Increased bone mass in a mouse model with low fat mass.

Area of Science:

• Biomedical Science
• Metabolic Research
• Skeletal Biology

Background:

• Acute adipose tissue inflammation is crucial for healthy fat expansion and metabolic homeostasis.
• Inflammatory disorders are often linked to bone loss, prompting investigation into the adipose tissue-bone axis.
• Systemic inflammation can negatively impact bone density.

Purpose of the Study:

• To investigate the impact of impaired adipose tissue inflammation on bone mass.
• To test the hypothesis that reduced adipose tissue inflammation leads to lower bone mass due to increased systemic inflammation.
• To explore the relationship between fat mass, inflammation, and skeletal integrity.

Main Methods:

• Utilized transgenic mice (RID tg mice) overexpressing a receptor internalization and degradation (RID) complex to suppress inflammatory signaling in adipocytes.
• Administered a high-fat diet to induce weight and fat mass gain.
• Assessed body composition, systemic inflammation markers, bone mass (long bones, vertebrae), bone microarchitecture, biomechanical properties, bone formation/resorption markers, and bone marrow adiposity.

Main Results:

• RID tg mice exhibited reduced high-fat diet-induced weight and fat mass gain, alongside increased systemic inflammation.
• Contrary to the hypothesis, RID tg mice displayed significantly increased bone mass in long bones and vertebrae.
• Bone marrow adiposity was decreased in male RID tg mice, while bone formation and resorption markers remained unchanged.

Conclusions:

• Impaired adipose tissue inflammation, leading to reduced fat mass, is associated with increased bone mass.
• The study challenges the direct link between adipose tissue inflammation and bone loss, suggesting a more nuanced relationship.
• Reduced bone marrow adiposity may contribute to the observed increase in bone mass in the context of suppressed adipose tissue inflammation.