Photoactivation of Dok1/ERK/PPARγ signaling axis inhibits excessive lipolysis in insulin-resistant adipocytes

Advances in Targeted Drug Resistance Associated with Dysregulation of Lipid Metabolism in Hepatocellular Carcinoma

Hepatocellular carcinoma is the prevailing malignant neoplasm affecting the liver, often diagnosed at an advanced stage and associated with an unfavorable overall prognosis. Sorafenib and Lenvatinib have emerged as first-line therapeutic drugs for advanced hepatocellular carcinoma, improving the prognosis for these patients. Nevertheless, the issue of tyrosine kinase inhibitor (TKI) resistance poses a substantial obstacle in the management of advanced hepatocellular carcinoma. The pathogenesis and advancement of hepatocellular carcinoma exhibit a close association with metabolic reprogramming, yet the attention given to lipid metabolism dysregulation in hepatocellular carcinoma development remains relatively restricted. This review summarizes the potential significance and research progress of lipid metabolism dysfunction in Sorafenib and Lenvatinib resistance in hepatocellular carcinoma. Targeting hepatocellular carcinoma lipid metabolism holds promising potential as an effective strategy to overcome hepatocellular carcinoma drug resistance in the future.

Transcranial photobiomodulation improves insulin therapy in diabetic microglial reactivity and the brain drainage system

The dysfunction of microglia in the development of diabetes is associated with various diabetic complications, while traditional insulin therapy is insufficient to rapidly restore the function of microglia. Therefore, the search for new alternative methods of treating diabetes-related dysfunction of microglia is urgently needed. Here, we evaluate the effects of transcranial photobiomodulation (tPBM) on microglial function in diabetic mice and investigate its mechanism. We find tPBM treatment effectively improves insulin therapy on microglial morphology and reactivity. We also show that tPBM stimulates brain drainage system through activation of meningeal lymphatics, which contributes to the removal of inflammatory factor, and increase of microglial purinergic receptor P2RY12. Besides, the energy expenditure and locomotor activity of diabetic mice are also improved by tPBM. Our results demonstrate that tPBM can be an efficient, non-invasive method for the treatment of microglial dysfunction caused by diabetes, and also has the potential to prevent diabetic physiological disorders.

Photoactivation of mitochondrial reactive oxygen species-mediated Src and protein kinase C pathway enhances MHC class II-restricted T cell immunity to tumours

High fluence low-level laser (HF-LLL), a mitochondria-targeted tumour phototherapy, results in oxidative damage and apoptosis of tumour cells, as well as damage to normal tissue. To circumvent this, the therapeutic effect of low fluence LLL (LFL), a non-invasive and drug-free therapeutic strategy, was identified for tumours and the underlying molecular mechanisms were investigated. We observed that LFL enhanced antigen-specific immune response of macrophages and dendritic cells by upregulating MHC class II, which was induced by mitochondrial reactive oxygen species (ROS)-activated signalling, suppressing tumour growth in both CD11c-DTR and C57BL/6 mice. Mechanistically, LFL upregulated MHC class II in an MHC class II transactivator (CIITA)-dependent manner. LFL-activated protein kinase C (PKC) promoted the nuclear translocation of CIITA, as inhibition of PKC attenuated the DNA-binding efficiency of CIITA to MHC class II promoter. CIITA mRNA and protein expression also improved after LFL treatment, characterised by direct binding of Src and STAT1, and subsequent activation of STAT1. Notably, scavenging of ROS downregulated LFL-induced Src and PKC activation and antagonised the effects of LFL treatment. Thus, LFL treatment altered the adaptive immune response via the mitochondrial ROS-activated signalling pathway to control the progress of neoplastic disease.

Docking protein 1 and free fatty acids are associated with insulin resistance in patients with type 2 diabetes mellitus

OBJECTIVE

Insulin resistance (IR) is a key defect in type 2 diabetes mellitus (T2DM); therefore, effective means of ameliorating IR are sought.

METHODS

We performed a retrospective cohort study of 154 patients with T2DM and 39 with pre-diabetes (pre-DM). The effects of IR and a high concentration of FFA on gene expression were determined using microarray analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR) in patients with T2DM or pre-DM.

RESULTS

Serum FFA concentration and homeostasis model assessment of IR (HOMA-IR) were significantly higher in patients with T2DM but no obesity and in those with pre-DM than in controls. HOMA-IR was significantly associated with T2DM. RT-qPCR showed that the expression of FBJ murine osteosarcoma viral oncogene homolog (FOS) and AE binding protein 1 (AEBP1) was much lower in the circulation of participants with obesity and diabetes. RT-qPCR showed that the expression of docking protein 1 (DOK1) was significantly lower in the blood of participants with diabetes but no obesity and in those with pre-DM than in controls.

CONCLUSIONS

FFA and DOK1 are associated with IR in patients with T2DM but no obesity or pre-DM. The downregulation of DOK1 might inhibit lipid synthesis and induce lipolysis, inducing or worsening IR.

Photobiomodulation therapy ameliorates hyperglycemia and insulin resistance by activating cytochrome c oxidase-mediated protein kinase B in muscle

Ameliorating hyperglycemia and insulin resistance are major therapeutic strategies for type 2 diabetes. Previous studies have indicated that photobiomodulation therapy (PBMT) attenuates metabolic abnormalities in insulin-resistant adipose cells and tissues. However, it remains unclear whether PBMT ameliorates glucose metabolism in skeletal muscle in type 2 diabetes models. Here we showed that PBMT reduced blood glucose and insulin resistance, and reversed metabolic abnormalities in skeletal muscle in two diabetic mouse models. PBMT accelerated adenosine triphosphate (ATP) and reactive oxygen species (ROS) generation by elevating cytochrome c oxidase (CcO) activity. ROS-induced activation of phosphatase and tensin homolog (PTEN)/ protein kinase B (AKT) signaling after PBMT promoted glucose transporter GLUT4 translocation and glycogen synthase (GS) activation, accelerating glucose uptake and glycogen synthesis in skeletal muscle. CcO subunit III deficiency, ROS elimination, and AKT inhibition suppressed the PBMT effects of glucose metabolism in skeletal muscle. This study indicated amelioration of glucose metabolism after PBMT in diabetic mouse models and revealed the metabolic regulatory effects and mechanisms of PBMT on skeletal muscle.

Photobiomodulation reduces hepatic lipogenesis and enhances insulin sensitivity through activation of CaMKKβ/AMPK signaling pathway

Photobiomodulation (PBM) could improve systemic blood glucose and insulin resistance in diet-induced diabetic mice. A few possible molecular mechanisms for the beneficial effects of PBM on diabetes have been proposed, but there is still an urgent need to explore the underlying mechanisms that support the application of PBM in the treatment of diabetes. Our study aimed to evaluate the effects of PBM on lipid metabolism in the liver of high-fat diet (HFD)-induced mice and explore the potential mechanisms of PBM on obesity and type 2 diabetes. Here, we administered PBM therapy (wavelength: 635 nm, energy density: 8 J/cm²) daily for eight weeks to HFD-induced mice. We detected that eight-week daily administration of PBM ameliorated HFD-induced gain weight, hyperlipidemia, and hyperglycemia, but also protected against diet-induced hepatic steatosis and insulin resistance. Furthermore, PBM increased AMP-activated protein kinase (AMPK) activation, lowered nuclear translocation of sterol regulatory element binding protein 1 (SREBP1), decreased aberrant lipogenesis, and enhanced insulin sensitive in HFD-induced mice livers. We also observed that Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ) activation was responsible for AMPK activation in insulin-resistant HepG2 cells exposed to PBM. In summary, PBM at 635 nm and 8 J/cm² improved hepatic lipid metabolism and inhibited the development of HFD-induced obesity and type 2 diabetes. Moreover, increased intracellular Ca²⁺ content and CaMKKβ-dependent AMPK activation were possible molecular mechanisms underlying the PBM-induced improvement on obesity and type 2 diabetes.

Rosiglitazone ameliorates skeletal muscle insulin resistance by decreasing free fatty acids release from adipocytes

Skeletal muscle and white adipose tissue are important organs of glucose-lipid metabolism. However, excessive lipolysis and free fatty acids (FFA) release in adipocytes elevate plasma FFA, leading to insulin resistance in skeletal muscle. Here, we investigated effects of insulin-resistant adipocytes on skeletal muscle in vitro by simulating body environment using a transwell coculture method. Insulin-resistant 3T3-L1 adipocytes increased lipolysis and FFA release, which reduced insulin sensitivity in the cocultured C2C12 myotubes. Rosiglitazone (RSG) decreased excessive lipolysis by reducing expression of adipose triglyceride lipase (ATGL) and activity of hormone-sensitive lipase (HSL), which led to decrease of FFA release from insulin-resistant 3T3-L1 adipocytes. Meanwhile, insulin resistance in C2C12 myotubes cocultured with insulin-resistant 3T3-L1 adipocytes was ameliorated after RSG treatment. Taken together, our present study provided direct evidence to better understand insulin resistance between skeletal muscle and adipose tissue in type 2 diabetes.

Docking protein-1 promotes inflammatory macrophage signaling in gastric cancer

Docking protein-1 (DOK1) is a tumor suppressor frequently lost in malignant cells, however, it retains the ability to control activities of immune receptors in adjacent stroma cells of the tumor microenvironment. We therefore hypothesized that addressing DOK1 may be useful for cancer immunotherapy. DOK1 mRNA and DOK1 protein expression were downregulated in tumor cells of gastric cancer patients (n = 249). Conversely, its expression was up-regulated in cases positive for Epstein Barr Virus (EBV+) together with genes related to macrophage biology and targets of clinical immunotherapy such as programmed-cell-death-ligand-1 (PD-L1). Notably, high DOK1 positivity in stroma cells conferred poor prognosis in patients and correlated with high levels of inducible nitric oxide synthase in CD68+ tumor-associated macrophages. In macrophages derived from human monocytic leukemia cell lines, DOK1 (i) was inducible by agonists of the anti-diabetic transcription factor peroxisome proliferator-activated receptor-gamma (PPARγ), (ii) increased polarization towards an inflammatory phenotype, (iii) augmented nuclear factor-κB-dependent transcription of pro-inflammatory cytokines and (iv) reduced PD-L1 expression. These properties empowered DOK1+ macrophages to decrease the viability of human gastric cancer cells in contact-dependent co-cultures. DOK1 also reduced PD-L1 expression in human primary blood monocytes. Our data propose that the drugability of DOK1 may be exploited to reprogram myeloid cells and enforce the innate immune response against EBV+ human gastric cancer.

Bidirectional modulation of insulin action by reactive oxygen species in 3T3‑L1 adipocytes

Reactive oxygen species (ROS) serve an important role in glucose‑lipid metabolic regulation. In the present study, the results demonstrated that there was bidirectional regulation of insulin action in 3T3‑L1 adipocytes treated with ROS. Transient and acute ROS exposure improved insulin‑induced metabolic effects in 3T3‑L1 adipocytes. Hydrogen peroxide (H2O2), as a stable and diffusible ROS, diffused into adipocytes and altered intracellular redox homeostasis, resulting in oxidation and inactivation of phosphatase and tensin homologue deleted on chromosome 10 (PTEN). Inactivation of PTEN enhanced the activation of insulin‑induced protein kinase B (AKT), leading to increased glucose transporter 4 (GLUT4) redistribution and glucose uptake in 3T3‑L1 adipocytes. However, chronic ROS treatment induced insulin resistance in 3T3‑L1 adipocytes. It was also revealed that insulin‑induced AKT activation, GLUT4 translocation to cell membrane and glucose uptake were significantly inhibited in chronic ROS‑treated 3T3‑L1 adipocytes. Taken together, the present study provided further demonstration that transient ROS treatment improved insulin sensitivity; however, chronic ROS exposure induced insulin resistance in 3T3‑L1 adipocytes.

Metarhizium anisopliae s.l. modulation of lipid metabolism during tick infection is independent of AMPK and ERK pathways

Despite the importance of fat body in metabolism of arthropods, studies in ticks are scarce. This study evaluated the lipid composition and activation of extracellular signal-regulated protein kinase (ERK) and AMP-activated protein kinase (AMPK) enzymes in Rhipicephalus microplus fat body after infection with different isolates of the fungus Metarhizium anisopliae sensu lato (Metschnikoff, 1879) Sorokin, 1883. The isolates CG 32, GC 112, GC 148, GC 347, and GC 629 were inoculated as viable or non-viable conidia in the ticks. The engorged females were dissected, and their fat bodies were collected 24 and 48 h after infection. The lipid composition was assessed by thin layer chromatography, and enzyme activation was detected by Western blotting with antibodies against p-AMPK and p-ERK. The study showed increased levels of triacylglycerol 24 and 48 h and fatty acid after 48 h after inoculation with different isolates of viable fungi in the tick's hemocoel. Detection of the active form of ERK was demonstrated only after inoculation with non-viable conidia of all isolates tested. The active form of AMPK, only isolate CG 112 was able to activate with viable or non-viable conidia, whereas isolates CG 32 and CG 629 were able to activate with non-viable conidia. This study provides the first report about changes in important metabolic pathways in ticks infected with entomopathogenic fungi and suggests that the lipid content is modulated by non-usual pathways. However, further studies may be necessary for a better elucidation of this interaction.

Transcriptional co-regulator RIP140: An important mediator of the inflammatory response and its associated diseases (Review)

The inflammatory response is a physiological process that is essential for maintaining homeostasis of the immune system. Inflammation is classified into acute inflammation and chronic inflammation, both of which pose a risk to human health. However, specific regulatory mechanisms of the inflammatory response remain to be elucidated. Receptor interacting protein (RIP) 140 is a nuclear receptor that affects an extensive array of biological and pathological processes in the body, including energy metabolism, inflammation and tumorigenesis. RIP140‑mediated macrophage polarization is important in regulating the inflammatory response. Overexpression of RIP140 in macrophages results in M1‑like polarization and expansion during the inflammatory response. Conversely, decreased expression of RIP140 in macrophages reduces the number of M1‑like macrophages and increases the number of alternatively polarized cells, which collectively promote endotoxin tolerance (ET) and relieve inflammation. This review summarizes the role of RIP140 in acute and chronic inflammatory diseases, with a focus on insulin resistance, atherosclerosis, sepsis and ET.

Glycolysis regulates LPS-induced cytokine production in M2 polarized human macrophages

M1 and M2 macrophages are the key players in innate immunity, and are associated with tissue homeostasis and diseases. Although M2 macrophages are known to depend on fatty acid oxidation (FAO) for their activation, how metabolic pathways affect the production of each cytokine induced by pathogen or bacterial components is unclear. Here, we examined the role of the glycolytic pathway in M2 polarized human macrophages in cytokine production induced by lipopolysaccharide (LPS) stimulation. Human monocytes were isolated from peripheral blood by positive selection for CD14 expression and cultured with macrophage colony-stimulating factor (M-CSF), to obtain M-CSF-induced macrophages (M-MΦ). LPS-induced cytokine production by M-MΦ in the presence or absence of metabolic inhibitors was evaluated. M-MΦ showed a M2 macrophage phenotype with a high IL-10 production level. Glycolytic pathway inhibitors reduced IL-6 production by M-MΦ. Meanwhile, an FAO inhibitor suppressed IL-10 production, while it did not suppress IL-6 production. Interestingly, glycolytic pathway inhibitors downregulated extracellular signal-regulated kinase (ERK) phosphorylation, but FAO inhibitor did not. Nuclear factor kappa B (NF-κB) and the other mitogen-activated protein kinases (MAPKs), p38 and c-jun N-terminal kinase (JNK), were not affected by these metabolic inhibitors. These results suggest that M2 polarized human macrophages use the glycolytic pathway in addition to FAO for cytokine production. Furthermore, ERK may be the key molecule that links metabolic pathways to cytokine production, especially the glycolytic pathway.

Divergent selection-induced obesity alters the composition and functional pathways of chicken gut microbiota

Background

The gastrointestinal tract is populated by a complex and vast microbial network, with a composition that reflects the relationships of the symbiosis, co-metabolism, and co-evolution of these microorganisms with their host. The mechanism that underlies such interactions between the genetics of the host and gut microbiota remains elusive.

Results

To understand how genetic variation of the host shapes the gut microbiota and interacts with it to affect the metabolic phenotype of the host, we compared the abundance of microbial taxa and their functional performance between two lines of chickens (fat and lean) that had undergone long-term divergent selection for abdominal fat pad weight, which resulted in a 4.5-fold increase in the fat line compared to the lean line. Our analysis revealed that the proportions of Fusobacteria and Proteobacteria differed significantly between the two lines (8 vs. 18% and 33 vs. 24%, respectively) at the phylum level. Eight bacterial genera and 11 species were also substantially influenced by the host genotype. Differences between the two lines in the frequency of host alleles at loci that influence accumulation of abdominal fat were associated with differences in the abundance and composition of the gut microbiota. Moreover, microbial genome functional analysis showed that the gut microbiota was involved in pathways that are associated with fat metabolism such as lipid and glycan biosynthesis, as well as amino acid and energy metabolism. Interestingly, citrate cycle and peroxisome proliferator activated receptor (PPAR) signaling pathways that play important roles in lipid storage and metabolism were more prevalent in the fat line than in the lean line.

Conclusions

Our study demonstrates that long-term divergent selection not only alters the composition of the gut microbiota, but also influences its functional performance by enriching its relative abundance in microbial taxa. These results support the hypothesis that the host and gut microbiota interact at the genetic level and that these interactions result in their co-evolution.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-016-0270-5) contains supplementary material, which is available to authorized users.

Regulation of Autophagy-Related Protein and Cell Differentiation by High Mobility Group Box 1 Protein in Adipocytes

High mobility group box 1 protein (HMGB1) is a molecule related to the development of inflammation. Autophagy is vital to maintain cellular homeostasis and protect against inflammation of adipocyte injury. Our recent work focused on the relationship of HMGB1 and autophagy in 3T3-L1 cells. In vivo experimental results showed that, compared with the normal-diet group, the high-fat diet mice displayed an increase in adipocyte size in the epididymal adipose tissues. The expression levels of HMGB1 and LC3II also increased in epididymal adipose tissues in high-fat diet group compared to the normal-diet mice. The in vitro results indicated that HMGB1 protein treatment increased LC3II formation in 3T3-L1 preadipocytes in contrast to that in the control group. Furthermore, LC3II formation was inhibited through HMGB1 knockdown by siRNA. Treatment with the HMGB1 protein enhanced LC3II expression after 2 and 4 days but decreased the expression after 8 and 10 days among various differentiation stages of adipocytes. By contrast, FABP4 expression decreased on the fourth day and increased on the eighth day. Hence, the HMGB1 protein modulated autophagy-related proteins and lipid-metabolism-related genes in adipocytes and could be a new target for treatment of obesity and related metabolic diseases.

Urolithin A attenuates ox-LDL-induced endothelial dysfunction partly by modulating microRNA-27 and ERK/PPAR-γ pathway

SCOPE

Endothelial dysfunction and inflammation are both common events occurring during the development of atherosclerosis. Previous studies have shown that urolithins, the intestinal microflora metabolites of ellagitannin, exhibit anti-inflammation and antioxidative properties. This study aims to investigate the protective effect of urolithin A (UA) on ox-LDL-induced (where ox-LDL is oxidized low-density lipoprotein) endothelial dysfunction and possible modes of action.

METHODS AND RESULTS

Human artery endothelial cells were incubated with 50 μg/mL ox-LDL and various concentrations of UA for 24 h. UA improved the productions of nitric oxide and endothelial nitric oxide synthase in a dose-dependent manner. UA markedly reduced the expressions of ICAM-1 (intercellular adhesion molecule 1) and MCP-1 (monocyte chemotactic protein 1) and further attenuated THP-1 (human acute monocytic leukemia cell line) cell adhesion. In addition, UA suppressed expressions of tumor necrosis factor α, interleukin 6, and endothelin 1, and increased PPAR-γ (peroxisome proliferators activated receptor gamma) mRNA expression. Moreover, UA decreased miR-27 expression, and overexpression of miR-27 by adding pre-miR-27 abolished the ability of UA to improve ox-LDL-induced PPAR-γ decrease. Furthermore, UA significantly downregulated phosphorylated ERK1/2 (where ERK is extracellular signal-regulated kinase) while decreasing interleukin 6 level and elevating PPAR-γ.

CONCLUSIONS

UA could alleviate endothelial dysfunction induced by ox-LDL partially through modulating miR-27 expression and ERK/PPAR-γ pathway.

Subcellular compartmentalization of docking protein-1 contributes to progression in colorectal cancer

Full-length (FL) docking protein-1 (DOK1) is an adapter protein which inhibits growth factor and immune response pathways in normal tissues, but is frequently lost in human cancers. Small DOK1 variants remain in cells of solid tumors and leukemias, albeit, their functions are elusive. To assess the so far unknown role of DOK1 in colorectal cancer (CRC), we generated DOK1 mutants which mimic the domain structure and subcellular distribution of DOK1 protein variants in leukemia patients. We found that cytoplasmic DOK1 activated peroxisome-proliferator-activated-receptor-gamma (PPARγ) resulting in inhibition of the c-FOS promoter and cell proliferation, whereas nuclear DOK1 was inactive. PPARγ-agonist increased expression of endogenous DOK1 and interaction with PPARγ. Forward translation of this cell-based signaling model predicted compartmentalization of DOK1 in patients. In a large series of CRC patients, loss of DOK1 protein was associated with poor prognosis at early tumor stages (*p = 0.001; n = 1492). In tumors with cytoplasmic expression of DOK1, survival was improved, whereas nuclear localization of DOK1 correlated with poor outcome, indicating that compartmentalization of DOK1 is critical for CRC progression. Thus, DOK1 was identified as a prognostic factor for non-metastatic CRC, and, via its drugability by PPARγ-agonist, may constitute a potential target for future cancer treatments.

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Forward translation of a cell-based signaling model predicted clinical relevance for DOK1 in colorectal cancer (CRC).

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DOK1 is an independent prognostic factor in CRC patients, and its loss associated with poor survival.

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Cancer cell growth inhibition by DOK1 was increased (“drugable”) by PPARγ-agonist.

Poor survival due to failure to respond to clinical therapies prevents effective treatment of cancer. Thus, there is a high medical need for novel drug targets and biomarkers. DOK1 blocks pro-cancer signaling in the healthy body, but is often lost in tumors. We show that colorectal cancer patients who are positive for DOK1 have a better survival outcome than patients who are negative. Anti-diabetic drugs up-regulated DOK1 and promoted its protective actions against tumor cells. Our study therefore suggests DOK1 as a marker for good prognosis and as a potential drug target for therapy of colorectal cancer.