Glucagon-like peptide 1 (GLP-1).

BACKGROUND: The glucagon-like peptide-1 (GLP-1) is a multifaceted hormone with broad pharmacological potential. Among the numerous metabolic effects of GLP-1 are the glucose-dependent stimulation of insulin secretion, decrease of gastric emptying, inhibition of food intake, increase of natriuresis and diuresis, and modulation of rodent ß-cell proliferation. GLP-1 also has cardio- and neuroprotective effects, decreases inflammation and apoptosis, and has implications for learning and memory, reward behavior, and palatability. Biochemically modified for enhanced potency and sustained action, GLP-1 receptor agonists are successfully in clinical use for the treatment of type-2 diabetes, and several GLP-1-based pharmacotherapies are in clinical evaluation for the treatment of obesity. SCOPE OF REVIEW: In this review, we provide a detailed overview on the multifaceted nature of GLP-1 and its pharmacology and discuss its therapeutic implications on various diseases. MAJOR CONCLUSIONS: Since its discovery, GLP-1 has emerged as a pleiotropic hormone with a myriad of metabolic functions that go well beyond its classical identification as an incretin hormone. The numerous beneficial effects of GLP-1 render this hormone an interesting candidate for the development of pharmacotherapies to treat obesity, diabetes, and neurodegenerative disorders.

[Incretin-based co- and tri-agonists : Innovative polypharmacology for the treatment of obesity and diabetes]. / Inkretinbasierte Ko- und Triagonisten : Innovative Polypharmakologie zur Behandlung von Adipositas und Diabetes.

BACKGROUND: The worldwide rise in overweight and obesity is paralleled by an increasing prevalence of type-2 diabetes. Apart from bariatric surgery, treatment options to decrease body weight are often underwhelming. Innovative pharmacological options are required to cope with the global "diabesity" pandemic. OBJECTIVES: Particular novel pharmacological approaches are discussed, with a special focus on polyagonist-based pharmacotherapies. MATERIALS AND METHODS: Articles on co- and tri-agonists for the treatment of obesity and diabetes are presented and discussed. RESULTS: Unimolecular peptides have been developed for the treatment of obesity and type-2 diabetes. These peptides activate the receptors of multiple hormones and bundle their positive effects in one single molecule. In preclinical studies, polyagonists targeting the receptors for glucagon-like peptide-1 (GLP-1), glucagon, or glucose-dependent insulinotropic peptide (GIP) were promising to reduce body weight and blood glucose. GLP-1-mediated delivery of the nuclear hormones estrogen or dexamethasone also yielded beneficial effects in preclinical studies of obesity. CONCLUSIONS: Polyagonists represent an innovative strategy for the development of novel pharmacotherapies to treat obesity and diabetes.

Peptide-based multi-agonists: a new paradigm in metabolic pharmacology.

Obesity and its comorbidities, such as type 2 diabetes, are pressing worldwide health concerns. Available anti-obesity treatments include weight loss pharmacotherapies and bariatric surgery. Whilst surgical interventions typically result in significant and sustained weight loss, available pharmacotherapies are far less effective, typically decreasing body weight by no more than 5-10%. An emerging class of multi-agonist drugs may eventually bridge this gap. This new class of specially tailored drugs hybridizes the amino acid sequences of key metabolic hormones into one single entity with enhanced potency and sustained action. Successful examples of this strategy include multi-agonist drugs targeting the receptors for glucagon-like peptide-1 (GLP-1), glucagon and the glucose-dependent insulinotropic polypeptide (GIP). Due to the simultaneous activity at several metabolically relevant receptors, these multi-agonists offer improved body weight loss and glucose tolerance relative to their constituent monotherapies. Further advancing this concept, chimeras were generated that covalently link nuclear acting hormones such as oestrogen, thyroid hormone (T3 ) or dexamethasone to peptide hormones such as GLP-1 or glucagon. The benefit of this strategy is to restrict the nuclear hormone action exclusively to cells expressing the peptide hormone receptor, thereby maximizing combinatorial metabolic efficacy of both drug constituents in the target cells whilst preventing the nuclear hormone cargo from entering and acting on cells devoid of the peptide hormone receptor, in which the nuclear hormone might have unwanted effects. Many of these multi-agonists are in preclinical and clinical development and may represent new and effective tools in the fight against obesity and its comorbidities.

Thermoneutral housing is a critical factor for immune function and diet-induced obesity in C57BL/6 nude mice.

OBJECTIVES: Obesity-related cancers represent public health burdens of the first order. Nevertheless, suitable mouse models to unravel molecular mechanisms linking obesity to human cancer are still not available. One translational model is the immunocompromised Foxn1 (winged-helix/forkead transcription factor) nude mouse transplanted with human tumor xenografts. However, most xenograft studies are conducted in nude mice on an in-bred BALB/c background that entails protection from diet-induced obesity. To overcome such resistance to obesity and its sequelae, we here propose the dual strategy of utilizing Foxn1 nude mice on a C57BL/6 background and housing them at their thermoneutral zone. METHODS: C57BL/6 nude and corresponding wild-type mice, housed at 23 or 33 °C, were subjected to either low-fat diet or high-fat diet (HFD). Energy expenditure, locomotor activity, body core temperature, respiratory quotient as well as food and water intake were analyzed using indirect calorimetry. Immune function at different housing temperatures was assessed by using an in vivo cytokine capture assay. RESULTS: Our data clearly demonstrate that conventional housing protects C57BL/6 nude mice from HFD-induced obesity, potentially via increased energy expenditure. In contrast, HFD-fed C57BL/6 nude mice housed at thermoneutral conditions develop adiposity, increased hepatic triglyceride accumulation, adipose tissue inflammation and glucose intolerance. Moreover, increased circulating levels of lipopolysaccharide-driven cytokines suggest a greatly enhanced immune response in C57BL/6 nude mice housed at thermoneutrality. CONCLUSION: Our data reveals mild cold stress as a major modulator for energy and body weight homeostasis as well as immune function in C57BL/6 nude mice. Adjusting housing temperatures to the thermoneutral zone may ultimately be key to successfully study growth and progression of human tumors in a diet-induced obese environment.

The role of organic anion transporting polypeptides (OATPs/SLCOs) in the toxicity of different microcystin congeners in vitro: a comparison of primary human hepatocytes and OATP-transfected HEK293 cells.

Cellular uptake of microcystins (MCs), a family of cyclic cyanobacterial heptapeptide toxins, occurs via specific organic anion transporting polypeptides (OATPs), where MCs inhibit serine/threonine-specific protein phosphatase (PP). Despite comparable PP-inhibitory capacity, MCs differ greatly in their acute toxicity, thus raising the question whether this discrepancy results from MC-specific toxikokinetic rather than toxicodynamic differences. OATP-mediated uptake of MC congeners MCLR, -RR, -LW and -LF was compared in primary human hepatocytes and HEK293 cells stably expressing recombinant human OATP1B1/SLCO1B1 and OATP1B3/SLCO1B3 in the presence/absence of OATP substrates taurocholate (TC) and bromosulfophthalein (BSP) and measuring PP-inhibition and cytotoxicity. Control vector expressing HEK293 were resistant to MC cytotoxicity, while TC and BSP competition experiments reduced MC cytotoxicity in HEK293-OATP transfectants, thus confirming the requirement of OATPs for trans-membrane transport. Despite comparable PP-inhibiting capabilities, MCLW and -LF elicited cytotoxic effects at lower equimolar concentrations than MCLR and MCRR, hence suggesting congener selective transport into HEK293-OATP transfectants and primary human hepatocytes. Primary human hepatocytes appeared one order of magnitude more sensitive to MC congeners than the corresponding HEK293 -OATP transfectants. Although the latter maybe due to a much lower level of PPs in primary human hepatocytes, the presence of OATPs other than 1B1 or 1B3 may have added to an increased uptake of MCs. In view of the high sensitivity of human hepatocytes and currently MCLR-only based risk calculations, the actual risk of human MC-intoxication and ensuing liver damage could be underestimated in freshwater cyanobacterial blooms where MCLW and-LF predominate.

Animal models for transdermal drug delivery.

The purpose of this investigation was to compare the permeation characteristics of two different compounds (extremely polar and nonpolar), i.e., tritium-labeled water (W) and 14C-labeled 7-hydroxycoumarin (7-OHC), among 16 different species, including human skin. Snake skin exhibited highest permeability for both W and 7-OHC. Permeability and lag time values of W and 7-OHC across Brattleboro rat and hairless guinea pig are very close to human skin. Skin thickness in micrometers (full thickness, epidermis and stratum corneum, and stratum corneum), and number of hair follicles present in each cm2 were determined for each species. There was no relationship between number of hair follicles and permeability values for both W and 7-OHC. The skin thickness (full) was related to the relative permeability values of W, whereas for 7-OHC it was not.

Development of an intracutaneous depot for drugs. Binding, drug accumulation and retention studies, and mechanism of depot.

In previous studies we reported that the permeation of dexamethasone and hydrocortisone across the skin was decreased and penetration into the skin was increased in the presence of Transcutol (TC) when compared to water as a solvent. The objective of this investigation was to study the effect of TC on the binding of dexamethasone and hydrocortisone to the skin, and on the accumulation and retention in the skin. Adsorption and desorption studies were conducted for dexamethasone and hydrocortisone with full thickness skin (FTS), and epidermis. The amount of dexamethasone and hydrocortisone adsorbed and desorbed with FTS and epidermis was essentially the same. In the presence of TC the amount of dexamethasone and hydrocortisone adsorbed was increased by 100% with both FTS and epidermis, whereas there was no difference in the amount of dexamethasone and hydrocortisone desorbed. A topical delivery system was developed with and without TC and was evaluated in vivo using the rat as an animal model for hydrocortisone accumulation after multiple dosing. The systemic body burden was reduced by 70% and skin retention of hydrocortisone was increased by 100% in all the layers of the skin. The detection of hydrocortisone accumulation and retention were studied by autoradiography and electron microscopy, and the results support the hydrocortisone depot in the skin due to TC.

Interaction of aluminum with zinc and copper and its effects on pituitary-testicular axis: a histological study.

To elucidate the interactions between aluminum and certain essential trace metals, an experiment was performed on rats fed diets with suboptimal or optimal levels of zinc or copper. Half of each group of animals were fed the same diet but with 1000 ppm aluminum added. Changes were noted after 120 days. Severe testicular damage was seen in rats fed either the low zinc or the low copper diet. The lesions included a wide range of spermatogenic cell degeneration and tubular atrophy. When aluminum was added to the diet, the testicular destruction of Zn-deficient rats was significantly reduced. This indicated that the presence of aluminum in the diet protected the testis against the damage caused by zinc deficiency. Pituitary glands were examined. Hypertrophy of basophiles was more pronounced in rats fed the suboptimal zinc or copper diet. When aluminum was added to their diet, the changes were reversed. The mechanisms by which aluminum protects male gonadal functions against Zn deficiency are discussed. This study is the first to demonstrate the preventive effect of aluminum against testicular damage caused by zinc deficiency.

Interaction between aluminum and zinc or copper and its effects on the pituitary-testicular axis. II. Testicular enzyme and serum gonadotropin assay.

Sprague-Dawley male rats were divided into groups and maintained on a semipurified diet containing either 5 or 40 ppm of zinc or 2 or 8 ppm of copper. Half of the rats in each group received 1000 ppm aluminum in the diet. It was found that aluminum accumulated in the pituitary glands and testes when dietary copper levels were suboptimal. The ALP activity in testes was depressed by the added aluminum when the intake of zinc or copper was suboptimal. SDH, LDH, and LDH-X activities were inhibited and GRS and GGTP activities were elevated in rats fed either the suboptimal zinc or copper diet. However, the added aluminum in the diet reversed the changes to normal levels. The testosterone levels in plasma changed very little when the zinc or copper intake was suboptimal. An increase in plasma FSH was demonstrated in groups of both suboptimal zinc and copper intake. But the plasma LH was elevated only in the group receiving the suboptimal copper diet, and the added aluminum reversed plasma LH to control levels. A lower level of testosterone was demonstrated in the group given suboptimal copper with aluminum. It was concluded that dietary aluminum influenced the pituitary-testicular axis by interacting with certain essential trace metals, particularly zinc.

Iron deficiency in growing male rats: a cause of development of cardiomyopathy.

Weanling male rats were fed a purified iron-adequate, a purified iron-deficient or a commercial diet for 12 weeks. At that time the rats were sacrificed, their hearts and livers were excised, and blood samples were taken. Heart and liver weights were recorded; organ tissue and serum samples were analyzed for Zn, Cu and Fe. Hemoglobin and hematocrit values were also obtained. The iron-deficient rats grew much more slowly than controls on the iron-adequate or commercial diets. The iron-deficient rats were severely anemic and had enlarged hearts (cardiomegaly). A histopathologic examination of the hearts of all animals showed that each heart of the iron-deficient rats had lesions characteristic of cardiomyopathy by dilatation, whereas none of the hearts of the iron-adequate group or the chow controls showed any lesions at all. The iron-deficient animals had only about 25% of the hepatic iron found in the iron-adequate animals but about 5 times the hepatic copper of the latter group or the chow controls. Heart iron of the iron-deficient group was 27% of the concentration found in hearts of the iron-adequate rats; heart copper was similar in all groups. Animals on the commercial stock diet accumulated significantly more iron in their hearts than did those on the purified iron-adequate diet but not in the livers. There was also a direct correlation of heart iron or heart zinc with log concentrations of dietary iron and consequently a direct correlation between heart iron and zinc concentrations.

Copper deficiency effects on cardiovascular system and lipid metabolism in the rat; the role of dietary proteins and excessive zinc.

Weanling rats were fed a copper-deficient purified diet. The effects of varying the type of protein and supplements of copper and zinc on cardiovascular pathology and some biochemical parameters were investigated. It was found that cardiomyopathy developed in the copper-deficient groups. Milk powder caused significant exacerbation of this development relative to dietary casein or egg white. Angiopathy developed only when dietary zinc was 20 ppm. Dietary copper did not change this situation. Serum cholesterol was elevated when copper was low and casein or milk powder were the protein source. The data point to an interaction between type of protein and dietary copper or zinc in the pathogenesis of cardiovascular lesions.

Essential trace metals and specific organ weights in diet-restricted and ad lib-fed rats.

Manganese, copper, iron, zinc, and specific organ weights (relative to body weight) of the heart, liver, and kidney were compared between a 65% diet-restricted group and an ad lib-fed control group of young male Sprague-Dawley rats. Elevated concentrations of Cu (12%) in the liver, and of Mn (12-26%) and Fe (17-69%) in all three organs, occurred in the diet-restricted group. Specific heart weight was unchanged despite the 40% difference in group body weights. Specific liver weight decreased 13% and specific kidney weight increased 13%.

Lung tumorigenesis and hyperplasia in offspring associated with the Ahd allele following in utero exposure to 3-methylcholanthrene.

This study was conducted to determine if the Ah genotype could influence the incidence of tumorigenesis in offspring exposed to 3-methylcholanthrene (3-MC) during the fetal period. Male F1 hybrids (Ahb/Ahd) were backcrossed to Ahd/Ahd females, resulting in pregnant mice containing litters with a 1:1 ratio of Ahb/Ahd (AHH-inducible) and Ahd/Ahd (AHH-noninducible) fetuses. Dams were exposed by gavage to corn oil or to 3-MC at 7, 21, or 63 mg/kg on Days 15, 16, and 17 of gestation, or to the positive control urethane at 1 mg/g ip on Day 17. The phenotype of surviving offspring was determined by hepatic aryl hydrocarbon hydroxylase (AHH) activity. The lung was the major site of neoplastic involvement in adult offspring 6 months after in utero exposure to 3-MC. Dose-related responses in all 3-MC treatment groups were obtained for percent nodule-bearing animals, percentage adenoma-bearing animals, mean number of nodules per animal, mean nodular size per animal, and diffuse bronchiolar hyperplasia. Correlation of Ah phenotype with adult tumorigenesis indicated that genetically nonresponsive (Ahd/Ahd) offspring had a higher incidence of nodules, adenomas, and diffuse bronchiolar hyperplasia than responsive offspring within the same treatment group. Thus, when fetuses are exposed in the same maternal environment to 3-MC, genetic differences in Ah genotype may influence susceptibility to transplacental carcinogenesis.

Suboptimal dietary zinc intake increases aluminum accumulation into the rat brain.

The aluminum concentration in the frontal cortex and hippocampus increased when rats were fed semi-synthetic diets containing suboptimal levels of zinc and elevated levels (1000 parts per million, ppm) of aluminum.

Behavioral consequences of prenatal diazepam exposure in rats.

Diazepam was administered to gravid rat dams on days 13 through 20 of gestation, at either 1 or 5 mg/kg/day. Pups were observed on several behavioral paradigms throughout the preweaning period. The high dose resulted in a failure to maintain weight gain at the same rate as controls. Additionally, this dose produced a deficit in the ability of 8-day-old pups to autonomically thermoregulate. Female littermates of these pups displayed altered habituation behavior on a holeboard apparatus when tested on postnatal day 12 (PN 12). The low dose attenuated the normal drop in body temperature produced by removal of the pup from its home cage on PN8. This dose also slightly decreased responding on a photocell activity task on PN15. Neither dose was found to affect muscle strength, as measured by hang time. The results suggest that the postnatal effects of prenatal diazepam exposure are dose-specific, in that low dose treatment leads to a different type of behavioral consequence than does exposure to higher doses.

Activity of the enzymes dopamine-beta-hydroxylase and phenylethanolamine-N-methyltransferase in discrete brain regions of the copper-zinc deficient rat following aluminum ingestion.

We have investigated the possible interactions between the dietary intake of copper, zinc, or aluminum and the activities of the enzymes dopamine-beta-hydroxylase (DBH, EC.1.14.2.1) and phenylethanolamine-N-methyltransferase (PNMT, EC.2.1.1.28) in the male rat brain. Exposure to aluminum was for 120 days at 1000 ppm. The results showed that a diet suboptimal in copper or zinc decreased the activity of both enzymes in the three brain regions studied, including the frontal cortex, hippocampus, and cerebellum. The addition of aluminum to the suboptimal zinc diet restored the activity of both enzymes to within range of control values. The data are discussed with respect to an interaction between zinc and aluminum.

Effect of ethanol on vinyl chloride carcinogenesis.

Four treatment groups (80 male Sprague-Dawley rats/group) were used in a 2 X 2 factorial design: inhalation of 600 ppm vinyl chloride (VC) 4 hr/day, 5 days/week for 1 year; VC and ingestion of 5% ethanol in water (v/v); filtered air and ethanol; filtered air. Ingestion of ethanol was begun 4 weeks prior to inhalation of VC and continued for life or termination of the study at two and one-half years from the first VC exposure. In this model system, ethanol potentiated the carcinogenic response to VC in the liver and produced an excess of neoplasms in animals receiving ethanol alone. Inhalation of VC induced angiosarcoma of the liver in 23% of the exposed animals; ethanol in addition to VC inhalation increased the incidence to 50%. Concomitant administration of VC and ethanol also produced an excess of hepatocellular carcinoma and lymphosarcoma. Ethanol with or without VC had a strong tumorigenic effect on the endocrine system. These results indicate that ethanol is a cocarcinogen in relation to the carcinogen VC.

The influence of ingested aluminum upon norepinephrine and dopamine levels in the rat brain.

The clinical and neuropathological effects of elevated brain aluminum levels have only recently been described. The clinical symptoms, and localization of aluminum in the brain, suggest an altered catecholamine balance. We report the effects of elevated brain aluminum upon the endogenous steady-state levels of norepinephrine and dopamine in the frontal cortex, hippocampus and cerebellum. The neurotoxic effects of ingested aluminum are shown to be dependent upon the dietary intake of copper, zinc, iron, and magnesium. Norepinephrine levels in the cortex and cerebellum decreased in rats fed a low copper diet with aluminum added (0.1%, w/w). Suboptimal iron levels decreased norepinephrine in the cerebellum. The presence of aluminum in diets low in copper or zinc decreased dopamine levels in the cortex. The data are interpreted with respect to the clinical symptomatologies seen in demented, chronic renal dialysis patients with depressed serum copper and zinc levels.

[Microbiological test for the determination of the maximum permissible standing time for non-sterilised ampoule solutions (author's transl)]. / Mikrobiologischer Test zur Ermittlung der maximal zulässigen Standzeit von nicht-sterilisierten Ampullenlösungen.

As opposed to most large volume parenterals (LVP), which on account of their composition provide good nutrient media for microbial growth, it can be expected that many ampoule solutions have an antimicrobial activity of their own, due to the high activity of their drug substances. It is therefore questionable as to whether the requirements laid down by the American Food and Drug Administration (FDA) for LVP, demanding a maximum time limit of 8 hours for the manufacture, filling and sterilisation, can simply be extrapolated to apply to small volume parenterals. A method is now described whereby the behaviour of various micro-organisms can be studied in non-sterilised ampoule solutions. The tests carried out show that only a negligible fraction of the ampoule solutions permit proliferation of contaminating organisms. On the contrary, the majority of the preparations examined had an inhibitory or even microbicidal effect. On the basis of the findings, it is proposed to make a generally valid classification of ampoule solutions into 5 different risk classes. While it is essential to adopt the rigorous FDA restrictions for the entire manufacturing period in the case of those preparations most susceptible to microbial proliferation, the standing times, i.e. the period of time between the manufacture of the solution and the subsequent antimicrobial treatment of the ampoules, can be prolonged without risk for the other groups. This maximum standing time, laid down specifically for each product, in many cases enables the manufacturer to produce larger batches or to improve exploitation of production capacity, yet at the same time maintain security for the product and the user.