Long-Term Over-Expression of Neuropeptide Y in Hypothalamic Paraventricular Nucleus Contributes to Adipose Tissue Insulin Resistance Partly via the Y5 Receptor
May
Long-Term Over-Expression of Neuropeptide Y in Hypothalamic Paraventricular Nucleus Contributes to Adipose Tissue Insulin Resistance Partly via the Y5 Receptor
Min Long 0 1 2
Jiyin Zhou 0 1 2
Dandan Li 0 1 2
Lu Zheng 0 1 2
Zihui Xu 0 1 2
Shiwen Zhou 0 1 2
0 1 Department of Endocrinology, Xinqiao Hospital, Third Military Medical University , Chongqing, 400037 , P.R. China , 2 Base for Drug Clinical Trial, Xinqiao Hospital, Third Military Medical University , Chongqing, 400037 , P.R. China , 3 Department of hepatobiliary surgery, Xinqiao Hospital, Third Military Medical University , Chongqing, 400037 , P.R. China
1 Data Availability Statement: All relevant data are within the paper
2 Academic Editor: Zane Andrews, Monash University , AUSTRALIA
Intracerebroventricular injection and overexpression of Neuropeptide Y (NPY) in the paraventricular nucleus (PVN) has been shown to induce obesity and glucose metabolism disorder in rodents; however, the underlying mechanisms are still unclear. The aim of this study was to investigate the mechanism contributing to glucose metabolic disturbance induced by NPY. Recombinant lentiviral NPY vectors were injected into the PVN of rats fed a high fat (HFD) or low-fat diet. 8 weeks later, in vivo intravenous glucose tolerance tests and euglycemic-hyperinsulinemic clamp revealed that insulin resistance of adipose tissue were induced by NPY overexpression with or without HFD. NPY increased food intake, but did not change blood glucose, glycated hemoglobin A1c (HbA1c) or lipid levels. However, NPY decreased the expression of pGSK3, PI3K p85 and pAKTSer473in adipose tissue of rats. In vitro, 3T3L1 adipocytes were treated with NPY, NPY Y1 and Y5 receptor antagonists. Glucose consumption and 2-deoxy-D-[3H] glucose uptake were partly inhibited by NPY, while a decrease in PI3K-AKT pathway signaling and a decreased expression of pGSK3 and pGSK3 were observed. Nevertheless, a Y5 receptor antagonist (L-152,804) reversed the effects of NPY on glucose uptake and consumption. These data suggest that long-term over-expression of NPY in PVN contributes to the establishment of adipose tissue insulin resistance, at least partly via the Y5 Receptor.
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Competing Interests: The authors have declared
that no competing interests exist.
Neuropeptide Y (NPY) is one of the most common peptides in the brain and is an abundant
neurotransmitter in the peripheral sympathetic nervous system (SNS). NPY has been shown to
play a role in energy metabolism, appetite regulation, cardiac rhythm, blood pressure, smooth
muscle contraction and relaxation [1]. Cumulative evidence also suggests that NPY acts as a
metabolic signal that may contribute to obesity, hyperinsulinemia, and hyperglycemia [2, 3].
Intracerebroventricular injection of NPY and overexpression of NPY in the paraventricular
nucleus (PVN) of the hypothalamus, for example, have been shown to temporarily increase food
intake and promote insulin release [4, 5].
The activity of NPY in cellular metabolism appears to be mediated through its ability to
bind the transmembrane domain G protein coupled receptors NPY Y1Y5 [6]. These receptors
are found in a broad array of tissues including those involved in metabolism, like adipose tissue
and liver. There is evidence suggesting that NPY influences metabolic function in peripheral
tissue mostly via Y1 and Y5 receptor signaling [7]. However, in a stress-induced obesity model,
NPY induction in fat correlated with insulin resistance that could be attenuated by blockage of
the Y2 receptor [8]. The mechanism by which NPY contributes to insulin resistance in adipose
tissue, therefore, is not well understood.
In this study we investigated the molecular mechanisms of NPY that contribute to
peripheral insulin resistance. Our hypothesis was that NPY contributes to peripheral insulin resistance
in adipose tissue via the Y5 receptor. To test this hypothesis, we created an insulin resistant in
vivo model by injecting NPY in the PVN of the hypothalamus in rats. Eight weeks after
injection, euglycemic-hyperinsulinemic clamp and intravenous glucose tolerance tests confirmed
that the rats had developed insulin resistance in adipose tissue. As the main glucose
metabolism pathway, PI3K-AKT signaling changes in adipose tissue were assessed in our study.
Glycogen synthase kinase 3 (GSK3) and were also detected, since there is evidence suggesting
that GSK3 contributes to the induction by insulin resistance independently of insulin receptor
signaling or PI3K-AKT activity [9]. NPY Y1 and Y5 receptor antagonists were used to unravel
the mechanism disorders induced by NPY in adipocytes.
Methods and Procedures
Reagents and antibodies
Dexamethasone, 3-isobutyl-1-methylxanthine (IBMX), bovine insulin, human NPY, and
2-deoxy-D-glucose were purchased from Sigma-Aldrich (St Louis, MO, USA). The Y5 receptor
antagonist L-152,804 was purchased from Tocris Bioscience (Bristol, UK). The Y1 receptor
antagonist BIBP-3226 (Diphenylacetyl-D- (...truncated)