Biology subjects

Handelsman, D. J.

Publications and source records attributed to Handelsman, D. J..

3 recordsLinked to original sources

bioRxiv2024

The GnRH pulse generator activity in mouse models of polycystic ovary syndrome

One in ten women in their reproductive age suffer from polycystic ovary syndrome (PCOS) that, alongside subfertility and hyperandrogenism, typically presents with increased luteinizing hormone (LH) pulsatility. As such, it is suspected that the arcuate kisspeptin (ARNKISS) neurons that represent the GnRH pulse generator are dysfunctional in PCOS. We used here in vivo GCaMP fiber photometry and other approaches to examine the behavior of the GnRH pulse generator in two mouse models of PCOS. We began with the peripubertal androgen (PPA) mouse model of PCOS but found that it had a reduction in the frequency of ARNKISS neuron synchronization events (SEs) that drive LH pulses. Examining the prenatal androgen (PNA) model of PCOS, we observed highly variable patterns of pulse generator activity with no significant differences detected in ARNKISS neuron SEs, pulsatile LH secretion, or serum testosterone, estradiol, and progesterone concentrations. However, an unsupervised machine learning approach identified that the ARNKISS neurons of acyclic PNA mice continued to exhibit cyclical patterns of activity similar to that of normal mice. The frequency of ARNKISS neuron SEs was significantly increased in algorithm-identified "diestrous stage" PNA mice compared to controls. In addition, ARNKISS neurons exhibited reduced feedback suppression to progesterone in PNA mice and their pituitary gonadotrophs were also less sensitive to GnRH. These observations demonstrate the importance of understanding GnRH pulse generator activity in mouse models of PCOS. The existence of cyclical GnRH pulse generator activity in the acyclic PNA mouse indicates the presence of a complex phenotype with deficits at multiple levels of the hypothalamo-pituitary-gonadal axis.

neuroscience↗

bioRxiv2024

ACTN3 genotype influences androgen response in skeletal muscle

AbstractAndrogens are vital for the maintenance of muscle mass and their anabolic effects are primarily exerted through the androgen receptor (AR). Accumulating evidence in humans and mice suggests that circulating androgens, AR and androgen response are influenced by ACTN3 (- actinin-3), also known as "the gene for speed". One in 5 people worldwide are -actinin-3 deficient due to homozygous inheritance of a common null polymorphism (577X) in ACTN3. In this study, we show that -actinin-3 deficiency decreases baseline AR in skeletal muscles of mice and humans, in both males and females, and that AR expression directly correlates with ACTN3 in a dosage dependent manner. We further demonstrate in Actn3 knockout mice that - actinin-3 deficiency increases muscle wasting induced by androgen deprivation and reduces the muscle hypertrophic response to dihydrotestosterone and this is mediated by differential activation of pathways regulating amino acid metabolism, intracellular transport, MAPK signalling, autophagy, mitochondrial activity and calcineurin signalling. Gene set enrichment and protein analyses indicate that the absence of -actinin-3 results in a failure to coactivate many of these pathways in response to changes in androgens, and relies on leveraging mitochondrial remodelling and calcineurin signalling to restore muscle homeostasis. We further identified 7 genes that are androgen sensitive and -actinin-3-dependent in expression, and whose functions correspond to these processes. Our results highlight the pivotal role of - actinin-3 in various processes associated with the regulation of protein turnover and muscle mass, and suggest that ACTN3 genotype is a genetic modifier of androgen action in skeletal muscle.

genetics↗

bioRxiv2023

Unexpected plasma gonadal steroid and reproductive hormone levels across the mouse estrous cycle

Despite the importance of the mouse in biomedical research, the levels of circulating gonadal steroids across the estrous cycle are not established with any temporal precision. Using liquid chromatography-mass spectrometry, now considered the gold standard for steroid hormone analysis, we aimed to generate a detailed profile of gonadal steroid levels across the estrous cycle of C57BL/6J mice. For reference, luteinizing hormone (LH) and prolactin concentrations were measured in the same samples by sandwich ELISA. Terminal blood samples were collected at 8-hour intervals (10 am, 6 pm, 2 am) throughout the four stages of the estrous cycle. As expected, the LH surge was detected at 6 pm on proestrus with a mean ({+/-}SEM) concentration of 11{+/-}3 ng/mL and occurred coincident with the peak in progesterone levels (22{+/-}4 ng/mL). Surprisingly, estradiol concentrations peaked at 10 am on diestrus (51{+/-}8 pg/mL), with levels on proestrus 6 pm reaching only two-thirds of this value (31{+/-}5 pg/mL). We also observed a proestrous peak in prolactin concentrations (132.5{+/-}17 ng/mL) that occurred earlier than expected at 2 am. Estrone and androstenedione levels were often close to the LOD and showed no consistent changes across the estrous cycle. Testosterone levels were rarely above the LOD (0.01 ng/mL). These observations provide the first detailed assessment of fluctuating gonadal steroid and reproductive hormone levels across the mouse estrous cycle and indicate that species differences exist between mice and other spontaneously ovulating species.

physiology↗