Increasing evidence suggests that a history of diabetes mellitus (DM) may be associated with an increased risk of colorectal cancer (CRC). To provide a quantitative assessment of the association between DM and risk of CRC, We evaluated the relation between DM and incidence and mortality of CRC in a systematic review of cohort studies. Full publications of cohort studies were identified in MEDLINE, EMBASE and Science Citation Index Expanded, through February 28, 2011. Summary relative risks (SRRs) with 95% confidence intervals (CIs) were summarized using a random-effects model. Between-study heterogeneity was assessed using the Cochran's Q and I2 statistics. A total of 41 cohort studies (35 articles) were included in this systematic review. Combining 30 cohort studies which presented results on diabetes and CRC incidence, diabetes was associated with an increased incidence of CRC (SRRs 1.27, 95% CI: 1.21-1.34), with evident heterogeneity among studies (P=0.002, I2=48.4%). Subgroup analysis and meta-regression analysis by controlling the confounders showed that the increased incidence of CRC was independent of geographic locations, sex, family history of colorectal cancer, smoking, physical activity and body mass index. Diabetes was also positively associated with CRC mortality (SRR 1.20, 95% CI: 1.03-1.40), with evidence of heterogeneity between studies (P<0.001, I2=81.4%). Results from this systematic review support that compared to non-diabetic individuals, diabetic individuals have an increased risk of CRC.

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Nickel is associated with reproductive toxicity. However, the reproductive toxicity of nickel nanoparticles (Ni NPs) is unclear. Our goal was to determine the association between nickel nanoparticle exposure and reproductive toxicity. According to the one-generation reproductive toxicity standard, rats were exposed to nickel nanoparticles by gavage and we selected indicators including sex hormone levels, sperm motility, histopathology, and reproductive outcome etc. Experimental results showed nickel nanoparticles increased follicle stimulating hormone (FSH) and luteinizing hormone (LH), and lowered etradiol (E2) serum levels at a dose of 15 and 45 mg/kg in female rats. Ovarian lymphocytosis, vascular dilatation and congestion, inflammatory cell infiltration, and increase in apoptotic cells were found in ovary tissues in exposure groups. For male rats, the weights decreased gradually, the ratio of epididymis weight over body weight increased, the motility of rat sperm changed, and the levels of FSH and testosterone (T) diminished. Pathological results showed the shedding of epithelial cells of raw seminiferous tubule, disordered arrangement of cells in the tube, and the appearance of cell apoptosis and death in the exposure group. At the same time, Ni NPs resulted in a change of the reproductive index and the offspring development of rats. Further research is needed to elucidate exposure to human populations and mechanism of actions.