Fatty marrow, also known as bone marrow adipose tissue (BMAT), results from an increase in fat cells within the bone marrow. Several factors contribute to its development.
Conditions Associated with Increased Marrow Fat
Higher levels of marrow fat are observed in various conditions, often linked to reduced bone density. These include:
- Starvation: Severe caloric restriction can lead to increased fat storage in the bone marrow.
- Alcoholism: Chronic alcohol abuse is associated with higher marrow fat content.
- Spinal Cord Injury: Individuals with spinal cord injuries often exhibit increased fatty marrow.
- Prolonged Bed Rest: Extended periods of immobility can result in elevated marrow fat levels.
- Osteoporosis: This bone disease is frequently linked to increased marrow fat content.
- Aging: Natural aging processes contribute to an increase in BMAT.
- Type 1 Diabetes: Individuals with type 1 diabetes often show higher marrow fat levels.
- Cushing's Disease: This hormonal disorder is associated with increased BMAT.
- Estrogen Deficiency: Lack of estrogen can contribute to elevated marrow fat.
- Anorexia Nervosa: This eating disorder is linked to increased marrow fat content.
Mechanisms of Fatty Marrow Development
While the precise mechanisms aren't fully understood for all cases, caloric restriction and conditions impacting bone health significantly influence marrow fat accumulation. For instance, in growing mice, caloric restriction leads to both high marrow adiposity and low bone mass. The body may shift resources from bone formation to fat storage under these stressful conditions. Other conditions, such as hormonal imbalances, may directly impact the balance between fat cell development and bone cell activity within the marrow.
Focal Fatty Deposits
It's important to note that focal fatty deposits, also known as marrow islands or replacements, are distinct from generalized increases in marrow fat. These are well-defined areas of fat within the bone marrow, often seen in imaging studies. The exact causes of these focal deposits are not always clear but may be related to localized bone pathology.
