Longevity Briefs: How Fat Tissue Drives Ageing, And What You Can Do About It

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

Fat tissue (specifically white adipose tissue) acts as a place to store excess calories, but it is also far more than that. Fat cells release many signalling molecules that can affect the function of other tissues and organs, as well as the immune system. Brown fat on the other hand (also known as thermogenic adipose tissue) exists not to store excess calories, but to burn them in order to generate heat. During ageing, the distribution and function of different types of fat tissue changes, and it increasingly seems as though fat tissue plays a key role in the ageing process. This study summarises what we know so far, as well as some strategies we might use to slow ageing by targeting fat tissue.

The discovery:

The article begins by summarising how different types of fat tissue change with age. 

• Subcutaneous adipose tissue is the adipose tissue that lies beneath the skin. It’s specialised for storing and releasing energy, but also releases hormones that help regulate weight and blood sugar. Subcutaneous adipose tissue declines with age, which means other less suitable tissues increasingly need to metabolise fats.
• Visceral adipose tissue is located mainly around the organs in the abdomen, and seems to harbour protective immune cells. However, as we age, visceral adipose tissue releases inflammatory signals that contribute to the dysfunction of the immune system, which also becomes more inflammatory. This, coupled with the growth of visceral fat that occurs in both ageing and obesity, seems to contribute to the development of many age-related diseases including type II diabetes and cardiovascular disease.
• Brown and beige adipose tissue consume calories in order to generate heat, but both of these tissue types decline with age. This contributes to a reduction in overall calorie expenditure and a reduced ability to maintain body temperature.
• Bone marrow adipose tissue is, as its name suggests, located in the bone marrow. It is less well studied than other types of fat tissue, but it appears to expand with age, which might play a role in the loss of bone strength that occurs during ageing. It may also contribute to changes in white blood cell production in the bone marrow, which results in an increase in inflammatory cell types and the weakening of the immune system overall.

The researchers also note that many gene expression changes occur in ageing adipose tissue as well as the immune cells that live there. These changes involve increased inflammation and increased synthesis and storage of lipids (fat). Individual fat cells grow larger (hypertrophy), while the ability to produce new fat cells is diminished, and inflammatory immune cells are attracted to the fat tissue. Animal models suggest that these changes are caused by ageing, not the other way around. For example, when visceral fat from old mice is transplanted into young mice, the young mice suffer from metabolic dysfunction.

The implications:

It seems that changes in our fat tissues play a significant role in the ageing process, but what can we do about it? Maintaining a healthy weight is one obvious strategy, as obesity accelerates the age-related changes to adipose tissue. Various forms of fasting and calorie restriction may be particularly valuable. These diets seem to be uniquely effective in promoting the breakdown of lipids within fat tissue, altering metabolic activity and preventing insulin resistance and diabetes, with very beneficial effects on adipose tissue ageing. However, we need much more research to study their long-term effects on human health. Though far less studied, there are also suggestions that deliberate cold exposure may be beneficial, since cold exposure promotes the maintenance and growth of brown adipose tissue.

Beyond lifestyle changes, several drugs used in diabetes have been found to improve adipose tissue function in mice in numerous ways, such as by reducing visceral adipose tissue and boosting the division of adipose tissue stem cells. We may eventually be able to use this knowledge to develop drugs that slow adipose tissue ageing and consequently help prevent many age-related diseases.