Interleukin-38 alleviates hepatic steatosis through AMPK/autophagy-mediated suppression of endoplasmic reticulum stress in obesity models.

Interleukin-38 (IL-38), recently recognized as a cytokine with anti-inflammatory properties that mitigate type 2 diabetes, has been associated with indicators of insulin resistance and nonalcoholic fatty liver disease (NAFLD). This study investigated the impact of IL-38 on hepatic lipid metabolism and endoplasmic reticulum (ER) stress. We assessed protein expression levels using Western blot analysis, while monodansylcadaverine staining was employed to detect autophagosomes in hepatocytes. Oil red O staining was utilized to examine lipid deposition. The study revealed elevated serum IL-38 levels in high-fat diet (HFD)-fed mice and IL-38 secretion from mouse keratinocytes. IL-38 treatment attenuated lipogenic lipid accumulation and ER stress markers in hepatocytes exposed to palmitate. Furthermore, IL-38 treatment increased AMP-activated protein kinase (AMPK) phosphorylation and autophagy. The effects of IL-38 on lipogenic lipid deposition and ER stress were nullified in cultured hepatocytes by suppressing AMPK through small interfering (si) RNA or 3-methyladenine (3MA). In animal studies, IL-38 administration mitigated hepatic steatosis by suppressing the expression of lipogenic proteins and ER stress markers while reversing AMPK phosphorylation and autophagy markers in the livers of HFD-fed mice. Additionally, AMPK siRNA, but not 3MA, mitigated IL-38-enhanced fatty acid oxidation in hepatocytes. In summary, IL-38 alleviates hepatic steatosis through AMPK/autophagy signaling-dependent attenuation of ER stress and enhancement of fatty acid oxidation via the AMPK pathway, suggesting a therapeutic strategy for treating NAFLD.

IL-38 alleviates atherogenic responses via SIRT6/HO-1 signaling: A promising strategy against obesity-related atherosclerosis.

Interleukin-38 (IL-38), a member of the IL-1 family, is known for its anti-inflammatory properties mediated through ligand signaling in various disease models. It plays a significant role in atherosclerosis development, forming a theoretical basis for therapeutic strategies. However, the direct effects of IL-38 on atherogenic responses in the vascular endothelium and monocytes remain unclear. In this investigation, IL-38 treatment reduced THP-1 monocyte adhesion to HUVECs, decreased the expression of vascular adhesion molecules, and mitigated inflammation in the presence of palmitate. IL-38 treatment upregulated SIRT6 expression and enhanced autophagy markers such as LC3 conversion and p62 degradation. The effects of IL-38 were nullified by siRNA-mediated suppression of SIRT6 or heme oxygenase-1 (HO-1) in HUVECs and palmitate-treated THP-1 cells. These findings reveal that IL-38 mitigates inflammation through the SIRT6/HO-1 pathway, offering a potential therapeutic approach for addressing obesity-related atherosclerosis.

Interleukin-27 as a novel player in alleviating hepatic steatosis: Mechanistic insights from an in vitro analysis.

Interleukin-27 (IL-27) is a recently discovered cytokine that has been implicated in inflammatory and metabolic conditions, such as atherosclerosis and insulin resistance. However, the mechanisms by which IL-27 attenuates hepatic lipid accumulation in hyperlipidemic conditions and counteracts endoplasmic reticulum (ER) stress, a known risk factor for impaired hepatic lipid metabolism, have not been elucidated. This in vitro study was designed to examine the effect of IL-27 on hepatic lipid metabolism. The study included the evaluation of lipogenesis-associated proteins and ER stress markers by Western blotting, the determination of hepatic lipid accumulation by Oil Red O staining, and the examination of autophagosome formation by MDC staining. The results showed that IL-27 treatment reduced lipogenic lipid deposition and the expression of ER stress markers in cultured hepatocytes exposed to palmitate. Moreover, treatment with IL-27 suppressed CD36 expression and enhanced fatty acid oxidation in palmitate-treated hepatocytes. The effects of IL-27 on hyperlipidemic hepatocytes were attenuated when adenosine monophosphate-activated protein kinase (AMPK) or 3-methyladenine (3 MA) were inhibited by small interfering RNA (siRNA). These results suggest that IL-27 attenuates hepatic ER stress and fatty acid uptake and stimulates fatty acid oxidation via AMPK/autophagy signaling, thereby alleviating hepatic steatosis. In conclusion, this study identified IL-27 as a promising therapeutic target for nonalcoholic fatty liver disease (NAFLD).

CTRP4 ameliorates inflammation, thereby attenuating the interaction between HUVECs and THP-1 monocytes through SIRT6/Nrf2 signaling.

CTRP4, identified as an adipokine, has demonstrated notable anti-inflammatory and anti-obesity effects in various disease models. Consequently, our research sought to explore the impact of CTRP4 on inflammation and the interaction between endothelial cells and monocytes in hyperlipidemic conditions. Using Western blotting, we assessed the expression levels of various proteins in HUVECs and THP-1 monocytes. Our study findings indicate that treatment with CTRP4 effectively mitigated the attachment of THP-1 monocytes to HUVECs. Furthermore, it reduced the expression of adhesion molecules and inflammation indicators in experimental cells exposed to hyperlipidemic conditions. Notably, CTRP4 treatment led to an increase in SIRT6 expression and the nuclear translocation of Nrf2. Interestingly, when SIRT6 or Nrf2 was silenced using siRNA, the positive effects of CTRP4 in HUVECs and THP-1 cells were nullified. Our results suggest that CTRP4 exhibits anti-inflammatory properties, thereby improving the interaction between endothelial cells and monocytes through the SIRT6/Nrf2-dependent pathway. This study provides insights into CTRP4 as a potential therapeutic target for mitigating obesity-related atherosclerosis.

Uvaol ameliorates lipid deposition in hyperlipidemic hepatocytes by suppressing protein-tyrosine phosphatase 1B/ER stress signaling.

Uvaol (UV), a pentacyclic triterpene found in olives and virgin olive oil, is known for its anti-inflammatory and antioxidant effects in various disease models. While olive oil is reported to reduce obesity and insulin resistance, the specific impact of UV on liver lipid metabolism and its molecular mechanisms are not fully understood. In this study, hepatic lipid accumulation was measured using oil red O staining, and protein expression levels in liver cells were assessed via Western blot analysis. Apoptosis was evaluated through cell viability and caspase 3 activity assays. UV treatment reduced lipid accumulation, fatty acid uptake, apoptosis, and ER stress in palmitate-treated liver cells. Additionally, UV enhanced fatty acid oxidation. Mechanistically, increased SIRT6 expression and autophagy were observed in UV-treated cells. SIRT6-targeted siRNA or 3-methyladenine blocked the effects of UV in hyperlipidemic cells. In conclusion, UV improves SIRT6/autophagy signaling, reducing lipid deposition and apoptosis in liver cells under high lipid conditions. This in vitro study provides strong evidence for potential therapeutic strategies for hepatic steatosis.

Interleukin 38 improves insulin resistance in hyperlipidemic skeletal muscle cells via PPARδ/SIRT1-mediated suppression of STAT3 signaling and oxidative stress.

The cytokine interleukin-38 (IL-38), a recently discovered member of the IL-1 family, has been shown to regulate inflammation and improve hepatic endoplasmic reticulum stress and lipid metabolism in individuals with obesity. However, its impact on insulin signaling in skeletal muscle cells and the underlying mechanisms remain unclear. In vitro obesity models were established using palmitate treatment, and Western blot analysis was performed to assess target proteins. Commercial kits were used to measure glucose uptake in cultured myocytes. Our study showed that IL-38 treatment alleviated the impairment of insulin signaling, including IRS-1 and Akt phosphorylation, and increased glucose uptake in palmitate-treated C2C12 myocytes. Increased levels of STAT3-mediated signaling and oxidative stress were observed in these cells following palmitate treatment, and these effects were reversed by IL-38 treatment. In addition, IL-38 treatment upregulated the expression of PPARδ, SIRT1 and antioxidants. Knockdown of PPARδ or SIRT1 using appropriate siRNAs abrogated the effects of IL-38 on insulin signaling, oxidative stress, and the STAT3-dependent pathway. These results suggest that IL-38 alleviates insulin resistance by inhibiting STAT3-mediated signaling and oxidative stress in skeletal muscle cells through PPARδ/SIRT1. This study provides fundamental evidence to support the potential use of IL-38 as a safe therapeutic agent for the treatment of insulin resistance and type 2 diabetes.

DEL-1: a promising treatment for AMD-associated ER stress in retinal pigment epithelial cells.

BACKGROUND: Age-related macular degeneration (AMD) is an irreversible eye disease that can cause blurred vision. Regular exercise has been suggested as a therapeutic strategy for treating AMD, but how exercise improves AMD is not yet understood. This study investigated the protective effects of developmental endothelial locus-1 (DEL-1), a myokine upregulated during exercise, on endoplasmic reticulum (ER) stress-induced injury in retinal pigment epithelial cells. METHODS: We evaluated the levels of AMPK phosphorylation, autophagy markers, and ER stress markers in DEL-1-treated human retinal pigment epithelial cells (hRPE) using Western blotting. We also performed cell viability, caspase 3 activity assays, and autophagosome staining. RESULTS: Our findings showed that treatment with recombinant DEL-1 dose-dependently reduced the impairment of cell viability and caspase 3 activity in tunicamycin-treated hRPE cells. DEL-1 treatment also alleviated tunicamycin-induced ER stress markers and VEGF expression. Moreover, AMPK phosphorylation and autophagy markers were increased in hRPE cells in the presence of DEL-1. However, the effects of DEL-1 on ER stress, VEGF expression, and apoptosis in tunicamycin-treated hRPE cells were reduced by AMPK siRNA or 3-methyladenine (3-MA), an autophagy inhibitor. CONCLUSIONS: Our study suggests that DEL-1, a myokine, may have potential as a treatment strategy for AMD by attenuating ER stress-induced injury in retinal pigment epithelial cells.

Adipokine gremlin-1 promotes hepatic steatosis via upregulation of ER stress by suppressing autophagy-mediated signaling.

Gremlin-1 (GR1) is a novel adipokine that is highly expressed in human adipocytes and has been shown to inhibit the BMP2/4-TGFb signaling pathway. It has an effect on insulin sensitivity. Elevated levels of Gremlin have been shown to lead to insulin resistance in skeletal muscle, adipocytes, and hepatocytes. In this study, we investigated the effect of GR1 on hepatic lipid metabolism under hyperlipidemic conditions and explored the molecular mechanisms associated with GR1 by in vitro and in vivo studies. We found that palmitate increased GR1 expression in visceral adipocytes. Recombinant GR1 increased lipid accumulation, lipogenesis, and ER stress markers in cultured primary hepatocytes. Treatment with GR1 increased EGFR expression and mTOR phosphorylation and reduced autophagy markers. EGFR or rapamycin siRNA reduced the effects of GR1 on lipogenic lipid deposition and ER stress in cultured hepatocytes. Administration of GR1 via the tail vein induced lipogenic proteins and ER stress while suppressing autophagy in the livers of experimental mice. Suppression of GR1 by in vivo transfection reduced the effects of a high-fat diet on hepatic lipid metabolism, ER stress, and autophagy in mice. These results suggest that the adipokine GR1 promotes hepatic ER stress due to the impairment of autophagy, ultimately causing hepatic steatosis in the obese state. The current study demonstrated that targeting GR1 may be a potential therapeutic approach for treating metabolic diseases, including metabolic-associated fatty liver disease (MAFLD).

CTRP4 attenuates apoptosis and epithelial-mesenchymal transition markers in podocytes through an AMPK/autophagy-dependent pathway.

Hyperglycemia, characterized by high blood glucose levels resulting from pancreatic beta cell dysfunction or impaired insulin signaling, is a contributing factor in the development of diabetic nephropathy. This study aimed to investigate the effects of C1q/TNF-related protein 4 (CTRP4), known for its anti-obesity and anti-inflammatory properties in various disease models, on podocyte apoptosis and endoplasmic reticulum (ER) stress in the presence of elevated glucose levels. The expression levels of various proteins in podocytes and adipocytes were evaluated by Western blotting. Autophagosomes in podocytes were stained by MDC. Chromatin condensation in podocytes was examined by Hoechst staining. The research revealed increased expression of CTRP4 in 3T3-L1 adipocytes and CIHP-1 podocytes exposed to high glucose (HG) conditions. Treatment with CTRP4 effectively mitigated HG-induced apoptosis and ER stress and normalized epithelial-to-mesenchymal transition (EMT) markers in CIHP-1 cells. Furthermore, elevated levels of AMPK phosphorylation and autophagy were observed in CIHP-1 cells treated with CTRP4. Silencing of AMPK or the use of 3-methyl adenine (3 MA) reduced the impacts of CTRP4 on apoptosis, EMT markers and ER stress in CIHP-1 cells. In conclusion, these findings suggest that CTRP4 alleviates ER stress in podocytes under hyperglycemic conditions, leading to the suppression of apoptosis and the restoration of EMT through AMPK/autophagy-mediated signaling. These insights provide valuable information for the development of therapeutic strategies for diabetic nephropathy.

Myokine musclin alleviates lipid accumulation in 3T3-L1 adipocytes through PKA/p38-mediated upregulation of lipolysis and suppression of lipogenesis.

Musclin (MUS), an exercise-responsive myokine, has been documented to attenuate inflammation and enhance physical endurance. However, the effects of MUS on differentiation and related molecular mechanisms in adipocytes have not yet been studied. In this study, we found that treatment with MUS attenuated lipid accumulation in fully differentiated 3T3-L1 cells. Furthermore, MUS treatment enhanced lipolysis assessed by glycerol release, and caused apoptosis, whereas it reduced the expression of lipogenic proteins, such as PPARγ and processed SREBP1. Treatment with MUS augmented phosphorylated PKA expression, whereas suppressed p38 phosphorylation in 3T3-L1 adipocytes. H89, a selective PKA inhibitor reduced the effects of MUS on lipogenic lipid accumulation as well as lipolysis except for apoptosis. These results suggest that MUS promotes lipolysis and suppresses lipogenesis through a PKA/p38-dependent pathway, thereby ameliorating lipid deposition in cultured adipocytes. The current study offers the potential of MUS as a therapeutic approach for treating obesity with few side effects.

Oroxylin-A alleviates hepatic lipid accumulation and apoptosis under hyperlipidemic conditions via AMPK/FGF21 signaling.

Oroxylin-A (OA) is an O-methylated flavone that has been demonstrated to have anti-inflammatory properties in various disease models. However, the roles of OA in hepatic lipid metabolism and the specific molecular mechanisms by which it exerts these effects are not yet fully understood. In the current study, we aimed to investigate the effects of OA on hepatic lipid deposition and apoptosis, which play a pivotal role in the development of nonalcoholic fatty liver disease (NAFLD) in obesity in vitro models. We found that treatment with OA attenuated lipid accumulation, the expression of lipogenesis-associated proteins and apoptosis in palmitate-treated primary mouse hepatocytes. OA treatment suppressed phosphorylated NFκB and IκB expression in as well as TNFα and MCP-1 release from hepatocytes treated with palmitate. Treatment of hepatocytes with OA augmented AMPK phosphorylation and FGF21 expression. siRNA of AMPK or FGF21 abolished the effects of OA on inflammation as well as lipid accumulation and apoptosis in hepatocytes under palmitate treatment conditions. In conclusion, OA improves inflammation through the AMPK/FGF21 pathway, thereby attenuating lipid accumulation and apoptosis in hepatocytes. This study may help identify new targets for developing treatments for NAFLD.

Musclin attenuates lipid deposition in hepatocytes through SIRT7/autophagy-mediated suppression of ER stress.

Musclin, an exercise-responsive myokine, has the ability to attenuate inflammation, oxidative stress, and apoptosis in cardiomyocytes under pathogenic conditions. While the potential benefits of musclin in the cardiovascular system have been well documented, its effects on hepatic endoplasmic reticulum (ER) stress and lipid metabolism are not fully understood. The present study showed that musclin treatment reduced lipid accumulation and lipogenic protein expression in primary hepatocytes exposed to palmitate. Palmitate treatment led to an increase in markers of ER stress, which was reversed by musclin treatment. Musclin treatment increased SIRT7 expression and markers of autophagy in a dose-dependent manner. Small interfering (si) RNA of SIRT7 or 3-methyladenine (3 MA) reduced the effects of musclin on lipogenic lipid deposition in hepatocytes under hyperlipidemic conditions. These findings suggest that musclin can suppress palmitate-induced ER stress by upregulating SIRT7 and autophagy signaling, thereby alleviating lipid accumulation in primary hepatocytes. The current study provides a potential therapeutic strategy for the treatment of liver diseases characterized by lipid accumulation and ER stress, such as nonalcoholic fatty liver disease (NAFLD).

Sclerostin aggravates insulin signaling in skeletal muscle and hepatic steatosis via upregulation of ER stress by mTOR-mediated inhibition of autophagy under hyperlipidemic conditions.

Recently, sclerostin (SCL), a circulating glycoprotein, was proposed to be a novel myokine involved in developing metabolic disorders. The association between SCL levels and insulin resistance in skeletal muscle, liver, and adipose tissue was studied in individuals with aggravated glucose tolerance. Thus, we hypothesized that elevated circulating SCL might affect skeletal muscle insulin signaling and hepatic lipid metabolism, and aimed to investigate the effects of SCL on skeletal muscle insulin resistance and hepatic steatosis in obesity using in vitro and in vivo experimental models under hyperlipidemic conditions. In the current study, we found elevated SCL messenger RNA expression levels in myocytes in obese patients. In addition to a higher blood level, SCL was expressed at an elevated level in the skeletal muscle of mice fed a high-fat diet (HFD). Higher SCL release levels and expression were also noticed in palmitate-treated C2C12 myocytes. SCL suppression by in vivo transfection improves skeletal muscle insulin resistance and hepatic steatosis in HFD-fed mice. The treatment of C2C12 myocytes with recombinant SCL aggravated insulin signaling. Furthermore, treatment with SCL augmented lipogenic lipid deposition in human primary hepatocytes. Treatment with SCL upregulated mammalian target of rapamycin (mTOR) phosphorylation and suppressed autophagy markers, thereby causing endoplasmic reticulum (ER) stress. 4-Phenylbutyric acid, a pharmacological ER stress inhibitor, abolished the effects of SCL on insulin signaling in C2C12 myocytes and lipid accumulation in primary hepatocytes. In conclusion, SCL promotes skeletal muscle insulin resistance and hepatic steatosis by upregulating ER stress via the mTOR/autophagy-mediated pathway. The present study suggests that antagonizing SCL might be a novel therapeutic strategy for simultaneously managing insulin resistance and hepatic steatosis in obesity.

α-ketoisocaproic acid promotes ER stress through impairment of autophagy, thereby provoking lipid accumulation and insulin resistance in murine preadipocytes.

α-ketoisocaproic acid (AKA), a metabolite of l-leucine, is one of the branched-chain amino acids (BCAAs) involved in energy metabolism. However, the effects of AKA on lipid metabolism, insulin signaling, and related mechanisms in preadipocytes have not been reported. Herein, we investigated the impacts of AKA on lipid accumulation in 3T3-L1 murine preadipocytes. Treatment with AKA for 4 days enhanced lipid accumulation and expression of lipogenic proteins, such as cleaved sterol-regulatory element-binding proteins (SREBP1) and stearoyl-CoA desaturase-1 (SCD1) in 3T3-L1 cells. Increased endoplasmic reticulum (ER) stress markers, such as phosphorylation of eukaryotic initiation factor 2 (eIF2) and CHOP, were observed in the presence of AKA. AKA treatment increased mTOR phosphorylation and reducing autophagy markers, such as LC3 conversion and degradation of p62. Treatment with rapamycin, an mTOR inhibitor, reduced the effects of AKA on ER stress and lipogenesis in 3T3-L1 preadipocytes. The present study demonstrates that AKA increases ER stress by impairing mTOR/autophagy signaling, thus promoting lipid accumulation and insulin resistance in preadipocytes. In particular, if AKA is taken together with substances that can suppress ER stress, more effective skeletal muscle gain will be possible.

Abietic acid alleviates endoplasmic reticulum stress and lipid accumulation in human primary hepatocytes through the AMPK/ORP150 signaling.

Abietic acid (AA), the main component of pine resin that has been traditionally used as Asian medicine, has been reported to demonstrate anti-inflammatory activities. Despite this, little is known about the effects of AA on hepatic endoplasmic reticulum (ER) stress and lipid metabolism. This study investigated the impacts of AA on ER stress and steatosis in in vitro obesity models. We found that Treatment with AA reduced lipid deposition and lipogenesis-related proteins expression in human primary hepatocytes. Augmented expression of ER stress markers (phospho-eukaryotic initiation factor-2α (eIF2α) and C/EBP homologous protein (CHOP)) in palmitate-treated hepatocytes were reversed by AA treatment. Further, AA treatment increased the expression of phospho-AMPK and oxygen-regulated protein 150 (ORP150) in hepatocytes. siRNA-associated knockdown of AMPK or ORP150 expression reduced the effects of AA on not only hepatic ER stress but also lipogenesis and apoptosis. These results denote that AA attenuates lipid accumulation in hepatocytes in the presence of palmitate through the suppression of ER stress by AMPK/ORP150 signaling. AA could be a potential candidate for treating non-alcoholic fatty liver disease.

Endogenous metabolite, kynurenic acid, attenuates nonalcoholic fatty liver disease via AMPK/autophagy- and AMPK/ORP150-mediated signaling.

Endoplasmic reticulum (ER) stress plays a causative role in the development of nonalcoholic fatty liver disease (NAFLD). Kynurenic acid (KA) is a tryptophan metabolite that has been shown to exert anti-inflammatory effects in macrophages and endothelial cells. However, the role of KA in ER stress-associated development of NAFLD has not been fully explored. In the current study, we observed decreased KA levels in the serum of obese subjects. Treated hepatocytes with KA attenuated palmitate-induced lipid accumulation and downregulated lipogenesis-associated genes as well as ER stress markers in a dose-dependent manner. Furthermore, KA augmented AMP-activated protein kinase (AMPK) phosphorylation, oxygen-regulated protein 150 (ORP150) expression, and autophagy markers. The small interfering RNA-mediated suppression of AMPK and ORP150, or 3-methyladenine also abrogated the effects of KA on ER stress and lipid accumulation in hepatocytes. In accordance with in vitro observations, KA administration to mice fed a high-fat diet ameliorated hepatic lipid accumulation and decreased the expression of lipogenic genes as well as ER stress. Moreover, KA treatment increased hepatic AMPK phosphorylation, ORP150 expression, and autophagy related markers in mouse livers. Knockdown of AMPK using in vivo transfection mitigated the effects of KA on hepatic steatosis and ER stress as well as autophagy and ORP150 expression. These results suggest that KA ameliorates hepatic steatosis via the AMPK/autophagy- and AMPK/ORP150-mediated suppression of ER stress. In sum, KA might be used as a promising therapeutic agent for treatment of NAFLD.

Patchouli alcohol improves wound healing in high fat diet-fed mice through AMPK-mediated suppression of inflammation and TGFb1 signaling.

Obesity impairs wound healing with substantial alterations in skin inflammation. Patchouli alcohol (PA), extracted from patchouli, has been reported to ameliorate inflammation in various cell types. However, the effects of PA on inflammation and wound healing have not been reported to date. In the present study, we examined whether PA affects cutaneous wound healing in high fat diet (HFD)-fed mice and explored PA-mediated molecular mechanisms through in vitro experiments. We found that PA administration accelerated wound healing as well as ameliorates inflammation in skin of HFD-fed mice. PA treatment augmented AMP-activated protein kinase (AMPK) phosphorylation and TGFb1 expression. PA enhanced cell migration and suppressed inflammation in LPS-treated HaCaT cells. Further, PA increased dose-dependently AMPK phosphorylation as along with TGFb1 and cell migration markers expression. siRNA for AMPK or TGFb1 abrogated the effects of PA on cell migration and inflammation. TGFb1 siRNA mitigated PA-induced expression of cell migration markers. These results suggest that PA ameliorates wound healing via AMPK and TGFb1-mediated suppression of inflammation. In sum, PA can be used as a novel treatment strategy for wound healing in obesity or insulin resistance.

3-hydroxymorphinan enhances mitochondrial biogenesis and adipocyte browning through AMPK-dependent pathway.

3-hydroxymorphinan (3-HM), a metabolite of dextromethorphan, has previously been reported to have anti-inflammatory, anti-oxidative stress, and neuroprotective effects. However, its effect on energy metabolism in adipocytes remains unclear. Herein, we investigated 3-hydroxymorphinan (3-HM) effects on mitochondrial biogenesis, oxidative stress, and lipid accumulation in 3T3-L1 adipocytes. Further, we explored 3-HM-associated molecular mechanisms. Mouse adipocyte 3T3-L1 cells were treated with 3-HM, and various protein expression levels were determined by western blotting analysis. Mitochondria accumulation and lipid accumulation were measured by staining methods. Cell toxicity was assessed by cell viability assay. We found that treatment of 3T3-L1 adipocytes with 3-HM increased expression of brown adipocyte markers, such as uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α). 3-HM promotes mitochondrial biogenesis and its-mediated gene expression. Additionally, 3-HM treatment suppressed mitochondrial ROS generation and superoxide along with improved mitochondrial complex I activity. We found that treatment of 3-HM enhanced AMPK phosphorylation. siRNA-mediated suppression of AMPK reversed all these changes in 3T3-L1 adipocytes. In sum, 3-HM promotes mitochondrial biogenesis and browning and attenuates oxidative stress and lipid accumulation in 3T3-L1 adipocytes via AMPK signaling. Thus, 3-HM-mediated AMPK activation can be considered a therapeutic approach for treating obesity and related diseases.

Capmatinib attenuates lipogenesis in 3T3-L1 adipocytes through an adenosine monophosphate-activated protein kinase-dependent pathway.

Recently, there is a rapid increase in the incidence of obesity, a condition for which there are no effective therapeutic agents. Capmatinib (CAP), a novel mesenchymal-to-epithelial transition inhibitor, is reported to attenuate pro-inflammatory mediators and oxidative stress. In this study, the effects of CAP on lipogenesis in the adipocytes were examined. Treatment with CAP dose-dependently suppressed lipid accumulation in, and differentiation of, and increased lipolysis in, 3T3-L1 adipocytes. Additionally, CAP treatment augmented adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and FNDC5 expression in the adipocytes. Transfection with si-AMPK or si-FNDC5 mitigated the CAP-induced suppression of lipogenesis and enhanced lipolysis. Furthermore, transfection with si-FNDC5 mitigated the CAP-induced phosphorylation of AMPK. These results suggest that the anti-obesity effect of CAP is mediated through the irisin/AMPK pathway and that CAP is a novel therapeutic agent for obesity.

Humanin attenuates palmitate-induced hepatic lipid accumulation and insulin resistance via AMPK-mediated suppression of the mTOR pathway.

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) remains unclear. Humanin (HN), a cytoprotective polypeptide, reportedly exhibits neuroprotective effects via suppression of inflammation and improvement of insulin resistance in neurons. This study aim was to investigate effects of HN on lipid accumulation in the hepatocytes and insulin signaling, and explore the underlying mechanisms. Protein expression levels were analyzed by Western blotting. Hepatic lipid accumulation was confirmed by Oil red-O staining. We found that HN-treatment ameliorated palmitate-induced lipid accumulation, expression of lipogenesis-associated genes (processed SREBP1, FAS, and SCD1), cell death, and caspase 3 activity in hepatocytes in a dose-dependent manner. Additionally, HN attenuated palmitate-induced impairment of insulin signaling. HN enhanced AMPK phosphorylation, whereas it suppressed palmitate-induced phosphorylation of mTOR. AMPK knockdown by siRNA neutralized the effects of HN on palmitic acid-treated hepatocytes. Collectively, HN prevents palmitate-induced hepatic lipid accumulation, apoptosis, and insulin resistance via AMPK-mediated suppression of the mTOR/SREBP1 pathway, suggesting that it may serve as a potential therapeutic agent in NAFLD treatment.