In the present study Fourier Transform Infrared Spectroscopy was used to examine the effects of streptozotocin-induced diabetes mellitus on the structural components of slow- and fast-twitch rat skeletal muscles, at molecular level. Diabetes mellitus is a chronic disorder of carbohydrate, fat and protein metabolism, which is characterized by hyperglycemia caused by a defective or deficient insulin secretory response. The effect of diabetes is seen on a variety of tissues leading to important secondary complications such as kidney failure, liver dysfunction, cardiac disorders, etc. Skeletal muscle is one of the major tissues determining carbohydrate and lipid metabolism in the body / therefore, is one of the target tissues of diabetes. The two main types of muscle fibers are type I (slow-twitch) and type II (fast-twitch) fibers / having different structural organization and metabolic features. The FTIR spectra revealed a considerable decrease in lipid and protein content of diabetic skeletal muscles, indicating an increased lipolysis and protein breakdown or decreased protein synthesis. Moreover changes in protein structure and conformation were observed. In diabetes, muscle membrane lipids were more ordered and the amount of unsaturated lipids was decreased possibly due to lipid peroxidation. Diabetes caused a decrease in the content of nucleic acids, especially RNA, and hydrogen bonded phospholipids in the membrane structures of skeletal muscles. In all of the spectral parameters investigated slow-twitch muscle was more severely affected from diabetes. Thus, FTIR spectroscopy appears to be a useful method to evaluate the effect of diabetes on skeletal muscle tissues at molecular level.

Un análisis de los tipos de fibras y de su distribución fue realizado en muestras de músculos de la lengua (mm. geniogloso, estilogloso, hiogloso y lingual propio), del paladar y fauces (mm. palatofaríngeo, palatino, elevador y tensor del velo palatino) y de la faringe (mm. terigofaríngeo, estilofaríngeo caudal, hiofaríngeo, tirofaríngeo y cricofaríngeo) en la especie canina. Asimismo, se procesaron muestras del músculo semitendinoso, que fue utilizado como músculo control. La tipificación fibrilar se basó en técnicas histoquímicas (mATPasa y NADH-TR) e inmunohistoquímicas (aplicación de anticuerpos monoclonales específicos frente a las cadenas pesadas de miosina tipos I, IIa y IIx). En todos los músculos estudiados se evidenciaron fibras puras (tipos I, IIA y IIX) e híbridas (tipos IIAX, IIXA y IIC). Por otra parte, en el músculo tensor del velo palatino también fueron identificadas fibras tipo IIM. / An analysis of fiber types and its distribution in canine muscles of the tongue (genioglossus, hyoglossus, styloglossus and lingualis propius muscles), soft palate (palatinus, levator veli palatini, tensor veli palatini and palatopharyngeus muscles), and pharynx (pterygopharyngeus, stylopharyngeus caudalis, hyopharyngeus, thyropharyngeus and cricopharyngeus muscles) was carried out. Additional samples were obtained from the semitendinosus muscle to be used as a control. Muscle fiber types were defined by histochemical (mATPase and NADH-TR), and immunohistochemical (monoclonal antibodies against myosin heavy chain isoforms I, IIa and IIx) techniques. In all analyzed muscles pure I, IIA and IIX fibers and hybrid IIAX, IIXA and IIC fibers were observed. Furthermore, type IIM fibers were identified in tensor veli palatini muscle

In the present study Fourier Transform Infrared (FTIR) and Attenuated Total Reflectance FTIR (ATR-FTIR) Spectroscopy were used to examine the effects of simvastatin on structure, composition and function of macromolecules of three different rat skeletal muscles EDL (Extensor Digitorium Longus), DIA (Diaphragm) and SOL (Soleus) containing different amount of slow and fast twitch fibers, at molecular level. Simvastatin, a lipophilic statin, is widely used in the treatment of hypercholesterolemia and cardiovascular diseases due to its higher efficacy. However, long term usage of statins give rise to many adverse effects on different tissues and organs. Skeletal muscle accounts for around 45 % of the total body weight and has a high metabolic rate and blood flow. As a consequence, it is highly exposed to drugs within the circulation. Therefore, it is one of the target tissues of statins. The two main types of muscle fibers are type I (slow-twitch) and type II (fast-twitch) fibers / having different structural organization and metabolic features. EDL is a fast twitch muscle while SOL is slow twitch muscle. On the other hand, DIA shows intermediate properties between slow and fast twitch muscle. The results of ATR-FTIR and FTIR spectra revealed a considerable decrease in protein and lipid content of simvastatin treated skeletal muscles, indicating protein breakdown or decreased protein synthesis and increased lipolysis. Moreover changes in protein structure and conformation were observed. In simvastatin treatment, muscle membrane lipids were more ordered and the amount of unsaturated lipids was decreased possibly due to lipid peroxidation. The drug treatment caused a decrease in the content of nucleic acids, especially RNA, and hydrogen and non-hydrogen bonded phospholipids in the membrane structures of skeletal muscles. In all of the spectral parameters investigated EDL muscle was more severely affected from statin treatments while SOL was less affected from the drug treatments. Thus, FTIR and ATR-FTIR spectroscopy appear to be useful methods to evaluate the effects of statin on skeletal muscle tissues at molecular level.

Metabolic Syndrome Insulin Resistance Is Associated with Discordant Distribution of GLUT4 and the Insulin Receptor in Fast-Twitch and Slow-Twitch Muscle Fiber Types We have previously shown that We have previously shown that strength training alone improved insulin responsiveness in sedentary controls but not in metabolic syndrome subjects. Immunoblots of metabolic syndrome subjects[apos] muscle homogenates showed training-related increases in GLUT4 and mitochondrial enzymes was half that seen in the controls. To determine if this was due to changes primarily in fast-twitch fibers (strength fibers), we performed immunohistochemical (IHC) studies on muscle sections from these subjects to quantify fiber-specific changes in GLUT4, phospho-AMPK, phospho-mTOR, ATP synthase, and the insulin receptor. Signal intensity in confocal microscopic images was digitally quantified and the amount in each fiber type was adjusted by the fiber composition and the average size of each fiber type. Fiber type was classified using monoclonal antibodies against slow-twitch (type 1 fibers) and fast-twitch (type 2a and 2b fibers) myosin heavy chains. At baseline, both groups had slightly more insulin receptor in slow-twitch fibers, and most of the ATP synthase (mitochondrial marker) was in fast-twitch fibers. In controls, 55% of GLUT4 was in slow-twitch fibers, whereas metabolic syndrome subjects had only 33% of their GLUT4 in slow-twitch fibers. The IHC data showed modest increases in GLUT4 (9-25%), and substantial increases of ATP synthase (55-95%), and insulin receptors (44-104%) in both fiber types in both groups. Training-related increases were seen in phospho-AMPK (25% in slow-twitch, 15% in fast-twitch) only in the control subjects but no change in phospho-mTOR in either subject group. At baseline, metabolic syndrome subjects[apos] muscle had 56% of insulin receptors expressed in slow-twitch fibers, but only 33% of the GLUT4 was in these fibers. Thus, the untrained muscle composition of the metabolic syndrome subjects exhibited a mismatch between insulin receptors and GLUT4 in their fiber-specific distributions. This mismatch may contribute to the insulin resistance seen in the metabolic syndrome and may be involved in the diminished insulin sensitivity response to strength training in these subjects.

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