Up-Regulation of Glycogen Synthesis and Degradation Enzyme Level Maintained Myocardial Glycogen in Huddling Brandt's Voles Under Cool Environments.

Small mammals exhibit limited glucose use and glycogen accumulation during hypothermia. Huddling is a highly evolved cooperative behavioral strategy in social mammals, allowing adaptation to environmental cooling. However, it is not clear whether this behavior affects the utilization of glycogen in cold environments. Here, we studied the effects of huddling on myocardial glycogen content in Brandt's voles (Lasiopodomys brandtii) under a mild cold environment (15°C). Results showed that (1) Compared to the control (22°C) group (CON), the number of glycogenosomes more than tripled in the cool separated group (CS) in both males and females; whereas the number of glycogenosomes increased in females but was maintained in males in the cool huddling group (CH). (2) Glycogen synthase (GS) activity in the CS group remained unchanged, whereas glycogen phosphorylase (GYPL) activity decreased, which mediated the accumulation of glycogen content of the CS group. (3) Both GS and GYPL activity increased which may contribute to the stability of glycogen content in CH group. (4) The expression levels of glucose transporters GLUT1 and GLUT4 increased in the CS group, accompanied by an increase in glucose metabolism. These results indicate that the reduced glycogen degradation enzyme level and enhanced glucose transport may lead to an increase in myocardial glycogen content of the separated voles under cool environment; while the up-regulation of glycogen synthesis and degradation enzyme level maintained myocardial glycogen content in the huddling vole.

Change on apoptosis, autophagy and mitochondria of the Harderian gland in Cricetulus barabensis during age.

Harderian gland (HG) plays an important role in the physiological adaptation to terrestrial life, however, the mechanisms underlying the changes in the structure and function of the HG during aging remain unclear. This study investigated autophagy and apoptosis in the HG of striped dwarf hamsters (Cricetulus barabensis) of different ages (sub-adult, adult and aged groups) in both males and females. The results showed that LC3II/LC3I and puncta of LC3 were significantly higher in adult and aged individuals than sub-adults, whereas P62 decreased with age. Bax/bcl2was the highest in sub-adults of male and female individuals. Caspase3 activity was the highest in sub-adults of male and female individuals, and the citrate synthase activity was highest in sub-adults of females. ATP synthase, citrate synthase, dynamin-related protein 1 and mitochondrial fission factor (Mff) were the highest in sub-adults of females. Peptidylglycine α-amidating monooxygenase were the highest in the aged group, and those of gonadotropin-releasing hormone was the highest in the adult group. LC3II/LC3I, P62, Drp1, Fis, and bax/bcl2 were higher in males than that in females. These results suggest that apoptosis mainly affects growth and development in the HG, whereas autophagy affects aging. The difference of the HG weight and mitochondrial function between sexes is mainly related to the apoptosis.

The effect of autophagy and mitochondrial fission on Harderian gland is greater than apoptosis in male hamsters during different photoperiods.

Photoperiod is an important factor of mammalian seasonal rhythm. Here, we studied morphological differences in the Harderian gland (HG), a vital photosensitive organ, in male striped dwarf hamsters (Cricetulus barabensis) under different photoperiods (short photoperiod, SP; moderate photoperiod, MP; long photoperiod, LP), and investigated the underlying molecular mechanisms related to these morphological differences. Results showed that carcass weight and HG weight were lower under SP and LP conditions. There was an inverse correlation between blood melatonin levels and photoperiod in the order SP > MP > LP. Protein expression of hydroxyindole-O-methyltransferase (HIOMT), a MT synthesis-related enzyme, was highest in the SP group. Protein expression of bax/bcl2 showed no significant differences, indicating that the level of apoptosis remained stable. Protein expression of LC3II/LC3I was higher in the SP group than that in the MP group. Furthermore, comparison of changes in the HG ultrastructure demonstrated autolysosome formation in the LP, suggesting the lowest autophagy level in under MP. Furthermore, the protein expression levels of ATP synthase and mitochondrial fission factor were highest in the MP group, whereas citrate synthase, dynamin-related protein1, and fission1 remained unchanged in the three groups. The change trends of ATP synthase and citrate synthase activity were similar to that of protein expression among the three groups. In summary, the up-regulation of autophagy under SP and LP may be a primary factor leading to loss of HG weight and reduced mitochondrial energy supply capacity.

Novel ultrastructural findings on cardiac mitochondria of huddling Brandt's voles in mild cold environment.

Reduced ambient temperature has a damaging effect on mammalian myocardium. Huddling as a cooperative behavior has evolved in social mammals as a strategy to maximize adaptation to environmental cooling. Here, we studied the effects of huddling behavior on mitochondrial morphology, number, and function in the myocardia of Brandt's voles (Lasiopodomys brandtii) under cool environmental temperatures (15 °C). Results showed (1) mitochondrial swelling and cristae disruption in the cool huddling group (CH) and cool separated group (CS). Compared to the control group (CON, 22 °C), damaged mitochondria in the cool huddling and separated groups reached >90%; however, total number of mitochondria in the CH group was similar to that in the CON group. (2) ATP synthase activity was lowest in the CS group, whereas citrate synthetase activity was maintained among the three treatment groups. (3) Bax/bcl2 protein expression in the CH and CS groups was higher than that in the CON group, whereas DNA fragmentation, nuclear number, and caspase3 activity showed no significant differences among the three groups. (4) The protein expression levels of dynamin-related protein1 and mitochondrial fission factor were highest in the CH group. (5) Both protein expression of PINK1 and phosphorylation ratio of Parkin showed the pattern CS > CH > CON. (6) Total number of mitochondria was higher in males than in females. In general, the increased mitochondrial fission level observed in huddling voles partially counteracted the decrease in myocardial mitochondria caused by the increase in autophagy.

Photoperiod Affects Harderian Gland Morphology and Secretion in Female Cricetulus barabensis: Autophagy, Apoptosis, and Mitochondria.

Photoperiod is an important factor of mammalian seasonal rhythm. The Harderian gland (HG) appears to act as a "standby" structure of the retinal-pineal axis, mediating light signals in vitro and neuroendocrine regulation in vivo; however, the effect of photoperiod on the HG is not clear. Here, we studied morphological differences in the HG of female striped dwarf hamsters (Cricetulus barabensis), a small mammal that experiences an annual rhythm, under different photoperiods (i.e., SP, short photoperiod; MP, moderate photoperiod; LP, long photoperiod), and further investigated the molecular mechanisms related to these morphological differences. Results showed that body weight, carcass weight, and HG weight were higher in the SP and LP groups than that in the MP group. Protein expression of hydroxyindole-o-methyltransferase, a key enzyme in melatonin synthesis, was higher in the SP group than in the other two groups. Somatostatin showed highest expression in the LP group. Furthermore, comparison of changes in the HG ultrastructure demonstrated autolysosome formation in the SP group. Protein aggregation and mRNA expression of LC3 and protein expression of LC3II/LC3I were higher in the SP group than in the MP group, indicating elevated autophagy under SP. Chromatin agglutination and mitochondrial damage were observed and bax/bcl2 and cytochrome C expression increased at the protein and mRNA levels in the SP and LP groups, suggesting increased apoptosis. Protein expression of dynamin-related protein 1 and mitochondrial fission factor (Mff) were highest in the SP group, suggesting elevated mitochondrial fission. Protein expression levels of adenosine triphosphate (ATP) synthase and citrate synthase were lower in the LP group than in the SP and MP groups. These results indicated that autophagy and apoptosis imbalance under SP and LP conditions may have led to HG weight loss and up-regulation of mitochondrial apoptosis may have weakened mitochondrial function under LP conditions. Finally, melatonin synthesis appeared to be positively correlated with the time hamsters entered darkness.