Liver Triacylglycerol Research Articles

186 Young Scholar Presentation: Immunometabolism during periods of negative nutrient balance or heat stress is altered by dietary methyl donor supply in dairy cows

Abstract Our research examined the effects of enhancing methyl donor supply on immunometabolism during periods of negative nutrient balance (NNB) or heat stress (HS). The first experiment examined the effects of post-ruminal choline supply during NNB on production and pathways of 1-carbon metabolism. Ten primiparous rumen-cannulated cows (158±24 DIM) were used in a replicated 5×5 Latin square design with 4d treatment periods and 10d of recovery. Treatments were unrestricted intake with abomasal infusion of water, restricted intake (R; 60% of net energy for lactation requirements) with abomasal infusion of water or R plus abomasal infusion of 6.25, 12.5, or 25 g/d choline ion. Liver tissue was collected at the end of each treatment period. Enhancing choline supply increased milk yields, but decreased liver triacylglycerol. Activity of betaine homocysteine methyltransferase increased with choline, while methionine synthase tended to increase, and cystathionine β-synthase was decreased. These changes were associated with increased liver and plasma Met. Overall, enhanced supply of choline during NNB increases flux through the Met cycle to regenerate Met and reduce liver triacylglycerol. The second experiment examined the effects of rumen-protected Met (RPM) during HS on mTOR (mechanistic target of rapamycin)-related signaling proteins in the mammary gland. Thirty-two multiparous cows (184±59 DIM) were assigned to an environmental treatment, and a dietary treatment [TMR with RPM (0.105% DM) or without (CON)] in a crossover design. There were 2 periods with 2 phases per period. In phase 1 (9d), all cows were in thermoneutral conditions (TN) and fed ad libitum. During phase 2 (9d), group 1 (n=16) was exposed to HS using electric heat blankets while group 2 (n=16) remained in TN but were pair-fed to HS counterparts. After a washout period (21d), the study was repeated (period 2), with environmental treatments being inverted and dietary treatments remaining the same. Mammary tissue was collected at the end of phase 2. Abundance of phosphorylated mTOR was greater with RPM and tended to be greater with HS. Control cows had a greater decrease in milk protein (%) during phase 2 (difference from phase 1) compared with RPM cows, suggesting that RPM supplementation during HS may support greater milk protein synthesis via mTOR activation. The third experiment investigated the effects of RPM during HS on the response of mammary gland explants to lipopolysaccharide (LPS). Twenty-five mg of tissue obtained from cows in the second experiment was incubated with 0 or 3 μg/mL of LPS for 2h. Incubation with LPS increased abundance of genes associated with inflammation, while HS decreased genes associated with antioxidant responses. Expression of NFKB1was greater in LPS-treated explants from non-HS compared with HS cows. These data indicate that HS reduced immune and antioxidant responses while RPM did not attenuate the inflammatory response induced by LPS in vitro. Overall, data indicated a beneficial effect of choline during NNB and Met during HS on immunometabolism in dairy cows.

Characterization of the circulating and tissue-specific alterations to the lipidome in response to moderate and major cold stress in mice.

This study analyzed the effects of 24 h of cold stress (22°C or 5°C vs. mice maintained at 30 °C) on the plasma, brown adipose tissue (BAT), subcutaneous (SubQ) and epididymal (Epi) white adipose tissue (WAT), liver, and skeletal muscle lipidome of mice. Using mass spectrometry-lipidomics, 624 lipid species were detected, of which 239 were significantly altered in plasma, 134 in BAT, and 51 in the liver. In plasma, acylcarnitines and free fatty acids were markedly increased at 5°C. Plasma triacylglycerols (TGs) were reduced at 22°C and 5°C. We also identified ether lipids as a novel, cold-induced lipid class. In BAT, TGs were the principal lipid class affected by cold stress, being significantly reduced at both 22°C and 5°C. Interestingly, although BAT TG species were uniformly affected at 5°C, at 22°C we observed species-dependent effects, with TGs containing longer and more unsaturated fatty acids particularly sensitive to the effects of cold. In the liver, TGs were the most markedly affected lipid class, increasing in abundance at 5 °C. TGs containing longer and more unsaturated fatty acids accumulated to a greater degree. Our work demonstrates the following: 1) acute exposure to moderate (22°C) cold stress alters the plasma and BAT lipidome; although this effect is markedly less pronounced than at 5°C. 2) Cold stress at 5°C dramatically alters the plasma lipidome, with ether lipids identified as a novel lipid class altered by cold exposure. 3) Cold-induced alterations in liver and BAT TG levels are not uniform, with changes being influenced by acyl chain composition.

Whole-body vibration promotes lipid mobilization in hypothalamic obesity rat

ObjectivesThis study aimed to analyze the effect of whole-body vibration (WBV) on metabolic parameters using the monosodium l-glutamate (MSG) model of obesity. MethodMSG-obese rats that were exposed to WBV on a vibrating platform with 60 Hz frequency, 2 mm amplitude, three times/week, 10 min/day, during eight weeks (from postnatal day (PN) 80 to PN136). Blood glucose, creatine kinases (CK and CK-MB) and lipid profile through plasma and liver levels of lipids and lipoproteins were evaluated. Morphology and oxidative stress of adipose and hepatic tissues were further evaluated. ResultsWhen performing a WBV exercise, animals showed contrasting metabolic responses. Vibration Control group (CTL-WBV) presented a reduction in CK and liver triacylglycerol, an increase in glucose, lactate, total cholesterol, liver cholesterol, and LDL while MSG Vibration group (MSG-WBV) showed an increase in total triacylglycerol, VLDL, lactate, CK, liver cholesterol, additional liver lipid peroxidation and LDL, total cholesterol and CKMB reduction. ConclusionEven although the MSG is a model of impacting injury, the metabolic demand of WBV exercise was able to induce mobilization of substrates, highlighting the lipid mobilization in obese animals, it should be used as a metabolic rehabilitation tool in patients with metabolic diseases, such as obesity and diabetes.

EFFECTS OF TYPE 2 DIABETES MELLITUS INDUCTION AND OF MODERATE PHYSICAL EXERCISE ON THE HEPATIC METABOLISM AND OXIDATIVE STRESS IN WISTAR RATS

AIMS: The aim of the study was to verify if the induction of Type 2 Diabetes Mellitus (T2DM) by the association of streptozotocin and high fat diet causes hepatic alterations and if physical exercise can improve these alterations. METHODS: Forty-six Wistar rats were divided into two groups. One group received a diet containing 60% of fat for 9 weeks and on the 14th day they were injected with a single dose of streptozotocin (25mg/kg). The other group, named control group, received a standard diet and a single dose of citrate buffer was given. Animals were them divided into two subgroups: one sedentary (S) and the other submitted to physical exercise (PE), totalizing four groups: C-S; C-PE; HF-S; HF-PE. After euthanasia blood and liver were collected. Plasma and hepatic concentrations of triacylglycerol and very low density lipoprotein; enzyme alanine transaminase, aspartate transaminase and arginase; urea, lactate and 8-isoprostane (an oxidative stress marker) were dosed. RESULTS: Capillary glucose was significantly higher in HF-S and HF-PE group animals compared to C-S and C-PE groups. There were no significant differences in alanine transaminase, arginase, oxidative stress and lactate concentration among the groups. Plasma urea concentration and hepatic aspartate transaminase concentration was lower in HF-S and HF-PE than in C-PE. Concerning liver triacylglycerol and very low density lipoproteins, both were higher in the HF-PE group when compared to the C-S. CONCLUSIONS: We conclude that diet was decisive for the aforementioned parameters alterations and that physical exercise protocol was not efficient to improve analyzed parameters.

Menthol to Induce Non-shivering Thermogenesis via TRPM8/PKA Signaling for Treatment of Obesity.

Increasing basal energy expenditure via uncoupling protein 1 (UCP1)-dependent non-shivering thermogenesis is an attractive therapeutic strategy for treatment of obesity. Transient receptor potential melastatin 8 (TRPM8) channel activation by cold and cold mimetics induces UCP1 transcription and prevents obesity in animals, but the clinical relevance of this relationship remains incompletely understood. A review of TRPM8 channel agonism for treatment of obesity focusing on menthol was undertaken. Adipocyte TRPM8 activation results in Ca2+ influx and protein kinase A (PKA) activation, which induces mitochondrial elongation, mitochondrial localization to lipid droplets, lipolysis, β-oxidation, and UCP1 expression. Ca2+-induced mitochondrial reactive oxygen species activate UCP1. In animals, TRPM8 agonism increases basal metabolic rate, non-shivering thermogenesis, oxygen consumption, exercise endurance, and fatty acid oxidation and decreases abdominal fat percentage. Menthol prevents high-fat diet-induced obesity, glucose intolerance, insulin resistance, and liver triacylglycerol accumulation. Hypothalamic TRPM8 activation releases glucagon, which activates PKA and promotes catabolism. TRPM8 polymorphisms are associated with obesity. In humans, oral menthol and other TRPM8 agonists have little effect. However, topical menthol appears to increase core body temperature and metabolic rate. A randomized clinical control trial of topical menthol in obese patients is warranted.

Pollutants and nutrition: Are methylmercury effects on blood pressure and lipoprotein profile comparable to high-fat diet in mice?

Human exposure to methylmercury (MeHg) due to contaminated fish intake as part of a high-fat (HFD), high-carbohydrate diets is a reality today for many populations. HFD is associated with hypertension and hyperlipidemia, primary cardiovascular disease (CVD) risk factors. Some studies suggest that MeHg induces those risk factors. We evaluated the effect of MeHg exposure in mice fed with HFD or control diet for eight weeks. In the last experimental 15 days, the half group received a MeHg solution (20 mg/L) replacing water. Blood pressure (BP), heart rate, lipoprotein concentrations, and paraoxonase activity were evaluated. Liver cholesterol, triacylglycerol, and IBA-1+ cells, as well as transcriptional levels of genes related to lipid metabolism and inflammatory response, were also assessed. HFD and both MeHg groups presented increased BP and total cholesterol (TC). In the liver, HFD but not MeHg was related to an increase in TC. Also, MeHg intoxication reduced paraoxonase activity regardless of diet. MeHg intoxication and HFD increased steatosis and the number of IBA-1+ cells and modified some gene transcripts associated with lipid metabolism. In conclusion, we demonstrated that MeHg effects on CVD risk factors resemble those caused by HFD.

Human GDPD3 overexpression promotes liver steatosis by increasing lysophosphatidic acid production and fatty acid uptake

The glycerol phosphate pathway produces more than 90% of the liver triacylglycerol (TAG). LysoPA, an intermediate in this pathway, is produced by glycerol-3-phosphate acyltransferase. Glycerophosphodiester phosphodiesterase domain containing 3 (GDPD3), whose gene was recently cloned, contains lysophospholipase D activity, which produces LysoPA from lysophospholipids. Whether human GDPD3 plays a role in hepatic TAG homeostasis is unknown. We hypothesized that human GDPD3 increases LysoPA production and availability in the glycerol phosphate pathway, promoting TAG biosynthesis. To test our hypothesis, we infected C57BL/6J mice with adeno-associated virus encoding a hepatocyte-specific albumin promoter that drives GFP (control) or FLAG-tagged human GDPD3 overexpression and fed the mice chow or a Western diet to induce hepatosteatosis. Hepatic human GDPD3 overexpression induced LysoPA production and increased FA uptake and incorporation into TAG in mouse hepatocytes and livers, ultimately exacerbating Western diet-induced liver steatosis. Our results also showed that individuals with hepatic steatosis have increased GDPD3 mRNA levels compared with individuals without steatosis. Collectively, these findings indicate that upregulation of GDPD3 expression may play a key role in hepatic TAG accumulation and may represent a molecular target for managing hepatic steatosis.

Dietary fat concentrations influence fatty acid assimilation patterns in Atlantic pollock (Pollachius virens).

A key aspect in the use of fatty acids (FA) to estimate predator diets using quantitative FA signature analysis (QFASA) is the ability to account for FA assimilation through the use of calibration coefficients (CC). Here, we tested the assumption that CC are independent of dietary fat concentrations by feeding Atlantic pollock (Pollachius virens) three formulated diets with very similar FA proportions but different fat concentrations (5-9% of diet) for 20 weeks. CC calculated using FA profiles of diet and triacylglycerols in pollock liver were significantly different for the three diets. To test the robustness of diet estimates to these differences, we used the CC set derived from feeding the diet with the lowest fat concentration, published prey FA profiles and realistic diet estimates of pollock to construct 'pseudo-predators'. Application of QFASA to each pseudo-predator using the three sets of CC and the same prey FA profiles resulted in diet estimate biases of twofold for major prey items and approximately fivefold for minor prey items. This work illustrates the importance of incorporating diets with fat concentrations that are similar to natural prey when conducting feeding experiments to calculate CC. This article is part of the theme 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.

PHGDH supports liver ceramide synthesis and sustains lipid homeostasis

Backgroundd-3-phosphoglycerate dehydrogenase (PHGDH), which encodes the first enzyme in serine biosynthesis, is overexpressed in human cancers and has been proposed as a drug target. However, whether PHGDH is critical for the proliferation or homeostasis of tissues following the postnatal period is unknown.MethodsTo study PHGDH inhibition in adult animals, we developed a knock-in mouse model harboring a PHGDH shRNA under the control of a doxycycline-inducible promoter. With this model, PHGDH depletion can be globally induced in adult animals, while sparing the brain due to poor doxycycline delivery.ResultsWe found that PHGDH depletion is well tolerated, and no overt phenotypes were observed in multiple highly proliferative cell compartments. Further, despite detectable knockdown and impaired serine synthesis, liver and pancreatic functions were normal. Interestingly, diminished PHGDH expression reduced liver serine and ceramide levels without increasing the levels of deoxysphingolipids. Further, liver triacylglycerol profiles were altered, with an accumulation of longer chain, polyunsaturated tails upon PHGDH knockdown.ConclusionsThese results suggest that dietary serine is adequate to support the function of healthy, adult murine tissues, but PHGDH-derived serine supports liver ceramide synthesis and sustains general lipid homeostasis.

Effects of supplementation of green tea extract on the milk performance of peripartal dairy cows and the expression of stress response genes in the liver

BackgroundWe hypothesised that supplementation of green tea extract (GTE) in dairy cows during the transition period can attenuate proinflammatory conditions and prevent endoplasmic reticulum (ER) stress in the liver of these cows. Thirty Holstein cows with an average parity of 3.06 (± 1.31, SD) were divided into a control group and a group that received a daily amount of 10 g of GTE from d 7 before the calving day and a daily amount of 20 g of GTE from the day of calving until d 7 of lactation.ResultsCows supplemented with GTE did not show differences in energy intake or milk yield in weeks 2–7 of lactation. However, these cows had a lower milk fat concentration and a lower energy corrected milk yield than the control cows and showed a trend of improved energy balance. The relative mRNA concentrations of proinflammatory genes, genes involved in the acute phase reaction and antioxidant genes in the liver in weeks 1, 4 and 7 of lactation were not different between the two groups of cows. The concentrations of α-tocopherol and the Trolox equivalent antioxidant capacity in plasma were not different between the two groups. However, the group supplemented with GTE showed significant reductions of some genes of the unfolded protein response (UPR) in week 1 and a trend of lower liver triacylglycerol (TAG) concentrations in the liver compared to the control group.ConclusionsThis study shows that supplementation of GTE in dairy cows lowers the fat concentration in the milk but overall has no effect on the expression of inflammatory genes and the antioxidative status in dairy cows during early lactation. The finding of reduced mRNA levels of genes involved in the UPR at week 1, however, supports other results showing that supplementation of polyphenols could prevent the development of ER stress in the liver of cows during early lactation. The finding of a tendency towards a reduced TAG concentration in the liver of cows supplemented with GTE might be due to an improved energy balance in these cows.

Lactobacillus plantarum FRT10 alleviated high-fat diet-induced obesity in mice through regulating the PPARα signal pathway and gut microbiota.

Previous studies showed that probiotics supplementation contributed to alleviate obesity. This work was to assess the efficacy of Lactobacillus plantarum FRT10 from sour dough in alleviating obesity in mice fed with a high-fat diet (HFD), and the underlying mechanisms focusing on modulation of the gut microbiota profile. Kunming mice were fed with a regular diet (CT), a high-fat diet (HFD), and two HFDs containing low and high doses of L. plantarum FRT10 for 8weeks. The physiological and biochemical modulations in liver were analyzed. Cecal contents were analyzed by high-throughput 16S ribosomal RNA sequencing. FRT10 supplementation significantly reduced body weight gain, fat weight, and liver triacylglycerols (TGs) and alanine aminotransferase (ALT) concentrations (P < 0.05). FRT10 significantly ameliorated the HFD-induced gut dysbiosis, as evidenced by increased abundance of microbes, including Butyricicoccus, Butyricimonas, Intestinimonas, Odoribacter, and Alistipes, and decreased abundance of Desulfovibrionaceae, Roseburia, and Lachnoclostridium. Lactobacillus, Bifidobacterium, and Akkermansia were markedly increased after FRT10 intervention. In addition, real-time quantitative PCR revealed that FRT10 upregulated the mRNA expression levels of peroxisome proliferator-activated receptor-α (PPARα) and carnitine palmitoyltransferase-1α (CPT1α), and downregulated the mRNA expression levels of sterol regulatory element-binding protein 1 (SREBP-1) and TG-synthesizing enzyme diacylglycerol acyltransferase 1 (DGAT1) in liver. These findings suggested that FRT10 had anti-obesity effects in obese mice partly related to the activation of PPARα/CPT1α pathway. FRT10 can be considered a single probiotic agent for preventing HFD-induced obesity in humans and animals.

Mitochondrial membrane protein mitofusin 2 as a potential therapeutic target for treating free fatty acid–induced hepatic inflammation in dairy cows during early lactation

Inflammation is critical in the progression from benign hepatic lipidosis to pathological hepatic steatosis. The objective of this study was to examine the potential role of the outer mitochondrial membrane protein mitofusin 2 (MFN2) in the etiology of hepatic steatosis in dairy cows during early lactation. Using a nested case-control design, we compared blood and liver samples from 10 healthy cows and 10 age-matched cows with moderate fatty liver. Cows with moderate fatty liver had high liver triacylglycerols, elevated plasma concentrations of free fatty acids (FFA) and β-hydroxybutyrate, and low concentrations of glucose. Cows with moderate fatty liver had overactivated inflammatory pathways in the liver, as indicated by increased abundance of phosphorylated nuclear factor κB (NF-κB) p65, NLR family pyrin domain containing 3 (NLRP3) and caspase-1 inflammasome protein, and elevated plasma concentrations and hepatic mRNA abundance of their molecular targets IL-1β, IL-6, and tumor necrosis factor α (TNF-α). In the cell culture model, we were able to replicate our findings in cows with moderate fatty liver: 1.2 mM exogenous FFA decreased the abundance of MFN2 and upregulated phosphorylation levels of the inhibitor of NF-κB (IκB) α and NF-κB p65, the IκB kinase β activity, and the abundance of NLRP3, caspase-1, IL-1β, IL-6, and TNF-α. Whereas MFN2 knockdown potentiated the FFA-induced activation of these inflammatory pathways, overexpression of MFN2 attenuated the detrimental effect of excess exogenous FFA by improving mitochondrial function and decreasing the release of reactive oxygen species, suggesting that MFN2 may be a potential therapeutic target for FFA-induced hepatic inflammation in dairy cows during early lactation.

Long-term bisphenol S exposure aggravates non-alcoholic fatty liver by regulating lipid metabolism and inducing endoplasmic reticulum stress response with activation of unfolded protein response in male zebrafish

Environmental chemical exposures have been implicated as risk factors for the development of non-alcoholic fatty liver (NAFLD). Bisphenol S (BPS), widely used in multitudinous consumer products, could disrupt lipid metabolism in the liver. This study aimed at examining the hypothesis that long-term exposure to BPS promotes the development of liver fibrosis and inflammation by means of the application of a semi-static exposure experiment that exposed zebrafish to 1, 10, and 100 μg/L BPS from 3 h post fertilization to 120 day post fertilization. Results showed that the 120-d BPS exposure elevated plasma aspartate aminotransferase and alanine aminotransferase activities, increased triacylglycerol (TAG) and total cholesterol levels in male liver, and even induced hepatic apoptosis and fibrosis. Hepatic lipid accumulation observed in the 30-d BPS-exposed zebrafish was recovered after a 90-d depuration phase, thereby indicating that long-term BPS exposure promotes the progression of simple steatosis to non-alcoholic steatohepatitis. Furthermore, BPS exposure for 120-d promoted the synthesis of TAG and lipotoxic free fatty acids by elevating the transcription of srebp1, acc, fasn, and elovl6, induced endoplasmic reticulum (ER) stress with increasing expression levels of unfolded protein response (UPR) genes (perk, hsp5, atf4a, and ddit3), and then stimulated the expression of two key autophagy genes (atg3 and lc3) and inflammatory genes (il1b and tnfα). It is indicated that BPS can induce the development of steatohepatitis via the activation of the PERK-ATF4a pathway of the UPR. Data gathered suggest that environmental pollutants-induced ER stress with the activation of UPR can potentially trigger the NAFLD development in males. Overall, our study provided new sights into understanding of the adverse health effects of metabolism disrupting chemicals.

Rapid Accumulation of Triacylglycerol in the Liver is a Component of the Acute Exercise Response and May Serve a Protective Role Against Lipotoxicity

We have previously shown that the content of triacylglycerol (TAG) in the liver transiently increases after a single bout of exercise in untrained mice, and this phenomenon has been observed in human subjects as well. This discovery depicted a new phenomenon in the metabolic exercise response. Here we propose the term “lipogenic flexibility” to describe this ability to rapidly alter hepatic TAG content in response to FFA supply. To explore lipogenic flexibility after exercise, we performed lipidomics analysis on liver samples obtained 3 hours after exercise and the following day. Female mice performed a single bout of continuous exercise (CE), high intensity interval exercise (HIIE), or no exercise (CON). The total concentration of hepatic TAG rose 3 hours after exercise (P &lt; 0.05 for both CE and HIIE vs CON), but the total concentration of all other measured lipid classes remained unchanged after exercise (NSD). Hepatic TAG declined back to control levels by the day after exercise. We performed correlation analysis to test the association of TAG (an inert lipid depot) with lipotoxic lipid classes in the liver. Hepatic TAG was positively correlated with hepatic diacylglycerol (DAG) in CON (P &lt; 0.05); however, during the hepatic TAG pool expansion after exercise, liver TAG and DAG were no longer significantly correlated with one another (NSD). Exhibiting lipogenic flexibility after exercise appears to break the equilibration between DAG and TAG, allowing fatty acids to be drawn toward the inert lipid pool (TAG) and away from the lipotoxic lipid pool (DAG). The results suggest that the TAG pool actively expands to buffer elevated FFA supply after exercise and may act to prevent lipotoxicity.Support or Funding InformationThis work was supported by the Faculty Research Grant Program of Rutgers University, the American Diabetes Association grant # 7‐13‐JF‐27‐BR to G Henderson, and the Purdue University College of Health and Human Sciences.

Lipid profile and liver lipids of OLETF rats during ARB treatment and after its removal

The metabolic syndrome (MetS) affects 20% of the US population. MetS comprises several disorders that raise the risk of atherosclerosis, insulin resistance, and diabetes. Angiotensin receptor blockers (ARBs) are used to ameliorate hypertension associated with metabolic disorders. Nonetheless, the potential benefits of ARBs on the metabolic state are not fully appreciated. ARB treatment reduces overproduction and accumulation of hepatic triacylglycerols (TAG), but whether ARB treatment has favorable effects in fatty livers associated with insulin resistance is still unknown. Furthermore, the compliance on the usage of ARBs should also be addressed, as MetS patients may be under variating treatments, exposing them to secondary effects due to the ARB treatment removal. To evaluate the benefits of ARB treatment and implications of its removal on the lipid profile, four groups (n=4–6) of 25‐week‐old rats were used: (1) lean, strain‐control Long‐Evans Tokoshima Otsuka (LETO), (2) obese, insulin resistant Otsuka Long‐Evans Tokoshima Fatty (OLETF), 3) ARB‐treated OLETF, (10 mg olmesartan/kg/d × 8 wks), and 4) OLETF ± ARB (10 mg olmesartan/kg/d × 4 wks then removed until dissection). An oral glucose challenge (GC) was performed prior to dissection and tissues collected from a subset of animals in each group at defined time points (T0, 3 an 6hr). We measured different components of the lipid profile, during the ARB treatment and after its removal. Plasma NEFA, TAG and cholesterol levels remain unchanged with ARB treatment, as well as with ARB removal. ARB treatment did not change the liver levels of cholesterol, but prevented the increase shown by OLETFs during the GC. ARB removal shown increased cholesterol after 6 hr of the GC. ARB treatment decreased liver TAG and throughout the GC. ARB removal increased TAG liver levels during the GC. Suggesting that lipid profiles may not change during static sampling during or after ARB treatment. ARB treatment reduces liver TAG concentration, and even with ARB removal suggesting that plasma levels do not accurately reflect tissue levels. Following the GC, the ARB removal group demonstrated an increase in levels, suggesting that treatment non‐compliance results in rapid return to basal levels and increased potential for hepatic dysfunction. Further investigation on lipid transport and metabolic regulation during ARB treatment and removal may yield insight for a wider perspective for treatment of traits linked to MetS.Support or Funding InformationThis work was supported by NIH MHIRT.

Dietary betaine improves egg-laying rate in hens through hypomethylation and glucocorticoid receptor–mediated activation of hepatic lipogenesis-related genes

In avian species, liver lipid metabolism plays an important role in egg laying performance. Previous studies indicate that betaine supplementation in laying hens improves egg production. However, it remains unclear if betaine improves laying performance by affecting hepatic lipid metabolism and what mechanisms are involved. We fed laying hens a 0.5% betaine-supplemented diet for 4 wks to investigate its effect on hepatic lipids metabolism in vivo and confirmed its mechanism via in vitro experiments using embryonic chicken hepatocytes. Results showed that betaine supplemented diet enhanced laying production by 4.3% compared with normal diet, accompanied with increased liver and plasma triacylglycerol concentrations (P < 0.05) in hens. Simultaneously, key genes involved in hepatic lipid synthesis, such as sterol regulatory element binding protein 1 (SREBP-1), fatty acid synthase, acetyl-CoA carboxylase, and stearoyl-CoA desaturase 1 (SCD1) were markedly upregulated at the mRNA level (P < 0.05). Western blot results showed that SREBP-1 and SCD1 protein levels were also increased (P < 0.05). Moreover, mRNA expression of main apolipoprotein components of yolk-targeted lipoproteins, apolipoprotein B (ApoB) and apolipoprotein-V1 (ApoV1), in addition to microsomal triglyceride transfer proteins, which is closely related to the synthesis and release of very-low density lipoprotein, were also markedly elevated (P < 0.05). Methylated DNA immunoprecipitation combined with PCR detects reduction of methylation levels in certain regions of the above gene promoters. Chromatin immunoprecipitation PCR assays showed increased binding of glucocorticoid receptor (GR) to SREBP1 and ApoB gene promoters. Similar results of ApoV1 gene expression were obtained from cultured hepatocytes treated with betaine. Additionally, betaine increased the expression of GR and some genes involved in methionine cycle in vitro. These results suggest that betaine supplementation could alter the expression of liver lipid synthesis and transport-related genes by modifying the methylation status and GR binding on their promoter and hence promote the synthesis and release of yolk precursor substances in the liver.

The PPAR pan-agonist tetradecylthioacetic acid promotes redistribution of plasma cholesterol towards large HDL

Tetradecylthioacetic acid (TTA) is a synthetic fatty acid with a sulfur substitution in the β-position. This modification renders TTA unable to undergo complete β-oxidation and increases its biological activity, including activation of peroxisome proliferator activated receptors (PPARs) with preference for PPARα. This study investigated the effects of TTA on lipid and lipoprotein metabolism in the intestine and liver of mice fed a high fat diet (HFD). Mice receiving HFD supplemented with 0.75% (w/w) TTA had significantly lower body weights compared to mice fed the diet without TTA. Plasma triacylglycerol (TAG) was reduced 3-fold with TTA treatment, concurrent with increase in liver TAG. Total cholesterol was unchanged in plasma and liver. However, TTA promoted a shift in the plasma lipoprotein fractions with an increase in larger HDL particles. Histological analysis of the small intestine revealed a reduced size of lipid droplets in enterocytes of TTA treated mice, accompanied by increased mRNA expression of fatty acid transporter genes. Expression of the cholesterol efflux pump Abca1 was induced in the small intestine, but not in the liver. Scd1 displayed markedly increased mRNA and protein expression in the intestine of the TTA group. It is concluded that TTA treatment of HFD fed mice leads to increased expression of genes involved in uptake and transport of fatty acids and HDL cholesterol in the small intestine with concomitant changes in the plasma profile of smaller lipoproteins.

Lipoatrophy-Associated Insulin Resistance and Hepatic Steatosis are Attenuated by Intake of Diet Rich in Omega 3 Fatty Acids.

Glucose homeostasis and progression of nonalcoholic fatty liver disease (NAFLD) and hepatomegaly in severe lipoatrophic mice and their modulation by intake of a diet rich in omega 3 (n-3) fatty acids (HFO) are evaluated. Severe lipoatrophic mice induced by PPAR-γ deletion exclusively in adipocytes (A-PPARγ KO) and littermate controls (A-PPARγ WT) are evaluated for glucose homeostasis and liver mass, proteomics, lipidomics, inflammation, and fibrosis. Lipoatrophic mice are heavier than controls, severely glucose intolerant, and hyperinsulinemic, and develop NAFLD characterized by increased liver glycogen, triacylglycerol, and diacylglycerol contents, mitotic index, apoptosis, inflammation, steatosis score, fibrosis, and fatty acid synthase (FAS) content and activity. Lipoatrophic mice also display liver enrichment with monounsaturated in detriment of polyunsaturated fatty acids including n-3 fatty acids, and increased content of cardiolipin, a tetracyl phospholipid exclusively found at the mitochondria inner membrane. Administration of a high-fat diet rich in n-3 fatty acids (HFO) to lipoatrophic mice enriches liver with n-3 fatty acids, reduces hepatic steatosis, FAS content and activity, apoptosis, inflammation, and improves glucose homeostasis. Diet enrichment with n-3 fatty acids improves glucose homeostasis and reduces liver steatosis and inflammation without affecting hepatomegaly in severe lipoatrophic mice.

Low doses of eriocitrin attenuate metabolic impairment of glucose and lipids in ongoing obesogenic diet in mice.

Eriocitrin is a citrus flavonoid with a high capacity to reduce the oxidative stress related to metabolic disorders and obesity. We assessed the effects of low doses of eriocitrin on the oxidative stress, inflammation, and metabolism of glucose and lipids of high-fat diet (HFD)-fed obese mice. Fifty male C57BL/6J mice were randomly assigned into five groups (n 10). The mice were fed an HFD (45 % kcal from fat, i.e. lard) for 4 weeks for obesity induction. After this period, the mice continued receiving the same HFD, but supplemented with eriocitrin at 10, 25 or 100 mg/kg body weight (bw) for an additional 4 weeks. Control groups were fed with standard diet (10 % kcal of fat, i.e. soy oil) or with HFD without eriocitrin, for eight consecutive weeks. At the end of the study, mice supplemented with eriocitrin showed lower levels of blood serum glucose and blood and liver triacylglycerols (P < 0⋅05). There was also improved levels of insulin, HOMA-IR, total-cholesterol, resistin and lipid peroxidation in the supplemented mice. It was concluded that the 25 mg dose of eriocitrin improved all the parameters studied and had positive effects on oxidative stress, systemic inflammation and metabolism of lipids and glucose in general.

Effects of dietary phytol on tissue accumulation of phytanic acid and pristanic acid and on the tissue lipid profiles in mice.

Recent in vitro evidence suggests that the phytol-derived fatty acids, phytanic acid (PA) and pristanic acid (PrA), are components of animal products with the potential to cause both beneficial and harmful effects on human health. In this study, we investigated the in vivo tissue accumulation of PA and PrA and the changes in tissue lipid profiles, using mice fed a phytol-containing diet. After 4weeks of treatment with a diet containing 1.0% phytol, plasma, adipose tissue, liver, and brain were collected and their lipid profiles were biochemically and gas-chromatographically determined. Dietary phytol caused PA and PrA accumulation in the adipose tissue and liver but not in the brain, and reduced plasma and liver triacylglycerol levels. Phytol intake also decreased the fatty acid concentrations in the adipose tissue, especially polyunsaturated fatty acids such as linoleic acid, but increased the concentrations of these fatty acids in the liver. However, dietary phytol had a low impact on the brain lipid profile. This study suggests that dietary phytol intake caused accumulation of PA and PrA and modified lipid profiles in the adipose tissue and liver, but that the brain is an insusceptible tissue to dietary phytol-induced changes.