Immunoreactive pancreatic polypeptide components in plasma from normal subjects and patients with chronic renal failure in basal and postprandial conditions

Degradation Paradigm of the Gut Hormone, Pancreatic Polypeptide, by Hepatic and Renal Peptidases

Pancreatic polypeptide (PP) is a gut hormone that acts on Y4 receptors to reduce appetite. Obese humans display a reduced postprandial increase in PP and remain fully sensitive to the anorectic effects of exogenous PP. The utility of PP as an anti-obesity treatment is limited by its short circulating half-life. Insight into the mechanisms by which PP is degraded could aid in the design of long-acting PP analogs. We investigated the role of peptidases in PP degradation to determine whether inhibition of these enzymes enhanced PP plasma levels and bioactivity in vivo. Dipeptidyl peptidase IV (DPPIV) and neprilysin (NEP) were two peptidase found to cleave PP. Limiting the effect of both peptidases improved the in vivo anorectic effect of PP and PP-based analogs. These findings suggest that inhibiting the degradation of PP using specific inhibitors and/or the design of analogs resistant to cleavage by DPPIV and NEP might be useful in the development of PP as an anti-obesity pharmacotherapy.

Endogenous pancreatic polypeptide in different vascular beds: relationship to release and degradation in subjects with normal and decreased kidney function

The plasma concentration of pancreatic polypeptide (PP-like immunoreactivity) was measured in different vascular beds in order to determine regional kinetics of endogenous PP in fasting, supine subjects with normal or moderately decreased kidney function. Patients with kidney disease (n = 10) had a significantly higher level of circulating PP than controls (n = 10): median PP = 52 (range 21 to 352) v 20 (6 to 143) pmol/L, respectively (P less than 0.02). Circulating PP was inversely correlated to 51Cr-EDTA plasma clearance (r = -0.57, P less than 0.02, n = 14) and directly correlated to serum creatinine concentration (r = 0.70, P less than 0.01). Hepatic venous PP was significantly higher than systemic PP in both controls and patients with kidney disease (P less than 0.001, n = 15). The values were positively correlated (r = 0.98, P less than 0.001; slope = 1.37 +/- 0.05, P less than 0.001), indicating a progressively increasing rate of PP secretion in subjects with raised circulating PP. No statistically significant difference could be detected between systemic and renal venous PP or across the lung, left adrenal gland, or lower limb. Assuming steady state between secretion and biodegradation, the metabolic clearance rate of the peptide was estimated to be approximately 600 to 800 mL/min in controls and slightly below this value in patients with nephropathy. These results suggest that the raised circulating PP found in patients with decreased kidney function is due to both increased secretion and decreased degradation.(ABSTRACT TRUNCATED AT 250 WORDS)