Title:
Restricting Specific Amino Acid Could Extend Lifespan and Improve Health in Mice
According to a widely held belief, "a calorie is a calorie," but scientific research suggests otherwise. In fact, it appears that consuming more of certain types of calories could potentially enhance overall health.
Dudley Lamming, a professor and metabolism researcher at the University of Wisconsin School of Medicine and Public Health, emphasizes the distinction, stating, "We prefer to say that a calorie is not just a calorie. Different elements of your diet possess intrinsic value and influence that extends beyond their role as a mere calorie. Our focus has been on one particular component that many individuals may be overconsuming."
Lamming and his colleagues are investigating the relationship between amino acids, the molecular components of proteins, and their impact on the process of healthy aging. Previous studies using data from UW–Madison’s Survey of the Health of Wisconsin revealed that individuals with higher body mass index measurements in Wisconsin tend to have higher consumption of isoleucine, an essential amino acid found in a variety of foods including eggs, dairy, soy protein, and various types of meat.
Lamming and colleagues from various disciplines at UW–Madison conducted a study to gain a deeper understanding of the health implications of different diets on genetically diverse mice. The mice were fed one of three diets: a balanced control diet, a modified version of the balanced diet with reduced levels of about 20 amino acids, or a diet designed to eliminate two-thirds of the isoleucine content. The mice, which were equivalent to 30-year-old individuals at the start of the study, were allowed to consume food ad libitum.
According to Lamming, "We observed rapid reduction in adiposity among the mice on the reduced isoleucine diet, resulting in a leaner body composition and decreased fat." On the other hand, mice on the low-amino-acid diet initially experienced a similar decrease in body fat, but eventually regained weight and fat.
Mice following the low-isoleucine diet experienced a longer lifespan, averaging 33% longer for males and 7% longer for females. Additionally, based on 26 health assessments, including measures of muscle strength, endurance, tail use, and hair loss, the low-isoleucine mice exhibited significantly better physical condition throughout their extended lives.
Lamming, whose research is funded by the National Institutes of Health, commented, "Previous studies have demonstrated an increase in lifespan with low-calorie and low-protein or low-amino-acid diets in very young mice. We began our study with older mice, and it is fascinating and promising to see that a dietary change could yield such significant improvements in lifespan and overall health, even when implemented later in life."
The mice following low-isoleucine diets consumed significantly more calories than their counterparts in the study, likely in an effort to compensate for the reduced isoleucine intake, according to Lamming. However, they also expended a higher amount of calories, thereby achieving and maintaining leaner body weights solely through metabolic adjustments, without increasing their physical activity.
Additionally, Lamming notes that the mice on the low-isoleucine diets maintained more stable blood sugar levels and exhibited reduced age-related prostate enlargement in male subjects. Furthermore, although cancer is the leading cause of death for the diverse strain of mice in the study, the low-isoleucine males were less prone to tumor development.
Dietary amino acids are associated with the mTOR gene, which appears to influence the aging process in mice and other animals, as well as a hormone that regulates the body's response to cold. Additionally, this gene has been considered a potential candidate for a diabetes drug in humans. However, the precise mechanism behind the significant benefits of low-isoleucine intake is not well understood. Dr. Lamming believes that the results of the new study may provide valuable insights for future research in understanding the underlying causes. He also suggests that the observed differences in benefit between male and female mice could offer important clues for uncovering this mechanism.
While the findings show promise, humans indeed require isoleucine for survival. Extracting a substantial amount of isoleucine from a non-preformulated diet poses significant challenges.
"We cannot simply transition everyone to a low-isoleucine diet," explains Lamming. "However, narrowing the observed benefits to a single amino acid brings us closer to comprehending the biological processes and potentially developing interventions for humans, such as an isoleucine-blocking medication.
The Survey of the Health of Wisconsin revealed variations in isoleucine intake among individuals, indicating that leaner participants generally consume lower levels of isoleucine in their diet. Additionally, data from Lamming’s lab indicates that overweight and obese Americans may be consuming an excessive amount of isoleucine compared to their dietary requirements.
