Anti-steatotic effects of an n-3 LCPUFA and extra virgin olive oil mixture in the liver of mice subjected to high-fat diet

Abstract

Non-alcoholic fatty liver disease (NAFLD) is characterized by liver steatosis, oxidative stress, and drastic depletion of n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA), namely, eicosapentaenoic acid (C20:5 n-3, EPA) and docosahexaenoic acid (C22:6 n-3, DHA), which trigger lipolysis stimulation and lipogenesis inhibition. Extra virgin olive oil (EVOO) has important antioxidant effects. This study evaluated the anti-steatotic effects of n-3 LCPUFA plus EVOO in the liver of male C57BL/6J mice subjected to a control diet (CD) (10% fat, 20% protein, 70% carbohydrate) or high fat diet (HFD) (60% fat, 20% protein, 20% carbohydrate), without and with supplementation with n-3 LCPUFA (100 mg per kg per day) plus EVOO (100 mg per kg per day) for 12 weeks. HFD induced (i) liver steatosis (increased total fat, triacylglycerols, and free fatty acid total contents), (ii) higher fasting serum glucose and insulin levels and HOMA index, total cholesterol, triacylglycerols and TNF-α and IL-6, (iii) liver and plasma oxidative stress enhancement, (iv) depletion of the n-3 LCPUFA hepatic content, and (v) increment in lipogenic enzyme activity and reduction in lipolytic enzyme activity. These changes were either reduced (p < 0.05) or normalized to control the values in animals subjected to HFD supplemented with n-3 LCPUFA plus EVOO. In conclusion, n-3 LCPUFA plus EVOO intervention exerts anti-steatotic effects underlying antioxidant and anti-inflammatory responses, improved insulin sensitivity, and recovery of the lipolytic/lipogenic status of the liver altered by HFD, and supports the potential therapeutic use of n-3 LCPUFA plus EVOO supplementation in the treatment of human liver steatosis induced by nutritional factors or other etiologies.

Supplementation with Docosahexaenoic Acid and Extra Virgin Olive Oil Prevents Liver Steatosis Induced by a High‐Fat Diet in Mice through PPAR‐α and Nrf2 Upregulation with Concomitant SREBP‐1c and NF‐kB Downregulation

“…Enhancement in hepatic levels of LA and AA and higher n‐6 LCPUFA/n‐3 LCPUFA ratios were observed in HFD‐fed animals concomitantly with a decreased EPA and DHA availability (Table ). In this context, a characteristic of HFD‐induced hepatic steatosis is the decrease in the activity of the Δ‐5 and Δ‐6 desaturases, a finding also reported in obese NAFLD patients, which has a direct negative impact on LCPUFA biosynthesis, especially that of EPA and DHA . In addition to defective liver FA desaturation, higher oxidative stress may further favor the lipoperoxidation of EPA and DHA leading to n‐3 LCPUFA depletion, effect contributed by the low dietary consumption of ALA, as was found in NAFLD subjects, and supported by the direct correlations of n‐3 LCPUFA depletion and insulin resistance, oxidative stress, and lower activity of desaturase enzymes, especially Δ‐6 desaturase .…”

“…HFD‐fed mice receiving 60% of calories as fat that include 10.6 g SFA/100 g diet and 6.5 g palmitic acid/100 g diet represent the major contributory factors to the induction of metabolic and hepatic alterations comprising oxidative stress and lipotoxicity, endoplasmic reticulum stress, and the establishment of a systemic pro‐inflammatory state and insulin resistance . Under these conditions, HFD‐fed animals receiving DHA + EVOO exhibited a greater protection compared to HFD groups supplemented either with DHA or EVOO, with a significant reduction in hepatic steatosis.…”

“…The latter redox imbalance is associated with fatty acid (FA) overload generating a substrate pressure, which leads to high amounts of reactive oxygen species . Previous work by our group reported that mice fed a high‐fat diet (HFD) for 12 weeks produce dyslipidemia and obesity with altered levels of both fasting glycemia and insulinemia, similarly to metabolic syndrome . Under these conditions, HFD elicited liver lipotoxicity, causing significant increases in oxidative stress related markers and a reduced glutathione (GSH)/glutathione disulfide (GSSG) ratio decrease …”

Docosahexaenoic acid and hydroxytyrosol co‐administration fully prevents liver steatosis and related parameters in mice subjected to high‐fat diet: A molecular approach

“…The suppressive effect of HFD‐induced liver steatosis by the co‐administration of DHA and HT underlies several mechanisms exerted by both natural products. First, DHA has a strong anti‐lipogenic action coupled to (a) down‐regulation of SREBP‐1c signaling and the expression of the associated lipogenic enzymes (Figure ) and the citrate carrier (CIC), which involves the inhibition of SREBP‐1c proteolytic processing; (b) up‐regulation of PPAR‐α signaling, which implicates a DHA interaction with the DNA binding domain inducing conformational changes favoring gene transcription of FAO enzymes (Figure ) and the carnitine/acylcarnitine carrier (CAC); (c) suppression of the induced oxidative stress (Figure ), which correlates with enhancement in Nrf2 signaling over CD values via J 3 ‐isoprostanes formation that increases the antioxidation potential of the liver (Figure ), thus avoiding n‐3 LCPUFA depletion and chronic UPR‐associated lipogenesis; and (d) enhancement in adiponectin expression and secretion in adipocytes . The latter finding is associated with decreased liver FFA influx and increased FAO that may contribute to diminish hepatic TG and VLDL synthesis .…”

“…This contention is based in that co‐administration protocols employ (a) lower doses of the therapeutic agents than those of the monotherapies; and (b) shorter supplementation periods that reduce possible adverse effects, with the involved mechanisms triggering different processes or similar pathways exhibiting additivity or potentiation . For example, experimental animals subjected to co‐administration of n‐3 long‐chain polyunsaturated fatty acids (n‐3 LCPUFAs) and L‐3,3′,5‐triiodothyronine (T 3 ) show prevention of liver ischemia–reperfusion inflammatory injury, whereas those given a combined n‐3 LCPUFA and extra virgin olive oil (EVOO) protocol exhibit attenuation of high‐fat diet (HFD)‐induced hepatic steatosis …”