High-Fat Diet Induces Resistance to Ghrelin and LEAP2 Peptide Analogs in Mice

Recent data suggest that the orexigenic peptide ghrelin and liver-expressed antimicrobial peptide 2 (LEAP2) have opposing effects on food intake regulation. Although circulating ghrelin is decreased in obesity, peripheral ghrelin administration does not induce food intake in obese mice. Limited information is available on ghrelin resistance in relation to LEAP2. In this study, the interplay between ghrelin and LEAP2 in obesity induced by a high-fat (HF) diet in mice was studied. First, the progression of obesity and intolerance to glucose together with plasma levels of active and total ghrelin, leptin, as well as liver LEAP2 mRNA expression at different time points of HF diet feeding was examined. In addition, the impact of switch from a HF diet to a standard diet on plasma ghrelin and LEAP2 production was studied. Second, sensitivity to the stable ghrelin analogue [Dpr3]Ghrelin or our novel LEAP2 analogue palm-LEAP2(1-14) during the progression of HF diet-induced obesity and after the switch for standard diet was investigated. Food intake was monitored after acute subcutaneous administration. HF diet feeding decreased both active and total plasma ghrelin and increased liver LEAP2 mRNA expression along with intolerance to glucose and the switch to a standard diet normalized liver LEAP2 mRNA expression and plasma level of active ghrelin, but not of total ghrelin. Additionally, our study demonstrates that a HF diet causes resistance to [Dpr3]Ghrelin, reversible by switch to St diet, followed by resistance to palm-LEAP2(1-14). Further studies are needed to determine the long-term effects of LEAP2 analogues on obesity-related ghrelin resistance.

Obesity, Cardiovascular and Neurodegenerative Diseases: Potential Common Mechanisms

The worldwide increase in the incidence of obesity and cardiovascular and neurodegenerative diseases, e.g. Alzheimer's disease, is related to many factors, including an unhealthy lifestyle and aging populations. However, the interconnection between these diseases is not entirely clear, and it is unknown whether common mechanisms underlie these conditions. Moreover, there are currently no fully effective therapies for obesity and neurodegeneration. While there has been extensive research in preclinical models addressing these issues, the experimental findings have not been translated to the clinic. Another challenge relates to the time of onset of individual diseases, which may not be easily identified, since there are no specific indicators or biomarkers that define disease onset. Hence knowing when to commence preventive treatment is unclear. This is especially pertinent in neurodegenerative diseases, where the onset of the disease may be subtle and occur decades before the signs and symptoms manifest. In metabolic and cardiovascular disorders, the risk may occur in-utero, in line with the concept of fetal programming. This review provides a brief overview of the link between obesity, cardiovascular and neurodegenerative diseases and discusses potential common mechanisms including the role of the gut microbiome.

Cholecystokinin system is involved in the anorexigenic effect of peripherally applied palmitoylated prolactin-releasing peptide in fasted mice

Prolactin-releasing peptide (PrRP) has been proposed to mediate the central satiating effects of cholecystokinin (CCK) through the vagal CCK1 receptor. PrRP acts as an endogenous ligand of G protein-coupled receptor 10 (GPR10), which is expressed at the highest levels in brain areas related to food intake regulation, e.g., the paraventricular hypothalamic nucleus (PVN) and nucleus of the solitary tract (NTS). The NTS and PVN are also significantly activated after peripheral CCK administration. The aim of this study was to determine whether the endogenous PrRP neuronal system in the brain is involved in the central anorexigenic effect of the peripherally administered CCK agonist JMV236 or the CCK1 antagonist devazepide and whether the CCK system is involved in the central anorexigenic effect of the peripherally applied lipidized PrRP analog palm-PrRP31 in fasted lean mice. The effect of devazepide and JMV236 on the anorexigenic effects of palm-PrRP31 as well as devazepide combined with JMV236 and palm-PrRP31 on food intake and Fos cell activation in the PVN and caudal NTS was examined. Our results suggest that the anorexigenic effect of JMV236 is accompanied by activation of PrRP neurons of the NTS in a CCK1 receptor-dependent manner. Moreover, while the anorexigenic effect of palm-PrRP31 was not affected by JMV236, it was partially attenuated by devazepide in fasted mice. The present findings indicate that the exogenously influenced CCK system may be involved in the central anorexigenic effect of peripherally applied palm-PrRP31, which possibly indicates some interaction between the CCK and PrRP neuronal systems.

Potential neuroprotective and anti-apoptotic properties of a long-lasting stable analog of ghrelin: an in vitro study using SH-SY5Y cells

Neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD), are increasing in prevalence. Currently, there are no effective and specific treatments for these disorders. Recently, positive effects of the orexigenic hormone ghrelin on memory and learning were demonstrated in mouse models of AD and PD. In this study, we tested the potential neuroprotective properties of a stable and long-lasting ghrelin analog, Dpr(3)ghrelin (Dpr(3)ghr), in SH-SY5Y neuroblastoma cells stressed with 1.2 mM methylglyoxal (MG), a toxic endogenous by-product of glycolysis, and we examined the impact of Dpr(3)ghr on apoptosis. Pre-treatment with both 10(-5) and 10(-7) M Dpr(3)ghr resulted in increased viability in SH-SY5Y cells (determined by MTT staining), as well as reduced cytotoxicity of MG in these cells (determined by LDH assay). Dpr(3)ghr increased viability by altering pro-apoptotic and viability markers: Bax was decreased, Bcl-2 was increased, and the Bax/Bcl-2 ratio was attenuated. The ghrelin receptor GHS-R1 and Dpr(3)ghr-induced activation of PBK/Akt were immuno-detected in SH-SY5Y cells to demonstrate the presence of GHS-R1 and GHS-R1 activation, respectively. We demonstrated that Dpr(3)ghr protected SH-SY5Y cells against MG-induced neurotoxicity and apoptosis. Our data suggest that stable ghrelin analogs may be candidates for the effective treatment of neurodegenerative disorders.

The role of food intake regulating peptides in cardiovascular regulation

Obesity is a risk factor that worsens cardiovascular events leading to higher morbidity and mortality. However, the exact mechanisms of relation between obesity and cardiovascular events are unclear. Nevertheless, it has been demonstrated that pharmacological therapy for obesity has great potential to improve some cardiovascular problems. Therefore, it is important to determine the common mechanisms regulating both food intake and blood pressure. Several hormones produced by peripheral tissues work together with neuropeptides involved in the regulation of both food intake and blood pressure. Anorexigenic (food intake lowering) hormones such as leptin, glucagon-like peptide-1 and cholecystokinin cooperate with α-melanocyte-stimulating hormone, cocaine- and amphetamine-regulated peptide as well as prolactin-releasing peptide. Curiously their collective actions result in increased sympathetic activity, especially in the kidney, which could be one of the factors responsible for the blood pressure increases seen in obesity. On the other hand, orexigenic (food intake enhancing) peptides, especially ghrelin released from the stomach and acting in the brain, cooperates with orexins, neuropeptide Y, melanin-concentrating hormone and galanin, which leads to decreased sympathetic activity and blood pressure. This paradox should be intensively studied in the future. Moreover, it is important to know that the hypothalamus together with the brainstem seem to be major structures in the regulation of food intake and blood pressure. Thus, the above mentioned regions might be essential brain components in the transmission of peripheral signals to the central effects. In this short review, we summarize the current information on cardiovascular effects of food intake regulating peptides.

Triazole GHS-R1a antagonists JMV4208 and JMV3002 attenuate food intake, body weight, and adipose tissue mass in mice

The only peripherally released orexigenic hormone, ghrelin, plays a key role in food intake and body weight regulation. Antagonizing the ghrelin receptor, GHS-R1a, represents a promising approach for anti-obesity therapy. In our study, two novel GHS-R1a antagonists JMV4208 and JMV3002, which are trisubstituted 1,2,4-triazoles, decreased food intake in fasted lean mice in a dose-dependent manner, with ED50 values of 5.25 and 2.05 mg/kg, respectively. Both compounds were stable in mouse blood, with half-lives of 90 min (JMV4208) and 60 min (JMV3002), and disappeared from the blood 8h after administration. Fourteen days of treatment with the ghrelin antagonists (20 mg/kg twice a day) decreased food intake, body weight and adipose tissue mass in mice with diet-induced obesity (DIO). These results are likely attributable to an impact on food intake reduction and an attenuated expression of the lipogenesis-promoting enzymes (acetyl-CoA carboxylase 1 in subcutaneous fat and fatty acid synthase in subcutaneous and intraperitoneal fat). The decrease in fat mass negatively impacted circulating leptin levels. These data suggest that JMV4208 and JMV3002 could be useful therapeutic agents for the treatment of obesity.

Changes in FGF21 serum concentrations and liver mRNA expression in an experimental model of complete lipodystrophy and insulin-resistant diabetes

Patients with obesity and type 2 diabetes often display high levels of the anti-diabetic factor fibroblast growth factor-21 (FGF21), suggesting that the overproduction of FGF21 may result from increased adiposity in an attempt by white adipose tissue (WAT) to counteract insulin resistance. However, the production of FGF21 diabetes in the absence of WAT has not been examined. In this study, we investigated the effects of lipodystrophy in A-ZIP F-1 mice on FGF21 production in relation to diabetes. A-ZIP F-1 mice displayed high FGF21 plasma levels resulting from enhanced FGF21 mRNA expression in the liver. Concomitant enhancement of FGF21 receptor (FGFR1) and glucose transporter 1 (GLUT-1) mRNA expression was observed in the muscles of A-ZIP F-1 mice. Furthermore, the activation of hypothalamic NPY and AgRP mRNA expression positively correlated with plasma levels of FGF21 but not active ghrelin. Our study demonstrates that an increased FGF21 plasma level in lipodystrophic A-ZIP F-1 mice results mainly from up-regulated liver production but does not suffice to overcome the lipodystrophy-induced severe type 2-diabetes and insulin resistance in the liver linked to the augmented liver fat deposition.

The Peptidic GHS-R antagonist [D-Lys(3)]GHRP-6 markedly improves adiposity and related metabolic abnormalities in a mouse model of postmenopausal obesity

It was demonstrated that estrogen deficiency and consuming high fat (HF) diet enhanced orexigenic activity of ghrelin. Therefore, we hypothesized that antagonizing of ghrelin action would attenuate food intake and body weight in mice obese both from ovariectomy (OVX) and feeding a HF diet. Ghrelin receptor antagonist [D-Lys(3)]GHRP-6 after seven days of subcutaneous treatment markedly decreased food intake in OVX mice fed both HF and standard diets; furthermore, it reduced body weight and blood glucose, insulin and leptin, and increased β-hydroxybutyrate level and uncoupling-protein-1 mRNA in brown adipose tissue. Pair-feeding revealed that effect of [D-Lys(3)]GHRP-6 was primary anorexigenic. Estrogen supplementation reduced anorexigenic effects of [D-Lys(3)]GHRP-6. OVX [D-Lys(3)]GHRP-6 treatment in mice on HF diet resulted in markedly increased circulating level and liver expression of a major metabolic regulator, fibroblast growth factor 21. Our data suggest that ghrelin antagonists could be especially beneficial in individuals with common obesity combined with estrogen deficiency.

Ghrelin agonists impact on Fos protein expression in brain areas related to food intake regulation in male C57BL/6 mice

Many peripheral substances, including ghrelin, induce neuronal activation in the brain. In the present study, we compared the effect of subcutaneously administered ghrelin and its three stable agonists: Dpr(3)ghr ([Dpr(N-octanoyl)(3)] ghrelin) (Dpr - diaminopropionic acid), YA GHRP-6 (H-Tyr-Ala-His-DTrp-Ala-Trp-DPhe-Lys-NH(2)), and JMV1843 (H-Aib-DTrp-D-gTrp-CHO) on the Fos expression in food intake-responsive brain areas such as the hypothalamic paraventricular (PVN) and arcuate (ARC) nuclei, the nucleus of the solitary tract (NTS), and area postrema (AP) in male C57BL/6 mice. Immunohistochemical analysis showed that acute subcutaneous dose of each substance (5mg/kg b.w.), which induced a significant food intake increase, elevated Fos protein expression in all brain areas studied. Likewise ghrelin, each agonist tested induced distinct Fos expression overall the PVN. In the ARC, ghrelin and its agonists specifically activated similarly distributed neurons. Fos occurrence extended from the anterior (aARC) to middle (mARC) ARC region. In the latter part of the ARC, the Fos profiles were localized bilaterally, especially in the ventromedial portions of the nucleus. In the NTS, all substances tested also significantly increased the number of Fos profiles in neurons, which also revealed specific location, i.e., in the NTS dorsomedial subnucleus (dmNTS) and the area subpostrema (AsP). In addition, cells located nearby the NTS, in the AP, also revealed a significant increase in number of Fos-activated cells. These results demonstrate for the first time that ghrelin agonists, regardless of their different chemical nature, have a significant and similar activating impact on specific groups of neurons that can be a part of the circuits involved in the food intake regulation. Therefore there is a real potency for ghrelin agonists to treat cachexia and food intake disorders. Thus, likewise JMV1843, the other ghrelin agonists represent substances that might be involved in trials for clinical purposes.

Estradiol supplementation helps overcome central leptin resistance of ovariectomized mice on a high fat diet

Ovariectomized mice on a high fat diet represent a model of diet-induced obesity during estrogen deficiency. Here, we tested the hypothesis that sensitivity to centrally administered leptin in ovariectomized mice with diet-induced obesity could be restored by estrogen supplementation. Ovariectomized C57BL/6 female mice were fed either a standard or high fat diet until they were 27 weeks old. Ovariectomized mice on a high fat diet developed extreme obesity and hyperleptinemia and moderate hyperinsulinemia compared to those on a standard diet. For the last 4 weeks, 17beta-estradiol-3-benzoate or its vehicle was administered subcutaneously in a 4-day cyclic regimen. Finally, leptin or saline was injected into the third ventricle, and food intake and body weight were measured for 36 h. In ovariectomized mice fed a standard diet, the decrease in food intake and body weight was significant and was pronounced in 17beta-estradiol-3-benzoate-supplemented mice. The response to centrally injected leptin in ovariectomized mice on a high fat diet was insignificant, whereas in 17beta-estradiol-3-benzoate-supplemented mice, the effect was significant, particularly with respect to body weight. We showed for the first time that central insensitivity to leptin in ovariectomized diet-induced obese mice was restored with 17beta-estradiol-3-benzoate supplementation, which also attenuated most of the parameters of metabolic syndrome. Only circulating adiponectin, a peripheral insulin sensitivity marker, was lowered following 17beta-estradiol-3-benzoate administration in both high fat and standard diet-fed ovariectomized mice, despite of decreased or unchanged glycemia, respectively.

Anorexigenic effect of cholecystokinin is lost but that of CART (Cocaine and Amphetamine Regulated Transcript) peptide is preserved in monosodium glutamate obese mice

Monosodium glutamate (MSG) treatment of neonatal mice results in a selective damage to the arcuate nucleus (ARC) and development of obesity with increased adiposity at sustained body weight in the adulthood. Feeding pattern of the MSG obese mice is unusual. Our previous results showed that after 24-h fasting, MSG mice consumed negligible amount of food in several hours and therefore, it was impossible to register the effect of peptides attenuating food intake such as cholecystokinin (CCK) or cocaine- and amphetamine-regulated transcript (CART) peptide. To overcome this problem, two findings were used: firstly, orexigenic effect of neuropeptide Y (NPY) was attenuated both by CCK or CART peptide in lean fed mice and secondly, orexigenic effect of NPY was preserved in fed rats with MSG obesity. In this study, short-term food intake in fed lean and MSG obese C57BL/6 male mice was measured after simultaneous central administration of orexigenic NPY with either CART peptide or peripherally administered CCK. Anorexigenic action of exogenous CART peptide was preserved in MSG obese mice. On the other hand, satiety effect of exogenous CCK was completely lost in MSG obese mice. In conclusion, effective leptin signaling in ARC is necessary for satiety effect of CCK.

Comparison of the obesity phenotypes related to monosodium glutamate effect on arcuate nucleus and/or the high fat diet feeding in C57BL/6 and NMRI mice

In this study, susceptibility of inbred C57BL/6 and outbred NMRI mice to monosodium glutamate (MSG) obesity or diet-induced obesity (DIO) was compared in terms of food intake, body weight, adiposity as well as leptin, insulin and glucose levels. MSG obesity is an early-onset obesity resulting from MSG-induced lesions in arcuate nucleus to neonatal mice. Both male and female C57BL/6 and NMRI mice with MSG obesity did not differ in body weight from their lean controls, but had dramatically increased fat to body weight ratio. All MSG obese mice developed severe hyperleptinemia, more remarkable in females, but only NMRI male mice showed massive hyperinsulinemia and an extremely high HOMA index that pointed to development of insulin resistance. Diet-induced obesity is a late-onset obesity; it developed during 16-week-long feeding with high-fat diet containing 60 % calories as fat. Inbred C57BL/6 mice, which are frequently used in DIO studies, both male and female, had significantly increased fat to body weight ratio and leptin and glucose levels compared with their appropriate lean controls, but only female C57BL/6 mice had also significantly elevated body weight and insulin level. NMRI mice were less prone to DIO than C57BL/6 ones and did not show significant changes in metabolic parameters after feeding with high-fat diet.

Magnesium and biological activity of oxytocin analogues modified on aromatic ring of amino acid in position 2

For the purpose of evaluating substitution effects in the ortho, meta or para positions of the aromatic ring of tyrosine or phenylalanine in position 2 of oxytocin on uterotonic activity in vitro in the presence and absence of magnesium ions, six new analogues of oxytocin ([D- and L-m-methylphenylalanine2]oxytocin, [D- and L-m-methoxyphenylalanine2]oxytocin and [D- and L-o-methyltyrosine2]-oxytocin) were synthesized and several previously described analogues resynthesized. For the phenylalanine series, it is found that, in the absence of magnesium ions, substitution of the ortho and meta positions leads to loss of intrinsic activity (the analogues are antagonists) in contrast to the para position. In the tyrosine series, only methyl substitution in the meta position has this effect (substitution of ortho position only attenuates the agonistic biological activity). Addition of Mg ions restores to a certain degree the agonistic activity in the case of the o-methylphenylalanine analogue and enhances the agonistic activity of o-methyltyrosine oxytocin. All other analogues keep the original qualities as in the absence of Mg. Molecular modelling calculations of the structure of the above analogues was carried out to help explain these findings of the molecular level.

Human glioblastoma cell lines: levels of low-density lipoprotein receptor and low-density lipoprotein receptor-related protein

The status of the low-density lipoprotein (LDL) receptor and LDL receptor-related protein (LRP) in seven human glioma cell lines was evaluated to extend our knowledge of human glioblastoma multiforme tumor metabolism for future drug design. Cell lines SF-767, SF-763, A-172, U-87 MG, U-251 MG, U-343 MG, and SF-539 were used. Binding of 125I-labeled LDL to these cells at 4 degrees C was carried out to determine the number of LDL receptors on cells and the affinity of LDL for these receptors. The content of LRP was measured by immunoblotting. The presence of specific saturable LDL receptors was proven in six of the cell lines investigated. SF-767 cells revealed high-affinity LDL binding (equilibrium dissociation constant, Kd = 7 nM) and maximum binding capacity approximating 300,000 receptors/cell. Most of the remaining cell lines had relatively lower affinity (Kd = 38-62 nM) but also had very high numbers of receptors (128,000-950,000/cell). All cell lines exhibited LRP, but the expression was variable. The cell lines SF-539, U-87 MG, and U-343 MG were particularly rich in this protein. The data suggest that glioblastoma cells have high numbers of LDL receptors; however, there is considerable variation in binding affinity. Overall, this finding suggests that LDL receptors on glioblastoma cells could potentially be useful for targeting antitumor agents. LRP, a multifunctional receptor expressed on glioblastoma cells, also has the possibility for serving as a therapeutic target.

Direct evidence for an angiotensin AT1 receptor type in rat vas deferens

Physiological experiments suggest that the angiotensin AT1 receptor type predominates in rat vas deferens. Membrane binding experiments, using 125I-[Sarl,Ile8]angiotensin II, confirm the presence of angiotensin AT1 receptors and the absence of angiotensin AT2 receptors in this tissue. Angiotensin II and the angiotensin AT1 receptor-specific antagonist, losartan, bind to rat vas deferens membranes with comparable affinity, with KD equal to 22.7 and 34.1 nM, respectively. The affinities of angiotensin AT2 receptor-specific ligands are 3 orders of magnitude lower. According to the numbers of binding sites and Western blotting of membrane proteins, the concentration of angiotensin AT1 receptors in the rat vas deferens is rather low. The fact that similar numbers of binding sites were obtained from binding data for angiotensin II and losartan further supports the hypothesis of exclusive existence of angiotensin AT1 receptor type in rat vas deferens.

N- and C-terminal structure-activity study of angiotensin II on the angiotensin AT2 receptor

The predominant angiotensin II receptor expressed in the human myometrium is the angiotensin AT2 receptor. This preparation was used for a structure-activity relationship study on angiotensin II analogues modified in positions 1 and 8. The angiotensin AT2 receptor present on human myometrium membranes displayed a high affinity (pKd = 9.18) and was relatively abundant (53-253 fmol/mg of protein). The pharmacological profile was typical of an angiotensin AT2 receptor with the following order of affinities: (angiotensin III > or = angiotensin II > angiotensin I > PD123319 > angiotensin-(1-7) > angiotensin-(1-6) approximately angiotensin IV >> Losartan). Modifications of the N-terminal side chain and of the primary amine of angiotensin II were evaluated. Neutralisation of the methylcarboxylate (Asp) to a methylcarboxamide (Asn) or to a hydroxymethyl (Ser) or substitution for a methylsulfonate group (cysteic acid) improved the affinity. Extension from methylcarboxylate (Asp) to ethylcarboxylate (Glu) did not affect the affinity. Introduction of larger side chains such as the bulky p-benzoylphenylalanine (p-Bpa) or the positively charged Lys did not substantially affect the affinity. Complete removal of the side chain (angiotensin III), however, resulted in a significant affinity increase. Removal or acetylation of the primary amine of angiotensin II did not noticeably influence the affinity. Progressive alkylation of the primary amine significantly increased the affinity, betain structures being the most potent. It appears that quite important differences exist between the angiotensin AT1 and AT2 receptors concerning their pharmacological profile towards analogues of angiotensin II modified in position 1. On position 8 of angiotensin II, a structure-activity relationship on the angiotensin AT2 receptor was quite similar to that observed with angiotensin AT1 receptor. Bulky, hydrophobic aromatic residues displayed affinities similar to or even better than [Sarcosine1]angiotensin II. Aliphatic residues, especially those of reduced size, caused a significant decrease in affinity especially [Sarcosine1, Gly8]angiotensin II who showed a 30-fold decrease. Introduction of a positive charge (Lys) at position 8 reduced the affinity even further. Stereoisomers in position 8 (L-->D configuration) also induced lower affinities. The angiotensin AT2 receptor display a structure-activity relationship similar to that observed on the AT1 receptor for the C-terminal position of the peptide hormone. Position 1 structure-activity relationships are however fundamentally different between the angiotensin AT1 and AT2 receptor.

Cholecystokinin analogs with suppressed central activities

Several analogs of Boc-protected C-terminal heptapeptide of cholecystokinin (Boc-CCK-7) with modified C-end Phe were pharmacologically characterized. The influence of the number of methyl groups on aromatic side chain of Phe was investigated in following tests: binding to pancreatic and brain membrane receptors, gall bladder contraction, amylase secretion, anorexia, sedation and analgesia. Two analogs seem to be promising selective anorectic agents with strongly protracted effect: Boc-[Phe(triMe)7]CCK-7 and Boc-[Phe(pentaMe)7]CCK-7. The first analog exhibits the same spectrum of activities as CCK-8, however partially decreased central effects, the second one shows partially decreased peripheral activities and totally suppressed central ones. Our study supports the idea that C-terminal residue of CCK is more important for biological potency than for binding to CCK receptors.

Angiotensin analogues palmitoylated in positions 1 and 4

Lipidated angiotensin II (Ang) agonists and antagonists were synthesized and evaluated for their biological activities for eventual use an antimyoproliferative agents. Solid phase peptide synthesis was used for the assembly of the peptides with the Fmoc protection scheme. N-Acetyl-Ser1 Ang was palmitoylated on the serine hydroxyl function. The nonpalmitoylated analogue retained one-third of Ang's affinity toward the AT1 receptor on bovine adrenal cortex membranes, and the palmitoylated analogue was essentially inactive. Upon enzymatic lipolysis or mild saponification of the palmitoylated peptide, biological activity was restored. An analogous compound of Ang, N-acetyl-Ser1,beta-D-naphthylalanine8 ([NAcSer1,D-Nal8]Ang), was a pure antagonist on rabbit aorta but with lower affinity. Its O-palmitoylated form was inactive as well but was easily converted to the nonlipidated active form by lipolysis or saponification. Direct palmitoylation of [sarcosine1]Ang with palmitoyl chloride was obtained on the free phenolic hydroxyl of Tyr4 on solid phase on an otherwise fully protected peptide. This lipopeptide was fully active, was comparable to [Sar1]Ang, and exhibited strongly prolonged activity. Lipolysis and saponification under mild conditions yielded standard [Sar1]Ang. The corresponding [Sar1,D-Nal8]Ang was a potent and very long-lasting antagonist (pA2 = 8.1), and its analogous palmitoyl phenyl ester in position 4 was active in its palmitoylated form (antagonist) and, again, returned to the nonlipidated form upon saponification or lipolysis. [Sar1,Tyr4(O-octadecyl)]Ang, an analogue to Tyr-palmitoylated [Sar1]Ang with an octadecyl phenyl ether in position 4, was also prepared. Surprisingly, the ether compound was inactive. Premature hydrolysis of the palmitoyl phenyl ester peptide was excluded by HPLC analysis, and the activity of the ester peptide is attributed to a putative hydrogen bond that may be critical for biological activity. The discovery of potent biologically active lipidated antagonists of Ang gives access to potential antimyoproliferative agents with numerous application possibilities.

Contribution to characterization of anorectic protein similar to satietin from urine

An anorectic substance similar to satietin was purified from ethanolic-acid precipitate of rat urine by gel filtration and ion exchange chromatography. The obtained glycoprotein (molecular mass 67 kDa) reduced food intake after intraperitoneal and intracisternal administration in mice in a dose-dependent manner (in the range of 5-80 mg/kg). The anorectic effect was specific. In the presence of sodium dodecylsulphate the substance dissociated into small proteins with a molecular mass of 9-11 kDa. Its anorectic effect was long lasting and differed from that of the anorectic peptide cholecystokinin octapeptide. Our finding supports the idea that anorectic protein isolated from plasma, membranes, and urine may be related substances.

Pharmacological characterization of new cholecystokinin analogues

New analogues of cholecystokinin-7 (CCK-7) modified at amino acid residues 5 and 7 were assayed for their effect on gall bladder, pancreatic secretion, food intake (anorectic activity), amount of rearing (sedative activity) and analgesia, as well as their ability to inhibit 125I-CCK-8 binding to pancreatic cell membrane receptors and brain membrane receptors. The results were compared to the activities of standard compounds, CCK-8, cerulein, BOC-CCK-7 (BOC = tertbutyloxycarbonyl) and BOC-[Nle2,Nle5]CCK-7. All analogues exhibited agonistic effects. Their anorectic activity was significantly prolonged.