Biology subjects

Mattis, A. N.

Publications and source records attributed to Mattis, A. N..

9 recordsLinked to original sources

bioRxiv2025

MIR192 Upregulates GLP-1 Receptor and Improves Statin-Induced Impairment of Insulin Secretion

Statins are a commonly prescribed cholesterol lowering drug class that can increase the risk of new-onset diabetes (NOD). To investigate the molecular mechanisms underlying this effect, we generated human induced pluripotent stem cells (iPSCs) from individuals identified from electronic health records of Kaiser Permanente of Northern California who were susceptible to developing NOD after statin initiation or controls who maintained stable fasting glucose on statin treatment. RNA-seq analysis of iPSCs incubated with atorvastatin, simvastatin or mock buffer for 24 hours identified the long non-coding RNA MIR194-2HG as a top candidate gene. Statin-induced increases in its expression were observed in NOD resistant controls, while statin-induced reductions occurred in NOD susceptible cases. MIR194-2HG encompasses two microRNA genes: MIR192 and MIR194-2. The mature microRNA miR-192-5p, derived from the 5 arm of MIR192, was predicted to bind the 3UTR of the glucagon like peptide 1 (GLP-1) receptor (GLP1R) transcript. Transfection of a rat insulinoma cell line INS-1 with a miR-192-5p mimic increased Glp1r transcript (1.41-fold) and protein (1.51-fold) levels compared to a scrambled control. Using a luciferase reporter containing the human GLP1R 3UTR, miR-192-5p overexpression similarly increased luciferase signal (1.44-fold). The miR-192-5p mimic enhanced glucose stimulated insulin secretion (GSIS) in response to GLP1R agonists (1.64-1.81-fold) and rescued simvastatin-induced GSIS impairment in INS-1 cells. Wild-type mice treated with miR-192 AAV8 had improved glucose sensitivity. Islets isolated from these mice exhibited enhanced GLP-1 potentiated GSIS during perifusion ex vivo. These effects were absent in the DIRKO (Glp1r/Gipr double knockout) mouse islets, consistent with the idea that miR-192 promotes GLP-1 mediated GSIS through GLP1R. These findings implicate MIR192 in statin-induced impairment of GSIS by modulating GLP1R, potentially contributing to the susceptibility to NOD in statin users.

cell biology↗

bioRxiv2025

Predicting Metabolic Dysfunction Associated Steatotic Liver Disease Risk Using Patient-Derived Induced Pluripotent Stem Cells

Background and AimsMetabolic Dysfunction Associated Steatotic Liver Disease (MASLD) is reversible at early stages, making early identification of high-risk individuals clinically valuable. Previously, we demonstrated that patient-derived induced pluripotent stem cells (iPSCs) harboring MASLD DNA risk variants exhibit greater oleate-induced intracellular lipid accumulation than those without these variants. This study aimed to develop an iPSC-based MASLD risk predictor using functional lipid accumulation assessments. MethodsWe quantified oleate-induced intracellular lipid accumulation in iPSCs derived from three cohorts of diverse ancestry: 1) CIRM cohort (20 biopsy-confirmed MASH cases, 2 biopsy-confirmed MASLD cases, 17 controls), 2) POST cohort (18 MASLD cases, 17 controls), and 3) UCSF cohort (4 biopsy-confirmed MASH cases, 8 controls). Lipid accumulation levels in the CIRM cohort were used to define an iPSC-based MASLD risk score, which was used to predict case/control status in the POST and UCSF cohorts. ResultsIn all three cohorts, lipid accumulation was higher in MASLD/MASH cases vs. controls (CIRM cases vs. controls 3.32 {+/-} 0.25 vs. 2.70 {+/-} 0.19 -fold change, p=0.06; POST cases vs. controls 3.63 {+/-} 0.33 vs. 2.70 {+/-} 0.31, p=0.05; and UCSF cases vs. controls 4.39{+/-}0.46 vs. 2.03{+/-}0.20, p=0.0002). The iPSC-based MASLD risk score achieved a sensitivity of 44% and specificity of 75% in the POST cohort and 75% and 100%, respectively, in the UCSF cohort. Differences in cohort disease severity and cardiometabolic profiles may explain performance variability. ConclusionWhile validation in larger cohorts is needed, these findings suggest that oleate-induced intracellular lipid accumulation in subject-derived iPSCs is predictive of MASH development. Additional cellular phenotypes and donor information should be explored to improve predictive accuracy to inform MASLD surveillance and prevention strategies.

cell biology↗

bioRxiv2024

Loss of TMEM55B modulates lipid metabolism through dysregulated lipophagy and mitochondrial function

Lipophagy is a form of selective autophagy that targets the lipid droplets for lysosomal decay and has been implicated in the onset and progression of metabolic dysfunction-associated steatotic liver disease (MASLD). Factors that augment lipophagy have been identified as targets for MASLD therapeutic development. TMEM55B is a key regulator of lysosomal positioning which is critical for the lysosome fusion with the autophagosome, but less studied. Here, we demonstrate that inhibition of TMEM55B in murine models accelerates MASLD onset and progression. In cellular models, TMEM55B deficiency enhances lipophagy, leading to increased fatty acid release from lysosomes to mitochondria but simultaneously impairs mitophagy, causing an accumulation of dysfunctional mitochondria. This imbalance leads to increased lipid accumulation and oxidative stress, worsening MASLD. These findings underscore the importance of lysosomal positioning in lipid metabolism and suggest that augmenting lipophagy may exacerbate disease in the context of mitochondrial dysfunction.

cell biology↗

bioRxiv2023

Group 2 innate lymphoid cells constrain type 3/17 lymphocytes in shared stromal niches to restrict liver fibrosis

Group 2 innate lymphoid cells (ILC2s) cooperate with adaptive Th2 cells as key organizers of tissue type 2 immune responses, while a spectrum of innate and adaptive lymphocytes coordinate early type 3/17 immunity. Both type 2 and type 3/17 lymphocyte associated cytokines are linked to tissue fibrosis, but how their dynamic and spatial topographies may direct beneficial or pathologic organ remodelling is unclear. Here we used volumetric imaging in models of liver fibrosis, finding accumulation of periportal and fibrotic tract IL-5+ lymphocytes, predominantly ILC2s, in close proximity to expanded type 3/17 lymphocytes and IL-33high niche fibroblasts. Ablation of IL-5+ lymphocytes worsened carbon tetrachloride-and bile duct ligation-induced liver fibrosis with increased niche IL-17A+ type 3/17 lymphocytes, predominantly {gamma}{delta} T cells. In contrast, concurrent ablation of IL-5+ and IL-17A+ lymphocytes reduced this progressive liver fibrosis, suggesting a cross-regulation of type 2 and type 3 lymphocytes at specialized fibroblast niches that tunes hepatic fibrosis.

immunology↗

bioRxiv2022

Targeting Acid Ceramidase Ameliorates Fibrosis in Mouse Models of Nonalcoholic Steatohepatitis

1)Nonalcoholic fatty liver disease (NAFLD) is a common cause of liver disease worldwide, and is characterized by the accumulation of fat in the liver. Nonalcoholic steatohepatitis (NASH), an advanced form of NAFLD, is a leading cause of liver transplantation. Fibrosis is the histologic feature most associated with liver-related morbidity and mortality in patients with NASH, and treatment options remain limited. In previous studies, we discovered that acid ceramidase (aCDase) is a potent antifibrotic target using human hepatic stellate cells (HSCs) and models of hepatic fibrogenesis. Using two dietary mouse models, we demonstrate that depletion of aCDase in HSC reduces fibrosis without worsening metabolic features of NASH, including steatosis, inflammation, and insulin resistance. Consistently, pharmacologic inhibition of aCDase ameliorates fibrosis but does not alter metabolic parameters. The findings suggest that targeting aCDase is a viable therapeutic option to reduce fibrosis in patients with NASH.

systems biology↗

bioRxiv2020

Hepatocyte-specific deletion of XBP1 sensitizes mice to liver injury through hyperactivation of IRE1α

X-box binding protein-1 (XBP1) is a transcription factor that plays a central role in controlling cellular responses to endoplasmic reticulum (ER) stress. Under stress conditions, the transcriptionally active form of XBP1 is generated by unique splicing of Xbp1 mRNA by the ER-resident protein inositol-requiring enzyme-1 (IRE1). Genetic deletion of XBP1 has multiple consequences: some resulting from the loss of the transcription factor per se, and others related to compensatory upstream activation of IRE1. The objective of the current study was to investigate the effects of XBP1 deletion in adult mouse liver and determine to what extent they are direct or indirect. XBP1 was deleted specifically from hepatocytes in adult Xbp1fl/fl mice using AAV8-Transthyretin-Cre (Xbp1{Delta}hep). Xbp1{Delta}hep mice exhibited no liver disease at baseline, but developed acute biochemical and histologic liver injury in response to a dietary challenge with fructose for 4 wk. Fructose-mediated liver injury in Xbp1{Delta}hep mice coincided with heightened IRE1 activity, as demonstrated by cJun phosphorylation and regulated IRE1 -dependent RNA decay (RIDD). Activation of eIF2 was also evident, with associated up-regulation of the pro-apoptotic molecules CHOP, BIM and PUMA. To determine whether the adverse consequences of liver-specific XBP1 deletion were due to XBP1 loss or heightened IRE1 activity, we repeated a fructose challenge in mice with liver-specific deletion of both XBP1 and IRE1 (Xbp1{Delta}hep;IRE1{Delta}hep). Xbp1{Delta}hep;IRE1{Delta}hep mice were protected from fructose-mediated liver injury and failed to exhibit any of the signs of ER stress seen in mice lacking XBP1 alone. The protective effect of IRE1 deletion persisted even with long-term exposure to fructose. Xbp1{Delta}hep mice developed liver fibrosis at 16 wk, but Xbp1{Delta}hep;IRE1{Delta}hep mice did not. Overall, the results indicate that the deleterious effects of hepatocyte-specific XBP1 deletion are due primarily to hyperactivation of IRE1. They support further exploration of IRE1 as a contributor to acute and chronic liver diseases.

cell biology↗

bioRxiv2020

iPSC-derived hepatocytes from patients with nonalcoholic fatty liver disease display a disease-specific gene expression profile

Nonalcoholic fatty liver disease (NAFLD) is one of the leading causes of liver disease worldwide.1 Animal models are widely used to investigate the mechanisms of fatty liver disease, but they do not faithfully represent NAFLD in humans.2 Thus, there is strong interest in studying NAFLD pathogenesis directly in humans whenever possible. One strategy that is gaining momentum is to utilize iPSC-derived hepatocytes from individual human subjects in complex cell/organ platforms with the goal of reproducing a NAFLD-like state in vitro.3-6 Our group has taken a different approach, positing that iPSC-Heps from a population of NAFLD patients would provide independent insight into the human disease. In this study we generated iPSCs and iPSC-Heps from a well-defined cohort of NAFLD patients. Our objective was to determine whether as a group, in the absence of any metabolic challenge, they exhibit common disease-specific signatures that are distinct from healthy controls.Competing Interest StatementThis work was funded by research grants from the California Institute for Regenerative Medicine (IT1-06563), AbbVie, Inc. and NIH: R21 DK118380 (JJM), UG3 DK120004 (HW) and K08 DK098270 (ANM). Additional support was provided by core facilities within the UCSF Liver Center (P30 DK026743).View Full Text

pathology↗

bioRxiv2020

Doxycycline Significantly Enhances Induction of iPSCs to Endoderm by Enhancing survival via AKT Phosphorylation

Induced pluripotent stem cells (iPSCs) provide an important tool for the generation patient-derived cells including hepatocyte-like cells via developmental cues through an endoderm intermediate. However, most iPSCs fail to differentiate into endoderm, with induction resulting in apoptosis. To address this issue, we built upon published methods to develop an improved protocol with our discovery that doxycycline dramatically enhances the iPSC to endoderm differentiation efficiency by inhibiting apoptosis and promoting proliferation via the AKT pathway. We tested this new protocol in more than 70 iPSC lines with consistent formation of complete sheets of endoderm in 90%. Endoderm generated by our method achieves similar transcriptomic profiles, including FOXA2, HNF1{beta}, CXCR4, and SOX17 positive cells, and the ability to be further differentiated. Furthermore this method achieves a four-fold increase in endoderm cell number and will accelerate studies of human diseases in vitro and facilitate the expansion of iPSC-derived cells for transplantation studies.

developmental biology↗

bioRxiv2019

Adipocyte JAK2 mediates aging-associated metabolic liver disease and progression to hepatocellular carcinoma

Non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH) are liver manifestations of the metabolic syndrome and can progress to hepatocellular carcinoma (HCC). Loss of Growth Hormone (GH) signaling is reported to predispose to NAFLD and NASH through direct actions on the liver. Here, we report that aged mice lacking hepatocyte Jak2 (JAK2L), an obligate transducer of Growth Hormone (GH) signaling, spontaneously develop the full spectrum of phenotypes found in patients with metabolic liver disease, beginning with insulin resistance and lipodystrophy and manifesting as NAFLD, NASH and even HCC, independent of dietary intervention. Remarkably, insulin resistance, metabolic liver disease, and carcinogenesis are prevented in JAK2L mice via concomitant deletion of adipocyte Jak2 (JAK2LA). Further, we demonstrate that GH increases hepatic lipid burden but does so indirectly via signaling through adipocyte JAK2. Collectively, these data establish adipocytes as the mediator of GH-induced metabolic liver disease and carcinogenesis. In addition, we report a new spontaneous model of NAFLD, NASH, and HCC that recapitulates the natural sequelae of human insulin resistance-associated disease progression. The work presented here suggests a attention be paid towards inhibition of adipocyte GH signaling as a therapeutic target of metabolic liver disease.

physiology↗