High Fat Diet and Inflammation – Modulation of Haptoglobin Level in Rat Brain

Abstract

Obesity and dietary fats are well known risk factors for the pathogenesis of neurodegenerative diseases. The analysis of specific markers, whose brain level can be affected by diet, might contribute to unveil the intersection between inflammation/obesity and neurodegeneration. Haptoglobin (Hpt) is an acute phase protein, which acts as antioxidant by binding free haemoglobin (Hb), thus neutralizing its pro-oxidative action. We previously demonstrated that Hpt plays critical functions in brain, modulating cholesterol trafficking in neuroblastoma cell lines, beta-amyloid (Aβ) uptake by astrocyte, and limiting Aβ toxicity on these cells. A major aim of this study was to evaluate whether a long term (12 or 24 weeks) high-fat diet (HFD) influences Hpt and Hb expression in rat hippocampus. We also assessed the development of obesity-induced inflammation by measuring hippocampal level of TNF-alpha, and the extent of protein oxidation by titrating nitro-tyrosine (N-Tyr). Hpt concentration was lower (p < 0.001) in hippocampus of HFD rats than in control animals, both in the 12 and in the 24 weeks fed groups. HFD was also associated in hippocampus with the increase of Hb level (p < 0.01), inflammation and protein oxidative modification, as evidenced by the increase in the concentration of TNF-alpha and nitro-tyrosine. In fact, TNF-alpha concentration was higher in rats receiving HFD for 12 (p < 0.01) or 24 weeks (p < 0.001) compared to those receiving the control diet. N-Tyr concentration was more elevated in hippocampus of HFD than in control rats in both 12 weeks (p = 0.04) and 24 weeks groups (p = 0.01), and a positive correlation between Hb and N-Tyr concentration was found in each group. Finally, we found that the treatment of the human glioblastoma-astrocytoma cell line U-87 MG with cholesterol and fatty acids, such as palmitic and linoleic acid, significantly impairs (p < 0.001) Hpt secretion in the extracellular compartment. We hypothesize that the HFD-dependent decrease of Hpt in hippocampus, as associated with Hb increase, might enhance the oxidative stress induced by free Hb. Altogether our data, identifying Hpt as a molecule modulated in the brain by dietary fats, may represent one of the first steps in the comprehension of the molecular mechanisms underlying the diet-related effects in the nervous system.

Adipose Tissue and Brain Metabolic Responses to Western Diet—Is There a Similarity between the Two?

“…Samples were diluted (plasma = 1:9000-1:70,000; adipose tissue, 1:1000-1:30,000; frontal cortex and hippocampus, 1:1000-1:30,000) with coating buffer (7 mM Na 2 CO 3 , 17 mM NaHCO 3 , 1.5 mM NaN 3 , pH 9.6), and aliquots (50 µL) were then incubated in the wells of a microtitre plate (Immuno MaxiSorp; overnight, 4 • C). Washing and blocking were carried out as previously reported [57], then, the wells were incubated (1 h, 37 • C) with 50 µL of rabbit anti-human haptoglobin (1:500 in 130 mM NaCl, 20 mM Tris-HCl, 0.05% Tween, pH 7.4, containing 0.25% BSA), followed by 60 µl of HRP-coniugated secondary antibody (1:5000 dilution). Peroxidase-catalyzed color development from o-phenylenediamine was measured at 492 nm.…”

Conjugated linoleic acid prevents age-dependent neurodegeneration in a mouse model of neuropsychiatric lupus via the activation of an adaptive response

“…PC concentration was evaluated in serum, brain, and liver extracts by using a standard procedure (28) and it was expressed as nmol of PC mg 1 protein. N-Tyr content in brain homogenates was quantified by ELISA according to a published protocol (29). Brain samples were diluted (1:1500, 1:3000, 1:6000), and data were expressed as Optical Density mg 1 of protein.…”

Neurodegeneration Alters Metabolic Profile and Sirt 1 Signaling in High-Fat-Induced Obese Mice

“…High concentrations of this compound leads to an excitotoxic process by excessive increase of glutamate release, influx of calcium ions, and neuronal death [11] as well as an inflammation process and mitochondrial dysfunction with impaired energy metabolism and oxidative stress [16,17]. This model is considered a chemical model of HD because it mimics the deficits observed in the early stages of neurodegeneration observed in the disease [18,19], even though no genetic mutation occurs.…”

“…Indeed, 10 % of the cases of dementia worldwide may be attributable to the metabolic disturbances associated with MS. Thus, one could speculate that metabolic change is associated with neurodegenerative processes [7][8][9][10][11].…”