xu, Lin Leng, Sukhinder Cheema, Guang Sun, Zhengyuan Xia, John McGuire, Brian Rodrigues, Lawrence H. Young, Richard Bucala, Dake Qi
Pulmonary disorders impact 40% to 80% of individuals with obesity. Respiratory muscle dysfunction is linked to these conditions; however, its pathophysiology remains largely undefined. Mice subjected to diet-induced obesity (DIO) develop diaphragmatic weakness. Increased intra-diaphragmatic adiposity and extracellular matrix (ECM) content correlate with reductions in contractile force. Thrombospondin-1 (THBS1) is an obesity-associated matricellular protein linked with muscular damage in genetic myopathies. THBS1 induces proliferation of fibro-adipogenic progenitors (FAPs) — mesenchymal cells that differentiate into adipocytes and fibroblasts. We hypothesized that THBS1 drives FAP-mediated diaphragm remodeling and contractile dysfunction in DIO. We tested this by comparing the effects of dietary challenge on diaphragms of wild-type (WT) and Thbs1 knockout (Thbs1–/–) mice. Bulk and single-cell transcriptomics demonstrated DIO-induced stromal expansion in WT diaphragms. Diaphragm FAPs displayed upregulation of ECM and TGF β-related expression signatures and augmentation of a Thy1-expressing sub-population previously linked to type 2 diabetes. Despite similar weight gain, Thbs1–/– mice were protected from these transcriptomic changes and from obesity-induced increases in diaphragm adiposity and ECM deposition. Unlike WT controls, Thbs1–/– diaphragms maintained normal contractile force and motion after DIO challenge. These findings establish THBS1 as a necessary mediator of diaphragm stromal remodeling and contractile dysfunction in overnutrition and a potential therapeutic target in obesity-associated respiratory dysfunction.
Eric D. Buras, Moon-Sook Woo, Romil Kaul Verma, Sri Harshita Kondisetti, Carol S. Davis, Dennis R. Claflin, Kimber Converso-Baran, Daniel E. Michele, Susan V. Brooks, Tae-Hwa Chun
Beside suppressing immune responses, regulatory T cells (Tregs) maintain tissue homeostasis and control systemic metabolism. Whether iron is involved in Treg-mediated tolerance is completely unknown. Here, we showed that the transferrin receptor CD71 was upregulated on activated Tregs infiltrating human liver cancer. Mice with a Treg-restricted CD71 deficiency spontaneously developed a scurfy-like disease, caused by impaired perinatal Treg expansion. CD71-null Tregs displayed decreased proliferation and tissue-Treg signature loss. In perinatal life, CD71 deficiency in Tregs triggered hepatic iron overload response, characterized by increased hepcidin transcription and iron accumulation in macrophages. Lower bacterial diversity, and reduction of beneficial species, were detected in the fecal microbiota of CD71 conditional knock-out neonates. Our findings indicate that CD71-mediated iron absorption is required for Treg perinatal expansion and related to systemic iron homeostasis and bacterial gut colonization. Therefore, we hypothesize that Tregs establish nutritional tolerance through competition for iron during bacterial colonization after birth.
Ilenia Pacella, Alessandra Pinzon Grimaldos, Alessandra Rossi, Gloria Tucci, Marta Zagaglioni, Elena Potenza, Valeria Pinna, Ivano Rotella, Ilenia Cammarata, Valeria Cancila, Beatrice Belmonte, Claudio Tripodo, Giuseppe Pietropaolo, Chiara Di Censo, Giuseppe Sciumè, Valerio Licursi, Giovanna Peruzzi, Ylenia Antonucci, Silvia Campello, Francesca Guerrieri, Valerio Iebba, Rita Prota, Maria Di Chiara, Gianluca Terrin, Valerio De Peppo, Gian Luca Grazi, Vincenzo Barnaba, Silvia Piconese
Loss-of-function mutations of the gene encoding the trafficking protein particle complex subunit 9 (trappc9) cause autosomal recessive intellectual disability and obesity by unknown mechanisms. Genome-wide analysis links trappc9 to non-alcoholic fatty liver disease (NAFLD). Trappc9-deficient mice have been shown to appear overweight shortly after weaning. Here, we analyzed serum biochemistry and histology of adipose and liver tissues to determine the incidence of obesity and NAFLD in trappc9-deficient mice and combined transcriptomic and proteomic analyses, pharmacological studies, and biochemical and histological examinations of postmortem mouse brains to unveil mechanisms involved. We found that trappc9-deficient mice presented with systemic glucose homeostatic disturbance, obesity and NAFLD, which were relieved upon chronic treatment combining dopamine receptor D2 (DRD2) agonist quinpirole and DRD1 antagonist SCH23390. Blood glucose homeostasis in trappc9-deficient mice was restored upon administrating quinpirole alone. RNA-sequencing analysis of DRD2-containing neurons and proteomic study of brain synaptosomes revealed signs of impaired neurotransmitter secretion in trappc9-deficient mice. Biochemical and histological studies of mouse brains showed that trappc9-deficient mice synthesized dopamine normally, but their dopamine-secreting neurons had a lower abundance of structures for releasing dopamine in the striatum. Our study suggests that trappc9 loss-of-function causes obesity and NAFLD by constraining dopamine synapse formation.
Yan Li, Usman Muhammad, Ellen Sapp, Yuting Ke, Zejian Wang, Adel Boudi, Marian DiFiglia, Xueyi Li
Monogenic diabetes is a gateway to precision medicine through molecular mechanistic insight. Hepatocyte nuclear factor 1A (HNF-1A) and HNF-4A are transcription factors that engage in crossregulatory gene transcription networks to maintain glucose-stimulated insulin secretion in pancreatic β cells. Variants in the HNF1A and HNF4A genes are associated with maturity-onset diabetes of the young (MODY). Here, we explored 4 variants in the P2-HNF4A promoter region: 3 in the HNF-1A binding site and 1 close to the site, which were identified in 63 individuals from 21 families of different MODY disease registries across Europe. Our goal was to study the disease causality for these variants and to investigate diabetes mechanisms on the molecular level. We solved a crystal structure of HNF-1A bound to the P2-HNF4A promoter and established a set of techniques to probe HNF-1A binding and transcriptional activity toward different promoter variants. We used isothermal titration calorimetry, biolayer interferometry, x-ray crystallography, and transactivation assays, which revealed changes in HNF-1A binding or transcriptional activities for all 4 P2-HNF4A variants. Our results suggest distinct disease mechanisms of the promoter variants, which can be correlated with clinical phenotype, such as age of diagnosis of diabetes, and be important tools for clinical utility in precision medicine.
Laura Kind, Janne Molnes, Erling Tjora, Arne Raasakka, Matti Myllykoski, Kevin Colclough, Cécile Saint-Martin, Caroline Adelfalk, Petra Dusatkova, Stepanka Pruhova, Camilla Valtonen-André, Christine Bellanné-Chantelot, Thomas Arnesen, Petri Kursula, Pål Rasmus Njølstad
Acute Pancreatitis (AP) is among the most common hospital gastrointestinal diagnosis; understanding the mechanisms underlying the severity of AP are critical for development of new treatment options for this disease. Here, we evaluate the biological function of phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in AP pathogenesis in two independent genetically engineered mouse models of AP. PFKFB3 is elevated in AP and severe AP (SAP) and knockout of Pfkfb3 abrogates the severity of alcoholic SAP (FAEE-SAP). Using a combination of genetic, pharmacological, and molecular studies we define the interaction of PFKFB3 with inositol 1,4,5-trisphosphate receptor (IP3R) as a key event mediating this phenomenon. Further analysis demonstrated that the interaction between PFKFB3 and IP3R promotes FAEE-SAP severity by altering intracellular calcium homeostasis in acinar cells. Together our results support a PFKFB3-driven mechanism controlling AP pathobiology and define this enzyme as a therapeutic target to ameliorate the severity of this dismal condition.
Tan Zhang, Shengchuan Chen, Liang Li, Yuepeng Jin, Siying Liu, Zhu Liu, Fengyu Shi, Lifen Xie, Panpan Guo, Andrew C. Cannon, Akmal Ergashev, Haiping Yao, Chaohao Huang, Baofu Zhang, Lijun Wu, Hongwei Sun, Siming Chen, Yunfeng Shan, Zhengping Yu, Ezequiel J. Tolosa, Jianghuai Liu, Martin E. Fernandez-Zapico, Feng Ma, Gang Chen
Caloric restriction improves metabolic health, but is often complicated by bone loss. We studied bone parameters in humans during a 10-day fast and identified candidate metabolic regulators of bone turnover. P1NP, a bone formation marker, decreased within 3 days of fasting. Whereas dual-energy X-ray absorptiometry measures of bone mineral density were unchanged after 10 days of fasting, high-resolution peripheral quantitative CT demonstrated remodeling of bone microarchitecture. Pathway analysis of longitudinal metabolomics data identified one-carbon metabolism as fasting-dependent. In cultured osteoblasts, we tested the functional significance of one-carbon metabolites modulated by fasting, finding that methionine — which surged after 3 days of fasting — impacted markers of osteoblast cell state in a concentration dependent manner, in some instances exhibiting a U-shaped response with both low and high concentrations driving putative anti-bone responses. Administration of methionine to mice for 5 days recapitulated some fasting effects on bone, including a reduction in serum P1NP. In conclusion, a 10-day fast in humans led to remodeling of bone microarchitecture, potentially mediated by a surge in circulating methionine. These data support an emerging model that points to a window of optimal methionine exposure for bone health.
Tânia Amorim, Naveen G.V. Kumar, Natalie L. David, William Dion, Trishya Pagadala, Nandini K. Doshi, Bokai Zhu, Andrey Parkhitko, Matthew L. Steinhauser, Pouneh K. Fazeli
Diabetes increases the risk of both cardiovascular disease and kidney disease. Notably, most of the excess cardiovascular risk in people with diabetes is in those with kidney disease. Apolipoprotein C3 (APOC3) is a key regulator of plasma triglycerides, and it has recently been suggested to play a role in both type 1 diabetes-accelerated atherosclerosis and kidney disease progression. To investigate if APOC3 plays a role in kidney disease in people with type 2 diabetes, we analyzed plasma levels of APOC3 from the Veterans Affairs Diabetes Trial (VADT). Elevated baseline APOC3 levels predicted a greater loss of renal function. To mechanistically test if APOC3 plays a role in diabetic kidney disease and associated atherosclerosis, we treated BTBR wildtype (WT) and leptin-deficient (OB; diabetic) mice, a model of type 2 diabetes, with an antisense oligonucleotide (ASO) to APOC3 or a control ASO (cASO), all in the setting of human-like dyslipidemia. Silencing APOC3 prevented diabetes-augmented albuminuria, renal glomerular hypertrophy, monocyte recruitment, and macrophage accumulation, partly driven by reduced ICAM1 expression. Furthermore, reduced levels of APOC3 suppressed atherosclerosis associated with diabetes. This suggests that targeting APOC3 might benefit both diabetes-accelerated atherosclerosis and kidney disease.
Jocelyn Cervantes, Juraj Koska, Farah Kramer, Shreeram Akilesh, Charles E. Alpers, Adam E. Mullick, Peter Reaven, Jenny E. Kanter
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