Cloning, Characterization and Tissue Specific Expression of Amur Tiger (Panthera tigris altaica) IGF-I

Insulin-like growth factor I (IGF-I) in Chinese alligator, Alligator sinensis: Molecular characterization, tissue distribution and mRNA expression changes during the active and hibernating periods

The Chinese alligator Alligator sinensis is an endangered species endemic to China, up to date, little is known about the regulation of its growth and development. Insulin-like growth factor I (IGF-I) plays a vital role in regulating vertebrate growth and development. In this study, the full-length cDNA of IGF-I in Chinese alligator (caIGF-I) was obtained for the first time, it contains 890-bp nucleotides encoding a 153-amino acid precursor, the mature caIGF-I consists of 70 amino acids by cleaving the signal peptide and C-terminal extension (E domain). The caIGF-I contains all the features of IGF-I peptide with B, C, A, and D domains and the six conservative cysteine residues involved in the stable tertiary structure. Multiple alignment analysis showed that the amino acid sequence of caIGF-I shares high identity with American alligator Alligator mississippiensis (100%) and birds (95-97%). Phylogenetic tree analysis of the IGF-I amino acid sequences indicated that alligators cluster into the bird branch. Real-time quantitative PCR technique showed that caIGF-I is widely expressed in all the examined tissues with the highest expression level in liver, higher in pancreas and oviduct while lower in heart, spleen, lung, kidney, stomach, intestines, ovary and muscles. During hibernation, the caIGF-I expression level decreased significantly in liver, pancreas, oviduct and kidney, while did not significantly change in heart, spleen, lung, stomach, small intestine, ovary and muscles. The mRNA expression changes during the two periods implicate that caIGF-I might play an important role in the regulation of feeding and growth in the Chinese alligator.

The effect of experimentally induced chronic hyperglycaemia on serum and pancreatic insulin, pancreatic islet IGF-I and plasma and urinary ketones in the domestic cat (Felis felis)

Like in humans, diabetes mellitus is on the rise in cats. Feline diabetes is a suitable model for human type-2 diabetes. We investigated magnitude and timing of insulin suppression with induced hyperglycaemia and its relationship to plasma and urinary ketones and to pancreatic islet insulin. IGF-I is under discussion as a protective mechanism but little is known about its role in diabetes in general and its distinct localisation in feline pancreatic islets in particular. Thirteen healthy, adult cats were allocated to 2 groups and infused with glucose to maintain their blood glucose at a high or moderate concentration for 42 days resulting in insulin secretion suppression. After initial increase, insulin levels declined to baseline but were still detectable in the blood at a very low level after 6 weeks of glucose infusion and then increased after a 3 week recovery period. While IGF-I in healthy cats was primarily located in glucagon cells, in hyperglycaemia-challenge IGF-I was pronounced in the β-cells 3 weeks after ceasation of infusion. Six/8 cats developing glucose toxicity became ketonuric after 3-4 weeks. Gross lipaemia occurred approx 1 week prior to ketonuria. Ketonuric cats required 1-2 weeks of insulin therapy after-infusion until β-cell recovery. In conclusion, ketosis and hyperlipidaemia are likely to occur in diabetic cats with glucose at 30 mmol/L, especially after ≥2 weeks. Three weeks after ceasation of infusions, clinical and morphological recovery occurred. We propose a local protective effect of IGF-I to support survival and insulin production in the hyperglycaemic state and recovery period.