The Role of Tea Tree Oil in Alleviating Palmitic Acid-Induced Lipid Accumulation in Bovine Hepatocytes

Cellular and molecular effects of fipronil in lipid metabolism of HepG2 and its possible connection to non-alcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a global public health problem that affects more than a quarter of the population. The development of this disease is correlated with metabolic dysfunctions that lead to lipid accumulation in the liver. Pesticides are one of etiologies that support NAFLD establishment. Therefore, the effects of the insecticide fipronil on the lipid metabolism of the human hepatic cell line, HepG2, was investigated, considering its widespread use in field crops and even to control domestic pests. To address the goals of the study, biochemical, cellular, and molecular analyses of different concentrations of fipronil in cell cultures were investigated, after 24 h of incubation. Relevant metabolites such as triglycerides, glucose levels, β-oxidation processes, and gene expression of relevant elements correlated with lipid and metabolism of xenobiotics were investigated. The results suggested that at 20 μM, the pesticide increased the accumulation of triglycerides and neutral lipids by reducing fatty acid oxidation and increasing de novo lipogenesis. In addition, changes were observed in genes that control oxidative stress and the xenobiotic metabolism. Together, the results suggest that the metabolic changes caused by the insecticide fipronil may be deleterious if persistent, favoring the establishment of hepatic steatosis.

Effects of Tea Tree Oil on Production Performance, Serum Parameter Indices, and Immunity in Postpartum Dairy Cows

Tea tree oil (TTO) plays an important role in regulating lipid metabolism and has anti-inflammatory properties. In postpartum dairy cows, dry matter intake (DMI) is dramatically decreased, resulting in lipid metabolism disorder and the systemic pro-inflammatory response. However, the effects of TTO on glucolipid metabolism and immunity in postpartum dairy cows remain uninvestigated. Therefore, this study aimed to evaluate the effects of TTO on production performance, serum biochemical indicators, and immunity in postpartum dairy cows. Our results demonstrate that DMI tended to increase (p = 0.07) in the total mixed ration (TMR) diets supplemented with 0.01% TTO/dry matter (DM) basis relative to that in the control group. The 4% fat-corrected milk (FCM) content in the 0.01% and 0.02% TTO groups showed an increase (p = 0.09) compared with that in the control. Remarkably, the levels of globulin (GLO) and immunoglobulin G (IgG) were elevated (p < 0.05) in the TMR diet supplemented with 0.02% TTO compared to those in the control group. The TTO caused no profound changes in cholesterol (CHO), triglyceride (TG), high-density lipoprotein (HDL), or low-density lipoprotein (LDL). Notably, 0.02% TTO increased (p < 0.05) the serum glucose concentration relative to that in the control group. In conclusion, our results demonstrate that TTO could improve glucolipid metabolism and enhance immunity in postpartum dairy cows. It may be a novel resolution strategy for body condition recovery and the improvement of milk performance.

Lavender Essential Oil Modulates Hepatic Cholesterol Metabolism in HepG2 Cells

Cholesterol is an essential lipid that guarantees several biological processes in eukaryotic cells. Its metabolism is regulated by a complex protein network that could be significantly influenced by numerous exogenous sources, such as essential oils (EOs). For instance, it has been speculated that monoterpenoid and sesquiterpenoid compounds contained in lavender essential oil (LEO) may exert important hypocholesterolemic activities. However, the molecular mechanisms by which LEO influences cholesterol homeostasis are not characterized. In this work, we evaluated the ability of LEO to regulate the protein network that controls cholesterol metabolism in the HepG2 cell line. The main findings indicate that LEO administration increases intracellular cholesterol content. Concurrently, LEO affects the expression of proteins involved in cholesterol uptake, biosynthesis, and trafficking. These effects are partially mediated by terpinene-4-ol, one of the most abundant compounds in LEO. These results demonstrate that LEO modulates cholesterol metabolism in hepatic cells.

Overexpression of GPR41 attenuated glucose production in propionate-induced bovine hepatocytes

Bovine liver mainly utilizes the propionate as a gluconeogenic substrate to synthesize the glucose. However, the mechanism underlying the regulatory effects of propionate on the glucose production in bovine hepatocytes remains less known. Previous studies have demonstrated G protein-coupled receptor 41 (GPR41) as receptors for propionate. We hypothesized that propionate may regulate the glucose production by GPR41 in bovine hepatocytes. Therefore, the aim of the study was to investigate the regulatory effects of propionate and GPR41 on glucose production in bovine hepatocytes. Hepatocytes with GPR41 overexpression were incubated in the presence of either 0 or 3 mM propionate for 24 h. These results showed that the expression of phosphoenolpyruvate carboxykinase 2 (PCK2) and pyruvate carboxylase (PC) genes involved in gluconeogenesis was enhanced (P &lt; 0.01) with propionate treatment. Remarkably, the addition of propionate promotes the glucose production in bovine hepatocytes. Expression of GPR41 was increased by the addition of propionate in bovine hepatocytes overexpressed GPR41 by overexpression plasmid AAV1 compared with the absence of propionate. Interestingly, expression of PCK2 was markedly attenuated in GPR41 overexpressed-hepatocytes with propionate. Importantly, overexpression of GPR41 attenuated glucose output in propionate-induced bovine hepatocytes. These findings revealed that GPR41 negatively regulates glucose production by downregulating the expression of PCK2 in propionate-induced bovine hepatocytes.

Effect of the Tea Tree Oil on Growth Performance, Meat Quality, Serum Biochemical Indices, and Antioxidant Capacity in Finishing Pigs

The increased use of antibiotics continues to pose a threat to public health because of the increasing concern of antibiotic residue. Tea tree oil (TTO) is an extract of the Australian plant Melaleuca alternifolia with anti-inflammatory and antioxidant properties. However, there is little information on TTO supplementation in the diet of finishing pigs. Hence, the present study aimed to investigate the effect of TTO supplemented diets on the growth performance, meat quality, serum biochemical indices, and antioxidant capacity of the finishing pigs. Our results showed that TTO supplementation increased (P < 0.05) the mRNA expression of insulin-like growth factors -I (IGFs-I), growth acceleration hormone (GH), and heart fatty acid-binding protein (H-FABP), while the mRNA expression of myostatin gene (MSTN), and calpain-1 (CAST) decreased by the TTO supplementation, compared with the control group. In addition, TTO supplementation increased (P < 0.05) serum alkaline phosphatase (ALP), immunoglobulin G (IgG), and IgM levels but decreased (P < 0.05) serum aspartate transaminase (AST) concentration, relative to the control group. In addition, we found that the live weight and intramuscular fat enhanced (P < 0.05) significantly, and muscle pH 24 min value, cooking loss, and shear force decreased (P < 0.05) dramatically in the TTO group. The TTO supplementation increased (P < 0.05) C18:2n6t concentration and decreased (P < 0.05) C12:0 and C16:0 concentration, relative to the control group. Dietary supplementation with TTO decreased (P < 0.05) malondialdehyde (MDA) and increased (P < 0.05) glutathione peroxidase (GSH-Px) activity in serum. These results indicated that TTO supplementation could improve immunity and antioxidant, carcass traits, the nutritional value of pork, and the antioxidant capacity of finishing pigs. Therefore, TTO has potential positive effects as a feed additive in the pig industry.