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Nonthyrotoxic prevention of diet-induced insulin resistance by 3,5-diiodo-L-thyronine in rats.

de Lange P, Cioffi F, Senese R, Moreno M, Lombardi A, Silvestri E, De Matteis R, Lionetti L, Mollica MP, Goglia F, Lanni A - Diabetes (2011)

Bottom Line: T2 did so by rapidly stimulating hepatic fatty acid oxidation, decreasing hepatic triglyceride levels, and improving the serum lipid profile, while at the same time sparing skeletal muscle from fat accumulation.At the mechanistic level, 1) transfection studies show that T2 does not act via thyroid hormone receptor β; 2) AMP-activated protein kinase is not involved in triggering the effects of T2; 3) in HFD rats, T2 rapidly increases hepatic nuclear sirtuin 1 (SIRT1) activity; 4) in an in vitro assay, T2 directly activates SIRT1; and 5) the SIRT1 targets peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC-1α) and sterol regulatory element-binding protein (SREBP)-1c are deacetylated with concomitant upregulation of genes involved in mitochondrial biogenesis and downregulation of lipogenic genes, and PPARα/δ-induced genes are upregulated, whereas genes involved in hepatic gluconeogenesis are downregulated.Proteomic analysis of the hepatic protein profile supported these changes.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Scienze della Vita, Seconda Università degli Studi di Napoli, Caserta, Italy.

ABSTRACT

Objective: High-fat diets (HFDs) are known to induce insulin resistance. Previously, we showed that 3,5-diiodothyronine (T2), concomitantly administered to rats on a 4-week HFD, prevented gain in body weight and adipose mass. Here we investigated whether and how T2 prevented HFD-induced insulin resistance.

Research design and methods: We investigated the biochemical targets of T2 related to lipid and glucose homeostasis over time using various techniques, including genomic and proteomic profiling, immunoblotting, transient transfection, and enzyme activity analysis.

Results: Here we show that, in rats, HFD feeding induced insulin resistance (as expected), whereas T2 administration prevented its onset. T2 did so by rapidly stimulating hepatic fatty acid oxidation, decreasing hepatic triglyceride levels, and improving the serum lipid profile, while at the same time sparing skeletal muscle from fat accumulation. At the mechanistic level, 1) transfection studies show that T2 does not act via thyroid hormone receptor β; 2) AMP-activated protein kinase is not involved in triggering the effects of T2; 3) in HFD rats, T2 rapidly increases hepatic nuclear sirtuin 1 (SIRT1) activity; 4) in an in vitro assay, T2 directly activates SIRT1; and 5) the SIRT1 targets peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC-1α) and sterol regulatory element-binding protein (SREBP)-1c are deacetylated with concomitant upregulation of genes involved in mitochondrial biogenesis and downregulation of lipogenic genes, and PPARα/δ-induced genes are upregulated, whereas genes involved in hepatic gluconeogenesis are downregulated. Proteomic analysis of the hepatic protein profile supported these changes.

Conclusions: T2, by activating SIRT1, triggers a cascade of events resulting in improvement of the serum lipid profile, prevention of fat accumulation, and, finally, prevention of diet-induced insulin resistance.

Show MeSH

Related in: MedlinePlus

Four weeks of T2 administration prevents HFD-induced changes in systemic metabolic parameters and fat accumulation, independently of TRβ. A: T2 normalizes HFD-altered metabolic parameters and B: glucose tolerance (upper) and insulin resistance (lower). Upper and lower insets: area under the curve (AUC). C–F: T2 prevents fat (C) and triglyceride (D) accumulation and increases mitochondrial fatty acid oxidation (E) and phosphorylation of AMPK (Thr172) (F) in the indicated tissues. G: In contrast to T3, T2 does not activate the human uncoupling protein 3 promoter through interaction with TRβ in transiently transfected rat L6 myotubes. Error bars represent SEM. *P < 0.05 vs. untreated controls; **P < 0.05 vs. both untreated controls and HFD-fed groups; ***P < 0.05 vs. HFD-fed group. Energy efficiency = body weight gain/metabolized energy intake. BW, body weight; GW, gastrocnemius weight; LW, liver weight; NEFA, nonesterified fatty acids; prot, protein; VCO2, carbon dioxide production; WW, white adipose weight. Vo2 and energy expenditure are normalized to lean body weight. A–E: □/◇ = N; ■ = HFD; ▨/△ = HFD-T2. G: ♦ = T2, △ = T3. (A high-quality color representation of this figure is available in the online issue.)
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Figure 1: Four weeks of T2 administration prevents HFD-induced changes in systemic metabolic parameters and fat accumulation, independently of TRβ. A: T2 normalizes HFD-altered metabolic parameters and B: glucose tolerance (upper) and insulin resistance (lower). Upper and lower insets: area under the curve (AUC). C–F: T2 prevents fat (C) and triglyceride (D) accumulation and increases mitochondrial fatty acid oxidation (E) and phosphorylation of AMPK (Thr172) (F) in the indicated tissues. G: In contrast to T3, T2 does not activate the human uncoupling protein 3 promoter through interaction with TRβ in transiently transfected rat L6 myotubes. Error bars represent SEM. *P < 0.05 vs. untreated controls; **P < 0.05 vs. both untreated controls and HFD-fed groups; ***P < 0.05 vs. HFD-fed group. Energy efficiency = body weight gain/metabolized energy intake. BW, body weight; GW, gastrocnemius weight; LW, liver weight; NEFA, nonesterified fatty acids; prot, protein; VCO2, carbon dioxide production; WW, white adipose weight. Vo2 and energy expenditure are normalized to lean body weight. A–E: □/◇ = N; ■ = HFD; ▨/△ = HFD-T2. G: ♦ = T2, △ = T3. (A high-quality color representation of this figure is available in the online issue.)

Mentions: All animals received humane care according to the criteria outlined in the Guide for the Care and Use of Laboratory Animals prepared by the National Academy of Sciences and published by the National Institutes of Health. Male Wistar rats (250–300 g) (Charles River Laboratories) were kept one per cage in a temperature-controlled room at 28°C under a 12-h light/12-h dark cycle. Water was available ad libitum. Rats were divided into five groups. The first group (group N) received a standard diet (total metabolizable percentage of energy: 60.4 carbohydrates, 29 proteins, 10.6 fat J/J; 15.88 KJ gross energy/g; Muscedola, Milan, Italy). The second (group HFD) received an HFD (consisting of 280 g diet supplemented with 395 g lyophilized lamb meat [Liomellin, Milan, Italy], 120 g cellulose [Sigma-Aldrich, St. Louis, MO], 20 g mineral mix [ICN Biomedical, Solon, OH], 7 g vitamin mix [ICN], and 200 g low-salt butter [Lurpak, Denmark]) (total metabolizable percentage of energy: 21 carbohydrates, 29 proteins, 50 fat J/J; 19.85 KJ gross energy/g). The third group (group HFD-T2) received the same HFD together with a daily injection of T2 (25 μg/100 g body wt intraperitoneally) (Sigma-Aldrich). Animals in groups N and HFD were sham-injected. In most experiments, animals of the first, second, and third groups were killed at 1 h, 6 h, 1 day, 1 week, 2 weeks, or 4 weeks after the beginning of their diet/treatment schedule. The fourth group [group HFD-(T2)-C] received the above HFD for 1 or 6 h with a concomitant intraperitoneal injection of T2 (see third group) and/or Compound C (an AMPK inhibitor) (Sigma-Aldrich) at 1 mg/100 g body wt. The fifth group [group HFD-(T2)-EX] received the above HFD for 1 day with a concomitant intraperitoneal injection of T2 (see third group) and/or EX-527 (a SIRT1 inhibitor) (Sigma-Aldrich) at 1 mg/100 g body wt. Body weight and food consumption were monitored throughout the course of treatment (Fig. 1A). At the end of the schedules, rats were anesthetized by an intraperitoneal injection of chloral hydrate (40 mg/100 g body wt) and then killed by decapitation. For each experimental condition, 10 animals were used. Liver, heart, gastrocnemius muscle, and abdominal white adipose tissue were excised, weighed, and either immediately processed for isolation of mitochondria or histochemical analysis or immediately frozen in liquid nitrogen and stored at −80°C for later processing.


Nonthyrotoxic prevention of diet-induced insulin resistance by 3,5-diiodo-L-thyronine in rats.

de Lange P, Cioffi F, Senese R, Moreno M, Lombardi A, Silvestri E, De Matteis R, Lionetti L, Mollica MP, Goglia F, Lanni A - Diabetes (2011)

Four weeks of T2 administration prevents HFD-induced changes in systemic metabolic parameters and fat accumulation, independently of TRβ. A: T2 normalizes HFD-altered metabolic parameters and B: glucose tolerance (upper) and insulin resistance (lower). Upper and lower insets: area under the curve (AUC). C–F: T2 prevents fat (C) and triglyceride (D) accumulation and increases mitochondrial fatty acid oxidation (E) and phosphorylation of AMPK (Thr172) (F) in the indicated tissues. G: In contrast to T3, T2 does not activate the human uncoupling protein 3 promoter through interaction with TRβ in transiently transfected rat L6 myotubes. Error bars represent SEM. *P < 0.05 vs. untreated controls; **P < 0.05 vs. both untreated controls and HFD-fed groups; ***P < 0.05 vs. HFD-fed group. Energy efficiency = body weight gain/metabolized energy intake. BW, body weight; GW, gastrocnemius weight; LW, liver weight; NEFA, nonesterified fatty acids; prot, protein; VCO2, carbon dioxide production; WW, white adipose weight. Vo2 and energy expenditure are normalized to lean body weight. A–E: □/◇ = N; ■ = HFD; ▨/△ = HFD-T2. G: ♦ = T2, △ = T3. (A high-quality color representation of this figure is available in the online issue.)
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198093&req=5

Figure 1: Four weeks of T2 administration prevents HFD-induced changes in systemic metabolic parameters and fat accumulation, independently of TRβ. A: T2 normalizes HFD-altered metabolic parameters and B: glucose tolerance (upper) and insulin resistance (lower). Upper and lower insets: area under the curve (AUC). C–F: T2 prevents fat (C) and triglyceride (D) accumulation and increases mitochondrial fatty acid oxidation (E) and phosphorylation of AMPK (Thr172) (F) in the indicated tissues. G: In contrast to T3, T2 does not activate the human uncoupling protein 3 promoter through interaction with TRβ in transiently transfected rat L6 myotubes. Error bars represent SEM. *P < 0.05 vs. untreated controls; **P < 0.05 vs. both untreated controls and HFD-fed groups; ***P < 0.05 vs. HFD-fed group. Energy efficiency = body weight gain/metabolized energy intake. BW, body weight; GW, gastrocnemius weight; LW, liver weight; NEFA, nonesterified fatty acids; prot, protein; VCO2, carbon dioxide production; WW, white adipose weight. Vo2 and energy expenditure are normalized to lean body weight. A–E: □/◇ = N; ■ = HFD; ▨/△ = HFD-T2. G: ♦ = T2, △ = T3. (A high-quality color representation of this figure is available in the online issue.)
Mentions: All animals received humane care according to the criteria outlined in the Guide for the Care and Use of Laboratory Animals prepared by the National Academy of Sciences and published by the National Institutes of Health. Male Wistar rats (250–300 g) (Charles River Laboratories) were kept one per cage in a temperature-controlled room at 28°C under a 12-h light/12-h dark cycle. Water was available ad libitum. Rats were divided into five groups. The first group (group N) received a standard diet (total metabolizable percentage of energy: 60.4 carbohydrates, 29 proteins, 10.6 fat J/J; 15.88 KJ gross energy/g; Muscedola, Milan, Italy). The second (group HFD) received an HFD (consisting of 280 g diet supplemented with 395 g lyophilized lamb meat [Liomellin, Milan, Italy], 120 g cellulose [Sigma-Aldrich, St. Louis, MO], 20 g mineral mix [ICN Biomedical, Solon, OH], 7 g vitamin mix [ICN], and 200 g low-salt butter [Lurpak, Denmark]) (total metabolizable percentage of energy: 21 carbohydrates, 29 proteins, 50 fat J/J; 19.85 KJ gross energy/g). The third group (group HFD-T2) received the same HFD together with a daily injection of T2 (25 μg/100 g body wt intraperitoneally) (Sigma-Aldrich). Animals in groups N and HFD were sham-injected. In most experiments, animals of the first, second, and third groups were killed at 1 h, 6 h, 1 day, 1 week, 2 weeks, or 4 weeks after the beginning of their diet/treatment schedule. The fourth group [group HFD-(T2)-C] received the above HFD for 1 or 6 h with a concomitant intraperitoneal injection of T2 (see third group) and/or Compound C (an AMPK inhibitor) (Sigma-Aldrich) at 1 mg/100 g body wt. The fifth group [group HFD-(T2)-EX] received the above HFD for 1 day with a concomitant intraperitoneal injection of T2 (see third group) and/or EX-527 (a SIRT1 inhibitor) (Sigma-Aldrich) at 1 mg/100 g body wt. Body weight and food consumption were monitored throughout the course of treatment (Fig. 1A). At the end of the schedules, rats were anesthetized by an intraperitoneal injection of chloral hydrate (40 mg/100 g body wt) and then killed by decapitation. For each experimental condition, 10 animals were used. Liver, heart, gastrocnemius muscle, and abdominal white adipose tissue were excised, weighed, and either immediately processed for isolation of mitochondria or histochemical analysis or immediately frozen in liquid nitrogen and stored at −80°C for later processing.

Bottom Line: T2 did so by rapidly stimulating hepatic fatty acid oxidation, decreasing hepatic triglyceride levels, and improving the serum lipid profile, while at the same time sparing skeletal muscle from fat accumulation.At the mechanistic level, 1) transfection studies show that T2 does not act via thyroid hormone receptor β; 2) AMP-activated protein kinase is not involved in triggering the effects of T2; 3) in HFD rats, T2 rapidly increases hepatic nuclear sirtuin 1 (SIRT1) activity; 4) in an in vitro assay, T2 directly activates SIRT1; and 5) the SIRT1 targets peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC-1α) and sterol regulatory element-binding protein (SREBP)-1c are deacetylated with concomitant upregulation of genes involved in mitochondrial biogenesis and downregulation of lipogenic genes, and PPARα/δ-induced genes are upregulated, whereas genes involved in hepatic gluconeogenesis are downregulated.Proteomic analysis of the hepatic protein profile supported these changes.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Scienze della Vita, Seconda Università degli Studi di Napoli, Caserta, Italy.

ABSTRACT

Objective: High-fat diets (HFDs) are known to induce insulin resistance. Previously, we showed that 3,5-diiodothyronine (T2), concomitantly administered to rats on a 4-week HFD, prevented gain in body weight and adipose mass. Here we investigated whether and how T2 prevented HFD-induced insulin resistance.

Research design and methods: We investigated the biochemical targets of T2 related to lipid and glucose homeostasis over time using various techniques, including genomic and proteomic profiling, immunoblotting, transient transfection, and enzyme activity analysis.

Results: Here we show that, in rats, HFD feeding induced insulin resistance (as expected), whereas T2 administration prevented its onset. T2 did so by rapidly stimulating hepatic fatty acid oxidation, decreasing hepatic triglyceride levels, and improving the serum lipid profile, while at the same time sparing skeletal muscle from fat accumulation. At the mechanistic level, 1) transfection studies show that T2 does not act via thyroid hormone receptor β; 2) AMP-activated protein kinase is not involved in triggering the effects of T2; 3) in HFD rats, T2 rapidly increases hepatic nuclear sirtuin 1 (SIRT1) activity; 4) in an in vitro assay, T2 directly activates SIRT1; and 5) the SIRT1 targets peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC-1α) and sterol regulatory element-binding protein (SREBP)-1c are deacetylated with concomitant upregulation of genes involved in mitochondrial biogenesis and downregulation of lipogenic genes, and PPARα/δ-induced genes are upregulated, whereas genes involved in hepatic gluconeogenesis are downregulated. Proteomic analysis of the hepatic protein profile supported these changes.

Conclusions: T2, by activating SIRT1, triggers a cascade of events resulting in improvement of the serum lipid profile, prevention of fat accumulation, and, finally, prevention of diet-induced insulin resistance.

Show MeSH
Related in: MedlinePlus