Anti-inflammatory role of Leptin in glial cells through p38 MAPK pathway inhibition.

BACKGROUND: In the present work, we studied the modulatory effect of Leptin (Lep) against pro-inflammatory cytokines, tumour necrosis factor-alpha (TNFα), interleukin 1-beta (IL1ß) and interferon-gamma (IFNγ), in primary glial cell cultures. METHODS: Glial cultures were treated with pro-inflammatory cytokines (TNFα, 20ng/ml; IL1ß, 20ng/ml; IFNγ 20ng/ml). Cells were pre-treated with Lep 500nM, 1h prior to cytokine treatment. NO released from glial cells was determined using the Griess reaction. Cell viability was determined by the MTT method. Protein expression was determined by western blot. RESULTS: Pre-treatment with 500nM Lep produced an inhibitory effect on inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production after glial cells exposure to pro-inflammatory cytokines. Anti-inflammatory effect can be related to a decrease in P38 MAP Kinase (MAPK) pathway activity. Treatment of glial cell cultures with Lep also reduced the intrinsic apoptotic pathway (cytochrome c release and caspase-3 activation). CONCLUSIONS: We suggest that Lep would act as an anti-inflammatory factor in glial cells exposed to pro-inflammatory cytokines, exerting its function on p38 MAPK pathway and reducing NO production.

Molecular links between early energy metabolism alterations and Alzheimer's disease.

Recent studies suggest that the neurobiology of Alzheimer's disease (AD) pathology could not be explained solely by an increase in beta-amyloid levels. In fact, success with potential therapeutic drugs that inhibit the generation of beta amyloid has been low. Therefore, due to therapeutic failure in recent years, the scientists are looking for alternative hypotheses to explain the causes of the disease and the cognitive loss. Accordingly, alternative hypothesis propose a link between AD and peripheral metabolic alteration. Then, we review in depth changes related to insulin signalling and energy metabolism in the context of the APPSwe/PS1dE9 (APP/PS1) mice model of AD. We show an integrated view of the changes that occur in the early stages of the amyloidogenic process in the APP/PS1 double transgenic mice model. These early changes affect several key metabolic processes related to glucose uptake and insulin signalling, cellular energy homeostasis, mitochondrial biogenesis and increased Tau phosphorylation by kinase molecules like mTOR and Cdk5.

The role of leptin in the sporadic form of Alzheimer's disease. Interactions with the adipokines amylin, ghrelin and the pituitary hormone prolactin.

Leptin (Lep) is emerging as a pivotal molecule involved in both the early events and the terminal phases of Alzheimer's disease (AD). In the canonical pathway, Lep acts as an anorexigenic factor via its effects on hypothalamic nucleus. However, additional functions of Lep in the hippocampus and cortex have been unravelled in recent years. Early events in the sporadic form of AD likely involve cellular level alterations which can have an effect on food intake and metabolism. Thus, AD can be conceivably interpreted as a multiorgan pathology that not only results in a dramatic neuronal loss in brain areas such as the hippocampus and the cortex (ultimately leading to a significant cognitive impairment) but as a disease which also affects body-weight homeostasis. According to this view, body-weight control disruptions are to be expected in both the early- and late-stage AD, concomitant with changes in serum Lep content, alterations in Lep transport across the blood-brain barrier (BBB) and Lep receptor-related signalling abnormalities. Lep is a member of the adipokine family of molecules, while the Lep receptor belongs to the class I cytokine receptors. Since cellular response to adipokine signalling can be either potentiated or diminished as a result of specific ligand-receptor interactions, Lep interactions with other members of the adipokine family including amylin, ghrelin and hormones such as prolactin require further investigation. In this review, we provide a general perspective on the functions of Lep in the brain, with a particular focus on the sporadic AD.

Metabolic basis of sporadic Alzeimer's disease. role of hormones related to energy metabolism.

The more common sporadic form of Alzheimer disease (SAD) and the metabolic syndrome are two highly prevalent pathological conditions of Western society due to incorrect diet, lifestyle, and vascular risk factors. Due to the increasing aging of populations, prevalence of AD in western industrialized countries will rise in the near future and, thus, new knowledge in the area of molecular biology and epigenetics will probably help to reverse the neurodegenerative process. Recent data have suggested metabolic syndrome as an independent risk factor for SAD. Furthermore, biological plausibility for this relationship has been framed within the metabolic cognitive syndrome concept, and some authors designed SAD as a brain diabetes or diabetes 3. Then, impaired signaling of insulin and from some adipokines involved in the so called adipoinsular axis, like leptin, ghrelin or amylin could give a metabolic basis to explain the origin and progression of SAD. Thus, dipokines like leptin, ghrelin and amylin, or their mimetic compounds, could contribuite to inhibit apoptosis and inflammation processes and, thus, generate protective responses in the nervous system. Moreover, these adipokines might promote the activation of a cognitive process which may retard or even partially reverse selected aspects of Alzheimer's disease or ageing memory loss.

Neuroprotective and anti-ageing role of leptin.

Leptin (Lep), an adipose-derived hormone, exerts very important functions in the body mainly on energy storage and availability. The physiological effects of Lep controlling the body weight and suppressing appetite are mediated by the long form of Lep receptor in the hypothalamus. Lep receptor activates several downstream molecules involved in key pathways related to cell survival such as STAT3, PI3K, MAPK, AMPK, CDK5 and GSK3ß. Collectively, these pathways act in a coordinated manner and form a network that is fully involved in Lep physiological response. Although the major interest in Lep is related to its role in the regulation of energy balance, and since resistance to Lep affects is the primary risk factor for obesity, the interest on their effects on brain cognition and neuroprotection is increasing. Thus, Lep and Lep mimetic compounds now await and deserve systematic exploration as the orchestrator of protective responses in the nervous system. Moreover, Lep might promote the activation of a cognitive process that may retard or even partially reverse selected aspects of Alzheimer's disease or ageing memory loss.