Glucose intolerance after chronic stress is related with downregulated PPAR-γ in adipose tissue

Complement C5a Receptor Signaling Alters Stress Responsiveness and Modulates Microglia Following Chronic Stress Exposure

Background

Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5-cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown.

Methods

To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters.

Results

Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice.

Conclusions

C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions.

A hamster model for stress-induced weight gain

This review addresses the translational relevance of animal models of stress and their effects on body weight. In humans, stress, whether chronic or acute, has often been associated with increased food intake and weight gain. In view of the current obesity epidemic, this phenomenon is especially relevant. Such observations contrast with reports with commonly used laboratory animals, especially rats and mice. In these species, it is common to find individuals gaining less weight under stress, even with potent social stressors. However, there are laboratory species that present increased appetite and weight gain under stress, such as golden hamsters. Furthermore, these animals also include metabolic and behavioral similarities with humans, including hoarding behavior which is also enhanced under stress. Consequently, we propose that our comparative perspective provides useful insights for future research on the development of obesity in humans as a consequence of chronic stress exposure.

Individual differences in cephalic-phase insulin response are stable over time and predict glucose tolerance in mice

Oral stimulation by glucose triggers a rapid insulin response, which enhances glucose tolerance. This so-called cephalic-phase insulin response (CPIR) has been documented in many mammal species, but its functional properties are poorly characterized. Here, we studied CPIR in lean C57BL/6 mice. Experiment 1 asked whether the large individual differences in CPIR magnitude were real or reflected experimental noise. We measured CPIR magnitude four times across a period of 30 days in the same mice. The individual differences in CPIR magnitude were remarkably stable across the repeated trials, indicating that they were real. Experiment 2 examined the functional consequences of individual differences in CPIR magnitude. We found that higher CPIR magnitudes contributed to larger postprandial insulin responses and greater glucose tolerance. Experiment 3 examined the observation that the CPIRs in Experiments 1 and 2 were associated with a rapid rise in blood glucose. To determine whether the rapid rise in blood glucose caused the CPIRs, we asked whether mice would generate a CPIR if we prevented cephalic-phase stimulation of beta cells by either delivering the glucose intragastrically or blocking parasympathetic input to the pancreatic beta cells with atropine. The mice subjected to these treatments experienced a rapid rise in blood glucose, but they did not exhibit a CPIR. This indicates that it was the oral glucose stimulation, and not the rise in blood glucose, that triggered the CPIRs in Experiments 1 and 2. We conclude that (i) individual differences in CPIR magnitude are stable over time; (ii) CPIR magnitudes predicted postprandial insulin responses and glucose tolerance; and (iii) a rapid rise in blood glucose is not sufficient to trigger a CPIR in mice.

Chronic cortisol elevation restricts glucose uptake but not insulin responsiveness in zebrafish skeletal muscle

Although teleosts show an elevated insulin response to hyperglycemia, the circulating glucose levels are not normalized as rapidly as in mammals. While this may suggest a lack of target tissue insulin responsiveness, the underlying mechanisms are unclear. We investigated whether changes in skeletal muscle insulin sensitivity and glucose uptake underlie the cortisol-mediated elevated blood glucose levels. Adult zebrafish (Danio rerio) were exposed to water-borne cortisol for 3 days followed by an intraperitoneal injection of glucose with or without insulin. Cortisol treatment resulted in a temporal delay in the reduction in blood glucose levels, and this corresponded with a reduced glucose uptake capacity and lower glycogen content in the skeletal muscle. The transcript abundance of slc2a1b (which encodes for GLUT1b) and a suite of genes encoding enzymes involved in muscle glycogenesis and glycolysis were upregulated in the cortisol group. Both the control and cortisol groups showed higher whole body insulin expression in response to blood glucose elevation, which also resulted in enhanced insulin-stimulated phosphorylation of AKT in the skeletal muscle. The insulin-mediated phosphorylation of S6 kinase was lower in the cortisol group. Altogether, chronic cortisol stimulation restricts glucose uptake and enhances the glycolytic capacity without affecting insulin responsiveness in zebrafish skeletal muscle.

Xiaoyaosan ameliorates depressive-like behavior and susceptibility to glucose intolerance in rat: involvement of LepR-STAT3/PI3K pathway in hypothalamic arcuate nucleus

BACKGROUND

Accumulating evidence has demonstrated that arcuate nucleus (ARC) of the hypothalamus is likely responsible for the close association between chronic stress, depression, and diabetes. Xiaoyaosan (XYS), a Chinese herbal formula, remarkably improves depressive-like behavior and glucose intolerance, but the mechanism remains unclear. Leptin receptor (LepR) regulates energy expenditure and depression by mediating the action of leptin on the ARC. Therefore, we hypothesized that XYS may regulate depressive-like behavior and glucose intolerance via the leptin and its cascade LepR-STAT3/PI3K pathway in the ARC.

METHODS

A rat model of depressive-like behavior and susceptibility to glucose intolerance was induced by exposure to chronic unpredictable mild stress (CUMS) for six weeks. XYS (2.224 g/kg) was orally gavaged for six weeks, and fluoxetine (2.0 mg/kg) was administrated to the positive control group. Depressive-like behaviors were assessed using the open field test (OFT), sucrose preference test (SPT) and forced swim test (FST). Fasting blood glucose (FBG) and oral glucose tolerance test (OGTT) were performed to evaluate the effects of XYS on blood glucose. Peripheral leptin and blood lipids were detected using enzyme-linked immunosorbent assay and an automatic biochemical analyzer, respectively. The effects of XYS on the LepR-STAT3/PI3K pathway were detected by quantitative real-time PCR and western blotting.

RESULTS

XYS ameliorated CUMS-induced depressive-like behaviors and elevated blood glucose. XYS improved the food intake but have no significant effects on the body weight. Peripheral leptin and its central receptor were also suppressed by XYS, accompanied by the downregulation of JAK2/STAT3 and PI3K/AKT pathway in the ARC. Additionally, XYS increased AGRP and NPY expression but inhibited POMC in the ARC.

CONCLUSIONS

XYS improves depressive-like behaviors and susceptibility to glucose intolerance induced by CUMS, which may be achieved by the downregulation of the LepR-STAT3/PI3K signaling pathway in the ARC.

Stress-induced body weight loss and improvements in cardiometabolic risk factors do not translate to improved myocardial ischemic tolerance in western diet-fed mice

Although both diet-induced obesity and psychological stress are recognized as significant independent contributors to cardiometabolic and behavioral disorders, our understanding of how these two disorders interact and influence cardiometabolic risk and myocardial ischemic tolerance is limited. The aim of this study was to assess the combined effects of an obesogenic diet and psychological stress on cardiometabolic risk factors (body weight, dyslipidemia, insulin sensitivity) and postischemic cardiovascular outcomes. C57Bl/6J mice (n = 48) were subject to a combination of 22 weeks of western diet (WD) feeding and chronic restraint stress (CRS) for the last 4 weeks. Metabolic and behavioral changes were assessed using glucose tolerance tests and open field tests (OFTs), respectively. After 22 weeks, cardiac function and ischemic tolerance were assessed in Langendorff perfused hearts. WD feeding increased body weight and worsened blood lipids and insulin sensitivity. WD-fed mice also exhibited reduced exploratory behavior within the OFT. CRS reduced body weight and increased locomotion in both dietary groups and had differential effects on fasting glucose metabolism in the two dietary groups while not impacting non-fasting insulin. Although the WD only marginally reduced reperfusion left ventricular developed pressure recovery, CRS worsened reperfusion diastolic dysfunction in both dietary groups. Interestingly, despite WD+CRS animals exhibiting improved cardiometabolic parameters compared to the WD group, these changes did not translate to marked improvements to postischemic cardiac outcomes. In conclusion, in this study, combined WD feeding and CRS did not act synergistically to worsen cardiometabolic risk factors but instead improved them. Despite these cardiometabolic improvements, WD+CRS increased reperfusion end diastolic pressure which may be indicative of worsened ischemia/reperfusion injury.

Glucoregulation and coping behavior after chronic stress in rats: Sex differences across the lifespan

The purpose of the current study was to determine how biological sex shapes behavioral coping and metabolic health across the lifespan after chronic stress. We hypothesized that examining chronic stress-induced behavioral and endocrine outcomes would reveal sex differences in the biological basis of susceptibility. During late adolescence, male and female Sprague-Dawley rats experienced chronic variable stress (CVS). Following completion of CVS, all rats experienced a forced swim test (FST) followed 3 days later by a fasted glucose tolerance test (GTT). The FST was used to determine coping in response to a stressor. Endocrine metabolic function was evaluated in the GTT by measuring glucose and corticosterone, the primary rodent glucocorticoid. Rats then aged to 15 months when the FST and GTT were repeated. In young rats, chronically stressed females exhibited more passive coping and corticosterone release in the FST. Additionally, chronically stressed females had elevated corticosterone and impaired glucose clearance in the GTT. Aging affected all measurements as behavioral and endocrine outcomes were sex specific. Furthermore, regression analysis between hormonal and behavioral responses identified associations depending on sex and stress. Collectively, these data indicate increased female susceptibility to the effects of chronic stress during adolescence. Further, translational investigation of coping style and glucose homeostasis may identify biomarkers for stress-related disorders.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

In utero substrate restriction by placental insufficiency or maternal undernutrition decreases optical redox ratio in foetal perirenal fat

Intrauterine growth restriction (IUGR) can result from reduced delivery of substrates, including oxygen and glucose, during pregnancy and may be caused by either placental insufficiency or maternal undernutrition. As a consequence of IUGR, there is altered programming of adipose tissue and this can be associated with metabolic diseases later in life. We have utilised two sheep models of IUGR, placental restriction and late gestation undernutrition, to determine the metabolic effects of growth restriction on foetal perirenal adipose tissue (PAT). Two-photon microscopy was employed to obtain an optical redox ratio, which gives an indication of cell metabolism. PAT of IUGR foetuses exhibited higher metabolic activity, altered lipid droplet morphology, upregulation of cytochrome c oxidase subunit genes and decreased expression of genes involved in growth and differentiation. Our results indicate that there are adaptations in PAT of IUGR foetuses that might be protective and ensure survival in response to an IUGR insult.

The impact of chronic stress on energy metabolism

The brain is exceptionally demanding in terms of energy metabolism. Approximately 20% of the calories consumed are devoted to our cerebral faculties, with the lion's share provided in the form of glucose. The brain's stringent energy dependency requires a high degree of harmonization between the elements responsible for supplying- and metabolizing energetic substrates. However, chronic stress may jeopardize this homeostatic energy balance by disruption of critical metabolic processes. In agreement, stress-related mental disorders have been linked with perturbations in energy metabolism. Prominent stress-induced metabolic alterations include the actions of hormones, glucose uptake and mitochondrial adjustments. Importantly, fundamental stress-responsive metabolic adjustments in humans and animal models bear a striking resemblance. Here, an overview is provided of key findings, demonstrating the pervasive impact of chronic stress on energy metabolism. Furthermore, I argue that medications, aimed primarily at restoring metabolic homeostasis, may constitute a novel approach to treat mental disorders.

Food Addiction Mediates the Relationship between Perceived Stress and Body Mass Index in Taiwan Young Adults

Perceived stress is the degree of stress experienced by an individual in the face of a stressor. Studies have shown that stress affects emotions, leads to behavioral changes, and is likely to trigger physical illnesses. According to the World Health Organization (WHO), stress is classified as a health epidemic of the 21st century; in the meantime, the percentage of adults being overweight and with obesity has continued to grow after reaching 38.9% in 2016. Hence, it is unclear whether perceived stress has become a factor affecting progressive obesity and whether food addiction (FA) is an intermediate factor. The purposes of this study were to (1) investigate the FA prevalence among young adults in Taiwan, (2) understand correlations among perceived stress, FA, and the body mass index (BMI), and (3) determine the potential mediating effect of FA due to perceived stress on BMI. The study was conducted through an online questionnaire, composed of a basic data form, the Perceived Stress Scale (PSS), and the Yale Food Addiction Scale (YFAS). We received 1994 responses and analyzed 1780 valid samples. Results showed that 231 participants met the FA criteria, accounting for 12.98%. Perceived stress was positively correlated with BMI (95% confidence interval (CI) 0.013~0.088, p-value 7.8 × 10⁻³), and perceived stress was positively associated to FA (95% CI 1.099~1.154, p-value < 10⁻⁴), which was also positively correlated with BMI (95% CI 0.705~2.176, p-value 10⁻⁴). FA significantly mediated the relationship between PSS and BMI with an indirect effect size of 25.18% and 25.48% in the group that scored 31~40 on the PSS. The study concluded that among people seeking weight loss, proper stress management and screening for FA in order to apply related therapies may be an effective method for weight management.

Lipocalin 2 links inflammation and ankylosis in the clinical overlap of inflammatory bowel disease (IBD) and ankylosing spondylitis (AS)

Background

Little is known about the mechanisms underlying the clinical overlap between gut inflammation and joint ankylosis, as exemplified by the concurrence of inflammatory bowel diseases (IBD) and ankylosing spondylitis (AS). As dysbiosis may serve as a common contributor, the anti-microbial pleiotropic factor lipocalin 2 could be a potential mediator due to its roles in inflammation and bone homeostasis.

Methods

Baseline colonic pathology was conducted in the ank/ank mouse model. Serum lipocalin 2 was analyzed by ELISA, in ank/ank mutants versus C3FeB6-A/A^w-jwt/wt, in patients with concurrent AS-IBD, AS alone, IBD alone, or mechanical back pain, and in healthy controls. In the ank/ank mouse model, the expression of nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) was examined by real-time PCR. Intraperitoneal injection was done with the PPARγ agonist rosiglitazone or antagonist bisphenol A diglycidyl ether for four consecutive days. Serum levels of lipocalin 2 were examined on the sixth day.

Results

This study showed that the ank/ank mice with fully fused spines had concurrent colonic inflammation. By first using the ank/ank mouse model with progressive ankylosis and subclinical colonic inflammation, confirmed in patients with concurrent AS and IBD, elevated circulating lipocalin 2 levels were associated with the coexisting ankylosis and gut inflammation. The intracellular pathway of lipocalin 2 was further investigated with the ank/ank mouse model involving PPARγ. Colonic expression of PPARγ was negatively associated with the degree of gut inflammation. The PPARγ agonist rosiglitazone treatment significantly upregulated the serum levels of lipocalin 2, suggesting a potential regulatory role of PPARγ in the aberrant expression of lipocalin 2.

Conclusions

In summary, lipocalin 2 modulated by PPARγ could be a potential pathway involved in concurrent inflammation and ankylosis in AS and IBD.

Toll-like receptors control p38 and JNK MAPK signaling pathways in rat astrocytes differently, when cultured in normal or high glucose concentrations

Astrocytes play a vital role in regulating central nervous system inflammation, energy metabolism and brain homeostasis. Unlike macrophages and microglia, which are cells of myeloid ancestry, astrocytes are of ectodermal origin. However, regulatory specificities of signaling pathways connecting inflammatory and metabolic processes are still largely unknown. We analyzed firstly cellular responses to toll-like receptor (TLR) agonists and secondly, modulation of the mRNA of the three isoforms of the transcription factors PPARs (peroxisome proliferator-activated receptors) in primary rat astrocytes exposed to normal glucose (5.5 mM) and high glucose (25 mM). Cell culturing of rat brain astrocytes for 2 days in high glucose did not alter cellular morphology, but i) enhanced the release of TNFα that was induced by TLR4 agonist LPS or TLR3 agonist PIC and the synthesis of prostaglandin E₂ (PGE₂), ii) changed the signaling pathways of TLR4/MAPK (increase in p38 MAPK, and decrease in JNK activities at early stages of TLR activation) and iii) modulated mRNA expression of PPARs. High glucose cultivation reduced PPARα and PPARβ mRNA levels, without altering PPARγ mRNA level and changed the sensitivity of expressions to agonists of TLR1/2 (PGN), TLR4 (LPS), TLR3 (PIC), and TLR5 (FGN). Differences between low and high glucose-adapted cells were obtained for agonists of TLR1/2 (PPARα, PPARβ), TLR4 (PPAR β), TLR3 (PPARα). In the TLR4/p38/PPARβ signaling pathway, there was a stimulatory connection in normal glucose but an inhibitory connection in high glucose. TLR4/JNK/activated PPARβ, TLR4/JNK/inhibited PPARγ both in cells adapted to normal or high glucose, but PPARα expression was not affected. As PPARs in astrocytes are involved in inflammatory processes in the form of the recently published PPAR triad, the changes in expression revealed here are most likely resulting in implications of high glucose in inflammatory processes. Our data underline the complexity of multiple regulatory interactions between inflammatory responses and energy metabolism in astrocytes.

Effects of sleeve gastrectomy on lipid and energy metabolism in ZDF rats via PI3K/AKT pathway

Sleeve Gastrectomy (SG), as the most effective bariatric surgery, has been using to chronically lose weight and control glucose metabolism in Type 2 diabetes mellitus patients. However, the underlining mechanism is still unclear. In this study, we performed SG on Zucker diabetes fatty (ZDF) rat and investigated visceral lipid metabolism and energy metabolism. After performance of SG, weight, food intake, fasting plasma glucose (FPG) and oral glucose tolerance teat (OGTT) of rats were measured. Furthermore, whole-body metabolic parameters were obtained through TSE LabMaster. Blood lipid and renal function were analyzed by serum from rats' tail vein. Furthermore, the renal genes expression was either detected by real-time PCR, while western blotting was employed to detect the AKT/PI3K proteins level in rats' kidney. Compared to control groups, body weight of ZDF rats treated with SG were significantly reduced, simultaneously with glucose homeostasis and energy metabolism improved including RER (P<0.05), energy expenditure (P<0.05) at night and activity of animal. Meanwhile, serum lipid of ZDF rats after SG was decreased, and renal function recovered. Histology analysis confirmed that the size of perirenal adipose from SD treated ZDF rats obviously decreased (P<0.001), effectively stimulating up-regulation of lipogenesis genes (P<0.05), while adipogenesis genes (P<0.05) in kidney was down-regulated. In addition, phosphorylation of PI3K (p-PI3K) and AKT (p-AKT) in rats kidney were significantly decreased in SG group (P<0.05). Weight loss, food intake, fasting plasma glucose and glucose tolerance in SG surgery rats were improved, which were coincident with energy metabolism changes. In conclusion, SG improves lipid and energy metabolism in ZDF rats model due to activating PI3K/Akt signaling pathway, which was contributed to the mechanism of bariatric surgery toward kidney.

Lipocalin-2 abrogates epithelial cell cycle arrest by PPARγ inhibition

Macrophage-epithelial cross-talk regulates cell cycle progression and represents an important factor in rescuing epithelial cells from cell cycle arrest in order to maintain a healthy epithelial phenotype. However, the underlying mechanisms are still not well defined. We provide evidence that macrophage-secreted lipocalin-2 (Lcn-2) plays a key role during this process. In a co-culture setup using cell cycle arrested NRK52e renal epithelial cells and primary bone marrow-derived macrophages, Lcn-2 restores proliferation through inhibition of peroxisome proliferator-activated receptor (PPAR)-γ. Lcn-2 overexpression in macrophages overcomes epithelial cell cycle arrest and enhances epithelial markers via megalin and the downstream activation of PI3K/Akt signalling pathway, whereas a knockdown of Lcn-2 in macrophages prevented this effect. Our results show that macrophage-secreting Lcn-2 is crucial in rescuing epithelial cells from cell cycle arrest and in promoting epithelial proliferation.

Perivascular adipose tissue (PVAT) in atherosclerosis: a double-edged sword

Perivascular adipose tissue (PVAT), the adipose tissue that surrounds most of the vasculature, has emerged as an active component of the blood vessel wall regulating vascular homeostasis and affecting the pathogenesis of atherosclerosis. Although PVAT characteristics resemble both brown and white adipose tissues, recent evidence suggests that PVAT develops from its own distinct precursors implying a closer link between PVAT and vascular system. Under physiological conditions, PVAT has potent anti-atherogenic properties mediated by its ability to secrete various biologically active factors that induce non-shivering thermogenesis and metabolize fatty acids. In contrast, under pathological conditions (mainly obesity), PVAT becomes dysfunctional, loses its thermogenic capacity and secretes pro-inflammatory adipokines that induce endothelial dysfunction and infiltration of inflammatory cells, promoting atherosclerosis development. Since PVAT plays crucial roles in regulating key steps of atherosclerosis development, it may constitute a novel therapeutic target for the prevention and treatment of atherosclerosis. Here, we review the current literature regarding the roles of PVAT in the pathogenesis of atherosclerosis.

Ginsenoside Rg3 stereoisomers differentially inhibit vascular smooth muscle cell proliferation and migration in diabetic atherosclerosis

Ginsenoside 20(R/S)‐Rg3, as a natural peroxisome proliferator‐activated receptor gamma (PPARγ) ligand, has been reported to exhibit differential biological effects. It is of great interest to understand the stereochemical selectivity of 20(R/S)‐Rg3 and explore whether differential PPARγ activation by Rg3 stereoisomers, if it exists, could lead to differential physiological outcome and therapeutic effects in diabetic atherosclerosis. Here, we investigated the binding modes of 20(R/S)‐Rg3 stereoisomers in the PPARγ ligand‐binding domain (PPARγ‐LBD) using molecular modelling and their effects on smooth muscle cell proliferation and migration induced by advanced glycation end products (AGEs). The results revealed that 20(S)‐Rg3 exhibited stronger antiproliferative and antimigratory effects due to stronger PPARγ activation. To validate the in vitro results, we used a mice model with diabetic atherosclerosis and obtained that 20(S)‐Rg3 markedly reduced the plaque size secondary to reducing the proliferation and migration of VSMCs, while the plaques were more stable due to improvements in other plaque compositions. The results shed light on the structural difference between Rg3 stereoisomers that can lead to significant differential physiological outcome, and the (S)‐isomer seems to be the more potent isomer to be developed as a promising drug for diabetic atherosclerosis.

Low Circulating TRAIL Levels Are Associated with Increase of Resistin and Lipocalin-2/ngal Adipokines in Postmenopausal Women

Objective

Tumor necrosis factor- (TNF-) related apoptosis-inducing ligand (TRAIL) is attracting attention for its role in the physiopathology of metabolic disease/diabetes. Evidence suggests that it might protect against metabolic abnormalities driven by obesity-induced dysregulated secretion of adipokines, but this role of TRAIL has not yet been fully established. On this basis, we aimed to investigate the potential association between TRAIL and adipokine levels in a cohort of subjects in which age/gender/hormonal interferences were excluded.

Methods

Serum levels of TRAIL and a panel of adipokines were measured in postmenopausal women (n = 147) stratified according to waist circumference measures as normal, overweight, or obese. The panel of adipokines included interleukin- (IL-) 6, IL-8, IL-1β, adipsin, lipocalin-2/neutrophil gelatinase-associated lipocalin (ngal), TNF-alpha, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, hepatocyte growth factor, resistin, leptin, adiponectin, and nerve growth factor.

Results

Low serum TRAIL concentration (deciles I–IV) was significantly and inversely correlated with resistin and lipocalin 2/ngal levels (r = −0.502 and p < 0.001 and r = −0.360 and p < 0.01, resp.). Both associations retained their statistical significance after adjustment for confounding factors, such as waist circumference and age.

Conclusions

Our data indicate a link between low circulating levels of TRAIL and markers of obesity-induced diseases (resistin and lipocalin-2/ngal), highlighting a new potential axis of TRAIL functions.

High-fat diet effects on metabolic responses to chronic stress

CONTEXT

High-fat diets and chronic stress are prevalent risk factors for various chronic diseases in modern societies.

OBJECTIVE

This study investigated the effect of high-fat diet on glucose-related metabolic responses to chronic foot-shock stress.

MATERIALS AND METHODS

Male rats were divided into high-fat diet (containing 54.21% saturated and 44.89% unsaturated fatty acids) and normal diet groups and then into stress and non-stress subgroups. The diets were applied for 5 weeks, and stress was induced during the last week of the diet course. Plasma levels of metabolic parameters, HOMA-IR index, intra-abdominal fat weight, and islets' insulin secretion were assessed.

RESULTS

High-fat diet increased abdominal fat weight and plasma leptin, and insulin levels in response to stress without affecting HOMA-IR index and islets' insulin secretion.

CONCLUSIONS

High proportion of unsaturated fat may not lead to deleterious metabolic responses; however combined with chronic stress has a synergistic and adverse effect on visceral adiposity and results in elevated plasma leptin.

β3-Adrenergic receptors, adipokines and neuroendocrine activation during stress induced by repeated immune challenge in male and female rats

The main hypothesis of the study is that stress associated with repeated immune challenge has an impact on β₃-adrenergic receptor gene expression in the brain. Sprague-Dawley rats were intraperitoneally injected with increasing doses of lipopolysaccharide (LPS) for five consecutive days. LPS treatment was associated with body weight loss and increased anxiety-like behavior. In LPS-treated animals of both sexes, β₃-receptor gene expression was increased in the prefrontal cortex but not the hippocampus. LPS treatment decreased β₃-receptor gene expression in white adipose tissue with higher values in males compared to females. In the adipose tissue, LPS reduced peroxisome proliferator-activated receptor-gamma, leptin and adiponectin gene expression, but increased interleukin-6 expression, irrespective of sex. Repeated immune challenge resulted in increased concentrations of plasma aldosterone and corticosterone with higher values of corticosterone in females compared to males. Concentrations of dehydroepiandrosterone (DHEA) in plasma were unaffected by LPS, while DHEA levels in the frontal cortex were lower in the LPS-treated animals compared to the controls. Thus, changes of DHEA levels in the brain take place irrespective of the changes of this neurosteroid in plasma. We have provided the first evidence on stress-induced increase in β₃-adrenergic receptor gene expression in the brain. Greater reduction of β₃-adrenergic receptor expression in the adipose tissue and of the body weight gain by repeated immune challenge in male than in female rats suggests sex differences in the role of β₃-adrenergic receptors in the metabolic functions. LPS-induced changes in adipose tissue regulatory factors and hormone concentrations might be important for coping with chronic infections.