Growth hormone regulation of sex-dependent liver gene expression

Hypogonadism and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), recently proposed to be renamed to metabolic dysfunction-associated steatotic liver disease (MASLD), is a major global public health concern, affecting approximately 25-30% of the adult population and possibly leading to cirrhosis, hepatocellular carcinoma, and liver transplantation. The liver is involved in the actions of sex steroids via their hepatic metabolism and production of the sex hormone-binding globulin (SHBG). Liver disease, including NAFLD, is associated with reproductive dysfunction in men and women, and the prevalence of NAFLD in patients with hypogonadism is considerable. A wide spectrum of possible pathophysiological mechanisms linking NAFLD and male/female hypogonadism has been investigated. As therapies targeting NAFLD may impact hypogonadism in men and women, and vice versa, treatments of the latter may affect NAFLD, and an insight into their pathophysiological pathways is imperative. This paper aims to elucidate the complex association between NAFLD and hypogonadism in men and women and discuss the therapeutic options and their impact on both conditions.

Combined transcriptomics and proteomics unveil the impact of vitamin C in modulating specific protein abundance in the mouse liver

BACKGROUND

Vitamin C (ascorbate) is a water-soluble antioxidant and an important cofactor for various biosynthetic and regulatory enzymes. Mice can synthesize vitamin C thanks to the key enzyme gulonolactone oxidase (Gulo) unlike humans. In the current investigation, we used Gulo-/- mice, which cannot synthesize their own ascorbate to determine the impact of this vitamin on both the transcriptomics and proteomics profiles in the whole liver. The study included Gulo-/- mouse groups treated with either sub-optimal or optimal ascorbate concentrations in drinking water. Liver tissues of females and males were collected at the age of four months and divided for transcriptomics and proteomics analysis. Immunoblotting, quantitative RT-PCR, and polysome profiling experiments were also conducted to complement our combined omics studies.

RESULTS

Principal component analyses revealed distinctive differences in the mRNA and protein profiles as a function of sex between all the mouse cohorts. Despite such sexual dimorphism, Spearman analyses of transcriptomics data from females and males revealed correlations of hepatic ascorbate levels with transcripts encoding a wide array of biological processes involved in glucose and lipid metabolisms as well as in the acute-phase immune response. Moreover, integration of the proteomics data showed that ascorbate modulates the abundance of various enzymes involved in lipid, xenobiotic, organic acid, acetyl-CoA, and steroid metabolism mainly at the transcriptional level, especially in females. However, several proteins of the mitochondrial complex III significantly correlated with ascorbate concentrations in both males and females unlike their corresponding transcripts. Finally, poly(ribo)some profiling did not reveal significant enrichment difference for these mitochondrial complex III mRNAs between Gulo-/- mice treated with sub-optimal and optimal ascorbate levels.

CONCLUSIONS

Thus, the abundance of several subunits of the mitochondrial complex III are regulated by ascorbate at the post-transcriptional levels. Our extensive omics analyses provide a novel resource of altered gene expression patterns at the transcriptional and post-transcriptional levels under ascorbate deficiency.

Tmem263 deletion disrupts the GH/IGF-1 axis and causes dwarfism and impairs skeletal acquisition

Genome-wide association studies (GWAS) have identified a large number of candidate genes believed to affect longitudinal bone growth and bone mass. One of these candidate genes, TMEM263, encodes a poorly characterized plasma membrane protein. Single nucleotide polymorphisms in TMEM263 are associated with bone mineral density in humans and mutations are associated with dwarfism in chicken and severe skeletal dysplasia in at least one human fetus. Whether this genotype-phenotype relationship is causal, however, remains unclear. Here, we determine whether and how TMEM263 is required for postnatal growth. Deletion of the Tmem263 gene in mice causes severe postnatal growth failure, proportional dwarfism, and impaired skeletal acquisition. Mice lacking Tmem263 show no differences in body weight within the first 2 weeks of postnatal life. However, by P21 there is a dramatic growth deficit due to a disrupted growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis, which is critical for longitudinal bone growth. Tmem263-null mice have low circulating IGF-1 levels and pronounced reductions in bone mass and growth plate length. The low serum IGF-1 in Tmem263-null mice is associated with reduced hepatic GH receptor (GHR) expression and GH-induced JAK2/STAT5 signaling. A deficit in GH signaling dramatically alters GH-regulated genes and feminizes the liver transcriptome of Tmem263-null male mice, with their expression profile resembling wild-type female, hypophysectomized male, and Stat5b-null male mice. Collectively, our data validates the causal role for Tmem263 in regulating postnatal growth and raises the possibility that rare mutations or variants of TMEM263 may potentially cause GH insensitivity and impair linear growth.

Modifications of the GH Axis Reveal Unique Sexually Dimorphic Liver Signatures for Lcn13, Asns, Hamp2, Hao2, and Pgc1a

Growth hormone (GH) modifies liver gene transcription in a sexually dimorphic manner to meet liver metabolic demands related to sex; thus, GH dysregulation leads to sex-biased hepatic disease. We dissected the steps of the GH regulatory cascade modifying GH-dependent genes involved in metabolism, focusing on the male-predominant genes Lcn13, Asns, and Cyp7b1, and the female-predominant genes Hao2, Pgc1a, Hamp2, Cyp2a4, and Cyp2b9. We explored mRNA expression in 2 settings: (i) intact liver GH receptor (GHR) but altered GH and insulin-like growth factor 1 (IGF1) levels (NeuroDrd2KO, HiGH, aHepIGF1kd, and STAT5bCA mouse lines); and (ii) liver loss of GHR, with or without STAT5b reconstitution (aHepGHRkd, and aHepGHRkd + STAT5bCA). Lcn13 was downregulated in males in most models, while Asns and Cyp7b1 were decreased in males by low GH levels or action, or constant GH levels, but unexpectedly upregulated in both sexes by the loss of liver Igf1 or constitutive Stat5b expression. Hao, Cyp2a4, and Cyp2b9 were generally decreased in female mice with low GH levels or action (NeuroDrd2KO and/or aHepGHRkd mice) and increased in HiGH females, while in contrast, Pgc1a was increased in female NeuroDrd2KO but decreased in STAT5bCA and aHepIGF1kd females. Bioinformatic analysis of RNAseq from aHepGHRkd livers stressed the greater impact of GHR loss on wide gene expression in males and highlighted that GH modifies almost completely different gene signatures in each sex. Concordantly, we show that altering different steps of the GH cascade in the liver modified liver expression of Lcn13, Asns, Cyp7b1, Hao2, Hamp2, Pgc1a, Cyp2a4, and Cyp2b9 in a sex- and gene-specific manner.

Food deprivation reduces sensitivity of liver Igf1 synthesis pathways to growth hormone in juvenile gopher rockfish (Sebastes carnatus)

Growth hormone (Gh) regulates growth in part by stimulating the liver to synthesize and release insulin-like growth factor-1 (Igf1), which then promotes somatic growth. However, for fish experiencing food limitation, elevated blood Gh can occur even with low circulating Igf1 and slow growth, suggesting that nutritional stress can alter the sensitivity of liver Igf1 synthesis pathways to Gh. Here, we examined how recent feeding experience affected Gh regulation of liver Igf1 synthesis pathways in juvenile gopher rockfish (Sebastes carnatus) to illuminate mechanisms underlying the nutritional modulation of Igf1 production. Juvenile gopher rockfish were maintained under conditions of feeding or complete food deprivation (fasting) for 14 d and then treated with recombinant sea bream (Sparus aurata) Gh or saline control. Gh upregulated hepatic igf1 mRNA levels in fed fish but not in fasted fish. The liver of fasted rockfish also showed a lower relative abundance of gene transcripts encoding teleost Gh receptors 1 (ghr1) and 2 (ghr2), as well as reduced protein levels of phosphorylated janus tyrosine kinase 2 (pJak2) and signal transducer and activator of transcription 5 (pStat5), which function to induce igf1 gene transcription following Gh binding to Gh receptors. Relative hepatic mRNA levels for suppressors of cytokine signaling (Socs) genes socs2, socs3a, and socs3b were also lower in fasted rockfish. Socs2 can suppress Gh activation of Jak2/Stat5, and fasting-related variation in socs expression may reflect modulated inhibitory control of igf1 gene transcription. Fasted rockfish also had elevated liver mRNA abundances for lipolytic hormone-sensitive lipase 1 (hsl1) and Igf binding proteins igfbp1a, -1b and -3a, reduced liver mRNAs encoding igfbp2b and an Igfbp acid labile subunit-like (igfals) gene, and higher transcript abundances for Igf1 receptors igf1ra and igf1rb in skeletal muscle. Together, these findings suggest that food deprivation impacts liver Igf1 responsiveness to Gh via multiple mechanisms that include a downregulation of hepatic Gh receptors, modulation of the intracellular Jak2/Stat5 transduction pathway, and possible shifts in Socs-inhibitory control of igf1 gene transcription, while also demonstrating that these changes occur in concert with shifts in liver Igfbp expression and muscle Gh/Igf1 signaling pathway components.

Chemical Catalysis Guides Structural Identification for the Major In Vivo Metabolite of the BET Inhibitor JQ1

The bromodomain inhibitor (+)-JQ1 is a highly validated chemical probe; however, it exhibits poor in vivo pharmacokinetics. To guide efforts toward improving its pharmacological properties, we identified the (+)-JQ1 primary metabolite using chemical catalysis methods. Treatment of (+)-JQ1 with tetrabutylammonium decatungstate under photochemical conditions resulted in selective formation of an aldehyde at the 2-position of the thiophene ring [(+)-JQ1-CHO], which was further reduced to the 2-hydroxymethyl analog [(+)-JQ1-OH]. Comparative LC/MS analysis of (+)-JQ1-OH to the product obtained from liver microsomes suggested (+)-JQ1-OH as the major metabolite of (+)-JQ1. The 2-thienyl position was then substituted to generate a trideuterated (-CD3, (+)-JQ1-D) analog having half-lives that were 1.8- and 2.8-fold longer in mouse and human liver microsomes, respectively. This result unambiguously confirmed (+)-JQ1-OH as the major metabolite of (+)-JQ1. These studies demonstrate an efficient process for studying drug metabolism and identifying the metabolic soft spots of bioactive compounds.

Maternal separation influences hepatic drug-metabolizing CYP450 gene expression without pathological changes in adult mice

OBJECTIVES

The principal motive of this study is to explore the influence maternal separation (MS) exhibits on the mRNA expression of major drug metabolizing-cyp450s in parallel with the assessment of pathological changes that can be induced by MS in the livers of experimental mice.

METHODS

Eighteen Balb/c mouse pups, comprising of both males and females, were separated from their mothers after birth. Following a six-week period during when the pups became adults, the mice were sacrificed and their livers were isolated for analysis of weight, pathohistological alterations, and the mRNA expression of drug metabolizing cyp450 genes: cyp1a1, cyp3a11, cyp2d9, and cyp2c29.

RESULTS

The study demonstrated that MS markedly downregulated (p<0.05) the mRNA expression of all tested drug-metabolizing cyp450s in livers of female and male mice. Furthermore, the mRNA levels of major drug-metabolizing cyp450s were notably lower (p<0.05) in livers of female MS mice as compared with male MS mice. It was found that values of the total body weight and liver weight of MS mice did not vary significantly (p>0.05) from those of the control groups. Additionally, histological examination revealed that the hepatic tissue of MS mice was normal, similar to that of the control mice.

CONCLUSIONS

In summary, MS downregulates the gene expression of major hepatic drug-metabolizing cyp450s without inducing pathological alterations in the livers of mice. These findings provide an explanation for the heterogeneity in pharmacokinetics and drug response of patients with early life stress.

Practical solutions for including sex as a biological variable (SABV) in preclinical neuropsychopharmacological research

Recently, many funding agencies have released guidelines on the importance of considering sex as a biological variable (SABV) as an experimental factor, aiming to address sex differences and avoid possible sex biases to enhance the reproducibility and translational relevance of preclinical research. In neuroscience and pharmacology, the female sex is often omitted from experimental designs, with researchers generalizing male-driven outcomes to both sexes, risking a biased or limited understanding of disease mechanisms and thus potentially ineffective therapeutics. Herein, we describe key methodological aspects that should be considered when sex is factored into in vitro and in vivo experiments and provide practical knowledge for researchers to incorporate SABV into preclinical research. Both age and sex significantly influence biological and behavioral processes due to critical changes at different timepoints of development for males and females and due to hormonal fluctuations across the rodent lifespan. We show that including both sexes does not require larger sample sizes, and even if sex is included as an independent variable in the study design, a moderate increase in sample size is sufficient. Moreover, the importance of tracking hormone levels in both sexes and the differentiation between sex differences and sex-related strategy in behaviors are explained. Finally, the lack of robust data on how biological sex influences the pharmacokinetic (PK), pharmacodynamic (PD), or toxicological effects of various preclinically administered drugs to animals due to the exclusion of female animals is discussed, and methodological strategies to enhance the rigor and translational relevance of preclinical research are proposed.

Plasma growth hormone pulses induce male-biased pulsatile chromatin opening and epigenetic regulation in adult mouse liver

Sex differences in plasma growth hormone (GH) profiles, pulsatile in males and persistent in females, regulate sex differences in hepatic STAT5 activation linked to sex differences in gene expression and liver disease susceptibility, but little is understood about the fundamental underlying, GH pattern-dependent regulatory mechanisms. Here, DNase-I hypersensitivity site (DHS) analysis of liver chromatin accessibility in a cohort of 18 individual male mice established that the endogenous male rhythm of plasma GH pulse-stimulated liver STAT5 activation induces dynamic, repeated cycles of chromatin opening and closing at several thousand liver DHS and comprises a novel mechanism conferring male bias to liver chromatin accessibility. Strikingly, a single physiological replacement dose of GH given to hypophysectomized male mice restored, within 30 min, liver STAT5 activity and chromatin accessibility at 83% of the dynamic, pituitary hormone-dependent male-biased DHS. Sex-dependent transcription factor binding patterns and chromatin state analysis identified key genomic and epigenetic features distinguishing this dynamic, STAT5-driven mechanism of male-biased chromatin opening from a second GH-dependent mechanism operative at static male-biased DHS, which are constitutively open in male liver. Dynamic but not static male-biased DHS adopt a bivalent-like epigenetic state in female liver, as do static female-biased DHS in male liver, albeit using distinct repressive histone marks in each sex, namely, H3K9me3 at male-biased DHS in female liver and H3K27me3 at female-biased DHS in male liver. Moreover, sex-biased H3K36me3 marks are uniquely enriched at static sex-biased DHS, which may serve to keep these sex-dependent hepatocyte enhancers free of H3K27me3 repressive marks and thus constitutively open. Pulsatile chromatin opening stimulated by endogenous, physiological hormone pulses is thus one of two distinct GH-determined mechanisms for establishing widespread sex differences in hepatic chromatin accessibility and epigenetic regulation, both closely linked to sex-biased gene transcription and the sexual dimorphism of liver function.

The effect of brain serotonin deficit (TPH2-KO) on the expression and activity of liver cytochrome P450 enzymes in aging male Dark Agouti rats

BACKGROUND

Liver cytochrome P450 (CYP) greatly contributes to the metabolism of endogenous substances and drugs. Recent studies have demonstrated that CYP expression in the liver is controlled by the central nervous system via hormonal pathways. In particular, the expression of hepatic CYPs is negatively regulated by the brain serotoninergic system. The present study aimed to investigate changes in the function of the main liver drug-metabolizing CYP enzymes as a result of serotonin depletion in the brain of aging rats, caused by knockout of brain tryptophan hydroxylase gene (TPH2-KO).

METHODS

The hepatic CYP mRNA (qRT-PCR), protein level (Western blotting) and activity (HPLC), and serum hormone levels (ELISA) were measured in Dark Agouti wild-type (WT) male rats (mature 3.5-month-old and senescent 21-month-old) and in TPH2-KO senescent animals.

RESULTS

The expression/activity of the studied CYPs decreased with age in the liver of wild-type rats. The deprivation of serotonin in the brain of aging males decreased the mRNA level of most of the studied CYPs (CYP1A/2A/2B/3A), and lowered the protein level of CYP2C11 and CYP3A. In contrast, the activities of CYP2C11, CYP3A and CYP2C6 were increased. The expression of cytochrome b5 decreased in aging rats, but increased in TPH2-deficient senescent animals. The serum concentration of growth hormone declined in the aged and further dropped down in TPH2-deficient senescent rats.

CONCLUSIONS

Rat liver cytochrome P450 functions deteriorate with age, which may impair drug metabolism. The TPH2 knockout, which deprives brain serotonin, affects cytochrome P450 expression and activity differently in mature and senescent male rats.

Hepatic Transcriptome Comparative In Silico Analysis Reveals Similar Pathways and Targets Altered by Legacy and Alternative Per- and Polyfluoroalkyl Substances in Mice

Per- and poly-fluoroalkyl substances (PFAS) are a large class of fluorinated carbon chains that include legacy PFAS, such as perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorohexane sulfonate (PFHxS). These compounds induce adverse health effects, including hepatotoxicity. Potential alternatives to the legacy PFAS (HFPO-DA (GenX), HFPO4, HFPO-TA, F-53B, 6:2 FTSA, and 6:2 FTCA), as well as a byproduct of PFAS manufacturing (Nafion BP2), are increasingly being found in the environment. The potential hazards of these new alternatives are less well known. To better understand the diversity of molecular targets of the PFAS, we performed a comparative toxicogenomics analysis of the gene expression changes in the livers of mice exposed to these PFAS, and compared these to five activators of PPARα, a common target of many PFAS. Using hierarchical clustering, pathway analysis, and predictive biomarkers, we found that most of the alternative PFAS modulate molecular targets that overlap with legacy PFAS. Only three of the 11 PFAS tested did not appreciably activate PPARα (Nafion BP2, 6:2 FTSA, and 6:2 FTCA). Predictive biomarkers showed that most PFAS (PFHxS, PFOA, PFOS, PFNA, HFPO-TA, F-53B, HFPO4, Nafion BP2) activated CAR. PFNA, PFHxS, PFOA, PFOS, HFPO4, HFPO-TA, F-53B, Nafion BP2, and 6:2 FTSA suppressed STAT5b, activated NRF2, and activated SREBP. There was no apparent relationship between the length of the carbon chain, type of head group, or number of ether linkages and the transcriptomic changes. This work highlights the similarities in molecular targets between the legacy and alternative PFAS.

Molecular Mechanisms of the Regulation of Liver Cytochrome P450 by Brain NMDA Receptors and via the Neuroendocrine Pathway-A Significance for New Psychotropic Therapies

Recent investigations have highlighted the potential utility of the selective antagonist of the NMDA receptor GluN2B subunit for addressing major depressive disorders. Our previous study showed that the systemic administration of the antagonist of the GluN2B subunit of the NMDA receptor, the compound CP-101,606, affected liver cytochrome P450 expression and activity. To discern between the central and peripheral mechanisms of enzyme regulation, our current study aimed to explore whether the intracerebral administration of CP-101,606 could impact cytochrome P450. The injection of CP-101,606 to brain lateral ventricles (6, 15, or 30 µg/brain) exerted dose-dependent effects on liver cytochrome P450 enzymes and hypothalamic or pituitary hormones. The lowest dose led to an increase in the activity, protein, and mRNA level of CYP2C11 compared to the control. The activities of CYP2A, CYP2B, CYP2C11, CYP2C6, CYP2D, and protein levels of CYP2B, CYP2C11 were enhanced compared to the highest dose. Moreover, CP-101,606 increased the CYP1A protein level coupled with elevated CYP1A1 and CYP1A2 mRNA levels, but not activity. The antagonist decreased the pituitary somatostatin level and increased the serum growth hormone concentration after the lowest dose, while independently decreasing the serum corticosterone concentration of the dose. The findings presented here unveil a novel physiological regulatory mechanism whereby the brain glutamatergic system, via the NMDA receptor, influences liver cytochrome P450. This regulatory process appears to involve the endocrine system. These results may have practical applications in predicting alterations in cytochrome P450 activity and endogenous metabolism, and potential metabolic drug-drug interactions elicited by drugs that cross the blood-brain barrier and affect NMDA receptors.

Corticosteroid-Binding Globulin (SERPINA6) Consolidates Sexual Dimorphism of Adult Rat Liver

Produced by the liver, corticosteroid-binding globulin (CBG) regulates the plasma distribution and actions of glucocorticoids. A sex difference in pituitary growth hormone secretion patterns established during puberty in rats results in increased hepatic CBG production and 2-fold higher plasma corticosterone levels in females. Glucocorticoids control hepatic development and metabolic activities, and we have therefore examined how disrupting the SerpinA6 gene encoding CBG influences plasma corticosterone dynamics, as well as liver gene expression in male and female rats before and after puberty. Comparisons of corticosterone plasma clearance and hepatic uptake in adult rats, with or without CBG, indicated that CBG limits corticosterone clearance by reducing its hepatic uptake. Hepatic transcriptomic profiling revealed minor sex differences (207 differentially expressed genes) and minimal effect of CBG deficiency in 30-day-old rats before puberty. While liver transcriptomes in 60-day-old males lacking CBG remained essentially unchanged, 2710 genes were differentially expressed in wild-type female vs male livers at this age. Importantly, ∼10% of these genes lost their sexually dimorphic expression in adult females lacking CBG, including those related to cholesterol biosynthesis, inflammation, and lipid and amino acid catabolism. Another 203 genes were altered by the loss of CBG specifically in adult females, including those related to xenobiotic metabolism, circadian rhythm, and gluconeogenesis. Our findings reveal that CBG consolidates the sexual dimorphism of the rat liver initiated by sex differences in growth hormone secretion patterns and provide insight into how CBG deficiencies are linked to glucocorticoid-dependent diseases.

Plasma Growth Hormone Pulses Induce Male-biased Pulsatile Chromatin Opening and Epigenetic Regulation in Adult Mouse Liver

Sex-differences in plasma growth hormone (GH) profiles, pulsatile in males and persistent in females, regulate sex differences in hepatic STAT5 activation linked to sex differences in gene expression and liver disease susceptibility, but little is understood about the fundamental underlying, GH pattern-dependent regulatory mechanisms. Here, DNase hypersensitivity site (DHS) analysis of liver chromatin accessibility in a cohort of 18 individual male mice established that the endogenous male rhythm of plasma GH pulse-stimulated liver STAT5 activation induces dynamic, repeated cycles of chromatin opening and closing at several thousand liver DHS and comprises a novel mechanism conferring male bias to liver chromatin accessibility. Strikingly, a single physiological replacement dose of GH given to hypophysectomized male mice restored, within 30 min, liver STAT5 activity and chromatin accessibility at 83% of the pituitary hormone-dependent dynamic male-biased DHS. Sex-dependent transcription factor binding patterns and chromatin state analysis identified key genomic and epigenetic features distinguishing this dynamic, STAT5-driven mechanism of male-biased chromatin opening from a second GH-dependent mechanism operative at static male-biased DHS, which are constitutively open in male liver. Dynamic but not static male-biased DHS adopt a bivalent-like epigenetic state in female liver, as do static female-biased DHS in male liver, albeit using distinct repressive histone marks in each sex, namely, H3K27me3 at female-biased DHS in male liver, and H3K9me3 at male-biased DHS in female liver. Moreover, sex-biased H3K36me3 marks are uniquely enriched at static sex-biased DHS, which may serve to keep these sex-dependent hepatocyte enhancers free of H3K27me3 repressive marks and thus constitutively open. Pulsatile chromatin opening stimulated by endogenous, physiological hormone pulses is thus one of two distinct GH-determined mechanisms for establishing widespread sex differences in hepatic chromatin accessibility and epigenetic regulation, both closely linked to sex-biased gene transcription and the sexual dimorphism of liver function.

Species differences in hormonally mediated gene expression underlie the evolutionary loss of sexually dimorphic coloration in Sceloporus lizards

Phenotypic sexual dimorphism often involves the hormonal regulation of sex-biased expression for underlying genes. However, it is generally unknown whether the evolution of hormonally mediated sexual dimorphism occurs through upstream changes in tissue sensitivity to hormone signals, downstream changes in responsiveness of target genes, or both. Here, we use comparative transcriptomics to explore these possibilities in 2 species of Sceloporus lizards exhibiting different patterns of sexual dichromatism. Sexually dimorphic S. undulatus develops blue and black ventral coloration in response to testosterone, while sexually monomorphic S. virgatus does not, despite exhibiting similar sex differences in circulating testosterone levels. We administered testosterone implants to juveniles of each species and used RNAseq to quantify gene expression in ventral skin. Transcriptome-wide responses to testosterone were stronger in S. undulatus than in S. virgatus, suggesting species differences in tissue sensitivity to this hormone signal. Species differences in the expression of genes for androgen metabolism and sex hormone-binding globulin were consistent with this idea, but expression of the androgen receptor gene was higher in S. virgatus, complicating this interpretation. Downstream of androgen signaling, we found clear species differences in hormonal responsiveness of genes related to melanin synthesis, which were upregulated by testosterone in S. undulatus, but not in S. virgatus. Collectively, our results indicate that hormonal regulation of melanin synthesis pathways contributes to the development of sexual dimorphism in S. undulatus, and that changes in the hormonal responsiveness of these genes in S. virgatus contribute to the evolutionary loss of ventral coloration.

Tmem263 deletion disrupts the GH/IGF-1 axis and causes dwarfism and impairs skeletal acquisition

Genome-wide association studies (GWAS) have identified a large number of candidate genes believed to affect longitudinal bone growth and bone mass. One of these candidate genes, TMEM263, encodes a poorly characterized plasma membrane protein. Single nucleotide polymorphisms in TMEM263 are associated with bone mineral density in humans and mutations are associated with dwarfism in chicken and severe skeletal dysplasia in at least one human fetus. Whether this genotype-phenotype relationship is causal, however, remains unclear. Here, we determine whether and how TMEM263 is required for postnatal growth. Deletion of the Tmem263 gene in mice causes severe postnatal growth failure, proportional dwarfism, and impaired skeletal acquisition. Mice lacking Tmem263 show no differences in body weight within the first two weeks of postnatal life. However, by P21 there is a dramatic growth deficit due to a disrupted GH/IGF-1 axis, which is critical for longitudinal bone growth. Tmem263-null mice have low circulating IGF-1 levels and pronounced reductions in bone mass and growth plate length. The low serum IGF-1 in Tmem263-null mice is associated with reduced hepatic GH receptor (GHR) expression and GH-induced JAK2/STAT5 signaling. A deficit in GH signaling dramatically alters GH-regulated genes and feminizes the liver transcriptome of Tmem263-null male mice, with their expression profile resembling a wild-type female, hypophysectomized male, and Stat5b-null male mice. Collectively, our data validates the causal role for Tmem263 in regulating postnatal growth and raises the possibility that rare mutations or variants of TMEM263 may potentially cause GH insensitivity and impair linear growth.

Direct androgen receptor control of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility, and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA sequencing (RNA-seq) data demonstrated that sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR)-mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation, whereas analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, disease, and metabolic linkage of sexually dimorphic gene activity.

Differences in Cholesterol Metabolism, Hepato-Intestinal Aging, and Hepatic Endocrine Milieu in Rats as Affected by the Sex and Age

Age and sex influence serum cholesterol levels, but the underlying mechanisms remain unclear. To investigate further, we measured cholesterol, precursors (surrogate synthesis markers), degradation products (oxysterols and bile acid precursors) in serum, the liver, jejunum, and ileum, as well as serum plant sterols (intestinal absorption markers) in male and female Wistar rats (4 and 24 months old). The analysis of histomorphometric and oxidative stress parameters (superoxide dismutase, catalase, glutathione-related enzyme activities, lipid peroxide, and protein carbonyl concentrations) in the liver and jejunum offered further insights into the age- and sex-related differences. The hepatic gene expression analysis included AR, ERα, and sex-specific growth hormone-regulated (Cyp2c11 and Cyp2c12) and thyroid-responsive (Dio1, Tbg, and Spot 14) genes by qPCR. We observed age-related changes in both sexes, with greater prominence in females. Aged females had significantly higher serum cholesterol (p < 0.05), jejunum cholesterol (p < 0.05), and serum plant sterols (p < 0.05). They exhibited poorer hepato-intestinal health compared with males, which was characterized by mild liver dysfunction (hydropic degeneration, increased serum ALT, p < 0.05, and decreased activity of some antioxidant defense enzymes, p < 0.05), mononuclear inflammation in the jejunal lamina propria, and age-related decreases in jejunal catalase and glutathione peroxidase activity (p < 0.05). Aged females showed increased levels of 27-hydroxycholesterol (p < 0.05) and upregulated ERα gene expression (p < 0.05) in the liver. Our study suggests that the more significant age-related increase in serum cholesterol in females is associated with poorer hepato-intestinal health and increased jejunal cholesterol absorption. The local increase in 27-hydroxycholesterol during aging might reduce the hepatoprotective effects of endogenous estrogen in the female liver.

Growth hormone and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a prevalent cause of liver disease and metabolic comorbidities. Obesity is strongly associated with NAFLD and is also a state of relative deficiency of growth hormone (GH). Evidence supports a role of reduced GH and insulin-like growth factor-1 (IGF-1) in NAFLD pathogenesis. Physiological actions of GH in the liver include suppression of de novo lipogenesis (DNL) and promotion of lipid beta-oxidation, and GH also appears to have anti-inflammatory actions. Physiologic actions of IGF-1 include suppression of inflammatory and fibrogenic pathways important in the evolution from steatosis to steatohepatitis and fibrosis. Rodent models of impaired hepatic GH signaling show the development of steatosis, sometimes accompanied by inflammation, hepatocellular damage, and fibrosis, and these changes are ameliorated by treatment with GH and/or IGF-1. In humans, individuals with GH deficiency and GH resistance demonstrate an increased prevalence of NAFLD compared to controls, with improvement in hepatic lipid, steatohepatitis, and fibrosis following GH replacement. As a corollary, individuals with GH excess demonstrate lower hepatic lipid compared to controls along with increased hepatic lipid following treatment to normalize GH levels. Clinical trials demonstrate that augmentation of GH reduces hepatic lipid content in individuals with NAFLD and may also ameliorate steatohepatitis and fibrosis. Taken together, evidence supports an important role for perturbations in the GH/IGF-1 axis as one of the pathogenic mechanisms of NAFLD and suggests that further study is needed to assess whether augmentation of GH and/or IGF-1 may be a safe and effective therapeutic strategy for NAFLD.

Direct and systemic actions of growth hormone receptor (GHR)-signaling on hepatic glycolysis, de novo lipogenesis and insulin sensitivity, associated with steatosis

BACKGROUND

Evidence is accumulating that growth hormone (GH) protects against the development of steatosis and progression of non-alcoholic fatty liver disease (NAFLD). GH may control steatosis indirectly by altering systemic insulin sensitivity and substrate delivery to the liver and/or by the direct actions of GH on hepatocyte function.

APPROACH

To better define the hepatocyte-specific role of GH receptor (GHR) signaling on regulating steatosis, we used a mouse model with adult-onset, hepatocyte-specific GHR knockdown (aHepGHRkd). To prevent the reduction in circulating insulin-like growth factor 1 (IGF1) and the subsequent increase in GH observed after aHepGHRkd, subsets of aHepGHRkd mice were treated with adeno-associated viral vectors (AAV) driving hepatocyte-specific expression of IGF1 or a constitutively active form of STAT5b (STAT5bCA). The impact of hepatocyte-specific modulation of GHR, IGF1 and STAT5b on carbohydrate and lipid metabolism was studied across multiple nutritional states and in the context of hyperinsulinemic:euglycemic clamps.

RESULTS

Chow-fed male aHepGHRkd mice developed steatosis associated with an increase in hepatic glucokinase (GCK) and ketohexokinase (KHK) expression and de novo lipogenesis (DNL) rate, in the post-absorptive state and in response to refeeding after an overnight fast. The aHepGHRkd-associated increase in hepatic KHK, but not GCK and steatosis, was dependent on hepatocyte expression of carbohydrate response element binding protein (ChREBP), in re-fed mice. Interestingly, under clamp conditions, aHepGHRkd also increased the rate of DNL and expression of GCK and KHK, but impaired insulin-mediated suppression of hepatic glucose production, without altering plasma NEFA levels. These effects were normalized with AAV-mediated hepatocyte expression of IGF1 or STAT5bCA. Comparison of the impact of AAV-mediated hepatocyte IGF1 versus STAT5bCA in aHepGHRkd mice across multiple nutritional states, indicated the restorative actions of IGF1 are indirect, by improving systemic insulin sensitivity, independent of changes in the liver transcriptome. In contrast, the actions of STAT5b are due to the combined effects of raising IGF1 and direct alterations in the hepatocyte gene program that may involve suppression of BCL6 and FOXO1 activity. However, the direct and IGF1-dependent actions of STAT5b cannot fully account for enhanced GCK activity and lipogenic gene expression observed after aHepGHRkd, suggesting other GHR-mediated signals are involved.

CONCLUSION

These studies demonstrate hepatocyte GHR-signaling controls hepatic glycolysis, DNL, steatosis and hepatic insulin sensitivity indirectly (via IGF1) and directly (via STAT5b). The relative contribution of these indirect and direct actions of GH on hepatocytes is modified by insulin and nutrient availability. These results improve our understanding of the physiologic actions of GH on regulating adult metabolism to protect against NAFLD progression.

Direct androgen receptor regulation of sexually dimorphic gene expression in the mammalian kidney

Mammalian organs exhibit distinct physiology, disease susceptibility and injury responses between the sexes. In the mouse kidney, sexually dimorphic gene activity maps predominantly to proximal tubule (PT) segments. Bulk RNA-seq data demonstrated sex differences were established from 4 and 8 weeks after birth under gonadal control. Hormone injection studies and genetic removal of androgen and estrogen receptors demonstrated androgen receptor (AR) mediated regulation of gene activity in PT cells as the regulatory mechanism. Interestingly, caloric restriction feminizes the male kidney. Single-nuclear multiomic analysis identified putative cis-regulatory regions and cooperating factors mediating PT responses to AR activity in the mouse kidney. In the human kidney, a limited set of genes showed conserved sex-linked regulation while analysis of the mouse liver underscored organ-specific differences in the regulation of sexually dimorphic gene expression. These findings raise interesting questions on the evolution, physiological significance, and disease and metabolic linkage, of sexually dimorphic gene activity.

Growth Hormone Accelerates Recovery From Acetaminophen-Induced Murine Liver Injury

Background and Aims

Acetaminophen (APAP) overdose is the leading cause of acute liver failure, with one available treatment, N-acetyl cysteine (NAC). Yet, NAC effectiveness diminishes about ten hours after APAP overdose, urging for therapeutic alternatives. This study addresses this need by deciphering a mechanism of sexual dimorphism in APAP-induced liver injury, and leveraging it to accelerate liver recovery via growth hormone (GH) treatment. GH secretory patterns, pulsatile in males and near-continuous in females, determine the sex bias in many liver metabolic functions. Here, we aim to establish GH as a novel therapy to treat APAP hepatotoxicity.

Approach and Results

Our results demonstrate sex-dependent APAP toxicity, with females showing reduced liver cell death and faster recovery than males. Single-cell RNA sequencing analyses reveal that female hepatocytes have significantly greater levels of GH receptor expression and GH pathway activation compared to males. In harnessing this female-specific advantage, we demonstrate that a single injection of recombinant human GH protein accelerates liver recovery, promotes survival in males following sub-lethal dose of APAP, and is superior to standard-of-care NAC. Alternatively, slow-release delivery of human GH via the safe nonintegrative lipid nanoparticle-encapsulated nucleoside-modified mRNA (mRNA-LNP), a technology validated by widely used COVID-19 vaccines, rescues males from APAP-induced death that otherwise occurred in control mRNA-LNP-treated mice.

Conclusions

Our study demonstrates a sexually dimorphic liver repair advantage in females following APAP overdose, leveraged by establishing GH as an alternative treatment, delivered either as recombinant protein or mRNA-LNP, to potentially prevent liver failure and liver transplant in APAP-overdosed patients.

Association Between Serum Trace Heavy Metals and Liver Function Among Adolescents

BACKGROUND

Exposure to metals has been associated with liver-related disease. Few studies have explored the effect of sex stratification on adolescent liver function.

METHOD

From the National Health and Nutrition Examination Survey (2011-2016), 1143 subjects aged 12-19 years were selected for analysis. The outcome variables were the levels of alanine aminotransferase (ALT), aspartate aminotransferase, and gamma-glutamyl transpeptidase.

RESULTS

The results showed a positive association between serum zinc and ALT in boys (odds ratio [OR], 2.37; 95% confidence interval [CI], 1.11-5.06). Serum mercury was associated with an increase in ALT level in girls (OR, 2.73; 95% CI, 1.14-6.57). Mechanistically, the efficacy mediated by total cholesterol accounted for 24.38% and 6.19% of the association between serum zinc and ALT.

CONCLUSIONS

The results imply that serum heavy metals were associated with the risk of liver injury, possibly mediated by serum cholesterol, in adolescents.

Paternal phthalate exposure-elicited offspring metabolic disorders are associated with altered sperm small RNAs in mice

Exposure to ubiquitous plastic-associated endocrine disrupting chemicals (EDCs) is associated with the increased risk of many chronic diseases. For example, phthalate exposure is associated with cardiometabolic mortality in humans, with societal costs ∼ $39 billion/year or more. We recently demonstrated that several widely used plastic-associated EDCs increase cardiometabolic disease in appropriate mouse models. In addition to affecting adult health, parental exposure to EDCs has also been shown to cause metabolic disorders, including obesity and diabetes, in the offspring. While most studies have focused on the impact of maternal EDC exposure on the offspring's health, little is known about the effects of paternal EDC exposure. In the current study, we investigated the adverse impact of paternal exposure to a ubiquitous but understudied phthalate, dicyclohexyl phthalate (DCHP) on the metabolic health of F1 and F2 offspring in mice. Paternal DCHP exposure led to exacerbated insulin resistance and impaired insulin signaling in F1 offspring without affecting diet-induced obesity. We previously showed that sperm small non-coding RNAs including tRNA-derived small RNAs (tsRNAs) and rRNA-derived small RNAs (rsRNAs) contribute to the intergenerational transmission of paternally acquired metabolic disorders. Using a novel PANDORA-seq, we revealed that DCHP exposure can lead to sperm tsRNA/rsRNA landscape changes that were undetected by traditional RNA-seq, which may contribute to DCHP-elicited adverse effects. Lastly, we found that paternal DCHP can also cause sex-specific transgenerational adverse effects in F2 offspring and elicited glucose intolerance in female F2 descendants. Our results suggest that exposure to endocrine disrupting phthalates may have intergenerational and transgenerational adverse effects on the metabolic health of their offspring. These findings increase our understanding of the etiology of chronic human diseases originating from chemical-elicited intergenerational and transgenerational effects.

Androgen-Dependent Expression of CUX2 mRNA in the Pig Liver Is Associated with That of Drug Metabolizing Enzymes and Drug Transporters

We previously identified androgen-dependent sex differences in the mRNA expression of drug metabolizing enzymes (DMEs), including CYPs, sulfotransferases and uridine 5'-diphospho-glucuronosyltransferases, and drug transporters in the pig liver and kidney. To elucidate the mechanism for such sex differences in pigs, we herein focused on the key regulators cut-like homeobox 2 (Cux2), B-cell lymphoma 6 (Bcl6), and signal transducer and activator of transcription 5b (Stat5b), which are reported to be responsible for the sex-biased gene expression of Cyps in the mouse liver. We used real-time RT-PCR to examine androgen-dependent sex differences in the mRNA levels of these regulators in the liver and kidney basically using Meishan and Landrace pigs. Significant sex differences (male > female) in the level of CUX2 mRNA were detected in the liver of both breeds, and levels were significantly decreased in males by castration and increased in castrated males and intact females by administering testosterone propionate. No such clear androgen-dependent sex differences in hepatic BCL6 or STAT5B mRNA expression were observed in either breed. In the kidney, androgen-dependent gene expression of these regulators was not observed. In the liver, CUX2 mRNA expression closely correlated with that of DMEs and drug transporters, which were previously shown to have androgen-dependent expression. Together, these findings demonstrate that hepatic CUX2 mRNA is expressed in an androgen-dependent manner, and strongly suggest that CUX2 plays a key role in the androgen-dependent gene expression of hepatic DMEs and drug transporters.

Drug-disease interaction: Clinical consequences of inflammation on drugs action and disposition

Inflammation is a culprit in many conditions affecting millions of people worldwide. A plethora of studies has revealed that inflammation and inflammatory mediators such as cytokines and chemokines are associated with altered expression and activity of various proteins such as those involved in drug metabolism, specifically cytochrome P450 enzymes (CYPs). Emphasis of most available reports is on the inflammation-induced downregulation of CYPs, subsequently an increase in their substrate concentrations, and the link between the condition and the inflammatory mediators such as interleukin-6 and tumor necrosis factor alpha. However, reports also suggest that inflammation influences expression and/or activity of other proteins such as those involved in the drug-receptor interaction. These multifaced involvements render the clinical consequence of the inflammation unexpected. Such changes are shown in many inflammatory conditions including rheumatoid arthritis, Crohn's disease, acute respiratory illnesses as well as natural processes such as aging, among others. For example, some commonly used cardiovascular drugs lose their efficacy when patients get afflicted with inflammatory conditions such as rheumatoid arthritis and Crohn's disease. Interestingly, this is despite increased concentration subsequent to reduced clearance. The observation is attributed to a simultaneous reduction in the expression of target receptor proteins such as the calcium and potassium channel and β-adrenergic receptor as well as the metabolic enzymes. This narrative review summarizes the current understanding and clinical implications of the inflammatory effects on both CYPs and drug-receptor target proteins.

Liver Injury and Cell Survival in Non-Alcoholic Steatohepatitis Regulated by Sex-Based Difference through B Cell Lymphoma 6

The liver is a crucial organ for maintaining homeostasis in living organisms and is the center of various metabolic functions. Therefore, abnormal metabolic activity, as in metabolic syndrome, leads to pathological conditions, such as abnormal accumulation of lipids in the liver. Inflammation and cell death are induced by several stresses in the fatty liver, namely steatohepatitis. In recent years, an increase in non-alcoholic steatohepatitis (NASH), which is not dependent on excessive alcohol intake, has become an issue as a major cause of liver cirrhosis and liver cancer. There are several recent findings on functional sex-based differences, NASH, and cell stress and death in the liver. In particular, NASH-induced liver injury and tumorigeneses were suppressed by B cell lymphoma 6, the transcriptional factor regulating sex-based liver functional gene expression. In this review, we discuss cell response to stress and lipotoxicity in NASH and its regulatory mechanisms.

Chromosomal and gonadal sex drive sex differences in lipids and hepatic gene expression in response to hypercholesterolemia and statin treatment

BACKGROUND

Biological sex impacts susceptibility and presentation of cardiovascular disease, which remains the leading cause of death for both sexes. To reduce cardiovascular disease risk, statin drugs are commonly prescribed to reduce circulating cholesterol levels through inhibition of cholesterol synthesis. The effectiveness of statin therapy differs between individuals with a sex bias in the frequency of adverse effects. Limited information is available regarding the mechanisms driving sex-specific responses to hypercholesterolemia or statin treatment.

METHODS

Four Core Genotypes mice (XX and XY mice with ovaries and XX and XY mice with testes) on a hypercholesteremic Apoe-/- background were fed a chow diet without or with simvastatin for 8 weeks. Plasma lipid levels were quantified and hepatic differential gene expression was evaluated with RNA-sequencing to identify the independent effects of gonadal and chromosomal sex.

RESULTS

In a hypercholesterolemic state, gonadal sex influenced the expression levels of more than 3000 genes, and chromosomal sex impacted expression of nearly 1400 genes, which were distributed across all autosomes as well as the sex chromosomes. Gonadal sex uniquely influenced the expression of ER stress response genes, whereas chromosomal and gonadal sex influenced fatty acid metabolism gene expression in hypercholesterolemic mice. Sex-specific effects on gene regulation in response to statin treatment included a compensatory upregulation of cholesterol biosynthetic gene expression in mice with XY chromosome complement, regardless of presence of ovaries or testes.

CONCLUSION

Gonadal and chromosomal sex have independent effects on the hepatic transcriptome to influence different cellular pathways in a hypercholesterolemic environment. Furthermore, chromosomal sex in particular impacted the cellular response to statin treatment. An improved understanding of how gonadal and chromosomal sex influence cellular response to disease conditions and in response to drug treatment is critical to optimize disease management for all individuals.

Determinants of gene expression in the human liver: Impact of aging and sex on xenobiotic metabolism

There is a need to characterize the potential susceptibility of older adults to toxicity from environmental chemical exposures. Liver xenobiotic metabolizing enzymes (XMEs) play important roles in detoxifying and eliminating xenobiotics. We examined global gene expression in the livers of young (21-45 years) and old (69+ years) men and women. Differentially expressed genes (DEG) were identified using two-way ANOVA (p ≤ 0.05). We identified 1437 and 1670 DEGs between young and old groups in men and women, respectively. Only a minor number of the total number of genes overlapped (146 genes). Aging increased or decreased pathways involved in inflammation and intermediary metabolism, respectively. Aging led to numerous changes in the expression of XME genes or genes known to control their expression (~90 genes). Out of 10 cytochrome P450s activities examined, there were increased activities of CYP1A2 and CYP2C9 enzymes in the old groups. We also identified sex-dependent genes that were more numerous in the young group (1065) than in the old group (202) and included changes in XMEs. These studies indicate that the livers from aging humans when compared to younger adults exhibit changes in XMEs that may lead to differences in the metabolism of xenobiotics.

Postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary gland

BACKGROUND

The pituitary gland regulates essential physiological processes such as growth, pubertal onset, stress response, metabolism, reproduction, and lactation. While sex biases in these functions and hormone production have been described, the underlying identity, temporal deployment, and cell-type specificity of sex-biased pituitary gene regulatory networks are not fully understood.

METHODS

To capture sex differences in pituitary gene regulation dynamics during postnatal development, we performed 3' untranslated region sequencing and small RNA sequencing to ascertain gene and microRNA expression, respectively, across five postnatal ages (postnatal days 12, 22, 27, 32, 37) that span the pubertal transition in female and male C57BL/6J mouse pituitaries (n = 5-6 biological replicates for each sex at each age).

RESULTS

We observed over 900 instances of sex-biased gene expression and 17 sex-biased microRNAs, with the majority of sex differences occurring with puberty. Using miRNA-gene target interaction databases, we identified 18 sex-biased genes that were putative targets of 5 sex-biased microRNAs. In addition, by combining our bulk RNA-seq with publicly available male and female mouse pituitary single-nuclei RNA-seq data, we obtained evidence that cell-type proportion sex differences exist prior to puberty and persist post-puberty for three major hormone-producing cell types: somatotropes, lactotropes, and gonadotropes. Finally, we identified sex-biased genes in these three pituitary cell types after accounting for cell-type proportion differences between sexes.

CONCLUSION

Our study reveals the identity and postnatal developmental trajectory of sex-biased gene expression in the mouse pituitary. This work also highlights the importance of considering sex biases in cell-type composition when understanding sex differences in the processes regulated by the pituitary gland.

The impact of noradrenergic neurotoxin DSP-4 and noradrenaline transporter knockout (NET-KO) on the activity of liver cytochrome P450 3A (CYP3A) in male and female mice

Background

Our earlier studies have shown that the brain noradrenergic system regulates cytochrome P450 (CYP) in rat liver via neuroendocrine mechanism. In the present work, a comparative study on the effect of intraperitoneal administration of the noradrenergic neurotoxin DSP-4 and the knockout of noradrenaline transporter (NET-KO) on the CYP3A in the liver of male and female mice was performed.

Methods

The experiments were conducted on C57BL/6J WT and NET^–/– male/female mice. DSP-4 was injected intraperitoneally as a single dose (50 mg/kg ip.) to WT mice. The activity of CYP3A was measured as the rate of 6β-hydroxylation of testosterone in liver microsomes. The CYP3A protein level was estimated by Western blotting.

Results

DSP-4 evoked a selective decrease in the noradrenaline level in the brain of male and female mice. At the same time, DSP-4 reduced the CYP3A activity in males, but not in females. The level of CYP3A protein was not changed. The NET knockout did not affect the CYP3A activity/protein in both sexes.

Conclusions

The results with DSP-4 treated mice showed sex-dependent differences in the regulation of liver CYP3A by the brain noradrenergic system (with only males being responsive), and revealed that the NET knockout did not affect CYP3A in both sexes. Further studies into the hypothalamic–pituitary–gonadal hormones in DSP-4 treated mice may explain sex-specific differences in CYP3A regulation, whereas investigation of monoaminergic receptor sensitivity in the hypothalamic/pituitary areas of NET^–/– mice will allow for understanding a lack of changes in the CYP3A activity in the NET-KO animals.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43440-022-00406-8.

Butyrate Treatment of DSS-Induced Ulcerative Colitis Affects the Hepatic Drug Metabolism in Mice

The development of inflammatory bowel disease (IBD) is associated with alterations in the gut microbiota. There is currently no universal treatment for this disease, thus emphasizing the importance of developing innovative therapeutic approaches. Gut microbiome-derived metabolite butyrate with its well-known anti-inflammatory effect in the gut is a promising candidate. Due to increased intestinal permeability during IBD, butyrate may also reach the liver and influence liver physiology, including hepatic drug metabolism. To get an insight into this reason, the aim of this study was set to clarify not only the protective effects of the sodium butyrate (SB) administration on colonic inflammation but also the effects of SB on hepatic drug metabolism in experimental colitis induced by dextran sodium sulfate (DSS) in mice. It has been shown here that the butyrate pre-treatment can alleviate gut inflammation and reduce the leakiness of colonic epithelium by restoration of the assembly of tight-junction protein Zonula occludens-1 (ZO-1) in mice with DSS-induced colitis. In this article, butyrate along with inflammation has also been shown to affect the expression and enzyme activity of selected cytochromes P450 (CYPs) in the liver of mice. In this respect, CYP3A enzymes may be very sensitive to gut microbiome-targeted interventions, as significant changes in CYP3A expression and activity in response to DSS-induced colitis and/or butyrate treatment have also been observed. With regard to medications used in IBD and microbiota-targeted therapeutic approaches, it is important to deepen our knowledge of the effect of gut inflammation, and therapeutic interventions were followed concerning the ability of the organism to metabolize drugs. This gut–liver axis, mediated through inflammation as well as microbiome-derived metabolites, may affect the response to IBD therapy.

"The ubiquitin ligase SIAH2 is a female-specific regulator of circadian rhythms and metabolism"

Circadian clocks enable organisms to predict and align their behaviors and physiologies to constant daily day-night environmental cycle. Because the ubiquitin ligase Siah2 has been identified as a potential regulator of circadian clock function in cultured cells, we have used SIAH2-deficient mice to examine its function in vivo. Our experiments demonstrate a striking and unexpected sexually dimorphic effect of SIAH2-deficiency on the regulation of rhythmically expressed genes in the liver. The absence of SIAH2 in females, but not in males, altered the expression of core circadian clock genes and drastically remodeled the rhythmic transcriptome in the liver by increasing the number of day-time expressed genes, and flipping the rhythmic expression from nighttime expressed genes to the daytime. These effects are not readily explained by effects on known sexually dimorphic pathways in females. Moreover, loss of SIAH2 in females, not males, preferentially altered the expression of transcription factors and genes involved in regulating lipid and lipoprotein metabolism. Consequently, SIAH2-deficient females, but not males, displayed disrupted daily lipid and lipoprotein patterns, increased adiposity and impaired metabolic homeostasis. Overall, these data suggest that SIAH2 may be a key component of a female-specific circadian transcriptional output circuit that directs the circadian timing of gene expression to regulate physiological rhythms, at least in the liver. In turn, our findings imply that sex-specific transcriptional mechanisms may closely interact with the circadian clock to tailor overt rhythms for sex-specific needs.

Lysosomal targetomics of ghr KO mice shows chaperone-mediated autophagy degrades nucleocytosolic acetyl-coA enzymes

Mice deficient in GHR (growth hormone receptor; ghr KO) have a dramatic lifespan extension and elevated levels of hepatic chaperone-mediated autophagy (CMA). Using quantitative proteomics to identify protein changes in purified liver lysosomes and whole liver lysates, we provide evidence that elevated CMA in ghr KO mice downregulates proteins involved in ribosomal structure, translation initiation and elongation, and nucleocytosolic acetyl-coA production. Following up on these initial proteomics findings, we used a cell culture approach to show that CMA is necessary and sufficient to regulate the abundance of ACLY and ACSS2, the two enzymes that produce nucleocytosolic (but not mitochondrial) acetyl-coA. Inhibition of CMA in NIH3T3 cells has been shown to lead to aberrant accumulation of lipid droplets. We show that this lipid droplet phenotype is rescued by knocking down ACLY or ACSS2, suggesting that CMA regulates lipid droplet formation by controlling ACLY and ACSS2. This evidence leads to a model of how constitutive activation of CMA can shape specific metabolic pathways in long-lived endocrine mutant mice.Abbreviations: CMA: chaperone-mediated autophagy; DIA: data-independent acquisition; ghr KO: growth hormone receptor knockout; GO: gene ontology; I-WAT: inguinal white adipose tissue; KFERQ: a consensus sequence resembling Lys-Phe-Glu-Arg-Gln; LAMP2A: lysosomal-associated membrane protein 2A; LC3-I: non-lipidated MAP1LC3; LC3-II: lipidated MAP1LC3; PBS: phosphate-buffered saline; PI3K: phosphoinositide 3-kinase.

Genome-wide association study reveals the genetic basis of growth trait in yellow catfish with sexual size dimorphism

Sexual size dimorphism has been widely observed in a large number of animals including fish species. Genome-wide association study (GWAS) is a powerful tool to dissect the genetic basis of complex traits, whereas the sex-differences in the genomics of animal complex traits have been ignored in the GWAS analysis. Yellow catfish (Pelteobagrus fulvidraco) is an important aquaculture fish in China with significant sexual size dimorphism. In this study, GWAS was conducted to identify candidate SNPs and genes related to body length (BL) and body weight (BW) in 125 female yellow catfish from a breeding population. In total, one BL-related SNP and three BW-related SNPs were identified to be significantly associated with the traits. Besides, one of these SNPs (Chr15:19195072) was shared in both the BW and BL traits in female yellow catfish, which was further validated in 185 male individuals and located on the exon of stat5b gene. Transgenic yellow catfish and zebrafish that expressed yellow catfish stat5b showed increased growth rate and reduction of sexual size dimorphism. These results not only reveal the genetic basis of growth trait and sexual size dimorphism in fish species, but also provide useful information for the marker-assisted breeding in yellow catfish.

The effect of heat stress on the cellular behavior, intracellular signaling profile of porcine growth hormone (pGH) in swine testicular cells

At present, heat stress caused by the thermal environment is the main factor that endangers the reproductive function of animals. Growth hormone (GH) is a polypeptide hormone, the biological function of reproductive organs has been reported, and it has many important physiological functions in the body. However, so far, the behavior and signal transduction of GH in testicular cells under heat stress are still unclear. To this end, in the current work, we use a swine testicular cell line (ST) as an in vitro model to explore the cell behavior and intracellular signaling profile of porcine growth hormone (pGH) under heat stress; the results showed that when cells were under heat stress, pGH and GHR were basically not internalized, and a large number of them accumulated on the cell membrane. In addition, we also studied the effect of pGH on the JAK2-STATs signaling pathway and IGF-1 expression under heat stress, we found that the ability of pGH to activate the JAK-STATs signaling pathway and IGF-1 under heat stress was greatly reduced (p < 0.05). In conclusion, our research shows that when cells undergo heat stress, the internalization of pGH and GHR were inhibited, and the activation of the JAK2-STATs signaling pathway and IGF-1 expression were reduced; this lays a solid foundation for further research on the effect of pGH on swine testicular tissue under thermal environment.

Sex differences in the intergenerational inheritance of metabolic traits

Strong evidence suggests that early-life exposures to suboptimal environmental factors, including those in utero, influence our long-term metabolic health. This has been termed developmental programming. Mounting evidence suggests that the growth and metabolism of male and female fetuses differ. Therefore, sexual dimorphism in response to pre-conception or early-life exposures could contribute to known sex differences in susceptibility to poor metabolic health in adulthood. However, until recently, many studies, especially those in animal models, focused on a single sex, or, often in the case of studies performed during intrauterine development, did not report the sex of the animal at all. In this review, we (a) summarize the evidence that male and females respond differently to a suboptimal pre-conceptional or in utero environment, (b) explore the potential biological mechanisms that underlie these differences and (c) review the consequences of these differences for long-term metabolic health, including that of subsequent generations.

Effects of Overexpression of Fibroblast Growth Factor 15/19 on Hepatic Drug Metabolizing Enzymes

Fibroblast growth factors 15 (FGF15) and 19 (FGF19) are endocrine growth factors that play an important role in maintaining bile acid homeostasis. FGF15/19-based therapies are currently being tested in clinical trials for the treatment of nonalcoholic steatohepatitis and cholestatic liver diseases. To determine the physiologic impact of long-term elevations of FGF15/19, a transgenic mouse model with overexpression of Fgf15 (Fgf15 Tg) was used in the current study. The RNA sequencing (RNA-seq) analysis revealed elevations of the expression of several genes encoding phase I drug metabolizing enzymes (DMEs), including Cyp2b10 and Cyp3a11, in Fgf15 Tg mice. We found that the induction of several Cyp2b isoforms resulted in increased function of CYP2B in microsomal metabolism and pharmacokinetics studies. Because the CYP2B family is known to be induced by constitutive androstane receptor (CAR), to determine the role of CAR in the observed inductions, we crossed Fgf15 Tg mice with CAR knockout mice and found that CAR played a minor role in the observed alterations in DME expression. Interestingly, we found that the overexpression of Fgf15 in male mice resulted in a phenotypical switch from the male hepatic expression pattern of DMEs to that of female mice. Differences in secretion of growth hormone (GH) between male and female mice are known to drive sexually dimorphic, STAT5b-dependent expression patterns of hepatic genes. We found that male Fgf15 Tg mice presented with many features similar to GH deficiency, including lowered body length and weight, Igf-1 and Igfals expression, and STAT5 signaling. SIGNIFICANCE STATEMENT: The overexpression of Fgf15 in mice causes an alteration in DMEs at the mRNA, protein, and functional levels, which is not entirely due to CAR activation but associated with lower GH signaling.

Regulation of Sexually Dimorphic Expression of Major Urinary Proteins

Male house mice excrete large amounts of protein in their urinary scent marks, mainly composed of Major Urinary Proteins (MUPs), and these lipocalins function as pheromones and pheromone carriers. Here, we review studies on sexually dimorphic MUP expression in house mice, including the proximate mechanisms controlling MUP gene expression and their adaptive functions. Males excrete 2 to 8 times more urinary protein than females, though there is enormous variation in gene expression across loci in both sexes. MUP expression is dynamically regulated depending upon a variety of factors. Males regulate MUP expression according to social status, whereas females do not, and males regulate expression depending upon health and condition. Male-biased MUP expression is regulated by pituitary secretion of growth hormone (GH), which binds receptors in the liver, activating the JAK2-STAT5 signaling pathway, chromatin accessibility, and MUP gene transcription. Pulsatile male GH secretion is feminized by several factors, including caloric restriction, microbiota depletion, and aging, which helps explain condition-dependent MUP expression. If MUP production has sex-specific fitness optima, then this should generate sexual antagonism over allelic expression (intra-locus sexual conflict) selectively favoring sexually dimorphic expression. MUPs influence the sexual attractiveness of male urinary odor and increased urinary protein excretion is correlated with the reproductive success of males but not females. This finding could explain the selective maintenance of sexually dimorphic MUP expression. Producing MUPs entails energetic costs, but increased excretion may reduce the net energetic costs and predation risks from male scent marking as well as prolong the release of chemical signals. MUPs may also provide physiological benefits, including regulating metabolic rate and toxin removal, which may have sex-specific effects on survival. A phylogenetic analysis on the origins of male-biased MUP gene expression in Mus musculus suggests that this sexual dimorphism evolved by increasing male MUP expression rather than reducing female expression.

The mechanisms of interactions of psychotropic drugs with liver and brain cytochrome P450 and their significance for drug effect and drug-drug interactions

Cytochrome P450 (CYP) plays an important role in psychopharmacology. While liver CYP enzymes are responsible for the biotransformation of psychotropic drugs, brain CYP enzymes are involved in the local metabolism of these drugs and endogenous neuroactive substances, such as neurosteroids, and in alternative pathways of neurotransmitter biosynthesis including dopamine and serotonin. Recent studies have revealed a relation between the brain nervous system and cytochrome P450, indicating that CYP enzymes metabolize endogenous neuroactive substances in the brain, while the brain nervous system is engaged in the central neuroendocrine and neuroimmune regulation of cytochrome P450 in the liver. Therefore, the effect of neuroactive drugs on cytochrome P450 should be investigated not only in vitro, but also at in vivo conditions, since only in vivo all mechanisms of drug-enzyme interaction can be observed, including neuroendocrine and neuroimmune modulation. Psychotropic drugs can potentially affect cytochrome P450 via a number of mechanisms operating at the level of the nervous, hormonal and immune systems, and the liver. Their effect on cytochrome P450 in the brain is often different than in the liver and region-dependent. Since psychotropic drugs can affect cytochrome P450 both in the liver and brain, they can modify their own pharmacological effect at both pharmacokinetic and pharmacodynamic level. The article describes the mechanisms by which psychotropic drugs can change the expression/activity of cytochrome P450 in the liver and brain, and discusses the significance of those mechanisms for drug action and drug-drug interactions. Moreover, the brain CYP2D6 is considered as a potential target for psychotropics.

The Cellular Behavior, Intracellular Signaling Profile and Nuclear-Targeted Potential Functions of Porcine Growth Hormone (pGH) in Swine Testicular Cells

Porcine growth hormone (pGH) has many important biological functions and roles, and the biological activity of pGH is closely related with its cell behavior and characteristics. However, so far, the behavior of pGH in swine testicular cell remains unclear. For this, in the current work, the swine testicular cell line (ST) was used as an in vitro model, and CLSM (Confocal laser scanning microscope), IFA (Indirect immunofluorescence assay), FCM (Flow cytometry) and WB (Western-blotting) were used to explore the pGH's cell behivior and function, and the results showed that pGH and GHR could internalize into ST cell and transported to the nucleus. Furthermore, we studied the internalization kinetics of pGH and GHR on ST cell, and found that pGH and GHR internalizes into ST cell in a time-dependent manner. More importantly, we also investigated the potential molecular functions of pGH-GHR after it entered into the cell nuclei. The results indicated that nuclear-localized GHR could participate in cell proliferation by regulating the signal intensity of STAT5. In summary, our current research shows that the nuclear-localized pGH-GHR participates in the cell proliferation of ST cell, which lays a solid foundation for further research on the regulatory effect of pGH on testicular tissue.

Genomic comparisons between hepatocarcinogenic and non-hepatocarcinogenic organophosphate insecticides in the mouse liver

Short-term biomarkers of toxicity have an increasingly important role in the screening and prioritization of new chemicals. In this study, we examined early indicators of liver toxicity for three reference organophosphate (OP) chemicals, which are among the most widely used insecticides in the world. The OP methidathion was previously shown to increase the incidence of liver toxicity, including hepatocellular tumors, in male mice. To provide insights into the adverse outcome pathway (AOP) that underlies these tumors, effects of methidathion in the male mouse liver were examined after 7 and 28 day exposures and compared to those of two other OPs that either do not increase (fenthion) or possibly suppress liver cancer (parathion) in mice. None of the chemicals caused increases in liver weight/body weight or histopathological changes in the liver. Parathion decreased liver cell proliferation after 7 and 28 days while the other chemicals had no effects. There was no evidence for hepatotoxicity in any of the treatment groups. Full-genome microarray analysis of the livers from the 7 and 28 day treatments demonstrated that methidathion and fenthion regulated a large number of overlapping genes, while parathion regulated a unique set of genes. Examination of cytochrome P450 enzyme activities and use of predictive gene expression biomarkers found no consistent evidence for activation of AhR, CAR, PXR, or PPARα. Parathion suppressed the male-specific gene expression pattern through STAT5b, similar to genetic and dietary conditions that decrease liver tumor incidence in mice. Overall, these findings indicate that methidathion causes liver cancer by a mechanism that does not involve common mechanisms of liver cancer induction.

Nature of the liver volume depending on the gender and age assessing volumetry from a reconstruction of the computed tomography

Although the liver is a regenerating organ, excessive loss of liver volume (LV) can cause fatal liver failure. It is unclear whether LV is correlated with age; however, it is known that liver function decreases with age. In addition, the gender-related role of LV remains unclear. This study aimed to investigate the changes in LV by age and gender. Between January and December 2018, 374 consecutive patients who underwent abdominal multidetector computed tomography (MDCT) for any abdominal examinations were enrolled. LV was evaluated using MDCT. The relationship between the LV and body mass index (BMI), body surface area (BSA), age, and gender was investigated. The modified LV (mLV) was calculated by a formula measured LV × 1.5/BSA. LV correlated to BSA more than to BMI in both the males (R: 0.559 vs. 0.416) and females (R: 0.479 vs. 0.300) in our study. Age was negatively correlated to LV and BSA, and correlated to LV more than to BSA in males (R: 0.546 vs. 0.393) and females (R: 0.506 vs. 0.385). In addition, the absolute slope between age and LV in the males was higher than that in the females (14.1 vs. 10.2, respectively). Furthermore, the absolute slope of age and mLV in the males was slightly higher than in the females (9.1 vs. 7.3, respectively). In conclusion, LV in the normal liver is correlated to age rather than the one in the diseased liver. Liver volume in the males decreased more with age than LV in the females.

Hepatic sexual dimorphism - implications for non-alcoholic fatty liver disease

The liver is often thought of as a single functional unit, but both its structural and functional architecture make it highly multivalent and adaptable. In any given physiological situation, the liver can maintain metabolic homeostasis, conduct appropriate inflammatory responses, carry out endobiotic and xenobiotic transformation and synthesis reactions, as well as store and release multiple bioactive molecules. Moreover, the liver is a very resilient organ. This resilience means that chronic liver diseases can go unnoticed for decades, yet culminate in life-threatening clinical complications once the adaptive capacity of the liver is overwhelmed. Non-alcoholic fatty liver disease (NAFLD) predisposes individuals to cirrhosis and increases liver-related and cardiovascular disease-related mortality. This Review discusses the accumulating evidence of sexual dimorphism in NAFLD, which is currently rarely considered in preclinical and clinical studies. Increased awareness of the mechanistic causes of hepatic sexual dimorphism could lead to improved understanding of the biological processes that are dysregulated in NAFLD, to the identification of relevant therapeutic targets and to improved risk stratification of patients with NAFLD undergoing therapeutic intervention.

The Selective NMDA Receptor GluN2B Subunit Antagonist CP-101,606 with Antidepressant Properties Modulates Cytochrome P450 Expression in the Liver

Recent research indicates that selective NMDA receptor GluN2B subunit antagonists may become useful for the treatment of major depressive disorders. We aimed to examine in parallel the effect of the selective NMDA receptor GluN2B subunit antagonist CP-101,606 on the pituitary/serum hormone levels and on the regulation of cytochrome P450 in rat liver. CP-101,606 (20 mg/kg ip. for 5 days) decreased the activity of CYP1A, CYP2A, CYP2B, CYP2C11 and CYP3A, but not that of CYP2C6. The alterations in enzymatic activity were accompanied by changes in the CYP protein and mRNA levels. In parallel, a decrease in the pituitary growth hormone-releasing hormone, and in serum growth hormone and corticosterone (but not T₃ and T₄) concentration was observed. After a 3-week administration period of CP-101,606 less changes were found. A decrease in the CYP3A enzyme activity and protein level was still maintained, though no change in the mRNA level was found. A slight decrease in the serum concentration of corticosterone was also maintained, while GH level returned to the control value. The obtained results imply engagement of the glutamatergic system in the neuroendocrine regulation of cytochrome P450 and potential involvement of drugs acting on NMDA receptors in metabolic drug–drug interactions.

Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism

Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, being frequently associated with obesity, unbalanced dietary regimens, and reduced physical activity. Despite their greater adiposity and reduced physical activity, women show a lower risk of developing NAFLD in comparison to men, likely a consequence of a sex-specific regulation of liver metabolism. In the liver, sex differences in the uptake, synthesis, oxidation, deposition, and mobilization of lipids, as well as in the regulation of inflammation, are associated with differences in NAFLD prevalence and progression between men and women. Given the major role of sex hormones in driving hepatic sexual dimorphism, this review will focus on the role of sex hormones and their signaling in the regulation of hepatic metabolism and in the molecular mechanisms triggering NAFLD development and progression.

The Effect of Chronic Iloperidone Treatment on Cytochrome P450 Expression and Activity in the Rat Liver: Involvement of Neuroendocrine Mechanisms

In order to achieve a desired therapeutic effect in schizophrenia patients and to maintain their mental wellbeing, pharmacological therapy needs to be continued for a long time, usually from the onset of symptoms and for the rest of the patients' lives. The aim of our present research is to find out the in vivo effect of chronic treatment with atypical neuroleptic iloperidone on the expression and activity of cytochrome P450 (CYP) in rat liver. Male Wistar rats received a once-daily intraperitoneal injection of iloperidone (1 mg/kg) for a period of two weeks. Twenty-four hours after the last dose, livers were excised to study cytochrome P450 expression (mRNA and protein) and activity, pituitaries were isolated to determine growth hormone-releasing hormone (GHRH), and blood was collected for measuring serum concentrations of hormones and interleukin. The results showed a broad spectrum of changes in the expression and activity of liver CYP enzymes, which are important for drug metabolism (CYP1A, CYP2B, CYP2C, and CYP3A) and xenobiotic toxicity (CYP2E1). Iloperidone decreased the expression and activity of CYP1A2, CP2B1/2, CYP2C11, and CYP3A1/2 enzymes but increased that of CYP2E1. The CYP2C6 enzyme remained unchanged. At the same time, the level of GHRH, GH, and corticosterone decreased while that of T₃ increased, with no changes in IL-2 and IL-6. The presented results indicate neuroendocrine regulation of the investigated CYP enzymes during chronic iloperidone treatment and suggest a possibility of pharmacokinetic/metabolic interactions produced by the neuroleptic during prolonged combined treatment with drugs that are substrates of iloperidone-affected CYP enzymes.

Sex-dependent dynamics of metabolism in primary mouse hepatocytes

The liver is one of the most sexually dimorphic organs. The hepatic metabolic pathways that are subject to sexual dimorphism include xenobiotic, amino acid and lipid metabolism. Non-alcoholic fatty liver disease and hepatocellular carcinoma are among diseases with sex-dependent prevalence, progression and outcome. Although male and female livers differ in their abilities to metabolize foreign compounds, including drugs, sex-dependent treatment and pharmacological dynamics are rarely applied in all relevant cases. Therefore, it is important to consider hepatic sexual dimorphism when developing new treatment strategies and to understand the underlying mechanisms in model systems. We isolated primary hepatocytes from male and female C57BL6/N mice and examined the sex-dependent transcriptome, proteome and extracellular metabolome parameters in the course of culturing them for 96 h. The sex-specific gene expression of the general xenobiotic pathway altered and the female-specific expression of Cyp2b13 and Cyp2b9 was significantly reduced during culture. Sex-dependent differences of several signaling pathways increased, including genes related to serotonin and melatonin degradation. Furthermore, the ratios of male and female gene expression were inversed for other pathways, such as amino acid degradation, beta-oxidation, androgen signaling and hepatic steatosis. Because the primary hepatocytes were cultivated without the influence of known regulators of sexual dimorphism, these results suggest currently unknown modulatory mechanisms of sexual dimorphism in vitro. The large sex-dependent differences in the regulation and dynamics of drug metabolism observed during cultivation can have an immense influence on the evaluation of pharmacodynamic processes when conducting initial preclinical trials to investigate potential new drugs.