Central Nervous System Neuropeptide Y Signaling Modulates VLDL Triglyceride Secretion

  1. John M. Stafford1,
  2. Fang Yu2,
  3. Richard Printz12,
  4. Alyssa H. Hasty2,
  5. Larry L. Swift3 and
  6. Kevin D. Niswender412
  1. 1Division of Diabetes, Endocrinology, and Metabolism, Department of Internal Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee
  2. 2Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
  3. 3Department of Pathology, Vanderbilt University School of Medicine, Nashville, Tennessee
  4. 4Tennessee Valley Healthcare System, Nashville, Tennessee
  1. Corresponding author: Kevin Niswender, 7435G Medical Research Building IV, Nashville, TN 37232-4705. E-mail: kevin.niswender{at}vanderbilt.edu

Abstract

OBJECTIVE—Elevated triglyceride (TG) is the major plasma lipid abnormality in obese and diabetic patients and contributes to cardiovascular morbidity in these disorders. We sought to identify novel mechanisms leading to hypertriglyceridemia. Resistance to negative feedback signals from adipose tissue in key central nervous system (CNS) energy homeostatic circuits contributes to the development of obesity. Because triglycerides both represent the largest energy depot in the body and are elevated in both the plasma and adipose in obesity and diabetes, we hypothesized that the same neural circuits that regulate energy balance also regulate the secretion of TGs into plasma.

RESEARCH DESIGN AND METHODS—In normal fasting rats, the TG secretion rate was estimated by serial blood sampling after intravascular tyloxapol pretreatment. Neuropeptide Y (NPY) signaling in the CNS was modulated by intracerebroventricular injection of NPY, receptor antagonist, and receptor agonist.

RESULTS—A single intracerebroventricular injection of NPY increased TG secretion by 2.5-fold in the absence of food intake, and this was determined to be VLDL by fast performance liquid chromatography (FPLC). This effect was recapitulated by activating NPY signaling in downstream neurons with an NPY-Y5 receptor agonist. An NPY-Y1 receptor antagonist decreased the elevated TGs in the form of VLDL secretion rate by 50% compared with vehicle. Increased TG secretion was due to increased secretion of VLDL particles, rather than secretion of larger particles, because apolipoprotein B100 was elevated in FPLC fractions corresponding to VLDL.

CONCLUSIONS—We find that a key neuropeptide system involved in energy homeostasis in the CNS exerts control over VLDL-TG secretion into the bloodstream.

Footnotes

  • Published ahead of print at http://diabetes.diabetesjournals.org on 10 March 2008. DOI: 10.2337/db07-1702.

    The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

    • Accepted February 24, 2008.
    • Received December 3, 2007.
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  1. Diabetes vol. 57 no. 6 1482-1490
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