Brain Trauma Disrupts Hepatic Lipid Metabolism: Blame It on Fructose?

SCOPE: The action of brain disorders on peripheral metabolism is poorly understood. The impact of traumatic brain injury (TBI) on peripheral organ function and how TBI effects can be influenced by the metabolic perturbation elicited by fructose ingestion are studied. METHODS AND RESULTS: It is found that TBI affects glucose metabolism and signaling proteins for insulin and growth hormone in the liver; these effects are exacerbated by fructose ingestion. Fructose, principally metabolized in the liver, potentiates the action of TBI on hepatic lipid droplet accumulation. Studies in isolated cultured hepatocytes identify GH and fructose as factors for the synthesis of lipids. The liver has a major role in the synthesis of lipids used for brain function and repair. TBI results in differentially expressed genes in the hypothalamus, primarily associated with lipid metabolism, providing cues to understand central control of peripheral alterations. Fructose-fed TBI animals have elevated levels of markers of inflammation, lipid peroxidation, and cell energy metabolism, suggesting the pro-inflammatory impact of TBI and fructose in the liver. CONCLUSION: Results reveal the impact of TBI on systemic metabolism and the aggravating action of fructose. The hypothalamic-pituitary-growth axis seems to play a major role in the regulation of the peripheral TBI pathology.

Can Diet and Physical Activity Limit Alzheimer's Disease Risk?

BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disease affecting elderly individuals at an alarming rate. It has become a global health crisis imposing tremendous social and economic burden on society. Although there is no cure for AD, it is important to identify and implement preventive strategies that may delay or prevent the symptoms, limit the burden, and improve the quality of life of those afflicted. Adequate nutrition and physical activity are the two potential lifestyle modifiable factors that have gained considerable interest for their potential in the prevention or management of this challenging disease. In this review, we discuss the beneficial effects of physical activity and adequate nutrition on minimizing the risk of developing AD. METHODS: The research question was initially formulated in a structured and explicit way. Relevant studies were identified using a wide range of scientific databases. Their potential relevance was based on the criteria for inclusion and exclusion. The quality of selected studies was subjected to a more precise quality assessment using standard tools. A detailed description of the implemented intervention and how it differed from what the control group received was outlined. The effects of intervention on measurable outcomes for the study sample were applied. RESULTS: One hundred and sixty-four references were included in the review comprising of epidemiological, longitudinal, cross-sectional, intervention and randomized controlled studies. This review highlighted the effect of various nutrient diet supplements on cognitive performance in humans as well as animals with AD and mild cognitive impairment (MCI). Moreover, the effect of physical exercise on the cognitive function in animal models with AD was outlined. CONCLUSION: The findings of this review highlight the therapeutic potential of combination of nutritionally adequate diet and physical activity in preventing or delaying the symptoms associated with AD pathology.

Resveratrol protects ß amyloid-induced oxidative damage and memory associated proteins in H19-7 hippocampal neuronal cells.

Resveratrol (trans-3, 5, 4'-trihydroxystilbene) is a polyphenolic phytoalexin known to exhibit antioxidant and neuroprotective effects in several experimental models. Amyloid ß peptide (Aß), a core component of extracellular senile plaques accumulates in the brains of patients with Alzheimer's disease and is related to the development of cognitive impairment and neuronal loss. The present study evaluates the neuroprotective action of resveratrol on Aß-induced oxidative stress and memory loss. Cultured rat hippocampal H19-7 neuronal cell line was pretreated with 75 µM of resveratrol for 2 hrs followed by 25 µM of Aß (1-40) for 24 hrs. H19-7 cells treated with Aß exhibited increased lipid peroxide levels. Enzymatic antioxidants including superoxide dismutase, catalase, glutathione reductase, and non-enzymatic antioxidants such as tocopherol, ascorbic acid and glutathione were decreased in the Aß treated group when compared to the control group. Aß treatment also increased the expression of total tau as well as phosphorylated forms of tau (CP13, S202/205; PHF1, S396/404) and decreased the expression of insulin degrading enzyme (IDE), phosphoglycogen synthase kinase 3ß involved in Aß degradation and tau hyper phosphorylation. Expression of PSD-95 and Arc proteins, essential for synaptic maturity and plasticity, was decreased by Aß treatment. Resveratrol treatment attenuated the accumulation of lipid peroxide levels, up-regulated the antioxidant activities and improved the expression of memory-associated proteins in Aß treated H19-7 cells. These findings highlight the neuroprotective effect of resveratrol in preventing Aß-induced oxidative damage and memory loss in vitro.

Mg2+/Mn2+-dependent phosphatase 1A is involved in regulating pregnane X receptor-mediated cytochrome p450 3A4 gene expression.

Variations in the expression of human pregnane X receptor (hPXR)-mediated cytochrome p450 3A4 (CYP3A4) in liver can alter therapeutic response to a variety of drugs and may lead to potential adverse drug interactions. We sought to determine whether Mg(2+)/Mn(2+)-dependent phosphatase 1A (PPM1A) regulates hPXR-mediated CYP3A4 expression. PPM1A was found to be coimmunoprecipitated with hPXR. Genetic or pharmacologic activation of PPM1A led to a significant increase in hPXR transactivation of CYP3A4 promoter activity. In contrast, knockdown of endogenous PPM1A not only attenuated hPXR transactivation, but also increased proliferation of HepG2 human liver carcinoma cells, suggesting that PPM1A expression levels regulate hPXR, and that PPM1A expression is regulated in a proliferation-dependent manner. Indeed, PPM1A expression and hPXR transactivation were found to be significantly reduced in subconfluent HepG2 cells compared with confluent HepG2 cells, suggesting that both PPM1A expression and hPXR-mediated CYP3A4 expression may be downregulated in proliferating livers. Elevated PPM1A levels led to attenuation of hPXR inhibition by tumor necrosis factor-α and cyclin-dependent kinase-2, which are known to be upregulated and essential during liver regeneration. In mouse regenerating livers, similar to subconfluent HepG2 cells, expression of both PPM1A and the mouse PXR target gene cyp3a11 was found to be downregulated. Our results show that PPM1A can positively regulate PXR activity by counteracting PXR inhibitory signaling pathways that play a major role in liver regeneration. These results implicate a novel role for PPM1A in regulating hPXR-mediated CYP3A4 expression in hepatocytes and may explain a mechanism for CYP3A repression in regenerating livers.

Neuroprotective effects of resveratrol in Alzheimer disease pathology.

Alzheimer's disease is a chronic neurodegenerative disorder characterized by a progressive loss of cognitive and behavioral abilities. Extracellular senile plaques and intracellular neurofibrillary tangles are hallmarks of AD. Researchers aim to analyze the molecular mechanisms underlying AD pathogenesis; however, the therapeutic options available to treat this disease are inadequate. In the past few years, several studies have reported interesting insights about the neuroprotective properties of the polyphenolic compound resveratrol (3, 5, 4'-trihydroxy-trans-stilbene) when used with in vitro and in vivo models of AD. The aim of this review is to focus on the neuroprotective and antioxidant effects of resveratrol on AD and its multiple potential mechanisms of action. In addition, because the naturally occurring forms of resveratrol have a very limited half-life in plasma, a description of potential analogs aimed at increasing the bioavailability in plasma is also discussed.

Resveratrol protects the brain of obese mice from oxidative damage.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a polyphenolic phytoalexin that exerts cardioprotective, neuroprotective, and antioxidant effects. Recently it has been shown that obesity is associated with an increase in cerebral oxidative stress levels, which may enhance neurodegeneration. The present study evaluates the neuroprotective action of resveratrol in brain of obese (ob/ob) mice. Resveratrol was administered orally at the dose of 25 mg kg(-1) body weight daily for three weeks to lean and obese mice. Resveratrol had no effect on body weight or blood glucose levels in obese mice. Lipid peroxides were significantly increased in brain of obese mice. The enzymatic antioxidants superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and nonenzymatic antioxidants tocopherol, ascorbic acid, and glutathione were decreased in obese mice brain. Administration of resveratrol decreased lipid peroxide levels and upregulated the antioxidant activities in obese mice brain. Our findings indicate a neuroprotective effect of resveratrol by preventing oxidative damage in brain tissue of obese mice.

Nerve growth factor receptor TrkA, a new receptor in insulin signaling pathway in PC12 cells.

TrkA is a cell surface transmembrane receptor tyrosine kinase for nerve growth factor (NGF). TrkA has an NPXY motif and kinase regulatory loop similar to insulin receptor (INSR) suggesting that NGF→TrkA signaling might overlap with insulin→INSR signaling. During insulin or NGF stimulation TrkA, insulin receptor substrate-1 (IRS-1), INSR (and presumably other proteins) forms a complex in PC12 cells. In PC12 cells, tyrosine phosphorylation of INSR and IRS-1 is dependent upon the functional TrkA kinase domain. Moreover, expression of TrkA kinase-inactive mutant blocked the activation of Akt and Erk5 in response to insulin or NGF. Based on these data, we propose that TrkA participates in insulin signaling pathway in PC12 cells.

Noncoding RNAs in Neurodegenerative Diseases.

Noncoding RNAs are widely known for their various essential roles in the development of central nervous system. It involves neurogenesis, neural stem cells generation, maintenance and maturation, neurotransmission, neural network plasticity, formation of synapses, and even brain aging and DNA damage responses. In this review, we will discuss the biogenesis of microRNA, various functions of noncoding RNA's specifically microRNAs (miRNAs) that act as the chief regulators of gene expression, and focus in particular on misregulation of miRNAs which leads to several neurodegenerative diseases as well as its therapeutic outcome. Recent evidences has shown that miRNAs expression levels are changed in patients with neurodegenerative diseases; hence, miRNA can be used as a potential diagnostic biomarker and serve as an effective therapeutic tool in overcoming various neurodegenerative disease processes.