Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / No presente estudo, foram investigados o mecanismo central e a termogênese pelo tecido adiposo marrom (BAT) envolvidos com a perda de massa corporal (MC) observada com a administração de liraglutida (análoga do hormônio GLP1). Camundongos machos C57BL/6, foram alimentados com dieta padrão e tratados com veículo (SC) ou com liraglutida (SC/Lir) ou com dieta hiperlipídica e tratados com veículo (HF) ou com liraglutida (HF/Lir) Nossos resultados demostram que a administração de liraglutida aumentou o neuropeptídeo anorexigênico pro-opiomelanocortina no hipotálamo e diminuiu a expressão do mRNA da proteína supressora da sinalização de citocinas-3. A administração de liraglutida melhorou os níveis plasmáticos de adiponectina e diminuiu tanto a intolerância à glicose, como a resistência à insulina. Além do mais, tanto o grupo SC como o grupo HF, consumiram a mesma quantidade de comida, já o grupo SC/Lir comeu 17,5 menos comida comparado com o grupo SC e, da mesma forma, o grupo HF/lir diminuiu o consumo alimentar em 22,5% comparado com o grupo HF. A massa corporal final foi 8,5% menor no grupo SC/Lir comparado com o grupo SC e 16% menor no grupo HF comparado com o grupo HF/Lir. Além do mais, a administração de liraglutida aumentou o consumo de oxigênio e a produção de dióxido de carbono, e diminuiu o quociente respiratório. A liraglutida aumentou ainda os níveis do receptor beta 3 adrenérgico, da proteína desacopladora mitocondrial-1, do TC10 e do transportador de glicose estimulado pela insulina (GLUT)-4 no BAT. Em conclusão, a administração de liraglutida em camundongos obesos induzidos por dieta ativou a via anorexigênica, diminuindo o consumo alimentar, atuando sinergicamente com o aumento do gasto energético.

Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro / Indivíduos obesos apresentam maior risco de morbidade e mortalidade atribuída às doenças cardiovasculares. A composição da dieta é um fator que prediz o fenótipo cardíaco em resposta a obesidade e, o tipo de ácido graxo pode afetar de forma diferencial a estrutura e a função do miocárdio. Estudos têm mostrado que a disfunção mitocondrial exerce um papel chave na patogênese da insuficiência e hipertrofia cardíaca, e as alterações mitocondriais observadas em falhas cardíacas apontam para defeitos em sítios específicos da cadeia transportadora de elétrons. Desta forma, o objetivo deste estudo foi avaliar a função contrátil ventricular em camundongos, alimentados com dieta hiperlipídica, rica em ácidos graxos poliinsaturados, buscando elucidações através da bioenergética mitocondrial. Após desmame, camundongos machos C57Bl/6 passaram a receber dieta manipulada contendo 7% (C) ou 19% (HF) de óleo de soja, até os 135 dias de idade. A ingestão alimentar e a massa corporal foram monitoradas e foi realizado teste de tolerância à glicose. No final do período experimental, os animais foram anestesiados e submetidos à avaliação da composição corporal por Absortimetria de Raios X de Dupla Energia (DXA), e em seguida, sacrificados por exsanguinação. No plasma foram determinados o perfil lipídico e a insulina. O coração, o tecido adiposo intra-abdominal e o subcutâneo foram coletados, pesados, processados para análise histomorfológica. Fibras cardíacas do ventrículo esquerdo foram utilizadas para análise da respiração mitocondrial através de oxígrafo. O coração também foi utilizado para a técnica de perfusão de coração isolado de Langendorff, e para análise da expressão de proteínas relacionadas à bioenergética de cardiomiócitos, através de Western Blotting. O índice de HOMA e de adiposidade foram calculados. O grupo HF apresentou maior adiposidade, sem alteração na ingestão alimentar. Foi observada intolerância a glicose, hiperinsulinemia e resistência à insulina, além de alterações desfavoráveis no perfil lipídico. Foi observado alteração na morfologia cardíaca e quadro de cardiomiopatia hipertrófica, refletindo em alteração hemodinâmica, determinando maior contratilidade, maior pressão ventricular e função diastólica prejudicada. Em relação à atividade mitocondrial dos cardiomiócitos foi observada menor oxidação de carboidratos (-47%) e de ácidos graxos (-60%). Porém, sem alteração na expressão de proteínas relacionadas à bioenergética de cardiomiócitos, CPT1, UCP2, GLUT1, GLUT4, AMPK e pAMPK. A partir desses resultados, concluímos que o tipo e a quantidade de ácidos graxos predizem o fenótipo cardíaco na obesidade, promovendo alteração na capacidade oxidativa mitocondrial, na morfologia e na hemodinâmica cardíaca / Obese individuals have a higher risk of morbidity and mortality attributed to cardiovascular disease. The diet composition is one factor that predicts the cardiac phenotype in response to obesity and the type of fatty acid differentially influences the myocardial structure and function. Studies have showed that mitochondrial dysfunction is considered to play a key role in the pathogenesis of cardiac hypertrophy and failure, also the mitochondrial alterations present in heart failure indicate to defects at specific sites in electron transport chain. Thus, the aim of the study was evaluated the ventricular contractile function in mice fed high fat diet, rich in polyunsaturated fatty acids, looking through mitochondrial bioenergetics. After weaning, mouse C57Bl/6 received manipulated diet containing 7% (C) or 19% (HF) of soybean oil, until 135 days of age. The food intake and the body mass were monitored, and the glucose tolerance test was realized. At the end of the experimental period, the animals had their body composition evaluated by Dual-energy X-ray Absorptiometry (DXA), after, were sacrificed by exsanguination. In plasma was determined the lipid profile and insulin. The heart, intraabdominal and subcutaneous adipose tissue were collected, weighted and processed to morphological analysis. The left ventricular myocardial fibers were used to analyze mitochondrial respiration by technique of high resolution respirometry. The heart was used to the Langendorff technique of isolated heart perfusion, and to analyze the expression of proteins related to the cardiomyocytes bioenergetics, through of Western Blotting. The HOMA-IR and the adiposity index were calculated. The group HF showed higher adiposity, but did not differ about food intake. Was observed glucose intolerance, hiperinsulinemia, insulin resistance and also unfavorable alterations in lipid profile. Was observed alterations in cardiac morphology and hypertrophic cardiomyopathy, reflecting in hemodinamic alterations with increase of contractility, higher ventricular pressure and impaired diastolic function. About the mitochondrial activity of cardiomyocytes was observed lower oxidation of carbohydrates (-47%) and fatty acids (-60%). However, the expression of proteins related to the cardiomyocytes bioenergetics, CPT1, UCP2, GLUT1, GLUT4, AMPK e pAMPK, did not differ between the groups. From these results, we conclude that the type and amount of fatty acids predict the cardiac phenotype in obesity, promoting the impairment of mitochondrial oxidative capacity, alterations in cardiac morphology and hemodynamics

Orientador: Thais Borges César / Banca: Elizabeth A. Baldwin / Banca: Paulo Inácio Costa / Banca: Anderson Marliere Navarro / Banca: Paula Garcia Chiarello / Resumo: Objetivos: Avaliar os efeitos da eriocitrina nas alterações do metabolismo, inflamação e estresse oxidativo causados pela dieta hiperlipídica em camundongos e seu metabolismo, farmacocinética e biodistribuição em ratos. Métodos: Sessenta camundongos C57BL/6J foram divididos aleatoriamente em seis grupos (n=10 cada), quatro grupos foram alimentados com dieta hiperlipídica por quatro semanas, e então suplementados com 10, 25, 50 ou 100 mg/kg de eriocitrina por mais quatro semanas. Outros dois grupos incluíram um grupo alimentado com dieta padrão, e outro com dieta hiperlipídica sem suplemento por oito semanas. Foram avaliados o perfil lipídico, glicêmico, lipídios e gordura hepática, inflamação e estresse oxidativo sistêmicos. Para o estudo farmacocinético, e de biodistribuição, 36 ratos Wistar machos receberam 100 mg/kg de eriocitrina e foram divididos em 12 grupos de 3 ratos cada, de acordo com os tempos de coleta: 0, 0,5, 1, 3, 4, 5, 6, 8, 10, 12, 15 e 24 h. Foram coletados o sangue, órgãos e urina para análises de HPLC-MS e espectroscopia de infravermelho dos metabólitos de eriocitrina. Resultados: No primeiro estudo, o grupo alimentado com dieta hiperlipídica apresentou aumento do peso corporal, gordura abdominal e dos níveis séricos de glicose, insulina, triglicerídeos, colesterol total, resistina, leptina e peroxidação lipídica (p <0,05). No entanto, reduções desses marcadores foram observadas com todas as doses de eriocitrina, entre as quais a dose de 25 mg/kg foi a mai... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Aim: To assess the effect of eriocitrin on metabolic, inflammatory and oxidative stress changes caused by high-fat diet induced obesity in mice; and its metabolism, pharmacokinetics and biodistribution in rats. Methods: Sixty C57BL/6J mice were randomly divided into six groups (n = 10 each), four of them were fed a high-fat diet for four weeks, and then supplemented with 10, 25, 50 or 100 mg/kg eriocitrin for another four weeks. Two other groups included one group fed a standard diet, and one group fed high-fat diet for eight weeks, both without supplementation. The lipidemia, glycemia, hepatic fats, systemic inflammation and oxidative stress were evaluated. For the pharmacokinetic and biodistribution study, 36 male Wistar rats were orally administered 100 mg/kg eriocitrin and divided into 12 groups of 3 rats each, according to the following time points: 0, 0.5, 1, 3, 4, 5, 6, 8, 10, 12, 15 and 24 h. Blood, organs, and urine were collected at each time point, and the eriocitrin metabolites were extracted and analyzed by HPLC-MS and infrared spectroscopy. Results: In the first study, the group fed high-diet presented increased body weight, abdominal fat, and glucose, insulin, triglycerides, total-cholesterol, resistin, leptin and lipid peroxidation in the serum (p< 0.05). However, positive effects of eriocitrin were observed with all of the doses tested, whereas the dose 25 mg/kg bw was the most effective. It decreased significantly the triglycerides (-33%), and improved gluco... (Complete abstract click electronic access below) / Doutor

Ad libitum high-fat diet (HFD)-induced obesity leads to insulin resistance in skeletal muscle, altered gene expression, and altered growth signaling, all of which contributes to pathological changes in metabolism. Liver kinase B1 (LKB1) is an important metabolism regulator. The purpose of this dissertation was to understand how knocking out LKB1 influences HFD induced adaptations in mouse skeletal muscle. To do so, control and skeletal muscle LKB1 knock-out (LKB1-KO) mice were put on either standard diet (STD) or HFD for 1 week or 14 weeks, or put on the HFD for 14 weeks and then switched to STD for 1 week (switched diet). The major differences in adaptation in the LKB1-KO mice include: 1) lower fasting blood glucose levels but impaired glucose tolerance compared to WT mice (although conflicting results are generated if the data is not normalized to fasting blood glucose levels), 2) altered expression of 16 HFD-induced genes, and 3) decreased muscle weight. The lower fasting blood glucose in LKB1-KO mice was likely due to elevated serum insulin levels, and the impaired glucose tolerance was associated with decreased phosphorylation of TBC1D1, an important regulator of insulin stimulated glucose uptake. 16 potential important target genes (metabolism, mitochondrial, cytoskeleton, cell cycle, cell-cell interactions, enzyme, ion channel) were identified in the context of HFD feeding and LKB1-KO. These genes were quantified by RT-PCR and grouped according to changes in their patterns of expression among the different groups. Among several other interesting changes in gene expression, the muscle growth-related protein, Ky was not affected by short-term HFD, but increased after long-term HFD, and did not decrease after switched diet, showing that its expression may be an important long-term adaptation to HFD. LKB1-KO promoted anabolic signaling through increasing t-eIF2α and eIF4E expression, and promoted protein degradation through increasing protein ubiquitination. Because the degradation is the main effect and lead to muscle weight decrease. The effect of HFD and/or LKB1-KO on the LKB1-AMPK system was also determined. The results showed that knocking-out LKB1 decreased AMPK activity, decreased nuclear distribution for AMPK α2 and increased AMPK α1 expression. Long-term HFD increased t-AMPK expression in LKB1-KO mice, decreased the cytoplasm p-AMPK and nuclear p/t-AMPK ratio in CON mice. Together the findings of this dissertation demonstrated HFD induced glucose/insulin tolerance, while LKB1-KO had a controversial effect on glucose/insulin sensitivity. Both HFD and LKB1-KO affect AMPK expression and cellular location, while LKB1-KO also affects AMPK activity. LKB1-KO promoted protein degradation through ubiquitination in skeletal muscle.

Diabetic cardiomyopathy characterized by left ventricular hypertrophy predisposes diabetic and obese individuals to development of cardiac dysfunction and subsequently to heart failure. Whether hyperinsulinemia has an underlying role in development and or progression of diabetic heart disease is not well understood. We therefore studied the effects of acute hyperinsulinemia on cardiac function in euglycemic states. Acute hyperinsulinemia neither affected baseline nor inotropic response to β-adrenergic stimulation. Previous studies from our laboratory have indicated a potential role for GRK2, a serine threonine kinase in development of cardiac dysfunction in diabetic states in humans as well as in mice. To assess whether GRK2 mediates the detrimental effects of chronic hyperinsulinemia on cardiac dysfunction in mouse model of diet induced obesity, we utilized cardiomyocyte knockout of GRK2. Our results suggested lack of cardiac functional impairments in high fat fed wildtype mice, which hindered our attempts to ascertain the role of GRK2 in diabetic cardiomyopathy. Mouse models of diet induced obesity have been routinely used to study the effects of obesity and diabetes on cardiac dysfunction but recent evidence from multiple research groups has emphasized the need for evaluation of the utility and relevance of the murine diet induced obesity model for studying cardiovascular abnormalities associated with hyperinsulinemic states, including T2DM and obesity. We therefore studied the effect of chronic fat feeding (>20 weeks) alone or in combination with concomitant hypertension on cardiac function in C57BL/6J mice. Different diets were formulated with either lard (32% saturated fat, 68% unsaturated fat) or hydrogenated coconut oil (95% saturated fat) as the source of fat and fatty acids, which contributed 60% of total calories. Insulin resistance and glucose intolerance were readily observed in mice fed a high fat diet in each of the studies. HFD resulted in the development of cardiac hypertrophy; however cardiac function as measured by B-mode echocardiography and LV catheterization was unaffected in high fat diet groups compared to their respective control diet groups. Further, dietary fat feeding regardless of the source of fat modestly altered the gene expression of a few pathological hypertrophic markers or of fibrosis related genes. However, there was an increase in expression of PPARa target genes such as Pdk4 and fatty acid metabolism genes including CD36, AcadL and Cpt1b. Cardiac mitochondrial function as assessed by oxygen consumption rates, ATP synthesis rates and reactive oxygen species production rates were unaltered in high fat diet fed mice. These results suggest that while chronic fat feeding in mice causes cardiac hypertrophy and potentially cardiometabolic remodeling, it might not be sufficient to activate pathological hypertrophic mechanisms that impair cardiac function and cause cardiac fibrosis.

Peripheral blood mononuclear cells (PBMCs) can respond to dietary stimuli modulating the up-regulation of pro-inflammatory cell signaling, which is associated with metabolic disease and has been seen to be elevated in African American (AA) when compared to Caucasian American (CA) women. Little is known about the response of PBMCs to a high fat meal among women and the potential impact of ethnicity and/or weight status on this response. The purpose of this study was to examine PBMC response to consuming a high fat meal and the response to culturing PBMCs in media supplemented with lipid among AA and CA women, and to determine the impact that ethnicity and/or weight status may have on this response. Twenty-one women participated in the study: 10 AA (age: 28.00±6.60), 11 CA (age: 26.91±6.28), of whom 11 were lean (BMI

Thesis (M.Sc. (Chemical Pathology)) --University of Limpopo, 2013 / Objectives The present study investigated how the serum lipids responded to a high-fat meal in black South African subjects with different APOE genotypes, a population that until recently was reported to be consuming a traditional diet of low fat and high carbohydrates. Methods Sixty students (males and females) of the University of Limpopo, Turfloop Campus were successfully genotyped using Restriction Fragment Length Polymorphism (RFLP) and grouped into four APOE genotype groups; ε2, ε2/ε4, ε3 and ε4. Only thirty-three subjects volunteered to participate in the oral fat-tolerance test (OFTT), but two were excluded for having abnormal total cholesterol (6.05 mmol/l) and LDL cholesterol (3.12 mmol/l) so only 31 subjects were left. The numbers per group were ε2=5, ε2/ε4=8, ε3=9 and ε4=9. After an overnight fast blood was drawn for measurements of baseline serum parameters. Subjects were administered a high fat meal 30 minutes after the baseline blood sample was drawn. Blood was drawn at intervals of 20, 40, 60, 120, 180, 240, 300 and 360 minutes for measurements of postprandial serum parameter levels. Serum parameters measured were triglyceride, total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, glucose and insulin. Results Mean levels of serum lipids at baseline in mmol/l were as follows; group 1[TG=0.69(0.55-0.81), TCHOL=3.10±0.29, HDL-C=1.12±0.32, LDLC= 1.67±0.28]; group 2 [TG=0.61(0.53-1.00), TCHOL=2.98±0.53, HDLC= 1.20±0.37, LDL-C=1.43±0.37]; group 3 [TG=0.67(0.28-0.86), TCHOL=2.96±0.54, HDL-C=1.22±0.30, LDL-C=1.46±0.47]; group 4 [TG=0.76(0.51-1.16), TCHOL=3.27±0.51, HDL-C=1.12±0.17, LDLC= 1.79±0.47]. There was no significant difference in the mean levels of baseline triglyceride, total cholesterol, low density lipoprotein cholesterol, and ix high density lipoprotein cholesterol between the APOE groups hence no significant difference in the response to a fatty meal. Conclusions There was no significant change in serum lipid concentrations after a fatty meal in individuals with different APOE genotypes in a population that consume a traditional diet of low fat and high carbohydrates. Due to the small sample size, the results should be interpreted with caution. A larger study is recommended to ascertain the role of APOE genotypes on serum lipid response to a fatty meal in Black South African population.

Syftet med denna pilotstudie var att studera om man hos pediatriska patienter som lider av sjuklig fetma kan se förändringar i metabolismen genom att ersätta den traditionella kosten med en kost bestående av hög andel fett och låg andel kolhydrater. De frågeställningar som används är om den förändrade kosten leder till en gynnsam förändring av metabola markörer samt hur patientupplevelsen av de nya kostråden är. Studien har både en kvantitativ och kvalitativ design. Totalt ingår 4 barn i åldern 4-17 år. Två av dessa har under fyra veckor ätit en kost bestående av hög andel fett (50-60E%) och låg andel kolhydrater (15-20E%). Efter avslutad intervention undersöktes hur metabola parametrar förändrats (blodprov) samt hur patienterna upplevt kosten (frågeformulär). Resultatet visar på att kostråden leder till en sänkning av triglycerider, glukos, HDL, total kolesterol och ASAT. Bland kontrollpatienterna ser man en ökning av triglycerider, HDL och total kolesterol. Upplevelsen av kostråden beskrivs som positiva, trots att nackdelar finns. Det finns en positiv attityd till att fortsätta med kostråden.

Type II diabetes mellitus (T2DM) has been associated with the onset of diet-induced obesity, which is currently on the rise worldwide. T2DM is typically characterized by insulin resistance in peripheral tissues such as adipose tissue, liver, and skeletal muscle. In skeletal muscle it is widely accepted that the defective insulin action is due to the inability of the cell to sufficiently activate the insulin signalling pathway and promote systemic glucose uptake. The sarcolipin-null (KO) mouse is a potential novel model for diet-induced obesity and diabetes. KO mice become significantly more obese and display a greater glucose intolerance than wildtype (WT) mice following an 8-week high-fat diet (HFD; 42% calories from fat) but the underlying mechanisms are still unknown. In this study the role of defective skeletal muscle insulin signalling in the development of the impaired glucose tolerance in KO mice was investigated. It was hypothesized that the HFD fed KO mice would exhibit greater reductions in IRS1 tyr628 and Akt ser473 phosphorylation (i.e. decreased activation of the insulin signalling pathway) than controls. Furthermore, it was believed that KO mice would display increased phosphorylation of IRS1 ser307, which is commonly associated with insulin resistance. At 16-weeks of age KO mice and littermates were subdivided into two groups and placed on either a HFD (n=30) or chow diet (n=24) for an 8-week period. Changes in body weight, glucose tolerance, and insulin tolerance were assessed pre- and post-diet period. Following the completion of the diet intervention mice were treated with an intraperitoneal injection of insulin (0.75U/kg) or vehicle solution and sacrificed for tissue collection. Epididymal/inguinal and retroperitoneal fat pads were removed for assessment of whole body adiposity. Whole gastrocnemius muscle was excised and homogenized for Western blot analysis of several key proteins of the insulin signalling cascade. Following completion of the HFD KO mice (48.6 ± 1.6 g) weighed significantly more than HFD fed wildtype (WT) mice (41.5 ± 1.6 g), and all chow fed mice (KO: 36.8 ± 1.5 g; WT: 35.2 ± 1.2 g; p<0.001). Glucose tolerance testing showed that KO mice exhibited significantly greater glucose intolerance compared to control mice post-HFD (p<0.001). Insulin tolerance testing, however, revealed no change in insulin sensitivity in KO or WT mice post-HFD (p>0.05). The HFD fed KO mice (0.73 ± 0.06 g) had an elevated retroperitoneal fat pad weight than HFD fed WT (0.49 ± 0.05 g) and all chow fed mice (KO: 0.28 ± 0.04 g; WT: 0.24 ± 0.04 g; p<0.01). Western blot analysis revealed a similar reduction in insulin receptor substrate-1 (IRS1) tyr628 phosphorylation in both KO and WT mice following the HFD (Con WT: 2.82 ± 0.69; Con KO: 3.06 ± 0.73; HFD WT: 1.71 ± 0.28; HFD KO: 1.28 ± 0.11 fold increase over non-insulin stimulated mice; p<0.02). IRS1 ser307 phosphorylation was elevated in both genotypes post-HFD (HFD WT: 2.97 ± 1.19; HFD KO: 2.17 ± 0.59 fold increase over standard chow fed control mice; p<0.03). Insulin treatment did not stimulate phosphorylation of Akt ser473 in KO or WT mice regardless of diet (p>0.05). In summary there was no difference between KO and WT mice in skeletal muscle insulin sensitivity as assessed by the phosphorylation of insulin signalling intermediates. An increase in IRS1 ser307 phosphorylation appears to be the primary mechanism for the reduced activation of IRS1 following the HFD in both KO and WT mice. However, the results from the current investigation did not support the notion that impaired skeletal muscle insulin signalling is responsible for the more pronounced diet-induced glucose intolerance observed in KO mice. Future studies investigating the viability of skeletal muscle GLUT4 translocation and glucose uptake as well as the glucose-induced insulin secretion of pancreatic β-cells following consumption of a HFD would help elucidate the mechanism of glucose intolerance in KO mice.

Type II diabetes mellitus (T2DM) has been associated with the onset of diet-induced obesity, which is currently on the rise worldwide. T2DM is typically characterized by insulin resistance in peripheral tissues such as adipose tissue, liver, and skeletal muscle. In skeletal muscle it is widely accepted that the defective insulin action is due to the inability of the cell to sufficiently activate the insulin signalling pathway and promote systemic glucose uptake. The sarcolipin-null (KO) mouse is a potential novel model for diet-induced obesity and diabetes. KO mice become significantly more obese and display a greater glucose intolerance than wildtype (WT) mice following an 8-week high-fat diet (HFD; 42% calories from fat) but the underlying mechanisms are still unknown. In this study the role of defective skeletal muscle insulin signalling in the development of the impaired glucose tolerance in KO mice was investigated. It was hypothesized that the HFD fed KO mice would exhibit greater reductions in IRS1 tyr628 and Akt ser473 phosphorylation (i.e. decreased activation of the insulin signalling pathway) than controls. Furthermore, it was believed that KO mice would display increased phosphorylation of IRS1 ser307, which is commonly associated with insulin resistance. At 16-weeks of age KO mice and littermates were subdivided into two groups and placed on either a HFD (n=30) or chow diet (n=24) for an 8-week period. Changes in body weight, glucose tolerance, and insulin tolerance were assessed pre- and post-diet period. Following the completion of the diet intervention mice were treated with an intraperitoneal injection of insulin (0.75U/kg) or vehicle solution and sacrificed for tissue collection. Epididymal/inguinal and retroperitoneal fat pads were removed for assessment of whole body adiposity. Whole gastrocnemius muscle was excised and homogenized for Western blot analysis of several key proteins of the insulin signalling cascade. Following completion of the HFD KO mice (48.6 ± 1.6 g) weighed significantly more than HFD fed wildtype (WT) mice (41.5 ± 1.6 g), and all chow fed mice (KO: 36.8 ± 1.5 g; WT: 35.2 ± 1.2 g; p<0.001). Glucose tolerance testing showed that KO mice exhibited significantly greater glucose intolerance compared to control mice post-HFD (p<0.001). Insulin tolerance testing, however, revealed no change in insulin sensitivity in KO or WT mice post-HFD (p>0.05). The HFD fed KO mice (0.73 ± 0.06 g) had an elevated retroperitoneal fat pad weight than HFD fed WT (0.49 ± 0.05 g) and all chow fed mice (KO: 0.28 ± 0.04 g; WT: 0.24 ± 0.04 g; p<0.01). Western blot analysis revealed a similar reduction in insulin receptor substrate-1 (IRS1) tyr628 phosphorylation in both KO and WT mice following the HFD (Con WT: 2.82 ± 0.69; Con KO: 3.06 ± 0.73; HFD WT: 1.71 ± 0.28; HFD KO: 1.28 ± 0.11 fold increase over non-insulin stimulated mice; p<0.02). IRS1 ser307 phosphorylation was elevated in both genotypes post-HFD (HFD WT: 2.97 ± 1.19; HFD KO: 2.17 ± 0.59 fold increase over standard chow fed control mice; p<0.03). Insulin treatment did not stimulate phosphorylation of Akt ser473 in KO or WT mice regardless of diet (p>0.05). In summary there was no difference between KO and WT mice in skeletal muscle insulin sensitivity as assessed by the phosphorylation of insulin signalling intermediates. An increase in IRS1 ser307 phosphorylation appears to be the primary mechanism for the reduced activation of IRS1 following the HFD in both KO and WT mice. However, the results from the current investigation did not support the notion that impaired skeletal muscle insulin signalling is responsible for the more pronounced diet-induced glucose intolerance observed in KO mice. Future studies investigating the viability of skeletal muscle GLUT4 translocation and glucose uptake as well as the glucose-induced insulin secretion of pancreatic β-cells following consumption of a HFD would help elucidate the mechanism of glucose intolerance in KO mice.