Adipocyte apoptosis is a key initial event that contributes to macrophage infiltration into adipose tissue (AT) and thus triggers AT inflammation in obesity. MicroRNA-27a (miR-27a) was shown to ...mediate the pathological processes of many metabolic disorders; however, whether miR-27a is involved in adipocyte apoptosis of obese AT remains unknown. The present study aimed to investigate the alteration of miR-27a in obese individuals and its antiapoptotic function in adipocytes. In vivo, serum samples and omental adipose tissue from humans as well as epididymal fat pads from mice were collected to detect miR-27a expression. In vitro, 3T3-L1 preadipocytes and mature adipocytes were treated with TNF-α to induce apoptosis and transfected with a mimic for overexpressing miR-27a-3p. The results showed that miR-27a was markedly decreased in the serum and AT of obese human patients and in the AT of high-fat diet-fed mice. Regression analyses revealed that the serum level of miR-27a was correlated with metabolic parameters in human obesity. Notably, TNF-α induced cell apoptosis in both preadipocytes and mature adipocytes, as evidenced by the upregulation of cleaved caspase 3 and cleaved caspase 8 and the ratio of Bax to Bcl-2, while these effects were partly diminished by miR-27a overexpression. In addition, TUNEL and Hoechst 33258 staining verified that miR-27a overexpression markedly inhibited the apoptosis of adipocytes under TNF-α stimulation. Thus, miR-27a was downregulated in the AT of obese subjects with proapoptotic status, and overexpression of miR-27a exerted an antiapoptotic effect on preadipocytes, providing a novel potential target for preventing AT dysfunction.
Non-alcoholic fatty liver disease (NAFLD) is closely associated with obesity and insulin resistance. To better understand the pathophysiology of obesity-associated NAFLD, the present study examined ...the involvement of liver and adipose tissues in metformin actions on reducing hepatic steatosis and inflammation during obesity. C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity-associated NAFLD and treated with metformin (150 mg/kg/d) orally for the last four weeks of HFD feeding. Compared with HFD-fed control mice, metformin-treated mice showed improvement in both glucose tolerance and insulin sensitivity. Also, metformin treatment caused a significant decrease in liver weight, but not adiposity. As indicated by histological changes, metformin treatment decreased hepatic steatosis, but not the size of adipocytes. In addition, metformin treatment caused an increase in the phosphorylation of liver AMP-activated protein kinase (AMPK), which was accompanied by an increase in the phosphorylation of liver acetyl-CoA carboxylase and decreases in the phosphorylation of liver c-Jun N-terminal kinase 1 (JNK1) and in the mRNA levels of lipogenic enzymes and proinflammatory cytokines. However, metformin treatment did not significantly alter adipose tissue AMPK phosphorylation and inflammatory responses. In cultured hepatocytes, metformin treatment increased AMPK phosphorylation and decreased fat deposition and inflammatory responses. Additionally, in bone marrow-derived macrophages, metformin treatment partially blunted the effects of lipopolysaccharide on inducing the phosphorylation of JNK1 and nuclear factor kappa B (NF-κB) p65 and on increasing the mRNA levels of proinflammatory cytokines. Taken together, these results suggest that metformin protects against obesity-associated NAFLD largely through direct effects on decreasing hepatocyte fat deposition and on inhibiting inflammatory responses in both hepatocytes and macrophages.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Adenosine 2A receptor (A2AR) exerts protective roles in endotoxin‐ and/or ischemia‐induced tissue damage. However, the role for A2AR in nonalcoholic fatty liver disease (NAFLD) remains largely ...unknown. We sought to examine the effects of global and/or myeloid cell‐specific A2AR disruption on the aspects of obesity‐associated NAFLD and to elucidate the underlying mechanisms. Global and/or myeloid cell–specific A2AR‐disrupted mice and control mice were fed a high‐fat diet (HFD) to induce NAFLD. In addition, bone marrow–derived macrophages and primary mouse hepatocytes were examined for inflammatory and metabolic responses. Upon feeding an HFD, both global A2AR‐disrupted mice and myeloid cell–specific A2AR‐defcient mice revealed increased severity of HFD‐induced hepatic steatosis and inflammation compared with their respective control mice. In in vitro experiments, A2AR‐deficient macrophages exhibited increased proinflammatory responses, and enhanced fat deposition of wild‐type primary hepatocytes in macrophage–hepatocyte cocultures. In primary hepatocytes, A2AR deficiency increased the proinflammatory responses and enhanced the effect of palmitate on stimulating fat deposition. Moreover, A2AR deficiency significantly increased the abundance of sterol regulatory element‐binding protein 1c (SREBP1c) in livers of fasted mice and in hepatocytes upon nutrient deprivation. In the absence of A2AR, SREBP1c transcription activity was significantly increased in mouse hepatocytes. Conclusion: Taken together, our results demonstrate that disruption of A2AR in both macrophage and hepatocytes accounts for increased severity of NAFLD, likely through increasing inflammation and through elevating lipogenic events due to stimulation of SREBP1c expression and transcription activity. (Hepatology 2018;68:48‐61).
Elevated circulating homocysteine (Hcy) has been proposed to be associated with non-alcoholic fatty liver disease (NAFLD). It is also reported that Hcy causes protein misfolding in the endoplasmic ...reticulum (ER). In this study, we used a high methionine diet (HMD)-fed mouse model and cultured primary hepatocytes to investigate the effects of Hcy on hepatic lipids metabolism. C57BL/6J mice received either standard chow diet (CT,
= 10) or diet supplemented with 2% methionine (MET,
= 10) for 16 weeks. In in vitro experiments, cultured mouse primary hepatocytes were treated with Hcy, or Hcy combined with 4-phenylbutyric acid (4-PBA), or tunicamycin (TM), respectively. HMD-fed mice exhibited a mild increase in plasma Hcy level. There was no significant difference of body weight gain between the two groups. Nevertheless, HMD feeding increased epididymal fat/body weight ratio, elevated plasma triglyceride (TG) level, and decreased high-density lipoprotein cholesterol (HDL) level. Similarly, mice on HMD displayed higher liver/body weight ratio, plasma aspartate aminotransferase (AST) and its ratio to alanine aminotransferase (ALT), which was supported by the morphological observations of hepatic triglyceride accumulation in liver tissue as well as primary hepatocytes. Activation of the sterol response element-binding protein 1c (SREBP1c) in Hcy-treated hepatocytes with increased expression of genes involved in hepatic de novo lipogenesis was partially reduced by pretreatment of 4-PBA. Hcy-induced ER stress was also ameliorated by 4-PBA pretreatment, thus demonstrating an important role of Hcy-induced ER stress response in hepatic steatosis. These findings suggest that elevated Hcy was a critical factor in the pathogenesis of NAFLD. Activation of the ER stress response may be involved in Hcy-induced hepatic steatosis.
Parental history with obesity or diabetes will increase the risk for developing metabolic diseases in offspring. However, literatures as to transgenerational inheritance of metabolic dysfunctions ...through male lineage are relatively scarce. In the current study, we aimed to evaluate influences of paternal hyperglycemia on metabolic phenotypes in offspring. Male SD rats were i.p. injected with streptozotocin (STZ) or citrate buffer (CB, as control). STZ-injected rats with glucose levels higher than 16.7 mM were selected to breed with normal female rats. Offspring from STZ or CB treated fathers (STZ-O and CB-O) were maintained in the identical condition. We monitored body weight and food intake, and tests of glucose and insulin tolerance (GTTs and ITTs), fasting–refeeding and cold exposure were performed. Expression of factors involved in hypothalamic feeding and brown adipose tissue (BAT) thermogenic activity was performed by real-time PCR and Western blot. Adult STZ-O were heavier than CB-O. Impairment of GTTs was observed in STZ-O compared with CB-O at 22 and 32 weeks of age; ITTs results showed decreased insulin sensitivity in STZ-O. Daily food intake and accumulated food intake during 12-h refeeding after fasting were significantly higher in STZ-O. UCP1 levels were downregulated in BAT from STZ-O at room temperature and cold exposure. Finally, STZ-O rats showed suppressed leptin signaling in the hypothalamus as evidenced by upregulated SOCS3, reduced phosphorylation of STAT3, impaired processing POMC and decreased α-MSH production. Our study revealed that paternal hyperglycemia predisposes offspring to developing obesity, which is possibly associated with impaired hypothalamic leptin signaling.
Exosome-like vesicles (ELVs), the smallest class of extracellular vesicles released from cells, function in cellular crosstalk and therefore profoundly affect physiologic responses and pathologic ...progression. A growing body of evidence supports a novel role for ELVs as important mediators and therapeutic targets due to their effects on regulation of both insulin signaling and β-cell mass. Pathologic conditions associated with type 2 diabetes (such as high blood glucose, inflammation, hypoxia, and fatty acids) can alter the quantity and components of ELVs secreted from the pancreas or peripheral insulin-targeting tissues. These released ELVs can either enter the blood circulation or be taken up by neighboring cells or macrophages, which can lead to insulin resistance or β-cell apoptosis. This review focuses on the roles of ELVs in insulin resistance and β-cell failure and also highlights the potential use of ELVs and exosome-based delivery systems in therapeutic interventions aimed at treating type 2 diabetes mellitus as well as the challenges associated with exosome-targeting therapeutics.
Epidemiological data showed a positive correlation between GDM and the risk of autism spectrum disorder (ASD) in offspring, but specific mechanisms remain unclear. C57BL/6 female mice were fed with ...60% HFD for 4 weeks, and then bred with healthy male mice. On gestational days 0.5 and 7.5, pregnant mice were injected with streptozocin (STZ, 110mg/kg, ip) to establish GDM model. Male offspring were selected for ASD related behavior at P42-P60. LC/MC was used to detect 5-hydroxytryptamine (5-HT) levels, while Western blot and immunofluorescence (IF) were used to detect functional indicators related to the dorsal raphe nucleus (DRN)5-HT system. Male GDM offspring showed impaired social function as evidenced by poor performance in three box test, and repetitive stereotypical behavior. LC/MS detection revealed a significant decrease in 5-HT levels in brain tissue and a significant increase in GDM offspring plasma. WB and IF showed that the abnormal differentiation of neural stem cells in DRN region in GDM offspring, with a significant decrease in the number of 5-HT positive neurons and 5-HT nerve fibers, and a significant downregulation of SYP and PSD95 protein levels. Ahi1, a highly susceptible gene to schizophrenia and ASD, as well as two key related proteins, B9D1 and Shh, were significantly downregulated. Treatment of meptazinol in GDM offspring increased Ahi1 mRNA and protein levels and effectively reversed the loss of 5-HT neurons in DRN and improved ASD-like behavioral signs. Notably, injection of AAV B9D1 shRNA into DRN, while decreasing B9D1 protein levels, attenuated the improvement of meptazinol on ASD-like behavioral changes in GDM offspring. Taken together, our studies suggested that GDM male offspring are susceptible to ASD, which may be related to the abnormal neural stem cells differentiation and maturation due to the impairment of Ahi1/ B9D1/Shh axis, resulting in the loss of 5-HT neurons in the DRN region. Disclosure X. Xiao: None. G. Qin: None. Funding The National Natural Science Foundation of China (82071734)
Obesity is associated with chronic inflammation in the central nervous system (CNS), and neuroinflammation has been shown to have detrimental effects on mood and cognition. The growth hormone ...secretagogue receptor (GHSR), the biologically relevant receptor of the orexigenic hormone ghrelin, is primarily expressed in the brain. Our previous study showed that neuronal GHSR deletion prevents high-fat diet-induced obesity (DIO). Here, we investigated the effect of neuronal GHSR deletion on emotional and cognitive functions in DIO. The neuron-specific GHSR-deficient mice exhibited reduced depression and improved spatial memory compared to littermate controls under DIO. We further examined the cortex and hippocampus, the major regions regulating cognitive and emotional behaviors, and found that the neuronal deletion of GHSR reduced DIO-induced neuroinflammation by suppressing proinflammatory chemokines/cytokines and decreasing microglial activation. Furthermore, our data showed that neuronal GHSR deletion suppresses neuroinflammation by downregulating AMPK-autophagy signaling in neurons. In conclusion, our data reveal that neuronal GHSR inhibition protects against DIO-induced depressive-like behavior and spatial cognitive dysfunction, at least in part, through AMPK-autophagy signaling-mediated neuroinflammation.
Adenosine 2A receptor (A2AR) exerts a protective role in obesity-related non-alcoholic fatty liver disease. Here, we examined whether A2AR protects against non-alcoholic steatohepatitis (NASH). In ...C57BL/6J mice, feeding a methionine- and choline-deficient diet (MCD) resulted in significant weight loss, overt hepatic steatosis, and massive aggregation of macrophages in the liver compared with mice fed a chow diet. MCD feeding also significantly increased the numbers of A2AR-positive macrophages/Kupffer cells in liver sections although decreasing A2AR amount in liver lysates compared with chow diet feeding. Next, MCD-induced NASH phenotype was examined in A2AR-disrupted mice and control mice. Upon MCD feeding, A2AR-disruptd mice and control mice displayed comparable decreases in body weight and fat mass. However, MCD-fed A2AR-disrupted mice revealed greater liver weight and increased severity of hepatic steatosis compared with MCD-fed control mice. Moreover, A2AR-disupted mice displayed increased severity of MCD-induced liver inflammation, indicated by massive aggregation of macrophages and increased phosphorylation states of Jun-N terminal kinase (JNK) p46 and nuclear factor kappa B (NFκB) p65 and mRNA levels of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6. In vitro, incubation with MCD-mimicking media increased lipopolysaccharide (LPS)-induced phosphorylation states of JNK p46 and/or NFκB p65 and cytokine mRNAs in control macrophages and RAW264.7 cells, but not primary hepatocytes. Additionally, MCD-mimicking media significantly increased lipopolysaccharide-induced phosphorylation states of p38 and NFκB p65 in A2AR-deficient macrophages, but insignificantly decreased lipopolysaccharide-induced phosphorylation states of JNK p46 and NFκB p65 in A2AR-deficient hepatocytes. Collectively, these results suggest that A2AR disruption exacerbates MCD-induced NASH, which is attributable to, in large part, increased inflammatory responses in macrophages.
Type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) share several common pathophysiological features. Rare variants of triggering receptor expressed on myeloid cells 2 (TREM2) increase the ...risk of developing AD, suggesting the involvement of TREM2 and innate immunity in AD development. It is still unknown whether TREM2 is related to cognitive impairment in T2DM. Here, we investigated the effects of the hippocampal overexpression of TREM2 on cognitive in long-term high-fat diet (HFD)-fed mice. Male C57BL/6J mice were maintained on HFD for 50 weeks. TREM2 was overexpressed in the hippocampus 36 weeks after HFD feeding using adeno-associated virus vector (AAV)-mediated gene delivery. The results showed that the HFD feeding induced rapid and persistent weight gain, glucose intolerance and significant impairments in learning and memory. Compared with AAV-con, AAV-TREM2 significantly ameliorated cognitive impairment without altering body weight and glucose homeostasis in HFD mice. The overexpression of TREM2 upregulated the synaptic proteins spinophilin, PSD95 and synaptophysin, suggesting the improvement in synaptic transmission. Dendritic complexity and spine density in the CA1 region were rescued after TREM2 overexpression. Furthermore, TREM2 markedly increased the number of iba-1/Arg-1-positive microglia in the hippocampus, suppressed neuroinflammation and microglial activation. In sum, hippocampal TREM2 plays an important role in improving HFD-induced cognitive dysfunction and promoting microglial polarization towards the M2 anti-inflammatory phenotype. Our study also suggests that TREM2 might be a novel target for the intervention of obesity/diabetes-associated cognitive decline.
PDF
