Ovariectomy influences the circadian rhythm of locomotor activity and the photic phase shifts in the volcano mouse

Sex Hormone Suppression and Physical Activity: Possible Implications for Transgender Individuals

Purpose

Transgender individuals tend to be less physically active than cisgender individuals, and the primary focus of these physical activity barriers have been psychosocial in nature. Very little attention has been given to the role that changes in the sex hormone milieu (such as that occurring during gender-affirming hormone therapy) play on physical activity. The purpose of this study was to explore the effects of sex hormone suppression using a gonadotropin-releasing hormone agonist (GnRHa) on physical activity levels and patterns.

Methods

Female and male rats received 4 weeks of sex hormone suppression using the GnRHa goserelin acetate (GA) or received a placebo as a control (CON). Animals were then allowed free access to voluntary running wheels, and activity was recorded throughout the treatment period.

Results

Female rats receiving GA (F GA) had a significantly lower total wheel running distance than female CON (F CON, 53±11 km vs. 113±28 km, respectively, p=0.042), and male rats receiving GA (M GA) had a significantly lower total wheel running distance when compared with male CON (M CON, 31±7 km vs. 69±18 km, respectively, p=0.037). Differences in daily wheel running distances were first observed at day 18 between F GA and F CON (p=0.037) and at day 2 between M GA and M CON (p=0.021).

Conclusion

Reduced sex hormone availability reduced wheel running activity in female and male rats. Understanding the role that sex hormone manipulation has on physical activity may be an important consideration in promoting physical activity in transgender individuals receiving treatments that reduce sex hormone availability.

Transcriptomic changes in the hypothalamus of ovariectomized mice: Data from RNA-seq analysis

BACKGROUND

Menopausal symptoms can affect the physical and mental health of females and are often related to abnormal function of the hypothalamus. In this study, we evaluated changes in the hypothalamus transcriptome in ovariectomized mice to identify key mRNAs, and systematically elucidated the possible molecular mechanisms underlying the menopausal syndrome to provide a theoretical basis for clinical diagnosis and treatment.

METHODS

Forty-six adult female C57BL/6J mice were randomly divided into SHAM and OVX groups, 23 mice per group. Eight weeks after the procedure, differentially expressed genes (DEGs) in the hypothalamus were identified through RNA-sequencing. DEGs were analyzed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genome (KEGG) analyses. Key DEGs were then evaluated using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemical staining.

RESULTS

Compared with SHAM group, 7295 genes were upregulated, and 8979 genes were downregulated in the hypothalamus of OVX mice with a fold change of 1.5 (log2 fold change ≥0.585). GO and KEGG analyses suggested these key genes were involved in thermoregulation, food intake, glucose and lipid metabolism, cardiovascular regulation, biological rhythm, and endocrine regulation.

CONCLUSIONS

Differential expression of genes in the hypothalamus of OVX mice involved in thermoregulation, eating, sleeping, homeostasis, and endocrine regulation 8 weeks after ovariectomy suggest potential roles in the pathogenesis of climacteric syndrome.

Ovariectomy-induced hormone deprivation aggravates Aβ1-42 deposition in the basolateral amygdala and cholinergic fiber loss in the cortex but not cognitive behavioral symptoms in a triple transgenic mouse model of Alzheimer's disease

Alzheimer's disease is the most common type of dementia, being highly prevalent in elderly women. The advanced progression may be due to decreased hormone synthesis during post-menopause as estradiol and progesterone both have neuroprotective potentials. We aimed to confirm that female hormone depletion aggravates the progression of dementia in a triple transgenic mouse model of Alzheimer's disease (3xTg-AD). As pathological hallmarks are known to appear in 6-month-old animals, we expected to see disease-like changes in the 4-month-old 3xTg-AD mice only after hormone depletion. Three-month-old female 3xTg-AD mice were compared with their age-matched controls. As a menopause model, ovaries were removed (OVX or Sham surgery). After 1-month recovery, the body composition of the animals was measured by an MRI scan. The cognitive and anxiety parameters were evaluated by different behavioral tests, modeling different aspects (Y-maze, Morris water maze, open-field, social discrimination, elevated plus maze, light-dark box, fox odor, operant conditioning, and conditioned fear test). At the end of the experiment, uterus was collected, amyloid-β accumulation, and the cholinergic system in the brain was examined by immunohistochemistry. The uterus weight decreased, and the body weight increased significantly in the OVX animals. The MRI data showed that the body weight change can be due to fat accumulation. Moreover, OVX increased anxiety in control, but decreased in 3xTg-AD animals, the later genotype being more anxious by default based on the anxiety z-score. In general, 3xTg-AD mice moved less. In relation to cognition, neither the 3xTg-AD genotype nor OVX surgery impaired learning and memory in general. Despite no progression of dementia-like behavior after OVX, at the histological level, OVX aggravated the amyloid-β plaque deposition in the basolateral amygdala and induced early cholinergic neuronal fiber loss in the somatosensory cortex of the transgenic animals. We confirmed that OVX induced menopausal symptoms. Removal of the sexual steroids aggravated the appearance of AD-related alterations in the brain without significantly affecting the behavior. Thus, the OVX in young, 3-month-old 3xTg-AD mice might be a suitable model for testing the effect of new treatment options on structural changes; however, to reveal any beneficial effect on behavior, a later time point might be needed.

Disentangling environmental drivers of circadian metabolism in desert-adapted mice

Metabolism is a complex phenotype shaped by natural environmental rhythms, as well as behavioral, morphological and physiological adaptations. Metabolism has been historically studied under constant environmental conditions, but new methods of continuous metabolic phenotyping now offer a window into organismal responses to dynamic environments, and enable identification of abiotic controls and the timing of physiological responses relative to environmental change. We used indirect calorimetry to characterize metabolic phenotypes of the desert-adapted cactus mouse (Peromyscus eremicus) in response to variable environmental conditions that mimic their native environment versus those recorded under constant warm and constant cool conditions, with a constant photoperiod and full access to resources. We found significant sexual dimorphism, with males being more prone to dehydration than females. Under circadian environmental variation, most metabolic shifts occurred prior to physical environmental change and the timing was disrupted under both constant treatments. The ratio of CO2 produced to O2 consumed (the respiratory quotient) reached greater than 1.0 only during the light phase under diurnally variable conditions, a pattern that strongly suggests that lipogenesis contributes to the production of energy and endogenous water. Our results are consistent with historical descriptions of circadian torpor in this species (torpid by day, active by night), but reject the hypothesis that torpor is initiated by food restriction or negative water balance.

Estrogens and the circadian system

Circadian rhythms are ~24 h cycles of behavior and physiology that are generated by a network of molecular clocks located in nearly every tissue in the body. In mammals, the circadian system is organized hierarchically such that the suprachiasmatic nucleus (SCN) is the main circadian clock that receives light information from the eye and entrains to the light-dark cycle. The SCN then coordinates the timing of tissue clocks so internal rhythms are aligned with environmental cycles. Estrogens interact with the circadian system to regulate biological processes. At the molecular level, estrogens and circadian genes interact to regulate gene expression and cell biology. Estrogens also regulate circadian behavior across the estrous cycle. The timing of ovulation during the estrous cycle requires coincident estrogen and SCN signals. Studies using circadian gene reporter mice have also elucidated estrogen regulation of peripheral tissue clocks and metabolic rhythms. This review synthesizes current understanding of the interplay between estrogens and the circadian system, with a focus on female rodents, in regulating molecular, physiological, and behavioral processes.

Obese Neotomodon alstoni mice exhibit sexual dimorphism in the daily profile of circulating melatonin and clock proteins PER1 and BMAL1 in the hypothalamus and peripheral oscillators

Obesity is a global health threat and a risk factor for several metabolic conditions. Though circadian dysfunction has been considered among the multiple causes of obesity, little work has been done to explore the relationship between obesity, circadian dysfunction, and sexual dimorphism. The Neotomodon alstoni mouse is a suitable model for such research. This study employed N. alstoni mice in a chronobiological analysis to determine whether there is circadian desynchronization of relative PER1 and BMAL1 protein levels in the hypothalamus, liver, visceral white adipose tissue, kidney, and heart. It also compared differences between sexes and lean and obese N. alstoni adult mice, by recording behavior and daily circulating serum melatonin as markers of circadian output. We found that obese mice display reduced locomotor activity. Additionally, Cosinor analyses of the relative expression of PER1 and BMAL1 show differences between lean and obese mice in a sex-linked manner. The PER1 24 h rhythm was absent in all tissues of obese males and significant in the tissues of obese females. The BMAL1 24 h rhythm also was significant in most of the tissues tested in lean males, whereas it was significant and shifted the acrophase (peak time of rhythm) in most of the tissues in obese females. Both lean male and female mice showed a rhythmic 24 h pattern of circulating serum melatonin. This daily profile was not only absent in obese mice of both sexes but showed sexual dimorphism. Obese male mice showed lower circulating levels of melatonin compared to lean male mice, but they were higher in obese females compared to lean females. Our results suggest that obesity in N. alstoni is associated with an internal circadian desynchronization in a sex-dependent manner. Overall, this study reinforces the need for further research on the neuroendocrinology of obesity and circadian rhythms using this biological model.

Cross-species physiological interactions of endocrine disrupting chemicals with the circadian clock

Endocrine disrupting chemicals (EDCs) are endocrine-active chemical pollutants that disrupt reproductive, neuroendocrine, cardiovascular and metabolic health across species. The circadian clock is a transcriptional oscillator responsible for entraining 24-hour rhythms of physiology, behavior and metabolism. Extensive bidirectional cross talk exists between circadian and endocrine systems and circadian rhythmicity is present at all levels of endocrine control, from synthesis and release of hormones, to sensitivity of target tissues to hormone action. In mammals, a range of hormones directly alter clock gene expression and circadian physiology via nuclear receptor (NR) binding and subsequent genomic action, modulating physiological processes such as nutrient and energy metabolism, stress response, reproductive physiology and circadian behavioral rhythms. The potential for EDCs to perturb circadian clocks or circadian-driven physiology is not well characterized. For this reason, we explore evidence for parallel endocrine and circadian disruption following EDC exposure across species. In the reviewed studies, EDCs dysregulated core clock and circadian rhythm network gene expression in brain and peripheral organs, and altered circadian reproductive, behavioral and metabolic rhythms. Circadian impacts occurred in parallel to endocrine and metabolic alterations such as impaired fertility and dysregulated metabolic and energetic homeostasis. Further research is warranted to understand the nature of interaction between circadian and endocrine systems in mediating physiological effects of EDC exposure at environmental levels.

The volcano mouse Neotomodon alstoni of central Mexico, a biological model in the study of breeding, obesity and circadian rhythms

The "Mexican volcano mouse" Neotomodon alstoni, is endemic of the Transverse Neovolcanic Ridge in central Mexico. It is considered as least concern species and has been studied as a potential laboratory model from different perspectives. Two lines of research in neuroendocrinology have been addressed: reproduction and parental care, particularly focused on paternal attention and the influence of testosterone, and studies on physiology and behavior of circadian rhythms, focused on the circadian biology of the species, its circadian locomotor activity and daily neuroendocrine regulation of metabolic parameters related to energy balance. Some mice, when captive, spontaneously develop obesity, which allows for comparisons between lean and obese mice of daily changes in neuronal and metabolic parameters associated with changes in food intake and locomotor activity. This review includes studies that consider this species an attractive animal model where the alteration of circadian rhythms influences the pathogenesis of obesity, specifically with the basic regulation of food intake and metabolism and differences related to sex. This study can be considered as a reference to the comparative animal physiology among rodents.

Daily cycle in hepatic lipid metabolism in obese mice, Neotomodon alstoni: Sex differences

Disruption of circadian rhythms influences the pathogenesis of obesity, particularly with the basic regulation of food intake and metabolism. A link between metabolism and the circadian clock is the peroxisome proliferator-activated receptors (PPARs). The Neotomodon alstoni mouse, known as the "Mexican volcano mouse," may develop obesity if fed a normo-caloric diet. This manuscript documents the changes in part of the hepatic lipid homeostasis in both sexes of lean and obese N. alstoni mice, comparing the daily changes in the BMAL1 clock protein, in regulators of lipid metabolism (PGC-1α, PPARα-γ, SREBP-1c, and CPT-1α) and in free fatty acid (FFA) and hepatic triacylglyceride (TAG) metabolites in light-dark cycles. Hepatic tissue and blood were collected at 5, 10, 15, 19, and 24 h. Samples were analyzed by western blotting to determine the relative presence of protein. The results indicate that obesity affects daily changes in lipid metabolism and the BMAL1 profile in females considerably more than in males. These results suggest that the impact of obesity on lipid metabolism has important differences according to sex.