Relationship Between Testosterone and Cognitive Function in Elderly Men with Dementia

The biological and clinical advances of androgen receptor function in age-related diseases and cancer [Review]

Hormonal alterations with aging contribute to the pathogenesis of several diseases. Androgens mediate their effects predominantly through binding to the androgen receptor (AR), a member of the ligand-dependent nuclear receptor superfamily. By androgen treatment, AR is recruited to specific genomic loci dependent on tissue specific pioneer factors to regulate target gene expression. Recent studies have revealed the epigenetic modulation by AR-associated histone modifiers and the roles of non-coding RNAs in AR signaling. Androgens are male sex hormone to induce differentiation of the male reproductive system required for the establishment of adult sexual function. As shown by several reports using AR knockout mouse models, androgens also have anabolic functions in several tissues such as bone, muscle and central nervous systems. Notably, AR has a central role in prostate cancer progression. Prostate cancer is the most frequently diagnosed cancer in men. Androgen-deprivation therapy for cancer patients and decline of serum androgen with aging promote several diseases associated with aging and quality of life of older men such as osteoporosis, sarcopenia and dementia. Thus, androgen replacement therapy for treating late onset hypogonadism (LOH) or new epigenetic regulators have the potential to overcome the symptoms caused by the low androgen, although adverse effects for cardiovascular diseases have been reported. Given the increasing longevity and consequent rise of age-related diseases and prostate cancer patients, a more understanding of the AR actions in male health remains a high research priority.

Hip Fracture in People with Erectile Dysfunction: A Nationwide Population-Based Cohort Study

The aims of this study were to investigate the risk of hip fracture and contributing factors in patients with erectile dysfunction(ED). This population-based study was performed using the Taiwan National Health Insurance Research Database. The analysis included4636 patients aged ≥ 40 years who had been diagnosed with ED (International Classification of Diseases, Ninth Revision, Clinical Modification codes 302.72, 607.84) during 1996–2010. The control group included 18,544 randomly selected age-matched patients without ED (1:4 ratio). The association between ED and hip fracture risk was estimated using a Cox proportional hazard regression model. During the follow-up period, 59 (1.27%) patients in the ED group and 140 (0.75%) patients in the non-ED group developed hip fracture. After adjusting for covariates, the overall incidence of hip fracture was 3.74-times higher in the ED group than in the non-ED group (2.03 vs. 0.50 per 1000 person-years, respectively). The difference in the overall incidence of hip fracture was largest during the 3-year follow-up period (hazard ratio = 7.85; 95% confidence interval = 2.94–20.96; P <0.0001). To the best of our knowledge, this nationwide population-based study is the first to investigate the relationship between ED and subsequent hip fracture in an Asian population. The results showed that ED patients had a higher risk of developing hip fracture. Patients with ED, particularly those aged 40–59 years, should undergo bone mineral density examinations as early as possible and should take measures to reduce the risk of falls.

Increased Risk of Dementia in Patients With Erectile Dysfunction: A Population-Based, Propensity Score-Matched, Longitudinal Follow-Up Study

Erectile dysfunction (ED) is a well-known predictor for future cardiovascular and cerebrovascular disease. However, the relationship between ED and dementia has rarely been examined. This study investigates the longitudinal risk for Alzheimer's disease and non-Alzheimer dementia in patients with ED. We collected a random sample of 1,000,000 individuals from Taiwan's National Health Insurance database. From this sample, we identified 4153 patients with newly diagnosed ED between 2000 and 2009 and compared them with a matched cohort of 20,765 patients without ED. All patients were tracked for 7 years from the index date to identify which of them subsequently developed dementia. During the 7-year follow-up period, the incidence rate of dementia in the ED cohort was 35.33 per 10,000 person-years. In the comparison groups, it was 21.67 per 10,000 person-years. After adjustment for patients characteristics and comorbidities, patients with ED were 1.68-times more likely to develop dementia than patients without ED (95% CI = 1.34-2.10, P < 0.0001). In addition, older patients and those with diabetes, hypertension, chronic kidney disease, stroke, depression, and anxiety were found to be at increased risk for dementia. Analyzing the data by dementia type, we found the hazard risk for Alzheimer's disease and non-Alzheimer dementia to be greater in patients with ED (adjusted HR 1.68, 95% CI = 1.31-2.16, P < 0.0001 and 1.63, 95% CI = 1.02-2.62, P = 0.0429, respectively). Log-rank test revealed that patients with ED had significantly higher cumulative incidence rates of dementia than those without (P < 0.0001). Patients with ED are at an increased risk for dementia later in life.

Effects of dihydrotestosterone on synaptic plasticity of hippocampus in male SAMP8 mice

The senescence-accelerated-prone mouse 8 (SAMP8) has been proposed as a suitable, naturally derived animal model for investigating the fundamental mechanisms of Alzheimer's disease (AD). In addition, the serum testosterone levels decrease quickly in the natural growth process of this model. This study investigated the effect of androgen deficiency on the synaptic plasticity of hippocampus in male SAMP8 mice after castration and dihydrotestosterone (DHT) administration. We observed the dendritic spines and synapses using Golgi staining and transmission electron microscope. Androgen deficiency after castration significantly reduced the number of apical dendritic thorns, and the abnormal ultrastructure of excitatory synapses was more obvious. Androgen replacement therapy reversed this change. To explore the protective mechanisms and neurological basis of DHT, we researched the changes of expression of GluN1 subunit-containing N-methyl-D-aspartate receptors (NMDARs) and synaptophysin (SYN), which are closely related to synaptic plasticity. Comparisons were made among results observed with immunohistochemistry techniques, Western blots analysis and RT-PCR analysis. The GluN1 and SYN regulation at the protein and mRNA levels probably be related to the DHT-induced morphological synaptic plasticity. This study will be helpful for understanding the function of androgen, and it provides a valuable theoretical basis about the protective and therapeutic targets of androgen in AD.