High Fat Diet Induced Obesity Impairs Skeletal Muscle Glycogen and Lipid Preservation After Adiponectin Incubation

High fat diets have been attributed as critical factors contributing to obesity and type 2 diabetes, characterized by increased lipid accumulation, impaired glucose uptake, and defects in glycogen storage in skeletal muscle. Adiponectin, an adipokine, has been shown to have antidiabetic effects by improving fat oxidation and glucose uptake. PURPOSE: To investigate the effects of adiponectin incubation, in high fat diet induced obese rats, on measures of skeletal muscle substrate metabolism including glycogen, glucose transporter 4 (GLUT4), lipid, and mitochondrial contents. METHODS: Male Sprague Dawley rats were fed a Western-style (21% fat by weight; 41% total energy) high fat diet for 9 weeks to induce obesity, then, for 6 weeks, either continued the Western Diet (WD) or were fed a standard Chow Diet (WCD) (4.8% fat; 0.74% saturated; 2% mono; 1.77% poly); a control group followed a 15-week chow diet (CD). Following the 15-week diet intervention, right and left hind-leg extensor digitorum longus (EDL) muscles were incubated in an organ bath (Krebs-Henseleit buffer containing 2000 mg/L glucose) with or without 0.1 mg/ml adiponectin for 30 minutes. Glycogen content was measured with periodic acid-schiff staining, GLUT4 (ab654), lipid (bodipy), and mitochondrial (ab14744) contents were measured using immunohistochemical techniques and quantified with imageJ software. RESULTS: There were no changes in substrate concentrations with adiponectin incubation in any diet group. However, the change (D) in glycogen, with adiponectin, was greater in animals fed a control chow diet compared to animals that followed a 15-week high fat Western-style diet (WD) (change (D); CD: 0.11±0.07 vs. WD: -0.25±0.14; one-way ANOVA p=0.048). When change in lipid content, after adiponectin treatment, was compared, animals fed high fat diets showed impaired preservation of lipid compared to the control group (change (D); CD: 25.9±11.2 vs. WD: -21.1±14.8 p=0.02; CD: 25.9±11.2 vs. WCD: -18.8±7.7 p=0.02). CONCLUSION: 9 weeks of a high fat Western-style diet is sufficient to induce defects in skeletal muscle substrate concentrations, including glycogen and lipid contents. Although adiponectin incubation did not increase substrate concentrations, a control chow diet demonstrated a better ability to preserve glycogen and lipid contents compared to high fat diet induced obese rats. Despite reverting to a standard chow diet, high fat diet induced obese rats did not demonstrate an insulin-sensitizing response from adiponectin incubation

High Fat Diet Rich in Saturated Fatty Acids, but Not Monounsaturated Fatty Acids, Impairs Glycogen Preservation after Adiponectin Treatment

High fat diet (HFD) is associated with the progression of obesity, type 2 diabetes and diminished insulin sensitivity, which is characterized by a lower glucose uptake and glycogen synthesis capacity in skeletal muscle. Adiponectin (Ad), on the other hand, is a cytokine secreted by adipose tissue that promotes glucose uptake and fatty acid oxidation in skeletal muscle. PURPOSE: To determine the effects of Ad on skeletal muscle glycogen, GLUT 4, mitochondrial and lipid content in animals fed with a HFD but with alterations in dietary fatty acids (mixed fat western diet and predominately monounsaturated fatty acid). METHODS: Male Sprague Dawley rats were fed a Western-style (21% fat) HFD for 9 weeks to induce obesity, then, for 6 weeks, continued the mixed fat Western diet (WD) (9.8% saturated fat; 7.7% mono; 3.5% poly; n=8) or a HFD high in monounsaturated fatty acids (MUFA) (21% fat; 17.76% mono; 1.8% poly; n=8). A control group followed a 15-week standard Chow diet (CD) (4.8% fat; 0.74% saturated fat; 2% mono; 1.77% poly; n=9). Right and left hind-leg extensor digitorum longus (EDL) muscles were incubated in an organ bath (containing Krebs-Henseleit buffer with 2000 mg/L glucose, without calcium chloride and sodium bicarbonate) with or without 0.1 mg/ml Ad for 30 minutes. Glycogen content in the EDL muscle was measured by using periodic acid-schiff staining, while GLUT 4 protein content was measured using rabbit polyclonal antibody against GLUT 4 (ab654), mitochondrial content was measured using a mouse polyclonal antibody against COX 4 protein (ab14744) and lipid content was measured using BODIPY 493/503, using immunohistochemistry techniques. Images were quantified with ImageJ software. RESULTS: The Ad incubation resulted in a decrease in muscle glycogen content in animas fed with WD (4.85 ± 0.13 to 4.29 ± 0.11 AU; p=0.05). This decrease in glycogen content in the WD group was significantly different compared to a better preservation of glycogen in both CD (p=0.04) and the MUFA diet groups (p=0.012) (CD: 0.11 ± 0.071 AU; WD: -0.25 ± 0.14 AU; MUFA: 0.18 ± 0.05 AU; one way ANOVA, p=0.01). Animals fed with CD tended to have a better preservation of lipid content compared to animals fed with WD (p=0.07) and a diet high in MUFA (p=0.09) (CD: 25.93 ± 11.2 AU; WD: -21.09 ± 14.81 AU; MUFA: 25.97 ± 16.17 AU; one way ANOVA, p=0.06). There were no significant changes in GLUT 4 and mitochondrial content regardless of diet and adiponectin incubation. CONCLUSIONS: Animals fed with a western style HFD rich in saturated fat show an impaired response to adiponectin induced increase/preservation of glycogen in skeletal muscle compared to a chow diet, as well as a HFD rich in MUFA. Diets high in saturated fatty acids may have an impaired response to adiponectin treatment

Lower Skeletal Muscle Mitochondrial Content After a High Fat Diet Rich in Polyunsaturated Fatty Acids Compared to a High Fat Diet Rich in Monounsaturated Fatty Acids

High fat diet (HFD) has been associated with weight gain, insulin resistance, and type 2 diabetes. The composition of fatty acids in various diets (monounsaturated, polyunsaturated, saturated) influence levels of blood insulin, glucose, and the onset of metabolic and cardiovascular diseases. PURPOSE: Determine the effects of high fat diets with alterations in the major dietary fatty acid content (a mixed fat western diet, a polyunsaturated fatty acid diet or a monounsaturated fatty acid diet) on skeletal muscle glycogen, lipid, glucose transporter 4 (GLUT4), and mitochondrial content. METHODS: Male Sprague Dawley rats were fed a 21% (by weight; 41% total energy) high fat western-style diet for 9 weeks to induce obesity. They were then divided into 3 dietary groups that continued on a HFD for the next 6 weeks of 1) mixed fat western diet (WD) (9.8% saturated, 7.7% mono; 3.5% poly; n=9); 2) monounsaturated fat (MUFA) (2.8% saturated, 15.8% mono; 2.2% poly; n=9); or 3) polyunsaturated fat (PUFA) (3.0% saturated; 2.9%mono; 15.7% poly; n=8). A control group followed a 15-week low fat Chow diet (CD) (4.8% fat; 0.74% saturated fat; 2% mono; 1.77% poly; n=9). At the end of the dietary intervention, glycogen content was measured in extensor digitorum longus (EDL) with periodic acid-schiff staining. GLUT4 protein content was measured using rabbit polyclonal antibody against GLUT4 (ab654), mitochondrial content was measured using mouse polyclonal antibody against COX4 protein (ab14744), and lipid content was measured using BODIPY 493/503, using immunohistochemistry techniques. Images were captured by ZEN imaging software by ZEIS and data was analyzed with ImageJ. RESULTS: There were no significant differences in glycogen content after 6 weeks of HFD with different dietary fatty acid composition, compared to control chow diet. (AU± SEM; CD: 4.41±0.04, WD: 4.74± 0.13, MUFA: 4.54± 0.08, PUFA: 4.54± 0.11, one-way ANOVA p= 0.11). There were also no significant differences in GLUT4 protein content (AU± SEM; CD: 74.68± 5.91, WD: 64.42 ± 2.88, MUFA: 76.12± 6.51, PUFA: 62.83± 4.12; one-way ANOVA p= 0.17) and lipid content after a HFD differing in dietary fatty acids compared to a control chow diet. (AU± SEM; CD: 168± 19.28, WD: 141.3 ± 15.5, MUFA: 193.7 ± 15.3, PUFA: 152.1± 16,69; one-way ANOVA p=0.18). Mitochondria content was less in HFD rich in PUFA when compared to HFD rich in MUFA (CD; WD; AU± SEM; MUFA 60.33±7.31 vs. PUFA 37.42±5.53; MUFA vs. PUFA p= 0.03). CONCLUSION: Our data suggest that six weeks of high fat diet does not affect skeletal muscle glycogen content, lipid content and GLUT4 content regardless of dietary fatty acid composition. Six weeks of high fat diet rich in polyunsaturated fatty acids results in lower mitochondrial content compared to high fat diet rich in monounsaturated fatty acid. Our data suggest that high fat diet rich in polyunsaturated fatty acids may negatively impact skeletal muscle oxidative capacity compared to a diet rich in monounsaturated fatty acids

Atypical cannabinoid ligands O-1602 and O-1918 administered chronically in diet-induced obesity

Atypical cannabinoid compounds O-1602 and O-1918 are ligands for the putative cannabinoid receptors G protein-coupled receptor 55 and G protein-coupled receptor 18. The role of O-1602 and O-1918 in attenuating obesity and obesity-related pathologies is unknown. Therefore, we aimed to determine the role that either compound had on body weight and body composition, renal and hepatic function in diet-induced obesity. Male Sprague-Dawley rats were fed a high-fat diet (40% digestible energy from lipids) or a standard chow diet for 10 weeks. In a separate cohort, male Sprague-Dawley rats were fed a high-fat diet for 9 weeks and then injected daily with 5 mg/kg O-1602, 1 mg/kg O-1918 or vehicle (0.9% saline/0.75% Tween 80) for a further 6 weeks. Our data demonstrated that high-fat feeding upregulates whole kidney G protein receptor 55 expression. In diet-induced obesity, we also demonstrated O-1602 reduces body weight, body fat and improves albuminuria. Despite this, treatment with O-1602 resulted in gross morphological changes in the liver and kidney. Treatment with O-1918 improved albuminuria, but did not alter body weight or fat composition. In addition, treatment with O-1918 also upregulated circulation of pro-inflammatory cytokines including IL-1α, IL-2, IL-17α, IL-18 and RANTES as well as plasma AST. Thus O-1602 and O-1918 appear not to be suitable treatments for obesity and related comorbidities, due to their effects on organ morphology and pro-inflammatory signaling in obesity

CB1 Ligand AM251 induces weight loss and fat reduction in addition to increased systemic inflammation in diet-induced obesity

Diet-induced obesity (DIO) reduces fatty acid oxidation in skeletal muscle and decreases circulating levels of adiponectin. Endocannabinoid signaling is overactive in obesity, with some effects abated by antagonism of cannabinoid receptor 1 (CB1). This research aimed to determine if treatment with the global CB1 antagonist/inverse agonist, AM251, in high-fat diet (HFD) fed rats influenced adiponectin signaling in skeletal muscle and a “browning” of white adipose tissue (WAT) defined by UCP1 expression levels. Male Sprague Dawley rats consumed an HFD (21% fat) for 9 weeks before receiving daily intraperitoneal injections with vehicle or AM251 (3 mg/kg) for 6 weeks. mRNA expression of genes involved in metabolic functions were measured in skeletal muscle and adipose tissue, and blood was harvested for the measurement of hormones and cytokines. Muscle citrate synthase activity was also measured. AM251 treatment decreased fat pad weight (epididymal, peri-renal, brown), and plasma levels of leptin, glucagon, ghrelin, and GLP-1, and increased PAI-1 along with a range of pro-inflammatory and anti-inflammatory cytokines; however, AM251 did not alter plasma adiponectin levels, skeletal muscle citrate synthase activity or mRNA expression of the genes measured in muscle. AM251 treatment had no effect on white fat UCP1 expression levels. AM251 decreased fat pad mass, altered plasma hormone levels, but did not induce browning of WAT defined by UCP1 mRNA levels or alter gene expression in muscle treated acutely with adiponectin, demonstrating the complexity of the endocannabinoid system and metabolism. The CB1 ligand AM251 increased systemic inflammation suggesting limitations on its use in metabolic disorders

Cannabinoids Modulate Neuronal Activity and Cancer by CB1 and CB2 Receptor-Independent Mechanisms

Cannabinoids include the active constituents of Cannabis or are molecules that mimic the structure and/or function of these Cannabis-derived molecules. Cannabinoids produce many of their cellular and organ system effects by interacting with the well-characterized CB1 and CB2 receptors. However, it has become clear that not all effects of cannabinoid drugs are attributable to their interaction with CB1 and CB2 receptors. Evidence now demonstrates that cannabinoid agents produce effects by modulating activity of the entire array of cellular macromolecules targeted by other drug classes, including: other receptor types; ion channels; transporters; enzymes, and protein- and non-protein cellular structures. This review summarizes evidence for these interactions in the CNS and in cancer, and is organized according to the cellular targets involved. The CNS represents a well-studied area and cancer is emerging in terms of understanding mechanisms by which cannabinoids modulate their activity. Considering the CNS and cancer together allow identification of non-cannabinoid receptor targets that are shared and divergent in both systems. This comparative approach allows the identified targets to be compared and contrasted, suggesting potential new areas of investigation. It also provides insight into the diverse sources of efficacy employed by this interesting class of drugs. Obtaining a comprehensive understanding of the diverse mechanisms of cannabinoid action may lead to the design and development of therapeutic agents with greater efficacy and specificity for their cellular targets

Effects of Fatty Acid Composition in a High Fat Diet on Skeletal Muscle Mitochondrial Content

High fat diets (HFD) have been shown to impair skeletal muscle mitochondrial content and function, resulting in impaired lipid oxidation and insulin resistance. However, it is not well understood how the type of fatty acid (mixed fats, monounsaturated fatty acids (MUFA; predominately oleic acid) and polyunsaturated fatty acids (PUFA; primarily linoleic acid)) affects mitochondrial content. PURPOSE: The purpose of this study was to determine the effects of HFD, differing in the major type of fatty acids, on skeletal muscle mitochondrial content. METHODS: Male Sprague Dawley rats were fed a Western-style (21% by weight; 41% total energy) HFD for nine weeks to induce obesity. They were then divided into three dietary groups and a control chow group for the following six weeks. The dietary groups consisted of 1) a mixed fat Western diet (WD) (9.8% saturated fat, 7.7% monounsaturated fat; 3.5% polyunsaturated fat; n=10), 2) a HFD consisting of high MUFA (2.8% saturated, 15.8% mono; 2.2% poly; n=10), and 3) a HFD consisting of high PUFA (3.0% saturated; 2.9%mono; 15.7% poly; n=10). The control chow diet consisted of 4.8% fat (n=10). At the end of the dietary intervention, soleus muscle was extracted from the rats. Mitochondrial content was measured by quantifying oxidative phosphorylation (OXPHOS) complex I-V proteins by western immunoblotting using Odyssey CLx imaging. RESULTS: After the six-week intervention, there was no significant differences (One-way ANOVA p\u3e0.05) in OXPHOS protein content among different diet groups. Specifically, protein content of Complex I (Chow: 1.33 ± 0.83 n=9; WD: 1.23 ± 0.52; MUFA: 0.81 ± 0.26; PUFA: 0.66 ± 0.16), Complex II (Chow: 1.02 ± 0.45 n=9; WD: 0.51 ± 0.21; MUFA: 0.33 ± 0.18; PUFA: 0.56 ± 0.23), Complex III (Chow: 11.63 ± 8.216 n=9; WD: 6.52 ± 3.16; MUFA: 5.05 ± 1.90; PUFA: 3.44 ± 1.23), Complex IV (Chow: 3.95 ± 1.98 n=9; WD: 2.60 ± 0.86; MUFA: 2.20 ± 0.69; PUFA: 1.65 ± 0.55), and Complex V (Chow: 13.00 ± 9.87 n=9; WD: 6.52 ± 3.45; MUFA: 4.12 ± 1.57; PUFA: 3.26 ± 1.22) were not different among different diet groups. CONCLUSION: Our data suggests that skeletal muscle mitochondrial content is not affected by a HFD or dietary fatty acid composition (saturated, monounsaturated, and polyunsaturated) in rodents

The Role of Atypical Cannabinoid Ligands O-1602 and O-1918 on Skeletal Muscle Homeostasis with a Focus on Obesity.

O-1602 and O-1918 are atypical cannabinoid ligands for GPR55 and GPR18, which may be novel pharmaceuticals for the treatment of obesity by targeting energy homeostasis regulation in skeletal muscle. This study aimed to determine the effect of O-1602 or O-1918 on markers of oxidative capacity and fatty acid metabolism in the skeletal muscle. Diet-induced obese (DIO) male Sprague Dawley rats were administered a daily intraperitoneal injection of O-1602, O-1918 or vehicle for 6 weeks. C2C12 myotubes were treated with O-1602 or O-1918 and human primary myotubes were treated with O-1918. GPR18 mRNA was expressed in the skeletal muscle of DIO rats and was up-regulated in red gastrocnemius when compared with white gastrocnemius. O-1602 had no effect on mRNA expression on selected markers for oxidative capacity, fatty acid metabolism or adiponectin signalling in gastrocnemius from DIO rats or in C2C12 myotubes, while APPL2 mRNA was up-regulated in white gastrocnemius in DIO rats treated with O-1918. In C2C12 myotubes treated with O-1918, PGC1α, NFATc1 and PDK4 mRNA were up-regulated. There were no effects of O-1918 on mRNA expression in human primary myotubes derived from obese and obese T2DM individuals. In conclusion, O-1602 does not alter mRNA expression of key pathways important for skeletal muscle energy homeostasis in obesity. In contrast, O-1918 appears to alter markers of oxidative capacity and fatty acid metabolism in C2C12 myotubes only. GPR18 is expressed in DIO rat skeletal muscle and future work could focus on selectively modulating GPR18 in a tissue-specific manner, which may be beneficial for obesity-targeted therapies

The effect of cyanidin-3-omicron-beta-glucoside and peptides extracted from yoghurt on glucose uptake and gene expression in human primary skeletal muscle myotubes from obese and obese diabetic participants

Title on article: The effect of cyanidin-3-O-β-glucoside and peptides extracted from yoghurt on glucose uptake and gene expression in human primary skeletal muscle myotubes from obese and obese diabetic participant

The cannabinoid receptor 1 and its role in influencing peripheral metabolism

Evidence from in vitro and in vivo studies has demonstrated the deleterious pathological effects of a dysregulated endocannabinoid system. Increased stimulation of the cannabinoid receptor 1 (CB1) and subsequent downstream cellular signalling are both causative in the deleterious pathological effects observed in a number of diseases. When the CB1 cell signalling cascade is blocked, this results in whole body weight-loss, leading to a reduction in obesity and associated co-morbidities. In the central nervous system; however, CB1 antagonism results in adverse psychological side effects. Blockade of CB1 via peripheral acting compounds that do not cross the blood–brain barrier have been determined to have beneficial effects in metabolic tissues such as the liver and skeletal muscle. These results support the notion that peripheral blockade of CB1 using pharmacological antagonists is a viable target for the treatment of the current epidemic of obesity and its associated co-morbidities