Increased Body Weight and Fat Mass After Subchronic GIP Receptor Antagonist, but Not GLP-2 Receptor Antagonist, Administration in Rats

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-2 (GLP-2) are hormones secreted from the enteroendocrine cells after a meal. They exert their actions through activation of G protein-coupled receptors (R), the GIPR and GLP-2R, respectively. Both have been reported to influence metabolism. The purpose of the study was to investigate the role of the hormones in the regulation of lipid and bone homeostasis by subchronic treatment with novel GIPR and GLP-2R antagonists. Rats were injected once daily with vehicle, GIPR, or GLP-2R antagonists for 3 weeks. Body weight, food intake, body composition, plasma lipoprotein lipase (LPL), adipokines, triglycerides and the marker of bone resorption carboxy-terminal collagen crosslinks (CTX), were examined. In rats, subchronic treatment with GIPR antagonist, rat GIP (3-30)NH2, did not modify food intake and bone resorption, but significantly increased body weight, body fat mass, triglycerides, LPL, and leptin levels compared with vehicle treated rats. Subchronic (Pro3)GIP (a partial GIPR agonist), GLP-2(11-33), and GLP-2(3-33) (GLP-2R antagonists) treatment did not affect any parameter. The present results would be consistent with a role for GIP, but not GLP-2, in the maintenance of lipid homeostasis in rats, while neither GIPR nor GLP-2R antagonism appeared to influence bone resorption in rats

Circulating Glucagon 1-61 Regulates Blood Glucose by Increasing Insulin Secretion and Hepatic Glucose Production

Glucagon is secreted from pancreatic a cells, and hypersecretion (hyperglucagonemia) contributes to diabetic hyperglycemia. Molecular heterogeneity in hyperglucagonemia is poorly investigated. By screening human plasma using high-resolution-proteomics, we identified several glucagon variants, among which proglucagon 1-61 (PG 1-61) appears to be the most abundant form. PG 1-61 is secreted in subjects with obesity, both before and after gastric bypass surgery, with protein and fat as the main drivers for secretion before surgery, but glucose after. Studies in hepatocytes and in b cells demonstrated that PG 1-61 dose-dependently increases levels of cAMP, through the glucagon receptor, and increases insulin secretion and protein levels of enzymes regulating glycogenolysis and gluconeogenesis. In rats, PG 1-61 increases blood glucose and plasma insulin and decreases plasma levels of amino acids in vivo. We conclude that glucagon variants, such as PG 1-61, may contribute to glucose regulation by stimulating hepatic glucose production and insulin secretion

Hekkesuksess hos krykkje (Rissa tridactyla) på Svalbard i forhold til diett og temperatur i havoverflaten

Seabird and prey interactions are largely influenced by dynamics in marine ecosystems, especially during the breeding season. The availability of prey is affected by oceanographic processes and environmental factors. Black-legged kittiwakes (Rissa tridactyla) in Kongsfjorden on Svalbard have experienced a change in available prey species during the last three years. Warm saline Atlantic water has dominated Kongsfjorden since 2005. As a result of the after a large inflow of Atlantic water masses to the western part of Svalbard in 2007 capelin (Mallotus villosus) has substituted polar cod (Boreogadus saida) in the diet of breeding kittiwakes. Diet data from the field season of 2009 has been compared with diet data from 1997, 1998 and 2004-2008. The diet samples has been analysed to classify the prey species to the nearest possible taxon. Hatching date, body condition, amount of fish in the diet and sea surface temperature were used as parameters to determine the effect availability of fish had on the birds breeding success (chicks per active nest). A distinct seasonal variation of capelin and polar cod was found during the incubation and chick-rearing period, respectively, in 2008 and 2009. The hatching date which reflects the body condition of kittiwakes in the period before egg laying was significantly correlated with the breeding success. Also, the body condition during the chick-rearing period was correlated with frequency of fish in the diet. Additionally, there was a tendency for a positive relationship between the frequency of capelin in the diet and sea surface temperature. These findings show that for kittiwakes in Kongsfjorden, fish is the most important prey during the breeding period. Especially the fish availability during the period before the egg laying is assumed to be critical for the outcome of reproduction. The increase of capelins in Kongsfjorden did not affect the breeding success, probably because capelins were first available as prey in mid July (i.e. the chick-rearing period). Kittiwakes are excellent indicators of ecosystem changes, and results from the present thesis support other marine studies: that the ecosystem in Kongsfjorden is changing. Sammenhengen mellom sjøfugl og deres byttedyr er i stor grad påvirket av dynamikken i marine økosystemer, spesielt i hekkesesongen. Tilgangen på byttedyr er påvirket av oseaniske prosesser og miljøfaktorer. Krykkjen (Rissa tridactyla) i Kongsfjorden på Svalbard har gjennom de siste tre årene opplevd en endring i tilgjengelige arter av byttedyr. Varmt og saltholdig atlantisk vann har domineret Kongsfjorden siden 2005. Som et resultat av stor innstrømning av atlantisk vann på vest siden av Svalbard i 2007, har lodden (Mallotus villosus) erstattet polartorsk (Boreogadus saida) i diett prøver hos hekkende krykkjer for polartorsk. Diettdata fra feltsesongen i 2009 ble sammenlignet med diettdata fra 1997, 1998 og 2004-2008. Diettprøvene ble analysert og byttedyrene ble klassifisert til nærmeste familie. Hekke dato, kondition og mengden av fisk i dietten i ungeperioden samt havtemperatur ble brukt til å finne ut effekten av tilgjengelig fisk på hekkeksuksessen (unger per aktive reir). Det ble funnnet en markant sesongvariasjon i mengde lodde og polartorsk mellom ruge- og ungeperioden i 2008 og 2009. Klekkedato, som reflekterer kondisjonen til hekkende krykkjer i perioden før egglegging, korrelerte signifikant med hekkesuksessen. Kondisjonen i ungeperioden korrelerte også med mengden fisk i dietten. I tillegg ble en trend mellom havtemperaturen og mengde lodde i dietten funnet. Disse resultatene viser at fisk er det viktigste byttedyr for krykkjer i Kongsfjorden i hekkeperioden. Særlig viktig er tilgjengeligheten av fisk i perioden før egglegging for resultatet av reproduksjonen.. Den økte mengden lodde i Kongsfjorden hadde ikke noen påvirkning på hekkesukssen, sannsynligvis fordi lodden først er tilgjengelig som byttedyr i midten av juli (eksempelvis ungeperioden). Krykkjer er en perfekt indikatorart for endringer i et økosystem og resultatene presentert i denne mastergraden støtter konklusjonene hos andre marine studier om at Kongsfjordens økosystem er i endring.Norsk Polarinstitutt og UM

Breeding success of black-legged kittiwakes (Rissa tridactyla) at Svalbard in relation to diet and sea surface temperature

Seabird and prey interactions are largely influenced by dynamics in marine ecosystems, especially during the breeding season. The availability of prey is affected by oceanographic processes and environmental factors. Black-legged kittiwakes (Rissa tridactyla) in Kongsfjorden on Svalbard have experienced a change in available prey species during the last three years. Warm saline Atlantic water has dominated Kongsfjorden since 2005. As a result of the after a large inflow of Atlantic water masses to the western part of Svalbard in 2007 capelin (Mallotus villosus) has substituted polar cod (Boreogadus saida) in the diet of breeding kittiwakes. Diet data from the field season of 2009 has been compared with diet data from 1997, 1998 and 2004-2008. The diet samples has been analysed to classify the prey species to the nearest possible taxon. Hatching date, body condition, amount of fish in the diet and sea surface temperature were used as parameters to determine the effect availability of fish had on the birds breeding success (chicks per active nest). A distinct seasonal variation of capelin and polar cod was found during the incubation and chick-rearing period, respectively, in 2008 and 2009. The hatching date which reflects the body condition of kittiwakes in the period before egg laying was significantly correlated with the breeding success. Also, the body condition during the chick-rearing period was correlated with frequency of fish in the diet. Additionally, there was a tendency for a positive relationship between the frequency of capelin in the diet and sea surface temperature. These findings show that for kittiwakes in Kongsfjorden, fish is the most important prey during the breeding period. Especially the fish availability during the period before the egg laying is assumed to be critical for the outcome of reproduction. The increase of capelins in Kongsfjorden did not affect the breeding success, probably because capelins were first available as prey in mid July (i.e. the chick-rearing period). Kittiwakes are excellent indicators of ecosystem changes, and results from the present thesis support other marine studies: that the ecosystem in Kongsfjorden is changing. Sammenhengen mellom sjøfugl og deres byttedyr er i stor grad påvirket av dynamikken i marine økosystemer, spesielt i hekkesesongen. Tilgangen på byttedyr er påvirket av oseaniske prosesser og miljøfaktorer. Krykkjen (Rissa tridactyla) i Kongsfjorden på Svalbard har gjennom de siste tre årene opplevd en endring i tilgjengelige arter av byttedyr. Varmt og saltholdig atlantisk vann har domineret Kongsfjorden siden 2005. Som et resultat av stor innstrømning av atlantisk vann på vest siden av Svalbard i 2007, har lodden (Mallotus villosus) erstattet polartorsk (Boreogadus saida) i diett prøver hos hekkende krykkjer for polartorsk. Diettdata fra feltsesongen i 2009 ble sammenlignet med diettdata fra 1997, 1998 og 2004-2008. Diettprøvene ble analysert og byttedyrene ble klassifisert til nærmeste familie. Hekke dato, kondition og mengden av fisk i dietten i ungeperioden samt havtemperatur ble brukt til å finne ut effekten av tilgjengelig fisk på hekkeksuksessen (unger per aktive reir). Det ble funnnet en markant sesongvariasjon i mengde lodde og polartorsk mellom ruge- og ungeperioden i 2008 og 2009. Klekkedato, som reflekterer kondisjonen til hekkende krykkjer i perioden før egglegging, korrelerte signifikant med hekkesuksessen. Kondisjonen i ungeperioden korrelerte også med mengden fisk i dietten. I tillegg ble en trend mellom havtemperaturen og mengde lodde i dietten funnet. Disse resultatene viser at fisk er det viktigste byttedyr for krykkjer i Kongsfjorden i hekkeperioden. Særlig viktig er tilgjengeligheten av fisk i perioden før egglegging for resultatet av reproduksjonen.. Den økte mengden lodde i Kongsfjorden hadde ikke noen påvirkning på hekkesukssen, sannsynligvis fordi lodden først er tilgjengelig som byttedyr i midten av juli (eksempelvis ungeperioden). Krykkjer er en perfekt indikatorart for endringer i et økosystem og resultatene presentert i denne mastergraden støtter konklusjonene hos andre marine studier om at Kongsfjordens økosystem er i endring