EARLY ELEVATIONS IN ARTERIAL PRESSURE: A CONTRIBUTOR TO RAPID DEPRESSIVE SYMPTOM EMERGENCE IN FEMALE ZUCKER RATS WITH METABOLIC DISEASE?

One of the growing challenges to public health and clinical outcomes is the emergence of cognitive impairments, particularly depressive symptom severity because of chronic elevations in metabolic disease and cerebrovascular disease risk. To more clearly delineate these relationships and to assess the potential for sexual dimorphism, we used lean (LZR) and obese Zucker rats (OZR) of increasing age to determine relationships between internal carotid artery (ICA) hemodynamics, cerebral vasculopathies and the emergence of depressive symptoms. Male OZR exhibited progressive elevations in perfusion pressure within the ICA, which was paralleled by endothelial dysfunction, increased cerebral arterial myogenic activation, and reduced cerebral cortex microvessel density. In contrast, female OZR exhibited a greater degree of ICA hypertension than male OZR, but maintained normal endothelial function, myogenic activation and microvessel density to an older age range than did males. While both male and female OZR exhibited significant and progressive elevations in depressive symptom severity, these were significantly worse in females. Finally, plasma cortisol concentration was elevated higher and at a younger age in female OZR as compared to males and this difference was maintained to final animal usage at ~17 weeks of age. These results suggest that an increased severity of blood pressure waves may penetrate the cerebral circulation more deeply in female OZR than in males, which may predispose the females to a more severe emergence of depressive symptoms with chronic metabolic disease while males may be more predisposed to more direct cerebral vasculopathies (e.g., stroke, transient ischemic attack).

Gene co-expression networks reveal sex-biased differences in musculoskeletal ageing.

Aging is a universal and progressive process involving the deterioration of physiological functions and the accumulation of cellular damage. Gene regulation programs influence how phenotypes respond to environmental and intrinsic changes during aging. Although several factors, including sex, are known to impact this process, the underlying mechanisms remain incompletely understood. Here, we investigate the functional organization patterns of skeletal muscle genes across different sexes and ages using gene co-expression networks (GCNs) to explore their influence on aging. We constructed GCNs for three different age groups for male and female samples, analyzed topological similarities and differences, inferred significant associated processes for each network, and constructed null models to provide statistically robust results. We found that each network is topologically and functionally distinct, with young women having the most associated processes, likely due to reproductive tasks. The functional organization and modularity of genes decline with age, starting from middle age, potentially leading to age-related deterioration. Women maintain better gene functional organization throughout life compared to men, especially in processes like macroautophagy and sarcomere organization. The study suggests that the loss of gene co-expression could be a universal aging marker. This research offers insights into how gene organization changes with age and sex, providing a complementary method to analyze aging.

Pre-Copulatory Sexual Selection Predicts Sexual Size Dimorphism: A Meta-Analysis of Comparative Studies.

Size differences between males and females are common across the tree of life (termed sexual size dimorphism; SSD), and have fundamental implications for ecology, life history and behaviour of both sexes. Conventionally, SSD is thought to evolve in response to sex-specific sexual selection but more recent work suggests that ecological processes can also promote sex-differences in size. Here, we provide a global test for the role of sexual selection in the evolution of sexual size dimorphism using data from 77 comparative studies spanning the major classes of the animal kingdom. We show that intense sexual selection typically correlates with male-biased SSD across species. Importantly, pre-copulatory but not post-copulatory sexual selection predicts SSD, suggesting a pervasive role of premating male-male competition and female choice to drive sex differences in body size. Collectively, our findings suggest that pre-copulatory sexual selection plays a major role in the evolution of male-biased SSD.

Metabolic dysfunction-associated steatotic liver disease exhibits sex-specific microbial heterogeneity within intestinal compartments.

Background: Evidence suggests that the gastrointestinal microbiome plays a significant role in the biology of metabolic dysfunction-associated steatotic liver disease (MASLD). However, it remains unclear whether disparities in the gut microbiome across intestinal tissular compartments between the sexes lead to MASLD pathogenesis. Methods: Sex-specific analyses of microbiome composition in two anatomically distinct regions of the gut, the small intestine and colon, were performed using an experimental model of MASLD. The study involved male and female spontaneously hypertensive rats and the Wistar-Kyoto control rat strain, which were fed either a standard chow diet or a high-fat diet for 12 weeks to induce MASLD (12 rats per group). High-throughput 16S sequencing was used for microbiome analysis. Results: There were significant differences in the overall microbiome composition of male and female rats with MASLD, including variations in topographical gut regions. The beta diversity of the jejunal and colon microbiomes was higher in female rats than in male rats (PERMANOVA p-value=0.001). Sex-specific analysis and discriminant features using LEfSe showed considerable variation in bacterial abundance, along with distinct functional properties, in the jejunum and colon of animals with MASLD. Significantly elevated levels of lipopolysaccharide and protein expression of Toll-like receptor 4 were observed in the livers of male rats with MASLD compared with their female counterparts. Conclusion: This study uncovered sexual dimorphism in the gut microbiome of MASLD and identified microbial heterogeneity within intestinal compartments. Insights into sex-specific variations in gut microbiome composition could facilitate customised treatment strategies.

Novel sex-specific genes and diverse interspecific expression in the antennal transcriptomes of ithomiine butterflies.

The olfactory sense is crucial for organisms, facilitating environmental recognition and inter-individual communication. Ithomiini butterflies exemplify this importance not only because they rely strongly on olfactory cues for both inter- and intra-sexual behaviours, but also because they show convergent evolution of specialized structures within the antennal lobe, called macro-glomerular complexes (MGCs). These structures, widely absent in butterflies, are present in moths where they enable heightened sensitivity to, and integration of information from various types of pheromones. In this study we investigate chemosensory evolution across six ithomiini species and identify possible links between expression profiles and neuroanatomical. To enable this, we sequenced four new high-quality genome assemblies and six sex-specific antennal transcriptomes for three of these species with different MGC morphologies. With extensive genomic analyses we found that the expression of antennal transcriptomes across species exhibit profound divergence, and identified highly expressed ORs, which we hypothesise may be associated to MGCs, as highly expressed ORs are absent in Methona, an Ithomiini lineage which also lacks MGCs. More broadly, we show how antennal sexual dimorphism is prevalent in both chemosensory genes and non-chemosensory genes, with possible relevance for behaviour. As an example, we show how lipid-related genes exhibit consistent sexual dimorphism, potentially linked to lipid transport or host selection. This study broadens the understanding of antennal chemosensory adaptations, suggesting a link between genetic diversity, ecological specialization, and sensory perception with the convergent evolution of MCGs. Insights into chemosensory gene evolution, expression patterns, and potential functional implications enhance our knowledge of sensory adaptations and sexual dimorphisms in butterflies, laying the foundation for future investigations into the genetic drivers of insect behaviour, adaptation, and speciation.

The roles of Growth Hormone dependent JAK-STAT5 and Lyn kinase signalling in determining lifespan and cancer incidence.

In rodents, loss of GH or its receptor is associated with extended lifespan. We aimed to determine the signalling process resulting in this longevity using GH receptor (GHR) mutant mice with key signalling pathways deleted and correlate this with cancer incidence and expression of genes associated with longevity. GHR uses both canonical JAK2-STAT signalling as well as signalling via LYN-ERK1/2 pathway. We utilised C57BL/6 mice with loss of key receptor tyrosines and truncation resulting in (1) loss of most STAT5 response to GH or (2) total inability to generate STAT5 to GH or (3) loss of Box1 to prevent activation of JAK2 but not LYN kinase or (4) total knockout of the receptor. For each mutant we analysed lifespan, histopathology to determine likely cause of death, and hepatic gene and protein expression. The extended lifespan is evident in the Box1 mutant males (retains Lyn activation) have median lifespan of 1016 days compared to 890 days for the Ghr-/- males. In the females, GhrBox1-/- mice have a median lifespan of 970 days compared to 911 days for the knockout females. Sexually dimorphic GHR-STAT5 is repressive for longevity, since its removal results in a median lifespan of 1003 days in females compared to 734 days for wild type females. Numerous transcripts related to insulin sensitivity, oxidative stress response and mitochondrial function are regulated by GHR-STAT5, however LYN responsive genes involve DNA repair, cell cycle control, and anti-inflammatory response. There appears to be a yin-yang relationship between JAK2 and LYN that determines lifespan.

The Sexual Dimorphism in Rectum and Protein Digestion Pathway Influence Sex Pheromone Synthesis in Male Bactrocera Dorsalis.

Sexual dimorphism is a crucial aspect of mating and reproduction in many animals, yet the molecular mechanisms remain unclear. In Bactrocera dorsalis, sex pheromones trimethylpyrazine (TMP) and tetramethylpyrazine (TTMP) are specifically synthesized by Bacillus strains in the male rectum. In the female rectum, Bacillus strains are found, but TMP and TTMP are not, indicating sexually dimorphic differences in sex pheromone synthesis. Our anatomical observations and precursor measurements revealed significant differences in rectal structure and ammonium levels between sexes.  In vitro and in vivo experiments reveal that ammonium is vital for sex pheromone synthesis in rectal Bacillus strains. Comparative transcriptome analysis identified ammonium-producing genes (carboxypeptidase B and peptide transporter) in the protein digestion pathway that show much higher expression in the male rectum than in the female rectum. Knocking down the expression of either carboxypeptidase B (or inhibiting enzyme activity) or peptide transporter decreases rectal ammonium levels significantly, resulting in the failure of sex pheromone synthesis in the male rectum. This study provides insights into the presence of sexual dimorphism in internal organs and their functionalities in male-specific sex pheromone synthesis and has significant implications for understanding the molecular mechanisms underlying sex pheromone synthesis by symbionts in insects.

The high-fat diet and low-dose streptozotocin type-2 diabetes model induces hyperinsulinemia and insulin resistance in male but not female C57BL/6J mice.

Translation of preclinical findings on the efficacy of dietary interventions for metabolic disease to human clinical studies is challenging due to the predominant use of male rodents in animal research. Our objective was to evaluate a combined high-fat (HF) diet and low-dose streptozotocin (STZ) model for induction of type-2 diabetes (T2D) in male and female C57BL/6J mice. We hypothesized that T2D biomarkers would differ significantly between sexes. Mice were administered either a low-fat (LF) diet (10% kcal from fat), or HF diet (60% kcal from fat) + STZ injections (30 mg/kg/d for 3 days). Both sexes gained weight and developed impaired postprandial oral glucose tolerance on the HF+STZ treatment compared to LF. Only male mice on HF + STZ developed fasting hyperglycemia, fasting hyperinsulinemia and insulin resistance, suggesting that the underlying causes of postprandial hyperglycemia differed between sexes. Principal component analysis of measures such as body weights, glucose and insulin concentrations indicated metabolic derangement for males only on HF+STZ treatment, while LF group males and both groups of females significantly overlapped. Based on our data, we accept our hypothesis that the combined high-fat diet and low-dose STZ model for T2D phenotypes differs significantly in its effect on mice based on sex. The HF diet + low-dose STZ model is not useful for studying insulin resistance in females. Other models are needed to model T2D, and study the effects of dietary interventions in this disease, in females. Sexual dimorphism remains a significant challenge for both preclinical and clinical research.

Sex-dependent effects of acute stress and alcohol exposure during adolescence on mRNA expression of brain signaling systems involved in reward and stress responses in young adult rats.

BACKGROUND: Adolescent stress and alcohol exposure increase the risk of maladaptive behaviors and mental disorders in adulthood, with distinct sex-specific differences. Understanding the mechanisms underlying these early events is crucial for developing targeted prevention and treatment strategies. METHODS: Male and female Wistar rats were exposed to acute restraint stress and intermittent alcohol during adolescence. We assessed lasting effects on plasma corticosterone (CORT) and adrenocorticotropic hormone (ACTH) levels, and mRNA expression of genes related to corticotropin releasing hormone (CRH), neuropeptide Y (NPY), corticoid, opioid, and arginine vasopressin systems in the amygdala and hypothalamus. RESULTS: The main findings are as follows: (1) blood alcohol concentrations (BAC) increased after the final alcohol administration, but stressed males had lower BAC than non-stressed males; (2) Males gained significantly more weight than females; (3) Stressed females showed higher ACTH levels than non-stressed females, with no changes in males; (4) Stress increased CORT levels in males, while stressed, alcohol-treated females had lower CORT levels than non-stressed females; (5) CRH: Females had lower Crhr1 levels in the amygdala, while alcohol reduced Crhr2 levels in males but not females. Significant interactions among sex, stress, and alcohol were found in the hypothalamus, with distinct patterns between sexes; (6) NPY: In the amygdala, stress reduced Npy and Npy1r levels in males but increased them in females. Alcohol decreased Npy2r levels in males, with varied effects in females. Similar sex-specific patterns were observed in the hypothalamus; (7) Corticoid system: Stress and alcohol had complex, sex-dependent effects on Pomc, Nr3c1, and Nr3c2 in both brain regions; (8) Opioid receptors: Stress and alcohol blunted the elevated expression of Oprm1, Oprd1, and Oprk1 in the amygdala of males and the hypothalamus of females; (8) Vasopressin: Stress and alcohol interacted significantly to affect Avp and Avpr1a expression in the amygdala, with stronger effects in females. In the hypothalamus, alcohol increased Avp levels in females. CONCLUSIONS: This study demonstrates that adolescent acute stress and alcohol exposure induce lasting, sex-specific alterations in systems involved in reward and stress responses. These findings emphasize the importance of considering sex differences in the prevention and management of HPA dysfunction and psychiatric disorders.

Mitochondrial antioxidant SkQ1 attenuates C26 cancer-induced muscle wasting in males and improves muscle contractility in female tumor-bearing mice.

Mitochondrial dysfunction is a hallmark of cancer cachexia (CC). Mitochondrial reactive oxygen species (ROS) are elevated in muscle shortly after tumor onset. Targeting mitochondrial ROS may be a viable option to prevent CC. The aim of this study was to evaluate the efficacy of a mitochondria-targeted antioxidant, SkQ1, to mitigate CC in both biological sexes. Male and female Balb/c mice were injected bilaterally with colon 26 adenocarcinoma (C26) cells (total 1x106 cells) or PBS (equal volume control). SkQ1 was dissolved in drinking water (~250 nmol/kg body weight/day) and administered to mice beginning seven days following tumor induction, while control groups consumed normal drinking water. In vivo muscle contractility of dorsiflexors, deuterium oxide-based protein synthesis, mitochondrial respiration and mRNA content of mitochondrial, protein turnover and calcium channel-related markers were assessed at endpoint (25 days following tumor induction). Two-way ANOVAs, followed by Tukey's post-hoc test when interactions were significant (p≤0.05), were performed. SkQ1 attenuated cancer-induced atrophy, promoted protein synthesis and abated Redd1 and Atrogin induction in gastrocnemius of C26 male mice. In female mice, SkQ1 decreased muscle mass and increased catabolic signaling in the plantaris of tumor-bearing mice, as well as reduced mitochondrial oxygen consumption, regardless of tumor. However, in females SkQ1 enhanced muscle contractility of the dorsiflexors with concurrent induction of Ryr1, Serca1 and Serca2a in TA. In conclusion, the mitochondria-targeted antioxidant SkQ1 may attenuate CC-induced muscle loss in males, while improving muscle contractile function in tumor-bearing female mice, suggesting sexual dimorphism in the effects of this mitochondrial therapy in CC.

Latitudinal gradients and sex differences in morphology of the Black Oystercatcher (Haematopus bachmani).

Environment and behavior are widely understood to affect bird morphology, which can lead to differences among subspecies or populations within a wide-ranging species. Several patterns of latitudinal gradients in morphology have been described, though Allen's and Bergmann's rules are the most well-known and have been tested and confirmed across a diversity of taxa and species. These state that individuals at higher latitudes will have larger bodies (Bergmann's Rule) but smaller extremities (Allen's Rule) to conserve heat in colder climates. Migratory behavior also can influence avian morphology, particularly wing shape, where migratory birds tend to have longer, more pointed wings than residents. The Black Oystercatcher (Haematopus bachmani) is a large, partially migratory shorebird species restricted to intertidal habitats and distributed from Alaska to Baja California, spanning about 35° of latitude. A large proportion of Black Oystercatchers that breed in Alaska are migratory, where nearly all individuals breeding in British Columbia through the southern end of their range remain resident through the annual cycle. Their broad latitudinal range and diversity in migratory behavior may drive geographic variation in morphology. Here we evaluate three explanations for geographic variation in morphology of the Black Oystercatcher using data from seven sites across two regions: Alaska and British Columbia. We found evidence consistent with Allen's but not Bergmann's rule; birds in Alaska have shorter bills than those in British Columbia, and these findings held when controlling for body size using wing length. Despite regional differences in migratory behavior, we detected no difference in the wing shape of birds in Alaska and British Columbia. Differences between sexes and among sites suggest that multiple factors drive patterns of morphological variation in the Black Oystercatcher.

Sensory cues of predation risk generate sex-specific changes in neural activity and behavior, but not hormones, in Trinidadian guppies.

How an organism responds to risk depends on how that individual perceives such risk. Integrating cues from multiple sensory modalities allows individuals to extract information from their environment, and whether and how the brain and body respond differently to different sensory cues can help reveal mechanistic decision-making processes. Here, we assessed neural, hormonal, and behavioral responses to different sensory cues of predation risk in Trinidadian guppies (Poecilia reticulata). Adult guppies were assigned to one of four treatment groups: control, visual, olfactory, and both sensory cues combined from a natural predator, the pike cichlid (Crenicichla alta), for 2 h. We found no difference in glucocorticoid response to any cue. However, we found behavioral and neural activation responses to olfactory-only cues. In addition, we found a sex by treatment effect, where males showed greater changes in neural activation in brain regions associated with avoidance behavior, while females showed greater changes in neural activation in regions associated with social behavior and memory, mirroring sex by treatment differences in behavioral antipredator responses. Altogether, our results demonstrate that single and combinatory cues may influence risk-taking behavior differently based on sex, suggesting that perception and integration of cues can cascade into sex differences in behavior.

Sexual Dimorphism in the Musculoskeletal System: Sex Hormones and Beyond.

Mounting evidence indicates that whereas some fundamental aspects of bone cell differentiation and function are similar in females and males, there is a clear contribution of sex/gender on the effects of signaling molecules on bone mass and strength and, consequently, on the effects of pharmacologic approaches to treat skeletal disorders. However, until recently, most studies were designed and performed using only 1 sex, resulting in a scarcity of published information on sexual dimorphism of the musculoskeletal system, including the mandible/masticatory muscles and the axial and appendicular bones and skeletal muscles. Further, it is now recognized that scientific rigor requires the study of both males and females. Therefore, there is an increasing need to understand the molecular and cellular basis for the differential outcomes of genetic manipulations and therapeutic agent administration depending on the sex of the experimental animals. Studies have shown higher muscle mass, cancellous bone mass, and long bone width in males compared with females as well as different traits in the pelvis and the skull, which are usually used for gender identification in forensic anthropology. Yet, most reports focus on the role of sex hormones, in particular, the consequences of estrogen deficiency with menopause in humans and in ovariectomized animal models. In addition, emerging data is starting to unveil the effects of gender-affirming hormonal therapy on the musculoskeletal system. We summarize here the current knowledge on the sex/gender-dependent phenotypic characteristics of the bone and skeletal muscles in humans and rodents, highlighting studies in which side by side comparisons were made.

Sex-dimorphic functions of orexin in neuropsychiatric disorders.

The orexin system regulates a variety of physiological functions, including the sleep-wake cycle, addiction, foraging behavior, stress and cognitive functioning. Orexin levels in central and peripheral are related to the pathogenesis of many diseases, most notably the narcolepsy, eating disorders, stress-related psychiatric disorders, and neurodegenerative diseases. Recently, it has been reported that the orexin system is distinctly sexually dimorphic, and is strongly associated with neuropsychiatric disorders. In this review, we analyzed advancements in the sex differences in the orexin system and their connection to psychoneurological conditions. Considering the scarcity of research in this domain, more research is imperative to reveal the underlying mechanisms.

Sex-specific effects of PNPLA3 I148M.

Metabolic dysfunction-associated steatotic liver disease (MASLD, previously termed NAFLD, nonalcoholic fatty liver disease) is a complex multifactorial disease showing generally higher prevalence and severity in men than in women. With respect to women, men are also more prone to develop metabolic dysfunction-associated steatohepatitis, fibrosis and liver-related complications. Several genetic, hormonal, environmental and lifestyle factors may contribute to sex differences in MASLD development, progression and outcomes. However, after menopause, the sex-specific prevalence of MASLD shows an opposite trend between men and women, pointing to the relevance of oestrogen signalling in the sexual dimorphism of MASLD. The patatin-like phospholipase domain-containing protein 3 (PNPLA3) gene, that encodes a triacylglycerol lipase that plays a crucial role in lipid metabolism, has emerged as a key player in the pathogenesis of MASLD, with the I148M variant being strongly associated with increased liver fat content and disease severity. Recent advances indicate that carrying the PNPLA3 I148M variant can be a risk factor for MASLD especially for women. To elucidate the molecular mechanisms underlying the sex-specific role of PNPLA3 I148M in the development of MASLD, several in vitro, ex vivo and in vivo models have been developed.

Autoimmune Hashimoto's Disease and Feminization Level-Testing the Immunocompetence Hypothesis.

Morphological femininity depends mainly on estrogen levels at puberty and is perceived as a cue of a woman's biological condition. Due to the immunostimulant properties of estradiol, estradiol-dependent feminine traits are expected to be positively related to immunity. However, heightened immunity in women may increase the risk of autoimmune disease, thus the relationship between femininity and immune quality may be complex. This study aimed to assess the relationship between morphological femininity and both the occurrence and severity of Hashimoto thyroiditis (HT) in women of reproductive age. Moreover, 95 women with HT and 84 without HT (all between 20 and 37 years) participated in the study. Morphological femininity was assessed based on somatic measurements of sexually dimorphic traits (2D:4D ratio, WHR, breast size, facial sexual dimorphism). The occurrence and severity of HT were assessed by serum TPOAb levels. The results showed that only the 2D:4D ratio of the right hand was higher in the HT group, indicating higher femininity in these women. However, there was also a positive relationship between facial femininity and TPOAb level in women with HT, indicating a higher severity of the disease. The results suggest that prenatal and pubertal exposure to estrogens may increase the probability or severity of autoimmune diseases in adulthood, but the relationship is tentative.

Assessment of age-dependent sexual dimorphism in paediatric vertebral size and density using a statistical shape and statistical appearance modelling approach.

This work focuses on the growth patterns of the human fourth lumbar vertebra (L4) in a paediatric population, with specific attention to sexual dimorphism. The study aims to understand morphological and density changes in the vertebrae through age-dependent statistical shape and statistical appearance models, which can describe full three-dimensional anatomy. Results show that the main growth patterns are associated with isotropic volumetric vertebral growth, a decrease in the relative size of the vertebral foramen, and an increase in the length of the transverse processes. Moreover, significant sexual dimorphism was demonstrated during puberty. We observe significant age and sex interaction in the anterior vertebral body height (P = 0.005), where females exhibited an earlier increase in rates of vertebral height evolution. Moreover, we also observe an increase in cross-sectional area (CSA) with age (P = 0.020), where the CSA is smaller in females than in males (significant sex effect P = 0.042). Finally, although no significant increase in trabecular bone density with age is observed (P = 0.363), a trend in the statistical appearance model suggests an increase in density with age.

Age, Sex, and Training Specific Effects on Cross-Education Training.

An extensive number of publications have examined cross-education effects with adults, primarily investigating contralateral homologous (same) muscles. There are far fewer investigations on cross-education effects on contralateral heterologous (different) muscles and age (youth vs adult) and no studies investigating sex differences. Hence, the objective was to compare cross-education in female and male youth and young adults to contralateral homologous (chest press [CP], elbow flexors and extensors, handgrip isometric strength, and shot put) and heterologous (leg press, knee extension isometric strength, and countermovement jump) muscles. Twenty-eight female adults, 28 female youth, 28 male adults, and 28 male youth (total: 112) were examined before and after an 8-week (3 sessions/wk) unilateral, dominant arm, CP training program. Unilateral testing assessed dominant and nondominant leg press and CP 1-repetition maximum, knee extensors, elbow extensors, elbow flexors, and handgrip maximum voluntary isometric contraction (MVIC) strength, as well as shot put distance and countermovement jump height. Unilateral CP training induced training specific (CP 1-repetition maximum) and nonspecific (elbow extensors, elbow flexors, handgrip MVIC force, and shot put distance) improvements (P < .04, η2: .45-.85) but no significant lower body improvements. There was evidence for testing limb specificity as the dominant arm provided significantly (P < .021, η2: .17-.75) greater training gains than the nondominant arm. Youth's training adaptations exceeded with unilateral CP 1-repetition maximum, elbow extensors MVIC force, and shot put distance (P < .049, η2: .14-.49). No sex main effect differences were apparent. In conclusion, cross-education was training specific (greatest gains with upper body and dominant limbs) with greater benefits for youth and generally no sex differences with the exception of elbow extensors MVIC.

Associations of Facial Shape With Physical Strength and 2D:4D in a Turkish Male and Female Sample.

OBJECTIVE: Human sexual dimorphism in physical strength manifests itself in men having a greater muscle mass than women, reflecting ancestral roles in competition, protection, and provisioning. Prenatal testosterone exposure, approximated via the second-to-fourth digit ratio (2D:4D), is linked to increased muscular strength in both sexes, indicating a developmental influence. Previous research has shown that both physical strength and 2D:4D have facial shape correlates, especially in men, but most studies have focused on Western populations and one trait. We therefore hypothesized a broader relationship between facial shape and both physical strength and 2D:4D. MATERIALS AND METHODS: In this study, we quantified the association between facial shape, handgrip strength (HGS), and 2D:4D in a non-Western Turkish sample (72 men, 55 women; Md = 22 y, SIR = 1.8 y) using two dimensional geometric morphometrics. Thirty-eight somatometric and 32 semi-landmarks were digitized on facial photographs taken in frontal view. Physical strength was assessed via handgrip strength (HGS), and the second digit length was divided by the fourth digit length to calculate 2D:4D. RESULTS: Both HGS and 2D:4D were significantly associated with shape in both sexes, but only in men did they explain a significant amount of facial variation. Thin-plates spline deformation grids and geometric morphometric morphs visualized the facial shape changes related to variations in handgrip strength, 2D:4D, and sexual dimorphism, enabling trait comparisons. CONCLUSION: This study contributes a comparative sample from the Middle East, which is indispensable to discern universalities from Western peculiarities. It provides evidence to better understand the biological basis of facial traits, which can potentially serve as increasingly relevant social cues in today's online and digital environments.