A ubiquitous endocrine disruptor tributyltin induces muscle wasting and retards muscle regeneration.

BACKGROUND: Organotin pollutant tributyltin (TBT) is an environmental endocrine disrupting chemical and is a known obesogen and diabetogen. TBT can be detected in human following consumption of contaminated seafood or water. The decrease in muscle strength and quality has been shown to be associated with type 2 diabetes in older adults. However, the adverse effects of TBT on the muscle mass and function still remain unclear. Here, we investigated the effects and molecule mechanisms of low-dose TBT on skeletal muscle regeneration and atrophy/wasting using the cultured skeletal muscle cell and adult mouse models. METHODS: The mouse myoblasts (C2C12) and differentiated myotubes were used to assess the in vitro effects of low-dose tributyltin (0.01-0.5 µM). The in vivo effects of TBT at the doses of 5 and 25 µg/kg/day (n = 6/group), which were five times lower than the established no observed adverse effect level (NOAEL) and equal to NOAEL, respectively, by oral administration for 4 weeks on muscle wasting and muscle regeneration were evaluated in a mouse model with or without glycerol-induced muscle injury/regeneration. RESULTS: TBT reduced myogenic differentiation in myoblasts (myotube with 6-10 nuclei: 53.9 and 35.8% control for 0.05 and 0.1 µM, respectively, n = 4, P < 0.05). TBT also decreased myotube diameter, upregulated protein expression levels of muscle-specific ubiquitin ligases (Atrogin-1 and MuRF1), myostatin, phosphorylated AMPKα, and phosphorylated NFκB-p65, and downregulated protein expression levels of phosphorylated AKT and phosphorylated FoxO1 in myotubes (0.2 and 0.5 µM, n = 6, P < 0.05). Exposure of TBT in mice elevated body weight, decreased muscle mass, and induced muscular dysfunction (5 and 25 µg/kg, P > 0.05 and P < 0.05, respectively, n = 6). TBT inhibited soleus muscle regeneration in mice with glycerol-induced muscle injury (5 and 25 µg/kg, P > 0.05 and P < 0.05, respectively, n = 6). TBT upregulated protein expression levels of Atrogin-1, MuRF1, myostatin, and phosphorylated AMPKα and downregulated protein expression level of phosphorylated FoxO1 in the mouse soleus muscles (5 and 25 µg/kg, P > 0.05 and P < 0.05, respectively, n = 6). CONCLUSIONS: This study demonstrates for the first time that low-dose TBT significantly inhibits myogenic differentiation and triggers myotube atrophy in a cell model and significantly decreases muscle regeneration and muscle mass and function in a mouse model. These findings suggest that low-dose TBT exposure may be an environmental risk factor for muscle regeneration inhibition, atrophy/wasting, and disease-related myopathy.

Improvement of Glycemic Control by a Functional Food Mixture Containing Maltodextrin, White Kidney Bean Extract, Mulberry Leaf Extract, and Niacin-Bound Chromium Complex in Obese Diabetic db/db Mice.

Steady-fiber granule (SFG) is a mixture containing maltodextrin, white kidney bean extract, mulberry leaf extract, and niacin-bound chromium complex. These active ingredients have been shown to be associated with improving either hyperglycemia or hyperlipidemia. This study was undertaken to evaluate the potential of SFG in the regulation of blood glucose homeostasis under obese diabetic conditions. Accordingly, db/db mice (8 weeks old) were administered with SFG at doses of 1.025, 2.05, or 5.125 g/kg BW daily via oral gavage for 4 weeks. No body weight loss was observed after SFG supplementation at all three doses during the experimental period. Supplementation of SFG at 2.05 g/kg BW decreased fasting blood glucose, blood fructosamine, and HbA1c levels in db/db mice. Insulin sensitivity was also improved, as indicated by HOMA-IR assessment and oral glucose tolerance test, although the fasting insulin levels were no different in db/db mice with or without SFG supplementation. Meanwhile, the plasma levels of triglyceride were reduced by SFG at all three doses. These findings suggest that SFG improves glycemic control and insulin sensitivity in db/db mice and can be available as an option for functional foods to aid in management of type 2 diabetes mellitus in daily life.

Protective Effect of Djulis (Chenopodium formosanum) Extract against UV- and AGEs-Induced Skin Aging via Alleviating Oxidative Stress and Collagen Degradation.

Skin aging is a complex process involving photoaging and glycation stress, which share some fundamental pathways and have common mediators. They can cause skin damage and collagen degradation by inducing oxidative stress and the accumulation of reactive oxygen species (ROS). Chenopodium formosanum (CF), also known as Djulis, is a traditional cereal in Taiwan. This study investigated the protection mechanisms of CF extract against ultraviolet (UV) radiation and advanced glycation end products (AGEs)-induced stress. The results indicated that CF extract had strong antioxidant and free radical scavenging effects. It could reduce UV-induced intracellular ROS generation and initiate the antioxidant defense system by activating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway in human skin fibroblasts. CF extract modulated mitogen-activated protein kinase (MAPK) and transformed growth factor-beta (TGF-ß) signaling pathways to alleviate oxidative stress-induced skin aging. Moreover, the results revealed that CF extract not only promoted collagen synthesis but also improved aging-induced collagen degradation. CF extract attenuated AGEs-induced ROS production and the upregulation of receptor for AGEs (RAGE). The overall results suggest that CF extract provides an effective anti-aging strategy by preventing skin damage from oxidative stress and collagen loss with potent antioxidant, anti-photoaging, and antiglycation activities.

ANGPTL1 attenuates cancer migration, invasion, and stemness through regulating FOXO3a-mediated SOX2 expression in colorectal cancer.

Angiopoietin-like protein 1 (ANGPTL1) is a member of the ANGPTL family that suppresses angiogenesis, cancer invasion, metastasis, and cancer progression. ANGPTL1 is down-regulated in various cancers including colorectal cancer (CRC); however, the effects and mechanisms of ANGPTL1 on liver metastasis and cancer stemness in CRC are poorly understood. In the present study, we identified that ANGPTL1 was down-regulated in CRC and inversely correlated with metastasis and poor clinical outcomes in CRC patients form the ONCOMINE database and Human Tissue Microarray staining. ANGPTL1 significantly suppressed the migration/invasion abilities, the expression of cancer stem cell (CSC) markers, and sphere formation by enhancing FOXO3a expression, which contributed to the reduction of stem cell transcription factor SOX2 expression in CRC cells. Consistently, overexpression of ANGPTL1 reduced liver metastasis, tumor growth, and tumorigenicity in tumor-bearing mice. ANGPTL1 expression was negatively correlated with CSC markers expression and poor clinical outcomes in CRC patients. Taken together, these findings demonstrate that the molecular mechanisms of ANGPTL1 in colorectal cancer stem cell progression may provide a novel therapeutic strategy for CRC.

Influence of Dietary Chitosan Feeding Duration on Glucose and Lipid Metabolism in a Diabetic Rat Model.

This study was designed to investigate the influence of dietary chitosan feeding-duration on glucose and lipid metabolism in diabetic rats induced by streptozotocin and nicotinamide [a non-insulin-dependent diabetes mellitus (NIDDM) model]. Male Sprague-Dawley rats were used as experimental animals and divided into short-term (6 weeks) and long-term (11 weeks) feeding durations, and each duration contained five groups: (1) control, (2) control + 5% chitosan, (3) diabetes, (4) diabetes + 0.8 mg/kg rosiglitazone (a positive control), and (5) diabetes + 5% chitosan. Whether the chitosan feeding was for 6 or 11 weeks, the chitosan supplementation decreased blood glucose and lipids levels and liver lipid accumulation. However, chitosan supplementation decreased plasma tumor necrosis factor (TNF)-α, insulin levels, alanine aminotransferase (ALT) activity, insulin resistance (HOMA-IR), and adipose tissue lipoprotein lipase activity. Meanwhile, it increased plasma high-density lipoproteins (HDL)-cholesterol level, plasma angiopoietin-like-4 protein expression, and plasma triglyceride levels (at 11-week feeding duration only). Taken together, 11-week (long-term) chitosan feeding may help to ameliorate the glucose and lipid metabolism in a NIDDM diabetic rat model.

Low-Dose Acrolein, an Endogenous and Exogenous Toxic Molecule, Inhibits Glucose Transport via an Inhibition of Akt-Regulated GLUT4 Signaling in Skeletal Muscle Cells.

Urinary acrolein adduct levels have been reported to be increased in both habitual smokers and type-2 diabetic patients. The impairment of glucose transport in skeletal muscles is a major factor responsible for glucose uptake reduction in type-2 diabetic patients. The effect of acrolein on glucose metabolism in skeletal muscle remains unclear. Here, we investigated whether acrolein affects muscular glucose metabolism in vitro and glucose tolerance in vivo. Exposure of mice to acrolein (2.5 and 5 mg/kg/day) for 4 weeks substantially increased fasting blood glucose and impaired glucose tolerance. The glucose transporter-4 (GLUT4) protein expression was significantly decreased in soleus muscles of acrolein-treated mice. The glucose uptake was significantly decreased in differentiated C2C12 myotubes treated with a non-cytotoxic dose of acrolein (1 µM) for 24 and 72 h. Acrolein (0.5-2 µM) also significantly decreased the GLUT4 expression in myotubes. Acrolein suppressed the phosphorylation of glucose metabolic signals IRS1, Akt, mTOR, p70S6K, and GSK3α/ß. Over-expression of constitutive activation of Akt reversed the inhibitory effects of acrolein on GLUT4 protein expression and glucose uptake in myotubes. These results suggest that acrolein at doses relevant to human exposure dysregulates glucose metabolism in skeletal muscle cells and impairs glucose tolerance in mice.

Advanced glycation end products activated endothelial-to-mesenchymal transition in pancreatic islet endothelial cells and triggered islet fibrosis in diabetic mice.

Advanced glycation end products (AGEs) are associated with the pathogenesis of diabetic vascular complications. Induction of the endothelial-to-mesenchymal transition (EndMT) is associated with the pathogenesis of fibrotic diseases. The roles of AGEs in islet EndMT induction and diabetes-related islet microvasculopathy and fibrosis remain unclear. This study investigated the pathological roles of AGEs in islet EndMT induction and fibrosis in vitro and in vivo. Non-cytotoxic concentrations of AGEs upregulated the protein expression of fibronectin, vimentin, and α-smooth muscle actin (α-SMA) (mesenchymal/myofibroblast markers) and downregulated the protein expression of vascular endothelial (VE)-cadherin and cluster of differentiation (CD) 31 (endothelial cell markers) in cultured mouse pancreatic islet endothelial cells, which was prevented by the AGE cross-link breaker alagebrium chloride. In streptozotocin-induced diabetic mice, the average islet area and islet immunoreactivities for insulin and CD31 were decreased and the islet immunoreactivities for AGEs and α-SMA and fibrosis were increased, which were prevented by the AGE inhibitor aminoguanidine. Immunofluorescence double staining showed that α-SMA-positive staining co-localized with CD31-positive staining in the diabetic islets, which was effectively prevented by aminoguanidine. These results demonstrate that AGEs can induce EndMT in islet endothelial cells and islet fibrosis in diabetic mice, suggesting that AGE-induced EndMT may contribute to islet fibrosis in diabetes.

The Anti-Melanogenesis Effect of 3,4-Dihydroxybenzalacetone through Downregulation of Melanosome Maturation and Transportation in B16F10 and Human Epidermal Melanocytes.

The biosynthesis pathway of melanin is a series of oxidative reactions that are catalyzed by melanin-related proteins, including tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1), and tyrosinase-related protein-2 (TRP-2). Reagents or materials with antioxidative or free radical-scavenging activities may be candidates for anti-melanogenesis. 3,4-Dihydroxybenzalacetone (DBL) is a polyphenol isolated from fungi, such as Phellinus obliguus (Persoon) Pilat and P. linteus. In this study, we investigated the effects and mechanisms of DBL on antioxidation and melanogenesis in murine melanoma cells (B16F10) and human epidermal melanocytes (HEMs). The results indicated that DBL scavenged 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radicals, and exhibited potent reducing power, indicating that it displays strong antioxidative activity. DBL also inhibited the expression of TYR, TRP-1, TRP-2, and microphthalmia-related transcription factor (MITF) in both the cells. In addition, DBL inhibited hyperpigmentation in B16F10 and HEMs by regulating the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA), v-akt murine thymoma viral oncogene homolog (AKT)/glycogen synthase kinase 3 beta (GSK3ß), and mitogen-activated protein kinase kinase (MEK)/extracellular regulated protein kinase (ERK) signaling pathways. DBL not only shortened dendritic melanocytes but also inhibited premelanosome protein 17 (PMEL17) expression, slowing down the maturation of melanosome transportation. These results indicated that DBL promotes anti-melanogenesis by inhibiting the transportation of melanosomes. Therefore, DBL is a potent antioxidant and depigmenting agent that may be used in whitening cosmetics.

Inorganic Arsenic Exposure Decreases Muscle Mass and Enhances Denervation-Induced Muscle Atrophy in Mice.

Arsenic is a toxic metalloid. Infants with a low birth-weight have been observed in areas with high-level arsenic in drinking water ranging from 463 to 1025 µg/L. A distal muscular atrophy side effect has been observed in acute promyelocytic leukemia patients treated with arsenic trioxide (As2O3) for therapy. The potential of As2O3 on muscle atrophy remains to be clarified. In this study, the myoatrophic effect of arsenic was evaluated in normal mice and sciatic nerve denervated mice exposed with or without As2O3 (0.05 and 0.5 ppm) in drinking water for 4 weeks. We found that both 0.05 and 0.5 ppm As2O3 increased the fasting plasma glucose level; but only 0.5 ppm arsenic exposure significantly decreased muscle mass, muscle endurance, and cross-sectional area of muscle fibers, and increased muscle Atrogin-1 protein expression in the normal mice. Both 0.05 and 0.5 ppm As2O3 also significantly enhanced the inhibitory effects on muscle endurance, muscle mass, and cross-sectional area of muscle fibers, and increased the effect on muscle Atrogin-1 protein expression in the denervated mice. These in vivo results suggest that inorganic arsenic at doses relevant to humans may possess myoatrophic potential.

Exposure of low-concentration arsenic induces myotube atrophy by inhibiting an Akt signaling pathway.

Arsenic, a widely distributed toxic metalloid, has been found to be associated with the low-birth-weight infants and the impairment of muscle regenerative capacity in areas with high levels of arsenic in drinking water. The distal muscular atrophy is one of side effects of arsenic trioxide (As2O3) for acute promyelocytic leukemia therapy. We hypothesized that arsenic may be a potential risk factor for skeletal muscle atrophy. Here, we investigated the action and molecular mechanism of low-dose arsenic on the induction of skeletal muscle atrophy in a skeletal muscle cell model. The differentiated C2C12 myotubes were treated with As2O3 (0.25-1 µM) for 48 h without apparent effects on cell viability. The signaling molecules for myotube atrophy were assessed. Submicromolar-concentration As2O3 dose-dependently triggered C2C12 myotube atrophy and increased the protein expressions of atrogenes Atrogin1 and MuRF1 and inhibited the upstream phosphorylated proteins Akt and FoxO1, while As2O3 dose-dependently increased AMPK phosphorylation in myotubes. Akt activator SC79 could significantly reverse the As2O3-induced myotube atrophy. These results suggest that arsenic is capable of inducing myotube atrophy by inhibiting an Akt signaling pathway.

Studies of Coumarin Derivatives for Constitutive Androstane Receptor (CAR) Activation.

Constitutive androstane receptor (CAR) activation has found to ameliorate diabetes in animal models. However, no CAR agonists are available clinically. Therefore, a safe and effective CAR activator would be an alternative option. In this study, sixty courmarin derivatives either synthesized or purified from Artemisia capillaris were screened for CAR activation activity. Chemical modifications were on position 5,6,7,8 with mono-, di-, tri-, or tetra-substitutions. Among all the compounds subjected for in vitro CAR activation screening, 6,7-diprenoxycoumarin was the most effective and was selected for further preclinical studies. Chemical modification on the 6 position and unsaturated chains were generally beneficial. Electron-withdrawn groups as well as long unsaturated chains were hazardous to the activity. Mechanism of action studies showed that CAR activation of 6,7-diprenoxycoumarin might be through the inhibition of EGFR signaling and upregulating PP2Ac methylation. To sum up, modification mimicking natural occurring coumarins shed light on CAR studies and the established screening system provides a rapid method for the discovery and development of CAR activators. In addition, one CAR activator, scoparone, did showed anti-diabetes effect in db/db mice without elevation of insulin levels.

Comparative Effects and Mechanisms of Chitosan and Its Derivatives on Hypercholesterolemia in High-Fat Diet-Fed Rats.

The present study investigated and compared the effects of different molecular weights of chitosan (high molecular weight chitosan (HC) and low molecular weight chitosan (LC)) and its derivatives (chitosan oligosaccharide (CO)) on cholesterol regulation in high-fat (HF) diet-fed rats. A diet supplementation of 5% HC, 5% LC, or 5% CO for 8 weeks showed hypocholesterolemic potential in HF diet-fed rats. Unexpectedly, a 5% CO-supplemented diet exerted hepatic damage, producing increased levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and tumor necrosis factor-alpha (TNF-α). The supplementation of HC and LC, unlike CO, significantly decreased the hepatic total cholesterol (TC) levels and increased the fecal TC levels in HF diet-fed rats. The hepatic protein expression of the peroxisome proliferator-activated receptor-α (PPARα) in the HF diet-fed rats was markedly decreased, which could be significantly reversed by both HC and LC, but not CO, supplementation. Unlike the supplementation of CO, both HC and LC supplementation could effectively reverse the HF-inhibited/induced gene expressions of the low-density lipoprotein receptor (LDLR) and cholesterol 7α-hydroxylase (CYP7A1), respectively. The upregulated intestinal acyl-CoA cholesterol acyltransferase 2 (ACAT2) protein expression in HF diet-fed rats could be reversed by HC and LC, but not CO, supplementation. Taken together, a supplementation of 5% CO in HF diet-fed rats may exert liver damage via a higher hepatic cholesterol accumulation and a higher intestinal cholesterol uptake. Both HC and LC effectively ameliorated the hypercholesterolemia and regulated cholesterol homeostasis via the activation and inhibition of hepatic (AMPKα and PPARα) and intestinal (ACAT2) cholesterol-modulators, respectively, as well as the modulation of downstream signals (LDLR and CYP7A1).

The Anti-Obesity Effect of Polysaccharide-Rich Red Algae (Gelidium amansii) Hot-Water Extracts in High-Fat Diet-Induced Obese Hamsters.

This study investigated the anti-obesity effect of a polysaccharide-rich red algae Gelidium amansii hot-water extract (GHE) in high-fat (HF) diet-induced obese hamsters. GHE contained 68.54% water-soluble indigestible carbohydrate polymers. Hamsters were fed with a HF diet for 5 weeks to induce obesity, and then randomly divided into: HF group, HF with 3% guar gum diet group, HF with 3% GHE diet group, and HF with orlistat (200 mg/kg diet) group for 9 weeks. The increased weights of body, liver, and adipose in the HF group were significantly reversed by GHE supplementation. Lower plasma leptin, tumor necrosis factor-α, and interleukin-6 levels were observed in the GHE+HF group compared to the HF group. GHE also increased the lipolysis rate and decreased the lipoprotein lipase activity in adipose tissues. GHE induced an increase in the phosphorylation of AMP-activated protein kinase (AMPK) and the protein expressions of peroxisome proliferator-activated receptor alpha (PPARα) and uncoupling protein (UCP)-2 in the livers. The decreased triglyceride and total cholesterol in the plasma and liver were also observed in obese hamsters fed a diet with GHE. These results suggest that GHE exerts a down-regulation effect on hepatic lipid metabolism through AMPK phosphorylation and up-regulation of PPARα and UCP-2 in HF-induced obese hamsters.

Omega-3 Fatty Acids-Enriched Fish Oil Activates AMPK/PGC-1α Signaling and Prevents Obesity-Related Skeletal Muscle Wasting.

Obesity is known to cause skeletal muscle wasting. This study investigated the effect and the possible mechanism of fish oil on skeletal muscle wasting in an obese rat model. High-fat (HF) diets were applied to induce the defects of lipid metabolism in male Sprague-Dawley rats with or without substitution of omega-3 fatty acids-enriched fish oil (FO, 5%) for eight weeks. Diets supplemented with 5% FO showed a significant decrease in the final body weight compared to HF diet-fed rats. The decreased soleus muscle weights in HF diet-fed rats could be improved by FO substitution. The decreased myosin heavy chain (a muscle thick filament protein) and increased FOXO3A and Atrogin-1 (muscle atrophy-related proteins) protein expressions in soleus muscles of HF diet-fed rats could also be reversed by FO substitution. FO substitution could also significantly activate adenosine monophosphate (AMP)-activated protein kinase (AMPK) phosphorylation, peroxisome-proliferator-activated receptor-γ (PPARγ) coactivator 1α (PGC-1α), and PPARγ protein expression and lipoprotein lipase (LPL) mRNA expression in soleus muscles of HF diet-fed rats. These results suggest that substitution of FO exerts a beneficial improvement in the imbalance of lipid and muscle metabolisms in obesity. AMPK/PGC-1α signaling may play an important role in FO-prevented obesity-induced muscle wasting.

Gender difference of CCAAT/enhancer binding protein homologous protein deficiency in susceptibility to osteopenia.

Expression of CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) is induced during endoplasmic reticulum (ER) stress, which is related to apoptosis in several cell types. CHOP null mice have been exhibited to decrease bone formation. However, a study of transgenic mice overexpressing CHOP in the bone microenvironment showed that CHOP overexpression impairs the osteoblastic function leading to osteopenia. The regulatory role of CHOP in bone formation is controversial and still remains to be clarified. Here, we investigated the alterations in bone microstructure of CHOP knockout (Chop-/- ) mice and tested the gender difference of CHOP deficiency in susceptibility to osteopenia. Adult female and male mice (WT) and Chop-/- mice were used. The microcomputed tomography (µCT) analysis in trabecular bone and cortical bone of tibia was determined. Trabecular bone volume fraction (BV/TV), trabecular number, and bone mineral density (BMD) in tibia are markedly decreased in both male and female Chop-/- mice compared to the control WT mice. Unexpectedly, the BMD and BV/TV in trabecular bone of tibia in female Chop-/- mice were significantly lower than in male Chop-/- mice. The similar results could also be observed in the cortical bone of tibia in Chop-/- mice. This gender difference was also observed in the decreased capacity of osteoblast differentiation of bone marrow cells isolated from Chop-/- mice. These results indicated that ER stress-related CHOP signaling might play an important role in the bone formation in a mouse model, especially in females. There is the gender difference of CHOP deficiency in susceptibility to osteopenia. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Resistant Maltodextrin Ameliorates Altered Hepatic Lipid Homeostasis via Activation of AMP-Activated Protein Kinase in a High-Fat Diet-Fed Rat Model.

Many studies have shown that resistant maltodextrin (RMD) possesses blood cholesterol lowering and anti-obesity effects. In order to investigate the effect of RMD on lipid metabolism in the liver, rats were fed with a high-fat (HF) diet for 7 weeks to induce hyperlipidemia and fatty liver. Normal control rats were fed with a normal diet. HF-diet-fed rats were treated with 5% RMD for 8 weeks. The results showed that the increased plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, the increased hepatic triglyceride and total cholesterol levels, and fatty liver in HF-diet-fed rats were significantly decreased after supplementation with RMD. Supplementation with RMD significantly (1) induced AMP-activated protein kinase (AMPK) phosphorylation; (2) inhibited the activities of acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and HMG-CoA reductase (HMGCR); (3) suppressed the protein expression of peroxisome proliferator activated receptor (PPAR)-γ; (4) increased ß-oxidation of fatty acids by increasing the protein expression carnitine palmitoyl transferase 1α (CPT-1α) in the livers of HF-diet-fed rats. Taken together, supplementation of RMD was capable of inhibiting lipogenic enzyme activities and inducing fatty acid ß-oxidation through increasing AMPK activation, thereby reducing lipid accumulation in the liver.

Adverse effects of acrolein, a ubiquitous environmental toxicant, on muscle regeneration and mass.

BACKGROUND: Acrolein is an extremely electrophilic aldehyde. Increased urinary acrolein adducts have been found in type 2 diabetic patients and people with a smoking habit. The increased blood acrolein was shown in patients who received the cancer drug cyclophosphamide. Both diabetes and smoking are risk factors for skeletal muscle wasting or atrophy. Acrolein has been found to induce myotube atrophy in vitro. The in vitro and in vivo effects and mechanisms of acrolein on myogenesis and the in vivo effect of acrolein on muscle wasting still remain unclear. METHODS: C2C12 myoblasts were used to assess the effects of low-dose acrolein (0.125-1 µM) on myogenesis in vitro. Mice were exposed daily to acrolein in distilled water by oral administration (2.5 and 5 mg/kg) for 4 weeks with or without glycerol-induced muscle injury to investigate the effects of acrolein on muscle wasting and regeneration. RESULTS: Non-cytotoxic-concentration acrolein dose dependently inhibited myogenic differentiation in myoblasts (myotube formation inhibition: 0.5 and 1 µM, 66.25% and 46.25% control, respectively, n = 4, P < 0.05). The protein expression for myogenesis-related signalling molecules (myogenin and phosphorylated Akt: 0.5 and 1 µM, 85.15% and 51.52% control and 62.63% and 56.57% control, respectively, n = 4, P < 0.05) and myosin heavy chain (MHC: 0.5 and 1 µM, 63.64% and 52.53% control, n = 4, P < 0.05) were decreased in acrolein-treated myoblasts. Over-expression of the constitutively active form of Akt in myoblasts during differentiation prevented the inhibitory effects of acrolein (1 µM) on myogenesis (MHC and myogenin protein expression: acrolein with or without constitutively active Akt, 64.65% and 105.21% control and 69.14% and 102.02% control, respectively, n = 5, P < 0.05). Oral administration of acrolein for 4 weeks reduced muscle weights (5 mg/kg/day: 65.52% control, n = 6, P < 0.05) and cross-sectional area of myofibers in soleus muscles (5 mg/kg/day: 79.92% control, n = 6, P < 0.05) with an up-regulation of atrogin-1 and a down-regulation of phosphorylated Akt protein expressions. Acrolein retarded soleus muscle regeneration in a glycerol-induced muscle regeneration mouse model (5 mg/kg/day: 49.29% control, n = 4, P < 0.05). Acrolein exposure reduced muscle endurance during rotarod fatigue performance in mice with or without glycerol-induced muscle injury (5 mg/kg/day without glycerol: 30.43% control, n = 4, P < 0.05). Accumulation of acrolein protein adducts could be detected in the soleus muscles of acrolein-treated mice. CONCLUSIONS: Low-dose acrolein significantly inhibited myogenic differentiation in vitro, which might be through inhibition of Akt signalling. Acrolein induced muscle wasting and retarded muscle regeneration in mice. These results suggest that acrolein may be a risk factor for myogenesis and disease-related myopathy.

Prenatal developmental toxicity study of strontium citrate in Sprague Dawley rats.

In this study, the pregnant female Sprague Dawley (SD) rats were used to evaluate the potential toxicological effect of strontium citrate, a dietary supplement, on embryo-fetal development. Strontium citrate at doses of 0 mg/kg, 680 mg/kg, 1360 mg/kg, and 2267 mg/kg was administrated orally by gavage to rats at day 6 to day 15 of pregnancy. Each group contained 20 pregnant rats. On the 20th day of gestation, rats was anesthetized and dissected by cesarean section. The appearance, internal organs, gravid uterus weight, embryo implantation number, and implantation loss rate in maternal rats of each group did not reveal any lesions. In fetuses, there were no statistical differences in the fetus weight, sex ratio, embryo resorption number, stillbirth number, and fetal visceral examination in all testing groups compared to the control group. However, in 2267 mg/kg strontium citrate group, the fetuses showed the statistical differences in the anomalies of the bones and eyes compared to the control group. These findings indicate that high-dose strontium citrate possesses an adverse effect on embryonic and fetal development in SD rats. The no observed adverse effect level (NOAEL) of strontium citrate for prenatal development toxicity in SD rats may be regarded as 1360 mg/kg/day.

Functional Comparison of High and Low Molecular Weight Chitosan on Lipid Metabolism and Signals in High-Fat Diet-Fed Rats.

The present study examined and compared the effects of low- and high-molecular weight (MW) chitosan, a nutraceutical, on lipid metabolism in the intestine and liver of high-fat (HF) diet-fed rats. High-MW chitosan as well as low-MW chitosan decreased liver weight, elongated the small intestine, improved the dysregulation of blood lipids and liver fat accumulation, and increased fecal lipid excretion in rats fed with HF diets. Supplementation of both high- and low-MW chitosan markedly inhibited the suppressed phosphorylated adenosine monophosphate (AMP)-activated protein kinase-α (AMPKα) and peroxisome proliferator-activated receptor-α (PPARα) protein expressions, and the increased lipogenesis/cholesterogenesis-associated protein expressions [peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element binding protein-1c and -2 (SREBP1c and SREBP2)] and the suppressed apolipoprotein E (ApoE) and microsomal triglyceride transfer protein (MTTP) protein expressions in the livers of rats fed with HF diets. Supplementation with both a low- and high-MW chitosan could also suppress the increased MTTP protein expression and the decreased angiopoietin-like protein-4 (Angptl4) expression in the intestines of rats fed with HF diets. In comparison between low- and high-MW chitosan, high-MW chitosan exhibits a higher efficiency than low-MW chitosan on the inhibition of intestinal lipid absorption and an increase of hepatic fatty acid oxidation, which can improve liver lipid biosynthesis and accumulation.