Effect of dietary α-lipoic acid on growth, body composition, muscle pH, and AMP-activated protein kinase phosphorylation in mice1

Comparing the effects of developmental exposure to alpha lipoic acid (ALA) and perfluorooctanesulfonic acid (PFOS) in zebrafish (Danio rerio)

Alpha lipoic acid (ALA) is a dietary supplement that has been used to treat a wide range of diseases, including obesity and diabetes, and have lipid-lowering effects, making it a potential candidate for mitigating dyslipidemia resulting from exposures to the per- and polyfluoroalkyl substance (PFAS) family member perfluorooctanesulfonic acid (PFOS). ALA can be considered a non-fluorinated structural analog to PFOS due to their similar 8-carbon chain and amphipathic structure, but, unlike PFOS, is rapidly metabolized. PFOS has been shown to reduce pancreatic islet area and induce β-cell lipotoxicity, indicating that changes in β-cell lipid microenvironment is a mechanism contributing to hypomorphic islets. Due to structural similarities, we hypothesized that ALA may compete with PFOS for binding to proteins and distribution throughout the body to mitigate the effects of PFOS exposure. However, ALA alone reduced islet area and fish length, with several morphological endpoints indicating additive toxicity in the co-exposures. Individually, ALA and PFOS increased fatty acid uptake from the yolk. ALA alone increased liver lipid accumulation, altered fatty acid profiling and modulated PPARɣ pathway signaling. Together, this work demonstrates that ALA and PFOS have similar effects on lipid uptake and metabolism during embryonic development in zebrafish.

Regulation of yak longissimus lumborum energy metabolism and tenderness by the AMPK/SIRT1 signaling pathways during postmortem storage

AMPK can activate nicotinamide phosphoribosyltransferase (NAMPT), increasing the ratio of oxidized nicotinamide adenine dinucleotide (NAD+)/reduced nicotinamide adenine dinucleotide (NADH) ratio, leading to the activation of the energy receptor SIRT1. This pathway is known as the AMPK/SIRT1 signaling pathway. SIRT1 deacetylates and activate LKB1, which is activated by phosphorylation of AMPK (Thr172) and inhibited by phosphorylase-mediated dephosphorylation of AMPK. At the same time, increased AMP/ATP and NAD+/NADH ratios lead to the activation of AMPK and SIRT1. SIRT1 and AMPK can activate each other forming a positive feedback loop, which can strengthen catabolism and weaken anabolism thus maintaining energy homeostasis of energy metabolism. At present, there has been no systematic study on AMPK-associated signaling cascades in stored yak meat and details of the AMPK/SIRT1 signaling under these conditions are not known. In this study, NAD+, NADH were added to yak longissimus thoracic muscles to study AMPK pathway regulation by AMPK/SIRT1 signaling. NAD+ significantly increased the activity of AMPK and glycolysis during postmortem maturation, increased the rate of energy metabolism, and increased the expression of AMPK protein, indicating that NAD+ increased energy metabolism in the stored muscle by promoting AMPK activity. NADH treatment inhibited both AMPK activation and glycolysis, together with increasing the pH in the muscle. The results showed that SIRT1 activation elevated the activity of AMPK, leading to its phosphorylation and the activation of glycolysis. Thus, AMPK activity was found to increase in yak meat as an adaptation to hypoxic conditions. This allows more effective regulation of energy production and improves the tenderness of the meat.

α-Lipoic Acid Alleviates Hepatic Lipid Deposition by Inhibiting FASN Expression via miR-3548 in Rats

Excessive liver lipid deposition is a vital risk factor for the development of many diseases. Here, we fed Sprague-Dawley rats with a control or α-lipoic acid-supplemented diet (0.2%) for 5 weeks to elucidate the effects of α-lipoic acid on preventive ability, hepatic lipid metabolism-related gene expression, and the involved regulatory mechanisms. In the current study, α-lipoic acid supplementation lowered plasma triglyceride level and hepatic triglyceride content. Reduced hepatic lipid deposition was closely associated with inhibiting fatty acid-binding protein 1 and fatty acid synthase expression, as well as increasing phosphorylated hormone-sensitive lipase expression at the protein level in α-lipoic acid-exposed rats. Hepatic miRNA sequencing revealed increased expression of miR-3548 targeting the 3'untranslated region of Fasn mRNA, and the direct regulatory link between miRNA-3548 and FASN was verified by dual-luciferase reporter assay. Taken together, α-lipoic acid lowered hepatic lipid accumulation, which involved changes in miRNA-mediated lipogenic genes.

Effects of protein posttranslational modifications on meat quality: A review

Meat quality plays an important role in the purchase decision of consumers, affecting producers and retailers. The formation mechanisms determining meat quality are intricate, as several endogenous and exogenous factors contribute during antemortem and postmortem periods. Abundant research has been performed on meat quality; however, unexpected variation in meat quality remains an issue in the meat industry. Protein posttranslational modifications (PTMs) regulate structures and functions of proteins in living tissues, and recent reports confirmed their importance in meat quality. The objective of this review was to provide a summary of the research on the effects of PTMs on meat quality. The effects of four common PTMs, namely, protein phosphorylation, acetylation, S-nitrosylation, and ubiquitination, on meat quality were discussed, with emphasis on the effects of protein phosphorylation on meat tenderness, color, and water holding capacity. The mechanisms and factors that may affect the function of protein phosphorylation are also discussed. The current research confirms that meat quality traits are regulated by multiple PTMs. Cross talk between different PTMs and interactions of PTMs with postmortem biochemical processes need to be explored to improve our understanding on factors affecting meat quality.

Study of the AMP-Activated Protein Kinase Role in Energy Metabolism Changes during the Postmortem Aging of Yak Longissimus dorsal

To explore the postmortem physiological mechanism of muscle, activity of adenosine monophosphate activated protein kinase (AMPK) as well as its role in energy metabolism of postmortem yaks were studied. In this experiment, we injected 5-amino-1-beta-d-furanonyl imidazole-4-formamide (AICAR), a specific activator of AMPK, and STO-609 to observe the changes in glycolysis, energy metabolism, AMPK activity, and AMPK gene expression (PRKA1 and PRKA2) in postmortem yaks during maturation. The results showed that AICAR could increase the expression of the PRKKA1 and PRKAA2 genes, activate AMPK and increase its activity. The effects of AICAR include a lower concentration of ATP, an increase in AMP production, an acceleration of glycolysis, an increase in the lactic acid concentration, and a decrease in the pH value. In contrast, STO-609 had the opposite effect. Under hypoxic adaptation, the activity of the meat AMPK increased, which accelerated glycolysis and metabolism and more effectively regulated energy metabolism. Therefore, this study lays the foundation for establishing a theoretical system of energy metabolism in postmortem yak meat.

Effect of stocking density and alpha-lipoic acid on the growth performance, physiological and oxidative stress and immune response of broilers

Objective

The study was conducted to evaluate the effect of stocking density and alpha-lipoic acid (ALA) on the growth performance, feed utilization, carcass traits, antioxidative ability and immune response of broilers.

Methods

A total of 1,530 22-day-old male broilers (Arbor Acres) with comparable body weights (731.92±5.26) were placed into 18 cages (2.46×2.02 m) in groups of 75 birds (15 birds/m², 37.5 kg/m²; low stocking density [LD]), 90 birds (18 birds/m², 45.0 kg/m²; high stocking density [HD]) and 90 birds with 300 mg/kg ALA added to the basal diet (18 birds/m², 45.0 kg/m²; HD+ALA, high stocking density+α-lipoic acid); each treatment was represented by 6 replicates. The experimental period was 3 weeks.

Results

The results showed that the high stocking density regimen resulted in a decreased growth, feed conversion ratio, carcass weight, thigh yield and bursa weight relative to body weight (p<0.05) on d 42. The abdominal fat yield in the HD+ALA group was lower (p = 0.031) than that of the LD group at 42 d. The superoxide dismutase and glutathione peroxidase activities in serum were increased, and malondialdehyde content decreased after adding ALA product (p<0.05) on d 42. Additionally, the serum concentrations of immunoglobulin A (IgA) and IgG were decreased (p<0.05) and the level of diamine oxidase was higher (p< 0.01) in the HD group on d 42.

Conclusion

The high stocking density significantly decreased broiler growth performance, feed utilization and carcass traits, increased physiological and oxidative stress and induced intestinal mucosal injury. The supplementation of ALA product in broiler diet at 300 mg/kg may reduce the adverse effects of high stocking density-mediated stress by maintaining the antioxidant system and humoral immune system.

Impact of dietary lipoic acid supplementation on liver mitochondrial bioenergetics and oxidative status on normally fed Wistar rats

The aim of this study was to examine the effects of α-lipoic acid (α-LA) on liver mitochondrial bioenergetics and oxidative status for 8 weeks in normal-healthy animals. A pair-fed group was included to differentiate between α-LA direct effects and those changes due to reduced food intake. α-LA decreased body weight gain, liver weight and insulin levels with no differences compared to its pair-fed group. α-LA significantly reduced energy efficiency, the activity of the electron transport chain complexes and induced a lower efficiency of oxidative phosphorylation with reduced ATP production. α-LA supplementation directly decreased plasma triglycerides (TGs), free fatty acids and ketone bodies levels. A significant reduction in hepatic TG content was also observed. A significant up-regulation of Cpt1a, Acadl and Sirt3, all β-oxidation genes, along with a significant deacetylation of the forkhead transcription factor 3a (FOXO3A) was found in α-LA-treated animals. Thus, α-LA along with a standard chow diet has direct actions on lipid metabolism and liver by modulating mitochondrial function in normal-weight rats. These results should be taken into account when α-LA is administered or recommended to a healthy population.

Stress Effects on Meat Quality: A Mechanistic Perspective

Stress inevitably occurs from the farm to abattoir in modern livestock husbandry. The effects of stress on the behavioral and physiological status and ultimate meat quality have been well documented. However, reports on the mechanism of stress effects on physiological and biochemical changes and their consequent effects on meat quality attributes have been somewhat disjointed and limited. Furthermore, the causes of variability in meat quality traits among different animal species, muscle fibers within an animal, and even positions within a piece of meat in response to stress are still not entirely clear. This review 1st summarizes the primary stress factors, including heat stress, preslaughter handling stress, oxidative stress, and other stress factors affecting animal welfare; carcass quality; and eating quality. This review further delineates potential stress-induced pathways or mediators, including AMP-activated protein kinase-mediated energy metabolism, crosstalk among calcium signaling pathways and reactive oxygen species, protein modification, apoptosis, calpain and cathepsin proteolytic systems, and heat shock proteins that exert effects that cause biochemical changes during the early postmortem period and affect the subsequent meat quality. To obtain meat of high quality, further studies are needed to unravel the intricate mechanisms involving the aforementioned signaling pathways or mediators and their crosstalk.

The effects of alpha-lipoic acid on diabetic myopathy

PURPOSE

Increased oxidative stress and impaired antioxidant defense are important mechanisms in the pathogenesis of diabetic myopathy. Since diabetes mellitus type 1 decreases muscle regeneration capacity the present study was designed to determine the influence of alpha-lipoic acid (ALA), a potent biological antioxidant, on the process of regeneration of diabetic rat skeletal muscles.

METHODS

40 Wistar rats were divided into three groups: control (n = 8), untreated diabetic group (n = 16) and ALA treated diabetic group (n = 16). The regeneration process was provoked in streptozotocin-induced diabetic rats in both slow (m.soleus, SOL) and fast (m.extensor digitorum longus, EDL) skeletal muscles by intramuscular injection of myotoxin bupivacaine. At intervals of 10 days and 4 weeks, muscle histochemical and morphometrical analysis (fiber cross areas and fiber type distribution) was performed.

RESULTS

Changes induced by diabetes are evident in redistribution of muscle fibers and in significant level of atrophy. After 4 weeks of diabetes, glycolytic muscle fibers are dominant in both slow and fast muscles. Muscle atrophy is present in all fiber types except in type I of slow skeletal muscle. Treatment with ALA reduce changes in the morphological properties caused by diabetes mellitus type 1 in slow and fast rat skeletal muscles during the process of regeneration.

CONCLUSION

Treatment with lipoic acid during 4 weeks has shown effects on the redistribution of muscle fibers, and can prevent atrophy in slow and fast diabetic muscle.

Different oxidative status and expression of calcium channel components in stress-induced dysfunctional chicken muscle

The objective of this study was to assess the effects of transport stress at high ambient temperatures on the oxidation status and the expression of essential elements responsible for the Ca transport (sarco- (endo-) plasmic reticulum Ca-ATPase (SERCA1) and the ryanodine receptor (RyR) in (PM) muscles of broilers. Briefly, Arbor Acres broiler chickens ( = 112) were randomly categorized into 2 treatments: unstressed control (C) and 0.5 h transport (T). Each treatment consisted of 8 replicates of 7 birds each. Birds were transported according to a designed protocol. PM muscle samples in T group were collected and classified as normal (T-NOR) or pale, soft, and exudative-like (T-PSE) using meat quality parameters. The results indicated that production of corticosterone (CORT) and reactive oxygen species (ROS) increased significantly after transportation ( < 0.05). Thiobarbituric acid reactive substance values and carbonyl contents increased significantly in the T group ( < 0.05). Moreover, the extent of lipid peroxidation and protein oxidation was more severe in the T-PSE group compared to the T-NOR group ( < 0.05). The mRNA and protein expression of SERCA1 and αRyR increased in the T-NOR group but decreased significantly in the T-PSE group compared to the CON group ( < 0.05). The mRNA expression of βRyR was found to be enhanced in the T-NOR group compared to the CON group, whereas there was no difference in the T-PSE group ( < 0.05). The results indicate that short-distance transport of broilers affects their physiological responses and biochemical changes which may lead to different oxidative states and, importantly, to different expressions of SERCA and RyR. These induced changes in abnormal sarcoplasmic Ca homeostasis have significant implications for the development of PSE-like meat.

Alpha-lipoic acid (ALA) as a supplementation for weight loss: results from a meta-analysis of randomized controlled trials

OBJECTIVES

Obesity is associated with significant morbidity and mortality rates. Even modest weight loss may be associated with health benefits. Alpha-lipoic acid (ALA) is a naturally occurring antioxidant. Studies have suggested anti-obesity properties of ALA; however, results are inconsistent. The purpose of this study is to conduct a meta-analysis of the effect of ALA on weight and body mass index (BMI).

METHODS

A comprehensive, systematic literature search identified 10 articles on randomized, double-blind, placebo-controlled studies involving ALA. We conducted a meta-analysis of mean weight and BMI change differences between ALA and placebo treatment groups.

RESULTS

Alpha-lipoic acid treatment coincided with a statistically significant 1.27 kg (confidence interval = 0.25 to 2.29) greater mean weight loss compared with the placebo group. A significant overall mean BMI difference of -0.43 kg/ m² (confidence interval = -0.82 to -0.03) was found between the ALA and placebo groups. Meta-regression analysis showed no significance in ALA dose on BMI and weight changes. Study duration significantly affected BMI change, but not weight change.

CONCLUSIONS

Alpha-lipoic acid treatment showed small, yet significant short-term weight loss compared with placebo. Further research is needed to examine the effect of different doses and the long-term benefits of ALA on weight management.

Antemortem stress regulates protein acetylation and glycolysis in postmortem muscle

Although exhaustive research has established that preslaughter stress is a major factor contributing to pale, soft, exudative (PSE) meat, questions remain regarding the biochemistry of postmortem glycolysis. In this study, the influence of preslaughter stress on protein acetylation in relationship to glycolysis was studied. The data show that antemortem swimming significantly enhanced glycolysis and the total acetylated proteins in postmortem longissimus dorsi (LD) muscle of mice. Inhibition of protein acetylation by histone acetyltransferase (HAT) inhibitors eliminated stress induced increase in glycolysis. Inversely, antemortem injection of histone deacetylase (HDAC) inhibitors, trichostatin A (TSA) and nicotinamide (NAM), further increased protein acetylation early postmortem and the glycolysis. These data provide new insight into the biochemistry of postmortem glycolysis by showing that protein acetylation regulates glycolysis, which may participate in the regulation of preslaughter stress on glycolysis in postmortem muscle.

Effects of Dietary L-carnosine and Alpha-lipoic Acid on Growth Performance, Blood Thyroid Hormones and Lipid Profiles in Finishing Pigs

The present study was conducted to determine the effects of L-carnosine (LC) and/or alpha-lipoic acid (ALA) supplementation on growth performance, blood thyroid hormones and lipid profiles in finishing pigs. A total of 40 (Landrace×Yorkshire) pigs with an initial body weight of 57.93±3.14 kg were randomly allocated to 4 experimental diets using a 2×2 factorial arrangement with 2 LC supplemental levels (0 or 0.1%) and 2 ALA supplemental levels (0 or 0.03%) in basal diets. The results showed that pigs fed LC-supplemented diets increased final live weight, average daily gain, and average daily feed intake compared to those of pigs fed without LC-supplemented diets (p<0.05). Dietary supplementation with ALA did not affect the growth performance and carcass traits of pigs (p>0.05). Additionally, LC supplementation increased serum triiodothyronine, thyroxine levels, and ALA supplementation increased serum triiodothyronine levels (p<0.05). Serum total cholesterol and triglycerides levels were significantly decreased in LC and ALA supplemented groups, respectively (p<0.05). Moreover, serum low density lipoprotein cholesterol levels were lower in the ALA-supplemented groups than those of pigs fed without ALA-supplemented diets (p<0.05). However, no significant LC×ALA interaction effect on growth performance, blood thyroid hormones and lipid profiles was found. This study suggested that dietary supplementation of LC resulted in better growth performance compared to that of ALA supplementation. L-carnosine and/or ALA supplementation positively modified blood lipid profiles, which may have the potential to prevent cardiovascular diseases.

α-Lipoic acid as a triglyceride-lowering nutraceutical

Considering the current obesity epidemic in the United States (>100 million adults are overweight or obese), the prevalence of hypertriglyceridemia is likely to grow beyond present statistics of ∼30% of the population. Conventional therapies for managing hypertriglyceridemia include lifestyle modifications such as diet and exercise, pharmacological approaches, and nutritional supplements. It is critically important to identify new strategies that would be safe and effective in lowering hypertriglyceridemia. α-Lipoic acid (LA) is a naturally occurring enzyme cofactor found in the human body in small quantities. A growing body of evidence indicates a role of LA in ameliorating metabolic dysfunction and lipid anomalies primarily in animals. Limited human studies suggest LA is most efficacious in situations where blood triglycerides are markedly elevated. LA is commercially available as dietary supplements and is clinically shown to be safe and effective against diabetic polyneuropathies. LA is described as a potent biological antioxidant, a detoxification agent, and a diabetes medicine. Given its strong safety record, LA may be a useful nutraceutical, either alone or in combination with other lipid-lowering strategies, when treating severe hypertriglyceridemia and diabetic dyslipidemia. This review examines the current evidence regarding the use of LA as a means of normalizing blood triglycerides. Also presented are the leading mechanisms of action of LA on triglyceride metabolism.

Tormentic acid, a major component of suspension cells of Eriobotrya japonica, suppresses high-fat diet-induced diabetes and hyperlipidemia by glucose transporter 4 and AMP-activated protein kinase phosphorylation

This study was designed to evaluate the effects and mechanism of tormentic acid (PTA) on diabetes and dyslipidemia in high-fat (HF)-fed mice. Feeding C57BL/6J mice with a HF diet for 12 weeks induced type 2 diabetes and hyperlipidemia. During the last 4 weeks, the mice were given orally PTA (at two dosages) or rosiglitazone (Rosi) or water. In this study, the HF diet increased glucose, triglyceride, insulin, and leptin levels, whereas PTA effectively prevented these phenomena and ameliorated insulin resistance. PTA reduced visceral fat mass and hepatic triacylglycerol contents; moreover, PTA significantly decreased both the area of adipocytes and ballooning degeneration of hepatocytes. PTA caused increased skeletal muscular AMP-activated protein kinase (AMPK) phosphorylation and Akt phosphorylation and glucose transporter 4 (GLUT4) proteins, but reduced the hepatic expressions of phosphenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6 Pase) genes. PTA enhanced skeletal muscular Akt phosphorylation and increased insulin sensitivity. PTA also enhanced phospho-AMPK in the liver. Therefore, it is possible that the activation of AMPK by PTA results in decreasing hepatic glucose production while increasing skeletal muscular GLUT4 contents, thus contributing to attenuating the diabetic state. Moreover, PTA exhibits an antihyperlipidemic effect by down-regulations of the hepatic sterol regulatory element binding protein-1c (SREBP-1c) and apolipoprotein C-III (apo C-III) and an increased peroxisome proliferator activated receptor (PPAR)-α expression, thus resulting in decreases in blood triglycerides. These findings demonstrated that PTA was effective for the treatment of diabetes and hyperlipidemia in HF-fed mice.

Effects of Bofu-Tsusho-San on diabetes and hyperlipidemia associated with AMP-activated protein kinase and glucose transporter 4 in high-fat-fed mice

This study was undertaken to examine the effect and mechanism of Bofu-tsusho-san formula (BO) on hyperglycemia and hyperlipidemia and in mice fed with a high-fat (HF) diet. The C57BL/6J mice were received control/HF diet for 12 weeks, and oral administration of BO (at three doses) or rosiglitazone (Rosi) or vehicle for the last 4 weeks. Blood, skeletal muscle and tissues were examined by means of measuring glycaemia and dyslipidaemia-associated events. BO treatment effectively prevented HF diet-induced increases in the levels of triglyceride (TG), free fatty acid (FFA) and leptin (p<0.01, p<0.01, p<0.01, respectively). BO treatment exhibited reduced both visceral fat mass and hepatic triacylglycerol content; moreover, BO treatment displayed significantly decreased both the average area of the cut of adipocytes and ballooning of hepatocytes. BO treatment exerted increased the protein contents of glucose transporter 4 (GLUT4) in skeletal muscle, and caused lowered blood glucose levels. BO treatment displayed increased levels of phosphorylated AMP-activated protein kinase (AMPK) in both skeletal muscle and liver tissue. Furthermore, BO reduced the hepatic expression of glucose-6-phosphatase (G6Pase) and phosphenolpyruvate carboxykinase (PEPCK) and glucose production. Therefore, it is possible that the activation of AMPK by BO leads to diminished gluconeogenesis in liver tissue. BO increased hepatic expressions of peroxisome proliferator-activated receptor α (PPARα), whereas down-regulating decreasing expressions of fatty acid synthesis, including sterol regulatory element binding protein 1c (SREBP1c) and fatty acid synthase (FAS), resulting in a decrease in circulating triglycerides. This study originally provides the evidence that amelioration of dyslipidemic and diabetic state by BO in HF-fed mice occurred by regulation of GLUT4, SREBP1c, FAS, PPARα, adiponectin and AMPK phosphorylation.

Effects of Dietary Alpha-lipoic Acid and Acetyl-L-carnitine on Growth Performance and Meat Quality in Arbor Acres Broilers

An experiment was conducted to evaluate the effects of dietary alpha-lipoic acid (LA) and acetyl-L-carnitine (ALC) on growth performance, carcass characteristics and meat quality in Arbor Acres broilers. A total of 486 1-d-old male Arbor Acres broilers were randomly allocated to 9 dietary treatments, 9 treatments were group A (0 mg/kg LA and 0 mg/kg ALC), group B (50 mg/kg LA and 0 mg/kg ALC), group C (100 mg/kg LA and 0 mg/kg ALC), group D (0 mg/kg LA and 50 mg/kg ALC), group E (50 mg/kg LA and 50 mg/kg ALC), group F (100 mg/kg LA and 50 mg/kg ALC), group G (0 mg/kg LA and 100 mg/kg ALC), group H (50 mg/kg LA and 100 mg/kg ALC), group I (100 mg/kg LA and 100 mg/kg ALC). Birds were slaughtered at 42 days old. Average daily gain (ADG), average feed intake (AFI), feed conversion rate (FCR), eviscerated rate, breast muscle percentage, thigh muscle percentage, abdominal fat percentage, liver weight, muscle color (L* value, a* value, b* value), pH values at 45 min and 24 h postmortem were measured. Results showed that there existed an interaction between LA and ALC in growth performance of broilers, carcass traits and meat quality. The overall result is that high level of LA and ALC led to lower AFI, ADG (p<0.01), lower abdominal fat percentage, liver weight (p<0.01), lower L* value, a* value, and b* value of breast muscle, L* value of thigh muscle (p<0.05), and higher FCR (p<0.01), eviscerated rate (p<0.01), breast muscle percentage, thigh muscle percentage (p<0.05), a* value, pH 45 min and pH 24 h of thigh muscle (p<0.01). These results suggested that dietary LA and ALC contributed to the improvement of meat quality in broilers.

Caffeamide 36-13 Regulates the Antidiabetic and Hypolipidemic Signs of High-Fat-Fed Mice on Glucose Transporter 4, AMPK Phosphorylation, and Regulated Hepatic Glucose Production

This study was to investigate the antidiabetic and antihyperlipidemic effects of (E)-3-[3, 4-dihydroxyphenyl-1-(piperidin-1-yl)prop-2-en-1-one] (36-13) (TS), one of caffeic acid amide derivatives, on high-fat (HF-) fed mice. The C57BL/6J mice were randomly divided into the control (CON) group and the experimental group, which was firstly fed a HF diet for 8 weeks. Then, the HF group was subdivided into four groups and was given TS orally (including two doses) or rosiglitazone (Rosi) or vehicle for 4 weeks. Blood, skeletal muscle, and tissues were examined by measuring glycaemia and dyslipidemia-associated events. TS effectively prevented HF diet-induced increases in the levels of blood glucose, triglyceride, insulin, leptin, and free fatty acid (FFA) and weights of visceral fa; moreover, adipocytes in the visceral depots showed a reduction in size. TS treatment significantly increased the protein contents of glucose transporter 4 (GLUT4) in skeletal muscle; TS also significantly enhanced Akt phosphorylation in liver, whereas it reduced the expressions of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Moreover, TS enhanced phosphorylation of AMP-activated protein kinase (phospho-AMPK) both in skeletal muscle and liver tissue. Therefore, it is possible that the activation of AMPK by TS resulted in enhanced glucose uptake in skeletal muscle, contrasting with diminished gluconeogenesis in liver. TS exhibits hypolipidemic effect by decreasing the expressions of fatty acid synthase (FAS). Thus, antidiabetic properties of TS occurred as a result of decreased hepatic glucose production by PEPCK and G6Pase downregulation and improved insulin sensitization. Thus, amelioration of diabetic and dyslipidemic state by TS in HF-fed mice occurred by regulation of GLUT4, G6Pase, and FAS and phosphorylation of AMPK.

Validation of the Antidiabetic and Hypolipidemic Effects of Clitocybe nuda by Assessment of Glucose Transporter 4 and Gluconeogenesis and AMPK Phosphorylation in Streptozotocin-Induced Mice

The study was designed to investigate the effects of extract of Clitocybe nuda (CNE) on type 1 diabetes mellitus and dyslipidemia in streptozotocin- (STZ-) induced diabetic mice. Diabetes was induced by injection of STZ. Diabetic mice were randomly divided into five groups and given orally CNE (C1: 0.2, C2: 0.5, and C3: 1.0 g/kg body weight) or metformin (Metf) or vehicle for 4 weeks. STZ induction decreased in the levels of insulin, body weight, and the weight of skeletal muscle, whereas the levels of blood glucose, hemoglobin nonenzymatically (percent HbA1c), and circulating triglyceride (P < 0.001, P < 0.001, and P < 0.01, resp.) were increased. CNE decreased the levels of blood glucose, HbA1c, and triglyceride levels, whereas it increased the levels of insulin and leptin compared with the vehicle-treated STZ group. STZ induction caused a decrease in the protein contents of skeletal muscular and hepatic phosphorylation of AMP-activated protein kinase (phospho-AMPK) and muscular glucose transporter 4 (GLUT4). Muscular phospho-AMPK contents were increased in C2-, C3-, and Metf-treated groups. CNE and Metf significantly increased the muscular proteins of GLUT4. Liver phospho-AMPK showed an increase in all CNE- and Metf-treated groups combined with the decreased hepatic glucose production by decreasing phosphenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase), and 11beta hydroxysteroid dehydroxygenase (11β-HSD1) gene, which contributed to attenuating diabetic state. The study indicated that the hypoglycemic properties of CNE were related to both the increased muscular glucose uptake and the reduction in hepatic gluconeogenesis. CNE exerts hypolipidemic effect by increasing gene expressions of peroxisome proliferator-activated receptor α (PPARα) and decreasing expressions of fatty acid synthesis, including acyl-coenzyme A: diacylglycerol acyltransferase (DGAT) 2. Therefore, amelioration of diabetic and dyslipidemic state by CNE in STZ-induced diabetic mice occurred by regulation of GLUT4, PEPCK, DGAT2, and AMPK phosphorylation.

Antidiabetic and Antihyperlipidemic Effects of Clitocybe nuda on Glucose Transporter 4 and AMP-Activated Protein Kinase Phosphorylation in High-Fat-Fed Mice

The objective of this study was to evaluate the antihyperlipidemic and antihyperglycemic effects and mechanism of the extract of Clitocybe nuda (CNE), in high-fat- (HF-) fed mice. C57BL/6J was randomly divided into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed with a HF diet for 8 weeks. Then, the HF group was subdivided into five groups and was given orally CNE (including C1: 0.2, C2: 0.5, and C3: 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks. CNE effectively prevented HF-diet-induced increases in the levels of blood glucose, triglyceride, insulin (P < 0.001, P < 0.01, P < 0.05, resp.) and attenuated insulin resistance. By treatment with CNE, body weight gain, weights of white adipose tissue (WAT) and hepatic triacylglycerol content were reduced; moreover, adipocytes in the visceral depots showed a reduction in size. By treatment with CNE, the protein contents of glucose transporter 4 (GLUT4) were significantly increased in C3-treated group in the skeletal muscle. Furthermore, CNE reduces the hepatic expression of glucose-6-phosphatase (G6Pase) and glucose production. CNE significantly increases protein contents of phospho-AMP-activated protein kinase (AMPK) in the skeletal muscle and adipose and liver tissues. Therefore, it is possible that the activation of AMPK by CNE leads to diminished gluconeogenesis in the liver and enhanced glucose uptake in skeletal muscle. It is shown that CNE exhibits hypolipidemic effect in HF-fed mice by increasing ATGL expression, which is known to help triglyceride to hydrolyze. Moreover, antidiabetic properties of CNE occurred as a result of decreased hepatic glucose production via G6Pase downregulation and improved insulin sensitization. Thus, amelioration of diabetic and dyslipidemic states by CNE in HF-fed mice occurred by regulation of GLUT4, G6Pase, ATGL, and AMPK phosphorylation.

Wheat germ oil enrichment in broiler feed with α-lipoic acid to enhance the antioxidant potential and lipid stability of meat

BACKGROUND

Lipid peroxidation is the cause of declining the meat quality. Natural antioxidants plays a vital role in enhancing the stability and quality of meat. The supplementation of natural antioxidants in feed decreases lipid peroxidation and improves the stability of meat.

METHODS

The present research was conducted to determine the effect of α-lipoic acid, α-tocopherol and wheat germ oil on the status of antioxidants, quality and lipid stability of broiler meat. One day old male broilers were fed with different feeds containing antioxidants i.e. natural (wheat germ oil) and synthetic α-tocopherol and α-lipoic acid during the two experimental years.

RESULTS

The feed treatments have significant variation on the body weight and feed conversion ratio (FCR) while having no influence on the feed intake. The broilers fed on wheat germ oil (natural α-tocopherol) gained maximum body weight (2451.97 g & 2466.07 g) in the experimental years 2010-11 & 2011-12, respectively. The higher total phenolic contents were found in the broilers fed on wheat germ oil plus α-lipoic acid in breast (162.73±4.8 mg Gallic acid equivalent/100 g & 162.18±4.5 mg Gallic acid equivalent/100 g) and leg (149.67±3.3 mg Gallic acid equivalent/100 g & 146.07±3.2 mg Gallic acid equivalent/100 g) meat during both experimental years. Similar trend was observed for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power assay (FRAP). The production of malondialdehydes in the breast and leg meat increased with progressive increase in the time period. The deposition of α-tocopherol (AT) and α-lipoic acid (ALA) contents were found to be higher in the broilers fed on wheat germ oil plus α-lipoic acid in breast and leg meat during the both experimental years.

CONCLUSION

In conclusion, the combination of wheat germ oil and α-lipoic acid has more beneficial for stability and the quality of the broiler meat and more work should be needed in future for the bio-evaluation of this kind of functional meat in humans.

The endocrine control of energy homeostasis in chickens

Energy homeostasis (balance) depends on the relationship between the amount of consumed feed energy and energy expenditure. Coordination of energy expenditure and feed intake (appetite) is necessary for the regulation of body composition. The hypothalamus integrates peripheral and central signals to generate satiety or hunger. Birds and mammals utilize common signaling molecules but some molecules possess different/opposite functions. If relevant, particular differences with the mammalian regulatory system are highlighted in this review. For example, obestatin had no significant effect on feed intake of chicks, but it was claimed to decrease food intake in mammalian species. Ghrelin displayed appetite-stimulating effects in mammals but appetite-decreasing effects in birds. Recently, the function of the hypothalamic AMPK signaling pathway on feed intake regulation has received considerable attention in poultry. Alpha-lipoic acid might exert its appetite-decreasing effect by the AMPK signaling pathway. This review discusses the central regulation of energy homeostasis, role of (an)orexigenic peptides, effect of feed deprivation on hypothalamic neuropeptide gene expression and provides a model for involvement of AMPK in the regulation of avian energy balance.

Validation of the Antidiabetic and Hypolipidemic Effects of Hawthorn by Assessment of Gluconeogenesis and Lipogenesis Related Genes and AMP-Activated Protein Kinase Phosphorylation

Since with the increased use of antidiabetic and antihyperlipidemic effect of phytonutrients for daily supplement has gained considerable attention worldwide, we examine the effect and molecular mechanism of Crataegus pinnatifida Bge. var. major N.E. Br. (hawthorn) by quantifying the expression of hepatic gluconeogenesis and lipogenesis on diabetes and dyslipidemia in high-fat (HF)-fed C57BL/6J mice. Firstly, mice were divided randomly into two groups: the control (CON) group was fed with a low-fat diet, whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was given orally hawthorn extract (including 0.2, 0.5, 1.0 g/kg/day extracts) or rosiglitazone (Rosi) or vehicle for 4 weeks afterward. Diabetic mice showed an increase in plasma glucose and insulin. Glucose lowering was comparable with Rosi-treated mice. This study demonstrated that hawthorn was effective in ameliorating the HF diet-induced hyperglycemia, hypertriglyceridemia and hypercholesterolaemia. Hawthorn extract significantly increases the hepatic protein contents of AMP-activated protein kinase (AMPK) phosphorylation and reduces expression of phosphenol pyruvate carboxykinase (PEPCK) and glucose production. Furthermore, hawthorn decreased in hepatic triacylglycerol and cholesterol synthesis (including sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), SREBP2). An increase in expressions of apoA-I gene and high-density lipoprotein cholesterol (HDL-C) was detected in HF-fed mice treated with high dose hawthorn. Our data suggest that hawthorn extract are capable of decreasing glucose production and triacylglycerol synthesis by inducing AMPK-phosphorylation and hawthorn is a candidate source of antidiabetic and antihyperlipidemic phytonutrients factors.

Dietary alpha lipoic Acid improves body composition, meat quality and decreases collagen content in muscle of broiler chickens

A total of 192 broiler chicks were used to evaluate the influence of dietary α-lipoic acid (ALA) on growth performance, carcass characteristics and meat quality of broiler chickens with the purpose of developing a strategy to prevent the occurrence of pale, soft, and exudative (PSE) meat and to improve the meat quality of broilers. At 22 d of age, birds were allocated to 4 ALA treatments (0, 400, 800, and 1200 ppm). The results showed that dietary ALA significantly decreased average feed intake (AFI), average daily gain (ADG), final live body weight (BW) and carcass weight (p<0.05), while no difference in feed conversion ratio (FCR) was detected among chickens fed with and without ALA. Abdominal fat weight significantly decreased (p<0.05) for broilers fed 800 and 1200 ppm ALA. However when calculated as the percentage of carcass weight there was no significant difference between control and ALA treatments. Meat quality measurements showed that dietary ALA regulated postmortem glycolysis and improved meat quality as evidenced by increased muscle pH and decreased drip loss of meat (p<0.05). Although ALA did not change the tenderness of meat as indicated by meat shear force, dietary ALA decreased collagen content and mRNA expression of COL3A1 gene (p<0.05). In conclusion, the results indicate that dietary ALA may contribute to the improvement of meat quality in broilers.

Cell suspension culture of Eriobotrya japonica regulates the diabetic and hyperlipidemic signs of high-fat-fed mice

The present study investigates the anti-hyperlipidemic and antihyperglycemic effects and mechanism in high-fat (HF)-fed mice of cell suspension culture of Eriobotrya japonica (TA), which contains a great number of pentacyclic terpenoids. Firstly, C57BL/6J mice were randomly divided into two groups: the control (CON) group was fed with a low-fat diet (n = 9), whereas the experimental group was fed a 45% HF diet for 8 weeks. Afterwards, the CON group was treated with vehicle, whereas the HF group was subdivided into five groups and was orally given TA or rosiglitazone or not for 4 weeks. Blood and visceral adipose tissue, liver tissue and skeletal muscle were examined. Treatment with TA reduced body weight gain, weights of white adipose tissue (WAT) (including epididymal, perirenal, mesenteric WAT and visceral fat), and hepatic triacylglycerol content significantly without affecting food intake in diet-induced diabetic mice. TA effectively prevented HF diet-induced increases in the levels of blood glucose, insulin, leptin and HOMA-IR index (p < 0.001, p < 0.05, p < 0.05, p < 0.01, respectively) and attenuated insulin resistance. Treatment with TA, adipocytes in the visceral depots showed a reduction in size. TA effectively significantly increased the protein contents of phosphorylation of AMPK-α (Thr172) both in liver and adipose tissue. It is shown that TA exhibits hypolipidemic effect in HF-fed mice by decreasing gene expressions of fatty acid synthesis, including acyl-coenzyme A: diacylglycerol acyltransferase (DGAT) 2, which catalyzes the final step in the synthesis of triglycerides, and antidiabetic properties occurred as a result of decreased hepatic glucose production via phosphenolpyruvate carboxykinase (PEPCK) down- regulation, improved insulin sensitization and TA (at 1.0 g/kg dose) decreased expression of hepatic and adipose 11-β-hydroxysteroid dehydroxygenase (11β-HSD1) gene, which contributed in attenuating diabetic state. Futhermore, TA at doses of 0.5 and 1.0 g/kg had serum lipid-lowering action characterized by the inhibition of DGAT 1 expression. Thus, amelioration of diabetic and dyslipidemic state by TA in HF-fed mice occurred by regulation of PEPCK, DGAT2 and AMPK phosphorylation.

α-Lipoic acid reduced weight gain and improved the lipid profile in rats fed with high fat diet

The purpose of this study was to investigate the effects of α-lipoic acid on body weight and lipid profiles in Sprague-Dawley rats fed a high fat diet (HFD). After 4 weeks of feeding, rats on the HFD were divided into three groups by randomized block design; the first group received the high-fat-diet (n = 10), and the second group received the HFD administered with 0.25% α-lipoic acid (0.25LA), and the third group received the high-fat diet with 0.5% α-lipoic acid (0.5LA). The high fat diet with α-lipoic acid supplemented groups had significantly inhibited body weight gain, compared to that in the HFD group (P < 0.05). Organ weights of rats were also significantly reduced in liver, kidney, spleen, and visible fat tissues in rats supplemented with α-lipoic acid (P < 0.05). Significant differences in plasma lipid profiles, such as total lipids, total cholesterol, triglycerides, low-density lipoprotein, and high-density lipoprotein, were observed between the HFD and 0.5LA groups. The atherogenic index and the plasma high density lipoprotein-cholesterol/total cholesterol ratio improved significantly with α-lipoic acid supplementation in a dose-dependent manner (P < 0.05). Total hepatic cholesterol and total lipid concentration decreased significantly in high fat fed rats supplemented with α-lipoic acid in a dose-dependent manner (P < 0.05), whereas liver triglyceride content was not affected. In conclusion, α-lipoic acid supplementation had a positive effect on weight gain and plasma and liver lipid profiles in rats.

Effects of lipoic acid on AMPK and adiponectin in adipose tissue of low- and high-fat-fed rats

BACKGROUND

Lipoic acid (LA) is an antioxidant with antiobesity and antidiabetic properties. Adiponectin is an adipokine with potent anti-inflammatory and insulin-sensitizing properties. AMP-activated protein kinase (AMPK) is a key enzyme involved in cellular energy homeostasis. Activation of AMPK has been considered as a target to reverse the metabolic abnormalities associated with obesity and type 2 diabetes.

AIM OF THE STUDY

The aim of this study was to determine the effects of LA on AMPK phosphorylation and adiponectin production in adipose tissue of low-fat (control diet) and high-fat diet-fed rats.

RESULTS

Dietary supplementation with LA reduced body weight and adiposity in control and high-fat-fed rats. LA also reduced basal hyperinsulinemia as well as the homeostasis model assessment (HOMA) levels, an index of insulin resistance, in high-fat-fed rats, which was in part independent of their food intake lowering actions. Furthermore, AMPK phosphorylation was increased in white adipose tissue (WAT) from LA-treated rats as compared with pair-fed animals. Dietary supplementation with LA also upregulated adiponectin gene expression in WAT, while a negative correlation between adiposity-corrected adiponectin levels and HOMA index was found. Our present data suggest that the ability of LA supplementation to prevent insulin resistance in high-fat diet-fed rats might be related in part to the stimulation of AMPK and adiponectin in WAT.

Early maternal undernutrition programs increased feed intake, altered glucose metabolism and insulin secretion, and liver function in aged female offspring

Insulin resistance and obesity are components of the metabolic syndrome that includes development of cardiovascular disease and diabetes with advancing age. The thrifty phenotype hypothesis suggests that offspring of poorly nourished mothers are predisposed to the various components of the metabolic syndrome due to adaptations made during fetal development. We assessed the effects of maternal nutrient restriction in early gestation on feeding behavior, insulin and glucose dynamics, body composition, and liver function in aged female offspring of ewes fed either a nutrient-restricted [NR 50% National Research Council (NRC) recommendations] or control (C: 100% NRC) diet from 28 to 78 days of gestation, after which both groups were fed at 100% of NRC from day 79 to lambing and through lactation. Female lambs born to NR and C dams were reared as a single group from weaning, and thereafter, they were fed 100% NRC recommendations until assigned to this study at 6 yr of age. These female offspring were evaluated by a frequently sampled intravenous glucose tolerance test, followed by dual-energy X-ray absorptiometry for body composition analysis prior to and after ad libitum feeding of a highly palatable pelleted diet for 11 wk with automated monitoring of feed intake (GrowSafe Systems). Aged female offspring born to NR ewes demonstrated greater and more rapid feed intake, greater body weight gain, and efficiency of gain, lower insulin sensitivity, higher insulin secretion, and greater hepatic lipid and glycogen content than offspring from C ewes. These data confirm an increased metabolic "thriftiness" of offspring born to NR mothers, which continues into advanced age, possibly predisposing these offspring to metabolic disease.

Effects of α-lipoic acid and L-carnosine supplementation on antioxidant activities and lipid profiles in rats

α-Lipoic acid and L-carnosine are powerful antioxidants and are often used as a health supplement and as an ergogenic aid. The objective of this study was to investigate the effects of α-lipoic acid and/or L-carnosine supplementation on antioxidant activity in serum, skin, and liver of rats and blood lipid profiles for 6 weeks. Four treatment groups received diets containing regular rat chow diet (control, CON), 0.5% α-lipoic acid (ALA), 0.25% α-lipoic acid + 0.25% L-carnosine (ALA + LC), or 0.5% L-carnosine (LC). Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and lipid peroxidation products, malondialdehyde (MDA) concentrations, were analyzed in serum, skin, and liver. Blood lipid profiles were measured, including triglycerides (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C). Skin and liver SOD activities of the ALA and LC groups were higher than those of the CON group (P < 0.05), but serum SOD activity was higher only in the LC group compared to that in the CON group (P < 0.05). Additionally, only liver GSH-Px activity in the LC group was higher than that of the CON and the other groups. Serum and skin MDA levels in the ALA and LC groups were lower than those in the CON group (P < 0.05). Serum TG and TC in the ALA and ALA + LC groups were lower than those in the CON and LC groups (P < 0.05). The HDL-C level in the LC group was higher than that in any other group (P < 0.05). LDL-C level was lower in the ALA + LC and LC groups than that in the CON group (P < 0.05). Thus, α-lipoic acid and L-carnosine supplementation increased antioxidant activity, decreased lipid peroxidation in the serum, liver, and skin of rats and positively modified blood lipid profiles.

Modulation of glycogen and breast meat processing ability by nutrition in chickens: effect of crude protein level in 2 chicken genotypes

The aim of the study was to evaluate the impact of 2 isoenergetic growing diets with different CP (17 vs. 23%) on the performance and breast meat quality of 2 lines of chicken divergently selected for abdominal fatness [i.e., fat and lean (LL) lines]. Growth performance, breast and abdominal fat yields, breast meat quality parameters (pH, color, drip loss), and muscle glycogen storage at death were measured. Increased dietary CP resulted in increased BW, increased breast meat yield, and reduced abdominal fatness at slaughter regardless of genotype (P < 0.001). By contrast, dietary CP affected glycogen storage and the related meat quality parameters only in the LL chickens. Giving LL chickens the low-CP diet led to reduced concentration of muscle glycogen (P < 0.01), and as a result, breast meat with a higher (P < 0.001) ultimate pH, decreased (P < 0.001) lightness, and reduced (P < 0.001) drip loss during storage. The decreased muscle glycogen content observed in LL receiving the low-CP diet compared with the high-CP diet occurred concomitantly with greater phosphorylation amount for the α-catalytic subunit of adenosine monophosphate-activated protein kinase and glycogen synthase. This was consistent with the reduced muscle glycogen content observed in LL fed the low-CP diet because adenosine monophosphate-activated protein kinase inhibits glycogen synthesis through its action on glycogen synthase. Our results demonstrated that nutrition is an effective means of modulating breast meat properties in the chicken. The results also highlighted the need to take into account interaction with the genetic background of the animal to select nutritional strategies to improve meat quality traits in poultry.

Eriobotrya japonica improves hyperlipidemia and reverses insulin resistance in high-fat-fed mice

The effect of Eriobotrya japonica Lindl. (loquat) on insulin resistance was examined in mice fed a high-fat (HF) diet. First, the mice were divided randomly into two groups: the control (CON) group was fed a low-fat diet, whereas the experimental group was fed with a 45% HF diet for 10 weeks. After 6 weeks of induction, the HF group was subdivided into five groups and was given orally loquat or not for 4 weeks afterward. It was demonstrated that loquat was effective in ameliorating the HF diet-induced hyperglycemia, hyperleptinemia, hyperinsulinemia and hypertriglyceridemia, as well as in decreasing the levels of free fatty acid (FFA), but increasing the adipose PPARγ (peroxisomal proliferator-activated receptor γ) and hepatic PPARα mRNA levels. Loquat significantly decreased the body weight gain, weights of white adipose tissue and visceral fat accompanying the suppressed leptin mRNA levels. Loquat not only suppressed the hepatic mRNA levels of enzymes involved in fatty acid and triacylglycerol synthesis and lowered the sterol regulatory element binding protein-1c (SREBP-1c) mRNA level, but also affected fatty acid oxidation enzyme levels. These regulations may contribute to triacylglycerol accumulation in white adipose tissue. The findings provide a nutritional basis for the use of loquat as a functional food factor that may have benefits for the prevention of hyperlipidemia and diabetes.

Role of obesity-associated dysfunctional adipose tissue in cancer: a molecular nutrition approach

Obesity is a complex disease caused by the interaction of a myriad of genetic, dietary, lifestyle and environmental factors, which favors a chronic positive energy balance, leading to increased body fat mass. There is emerging evidence of a strong association between obesity and an increased risk of cancer. However, the mechanisms linking both diseases are not fully understood. Here, we analyze the current knowledge about the potential contribution that expanding adipose tissue in obesity could make to the development of cancer via dysregulated secretion of pro-inflammatory cytokines, chemokines and adipokines such as TNF-α, IL-6, leptin, adiponectin, visfatin and PAI-1. Dietary factors play an important role in the risk of suffering obesity and cancer. The identification of bioactive dietary factors or substances that affect some of the components of energy balance to prevent/reduce weight gain as well as cancer is a promising avenue of research. This article reviews the beneficial effects of some bioactive food molecules (n-3 PUFA, CLA, resveratrol and lipoic acid) in energy metabolism and cancer, focusing on the molecular mechanisms involved, which may provide new therapeutic targets in obesity and cancer.

Dietary fructose accelerates the development of diabetes in UCD-T2DM rats: amelioration by the antioxidant, alpha-lipoic acid

Sustained fructose consumption has been shown to induce insulin resistance and glucose intolerance, in part, by promoting oxidative stress. Alpha-lipoic acid (LA) is an antioxidant with insulin-sensitizing activity. The effect of sustained fructose consumption (20% of energy) on the development of T2DM and the effects of daily LA supplementation in fructose-fed University of California, Davis-Type 2 diabetes mellitus (UCD-T2DM) rats, a model of polygenic obese T2DM, was investigated. At 2 mo of age, animals were divided into three groups: control, fructose, and fructose + LA (80 mg LA.kg body wt(-1).day(-1)). One subset was followed until diabetes onset, while another subset was euthanized at 4 mo of age for tissue collection. Monthly fasted blood samples were collected, and an intravenous glucose tolerance test (IVGTT) was performed. Fructose feeding accelerated diabetes onset by 2.6 +/- 0.5 mo compared with control (P < 0.01), without affecting body weight. LA supplementation delayed diabetes onset in fructose-fed animals by 1.0 +/- 0.7 mo (P < 0.05). Fructose consumption lowered the GSH/GSSG ratio, while LA attenuated the fructose-induced decrease of oxidative capacity. Insulin sensitivity, as assessed by IVGTT, decreased in both fructose-fed and fructose + LA-supplemented rats. However, glucose excursions in fructose-fed LA-supplemented animals were normalized to those of control via increased glucose-stimulated insulin secretion. Fasting plasma triglycerides were twofold higher in fructose-fed compared with control animals at 4 mo, and triglyceride exposure during IVGTT was increased in both the fructose and fructose + LA groups compared with control. In conclusion, dietary fructose accelerates the onset of T2DM in UCD-T2DM rats, and LA ameliorates the effects of fructose by improving glucose homeostasis, possibly by preserving beta-cell function.

Mouse AMP-activated protein kinase gamma3 subunit R225Q mutation affecting mouse growth performance when fed a high-energy diet

The Rendement Napole (RN) genotype widely exists in Hampshire pigs. Recently, RN gene was identified as a R200Q mutation in AMP-activated protein kinase (AMPK) gamma3 subunit. The effect of RN genotype on the growth performance of animals and the underlying mechanisms remain controversial. Using transgenic mice carrying an analogous R225Q mutation, the objective of this study was to study the role of RN gene in the growth performance of animals at different energy levels. Wild-type (WT) mice and those with the RN mutation were assigned to 4 groups: 1) WT plus normal diet, 2) RN plus normal diet, 3) WT plus high-energy diet, and 4) RN plus high-energy diet. Mice were weaned at 21 d old and fed the trial diets for 1 mo and then killed for carcass measurements. The pH of postmortem muscle from RN mice was less (P < 0.01) than that from WT mice. No difference in growth performance was observed when mice were fed a normal diet. When fed a high-energy diet, RN mice showed a greater fat accumulation (WT vs. RN, 1.11 vs. 1.63 g for gonadal fat and 1.40 vs. 1.84 g for subcutaneous fat; P < 0.05). Muscle weight was also increased (WT vs. RN, 0.27 vs. 0.30 g for gastrocnemius muscle; P < 0.05). The food consumption was greater in RN compared with WT mice (2.95 vs. 2.49 g; P < 0.05). The AMPK content and its downstream target, acetyl-CoA carboxylase (ACC), content were greater in RN mice (P < 0.05). The phosphorylation of ACC at Ser 79, a site exclusively phosphorylated by AMPK, was increased (P < 0.05), showing greater AMPK activity in RN mouse muscle. No difference in muscle fiber composition and mitochondrial content was observed between WT and RN mice. High fat diet downregulates protein kinase B but upregulates extracellular signal-regulated kinase signaling. In conclusion, the R225Q mutation has no major effect on the growth performance of animals fed a normal diet; a high-energy diet increased fatness in RN mice, likely due to their greater consumption of feed compared with WT mice.

Lipoic acid prevents body weight gain induced by a high fat diet in rats: effects on intestinal sugar transport

Several studies have suggested that oxidative stress might cause and aggravate the inflammatory state associated with obesity and could be the link between excessive weight gain and its related disorders such as insulin resistance and cardiovascular diseases. Thus, antioxidant treatment has been proposed as a therapy to prevent and manage obesity and associated complications. Therefore, the aim of the present study was to investigate the effects of supplementation of a standard or high fat diet with the antioxidant lipoic acid (LA) during 56 days, on body weight gain, adiposity, feed efficiency and intestinal sugar absorption, in male Wistar rats. LA supplementation induced a lower body weight gain and adipose tissue size in both control or high fat fed rats accompanied by a reduction in food intake. The group fed on a high fat diet and treated with LA (OLIP group) showed a lower body weight gain than its corresponding Pair-Fed (PF) group (P < 0.05), which received the same amount of food than LA-treated animals but with no LA. In fact, LA induced a reduction on feed efficiency and also significantly decreased intestinal alpha-methylglucoside (alpha-MG) absorption both in lean and obese rats. These results suggest that the beneficial effects of dietary supplementation with LA on body weight gain are mediated, at least in part, by the reduction observed in food intake and feed efficiency. Furthemore, the inhibitory action of LA on intestinal sugar transport could explain in part the lower feed efficiency observed in LA-treated animals and therefore, highlighting the beneficial effects of LA on obesity.

Dietary alpha-lipoic acid supplementation inhibits atherosclerotic lesion development in apolipoprotein E-deficient and apolipoprotein E/low-density lipoprotein receptor-deficient mice

BACKGROUND

Vascular inflammation and lipid deposition are prominent features of atherosclerotic lesion formation. We have shown previously that the dithiol compound alpha-lipoic acid (LA) exerts antiinflammatory effects by inhibiting tumor necrosis factor-alpha- and lipopolysaccharide-induced endothelial and monocyte activation in vitro and lipopolysaccharide-induced acute inflammatory responses in vivo. Here, we investigated whether LA inhibits atherosclerosis in apolipoprotein E-deficient (apoE-/-) and apoE/low-density lipoprotein receptor-deficient mice, 2 well-established animal models of human atherosclerosis.

METHODS AND RESULTS

Four-week-old female apoE-/- mice (n=20 per group) or apoE/low-density lipoprotein receptor-deficient mice (n=21 per group) were fed for 10 weeks a Western-type chow diet containing 15% fat and 0.125% cholesterol without or with 0.2% (wt/wt) R,S-LA or a normal chow diet containing 4% fat without or with 0.2% (wt/wt) R-LA, respectively. Supplementation with LA significantly reduced atherosclerotic lesion formation in the aortic sinus of both mouse models by approximately 20% and in the aortic arch and thoracic aorta of apoE-/- and apoE/low-density lipoprotein receptor-deficient mice by approximately 55% and 40%, respectively. This strong antiatherogenic effect of LA was associated with almost 40% less body weight gain and lower serum and very low-density lipoprotein levels of triglycerides but not cholesterol. In addition, LA supplementation reduced aortic expression of adhesion molecules and proinflammatory cytokines and aortic macrophage accumulation. These antiinflammatory effects of LA were more pronounced in the aortic arch and the thoracic aorta than in the aortic sinus, reflecting the corresponding reductions in atherosclerosis.

CONCLUSIONS

Our study shows that dietary LA supplementation inhibits atherosclerotic lesion formation in 2 mouse models of human atherosclerosis, an inhibition that appears to be due to the "antiobesity," antihypertriglyceridemic, and antiinflammatory effects of LA. LA may be a useful adjunct in the prevention and treatment of atherosclerotic vascular diseases.

Relationship between kinase phosphorylation, muscle fiber typing, and glycogen accumulation in longissimus muscle of beef cattle with high and low intramuscular fat

The objective of this study was to examine the association of adenosine monophosphate (AMP)-activated protein kinase (AMPK) with glycogen content in bovine muscle and their links with intramuscular fat (IMF) and muscle fiber type composition. Five steers with high intramuscular fat (High IMF, IMF content is 5.71 +/- 0.36%) and five steers with low intramuscular fat (Low IMF, IMF content is 2.09 +/- 0.19%) in the longissimus thoracis muscle (LM) were selected for immunoblotting, glycogen, and myofiber type composition analyses. The glycogen content was higher in Low IMF muscle than in High IMF muscle (1.07 +/- 0.07 versus 0.85 +/- 0.08 g/100 g muscle, P < 0.05). Phosphorylation of the AMPK alpha subunit at Thr 172, which is correlated with its activity, was lower (P < 0.05) in High IMF compared to Low IMF. In agreement with the lower AMPK phosphorylation in High IMF muscle, the phosphorylation of acetyl-CoA carboxylase (ACC) was also lower (P < 0.05) in High IMF muscle than in Low IMF muscle. Glycogen synthase kinase 3 (GSK3) down-regulates glycogen synthesis through phosphorylation of glycogen synthase. The phosphorylation of GSK3 in High IMF was lower (P < 0.05) than that in Low IMF, which should down-regulate glycogen synthase activity and reduce the glycogen content in High IMF beef. Type IIB myosin isoform was absent in beef muscle. No noticeable difference in myosin isoform composition was observed between Low and High IMF muscle. In summary, High IMF cattle had lower LM glycogen levels than low IMF cattle, and AMPK activity was less in High IMF than in Low IMF cattle. The difference in glycogen content between Low and High IMF muscle was not correlated with muscle fiber composition. This data shows that LM lipid and glycogen metabolisms are affected by AMPK activity. Thus, AMPK may be a molecular target to alter IMF and glycogen levels in beef muscle.

Ca2+/calmodulin-dependent protein kinase kinase is involved in AMP-activated protein kinase activation by alpha-lipoic acid in C2C12 myotubes

alpha-Lipoic acid (ALA) widely exists in foods and is an antidiabetic agent. ALA stimulates glucose uptake and increases insulin sensitivity by the activation of AMP-activated protein kinase (AMPK) in skeletal muscle, but the underlying mechanism for AMPK activation is unknown. Here, we investigated the mechanism through which ALA activates AMPK in C2C12 myotubes. Incubation of C2C12 myotubes with 200 and 500 microM ALA increased the activity and phosphorylation of the AMPK alpha-subunit at Thr(172). Phosphorylation of the AMPK substrate, acetyl CoA carboxylase (ACC), at Ser(79) was also increased. No difference in ATP, AMP, and the calculated AMP-to-ATP ratio was observed among the different treatment groups. Since the upstream AMPK kinase, LKB1, requires an alteration of the AMP-to-ATP ratio to activate AMPK, this data showed that LKB1 might not be involved in the activation of AMPK induced by ALA. Treatment of ALA increased the intracellular Ca(2+) concentration measured by fura-2 fluorescent microscopy (P < 0.05), showing that ALA may activate AMPK through enhancing Ca(2+)/calmodulin-dependent protein kinase kinase (CaMKK) signaling. Indeed, chelation of intracellular free Ca(2+) by loading cells with 25 microM BAPTA-AM for 30 min abolished the ALA-induced activation of AMPK and, in turn, phosphorylation of ACC at Ser(79). Furthermore, inhibition of CaMKK using its selective inhibitor, STO-609, abolished ALA-stimulated AMPK activation, with an accompanied reduction of ACC phosphorylation at Ser(79). In addition, ALA treatment increased the association of AMPK with CaMKK. To further show the role of CaMKK in AMPK activation, short interfering RNA was used to silence CaMKK, which abolished the ALA-induced AMPK activation. These data show that CaMKK is the kinase responsible for ALA-induced AMPK activation in C2C12 myotubes.

The halothane gene, energy metabolism, adenosine monophosphate-activated protein kinase, and glycolysis in postmortem pig longissimus dorsi muscle1

The presence of the halothane gene results in PSE meat. However, the exact mechanisms linking the halothane gene and the incidence of PSE meat remain unclear. We hypothesize that the presence of the halothane gene accelerates energy consumption in postmortem muscle, which activates adenosine monophosphate-activated protein kinase (AMPK), leading to enhanced glycolysis and PSE meat. To test our hypothesis, energy status, AMPK activity, and glycolysis in the postmortem LM of the halothane gene carrier and halothane-negative pigs were compared. The results showed that the presence of the halothane gene accelerated energy depletion in postmortem muscle immediately after exsanguination, leading to rapid and early depletion of ATP, as shown by an increase in the (adenosine monophosphate + inosine monophosphate):ATP ratio in postmortem LM. In addition, an early AMPK activation was observed in LM from halothane carriers. The fructose-2,6-diphosphate concentration in postmortem LM was well correlated with AMPK activation. To be a potent stimulator of phosphofructose kinase, the increase in fructose-2,6-diphosphate is expected to activate phosphofructose kinase, a key enzyme controlling glycolysis, leading to enhanced glycolysis and early accumulation of lactic acid. In summary, this study showed that the presence of the halothane gene induced early energy depletion, which could be a primary reason causing AMPK activation, leading to accelerated glycolysis and an increased incidence of PSE meat. However, AMPK might also be activated by other mechanisms besides energy depletion, which warrants further studies.