Dual role of interleukin-1ß in islet amyloid formation and its ß-cell toxicity: Implications for type 2 diabetes and islet transplantation.

AIMS: Islet amyloid, formed by aggregation of human islet amyloid polypeptide (hIAPP), contributes to ß-cell failure in type 2 diabetes, cultured and transplanted islets. We previously showed that biosynthetic hIAPP aggregates induce ß-cell Fas upregulation and activation of the Fas apoptotic pathway. We used cultured human and hIAPP-expressing mouse islets to investigate: (1) the role of interleukin-1ß (IL-1ß) in amyloid-induced Fas upregulation; and (2) the effects of IL-1ß-induced ß-cell dysfunction on pro-islet amyloid polypeptide (proIAPP) processing and amyloid formation. RESEARCH DESIGN AND METHODS: Human and h IAPP -expressing mouse islets were cultured to form amyloid without or with the IL-1 receptor antagonist (IL-1Ra) anakinra, in the presence or absence of recombinant IL-1ß. Human islets in which amyloid formation was prevented (amyloid inhibitor or Ad-prohIAPP-siRNA) were cultured similarly. ß-cell function, apoptosis, Fas expression, caspase-8 activation, islet IL-1ß, ß-cell area, ß-/α-cell ratio, amyloid formation, and (pro)IAPP forms were assessed. RESULTS: hIAPP aggregates were found to increase IL-1ß levels in cultured human islets that correlated with ß-cell Fas upregulation, caspase-8 activation and apoptosis, all of which were reduced by IL-1Ra treatment or prevention of amyloid formation. Moreover, IL-1Ra improved culture-induced ß-cell dysfunction and restored impaired proIAPP processing, leading to lower amyloid formation. IL-1ß treatment potentiated impaired proIAPP processing and increased amyloid formation in cultured human and h IAPP -expressing mouse islets, which were prevented by IL-1Ra. CONCLUSIONS: IL-1ß plays a dual role by: (1) mediating amyloid-induced Fas upregulation and ß-cell apoptosis; (2) inducing impaired proIAPP processing thereby potentiating amyloid formation. Blocking IL-1ß may provide a new strategy to preserve ß cells in conditions associated with islet amyloid formation.

Carnosine's effect on amyloid fibril formation and induced cytotoxicity of lysozyme.

Carnosine, a common dipeptide in mammals, has previously been shown to dissemble alpha-crystallin amyloid fibrils. To date, the dipeptide's anti-fibrillogensis effect has not been thoroughly characterized in other proteins. For a more complete understanding of carnosine's mechanism of action in amyloid fibril inhibition, we have investigated the effect of the dipeptide on lysozyme fibril formation and induced cytotoxicity in human neuroblastoma SH-SY5Y cells. Our study demonstrates a positive correlation between the concentration and inhibitory effect of carnosine against lysozyme fibril formation. Molecular docking results show carnosine's mechanism of fibrillogenesis inhibition may be initiated by binding with the aggregation-prone region of the protein. The dipeptide attenuates the amyloid fibril-induced cytotoxicity of human neuronal cells by reducing both apoptotic and necrotic cell deaths. Our study provides solid support for carnosine's amyloid fibril inhibitory property and its effect against fibril-induced cytotoxicity in SH-SY5Y cells. The additional insights gained herein may pave way to the discovery of other small molecules that may exert similar effects against amyloid fibril formation and its associated neurodegenerative diseases.

It takes two to tango: combined amylin/leptin agonism as a potential approach to obesity drug development.

The discovery of leptin in 1994 was a seminal event in obesity research. It helped to establish that body weight is tightly regulated by a complex neurohormonal feedback system and that obesity should be viewed as a disorder with a strong biological basis rather than simply the result of poor lifestyle choices and lack of willpower.Leptin, secreted from adipocytes, acts as a prototypic long-term (tonic) adiposity signal. Although nonclinical and clinical studies have provided unequivocal evidence that leptin plays a unique, pivotal role in body weight regulation, efforts to develop recombinant leptin (metreleptin) as a monotherapy for obesity have proven unsuccessful. Amylin, secreted from pancreatic beta-cells, fulfills the criteria for a short-term (episodic) satiety signal. The amylin analog pramlintide elicits sustained reductions in food intake and body weight in obese rodents and humans.A translational research program aimed at elucidating the interaction between different islet-, gut-, and adipocyte-derived hormones led to the discovery that combined amylin/leptin agonism induces marked, synergistic, fat-specific weight loss in leptin-resistant diet-induced obese rodents. In obese humans, combination treatment with pramlintide/metreleptin led to an approximately 13% weight loss after 24 weeks, significantly more than after treatment with pramlintide or metreleptin alone.Collectively, these findings suggest that combined amylin/leptin agonism may have therapeutic utility as part of an integrated, neurohormonal approach to obesity pharmacotherapy.

Implications of amylin receptor agonism: integrated neurohormonal mechanisms and therapeutic applications.

Amylin receptor agonism is emerging as part of an integrated neurohormonal therapeutic approach for managing diabetes mellitus (DM) and body weight. Pramlintide acetate, an analogue of the pancreatic hormone amylin, has been studied in the United States as an antihyperglycemic agent in patients with type 1 or type 2 DM treated with mealtime insulin(1). Further clinical testing of pramlintide in subjects with obesity demonstrated that pramlintide monotherapy induced significant, sustained, and dose-dependent weight loss(2). Recent clinical observations point to its compatibility as a combination therapy with the hormone leptin, eliciting double-digit weight loss in patients with overweight and obesity(3). Herein, we link amylin activation of central neural circuits to these therapeutic effects, and we speculate on other potential therapeutic applications of amylin receptor agonism.

[New therapies for diabetes: beyond injectable insulin and oral antidiabetics]. / Nuevas terapias en diabetes: más allá de la insulina inyectable y de los antidiabéticos orales.

New medicines for the therapy of the type 1 and type 2 diabetes have been incorporated in the list of traditional drugs: oral agents and injectable insulin. These treatment alternatives have a new mechanism of action that takes advantage of the antidiabetic properties of certain peptides such as amylin and glucagon like peptide-1 (GLP-1), whose levels are wanting or insufficient in diabetes. This is attained through amylin and GLP-1 analogues, although it can also be achieved by inhibiting the enzyme that degrades the latter. Furthermore, a new system to administer insulin in a noninvasive way through inhalation has become available in the market. This paper summarizes the most important and updated findings on the action mechanism, efficacy, adverse effects and indications of these innovative drugs.

Pramlintide in the treatment of diabetes mellitus.

Pramlintide, the first member of a new class of drugs for the treatment of insulin-using patients with type 2 or type 1 diabetes mellitus, is an analog of the peptide hormone amylin. Amylin is co-secreted with insulin from pancreatic beta cells and acts centrally to slow gastric emptying, suppress postprandial glucagon secretion, and decrease food intake. These actions complement those of insulin to regulate blood glucose concentrations. Amylin is relatively deficient in patients with type 2 diabetes, depending on the severity of beta-cell secretory failure, and is essentially absent in patients with type 1 diabetes. Through mechanisms similar to those of amylin, pramlintide improves overall glycemic control, reduces postprandial glucose levels, and reduces bodyweight in patients with diabetes using mealtime insulin. Reductions in postprandial glucose and bodyweight are important, since postprandial hyperglycemia is associated with an increased risk of microvascular and macrovascular complications, and increased weight is an independent risk factor for cardiovascular disease. Pramlintide is generally well tolerated, with the most frequent treatment-emergent adverse event being mild to moderate nausea, which decreases over time. Pramlintide treatment is also associated with improvements in markers of oxidative stress and cardiovascular risk and improved patient-reported treatment satisfaction. These factors make pramlintide an attractive option for the treatment of postprandial hyperglycemia in patients with diabetes using mealtime insulin.

Nuevas terapias en diabetes: más allá de la insulina inyectable y de los antidiabéticos orales: [revisión] / New therapies for diabetes: beyond injectable insulin and oral antidiabetics: [review]

Novos medicamentos para o tratamento do diabetes tipo 1 e tipo 2 foram incorporados à lista de fármacos tradicionais: antidiabéticos orais e insulinas injetáveis. Estas alternativas de tratamento têm novos mecanismos de ação que aproveitam as propriedades antidiabéticas de certos peptídeos como é o caso da amilina ou do peptídeo similar ao glucagon (GLP-1), cujos níveis são deficientes ou insuficientes no diabetes. Isto acontece pelos análogos da amilina ou do GLP-1, embora também possa ser obtido inibindo a enzima que degrada este último. Além disso, encontra-se disponível no mercado um novo sistema para administrar insulina de maneira não-invasiva por meio de inalação. Este artigo resume os resultados mais importantes e atualizados com relação ao mecanismo de ação, eficácia, efeitos adversos e indicações destes fármacos inovadores.

New medicines for the therapy of the type 1 and type 2 diabetes have been incorporated in the list of traditional drugs: oral agents and injectable insulin. These treatment alternatives have a new mechanism of action that takes advantage of the antidiabetic properties of certain peptides such as amylin and glucagon like peptide-1 (GLP-1), whose levels are wanting or insufficient in diabetes. This is attained through amylin and GLP-1 analogues, although it can also be achieved by inhibiting the enzyme that degrades the latter. Furthermore, a new system to administer insulin in a noninvasive way through inhalation has become available in the market. This paper summarizes the most important and updated findings on the action mechanism, efficacy, adverse effects and indications of these innovative drugs.

Leptin responsiveness restored by amylin agonism in diet-induced obesity: evidence from nonclinical and clinical studies.

Body weight is regulated by complex neurohormonal interactions between endocrine signals of long-term adiposity (e.g., leptin, a hypothalamic signal) and short-term satiety (e.g., amylin, a hindbrain signal). We report that concurrent peripheral administration of amylin and leptin elicits synergistic, fat-specific weight loss in leptin-resistant, diet-induced obese rats. Weight loss synergy was specific to amylin treatment, compared with other anorexigenic peptides, and dissociable from amylin's effect on food intake. The addition of leptin after amylin pretreatment elicited further weight loss, compared with either monotherapy condition. In a 24-week randomized, double-blind, clinical proof-of-concept study in overweight/obese subjects, coadministration of recombinant human leptin and the amylin analog pramlintide elicited 12.7% mean weight loss, significantly more than was observed with either treatment alone (P < 0.01). In obese rats, amylin pretreatment partially restored hypothalamic leptin signaling (pSTAT3 immunoreactivity) within the ventromedial, but not the arcuate nucleus and up-regulated basal and leptin-stimulated signaling in the hindbrain area postrema. These findings provide both nonclinical and clinical evidence that amylin agonism restored leptin responsiveness in diet-induced obesity, suggesting that integrated neurohormonal approaches to obesity pharmacotherapy may facilitate greater weight loss by harnessing naturally occurring synergies.

Central and peripheral administration of amylin induces energy expenditure in anesthetized rats.

Amylin is a peptide hormone that is co-released with insulin from pancreatic beta-cells following a meal. Intracerebroventricular (icv) administration of amylin (1-100 pmol), or an amylin agonist, salmon calcitonin, elicited dose-dependent thermogenic, tachycardic, and hyperthermic responses in urethane-anesthetized rats. Intravenous (iv) administration of higher doses of amylin (100 pmol-20 nmol) also induced similar responses, although the amplitudes of these responses were significantly smaller than those elicited by icv administration, suggesting the primary action of amylin to be in the brain. However, the iv administration of amylin induced the responses slightly faster than the icv injection, the former responses occurring<4 min and the latter, at 8-10 min, after the administration. The iv but not the icv injection of amylin increased the respiratory exchange ratio transiently (<20 min), though the thermogenic response lasted for a longer period after both injections, indicating a shift from mixed fuel to predominantly carbohydrate utilization in the initial phase of thermogenesis induced by the iv injection of amylin. The differences in substrate utilization and latency of the responses suggest that the actions of amylin include partly different targets when administered centrally and peripherally. Moreover, pretreatment with a beta-adrenergic blocker, propranolol (5 mg kg(-1), iv), blocked all responses elicited by either icv or iv administration of amylin, whereas ablation of the area postrema in the hindbrain did not influence the effects of icv-administered amylin. These results suggest the involvement of amylin in postprandial energy expenditure, mediated by peripheral beta-adrenoceptors.

The acute effect of amylin and salmon calcitonin on energy expenditure.

The pancreatic B-cell hormone amylin is known to be involved in the regulation of meal ending satiation and it also shares typical features of adiposity signals. Chronic amylin administration has recently been shown to increase energy expenditure under certain conditions. Here we investigate the acute effect of peripheral administration of amylin or its agonist salmon calcitonin (sCT) on energy expenditure and respiratory quotient (RQ). First, rats were injected with amylin (5 microg/kg IP) or saline just before dark onset. Despite significantly decreased food intake in amylin-treated rats compared to control until 2 h post-injection (p<0.05), amylin did not influence energy expenditure or RQ. Reduced food intake, which reduces energy expenditure, may have confounded a stimulatory effect of amylin on energy expenditure. Therefore, in the second experiment, amylin (1, 5 and 10 microg/kg IP) or saline was injected in the middle of the light phase (t=0 h) without access to food during 3 h post-injection. Amylin had no significant effects on energy expenditure or RQ. In a similar paradigm, the effect of sCT (0.1, 1.0 and 5.0 microg/kg IP) was tested. During food restriction, 5.0 microg/kg sCT significantly stimulated energy expenditure compared to control (p<0.05). Subsequent to refeeding at t=3 h, energy expenditure was decreased compared to control at t=8 h and t=10 h after 5.0 microg/kg sCT, probably due to sCT's strong anorectic action. Thus amylin may prevent the compensatory decrease in energy expenditure normally seen in animals that eat less. The longer acting sCT stimulated energy expenditure in animals without food access.

Amylin agonists: a novel approach in the treatment of diabetes.

Amylin is a peptide hormone that is cosecreted with insulin from the pancreatic beta-cell and is thus deficient in diabetic people. It inhibits glucagon secretion, delays gastric emptying, and acts as a satiety agent. Amylin replacement could therefore possibly improve glycemic control in some people with diabetes. However, human amylin exhibits physicochemical properties predisposing the peptide hormone to aggregate and form amyloid fibers, which may play a part in beta-cell destruction in type 2 diabetes. This obviously makes it unsuitable for pharmacological use. A stable analog, pramlintide, which has actions and pharmacokinetic and pharmacodynamic properties similar to the native peptide, has been developed. The efficacy and safety of pramlintide administration has been tested in a vast number of clinical trials. Approximately 5,000 insulin-treated patients have received pramlintide and approximately 250 for > or =2 years. The aims of this review are to 1) briefly describe actions of amylin as demonstrated in animal and human models and 2) primarily review results from clinical trials with the amylin analog pramlintide.

Effects of amylin and the amylin agonist pramlintide on glucose metabolism.

Since the discovery of the pancreatic islet hormone amylin in 1987, its metabolic effects have been investigated in a number of studies in animals and humans. Data from some early animal studies suggested that amylin might be associated with the development of insulin resistance, but other studies found that amylin had no effect on insulin sensitivity. More recently, studies performed using the human amylin analogue pramlintide in patients with Type 1 diabetes found that the hormone has no influence on either insulin-stimulated glucose uptake or the restraining effect of insulin on hepatic glucose production during periods of euglycaemia. Furthermore, during insulin-induced hypoglycaemia, pramlintide appears to increase the plasma concentrations of cortisol and growth hormone, and to stimulate the release of the gluconeogenic substrate lactate by the skeletal muscles. Taken together with evidence that, in short-term studies, pramlintide improved glycaemic control in patients with Type 1 diabetes who were also treated with insulin, these data suggest that pramlintide may have a role in the management of patients with diabetes. However, longer-term studies are required to ascertain whether these findings are sustained over time.

Amylin and glycaemic regulation: a possible role for the human amylin analogue pramlintide.

Clinical studies with the human amylin analogue, pramlintide, suggest that it may help to improve glycaemic control in patients with diabetes mellitus using insulin. This has been demonstrated by reductions in postprandial glycaemic excursion, 24-h glucose profile and serum fructosamine concentrations following administration of pramlintide for periods of up to 28 days in patients with Type 1 diabetes. Additionally, preliminary studies with pramlintide in patients with Type 2 diabetes using insulin have indicated its ability to reduce postprandial hyperglycaemia in this population. Thus, this data set suggests a potential role for pramlintide as a partner to insulin for the optimization of glycaemic control in patients with diabetes using insulin.