Biology of enterostatin. II. Development of enzyme-linked immunosorbentassay (ELISA) for enterostatin (Val-Pro-Asp-Pro-Arg), the procolipase activation peptide

Enterostatin (VPDPR) Has Anti-analgesic and Anti-amnesic Activites

Enterostatin (VPDPR), an anorexigenic peptide derived from the amino terminus of procolipase, significantly inhibited analgesia induced by the mu-opioid agonist morphine (5 mg/kg, s.c.) after i.c.v. administration to mice at a dose of 100 nmol. On the other hand, VPDPR (approximately 200 nmol, i.c.v.) did not attenuate analgesia induced by the kappa-opioid agonist D-Phe-D-Phe-D-Nle-D-Arg-NH2 (100 microg/mouse, i.c.v.) or delta-opioid agonist DTLET (4 nmol/mouse, i.c.v.). VPDPR (100 nmol, i.c.v.) significantly improved amnesia induced by scopolamine (0.2 mg/kg, i.p.) in mice. However, VPDPR did not enhance memory in normal mice at the same dose.

Anti-analgesic activity of enterostatin (VPDPR) is mediated by corticosterone

Although enterostatin (VPDPR) inhibited morphine-induced analgesia, it had no affinity for mu-opioid receptors. VPDPR administration was reported to elevate serum corticosterone levels. We found that corticosterone exhibited a similar anti-analgesic effect selective for mu-opioid. Furthermore, the anti-analgesic effect of VPDPR was inhibited by RU486, an antagonist for the glucocorticoid receptor. The anti-analgesic effect of VPDPR was not observed in adrenalectomized mice. These results suggest that the anti-analgesic activity of VPDPR is mediated by corticosterone released from the adrenal cortex.

Comparative study of enterostatin sequence in five rat strains and enterostatin binding proteins in rat and chicken serum

Enterostatin, a pentapeptide derived from the precursor protein procolipase has been shown to inhibit dietary fat intake and to reduce body fat after chronic administration in rats. We repeat that the enterostatin amino acid sequence from the genomic DNA of 5 different rat strains is APGPR. 125I-APGPR bound to three proteins (300, 205 and 60 kDa) in rat serum and one 60 kDa protein in chicken serum. These serum binding proteins were also eluted by APGPR affinity chromatography. Western blot analysis of serum protein identified enterostatin-like immunoreactivity associated with the same molecular weight bands. Our results demonstrate the enterostatin sequence in rat is APGPR and suggest the presence of enterostatin binding proteins in rat and chicken serum.

Dehydroepiandrosterone-mediated decrease in caloric intake by obese Zucker rats is not due to changes in serum entrostatin-like immunoreactivity

To understand the mechanism(s) of appetite modulation by DHEA, we have undertaken a series of studies to examine the effects of DHEA on neurotransmitters and neuropeptides known to affect appetitive behavior. Here, we report the effect of DHEA on serum enterostatin-VPDPR or E, a pentapeptide known to cause selective diminution in fat intake. Four-week-old lean (fa/+) and obese (fa/fa) Zucker rats were divided into control and treatment groups. DHEA-treated groups received powdered chow containing 0.6% DHEA ad lib for 16 weeks. Another group of obese rats was pair fed to match the intake of the obese DHEA-treated rats. At the end of this period, trunk blood was collected from fasted rats for assay of E-like immunoreactivity (E-LI) by ELISA. DHEA treatment caused a significant diminution in circulating E-LI in both lean (control: 2030 +/- 226; treated: 752 +/- 145 ng/mL; n = 10, p < 0.0001) and obese (control: 2489 +/- 391, n = 6; treated: 1123 +/- 185 ng/mL, n = 7; p = 0.0003) rats. Because DHEA treatment decreases caloric intake and body weight, we examined the effect of caloric intake and body weight on E-LI levels. Serum ELI levels were lower in the obese DHEA-treated group compared to that of obese pair fed (pair fed: 1589 +/- 313, n = 6; DHEA: 1123 +/- 185 ng/mL, n = 7), but the differences were statistically insignificant (p = 0.185). Also, both weight-matched lean and obese control rats had significantly (p < 0.008) higher E-LI than their DHEA-treated counterparts. To examine whether the decrease in serum E-LI following DHEA treatment could be due to increased peptide metabolism, the rate of disappearance of endogenous E-LI from serum (obese control and DHEA-treated) at 37 degrees C was evaluated. The results show an attenuation of peptide metabolism in serum from DHEA-treated rats, a finding contrary to our expectations. In summary, DHEA treatment lowers serum E-LI levels both in lean and obese Zucker rats. This decrement in peptide level is not secondary to changes in body weight or caloric intake due to DHEA, or due to altered serum peptide metabolism. Although DHEA appears to be a potent modulator of E-LI levels, the relationship between DHEA and E-LI in relation to appetitive behavior remains to be clarified.

Enterostatin (Val-Pro-Asp-Pro-Arg)-like immunoreactivity in rat urine: relationship to corticosterone output

Numerous studies have documented a role for enterostatins in appetitive behavior. However, due to the lack of knowledge about the distribution of enterostatins in tissues and body fluids, it has not been possible to examine the role of endogenous enterostatin in this process. To this end, using a polyclonal antibody raised against enterostatin -- Val-Pro-Asp-Pro-Arg (VPDPR), we examined the nature and distribution of enterostatin-like immunoreactivity in the rat urine by ELISA and chromatography. The results reported here show for the first time the presence of VPDPR-like immunoreactivity (VPDPR-LI) in rat urine. Further characterization of rat urine VPDPR-LI revealed that it is not due to VPDPR but to another peptide similar to VPDPR. Furthermore, as urinary excretion of corticosterone increases, the level of VPDPR-LI in urine decreases.

Hormones in Foods: Presence of Enterostatin-Like Immunoreactivities in Bovine Milk

Enterostatins, pentapeptides (Val-Pro-Asp-Pro-Arg [VPDPR], Val-Pro-Gly-Pro-Arg, Ala-Pro-Gly-Pro- Arg [APGPR], and others) derived from the amino terminus of procolipase, are endogenous to a variety of tissues and body fluids including brain, gut, blood, cerebrospinal fluid, and urine. The administration of exogenous peptides has been shown to elicit a variety of biologic activities, including a decrease in dietary fat preference and pancreatic insulin secretion. Since milk is a rich source of a variety of bioactive substances, especially peptides, we investigated the presence of enterostatin-like immunoreactivity in bovine milk. We measured enterostatins-APGPR and VPDPR-in milk from a herd of 19 cows randomly selected from the Louisiana State University Department of Dairy Science Research Herd in Baton Rouge; the results of this study show a mean peptide concentration in raw milk of 33.7 ± 2.9 ng/ml for APGPR and of 104.5 ± 16.3 ng/ml for VPDPR. A further chromatographic characterization of the nature of APGPR- and VPDPR-like immunoreactivities suggested the endogenous peptides share a common epitope with APGPR or VPDPR but are not APGPR or VPDPR. Unlike APGPR or VPDPR, the endogenous peptides were heat-labile and therefore their values were much lower in pasteurized milk.

On the nature and distribution of enterostatin (Val-Asp-Pro-Asp-Arg)-like immunoreactivity in rat plasma

Enterostatins, pentapeptides represented at the amino-terminus of the procolipase molecule, are derived following tryptic cleavage of the procolipase molecule in the lumen of the gut. Val-Pro-Asp-Pro-Arg or VPDPR is one such enterostatin. Despite pharmacologic studies suggesting a role for VPDPR in appetite regulation and insulin secretion, the function of this endogenous peptide has been impossible to discern due to the lack of a suitable assay. Using polyclonal antibodies raised against VPDPR and different chromatographic methods, we examined the nature and distribution of enterostatin-like immunoreactivity in rat plasma. The results reported here show for the first time the presence of VPDPR-like immunoreactivity in rat plasma. Further characterization of the plasma VPDPR-like immunoreactivity revealed that a) it is not due to APGPR, VPGPR, or VPDPR but to another peptide similar to VPDPR, and b) plasma VPDPR-like immunoreactivity may circulate bound to large carrier proteins.

Distribution and characterization of enterostatin-like immunoreactivity in human cerebrospinal fluid

Enterostatins belong to a family of peptides (e.g., Val-Pro-Asp-Pro-Arg, VPDPR; Ala-Pro-Gly-Pro-Arg, APGPR; and Val-Pro-Gly-Pro-Arg, VPGPR) derived from the tryptic cleavage of amino-terminal pentapeptide from procolipase. Pharmacologic studies have suggested a role for these peptides in appetite regulation and insulin secretion. Studies into the distribution of enterostatins or the role of endogenous peptides have not been possible until now due to the lack of a suitable method for assay. Using two polyclonal antibodies raised against VPDPR and APGPR and different chromatographic methods, we have examined the nature and distribution of enterostatin-like immunoreactivity in human cerebrospinal fluid. The results reported here show for the first time the presence of enterostatin-like immunoreactivity in the human cerebrospinal fluid. Further characterization of cerebrospinal fluid enterostatin-like immunoreactivity revealed that it is not due to APGPR, VPGPR, or VPDPR but to another peptide similar to VPDPR.

Endogenous Enterostatin, Proteases, and Dietary Fat Preference in Rats

Many studies clearly demonstrate inhibition of dietary fat preference by exogenous enterostatins in rodents. However, what role endogenous enterostatin, if any, may play in the regulation of fat intake is not clear. To this end, we examined whether there is a relationship between plasma enterostatin (VPDPR)-like immunoreactivity and fat preference. Additionally, since enterostatin is a product of tryptic cleavage of procolipase, we examined the effect of camostat, a protease inhibitor known to inhibit trypsin and other proteases, on dietary fat preference and plasma enterostatin concentration. The results of these studies show that while there was a significant inverse relationship between plasma enterostatin and fat preference, the effect of camostat on fat preference or plasma enterostatin concentration was not clear.

Fasting- and Feeding-associated Changes in Enterostatin (Val-Pro-Asp-Pro-Arg)-like Immunoreactivity in the Rat Brain

Enterostatin (Val-Pro-Asp-Pro-Arg)-like immunoreactivity (VPDPR-LI) is unevenly distributed in the rat brain, with the highest concentration in the striatum. Fasting elevates the level of VPDPR-LI in the striatum but not in other regions of the rat brain. When fasted rats were fed, however, the striatal VPDPR-LI returns to the control (fed ad lib) level. These results, coupled with the anorectic properties of enterostatin, suggest an appetite regulatory role for endogenous VPDPR-LI in the rat.