Lack of association between single polymorphic variants of the mitochondrial nicotinamide adenine dinucleotide dehydrogenase 3, and 4L (MT-ND3 and MT-ND4L) and male infertility

Integrating Metabolomics and Transcriptomics to Analyse and Reveal the Regulatory Mechanisms of Mung Bean Polyphenols on Intestinal Cell Damage Under Different Heat Stress Temperatures

BACKGROUND/OBJECTIVES

Polyphenols represent a new strategy of dietary intervention for heat stress regulation.

METHODS

The metabolic and genetic effects of three heat stress-regulated mung bean polyphenols on mouse small intestinal epithelial Mode-k cells were investigated by metabolomics-transcriptomics correlation analysis at different heat stress levels.

RESULTS

Lipid metabolism, energy metabolism, and nervous system pathways were the key metabolic regulatory pathways. Under the heat stresses of 39 °C, 41 °C, and 43 °C, the key pathways regulated by mung bean polyphenols on intestinal epithelial Mode-k cells were choline metabolism, pyrimidine metabolism, and the retrograde endorphin signalling pathway in cancer, respectively. FoxO, Rap1, and PI3K-Akt signalling pathways were the key environmental regulatory signalling pathways. Mung bean polyphenols can alleviate heat stress-induced cells at 39 °C by inhibiting cell apoptosis and promoting lipid and amino acid accumulation. Mung bean polyphenols can alleviate the threat of cell death caused by heat stress at 41 °C by regulating heat shock proteins, inhibiting mitochondrial function and some nerve disease-related genes. The threat of cell death by heat stress at 43 °C can be alleviated by regulating nerve-related genes.

CONCLUSIONS

This study confirmed that mung bean polyphenols can regulate heat stress. The results provide a reference for analysing the mechanism of dietary polyphenol regulating heat stress.

Sperm-Borne Mitochondrial Activity Influenced by Season and Age of Holstein Bulls

Sperm mitochondria are vital organelles for energy production and pre- and post-fertilization sperm functions. The potential influence of the age of the bull and season on the sperm-borne mitochondrial copy number and the transcription activity has not yet been investigated. Therefore, the expression patterns of all protein-coding mitochondrial genes were identified throughout the year along with mitochondrial copy numbers in young and old bulls' spermatozoa. For that, high-quality semen samples (n = 32) with more than 80% quality for the morphological parameters, from young (n = 4, aged 18-24 months old) and old (n = 4, aged 40-54 months old) Holstein bulls, were collected during the four seasons (n = 4 samples each animal/season). The DNA and RNA were isolated from sperm cells and subjected to the DNA copy number and expression analyses using qPCR. Furthermore, an in silico analysis using gene ontology online tools for the abundantly expressed genes was utilized. The data were statistically analyzed using Prism10 software. There was a significant reduction in the mitochondria copy number of young bulls' spermatozoa compared to their old counterparts during the summer (29 ± 3 vs. 51 ± 6, p < 0.001) and winter (27 ± 3 vs. 43 ± 7, p < 0.01) seasons. However, sperm-borne mitochondrial protein-coding genes were transcriptionally higher in young bulls throughout the year. Within the same group of bulls, unlike the old bulls, there was a significant (p < 0.05) induction in the transcription activity accompanied by a significant (p < 0.05) reduction in the mitochondrial copy numbers in the summer (29 ± 3) and winter (27 ± 3) compared to the spring (42 ± 9) and autumn (36 ± 5) seasons in young bulls. Additionally, the pathway enrichment of the top six expressed genes differed between age groups and seasons. In conclusion, under the same quality of semen, the early stages of age are associated with mitochondrial biogenesis and transcription activity dysregulation in a season-dependent manner.

A two-sample mendelian randomization analysis investigates associations between gut microbiota and infertility

Observational studies have provided evidence of a correlation between alterations in gut microbiota composition and infertility. However, concrete proof supporting the causal relationship is still lacking. We performed a Mendelian randomization study to assess whether genetically gut microbiota composition influences the risk of infertility. The genetic data pertaining to gut microbiota were obtained from a genome-wide association study meta-analysis, which was conducted among 24 cohorts (18,340 participants) from the international MiBioGen consortium. By the primary method of assessing causality, we have identified 2 family taxa, 2 genus taxa, and 1 order taxa that were linked to a low risk of male infertility, while 1 genus taxa were associated with a high risk of male infertility. Furthermore, we have discovered 6 genus taxa, 1 phylum taxa, 1 class taxa, 1 order taxa, and 1 family taxa that were associated with a low risk of female infertility, while 1 genus taxa were linked to a high risk of female infertility. This study successfully confirmed that there was a causal link between gut microbiota and infertility. The identification of these specific strains through genetic prediction offers a valuable insight for early diagnosis, prevention, and treatment of infertility.

Association between mitochondrial DNA genotype and sperm motility in humans

The relationship between genetic alterations in mitochondrial DNA (mtDNA) and progressive motility (PR) and rapid progressive motility (grade A) of ejaculated human spermatozoa remains unclear. In this study, we explored the association between human mtDNA genotype and sperm PR and grade A by analyzing mtDNA copy number, loci, haplogroup, rearrangement, deletions, and duplications and sperm motility parameters. Human sperm mtDNA copy number, loci and haplogroups were not associated with human sperm motility PR or A grade. However, the cumulative frequency of human sperm mtDNA rearrangements (including deletions and duplications) in participants with high PR and grade A ratio was higher than in participants with low PR and grade A ratio. Additional studies are needed to understand the relationship between mtDNA genotypes, including deletions and duplications, and human sperm motility.

A lack of a definite correlation between male sub-fertility and single nucleotide polymorphisms in sperm mitochondrial genes MT-CO3, MT-ATP6 and MT-ATP8

BACKGROUND

An inability of a man to conceive a potentially fertile woman after a year of unprotected intercourse is defined as male infertility. It is reported that 30-40% of males in their reproductive years have abnormalities in sperm production, either qualitatively or quantitatively, or both. However, genetic factors result in up to 15% of male infertility cases. The present study aimed to analyze the possible correlations between sub-fertility and polymorphisms in sperm mitochondrial CO3, ATP6 and ATP8 genes in sub-fertile men.

METHODS AND RESULTS

For 67 sub-fertile and 44 fertile male samples, Sanger sequencing of selected mitochondrial DNA genes was done. A total of twelve SNPs in the MT-CO3 gene: rs2248727, rs7520428, rs3134801, rs9743, rs28358272, rs2853824, rs2856985, rs2854139, rs41347846, rs28380140, rs3902407, and 28,411,821, fourteen SNPs in the MT-ATP6: rs2001031, rs2000975, rs2298011, rs7520428, rs9645429, rs112660509, rs6650105, rs6594033, rs6594034, rs6594035, rs3020563, rs28358887, rs2096044, and rs9283154, and ten SNPs in the MT-ATP8: rs9285835, rs9285836, rs9283154, rs8179289, rs121434446, rs1116906, rs2153588, rs1116905, rs1116907, and rs3020563 were detected in the case and control groups at different nucleotide positions. Only the rs7520428 in the MT-CO3 and MT-ATP6 showed a statistically significant difference between sub-fertile and fertile groups in the genotype's and allele's frequency test (P < 0.0001 for both).

CONCLUSION

The results of our study suggest that male sub-fertility is linked with rs7520428 SNP in MT-CO3 and MT-ATP6. The studied polymorphic variations in the MT-ATP8 gene, on the contrary, did not reveal any significant association with male sub-fertility.

A Systematic Review of the Impact of Mitochondrial Variations on Male Infertility

According to current estimates, infertility affects one in four couples trying to conceive. Primary or secondary infertility can be due either to both partners or only to the man or the woman. Up to 15% of infertility cases in men can be attributed to genetic factors that can lead to irreversible partial or complete spermatogenic arrest. The increased use of assisted reproductive technology (ART) has provided not only insights into the causes of male infertility but also afforded a diagnostic tool to detect and manage this condition among couples. Genes control a variety of physiological attributes, such as the hypothalamic–pituitary–gonadal axis, development, and germ cell differentiation. In the era of ART, it is important to understand the genetic basis of infertility so as to provide the most tailored therapy and counseling to couples. Genetic factors involved in male infertility can be chromosome abnormalities or single-gene disorders, mitochondrial DNA (mtDNA) mutations, Y-chromosome deletions, multifactorial disorders, imprinting disorders, or endocrine disorders of genetic origin. In this review, we discuss the role of mitochondria and the mitochondrial genome as an indicator of sperm quality and fertility.