Genetic activation of pyruvate dehydrogenase alters oxidative substrate selection to induce skeletal muscle insulin resistance

The pyruvate dehydrogenase complex (PDH) has been hypothesized to link lipid exposure to skeletal muscle insulin resistance through a glucose-fatty acid cycle in which increased fatty acid oxidation increases acetyl-CoA concentrations, thereby inactivating PDH and decreasing glucose oxidation. However, whether fatty acids induce insulin resistance by decreasing PDH flux remains unknown. To genetically examine this hypothesis we assessed relative rates of pyruvate dehydrogenase flux/mitochondrial oxidative flux and insulin-stimulated rates of muscle glucose metabolism in awake mice lacking pyruvate dehydrogenase kinase 2 and 4 [double knockout (DKO)], which results in constitutively activated PDH. Surprisingly, increased glucose oxidation in DKO muscle was accompanied by reduced insulin-stimulated muscle glucose uptake. Preferential myocellular glucose utilization in DKO mice decreased fatty acid oxidation, resulting in increased reesterification of acyl-CoAs into diacylglycerol and triacylglycerol, with subsequent activation of PKC-θ and inhibition of insulin signaling in muscle. In contrast, other putative mediators of muscle insulin resistance, including muscle acylcarnitines, ceramides, reactive oxygen species production, and oxidative stress markers, were not increased. These findings demonstrate that modulation of oxidative substrate selection to increase muscle glucose utilization surprisingly results in muscle insulin resistance, offering genetic evidence against the glucose-fatty acid cycle hypothesis of muscle insulin resistance.Lipid-induced muscle insulin resistance plays a major role in the pathogenesis of type 2 diabetes (T2D), but the cellular mechanisms remain unknown (1, 2). More than 50 y ago Randle et al. (3) postulated the glucose-fatty acid cycle to explain the impairment of insulin-stimulated glucose disposal by fatty acids in muscle. In this model, fat oxidation increases mitochondrial acetyl-CoA/CoA and NADH/NAD⁺ ratios. Acetyl-CoA and NADH allosterically inhibit pyruvate dehydrogenase complex (PDH), the mitochondrial enzyme that links glycolysis to the TCA cycle by converting pyruvate to acetyl-CoA. Additionally, fatty acid-derived acetyl-CoA produces citrate, which inhibits phosphofructokinase. This in turn increases glucose-6-phosphate (G6P), a potent allosteric inhibitor of hexokinase. By these mechanisms, increased fatty acid oxidation was hypothesized to reduce glycolytic flux and prevent further muscle glucose uptake. However, in vivo studies of human skeletal muscle metabolism have challenged the Randle hypothesis. Five hours of a lipid infusion, combined with heparin to activate lipoprotein lipase, raised plasma fatty acids and induced muscle insulin resistance in healthy individuals, yet intramyocellular G6P and glucose concentrations were reduced compared with control glycerol infusion studies, implicating defects in insulin-stimulated glucose transport activity (4, 5). An alternative hypothesis to explain the muscle insulin resistance associated with lipid exposure posits that accumulation of bioactive lipid intermediates initiates signaling cascades that impair insulin action. Lipid species implicated include diacylglycerols (DAGs) (6–10), ceramides (11, 12), and long-chain acyl-CoAs (13). DAG activation of PKC-θ in skeletal muscle has been shown to impair canonical insulin signaling at the level of insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation through increased IRS-1 serine phosphorylation at the 1101 position (2, 6, 7, 14).More recently, incomplete fat oxidation and subsequent accumulation of mitochondrially derived acylcarnitines has been proposed to contribute to lipid-induced muscle insulin resistance (15–17). According to this model, insulin resistance stems from increased fat oxidation, leading to increased conversion of acyl-CoA to medium- and long-chain acylcarnitines, which may mediate insulin resistance via unknown mechanisms. In contrast, short-chain acylcarnitines have been suggested to promote metabolic flexibility. The shortest acylcarnitine, acetylcarnitine, is synthesized from acetyl-CoA and carnitine by carnitine acetyltransferase (CrAT), a mitochondrial matrix enzyme, and is responsible for buffering the mitochondrial acetyl-CoA pool and mitigating acetyl-CoA inhibition of PDH (18). Consistent with the notion that CrAT regulates substrate selection by modulating PDH flux, mice with muscle-specific deletion of CrAT exhibited reduced PDH activity during the fed-to-fasted transition, resulting in glucose intolerance and metabolic inflexibility, a term coined by Kelley and Mandarino (19) to explain the impairment in the ability to adjust fuel oxidation to fuel availability.Although these studies emphasize the importance of PDH in the promotion of metabolic inflexibility, the role of PDH and mitochondrial oxidative substrate selection in the regulation of basal and insulin-stimulated muscle glucose metabolism has not been directly assessed in vivo. To examine this question, we sought to determine whether modulation of oxidative substrate selection in a genetic mouse model with constitutively active PDH activity would affect insulin sensitivity in skeletal muscle.     

Association of endothelial nitric oxide synthase gene variant (G894T) with coronary artery disease in Western Iran

There are conflicting reports about the association of endothelial nitric oxide synthase (eNOS) gene polymorphism and the risk of coronary artery disease (CAD). To determine the frequency of eNOS G894T variant and to find the possible association between this polymorphism with CAD we studied 207 unrelated patients with total CAD (with and without diabetes) and 92 controls. The eNOS variants were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The presence of GT + TT genotype was associated with 2.1-fold (P = .006), 2.29-fold (P = .006), and 1.93-fold (P = .032) increased risk of CAD in total CAD, CAD with diabetes, and in CAD without diabetes patients, respectively. The presence of T allele of eNOS increased the risk of CAD 2.15-fold (P = .001). The levels of low-density lipoprotein cholesterol (LDL-C) and triglycerides (TG) tended to be higher in patients carrier for T allele compared to those with G allele. The results of present study revealed that eNOS G894T polymorphism is associated with increased risk of CAD in our population.     

Osseous reaction to implantation of two endodontic cements: Mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM)

Aim: The aim of the present in vivo study was to determine bone tissue reaction to calcium enriched mixture (CEM) and mineral trioxide aggregate (MTA) using a rat femur model. Study Design: Sixty-three rats were selected and randomly divided into three groups of 21 each [experimental groups (n=15), control (n=6)]. Implantation cavities were prepared in each femoral bone and randomly filled with the biomaterials only in the experimental groups. The animals in three groups were sacrificed 1, 4, and 8 weeks postoperatively. Histologic evaluations comprising inflammation severity and new bone formation were blindly made on H&E-stained decalcified 6-μm sections. Results: At 1, 4, and 8 weeks after implantation number of inflammatory cells had decreased in the CEM, MTA and control groups, respectively, with no statistically significant differences. Conversely, new bone formation had increased in all the experimental and control groups, without statistically significant differences. Conclusion: The results suggest that biocompatibility of MTA, as gold standard, and CEM cement as a new endodontic biomaterial are comparable.     

Non-invasive management of fused upper incisors

The union of two different dental sprouts which can happen in any phase of dental development is commonly called fusion. This developmental anomaly may cause clinical problems including esthetic impairment, which are mainly treated by endodontic and surgical treatments. There are a few reports of conservative not invasive treatment of fused incisors teeth through restorative or prosthetic techniques. They are rarely reported in mandibular posterior teeth. This paper presents an unusual case of fusion of 7 and 8, and also 9 and 10 teeth which was treated with a nonendodontic and nonsurgical conservative approach. Patient was a healthy18-year-old female with chief complaint of bad-looking teeth that in intraoral examination revealed the fusion of 7 and 8, and also 9 and 10 teeth. The space between the mesial of the 6 and 11 teeth was reconstructed. Diastema between the fused teeth was closed. A new lateral tooth was replaced between the fused teeth (7 and 8) and 6 tooth with direct fiber-reinforced composite. The space between the fused teeth (9 and 10) and also tooth 11 was partially closed. Gingival papillas were reconstructed using pink composite. The mandibular anterior missing teeth were replaced with rochett bridge. At the end of treatment the esthetic of the patient was improved. As the treatment was not invasive, major complications are not expected; however, there is potential for eventual long-term periodontal problems due to poor oral hygiene. Debonding of the rochett bridge may happen as well.     

Prevalence and antimicrobial resistance of Salmonella isolated from fish, shrimp, lobster, and crab in Iran

The objective of this study was to determine the Salmonella prevalence, the serotypes involved, and antimicrobial susceptibility patterns of Salmonella isolates recovered from fish, shrimp, lobster, and crab in Iran. A total of 384 samples of fish, shrimp, lobster, and crab were collected in three provinces along the Persian Gulf in the south coast of Iran. Samples were collected at the end of each month from September 2009 to May 2011. All samples were evaluated for the presence of Salmonella, stereotyped and tested for antimicrobial susceptibility. There was an overall Salmonella prevalence of 5%. Salmonella was isolated from a significantly larger number of fish (10.4%) than shrimp (1.8%; P?≤?0.05). No Salmonella was isolated from lobster and crab samples. Salmonella isolates recovered from fish and shrimp samples were of five different serotypes including Salmonella typhimurium, Salmonella enteritidis, Salmonel la typhi, Salmonella paratyphi B, and Salmonella newport. Susceptibilities of Salmonella isolates were determined for 12 antimicrobial drugs using the disk-diffusion method. Resistance to nalidixic acid was the most common finding (47.4%), followed by resistance to tetracycline (36.8%), streptomycin (15.8%), trimethoprim (15.8%), and ciprofloxacin (5.3%). To our best knowledge, this is the first study on prevalence of Salmonella in fish, shrimp, lobster, and crab and the first report on the isolation of Salmonella spp. from retail fish and shrimp in Iran.     

Detection of classical enterotoxins of Staphylococcus aureus in raw sheep, goat, camel, and water buffalo milk by ELISA method

Milk is considered a nutritious food because it contains several important nutrients including proteins and vitamins. Conversely, it can be a vehicle for several pathogenic bacteria such as Staphylococcus aureus. The aim of the present study was to investigate the presence of classical enterotoxins of S. aureus in raw milk in Iran. For this purpose, from January 2011 to October 2011, a total of 88 raw milk samples from sheep (n?=?28), goat (n?=?27), camel (n?=?14), and water buffalo (n?=?19) were collected from 64 randomly selected herds in Isfahan, Chaharmahal va Bakhtiari, and Khuzestan provinces, Iran, and tested for staphylococcal enterotoxins (SEs) presence by enzyme-linked immunosorbent assay method. Out of 88 samples studied, 11 samples (12.5%) were positive for at least one SE. The prevalence rate of SEs contamination in raw sheep, goat, and water buffalo milk samples were 10.7%, 18.5%, and 15.8%. No classical SEs was founded from raw camel milk samples. Of these, four were positive for staphylococcal enterotoxin A (SEA), four for SEC, two SEA and SEC, and one for SEA and SED. None of the samples was positive for SEB and SEE. Statistical evaluation showed that there were no significant differences (P?>?0.05) between the presence of SEs raw sheep, goat, and water buffalo milk samples tested. The quality of Iranian milk is still low, and efforts from the government and the entire productive chain are required to attain consumer safety.     

The effect of He-Ne and Ga-Al-As laser light on the healing of hard palate mucosa of mice

Low-level laser therapy (LLLT) has been used to accelerate wound healing, yet questions remain concerning its therapeutic applications. This study aimed to compare the healing efficacy of helium-neon (He-Ne) red light (laser) and gallium aluminum arsenide (Ga-Al-As) infrared lasers at two different doses on hard palate wounds. In a randomized controlled study, 75 adult male mice were divided into five groups of 15 each, after undergoing identical surgical procedures; a control group, with no laser irradiation; HD1 and HD2 groups, treated with He-Ne laser (wavelengths 632.8 nm, power 5 mW, and spot size 0.02 cm²) at doses of 4 J/cm² and 7.5 J/cm² respectively; and GD1 and GD2 groups, treated with Ga-Al-As laser (wavelengths 830 nm, peak power 25 mW, and spot size 0.10 cm²) at the doses of 4 J/cm² and 7.5 J/cm², respectively. Five animals from each group were killed on the third, seventh, and 14 days after surgery, and biopsies were made for histological analysis. On the 3rd and 7th day after the surgery, the number of polymorphonuclear cells (PMN) in HD1, HD2, GD1, and GD2 groups was significantly lower than that of the control group. On the 7th and 14th day, the fibroblasts and new blood vessels counts and collagen density fibers in HD1, HD2, GD1, and GD2 groups were also significantly higher than that of the control groups, and the fibroblast counts and collagen density fibers in HD1 and HD2 groups were higher than that of the GD1 and GD2 groups. LLLT with He-Ne laser compared to Ga-Al-As laser has a positive healing effect on hard palate gingival wounds in mice regardless of the radiation dose.     

Knowledge levels and attitudes of health care professionals toward patients with hepatitis C infection

AIM: To study knowledge levels and attitudes of health care providers toward patients with hepatitis C virus infection in Guilan, a northern province of Iran.METHODS: This cross-sectional study was performed on 239 health care professionals from the Razi Hospital, including doctors, nurses, and operating room technicians. The questionnaires consisted of questions on demographic characteristics, knowledge levels, and attitudes toward hepatitis C patients. The questionnaire was tested in a pilot study and validated by Cronbach’s alpha coefficient. Data were analyzed using SPSS16 software.RESULTS: The mean ± SD knowledge score was 17.43 ± 2.65 (from a total of 22). 51.9% of the participants achieved scores higher than the mean. There was a significant relationship between knowledge score and age (P = 0.001), gender (P = 0.0001), occupational history (P = 0.0001), and educational history (P = 0.027). There was also a significant relationship between attitude level and age (P = 0.002), gender (P = 0.0001), occupational history (P = 0.0001), and educational history (P = 0.035). Physicians were significantly more knowledgeable and showed more positive attitudes. There was a positive correlation between knowledge and attitude scores (P = 0.02).CONCLUSION: Discriminatory attitudes are common among health care providers toward hepatitis C patients. It is therefore necessary to improve their knowledge level and attitude toward this disease.