ABSTRACT
Dysregulation of P70 ribosomal S6 kinase (P70S6K) has been observed in many cancers; therefore, the design of new molecules targeting p70S6K of paramount importance in cancer therapy. The current study employed a group-based quantitative structure-activity relationship (GQSAR) to develop global QSAR models capable of predicting the bioactivity of P70S6K inhibitors. A wide variety of chemical structures and biological activities (half maximal inhibitory concentration) of P70S6K inhibitors were collected from the binding database website. Compounds were classified into various chemical groups and then fragmented into R1, R2, and R3 fragments based on certain pharmacophoric features required for ligand-target biointeractions. Different two-dimensional fragment-based descriptors were calculated for each fragment. The dataset was then divided into a training set (n=40) and a test set (n=10) using a sphere exclusion algorithm. Multiple linear regressions coupled with simulated annealing or stepwise regression resulted in model A (r2=0.92) and model B (r2=0.87), respectively. Leave-one-out validation showed that models A and B have internal predictive abilities of 72% and 61%, respectively. External validation indicated that both models are robust, with squared cross-correlation coefficients of the training set (pred-r2) of 0.87 and 0.89, respectively. The developed GQSAR models indicate that fragment R3 plays a key role in activity variation (65%) with sound contribution of five-membered rings (5 chain count), aromatic carbons (SaaaCE-index), and aromatic nitrogens (SaaNcount). In contrast, fragments R1 and R2 together contribute 35% of activity variation, suggesting that sulfur atoms (Sulfur count) and hydrophobic threemembered rings (chi3 chain) at R1 are preferable for inhibitory activity.
ABSTRACT
The anticoagulant effect of leech saliva was traditionally employed in the treatment of diabetes mellitus complications such as peripheral vascular complications. This study was carried out to examine the effect of leech saliva extract (LSE) on blood glucose levels in alloxan-induced diabetic rats. First, LSE was collected from leeches which were fed on a phagostimulatory solution. Second, total protein concentration was estimated using the Bradford assay. Third, diabetic rats were injected subcutaneously (sc) with LSE at doses of 500 and 1 000 μg·kg(-1) body weight (bw). Other diabetic rats were injected sc with insulin at doses of 10 and 20 U·kg(-1) bw. Another group was injected simultaneously with LSE (250 μg·kg(-1) bw) and insulin (10 U·kg(-1) bw). Fasting blood glucose (FBG) concentrations were monitored during a study period of eight hours at regular intervals. Findings showed that both doses of LSE resulted in a significant and gradual decrease in FBG starting from 10%-18% downfall after two hours of injection reaching the maximal reduction activity of 58% after eight hours. Remarkably, LSE was sufficient to bring the rats to a near norm-glycemic state. The high dose of insulin induced a severe hypoglycemic condition after 2-4 h of injection. The lower dose was able to decline FBG for 2-6 h in rats which became diabetic again after 8 h. On the other hand, the concurrent injection of low doses of LSE and insulin produced a hypoglycemic effect with all rats showing normal FBG levels. Taken together, these findings indicated that the subcutaneous injection of LSE of the medicinal Malaysian leech was able to provide better glycemic control compared with insulin. Moreover, the synergism between LSE and insulin suggests that LSE could be utilized as an adjuvant medication in order to reduce insulin dosage or to achieve better control of blood glucose.