Protein and Peptide Letters - Volume 27, Issue 12, 2020

The spermatozoon has classically been seen only as a paternal DNA transporter into the oocyte, thus underestimating the entire contribution of the male gamete to the embryo development. The advancement of the research supports that not only the sperm genome, but the entire sperm transcriptome and proteome carry crucial information for fertilization and embryo development. Altogether, 6871 proteins have been reported in spermatozoa so far. Their functional analysis has recently addressed to the sperm proteome a role in fertilization, preimplantation embryo development and paternal epigenetic inheritance. Targeted analysis of human spermatozoa is warranted to compile an evidence-based list of sperm-carried molecular targets in infertile patients.

Male hypogonadism is “a clinical syndrome that results from failure of the testis to produce physiological concentrations of testosterone and/or a normal number of spermatozoa due to pathology at one or more levels of the hypothalamic-pituitary-testicular axis”. The diagnostic protocol of male hypogonadism includes accurate medical history, physical exam, as well as hormone assays and instrumental evaluation. Basal hormonal evaluation of serum testosterone, LH, and FSH is important in the evaluation of diseases of the hypothalamus-pituitary-testis axis. Total testosterone levels < 8 nmol/l profoundly suggest the diagnosis of hypogonadism. An inadequate androgen status is moreover possible if the total testosterone levels are 8-12 nmol/L. In this “grey zone” the diagnosis of hypogonadism is debated and the appropriateness for treating these patients with testosterone should be fostered by symptoms, although often non-specific. Up to now, no markers of androgen tissue action can be used in clinical practice. The identification of markers of androgens action might be useful in supporting diagnosis, Testosterone Replacement Treatment (TRT) and clinical follow-up. The aim of this review is to analyze the main findings of recent studies in the field of discovering putative diagnostic markers of male hypogonadism in seminal plasma by proteomic techniques. The identified proteins might represent a “molecular androtest” useful as a seminal fingerprint of male hypogonadism, for the diagnosis of patients with moderate grades of testosterone reduction and in the follow-up of testosterone replacement treatment.

Triple-A Syndrome (TAS) is a rare autosomal recessive disorder characterized by three cardinal symptoms: alacrimia, achalasia and adrenal insufficiency due to ACTH insensitivity. Various progressive neurological abnormalities and skin changes have been described in association with the syndrome. The disease is caused by mutation in the AAAS gene on chromosome 12q13. Mutations in AAAS were identified in more than 90% of individuals and families with TAS. The protein encoded by AAAS was termed ALADIN and is part of the WD repeat family of proteins, that have been found to be involved in many different functions such as protein-protein interaction, RNA processing, cytoskeleton assembly, control of cell division, signal transduction and apoptosis. Immunohistochemical analysis showed that mutated or truncated ALADIN localizes to the cytoplasm rather than to the nuclear pore complex. The exact function of ALADIN and the mechanisms that lead to the ACTH-resistant adrenal phenotype remains largely unknown. Nonetheless, recent studies provided some insights on the role of ALADIN as a member of the Nuclear Pore Complex not only implicated in the import of proteins involved in DNA repair and oxidative stress homeostasis but also in the strengthening of the mitotic spindle assembly. Early identification of the syndrome is challenging, given the rarity of the condition and high phenotypic heterogeneity even among members of the same family. In this review, we aim to summarize the current knowledge of clinical and molecular profile of patients with TAS and recommendations for the diagnosis, management, and follow-up of patients.

Obesity represents one of the most important health problems worldwide with increasing morbidity and mortality. Widespread prevalence of this disease justifies its actual definition of a “global epidemic”. Adipose tissue is nowadays considered a complex organ with lots of endocrine and metabolic functions. In addition to fulfilling its task for energy storage and thermal regulation, by virtue of its constituent white and brown cells, adipose tissue represents, considering its size, the biggest endocrine gland in the body. Both adipocytes and surrounding resident cells (macrophages, endothelial cells and others) produce a huge number of molecules, or adipokines, with endocrine or paracrine functions, that regulate various aspects of metabolism whose clinical relevance is emerging. By balancing pro-inflammatory and anti-inflammatory effects, the adipokines control insulin sensitivity and related glucose metabolism changes, lipid accumulation in the liver and other organs, and finally gonadal function. Collectively, literature data remains cloudy because of still conflicting results of pre-clinical and clinical studies. The aim of this review was to summarize scientific evidence about adipokines’ effects on human metabolism, by focusing on their role on either Metabolic Syndrome and NAFLD, or insulin-resistance in pregnancy, or finally, reproductive function disorders.

Biological markers (biomarkers) play a key role in drug development, regulatory approval and clinical care of patients and are linked to clinical and surrogate outcomes. Both acromegaly and Growth Hormone Deficiency (GHD) are pathological conditions related to important comorbidities that, in addition to having stringent diagnostic criteria, require valid markers for the definition of treatment, treatment monitoring and follow-up. GH and insulin-like growth factor-I (IGF-I) are the main biomarkers of GH action in children and adults while, in acromegaly, both GH and IGF-I are established biomarkers of disease activity. However, although GH and IGF-I are widely validated biomarkers of GHD and acromegaly, their role is not completely exhaustive or suitable for clinical classification and follow-up. Therefore, new biological markers for acromegaly and GH replacement therapy are strongly needed. The aim of this paper is to review and summarize the current state in the field pointing out new potential biomarkers for acromegaly and GH use/abuse.

This article reviews the role of INSL3 as biomarker of Leydig cell function and its systemic action in testis-bone-skeletal muscle crosstalk in adult men. Insulin-like factor 3 (INSL3) is a peptide hormone secreted constitutively in a differentiation-dependent mode by testicular Leydig cells. Besides the role for the testicular descent, this hormone has endocrine anabolic functions on the bone-skeletal muscle unit. INSL3 levels are low in many conditions of undifferentiated or altered Leydig cell status, however the potential clinical utility of INSL3 measurement is not yet well defined. INSL3 levels are modulated by the long-term cytotropic effect of the hypothalamicpituitary- gonadal axis, unlike testosterone that is acutely sensitive to the stimulus by luteinizing hormone (LH). INSL3 directly depends on the number and differentiation state of Leydig cells and therefore it represents the ideal marker of Leydig cell function. This hormone is more sensitive than testosterone to Leydig cell impairment, and the reduction of INSL3 in adult men can precociously detect an endocrine testicular dysfunction. Low INSL3 levels could cause or contribute to some symptoms and signs of male hypogonadism, above all sarcopenia and osteoporosis. The measurement provided suggested that the measurement of INSL3 levels should be considered in the clinical management of male hypogonadism and in the evaluation of testicular endocrine function. The monitoring of INSL3 levels could allow an early detection of Leydig cell damage, even when testosterone levels are still in the normal range.

Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue. Biomarkers of bone turnover have been used for years in bone disease management, especially to determine response to treatment. They are substances found in biological fluids, produced during the bone remodelling process. Recently, new approaches for the detection of bone physiology and pathology biomarkers have been proposed, among which proteomics, with particular interest in osteoporosis. The objective of this manuscript is to review current knowledge on proteomics applied to osteoporosis in vivo. The analysis of the 14 studies published to date showed a range of proteins whose expression is altered in patients with osteoporosis. The relatively small number of papers depends mainly on high costs and technical limitations; due to the difficulty to collect osteoclasts, most of the studies performed proteomics on peripheral blood monocytes (PBMs), already accepted as an excellent osteoporosis cell model in vivo. Among the identified proteins, the most promising are represented by Gelsolin (GSN), Annexin A2 (ANXA2), and Prolyl 4-hydroxylase (P4HB). They have been related to bone mineral density (BMD), sometimes in apparent disagreement (some upregulated and others downregulated in patients with low BMD). Finally, worthy of mention is the application of proteomics in the emerging field of microvesicles (MVs); they are important messengers, widely present in body fluids, and have recently emerged as novel targets for the diagnosis of multiple diseases, among which musculoskeletal diseases. In conclusion, the proteomic field is relatively novel in osteoporosis and has a considerable but theoretical potential; further investigations are needed in order to make proteome-derived markers applicable to clinical practice.

Acromegaly and Growth Hormone Deficiency (GHD) are associated with skeletal fragility and with an increased prevalence of Vertebral Fractures (VFs). In the most recent years, several authors tried to investigate surrogate markers that may predict the risk of bone fragility in these endocrine disorders. The aim of this review is to evaluate the role of GH receptor polymorphisms in skeletal fragility in patients affected by GHD and acromegaly. In fact, until now, two different isoforms of the GH Receptor (GHR) were described, that differ for the presence or the absence of transcription of the exon 3 of the GHR gene. Both the isoforms produce a functioning receptor, but the exon 3-deleted isoforms (d3-GHR) has a higher sensitivity to endogenous and recombinant GH as compared to the full-length isoform (fl-GHR).

During the last decade, the disclosure of systemic effects of osteocalcin (OCN) in its undercarboxylated form contributed to switch the concept of bone from a merely structural apparatus to a fully endocrine organ involved in the regulation of systemic functions. Since that time, the role of OCN as osteokine has been more and more widened appreciated and detailed by the major use of animal models, starting from the original function in the bone extracellular matrix as Gla-protein and spanning from the protective effects towards weight gain, insulin sensitivity and glucose homeostasis, to the anabolic and metabolic roles in skeletal muscle, to the stimulating effects on the testis endocrine function and male fertility, to the most recent preservation from anxious and depressive states through a direct activity on the central nervous system. In this review, experimental data supporting the inter-organ communication roles of this protein are discussed, together with the available data supporting the consistency between experimental data obtained in animals and those reported in humans. In addition, a specific session has been devoted to the possible significance the OCN as a template agonist on its receptor GPRC6A, for the development of novel therapeutic and pharmacological approaches for the treatment of dismetabolic states and male infertility.

Pancreatic neuroendocrine tumors (PanNETs) are rare tumors having usually an indolent behavior, but sometimes with unpredictable aggressiveness. PanNETs are more often non-functioning (NF), unable to produce functioning hormones, while 10-30% present as functioning (F) - PanNETs, such as insulinomas , gastrinomas , and other rare tumors. Diagnostic and prognostic markers, but also new therapeutic targets, are still lacking. Proteomics techniques represent therefore promising approaches for the future management of PanNETs. We conducted a systematic review to summarize the state of the art of proteomics in PanNETs. A total of 9 studies were included, focusing both on NF- and F-PanNETs. Indeed, proteomics is useful for the diagnosis, the prognosis and the detection of therapeutic targets. However, further studies are required. It is also warranted to standardize the analysis methods and the collection techniques, in order to validate proteins with a relevance in the personalized approach to PanNETs management.