Insulin-like factor 5 (INSL5), a member of the insulin superfamily, is expressed in the colorectum and hypothalamus. To facilitate studies into the role of INSL5, we generated Insl5(-/-) mice by gene targeting. Insl5(-/-) mice were born in the expected Mendelian ratio, reached normal body weight, but displayed impaired male and female fertility that are due to marked reduction in sperm motility and irregular length of the estrous cycle. Furthermore, Insl5(-/-) mice showed impairment in glucose homeostasis with characteristic elevation of serum glucose levels at an advanced age. Glucose and insulin tolerance tests revealed that the increased blood glucose in Insl5(-/-) mice was due to glucose intolerance resulting from reduced insulin secretion. Morphometric and immunohistological analyses revealed that the Insl5(-/-) mice had markedly reduced average islets area and β-cell numbers. Furthermore, immunohistochemistry showed the expression of INSL5 in enteroendocrine cells in the colorectal epithelium and the presence of its putative receptor relaxin family peptide receptor 4 in pancreatic islet cells. These results suggest the potential role of INSL5 signaling in the regulation of insulin secretion and β-cell homeostasis.

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Loss of the Y-chromosome (LOY) is described as both a normal age-related event and a marker of a neoplastic clone in hematologic diseases. To assess the significance of LOY in myelodysplastic syndromes (MDS), we determined the percentage of LOY in clonal CD34+ peripheral blood cells in comparison to normal CD3+ T-cells of 27 MDS patients using fluorescence in situ hybridization (FISH) analysis. Results were compared with the percentage of LOY in CD34+ and CD3+ cells of 32 elderly men without hematologic diseases and in 25 young blood donors. While LOY could not be detected in CD3+ cells of young men, it was observed in CD3+ cells of elderly men without hematologic diseases (2.5% LOY) as well as in CD3+ cells of elderly MDS patients (5.8% LOY). The percentage of CD34+ cells affected by LOY was significantly higher in MDS patients compared to elderly men without hematologic diseases (43.3% vs. 13.2%, P = 0.005), indicating that LOY has an age-related basis but is also associated with MDS. Furthermore, we aimed to define a threshold between age- and disease-associated LOY in MDS. Statistical analysis revealed that a value of 21.5% LOY in CD34+ peripheral blood cells provided the best threshold to discriminate between these two conditions in MDS. We conclude that LOY is clonal in a substantial number of MDS based on an age-related predisposition.