Fetal androgen signaling defects affect pancreatic ß-cell mass and function, leading to glucose intolerance in high-fat diet-fed male rats.

We previously demonstrated that androgen signaling expands pancreatic ß-cell mass in the sexual maturation period (Am J Physiol Endocrinol Metab 314: E274-E286, 2018). The aim of this study was to elucidate whether fetal androgen signaling plays important roles in ß-cell mass development and ß-cell function in adulthood, defects of which are associated with type 2 diabetes mellitus. In the pancreas of male fetuses, androgen receptor (AR) was strongly expressed in the cytoplasm and at the cell membrane of Nkx6.1-positive ß-cell precursor cells but was markedly reduced in insulin-positive ß-cells. Administration of the anti-androgen flutamide to pregnant dams during late gestation reduced ß-cell mass and Ki67-positive proliferating ß-cells at birth in a male-specific manner without affecting body weight. The decrease of ß-cell mass in flutamide-exposed male rats was not recovered when rats were fed a standard diet, whereas it was fully recovered when rats were fed a high-fat diet (HFD), at 6 and 12 wk of age. Flutamide exposure in utero led to the development of glucose intolerance in male rats due to a decrease in insulin secretion when fed HFD but not standard diet. Insulin sensitivity did not differ between the two groups irrespective of diet. These results indicated that the action of fetal androgen contributed to ß-cell mass expansion in a sex-specific manner at birth and to the development of glucose intolerance by decreasing the secretion of insulin in HFD-fed male rats. Our data demonstrated the involvement of fetal androgen signaling in hypothesized sex differences in the developmental origins of health and disease by affecting pancreatic ß-cell function.

Androgen signaling expands ß-cell mass in male rats and ß-cell androgen receptor is degraded under high-glucose conditions.

A deficient pancreatic ß-cell mass increases the risk of type 2 diabetes mellitus. Here, we investigated the effects of testosterone on the development of pancreatic ß-cell mass in male rats. The ß-cell mass of male rats castrated at 6 wk of age was reduced to ~30% of that of control rats at 16 wk of age, and castration caused glucose intolerance. Loss of ß-cell mass occurred because of decreases in islet density per pancreas and ß-cell cluster size. Castration was negatively associated with the number of Ki-67-positive ß-cells and positively associated with the number of TUNEL-positive ß-cells. These ß-cell changes could be prevented by testosterone treatment. In contrast, castration did not affect ß-cell mass in male mice. Androgen receptor (AR) localized differently in mouse and rat ß-cells. Testosterone enhanced the viability of INS-1 and INS-1 #6, which expresses high levels of AR, in rat ß-cell lines. siRNA-mediated AR knockdown or AR antagonism with hydroxyflutamide attenuated this enhancement. Moreover, testosterone did not stimulate INS-1 ß-cell viability under high d-glucose conditions. In INS-1 ß-cells, d-glucose dose dependently (5.5-22.2 mM) downregulated AR protein levels both in the presence and absence of testosterone. The intracellular calcium chelator (BAPTA-AM) could prevent this decrease in AR expression. AR levels were also reduced by a calcium ionophore (A23187), but not by insulin, in the absence of the proteasome inhibitor MG132. Our results indicate that testosterone regulates ß-cell mass, at least in part, by AR activation in the ß-cells of male rats and that the ß-cell AR is degraded under hyperglycemic conditions.

Food texture affects glucose tolerance by altering pancreatic ß-cell function in mice consuming high-fructose corn syrup.

The incidence of metabolic diseases, such as type 2 diabetes, has increased steadily worldwide. Diet, beverages, and food texture can all markedly influence these metabolic disorders. However, the combined effects of food texture and beverages on energy metabolism remains unclear. In the present study, we examined the effect of food texture on energy metabolism in mice administered high-fructose corn syrup (HFCS). Mice were fed a soft or hard diet along with 4.2% HFCS or tap water. Body weight and total caloric intake were not affected by food texture irrespective of HFCS consumption. However, caloric intake from HFCS (i.e., drinking volume) and diet were higher and lower, respectively, in the hard food group than in the soft food group. The hard food group's preference for HFCS was absent in case of mice treated with the µ-opioid receptor antagonist naltrexone. Despite increased HFCS consumption, blood glucose levels were lower in the hard-diet group than in the soft-diet group. In HFCS-fed mice, insulin levels after glucose stimulation and insulin content in the pancreas were higher in the hard food group than the soft food group, whereas insulin tolerance did not differ between the groups. These food texture-induced differences in glucose tolerance were not observed in mice fed tap water. Thus, food texture appears to affect glucose tolerance by influencing pancreatic ß-cell function in HFCS-fed mice. These data shed light on the combined effects of eating habits and food texture on human health.

Therapy-related acute myeloid leukemia 6 years after clonal detection of inv(11)(q21q23) and MLL gene rearrangement.

Results of recent studies with animal models suggest that expression of MLL fusion proteins promotes acute leukemogenesis. However, the most potent MLL fusion proteins are not sufficient for the development of acute myeloid leukemia (AML). The clinical data on the pathogenesis of this type of leukemia are limited. We analyzed the case of a patient with therapy-related AML with MLL rearrangement. The patient initially developed AML with t(8;21). Although the patient achieved complete remission with chemotherapy, an abnormal karyotype, inv(11)(q21q23), was detected. After 6-year persistence of a clone with the inversion 11 karyotype in the bone marrow, secondary AML developed. Results of fluorescence in situ hybridization analysis combined with magnet-activated cell sorting analysis showed that MLL rearrangement was detected in CD34+ and CD13+ fractions but not in a CD3+ fraction of the bone marrow. There were 2 important clinical findings. One was that MLL rearrangement was not sufficient for the development of leukemia. The other was that MLL rearrangement targets specific lineages.