Reduced dietary omega-6 to omega-3 fatty acid ratio and 12/15-lipoxygenase deficiency are protective against chronic high fat diet-induced steatohepatitis

Obesity is associated with metabolic perturbations including liver and adipose tissue inflammation, insulin resistance, and type 2 diabetes. Omega-6 fatty acids (ω6) promote and omega-3 fatty acids (ω3) reduce inflammation as they can be metabolized to pro- and anti-inflammatory eicosanoids, respectively. 12/15-lipoxygenase (12/15-LO) enzymatically produces some of these metabolites and is induced by high fat (HF) diet. We investigated the effects of altering dietary ω6/ω3 ratio and 12/15-LO deficiency on HF diet-induced tissue inflammation and insulin resistance. We examined how these conditions affect circulating concentrations of oxidized metabolites of ω6 arachidonic and linoleic acids and innate and adaptive immune system activity in the liver. For 15 weeks, wild-type (WT) mice were fed either a soybean oil-enriched HF diet with high dietary ω6/ω3 ratio (11∶1, HFH), similar to Western-style diet, or a fat Kcal-matched, fish oil-enriched HF diet with a low dietary ω6/ω3 ratio of 2.7∶1 (HFL). Importantly, the total saturated, monounsaturated and polyunsaturated fat content was matched in the two HF diets, which is unlike most published fish oil studies in mice. Despite modestly increased food intake, WT mice fed HFL were protected from HFH-diet induced steatohepatitis, evidenced by decreased hepatic mRNA expression of pro-inflammatory genes and genes involved in lymphocyte homing, and reduced deposition of hepatic triglyceride. Furthermore, oxidized metabolites of ω6 arachidonic acid were decreased in the plasma of WT HFL compared to WT HFH-fed mice. 12/15-LO knockout (KO) mice were also protected from HFH-induced fatty liver and elevated mRNA markers of inflammation and lymphocyte homing. 12/15-LOKO mice were protected from HFH-induced insulin resistance but reducing dietary ω6/ω3 ratio in WT mice did not ameliorate insulin resistance or adipose tissue inflammation. In conclusion, lowering dietary ω6/ω3 ratio in HF diet significantly reduces steatohepatitis.Fil: Lazic, Milos. University of California at San Diego; Estados UnidosFil: Inzaugarat, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Povero, Davide. University of California at San Diego; Estados UnidosFil: Zhao, Iris C.. University of California at San Diego; Estados UnidosFil: Chen, Mark. University of California at San Diego; Estados UnidosFil: Nalbandian, Madlena. University of California at San Diego; Estados UnidosFil: Miller, Yury I.. University of California at San Diego; Estados UnidosFil: Cherñavsky, Alejandra Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Feldstein, Ariel E.. University of California at San Diego; Estados UnidosFil: Sears, Dorothy D.. University of California at San Diego; Estados Unido

Study of Factors Regulating Metabolic Syndrome and Insulin Resistance

Metabolic syndrome, also known as syndrome X and insulin resistance syndrome, is a global pandemic that has been exponentially increasing throughout the last two decades. Obesity and insulin resistance are the primary components of metabolic syndrome. Our study aimed to identify factors regulating insulin resistance by further increasing our knowledge of 12/15 lipoxygenase along with a implementing a dietary intervention to reduce insulin resistance. We tested the hypothesis that 12/15 lipoxygenase transgenic mice on a 45% HFD after 10 weeks would have significantly greater insulin resistance than the wildtype mice. We also hypothesized that a dietary intervention with low glycemic index bread products along with omega-3 and polyphenol supplements for 12 weeks should decrease insulin resistance and lower the risk of developing chronic diseases more effectively than a placebo-controlled diet. The 12/15-lipoxygenase mice study showed that the 12/15 lipoxygenase transgenic mice had significantly higher fasting plasma glucose concentrations, fasting insulin concentrations, plasma triglyceride concentration, and greater gWAT percentage of body weight compared to the wildtype mice. The study also suggested that the 12/15- lipoxygenase mice had greater systemic insulin resistance than the wildtype mice. The dietary intervention study, although incomplete at this stage, showed trends for enhanced insulin sensitivity with the active diet, body weight loss, fat mass loss, waist circumference decrease and improvements in lipid panel were significant in both diet groups. These studies shed new light on mechanisms regulating insulin resistanc

Study of Factors Regulating Metabolic Syndrome and Insulin Resistance

Metabolic syndrome, also known as syndrome X and insulin resistance syndrome, is a global pandemic that has been exponentially increasing throughout the last two decades. Obesity and insulin resistance are the primary components of metabolic syndrome. Our study aimed to identify factors regulating insulin resistance by further increasing our knowledge of 12/15 lipoxygenase along with a implementing a dietary intervention to reduce insulin resistance. We tested the hypothesis that 12/15 lipoxygenase transgenic mice on a 45% HFD after 10 weeks would have significantly greater insulin resistance than the wildtype mice. We also hypothesized that a dietary intervention with low glycemic index bread products along with omega-3 and polyphenol supplements for 12 weeks should decrease insulin resistance and lower the risk of developing chronic diseases more effectively than a placebo-controlled diet. The 12/15-lipoxygenase mice study showed that the 12/15 lipoxygenase transgenic mice had significantly higher fasting plasma glucose concentrations, fasting insulin concentrations, plasma triglyceride concentration, and greater gWAT percentage of body weight compared to the wildtype mice. The study also suggested that the 12/15- lipoxygenase mice had greater systemic insulin resistance than the wildtype mice. The dietary intervention study, although incomplete at this stage, showed trends for enhanced insulin sensitivity with the active diet, body weight loss, fat mass loss, waist circumference decrease and improvements in lipid panel were significant in both diet groups. These studies shed new light on mechanisms regulating insulin resistanc

Reduced dietary omega-6 to omega-3 fatty acid ratio and 12/15-lipoxygenase deficiency are protective against chronic high fat diet-induced steatohepatitis.

Obesity is associated with metabolic perturbations including liver and adipose tissue inflammation, insulin resistance, and type 2 diabetes. Omega-6 fatty acids (ω6) promote and omega-3 fatty acids (ω3) reduce inflammation as they can be metabolized to pro- and anti-inflammatory eicosanoids, respectively. 12/15-lipoxygenase (12/15-LO) enzymatically produces some of these metabolites and is induced by high fat (HF) diet. We investigated the effects of altering dietary ω6/ω3 ratio and 12/15-LO deficiency on HF diet-induced tissue inflammation and insulin resistance. We examined how these conditions affect circulating concentrations of oxidized metabolites of ω6 arachidonic and linoleic acids and innate and adaptive immune system activity in the liver. For 15 weeks, wild-type (WT) mice were fed either a soybean oil-enriched HF diet with high dietary ω6/ω3 ratio (11∶1, HFH), similar to Western-style diet, or a fat Kcal-matched, fish oil-enriched HF diet with a low dietary ω6/ω3 ratio of 2.7∶1 (HFL). Importantly, the total saturated, monounsaturated and polyunsaturated fat content was matched in the two HF diets, which is unlike most published fish oil studies in mice. Despite modestly increased food intake, WT mice fed HFL were protected from HFH-diet induced steatohepatitis, evidenced by decreased hepatic mRNA expression of pro-inflammatory genes and genes involved in lymphocyte homing, and reduced deposition of hepatic triglyceride. Furthermore, oxidized metabolites of ω6 arachidonic acid were decreased in the plasma of WT HFL compared to WT HFH-fed mice. 12/15-LO knockout (KO) mice were also protected from HFH-induced fatty liver and elevated mRNA markers of inflammation and lymphocyte homing. 12/15-LOKO mice were protected from HFH-induced insulin resistance but reducing dietary ω6/ω3 ratio in WT mice did not ameliorate insulin resistance or adipose tissue inflammation. In conclusion, lowering dietary ω6/ω3 ratio in HF diet significantly reduces steatohepatitis

Schematic of diets and mouse groups.

<p>(A) Schematic illustrates the dietary ω6/ω3 fatty acid ratio, and the mg/kg/day intake of total ω3 fatty acid, EPA, DHA and EPA+DHA in the HFH and HFL diets consumed by the mice. For comparison, the approximate mg/kg/day dose of EPA+DHA for an 80 kg human taking a standard prescription of Lovaza fish oil (four 1 g capsules, containing 840 mg EPA+DHA each, per day) is shown. (B) 15-week diet regimens for WT mice: normal chow diet (13% Kcal from fat), high fat diet (46% kcal from fat) with high dietary ω6/ω3 ratio (HFH), or high fat diet (46% kcal from fat) with low dietary ω6/ω3 (HFL). (C) 15-week diet regimens for WT and 12/15-LOKO mice: high fat diet (46% kcal from fat) with high dietary ω6/ω3 ratio (HFH). FA, fatty acids; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid.</p

Plasma concentration of the major ω6 fatty acids and their corresponding pro-inflammatory metabolites.

<p>The effect of varying dietary ω6/ω3 ratio in high fat diet-fed WT mice on plasma concentrations of oxidized metabolites of (A) arachidonic acid and (B) linoleic acid. (C) Plasma concentrations of arachidonic and linoleic acids. NC n = 3 (open bars), HFH n = 7 (black bars), HFL n = 8 (gray bars). T-test analysis was restricted to HF diet animals only. Values are mean ±SE. *P<0.05 HFH vs. HFL. NC, normal control (chow); HFH, high dietary ω6/ω3 ratio; HFL, low dietary ω6/ω3 ratio; HETE, hydroxyeicosatetraenoic acid; HODE, hydroxyoctadecadienoic acid; oxoODE, oxooctadecadienoic acid.</p

Assessment of hepatic inflammation and steatosis in 12/15-LOKO mice on HFH diet.

<p>The effect of 12/15-lipoxygenase deficiency on (A) terminal body weight, food intake and gonadal white adipose tissue (gWAT) weight expressed as percent total body weight, and hepatic expression of (B) regulators of lymphocyte homing response, (C) pro/anti-inflammatory cytokines and (D) neutrophil chemoattractants. (E) Haematoxylin-eosin and Oil red O staining of paraffin-embedded liver sections to show hepatic steatosis. (F) Quantitative grading scale assessing the quantity of hepatic triglycerides, normalized to signal in WT NC (n = 7) mice (expressed as a fold increase in stained area relative to WT NC mice). (G) Plasma concentrations of oxidized metabolites of arachidonic acid in KO HFH n = 4 (dark gray bars) compared to WT HFH n = 7 (black bars) mice. Values are mean ±SE. *P<0.05, **P<0.01 WT HFH vs. 12/15-LOKO HFH. Scale bar, 50 µm. WT NC SEs for genes Ccr7, Ccl19, Ccl21, Ifng, Tnfa, Il10, Cxcl1 (KC), Cxcl2/3 (MIP-2) were 0.20, 0.21, 0.15, 0.08, 0.12, 0.17, 0.14, 0.13, respectively. WT NC SE value for oil red O stain was 0.15. KO, 12/15 lipoxygenase knockout; HFH, high dietary ω6/ω3 ratio; gWAT, gonadal white adipose tissue; HETE, hydroxyeicosatetraenoic acid.</p

Metabolic parameters in WT mice fed NC, HFH, and HFL diets.

<p>NC, normal chow; HFH, high dietary ω6/ω3 ratio; HFL, low dietary ω6/ω3 ratio; HOMA-IR, homeostatic model assessment of insulin resistance; gWAT, gonadal white adipose tissue.</p>a<p>Data were not available for liver weight, fasting insulin and glucose for 4 NC mice.</p>b<p>Student's t-test was restricted to high fat diet groups (HFH vs. HFL). NC data are shown for comparison.</p><p>Metabolic parameters in WT mice fed NC, HFH, and HFL diets.</p

Assessment of hepatic inflammation and steatosis.

<p>The effect of varying dietary ω6/ω3 ratio in high fat diet-fed WT mice on the hepatic mRNA expression of (A) cytokines driving a Th1 profile, (B) pro/anti-inflammatory cytokines, (C) neutrophil chemoattractants, and (D) regulators of lymphocyte homing response, all normalized to signal in WT NC mice (n = 7). (E) Haematoxylin-eosin and Oil red O staining of paraffin-embedded liver sections. Quantitative grading scale assessing the quantity of hepatic triglycerides, normalized to signal in WT NC mice (expressed as a fold increase in stained area relative to WT NC mice). (F) The effect of varying dietary ω6/ω3 ratio in high fat diet-fed WT mice on the hepatic mRNA expression of sterol regulatory element-binding protein 1 (Srebp1) normalized to signal in WT NC mice. WT HFH: black bars; WT HFL: gray bars. Values are mean ±SE. 5-7 animals per group. *P<0.05, **P<0.01, ***P<0.001 HFH vs. HFL. Scale bar, 50 µm. WT NC SEs for genes Il12a (p35), Il12b (p40), Il18, Ifng, Tnfa, Il10, Cxcl1 (KC), Cxcl2/3 (Mip2), Ccr7, Ccl19, Ccl21 and Srebp1 were 0.14, 0.09, 0.14, 0.08, 0.12, 0.17, 0.14, 0.13, 0.20, 0.21, 0.15, and 0.10, respectively. WT NC SE value for oil red O stain was 0.15. NC, normal control (chow); HFH, high dietary ω6/ω3 ratio; HFL, low dietary ω6/ω3 ratio.</p