Long-chain n-3 polyunsaturated fatty acids (Omega-3) and anti-diabetic drugs thiazolidinediones (TZDs) exhibit additive effects in counteraction of dietary obesity and associated metabolic dysfunctions in mice. The underlying mechanisms need to be clarified. Here, we aimed to learn whether the futile cycle based on the hydrolysis of triacylglycerol and re-esterification of fatty acids (TAG/FA cycling) in white adipose tissue (WAT) could be involved. We compared Omega-3 (30 mg/g diet) and two different TZDs-pioglitazone (50 mg/g diet) and a second-generation TZD, MSDC-0602K (330 mg/g diet)-regarding their effects in C57BL/6N mice fed an obesogenic high-fat (HF) diet for 8 weeks. The diet was supplemented or not by the tested compound alone or with the two TZDs combined individually with Omega-3. Activity of TAG/FA cycle in WAT was suppressed by the obesogenic HF diet. Additive effects in partial rescue of TAG/FA cycling in WAT were observed with both combined interventions, with a stronger effect of Omega-3 and MSDC-0602K. Our results (i) supported the role of TAG/FA cycling in WAT in the beneficial additive effects of Omega-3 and TZDs on metabolism of diet-induced obese mice, and (ii) showed differential modulation of WAT gene expression and metabolism by the two TZDs, depending also on Omega-3.

• Keywords
• adipocytes, glucose homeostasis, insulin, lipogenesis, obesity,
• MeSH
• Adipose Tissue, White metabolism   MeSH
• Diet, High-Fat MeSH
• Hypoglycemic Agents pharmacology   MeSH
• Lipogenesis drug effects   MeSH
• Fatty Acids metabolism   MeSH
• Lipid Metabolism drug effects   MeSH
• Mice, Inbred C57BL MeSH
• Mice, Obese MeSH
• Mice MeSH
• Obesity drug therapy   metabolism   MeSH
• Fatty Acids, Omega-3 administration & dosage   pharmacology   MeSH
• Pioglitazone pharmacology   MeSH
• Thiazolidinediones administration & dosage   pharmacology   MeSH
• Triglycerides metabolism   MeSH
• Adipocytes drug effects   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Hypoglycemic Agents MeSH
• Fatty Acids MeSH
• Fatty Acids, Omega-3 MeSH
• Pioglitazone MeSH
• Thiazolidinediones MeSH
• Triglycerides MeSH

Insulin resistance, the key defect in type 2 diabetes (T2D), is associated with a low capacity to adapt fuel oxidation to fuel availability, i.e., metabolic inflexibility. This, in turn, contributes to a further damage of insulin signaling. Effectiveness of T2D treatment depends in large part on the improvement of insulin sensitivity and metabolic adaptability of the muscle, the main site of whole-body glucose utilization. We have shown previously in mice fed an obesogenic high-fat diet that a combined use of n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and thiazolidinediones (TZDs), anti-diabetic drugs, preserved metabolic health and synergistically improved muscle insulin sensitivity. We investigated here whether n-3 LC-PUFA could elicit additive beneficial effects on metabolic flexibility when combined with a TZD drug rosiglitazone. Adult male C57BL/6N mice were fed an obesogenic corn oil-based high-fat diet (cHF) for 8 weeks, or randomly assigned to various interventions: cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids (cHF+F), cHF with 10 mg rosiglitazone/kg diet (cHF+ROSI), cHF+F+ROSI, or chow-fed. Indirect calorimetry demonstrated superior preservation of metabolic flexibility to carbohydrates in response to the combined intervention. Metabolomic and gene expression analyses in the muscle suggested distinct and complementary effects of the interventions, with n-3 LC-PUFA supporting complete oxidation of fatty acids in mitochondria and the combination with n-3 LC-PUFA and rosiglitazone augmenting insulin sensitivity by the modulation of branched-chain amino acid metabolism. These beneficial metabolic effects were associated with the activation of the switch between glycolytic and oxidative muscle fibers, especially in the cHF+F+ROSI mice. Our results further support the idea that the combined use of n-3 LC-PUFA and TZDs could improve the efficacy of the therapy of obese and diabetic patients.

• MeSH
• Diet, High-Fat adverse effects   MeSH
• Glycolysis drug effects   MeSH
• Muscle Fibers, Skeletal drug effects   metabolism   MeSH
• Muscle, Skeletal drug effects   metabolism   MeSH
• Metabolomics MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Obesity etiology   metabolism   MeSH
• Fatty Acids, Omega-3 pharmacology   MeSH
• Oxidation-Reduction drug effects   MeSH
• Gene Expression Regulation drug effects   MeSH
• Rosiglitazone MeSH
• Drug Synergism MeSH
• Thiazolidinediones pharmacology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fatty Acids, Omega-3 MeSH
• Rosiglitazone MeSH
• Thiazolidinediones MeSH

BACKGROUND: n-3 polyunsaturated fatty acids, namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), reduce the risk of cardiovascular disease and can ameliorate many of obesity-associated disorders. We hypothesised that the latter effect will be more pronounced when DHA/EPA is supplemented as phospholipids rather than as triglycerides. METHODOLOGY/PRINCIPAL FINDINGS: In a 'prevention study', C57BL/6J mice were fed for 9 weeks on either a corn oil-based high-fat obesogenic diet (cHF; lipids ∼35% wt/wt), or cHF-based diets in which corn oil was partially replaced by DHA/EPA, admixed either as phospholipids or triglycerides from marine fish. The reversal of obesity was studied in mice subjected to the preceding cHF-feeding for 4 months. DHA/EPA administered as phospholipids prevented glucose intolerance and tended to reduce obesity better than triglycerides. Lipemia and hepatosteatosis were suppressed more in response to dietary phospholipids, in correlation with better bioavailability of DHA and EPA, and a higher DHA accumulation in the liver, white adipose tissue (WAT), and muscle phospholipids. In dietary obese mice, both DHA/EPA concentrates prevented a further weight gain, reduced plasma lipid levels to a similar extent, and tended to improve glucose tolerance. Importantly, only the phospholipid form reduced plasma insulin and adipocyte hypertrophy, while being more effective in reducing hepatic steatosis and low-grade inflammation of WAT. These beneficial effects were correlated with changes of endocannabinoid metabolome in WAT, where phospholipids reduced 2-arachidonoylglycerol, and were more effective in increasing anti-inflammatory lipids such as N-docosahexaenoylethanolamine. CONCLUSIONS/SIGNIFICANCE: Compared with triglycerides, dietary DHA/EPA administered as phospholipids are superior in preserving a healthy metabolic profile under obesogenic conditions, possibly reflecting better bioavalability and improved modulation of the endocannabinoid system activity in WAT.

• MeSH
• Analysis of Variance MeSH
• Adipose Tissue, White metabolism   MeSH
• Biological Availability MeSH
• Diet, High-Fat * MeSH
• Endocannabinoids * MeSH
• Phospholipids metabolism   MeSH
• Immunohistochemistry MeSH
• Liver drug effects   metabolism   MeSH
• Muscle, Skeletal metabolism   MeSH
• Real-Time Polymerase Chain Reaction MeSH
• Eicosapentaenoic Acid metabolism   MeSH
• Docosahexaenoic Acids metabolism   MeSH
• Metabolomics MeSH
• Microscopy MeSH
• Cannabinoid Receptor Modulators metabolism   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Obesity diet therapy   prevention & control   MeSH
• Fatty Acids, Omega-3 administration & dosage   metabolism   pharmacology   MeSH
• Body Weight MeSH
• Triglycerides metabolism   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Names of Substances
• Endocannabinoids * MeSH
• Phospholipids MeSH
• Eicosapentaenoic Acid MeSH
• Docosahexaenoic Acids MeSH
• Cannabinoid Receptor Modulators MeSH
• Fatty Acids, Omega-3 MeSH
• Triglycerides MeSH

Combining pharmacological treatments and life style interventions is necessary for effective therapy of major diseases associated with obesity, which are clustered in the metabolic syndrome. Acting via multiple mechanisms, combination treatments may reduce dose requirements and, therefore, lower the risk of adverse side effects, which are usually associated with long-term pharmacological interventions. Our previous study in mice fed high-fat diet indicated additivity in preservation of insulin sensitivity and in amelioration of major metabolic syndrome phenotypes by the combination treatment using n-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) and rosiglitazone, i.e. an anti-diabetic drug of the thiazolidinedione (TZD) family. We investigated here whether pioglitazone, a TZD-drug in clinical use, could elicit the additive beneficial effects when combined with n-3 LC-PUFA. Adult male mice (C57BL/6N) were fed an obesogenic corn oil-based high-fat diet (cHF) for 8 weeks, or randomly assigned to various dietary treatments (i) cHF+F, cHF with n-3 LC-PUFA concentrate replacing 15% of dietary lipids; (ii) cHF+ROSI, cHF with 10 mg rosiglitazone/kg diet; (iii) cHF+F+ROSI; (iv) cHF+PIO, cHF with 50 mg pioglitazone/kg diet; and (v) cHF+F+PIO, or chow-fed. Plasma concentrations of 163 metabolites were evaluated using a targeted metabolomics approach. Both TZDs preserved glucose homeostasis and normal plasma lipid levels while inducing adiponectin, with pioglitazone showing better effectiveness. The beneficial effects of TZDs were further augmented by the combination treatments. cHF+F+ROSI but not cHF+F+PIO counteracted development of obesity, in correlation with inducibility of fatty acid β-oxidation, as revealed by the metabolomic analysis. By contrast, only cHF+F+PIO eliminated hepatic steatosis and this treatment also reversed insulin resistance in dietary obese mice. Our results reveal differential effects of rosiglitazone and pioglitazone, unmasked in the combination treatment with n-3 LC-PUFA, and support the notion that n-3 LC-PUFA could be used as add-on treatment to TZDs in order to improve diabetic patient's therapy.

• MeSH
• Dietary Fats administration & dosage   MeSH
• Homeostasis MeSH
• Hypoglycemic Agents administration & dosage   MeSH
• Blood Glucose analysis   MeSH
• Lipids blood   MeSH
• Metabolomics MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Obesity prevention & control   MeSH
• Fatty Acids, Omega-3 administration & dosage   MeSH
• Pioglitazone MeSH
• Rosiglitazone MeSH
• Thiazolidinediones administration & dosage   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Dietary Fats MeSH
• Hypoglycemic Agents MeSH
• Blood Glucose MeSH
• Lipids MeSH
• Fatty Acids, Omega-3 MeSH
• Pioglitazone MeSH
• Rosiglitazone MeSH
• Thiazolidinediones MeSH