Docosahexaenoic acid-enriched phospholipids and eicosapentaenoic acid-enriched phospholipids inhibit tumor necrosis factor-alpha-induced lipolysis in 3T3-L1 adipocytes by activating sirtuin 1 pathways

Effects of Low-Intensity Pulsed Ultrasound on the Regulation of Free Fatty Acid Release in 3T3-L1 Cells

OBJECTIVES

To investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the proliferation, differentiation, and tumor necrosis factor-α (TNF-α)-induced lipolysis of 3T3-L1 cells, and to explore the feasibility of regulating the release of free fatty acids (FFA) to prevent lipotoxicity.

METHODS

Different intensities (30, 60, 90, and 120 mW/cm2) of LIPUS were applied to 3T3-L1 preadipocytes for different durations (5, 10, 15, 20, 25, and 30 minutes). Appropriate parameters for subsequent experiments were selected by assessing cell viability. The effect of LIPUS on the proliferation and differentiation of 3T3-L1 cells was evaluated by microscope observation, flow cytometry, and lipid content determination. After treated with LIPUS and TNF-α (50 ng/mL), the degree of lipolysis was assessed by measuring the extracellular FFA content. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression of relevant genes.

RESULTS

Different parameters of LIPUS significantly enhance the viability of 3T3-L1 cells (P < .05), with 20 minutes and 30 mW/cm2 as the most suitable settings. After LIPUS treatment, 3T3-L1 cell proliferation accelerated, apoptosis rate and G1 phase cell proportion decreased, the content of lipid droplets and TG was increased in differentiated cells, while FFA release decreased (P < .05). The expression of PCNA, PPARγ, C/EBPα, Perilipin A mRNA increased, and the expression of TNF-α, ATGL, HSL mRNA decreased (P < .05).

CONCLUSIONS

LIPUS could promote the proliferation and differentiation of 3T3-L1 cells and inhibit TNF-α-induced lipolysis, indicating its potential as a therapy for mitigating lipotoxicity caused by decompensated adipocytes.

Lipolysis inhibition improves the survival of fat grafts through ameliorating lipotoxicity and inflammation

Fat grafting is a promising technique for correcting soft tissue abnormalities, but oil cyst formation and graft fibrosis frequently impede the therapeutic benefit of fat grafting. The lipolysis of released oil droplets after grafting may make the inflammation and fibrosis in the grafts worse; therefore, by regulating adipose triglyceride lipase (ATGL) via Atglistatin (ATG) and Forskolin (FSK), we investigated the impact of lipolysis on fat grafts in this study. After being removed from the mice and chopped into small pieces, the subcutaneous fat from wild-type C57BL/6J mice was placed in three different solutions for two hours: serum-free cell culture medium, culture medium+FSK (50 μM), and culture medium+ATG (100 μM). Following centrifugation to remove water and free oil droplets, 0.3 mL of the fat particles per mouse was subcutaneously injected into the back of mice. Additionally, the subcutaneous fat grafting area was immediately injected with PBS (control group), ATG (30 mg/kg), and FSK (15 mg/kg) following fat transplantation. Detailed cellular events after grafting were investigated by histological staining, real-time polymerase chain reaction, immunohistochemistry/immunofluorescent staining, and quantification. Two weeks after grafting, grafts treated with ATG showed lower expression of ATGL and decreased mRNA levels of TNFα and IL-6. In contrast, grafts treated with ATG showed elevated expression levels of IL-4 and IL-13 compared to the control grafts. In addition, fewer apoptotic cells and oil cysts were observed in ATG grafts. Meanwhile, a higher CD206+/CD68+ ratio of macrophages and more CD31+ vascular endothelial cells existed in the 2-month ATG grafts. In comparison to the control, ATG treatment improved the volume retention of grafts, and decreased graft fibrosis and oil cyst formation. By preventing oil droplet lipolysis, pharmacological suppression of ATGL shielded adipocytes from lipotoxicity following grafting. Additionally, ATG ameliorated the apoptosis and inflammation brought on by adipocyte death and oil droplet lipolysis in grafted fat. These all indicate that lipolysis inhibition improved transplanted fat survival and decreased the development of oil cysts and graft fibrosis, offering a potential postoperative pharmacological intervention for bettering fat grafting.

Long-term dietary DHA intervention prevents telomere attrition and lipid disturbance in telomerase-deficient male mice

PURPOSE

Previous evidence indicated anti-ageing potential of docosahexaenoic acid (DHA), but the underlying mechanism remains unclear. We investigated protective effect of DHA on telomere attrition and lipid disturbance in male mice with premature ageing caused by telomerase deficiency.

METHODS

Wild-type (WT) and fourth-generation telomerase-deficient (G4 Terc^-/-, Terc knockout, KO) male mice (C57BL/6, 2 months old) were fed control diet (WT-C and KO-C groups) or DHA-enriched diet containing 0.80% DHA by weight (WT-DHA and KO-DHA groups) for 10 months. The ageing phenotypes and metabolic level [carbon dioxide emission, oxygen consumption, and respiratory exchange ratio (RER)] were assessed at the end of the experiment. Telomere length in various tissues and the hepatic gene and protein expression for regulating lipid synthesis and lipolysis were measured. Data were tested using one- or two-factor ANOVA.

RESULTS

In KO male mice, DHA prevented weight loss, corrected high RER, and reduced fat loss. Telomere shortening was reduced by 22.3%, 25.5%, and 13.5% in heart, liver, and testes of the KO-DHA group compared with those in the KO-C group. The KO-DHA group exhibited higher gene transcription involved in glycerol-3-phosphate pathway [glycerol-3-phosphate acyltransferase (Gpat)], lower gene expression of β-oxidation [carnitine palmitoyltransferase 1a (Cpt1a)], and upregulation of proteins in lipid synthesis [mammalian target of rapamycin complex 1 (mTORC1) and sterol responsive element binding protein 1 (SREBP1)] in liver than the KO-C group.

CONCLUSION

Long-term DHA intervention attenuates telomere attrition and promotes lipid synthesis via the tuberous sclerosis complex 2 (TSC2)-mTORC1-SREBP1 pathway in KO male mice.

Abnormal lipid metabolism in cancer-associated cachexia and potential therapy strategy

Cancer-associated cachexia (CAC) is a major characteristic of advanced cancer, associates with almost all types of cancer. Recent studies have found that lipopenia is an important feature of CAC, and it even occurs earlier than sarcopenia. Different types of adipose tissue are all important in the process of CAC. In CAC patients, the catabolism of white adipose tissue (WAT) is increased, leading to an increase in circulating free fatty acids (FFAs), resulting in " lipotoxic". At the same time, WAT also is induced by a variety of mechanisms, browning into brown adipose tissue (BAT). BAT is activated in CAC and greatly increases energy expenditure in patients. In addition, the production of lipid is reduced in CAC, and the cross-talk between adipose tissue and other systems, such as muscle tissue and immune system, also aggravates the progression of CAC. The treatment of CAC is still a vital clinical problem, and the abnormal lipid metabolism in CAC provides a new way for the treatment of CAC. In this article, we will review the mechanism of metabolic abnormalities of adipose tissue in CAC and its role in treatment.

Docosahexaenoic Acid Counteracts the Hypoxic-Induced Inflammatory and Metabolic Alterations in 3T3-L1 Adipocytes

Background: Hypoxia is caused by the excessive expansion of the white adipose tissue (AT) and is associated with obesity-related conditions such as insulin resistance, inflammation, and oxidative stress. Docosahexaenoic acid (DHA) is an omega-3 fatty acid reported to have beneficial health effects. However, the effects of DHA in AT against hypoxia-induced immune-metabolic perturbations in adipocytes exposed to low O₂ tension are not well known. Consequently, this study aimed to evaluate the impact of DHA on markers of inflammation, metabolism, apoptosis, and oxidative stress in 3T3-L1 cell adipocytes exposed to low O₂ tension (1% O₂) induced hypoxia. Methods: The apoptosis and reactive oxygen species (ROS) rates were evaluated. Metabolic parameters such as lactate, FFA, glycerol release, glucose uptake, and ATP content were assessed by a fluorometer. The expression of HIF-1, GLUT1 and the secretion of adipocytokines such as leptin, adiponectin, and pro-inflammatory markers was evaluated. Results: DHA-treated hypoxic cells showed significantly decreased basal free fatty acid release, lactate production, and enhanced glucose consumption. In addition, DHA-treatment of hypoxic cells caused a significant reduction in the apoptosis rate and ROS production with decreased lipid peroxidation. Moreover, DHA-treatment of hypoxic cells caused a decreased secretion of pro-inflammatory markers (IL-6, MCP-1) and leptin and increased adiponectin secretion compared with hypoxic cells. Furthermore, DHA-treatment of hypoxic cells caused significant reductions in the expression of genes related to hypoxia (HIF-1, HIF-2), anaerobic metabolism (GLUT1 and Ldha), ATP production (ANT2), and fat metabolism (FASN and PPARY). Conclusion: This study suggests that DHA can exert potential anti-obesity effects by reducing the secretion of inflammatory adipokines, oxidative stress, lipolysis, and apoptosis.

α-glyceryl-phosphoryl-ethanolamine protects human hippocampal neurons from aging-induced cellular alterations

Brain ageing has been related to a decrease in cellular metabolism, to an accumulation of misfolded proteins and to an alteration of the lipid membrane composition. These alterations act as contributive aspects of age‐related memory decline by reducing membrane excitability and neurotransmitter release. In this sense, precursors of phospholipids (PLs) can restore the physiological composition of cellular membranes and ameliorate the cellular defects associated with brain ageing. In particular, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) have been shown to restore mitochondrial function, reduce the accumulation of amyloid beta (Aβ) and, at the same time, provide the amount of acetylcholine needed to reduce memory deficit. Among PL precursors, alpha‐glycerylphosphorylethanolamine (GPE) has shown to protect astrocytes from Aβ injuries and to slow‐down ageing of human neural stem cells. GPE has been evaluated in aged human hippocampal neurons, which are implicated in learning and memory, and constitute a good in vitro model to investigate the beneficial properties of GPE. In order to mimic cellular ageing, the cells have been maintained 21 days in vitro and challenged with GPE. Results of the present paper showed GPE ability to increase PE and PC content, glucose uptake and the activity of the chain respiratory complex I and of the GSK‐3β pathway. Moreover, the nootropic compound showed an increase in the transcriptional/protein levels of neurotrophic and well‐being related genes. Finally, GPE counteracted the accumulation of ageing‐related misfolded proteins (a‐synuclein and tau). Overall, our data underline promising effects of GPE in counteracting cellular alterations related to brain ageing and cognitive decline.

Disordered Gut Microbiota in Colorectal Tumor-Bearing Mice Altered Serum Metabolome Related to Fufangchangtai

Purpose: This study aimed to investigate the relationship between gut microbiota (GM) and serum metabolism using antineoplastic Fufangchangtai (FFCT) as the model prescription in the treatment of colorectal cancer (CRC).

Methods: Tumor-bearing mice and normal mice were administered different doses of FFCT. The tumor volume of tumor-bearing mice was observed. The levels of CD4+ and CD8+ T cells in the blood, spleen, and tumor of mice were determined using a flow cytometer. The bacterial microbiota in stool samples from mice and the serum metabolomics of FFCT-treated mice and fecal microbiota transplantation mice were detected using 16s RNA sequencing and liquid chromatography–mass spectrometry (LC/MS), respectively.

Results: The tumor volume of mice showed no significant decrease after FFCT intervention. The levels of CD4+ and CD8+T lymphocytes showed a significant increase under the intervention of FFCT. GM of colorectal tumor-bearing mice and healthy mice were determined, and the diversity and abundance of Firmicutes, Deferribacteres, Bacteroidetes, and Proteobacteria were significantly different between the two groups. Furthermore, we found that the levels of matrine, isogingerenone B, and armillaripin were significantly decreased in tumor-bearing mice after FFCT intervention, indicating that the tumor-induced dysbiosis of gut bacteria may affect the absorption and metabolism of FFCT. Under the intervention of FFCT, serum metabolism of mice transplanted with feces from CRC patients showed less metabolites related to FFCT than that from healthy people, indicating that GM could be a single factor affecting the metabolism of FFCT. Furthermore, we found that different doses of FFCT-treated mice had higher abundance of Roseburia, Turicibacter, and Flexispira than that in the non-intervention control group. Firmicutes and Bacteroidetes in FFCT-treated groups showed a similar trend compared to the healthy group, indicating that FFCT might correct the intestinal microenvironment by modulating gut microbiota in colorectal tumor-bearing mice.

Conclusion: The dysbiosis of GM in tumor-bearing mice reduced the serum metabolites related to FFCT, and FFCT could correct the disordered GM of colorectal tumor-bearing mice to exert efficacy.

DHA-Enriched Phospholipids and EPA-Enriched Phospholipids Alleviate Lipopolysaccharide-Induced Intestinal Barrier Injury in Mice via a Sirtuin 1-Dependent Mechanism

Intestinal barrier dysfunction has emerged as a potential contributor to the development of several severe diseases. Herein, the effect and underlying mechanism of DHA-enriched phospholipids (DHA-PL) and EPA-enriched phospholipids (EPA-PL) on protecting against lipopolysaccharide (LPS)-induced intestinal barrier injury were elucidated. C57BL/6J male mice were fed an AIN-93G diet containing 1% DHA-PL or EPA-PL for 4 weeks and then were intraperitoneally injected with LPS (10 mg/kg) to cause intestinal barrier injury. The results manifested that DHA-PL and EPA-PL pretreatment balanced apoptosis and autophagy in intestinal epithelial cells and maintained intestinal tight junction integrity. Our findings also demonstrated that cotreatment with EX-527, a sirtuin 1 specific inhibitor, hindered the role of DHA-PL and EPA-PL against LPS-evoked intestinal barrier injury through reversing the inhibitory action of them on NF-κB and MAPKs activation as well as their potentiating actions on Nrf2 nuclear translocation. Overall, DHA-PL and EPA-PL alleviated LPS-mediated intestinal barrier injury via inactivation of the NF-κB and MAPKs pathways as well as activating the Nrf2 antioxidant pathway via up-regulating sirtuin 1.

Bioactive Compounds from Lemon (Citrus limon) Extract Overcome TNF-α-Induced Insulin Resistance in Cultured Adipocytes

The consumption of plant-based food is important for health promotion, especially regarding the prevention and management of chronic diseases such as diabetes. We investigated the effects of a lemon extract (LE), containing ≥20.0% total flavanones and ≥1.0% total hydroxycinnamic acids, on insulin signaling in murine 3T3-L1 adipocytes treated with TNF-α, which was used to mimic in vitro the insulin resistance condition that characterizes diabetes mellitus. Our results showed LE increased PPARγ, GLUT4 and DGAT-1 levels, demonstrating the potential of this lemon extract in the management of insulin resistance conditions associated with TNF-α pathway activation. LE treatment further decreased the release of interleukin 6 (IL-6) and restored triglyceride synthesis, which is the main feature of a healthy adipocyte.