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Metabolomic analysis shows differential hepatic effects of T2 and T3 in rats after short-term feeding with high fat diet.

ABSTRACT: Nonalcoholic fatty liver disease (NAFLD) is a major health problem worldwide, and is often associated with lipotoxic injury, defective mitochondrial function, and insulin resistance. Thyroid hormones (THs) are important regulators of hepatic lipid metabolism. Among the THs, diiodothyronine (T2) and triiodothyronine (T3) have shown promising results in lowering hepatic fat content in various models of NAFLD. In this study, we used a targeted metabolomics approach to investigate the differential effects of T2 and T3 on the early metabolic adaptation in the livers of rats fed high fat diet (HFD), a period when hepatosteatosis is reversible. Our results showed that both T2 and T3 strongly induced autophagy and intra-hepatic acylcarnitine flux but prevented the generation of sphingolipid/ceramides in animals fed HFD. Interestingly, although both T2 and T3 decreased hepatic fat content, only T2 was able to rescue the impairment in AKT and MAPK/ERK pathways caused by HFD. In summary, we have identified and characterized the effects of T2 and T3 on hepatic metabolism during short-term exposure to HFD. These findings illuminate the common and divergent metabolic pathways by T2 and T3 that also may be important in the prevention and treatment of NAFLD.

SUBMITTER: Iannucci LF

PROVIDER: S-EPMC5435676 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Metabolomic analysis shows differential hepatic effects of T2 and T3 in rats after short-term feeding with high fat diet.

Iannucci Liliana F LF Cioffi Federica F Senese Rosalba R Goglia Fernando F Lanni Antonia A Yen Paul M PM Sinha Rohit A RA

Scientific reports 20170517 1

Nonalcoholic fatty liver disease (NAFLD) is a major health problem worldwide, and is often associated with lipotoxic injury, defective mitochondrial function, and insulin resistance. Thyroid hormones (THs) are important regulators of hepatic lipid metabolism. Among the THs, diiodothyronine (T2) and triiodothyronine (T3) have shown promising results in lowering hepatic fat content in various models of NAFLD. In this study, we used a targeted metabolomics approach to investig ...[more]

PMID: 28515456

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Project description:Iron deficiency-induced anemia is generally a representative nutritional problem in most populations. We reported that the anemia due to dietary iron deficiency causes a variety of changes in nutrient metabolism, even leading to apoptosis as a result of associated endoplasmic reticulum (ER) stress in the rat liver. On the other hand, it appears that non-anemic iron-deficiency causes no serious problem because no appreciable down-regulation of hemoglobin synthesis occurs. Biochemically, iron is essential for activation of cytochrome-related enzymes and its deficiency should yield some physiological problems. We performed a comprehensive transcriptome analysis to define the effects of non-anemic iron deficiency on hepatic gene expression. Four-week-old rats were fed a low-iron diet (ca. 3 ppm iron) for 2 days. These rats were compared with those fed a control diet (48 ppm iron) by pair feeding. On day 3, the rats were sacrificed under anesthesia, and their livers were dissected for DNA microarray analysis. Rats in the iron-deficient diet group, showed that their serum ferritin and iron levels decreased with an increase in the serum total iron binding capacity (TIBC) level, while the hemoglobin level was not changed. In the DNA microarray study, we identified 91 up-regulated and 186 down-regulated probe sets that characterized the iron-deficient diet group. In the up-regulated probe sets, genes involved in glucose and lipid metabolic processes were significantly enriched, whereas genes related to organic acid metabolic process, cellular ketone metabolic process, lipid metabolic process, oxidation reduction, response to drug, response to extracellular stimulus and gas transport were significantly enriched in the down-regulated probe sets. These results suggest that even the non-anemic iron-deficiency exerts various influences on nutrient metabolisms in the liver. Three-week-old male rats (Sprague Dawley) were purchased from Charles River Japan (Kanagawa, Japan) and housed in a room maintained at 24 M-BM-1 1M-BM-0C and 40 M-BM-1 5% humidity with a 12-h light/dark cycle (light 08:00M-bM-^@M-^S20:00; dark 20:00M-bM-^@M-^S08:00). Rats were given a normal diet (Research Diets, Inc., New Brunswick, NJ, USA) as control and water for 24 h ad libitum. The composition of the control diet, 48 ppm iron, was based on the AIN-93G diet; Avicel was used in place of cellulose which may contain a trace amount of iron. On day 3, diet was removed at 18:00 and the feeding was conducted between 09:00 and 17:00 for another 4 days to synchronize the feeding behaviors. On day 8, rats were divided into two groups with similar average body weights. Rats in the one group (n = 5) were given ad libitum an iron-deficient diet, ca. 3 ppm iron, that was prepared by removal of iron (ferric citrate) from the control diet, and those in the other group (n = 5) were fed the control diet by pair feeding. On day 1 and day 3 of feeding with the experiment diet, the hemoglobin level of each rat was measured for the blood samples collected from the tail vein. On day 3, each rat was sacrificed under anesthesia after 1.5 h feeding, prior to excising the liver which was soon immersed in RNAlater.

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Project description:Thyroid hormone mimetics are alluring potential therapies for diseases like dyslipidemia, nonalcoholic fatty liver disease (NAFLD), and insulin resistance. Though diiodothyronines are thought inactive, pharmacologic treatment with 3,5- Diiodo-L-Thyronine (T2) reportedly reduces hepatic lipid content and improves glucose tolerance in fat-fed male rats. To test this, male Sprague Dawley rats fed a safflower-oil based high-fat diet were treated with T2 (0.25 mg/kg-d) or vehicle. Neither 10 nor 30 days of T2 treatment had an effect on weight, adiposity, plasma fatty acids, or hepatic steatosis. Insulin action was quantified in vivo by a hyperinsulinemic-euglycemic clamp. T2 did not alter fasting plasma glucose or insulin concentration. Basal endogenous glucose production (EGP) rate was unchanged. During the clamp, there was no difference in insulin stimulated whole body glucose disposal. Insulin suppressed EGP by 60% ± 10 in T2-treated rats as compared with 47% ± 4 suppression in the vehicle group (p = 0.32). This was associated with an improvement in hepatic insulin signaling; insulin stimulated Akt phosphorylation was ~2.5 fold greater in the T2-treated group as compared with the vehicle-treated group (p = 0.003). There was no change in expression of genes thought to mediate the effect of T2 on hepatic metabolism, including genes that regulate hepatic lipid oxidation (ppara, carnitine palmitoyltransferase 1a), genes that regulate hepatic fatty acid synthesis (srebp1c, acetyl coa carboxylase, fatty acid synthase), and genes involved in glycolysis and gluconeogenesis (L-pyruvate kinase, glucose 6 phosphatase). Therefore, in contrast with previous reports, in Sprague Dawley rats fed an unsaturated fat diet, T2 administration failed to improve NAFLD or whole body insulin sensitivity. Though there was a modest improvement in hepatic insulin signaling, this was not associated with significant differences in hepatic insulin action. Further study will be necessary before diiodothyronines can be considered an effective treatment for NAFLD and dyslipidemia.

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Metabolomic analysis shows differential hepatic effects of T2 and T3 in rats after short-term feeding with high fat diet.

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Metabolomic analysis shows differential hepatic effects of T<sub>2</sub> and T<sub>3</sub> in rats after short-term feeding with high fat diet.

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