Irisin Inhibits Hepatic Cholesterol Synthesis via AMPK-SREBP2 Signaling

The therapeutic potential of irisin to mitigate the risk of metabolic syndrome in postmenopausal women

Oestradiol withdrawal at menopause predisposes women to metabolic syndrome, a cluster of interrelated conditions including obesity, insulin resistance, dyslipidaemia and hypertension that together confer an increased risk of developing type 2 diabetes mellitus and cardiovascular disease. Hormone replacement therapies are commonly used to treat acute symptoms of the perimenopausal period, and whilst they have been associated with metabolic improvements in many studies, long-term use is considered unviable. Novel approaches are required to mitigate the risk of postmenopausal metabolic syndrome. In 2012, the exercise-inducible myokine irisin was isolated from the skeletal muscle of mice and identified to have anti-obesity and antidiabetic effects in vivo. Irisin is now recognised to exert pleiotropic action on cognitive, bone and metabolic health. There is accumulating evidence from in vitro and in vivo rodent studies that irisin can mitigate each component condition of metabolic syndrome. In postmenopausal women, independent associations have been observed between (a) exercise and plasma irisin concentration and (b) plasma irisin concentration and reduced incidence of metabolic syndrome. To date, however, no study has considered the mechanistic basis by which irisin, whether exercise-induced or exogenously administered, could reduce the incidence or severity of metabolic syndrome in postmenopausal women. This review aims to analyse the literature concerning the metabolic actions of irisin, with a focus on its therapeutic potential for metabolic syndrome driven by a state of oestradiol depletion. It evaluates the practicality of exercise as a therapy and discusses other irisin-based therapeutic strategies that may alleviate postmenopausal metabolic syndrome. Finally, it highlights areas where future research is required to advance knowledge of irisin's biological action such that it could be considered a viable candidate for clinical application.

Tianma-Gouteng pair ameliorates the cognitive deficits on two transgenic mouse models of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Alzheimer's disease (AD) is a progressive neurodegenerative disease. Tianma-Gouteng Pair (TGP), commonly prescribed as a pair-herbs, can be found in many Chinese medicine formulae to treat brain diseases. However, the neuroprotective effects and molecular mechanisms of TGP remained unexplored.

AIM OF THE STUDY

This study investigated the difference between the TgCRND8 and 5 × FAD transgenic mice, the anti-AD effects of TGP, and underlying molecular mechanisms of TGP against AD through the two mouse models.

METHODS

Briefly, three-month-old TgCRND8 and 5 × FAD mice were orally administered with TGP for 4 and 6 months, respectively. Behavioral tests were carried out to determine the neuropsychological functions. Moreover, immunofluorescence and western blotting assays were undertaken to reveal the molecular mechanisms of TGP.

RESULTS

Although TgCRND8 and 5 × FAD mice had different beta-amyloid (Aβ) burdens, neuroinflammation status, and cognition impairments, TGP exerted neuroprotective effects against AD in the two models. In detail, behavioral tests revealed that TGP treatment markedly ameliorated the anxiety-like behavior, attenuated the recognition memory deficits, and increased the spatial learning ability as well as the reference memory of TgCRND8 and 5 × FAD mice. Moreover, TGP treatment could regulate the beta-amyloid precursor protein (APP) processing by inhibiting the Aβ production enzymes such as β- and γ-secretases and activating Aβ degrading enzyme to reduce Aβ accumulation. In addition, TGP reduced the Aβ42 level, the ratio of Aβ42/Αβ40, Aβ accumulation, and tau hyperphosphorylation in both the 5 × FAD and TgCRND8 mouse models. Furthermore, TGP ameliorated neuroinflammation by decreasing the densities of activated microglia and astrocytes, and inhibiting the production of inflammatory cytokines. TGP upregulated the SIRT1 and AMPK, and downregulated sterol response element binding protein 2 (SREBP2) in the brain of TgCRND8 mice and deactivation of the EPhA4 and c-Abl in the brain tissues of 5 × FAD mice.

CONCLUSION

Our experiments for the first time revealed the neuroprotective effects and molecular mechanism of TGP on 5 × FAD and TgCRND8 transgenic mouse models of different AD stages. TGP decreased the level of Aβ aggregates, improved the tauopathy, and reduced the neuroinflammation by regulation of the SIRT1/AMPK/SREBP2 axis and deactivation of EPhA4/c-Abl signaling pathway in the brains of TgCRND8 and 5 × FAD mice, respectively. All these findings unequivocally confirmed that the TGP would be promising in developing into an anti-AD therapeutic pharmaceutical.

Resveratrol and (-)-Epigallocatechin-3-gallate Regulate Lipid Metabolism by Activating the AMPK Pathway in Hepatocytes

The purpose of this study was to explore the effects of Res and EGCG on cell growth, cellular antioxidant levels, and cellular lipid metabolism in hepatocytes. In this experiment, leghorn male hepatoma (LMH) cells were used as hepatocytes. The results showed that 6.25-25 μM Res and EGCG had no adverse effects on cell viability and growth. Meanwhile, with the increasing dosage of Res and EGCG, the contents of total cholesterol (TC), total glyceride (TG), and malondialdehyde (MDA) in hepatocytes decreased significantly (p < 0.05), while the contents of glutathione peroxidase (GSH-Px), total superoxide dismutase (T-SOD), and catalase (CAT) increased significantly (p < 0.05). In addition, western blot results showed that Res and EGCG could significantly increase the expression of p-AMPK protein and reduce the expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) protein in hepatocytes (p < 0.05). Moreover, q-PCR results showed that with the increase in Res and EGCG, the expression of cholesterol- and fatty acid synthesis-related genes decreased significantly (p < 0.05). In conclusion, Res and EGCG can increase the antioxidant capacity of hepatocytes and reduce the synthesis of TC and TG in hepatocytes by activating AMPK, thereby regulating lipid metabolism in hepatocytes.

Exercise ameliorates muscular excessive mitochondrial fission, insulin resistance and inflammation in diabetic rats via irisin/AMPK activation

This study aimed to investigate the effects of exercise on excessive mitochondrial fission, insulin resistance, and inflammation in the muscles of diabetic rats. The role of the irisin/AMPK pathway in regulating exercise effects was also determined. Thirty-two 8-week-old male Wistar rats were randomly divided into four groups (n = 8 per group): one control group (Con) and three experimental groups. Type 2 diabetes mellitus (T2DM) was induced in the experimental groups via a high-fat diet followed by a single intraperitoneal injection of streptozotocin (STZ) at a dosage of 30 mg/kg body weight. After T2DM induction, groups were assigned as sedentary (DM), subjected to 8 weeks of treadmill exercise training (Ex), or exercise training combined with 8-week cycloRGDyk treatment (ExRg). Upon completion of the last training session, all rats were euthanized and samples of fasting blood and soleus muscle were collected for analysis using ELISA, immunofluorescence, RT-qPCR, and Western blotting. Statistical differences between groups were analyzed using one-way ANOVA, and differences between two groups were assessed using t-tests. Our findings demonstrate that exercise training markedly ameliorated hyperglycaemia, hyperlipidaemia, and insulin resistance in diabetic rats (p < 0.05). It also mitigated the disarranged morphology and inflammation of skeletal muscle associated with T2DM (p < 0.05). Crucially, exercise training suppressed muscular excessive mitochondrial fission in the soleus muscle of diabetic rats (p < 0.05), and enhanced irisin and p-AMPK levels significantly (p < 0.05). However, exercise-induced irisin and p-AMPK expression were inhibited by cycloRGDyk treatment (p < 0.05). Furthermore, the administration of CycloRGDyk blocked the effects of exercise training in reducing excessive mitochondrial fission and inflammation in the soleus muscle of diabetic rats, as well as the positive effects of exercise training on improving hyperlipidemia and insulin sensitivity in diabetic rats (p < 0.05). These results indicate that regular exercise training effectively ameliorates insulin resistance and glucolipid metabolic dysfunction, and reduces inflammation in skeletal muscle. These benefits are partially mediated by reductions in mitochondrial fission through the irisin/AMPK signalling pathway.

Saponins derived from Gynostemma pentaphyllum regulate triglyceride and cholesterol metabolism and the mechanisms: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Gynostemma pentaphyllum (Thunb.) Makino (G. pentaphyllum) can be used for both medicinal and tea and has lipid-lowering properties. Modern research has shown that its main bioactive components are flavonoids and saponins. It has many beneficial effects such as hypolipidemic, anti-cancer, cardioprotective, hepatoprotective, neuroprotective, anti-diabetic and anti-inflammatory.

AIMS OF THE REVIEW

This review aimed to summarize its anti-glycolipid metabolic models and mechanisms are reviewed to facilitate a deeper understanding of the mechanism in lowering lipids.

MATERIALS AND METHODS

Information related to lipid lowering in G. pentaphyllum was collated by reviewing the relevant literature in the PubMed database from 1985 to 2023.

RESULTS

Only 101 G. pentaphyllum compounds have been initially explored for their hypolipidemic activity. There are cell models, animal models and human subjects for lipid-lowering of it. It reduced triglyceride level via PPAR/UCP-1/PGC-1α/PRDM16 and (SREBP-1c)-ACC/FAS-CPT1 signal pathways. Cholesterol-lowering effects via (SREBP-2)-HMGCR, PCSK9-LDLR and bile acid biosynthetic pathways. Activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) is a key factor in the regulation of glycolipid metabolism in G. pentaphyllum. Other pathways of action of G. pentaphyllum in regulating glucolipid metabolism are also discussed in this paper.

CONCLUSION

To date, more than 328 saponins have been isolated and identified in Gynostemma. Further studies on these components, including molecular mechanisms and in vivo metabolic regulation, need to be further confirmed. G. pentaphyllum has the potential to be developed into drugs or functional foods, but further research is needed.

Explore novel molecular mechanisms of FNDC5 in ischemia-reperfusion (I/R) injury by analyzing transcriptome changes in mouse model of skeletal muscle I/R injury with FNDC5 knockout

BACKGROUND

Irisin, a myokine derived from proteolytic cleavage of the fibronectin type III domain-containing protein 5 (FNDC5) protein, is crucial in protecting tissues and organs from ischemia-reperfusion (I/R) injury. However, the underlying mechanism of its action remains elusive. In this study, we investigated the expression patterns of genes associated with FNDC5 knockout to gain insights into its molecular functions.

METHODS

We employed a mouse model of skeletal muscle I/R injury with FNDC5 knockout to examine the transcriptional profiles using RNA sequencing. Differentially expressed genes (DEGs) were identified and subjected to further analyses, including gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, protein-protein interaction (PPI) network analysis, and miRNA-transcription factor network analysis. The bioinformatics findings were validated using qRT-PCR and Western blotting.

RESULTS

Comparative analysis of skeletal muscle transcriptomes between wild-type (WT; C57BL/6), WT-I/R, FNDC5 knockout (KO), and KO-I/R mice highlighted the significance of FNDC5 in both physiological conditions and I/R injury. Through PPI network analysis, we identified seven key genes (Col6a2, Acta2, Col4a5, Fap, Enpep, Mmp11, and Fosl1), which facilitated the construction of a TF-hub genes-miRNA regulatory network. Additionally, our results suggested that the PI3K-Akt pathway is predominantly involved in FNDC5 deletion-mediated I/R injury in skeletal muscle. Animal studies revealed reduced FNDC5 expression in skeletal muscle following I/R injury, and the gastrocnemius muscle with FNDC5 knockout exhibited larger infarct size and more severe tissue damage after I/R. Moreover, Western blot analysis confirmed the upregulation of Col6a2, Enpep, and Mmp11 protein levels following I/R, particularly in the KO-I/R group. Furthermore, FNDC5 deletion inhibited the PI3K-Akt signaling pathway.

CONCLUSION

This study demonstrates that FNDC5 deletion exacerbates skeletal muscle I/R injury, potentially involving the upregulation of Col6a2, Enpep, and Mmp11. Additionally, the findings suggest the involvement of the PI3K-Akt pathway in FNDC5 deletion-mediated skeletal muscle I/R injury, providing novel insights into the molecular mechanisms underlying FNDC5's role in this pathological process.

Treadmill exercise with nanoselenium supplementation affects the expression of Irisin/FNDC5 and semaphorin 3A in rats exposed to cigarette smoke extract

In the current study, we investigated the impacts of 6 weeks of aerobic interval training (AIT) with selenium nanoparticles (SeNPs) on muscle, serum, and lung irisin (FNDC5) and Sema3A in rats exposed to cigarette smoke extract (CSE). To this end, 49 male Wistar rats (8 weeks old) were divided into seven groups: control, SeNPs (2.5 mg/kg b.w by oral gavage, 3 days/week, 6 weeks), AIT (49 min/day, 5 days/week for 6 weeks, interval), SeNPs + AIT, CSE (150 µL by IP injection, 1 day/week for 6 weeks), CSE + AIT, and CSE + SeNPs + AIT. The CSE group showed a significant reduction in irisin and Sema3A serum levels, as well as a decrease in FNDC5 and Sema3A gene expression in lung tissue (p < 0.05). A combined treatment (AIT with SeNPs) significantly increased the serum level and the expression of muscle and lung irisin (FNDC5) and Sema3A in CSE received groups (p < 0.05). There was a positive and significant correlation between muscle FNDC5 and lung FNDC5 in the CSE + SeNPs + AIT group (r = 0.92, p = 0.025). In addition, there was a positive and significant correlation between serum Sema3A and lung Sema3A of CSE + SeNPs + AIT group (r = 0.97, p = 0.004). Seemingly, performing aerobic exercises with the antioxidant and anti-inflammatory supplement nano-selenium in the model of lung damage (similar to COPD) can boost myokine irisin and Sema3A, especially in serum and lung tissue. These results displayed the paracrine/endocrine regulatory function of these myokines on other tissues. In other words, these interventions emphasized the creation of crosstalk between skeletal muscles and damaged lung, focusing on its recovery; however, further research is needed.

The Role of Adipokines and Myokines in the Pathogenesis of Different Obesity Phenotypes-New Perspectives

Obesity is a characteristic disease of the twenty-first century that is affecting an increasing percentage of society. Obesity expresses itself in different phenotypes: normal-weight obesity (NWO), metabolically obese normal-weight (MONW), metabolically healthy obesity (MHO), and metabolically unhealthy obesity (MUO). A range of pathophysiological mechanisms underlie the occurrence of obesity, including inflammation, oxidative stress, adipokine secretion, and other processes related to the pathophysiology of adipose tissue (AT). Body mass index (BMI) is the key indicator in the diagnosis of obesity; however, in the case of the NWO and MONW phenotypes, the metabolic disturbances are present despite BMI being within the normal range. On the other hand, MHO subjects with elevated BMI values do not present metabolic abnormalities. The MUO phenotype involves both a high BMI value and an abnormal metabolic profile. In this regard, attention has been focused on the variety of molecules produced by AT and their role in the development of obesity. Nesfatin-1, neuregulin 4, myonectin, irisin, and brain-derived neurotrophic factor (BDNF) all seem to have protective effects against obesity. The primary mechanism underlying the action of nesfatin-1 involves an increase in insulin sensitivity and reduced food intake. Neuregulin 4 sup-presses lipogenesis, decreases lipid accumulation, and reduces chronic low-grade inflammation. Myonectin lowers the amount of fatty acids in the bloodstream by increasing their absorption in the liver and AT. Irisin stimulates the browning of white adipose tissue (WAT) and consequently in-creases energy expenditure, additionally regulating glucose metabolism. Another molecule, BDNF, has anorexigenic effects. Decorin protects against the development of hyperglycemia, but may also contribute to proinflammatory processes. Similar effects are shown in the case of visfatin and chemerin, which may predispose to obesity. Visfatin increases adipogenesis, causes cholesterol accumulation in macrophages, and contributes to the development of glucose intolerance. Chemerin induces angiogenesis, which promotes the expansion of AT. This review aims to discuss the role of adipokines and myokines in the pathogenesis of the different obesity phenotypes.

Potential role of irisin in digestive system diseases

Digestive system diseases (DSD) are very complex conditions that severely threaten human health. Therefore, there is an urgent need to develop new pharmacological treatment strategies. Irisin, a myokine discovered in 2012, is produced by fibronectin type III domain-containing protein 5 (FNDC5), which is a transmembrane protein. Irisin is involved in promoting the browning of white adipose tissue, the regulation of energy metabolism, and the improvement of insulin resistance. Irisin is also an essential mediator of the inflammatory response, oxidative stress, and cell apoptosis. Recent studies have proved that irisin concentration is altered in DSD and exerts pivotal effects on the initiation, progression, and prognosis of these diseases through various mechanisms. Therefore, studying the expression and function of irisin may have great significance for the diagnosis and treatment of DSD. Here, we focus on irisin and explore the multiple molecular pathways targeted by irisin therapy. This review indicates that irisin can serve as a diagnostic marker or potential therapeutic agent for DSD. DATA AVAILABILITY: Not applicable.

AMPK and the Endocrine Control of Metabolism

Complex multicellular organisms require a coordinated response from multiple tissues to maintain whole-body homeostasis in the face of energetic stressors such as fasting, cold, and exercise. It is also essential that energy is stored efficiently with feeding and the chronic nutrient surplus that occurs with obesity. Mammals have adapted several endocrine signals that regulate metabolism in response to changes in nutrient availability and energy demand. These include hormones altered by fasting and refeeding including insulin, glucagon, glucagon-like peptide-1, catecholamines, ghrelin, and fibroblast growth factor 21; adipokines such as leptin and adiponectin; cell stress-induced cytokines like tumor necrosis factor alpha and growth differentiating factor 15, and lastly exerkines such as interleukin-6 and irisin. Over the last 2 decades, it has become apparent that many of these endocrine factors control metabolism by regulating the activity of the AMPK (adenosine monophosphate-activated protein kinase). AMPK is a master regulator of nutrient homeostasis, phosphorylating over 100 distinct substrates that are critical for controlling autophagy, carbohydrate, fatty acid, cholesterol, and protein metabolism. In this review, we discuss how AMPK integrates endocrine signals to maintain energy balance in response to diverse homeostatic challenges. We also present some considerations with respect to experimental design which should enhance reproducibility and the fidelity of the conclusions.

Effect of silymarin on the relative gene expressions of some inflammatory cytokines in the liver of CCl4-intoxicated male rats

The intensive exposure of the liver cells to any type of noxae, such as viruses, drugs, alcohols, and xenobiotics could induce hepatic inflammation through the upregulation of gene expression of several fibrotic and inflammatory mediators. So, our study assessed the role of silymarin on the inflammatory response induced by carbon tetrachloride (CCl4) as an example of xenobiotics on liver tissues in male rats. Forty-eight Wister male rats (weight: 130 ± 10) were housed for 14 days and then divided randomly into six groups: control, SLY: rats received only silymarin orally for 12 weeks (daily), CO: rats were injected with corn oil for 8 weeks (3 times weekly), CCl4: rats were injected with CCl4 solubilized in corn oil for 8 weeks (day by day), Treated: rats received silymarin for 4 weeks after CCl4 injection, Protected: rats received silymarin for 4 weeks before and 8 weeks during CCl4 injection. When the treatment period for the rats was over, they underwent scarification after anesthesia. Then, the sera were extracted from the collected blood for the determination of irisin levels, liver functions, and lipid profiles. Liver tissues were separated for the histopathological examinations, the determination of oxidative stress (OS) parameters content, and the relative gene expression of inflammatory cytokines; nuclear factor kappa (NF)-κB, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, cyclooxygenase (COX)-2, and transforming growth factor beta (TGF-β). The findings showed that silymarin reduced liver inflammation by overcoming the OS process and inflammatory cytokines production which was stimulated by CCl4. These results were confirmed by histopathology of liver tissues.

Serum irisin correlates to the severity of acute myocardial infarction and predicts the postoperative major adverse cardiovascular events

Irisin is a myogenic cytokine which plays an important role in the cardiovascular system. The aim of this study was to investigate the correlation between serum irisin levels and major adverse cardiovascular events (MACE) in patients with acute myocardial infarction (AMI) after percutaneous coronary intervention (PCI). A total of 207 patients with AMI who underwent PCI were selected as research subjects. Serum irisin levels at admission were measured, and patients were stratified according to the receiver operating characteristic curve to assess differences in MACE within one year after PCI. After one year of follow-up, 207 patients were divided into two groups, 86 with MACE and 121 without MACE. There were significant differences in age, Killip grade, left ventricular ejection fraction, cardiac troponin I, creatine kinase-muscle/brain, and serum irisin between the two groups. Serum irisin level at admission in AMI patients significantly correlated with the occurrence of MACE after PCI, and could be used as an effective marker for predicting the occurrence of MACE in AMI patients after PCI.

Move Your Body toward Healthy Aging: Potential Neuroprotective Mechanisms of Irisin in Alzheimer's Disease

Alzheimer's disease (AD) is the leading cause of dementia in older adults, having a significant global burden and increasing prevalence. Current treatments for AD only provide symptomatic relief and do not cure the disease. Physical activity has been extensively studied as a potential preventive measure against cognitive decline and AD. Recent research has identified a hormone called irisin, which is produced during exercise, that has shown promising effects on cognitive function. Irisin acts on the brain by promoting neuroprotection by enhancing the growth and survival of neurons. It also plays a role in metabolism, energy regulation, and glucose homeostasis. Furthermore, irisin has been found to modulate autophagy, which is a cellular process involved in the clearance of protein aggregates, which are a hallmark of AD. Additionally, irisin has been shown to protect against cell death, apoptosis, oxidative stress, and neuroinflammation, all of which are implicated in AD pathogenesis. However, further research is needed to fully understand the mechanisms and therapeutic potential of irisin in AD. Despite the current gaps in knowledge, irisin holds promise as a potential therapeutic target for slowing cognitive decline and improving quality of life in AD patients.

Canagliflozin Attenuates Hepatic Steatosis and Atherosclerosis Progression in Western Diet-Fed ApoE-Knockout Mice

Purpose

To investigate the effect of canagliflozin (20 mg/kg) on hepatic steatosis and atherosclerosis, and further to explore its possible mechanism.

Methods

Blood glucose, blood lipid, oxidative stress response and inflammatory cytokines were examined by intraperitoneal glucose tolerance test and ELISA assay. HE and Oil Red O staining were used to estimate the extent of hepatic steatosis and atherosclerosis. RNA-seq and qRT-PCR were used to further investigate the potential mechanism. The effects of canagliflozin on autophagy were detected using transmission electron microscopy and Western blotting. The endothelial function-related markers were determined by qRT-PCR.

Results

Canagliflozin notably alleviated the elevation in blood glucose and insulin resistance in western diet-fed ApoE-/- mice. In ApoE-/-+Cana group, ApoE-/- mice had lower levels of TG, TC, LDL-C, TNF-α, IL-6, IL-1β, and MCP-1. HE and Oil Red O staining presented that canagliflozin restrained the atherosclerotic plaque development and lipid accumulation. RNA-seq showed that 87 DEGs were relevant to improvement of hepatic steatosis and atherosclerosis by canagliflozin. Among them, CPS1, ASS1, ASL, ARG1, MATLA, GLS2, GOT1, SREBP1, Plin5, Retreg1, and C/EBPβ were verified. KEGG enrichment analysis indicated that DEGs were mainly involved in amino acid metabolism. Besides, we observed that canagliflozin reduced the contents of aspartic acid and citrulline in liver. Western blotting showed that ASS1 and p-AMPK/AMPK was remarkably elevated after administration of canagliflozin. Correspondingly, canagliflozin down-regulated SREBP1, FAS, ACC1, HMGCR, p-mTOR/m-TOR, p-ULK1/ULK1 and p62, but up-regulated CPT1, Beclin 1 and LC3 II/LC3I. TEM showed that canagliflozin reduced the number of lipid droplets and increased the autophagosomes. Moreover, we found that canagliflozin elevated the aortic endothelial function-associated markers including ASS1, ASL and eNOS.

Conclusion

Canagliflozin may attenuate hepatic steatosis by improving lipid metabolism, enhancing autophagy, and reducing inflammatory response through ASS1/AMPK pathway. Besides, canagliflozin further effectively improves the aortic endothelial function, thereby suppressing atherosclerosis development.

Ellagic acid protects against non-alcoholic fatty liver disease in streptozotocin-diabetic rats by activating AMPK

CONTEXT

Ellagic acid (EA) is used in traditional medicine to treated hyperlipidaemia.

OBJECTIVE

This study examined if AMPK mediates the anti-steatotic effect of ellagic acid (EA) in streptozotocin (STZ)-induced type 1 diabetes mellitus in rats.

MATERIALS AND METHODS

Adult male Wistar rats (130 ± 10 g) were divided into 6 groups (n = 8 rats/group) as control, control + EA, control + EA + CC an AMPK inhibitor), T1DM, T1DM + EA, and T1DM + EA + CC. The treatments with EA (50 mg/kg/orally) and CC (200 ng/rat/i.p.) were given the desired groups for 12 weeks, daily.

RESULTS

In T1DM-rats, EA reduced fasting glucose levels (44.8%), increased fasting insulin levels (92.8%), prevented hepatic lipid accumulation, and decreased hepatic and serum levels of total triglycerides (54% & 61%), cholesterol (57% & 48%), and free fatty acids (40% & 37%). It also reduced hepatic levels of ROS (62%), MDA (52%), TNF-α (62%), and IL-6 (57.2%) and the nuclear activity of NF-κB p65 (54%) but increased the nuclear activity of Nrf-2 (4-fold) and levels of GSH (107%) and SOD (87%). Besides, EA reduced downregulated SREBP1 (35%), SREBP2 (34%), ACC-1 (36%), FAS (38%), and HMG-CoAR (49%) but stimulated mRNA levels of PPARα (1.7-fold) and CPT1a (1.8-fold), CPT1b (2.9-fold), and p-AMPK (4-fold). All these events were prevented by the co-administration of CC.

DISCUSSION AND CONCLUSIONS

These findings encourage the use of EA to treat hepatic disorders, and non-alcoholic fatty liver disease (NAFLD). Further in vivo and in vitro studies are needed to validate its potential in clinical medicine.

Aqueous extract of Artemisia capillaris improves non-alcoholic fatty liver and obesity in mice induced by high-fat diet

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases and is a nutritional metabolic disease. Artemisia capillaris (AC) is the above-ground dried part of Artemisia capillaris Thunb. or Artemisia scoparia Waldst. et Kit., a natural medicinal plant with pharmacological effects of heat-clearing and biliary-promoting. In order to evaluate the therapeutic effect of Artemisia capillaris on NAFLD and obesity, experiments were conducted using aqueous extracts of Artemisia capillaris (WAC) to intervene in NAFLD models in vivo and in vitro. In vivo experiments were performed using HFD-fed (high fat diet) C57BL/6 mice to induce NAFLD model, and in vitro experiments were performed using oleic acid to induce HepG2 cells to construct NAFLD cell model. H.E. staining and oil red O staining of liver tissue were used to observe hepatocytes. Blood biochemistry analyzer was used to detect serum lipid levels in mice. The drug targets and mechanism of action of AC to improve NAFLD were investigated by western blotting, qRT-PCR and immunofluorescence. The results showed that C57BL/6 mice fed HFD continuously for 16 weeks met the criteria for NAFLD in terms of lipid index and hepatocyte fat accumulation. WAC was able to reverse the elevation of serum lipid levels induced by high-fat diet in mice. WAC promoted the phosphorylation levels of PI3K/AKT and AMPK in liver and HepG2 cells of NAFLD mice, inhibited SREBP-1c expression, reduced TG and lipogenesis, and decreased lipid accumulation. In summary, WAC extract activates PI3K/AKT pathway, reduces SREBP-1c protein expression by promoting AMPK phosphorylation, and decreases fatty acid synthesis and TG content in hepatocytes. AC can be used as a potential health herb to improve NAFLD and obesity.

Irisin improves adiposity and exercise tolerance in a rat model of postmenopausal obesity through enhancing adipo-myocyte thermogenesis

The prevalence of obesity and its associated metabolic disorders, along with their healthcare costs, is rising exponentially. Irisin, an adipomyokine, may serve as a critical cross-organ messenger, linking skeletal muscle with adipose tissue and the liver to integrate the energy homeostasis under diet-induced obesity. We aimed to explore the putative role of irisin in the protection against obesity in a postmenopausal rat model by modulating energy expenditure (EE). Bilateral ovariectomy (OVX) was performed. After 3 weeks of recovery, the OVX rats were classified according to their dietary protocol into rats maintained on normal diets (ND) (OVX) or high-fat diet (HFD) groups. The HFD-fed animals were equally divided into OVX/HFD, or irisin-treated OVX/HFD groups. Sham rats, maintained on ND, were selected as the control group. We evaluated anthropometric, EE, and molecular biomarkers of browning and thermogenesis in inguinal white adipose tissue and skeletal muscle, and the activity of the proteins related to mitochondrial long chain fatty acid transport, oxidation, and glycolysis. HFD of OVX further deteriorated the disturbed glucose homeostasis, lipid profile, and the reduced irisin, thermogenic parameters in adipose tissue and skeletal muscle, and EE. Irisin treatment improved the lipid profile and insulin resistance. That was associated with reduced hepatic gluconeogenic enzyme activities and restored hepatic glycogen content. Irisin reduced ectopic lipid infiltration. Irisin augmented EE by activating non-shivering thermogenesis in muscle and adipose tissues and decreasing metabolic efficiency. Our experimental evidence suggests irisin's use as a potential thermogenic agent, therapeutically targeting obesity in postmenopausal patients. Irisin modulates the non-shivering thermogenesis in skeletal muscle and adipose tissue in postmenopausal model.

Physical activity prevents tumor metastasis through modulation of immune function

Metastasis is responsible for 90% of deaths in cancer patients. Most patients diagnosed with metastatic cancer will die within 5 years. PA is good for health and has become an emerging adjuvant therapy for cancer survivors. Regular moderate exercise substantially lowers the incidence and recurrence of several cancers, alleviates cancer-related adverse events, enhances the efficacy of anti-cancer treatments, and improves the quality of life of cancer patients. Revealing the mechanisms of PA inhibiting tumor metastasis could upgrade our understanding of cancer biology and help researchers explore new therapeutic strategies to improve survival in cancer patients. However, it remains poorly understood how physical activity prevents metastasis by modulating tumor behavior. The immune system is involved in each step of tumor metastasis. From invasion to colonization, immune cells interact with tumor cells to secret cytokines and proteases to remodel the tumor microenvironment. Substantial studies demonstrated the ability of physical activity to induce antitumor effects of immune cells. This provides the possibility that physical activity can modulate immune cells behavior to attenuate tumor metastasis. The purpose of this review is to discuss and summarize the critical link between immune function and exercise in metastasis prevention.

Role of irisin in physiology and pathology

Irisin, out-membrane part of fibronectin type III domain-containing 5 protein (FNDC5), was activated by Peroxisome proliferator-activated receptor γ (PPARγ) coactivator-1α (PGC-1α) during physical exercise in skeletal muscle tissues. Most studies have reported that the concentration of irisin is highly associated with health status. For instance, the level of irisin is significantly lower in patients with obesity, osteoporosis/fractures, muscle atrophy, Alzheimer's disease, and cardiovascular diseases (CVDs) but higher in patients with cancer. Irisin can bind to its receptor integrin αV/β5 to induce browning of white fat, maintain glucose stability, keep bone homeostasis, and alleviate cardiac injury. However, it is unclear whether it works by directly binding to its receptors to regulate muscle regeneration, promote neurogenesis, keep liver glucose homeostasis, and inhibit cancer development. Supplementation of recombinant irisin or exercise-activated irisin might be a successful strategy to fight obesity, osteoporosis, muscle atrophy, liver injury, and CVDs in one go. Here, we summarize the publications of FNDC5/irisin from PubMed/Medline, Scopus, and Web of Science until March 2022, and we review the role of FNDC5/irisin in physiology and pathology.

Irisin inhibits PCSK9 expression through activating AMPK-SREBP2 pathway

AIMS

Previous studies found that irisin attenuated the vascular wall inflammation caused by Oxidized low-density lipoprotein (ox-LDL), and recent experiments have shown that proprotein convertase subtilisin/kexin type 9 (PCSK9) can act on various cells in the vascular wall to induce inflammatory responses. But, the relationship between irisin and PCSK9 has not been reported. The aim of this study was to investigate the effect of irisin on PSCK9 in endothelial cells and hepatocytes under the induction of ox-LDL.

METHODS

Experiments were performed using human umbilical vein endothelial cells and Hep G2, and cells were treated with irisin and (or) ox-LDL for evaluating expression of PCSK9 and downstream inflammatory proteins, while the expression levels of AMP-dependent protein kinase (AMPK) and sterol-regulatory element binding protein 2 (SREBP2) were also examined. Then Compound C was used to inhibit AMPK activation and SiAMPK for silencing of AMPK mRNA, and the above assays were also performed to deeply validate the role of the AMPK-SREBP2 pathway.

RESULTS

Irisin treatment significantly downregulated the expression of PCSK9 and inflammation-related proteins induced by ox-LDL, also restored the content of p-AMPK and reduced the SREBP2 content. After the use of Compound C or SiAMPK, the content of p-AMPK was obviously decreased, and the positive effect of irisin was greatly weakened.

CONCLUSIONS

This study demonstrates that irisin suppresses PCSK9 expression through the AMPK-SREBP2 pathway and ameliorates ox-LDL-induced endothelial cells inflammation.

Irisin, a fascinating field in our times

Irisin is a muscle-secreted hormone that is generated by cleavage of membrane protein FNDC-5 (fibronectin type III domain-containing protein 5). Irisin is considered to be a mediator of exercise-induced metabolic improvements, such as browning of white adipose tissue, and is known to alleviate several chronic non-metabolic diseases. Thus, irisin may be an ideal therapeutic target for metabolic and non-metabolic diseases. However, several controversies regarding irisin have hindered its clinical translation. We review the generation, regulation (especially in exercise), and metabolic as well as therapeutic effects of irisin on metabolic and non-metabolic diseases. Furthermore, we discuss controversies regarding irisin and highlight potential future research directions.

Astrocyte-specific loss of lactoferrin influences neuronal structure and function by interfering with cholesterol synthesis

Growing evidence indicates that circulating lactoferrin (Lf) is implicated in peripheral cholesterol metabolism disorders. It has emerged that the distribution of Lf changes in astrocytes of aging brains and those exhibiting neurodegeneration; however, its physiological and/or pathological role remains unknown. Here, we demonstrate that astrocyte-specific knockout of Lf (designated cKO) led to decreased body weight and cognitive abnormalities during early life in mice. Accordingly, there was a reduction in neuronal outgrowth and synaptic structure in cKO mice. Importantly, Lf deficiency in the primary astrocytes led to decreased sterol regulatory element binding protein 2 (Srebp2) activation and cholesterol production, and cholesterol content in cKO mice and/or in astrocytes was restored by exogenous Lf or a Srebp2 agonist. Moreover, neuronal dendritic complexity and total dendritic length were decreased after culture with the culture medium of the primary astrocytes derived from cKO mice and that this decrease was reversed after cholesterol supplementation. Alternatively, these alterations were associated with an activation of AMP-activated protein kinase (AMPK) and inhibition of SREBP2 nuclear translocation. These data suggest that astrocytic Lf might directly or indirectly control in situ cholesterol synthesis, which may be implicated in neurodevelopment and several neurological diseases.

Suppression of nitric oxide synthase aggravates non-alcoholic steatohepatitis and atherosclerosis in SHRSP5/Dmcr rat via acceleration of abnormal lipid metabolism

BACKGROUND

Non-alcoholic steatohepatitis (NASH) is a progressive subtype of non-alcoholic fatty liver disease (NAFLD) that is closely related to cardiovascular disease (CVD). Nitric oxide (NO) plays a critical role in the control of various biological processes. Dysfunction of the NO signaling pathway is associated with various diseases such as atherosclerosis, vascular inflammatory disease, and diabetes. Recently, it has been reported that NO is related to lipid and cholesterol metabolism. Chronic NO synthase (NOS) inhibition accelerates NAFLD by increasing hepatic lipid deposition. However, the detailed relationship between NO and abnormal lipid and cholesterol metabolism in NAFLD/NASH has not been completely explained. We aimed to determine the effects of NOS inhibition by N omega-nitro-L-arginine methyl ester hydrochloride (L-NAME), a NOS inhibitor, on NASH and CVD via lipid and cholesterol metabolism.

METHODS

Stroke-prone spontaneously hypertensive rats were fed a high-fat and high-cholesterol diet for 8 weeks and administered L-NAME for the last 2 weeks. Following blood and tissue sampling, biochemical analysis, histopathological staining, quantitative RT-PCR analysis, and western blotting were performed.

RESULTS

L-NAME markedly increased hepatic triglyceride (TG) and cholesterol levels by promoting TG synthesis and cholesterol absorption from the diet. L-NAME increased the mRNA levels of inflammatory markers and fibrotic areas in the liver. Cholesterol secretion from the liver was promoted in rats administered L-NAME, which increased serum cholesterol. L-NAME significantly increased the level of oxidative stress marker and lipid deposition in the arteries.

CONCLUSIONS

NOS inhibition simultaneously aggravates NASH and atherosclerosis via hepatic lipid and cholesterol metabolism.

The potential role of FNDC5/irisin in various liver diseases: awakening the sleeping beauties

Fibronectin type III domain-containing protein 5 (FNDC5) is a transmembrane protein and the precursor of irisin, which serves as a systemic exerkine/myokine with multiple origins. Since its discovery in 2012, this hormone-like polypeptide has rapidly evolved to a component significantly involved in a gamut of metabolic dysregulations and various liver diseases. After a decade of extensive investigation on FNDC5/irisin, we are still surrounded by lots of open questions regarding its diagnostic and therapeutic values. In this review, we first concentrated on the structure-function relationship of FNDC5/irisin. Next, we comprehensively summarised the current knowledge and research findings regarding pathogenic roles/therapeutic applications of FNDC5/irisin in the context of non-alcoholic fatty liver disease, fibrosis, liver injury due to multiple detrimental insults, hepatic malignancy and intrahepatic cholestasis of pregnancy. Moreover, the prominent molecules involved in the underlying mechanisms and signalling pathways were highlighted. As a result, emerging evidence reveals FNDC5/irisin may act as a proxy for diagnosing liver disease pathology, a sensitive biomarker for assessing damage severity, a predisposing factor for surveilling illness progression and a treatment option with protective/preventive impact, all of which are highly dependent on disease grading and contextually pathological features.

Monensin supplementation downregulated the expression signature of genes involved in cholesterol synthesis in the ruminal epithelium and adipose tissue of lambs

To understand the metabolic mechanisms regulating lipid metabolism by monensin, Afshari male lambs (n = 16) with 41.0 ± 2.4 kg body weight (BW, mean ± SD) at approximately 180 days of age were randomly assigned equally to two dietary treatments. After a 21-day pre-adaptation period, all animals in two groups continued to receive the basal diet, but one group received no monensin supplementation (control) while the other group received 30 mg/day of monensin per animal. Individual BW was recorded weekly to determine the average daily body weight gain (ADG). At the end of the 56-day experimental period, lambs were weighed and slaughtered. Monensin supplementation did not affect BW, ADG, and rumen fermentation characteristics. However, monensin significantly downregulated the sterol regulatory element-binding protein (SREBP)-2 gene expression in all sample tissues (p < 0.05). Also, monensin downregulated expressions of SREBP-1c and peroxisome proliferator-activated receptor (PPAR)-γ in back fat tissues. Monensin increased the expression of 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS)-2, but it decreased the mRNA abundance of HMGCS-1 in the rumen epithelial tissues (p < 0.05). Our data suggest that monensin downregulates cholesterol synthesis via inhibition of HMGCS-1 and impairment of the SREBP pathway, probably due to a crosstalk among different tissues to control energy metabolism.

Effects of the FNDC5/Irisin on Elderly Dementia and Cognitive Impairment

Population aging is an inevitable problem nowadays, and the elderly are going through a lot of geriatric symptoms, especially cognitive impairment. Irisin, an exercise-stimulating cleaved product from transmembrane fibronectin type III domain-containing protein 5 (FNDC5), has been linked with favorable effects on many metabolic diseases. Recently, mounting studies also highlighted the neuroprotective effects of irisin on dementia. The current evidence remains uncertain, and few clinical trials have been undertaken to limit its clinical practice. Therefore, we provided an overview of current scientific knowledge focusing on the preventive mechanisms of irisin on senile cognitive decline and dementia, in terms of the possible connections between irisin and neurogenesis, neuroinflammation, oxidative stress, and dementia-related diseases. This study summarized the recent advances and ongoing studies, aiming to provide a better scope into the effectiveness of irisin on dementia progression, as well as a mediator of muscle brain cross talk to provide theoretical support for exercise therapy for patients with dementia. Whether irisin is a diagnostic or prognostic factor for dementia needs more researches.

Antioxidant Effects of Irisin in Liver Diseases: Mechanistic Insights

Oxidative stress is a crucial factor in the development of various liver diseases. Irisin, a metabolic hormone discovered in 2012, is mainly produced by proteolytic cleavage of fibronectin type III domain containing 5 (FNDC5) in skeletal muscles. Irisin is induced by physical exercise, and a rapidly growing body of literature suggests that irisin is, at least partially, responsible for the beneficial effects of regular exercise. The major biological function of irisin is believed to be involved in the maintenance of metabolic homeostasis. However, recent studies have suggested the therapeutic potential of irisin against a variety of liver diseases involving its antioxidative function. In this review, we aim to summarize the accumulating evidence demonstrating the antioxidative effects of irisin in liver diseases, with an emphasis on the current understanding of the potential molecular mechanisms.

Crosstalk between Irisin Levels, Liver Fibrogenesis and Liver Damage in Non-Obese, Non-Diabetic Individuals with Non-Alcoholic Fatty Liver Disease

Background: Insulin resistance plays a relevant role in the onset of non-alcoholic fatty liver disease (NAFLD) and its progression to non-alcoholic steatohepatitis (NASH) and fibrosis. Irisin is an exercise-induced myokine involved in the regulation of energy homeostasis and glucose metabolism. Additionally, pre-clinical models have shown a potential role of irisin in the pathogenesis of NAFLD. The aim of this study is to explore the association between irisin, histological features and biomarkers of liver fibrogenesis in non-diabetic, non-obese, biopsy-proven NAFLD individuals. Methods: Forty-one patients with histological evidence of NAFLD were included. Circulating irisin and direct markers of fibrogenesis N-terminal type III collagen propeptide (PRO-C3) and type VI collagen cleavage product (PRO-C6) were measured by ELISA. Results: Median age of the cohort was 45 years (41–51) and 80.4% were male. Significant fibrosis (stage ≥ 2) was present in 36.6% of cases. Circulating irisin, PRO-C3 and PRO-C6 levels were significantly higher in subjects with fibrosis stage ≥ 2 when compared to those with fibrosis stage < 2 (5.96 ng/mL (95% CI = 4.42–9.19) vs. 2.42 ng/mL (95% CI = 1.73–5.95), p = 0.033; 9.5 ng/mL (95% CI = 7.7–13.6) vs. 6.2 ng/mL (95% CI = 4.9–8.9), p = 0.016; 6.6 ng/mL (95% CI = 5.6–7.9) vs. 5.1 ng/mL (95% CI = 4.2–5.4), p = 0.013, respectively). Irisin levels were similarly distributed between the features of NASH. Circulating irisin positively correlated with both PRO-C3 and PRO-C6 levels (r = 0.47, p = 0.008 and r = 0.46, p = 0.002). Conclusions: Increased circulating irisin levels may identify a more aggressive phenotype of liver disease with increased fibrogenesis and more severe liver damage.

Limonin, an AMPK Activator, Inhibits Hepatic Lipid Accumulation in High Fat Diet Fed Mice

NAFLD is the most prevalent liver disease in human history. The treatment is still limited yet. In the current study, we reported that limonin inhibited hepatic lipid accumulation and fatty acid synthesis in HFD fed mice. Using AMPK inhibitor and AMPK deficient C. elegans, we revealed the effect was dependent on the activation of AMPK. We found that limonin activated AMPK through inhibition of cellular energy metabolism and increasing ADP:ATP ratio. Furthermore, the treatment of limonin induced AMPK mediated suppression of the transcriptional activity of SREBP1/2. Our study suggests that limonin may a promising therapeutic agent for the treatment of NAFLD.

Irisin at the crossroads of inter-organ communications: Challenge and implications

The physiological functions of organs are intercommunicated occurring through secreted molecules. That exercise can improve the physiological function of organs or tissues is believed by secreting myokines from muscle to target remote organs. However, the underlying mechanism how exercise regulates the inter-organ communications remains incompletely understood yet. A recently identified myokine-irisin, primarily found in muscle and adipose and subsequently extending to bone, heart, liver and brain, provides a new molecular evidence for the inter-organ communications. It is secreted under the regulation of exercise and mediates the intercommunications between exercise and organs. To best our understanding of the regulatory mechanism, this review discusses the recent evidence involving the potential molecular pathways of the inter-organ communications, and the interactions between signalings and irisin in regulating the impact of exercise on organ functions are also discussed.

Protective effect of irisin against Alzheimer's disease

Despite being one of the greatest global challenges for health and social care in the 21st century, Alzheimer's disease (AD) lacks specific medicine. Irisin, an exercise-generated muscle factor, emerges as a potential hormone for AD prevention and treatment because of its role in promoting the browning of white adipose tissue, accelerating energy expenditure, regulating energy metabolism, and improving insulin resistance. The study reviews classic hallmarks of AD and irisin's physiology before discussing the possible mechanism by which irisin protects against AD in terms of its effects related to molecular biology and cellular biology. Results reveal that irisin sharpens learning memory by inducing the production of brain-derived neurotrophic factor (BDNF), lowers the production of inflammatory factors, protects neurology through astrocytes, and ameliorates AD symptoms by improving insulin resistance. The review aims to facilitate future experimental studies and clinical applications of irisin in preventing and treating AD.

Serum Irisin: A Potential Diagnostic Marker for Insulin Resistance in Acne Vulgaris

Background

Acne vulgaris (AV) is a chronic inflammatory disease of the pilosebaceous unit. Many factors are involved in the occurrence of acne. It has been confirmed that some adipokines play an important role in the development of AV. Irisin is a novel adipokine, which is highly expressed in skeletal muscle, liver, and fat. It improves insulin resistance (IR) by inducing the browning of white adipose tissue, increasing heat production and energy expenditure.

Objective

The purpose of this study was to investigate the role of serum irisin as an adipokine to explore its function in the pathogenesis of AV and its correlation with IR, and whether it can be used as a potential biomarker of insulin sensitivity. Although the hyperinsulinemic-euglycemic clamp remains the gold standard for accurate determination of IR, it cannot be performed routinely. Various alternative simpler measures have been used, the most common being homeostasis model assessment. However, these metrics are limited by their accuracy, cost, and blood collection requirements.[1] Therefore, an effective and feasible serum biomarker is an attractive and relatively straightforward method, which may provide clinicians with a more accurate and simple method for the prediction and diagnosis of IR. IR can often be detected before other symptoms appear, so establishing an early diagnosis method will allow for the appropriate treatment of patients before the disease develops.

Patients and Methods

The study included 171 subjects; 115 patients with newly diagnosed AV and 56 apparently healthy subjects. The contents of irisin and interleukin-1 alpha in serum were determined by enzyme-linked immunosorbent assay. The IR index was calculated by the homeostasis model.

Results

Serum irisin levels in AV patients and control group were (24.0 ± 11.3) and (104.3 ± 27.0) ng/dl, respectively, which were significantly lower than those in control group (P < 0.001). Serum irisin was negatively correlated with IR (r = -0.711, P 0.001). The sensitivity of irisin was 100.0%, the specificity was 92.8%, and the cutoff point was 53.32. The decrease of serum irisin level could predict the patients with IR in acne.

Conclusion

Serum irisin levels in AV patients were significantly decreased. Serum irisin showed acceptable performance criteria in the diagnosis of AV with IR. Serum irisin seems to be a good diagnostic and prognostic marker for IR. Further multi-center studies are needed to confirm this link, which could pave the way for new treatment options.

Physiological Changes and Pathological Pain Associated with Sedentary Lifestyle-Induced Body Systems Fat Accumulation and Their Modulation by Physical Exercise

A sedentary lifestyle is associated with overweight/obesity, which involves excessive fat body accumulation, triggering structural and functional changes in tissues, organs, and body systems. Research shows that this fat accumulation is responsible for several comorbidities, including cardiovascular, gastrointestinal, and metabolic dysfunctions, as well as pathological pain behaviors. These health concerns are related to the crosstalk between adipose tissue and body systems, leading to pathophysiological changes to the latter. To deal with these health issues, it has been suggested that physical exercise may reverse part of these obesity-related pathologies by modulating the cross talk between the adipose tissue and body systems. In this context, this review was carried out to provide knowledge about (i) the structural and functional changes in tissues, organs, and body systems from accumulation of fat in obesity, emphasizing the crosstalk between fat and body tissues; (ii) the crosstalk between fat and body tissues triggering pain; and (iii) the effects of physical exercise on body tissues and organs in obese and non-obese subjects, and their impact on pathological pain. This information may help one to better understand this crosstalk and the factors involved, and it could be useful in designing more specific training interventions (according to the nature of the comorbidity).

Zeaxanthin ameliorates obesity by activating the β3-adrenergic receptor to stimulate inguinal fat thermogenesis and modulating the gut microbiota

The stimulation of fat thermogenesis and modulation of the gut microbiota are promising therapeutic strategies against obesity. Zeaxanthin (ZEA), a carotenoid plant pigment, has been shown to prevent various diseases; however, the therapeutic mechanism for obesity remains unclear. Herein, whether ZEA improves obesity by activating the β3-adrenergic receptor (β3-AR) to stimulate white adipose tissue (WAT) thermogenesis and modulating the gut microbiota was investigated. C57BL6/N mice were fed a high-fat diet (HFD) supplemented with ZEA for 22 weeks. ZEA treatment reduced body weight, fat weight, adipocyte hypertrophy, liver weight, and lipid deposition, and improved dyslipidaemia, serum GPT, GOT, leptin, and irisin levels, glucose intolerance, and insulin resistance in HFD-fed mice. Mechanistically, ZEA treatment induced the expression of β3-AR and thermogenic factors, such as PRDM16, PGC-1α, and UCP1, in inguinal WAT (iWAT) and brown adipose tissue. ZEA treatment stimulated iWAT thermogenesis through the synergistic cooperation of key organelles, which manifested as an increased expression of lipid droplet degradation factors (ATGL, CGI-58 and pHSL), mitochondrial biogenesis factors (Sirt1, Nrf2, Tfam, Nampt and Cyt-C), peroxisomal biogenesis factors (Pex16, Pex19 and Pmp70), and β-oxidation factors (Cpt1, Cpt2, Acadm and Acox1). The thermogenic effect of ZEA was abolished by β3-AR antagonist (SR59230A) treatment. Additionally, dietary supplementation with ZEA reversed gut microbiota dysbiosis by regulating the abundance of Firmicutes, Clostridia, Proteobacteria, and Desulfovibrio, which were associated with the thermogenesis- and obesity-associated indices by Spearman's correlation analysis. Functional analysis of the gut microbiota indicated that ZEA treatment significantly enriched the lipid metabolism pathways. These results demonstrate that ZEA is a promising multi-target functional food for the treatment of obesity by activating β3-AR to stimulate iWAT thermogenesis, and modulating the gut microbiota.

Inverse correlation between serum irisin and cardiovascular risk factors among Chinese overweight/obese population

Background

Irisin is a novel myokine associated with obesity, which is a traditional cardiovascular risk factor (CVRF). The present study aimed to investigate the association between serum irisin and a single CVRF as well as the clustering of CVRFs among Chinese overweight/obese population.

Methods

A total of 98 overweight and 93 obese subjects without clinical treatments were enrolled in this study. Subjects were then divided into two groups, based on the serum irisin level: a low irisin group (1.10–13.44 ng/ml) and a high irisin group (13.49–29.9 ng/ml). The clustering of CVRFs, smoking, diabetes mellitus, dyslipidemia and hypertension, was classified as 0, 1, 2 and ≥ 3 CVRFs. The demographic and baseline clinical characteristics of all participants were collected and serum irisin was measured.

Results

The high serum irisin group had significantly higher high-density lipoprotein cholesterol but lower fasting plasma glucose than the low serum irisin group. Additionally, the high serum irisin group had a significantly lower prevalence of smoking, diabetes mellitus and dyslipidemia than the low serum irisin group. Increased serum irisin was significantly associated with a reduced risk of smoking and dyslipidemia in both the unadjusted and adjusted models. Furthermore, high serum irisin significantly reduced the risk of the prevalence of 1, 2 and ≥ 3 CVRFs.

Conclusions

among the Chinese overweight/obese populations, high serum irisin is negatively associated with smoking, dyslipidemia and the clustering of CVRFs. Thus, high serum irisin is potentially associated with a low risk of cardiovascular diseases in the Chinese overweight/obese population.

Exercise-Induced Irisin Decreases Inflammation and Improves NAFLD by Competitive Binding with MD2

Non-alcoholic fatty liver disease (NAFLD) is a global clinical problem. The MD2-TLR4 pathway exacerbates NAFLD progression by promoting inflammation. Long-term exercise is considered to improve NAFLD but the underlying mechanism is still unclear. In this study, we examined the protective effect and molecular mechanism of exercise on high-fat diet (HFD)-induced liver injury. In an HFD-induced NAFLD mouse model, exercise training significantly decreased hepatic steatosis and fibrosis. Interestingly, exercise training blocked the binding of MD2-TLR4 and decreased the downstream inflammatory response. Irisin is a myokine that is highly expressed in response to exercise and exerts anti-inflammatory effects. We found that circulating irisin levels and muscle irisin expression were significantly increased in exercised mice, suggesting that irisin could mediate the effect of exercise on NAFLD. In vitro studies showed that irisin improved lipid metabolism, fibrosis, and inflammation in palmitic acid (PA)-stimulated AML12 cells. Moreover, binding assay results showed that irisin disturbed MD2-TLR4 complex formation by directly binding with MD2 but not TLR4, and interfered with the recognition of stimuli such as PA and lipopolysaccharide with MD2. Our study provides novel evidence that exercise-induced irisin inhibits inflammation via competitive binding with MD2 to improve NAFLD. Thus, irisin could be considered a potential therapy for NAFLD.

TFCP2 Overcomes Senescence by Cooperating With SREBP2 to Activate Cholesterol Synthesis in Pancreatic Cancer

KRAS mutation is very common in pancreatic cancer. How pancreatic cancer cells overcome oncogene-induced senescence is not fully understood. Our previous studies showed that up-regulation of TFCP2 (transcription factor CP2) in pancreatic cancer promoted the growth and metastasis of pancreatic cancer cells. However, whether TFCP2 plays an important role in pancreatic cancer cell senescence is not clear. In this study, we found upregulation of TFCP2 expression in pancreatic cancer was associated with KRAS mutation. Overexpression of TFCP2 inhibited cell senescence. Knockdown of TFCP2 promoted cell senescence. Mechanistically, the interaction between TFCP2 and SREBP2 (sterol regulatory element binding transcription factor 2) synergistically activated the expression of HMGCR, a rate-limiting enzyme in cholesterol synthesis, and statins could reverse the inhibitory effect of TFCP2 on senescence. In conclusion, our study reveals a new mechanism underlying the TFCP2 regulation of pancreatic cancer cell senescence, providing a new target for the treatment of pancreatic cancer.

Irisin Stimulates the Release of CXCL1 From Differentiating Human Subcutaneous and Deep-Neck Derived Adipocytes via Upregulation of NFκB Pathway

Thermogenic brown and beige adipocytes might open up new strategies in combating obesity. Recent studies in rodents and humans have indicated that these adipocytes release cytokines, termed "batokines". Irisin was discovered as a polypeptide regulator of beige adipocytes released by myocytes, primarily during exercise. We performed global RNA sequencing on adipocytes derived from human subcutaneous and deep-neck precursors, which were differentiated in the presence or absence of irisin. Irisin did not exert an effect on the expression of characteristic thermogenic genes, while upregulated genes belonging to various cytokine signaling pathways. Out of the several upregulated cytokines, CXCL1, the highest upregulated, was released throughout the entire differentiation period, and predominantly by differentiated adipocytes. Deep-neck area tissue biopsies also showed a significant release of CXCL1 during 24 h irisin treatment. Gene expression data indicated upregulation of the NFκB pathway upon irisin treatment, which was validated by an increase of p50 and decrease of IκBα protein level, respectively. Continuous blocking of the NFκB pathway, using a cell permeable inhibitor of NFκB nuclear translocation, significantly reduced CXCL1 release. The released CXCL1 exerted a positive effect on the adhesion of endothelial cells. Together, our findings demonstrate that irisin stimulates the release of a novel adipokine, CXCL1, via upregulation of NFκB pathway in neck area derived adipocytes, which might play an important role in improving tissue vascularization.

Crataegus aronia prevents high-fat diet-induced hepatic steatosis in rats by activating AMPK-induced suppression of SREBP1 and activation of PPARα

This study examined if the aqueous extract of Crataegus aronia (C. aronia) can prevent high-fat diet (HFD)-induced hepatic steatosis in rats by activating AMPK. Adult male Wistar rats were fed either a control diet or HFD for 12 weeks and treated either with vehicle (normal saline) or C. aronia extract (200 mg/kg/orally), daily. Also, hepatocytes were treated with increasing concentrations of the extract in the presence or absence of compound C (CC), an AMPK inhibitor. C. aronia prevented the increase in serum and hepatic lipids, reduced hepatic levels of reactive oxygen species, and increased hepatic glutathione and superoxide dismutase levels. It also downregulated the hepatic expression of SREBP1/2, fatty acid synthase, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase but stimulated the activity of AMPK and levels of peroxisome proliferator-activated receptor-alpha. Similar effects were reported in the cultured cells, in a dose-dependent manner but were prevented by CC. In conclusion, C. aronia ameliorates HFD-induced hepatic steatosis and oxidative stress by activating AMPK. PRACTICAL APPLICATIONS: The use of the aqueous extract of Crataegus aronia has been extensively used during the last years in traditional medicine to treat chronic disorders including nonalcoholic fatty liver disease. The findings of this study support these findings and suggest that oral administration of C. aronia aqueous extract has potent hypoglycemic effect and demonstrate the mechanism of action mimics such drugs such as metformin and involves activation of AMPK and peroxisome proliferator-activated receptor-alpha. These findings are very encouraging for further biochemical analysis and isolation of active ingredients responsible for these effects to be used in more clinical trials.

Fibronectin type III domain-containing 5 in cardiovascular and metabolic diseases: a promising biomarker and therapeutic target

Cardiovascular and metabolic diseases are the leading causes of death and disability worldwide and impose a tremendous socioeconomic burden on individuals as well as the healthcare system. Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein that can be proteolytically cleaved and secreted as irisin to regulate glycolipid metabolism and cardiovascular homeostasis. In this review, we present the current knowledge on the predictive and therapeutic role of FNDC5 in a variety of cardiovascular and metabolic diseases, such as hypertension, atherosclerosis, ischemic heart disease, arrhythmia, metabolic cardiomyopathy, cardiac remodeling, heart failure, diabetes mellitus, and obesity.

Irisin in atherosclerosis

Irisin, a novel exercise-induced myokine, has been shown to play important roles in increasing white adipose tissue browning, regulating energy metabolism and improving insulin resistance. Growing evidence suggests a direct role for irisin in preventing atherosclerosis (AS) by inhibiting oxidative stress, improving dyslipidemia, facilitating anti-inflammation, reducing cellular damage and recovering endothelial function. In addition, some studies have noted that serum irisin levels play an essential role in cardiovascular diseases (CVDs) risk prediction, highlighting that irisin has the potential to be a useful predictive marker and therapeutic target of AS, especially in monitoring therapeutic efficacy. This review summarizes the understanding of irisin-mediated regulation in essential biological pathways and functions in atherosclerosis and prompts further exploitation of the biological properties of irisin in the pathogenesis of atherosclerosis.

Role of Irisin in Myocardial Infarction, Heart Failure, and Cardiac Hypertrophy

Irisin is a myokine derived from the cleavage of fibronectin type III domain-containing 5. Irisin regulates mitochondrial energy, glucose metabolism, fatty acid oxidation, and fat browning. Skeletal muscle and cardiomyocytes produce irisin and affect various cardiovascular functions. In the early phase of acute myocardial infarction, an increasing irisin level can reduce endothelial damage by inhibiting inflammation and oxidative stress. By contrast, higher levels of irisin in the later phase of myocardial infarction are associated with more cardiovascular events. During different stages of heart failure, irisin has various influences on mitochondrial dysfunction, oxidative stress, metabolic imbalance, energy expenditure, and heart failure prognosis. Irisin affects blood pressure and controls hypertension through modulating vasodilatation. Moreover, irisin can enhance vasoconstriction via the hypothalamus. Because of these dual effects of irisin on cardiovascular physiology, irisin can be a critical therapeutic target in cardiovascular diseases. This review focuses on the complex functions of irisin in myocardial ischemia, heart failure, and cardiac hypertrophy.

The Role of Peptide Hormones Discovered in the 21st Century in the Regulation of Adipose Tissue Functions

Peptide hormones play a prominent role in controlling energy homeostasis and metabolism. They have been implicated in controlling appetite, the function of the gastrointestinal and cardiovascular systems, energy expenditure, and reproduction. Furthermore, there is growing evidence indicating that peptide hormones and their receptors contribute to energy homeostasis regulation by interacting with white and brown adipose tissue. In this article, we review and discuss the literature addressing the role of selected peptide hormones discovered in the 21st century (adropin, apelin, elabela, irisin, kisspeptin, MOTS-c, phoenixin, spexin, and neuropeptides B and W) in controlling white and brown adipogenesis. Furthermore, we elaborate how these hormones control adipose tissue functions in vitro and in vivo.

High-Efficacy α,β-Dehydromonacolin S Improves Hepatic Steatosis and Suppresses Gluconeogenesis Pathway in High-Fat Diet-Induced Obese Rats

Isolated α,β-dehydromonacolin S (C5) from soil-derived fungus Aspergillus sclerotiorum PSU-RSPG178 was recently shown to exhibit an inhibitory effect against 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) activity in vitro. In this study, we investigated the effects of C5 on lipid-lowering, hepatic steatosis, and hepatic gluconeogenesis in vivo. The control rats received a daily dose of either vehicle or C5 at 10 mg/kg, while the high-fat diet-induced obese (HFD) rats were administered vehicle; 1, 3, or 10 mg/kg C5; or 10 mg/kg lovastatin (LO) for 6 weeks. C5 significantly improved dyslipidemia and diminished liver enzymes, HMGR activity, insulin resistance, and hepatic steatosis, comparable to LO without any hepatotoxicity and nephrotoxicity in HFD rats. A higher efficacy of C5 in lipid-lowering activity and anti-hepatic steatosis was associated with a significant decrease in genes involved in lipid metabolism including sterol regulatory element binding protein (SREBP) 1c, SREBP2, liver X receptor alpha (LXRα), and peroxisome proliferator-activated receptor (PPAR) gamma (PPARγ) together with an increase in the PPAR alpha (PPARα). Correspondingly, C5 was able to down-regulate the lipid transporters cluster of differentiation 36 (CD36) and Niemann-Pick C1 Like 1 (NPC1L1), increase the antioxidant superoxide dismutase gene expression, and decrease the proinflammatory cytokines, tumor necrosis factor alpha (TNFα) and interleukin 1 beta (IL-1β). Impairment of hepatic gluconeogenesis and insulin resistance in HFD rats was restored by C5 through down-regulation of the gluconeogenic genes phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), and the activation of AMP-dependent kinase serine (AMPK) and serine/threonine protein kinase B (Akt). Collectively, this novel C5 may be a therapeutic option for treating dyslipidemia, hepatic steatosis, and reducing potential risk for diabetes mellitus.

[Sports and exercise therapy in inflammatory rheumatic diseases]

Physical therapy has always been a pillar of the treatment of inflammatory rheumatic diseases in addition to targeted drug treatment; nevertheless, it is only established in the treatment guidelines for a few diseases. Within the last two decades the discovery of myokines has uncovered the physiological correlations of the anti-inflammatory effect of physical activity. For rheumatoid arthritis and spondylarthritis, several randomized controlled trials provide sufficient evidence to make well-founded recommendations. For connective tissue diseases (CTD) the data situation is clearly sparser but nevertheless shows that the positive effects of physical activity prevail. In the following article the authors present the most important clinical studies on sport and inflammatory rheumatic diseases and from these derive possible therapeutic recommendations.

NAD+-boosting therapy alleviates nonalcoholic fatty liver disease via stimulating a novel exerkine Fndc5/irisin

Rationale: Nicotinamide adenine dinucleotide⁺ (NAD⁺)-boosting therapy has emerged as a promising strategy to treat various health disorders, while the underlying molecular mechanisms are not fully understood. Here, we investigated the involvement of fibronectin type III domain containing 5 (Fndc5) or irisin, which is a novel exercise-linked hormone, in the development and progression of nonalcoholic fatty liver disease (NAFLD).

Methods: NAD⁺-boosting therapy was achieved by administrating of nicotinamide riboside (NR) in human and mice. The Fndc5/irisin levels in tissues and blood were measured in NR-treated mice or human volunteers. The therapeutic action of NR against NAFLD pathologies induced by high-fat diet (HFD) or methionine/choline-deficient diet (MCD) were compared between wild-type (WT) and Fndc5^-/- mice. Recombinant Fndc5/irisin was infused to NALFD mice via osmotic minipump to test the therapeutic action of Fndc5/irisin. Various biomedical experiments were conducted in vivo and in vitro to know the molecular mechanisms underlying the stimulation of Fndc5/irisin by NR treatment.

Results: NR treatment elevated plasma level of Fndc5/irisin in mice and human volunteers. NR treatment also increased Fndc5 expression in skeletal muscle, adipose and liver tissues in mice. In HFD-induced NAFLD mice model, NR displayed remarkable therapeutic effects on body weight gain, hepatic steatosis, steatohepatitis, insulin resistance, mitochondrial dysfunction, apoptosis and fibrosis; however, these actions of NR were compromised in Fndc5^-/- mice. Chronic infusion of recombinant Fndc5/irisin alleviated the NAFLD pathological phenotypes in MCD-induced NAFLD mice model. Mechanistically, NR reduced the lipid stress-triggered ubiquitination of Fndc5, which increased Fndc5 protein stability and thus enhanced Fndc5 protein level. Using shRNA-mediated knockdown screening, we found that NAD⁺-dependent deacetylase SIRT2, rather than other sirtuins, interacts with Fndc5 to decrease Fndc5 acetylation, which reduces Fndc5 ubiquitination and stabilize it. Treatment of AGK2, a selective inhibitor of SIRT2, blocked the therapeutic action of NR against NAFLD pathologies and NR-induced Fndc5 deubiquitination/deacetylation. At last, we identified that the lysine sites K127/131 and K185/187/189 of Fndc5 may contribute to the SIRT2-dependent deacetylation and deubiquitination of Fndc5.

Conclusions: The findings from this research for the first time demonstrate that NAD⁺-boosting therapy reverses NAFLD by regulating SIRT2-deppendent Fndc5 deacetylation and deubiquitination, which results in a stimulation of Fndc5/irisin, a novel exerkine. These results suggest that Fndc5/irisin may be a potential nexus between physical exercise and NAD⁺-boosting therapy in metabolic pathophysiology.

Irisin and Incretin Hormones: Similarities, Differences, and Implications in Type 2 Diabetes and Obesity

Incretins are gut hormones that potentiate glucose-stimulated insulin secretion (GSIS) after meals. Glucagon-like peptide-1 (GLP-1) is the most investigated incretin hormone, synthesized mainly by L cells in the lower gut tract. GLP-1 promotes β-cell function and survival and exerts beneficial effects in different organs and tissues. Irisin, a myokine released in response to a high-fat diet and exercise, enhances GSIS. Similar to GLP-1, irisin augments insulin biosynthesis and promotes accrual of β-cell functional mass. In addition, irisin and GLP-1 share comparable pleiotropic effects and activate similar intracellular pathways. The insulinotropic and extra-pancreatic effects of GLP-1 are reduced in type 2 diabetes (T2D) patients but preserved at pharmacological doses. GLP-1 receptor agonists (GLP-1RAs) are therefore among the most widely used antidiabetes drugs, also considered for their cardiovascular benefits and ability to promote weight loss. Irisin levels are lower in T2D patients, and in diabetic and/or obese animal models irisin administration improves glycemic control and promotes weight loss. Interestingly, recent evidence suggests that both GLP-1 and irisin are also synthesized within the pancreatic islets, in α- and β-cells, respectively. This review aims to describe the similarities between GLP-1 and irisin and to propose a new potential axis-involving the gut, muscle, and endocrine pancreas that controls energy homeostasis.

Relationship between Muscle Mass and Non-Alcoholic Fatty Liver Disease

Simple Summary

Sarcopenia and non-alcoholic fatty liver disease share common pathological and physiological mechanisms that can co-occur with aging. Low skeletal muscle mass index and non-alcoholic fatty liver disease were related, regardless of abdominal obesity. Maintenance of muscle mass should be emphasized for prevention of non-alcoholic fatty liver disease. Management of fatty liver also could be an important strategy to preserve muscle mass.

Abstract

Although sarcopenia is known to be a risk factor for non-alcoholic fatty liver disease (NAFLD), whether NAFLD is a risk factor for the development of sarcopenia is not clear. We investigated relationships between NAFLD and low skeletal muscle mass index (LSMI) using three different datasets. Participants were classified into LSMI and normal groups. LSMI was defined as a body mass index (BMI)-adjusted appendicular skeletal muscle mass <0.789 in men and <0.512 in women or as the sex-specific lowest quintile of BMI-adjusted total skeletal muscle mass. NAFLD was determined according to NAFLD liver fat score or abdominal ultrasonography. The NAFLD groups showed a higher hazard ratios (HRs) with 95% confidence intervals (CIs) for LSMI than the normal groups (HRs = 1.21, 95% CIs = 1.05–1.40). The LSMI groups also showed a higher HRs with 95% CIs for NAFLD than normal groups (HRs = 1.56, 95% CIs = 1.38–1.78). Participants with NAFLD had consistently less skeletal muscle mass over 12 years of follow-up. In conclusion, LSMI and NAFLD showed a relationship. Maintaining muscle mass should be emphasized in the management of NAFLD.