Publications by authors named "Justin Fletcher"

Article Synopsis
  • Acetyl-CoA carboxylase (ACC) is key for liver metabolism by creating malonyl-CoA, which aids in fat production and reduces fat burning.
  • Inhibiting ACC led to increased supply of TCA cycle intermediates and enhanced gluconeogenesis, even during fasting, by activating key enzymes like CPT-1 and pyruvate carboxylase.
  • This metabolic shift was linked to higher proteolysis and amino acid availability for glucose production, and was influenced by the activation of Nrf2, suggesting ACC's role goes beyond just fat metabolism.
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Type 1 diabetes (T1D) is an autoimmune disease initiated by genetic predisposition and environmental influences, which result in the specific destruction of insulin-producing pancreatic β-cells. Currently, there are over 1.6 million cases of T1D in the United States with a worldwide incidence rate that has been increasing since 1990.

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BACKGROUNDHepatic de novo lipogenesis (DNL) and β-oxidation are tightly coordinated, and their dysregulation is thought to contribute to the pathogenesis of nonalcoholic fatty liver (NAFL). Fasting normally relaxes DNL-mediated inhibition of hepatic β-oxidation, dramatically increasing ketogenesis and decreasing reliance on the TCA cycle. Thus, we tested whether aberrant oxidative metabolism in fasting NAFL subjects is related to the inability to halt fasting DNL.

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Type 1 diabetes (T1D) is an autoimmune disease initiated by genetic predisposition and environmental influences culminating in the immunologically mediated destruction of pancreatic β-cells with eventual loss of insulin production. Although T1D can be accurately predicted via autoantibodies, therapies are lacking that can intercede autoimmunity and protect pancreatic β-cells. There are no approved interventional modalities established for this purpose.

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Hepatic gluconeogenesis from amino acids contributes significantly to diabetic hyperglycemia, but the molecular mechanisms involved are incompletely understood. Alanine transaminases (ALT1 and ALT2) catalyze the interconversion of alanine and pyruvate, which is required for gluconeogenesis from alanine. We find that ALT2 is overexpressed in the liver of diet-induced obese and db/db mice and that the expression of the gene encoding ALT2 (GPT2) is downregulated following bariatric surgery in people with obesity.

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Background & Aims: Substitution of lysine for glutamic acid at residu 167 in Transmembrane 6 superfamily member 2 (TM6SF2) is associated with fatty liver disease and reduced plasma lipid levels. Tm6sf2 mice replicate the human phenotype but were not suitable for detailed mechanistic studies. As an alternative model, we generated Tm6sf2 rats to determine the subcellular location and function of TM6SF2.

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De novo lipogenesis (DNL) is disrupted in a wide range of human disease. Thus, quantification of DNL may provide insight into mechanisms and guide interventions if it can be performed rapidly and noninvasively. DNL flux is commonly measured by H incorporation into fatty acids following deuterated water (HO) administration.

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Computational models based on the metabolism of stable isotope tracers can yield valuable insight into the metabolic basis of disease. The complexity of these models is limited by the number of tracers and the ability to characterize tracer labeling in downstream metabolites. NMR spectroscopy is ideal for multiple tracer experiments since it precisely detects the position of tracer nuclei in molecules, but it lacks sensitivity for detecting low-concentration metabolites.

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Herein we introduce a deep learning (DL) application engine (DLAE) system concept, present potential uses of it, and describe pathways for its integration in clinical workflows. An open-source software application was developed to provide a code-free approach to DL for medical imaging applications. DLAE supports several DL techniques used in medical imaging, including convolutional neural networks, fully convolutional networks, generative adversarial networks, and bounding box detectors.

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Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent, and potentially morbid, disease that affects one-third of the U.S. population.

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The hepatic TCA cycle supports oxidative and biosynthetic metabolism. This dual responsibility requires anaplerotic pathways, such as pyruvate carboxylase (PC), to generate TCA cycle intermediates necessary for biosynthesis without disrupting oxidative metabolism. Liver-specific PC knockout (LPCKO) mice were created to test the role of anaplerotic flux in liver metabolism.

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New Findings: What is the central question of this study? Does a reduction in hepatic peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), which has been observed in an insulin-resistant obese state, impair the ability of fibroblast growth factor 21 (FGF21) to modulate metabolism? What is the main finding and its importance? A deficit in hepatic PGC-1α does not compromise the ability of FGF21 to increase hepatic fatty acid oxidation; however, the effects of FGF21 to regulate whole-body metabolism (i.e. total and resting energy expenditure), as well as ambulatory activity, were altered when hepatic PGC-1α was reduced.

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Background: Little research has been conducted on the quality, benefits, costs, and financial considerations associated with health information technology (HIT), particularly informatics technologies such as e-prescribing, from the perspective of all of its stakeholders.

Objectives: To (a) identify the stakeholders involved in e-prescribing and (b) identify and rank order the positives and negatives of e-prescribing from the perspective of stakeholders in order to create a framework for payers, integrated delivery systems, policymakers and legislators, and those who influence public policy to assist them in the development of incentives and payment mechanisms that result in the better management of care.

Methods: The Delphi method was used to enlist a panel of experts in e-prescribing, informatics, and/or HIT who have published in the field.

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Background: Little research has been conducted about the quality, benefits, costs, and financial considerations associated with health information technology (HIT), particularly informatics technologies, such as e-prescribing, from the perspective of all its stakeholders.

Objectives: This research effort sought to identify the stakeholders involved in e-prescribing and to identify and rank-order the positives and the negatives from the perspective of the stakeholders to create a framework to assist in the development of incentives and payment mechanisms which result in better managed care.

Methods: The Delphi method was employed by enlisting a panel of experts.

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Exercise enhances insulin sensitivity; it also improves adipocyte metabolism and reduces adipose tissue inflammation through poorly defined mechanisms. Fibroblast growth factor 21 (FGF21) is a pleiotropic hormone-like protein whose insulin-sensitizing properties are predominantly mediated via receptor signaling in adipose tissue (AT). Recently, FGF21 has also been demonstrated to have anti-inflammatory properties.

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Key Points: Low intrinsic aerobic capacity is associated with increased all-cause and liver-related mortality in humans. Low intrinsic aerobic capacity in the low capacity runner (LCR) rat increases susceptibility to acute and chronic high-fat/high-sucrose diet-induced steatosis, without observed increases in liver inflammation. Addition of excess cholesterol to a high-fat/high-sucrose diet produced greater steatosis in LCR and high capacity runner (HCR) rats.

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Rats selectively bred for high capacity running (HCR) or low capacity running (LCR) display divergence for intrinsic aerobic capacity and hepatic mitochondrial oxidative capacity, both factors associated with susceptibility for nonalcoholic fatty liver disease. Here, we tested if HCR and LCR rats display differences in susceptibility for hepatic steatosis after 16 wk of high-fat diets (HFD) with either 45% or 60% of kcals from fat. HCR rats were protected against HFD-induced hepatic steatosis, whereas only the 60% HFD induced steatosis in LCR rats, as marked by a doubling of liver triglycerides.

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Hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats develop obesity, insulin resistance, and nonalcoholic fatty liver disease (NAFLD), but lifestyle modifications, such as caloric restriction (CR), can prevent these conditions. We sought to determine if prior CR had protective effects on metabolic health and NAFLD development following a 4-wk return to ad libitum (AL) feeding. Four-week-old male OLETF rats (n = 8-10/group) were fed AL for 16 wk (O-AL), CR for 16 wk (O-CR; ∼70% kcal of O-AL), or CR for 12 wk followed by 4 wk of AL feeding (O-AL4wk).

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Exercise stimulates hepatic mitochondrial adaptations; however, the mechanisms remain largely unknown. Here we tested whether FGF21 plays an obligatory role in exercise induced hepatic mitochondrial adaptations by testing exercise responses in FGF21 knockout mice. FGF21 knockout (FGF21-KO) and wild-type (WT) mice (11-12 wk of age) had access to voluntary running wheels for exercise (EX) or remained sedentary for 8 wk.

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Article Synopsis
  • - Mitochondria play a vital role in respiration and are particularly important in the liver for processes like gluconeogenesis, but during nonalcoholic fatty liver disease (NAFLD), they can produce reactive oxygen species (ROS) that harm liver cells and contribute to inflammation and insulin resistance.
  • - Studies in mice showed that increased fatty acid delivery led to greater oxidative metabolism, which in turn elevated stress and inflammation, while knockout of a specific enzyme (Pck1) reduced these negative effects, indicating a strong link between metabolic processes and oxidative damage.
  • - Using metformin to lower oxidative metabolism in the liver normalized the associated anabolic pathways and reduced inflammation, linking oxidative stress in human NAFLD cases to metabolic changes from high
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Weight loss is recommended for patients with nonalcoholic fatty liver disease (NAFLD), while metformin may lower liver enzymes in type 2 diabetics. Yet, the efficacy of the combination of weight loss and metformin in the treatment of NAFLD is unclear. We assessed the effects of metformin, caloric restriction, and their combination on NAFLD in diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats.

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Background & Aims: Mounting evidence indicates that maternal exercise confers protection to adult offspring against various diseases. Here we hypothesized that maternal exercise during gestation would reduce high-fat diet (HFD)-induced hepatic steatosis in adult rat offspring.

Methods: Following conception, pregnant dams were divided into either voluntary wheel running exercise (GE) or wheel-locked sedentary (GS) groups throughout gestation (days 4-21).

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Purpose: Despite being commonly affected by degenerative disorders, there are few data on normal thoracic intervertebral disc dimensions. A morphometric analysis of adult thoracic intervertebral discs was, therefore, undertaken.

Methods: Archival computed tomography scans of 128 recently deceased individuals (70 males, 58 females, 20-79 years) with no known spinal pathology were analysed to determine thoracic disc morphometry and variations with disc level, sex and age.

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