Sex-based trade-offs in the innate and acquired immune systems ofSternotherus minor
JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY
Authors: Lopez-Perez, Jorge E.; Meylan, Peter A.; Goessling, Jeffrey M.
Longevity patterns in most vertebrates suggest that females benefit most from maintenance investment. A reversed longevity pattern in loggerhead musk turtles (Sternotherus minor) allowed us to test trade-offs between maintenance and survivorship. We tested the hypothesis that the sex with greater longevity has greater maintenance than the sex with shorter longevity. We also compared the following parameters between sexes: Bactericidal ability (BA) and heterophil:lymphocyte ratios (HLR). Baseline blood samples were collected from turtles in the field; a subset of turtles was returned to a laboratory for experiments of acquired immune responses to sheep red blood cells (SRBC). We found no support for the original hypothesis of reversal in sex-dependent immune trade-offs (difference between sex SRBC titers:p = .102; interaction between treatment and sex:p = .177; difference between treatments:p < .001; effect of sex on BA:p = .830; effect of sex on HLR:p = .717). However, we did find support for sex-dependent differences in immunity in the relationship between HLR and body condition (BCI) (effect of BCI on HLR:p = .015). In field conditions, we found that males with higher body condition indices express stressed phenotypes more than males with lower body condition indices (p = .002). However, females expressed similar stress loads across all body conditions (p = .900). Testosterone concentrations were assayed in free-living turtles and were not related to any of the immune parameters. Our results suggest that the immune systems play an important role in balancing sex-specific responses to different selective pressures inS. minor.
Deletion of Bmal1 Impairs Pancreatic beta-Cell Function via Mitochondrial Signaling Pathway
BIOMED RESEARCH INTERNATIONAL
Authors: Ye, Lu; Wu, Huaxiang; Xu, Weihong
Several studies have demonstrated that brain and muscle Arnt-like protein-1 (Bmal1) acts as a core clock gene for maintaining normal cell function, including hepatocytes and cardiomyocytes. Loss of Bmal1 is associated with type 2 diabetes due to pancreatic beta-cell failure. However, little information is available about its role and mechanism in pancreatic beta-cell. To address this, we investigated the consequences of Bmal1 inhibition in an insulinoma cell line (INS-1) by using small interfering RNA (siRNA). We observed that knockout of Bmal1 impaired glucose-stimulated insulin secretion in beta-cell. Meanwhile, the depletion of Bmal1 in beta-cell caused an adverse change in mitochondrial membrane potential and mitochondrial architecture. Deletion of Bmal1 attenuated mRNA and protein expression of mitofusin 1 (Mfn1) and mitofusin 2 (Mfn2) and enhanced the expression of fission 1 (Fis1). In summary, the deletion of Bmal1 impaired beta-cell function may be via the mitochondrial signaling pathway in INS-1 cells.