Histological Correlates of Penile Sexual Sensation: Does Circumcision Make a Difference?

INTRODUCTION

The question of whether removal of sensory receptors in the prepuce by circumcision affects sensitivity and/or sexual pleasure is often debated.

AIMS

To examine histological correlates relevant to penile sensitivity and sexual pleasure.

METHODS

Systematic review of the scientific literature on penile structures that might affect sensitivity and sexual sensation. Articles were included if they contained original data on human male penile histology or anatomy. Individual articles, including reference lists, were evaluated. They were then considered in relation to physiological data from articles retrieved by a previous systematic review.

RESULTS

We retrieved 41 publications on penile structure. Considered in the light of 12 reporting physiological measurements, our evaluation finds that sexual response is unlikely to involve Meissner's corpuscles, whose density in the prepuce diminishes at the time of life when male sexual activity is increasing. Free nerve endings also show no correlation with sexual response. Because tactile sensitivity of the glans decreases with sexual arousal, it is unrelated to sexual sensation. Thermal sensitivity seems part of the reward mechanism of intercourse. Vibrational sensitivity is not related to circumcision status. Observations that penile sexual sensation is higher post circumcision are consistent with greater access of genital corpuscles to sexual stimuli after removal of the prepuce. This is based on the distribution of these corpuscles (which are located in the glans) and, in uncircumcised men, the position of the retracted prepuce during intercourse, rather than any change in the number of genital corpuscles. The scientific literature suggests that any sexual effect of circumcised men may depend solely on exposure of the glans and not on the absence of the prepuce.

CONCLUSION

Based on histological findings and correlates of sexual function, loss of the prepuce by circumcision would appear to have no adverse effect on sexual pleasure. Our evaluation supports overall findings from physiological measurements and survey data.

Genetic variation in the raptor gene is associated with overweight but not hypertension in American men of Japanese ancestry

BACKGROUND

The mechanistic target of rapamycin (mTOR) pathway is pivotal for cell growth. Regulatory associated protein of mTOR complex I (Raptor) is a unique component of this pro-growth complex. The present study tested whether variation across the raptor gene (RPTOR) is associated with overweight and hypertension.

METHODS

We tested 61 common (allele frequency ≥ 0.1) tagging single nucleotide polymorphisms (SNPs) that captured most of the genetic variation across RPTOR in 374 subjects of normal lifespan and 439 subjects with a lifespan exceeding 95 years for association with overweight/obesity, essential hypertension, and isolated systolic hypertension. Subjects were drawn from the Honolulu Heart Program, a homogeneous population of American men of Japanese ancestry, well characterized for phenotypes relevant to conditions of aging. Hypertension status was ascertained when subjects were 45-68 years old. Statistical evaluation involved contingency table analysis, logistic regression, and the powerful method of recursive partitioning.

RESULTS

After analysis of RPTOR genotypes by each statistical approach, we found no significant association between genetic variation in RPTOR and either essential hypertension or isolated systolic hypertension. Models generated by recursive partitioning analysis showed that RPTOR SNPs significantly enhanced the ability of the model to accurately assign individuals to either the overweight/obese or the non-overweight/obese groups (P = 0.008 by 1-tailed Z test).

CONCLUSION

Common genetic variation in RPTOR is associated with overweight/obesity but does not discernibly contribute to either essential hypertension or isolated systolic hypertension in the population studied.

FOXO3: A Major Gene for Human Longevity--A Mini-Review

BACKGROUND

The gene FOXO3, encoding the transcription factor forkhead box O-3 (FoxO3), is one of only two for which genetic polymorphisms have exhibited consistent associations with longevity in diverse human populations.

OBJECTIVE

Here, we review the multitude of actions of FoxO3 that are relevant to health, and thus healthy ageing and longevity.

METHODS

The study involved a literature search for articles retrieved from PubMed using FoxO3 as keyword.

RESULTS

We review the molecular genetics of FOXO3 in longevity, then current knowledge of FoxO3 function relevant to ageing and lifespan. We describe how FoxOs are involved in energy metabolism, oxidative stress, proteostasis, apoptosis, cell cycle regulation, metabolic processes, immunity, inflammation and stem cell maintenance. The single FoxO in Hydra confers immortality to this fresh water polyp, but as more complex organisms evolved, this role has been usurped by the need for FoxO to control a broader range of specialized pathways across a wide spectrum of tissues assisted by the advent of as many as 4 FoxO subtypes in mammals. The major themes of FoxO3 are similar, but not identical, to other FoxOs and include regulation of cellular homeostasis, particularly of stem cells, and of inflammation, which is a common theme of age-related diseases. Other functions concern metabolism, cell cycle arrest, apoptosis, destruction of potentially damaging reactive oxygen species and proteostasis.

CONCLUSIONS

The mechanism by which longevity-associated alleles of FOXO3 reduce age-related mortality is currently of great clinical interest. The prospect of optimizing FoxO3 activity in humans to increase lifespan and reduce age-related diseases represents an exciting avenue of clinical investigation. Research strategies directed at developing therapeutic agents that target FoxO3, its gene and proteins in the pathway(s) FoxO3 regulates should be encouraged and supported.

The thalamic reticular nucleus: a functional hub for thalamocortical network dysfunction in schizophrenia and a target for drug discovery

The thalamus (comprising many distinct nuclei) plays a key role in facilitating sensory discrimination and cognitive processes through connections with the cortex. Impaired thalamocortical processing has long been considered to be involved in schizophrenia. In this review we focus on the thalamic reticular nucleus (TRN) providing evidence for it being an important communication hub between the thalamus and cortex and how it may play a key role in the pathophysiology of schizophrenia. We first highlight the functional neuroanatomy, neurotransmitter localisation and physiology of the TRN. We then present evidence of the physiological roles of the TRN in relation to oscillatory activity, cognition and behaviour. Next we discuss the role of the TRN in rodent models of risk factors for schizophrenia (genetic and pharmacological) and provide evidence for TRN deficits in schizophrenia. Finally we discuss new drug targets for schizophrenia in relation to restoring TRN circuitry dysfunction.

Functional brain connectivity phenotypes for schizophrenia drug discovery

While our knowledge of the pathophysiology of schizophrenia has increased dramatically, this has not translated into the development of new and improved drugs to treat this disorder. Human brain imaging and electrophysiological studies have provided dramatic new insight into the mechanisms of brain dysfunction in the disease, with a swathe of recent studies highlighting the differences in functional brain network and neural system connectivity present in the disorder. Only recently has the value of applying these approaches in preclinical rodent models relevant to the disorder started to be recognised. Here we highlight recent findings of altered functional brain connectivity in preclinical rodent models and consider their relevance to those alterations seen in the brains of schizophrenia patients. Furthermore, we highlight the potential translational value of using the paradigm of functional brain connectivity phenotypes in the context of preclinical schizophrenia drug discovery, as a means both to understand the mechanisms of brain dysfunction in the disorder and to reduce the current high attrition rate in schizophrenia drug discovery.

Genetic analysis of TOR complex gene variation with human longevity: a nested case-control study of American men of Japanese ancestry

The mechanistic target of rapamycin (mTOR) pathway is crucial for life span determination in model organisms. The aim of the present study was to test tagging single-nucleotide polymorphisms that captured most of the genetic variation across key TOR complex 1 (TORC1) and TOR complex 2 (TORC2) genes MTOR, RPTOR, and RICTOR and the important downstream effector gene RPS6KA1 for association with human longevity (defined as attainment of at least 95 years of age) as well as health span phenotypes. Subjects comprised a homogeneous population of American men of Japanese ancestry, well characterized for aging phenotypes and who have been followed for 48 years. The study used a nested case-control design involving 440 subjects aged 95 years and older and 374 controls. It found no association of 6 tagging single-nucleotide polymorphisms for MTOR, 61 for RPTOR, 7 for RICTOR, or 5 for RPS6KA1 with longevity. Of 40 aging-related phenotypes, no significant association with genotype was seen. Thus common genetic variation (minor allele frequency ≥10%) in MTOR, RPTOR, RICTOR, and RPS6KA1 is not associated with extreme old age or aging phenotypes in this population. Further research is needed to assess the potential genetic contribution of other mTOR pathway genes to human longevity, gene expression, upstream and downstream targets, and clinically relevant aging phenotypes.

Male circumcision for protection against HIV infection in sub-Saharan Africa: the evidence in favour justifies the implementation now in progress

This article responds to a recent 'controversy study' in Global Public Health by de Camargo et al. directed at three randomised controlled trials (RCTs) of male circumcision (MC) for HIV prevention. These trials were conducted in three countries in sub-Saharan Africa (SSA) and published in 2005 and 2007. The RCTs confirmed observational data that had accumulated over the preceding two decades showing that MC reduces by 60% the risk of HIV infection in heterosexual men. Based on the RCT results, MC was adopted by global and national HIV policy-makers as an additional intervention for HIV prevention. Voluntary medical MC (VMMC) is now being implemented in 14 SSA countries. Thus referring to MC for HIV prevention as 'debate' and viewing MC through a lens of controversy seems mistaken. In their criticism, de Camargo et al. misrepresent and misinterpret current science supporting MC for HIV prevention, omit previous denunciations of arguments similar to theirs, and ignore evidence from ongoing scientific research. Here we point out the flaws in three areas de Camargo et al. find contentious. In doing so, we direct readers to growing evidence of MC as an efficacious, safe, acceptable, relatively low-cost one-off biomedical intervention for HIV prevention.

Novel treatment strategies for schizophrenia from improved understanding of genetic risk

Recent years have seen significant advances in our understanding of the genetic basis of schizophrenia. In particular, genome-wide approaches have suggested the involvement of many common genetic variants of small effect, together with a few rare variants exerting relatively large effects. While unequivocal identification of the relevant genes has, for the most part, remained elusive, the genes revealed as potential candidates can in many cases be clustered into functionally related groups which are potentially open to therapeutic intervention. In this review, we summarise this information, focusing on the accumulating evidence that genetic dysfunction at glutamatergic synapses and post-synaptic signalling complexes contributes to the aetiology of the disease. In particular, there is converging support for involvement of post-synaptic JNK pathways in disease aetiology. An expansion of our neurobiological knowledge of the basis of schizophrenia is urgently needed, yet some promising novel pharmacological targets can already be discerned.

Abstract 661: Foxo3 Genotype Increases Lifespan By A Major Effect On Cardiovascular Mortality

The strongest, most consistently replicated genetic influences on human lifespan worldwide involve specific alleles of the ApoE and Foxo3 genes. For FOXO3 , the G allele of SNP rs2802292 exhibits the most robust association. The aim of the present study was to determine FOXO3 genotype-related cause-specific mortality over 9 years in 3,584 elderly American men of Japanese ancestry from the Kuakini Hawaii Lifespan Study, an extensively characterized, long-studied, robust cohort drawn from the Honolulu Heart Program, which recruited subjects in 1965–1968. A Cox proportional hazards model computed relative risk of mortality for coronary heart disease (CHD), cancer, stroke, other circulatory diseases, and remaining causes. We created multivariate models that included other major risk factors for all-cause and cause-specific mortality. We determined contribution of FOXO3 genotype and other risk factors to mortality by estimating population attributable risk over 9 years follow-up for cause-specific mortality, and total mortality over 21 years. The survival curve, age standardized at 78 years (mean subject age at baseline), for carriers and non-carriers of the longevity-associated G allele showed that G allele carriers had longer survival ( P =0.016) during follow-up over 9 years (1,272 total deaths), and 21 years ( P =0.004; 3,211 total deaths). Over the 9 years, the 1,683 carriers of the G allele exhibited risk reductions of 16% (RR 0.84, 95% CI 0.74–0.95; P =0.008) for all-cause mortality, 41% (RR 0.59, 95% CI 0.43–0.80; P <0.001) for CHD mortality (202 deaths) and 21% (RR 0.79, 95% CI 0.67–0.94; P =0.009) for 535 deaths from causes besides CHD, cancer or stroke, independent of other major risk factors. Population attributable risk for the TT non-protective genotype was 24% for 9-year CHD mortality, 24% for hypertension, 21% for diabetes, 18% for inflammation and 12% for hypercholesterolemia. In conclusion, the G allele of the FOXO3 SNP rs2802292 has a major effect on mortality, principally through reduction in CHD risk, independent of known major risk factors. The findings support research on FOXO3 as a target for therapeutic intervention in healthy aging.

Abstract 662: Association Analysis of Raptor Gene Variants with Overweight and Hypertension in American Men of Japanese Ancestry

The mechanistic target of rapamycin (mTOR) pathway is pivotal for cell growth and has been implicated in aging, cardiovascular disease, obesity, diabetes and cancer. mTOR signaling is involved in cardiac leptin-mediated cardiac hypertrophy and fibrosis associated with obesity. mTOR is a key component of two multiprotein complexes, mTOR complex 1 and mTOR complex 2. The former is pro-growth and contains a unique protein, raptor. The present study tested for the first time whether genetic variation across the raptor gene ( RPTOR ) is associated with overweight/obesity, essential hypertension (EHT) and isolated systolic hypertension (ISH). We genotyped 61 common (allele frequency ≥ 0.1) tagging single nucleotide polymorphisms (SNPs) that captured most of the genetic variation across RPTOR in 374 subjects of normal lifespan and 439 subjects with a lifespan exceeding 95 years. Subjects were drawn from the Honolulu Heart Program, a homogeneous population of American men of Japanese ancestry, well characterized for phenotypes relevant to conditions of aging. Hypertension status was ascertained when subjects were 45–68 years old. Statistical evaluation was performed by contingency table analysis, logistic regression and recursive partitioning (RP), which is regarded as amongst the most powerful methods for statistical analysis of large complex sets of genetic information. After analysis of RPTOR genotypes by each statistical approach we found no significant association between genetic variation in RPTOR and either EHT or ISH. For EHT, RP revealed that even the most predictive SNPs ( rs4969322 and rs4890052 ) provided little contribution to correctly assigning individuals to EHT or NT ( P =0.22 by Z test). In the case of ISH, RP revealed that only one SNP ( rs2589118 ) made a noticeable contribution, and that this was no better than the contribution from the weakest laboratory/examination variable (overweight/obesity). In contrast, for overweight/obesity, the RP model revealed that RPTOR SNPs significantly enhanced the predictive capacity of the model ( P =0.008 by one-tailed Z test). In conclusion, genetic variation across RPTOR is associated with overweight/obesity, but not EHT or ISH in the populations of normal lifespan and of long-lived subjects studied.

Veracity and rhetoric in paediatric medicine: a critique of Svoboda and Van Howe's response to the AAP policy on infant male circumcision

In a recent issue of the Journal of Medical Ethics,Svoboda and Van Howe commented on the 2012 changein the American Academy of Pediatrics (AAP) policy on newborn male circumcision, in which the AAP stated that benefits of the procedure outweigh the risks. Svoboda and Van Howe disagree with the AAP conclusions. We show here that their arguments against male circumcision are based on a poor understanding of epidemiology,erroneous interpretation of the evidence, selective citation of the literature, statistical manipulation of data, and circular reasoning. In reality, the scientific evidence indicates that male circumcision, especially when performed in the newborn period, is an ethically and medically sound low-risk preventive health procedure conferring a lifetime of benefits to health and well-being.Policies in support of parent-approved elective newborn circumcision should be embraced by the medical,scientific and wider communities.

Does Male Circumcision Protect against Sexually Transmitted Infections? Arguments and Meta-Analyses to the Contrary Fail to Withstand Scrutiny

We critically evaluate a recent article by Van Howe involving 12 meta-analyses that concludes, contrary to current evidence, that male circumcision increases the risk of various common sexually transmitted infections (STIs). Our detailed scrutiny reveals that these meta-analyses (1) failed to include results of all relevant studies, especially data from randomized controlled trials, (2) introduced bias through use of inappropriate control groups, (3) altered original data, in the case of human papillomavirus (HPV), by questionable adjustments for "sampling bias," (4) failed to control for confounders through use of crude odds ratios, and (5) used unnecessarily complicated methods without adequate explanation, so impeding replication by others. Interventions that can reduce the prevalence of STIs are important to international health. Of major concern is the global epidemic of oncogenic types of HPV that contribute to the burden of genital cancers. Meta-analyses, when well conducted, can better inform public health policy and medical practice, but when seriously flawed can have detrimental consequences. Our critical evaluation leads us to reject the findings and conclusions of Van Howe on multiple grounds. Our timely analysis thus reaffirms the medical evidence supporting male circumcision as a desirable intervention for STI prevention.

Shorter men live longer: association of height with longevity and FOXO3 genotype in American men of Japanese ancestry

Objectives

To determine the relation between height, FOXO3 genotype and age of death in humans.

Methods

Observational study of 8,003 American men of Japanese ancestry from the Honolulu Heart Program/Honolulu-Asia Aging Study (HHP/HAAS), a genetically and culturally homogeneous cohort followed for over 40 years. A Cox regression model with age as the time scale, stratified by year of birth, was used to estimate the effect of baseline height on mortality during follow-up. An analysis of height and longevity-associated variants of the key regulatory gene in the insulin/IGF-1 signaling (IIS) pathway, FOXO3, was performed in a HHP-HAAS subpopulation. A study of fasting insulin level and height was conducted in another HHP-HAAS subpopulation.

Results

A positive association was found between baseline height and all-cause mortality (RR = 1.007; 95% CI 1.003–1.011; P = 0.002) over the follow-up period. Adjustments for possible confounding variables reduced this association only slightly (RR = 1.006; 95% CI 1.002–1.010; P = 0.007). In addition, height was positively associated with all cancer mortality and mortality from cancer unrelated to smoking. A Cox regression model with time-dependent covariates showed that relative risk for baseline height on mortality increased as the population aged. Comparison of genotypes of a longevity-associated single nucleotide polymorphism in FOXO3 showed that the longevity allele was inversely associated with height. This finding was consistent with prior findings in model organisms of aging. Height was also positively associated with fasting blood insulin level, a risk factor for mortality. Regression analysis of fasting insulin level (mIU/L) on height (cm) adjusting for the age both data were collected yielded a regression coefficient of 0.26 (95% CI 0.10–0.42; P = 0.001).

Conclusion

Height in mid-life is positively associated with mortality, with shorter stature predicting longer lifespan. Height was, moreover, associated with fasting insulin level and the longevity genotype of FOXO3, consistent with a mechanistic role for the IIS pathway.

Circumcision rates in the United States: rising or falling? What effect might the new affirmative pediatric policy statement have?

The objective of this review was to assess the trend in the US male circumcision rate and the impact that the affirmative 2012 American Academy of Pediatrics policy statement might have on neonatal circumcision practice. We searched PubMed for the term circumcision to retrieve relevant articles. This review was prompted by a recent report by the Centers for Disease Control and Prevention that found a slight increase, from 79% to 81%, in the prevalence of circumcision in males aged 14 to 59 years during the past decade. There were racial and ethnic disparities, with prevalence rising to 91% in white, 76% in black, and 44% in Hispanic males. Because data on neonatal circumcision are equivocal, we undertook a critical analysis of hospital discharge data. After correction for underreporting, we found that the percentage had declined from 83% in the 1960s to 77% by 2010. A risk-benefit analysis of conditions that neonatal circumcision protects against revealed that benefits exceed risks by at least 100 to 1 and that over their lifetime, half of uncircumcised males will require treatment for a medical condition associated with retention of the foreskin. Other analyses show that neonatal male circumcision is cost-effective for disease prevention. The benefits of circumcision begin in the neonatal period by protection against infections that can damage the pediatric kidney. Given the substantial risk of adverse conditions and disease, some argue that failure to circumcise a baby boy may be unethical because it diminishes his right to good health. There is no long-term adverse effect of neonatal circumcision on sexual function or pleasure. The affirmative 2012 American Academy of Pediatrics policy supports parental education about, access to, and insurance and Medicaid coverage for elective infant circumcision. As with vaccination, circumcision of newborn boys should be part of public health policies. Campaigns should prioritize population subgroups with lower circumcision prevalence and a higher burden of diseases that can be ameliorated by circumcision.

Association analyses of insulin signaling pathway gene polymorphisms with healthy aging and longevity in Americans of Japanese ancestry

Evidence from model organisms suggests that the insulin/IGF-1 signaling pathway has an important, evolutionarily conserved influence over rate of aging and thus longevity. In humans, the FOXO3 gene is the only widely replicated insulin/IGF-1 signaling pathway gene associated with longevity across multiple populations. Therefore, we conducted a nested case-control study of other insulin/IGF-1 signaling genes and longevity, utilizing a large, homogeneous, long-lived population of American men of Japanese ancestry, well characterized for aging phenotypes. Genotyping was performed of single nucleotide polymorphisms, tagging most of the genetic variation across several genes in the insulin/IGF-1 signaling pathway or related gene networks that may be influenced by FOXO3, namely, ATF4, CBL, CDKN2, EXO1, and JUN. Two initial, marginal associations with longevity did not remain significant after correction for multiple comparisons, nor were they correlated with aging-related phenotypes.

Acid resistance in Francisella tularensis

Francisella tularensis, the etiologic agent of tularemia, can survive under acidic conditions. Tularemia can be acquired by several routes, including by ingestion of contaminated food or water. While acid resistance is usually associated with a low oral infective dose (ID), the ID for gastrointestinal illness is quite high. In this study, four strains of F. tularensis ssp. tularensis (type A) and four strains of F. tularensis ssp. holarctica (type B) were examined for innate acid resistance and the ability to survive in synthetic gastric fluid (SGF) under in vitro conditions similar to passage through the human stomach. Survival for all strains was significantly less in pH 2.5 SGF than in pH 2.5 phosphate-buffered saline and pH 4.0 SGF. Attenuated strains were consistently less resistant. Type B strains are most often associated with waterborne outbreaks and were examined after storage in natural water. Low-nutrient preadaptation resulted in increased resistance. Although F. tularensis can persist under certain acidic conditions, it is sensitive to conditions replicating the fasting human stomach. This may help explain the high ID required for gastrointestinal infections.