Fenofibrate reverses changes induced by high-fat diet on metabolism in mice muscle and visceral adipocytes

A novel fatty acid mimetic with pan-PPAR partial agonist activity inhibits diet-induced obesity and metabolic dysfunction-associated steatotic liver disease

OBJECTIVE

The prevalence of metabolic diseases is increasing globally at an alarming rate; thus, it is essential that effective, accessible, low-cost therapeutics are developed. Peroxisome proliferator-activated receptors (PPARs) are transcription factors that tightly regulate glucose homeostasis and lipid metabolism and are important drug targets for the treatment of type 2 diabetes and dyslipidemia. We previously identified LDT409, a fatty acid-like compound derived from cashew nut shell liquid, as a novel pan-active PPARα/γ/δ compound. Herein, we aimed to assess the efficacy of LDT409 in vivo and investigate the molecular mechanisms governing the actions of the fatty acid mimetic LDT409 in diet-induced obese mice.

METHODS

C57Bl/6 mice (6-11-month-old) were fed a chow or high fat diet (HFD) for 4 weeks; mice thereafter received once daily intraperitoneal injections of vehicle, 10 mg/kg Rosiglitazone, 40 mg/kg WY14643, or 40 mg/kg LDT409 for 18 days while continuing the HFD. During treatments, body weight, food intake, glucose and insulin tolerance, energy expenditure, and intestinal lipid absorption were measured. On day 18 of treatment, tissues and plasma were collected for histological, molecular, and biochemical analysis.

RESULTS

We found that treatment with LDT409 was effective at reversing HFD-induced obesity and associated metabolic abnormalities in mice. LDT409 lowered food intake and hyperlipidemia, while improving insulin tolerance. Despite being a substrate of both PPARα and PPARγ, LDT409 was crucial for promoting hepatic fatty acid oxidation and reducing hepatic steatosis in HFD-fed mice. We also highlighted a role for LDT409 in white and brown adipocytes in vitro and in vivo where it decreased fat accumulation, increased lipolysis, induced browning of WAT, and upregulated thermogenic gene Ucp1. Remarkably, LDT409 reversed HFD-induced weight gain back to chow-fed control levels. We determined that the LDT409-induced weight-loss was associated with a combination of increased energy expenditure (detectable before weight loss was apparent), decreased food intake, increased systemic fat utilization, and increased fecal lipid excretion in HFD-fed mice.

CONCLUSIONS

Collectively, LDT409 represents a fatty acid mimetic that generates a uniquely favorable metabolic response for the treatment of multiple abnormalities including obesity, dyslipidemia, metabolic dysfunction-associated steatotic liver disease, and diabetes. LDT409 is derived from a highly abundant natural product-based starting material and its development could be pursued as a therapeutic solution to the global metabolic health crisis.

The myokine CCL5 recruits subcutaneous preadipocytes and promotes intramuscular fat deposition in obese mice

Intramuscular fat (IMF) refers to the lipid stored in skeletal muscle tissue. The number and size of intramuscular adipocytes are the primary factors that regulate IMF content. Intramuscular adipocytes can be derived from either in situ or ectopic migration. In this study, it was discovered that the regulation of IMF levels is achieved through the chemokine (C-C motif) ligand 5 (CCL5)/chemokine (C-C motif) receptor 5 (CCR5) pathway by modulating adipocyte migration. In coculture experiments, C2C12 myotubes were more effective in promoting the migration of 3T3-L1 preadipocytes than C2C12 myoblasts, along with increasing CCL5. Correspondingly, overexpressing the CCR5, one of the receptors of CCL5, in 3T3-L1 preadipocytes facilitated their migration. Conversely, the application of the CCL5/CCR5 inhibitor, MARAVIROC (MVC), reduced this migration. In vivo, transplanted experiments of subcutaneous adipose tissue (SCAT) from transgenic mice expressing green fluorescent protein (GFP) provided evidence that injecting recombinant CCL5 (rCCL5) into skeletal muscle promotes the migration of subcutaneous adipocytes to the skeletal muscle. The level of CCL5 in skeletal muscle increased with obesity. Blocking the CCL5/CCR5 axis by MVC inhibited IMF deposition, whereas elevated skeletal muscle CCL5 promoted IMF deposition in obese mice. These results establish a link between the IMF and the CCL5/CCR5 pathway, which could have a potential application for modulating IMF through adipocyte migration.NEW & NOTEWORTHY C2C12 myotubes attract 3T3-L1 preadipocyte migration regulated by the chemokine (C-C motif) ligand 5 (CCL5)/ chemokine (C-C motif) receptor 5 (CCR5) axis. High levels of skeletal muscle-specific CCL5 promote the migration of subcutaneous adipocytes to skeletal muscle and induce the intramuscular fat (IMF) content.

An update on the secretory functions of brown, white, and beige adipose tissue: Towards therapeutic applications

Adipose tissue, including white adipose tissue (WAT), brown adipose tissue (BAT), and beige adipose tissue, is vital in modulating whole-body energy metabolism. While WAT primarily stores energy, BAT dissipates energy as heat for thermoregulation. Beige adipose tissue is a hybrid form of adipose tissue that shares characteristics with WAT and BAT. Dysregulation of adipose tissue metabolism is linked to various disorders, including obesity, type 2 diabetes, cardiovascular diseases, cancer, and infertility. Both brown and beige adipocytes secrete multiple molecules, such as batokines, packaged in extracellular vesicles or as soluble signaling molecules that play autocrine, paracrine, and endocrine roles. A greater understanding of the adipocyte secretome is essential for identifying novel molecular targets in treating metabolic disorders. Additionally, microRNAs show crucial roles in regulating adipose tissue differentiation and function, highlighting their potential as biomarkers for metabolic disorders. The browning of WAT has emerged as a promising therapeutic approach in treating obesity and associated metabolic disorders. Many browning agents have been identified, and nanotechnology-based drug delivery systems have been developed to enhance their efficacy. This review scrutinizes the characteristics of and differences between white, brown, and beige adipose tissues, the molecular mechanisms involved in the development of the adipocytes, the significant roles of batokines, and regulatory microRNAs active in different adipose tissues. Finally, the potential of WAT browning in treating obesity and atherosclerosis, the relationship of BAT with cancer and fertility disorders, and the crosstalk between adipose tissue with circadian system and circadian disorders are also investigated.

Bisphenol A Alters the Levels of miRNAs That Directly and/or Indirectly Target Neuropeptide Y in Murine Hypothalamic Neurons

The hypothalamus is a vital regulator of energy homeostasis. Orexigenic neuropeptide Y (NPY) neurons within the hypothalamus can stimulate feeding and suppress energy expenditure, and dysregulation of these neurons may contribute to obesity. We previously reported that bisphenol A (BPA), an endocrine disruptor with obesogenic properties, alters Npy transcription in hypothalamic neurons by inducing oxidative stress. We hypothesized that hypothalamic microRNAs (miRNAs), a class of small non-coding RNAs, could directly regulate Npy gene expression by binding the 3' untranslated region (UTR). Five predicted Npy-targeting miRNA candidates were uncovered through TargetScan and were detected in Npy-expressing hypothalamic neuronal cell models and hypothalamic neuronal primary cultures. BPA dysregulated the expression of a number of these hypothalamic miRNAs. We examined the effects of putative Npy-targeting miRNAs using miRNA mimics, and we found that miR-143-3p, miR-140-5p, miR-29b-1-5p, and let-7b-3p altered Npy expression in the murine hypothalamic cell lines. Importantly, miR-143-3p targets the mouse Npy 3' UTR, as detected using a luciferase construct containing the potential 3' UTR binding sites. Overall, this study established the first hypothalamic miRNA that directly targets the 3' UTR of mouse Npy, emphasizing the involvement of miRNAs in the NPY system and providing an alternative target for control of NPY levels.

Integrated miRNA-mRNA analysis reveals the dysregulation of lipid metabolism in mouse liver induced by developmental arsenic exposure

Developmental arsenic exposure leads to increased susceptibility to liver diseases including nonalcoholic fatty liver diseases, but the mechanism is incompletely understood. In this study, C57BL/6J mice were used to establish a lifetime arsenic exposure model covering developmental stage. We found that arsenic-exposed offspring in later life showed hepatic lipid deposition and increased triglyceride content. Despite no significant hepatic pathological changes in the offspring at weaning, 86 miRNAs and 136 mRNAs were differentially expressed according to miRNA array and mRNA sequencing. The differentially expressed genes (DEGs) were crossed with the target genes predicted by differentially expressed miRNAs (DEMs), and 47 differentially expressed target genes (DETGs) were obtained. Functional annotation suggested that lipid metabolism related pathways were significantly enriched. The pivotal regulator in the four major pathways to maintain liver lipid homeostasis were further determined, with significant alterations found in FABP5, SREBP1, ACOX1 and EHHADH. Of note, miRNA-mRNA integration analysis revealed that miR-7118-5p, miR-7050-5p, miR-27a/b-3p, and miR-103-3p acted as key regulators of fatty acid metabolism genes. Taken together, miRNA-mRNA integration analysis indicates that the lipid metabolism pathway in the liver of weaned mice was dysregulated by developmental arsenic exposure, which may contribute to the development of NAFLD in later life.

The Relationship between Serum Adipokines, miR-222-3p, miR-103a-3p and Glucose Regulation in Pregnancy and Two to Three Years Post-Delivery in Women with Gestational Diabetes Mellitus Adhering to Mediterranean Diet Recommendations

The San Carlos Gestational Diabetes Mellitus (GDM) prevention study, a nutritional intervention RCT based on a Mediterranean Diet (MedDiet), has been shown to reduce the incidence of GDM. The objective of this study is to investigate the relationship of leptin, adiponectin, interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-α), insulin and HOMA-IRand circulating miRNAs (miR-29a-3p, miR-103a-3p, miR-132-3p, miR-222-3p) with the appearance of GDM and with MedDiet-based nutritional intervention, at 24−28 gestational weeks (GW), and in glucose regulation 2−3 years post-delivery (PD). A total of 313 pregnant women, 77 with GDM vs. 236 with normal glucose tolerance (NGT), 141 from the control group (CG, MedDiet restricting the consumption of dietary fat including EVOO and nuts during pregnancy) vs. 172 from the intervention group (IG, MedDiet supplemented with extra virgin olive oil (EVOO) and pistachios during pregnancy) were compared at Visit 1 (8−12 GW), Visit 2 (24−28 GW) and Visit 3 (2−3 years PD). Expression of miRNAs was determined by the Exiqon miRCURY LNA RT-PCR system. Leptin, adiponectin, IL-6 and TNF-α, were measured by Milliplex® immunoassays on Luminex 200 and insulin by RIA. Women with GDM vs. NTG had significantly higher leptin median (Q1−Q3) levels (14.6 (9.2−19.4) vs. 9.6 (6.0−15.1) ng/mL; p < 0.05) and insulin levels (11.4 (8.6−16.5) vs. 9.4 (7.0−12.8) µUI/mL; p < 0.001) and lower adiponectin (12.9 (9.8−17.2) vs. 17.0 (13.3−22.4) µg/mL; p < 0.001) at Visit 2. These findings persisted in Visit 3, with overexpression of miR-222-3p (1.45 (0.76−2.21) vs. 0.99 (0.21−1.70); p < 0.05)) and higher levels of Il-6 and TNF-α. When the IG is compared with the CG lower levels of insulin, HOMA-IR-IR, IL-6 levels at Visit 2 and 3 and leptin levels only at Visit 2 were observed. An overexpression of miR-222-3p and miR-103a-3p were also observed in IG at Visit 2 and 3. The miR-222-3p and miR103a-3p expression correlated with insulin levels, HOMA-IR, IL-6 and TNF-α at Visit 2 (all p < 0.05). These data support the association of leptin, adiponectin and insulin/HOMA-IR with GDM, as well as the association of insulin/HOMA-IR and IL-6 and miR-222-3p and miR-103a-3p expression with a MedDiet-based nutritional intervention.

MiR-103-3p promotes hepatic steatosis to aggravate nonalcoholic fatty liver disease by targeting of ACOX1

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major risk factor for hepatocellular carcinoma, and alterations in miRNA expression are related to the development of NAFLD. However, the role of miRNAs in regulating the development of NAFLD is still poorly understood.

METHODS

We used qRT-PCR to detect the level of miR-103-3p in both cell and mouse models of NAFLD. Biochemical assays, DCF-DA assays, Oil red O staining and HE staining were used to detect the role of miR-103-3p in NAFLD development. Target genes of miR-103-3p were predicted using the TargetScan database and verified by qRT-PCR, western blot and dual-luciferase assays.

RESULTS

The expression of miR-103-3p increased in both NAFLD model cells and liver tissues from the NAFLD mouse model. Inhibition of miR-103-3p significantly alleviated the accumulation of lipid droplets in free fatty acid-treated L02 cells and liver tissues from mice with NAFLD. Inhibition of miR-103-3p reduced the contents of H2O2, TG, ALT, and AST and ROS production while increasing the ATP content. Moreover, the miR-103-3p antagomir alleviated liver tissue lesions in mice with NAFLD. Further studies identified ACOX1, a key enzyme for the oxidation and decomposition of fatty acids, as a direct target of miR-103-3p.

CONCLUSIONS

These findings identified a negative regulatory mechanism between ACOX1 and miR-103-3p that promotes the pathogenesis of NAFLD and suggested that inhibition of miR-103-3p may be a potential treatment strategy for NAFLD.

Ferulic Acid Prevents Nonalcoholic Fatty Liver Disease by Promoting Fatty Acid Oxidation and Energy Expenditure in C57BL/6 Mice Fed a High-Fat Diet

There is a consensus that ferulic acid (FA), the most prominent phenolic acid in whole grains, displays a protective effect in non-alcoholic fatty liver disease (NAFLD), though its underlying mechanism not fully elucidated. This study aimed to investigate the protective effect of FA on high-fat diet (HFD)-induced NAFLD in mice and its potential mechanism. C57BL/6 mice were divided into the control diet (CON) group, the HFD group, and the treatment (HFD+FA) group, fed with an HFD and FA (100 mg/kg/day) by oral gavage for 12 weeks. Hematoxylin and eosin (H&E) staining and Oil Red O staining were used to evaluate liver tissue pathological changes and lipid accumulation respectively. It was demonstrated that FA supplementation prevented HFD-induced NAFLD, which was evidenced by the decreased accumulation of lipid and hepatic steatosis in the HFD+FA group. Specifically, FA supplementation decreased hepatic triacylglycerol (TG) content by 33.5% (p < 0.01). Metabolic cage studies reveal that FA-treated mice have elevated energy expenditure by 11.5% during dark phases. Mechanistically, FA treatment increases the expression of rate-limiting enzymes of fatty acid oxidation and ketone body biosynthesis CPT1A, ACOX1 and HMGCS2, which are the peroxisome proliferator-activated receptors α (PPARα) targets in liver. In conclusion, FA could effectively prevent HFD-induced NAFLD possibly by activating PPARα to increase energy expenditure and decrease the accumulation of triacylglycerol in the liver.

Highly Purified Eicosapentaenoic Acid Alleviates the Inflammatory Response and Oxidative Stress in Macrophages during Atherosclerosis via the miR-1a-3p/sFRP1/Wnt/PCP-JNK Pathway

Highly purified eicosapentaenoic acid (EPA) has shown great effects in the prevention of atherosclerosis. In a murine model, it significantly reduced plaque accumulation, lowered plasma lipid levels, and decreased inflammation levels, which was also observed in vitro. Using microRNA sequencing, we identified differentially expressed microRNAs, among which miR-1a-3p was selected for further validation. Overexpression of miR-1a-3p in RAW264.7 cells worsened lipid accumulation, increased oxidative stress, and exacerbated inflammatory responses whereas its downregulation produced the opposite results. Potential targets of miR-1a-3p were analyzed by prediction tools. Then, secreted frizzled-related protein 1 (sFRP1), an antagonist of the Wnt pathway, was confirmed as the target gene of miR-1a-3p by a dual-luciferase reporter assay. Further research showed that in macrophages, EPA influenced the activation of the Wnt/planar cell polarity-c-Jun N-terminal kinase (Wnt/PCP-JNK) axis, which is consistent with the phenomenon that miR-1a-3p has an impact on this same axis. Collectively, our findings suggest that EPA mitigates inflammatory responses and oxidative responses both in vivo and in vitro by targeting the miR-1a-3p/sFRP1/Wnt/PCP-JNK axis in macrophages, which may explain the cardioprotective role of EPA and promote the application of EPA in clinical practice.

Highly Purified Eicosapentaenoic Acid Alleviates the Inflammatory Response and Oxidative Stress in Macrophages during Atherosclerosis via the miR-1a-3p/sFRP1/Wnt/PCP-JNK Pathway

Highly purified eicosapentaenoic acid (EPA) has shown great effects in the prevention of atherosclerosis. In a murine model, it significantly reduced plaque accumulation, lowered plasma lipid levels, and decreased inflammation levels, which was also observed in vitro. Using microRNA sequencing, we identified differentially expressed microRNAs, among which miR-1a-3p was selected for further validation. Overexpression of miR-1a-3p in RAW264.7 cells worsened lipid accumulation, increased oxidative stress, and exacerbated inflammatory responses whereas its downregulation produced the opposite results. Potential targets of miR-1a-3p were analyzed by prediction tools. Then, secreted frizzled-related protein 1 (sFRP1), an antagonist of the Wnt pathway, was confirmed as the target gene of miR-1a-3p by a dual-luciferase reporter assay. Further research showed that in macrophages, EPA influenced the activation of the Wnt/planar cell polarity-c-Jun N-terminal kinase (Wnt/PCP-JNK) axis, which is consistent with the phenomenon that miR-1a-3p has an impact on this same axis. Collectively, our findings suggest that EPA mitigates inflammatory responses and oxidative responses both in vivo and in vitro by targeting the miR-1a-3p/sFRP1/Wnt/PCP-JNK axis in macrophages, which may explain the cardioprotective role of EPA and promote the application of EPA in clinical practice.

Exosomal MicroRNAs as Potential Biomarkers of Hepatic Injury and Kidney Disease in Glycogen Storage Disease Type Ia Patients

Glycogen storage disease type Ia (GSDIa) is an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α). Affected individuals develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma and kidney failure. The purpose of this study was to identify potential biomarkers of the evolution of the disease in GSDIa patients. To this end, we analyzed the expression of exosomal microRNAs (Exo-miRs) in the plasma exosomes of 45 patients aged 6 to 63 years. Plasma from age-matched normal individuals were used as controls. We found that the altered expression of several Exo-miRs correlates with the pathologic state of the patients and might help to monitor the progression of the disease and the development of late GSDIa-associated complications.

A new therapeutic effect of fenofibrate in Duchenne muscular dystrophy: The promotion of myostatin degradation

BACKGROUND AND PURPOSE

Duchenne muscular dystrophy (DMD) is a degenerative muscle disease with no effective drug treatment. This study investigated the positive effects of fenofibrate on dystrophic muscles.

EXPERIMENTAL APPROACH

Myostatin expression in serum and muscle tissue of DMD patients and mdx mice were tested. Primary myoblasts isolated from mdx mice were challenged with an inflammatory stimulus and treated with fenofibrate. In animal experiments, 6-week-old male mdx mice were treated with fenofibrate (100 mg/kg) administered orally once per day for 6 weeks. Tests of muscle function plus histology and biochemical analyses of serum were conducted to evaluate the effects of fenofibrate. The expressions of myostatin, MuRF1, and atrogin-1 in skeletal muscle were evaluated by Western blotting and real-time PCR. Total and oxidative myosin heavy chain (MHC) were assessed via immunofluorescence.

KEY RESULTS

Increased expression of myostatin protein was found in dystrophic muscle of DMD patients and mdx mice. Fenofibrate enhanced myofibre differentiation by downregulating the expression of myostatin protein but not mRNA in primary myoblasts of mdx mice. Fenofibrate significantly improved muscle function while ameliorating muscle damage in mdx mice. These benefits are accompanied by an anti-inflammatory effect. Fenofibrate treatment returned myofibre function by inhibiting the expressions of myostatin, MuRF1, and atrogin-1 protein in the gastrocnemius muscle and diaphragm, while leaving the mRNA level of myostatin unaffected.

CONCLUSIONS AND IMPLICATIONS

Fenofibrate substantially slows muscle dystrophy by promoting the degradation of myostatin protein, which may indicate a new therapeutic focus for DMD patients.

α,β-Amyrin prevents steatosis and insulin resistance in a high-fat diet-induced mouse model of NAFLD via the AMPK-mTORC1-SREBP1 signaling mechanism

Nonalcoholic fatty liver disease (NAFLD), characterized by hepatosteatosis and steatohepatitis, is intrinsically related to obesity. Our previous study reported on the anti-obese activity of α,β-amyrin (AMY), a pentacyclic triterpene isolated from Protium heptaphyllum. This study investigated its ability to prevent fatty liver and the underlying mechanism using the mouse model of NAFLD. NAFLD was induced in male Swiss mice fed a high fat diet (HFD) for 15 weeks. The controls were fed a normal chow diet (ND). The mice were simultaneously treated with AMY at 10 and 20 mg/kg or fenofibrate at 50 mg/kg. Lipid levels along with metabolic and inflammatory parameters were assessed in liver and serum. The liver sections were histologically examined using H&E staining. RT-qPCR and western blotting assays were performed to analyze signaling mechanisms. Mice fed HFD developed severe hepatic steatosis with elevated triglycerides and lipid droplets compared with ND controls. This was associated with a decrease in AMP-activated protein kinase (AMPK) activity, an increase of mechanistic target of rapamycin complex 1 (mTORC1) signaling, and enhanced sterol regulatory element binding protein 1 (SREBP1) expression, which have roles in lipogenesis, inhibition of lipolysis, and inflammatory response. AMY treatment reversed these signaling activities and decreased the severity of hepatic steatosis and inflammatory response, evidenced by serum and liver parameters as well as histological findings. AMY-induced reduction in hepatic steatosis seemed to involve AMPK-mTORC1-SREBP1 signaling pathways, which supported its beneficial role in the prevention and treatment of NAFLD.

Intramuscular Injection of miR-1 Reduces Insulin Resistance in Obese Mice

The role of microRNAs in metabolic diseases has been recognized and modulation of them could be a promising strategy to treat obesity and obesity-related diseases. The major purpose of this study was to test the hypothesis that intramuscular miR-1 precursor replacement therapy could improve metabolic parameters of mice fed a high-fat diet. To this end, we first injected miR-1 precursor intramuscularly in high-fat diet-fed mice and evaluated glucose tolerance, insulin sensitivity, and adiposity. miR-1-treated mice did not lose weight but had improved insulin sensitivity measured by insulin tolerance test. Next, using an in vitro model of insulin resistance by treating C2C12 cells with palmitic acid (PA), we overexpressed miR-1 and measured p-Akt content and the transcription levels of a protein related to fatty acid oxidation. We found that miR-1 could not restore insulin sensitivity in C2C12 cells, as indicated by p-Akt levels and that miR-1 increased expression of Pgc1a and Cpt1b in PA-treated cells, suggesting a possible role of miR-1 in mitochondrial respiration. Finally, we analyzed mitochondrial oxygen consumption in primary skeletal muscle cells treated with PA and transfected with or without miR-1 mimic. PA-treated cells showed reduced basal respiration, oxygen consumption rate-linked ATP production, maximal and spare capacity, and miR-1 overexpression could prevent impairments in mitochondrial respiration. Our data suggest a role of miR-1 in systemic insulin sensitivity and a new function of miR-1 in regulating mitochondrial respiration in skeletal muscle.

Acacetin ameliorates insulin resistance in obesity mice through regulating Treg/Th17 balance via MiR-23b-3p/NEU1 Axis

BACKGROUND

The role of miR-23b-3p in insulin resistance (IR) remained poorly understood.

METHODS

After acacetin injection, obesity-induced IR model was constructed with or without miR-23b-3p upregulation and Neuraminidase 1 (NEU1) overexpression in mice. Body weight, serum metabolite and fat percent of the mice were measured. Tests on oral glucose and insulin tolerance were performed, and inflammatory cytokines C-reactive protein (CRP), Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein 1 (MCP1) levels were quantified with enzyme-linked immunosorbent assay (ELISA). The binding sites between miR-23b-3p and NEU1 were predicted by TargetScan, and verified using dual-luciferase reporter assay. Relative expressions were detected with quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Proportion of Treg and Th17 cells in total CD4+ T cells was detected with flow cytometry.

RESULTS

MiR-23b-3p offset the effects of acacetin on body weight, fat percent, inflammatory cytokines levels and expressions of markers of regulatory T cells (Treg cells) and T helper 17 cells (Th17 cells), NEU1 and miR-23b-3p. NEU1 was a target of miR-23b-3p, and overexpressed NEU1 reversed the effects of upregulated miR-23b-3p on reducing Treg cells but increased body weight, fat percent and inflammatory cytokines levels, percentage of Th17 cells, and upregulated NEU1 expression.

CONCLUSION

Upregulation of miR-23b-3p offset the effects of acacetin on obesity-induced IR through regulating Treg/Th17 cell balance via targeting NEU1.The present findings provide a possible prevention strategy for obesity-induced IR.

A Fenofibrate Diet Prevents Paclitaxel-Induced Peripheral Neuropathy in Mice

Simple Summary

Paclitaxel, a drug used in the treatment of malignancies such as lung, ovarian and breast cancer, often produces severe side effects, among which is peripheral neuropathy. This neuropathy involves diffuse or localized pain, notably burning pain, cold and mechanical hyperexcitability. Recently, fenofibrate, a Food and Drug Administration (FDA)-approved drug for the treatment of dyslipidemia, has been shown to reduce the severity of symptoms in other forms of peripheral neuropathy. In the current work, we tested whether fenofibrate could reverse mechanical and cold hypersensitivity and improve motivation and the reduction in nerve conduction in a mouse model of paclitaxel-induced neuropathy. Our behavioral, histological and molecular assessments indicate that fenofibrate prevents the development of paclitaxel-induced neuropathy. Taken together, our studies support the therapeutic potential of fenofibrate in the prevention of paclitaxel-induced neuropathy and suggest the possible repurposing of this drug for this purpose in the clinic.

Abstract

Background: Paclitaxel-induced peripheral neuropathy (PIPN) is a major adverse effect of this chemotherapeutic agent that is used in the treatment of a number of solid malignancies. PIPN leads notably to burning pain, cold and mechanical allodynia. PIPN is thought to be a consequence of alterations of mitochondrial function, hyperexcitability of neurons, nerve fiber loss, oxidative stress and neuroinflammation in dorsal root ganglia (DRG) and spinal cord (SC). Therefore, reducing neuroinflammation could potentially attenuate neuropathy symptoms. Peroxisome proliferator-activated receptor-α (PPAR-α) nuclear receptors that modulate inflammatory responses can be targeted by non-selective agonists, such as fenofibrate, which is used in the treatment of dyslipidemia. Methods: Our studies tested the efficacy of a fenofibrate diet (0.2% and 0.4%) in preventing the development of PIPN. Paclitaxel (8 mg/kg) was administered via 4 intraperitoneal (i.p.) injections in C57BL/6J mice (both male and female). Mechanical and cold hypersensitivity, wheel running activity, sensory nerve action potential (SNAP), sciatic nerve histology, intra-epidermal fibers, as well as the expression of PPAR-α and neuroinflammation were evaluated in DRG and SC. Results: Fenofibrate in the diet partially prevented the development of mechanical hypersensitivity but completely prevented cold hypersensitivity and the decrease in wheel running activity induced by paclitaxel. The reduction in SNAP amplitude induced by paclitaxel was also prevented by fenofibrate. Our results indicate that suppression of paclitaxel-induced pain by fenofibrate involves the regulation of PPAR-α expression through reduction in neuroinflammation. Finally, co-administration of paclitaxel and the active metabolite of fenofibrate (fenofibric acid) did not interfere with the suppression of tumor cell growth or clonogenicity by paclitaxel in ovarian and breast cancer cell lines. Conclusions: Taken together, our results show the therapeutic potential of fenofibrate in the prevention of PIPN development.

Combination of exercise training and resveratrol attenuates obese sarcopenia in skeletal muscle atrophy

Obese sarcopenia is a progressive loss of skeletal muscle mass and strength with increases in adipocytes. The aim of this study was to investigate the effects of combination of exercise training and resveratrol on the pathological pathway from obesity to sarcopenia, and potential therapy for skeletal muscle declines in physical function. Two animal models were experimented: (1) C57BL/6J male mice were fed either a high-fat diet (HFD) for 8 weeks to induce obesity and resveratrol (low-, middle-, and high-dose) for 4 weeks. (2) senescence-accelerated mouse prone 8 (SAMP8) mice with sarcopenia were used. Skeletal muscle function of SAMP8 mice expressed an age-associated decline. In SAMP8 mice, resveratrol (150 mg/Kg BW, daily) was administered by oral gavage two times a week for 1 month of the experimental period. Exercise training based on adaptations in the muscle is training twice a week for 4 weeks. SAMP8 mouse skeletal muscle in each group was analyzed by H and E staining, transferase dUTP nick end labeling, and Western blot analysis. Mitochondrial function expression, apoptosis and relative hypertrophy signaling in HFD-induced obesity mice and SAMP8 mice were determined by Western blot analysis. Results of the present study indicate that effect of resveratrol on skeletal muscles of HFD-induced obesity mice is linked to an increase in Bcl-2 and phosphatidylinositol 3 kinase/AKT expressions. On the other hand, resveratrol, and its combination with exercise training, attenuate the aging-related mitochondrial dysfunction involving Bad, caspase 3, and interleukin-6 expressions in SAMP8 mice. Combination of exercise training and resveratrol induced hypertrophy in skeletal muscles of sarcopenia SAMP8 mice. Therefore, we suggest combination of exercise training and resveratrol as a therapeutic potential in obese sarcopenia.

Protective effect of fenofibrate against high-fat-high-fructose diet induced non-obese NAFLD in rats

The present study evaluated the protective effects of fenofibrate on liver function, oxidant-antioxidant balance, and insulin resistance (IR) in rats fed high-fat-high-fructose diet (HFFD). Twenty-four male Sprague-Dawley rats (110-130 gm) were allocated into four equal groups (n = 6). Rats in group I were fed a normal diet for 4 weeks. Rats in group II were fed a normal diet with fenofibrate at 50 mg/kg/day orally for four weeks. Rats in group III were fed a normal diet mixed with 25% palm oil and given 60% fructose solution orally for 4 weeks. Rats in group IV were fed a normal diet mixed with 25% palm oil, 60% oral fructose solution, and fenofibrate at 50 mg/kg/day orally for four weeks. After experimental induction, serum and liver tissue samples were collected to determine lipid profiles, glycemic status, antioxidant status, oxidative and stress markers, and histopathology of liver tissues. The results of the present study revealed that fenofibrate prevents the occurrence of fatty liver, enhancing glycemic status, decreasing oxidative stress, and improving antioxidant status. It can be concluded that fenofibrate has a lipotropic and antidiabetic role.

A Randomised Controlled Trial Assessing the Effects of Peri-operative Fenofibrate Administration on Abdominal Aortic Aneurysm Pathology: Outcomes From the FAME Trial

OBJECTIVE

Experimental studies suggest that fenofibrate prevents abdominal aortic aneurysm (AAA) development by lowering aortic osteopontin (OPN) concentration and reducing the number of macrophages infiltrating the aortic wall. The current study examined the effects of a short course of fenofibrate on AAA pathology in people with large AAAs awaiting aortic repair.

METHODS

This randomised double blind parallel trial included male and female participants aged ≥ 60 years who had an asymptomatic AAA measuring ≥ 50 mm and were scheduled to undergo open AAA repair. Participants were allocated to fenofibrate (145 mg/day) or matching placebo for at least two weeks before elective AAA repair. Blood samples were collected at recruitment and immediately prior to surgery. AAA biopsies were obtained during aortic surgery. The primary outcomes were (1) AAA OPN concentration; (2) serum OPN concentration; and (3) number of AAA macrophages. Exploratory outcomes included circulating and aortic concentrations of other proteins previously associated with AAA. Outcomes assessed at a single time point were compared using logistic regression. Longitudinal outcomes were compared using linear mixed effects models.

RESULTS

Forty-three participants were randomised. After three withdrawals, 40 were followed until the time of surgery (21 allocated fenofibrate and 19 allocated placebo). As expected, serum triglycerides reduced significantly from recruitment to the time of surgery in participants allocated fenofibrate. No differences in any of the primary and exploratory outcomes were observed between groups.

CONCLUSION

A short course of 145 mg of fenofibrate/day did not lower concentrations of OPN or aortic macrophage density in people with large AAAs.

MicroRNA miR-222 mediates pioglitazone beneficial effects on skeletal muscle of diet-induced obese mice

Pioglitazone belongs to the class of drugs thiazolidinediones (TZDs) and is an oral hypoglycemic drug, used in the treatment of type 2 diabetes, which improves insulin sensitivity in target tissues. Adipose tissue is the main target of pioglitazone, a PPARg and PPARa agonist; however, studies also point to skeletal muscle as a target. Non-PPAR targets of TZDs have been described, thus we aimed to study the direct effects of pioglitazone on skeletal muscle and the possible role of microRNAs as targets of this drug. Pioglitazone treatment of obese mice increased insulin-mediated glucose transport as a result of increased fatty acid oxidation and mitochondrial activity. PPARg blockage by treatment with GW9662 nullified pioglitazone's effect on systemic and muscle insulin sensitivity and citrate synthase activity of obese mice. After eight weeks of high-fat diet, miR-221-3p expression in soleus muscle was similar among the groups and miR-23b-3p and miR-222-3p were up-regulated in obese mice compared to the control group, and treatment with pioglitazone was able to reverse this condition. In vitro studies in C2C12 cells suggest that inhibition of miR-222-3p protects C2C12 cells from insulin resistance and increased non-mitochondrial respiration induced by palmitate. Together, these data demonstrate a role of pioglitazone in the downregulation of microRNAs that is not dependent on PPARg. Moreover, miR-222 may be a novel PPARg-independent mechanism through which pioglitazone improves insulin sensitivity in skeletal muscle.

L-Carnitine Is Involved in Hyperbaric Oxygen-Mediated Therapeutic Effects in High Fat Diet-Induced Lipid Metabolism Dysfunction

Lipid metabolism dysfunction and obesity are serious health issues to human beings. The current study investigated the effects of hyperbaric oxygen (HBO) against high fat diet (HFD)-induced lipid metabolism dysfunction and the roles of L-carnitine. C57/B6 mice were fed with HFD or normal chew diet, with or without HBO treatment. Histopathological methods were used to assess the adipose tissues, serum free fatty acid (FFA) levels were assessed with enzymatic methods, and the endogenous circulation and skeletal muscle L-carnitine levels were assessed with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Additionally, western blotting was used to assess the expression levels of PPARα, CPT1b, pHSL/HSL, and UCP1. HFD treatment increased body/adipose tissue weight, serum FFA levels, circulation L-carnitines and decreased skeletal muscle L-carnitine levels, while HBO treatment alleviated such changes. Moreover, HFD treatment increased fatty acid deposition in adipose tissues and decreased the expression of HSL, while HBO treatment alleviated such changes. Additionally, HFD treatment decreased the expression levels of PPARα and increased those of CPT1b in skeletal muscle, while HBO treatment effectively reverted such changes as well. In brown adipose tissues, HFD increased the expression of UCP1 and the phosphorylation of HSL, which was abolished by HBO treatment as well. In summary, HBO treatment may alleviate HFD-induced fatty acid metabolism dysfunction in C57/B6 mice, which seems to be associated with circulation and skeletal muscle L-carnitine levels and PPARα expression.

Adiponectin is required for pioglitazone-induced improvements in hepatic steatosis in mice fed a high-fat diet

Pioglitazone has been used for the treatment of nonalcoholic fatty liver disease (NAFLD) related to diabetes. The role of adiponectin in pioglitazone-induced improvements in NAFLD was studied by using wild-type (adipoWT) and adiponectin knockout (adipoKO) mice. High-fat diet fed mice were insulin resistant, glucose intolerant and had increased hepatic lipid accumulation as evidenced by increased NAFLD activity score. Despite pioglitazone has improved insulin resistance in both genotypes, hepatic steatosis was only improved in adipoWT obese mice. Amelioration of NAFLD in adipoWT mice promoted by pioglitazone was associated with up-regulation of Pparg, Fgf21 and down-regulation of Pepck liver expression. On the other hand, resistance to pioglitazone treatment in adipoKO mice was associated with increased expression of miR-192 and Hsl, which was not followed by increased fatty acid oxidation. In conclusion, our data provides evidence that increased adiponectin production by pioglitazone is necessary for its beneficial action on NAFLD.

Effect of Low-Fat Diet in Obese Mice Lacking Toll-like Receptors

Background: This study aimed at assessing the effect of a low-fat diet (LFD) in obese mice lacking toll–like receptors (Tlr) and understanding the expression and regulation of microRNAs during weight reduction. Methods: C57BL/6, Tlr5^−/−, Tlr2^−/− and Tlr4^−/− mice were used in this study. A group of mice were fed with a high-fat diet (HFD) (58% kcal) for 12 weeks to induce obesity (diet-induced obesity, DIO). Another group that had been fed with HFD for eight weeks (obese mice) were switched to a low-fat diet (LFD) (10.5% kcal) for the next four weeks to reduce their body weight. The control mice were fed with a standard AIN-76A diet for the entire 12 weeks. The body weight of the mice was measured weekly. At the end of the experiment, epididymal fat weight and adipocyte size were measured. The differentially expressed miRNAs in the fat tissue was determined by next-generation sequencing with real-time quantitative reverse transcription polymerase chain reaction (RT–qPCR). Target prediction and functional annotation of miRNAs were performed using miRSystem database. Results: Switching to LFD significantly reduced the body weight and epididymal fat mass in the HFD-fed C57BL/6 and Tlr5^−/− mice but not in Tlr2^−/− and Tlr4^−/− mice. Weight reduction significantly decreased the size of adipocytes in C57BL/6 but not in the Tlr knockout mice. In Tlr2^−/− and Tlr4^−/− mice, feeding with HFD and the subsequent weight reduction resulted in an aberrant miRNA expression in the epididymal fat tissue unlike in C57BL/6 and Tlr5^−/−. However, target prediction and functional annotation by miRSystem database revealed that all the top 10 Kyoto Encyclopedia of Genes and Genomes (KEGG) database pathways of the dysregulated miRNAs during weight reduction in the C57BL/6 mice were also found in the regulated pathways of Tlr5^−/−, Tlr2^−/−, and Tlr4^−/− strains. However, among these pathways, gene sets involved in arginine and proline metabolism and glutathione metabolism were mainly involved in the Tlr knockout mice but not in the C57BL/6 mice. Conclusions: In this study, we demonstrated that feeding of LFD leads to significant body weight reduction in C57BL/6 and Tlr5^−/− mice, but not in Tlr2^−/− and Tlr4^−/− mice. Significant reduction in the size of adipocytes of epididymal fat was only found in C57BL/6, but not in Tlr5^−/−, Tlr2^−/−, and Tlr4^−/− mice. The dysregulated miRNAs in Tlr2^−/− and Tlr4^−/− mice were different from those in C57BL/6 and Tlr5^−/− strains. Among those miRNA-regulated pathways, arginine and proline metabolism as well as glutathione metabolism may have important roles in the Tlr knockout mice rather than in C57BL/6 mice.