Discovery and characterization of a small-molecule enteropeptidase inhibitor, SCO-792.

Enteropeptidase, localized into the duodenum brush border, is a key enzyme catalyzing the conversion of pancreatic trypsinogen proenzyme to active trypsin, thereby regulating protein digestion and energy homeostasis. We report the discovery and pharmacological profiles of SCO-792, a novel inhibitor of enteropeptidase. A screen employing fluorescence resonance energy transfer was performed to identify enteropeptidase inhibitors. Inhibitory profiles were determined by in vitro assays. To evaluate the in vivo inhibitory effect on protein digestion, an oral protein challenge test was performed in rats. Our screen identified a series of enteropeptidase inhibitors, and compound optimization resulted in identification of SCO-792, which inhibited enteropeptidase activity in vitro, with IC 50 values of 4.6 and 5.4 nmol/L in rats and humans, respectively. In vitro inhibition of enteropeptidase by SCO-792 was potentiated by increased incubation time, and the calculated Kinact/KI was 82 000/mol/L s. An in vitro dissociation assay showed that SCO-792 had a dissociation half-life of almost 14 hour, with a calculated koff rate of 0.047/hour, which suggested that SCO-792 is a reversible enteropeptidase inhibitor. In normal rats, a ≤4 hour prior oral dose of SCO-792 effectively inhibited plasma elevation of branched-chain amino acids in an oral protein challenge test, which indicated that SCO-792 effectively inhibited protein digestion in vivo. In conclusion, our new screen system identified SCO-792 as a potent and reversible inhibitor against enteropeptidase. SCO-792 slowly dissociated from enteropeptidase in vitro and inhibited protein digestion in vivo. Further study using SCO-792 could reveal the effects of inhibiting enteropeptidase on biological actions.

SCO-792, an enteropeptidase inhibitor, improves disease status of diabetes and obesity in mice.

AIMS: Enteropeptidase is a serine protease localized on the duodenal brush border that catalyzes the conversion of inactive trypsinogen into active trypsin, thereby regulating protein breakdown in the gut. We evaluated the effects of SCO-792, a novel enteropeptidase inhibitor, in mice. MATERIALS AND METHODS: In vivo inhibition of enteropeptidase was evaluated via an oral protein challenge. Pharmacological effects were evaluated in normal mice, in diet-induced obese (DIO) mice and in obese and diabetic ob/ob mice. RESULTS: A single oral administration of SCO-792 inhibited plasma branched-chain amino acids (BCAAs) in an oral protein challenge test in mice, indicating in vivo inhibition of enteropeptidase. Repeated treatment with SCO-792 induced reduction in food intake and decrease in body weight in DIO and ob/ob mice. Plasma FGF21 levels were increased in SCO-792-treated DIO mice, an observation that was probably independent of reduction in food intake. Hyperglycaemia was markedly improved in SCO-792-treated ob/ob mice. A hyperinsulinaemic-euglycaemic clamp study revealed improved muscle insulin sensitivity in SCO-792-treated ob/ob mice. SCO-792 also improved plasma and liver lipid profiles and decreased plasma alanine transaminase, suggesting a potential treatment for liver diseases. Dietary supplementation with essential amino acids attenuated the effect of SCO-792 on reduction in food intake and decrease in body weight in normal mice, suggesting a pivotal role for enteropeptidase in these biological phenomena. CONCLUSIONS: SCO-792 inhibited enteropeptidase in vivo, reduced food intake, decreased body weight, increased insulin sensitivity, improved glucose and lipid control, and ameliorated liver parameters in mouse models with obesity and/or diabetes. SCO-792 may exhibit similar effects in patients.

Losartan ameliorates progression of glomerular structural changes in diabetic KKAy mice.

Pathological changes in glomerular structure are typically associated with the progression of diabetic nephropathy. The involvement of angiotensin II (AII) in pathogenesis of diabetic nephropathy has been extensively studied and the therapeutic advantages associated with blockade of renin-angiotensin system (RAS), primarily with angiotensin converting enzyme (ACE) inhibitors, has been well-documented. We studied the effect of RAS blockade with an AII receptor antagonist (losartan) vs. an ACE inhibitor (enalapril) on glomerular lesions in KKAy mice, a model of type 2 diabetes mellitus. Losartan was administered at 3 and 10 mg/kg/day and enalapril at 3 mg/kg/day for 14 weeks in the drinking water. The doses of losartan at 10 mg/kg/day was expected to be equivalent to 3 mg/kg/day of enalapril when considering clinical doses for lowering blood pressure. The dose of 3 mg/kg/day of losartan was selected to compare the efficacy at equivalent dose of enalapril. Histologic observation demonstrated suppression of glomerular mesangial expansion and glomerulosclerosis with exudative lesion in the 10 mg/kg/day losartan group when compared to the untreated diabetic controls. A lesser degree of glomerulosclerosis was also observed with losartan and enalapril treatment at 3 mg/kg/day. Ultrastructural examination of renal glomeruli from the high dose losartan group revealed a decreased degree of effacement and/or irregular arrangement of glomerular podocytic foot process. The beneficial effect of RAS inhibition with the AII receptor antagonist losartan on diabetic glomerular lesions was clearly demonstrated in this study. These findings, therefore, provide mechanistic explanation for the clinical utility of losartan for use in the treatment of diabetic nephropathy in man.