The impact of vegetarian diet on sperm quality, sex hormone levels and fertility: a systematic review and meta-analysis.

BACKGROUND: An increasing number of people have adhered to a vegetarian diet for several years. Nowadays, the favourable effect of this dietary pattern on metabolic diseases is well established, but its impact on fertility and reproductive health as a serious health concern is not clear yet. Therefore, we aim to summarise existing evidence regarding the possible association between a vegetarian diet and fertility as measured by key indicators such as sperm quality and sex hormone levels. METHODS: We systematically searched online databases, including PubMed, ISI, Scopus and Google Scholar, up to 1 December 2022 using relevant keywords. We included observational studies that compared semen quality, sex hormone levels and infertility in people who adhered to a vegetarian diet versus an omnivore diet. Heterogeneity between studies was assessed using I2 and Q tests. Standardised mean differences (SMD) using a random/fixed model were calculated to assess outcomes between vegetarians and omnivores in included articles. RESULTS: Finally, out of 972 documents that were retrieved, 20 articles met our inclusion criteria, and 16 were eligible for quantitative synthesis. Results of meta-analyses showed that there were no significant differences between vegetarians and omnivores in terms of semen quality parameters, including total sperm count, total and progressive sperm motility, sperm morphology and sperm concentration. Seven studies on female sex hormone profiles were eligible for meta-analysis. The only significant difference was the lower level of plasma oestrone in vegetarians (pooled SMD: -0.56; 95% confidence interval [CI]: -1.08, -0.05; p-value = 0.03) compared to omnivores. Furthermore, our meta-analysis revealed significantly higher sex-hormone-binding globulin levels in vegetarian men than in omnivores (pooled SMD: 0.52; 95% CI: 0.18, 0.86; p-value = 0.002). CONCLUSION: Despite the numerous health benefits of a vegetarian diet, our review suggested that there were no conclusive positive or negative associations between vegetarian diet and semen quality, sex hormone levels and infertility. Further studies are recommended to better understand vegetarian dietary pattern effect on infertility and reproductive health.

The role of lncRNA CERS6-AS1 in cancer and its molecular mechanisms: A systematic review and meta-analysis.

BACKGROUND: LncRNAs have the potential to play a regulatory role in different processes of cancer development and progression. We conducted a systematic review and meta-analysis of evidence on the clinical significance and prognostic value of lncRNA CERS6-AS1 in cancer. METHODS: This systematic review was conducted following PRISMA guidelines. Medline and Embase databases were searched using the relevant key terms covering lncRNA CERS6-AS1 and cancer. We pooled the estimated effect sizes and their 95 % confidence interval (CI) using random-effects models in STATA 16.0 (StataCorp, College Station, TX, USA). RESULTS: Eleven articles on pancreatic, colorectal, gastric, papillary thyroid, breast, and hepatocellular cancers fulfilled our eligibility criteria. Studies consistently found that lncRNA CERS6-AS1 expression is upregulated in all assessed cancers. Based on our meta-analysis, its aberrant expression was directly associated with unfavorable clinical outcomes, including higher stage (pooled Odds ratios (95 % CI): 3.15 (2.01-4.93; I2 = 0.0 %), tumor size (1.97 (1.27-3.05; I2 = 37.8 %), lymph node metastasis (6.48 (4.01-10.45; I2 = 0.40 %), and poor survival (Pooled log-rank test P-value < 0.001) in patients. Regarding potential mechanisms, functional studies revealed that LncRNA CERS6-AS1 is involved in cancer growth mainly by sponging miRNAs and regulating their downstream targets. CONCLUSION: Available evidence suggests that LncRNA CERS6-AS1 is upregulated in different cancers and has an oncogenic role. LncRNA CERS6-AS1 expression level might predict cancer prognosis, highlighting its potential application as a prognostic biomarker for cancer.