Cited by 497Liver Disease Diagnosis and TreatmentMetabolism, Diabetes, and CancerDiet, Metabolism, and Disease

The DOI matches its Crossref record; 38 of the 39 references it cites were found in a registry or an index; none of the 21 sources its claims cite is checked for support yet.

Inhibition of protein kinase Cε prevents hepatic insulin resistance in nonalcoholic fatty liver disease

Open access

Abstract

Nonalcoholic fatty liver disease is strongly associated with hepatic insulin resistance and type 2 diabetes mellitus, but the molecular signals linking hepatic fat accumulation to hepatic insulin resistance are unknown. Three days of high-fat feeding in rats results specifically in hepatic steatosis and hepatic insulin resistance. In this setting, PKCepsilon, but not other isoforms of PKC, is activated. To determine whether PKCepsilon plays a causal role in the pathogenesis of hepatic insulin resistance, we treated rats with an antisense oligonucleotide against PKCepsilon and subjected them to 3 days of high-fat feeding. Knocking down PKCepsilon expression protects rats from fat-induced hepatic insulin resistance and reverses fat-induced defects in hepatic insulin signaling. Furthermore, we show that PKCepsilon associates with the insulin receptor in vivo and impairs insulin receptor kinase activity both in vivo and in vitro. These data support the hypothesis that PKCepsilon plays a critical role in mediating fat-induced hepatic insulin resistance and represents a novel therapeutic target for type 2 diabetes.

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

In rats, 3 days of high-fat feeding causes hepatic steatosis and hepatic insulin resistance with specific activation of PKCε. Knocking down PKCε with an antisense oligonucleotide prevents fat-induced hepatic insulin resistance and improves hepatic insulin signaling, apparently by preventing PKCε from directly inhibiting insulin receptor kinase activity.

Key findings

  • PKCε ASO specifically reduced PKCε expression in liver and white adipose tissue, but not muscle, without changing PKCδ; it caused no hepatotoxicity (AST: saline 57 ± 0.3 vs. PKCε 68 ± 3; ALT: saline 76 ± 3 vs. PKCε 87 ± 5), similar weight gain, and no differences in IL-6, leptin, adiponectin, or resistin.
  • Despite unchanged liver triglyceride and DAG content and identical fasting plasma glucose, PKCε ASO lowered fasting plasma insulin by approximately 50% versus saline- and control ASO-treated rats, and improved hepatic insulin action: greater suppression of hepatic glucose production during hyperinsulinemic-euglycemic clamping, modestly increased whole-body glucose disposal, nearly 2-fold higher epididymal white adipose tissue glucose uptake, and greater suppression of plasma fatty acids.
  • In PKCε ASO-treated rats, insulin increased IRS2 tyrosine phosphorylation approximately 300% above basal, whereas saline and control ASO rats failed to increase IRS2 phosphorylation; insulin-stimulated AKT2 activity increased approximately 400% versus approximately 50% in controls. Adipose insulin-stimulated AKT2 activity was 221% ± 16% in PKCε ASO rats versus 32% ± 11% and 23% ± 20% in saline- and control ASO-treated rats.
  • PKCε coimmunoprecipitated with the insulin receptor in vivo, and increasing molar ratios of PKCε to insulin receptor-β dose-dependently decreased insulin receptor-β tyrosine kinase activity in vitro. Liver insulin receptor kinase activation by insulin was diminished in saline- and control ASO-treated high-fat-fed rats but preserved in PKCε ASO-treated rats.

Methods

  • Male Sprague-Dawley rats weighing approximately 250 g were treated for 4 weeks with saline, control ASO, or PKCε ASO at 75 mg/kg per week by intraperitoneal injection, then fed a high-fat diet (26% carbohydrate, 59% fat, 15% protein calories; safflower oil major constituent) for 3 days.
  • Hyperinsulinemic-euglycemic clamp studies used [6,6-2H]glucose and 2-deoxy-d-[1-14C]glucose to assess basal and insulin-stimulated glucose turnover and tissue glucose uptake; liver triglyceride and DAG, plasma hormones and fatty acids, insulin signaling, PKC expression, and insulin receptor kinase activity were measured.
  • PKCε ASO was ISIS-232697; control ASO was ISIS-141923. A separate group of similarly treated rats underwent 20 minutes of hyperinsulinemic-euglycemic clamping for insulin signaling assays. Statistics used 1-way ANOVA followed by Tukey’s HSD test, with P < 0.05 considered significant.

Limitations

  • The paper does not include a dedicated limitations section. It states that the role of PKCε in the adipocyte is uncertain and that a similar mechanism in patients with diabetes is hypothesized based on prior human data, not directly tested here.
  • Evident from the text: the findings are in male Sprague-Dawley rats after only 3 days of high-fat feeding and 4 weeks of ASO treatment, so they cannot establish long-term causality, safety, or efficacy in human NAFLD or type 2 diabetes.
  • Evident from the text: PKCε ASO reduced PKCε in liver and white adipose tissue but not muscle, and muscle glucose uptake was unchanged, limiting conclusions about skeletal muscle insulin action.

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Integrity signals

Registry

Crossref · 10.1172/jci30400

Cites

38 of 38 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Verification

Claims the paper makes

0 of 21 cited sources checked · 0 supported · 0 flagged

Show all 45 claims

  • It may state two separate claims as one. 10
  • Probably not a substantial claim. 4
13 of 13
  • The paper relies on this without support.

    ASOs are avidly taken up by the liver, where they inhibit specific genes of interest.

    “ASOs are avidly taken up by the liver, where they inhibit specific genes of interest.”
  • The paper relies on this without support.

    The control ASO does not have perfect complementarity to any known gene in public databases.

    “The control ASO, ISIS-141923, has the sequence 5′-CCTTCCCT-GAAGGTTCCTCC-3′ and does not have perfect complementarity to any known gene in public databases.”
2 of 2

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Self-check

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Each contradiction between two passages listed here was confirmed by an independent check.

  • Glucose tracer enrichment is identified as both M+6 and M+2

    Minor

    The methods describe the measured glucose enrichment as M+6, but then identify it as M+2 when specifying the mass ratio used. Both statements refer to the enrichment measurement for the same tracer.

1 of 1

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Metadata

Authors
Samuel, V. T., Liu, Z.-X., Wang, A., Beddow, S. A., Geisler, J. G., Kahn, M., Zhang, X.-M., Monia, B. P., Bhanot, S., & Shulman, G. I.
Affiliations
  • Yale University (US)
  • Ionis Pharmaceuticals (United States) (US)
  • Howard Hughes Medical Institute (US)
Corresponding author
Shulman, Gerald I.
Venue
Journal of Clinical Investigation
Published
2007-03-01
Volume
117
Issue
3
Pages
739-745
ISSN
0021-9738 (ISSN-L)
OpenAlex
W2094051977
Cited by
497
References
39
Citations by year
2026: 17 · 2025: 10 · 2024: 24 · 2023: 14 · 2022: 19 · 2021: 12 · 2020: 25 · 2019: 26 · 2018: 36 · 2017: 21 · 2016: 37 · 2015: 29 · 2014: 28 · 2013: 25 · 2012: 27
FWCI
24.64
Type
journal article
Language
en
Open access
Locations
  • Journal of Clinical Investigation (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • U.S. Public Health Service (P30 DK45735, R01 DK-40936, DK40936)
  • National Institute of Diabetes and Digestive and Kidney Diseases (P30DK45735, R01-DK40936, R01DK040936, U24DK059635, P30DK045735)
  • National Center for Research Resources (K23RR017404, K23 RR-17404)
Topics
  • Health Sciences › Medicine › Hepatology › Liver Disease Diagnosis and Treatment
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Metabolism, Diabetes, and Cancer
  • Health Sciences › Medicine › Endocrinology, Diabetes and Metabolism › Diet, Metabolism, and Disease
Keywords
protein kinase C epsilon, hepatic insulin resistance, non-alcoholic fatty liver disease, hepatic steatosis, high-fat feeding, insulin receptor, antisense oligonucleotide knockdown, type 2 diabetes, insulin signaling, therapeutic target
MeSH terms
Animals, Fatty Liver, Insulin, Insulin Resistance, Male, Receptor, Insulin, Signal Transduction, Oligonucleotides, Antisense, Rats, Sprague-Dawley, Lipid Metabolism, Rats, Protein Kinase C-epsilon

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