Physical Activity from Adolescence through Midlife and Associations with Obesity and Endometrial Cancer Risk

PURPOSE: This study sought to describe the physical activity-endometrial cancer association and potential mediation of this relationship by obesity in midlife. METHODS: Participants were 67,705 women (aged 50–71 years) enrolled in the NIH-AARP cohort who reported their historical leisure-time physical activity patterns starting at age 15–18 years. We identified five long-term physical activity patterns between adolescence and cohort entry (i.e., inactive, maintained-low, maintained-high, increasers, decreasers). We used Cox regression (Hazard ratio - HR [95% CI]) to assess the relationship between these patterns and midlife obesity and endometrial cancer, adjusting for covariates. Mediation analysis was used to decompose the physical activity patterns-endometrial cancer association to estimate the proportion of the physical activity-endometrial cancer association mediated by midlife obesity. RESULTS: During an average 12.3 years of follow-up 1,468 endometrial cancers occurred. Long-term physical activity patterns were inactive, maintained-low, maintained-high, increasers, and decreasers. Compared to long- term inactive women, women who maintained-high or increased activity levels had a 19–26% lower risk for endometrial cancer (maintained-high: HR = 0.81 [0.67, 0.98]; increasers: HR = 0.74 [0.61, 0.91]). They also had a 45–77% lower risk for obesity in midlife (e.g., maintained-high, BMI 30–39.9: HR = 0.50 [0.46, 0.55]; maintained- high, BMI 40+: HR = 0.32 [0.26, 0.39]). Obesity was a significant mediator and appeared to account for 55–63% of the physical activity-endometrial cancer associations observed. CONCLUSIONS: Both initiating and maintaining physical activity throughout adulthood can play a role in preventing obesity and in turn, lowering the risk for endometrial cancer.

Contribution of Common Genetic Variants to Familial Aggregation of Disease and Implications for Sequencing Studies

Despite genetics being accepted as the primary cause of familial aggregation for most diseases, it is still unclear whether afflicted families are likely to share a single highly penetrant rare variant, many minimally penetrant common variants, or a combination of the two types of variants. We therefore use recent estimates of SNP heritability and the liability threshold model to estimate the proportion of afflicted families likely to carry a rare, causal variant. We then show that Polygenic Risk Scores (PRS) may be useful for identifying families likely to carry such a rare variant and therefore for prioritizing families to include in sequencing studies with that aim. Specifically, we introduce a new statistic that estimates the proportion of individuals carrying causal rare variants based on the family structure, disease pattern, and PRS of genotyped individuals. Finally, we consider data from the MelaNostrum consortium and show that, despite an estimated PRS heritability of only 0.05 for melanoma, families carrying putative causal variants had a statistically significantly lower PRS, supporting the idea that PRS prioritization may be a useful future tool. However, it will be important to evaluate whether the presence of rare mendelian variants are generally associated with the proposed test statistic or lower PRS in future and larger studies.

Multiple members in a family can be diagnosed with the same disease. In such families, genetics may be a significant factor in disease risk. However, it remains unclear whether such familial aggregation of disease is likely due to a single highly penetrant rare variant (HPRV), many minimally penetrant common variants, or a combination of the two types of variants. We therefore use recent estimates of SNP heritability and the liability threshold model to estimate the proportion of afflicted families likely to carry a rare, causal variant. We then show that Polygenic Risk Scores (PRS) may be useful for identifying families likely to carry such a rare variant and introduce a related statistic that can be used to select families for sequencing studies trying to identify HPRV.

Ring-closing metathesis of olefinic peptides: design, synthesis, and structural characterization of macrocyclic helical peptides

Heptapeptides containing residues with terminal olefin-derivatized side chains (3 and 4) have been treated with ruthenium alkylidene 1 and undergone facile ring-closing olefin metathesis (RCM) to give 21- and 23-membered macrocyclic peptides (5 and 6). The primary structures of peptides 3 and 4 were based upon a previously studied heptapeptide (2), which was shown to adopt a predominantly 3(10)-helical conformation in CDCl(3) solution and an alpha-helical conformation in the solid state. Circular dichroism, IR, and solution-phase (1)H NMR studies strongly suggested that acyclic precursors 3 and 4 and the fully saturated macrocyclic products 7 and 8 also adopted helical conformations in apolar organic solvents. Single-crystal X-ray diffraction of cyclic peptide 8 showed it to exist as a right-handed 3(10)-helix up to the fifth residue. Solution-phase NMR structures of both acyclic peptide 4 and cyclic peptide 8 in CD(2)Cl(2) indicated that the acyclic diene assumes a loosely 3(10)-helical conformation, which is considerably rigidified upon macrocyclization. The relative ease of introducing carbon-carbon bonds into peptide secondary structures by RCM and the predicted metabolic stability of these bonds renders olefin metathesis an exceptional methodology for the synthesis of rigidified peptide architectures.