Uncoupling the mechanisms of obesity and hypertension by targeting hypothalamic IKK-β and NF-κB

Hypothalamic programming of systemic ageing involving IKK-β, NF-κB and GnRH

Ageing is a result of gradual and overall functional deteriorations across the body; however, it is unknown whether an individual tissue primarily works to mediate the ageing progress and control lifespan. Here we show that the hypothalamus is important for the development of whole-body ageing in mice, and that the underlying basis involves hypothalamic immunity mediated by IκB kinase-β (IKK-β), nuclear factor κB (NF-κB) and related microglia-neuron immune crosstalk. Several interventional models were developed showing that ageing retardation and lifespan extension are achieved in mice by preventing ageing-related hypothalamic or brain IKK-β and NF-κB activation. Mechanistic studies further revealed that IKK-β and NF-κB inhibit gonadotropin-releasing hormone (GnRH) to mediate ageing-related hypothalamic GnRH decline, and GnRH treatment amends ageing-impaired neurogenesis and decelerates ageing. In conclusion, the hypothalamus has a programmatic role in ageing development via immune-neuroendocrine integration, and immune inhibition or GnRH restoration in the hypothalamus/brain represent two potential strategies for optimizing lifespan and combating ageing-related health problems.

Functional foods and nutraceuticals as therapeutic tools for the treatment of diet-related diseases

In Western societies, the incidence of diet-related diseases is progressively increasing due to greater availability of hypercaloric food and a sedentary lifestyle. Obesity, diabetes, atherosclerosis, and neurodegeneration are major diet-related pathologies that share a common pathogenic denominator of low-grade inflammation. Functional foods and nutraceuticals may represent a novel therapeutic approach to prevent or attenuate diet-related disease in view of their ability to exert anti-inflammatory responses. In particular, activation of intestinal T regulatory cells and homeostatic regulation of the gut microbiota have the potential to reduce low-grade inflammation in diet-related diseases. In this review, clinical applications of polyphenol-rich functional foods and nutraceuticals in postprandial inflammation, obesity, and ageing will be discussed. We have placed special emphasis on polyphenols since they are broadly distributed in plants.

Cross-talk between SIRT1 and p66Shc in vascular diseases

Accumulating evidence indicates that oxidative stress can occur through overproduction of reactive oxygen species (ROS) and/or reduced anti-oxidant potentials under pathophysiological conditions and plays an important role in the development of cardiovascular diseases (CVDs). Adapter protein p66Shc has the property to directly stimulate mitochondrial ROS generation by an oxidoreductase activity. A growing body of evidence implies that p66Shc plays a critical role in the pathophysiology of age-related vascular diseases. Silent mating type information regulator 2 homolog 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent class III histone deacetylase (HDAC), has also been implicated in protection against vascular aging and age-related vascular diseases. Recently, we demonstrated that SIRT1 protects blood vessels from hyperglycemia-induced endothelial dysfunction through a novel mechanism involving the downregulation of p66Shc expression. In this review, we discuss the cross-talk between these two longevity genes as a mechanism of preventing vascular diseases by involving anti-oxidative stress responses and inhibiting endothelial senescence.

Neuroimmune communication in hypertension and obesity: a new therapeutic angle?

Hypertension is an epidemic health concern and a major risk factor for the development of cardiovascular disease. Although there are available treatment strategies for hypertension, numerous hypertensive patients do not have their clinical symptoms under control and it is imperative that new avenues to treat or prevent high blood pressure in these patients are developed. It is well established that increases in sympathetic nervous system (SNS) outflow and enhanced renin-angiotensin system (RAS) activity are common features of hypertension and various pathological conditions that predispose individuals to hypertension. More recently, hypertension has also become recognized as an immune condition and accumulating evidence suggests that interactions between the RAS, SNS and immune systems play a role in blood pressure regulation. This review summarizes what is known about the interconnections between the RAS, SNS and immune systems in the neural regulation of blood pressure. Based on the reviewed studies, a model for RAS/neuroimmune interactions during hypertension is proposed and the therapeutic potential of targeting RAS/neuroimmune interactions in hypertensive patients is discussed. Special emphasis is placed on the applicability of the proposed model to obesity-related hypertension.

Hypothalamic neuronal toll-like receptor 2 protects against age-induced obesity

Toll-like receptors (TLRs) are traditionally associated with immune-mediated host defense. Here, we ascribe a novel extra-immune, hypothalamic-associated function to TLR2, a TLR-family member known to recognize lipid components, in the protection against obesity. We found that TLR2-deficient mice exhibited mature-onset obesity and susceptibility to high-fat diet (HFD)-induced weight gain, via modulation of food intake. Age-related obesity was still evident in chimeric mice, carrying comparable TLR2⁺ immune cells, suggesting a non-hematopoietic-related involvement of this receptor. TLR2 was up-regulated with age or HFD in pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus, a brain area participating in central-metabolic regulation, possibly modulating the hypothalamic-anorexigenic peptide, α-melanocyte-stimulating hormone (α-MSH). Direct activation of TLR2 in a hypothalamic-neuronal cell-line via its known ligands, further supports its capacity to mediate non-immune related metabolic regulation. Thus, our findings identify TLR2 expressed by hypothalamic neurons as a potential novel regulator of age-related weight gain and energy expenditure.

The brain subfornical organ mediates leptin-induced increases in renal sympathetic activity but not its metabolic effects

The adipocyte-derived hormone leptin acts within the central nervous system to decrease food intake and body weight and to increase renal and thermogenic brown adipose tissue sympathetic nerve activity (SNA). Previous studies have focused on hypothalamic brain regions, although recent findings have identified leptin receptors (ObR) in a distributed brain network, including the circumventricular subfornical organ (SFO), a forebrain region devoid of a blood-brain barrier. We tested the hypothesis that ObR in the SFO are functionally linked to leptin-induced decreases in food intake and body weight and increases in SNA. SFO-targeted microinjections of an adenovirus encoding Cre-recombinase in ObR(flox/flox) mice resulted in selective ablation of ObR in the SFO. Interestingly, deletion of ObR in the SFO did not influence the decreases in either food intake or body weight in response to daily systemic or cerebroventricular administration of leptin. In line with these findings, reduction in SFO ObR did not attenuate leptin-mediated increases in thermogenic brown adipose tissue SNA. In contrast, increases in renal SNA induced by systemic or cerebroventricular administration of leptin were abolished in mice with SFO-targeted deletion of ObR. These results demonstrate that ObR in the SFO play an important role in leptin-induced renal sympathoexcitation, but not in the body weight, food intake, or brown adipose tissue SNA thermogenic effects of leptin. These findings highlight the concept of a distributed brain network of leptin action and illustrate that brain regions, including the SFO, can mediate distinct cardiovascular and metabolic responses to leptin.

Neuroinflammation and neurodegeneration in overnutrition-induced diseases

Overnutrition-induced diseases such as obesity and type 2 diabetes (T2D) involve neural dysregulation of metabolic physiology. Recently, interdisciplinary research in neuroscience and immunology has linked overnutrition to a non-classical onset of inflammation in the brain, particularly in the hypothalamus. This neuroinflammation impairs central regulatory pathways of energy balance and nutrient metabolism, and leads to obesity, diabetes, and cardiovascular complications. This review describes recent findings on the roles of overnutrition-induced hypothalamic inflammation in neurodegeneration and defective adult neurogenesis, as well as in impaired neural stem cell regeneration, and their relevance to obesity and related diseases. In addition, commonalities in terms of neuroinflammation between neurodegenerative diseases and overnutrition-induced metabolic diseases are discussed. Targeting neuroinflammation and neurodegeneration will provide promising approaches for treating obesity and other overnutrition-related diseases.

Neuroinflammation in overnutrition-induced diseases

Inflammation is a biological response mounted by the immune system against dangerous assaults that threaten the integrity and normal physiology of an organism. During the past decades, cross-disciplinary research from immunology and endocrinology has much broadened this knowledge by demonstrating that chronic conditions of nutritional excess constitute an independent category of inflammatory activators, and the resulting chronic and low-grade inflammation is an important characteristic of overnutrition-induced diseases. A large body of research has demonstrated that these diseases are pathogenically associated with the local, negative actions of inflammation in peripheral tissues predominantly including the liver, muscle, and fat. In this research background, more recent research has advanced to a new level, with the important discoveries showing that overnutrition-induced inflammation occurs in the brain and thus plays a broad and leadership role in overnutrition-induced diseases. While much more research establishments are expected in this emerging and quickly expanding research, the appreciated understandings have been mainly based on proinflammatory IKKβ/NF-κB pathway and related molecules in the hypothalamus. In this chapter, the author focuses on describing IKKβ/NF-κB-induced neural inflammation in the context of overnutrition-induced metabolic inflammation and especially the central roles of this neural inflammation in the development of a spectrum of overnutrition-related diseases.

A novel major histocompatibility complex locus confers the risk of premature coronary artery disease in a Chinese Han population

Several novel loci have been proved to be associated with coronary artery disease and/or myocardial infarction risk by genome-wide association studies, however, the available coronary artery disease risk variants explain only a small proportion of the predicted genetic heritability of the disease. Recently, a novel coronary artery disease locus on chromosome 6p21.3 in the major histocompatibility complex was identified in an European population. We hereby investigated whether this single nucleotide polymorphisms (rs3869109) confers the risk of premature coronary artery disease in a Chinese Han population. A total of 422 patients were studied including 210 cases with coronary stenosis ≥50% or previous myocardial infarction (male <55 years and female <65 years) and 212 controls without documented coronary artery disease. Ligase detection reaction was performed to detect rs3869109. The 3 genotypes AA, AG, and GG were present in rs3869109. There were significant differences between the control and premature coronary artery disease groups in the frequencies of the rs3869109 variants and alleles (all P < 0.05). The distribution of 3 genotypes and alleles at rs3869109 does not differ between women and men (all P > 0.05). There was a significant association between rs3869109 genotypes and the severity of premature coronary artery disease (P = 0.038). Multivariate logistic regression showed that carriers with AG and GG genotypes at rs3869109 have a higher risk of premature coronary artery disease than carriers of AA genotype (odds ratio [OR] 1.997, 95% CI: 1.166-3.419, P = 0.012; OR 1.695, 95% CI: 1.044-2.752, P = 0.033; respectively). Our results indicate that the rs3869109 variants are associated with premature coronary artery disease in a Chinese Han population, suggesting this genetic risk marker is useful in early coronary artery disease risk prediction.

Obesity-related hypertension and its remission following gastric bypass surgery - a review of the mechanisms and predictive factors

It is well established that hypertension and obesity appear to be associated. The exact mechanism by which they are linked is unclear and remains a topic of a great deal of research. Current NICE guidelines recommend that patients with a BMI in excess of 35 kg/m(2) should be considered for bariatric surgery if they have a concomitant obesity-associated condition, of which hypertension is one. The commonest bariatric procedure in the UK is the Roux-en-Y gastric bypass, which has been shown to result in long-standing remission of hypertension in up to 93% of patients. This paper summarizes the existing literature on the main theories as to how obesity leads to hypertension as well as the literature concerning the effects of gastric bypass surgery on hypertension.

Brown rice and its component, γ-oryzanol, attenuate the preference for high-fat diet by decreasing hypothalamic endoplasmic reticulum stress in mice

Brown rice is known to improve glucose intolerance and prevent the onset of diabetes. However, the underlying mechanisms remain obscure. In the current study, we investigated the effect of brown rice and its major component, γ-oryzanol (Orz), on feeding behavior and fuel homeostasis in mice. When mice were allowed free access to a brown rice-containing chow diet (CD) and a high-fat diet (HFD), they significantly preferred CD to HFD. To reduce hypothalamic endoplasmic reticulum (ER) stress on an HFD, mice were administered with 4-phenylbutyric acid, a chemical chaperone, which caused them to prefer the CD. Notably, oral administration of Orz, a mixture of major bioactive components in brown rice, also improved glucose intolerance and attenuated hypothalamic ER stress in mice fed the HFD. In murine primary neuronal cells, Orz attenuated the tunicamycin-induced ER stress. In luciferase reporter assays in human embryonic kidney 293 cells, Orz suppressed the activation of ER stress-responsive cis-acting elements and unfolded protein response element, suggesting that Orz acts as a chemical chaperone in viable cells. Collectively, the current study is the first demonstration that brown rice and Orz improve glucose metabolism, reduce hypothalamic ER stress, and, consequently, attenuate the preference for dietary fat in mice fed an HFD.

Epidemiological and experimental links between air pollution and type 2 diabetes

There is increasing evidence suggesting links between exposure to environmental toxins and susceptibility to type 2 diabetes mellitus (DM). In this review, we summarize the experimental evidence to support this association that has been noted in many epidemiologic studies. Inflammation in response to particulate matter (PM(2.5)) exposure in air pollution represents a common mechanism that may interact with other pro-inflammatory influences in diet and life style to modulate susceptibility to cardiometabolic diseases. The role of innate immune cytokines released from macrophages in the lung is well known. In addition, chemokine triggers in response to air-pollution exposure may mediate a cellular response from the bone marrow/spleen through toll-like receptors (TLRs) and Nucleotide Oligomerization Domain receptors (NLRs) pathways to mediate inflammatory response in organs. Emerging data also seem to support a role for PM(2.5) exposure in endoplasmic reticulum stress-induced apoptosis and in brown adipose tissue dysfunction. Decreased expression of UCP1 in brown adipose tissue may account for reduced thermogenesis providing another link between PM(2.5) and insulin resistance. The implications of an experimental link between air-pollution exposure and type 2 DM are profound as air pollution is a pervasive risk factor throughout the world and even modest alleviation in exposure may provide substantial public health benefits.

Systemic immune activation shapes stroke outcome

Stroke is a major cause of morbidity and mortality, and activation of the immune system can impact on stroke outcome. Although the majority of research has focused on the role of the immune system after stroke there is increasing evidence to suggest that inflammation and immune activation prior to brain injury can influence stroke risk and outcome. With the high prevalence of co-morbidities in the Western world such as obesity, hypertension and diabetes, pre-existing chronic 'low-grade' systemic inflammation has become a customary characteristic of stroke pathophysiology that needs to be considered in the search for new therapies. The importance of the immune system in stroke has been demonstrated in a number of ways, both experimentally and in the clinical setting. This review will focus on the effect of immune activation arising from systemic inflammatory conditions and infection, how it affects the incidence and outcomes of stroke, and the possible underlying mechanisms involved. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

Molecular mechanisms of metabolic reprogramming in proliferating cells: implications for T-cell-mediated immunity

To engage in proliferation, cells need to increase their biomass and replicate their genome. This process presents a substantial bioenergetic challenge: proliferating cells must increase ATP production and acquire or synthesize raw materials, including lipids, proteins and nucleic acids. To do so, proliferating cells actively reprogramme their intracellular metabolism from catabolic mitochondrial oxidative phosphorylation (OXPHOS) to glycolysis and other anabolic pathways. This metabolic reprogramming, which directs nutrient uptake and metabolism during cell activation and proliferation, is under the control of specific signal transduction pathways. The underlying molecular mechanisms of cell metabolism reprogramming and their relevance to physiology and disease are currently under intense study. Several reports have uncovered the mechanisms of metabolic reprogramming that drive high rates of cell proliferation in cancer. Some recent studies have elucidated the physiological role of metabolic reprogramming during T-cell activation, differentiation and trafficking, which are potentially relevant to inflammatory disorders. This review describes the impact of metabolic reprogramming on the pathogenesis of cancer and the physiology of T-cell-mediated immune responses, with an emphasis on the phosphatidyl inositol 3-kinase-serine/threonine kinase-mammalian target of rapamycin pathway and the recently discovered metabolic processes regulated by nuclear factor-κB. These discoveries will hopefully translate into a better understanding of the role of metabolic reprogramming as a key regulator of T-cell-mediated immune responses and offer novel, immune-based therapeutic approaches.

IKKβ/NF-κB disrupts adult hypothalamic neural stem cells to mediate a neurodegenerative mechanism of dietary obesity and pre-diabetes

Adult neural stem cells (NSCs) are known to exist in a few regions of the brain; however, the entity and physiological/disease relevance of adult hypothalamic NSCs (htNSCs) remain unclear. This work shows that adult htNSCs are multipotent and predominantly present in the mediobasal hypothalamus of adult mice. Chronic high-fat-diet feeding led to not only depletion but also neurogenic impairment of htNSCs associated with IKKβ/NF-κB activation. In vitro htNSC models demonstrated that their survival and neurogenesis markedly decreased on IKKβ/NF-κB activation but increased on IKKβ/NF-κB inhibition, mechanistically mediated by IKKβ/NF-κB-controlled apoptosis and Notch signalling. Mouse studies revealed that htNSC-specific IKKβ/NF-κB activation led to depletion and impaired neuronal differentiation of htNSCs, and ultimately the development of obesity and pre-diabetes. In conclusion, adult htNSCs are important for the central regulation of metabolic physiology, and IKKβ/NF-κB-mediated impairment of adult htNSCs is a critical neurodegenerative mechanism for obesity and related diabetes.

Chronic intermittent hypoxia induces atherosclerosis by NF-κB-dependent mechanisms

Chronic intermittent hypoxia (CIH) causes atherosclerosis in mice fed a high cholesterol diet (HCD). The mechanisms by which CIH promotes atherosclerosis are incompletely understood. This study defined the mechanistic role of NF-κB pathway in CIH+HCD induced atherosclerosis. Wild type (WT) and mice deficient in the p50 subunit of NF-κB (p50-KO) were fed normal chow diet (ND) or HCD, and exposed to sham or CIH. Atherosclerotic lesions on the en face aortic preparation and cross-sections of aortic root were examined. In WT mice, neither CIH nor HCD exposure alone caused, but CIH+HCD caused evident atherosclerotic lesions on both preparations after 20weeks of exposure. WT mice on ND and exposed to CIH for 35.6weeks did not develop atherosclerotic lesions. P50 gene deletion diminished CIH+HCD induced NF-κB activation and abolished CIH+HCD induced atherosclerosis. P50 gene deletion inhibited vascular wall inflammation, reduced hepatic TNF-α level, attenuated the elevation in serum cholesterol level and diminished macrophage foam cell formation induced by CIH+HCD exposure. These results demonstrate that inhibition of NF-κB activation abrogates the activation of three major atherogenic mechanisms associated with an abolition of CIH+HCD induced atherosclerosis. NF-κB may be a central common pathway through which CIH+HCD exposure activates multiple atherogenic mechanisms, leading to atherosclerosis.

Regulation of cell death and autophagy by IKK and NF-κB: critical mechanisms in immune function and cancer

The cellular response to survive or to undergo death is fundamental to the benefit of the organism, and errors in this process can lead to autoimmunity and cancer. The transcription factor nuclear factor κB (NF-κB) functions to block cell death through transcriptional induction of genes encoding anti-apoptotic and antioxidant proteins. This is essential for survival of activated cells of the immune system and for cells undergoing a DNA damage response. In Ras-transformed cells and tumors as well as other cancers, NF-κB functions to suppress apoptosis--a hallmark of cancer. Critical prosurvival roles for inhibitor of NF-κB kinase (IKK) family members, including IKKε and TBK1, have been reported, which are both NF-κB-dependent and -independent. While the roles of NF-κB in promoting cell survival in lymphocytes and in cancers is relatively clear, evidence has been presented that NF-κB can promote cell death in particular contexts. Recently, IKK was shown to play a critical role in the induction of autophagy, a metabolic response typically associated with cell survival but which can lead to cell death. This review provides an historical perspective, along with new findings, regarding the roles of the IKK and NF-κB pathways in regulating cell survival.

Inflammatory cause of metabolic syndrome via brain stress and NF-κB

Metabolic syndrome, a network of medical disorders that greatly increase the risk for developing metabolic and cardiovascular diseases, has reached epidemic levels in many areas of today's world. Despite this alarming medicare situation, scientific understandings on the root mechanisms of metabolic syndrome are still limited, and such insufficient knowledge contributes to the relative lack of effective treatments or preventions for related diseases. Recent interdisciplinary studies from neuroendocrinology and neuroimmunology fields have revealed that overnutrition can trigger intracellular stresses to cause inflammatory changes mediated by molecules that control innate immunity. This type of nutrition-related molecular inflammation in the central nervous system, particularly in the hypothalamus, can form a common pathogenic basis for the induction of various metabolic syndrome components such as obesity, insulin resistance, and hypertension. Proinflammatory NF-κB pathway has been revealed as a key molecular system for pathologic induction of brain inflammation, which translates overnutrition and resulting intracellular stresses into central neuroendocrine and neural dysregulations of energy, glucose, and cardiovascular homeostasis, collectively leading to metabolic syndrome. This article reviews recent research advances in the neural mechanisms of metabolic syndrome and related diseases from the perspective of pathogenic induction by intracellular stresses and NF-κB pathway of the brain.

Interleukin-1 mediates neuroinflammatory changes associated with diet-induced atherosclerosis

BACKGROUND

Systemic inflammation contributes to brain pathology in cerebrovascular disease through mechanisms that are poorly understood.

METHODS AND RESULTS

Here we show that atherosclerosis, a major systemic inflammatory disease, is associated with severe cerebrovascular inflammation in mice and that this effect is mediated by the proinflammatory cytokine interleukin-1 (IL-1). Apolipoprotein E-deficient mice fed Paigen or Western diets develop vascular inflammation, microglial activation, and leukocyte recruitment in the brain, which are absent in apolipoprotein E-deficient mice crossed with IL-1 type 1 receptor-deficient mice. Systemic neutralization of IL-1β with an anti-IL-1β antibody reversed aortic plaque formation (by 34% after a Paigen and 45% after a Western diet) and reduced inflammatory cytokine expression in peripheral organs. Central, lipid accumulation-associated leukocyte infiltration into the choroid plexus was reversed by IL-1β antibody administration. Animals fed a Western diet showed 57% lower vascular inflammation in the brain than that of mice fed a Paigen diet, and this was reduced further by 24% after IL-1β antibody administration.

CONCLUSIONS

These results indicate that IL-1 is a key driver of systemically mediated cerebrovascular inflammation and that interventions against IL-1β could be therapeutically useful in atherosclerosis, dementia, or stroke. (J Am Heart Assoc. 2012;1:e002006 doi: 10.1161/JAHA.112.002006.).

Obesity and type 2 diabetes: which patients are at risk?

An estimated 72.5 million American adults are obese, and the growing US obesity epidemic is responsible for substantial increase in morbidity and mortality, as well as increased health care costs. Obesity results from a combination of personal and societal factors, but is often viewed as a character flaw rather than a medical condition. This leads to stigma and discrimination towards obese individuals and decreases the likelihood of effective intervention. Conditions related to obesity are increasingly common, such as metabolic syndrome, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), all of which indicate high risk for type 2 diabetes (T2DM). This paper reviews the progression from obesity to diabetes, identifying physiological changes that occur along this path as well as opportunities for patient identification and disease prevention. Patients with prediabetes (defined as having IFG, IGT or both) and/or metabolic syndrome require interventions designed to preserve insulin sensitivity and β-cell function, both of which start to deteriorate prior to T2DM diagnosis. Lifestyle modification, including both healthy eating choices and increased physical activity, is essential for weight management and diabetes prevention. Although sustained weight loss is often considered by patients and physicians as being impossible to achieve, effective interventions do exist. Specifically, the Diabetes Prevention Program (DPP) and programs modelled along its parameters have shown repeated successes, even with long-term maintenance. Recent setbacks in the development of medications for weight loss further stress the importance of lifestyle management. By viewing obesity as a metabolic disorder rather than a personal weakness, we can work with patients to address this increasingly prevalent condition and improve long-term health outcomes.

Hypothalamic inflammation: a double-edged sword to nutritional diseases

The hypothalamus is one of the master regulators of various physiological processes, including energy balance and nutrient metabolism. These regulatory functions are mediated by discrete hypothalamic regions that integrate metabolic sensing with neuroendocrine and neural controls of systemic physiology. Neurons and nonneuronal cells in these hypothalamic regions act supportively to execute metabolic regulations. Under conditions of brain and hypothalamic inflammation, which may result from overnutrition-induced intracellular stresses or disease-associated systemic inflammatory factors, extracellular and intracellular environments of hypothalamic cells are disrupted, leading to central metabolic dysregulations and various diseases. Recent research has begun to elucidate the effects of hypothalamic inflammation in causing diverse components of metabolic syndrome leading to diabetes and cardiovascular disease. These new understandings have provocatively expanded previous knowledge on the cachectic roles of brain inflammatory response in diseases, such as infections and cancers. This review describes the molecular and cellular characteristics of hypothalamic inflammation in metabolic syndrome and related diseases as opposed to cachectic diseases, and also discusses concepts and potential applications of inhibiting central/hypothalamic inflammation to treat nutritional diseases.

Glycine normalizes hepatic triglyceride-rich VLDL secretion by triggering the CNS in high-fat fed rats

RATIONALE

Dysregulation of hepatic triglyceride (TG)-rich very low-density lipoproteins (VLDL-TG) in obesity and type 2 diabetes contributes to the dyslipidemia that leads to cardiovascular morbidity. The central nervous system (CNS), particularly the hypothalamus, regulates hepatic lipid metabolism. Although the underlying neurocircuitry remains elusive, glycine has been documented to enhance CNS N-methyl-d-aspartate (NMDA) receptor-mediated transmission.

OBJECTIVE

We tested the hypothesis that glycine regulates hepatic VLDL-TG secretion by potentiating NMDA receptor-mediated transmission in the CNS.

METHODS AND RESULTS

Using 10-hour fasted male Sprague-Dawley rats implanted with stereotaxic cannulae into an extrahypothalamic region termed the dorsal vagal complex (DVC) and vascular catheters to enable direct DVC infusion and blood sampling, respectively, the rate of hepatic VLDL-TG secretion was measured following tyloxapol (an inhibitor of lipoprotein lipase) injection. Direct DVC infusion of glycine lowered VLDL-TG secretion, whereas NMDA receptor blocker MK-801 fully negated glycine's effect. NR1 subunit of NMDA receptor antagonist 7-chlorokynurenic acid, adenoviral injection of NR1 short hairpin RNA (shRNA), and hepatic vagotomy also nullified glycine's effect. Finally, DVC glycine normalized the hypersecretion of VLDL-TG induced by high-fat feeding.

CONCLUSIONS

Molecular and pharmacological inhibition of the NR1-containing NMDA receptors in the DVC negated the ability of glycine to inhibit hepatic secretion of VLDL-TG in vivo. Importantly, the hypersecretion of VLDL-TG from the liver induced by a model of high-fat feeding was restored by the hepatic lipid control of CNS glycine sensing. These findings collectively suggest that glycine or glycine analogues may have therapeutic benefits in lowering plasma lipid levels in diabetes and obesity by triggering the CNS.

Acidic polysaccharide extracts from Gastrodia Rhizomes suppress the atherosclerosis risk index through inhibition of the serum cholesterol composition in Sprague Dawley rats fed a high-fat diet

Obesity is associated with a broad spectrum of cardio-metabolic disturbances, including atherosclerosis and cardiovascular disease (CDV). A high-fat diet has been shown to cause an elevation of the plasma cholesterol levels in humans, and the control of serum cholesterol has been demonstrated to be important in the prevention of CVD and atherosclerosis. The aims of this study were to demonstrate that crude and acidic polysaccharide extracts from Gastrodia rhizomes suppress atherosclerosis through the regulation of serum lipids in Sprague Dawley (SD) rats fed a high-fat diet. We examined the concentrations of serum lipids, including total cholesterol, triglycerides, high-density lipoproteins (HDL) cholesterol, and low-density lipoproteins (LDL) cholesterol, in SD rats fed a high-fat diet and evaluated the atherogenic index. Here, we show that both crude and acidic polysaccharide extracts from Gastrodia rhizomes inhibited the total cholesterol and LDL levels. Moreover, there was a significantly suppressed atherosclerosis risk due to the acidic polysaccharide extract from Gastrodia rhizome. Taken together, our results suggested that acidic polysaccharide extracts from Gastrodia rhizomes might be beneficial for lowering the incidence of CVD and atherosclerosis by reducing the de novo synthesis of total cholesterol and the LDL levels.

Hypothalamic JNK1 and IKKβ activation and impaired early postnatal glucose metabolism after maternal perinatal high-fat feeding

Hypothalamic inflammation has been demonstrated to be an important mechanism in the pathogenesis of obesity-induced type 2 diabetes mellitus. Feeding pregnant and lactating rodents a diet rich in saturated fatty acids has consistently been shown to predispose the offspring for the development of obesity and impaired glucose metabolism. However, hypothalamic inflammation in the offspring has not been addressed as a potential underlying mechanism. In this study, virgin female C57BL/6 mice received high-fat feeding starting at conception until weaning of the offspring at postnatal d 21. The offspring developed increased body weight, body fat content, and serum leptin concentrations during the nursing period. Analysis of hypothalamic tissue of the offspring at postnatal d 21 showed up-regulation of several members of the toll-like receptor 4 signaling cascade and subsequent activation of c-Jun N-terminal kinase 1 and IκB kinase-β inflammatory pathways. Interestingly, glucose tolerance testing in the offspring revealed signs of impaired glucose tolerance along with increased hepatic expression of the key gluconeogenic enzyme phosphoenolpyruvate carboxykinase. In addition, significantly increased hepatic and pancreatic PGC1α expression suggests a role for sympathetic innervation in mediating the effects of hypothalamic inflammation to the periphery. Taken together, our data indicate an important role for hypothalamic inflammation in the early pathogenesis of glucose intolerance after maternal perinatal high-fat feeding.

Sirtuins mediate mammalian metabolic responses to nutrient availability

Metabolic diseases are an increasing threat in developed countries. Dysregulation of metabolic pathways, caused by imbalances in energy homeostasis, leads to obesity, diabetes and cardiovascular disease with devastating results for both individuals and societies. Sirtuins, a conserved family of NAD(+)-dependent deacetylase enzymes found in many species, regulate various metabolic pathways and have emerged as important sensors of energy status in mammals. The nuclear sirtuins, SIRT1, SIRT6 and SIRT7, regulate the activity of key transcription factors and cofactors of numerous metabolic pathways in almost all tissues by linking nutrient signals with the cellular responses to energy demands. The mitochondrial sirtuins, SIRT3, SIRT4 and SIRT5, regulate the activity of important mitochondrial enzymes and drive metabolic cycles in response to fasting and calorie restriction. Accumulating evidence indicates that sirtuins can be beneficial in the prevention of metabolic and age-related diseases and suggests that they can be pharmacologically activated to ameliorate such diseases. This Review describes the latest advances in the understanding of the function of sirtuins as regulators of mammalian metabolism and focuses on the role of these enzymes as mediators of nutrient availability.

Epidemiologic and Molecular Pathophysiology of Chronic Opioid Dependence and the Place of Naltrexone Extended-Release Formulations in its Clinical Management

Naltrexone implants and depot injections (NI) are a novel form of treatment for opiate dependence (OD). Major questions relate to their absolute and relative efficacy and safety. Opportunely, six recent clinical trial data from several continents have uniformly provided dramatic evidence of the potent, dose-related and highly significant efficacy of NI, with minimal or manageable accompanying toxicity and safety concerns. The opiate-free lifestyle is attained significantly more often with NI adjusted O.R. = 6.00 (95% C.I. 3.86–9.50), P < 10⁻¹⁰. Other drug use and drug craving are also rapidly reduced. The optimum manner in which to commence NI remains to be established. Of particular relevance is the relative safety of NI compared to the chronic opiate agonists (COA) usually employed, as the long-term toxicity of COA is only just being elucidated. Large population-based studies have found elevated rates of cardiovascular disease, six cancers, liver and respiratory disease, and all-cause mortality in COA. Whilst opiates have been shown to trigger numerous molecular pathways, the most interesting is the demonstration that the opiate morphinan’s nucleus binds to the endotoxin groove of the TLR4-MD2 heterodimer. This has the effect of triggering a low grade endotoxaemic-like state, which over time may account for these protean clinical findings, an effect which is reversed by opiate antagonists. This emerging evidence suggests an exciting new treatment paradigm for OD and a corresponding increase in the role of NI in treatment.

Weight loss is still an essential intervention in obesity and its complications: a review

The prevalence of obesity is more than 20% in many developed countries and it increases in developing countries. Obesity is associated with metabolic disorders, cardiovascular diseases, pulmonary diseases, digestive diseases, and cancers. Although other specific treatments for these complications exist, weight loss is still an essential intervention in obesity and its complications. Therapeutic life change, behavior modification, pharmacotherapy, and surgery are major approaches to weight loss. In addition, medicine used in diabetes such as Glucagon-like peptide-1 analogues may be a new type of medicine for obesity, at least for those obese patients with diabetes.

Alteration of hypothalamic cellular dynamics in obesity

The number of people who suffer from obesity and one or more of its adverse complications is rapidly increasing. It is becoming clear that diet, exercise, and other lifestyle modifications are insufficient strategies to combat this growing problem. Greater understanding of the mechanisms controlling our desire to feed and our ability to balance energy intake with energy expenditure are key to the development of pharmacological approaches for treating obesity. Although great strides have been made in our understanding of how the hypothalamus regulates feeding and energy balance, much less is known about how obesity affects the structure of the hypothalamus. The authors of two papers in this issue of the JCI have addressed this issue by examining the effects of obesity on neurons and glia in the hypothalamus. These studies reveal that obesity may be in part due to hypothalamic injury, which leads to inflammation and reduced neurogenesis. These findings support the notion that obesity is a disease that affects multiple organs, including the brain, and that disruption of normal brain function leads to abnormal regulation of peripheral metabolism.

Common cellular and molecular mechanisms in obesity and drug addiction

The hedonic properties of food can stimulate feeding behaviour even when energy requirements have been met, contributing to weight gain and obesity. Similarly, the hedonic effects of drugs of abuse can motivate their excessive intake, culminating in addiction. Common brain substrates regulate the hedonic properties of palatable food and addictive drugs, and recent reports suggest that excessive consumption of food or drugs of abuse induces similar neuroadaptive responses in brain reward circuitries. Here, we review evidence suggesting that obesity and drug addiction may share common molecular, cellular and systems-level mechanisms.

Inflaming hypothalamic neurons raises blood pressure

Obesity and hypertension are strongly associated, and neural dysfunction has been implicated in both. The hypothalamus integrates signals regulating blood pressure and energy homeostasis. A recent paper in Nature Medicine (Purkayastha et al., 2011) suggests that obesity and hypertension are caused by inflammation in distinct hypothalamic neuronal populations.