The online version of this article (https://doi.org/10.1186/s12974-017-1046-8) contains supplementary material, which is available to authorized users.
The consumption of large amounts of dietary fats activates an inflammatory response in the hypothalamus, damaging key neurons involved in the regulation of caloric intake and energy expenditure. It is currently unknown why the mediobasal hypothalamus is the main target of diet-induced brain inflammation. We hypothesized that dietary fats can damage the median eminence blood/spinal fluid interface.
Swiss mice were fed on a high-fat diet, and molecular and structural studies were performed employing real-time PCR, immunoblot, immunofluorescence, transmission electron microscopy, and metabolic measurements.
The consumption of a high fat diet was sufficient to increase the expression of inflammatory cytokines and brain-derived neurotrophic factor in the median eminence, preceding changes in other circumventricular regions. In addition, it led to an early loss of the structural organization of the median eminence β1-tanycytes. This was accompanied by an increase in the hypothalamic expression of brain-derived neurotrophic factor. The immunoneutralization of brain-derived neurotrophic factor worsened diet-induced functional damage of the median eminence blood/spinal fluid interface, increased diet-induced hypothalamic inflammation, and increased body mass gain.
The median eminence/spinal fluid interface is affected at the functional and structural levels early after introduction of a high-fat diet. Brain-derived neurotrophic factor provides an early protection against damage, which is lost upon a persisting consumption of large amounts of dietary fats.
Additional file 7: Figure S1. Evaluation of the impact of a high-fat diet on the expression of claudin-5 in the median eminence or mice. Six-week-old male Swiss mice were randomly divided to feed on chow or a high-fat diet for 1, 2, or 4 weeks; at the end of the respective experimental periods, the mice were used in experiments. Median eminence was eLaser microdissected for real-time PCR determination of claudin-5. Expression of target transcripts is presented as relative to paired controls fed chow (line in y = 1). In all conditions, n = 4; *p < 0.05 vs. respective control. W, week. (PDF 140 kb)12974_2017_1046_MOESM7_ESM.pdf
Additional file 8: Figure S2. Evaluation of the blood-brain barrier integrity. The protocol employed for evaluation of BBB integrity is shown in Fig. 2a. Confocal microscopy analysis was employed for determining FITC-dextran endogenous fluorescence in the regions of the vascular organ of lamina terminalis (OVLT), subfornical organ (SFO), and subcomissural organ (SCO); in all acquisitions, the same settings of the microscope were employed (laser 488, wavelength = 405, %laser = 20%, gain = 1015, offset = − 0.3799). The fluorescence in the distinct regions was determined using an ImageJ software and presented as relative to control. N = 4. (PDF 141 kb)
Additional file 9: Figure S3. Immunofluorescence staining of markers of the median eminence blood-brain barrier and markers of glial cells. Immunofluorescence staining using primary antibodies against IGFBP2 (green), GFAP (red) (A), and IBA1 (red) (B). Specimens were obtained from bregma-anteroposterior − 2.06 to − 2.18. The images are representative of three independent experiments. 3v, third ventricle; IGFBP2, insulin-like growth factor-binding protein 2; GFAP, glial fibrillary acidic protein; IBA1, ionized calcium-binding adapter molecule-1. (PDF 17432 kb)12974_2017_1046_MOESM9_ESM.pdf
Additional file 10: Figure S4. Evaluation of median eminence blood-brain barrier integrity in mice treated with an anti-BDNF immunoneutralizing antibody. The protocol employed for evaluation of BBB integrity is shown in Fig. 2a. Confocal microscopy analysis was employed for determining FITC-dextran endogenous fluorescence in the region of the median eminence in all acquisitions; the same settings of the microscope were employed (laser 488, wavelength = 405, %laser = 20%, gain = 1015, offset = − 0.3799). The fluorescence intensity was determined using an ImageJ software and presented as relative to control. N = 6. ABDNF, antibody-anti-BDNF; BDNF, brain-derived neurotrophic factor; CTR, control; HFD, high-fat diet; IGG, non-immune antiserum. (PDF 2780 kb)
Milanski M, Degasperi G, Coope A, Morari J, Denis R, Cintra DE, Tsukumo DM, Anhe G, Amaral ME, Takahashi HK, et al. Saturated fatty acids produce an inflammatory response predominantly through the activation of TLR4 signaling in hypothalamus: implications for the pathogenesis of obesity. J Neurosci. 2009;29:359–70. CrossRefPubMed
Sharma HS, Johanson CE. Intracerebroventricularly administered neurotrophins attenuate blood cerebrospinal fluid barrier breakdown and brain pathology following whole-body hyperthermia: an experimental study in the rat using biochemical and morphological approaches. Ann N Y Acad Sci. 2007;1122:112–29. CrossRefPubMed
Ainge H, Thompson C, Ozanne SE, Rooney KB. A systematic review on animal models of maternal high fat feeding and offspring glycaemic control. Int J Obes. 2011;35:325–35. CrossRef
Velloso LA, Schwartz MW. Altered hypothalamic function in diet-induced obesity. Int J Obes. 2011;35:1455–65. CrossRef
Dalvi PS, Chalmers JA, Luo V, Han DY, Wellhauser L, Liu Y, Tran DQ, Castel J, Luquet S, Wheeler MB, Belsham DD. High fat induces acute and chronic inflammation in the hypothalamus: effect of high-fat diet, palmitate and TNF-alpha on appetite-regulating NPY neurons. Int J Obes. 2017;41:149–58. CrossRef
Prada PO, Zecchin HG, Gasparetti AL, Torsoni MA, Ueno M, Hirata AE, Corezola do Amaral ME, Hoer NF, Boschero AC, Saad MJ. Western diet modulates insulin signaling, c-Jun N-terminal kinase activity, and insulin receptor substrate-1ser307 phosphorylation in a tissue-specific fashion. Endocrinology. 2005;146:1576–87. CrossRefPubMed
Langlet F, Levin BE, Luquet S, Mazzone M, Messina A, Dunn-Meynell AA, Balland E, Lacombe A, Mazur D, Carmeliet P, et al. Tanycytic VEGF-A boosts blood-hypothalamus barrier plasticity and access of metabolic signals to the arcuate nucleus in response to fasting. Cell Metab. 2013;17:607–17. CrossRefPubMedPubMedCentral
- Dietary fats promote functional and structural changes in the median eminence blood/spinal fluid interface—the protective role for BDNF
Albina F. Ramalho
Nathalia R. Dragano
Licio A. Velloso
Eliana P. Araujo
- BioMed Central