Effect of somatostatin analogs on gastric acid secretion in dogs and rats

SARS-CoV-2 RNA Dependent RNA polymerase (RdRp) - A drug repurposing study

The outbreak of SARS-CoV-2 in December 2019 in China subsequently lead to a pandemic. Lack of vaccine and specific anti-viral drugs started a global health disaster. For a sustained control and protection, development of potential anti-viral drugs is one of the targeted approach. Although, designing and developing a panel of new drugs molecules are always encouraged. However, in the current emergency, drug repurposing study is one of the most effective and fast track option. The crystal structure of a SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) RNA Dependent RNA Polymerase (RdRp) has recently been deciphered through X-ray crystallography. The single-chain of core RNA Dependent RNA Polymerase relies on virus-encoded cofactors nsp7 and two units of nsp8 for its optimum function. This study explored the FDA approved database of 7922 molecules and screened against the core polymerase along with cofactors. Here we report a panel of FDA approved drugs that show substantial interactions with key amino acid residues of the active site. Interestingly, some of the identified drugs (Ornipressin, Lypressin, Examorelin, Polymyxin B1) bind strongly within the binding pockets of both forms of RdRp. Besides, we found strong candidates for the complex form as well which include Nacortocin, Cistinexine, Cisatracurium (among others). These drugs have the potential to be considered while contriving therapeutic options.

Vapreotide: a somatostatin analog for the treatment of acute variceal bleeding

BACKGROUND

Portal hypertension is a clinically important consequence of cirrhosis that can lead to morbidities such as variceal bleeding, hepatic encephalopathy and ascites. All of these outcomes carry high mortality rates. There have been several drugs created to assist with endoscopic therapy for the treatment of acute variceal bleeding. Recently, vapreotide has been studied in patients to evaluate its efficacy as treatment for acute variceal hemorrhage. Although no comparisons have been made between vapreotide and other somatostatin analogues, this drug has been shown to have efficacy in the control of acute variceal bleeding as well as reducing the risk of recurrent bleeding and death, especially when started prior to endoscopy.

OBJECTIVE

This paper reviews the literature regarding the basic science and clinical efficacy of vapreotide in acute variceal bleeding.

METHODS

We used a PubMed/Medline search in order to review the literature regarding the drug, vapreotide.

RESULTS/CONCLUSIONS

Vapreotide appears to have benefit in the control of acute variceal bleeding. It is easy to administer and has few side effects, which are minor. These findings endorse the need for future trials to evaluate vapreotide and its use in acute variceal hemorrhage, a morbidity among patients with cirrhosis.

Vapreotide acetate for the treatment of esophageal variceal bleeding

Variceal bleeding is a life-threatening complication of portal hypertension. The recommended treatment includes the early administration of a vasoactive drug. Vapreotide is a somatostatin analogue with a different receptor affinity to octreotide. It decreases portal pressure and blood flow of collateral circulation in rats with cirrhosis. The pivotal study of early administration of vapreotide in patients with cirrhosis and variceal bleeding has shown a significant improvement in bleeding control and, in the subset of patients with significant bleeding, a significant reduction in mortality. In addition, a meta-analysis of four randomized studies has shown a significant improvement in bleeding control. Vapreotide administrated via the intravenous route is simple to use, with practically no contraindications and few, usually minor, side effects.

Acute in vivo effect of octreotide acetate, a somatostatin analogue on the cellular function of gastric mucosa in the rat

Somatostatin is known to suppress various cellular functions of the gastrointestinal tract. In the present study, octreotide acetate, a synthetic long-acting somatostatin analogue was tested for its effects on some cellular functions of gastric mucosa. Octreotide raised the gastric mucosal pH within 1 h after a single subcutaneous injection to rats at doses of 1-100 microg/kg bodyweight. Serum gastrin levels increased transiently at a dose of 10 microg/kg bodyweight but not at 100 microg/kg. Basal levels of serum gastrin were not affected, while famotidine-induced gastrin secretion was suppressed by octreotide at a single dose of 100 microg/kg. The increase in the intragastric acidity and histidine decarboxylase activity following pentagastrin treatment was significantly reduced by octreotide. These results suggested that this somatostatin analogue inhibits the function of not only the parietal cell and G cell but also the enterochromaffin-like (ECL) cell, resulting in intraluminal hypoacidity.

Effects of the long-acting somatostatin analogue octreotide on abomasal function and plasma level of insulin and glucagon in sheep

The effects of the long-acting somatostatin analogue octreotide were studied in sheep. Octreotide was given subcutaneously at a dose of 0.75 microgram/kg bodyweight and, as a control, 0.9% saline solution was injected in a change-over design. Octreotide inhibited abomasal acid secretion and retarded the turnover time of digesta through the abomasum. The plasma levels of insulin and glucagon decreased due to the octreotide injection, while the plasma glucose level was not affected. The effects of octreotide lasted for 3-4h. There were no significant effects of the saline injection. The effects of octreotide showed similarities with results from previous studies on monogastric species.

Central action of somatostatin analog, SMS 201-995, to stimulate gastric acid secretion in rats

The effects of intracisternal and intravenous injections of the somatostatin analog, SMS 201-995, on gastric acid secretion were investigated in rats with pylorus ligation or gastric cannula. Intracisternal injection of SMS 201-995 induced a dose-related (0.1-0.3 microgram) and long-lasting stimulation of gastric acid output with a peak response at 3 h postinjection in conscious, pylorus-ligated rats. Intracisternal SMS 201-995 increased histamine levels in the portal blood, whereas plasma gastrin levels were not modified. Atropine, cimetidine and adrenalectomy abolished the stimulatory effect of intracisternal SMS 201-995 (0.3 microgram). SMS 201-995 (0.03 microgram), microinjected unilaterally into the dorsal vagal complex, increased gastric acid output in urethane anesthetized rats. SMS 201-995, injected intravenously at 0.5 microgram, did not alter gastric secretion, whereas higher doses (5-20 micrograms) resulted in a dose-related inhibition of gastric acid secretion in conscious pylorus-ligated rats. These data indicate that SMS 201-995, a selective ligand for somatostatin-1 receptor subtype, induces a centrally mediated stimulatory effect on gastric acid secretion in rats. The central action involves the parasympathetic system, muscarinic and H2 receptors as well as adrenal-dependent pathways.

Somatostatin analogue RC-160 inhibits the growth of transplanted colon cancer in rats

The effect of somatostatin analogue RC-160 on the growth of DHD/K12 rat colon cancer has been investigated in vivo as well as in vitro. Twenty syngeneic BDIX rats with s.c. implanted tumors were divided randomly into 2 groups. The rats from each group received a daily s.c. injection of either RC-160 (100 micrograms/kg/day) or injection vehicle as control for 37 days starting from the day of tumor inoculation. Tumor volumes were measured every 3-4 days. At the end of the treatment, the mean tumor volume was 504.5 +/- 97.0 mm3 in the control group and 177.8 +/- 60.5 mm3 in the RC-160 treated group (p less than 0.01). The tumor volume doubling time was calculated to be 11 days in the control group and 13.5 days in the RC-160 group, respectively. The tumor growth delay time was 18 days. Using bromodeoxyuridine labelling in vivo, the mean labelling index in the tumors was decreased by 35% (p less than 0.01) after RC-160 treatment. Total protein and total DNA contents in the tumors were decreased by 70.1% (p less than 0.05) and 68.7% (p less than 0.05), respectively. The data indicate that somatostatin analogue RC-160 inhibits the growth of DHD/K12 colon cancer in vivo. In 2 studies in vitro, DHD/K12 cells were cultured for 72 hr with RC-160 and natural somatostatin-14 (S-S-14) at concentrations ranging from 62.5 ng/ml to 2,000 ng/ml. Tumor-cell growth was measured spectrophotometrically by the crystal violet staining assay. No direct effect on tumor cell growth in vitro was observed with either RC-160 or S-S-14, possibly because of the loss of somatostatin receptors in previous passages of the DHD/K12 cell line.