Effect of thyroid hormone on contractility and sarco/endoplasmic Reticulum Ca[2+] ATPase -1 [SERCA1] expression in adult rats; role in thermogenesis

Thyroid hormone is one of the main factors that determine skeletal muscle contractile properties and the slow-twitch vs. fast twitch muscle fiber phenotype. Sarcoplasmic reticulum Ca[2+] ATPase is one of the principal regulators of Ca[2+] homeostasis in the skeletal muscle cells. It has been previously shown that modification of thyroid hormone levels has a profound impact on cardiac function, predominantly through a direct regulation of the sarcoplasmic reticulum protein levels. The present study aimed to investigate the effects of thyroid hormone treatment for 4 weeks on slow twitch soleus muscle of rats via recording twitch tension, time to peak tension, and half relaxation time and determination of soleus muscle SERCA1 expression. 24 male rats of local strain were randomly divided into 2 groups [n=12], control euthyroid group and hyperthyroid group in which hyperthyroidism was induced by intra peritoneal [i.p] injection of L-troxin 200microg/kg B.W./day, for 4 weeks. The in-situ isometric measures were done for soleus muscle and twitch tension [TT], [expressed as screen units], time to peak tension [TPT], and half relaxation time, 1/2 Rt [expressed in milliseconds] were recorded. SERCA1 protein expression in rat soleus muscle was measured. Thyroid hormone treatment significantly reduced time to peak tension and half relaxation time and increased twitch tension. These contractile changes were accompanied with significant increase in expression of SERCA1 in soleus muscle of rats. Thyroid hormone stimulates the expression of SERCA1 in slow soleus muscle in rats, thereby speeding-up the contraction-relaxation cycle and this increases energy expenditure and these effects of thyroid hormone participate at least in part to thermogenic action of thyroid hormone

Oxidative stress and antioxidants in hepatitis C virus patients

Malondialdehyde [MDA] is widely used as an index of oxidative injury induced by oxygen free radical on lipid membranes. Vitamin E [Vit.E] has been found to protect the liver against oxidative stress. There are inverse correlations between the increase of peroxide and the decrease of the ceruloplasmin [Cp] in patients with hepatitis C virus [HCV]. To estimate serum levels of malondialdehyde [MDA], of vitamin E [Vit.E] and ceruloplasmin [Cp], and to correlate their serum levels with the presence of cirrhosis and hence their use as non invasive blood markers. This study is a cross sectional study conducted on 40 newly discovered HCV infected cases receiving no treatment for hepatitis C virus [HCV] attending the Tropical Clinic in Cairo University Hospitals. They were 25 females and 15 males [age ranged from 25 to 60 years] as well as 15 age and sex matched healthy control subjects. Diagnosis of HCV was made by hepatitis markers using microparticle enzyme immunoassay [MEIA]. All patients were subjected to full history taking, clinical examination, abdominal ultrasonography, Laboratory tests included serum AST, ALT, total protein and albumin by routine analytical methods. Serum MDA level was estimated by thiobarbituric acid [TBA] chemical method, serum vitamin E by isocratic HPLC/UV method and serum Cp by immuno-nephlometric method. Patients were classified into two groups: Group I [patients with HCV infection] that was further divided into; Group I [a]: Included 26 HCV patients without cirrhosis. Group I [b]: 14 HCV patients with cirrhosis according to their ultrasonographic findings. Group II [control group]: Were HCV-antibody negative. The level of serum Cp did not differ between groups I [a], I [b] and II. The mean values of serum levels of MDA were significantly higher in all HCV positive patients compared to controls [p<0.001] and were higher in group I [a] compared to group I [b] with statistically significant difference [p<0.000]. The mean values of serum levels of Vitamin E were significantly lower in all HCV positive patients compared to controls [p<0.001] and were higher in group I [b] compared to group I [a] with statistically significant difference [p<0.000]. Serum levels of MDA showed a highly significant positive correlation with serum levels of ALT in group I [a] [r=0.633; p=0.001]. Both MDA and vitamin E levels are reliable indicators for the extent of oxidative stress and antioxidant status in HCV patients. MDA can be used as a simple non-invasive blood marker for detection of progression of chronic HCV to fibrosis