ACETATE UTILIZATION BY LIVER AND ADIPOSE TISSUE OF RATS FASTED IN THE COLD

The in vitro incorporation of 1-C14and 2-C14acetate into fatty acids and carbon dioxide by liver and adipose tissue was studied in rats fasted at 5 °C. for 24 hours. Compared with fed rats at room temperature, there was a marked decrease in the incorporation of the acetate carbons into fatty acids and carbon dioxide by liver tissue. A pronounced decrease in acetate incorporation into fatty acid was also noted with adipose tissue from these same animals, but only a slight decrease in incorporation into carbon dioxide. Addition of glucose to the incubation medium caused increases in fatty acid formation by liver and adipose tissue from both normal and fasted animals, but glucose supplementation, while increasing the incorporation of acetate into carbon dioxide by liver tissue from cold fasted rats, did not affect carbon dioxide production by liver tissue from normal animals. Incorporation of acetate into carbon dioxide by adipose tissue was unaffected by glucose supplementation with tissue from both normal and cold fasted rats.

The incorporation of C14-labelled acetate into fatty acids and cholesterol was studied in vitro in castrated and gonadal hormone-treated male and female rats. Measurements were also made on the incorporation of C14-labelled octanoic acid into acetoacetic acid by liver tissue and the incorporation of acetate and octanoate into CO2.Castration in the male, but not in the female, was followed by an increased incorporation of acetate into both liver and adipose tissue fatty acids and into liver cholesterol.Testosterone treatment led to a decreased incorporation into fatty acids by liver tissue in the male, whereas estradiol treatment of the female led to an increase in the incorporation of acetate into fatty acids by both liver and adipose tissue. Acetate incorporation into cholesterol was unaltered by hormone treatment in both sexes. The incorporation of octanoic acid into acetoacetic acid by liver tissue was decreased in the estradiol-treated female rat but was unaltered in the testosterone-treated male rat or by castration in either sex.

The incorporation of C14-labelled acetate into fatty acids and cholesterol was studied in vitro in castrated and gonadal hormone-treated male and female rats. Measurements were also made on the incorporation of C14-labelled octanoic acid into acetoacetic acid by liver tissue and the incorporation of acetate and octanoate into CO2.Castration in the male, but not in the female, was followed by an increased incorporation of acetate into both liver and adipose tissue fatty acids and into liver cholesterol.Testosterone treatment led to a decreased incorporation into fatty acids by liver tissue in the male, whereas estradiol treatment of the female led to an increase in the incorporation of acetate into fatty acids by both liver and adipose tissue. Acetate incorporation into cholesterol was unaltered by hormone treatment in both sexes. The incorporation of octanoic acid into acetoacetic acid by liver tissue was decreased in the estradiol-treated female rat but was unaltered in the testosterone-treated male rat or by castration in either sex.

ACSL3 is a member of the long chain acyl-CoA synthetase (ACSL) family that plays key roles in fatty acid metabolism in various tissues in an isozyme-specific manner. Our previous studies showed that ACSL3 was transcriptionally up-regulated by the cytokine oncostatin M (OSM) in HepG2 cells, accompanied by reduced cellular triglyceride content and enhanced beta-oxidation. In this study, we investigated the molecular mechanism underlying the OSM-induced activation of ACSL3 gene transcription in HepG2 cells. We showed that OSM treatment resulted in a coordinated elevation of mRNA levels of ACSL3 and peroxisome proliferator-activated receptor delta (PPARdelta). The effect of OSM on ACSL3 mRNA expression was inhibited by cellular depletion of PPARdelta. By utilizing a PPARdelta agonist, L165041, we demonstrated that activation of PPARdelta led to increases in ACSL3 promoter activity, mRNA level, and protein level in HepG2 cells. Analysis of the ACSL3 promoter sequence identified two imperfect PPAR-responsive elements (PPRE) located in the ACSL3 promoter region -944 to -915, relative to the transcription start site. The up-regulation of ACSL3 promoter activity by PPARdelta was abolished by deletion of this PPRE-containing region or mutation to disrupt the binding sites. Direct interactions of PPARdelta with ACSL3-PPRE sequences were demonstrated by gel mobility shift and chromatin immunoprecipitation assays. Finally, we provided in vivo evidence showing that activation of PPARdelta by L165041 in hamsters increased ACSL3 mRNA and protein levels in the liver. These new findings define ACSL3 as a novel molecular target of PPARdelta in HepG2 cells and provide a regulatory mechanism for ACSL3 transcription in liver tissue.

Endocannabinoids and ghrelin are potent appetite stimulators and are known to interact at a hypothalamic level. However, both also have important peripheral actions, including beneficial effects on the ischemic heart and increasing adipose tissue deposition, while ghrelin has direct effects on carbohydrate metabolism. The AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme that functions as a fuel sensor to regulate energy balance at both cellular and whole body levels, and it may mediate the action of anti-diabetic drugs such as metformin and peroxisome proliferator-activated receptor gamma agonists. Here we show that both cannabinoids and ghrelin stimulate AMPK activity in the hypothalamus and the heart, while inhibiting AMPK in liver and adipose tissue. These novel effects of cannabinoids on AMPK provide a mechanism for a number of their known actions, such as the reduction in infarct size in the myocardium, an increase in adipose tissue, and stimulation of appetite. The beneficial effects of ghrelin on heart function, including reduction of myocyte apoptosis, and its effects on lipogenesis and carbohydrate metabolism, can also be explained by its ability to activate AMPK. Our data demonstrate that AMPK not only links the orexigenic effects of endocannabinoids and ghrelin in the hypothalamus but also their effects on the metabolism of peripheral tissues.

Reduction of Hepatosteatosis and Lipid Levels by an Adipose Differentiation-Related Protein Antisense Oligonucleotide

Dairy cows with high and low plasma non-esterified fatty acid (NEFA) concentrations in early lactation were compared for plasma parameters and mRNA expression of genes in liver and subcutaneous adipose tissue. The study involved 16 multiparous dairy cows with a plasma NEFA concentration of >500 μmol/l [n = 8, high NEFA (HNEFA)] and <140 μmol/l [n = 8, low NEFA (LNEFA)] in the first week post-partum (pp). Blood samples, adipose and liver tissues were collected on day 1 (+1d) and at week 3 pp (+3wk). Blood plasma was assayed for concentrations of metabolites and hormones. Subcutaneous adipose and liver tissues were analysed for mRNA abundance by real-time qRT-PCR encoding parameters related to lipid metabolism. Results showed that mean daily milk yield and milk fat quantity were higher in HNEFA than in LNEFA cows (p < 0.01), and the NEB was more negative in HNEFA than in LNEFA in +3wk too (p < 0.05). HNEFA cows had slightly lower (p < 0.1) insulin concentrations than LNEFA cows across the study period, and the body condition score decreased more from +1d to +3wk in HNEFA than in LNEFA (p = 0.09). The mRNA abundance of genes in the liver related to fatty acid oxidation (carnitine palmitoyltransferase 2 and very long chain acyl-coenzyme A dehydrogenase) and ketogenesis (3-hydroxy-3-methylglutaryl-coenzyme A synthase 2) were lower in HNEFA than in LNEFA cows. No differences between the two groups were observed for mRNA expression of genes in adipose tissue. The number of calculated significant correlation coefficients (moderately strong) between parameters in the liver and in adipose tissue was nearly similar on +1d, and higher for HNEFA compared with LNEFA cows in +3wk. In conclusion, dairy cows with high compared with low plasma NEFA concentrations in early lactation show differentially synchronized mRNA expression of genes in adipose tissue and liver in +3wk that suggests a different orchestrated homeorhetic regulation of lipid metabolism.

We hypothesized that exogenous fatty acids, and especially or 18:2 trans-10, cis-12 conjugated linoleic acid (CLA), would decrease adipogenic and lipogenic gene expression and de novo fatty acid biosynthesis in intramuscular (i.m.) and subcutaneous (s.c.) adipose tissues. Fresh i.m. and s.c. adipose tissues were collected from the longissimus thoracis muscle of Angus steers at 12, 14, and 16 months of age (n=4 per time point). Adipose tissue explants were incubated in duplicate for 48h with 40μM α-linolenic (ALA), oleic, stearic, trans-vaccenic, or CLA. Adipocyte size, acetate and glucose incorporation into fatty acids in vitro and mRNA levels for C/EBPβ, CPT1β, GPR43, PPARγ, PRKAA1 (AMPKα) and SCD1 were measured following the incubations. PRKAA1 and SCD1gene expression were greater (P<0.001) in s.c. adipose tissue than in i.m. adipose tissue and acetate incorporation into lipids and C/EBPβ, PPARγ, and SCD1gene expression were greater at 16months of age than at 12months of age in i.m. adipose (P<0.01). C/EBPβ gene expression increased by 16months of age and PRKAA1 gene expression decreased by 16months of age in s.c. adipose tissue. All fatty acids increased s.c. adipocyte volumes whereas CLA decreased acetate incorporation into lipids in s.c. adipose tissue (P<0.05), but none of the fatty acids affected gene expression in i.m. or s.c. adipose tissue (P>0.10). Thus, CLA depressed de novo fatty acid biosynthesis from acetate but neither CLA nor other fatty acids significantly affected adipogenic or lipogenic gene expression.

To investigate the incorporation of acetate into fatty acids and their turnover, the time courses for the incorporation of labeled acetate into lipids in the liver and epididymal adipose tissue (adipose tissue) after the oral administration to rats were examined for 10 d. The labeled acetate was abundantly incorporated into lipids, mainly into triacylglycerols (TAG) in the liver, reached a maximum at 2 h after the administration and then quickly decreased. In the adipose tissue, the incorporation of the acetate reached a maximum after 8 h and began to decrease slowly after 2 d. The acetate incorporation into the lipids was markedly lower in the liver, plasma and adipose tissue of rats fed the corn oil diet than in those fed the fat-free diet. However, the half-lives of esterified fatty acids were similar in both dietary groups. The half-lives of esterified C16:0 and C18:1 in the decreasing phase were 5.4 and 8.9 h, respectively, in the liver, and 4.3 and 5.6 d, in the adipose tissue. The time courses for incorporation into plasma lipids were parallel to those in the liver. Thus the fatty acids synthesized in the liver appeared to be transported to adipose tissues and to stay there longer. Moreover, it is remarkable that 30% of the acetate radioactivities administered were found after 2 h in the whole liver: 75% of the products from the acetate at the maximum were lipids and 61%, of the lipids, TAG. The major products from acetate in the liver were lipids.

The effect of growth hormone on the in vitro incorporation of C14acetate into fatty acids, carbon dioxide, and cholesterol by liver and adipose tissue from young, adult, and old rats was studied.In all three age groups of animals, growth hormone was found to depress the incorporation of acetate into fatty acids by liver slices but the CO2production was unaffected. In both young and old animals growth hormone did not significantly alter the incorporation of acetate into fatty acids and CO2by preparations of adipose tissue, but did result in a decline in the fat content of the adipose tissue. It was noted that the CO2production from acetate was much less with adipose tissue from old rats than with similar preparations from young rats.Incorporation of acetate into cholesterol was unaffected by growth hormone in young and old animals but was significantly increased in liver slices from adult animals.

The effect of growth hormone on the in vitro incorporation of C14acetate into fatty acids, carbon dioxide, and cholesterol by liver and adipose tissue from young, adult, and old rats was studied.In all three age groups of animals, growth hormone was found to depress the incorporation of acetate into fatty acids by liver slices but the CO2production was unaffected. In both young and old animals growth hormone did not significantly alter the incorporation of acetate into fatty acids and CO2by preparations of adipose tissue, but did result in a decline in the fat content of the adipose tissue. It was noted that the CO2production from acetate was much less with adipose tissue from old rats than with similar preparations from young rats.Incorporation of acetate into cholesterol was unaffected by growth hormone in young and old animals but was significantly increased in liver slices from adult animals.

El tejido adiposo (TA) y hepático influencian el metabolismo de ácidos grasos (AG), al ser en gran parte los responsables de regular su biosíntesis, degradación y almacenamiento en tejidos corporales, como también de su secreción en leche y carne de animales en producción. De esta forma, un mejor entendimiento de la funcionalidad del metabolismo de AG en estos tejidos y los factores que lo afectan, podría dar las bases para el diseño de estrategias productivas en rumiantes. Así, el objetivo de esta revisión es presentar un panorama general de la funcionalidad y metabolismo de los AG en el TA y hepático en rumiantes de producción. A partir de la revisión, se pudo establecer, que el tipo de lípidos mayoritarios en TA y hepático, lo forman los AG y triglicéridos. El TA es el principal sitio de almacenamientobenergético tanto en rumiantes como en no rumiantes. El TA se encuentra. metabólicamente asociado con el tejido hepático mediante un equilibrio que regula los procesos de β-oxidación, síntesis de novo y transporte de AG a nivel tisular. Finalmente, se pudo establecer que el metabolismo de AG en TA y hepático es afectado por diversos factores, tales como la nutrición, nivel de restricción dietaria, genética, estado fisiológico y medio ambiente, de los cuales, la nutrición tiene el mayor impacto.

Evodiamine, the major alkaloid component isolated from the fruit of dried, unripened Evodia rutaecarpa Bentham, affects the plasma levels of cholecystokinin and various biological events such as gastric emptying and gastrointestinal transit; these effects of evodiamine were previously investigated in male rats. In this study, we aimed to investigate the effects of evodiamine on average daily weight gain, rectal temperature, and expressions of genes involved in lipid metabolism in liver and adipose tissues. Evodiamine was added as a supplement, comprising 0.02, 0.04, and 0.06% of the diet fed to mice for 1, 2, 3, and 4 weeks. Results showed that average daily weight gain and rectal temperature decreased significantly over time in a dose-dependent manner. Evodiamine changed expressions of the peroxisome proliferator-activated receptor-g (PPARg) in mouse adipose and liver tissues in time- and dose-dependent manners. We found that evodiamine decreased mRNA expression of the sterol-regulatory element binding protein (SREBP-1c) and fatty acid synthase in adipose tissue. In addition, evodiamine increased expressions of hormone-sensitive lipase in both liver and adipose tissues. Interestingly, evodiamine increased the expression of triglyceride hydrolase only in adipose tissue. In conclusion, evodiamine could influence lipid metabolism through regulation of the expressions of its key genes, as well as reduce body heat and body weight.

Conjugated linoleic acid (CLA) is able to reduce adiposity by affecting lipid metabolism. In particular, CLA administration to mice reduces body fat mass with a concomitant lipid accumulation in the liver. We investigated the effects of CLA on the activity of the mitochondrial citrate carrier (CIC), which is implicated in hepatic lipogenesis. The transport activity of the CIC, measured both in intact mitochondria and in the proteoliposomes, progressively increased with the duration of CLA feeding. An increase in the CIC activity of approximately 1.7-fold was found in 16 week CLA-treated mice with respect to control animals. A kinetic analysis showed a 1.6-fold increase in the V(max) of citrate transport but no change in the K(m) value. Western blot experiments revealed an increase of approximately 1.7-fold in the expression of CIC after CLA treatment. A strict correlation between the increase in CIC activity and the stimulation of the cytosolic lipogenic enzymes was also found. These data indicate that the CIC may play a role in the onset of hepatic steatosis in CLA-fed mice by supplying the carbon source for de novo fatty acid synthesis.

Sodium butyrate (SB) is a potentially useful feed additive, however, its effects on lipid metabolism in adipose and liver tissues of lambs are still not fully explored. This study systematically examined the effects and underlying mechanisms of dietary SB supplementation on lipid metabolism in lamb adipose and liver tissues from an adipose-blood-liver-perspective. Twelve 3-month-old male lambs (22.37 ± 2.05 kg) were randomly divided into a control group and a SB group. The adipose tissue cellular morphology and lipid metabolism-related indices in both adipose and liver tissues were measured. The results indicated that SB significantly reduces abdominal and perirenal adipose tissue mass, as well as in the average area and diameter of adipocytes (P < 0.05). Dietary supplementation with SB activated adenosine 5'-monophosphate -activated protein kinase α1 (AMPKα1) in lamb adipose tissue, resulting in upregulated mRNA expression of hormone-sensitive triglyceride lipase (HSL) and downregulated mRNA expression of sterol regulatory element-binding protein 1 and fatty acid synthase (P < 0.05). Simultaneously, adiponectin secretion and receptor expression in adipose tissue, as well as serum adiponectin levels, were significantly elevated (P < 0.05). Moreover, dietary supplementation with SB increased the levels of TCA cycle metabolites in lamb liver, including oxaloacetate, citrate, cis-aconitate, and succinate (P < 0.05), while simultaneously activating the liver AMPKα1 signaling pathway. This led to upregulated HSL, platelet glycoprotein 4, and long-chain acyl-CoA synthetase mRNA expression (P < 0.05), thereby enhancing liver fatty acid metabolism. In summary, dietary supplementation with SB alters adiponectin levels in lambs, activates the AMPK signaling pathway, promotes adipose tissue lipolysis, and regulates liver lipid metabolism. The findings provide valuable insights into the use of SB for managing lamb body fat reserves and offer a robust basis for further research in animal bioscience.