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Author Spotlight: Investigating the Impact of Nutrition on Mouse Brain Function and Metabolic Disorders
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Hypothalamic glial cells isolated by MACS reveal that microglia and astrocytes induce hypothalamic inflammation via
Mariko Sugiyama1, Ryoichi Banno2, Hiroshi Yaginuma1
1Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8560, Japan.
Abstract:
Glial cells can mediate hypothalamic inflammatory processes induced in response to a high-fat diet (HFD). We used magnetic-activated cell sorting (MACS) to isolate microglia and astrocytes from hypothalamus of mice fed HFD and examined changes in expression of inflammation-related cytokines and markers related to glial cell activation status. Hypothalamus from male C57BL6 mice fed a chow diet (chow) or HFD for 1, 3, or 28 days were collected and microglia and astrocytes were isolated by MACS. After confirming cell viability by fluorescence activated cell sorting, mRNA expression levels of inflammation-related cytokines and markers of glial cell activation status were examined by qRT-PCR, which revealed that both glial cell types isolated by MACS retained specificity. On day 3 of HFD, both CD86 and TNFα mRNA expression was significantly increased in microglia relative to the chow group. In astrocytes, TNFα mRNA expression levels were similar between the chow and HFD groups on day 3, but anti-inflammatory cytokine IL-10 levels were significantly increased. On day 7 of HFD, TNFα expression in microglia decreased to levels comparable to the chow group while that in astrocytes remained unchanged. On day 28 of HFD, TNFα levels were significantly increased in both microglia and astrocytes, which had increased mRNA expression of CD86 and MAO-B, respectively. For both glial cell types, results for TNFα expression assessed by RT-PCR and immunohistochemical analysis were similar. These results indicate that the role of microglia and astrocytes in hypothalamic inflammation under HFD conditions changed with time and these changes were accompanied by changes in the activation status of glial cells. Our data suggest that early after initiating HFD, hypothalamic astrocytes suppress diet-induced inflammation at least in part by secreting IL-10, whereas continued HFD feeding impairs this suppressive function such that both microglia and astrocytes promote hypothalamic inflammation.
Insights
High-fat diets (HFD) trigger hypothalamic inflammation mediated by glial cells. Initially, astrocytes suppress inflammation via IL-10, but prolonged HFD causes both microglia and astrocytes to promote inflammation.
Area of Science:
- Neuroscience
- Immunology
- Metabolism
Background:
- Glial cells, including microglia and astrocytes, play a role in hypothalamic inflammation.
- High-fat diets (HFD) can induce inflammatory responses in the hypothalamus.
Purpose of the Study:
- To investigate the dynamic changes in microglia and astrocytes within the hypothalamus during HFD-induced inflammation.
- To examine the expression of inflammation-related cytokines and glial activation markers over time in response to HFD.
Main Methods:
- Isolation of microglia and astrocytes from mouse hypothalamus using magnetic-activated cell sorting (MACS).
- Analysis of mRNA expression levels of cytokines (TNFα, IL-10) and glial activation markers (CD86, MAO-B) via qRT-PCR.
- Confirmation of glial cell viability and specificity post-isolation.
Main Results:
- Early HFD (day 3) showed increased TNFα and CD86 in microglia, and increased IL-10 in astrocytes.
- Later HFD (day 28) revealed elevated TNFα in both microglia and astrocytes, with increased CD86 in microglia and MAO-B in astrocytes.
- RT-PCR and immunohistochemistry results for TNFα expression were consistent across both glial cell types.
Conclusions:
- Hypothalamic glial cell roles in inflammation evolve over time during HFD exposure.
- Astrocytes initially exert an anti-inflammatory effect via IL-10, but this function is impaired with sustained HFD.
- Both microglia and astrocytes contribute to hypothalamic inflammation under chronic HFD conditions.
