Beneficial Effects of Metformin and/or Salicylate on Palmitate- or TNFα-Induced Neuroinflammatory Marker and Neuropeptide Gene Regulation in Immortalized NPY/AgRP Neurons

PLoS One. 2016 Nov 28;11(11):e0166973. doi: 10.1371/journal.pone.0166973. eCollection 2016.

Abstract

Neuropeptide Y (NPY)/Agouti-related peptide (AgRP)-expressing neurons in the hypothalamus induce feeding and decrease energy expenditure. With consumption of a diet high in fat, there is an increase in circulating saturated free fatty acids, including palmitate, leading to the development of neuroinflammation and secretion of cytokines, such as TNFα, and in turn activation of the canonical IKKβ/NFκB cascade. We describe a model of palmitate- and TNFα-induced neuroinflammation in a functionally characterized, immortalized NPY/AgRP-expressing cell model, mHypoE-46, to study whether the anti-diabetic metformin alone or in combination with the anti-inflammatory agent salicylate can ameliorate these detrimental effects. Treatment with palmitate increased mRNA expression of feeding peptides Npy and Agrp, and inflammatory cytokines Tnfa and Il-6, whereas treatment with TNFα increased mRNA expression of Npy, Nfkb, Ikba, Tnfa, and Il-6. The effects of metformin and/or sodium salicylate on these genes were assessed. Metformin increased phosphorylation of AMPK and S6K, while sodium salicylate increased phospho-AMPK and decreased phospho-S6K, but neither had any effect on phospho-ERK, -JNK or -p38 in the mHypoE-46 NPY/AgRP neurons. Furthermore, we utilized a pre-treatment and/or co-treatment paradigm to model potential clinical regimens. We determined co-treatment with metformin or sodium salicylate alone was successful in alleviating changes observed in feeding peptide mRNA regulation, whereas a preventative pre-treatment with metformin and sodium salicylate together was able to alleviate palmitate- and TNFα-induced induction of NPY and/or AgRP mRNA levels. These results highlight important differences in reactive versus preventative treatments on palmitate- and TNFα-induced neuroinflammation in NPY/AgRP neurons.

MeSH terms

  • Agouti-Related Protein / genetics
  • Agouti-Related Protein / metabolism*
  • Animals
  • Anti-Inflammatory Agents, Non-Steroidal / pharmacology
  • Biomarkers / metabolism
  • Cells, Cultured
  • Embryo, Mammalian / cytology
  • Embryo, Mammalian / drug effects
  • Embryo, Mammalian / metabolism
  • Female
  • Gene Expression Regulation / drug effects*
  • Hypoglycemic Agents / pharmacology
  • Hypothalamus / drug effects
  • Hypothalamus / metabolism
  • Hypothalamus / pathology
  • Inflammation / chemically induced
  • Inflammation / metabolism
  • Male
  • Metformin / pharmacology*
  • Mice
  • Mice, Inbred BALB C
  • Neurons / drug effects*
  • Neurons / metabolism
  • Neurons / pathology
  • Neuropeptide Y / genetics
  • Neuropeptide Y / metabolism*
  • Palmitates / pharmacology*
  • Phosphorylation / drug effects
  • Salicylates / pharmacology*
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • Agouti-Related Protein
  • Anti-Inflammatory Agents, Non-Steroidal
  • Biomarkers
  • Hypoglycemic Agents
  • Neuropeptide Y
  • Palmitates
  • Salicylates
  • Tumor Necrosis Factor-alpha
  • Metformin

Grants and funding

This work was supported by Canadian Institutes for Health Research (CIHR) and Canada Foundation for Innovation and Canada Research Chairs Program (DDB). WY was supported by an Endocrine Society Summer Studentship, EHR was supported by a Banting and Best Diabetes Centre (BBDC) Summer Studentship, and BCW was supported by a Banting and Best Diabetes Centre (BBDC) Graduate Studentship.