Colorectal cancer: Two body types linked to higher risk

They divided participants in the cohort into four groups based on body shape as defined by height and fat distribution. They use data collected on body mass index (a calculation used to infer obesity), height, weight, waist-to-hip ratio, and waist-to-hip circumference to determine which group an individual fits into.

The four groups are:

• PC1 is generally obese
• Higher PC2, but more fat mass distribution
• PC3 high, central obesity
• PC4 had lower height, weight, and BMI, but lower hip and waist circumferences.

They found that within this group, individuals in the PC1 group had a 10% higher risk of colorectal cancer, while individuals in the PC3 group had a 12% higher risk of colorectal cancer, with women having an 18% higher risk.

The other two groups had a slight but not significant increase in cancer risk.

Dr. Heinz Freisling, study author and scientist at the Nutrition and Metabolism Branch of the International Agency for Research on Cancer in Lyon, France, said:

We believe that the most commonly used measures of body fat, such as body mass index or body fat distribution (e.g., waist circumference), underestimate cancer risk due to unhealthy weight. While these measures are useful, they lump individuals with similar body mass indexes but different body types into the same category, and we know that people with the same body mass index can have very different cancer risks.

Their findings confirmed that fat accumulation in the middle of the body or around the abdomen is associated with a higher risk of colorectal cancer.

Further analysis of the cohort found that people of Caucasian, African, Asian and/or Chinese ancestry were at increased risk of developing colorectal cancer.

There may be limited possibilities for how body measurements such as weight and height combine to form body shape, which is common across ancestral groups. Freisling said it also suggests that biological processes that determine body shape are evolutionarily conserved because they are key molecular pathways for individual survival.

A genome-wide association study was then conducted using genomic data from 460,198 UK Biobank participants. The researchers found 3,414 genetic variants associated with body size. The researchers found that these genes were differentially expressed in different tissues in four different body categories the researchers created.

Those genetic variants associated with PC1 body size had increased expression in brain and pituitary tissue, while those associated with PC3 body size had increased gene expression in adipose tissue, breasts, nerves, vascular tissue and female reproductive organs.

The results of our genetic analysis at the tissue level suggest several mechanisms that may reflect different obesity subtypes. These are disorders of blood sugar levels and metabolism, the process of converting food into energy, but also increase inflammation and the production of hormones (called adipokines) in fat tissue. One well-known adipokine is leptin, which regulates appetite but may be directly linked to the development of cancer. For example, Freisling explains, leptin increases the rate at which cells divide.

Leonard Nunney, a biology professor and evolutionary biologist at the University of California, San Francisco, who was not involved in the study, said there is strong evidence that height has a general effect on cancer risk. Medical News Today.

Previous analysis he conducted showed that for every 4 inches of height increase in humans, cancer risk increases by 10 percent because taller people have more cells in their bodies because of their larger body size.

The study’s authors suggested in the discussion that the role of height in cancer risk has been exaggerated in previous studies that did not consider the ratio of waist circumference to height and, therefore, central adiposity.

Calculating lean body mass will help test the cell number hypothesis, which is thought to support the link between height and increased cancer risk, Nani said.

In this study, the authors used height (not transformed in any way) to define their PC, an approach that may underestimate the role of height in CRC because height squared (if we assume BMI allometry) is a function of cancer risk Relevant variables, he said.

Does the risk of colorectal cancer increase with height or fat content?

Nani also explained that he is not aware of any data on the relative size or amount of colorectal tissue in people related to height, which makes it difficult to understand whether these findings of increased colorectal cancer risk are due to increased amounts of colorectal cancer. cells, or due to increased obesity, or both.

He adds that the amount of tissue may of course be affected not only by height but also by body size.

This publication is a useful step toward understanding the relative importance of cell number and obesity (and possibly obesity type) in colorectal cancer incidence. Height squared is a very imperfect indicator of lean body mass (we assume it is proportional to cell number), and studies that allow us to add body shape to the estimate could help us understand this cell number effect more fully, Na Ni said.

Next, the research team behind this latest paper hope to identify the genes responsible for the relationship between body shape and gene expression to help explain the mechanisms that underpin their latest findings.

Freisling said the next step will be to try to determine how these body shapes affect the makeup of proteins in our bodies, which will help better understand the connection between body shape and cancer development.