Relationship between advanced glycation end products and increased lipid peroxidation in semen of diabetic men

Redox Regulation and Glucose Metabolism in the Stallion Spermatozoa

Stallion spermatozoa are cells which exhibit intense metabolic activity, where oxidative phosphorylation in the mitochondria is the primary ATP generator. However, metabolism must be viewed as a highly interconnected network of oxidation-reduction reactions that generate the energy necessary for life. An unavoidable side effect of metabolism is the generation of reactive oxygen species, leading to the evolution of sophisticated mechanisms to maintain redox homeostasis. In this paper, we provide an updated overview of glucose metabolism in stallion spermatozoa, highlighting recent evidence on the role of aerobic glycolysis in these cells, and the existence of an intracellular lactate shuttle that may help to explain the particular metabolism of the stallion spermatozoa in the context of their redox regulation.

Membrane-bound receptor for advanced glycation end products (RAGE) is a stable biomarker of low-quality sperm

STUDY QUESTION

Does receptor for advanced glycation end products (RAGE) on the surface membrane of the sperm cell function as a biomarker of low-quality sperm?

SUMMARY ANSWER

Membrane-bound RAGE at a cellular level directly correlates with low sperm motility, high cell permeability, decreased mitochondrial function, DNA fragmentation, and higher levels of apoptosis.

WHAT IS KNOWN ALREADY

RAGE has previously been measured by ELISA in low-quality sperm in diabetic men and has been shown to correlate with DNA fragmentation (terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) assay).

STUDY DESIGN SIZE DURATION

Semen samples were recovered from 60 non-obese, non-diabetic and non-smoking subjects, washed with fresh media, and analysed directly or purified further by differential gradient centrifugation (DGC) or fractionated by direct swim-up before being analysed for sperm motility and molecular health parameters, including cell membrane permeability, cell death, mitochondrial membrane potential, DNA fragmentation, and RAGE protein expression.

PARTICIPANTS/MATERIALS SETTING METHODS

Sperm motility assessments were carried out by computer-assisted sperm analysis (CASA) on 1000 spermatozoa for washed samples and 300 spermatozoa for purified samples. Molecular sperm health parameters were evaluated using flow cytometry with the use of the following markers: DAPI for cell membrane permeability, Annexin V/DAPI for cell death (apoptosis and necrosis), MitoTracker® Red CMXRos for mitochondrial membrane potential, TUNEL assay for DNA fragmentation and 8-hydroxy-2-deoxyguanosine for identification of oxidative damage to sperm DNA, and contrasted to membrane-bound RAGE expression levels, which were evaluated using an anti-RAGE monoclonal mouse antibody.

MAIN RESULTS AND THE ROLE OF CHANCE

RAGE protein was shown to be present on the acrosomal and equatorial regions of sperm, with the levels of membrane bound receptor strongly correlating with poor sperm health across all parameters tested; motility (R 2 = 0.5441, P < 0.0001) and mitochondrial membrane potential (R 2 = 0.6181, P < 0.0001) being of particular note. The analysis was performed at a single cell level thereby removing confounding complications from soluble forms of the RAGE protein that can be found in seminal plasma. The expression of the RAGE protein was shown to be stable over time and its levels are therefore not subject to variation in sample handling or preparation time.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

Inclusion criteria for this study were non-diabetic, non-obese and non-smoking participants to assess the distribution of RAGE expression in the general population, thereby excluding disease conditions that may increase RAGE expression in sperm or contribute to low sperm quality. The study does not address how RAGE expression may be affected in other patient subpopulations or disease states associated with male infertility. Sperm analysis by flow cytometry is not amenable to the study of males with a low sperm count.

WIDER IMPLICATIONS OF THE FINDINGS

Results of this study suggest that RAGE expression is a molecular maker of sperm cell health, which may be used for improvements in assisted reproduction through the removal of RAGE expressing sperm and facilitate in the diagnoses of unexplained infertility through its use as a biomarker of male infertility.

STUDY FUNDING/COMPETING INTERESTS

The study was funded by the Irish Research Council under the Government of Ireland Programme (GOIPG/2015/3729) and the Enterprise Ireland Innovation Partnership Programme (IP-2020-0952). All authors declare no competing interests.

Effect of Advanced Glycation end Products (AGEs) on Sperm Parameters and Function in C57Bl/6 Mice

This study investigated the deleterious impact of advanced glycation end products (AGEs), commonly present in metabolic disorders like diabetes, obesity, and infertility-related conditions, on sperm structure and function using a mouse model where AGE generation was heightened through dietary intervention. Five-week-old C57BL/6 mice were divided into two groups, one on a regular diet (control) and the other on an AGE-rich diet. After 13 weeks, various parameters were examined, including fasting blood glucose, body weight, food consumption, sperm parameters and function, testicular superoxide dismutase levels, malondialdehyde content, total antioxidant capacity, Johnson score, AGE receptor (RAGE) content, and carboxymethyl lysine (CML) content. The results showed that mice in the AGE group exhibited increased body weight and elevated fasting blood glucose levels. Furthermore, the AGE group displayed adverse effects on sperm, including reduced sperm counts, motility, increased morphological abnormalities, residual histone, protamine deficiency, sperm DNA fragmentation, reduced testicular antioxidant capacity, and higher levels of RAGE and CML proteins. These findings underscore the negative impact of AGEs on male reproductive health, particularly within the context of metabolic disorders, emphasizing the crucial role of the AGE/RAGE axis in male infertility, especially in the context of Western dietary patterns.

Menstrual Blood-Derived Endometrial Stem Cell Transplantation Improves Male Reproductive Dysfunction in T1D Mice by Enhancing Antioxidative Capacity

Diabetes is known to negatively affect male reproduction. Recent clinical results have confirmed that mesenchymal stem cell (MSC)-based therapies are safe and effective for the treatment of diabetes. However, the effect and potential mechanism through which MSC transplantation improves diabetes-derived male reproductive dysfunction are still unknown. In the present study, we first established a male T1D mouse model through intraperitoneal injection of streptozotocin for five consecutive days. Subsequently, we evaluated the blood glucose levels, fertility, and histology and immunology of the pancreas, testes, and penis of T1D mice with or without transplantation of menstrual blood-derived endometrial stem cells (MenSCs) or umbilical cord mesenchymal stem cells (UCMSCs). Glucose was added to the medium in which the Leydig cells were cultured to imitate high glucose-injured cell viability. Subsequently, we evaluated the cellular viability, ROS levels, and mitochondrial membrane potential of Leydig cells treated with or without MenSC-conditioned medium (MenSC-CM) using a CCK8 assay, immunofluorescence, and flow cytometry. The targeted proteins are involved in the potential mechanism underlying MenSC-derived improvements, which was further validated via Western blotting. Collectively, our results indicated that MenSC transplantation significantly ameliorated reproductive dysfunction in male T1D mice by enhancing cellular antioxidative capacity and promoting angiogenesis. This study provides solid evidence and support for the application of MSCs to improve diabetes-induced male reproductive dysfunction.

Edible wild plants, chicory and purslane, alleviated diabetic testicular dysfunction, and insulin resistance via suppression 8OHdg and oxidative stress in rats

Testicular dysfunction is a prevalent health problem frequently reported in individuals with diabetes mellitus (DM). Oxidative-inflammatory reactions, hormonal and spermatic abnormalities often accompany this illness. Herbal remedies "particularly wild plants" including chicory (Chicorium Intybus) and purslane (Portulaca Oleracea) are emerging as popular agents for people dealing with these issues due to their ability to act as antioxidants, reduce inflammation, and exhibit antidiabetic effects. According to the collected data, the daily administration of chicory (Ch) seed-extract (250 mg/kg) or purslane (Pu) seed-extract (200 mg/kg) to streptozotocin (STZ)-induced diabetic rats (50 mg/kg) for 30 days resulted in the normalization of fasting blood glucose (FBG), serum fructosamine, insulin levels, and insulin resistance (HOMA-IR), as well as reducing lipid peroxidation end-product malondialdehyde (MDA) level, aldehyde oxidase (AO) and xanthene oxidase (XO) activities. While caused a considerable improvement in glutathione (GSH) content, superoxide dismutase (SOD), catalase (CAT) activity, and total antioxidant capacity (TAC) when compared to diabetic rats. Ch and Pu extracts had a substantial impact on testicular parameters including sperm characterization, testosterone level, vimentin expression along with improvements in body and testis weight. They also mitigated hyperlipidemia by reducing total lipids (TL), total cholesterol (TC) levels, and low-density lipoprotein cholesterol (LDL-C), while increasing high-density lipoprotein cholesterol (HDL-C). Furthermore, oral administration of either Ch or Pu notably attuned the elevated proinflammatory cytokines as tumor necrotic factor (TNF-α), C-reactive protein (CRP), and Interleukin-6 (IL-6) together with reducing apoptosis and DNA damage. This was achieved through the suppression of DNA-fragmentation marker 8OHdG, triggering of caspase-3 immuno-expression, and elevation of Bcl-2 protein. The histological studies provided evidence supporting the preventive effects of Ch and Pu against DM-induced testicular dysfunction. In conclusion, Ch and Pu seed-extracts mitigate testicular impairment during DM due to their antihyperglycemic, antilipidemic, antioxidant, anti-inflammatory, and antiapoptotic properties.

Zingiber officinale extract maximizes the efficacy of simvastatin as a hypolipidemic drug in obese male rats

Obesity became a serious public health problem with enormous socioeconomic implications among the Egyptian population. The present investigation aimed to explore the efficacy of Zingiber officinale extract as a hypolipidemic agent combined with the commercially well-known anti-obesity drug simvastatin in obese rats. Thirty-five male Wister rats were randomly divided into five groups as follows: group I received a standard balanced diet for ten weeks; high-fat diet was orally administered to rats in groups II-V for ten weeks. From the fifth week to the tenth week, group III orally received simvastatin (40 mg/kg B.W.), group IV orally received Z. officinale root extract (400 mg/kg B.W.), and group V orally received simvastatin (20 mg/kg B.W.) plus Z. officinale extract (200 mg/kg B.W.) separately. Liver and kidney function tests, lipid profiles, serum glucose, insulin, and leptin were determined. Quantitative RT-PCR analysis of PPAR-γ, iNOS, HMG-CoA reductase, and GLUT-4 genes was carried out. Caspase 3 was estimated in liver and kidney tissues immunohistochemically. Liver and kidney tissues were examined histologically. The administration of Z. officinale extract plus simvastatin to high-fat diet-fed rats caused a significant reduction in the expression of HMG-coA reductase and iNOS by 41.81% and 88.05%, respectively, compared to highfat diet (HFD)-fed rats that received simvastatin only. Otherwise, a significant increase was noticed in the expression of PPAR-γ and GLUT-4 by 33.3% and 138.81%, respectively, compared to those that received simvastatin only. Immunohistochemistry emphasized that a combination of Z. officinale extract plus simvastatin significantly suppressed caspase 3 in the hepatic tissue of high-fat diet-fed rats. Moreover, the best results of lipid profile indices and hormonal indicators were obtained when rats received Z. officinale extract plus simvastatin. Z. officinale extract enhanced the efficiency of simvastatin as a hypolipidemic drug in obese rats due to the high contents of flavonoid and phenolic ingredients.

Diabetes-induced male infertility: potential mechanisms and treatment options

Male infertility is a physiological phenomenon in which a man is unable to impregnate a fertile woman during a 12-month period of continuous, unprotected sexual intercourse. A growing body of clinical and epidemiological evidence indicates that the increasing incidence of male reproductive problems, especially infertility, shows a very similar trend to the incidence of diabetes within the same age range. In addition, a large number of previous in vivo and in vitro experiments have also suggested that the complex pathophysiological changes caused by diabetes may induce male infertility in multiple aspects, including hypothalamic-pituitary-gonadal axis dysfunction, spermatogenesis and maturation disorders, testicular interstitial cell damage erectile dysfunction. Based on the above related mechanisms, a large number of studies have focused on the potential therapeutic association between diabetes progression and infertility in patients with diabetes and infertility, providing important clues for the treatment of this population. In this paper, we summarized the research results of the effects of diabetes on male reproductive function in recent 5 years, elaborated the potential pathophysiological mechanisms of male infertility induced by diabetes, and reviewed and prospected the therapeutic measures.

Sperm DNA damage: The possible link between obesity and male infertility, an update of the current literature

Obesity prevalence worldwide is increasing significantly. Whilst maternal obesity has clear detrimental impacts on fertility, pregnancy and foetal outcomes, more recently there has been an increasing focus on the role of paternal obesity in human fertility. Recent meta-analyses have indicated that obesity in men negatively affects basic sperm parameters such as sperm count, concentration and motility, increases the incidence of infertility and reduces the chances of conception. Sperm DNA damage, typically characterised by DNA strand breaks and oxidation of DNA nucleotides, is a specialised marker of sperm quality that has been independently associated with recurrent miscarriage, reduced assisted reproduction success and increased mutational loads in subsequent offspring. Whilst, there are still conflicting data in humans as to the association of obesity in men with sperm DNA damage, evidence from rodent models is clear, indicating that male obesity increases sperm DNA damage. Human data are often conflicting because of the large heterogeneity amongst studies, the use of body mass index as the indicator of obesity and the methods used for detection of sperm DNA damage. Furthermore, comorbidities of obesity (i.e., heat stress, adipokines, insulin resistance, changes in lipids, hypogonadism and obstructive sleep apnoea) are also independently associated with increased sperm DNA damage that is not always modified in men with obesity, and as such may provide a causative link to the discrepancies amongst human studies. In this review, we provide an update on the literature regarding the associations between obesity in men and fertility, basic sperm parameters and sperm DNA damage. We further discuss potential reasons for the discrepancies in the literature and outline possible direct and indirect mechanisms of increased sperm DNA damage resulting from obesity. Finally, we summarise intergenerational obesity through the paternal linage and how sperm DNA damage may contribute to the transmission.

Dietary trends and the decline in male reproductive health

Over the twentieth century, male reproductive health has suffered a substantial decline, as evidenced by decreases in sperm counts and testosterone levels and increases in reproductive pathologies. At the same time, the prevalence of chronic diseases such as obesity, diabetes, and metabolic syndrome has risen dramatically. Metabolic and reproductive health are highly interconnected, suggesting that their respective trends are intertwined and, given the timeframe of such trends, environmental and not genetic factors are most likely to be the primary causes. Industrialization, which began in Europe in the mid-eighteenth century, has resulted in profound changes to our diet, lifestyle, and environment, many of which are causal factors in the rise in chronic diseases. Industrialization results in a nutrition transition from an agricultural unprocessed to a modern processed diet, incorporating increases in sugar, vegetable oils, ultra-processed foods, linoleic acid, trans-fats, and total energy. This dietary shift has incurred numerous adverse effects on metabolic and reproductive health, characterized by chronic inflammation, oxidative stress, and insulin resistance. Moreover, these effects appear to multiply across subsequent generations via epigenetic inheritance. Men's fertility is markedly affected by obesity and diabetes, with an increase in total energy via processed food intake arguably being the key factor driving the diabesity pandemic. In contrast, wholefoods rich in micronutrients and phytonutrients support male fertility and a healthy body weight. Therefore, men wanting to maximize their fertility should consider making positive dietary changes, such as replacing processed foods with unprocessed foods that support metabolic and reproductive health.

Effects of diabetes mellitus on sperm quality and fertility outcomes: Clinical evidence

BACKGROUND

Diabetes mellitus is a global epidemic characterized by high morbidity and mortality. Diabetes mellitus can lead to acute and chronic systemic complications. Among them, a negative effect of diabetes mellitus on sperm quality and male/couple fertility has been suggested. However, available studies in diabetes mellitus men evaluated relatively small cohorts with discordant results.

OBJECTIVES

To evaluate the clinical evidences of the effects of diabetes mellitus on sperm quality and fertility outcomes.

METHODS

An extensive Medline search was performed identifying studies in the English language.

RESULTS

The prevalence of diabetes mellitus in infertile men ranges from 0.7% to 1.4%, while the prevalence of infertility in diabetes mellitus men, evaluated in a few studies, ranges from 35% to 51%. Male diabetes mellitus seems to play a negative effect on couple fecundity, while being childless or subfertile men might increase the risk of diabetes mellitus. Available cross-sectional studies investigating semen parameters and male sexual hormones in men with diabetes mellitus are heterogeneous, assessed relatively small cohorts, show often discordant results and frequently are not directly comparable to derive robust conclusions. Two meta-analyses support a negative effect of diabetes mellitus on sperm normal morphology and no effect on sperm total count, with contradictory results regarding other semen parameters. Considering only studies on type 1 diabetes mellitus men, meta-analyses support a negative effect of diabetes mellitus on sperm motility and no effect on sperm total count, with contradictory results regarding other semen parameters. The rate of children observed among type 1 diabetes mellitus men was lower than controls, especially in subjects with a longer diabetes mellitus duration. Couples with a diabetes mellitus male partner undergoing assisted reproduction techniques showed lower pregnancy rates than controls. No study evaluated the impact of diabetes mellitus treatment on semen quality and male fertility.

CONCLUSIONS

Overall, available data show that diabetes mellitus might impair male reproductive health and couple fertility. However, further larger and full of details studies are needed.

Potential Mechanism of Platelet-rich Plasma Treatment on Testicular Problems Related to Diabetes Mellitus

Diabetes mellitus is a condition of continuously increased blood glucose levels that causes hyperglycemia. This condition can result in disorders of various organs including testicular problems. The use of platelet-rich plasma (PRP) which is contained in several growth factors shows its potential in overcoming testicular problems. This literature review study was conducted to identify the potential of PRP in overcoming various testicular problems due to diabetic conditions.

An integrated overview on the regulation of sperm metabolism (glycolysis-Krebs cycle-oxidative phosphorylation)

An overview of the sperm metabolism is presented; using the stallion as a model we review glycolysis, Krebs Cycle and oxidative phosphorylation, paying special attention to the interactions among them. In addition, metabolism implies a series of coordinated oxidation-reduction reactions and in the course of these reactions reactive oxygen species (ROS) and reactive oxoaldehydes are produced ; the electron transport chain (ETC) in the mitochondria is the main source of the anion superoxide and hydrogen peroxide, while glycolysis produces 2-oxoaldehydes such as methylglyoxal as byproducts; due to the adjacent carbonyl groups are strong electrophiles (steal electrons oxidizing other compounds). Sophisticated mechanisms exist to maintain redox homeostasis, because ROS under controlled production also have important regulatory functions in the spermatozoa. The interactions between metabolism and production of reactive oxygen species are essential for proper sperm function, and deregulation of these processes rapidly leads to sperm malfunction and finally death. Lastly, we briefly describe two techniques that will expand our knowledge on sperm metabolism in the coming decades, metabolic flow cytometry and the use of the "omics" technologies, proteomics and metabolomics, specifically the micro and nano proteomics/metabolomics. A better understanding of the metabolism of the spermatozoa will lead to big improvements in sperm technologies and the diagnosis and treatment of male factor infertility.

The Stallion Spermatozoa: A Valuable Model to Help Understand the Interplay Between Metabolism and Redox (De)regulation in Sperm Cells

Significance: Proper functionality of the spermatozoa depends on the tight regulation of their redox status; at the same time these cells are highly energy demanding and in the energetic metabolism, principally in the electron transport chain in the mitochondria, reactive oxygen species are continuously produced, in addition to that observed in the Krebs cycle and during the β-oxidation of fatty acids. Recent Advances: In addition, in glycolysis, elimination of phosphate groups from glyceraldehyde 3-phosphate and dihydroxyacetone phosphate results in the byproducts glyoxal (G) and methylglyoxal (MG); these products are 2-oxoaldehydes. The presence of adjacent carbonyl groups makes them strong electrophiles that react with nucleophiles in proteins, lipids, and DNA, forming advanced glycation end products. Critical Issues: This mechanism is behind subfertility in diabetic patients; in the animal breeding industry, commercial extenders for stallion semen contain a supraphysiological concentration of glucose that promotes MG production, constituting a potential model of interest. Future Directions: Increasing our knowledge of sperm metabolism and its interactions with redox regulation may improve current sperm technologies in use, and shall provide new clues to understanding infertility in males. Moreover, stallion spermatozoa due to its accessibility, intense metabolism, and suitability for proteomics/metabolomic studies may constitute a suitable model for studying regulation of metabolism and interactions between metabolism and redox homeostasis. Antioxid. Redox Signal. 37, 521-537.

Risk factors on testicular function in adolescents

PURPOSE

Adolescence represents an important window for gonadal development. The aim of this review is to carry out a critical excursus of the most recent literature on endogenous and exogenous risk factors related to testicular function, focusing the research on adolescence period.

METHODS

A comprehensive literature search within PubMed was performed to provide a summary of currently available evidence regarding the impact on adolescence of varicocele, cryptorchidism, cancer, diabetes, lifestyle factors, endocrine disruptors, obesity and sexually transmitted diseases. We focused on human studies that evaluated a possible impact of these factors on puberty timing and their effects on andrological health.

RESULTS

Evidence collected seems to suggest that andrological health in adolescence may be impaired by several factors, as varicocele, cryptorchidism, and childhood cancer. Despite an early diagnosis and treatment, many adolescents might still have symptoms and sign of a testicular dysfunction in their adult life and at the current time it is not possible to predict which of them will experience andrological problems. Lifestyle factors might have a role in these discrepancies. Most studies point out towards a correlation between obesity, insulin resistance, alcohol, smoking, use of illegal drugs and testicular function in pubertal boys. Also, endocrine disruptors and sexually transmitted diseases might contribute to impair reproductive health, but more studies in adolescents are needed.

CONCLUSION

According to currently available evidence, there is an emerging global adverse trend of high-risk and unhealthy behaviors in male adolescents. A significant proportion of young men with unsuspected and undiagnosed andrological disorders engage in behaviors that could impair testicular development and function, with an increased risk for later male infertility and/or hypogonadism during the adult life. Therefore, adolescence should be considered a key time for intervention and prevention of later andrological diseases.

Revisiting Methodologies for In Vitro Preparations of Advanced Glycation End Products

Chronic elevation of sugar and oxidative stress generally results in development of advanced glycation end products (AGEs) in diabetic individuals. Accumulation of AGEs in an individual can give rise to the activation of several pathways that will ultimately lead to various complications. Such AGEs can also be prepared in an in vitro environment. For an in vitro preparation of advanced glycation end products (AGEs), proteins, lipids, or nucleic acids are generally required to be incubated with reducing sugars at a physiological temperature or higher depending upon the protocol optimized for its preparation. Certain other factors are also optimized and added to the buffer to hasten its preparation or alter the properties of prepared AGEs. Through this review, we intend to highlight the various studies related to the experimental procedures for the preparation of different types of AGEs. In addition, we present the comparative study of methodologies optimized for the preparation of AGEs.

Effect of Different High-Fat and Advanced Glycation End-Products Diets in Obesity and Diabetes-Prone C57BL/6 Mice on Sperm Function

Background:

We aimed to compare the effects of using high-fat (HF) and advanced glycation end-products (AGEs) containing diets to induce obesity and diabetes on sperm function in mice.

Materials and Methods:

In this experimental study, twenty-five 4-week old C57BL/6 mice were divided into 5 groups and were fed with control, 45% HF, 60% HF, 45% AGEs-HF, or 60% AGEs-HF diet. After 28 weeks, fast blood sugar, glucose intolerance, insulin concentration, homeostatic model assessments (HOMA) for insulin resistance (IR) and HOMA for beta cells (HOMA beta) from systematic blood were assessed. In addition, body weight, morphometric characteristics of testes, sperm parameters, DNA damage (AO), protamine deficiency (CMAA3), and sperm membrane (DCFH-DA) and intracellular (BODIPY) lipid peroxidation were measured.

Results:

Body mass and fasting blood sugar increased significantly in all experimental groups compared to the control group. Insulin concentration, glucose intolerance, HOMA IR, and HOMA beta were also increased significantly with higher levels of fat and AGEs in all four diets (P<0.05). The changes in the 60% HF-AGEs group, however, were more significant (P<0.001). Morphometric characteristics of the testis, sperm concentration, and sperm morphology in the diet groups did not significantly differ from the control group, while sperm motility and DNA damage in the 45%HF were significantly low. Although for protamine deficiency, both 60% HF-AGEs and 45% HF showed a significant increase compared to the control, the mean of sperm lipid in the 45% HF group and intracellular peroxidation in the 60% HF-AGEs group had the highest and the lowest increases, respectively.

Conclusion:

Our results, interestingly, showed that is the negative effects of a diet containing AGEs on examined parameters are less than those in HF diets. One possible reason is detoxification through the activation of the protective glyoxalase pathway as the result of the chronic AGEs increase in the body.

Effects of exposure to methylglyoxal on sperm motility and embryonic development after fertilization in mice

Methylglyoxal (MG) is a precursor for the generation of endogenous advanced glycation end-products involved in various diseases, including infertility. The present study evaluated the motility and developmental competence after in vitro fertilization of mouse sperm which were exposed to MG in the capacitation medium for 1.5 h. Sperm motility was analyzed using an SQA-V automated sperm quality analyzer. Intracellular reactive oxygen species (ROS), membrane integrity, mitochondrial membrane potential, and DNA damage were assessed using flow cytometry. The matured oocytes were inseminated with MG-exposed sperm, and subsequently, the fertilization and embryonic development in vitro were evaluated in vitro. The exposure of sperm to MG did not considerably affect the swim-up of sperm but resulted in a deteriorated sperm motility in a concentration-dependent manner, which was associated with a decreased mitochondrial activity. However, these effects was not accompanied by obvious ROS accumulation or DNA damage. Furthermore, MG diminished the fertilization rate and developmental competence, even after normal fertilization. Collectively, a short-term exposure to MG during sperm capacitation had a critical impact on sperm motility and subsequent embryonic development after fertilization. Considering that sperm would remain in vivo for up to 3 days until fertilization, our findings suggest that sperm can be affected by MG in the female reproductive organs, which may be associated with infertility.

Diabetes Type 1 Negatively Influences Leydig Cell Function in Rats, Which is Partially Reversible By Insulin Treatment

Type 1 diabetes mellitus (T1DM) is associated with impaired spermatogenesis and lower testosterone levels and epididymal weight. However, the underlying processes in the testis are unknown and remain to be elucidated. Therefore, the present study focused on the effects of T1DM on testicular function in a spontaneously diabetic rat model. BB/OKL rats after diabetes manifestation were divided into 3 groups: those without insulin treatment and insulin treatment for a duration of 2 and of 6 weeks. Anthropometrical data, circulating levels of gonadotrophins, testosterone, and inhibin B were measured. Intratesticular testosterone, oxidative stress, inflammation, and apoptosis were analyzed. Key enzymes of steroidogenesis were evaluated in the testis. Untreated diabetic rats had significantly lower serum follicle-stimulating hormone and luteinizing hormone levels. Serum and intratesticular testosterone levels significantly decreased in untreated diabetic rats compared to healthy controls. Key markers of Leydig cell function were significantly downregulated at the RNA level: insulin-like factor 3 (Insl3) by 53% (P = .006), Star by 51% (P = .004), Cyp11A1 by 80% (P = .003), 3Beta-Hsd2 by 61% (P = .005), and Pbr by 52% (P = .002). In the insulin-treated group, only Cyp11A1 and 3Beta-Hsd2 transcripts were significantly lower. Interestingly, the long-term insulin-treated group showed significant upregulation of most steroidogenic enzymes without affecting testosterone levels. Tumor necrosis factor α and apoptosis were significantly increased in the long-term insulin-treated rats. In conclusion T1DM, with a severe lack of insulin, has an adverse action on Leydig cell function. This is partially reversible with well-compensated blood glucose control. Long-term T1DM adversely affects Leydig cell function because of the process of inflammation and apoptosis.

Effects of Obesity and Diabetes on Sperm Cell Proteomics in Rats

Infertility caused by male factors is potentially associated with metabolic disorders such as obesity and/or diabetes. This experimental study was conducted in a male rodent model to assess the effects of different diseases on semen quality and sperm proteomics. Ten Wistar rats were used for each treatment. Rats were fed commercial food provided controllably to the control group and the diabetic group, and a hypercaloric diet supplemented with 5% sucrose in water was provided ad libitum to the obese group for 38 weeks. Diabetes was induced with 35 mg/kg streptozotocin. After euthanasia, testicles, spermatozoa, fat, and blood (serum) samples were collected. Spermatozoa were evaluated for quality and subjected to proteomics analyses. Histology and cytology of the testis, and serum leptin, adiponectin, interleukin 8 (IL-8), blood glucose, and testosterone levels, were also assessed. Body weight, retroperitoneal and testicular fat, and the Lee index were also measured. Obesity and diabetes were induced. The diabetic group showed noticeable changes in spermatogenesis and sperm quality. The mass spectrometry proteomics data have been deposited in Mendeley Data (doi: 10.17632/rfp7kfjcsd.5). Fifteen proteins varied in abundance between groups, especially proteins related to energy production and structural function of the spermatozoa, suggesting disturbances in energy production with a subsequent alteration in sperm motility in both groups, but with a compensatory response in the obese group.

A study of the aphrodisiac properties of Cordyceps militaris in streptozotocin-induced diabetic male rats

Background and Aim:

Cordyceps militaris (CM) is a fungus that has been used to enhance aphrodisiac activity in men, but to date, no studies have focused on its antidiabetic properties. This study aimed to investigate the effects of CM on reproductive performance of streptozotocin (STZ)-induced diabetic male rats.

Materials and Methods:

Six-week-old Wistar rats were randomly divided into four groups: control Group 1 consisting of healthy rats; Group 2, healthy rats treated with CM (100 mg/kg); Group 3, diabetic untreated rats; and Group 4, diabetic rats treated with CM (100 mg/kg). Rats were orally administered with vehicle or CM for 21 days. The body weight, blood glucose level, food intake, epididymal sperm parameter, sexual behavior, serum testosterone level, and antioxidant parameters were determined.

Results:

The results indicated that CM treatment in STZ-induced diabetic rats significantly improved the epididymal sperm parameter and serum testosterone level and, in turn, their copulatory behavior. CM treatment in diabetic rats significantly ameliorated malondialdehyde level and significantly improved the glutathione and catalase levels.

Conclusion:

These results provide new information on the pharmacological properties of CM in ameliorating testicular damage due to oxidative stress and improving sexual performance in diabetic male rats.

Momordica cymbalaria improves reproductive parameters in alloxan-induced male diabetic rats

Male reproductive dysfunction is one of the common complications of diabetes mellitus that causes infertility. This study was designed to investigate the protective effect of Momordica cymbalaria (M. cymbalaria) extracts on diabetes mediated reproductive toxicity in male Wistar rats. The induction of diabetes was performed using a single intraperitoneal injection of alloxan (120 mg/kg). Skin and seed extracts (250 and 500 mg/kg) of M. cymbalaria were orally administered to alloxan-induced diabetic male rats for 28 days. Postprandial blood glucose (PBG) levels were recorded at 7-day interval for four weeks. The effects of the treatment on blood glucose, weight of reproductive organs, sperm count, testosterone levels, antioxidant capacity, and histomorphology were evaluated. Treatment with the above extracts of M. cymbalaria significantly (p < 0.05) improved the reproductive parameters as well as the antioxidant levels superoxide dismutase (SOD) and glutathione-s-transferase (GST) in the diabetic rats. Also, oral treatment with M. cymbalaria extracts significantly reduced the PBG and malondialdehyde (MDA) levels. Further, it revived the histomorphology of reproductive organs in diabetic rats. Interestingly, skin extract at a dose of 500 mg/kg was found to be more efficient in elevating the level of testosterone and sperm count in the diabetic rats. Based on the results, it is clear that M. cymbalaria not only regulates the postprandial blood glucose levels but also improves the reproductive health in the diabetic state.

Network pharmacology integrated molecular docking reveals the bioactive components and potential targets of Morinda officinalis-Lycium barbarum coupled-herbs against oligoasthenozoospermia

Oligoasthenozoospermia (OA) is one of the most common types of male infertility affecting sperm count and sperm motility. Unfortunately, it is difficult for existing drugs to fundamentally improve the sperm quality of OA patients, because the pathological mechanism of OA has not been fully elucidated yet. Morinda officinalis-Lycium barbarum coupled-herbs (MOLBCH), as traditional Chinese Medicines, has been widely used for treating OA over thousands of years, but its molecular mechanism is still unclear. For this purpose, we adopted a comprehensive approach integrated network pharmacology and molecular docking to reveal the bioactive components and potential targets of MOLBCH against OA. The results showed that MOLBCH alleviated apoptosis, promoted male reproductive function, and reduced oxidant stress in the treatment of OA. Ohioensin-A, quercetin, beta-sitosterol and sitosterol were the key bioactive components. Androgen receptor (AR), Estrogen receptor (ESR1), Mitogen-activated protein kinase 3 (MAPK3), RAC-alpha serine/threonine-protein kinase (AKT1), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were the core potential targets. PI3K/Akt signaling pathway, prostate cancer, AGE-RAGE signaling pathway in diabetic complications were the most representative pathways. Moreover, molecular docking was performed to validate the strong binding interactions between the obtained core components and targets. These observations provide deeper insight into the pathogenesis of OA and can be used to design new drugs and develop new therapeutic instructions to treat OA.

The effect of crocin supplementation on lipid concentrations and fasting blood glucose: A systematic review and meta-analysis and meta-regression of randomized controlled trials

OBJECTIVE

This meta-analysis aimed to assess the effects of crocin supplementation on fasting blood glucose (FBG) and lipid profile levels in clinical trial studies.

DESIGN

A systematic literature search was performed in PubMed, Scopus, Embase, Web of Science, and the Cochrane Library databases for clinical trials published from the beginning up to November 2019. Of the 547 papers identified from all searched databases, eight eligible studies with nine effect sizes have all needed criteria for inclusion in this meta-analysis.

RESULTS

Results of the pooled random-effect size analysis showed just a significant decreasing effect of crocin supplementation on FBG (WMD: -6.52 mg/l, 95 % CI, -11.96, -1.08; p = 0.019) and TC (WMD: -4.64 mg/l, 95 % CI, -8.19, -1.09; p = 0.010). Crocin supplements did not have any significant effect on serum TG (p = 0.144) levels, LDL-C (p = 0.161), and HDL-C (p = 0.872) levels. Results showed that crocin supplementation could beneficially have effect on TG level only when trial duration less than 12 weeks and LDL-C levels in trials that used high dose intervention and trials that conducted on subjects with metabolic disorders. However, crocin supplementation did not significantly change FBG in trials that used low dose intervention. Meta-regression analysis indicated a linear relationship between the duration of intervention and significant change in FBG (p = 0.019).

CONCLUSION

Results of this systematic review and meta-analysis study have shown that crocin supplementation can decrease significantly FBS and TC without any beneficial effects on TG, LDL-C, and HDL-C levels.

Modulation of reproductive dysfunctions associated with streptozocin-induced diabetes by Artemisia judaica extract in rats fed a high-fat diet

We investigated the palliative effect of Artemisia judaica extract (AjE) on testicular deterioration induced by DM in high-fat diet/streptozocin (HFD/STZ)-injected rats. Forty rats were allocated to the following five groups: control, AjE, HFD/STZ, HFD/STZ-AjE, and HFD/STZ-metformin. HFD/STZ-diabetic rats showed a marked decrease in testicular weight and male sex hormones. There was significant suppression of testicular antioxidant enzymes and glutathione content in HFD/STZ-diabetic rats. However, rats that had received the STZ injection and the high-fat diet displayed increased malondialdehyde content and nitric oxide levels as well as tumour necrosis factor-alpha. High levels of Bax and low levels of Bcl-2 were detected after the STZ injection. Obvious pathological alterations were found in the testicular tissue of the HFD/STZ-diabetic rats. Thus, the administration of AjE attenuated the biochemical, molecular, and histopathological changes in the testes of the diabetic rats. The obtained findings showed that AjE treatment attenuated the diabetes-induced reprotoxicity in male rats via its antioxidant, anti-inflammatory, and antiapoptotic properties.

The role of advanced glycation end products in human infertility

Advanced glycation end products (AGEs) are heterogeneous products of the non-enzymatic interaction between proteins and reducing sugars. Numerous studies have shown that AGEs are associated with senescence, diabetes, vascular disease, aging and kidney disease. Infertility has been affected approximately 10 to15% of couples of reproductive ages. AGEs accumulation has been shown to play a crucial role in pathogenesis of infertility-related diseases. The present review provides the generation process, mechanism and pathological significance of AGEs and the novel treatment targeting AGEs for infertility.

Loganin alleviates testicular damage and germ cell apoptosis induced by AGEs upon diabetes mellitus by suppressing the RAGE/p38MAPK/NF-κB pathway

Diabetes mellitus (DM) damages male reproduction at multiple levels, such as endocrine secretion, spermatogenesis and penile erection. We herein investigated the protective effects and mechanism of loganin targeting the advanced glycation end products (AGEs)/receptor for AGEs (RAGE)/p38 mitogen-activated protein kinase (p38MAPK)/NF-κB signalling pathway. Loganin relieved the general DM symptoms and decreased the blood glucose level of KK-Ay DM mice. Haematoxylin-eosin staining demonstrated that loganin ameliorated testicular histology and function and enhanced the activities of testis-specific markers lactate dehydrogenase (LDH), acid phosphatase (ACP) and gamma-glutamyl transferase (γ-GT). Loganin also showed evident anti-oxidative stress, anti-apoptotic and anti-inflammatory effects on DM-induced reproductive damage by restoring glutathione (GSH) level and superoxide dismutase (SOD) activity, as well as reducing reactive oxygen species (ROS) level and Bax/Bcl-2 ratio in vivo and in vitro. Western blotting exhibited that loganin significantly inhibited the AGEs/RAGE/p38MAPK/NF-κB signalling pathway. Acridine orange and ethidium bromide staining (AOEB) and Western blotting showed that loganin in combination with inhibitors of RAGE, p38MAPK and NF-κB exerted stronger anti-apoptotic effects on AGE-induced GC-2 cell damage compared with loganin alone. In conclusion, loganin can protect against DM-induced reproductive damage, probably by suppressing the AGEs/RAGE/p38MAPK/NF-κB pathway.

Zingiber officinale preserves testicular structure and the expression of androgen receptors and proliferating cell nuclear antigen in diabetic rats

The aim of this study was to assess the efficacy of Zingiber officinale, commonly referred to as ginger, in preserving the structural integrity of testis in streptozotocin (STZ)-induced diabetic rats compared to the efficacy of metformin, the traditional effective antidiabetic drug. STZ was utilised for the induction of diabetes mellitus in male Sprague Dawley rats. The study included five groups (n = 6 each), namely the normal control, ginger-treated normal, nontreated diabetic, metformin-treated diabetic and ginger-treated diabetic groups. Biochemical assessment of fasting blood glucose level (BGL) and total antioxidant capacity (TAC) was performed. Histopathological assessment of the testes was performed using routine and immunohistochemical techniques. Fasting BGL significantly (p = .01) reduced, whereas TAC significantly increased (p < .001) in metformin- and ginger-treated diabetic rats compared to those in untreated diabetic rats. Metformin and ginger reduced the degenerative changes observed in the testes of diabetic rats, significantly reduced (p < .001) caspase-3 immunoexpression, and significantly increased (p < .001) the immune-expression of androgen receptors and proliferating cell nuclear antigen. Ginger has antidiabetic effects and preserves testicular structural integrity and, thus, is recommended as an adjuvant therapy for male diabetic patients in the reproductive period.

Potential effect of advanced glycation end products (AGEs) on spermatogenesis and sperm quality in rodents

The aim of the present study was to assess whether dietary advanced glycation end products (AGEs) induce testicular dysfunction. Using a BALB/c mouse model, AGE intake and serum levels were found to increase in AGE diet-treated mice relative to the controls. Histopathological damage was detected in the testes and epididymides of the AGE diet-induced mice. The total number of epididymal sperm decreased, and increased abnormal sperm rate was found in the mice. Moreover, the mice testes showed an increased level of the receptor for AGEs (RAGE) and malondialdehyde (MDA). Using a Sprague-Dawley rat model, AGE diet-induced rats showed 3- to 4-fold higher AGE intake than the controls. In these rats, higher serum and sperm MDA levels, decreased epididymal sperm numbers, and increased abnormal sperm rates were also observed. Silymarin, a natural AGE inhibitor, was found to restore these AGE-induced phenomena. Concluding from the above findings, dietary AGEs may promote testicular dysfunction.

Post-translational modifications of seminal proteins and their importance in male fertility potential

Introduction: The seminal proteome has been shown to directly influence the male fertile potential. Post-translational modifications (PTMs) are significant changes that play a role in the biological regulation of proteins. Sperm cells are transcriptionally and translationally inactive and these modifications are essential to control protein function.Areas covered: Here we reviewed seven PTMs which importance for male reproductive function investigated in the past decade, namely S-nitrosylation and tyrosine nitration (both occurring by the action of NO), glycosylation, ubiquitination, acetylation, methylation, and SUMOylation. Since they were previously identified in human semen, we focus on their role in sperm function, as well as in physiological and pathophysiological processes which could contribute to the fertility potential. The following keywords were applied: 'post-translational modification', 'sperm', 'semen', 'seminal plasma', 'male infertility', 'nitrosylation', 'nitration', 'histone methylation', 'SUMOylation', 'ubiquitination', 'ubiquitilation', 'glycosylation', and 'acetylation'.Expert opinion: Most biological processes orchestrated by proteins require PTMs for their activation or inhibition. Most of them are dynamic and occur in mature sperm, modulating protein function, thus exerting a significant role in sperm function and fertility. Finally, the study of PTMs should be also addressed in pathophysiological processes, as different clinical conditions are known to alter the proteome.

Redox Regulation and Oxidative Stress: The Particular Case of the Stallion Spermatozoa

Redox regulation and oxidative stress have become areas of major interest in spermatology. Alteration of redox homeostasis is recognized as a significant cause of male factor infertility and is behind the damage that spermatozoa experience after freezing and thawing or conservation in a liquid state. While for a long time, oxidative stress was just considered an overproduction of reactive oxygen species, nowadays it is considered as a consequence of redox deregulation. Many essential aspects of spermatozoa functionality are redox regulated, with reversible oxidation of thiols in cysteine residues of key proteins acting as an “on–off” switch controlling sperm function. However, if deregulation occurs, these residues may experience irreversible oxidation and oxidative stress, leading to malfunction and ultimately death of the spermatozoa. Stallion spermatozoa are “professional producers” of reactive oxygen species due to their intense mitochondrial activity, and thus sophisticated systems to control redox homeostasis are also characteristic of the spermatozoa in the horse. As a result, and combined with the fact that embryos can easily be collected in this species, horses are a good model for the study of redox biology in the spermatozoa and its impact on the embryo.

Can Antidiabetic Drugs Improve Male Reproductive (Dys)Function Associated with Diabetes?

The alarming increase in the number of diabetic patients worldwide raises concerns regarding the impact of the disease on global health, not to mention on social and economic aspects. Furthermore, the association of this complex metabolic disorder with male reproductive impairment is worrying, mainly due to the increasing chances that young individuals, at the apex of their reproductive window, could be affected by the disease, further contributing to the disturbing decline in male fertility worldwide. The cornerstone of diabetes management is glycemic control, proven to be effective in avoiding, minimizing or preventing the appearance or development of disease-related complications. Nonetheless, the possible impact of these therapeutic interventions on male reproductive function is essentially unexplored. To address this issue, we have made a critical assessment of the literature on the effects of several antidiabetic drugs on male reproductive function. While the crucial role of insulin is clear, as shown by the recovery of reproductive impairments in insulin-deficient individuals after treatment, the same clearly does not apply to other antidiabetic strategies. In fact, there is an abundance of controversial reports, possibly related to the various study designs, experimental models and compounds used, which include biguanides, sulfonylureas, meglitinides, thiazolidinediones/glitazones, bile acid sequestrants, amylin mimetics, as well as sodiumglucose co-transporter 2 (SGLT2) inhibitors, glucagon-like peptide 1 (GLP1), α-glucosidase inhibitors and dipeptidyl peptidase 4 (DPP4) inhibitors. These aspects constitute the focus of the current review.

Hyperglycemia induces spermatogenic disruption via major pathways of diabetes pathogenesis

Diabetes-induced hyperglycemia has previously been shown to impact on male sub-/infertility, however, still little is known about the underlying mechanisms. In the present study we have addressed three major biochemical pathways implicated in the pathogenesis of hyperglycemia induced organ damage (the advanced glycation end product (AGE) formation pathway, the diacylglycerol-protein kinase C pathway (PKC), and the polyol pathway) in both testis and epididymis of the Ins2^Akita mouse model of Type 1 diabetes (T1DM). Hyperglycemia activated both the PKC and the polyol pathway in a significant and progressive manner within the testis, but not within the epididymis. While the AGE receptor was ubiquitiously expressed in the testis, concentrations of precursor methylglyoxal and AGE carboxymethyllysine were increased in both epididymis and testis in diabetic mice. However, AGEs did not activate intracellular pathways of ERK1, ERK2, Rela, Nrf-2, IkBkB, NFkB except CDC42, Akt1. In conclusion, two of the major pathways of hyperglycemia-induced organ damage were clearly activated within the testis of T1DM mice. This provides therapeutical opportunities in the treatment of diabetic male reproductive dysfunction.

Aqueous and ethanol extracts of Dracaena arborea (Wild) Link (Dracaenaceae) alleviate reproductive complications of diabetes mellitus in rats

Reproductive dysfunction is one of the most prevalent diabetes complications. Draceana arborea is known to enhance sexual function in diabetic rats, but the underlying mechanisms have not been thoroughly elucidated. This study examined the effects of D. arborea on some reproductive complications of diabetes in rats. Aqueous and ethanol (500 and 100 mg/kg respectively) extracts of D. arborea, Sildenafil citrate (1.44 mg/kg), trimethylamine-N-oxide (TMAO, 20 mg/kg) and distilled water (10 ml/kg) were orally administered for 28 days to streptozotocin-induced diabetic rats. Glycaemia, body and reproductive organ masses, fertility parameters, total proteins, antioxidant enzymes activities, serum and testicular testosterone and the histology of the testes and epididymis were determined. Results revealed significant decreases in body and absolute and relative masses of testes, epididymis, seminal vesicles, prostate and vas deferens, fertility parameters, epididymal and testicular total proteins, serum and testicular testosterone levels as well as antioxidant enzymes activities. Interestingly, while having minor anti-hyperglycaemic effects, these abnormalities associated with testicular and epididymal alterations were alleviated by D. arborea especially the aqueous extract (500 mg/kg). These outcomes provided evidence of the androgenic properties of D. arborea in diabetic rats, which could be useful for a better management of sexual dysfunctions in diabetic patients.

Troxerutin affects the male fertility in prepubertal type 1 diabetic male rats

OBJECTIVES

Diabetes can gradually cause damage to the function and structure of male gonads. This survey was conducted to investigate the effect of troxerutin on hormonal changes, serum oxidative stress indices, and testicular function and structure in prepubertal diabetic rats.

MATERIALS AND METHODS

Fifty prepubertal (6 weeks old) male Wistar rats were divided into five groups including Control, Troxerutin, Diabetic, Diabetic+Troxerutin, and Diabetic+Insulin. Type I diabetes was induced by 55 mg/kg of streptozotocin intraperitoneally. The groups were treated with 150 mg/kg/day troxerutin via oral gavage or 4-6 IU/day insulin via subcutaneous injection for 4 consecutive weeks. Blood sugar (BS) and serum levels of insulin, FSH, LH, testosterone, glutathione peroxidase (GPX), superoxide dismutase (SOD), malondialdehyde (MDA), and total antioxidant capacity (TAC) were analyzed. Testis and epididymis were removed for histopathologic study and analysis of sperm parameters.

RESULTS

Troxerutin significantly reduced the BS in the diabetic group similar to insulin but could not affect insulin, FSH, or LH significantly. Troxerutin caused a significant increase in testosterone and GPX but had no significant effect on serum MDA, TAC, and SOD levels. In addition, troxerutin had a better effect than insulin on diabetes-induced testicular structural damage. Sperm analysis results also revealed that troxerutin and insulin could improve sperm number, motility, and viability in diabetic rats.

CONCLUSION

According to these results, it can be derived that administration of troxerutin is a suitable protective strategy for side effects of diabetes in testis of prepubertal diabetic male rats.

Vitamin D3 Activates Phosphatidylinositol-3-Kinase/Protein Kinase B via Insulin-Like Growth Factor-1 to Improve Testicular Function in Diabetic Rats

OBJECTIVE

In diabetes mellitus, vitamin D₃ deficiency affects sex hormone levels and male fertility; however, the mechanism leading to the disorder is unclear. This research was designed to investigate the mechanism of vitamin D₃ deficiency and hypogonadism in diabetic rats. Our aim was to assess serum vitamin D₃ levels and the relationship among vitamin D₃, insulin-like growth factor-1 (IGF-1), and testicular function.

MATERIALS AND METHODS

Rats with streptozotocin-induced diabetes were randomly divided into four groups and treated with different doses of vitamin D₃: no vitamin D₃, low (0.025 μg/kg/day), high (0.1 μg/kg/day), and high (0.1 μg/kg/day) with JB-1 (the insulin-like growth factor-1 receptor inhibitor group, 100 μg/kg/day). The groups were compared with wild-type rats, which function as the control group. Various parameters such as vitamin D₃ and IGF-1 were compared between the experimental and wild-type groups, and their correlations were determined.

RESULTS

Twelve weeks of vitamin D₃ supplementation improved the testosterone levels, as shown by the increase in the level of serum IGF-1 in diabetic rats. Phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT), which was a downstream of the signaling pathway of IGF-1, was significantly increased after vitamin D₃ treatment.

CONCLUSIONS

The study shows that vitamin D₃ may promote the expression of testosterone and improve testicular function in diabetic rats by activating PI3K/AKT via IGF-1.

Investigating the Glycating Effects of Glucose, Glyoxal and Methylglyoxal on Human Sperm

Glycation is the non-enzymatic reaction between reducing sugars, such as glucose, and proteins, lipids or nucleic acids, producing Advanced Glycation End (AGE) products. AGEs, produced during natural senescence as well as through lifestyle factors such as diet and smoking, are key pathogenic compounds in the initiation and progression of diabetes. Importantly, many of these factors and conditions also have influence on male fertility, affecting sperm count and semen quality, contributing to the decreasing trend in male fertility. This study investigated the impact of AGEs on sperm damage. In vitro sperm glycation assays were used to determine the levels and localization of the potent AGE compound, carboxymethyl-lysine (CML) in response to treatment with the glycating compounds glucose, glyoxal and methylglyoxal. Sperm function assays were then used to assess the effects of glycation on motility and hyaluronan binding, and levels of oxidative DNA damage were analyzed through measurement of the marker, 8-oxoguanine. Results showed that glyoxal, but not glucose or methylglyoxal, induced significant increases in CML levels on sperm and this correlated with an increase in 8-oxoguanine. Immunocytochemistry revealed that AGEs were located on all parts of the sperm cell and most prominently on the head region. Sperm motility and hyaluronidase activity were not adversely affected by glycation. Together, the observed detrimental effects of the increased levels of AGE on DNA integrity, without an effect on motility and hyaluronidase activity, suggest that sperm may retain some fertilizing capacity under these adverse conditions.

Reduced Expression of Glutathione S-Transferase 4 Promotes Vascular Neointimal Hyperplasia in CKD

Neointima formation is the leading cause of arteriovenous fistula (AVF) failure. We have shown that CKD accelerates this process by transforming the vascular smooth muscle cells (SMCs) lining the AVF from a contractile to the synthetic phenotype. However, the underlying mechanisms affecting this transformation are not clear. Previous studies have shown that the α-class glutathione transferase isozymes have an important role in regulating 4-hydroxynonenal (4-HNE)-mediated proliferative signaling of cells. Here, using both the loss- and gain-of-function approaches, we investigated the role of glutathione S-transferase α4 (GSTA4) in modulating cellular 4-HNE levels for the transformation and proliferation of SMCs. Compared with non-CKD controls, mice with CKD had downregulated expression of GSTA4 at the mRNA and protein levels, with concomitant increase in 4-HNE in arteries and veins. This effect was associated with upregulated phosphorylation of MAPK signaling pathway proteins in proliferating SMCs. Overexpressing GSTA4 blocked 4-HNE-induced SMC proliferation. Additionally, inhibitors of MAPK signaling inhibited the 4-HNE-induced responses. Compared with wild-type mice, mice lacking GSTA4 exhibited increased CKD-induced neointima formation in AVF. Transient expression of an activated form of GSTA4, achieved using a combined Tet-On/Cre induction system in mice, lowered levels of 4-HNE and reduced the proliferation of SMCs. Together, these results demonstrate the critical role of GSTA4 in blocking CKD-induced neointima formation and AVF failure.

Protective effects of Lycium barbarum polysaccharide on male sexual dysfunction and fertility impairments by activating hypothalamic pituitary gonadal axis in streptozotocin-induced type-1 diabetic male mice

Diabetes-associated male sexual dysfunction and fertility impairments are both common clinical complications with limited therapeutic options; hence it seriously affects the quality of life of the patients, in particular, the patients of reproductive age. Lycium barbarum polysaccharide (LBP) has long being believed to maintain and to promote reproductive functions in the traditional medical practice in China. The current study was to investigate if LBP may contribute to recovery of male sexual dysfunction and fertility impairments in diabetic individuals. The effects of LBP on sexual behaviors and histological changes of testis were studied in the type-1 diabetes male mice induced by intra-peritoneal (i.p.) injection of streptozotocin (STZ). After oral administration of LBP (10, 20 or 40 mg/kg), sildenafil citrate (SC, 5 mg/kg) or saline for 62 consecutive days, the typical abnormal changes in the sperm parameters, in relative weight of reproductive organs and in morphology of testis were observed in diabetic mice. LBP treatment of the diabetic mice considerably reversed those changes and Johnsen's testicular score, serum testosterone (T), follicular stimulating hormone (FSH) and luteinizing hormone (LH) level were also increased to different degrees. Moreover, our data have also shown that a marked improvement in sexual behavior and fertility level after administration of LBP (40 mg/kg) compared to the diabetic group. These results suggested that LBP can exert functional recovery of male sexual dysfunction and fertility damages induced by diabetes in male mice, which is likely to be mediated through regulating the hypothalamus- pituitary-gonadal axis endocrine activity.

Hyperglycemia-related advanced glycation end-products is associated with the altered phosphatidylcholine metabolism in osteoarthritis patients with diabetes

To test whether type 2 diabetic patients have an elevated level of advanced glycation end-products (AGEs) and responsible for altered phosphatidylcholine metabolism, which we recently found to be associated with osteoarthritis (OA) and diabetes mellitus (DM), synovial fluid (SF) and plasma samples were collected from OA patients with and without DM. Hyperglycemia-related AGEs including methylglyoxal (MG), free methylglyoxal-derived hydroimidazolone (MG-H1), and protein bound N-(Carboxymethyl)lysine (CML) and N-(Carboxyethyl)lysine (CEL) levels were measured in both SF and plasma samples using liquid chromatography coupled tandem mass spectrometry methodology. The correlation between these AGEs and phosphatidylcholine acyl-alkyl C34:3 (PC ae C34:3) and C36:3 (PC ae C36:3) were examined. Eighty four patients with knee OA, including 46 with DM and 38 without DM, were included in the study. There was no significant difference in plasma levels of MG, MG-H1, CML, and CEL between OA patients with and without DM. However, the levels of MG and MG-H1, but not CML and CEL in SF were significantly higher in OA patients with DM than in those without (all p ≤0.04). This association strengthened after adjustment for age, body mass index (BMI), sex and hexose level (p<0.02). Moreover, the levels of MG-H1 in SF was negatively and significantly correlated with PC ae C34:3 (ρ = -0.34; p = 0.02) and PC ae C36:3 (ρ = -0.39; P = 0.03) after the adjustment of age, BMI, sex and hexose level. Our data indicated that the production of non-protein bound AGEs was increased within the OA-affected joint of DM patients. This is associated with changes in phosphatidylcholine metabolism and might be responsible for the observed epidemiological association between OA and DM.

Iridoid glycoside from Cornus officinalis ameliorated diabetes mellitus-induced testicular damage in male rats: Involvement of suppression of the AGEs/RAGE/p38 MAPK signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cornus officinalis (CO) has been widely used as a traditional Chinese medicine for treating diabetes mellitus (DM) and its complications. Iridoid glycoside from C. officinalis (IGCO) can resist apoptosis, hyperglycemia, oxidation and so on. The aim of this study was to investigate the therapeutic effects of IGCO on DM-induced testicular damage through inhibition of the AGEs/RAGE/p38 MAPK signaling pathway.

MATERIALS AND METHODS

A DM model of male Wistar rats was induced with streptozotocin injection (30mg/kg, i.p.) and high-fat diet. The DM rats were administrated with IGCO at low and high doses (15 and 30mg/kg, p.o.) for 12 weeks. Testicular damage was evaluated by estimating relative testicular weights, testicular pathohistology, sperm count, live sperm rate, endogenous sex hormone level and activity of testicular marker enzymes. Besides, general diabetic symptoms, renal function, oxidative stress parameters and testicular apoptosis marker were also determined. Finally, the mechanism was explored based on the AGEs/RAGE/p38 MAPK pathway.

RESULTS

IGCO effectively mitigated the general symptoms of DM rats including weight loss, polydipsia, polyphagia, polyuria, elevated blood glucose level and low serum insulin level. Nourishing the kidney evidently, IGCO reduced serum creatinine, urea nitrogen and urine protein excretion, and also markedly protected against DM-induced testicular damage by increasing testis/body weight ratio and live sperm rate, improving the histomorphology of testes, upregulating testosterone, LH, FSH and GnRH levels and preventing the decrease of testicular marker enzymes LDH, ACP and γ-GT. Moreover, IGCO showed considerable anti-oxidative and anti-apoptotic effects, which downregulated the increase of ROS and MDA levels, restored SOD and CAT activities, and decreased spermatogenic cell apoptosis and Bax/Bcl-2 ratio. In the end, the increased AGEs, RAGE and p-p38 MAPK protein levels in DM rats were also reversed by IGCO significantly.

CONCLUSIONS

The kidney tonic IGCO well protected DM rats from testicular damage, which may be related to suppression of the AGEs-RAGE-p38 MAPK pathway.

The effects of diabetes on male fertility and epigenetic regulation during spermatogenesis

The effects of diabetes mellitus include long-term damages, dysfunctions, and failures of various organs. An important complication of diabetes is the disturbance in the male reproductive system. Glucose metabolism is an important event in spermatogenesis. Moreover, glucose metabolism is also important for maintaining basic cell activity, as well as specific functions, such as motility and fertilization ability in mature sperm. Diabetic disease and experimentally induced diabetes both demonstrated that either type 1 diabetes or type 2 diabetes could have detrimental effects on male fertility, especially on sperm quality, such as sperm motility, sperm DNA integrity, and ingredients of seminal plasma. Epigenetic modifications are essential during spermatogenesis. The epigenetic regulation represents chromatin modifications including DNA methylation, histone modifications, remodeling of nucleosomes and the higher-order chromatin reorganization and noncoding RNAs. If spermatogenesis is affected during the critical developmental window, embryonic gonadal development, and germline differentiation, environmentally-induced epigenetic modifications may become permanent in the germ line epigenome and have a potential impact on subsequent generations through epigenetic transgenerational inheritance. Diabetes may influence the epigenetic modification during sperm spermatogenesis and that these epigenetic dysregulation may be inherited through the male germ line and passed onto more than one generation, which in turn may increase the risk of diabetes in offspring.

Diabetes mellitus and functional sperm characteristics: A meta-analysis of observational studies

OBJECTIVE

Insulin resistance and diabetes mellitus (DM) are well defined causes of female infertility. Animal studies present evidence for decreased sperm quality, but conflicting results have been presented in clinically-orientated studies. We sought to evaluate whether DM affects functional sperm characteristics.

STUDY DESIGN

We searched the Medline, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials databases.

RESULTS

DM seems to decrease the seminal volume (MD -0.66ml, 95% CI -1.10, -0.22) and the percentage of motile cells (MD -14.29%, 95% CI -22.76, -5.82) and increase the FSH values (MD 0.47mIU/ml, 95% CI 0.01, 0.93) of men who were screened for infertility. It does not, however, influence the total sperm count (MD 13.16 106 cells, 95% CI -22.75, 49.07), the percentage of normal sperm morphology (-3.06%, 95% CI -6.25, 0.14), or LH (MD 0.65mIU/ml, 95% CI -0.84, 2.13 Supp. Fig. 2) and testosterone values (MD -0.18ng/ml, 95% CI -0.60, 0.24).

CONCLUSION

Current evidence suggests that the presence of DM seems to influence functional sperm characteristics. Firm results are, however, precluded due to the significant heterogeneity of the included studies. Future prospective studies will clarify whether the DM affects semen quality and IVF outcome.

Advanced glycation end products inhibit testosterone secretion by rat Leydig cells by inducing oxidative stress and endoplasmic reticulum stress

Diabetes severely impairs male reproduction. The present study assessed the effects and mechanisms of action of advanced glycation end products (AGEs), which play an important role in the development of diabetes complications, on testosterone secretion by rat Leydig cells. Primary rat Leydig cells were cultured and treated with AGEs (25, 50, 100 and 200 µg/ml). Testosterone production induced by human chorionic gonadotropin (hCG) was determined by ELISA. The mRNA and protein expression levels of steroidogenic acute regulatory protein (StAR), cholesterol side-chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD), which are involved in testosterone biosynthesis, were measured by reverse transcription-quantitative PCR and western blot analyssi, respectively. Reactive oxygen species (ROS) production in Leydig cells was measured using the dichlorofluorescein diacetate (DCFH-DA) probe. The expression levels of endoplasmic reticulum stress-related proteins [C/EBP homologous protein (CHOP) and glucose-regulated protein 78 (GRP78)] in the Leydig cells were measured by western blot analysis. We found that the AGEs markedly suppressed testosterone production by rat Leydig cells which was induced by hCG in a concentration-dependent manner compared with the control (P<0.01). The mRNA and protein expression levels of StAR, 3β-HSD and P450scc were downregulated by the AGEs in a dose-dependent manner compared with the control (P<0.01). The antioxidant agent, N-acetyl‑L‑cysteine (NAC), and the endoplasmic reticulum stress inhibitor, tauroursodeoxycholic acid (TUDCA), reversed the inhibitory effects of AGEs. In addition, the content of ROS in Leydig cells treated with AGEs increased significantly. The expression levels of CHOP and GRP78 were markedly upregulated by the AGEs in the Leydig cells. From these findings, it can be concluded that AGEs inhibit testosterone production by rat Leydig cells by inducing oxidative stress and endoplasmic reticulum stress.

Spermatogenesis in humans and its affecting factors

Spermatogenesis is an extraordinary complex process. The differentiation of spermatogonia into spermatozoa requires the participation of several cell types, hormones, paracrine factors, genes and epigenetic regulators. Recent researches in animals and humans have furthered our understanding of the male gamete differentiation, and led to clinical tools for the better management of male infertility. There is still much to be learned about this intricate process. In this review, the critical steps of human spermatogenesis are discussed together with its main affecting factors.