Obesity may be risk factor for osteoporosis
medwireNews: Levels of ectopic and serum lipids positively correlate with levels of fat in bone marrow in young obese men and women, US researchers have discovered.
The finding is significant because bone marrow fat is known to be a risk factor for osteoporosis, meaning that obesity – once thought to protect against bone loss – may in fact have a detrimental impact on bone.
A team led by Miriam Bredella (Harvard Medical School, Boston, Massachusetts) studied 106 healthy individuals aged 19–45 years with body mass indices (BMIs) ranging from 18.1 to 48.8 kg/m2.
The participants underwent proton magnetic resonance spectroscopy for quantification of bone marrow fat content, intramyocellular lipids (IMCL), and intrahepatic lipids (IHL), as well as standard blood tests and assessment of exercise levels.
Reporting their findings in Radiology, Bredella et al reveal that obese participants had higher mean serum lipid levels, lower high-density lipoprotein (HDL) cholesterol, and higher IMCL, total muscle lipid content, IHL, and bone marrow fat compared with non-obese individuals.
The team identified a positive correlation between IHL levels and bone marrow fat, which remained significant after controlling for BMI, age, insulin resistance, and exercise status. There was also a significant positive correlation between IMCL and bone marrow fat.
Additional positive correlations were found between muscle lipid content and bone marrow fat, between IMCL and 2-hour glucose levels, and between serum triglyceride levels and bone marrow fat, while there was a negative correlation between HDL cholesterol levels and bone marrow fat.
In a multivariate analysis, serum triglycerides were the only significant predictor of bone marrow fat, explaining 10% of the variability in this parameter.
“Accumulation of bone marrow fat has traditionally been thought of as a space filler; however, findings in recent studies have suggested an important link between bone and fat,” the team remarks. “In our study, obese subjects had higher bone marrow fat content compared with normal-weight subjects, confirming the role of obesity as a regulator of stem cell differentiation.”
They conclude: “Because bone marrow fat is known to be inversely related to [bone mineral density], these results support the notion that ectopic and serum lipid levels are influenced by the same additional factors as bone marrow or may exert negative effects on bone.”
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Joanna Lyford, Senior medwireNews Reporter