Genetic Predisposition to Obesity Linked to Absence of Certain Blood Groups

While lifestyle choices are often associated with obesity, recent research underscores the significant role genetics can play.

A study published earlier this year highlighted how children can inherit obesity from their parents. Another study in February 2023 identified 21 genes associated with Alzheimer’s disease that may also influence obesity.

Now, researchers from the University of Exeter Medical School in England have discovered a genetic variant that links the absence of a specific blood group to a predisposition for obesity or overweight.

The Role of the SMIM1 Gene

In their study, scientists analyzed genetic data from approximately 500,000 individuals in the UK Biobank and four other cohorts to identify those with a genetic variant that suppresses the SMIM1 gene.

“SMIM1 encodes a 68-amino acid protein that protrudes from the membrane of red blood cells,” explained Dr. Mattia Frontini, Associate Professor of Cell Biology at the University of Exeter Medical School and lead author of the study. “This gene, part of a family encoding short transmembrane proteins, was initially discovered due to its association with the Vel blood group, which is difficult to type using traditional methods.”

Impact on Weight and Metabolism

Frontini and his team found that individuals lacking functional copies of the SMIM1 gene were more likely to be overweight.

“People with two defective copies of the SMIM1 gene—approximately 1 in 5,000 individuals—showed higher body weight, altered blood lipid levels, reduced energy expenditure despite similar caloric intake, leading to increased fat storage,” Frontini explained.

The researchers also observed other obesity-related indicators in these individuals, such as elevated blood lipid levels, signs of dysfunctional adipose tissue, higher liver enzyme levels, and lower thyroid hormone levels.

Insights into Thyroid Function and Obesity

“Our findings suggest that SMIM1 affects the hypothalamus-pituitary-thyroid axis, influencing hormone production,” Frontini elaborated. “The absence of SMIM1 leads to mild hypothyroidism, reducing resting energy expenditure. This results in more efficient energy storage as fat, which affects nearly 2% of the UK population receiving thyroid supplementation, a cost-effective treatment.”

Future Directions in Genetic Research

Commenting on the study, Dr. Hans J. Schmidt, Director of the Center for Weight Loss and Metabolic Health at Hackensack University Medical Center, emphasized the genetic underpinnings of obesity.

“While studying genes coding for specific blood groups, researchers incidentally identified an association with obesity,” Schmidt noted. “Further research should explore other genetic traits to better understand obesity, both in terms of excess weight and resistance to weight gain.”

Conclusion: Genetic and Multifactorial Nature of Obesity

Dr. Mir Ali, Medical Director of MemorialCare Surgical Weight Loss Center, highlighted the complex interplay of genetics and lifestyle in obesity.

“Genetics play a significant role in obesity, which is multifactorial,” Ali explained. “Understanding the genetic basis of obesity is crucial for developing effective treatments.”

In summary, while lifestyle factors remain pivotal in obesity prevention, advancements in genetic research like the discovery of the SMIM1 gene variant offer new insights into understanding and managing obesity.

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