Histamine regulation in glucose and lipid metabolism via histamine receptors: model for nonalcoholic steatohepatitis in mice

Efficacy of topiramate in reducing second-generation antipsychotic-associated weight gain among children: A systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis with the aim of synthesizing existing data on the efficacy and safety of topiramate as an adjunctive treatment for reducing second-generation antipsychotic (SGA)-associated weight gain in children aged 4-18 years.

METHODS

We conducted a comprehensive search of PubMed, Embase, PsychNet and Web of Science from time of their inception up to 12 February 2024, including randomized controlled trials that compared SGA treatment with and without topiramate co-administration in children. The primary outcomes were changes in body weight and body mass index (BMI). Heterogeneity was assessed using I2 statistics.

RESULTS

This systematic review included five randomized trials, totalling 139 participants (43.9% female; mean [SD] age 11.9 [3.5] years). Four of these trials were included in the meta-analysis, comprising 116 subjects. We found that topiramate was significantly effective both in reducing SGA-associated weight gain, with a mean difference of -2.80 kg (95% confidence interval [CI] -5.28 to -0.31; p = 0.037, I2 = 86.7%) and a standardized mean difference (SMD) of -1.33 (95% CI -2.14 to -0.51; p = 0.014, I2 = 31.7%), and in reducing BMI change compared to placebo (SMD -1.90, 95% CI -3.09 to -0.70; p = 0.02, I2 = 0%). Sedation risk was lower with topiramate than with placebo (odds ratio 0.19, 95% CI 0.11-0.32; p < 0.01, I2 = 0%). No significant differences were found in dropouts, any other side effects, and metabolic parameters, such as triglycerides, total cholesterol, low-density lipoprotein, high-density lipoprotein, and glucose. None of the included studies reported assessments on cognitive side effects.

CONCLUSION

This meta-analysis suggests that topiramate is an effective and safe option for mitigating SGA-associated weight gain in children.

Non-targeted metabolomics identifies biomarkers in milk with high and low milk fat percentage

Milk is widely recognized as an important food source with health benefits. Different consumer groups have different requirements for the content and proportion of milk fat; therefore, it is necessary to investigate the differential metabolites and their regulatory mechanisms in milk with high and low milk fat percentages (MFP). In this study, untargeted metabolomics was performed on milk samples from 13 cows with high milk fat percentage (HF) and 13 cows with low milk fat percentage (LF) using ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS). Forty-eight potential differentially labeled compounds were screened using the orthogonal partial least squares-discriminant analysis (OPLS-DA) combined with the weighted gene co-expression network analysis (WGCNA) method. Amino acid metabolism was the key metabolic pathway with significant enrichment of L-histidine, 5-oxoproline, L-aspartic acid, and L-glutamic acid. The negative correlation with MFP differentiated the HF and LF groups. To further determine the potential regulatory role of these amino acids on milk fat metabolism, the expression levels of marker genes in the milk fat synthesis pathway were explored. It was noticed that L-histidine reduced milk fat concentration primarily by inhibiting the triglycerides (TAG) synthesis pathway. L-aspartic acid and L-glutamic acid inhibited milk fat synthesis through the fatty acid de novo and TAG synthesis pathways. This study provides new insights into the mechanism underlying milk fat synthesis and milk quality improvement.

The Diverse Network of Brain Histamine in Feeding: Dissect its Functions in a Circuit-Specific Way

Feeding is an intrinsic and important behavior regulated by complex molecular, cellular and circuit-level mechanisms, one of which is the brain histaminergic network. In the past decades, many studies have provided a foundation of knowledge about the relationship between feeding and histamine receptors, which are deemed to have therapeutic potential but are not successful in treating feeding- related diseases. Indeed, the histaminergic circuits underlying feeding are poorly understood and characterized. This review describes current knowledge of histamine in feeding at the receptor level. Further, we provide insight into putative histamine-involved feeding circuits based on the classic feeding circuits. Understanding the histaminergic network in a circuit-specific way may be therapeutically relevant for increasing the drug specificity and precise treatment in feeding-related diseases.

Targeted Metabolomics Analysis of Individuals Carrying the ANGPTL8 R59W Variant

ANGPTL8 is recognized as a regulator of lipid metabolism through its role in inhibiting lipoprotein lipase activity. ANGPTL8 gene variants, particularly rs2278426 leading to the R59W variant in the protein, have been associated with lipid traits in various ethnicities. We aimed to use metabolomics to understand the impact of the ANGPTL8 R59W variant on metabolites in humans. We used the Biocrates-p400 kit to quantify 408 plasma metabolites in 60 adult male Arab individuals from Kuwait and identify differences in metabolite levels between individuals carrying reference genotypes and those with carrier genotypes at ANGPTL8 rs2278426. Individuals with carrier genotypes (CT+TT) compared to those carrying the reference genotype (CC) showed statistically significant differences in the following metabolites: acylcarnitine (perturbs metabolic pathways), phosphatidylcholine (supports liver function and cholesterol levels), cholesteryl ester (brings chronic inflammatory response to lipoprotein depositions in arteries), α-aminoadipic acid (modulates glucose homeostasis), histamine (regulates glucose/lipid metabolism), sarcosine (links amino acid and lipid metabolism), diacylglycerol 42:1 (regulates homeostasis of cellular lipid stores), and lysophosphatidylcholine (regulates oxidative stress and inflammatory response). Functional aspects attributed to these metabolites indicate that the ANGPTL8 R59W variant influences the concentrations of lipid- and inflammation-related metabolites. This observation further highlights the role of ANGPTL8 in lipid metabolism.

Histaminergic regulation of food intake

Histamine is a biogenic amine that acts as a neuromodulator within the brain. In the hypothalamus, histaminergic signaling contributes to the regulation of numerous physiological and homeostatic processes, including the regulation of energy balance. Histaminergic neurons project extensively throughout the hypothalamus and two histamine receptors (H1R, H3R) are strongly expressed in key hypothalamic nuclei known to regulate energy homeostasis, including the paraventricular (PVH), ventromedial (VMH), dorsomedial (DMH), and arcuate (ARC) nuclei. The activation of different histamine receptors is associated with differential effects on neuronal activity, mediated by their different G protein-coupling. Consequently, activation of H1R has opposing effects on food intake to that of H3R: H1R activation suppresses food intake, while H3R activation mediates an orexigenic response. The central histaminergic system has been implicated in atypical antipsychotic-induced weight gain and has been proposed as a potential therapeutic target for the treatment of obesity. It has also been demonstrated to interact with other major regulators of energy homeostasis, including the central melanocortin system and the adipose-derived hormone leptin. However, the exact mechanisms by which the histaminergic system contributes to the modification of these satiety signals remain underexplored. The present review focuses on recent advances in our understanding of the central histaminergic system's role in regulating feeding and highlights unanswered questions remaining in our knowledge of the functionality of this system.

Aqueous extract of Polygala japonica Houtt. ameliorated nonalcoholic steatohepatitis in mice through restoring the gut microbiota disorders and affecting the metabolites in feces and liver

BACKGROUND

Polygala japonica Houtt. (PJ) has been demonstrated with several biological potentials such as lipid-lowering and anti-inflammatory effects. However, the effects and mechanisms of PJ on nonalcoholic steatohepatitis (NASH) remain unclear.

PURPOSE

The aim of this study was to evaluate the effects of PJ on NASH and illustrate the mechanism based on modulating gut microbiota and host metabolism.

MATERIALS AND METHODS

NASH mouse model was induced using methionine and choline deficient (MCD) diet and orally treated with PJ. The therapeutic, anti-inflammatory, and anti-oxidative effects of PJ on mice with NASH were firstly assessed. Then, the gut microbiota of mice was analyzed using 16S rRNA sequencing to assess the changes. Finally, the effects of PJ on the metabolites in liver and feces were explored by untargeted metabolomics.

RESULTS

The results indicated that PJ could improve hepatic steatosis, liver injury, inflammatory response, and oxidative stress in NASH mice. PJ treatment also affected the diversity of gut microbiota and changed the relative abundances of Faecalibaculum. Lactobacillus, Muribaculaceae, Dubosiella, Akkermansia, Lachnospiraceae_NK4A136_group, and Turicibacter in NASH mice. In addition, PJ treatment modulated 59 metabolites both in liver and feces. Metabolites involved in histidine, and tryptophan metabolism pathways were identified as the key metabolites according to the correlation analysis between differential gut microbiota and metabolites.

CONCLUSION

Our study demonstrated the therapeutic, anti-inflammatory and anti-oxidative potentials of PJ on NASH. The mechanisms of PJ treatment were related to the improvement of gut microbiota dysbiosis and the regulation of histidine and tryptophan metabolism.

Hypolipemic effects of histamine is due to inhibition of VLDL secretion from the liver: involvement of both H1 and H2-receptors

The research was performed to study the mechanism whereby histamine affects the profile of plasma lipids. Six groups of ten male rats were received two injections with histamine or its H1- and H2-agonists and antagonists. Histamine caused a significant decrease in the concentrations of triglyceride, total cholesterol, and LDLc, while HDLc had no significant change. The rate of VLDL secretion was 263.6 ± 25.8 mg/h dL in control rats and was inhibited by about 68% in histamine injected rats. These changes have been mimicked by either histamine H1- or H2-agonists. The effects of H1- and H2-agonists were abolished in the presence of cetirizine and famotidine respectively. Histamine causes a significant decrease in serum triglyceride, total, and LDL-cholesterol by both H1 and H2-receptors. The decrease in serum lipids is due to the inhibitory effect of histamine or its agonists on VLDL secretion from the liver.

An H2R-dependent medial septum histaminergic circuit mediates feeding behavior

Novel targets for treating feeding-related diseases are of great importance, and histamine has long been considered an anorexigenic agent. However, understanding its functions in feeding in a circuit-specific way is still limited. Here, we report a medial septum (MS)-projecting histaminergic circuit mediating feeding behavior. This MS-projecting histaminergic circuit is functionally inhibited during food consumption, and bidirectionally modulates feeding behavior via downstream H2, but not H1, receptors on MS glutamatergic neurons. Further, we observed a pathological decrease of histamine 2 receptors (H2Rs) expression in MS glutamatergic neurons in diet-induced obesity (DIO) mice. Genetically, down-regulation of H2Rs expression in MS glutamatergic neurons accelerates body-weight gain. Importantly, chronic activation of H2Rs in MS glutamatergic neurons (with its clinical agonist amthamine) significantly slowed down the body-weight gain in DIO mice, providing a possible clinical utility to treat obesity. Together, our results demonstrate that this MS-projecting histaminergic circuit is critically involved in feeding, and H2Rs in MS glutamatergic neurons is a promising target for treating body-weight problems.

Could Histamine H1 Receptor Antagonists Be Used for Treating COVID-19?

COVID-19 has rapidly become a pandemic worldwide, causing extensive and long-term health issues. There is an urgent need to identify therapies that limit SARS-CoV-2 infection and improve the outcome of COVID-19 patients. Unbalanced lung inflammation is a common feature in severe COVID-19 patients; therefore, reducing lung inflammation can undoubtedly benefit the clinical manifestations. Histamine H1 receptor (H1 receptor) antagonists are widely prescribed medications to treat allergic diseases, while recently it has emerged that they show significant promise as anti-SARS-CoV-2 agents. Here, we briefly summarize the novel use of H1 receptor antagonists in combating SARS-CoV-2 infection. We also describe the potential antiviral mechanisms of H1 receptor antagonists on SARS-CoV-2. Finally, the opportunities and challenges of the use of H1 receptor antagonists in managing COVID-19 are discussed.

Atypical Antipsychotics and Metabolic Syndrome: From Molecular Mechanisms to Clinical Differences

Atypical antipsychotics (AAPs) are commonly prescribed medications to treat schizophrenia, bipolar disorders and other psychotic disorders. However, they might cause metabolic syndrome (MetS) in terms of weight gain, dyslipidemia, type 2 diabetes (T2D), and high blood pressure, which are responsible for reduced life expectancy and poor adherence. Importantly, there is clear evidence that early metabolic disturbances can precede weight gain, even if the latter still remains the hallmark of AAPs use. In fact, AAPs interfere profoundly with glucose and lipid homeostasis acting mostly on hypothalamus, liver, pancreatic β-cells, adipose tissue, and skeletal muscle. Their actions on hypothalamic centers via dopamine, serotonin, acetylcholine, and histamine receptors affect neuropeptides and 5'AMP-activated protein kinase (AMPK) activity, thus producing a supraphysiological sympathetic outflow augmenting levels of glucagon and hepatic glucose production. In addition, altered insulin secretion, dyslipidemia, fat deposition in the liver and adipose tissues, and insulin resistance become aggravating factors for MetS. In clinical practice, among AAPs, olanzapine and clozapine are associated with the highest risk of MetS, whereas quetiapine, risperidone, asenapine and amisulpride cause moderate alterations. The new AAPs such as ziprasidone, lurasidone and the partial agonist aripiprazole seem more tolerable on the metabolic profile. However, these aspects must be considered together with the differences among AAPs in terms of their efficacy, where clozapine still remains the most effective. Intriguingly, there seems to be a correlation between AAP's higher clinical efficacy and increase risk of metabolic alterations. Finally, a multidisciplinary approach combining psychoeducation and therapeutic drug monitoring (TDM) is proposed as a first-line strategy to avoid the MetS. In addition, pharmacological treatments are discussed as well.

Losartan and azelastine either alone or in combination as modulators for endothelial dysfunction and platelets activation in diabetic hyperlipidemic rats

AIM

The present study aimed mainly to demonstrate the effect of the antihistamine azelastine (AZ) and Angiotensin receptor blocker ( ARB), represented by losartan (LOS) either alone or in combined form on certain metabolic aspects, endothelial dysfunction and platelets activation markers in diabetic hyperlipidemic rat model.

METHODS

Rats were randomly classified to five groups: One group fed normal chow diet (NC). Four groups received alloxan and CCT-diet. One group received no treatment (DHC while the other three groups received AZ, LOS and their combination form, respectively for 8 weeks. Serum and tissue samples were collected for biochemical and histological evaluations.

RESULTS

DHC rats demonstrated significant hyperglycaemia, dyslipidemia, disturbances in endothelial and platelet activation markers. AZ or LOS administration demonstrated hypoglycaemic and hypolipidemic effects. VCAM-1 and sE-selectin (Endothelial function markers) along with CD63 (Platelet activation marker) showed significant decrease as compared to control group. AZ administration exerted little prominent effects than that of LOS, while their combination demonstrated remarkable changes compared to monotherapy. Histopathological findings were in agreement to certain extent with the biomarkers results.

CONCLUSIONS

Both drug categories may be expressed as suitable therapeutic tools for atherosclerotic complications either alone or along with other hypolipidemic drugs.

Stimulation of histamine H4 receptor participates in cold-induced browning of subcutaneous white adipose tissue

Although many studies have shown that histamine and its signaling regulate energy homeostasis through the central nervous system, their roles in adipose tissues remain poorly understood. Here, we identified that the histamine H4 receptor (HrH4) was highly expressed in adipocytes at a level higher than that of the other three receptors (i.e., HrH1, HrH2, and HrH3). The HrH4 expression in adipocytes responded to cold through thermogenesis and lipolysis, supported by results from both mouse and cell models. When HrH4 expression was knocked down in the subcutaneous white adipose tissue (scWAT), browning and lipolysis effects triggered by cold were ablated, and the oxygen consumption was also lowered both at the normal and cold conditions. Moreover, mice exhibited browned scWAT, accelerated metabolic rates, and tolerance to hypothermia when 4-methylhistamine (4MH), a selective HrH4 agonist, was adjacently injected to the scWAT. Consistent with these findings, 4MH also triggered the browning and lipolytic effects in cultured C3H10T1/2 adipocytes. Mechanically, we demonstrated that p38/MAPK and ERK/MAPK pathways were involved in these processes. In conclusion, our findings have uncovered an effective role of HrH4 in adipose tissue browning.

Mast Cell-Derived Histamine Regulates Liver Ketogenesis via Oleoylethanolamide Signaling

The conversion of lipolysis-derived fatty acids into ketone bodies (ketogenesis) is a crucial metabolic adaptation to prolonged periods of food scarcity. The process occurs primarily in liver mitochondria and is initiated by fatty-acid-mediated stimulation of the ligand-operated transcription factor, peroxisome proliferator-activated receptor-α (PPAR-α). Here, we present evidence that mast cells contribute to the control of fasting-induced ketogenesis via a paracrine mechanism that involves secretion of histamine into the hepatic portal circulation, stimulation of liver H₁ receptors, and local biosynthesis of the high-affinity PPAR-α agonist, oleoylethanolamide (OEA). Genetic or pharmacological interventions that disable any one of these events, including mast cell elimination, deletion of histamine- or OEA-synthesizing enzymes, and H₁ blockade, blunt ketogenesis without affecting lipolysis. The results reveal an unexpected role for mast cells in the regulation of systemic fatty-acid homeostasis, and suggest that OEA may act in concert with lipolysis-derived fatty acids to activate liver PPAR-α and promote ketogenesis.

Depletion of WNT10A Prevents Tumor Growth by Suppressing Microvessels and Collagen Expression

Background: We recently reported that WNT10A plays a pivotal role in wound healing by regulating collagen expression/synthesis, as the depletion of WNT10A dramatically delays skin ulcer formation. WNT signaling also has a close correlation with the cancer microenvironment and proliferation, since tumors are actually considered to be 'unhealing' or 'overhealing' wounds. To ascertain the in vivo regulatory functions of WNT10A in tumor growth, we examined the net effects of WNT10A depletion using Wnt10a-deficient mice (Wnt10a ^-/-). Methods and Results: We subjected C57BL/6J wild-type (WT) or Wnt10a ^-/- mice to murine melanoma B16-F10 cell transplantation. Wnt10a ^-/- mice showed a significantly smaller volume of transplanted melanoma as well as fewer microvessels and less collagen expression and more necrosis than WT mice. Conclusions: Taken together, our observations suggest that critical in vivo roles of Wnt10a-depleted anti-stromagenesis prevent tumor growth, in contrast with true wound healing/scarring.

Recent advances in pharmacological research on the management of irritable bowel syndrome

Irritable bowel syndrome (IBS), a common gastrointestinal (GI) disorder, is associated with various factors, including lifestyle, infection, stress, intestinal flora, and related diseases. The pharmacotherapeutic stimulation of receptors and downstream signaling pathways is effective in reducing IBS symptoms; however, it is still associated with adverse effects. Various receptors related to GI motility and visceral hypersensitivity should be considered to enhance the benefit/risk ratio of IBS treatments. This review discusses recent pharmacological advances in IBS management. Several receptors related to GI motility and abdominal pain are investigated in various angles. 5-Hydroxytryptamine (5-HT) is an important neurotransmitter that activates the colonic mucosal 5-HT₄ receptor without causing severe cardiovascular adverse effects. The clinical potential of ramosetron for diarrhea-predominant IBS has been suggested because of a lower risk of ischemic colitis than conventional 5-HT₃ receptor antagonists. Toll-like receptors (TLRs), especially TLR2 and TLR4, show a significant effect on the post-infection symptoms and lipopolysaccharide-mediated regulation of GI motility. Histamine is a well-known nitrogenous compound that regulates inflammatory responses and visceral hypersensitivity. Histamine 1 receptor-mediated sensitization of the transient receptor potential vanilloid 1 is associated with IBS. Pharmacological approaches based on these signaling pathways could be useful in the development of novel IBS treatments.

Activation of histamine H4 receptor suppresses the proliferation and invasion of esophageal squamous cell carcinoma via both metabolism and non-metabolism signaling pathways

Although dysregulation of histamine H₄ receptor (H4R) has widely and frequently been documented in digestive carcinomas and correlates with the malignancy and proliferation of these tumors, the existence of H4R and its pathophysiological function in esophageal squamous cell carcinoma (ESCC) remains unknown. In our present study, we explored the expression and function of H4R in human ESCC samples and cell lines. H4R was overexpressed in poorly differentiated ESCC samples and cell lines and correlated with the median survival of ESCC patients. H4R activation not only significantly blocked cell proliferation, cell cycle, and invasion but also inhibited the growth of TE-2 xenografts and increased the survival of xenograft-bearing mice. According to the mechanistic experiments, both metabolism (acetyl-coenzyme A synthetase 2 (ACSS2))- and non-metabolism (mitogen-activated protein kinase (MAPK))-related pathways were involved in the effect of H4R activation on suppressing tumor proliferation and invasion. Based on these findings, H4R was overexpressed in esophageal cancer and exerted antitumor effects on ESCC proliferation and invasion, suggesting that H4R may be a novel potential target of therapies for ESCC.

KEY MESSAGES

The function of H4R in ESCC and the underlying mechanisms were investigated. H4R expression was correlated with ESCC cell differentiation and patients' survival. Both metabolism (ACSS2) and non-metabolism (MAPK)-related pathways were involved. This study provided new insight into the relationship between H4R and ESCC. H4R may be a novel potential therapeutic target for ESCC.

The histamine H3 receptor inverse agonist pitolisant reduces body weight in obese mice

The pharmacological profile of pitolisant, a histamine H₃ receptor antagonist/inverse agonist, indicates that this compound might reduce body weight and metabolic disturbances. Therefore, we studied the influence of pitolisant on body weight, water and sucrose intake as well as metabolic disturbances in the high-fat and high-sugar diet-induced obesity model in mice. To induce obesity, male CD-1 mice were fed a high-fat diet consisting of 40% fat blend for 14 weeks, water and 30% sucrose solution available ad libitum. Glucose tolerance test was performed at the beginning of week 15. Insulin tolerance was tested the day after. At the end of study, plasma levels of triglycerides and cholesterol were determined. Pitolisant at dose of 10 mg/kg bw (ip) was administrated during 14 days, starting from the beginning of week 13. Metformin at dose of 100 mg/kg bw (ip) was used as reference drug. Mice fed with high-fat diet and sucrose solution showed more weight gain throughout the 12-week period of inducing obesity. Animals fed with high-fat diet and treated with pitolisant (for the next 14 days) showed significantly less weight gain than mice from the control group consuming a high-fat feed. In the group treated with pitolisant, glucose levels were significantly lower than glucose levels of control obese mice after glucose load. The plasma triglyceride levels in pitolisant-treated mice were significantly lower compared with those in control obese group. In conclusion, pitolisant has a favorable influence of body weight and improves glucose tolerance and the lipid profile in obese mice.

Critical in vivo roles of WNT10A in wound healing by regulating collagen expression/synthesis in WNT10A-deficient mice

Background

We have reported that WNT10A plays a critical role in the growth of fibroblasts/myofibroblasts and microvascular endothelial cells, i.e.; wound healing/scarring. To ascertain the in vivo regulatory, central functions of WNT10A, we examined the net effects of WNT10A depletion using WNT10A-deficient mice (WNT10A^–/–).

Methods and results

We generated WNT10A^–/–mice, displaying a range of unique phenotypes of morpho/organogenetic failure, such as growth retardation, alopecia, kyphosis and infertility, and then focused on the functions of WNT10A in wound healing. We subjected C57BL/6J wild-type (WT) or WNT10A^–/–mice to skin ulcer formation. The WNT10A^–/–mice had significantly larger injured areas and delayed wound healing, which were associated with (a) a smaller number of fibroblasts/myofibroblasts and microvessels; and (b) more reduced expression and synthesis of collagen, compared with WT mice with intact WNT10A expression, especially in those with activated myofibroblasts.

Conclusions

These observations indicate that WNT10A signaling can play a pivotal in vivo role in wound healing by regulating the expression and synthesis of collagen, as one of fibrogenic factors, at least in part, and critical in vivo roles of WNT10A-mediated effective wound healing are extremely closely associated with collagen expression.

Knockout of l-Histidine Decarboxylase Prevents Cholangiocyte Damage and Hepatic Fibrosis in Mice Subjected to High-Fat Diet Feeding via Disrupted Histamine/Leptin Signaling

Feeding a high-fat diet (HFD) coupled with sugar, mimicking a Western diet, causes fatty liver disease in mice. Histamine induces biliary proliferation and fibrosis and regulates leptin signaling. Wild-type (WT) and l-histidine decarboxylase (Hdc-/-) mice were fed a control diet or an HFD coupled with a high fructose corn syrup equivalent. Hematoxylin and eosin and Oil Red O staining were performed to determine steatosis. Biliary mass and cholangiocyte proliferation were evaluated by immunohistochemistry. Senescence and fibrosis were measured by quantitative PCR and immunohistochemistry. Hepatic stellate cell activation was detected by immunofluorescence. Histamine and leptin levels were measured by enzyme immunoassay. Leptin receptor (Ob-R) was evaluated by quantitative PCR. The HDC/histamine/histamine receptor axis, ductular reaction, and biliary senescence were evaluated in patients with nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, or end-stage liver disease. Hdc-/- HFD mice had increased steatosis compared with WT HFD mice. WT HFD mice had increased biliary mass, biliary proliferation, senescence, fibrosis, and hepatic stellate cell activation, which were reduced in Hdc-/- HFD mice. In Hdc-/- HFD mice, serum leptin levels increased, whereas biliary Ob-R expression decreased. Nonalcoholic steatohepatitis patients had increased HDC/histamine/histamine receptor signaling. Hdc-/- HFD mice are susceptible to obesity via dysregulated leptin/Ob-R signaling, whereas the lack of HDC protects from HFD-induced fibrosis and cholangiocyte damage. HDC/histamine/leptin signaling may be important in managing obesity-induced biliary damage.

Antipsychotic Drugs: From Receptor-binding Profiles to Metabolic Side Effects

BACKGROUND

Antipsychotic-induced metabolic side effects are major concerns in psychopharmacology and clinical psychiatry. Their pathogenetic mechanisms are still not elucidated.

METHODS

Herein, we review the impact of neurotransmitters on metabolic regulation, providing insights into antipsychotic-induced metabolic side effects.

RESULTS

Antipsychotic drugs seem to interfere with feeding behaviors and energy balance, processes that control metabolic regulation. Reward and energy balance centers in central nervous system constitute the central level of metabolic regulation. The peripheral level consists of skeletal muscles, the liver, the pancreas, the adipose tissue and neuroendocrine connections. Neurotransmitter receptors have crucial roles in metabolic regulation and they are also targets of antipsychotic drugs. Interaction of antipsychotics with neurotransmitters could have both protective and harmful effects on metabolism.

CONCLUSION

Emerging evidence suggests that antipsychotics have different liabilities to induce obesity, diabetes and dyslipidemia. However this diversity cannot be explained merely by drugs'pharmacodynamic profiles, highlighting the need for further research.

Cholic Acid Enhances Visceral Adiposity, Atherosclerosis and Nonalcoholic Fatty Liver Disease in Microminipigs

AIM

We have recently established a novel swine model for studies of atherosclerosis using MicrominipigsTM (µMPs) fed a high-fat/high-cholesterol diet (HcD). Using this swine model, we re-evaluated the effects of dietary cholic acid (CA) on serum lipid profile, atherosclerosis and hepatic injuries.

METHODS

The µMPs were fed HcD supplemented with 0.7% CA (HcD＋CA) for eight weeks, and the effect of CA on serum lipoprotein levels, expression of oxidative stress markers, adiposity and lesion formation in the aorta, liver, and other organs was investigated.

RESULTS

The HcD＋CA-fed group exhibited more visceral adiposity, progression of atherosclerosis and higher serum levels of oxidative stress markers than the HcD-fed group, even though they showed similar serum lipid levels. The liver demonstrated increased lipid accumulation, higher expression of oxidative stress markers, accelerated activation of foamy Kupffer cells and stellate cells, and increased hepatocyte apoptosis, indicating non-alcoholic fatty liver disease (NAFLD). Intriguingly, foamy macrophage mobilization was observed in various organs, including the reticuloendothelial system, pulmonary capillary vessels and skin very often in HcD＋CA-fed µMPs.

CONCLUSION

To our knowledge, this is the first large animal model, in which visceral obesity, NAFLD and atherosclerosis are concomitantly induced by dietary manipulation. These data suggest the detrimental effects of CA, potentially through local and systemic activation of oxidative stress-induced signaling to macrophage mobilization, on the acceleration of visceral adiposity, atherosclerosis and NAFLD.

Critical in vivo roles of histamine and histamine receptor signaling in animal models of metabolic syndrome

Histamine, a classic low-molecular-weight amine, is synthesized from L-histidine by histidine decarboxylase (HDC), and histamine-specific receptors (HRs) are essential for its actions. Our serial in vivo studies have uniquely reported that expression of histamine/HRs is variably identified in atherosclerotic lesions, and that HDC-gene knockout mice without histamine/HRs signaling show a marked reduction of atherosclerotic progression. These data have convinced us that histamine plays a pivotal role in the pathogenesis of atherosclerosis. Among four subclasses of HRs, the expression profile of the main receptors (H1/2R) has been shown to be switched from H2R to H1R during monocyte to macrophage differentiation, and H1R is also predominant in smooth muscle and endothelial cells of atheromatous plaque. Using various animal models of H1/2R-gene knockout mice, H1R and H2R were found to reciprocally but critically regulate not only hypercholesterolemia-induced atherosclerosis and injury-induced arteriosclerosis, but also hyperlipidemia-induced nonalcoholic fatty liver disease (NAFLD). Metabolic syndrome manifests obesity, dyslipidemia, insulin resistance, atherosclerosis, and/or NAFLD, i.e. the dysregulation of lipid/bile acid/glucose metabolism. Therefore, although its etiology is complicated and multifactorial, histamine/HRs signaling has a close relationship with the development of metabolic syndrome. We herein review diverse, key in vivo roles of histamine/HR signaling in the pathogenesis of metabolic syndrome.

Mastication Frequency and Postprandial Blood Sugar Levels in Normoglycaemic and Dysglycaemic Individuals: A Cross- Sectional Comparative Study

INTRODUCTION

Mastication has potential to affect postprandial blood glucose levels by affecting cephalic phase of insulin release. However, limited number of studies done in this regard has yielded conflicting results.

AIM

To evaluate effects of mastication on postprandial blood glucose levels.

MATERIALS AND METHODS

We compared routine and thorough mastication in 2 separate groups: dysglycaemic (prediabetics and diabetics) and normoglycaemic in prospective interventional study. Blood glucose levels were measured pre-prandial and postprandial (after 2 hours) on separate days after routine and thorough mastication in both groups.

RESULTS

In normoglycaemic group, thorough mastication significantly reduced postprandial blood glucose levels at 2 hours (128.25± 7.82 mg/dl on routine mastication vs 119.74±9.08 mg/dl on thorough mastication, p<0.05). Comparatively, in dysglycaemic group, thorough mastication had little effect on postprandial blood glucose levels at 2 hours (244.07±22.37 mg/dl vs. 243.55±22.87 mg/dl).

CONCLUSION

In normoglycaemic group, postprandial blood glucose concentration upon thorough mastication was significantly lower, due to early-phase insulin secretion. This simple lifestyle modification of thorough mastication can be a useful preventive measure against diabetes in people with a strong family history and other risk factors for diabetes who have not yet developed diabetes or prediabetes.

Histamine H2-Receptor Antagonist Use Is Associated With Lower Prevalence of Nonalcoholic Fatty Liver Disease: A Population-based Study From the National Health and Nutrition Examination Survey, 2001-2006

BACKGROUND & AIM

Recent basic mechanistic studies found that proton-pump inhibitors (PPIs) or histamine antagonists inhibited multiple pathways involved in nonalcoholic fatty liver disease (NAFLD) development. The aim of this study was to investigate an association between PPIs or H1/H2-receptor antagonist (H1RA/H2RA) use and NAFLD prevalence in the general US population.

METHODS

We conducted a cross-sectional analysis of data from the National Health and Nutrition Examination Survey, 2001-2006. We included 10,398 adults aged 20 to 74 years who had alanine aminotransferase data; of those, 2058 were identified as having NAFLD and 8340 as controls. PPI or H1RA/H2RA use was defined as use of prescription medications in the preceding month. The length of use was categorized as ≤60 days and >60 days. NAFLD was defined as elevated serum aminotransferases without any indication of other causes of chronic liver disease.

RESULTS

In the multivariate unconditional logistic regression analysis, H2RA use was inversely associated with prevalent NAFLD [odds ratio (OR)=0.43, 95% confidence interval (CI), 0.18-0.99], a finding that was primarily limited to men (OR=0.18, 95% CI, 0.04-0.79) and those with insulin resistance (OR=0.22, 95% CI, 0.05-0.95). However, no significant associations were found between PPI or H1RA use and prevalent NAFLD.

CONCLUSIONS

These findings, from the first human study to investigate an association of PPI or H1RA/H2RA use with NAFLD, suggest that H2RA use may be associated with a lower prevalence of NAFLD, primarily among men with insulin resistance.

Overexpression of Peroxiredoxin 4 Affects Intestinal Function in a Dietary Mouse Model of Nonalcoholic Fatty Liver Disease

Background

Accumulating evidence has shown that methionine- and choline-deficient high fat (MCD+HF) diet induces the development of nonalcoholic fatty liver disease (NAFLD), in which elevated reactive oxygen species play a crucial role. We have reported that peroxiredoxin 4 (PRDX4), a unique secretory member of the PRDX antioxidant family, protects against NAFLD progression. However, the detailed mechanism and potential effects on the intestinal function still remain unclear.

Methods & Results

Two weeks after feeding mice a MCD+HF diet, the livers of human PRDX4 transgenic (Tg) mice exhibited significant suppression in the development of NAFLD compared with wild-type (WT) mice. The serum thiobarbituric acid reactive substances levels were significantly lower in Tg mice. In contrast, the Tg small intestine with PRDX4 overexpression showed more suppressed shortening of total length and villi height, and more accumulation of lipid in the jejunum, along with lower levels of dihydroethidium binding. The enterocytes exhibited fewer apoptotic but more proliferating cells, and inflammation was reduced in the mucosa. Furthermore, the small intestine of Tg mice had significantly higher expression of cholesterol absorption-regulatory factors, including liver X receptor-α, but lower expression of microsomal triglyceride-transfer protein.

Conclusion

Our present data provide the first evidence of the beneficial effects of PRDX4 on intestinal function in the reduction of the severity of NAFLD, by ameliorating oxidative stress-induced local and systemic injury. We can suggest that both liver and intestine are spared, to some degree, by the antioxidant properties of PRDX4.

Hepatic adenylate cyclase 3 is upregulated by Liraglutide and subsequently plays a protective role in insulin resistance and obesity

OBJECTIVE

Recent studies have demonstrated that adenylate cyclase 3 (AC3) has a protective role in obesity. This gene resides at the pathway with glucagon-like peptide (GLP)-1. Liraglutide is a GLP-1 analog and has independent glucose and body weight (BW)-reducing effects. In the present study, we aimed to examine whether hepatic AC3 activity was regulated by Liraglutide and to further understand the effect of AC3 in reduction of BW and insulin resistance.

SUBJECTS

The diabesity and obese mice were induced from db/db and C57BL/6 J mice, respectively, by high-fat diet. Liraglutide (0.1 mg kg(-1) per 12 h) was given to the mice twice daily for 12 weeks. C57BL/6 J mice fed with chow diet and obese or diabesity mice treated with saline were used as the controls. Hepatic AC3 gene expression at mRNA and protein levels was analyzed with real-time reverse transcription-PCR and western blot. Fasting blood glucose and serum insulin levels were measured and followed insulin resistance index (HOMA-IR) was evaluated according to the homeostasis model assessment.

RESULTS

After administration of Liraglutide, BW and HOMA-IR in obese and diabesity mice were decreased, whereas hepatic AC3 mRNA and protein expression levels were upregulated. The AC3 gene expression was negatively correlated with BW, HOMA-IR and the area ratio of hepatic fat deposition in the liver.

CONCLUSIONS

The present study thus provides the evidence that hepatic AC3 gene expression is upregulated by Liraglutide. The reduction of BW and improvement of insulin resistance with Liraglutide may be partially explained by AC3 activation.

Long-term ketogenic diet contributes to glycemic control but promotes lipid accumulation and hepatic steatosis in type 2 diabetic mice

The ketogenic diet (KD) has been widely used in weight and glycemic control, although potential side effects of long-term KD treatment have caused persistent concern. In this study, we hypothesized that the KD would ameliorate the progression of diabetes but lead to disruptions in lipid metabolism and hepatic steatosis in a mouse model of diabetes. In type 2 diabetic mouse model, mice were fed a high-fat diet and administered streptozotocin treatment before given the test diets for 8 weeks. Subsequently, ameliorated glucose and insulin tolerance in KD-fed diabetic mice was found, although the body weight of high-fat diet- and KD-fed mice was similar. Interestingly, the weight of adipose tissue in KD mice was greater than in the other groups. The KD diet resulted in higher serum triacylglycerol and cholesterol levels in diabetic mice. Moreover, the KD-fed mice showed greater hepatic lipid accumulation. Mice fed the KD showed significant changes in several key genes such as sterol regulatory element-binding protein, fibroblast growth factor 21, and peroxisome proliferator-activated receptor α, which are all important in metabolism. In summary, KD ameliorates glucose and insulin tolerance in a mouse model of diabetes, but severe hepatic lipid accumulation and hepatic steatosis were observed, which should be considered carefully in the long-term application of KD.

Mass-Spectrometry-Based Serum Metabolomics of a C57BL/6J Mouse Model of High-Fat-Diet-Induced Non-alcoholic Fatty Liver Disease Development

Obesity, dyslipidemia, insulin resistance, oxidative stress, and inflammation are key clinical risk factors for the progression of non-alcoholic fatty liver disease (NAFLD). Currently, there is no comprehensive metabolic profile of a well-established animal model that effectively mimics the etiology and pathogenesis of NAFLD in humans. Here, we report the pathophysiological and metabolomic changes associated with NAFLD development in a C57BL/6J mouse model in which NAFLD was induced by feeding a high-fat diet (HFD) for 4, 8, 12, and 16 weeks. Serum metabolomic analysis was conducted using ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) and gas chromatography-mass spectrometry (GC-MS) to establish a metabolomic profile. Analysis of the metabolomic profile in combination with principal component analysis revealed marked differences in metabolites between the control and HFD group depending upon NAFLD severity. A total of 30 potential biomarkers were strongly associated with the development of NAFLD. Among these, 11 metabolites were mainly related to carbohydrate metabolism, hepatic biotransformation, collagen synthesis, and gut microbial metabolism, which are characteristics of obesity, as well as significantly increased serum glucose, total cholesterol, and hepatic triglyceride levels during the onset of NAFLD (4 weeks). At 8 weeks, 5 additional metabolites that are chiefly involved in perturbation of lipid metabolism and insulin secretion were found to be associated with hyperinsulinemia, hyperlipidemia, and hepatic steatosis in the mid-term of NAFLD progression. At the end of 12 and 16 weeks, 14 additional metabolites were predominantly correlated to abnormal bile acid synthesis, oxidative stress, and inflammation, representing hepatic inflammatory infiltration during NAFLD development. These results provide potential biomarkers for early risk assessment of NAFLD and further insights into NAFLD development.

The histaminergic system as a target for the prevention of obesity and metabolic syndrome

The control of food intake and body weight is very complex. Key factors driving eating behavior are hunger and satiety that are controlled by an interplay of several central and peripheral neuroendocrine systems, environmental factors, the behavioral state and circadian rhythm, which all concur to alter homeostatic aspects of appetite and energy expenditure. Brain histamine plays a fundamental role in eating behavior as it induces loss of appetite and has long been considered a satiety signal that is released during food intake (Sakata et al., 1997). Animal studies have shown that brain histamine is released during the appetitive phase to provide a high level of arousal preparatory to feeding, but also mediates satiety. Furthermore, histamine regulates peripheral mechanisms such as glucose uptake and insulin function. Preclinical research indicates that activation of H1 and H3 receptors is crucial for the regulation of the diurnal rhythm of food consumption; furthermore, these receptors have been specifically recognized as mediators of energy intake and expenditure. Despite encouraging preclinical data, though, no brain penetrating H1 receptor agonists have been identified that would have anti-obesity effects. The potential role of the H3 receptor as a target of anti-obesity therapeutics was explored in clinical trials that did not meet up to the expectations or were interrupted (clinicaltrials.gov). Nonetheless, interesting results are emerging from clinical trials that evaluated the attenuating effect of betahistine (an H1 agonist/H3 antagonist) on metabolic side effects associated with chronic antipsychotics treatment. Aim of this review is to summarize recent results that suggest the clinical relevance of the histaminergic system for the treatment of feeding disorders and provide an up-to-date summary of preclinical research. This article is part of the Special Issue entitled 'Histamine Receptors'.

The H1-receptor antagonist cetirizine ameliorates high-fat diet-induced glucose intolerance in male C57BL/6 mice, but not diabetes outcome in female non-obese diabetic (NOD) mice

BACKGROUND

It has been proposed that the histamine 1-receptor (H1-receptor) not only promotes allergic reactions, but also modulates innate immunity and autoimmune reactions. In line with this, we have recently reported that the H1-receptor antagonist cetirizine partially counteracts cytokine-induced beta-cell signaling and destruction. Therefore, the aim of this study was to determine whether cetirizine affects diabetes in NOD mice, a model for human type 1 diabetes, and glucose intolerance in high-fat diet C57BL/6 mice, a model for human glucose intolerance.

METHODS

Female NOD mice were treated with cetirizine in the drinking water (25 mg/kg body weight) from 9 until 30 weeks of age during which precipitation of diabetes was followed. Male C57BL/6 mice were given a high-fat diet from 5 weeks of age. When the mice were 12 weeks of age cetirizine was given for 2 weeks in the drinking water. The effects of cetirizine were analyzed by blood glucose determinations, glucose tolerance tests, and insulin sensitivity tests.

RESULTS

Cetirizine did not affect diabetes development in NOD mice. On the other hand, cetirizine treatment for 1 week protected against high-fat diet-induced hyperglycemia. The glucose tolerance after 2 weeks of cetirizine treatment was improved in high-fat diet mice. We observed no effect of cetirizine on the insulin sensitivity of high-fat diet mice.

CONCLUSION

Our results suggest a protective effect of cetirizine against high-fat diet-induced beta-cell dysfunction, but not against autoimmune beta-cell destruction.

CCL22/Macrophage-derived Chemokine Expression in Apolipoprotein E-deficient Mice and Effects of Histamine in the Setting of Atherosclerosis

AIM

Macrophage-derived chemokine (CCL22) is a member of the CC-family of chemokines synthesized by monocyte-derived macrophages. Previous studies have reported a relationship between CCL22 and atherosclerosis and the role of histamine in this pathway. Histamine ncreases the CCL22 expression in human monocytes via the H2 receptor. In this study, we investigated the effects of CCL22 and the role of histamine in mouse monocytes with respect to atherosclerosis.

METHODS AND RESULTS

The expression of CCL22 was investigated in apolipoprotein E (apoE)-deficient mice. The mice had high serum concentrations of CCL22 and their atherosclerotic lesions contained abundant levels of CCL22. In addition, when the mouse monocyte cell line (J774A.1 cells) differentiated into macrophage-like cells, the cells showed a similar expression of CCL22 and reduced expression of H2 receptors. Histamine is synthesized from l-histidine by histidine decarboxylase (HDC) in a single enzymatic step. HDC knockout mice were compared with apoE/HDC double knockout mice. The findings indicated that the expression of CCL22 in atherosclerosis models is under the influence of histamine. In addition, in vitro studies using J774A.1 cells and an in vivo study using histamine receptor knockout mice showed that histamine stimulates the CCL22 expression via the histamine H2 receptor.

CONCLUSIONS

The current results support our previous CCL22 studies in the setting of human atherosclerosis and suggest that this molecule is involved in the atherogenic processes in a mouse model of atherosclerosis.

H1-antihistamines exacerbate high-fat diet-induced hepatic steatosis in wild-type but not in apolipoprotein E knockout mice

We examined the effects of two over-the-counter H1-antihistamines on the progression of fatty liver disease in male C57Bl/6 wild-type and apolipoprotein E (ApoE)-/- mice. Mice were fed a high-fat diet (HFD) for 3 mo, together with administration of either cetirizine (4 mg/kg body wt) or fexofenadine (40 mg/kg body wt) in drinking water. Antihistamine treatments increased body weight gain, gonadal fat deposition, liver weight, and hepatic steatosis in wild-type mice but not in ApoE-/- mice. Lobular inflammation, acute inflammation, and necrosis were not affected by H1-antihistamines in either genotype. Serum biomarkers of liver injury tended to increase in antihistamine-treated wild-type mice. Serum level of glucose was increased by fexofenadine, whereas lipase was increased by cetirizine. H1-antihistamines reduced the mRNA expression of ApoE and carbohydrate response element-binding protein in wild-type mice, without altering the mRNA expression of sterol regulatory element-binding protein 1c, fatty acid synthase, or ApoB100, in either genotype. Fexofenadine increased both triglycerides and cholesterol ester, whereas cetirizine increased only cholesterol ester in liver, with a concomitant decrease in serum triglycerides by both antihistamines in wild-type mice. Antihistamines increased hepatic levels of conjugated bile acids in wild-type mice, with the effect being significant in fexofenadine-treated animals. The increase was associated with changes in the expression of organic anion transport polypeptide 1b2 and bile salt export pump. These results suggest that H1-antihistamines increase the progression of fatty liver disease in wild-type mice, and there seems to be an association between the severity of disease, presence of ApoE, and increase in hepatic bile acid levels.

Synthetic FXR agonist GW4064 is a modulator of multiple G protein-coupled receptors

The synthetic nuclear bile acid receptor (farnesoid X receptor [FXR]) agonist GW4064 is extensively used as a specific pharmacological tool to illustrate FXR functions. We noticed that GW4064 activated empty luciferase reporters in FXR-deficient HEK-293T cells. We postulated that this activity of GW4064 might be routed through as yet unknown cellular targets and undertook an unbiased exploratory approach to identify these targets. Investigations revealed that GW4064 activated cAMP and nuclear factor for activated T-cell response elements (CRE and NFAT-RE, respectively) present on these empty reporters. Whereas GW4064-induced NFAT-RE activation involved rapid intracellular Ca(2+) accumulation and NFAT nuclear translocation, CRE activation involved soluble adenylyl cyclase-dependent cAMP accumulation and Ca(2+)-calcineurin-dependent nuclear translocation of transducers of regulated CRE-binding protein 2. Use of dominant negative heterotrimeric G-protein minigenes revealed that GW4064 caused activation of Gαi/o and Gq/11 G proteins. Sequential pharmacological inhibitor-based screening and radioligand-binding studies revealed that GW4064 interacted with multiple G protein-coupled receptors. Functional studies demonstrated that GW4064 robustly activated H1 and H4 and inhibited H2 histamine receptor signaling events. We also found that MCF-7 breast cancer cells, reported to undergo GW4064-induced apoptosis in an FXR-dependent manner, did not express FXR, and the GW4064-mediated apoptosis, also apparent in HEK-293T cells, could be blocked by selective histamine receptor regulators. Taken together, our results demonstrate identification of histamine receptors as alternate targets for GW4064, which not only necessitates cautious interpretation of the biological functions attributed to FXR using GW4064 as a pharmacological tool but also provides a basis for the rational designing of new pharmacophores for histamine receptor modulation.

Sequence-structure based phylogeny of GPCR Class A Rhodopsin receptors

Current methods of G protein coupled receptors (GPCRs) phylogenetic classification are sequence based and therefore inappropriate for highly divergent sequences, sharing low sequence identity. In this study, sequence structure profile based alignment generated by PROMALS3D was used to understand the GPCR Class A Rhodopsin superfamily evolution using the MEGA 5 software. Phylogenetic analysis included a combination of Neighbor-Joining method and Maximum Likelihood method, with 1000 bootstrap replicates. Our study was able to identify potential ligand association for Class A Orphans and putative/unclassified Class A receptors with no cognate ligand information: GPR21 and GPR52 with fatty acids; GPR75 with Neuropeptide Y; GPR82, GPR18, GPR141 with N-arachidonylglycine; GPR176 with Free fatty acids, GPR10 with Tachykinin & Neuropeptide Y; GPR85 with ATP, ADP & UDP glucose; GPR151 with Galanin; GPR153 and GPR162 with Adrenalin, Noradrenalin; GPR146, GPR139, GPR142 with Neuromedin, Ghrelin, Neuromedin U-25 & Thyrotropin-releasing hormone; GPR171 with ATP, ADP & UDP Glucose; GPR88, GPR135, GPR161, GPR101with 11-cis-retinal; GPR83 with Tackykinin; GPR148 with Prostanoids, GPR109b, GPR81, GPR31with ATP & UTP and GPR150 with GnRH I & GnRHII. Furthermore, we suggest that this study would prove useful in re-classification of receptors, selecting templates for homology modeling and identifying ligands which may show cross reactivity with other GPCRs as signaling via multiple ligands play a significant role in disease modulation.

Depletion of apoptosis signal-regulating kinase 1 prevents bile duct ligation-induced necroinflammation and subsequent peribiliary fibrosis

Apoptosis signal-regulating kinase 1 (ASK1), also known as mitogen-activated protein kinase kinase kinase (MAP3K), is ubiquitously expressed and situated in an important upstream position of many signal transduction pathways. ASK1 plays a pivotal role in stressor-induced cell survival and inflammatory reactions. To ascertain the regulatory functions of ASK1 in bile duct ligation (BDL)-induced liver injury, we examined the net effects of ASK1 depletion on hepatic necroinflammation and/or fibrosis. We subjected C57BL/6 wild-type (WT) or ASK1-deficient (ASK1(-/-)) mice to sham or BDL surgery for 14 days. In day 3 BDL animals, ASK1(-/-) mice had significantly fewer bile infarcts along with more reduced interlobular or portal inflammatory infiltrate of various immune cells, including neutrophils, compared with WT mice in which ASK1 expression was markedly activated. Morphologically apoptotic hepatocytes or cholangiocytes were negligible in both the sham and BDL animals. In contrast, ASK1(-/-) mice had significantly less proliferating activity of not only hepatocytes but also large cholangiocytes than WT mice. Day 14 BDL ASK1(-/-) mice manifested potential antifibrogenic aspects of ASK1 deficiency, characterized by significantly fewer activated peribiliary fibrogenic cells and peribiliary fibrosis. These observations indicate that ASK1-mediated hepatic necroinflammation and proliferation, but not apoptosis, are closely linked to liver fibrosis and fibrogenesis. A specific ASK1 pathway blocker or inhibitor might offer a therapeutic strategy against human cholestatic diseases.

Peroxiredoxin 4 protects against nonalcoholic steatohepatitis and type 2 diabetes in a nongenetic mouse model

AIMS

Consumption of a high-fructose diet (HFrD) can induce the development of a metabolic syndrome, manifesting as nonalcoholic steatohepatitis (NASH) and/or type 2 diabetes mellitus (T2DM), via a process in which oxidative stress plays a critical role. Peroxiredoxin 4 (PRDX4) is a unique and only known secretory member of the PRDX antioxidant family. However, its putative roles in the development of NASH and/or T2DM have not been investigated.

RESULTS

To elucidate the functions of PRDX4 in a metabolic syndrome, we established a nongenetic mouse model of T2DM by feeding mice a HFrD after injecting a relatively low dose of streptozotocin. Compared with wild-type (WT), human PRDX4 transgenic (Tg) mice exhibited significant improvements in insulin resistance, characterized by a lower glucose and insulin concentration and faster responses in glucose tolerance tests. The liver of Tg also showed less severe vesicular steatosis, inflammation, and fibrosis, along with lower lipid concentrations, lower levels of oxidative stress markers, more decreased expression of hepatic aminotransferase, and more reduced stellate cell activation than those in the WT liver, reminiscent of human early NASH. Hepatocyte apoptosis was also significantly repressed in Tg mice. By contrast, serum adiponectin levels and hepatic adiponectin receptor expression were significantly lower in WT mice, consistent with greater insulin resistance in the peripheral liver tissue compared with Tg mice.

INNOVATION AND CONCLUSION

Our data for the first time show that PRDX4 may protect against NASH, T2DM, and the metabolic syndrome by ameliorating oxidative stress-induced injury.

The role of hypothalamic H1 receptor antagonism in antipsychotic-induced weight gain

Treatment with second generation antipsychotics (SGAs), notably olanzapine and clozapine, causes severe obesity side effects. Antagonism of histamine H1 receptors has been identified as a main cause of SGA-induced obesity, but the molecular mechanisms associated with this antagonism in different stages of SGA-induced weight gain remain unclear. This review aims to explore the potential role of hypothalamic histamine H1 receptors in different stages of SGA-induced weight gain/obesity and the molecular pathways related to SGA-induced antagonism of these receptors. Initial data have demonstrated the importance of hypothalamic H1 receptors in both short- and long-term SGA-induced obesity. Blocking hypothalamic H1 receptors by SGAs activates AMP-activated protein kinase (AMPK), a well-known feeding regulator. During short-term treatment, hypothalamic H1 receptor antagonism by SGAs may activate the AMPK-carnitine palmitoyltransferase 1 signaling to rapidly increase caloric intake and result in weight gain. During long-term SGA treatment, hypothalamic H1 receptor antagonism can reduce thermogenesis, possibly by inhibiting the sympathetic outflows to the brainstem rostral raphe pallidus and rostral ventrolateral medulla, therefore decreasing brown adipose tissue thermogenesis. Additionally, blocking of hypothalamic H1 receptors by SGAs may also contribute to fat accumulation by decreasing lipolysis but increasing lipogenesis in white adipose tissue. In summary, antagonism of hypothalamic H1 receptors by SGAs may time-dependently affect the hypothalamus-brainstem circuits to cause weight gain by stimulating appetite and fat accumulation but reducing energy expenditure. The H1 receptor and its downstream signaling molecules could be valuable targets for the design of new compounds for treating SGA-induced weight gain/obesity.