Published: Aug 28, 2013 | Updated: Aug 29, 2013
By Cole Petrochko, Staff Writer, MedPage Today

Bone strength — but not bone mineral density — was negatively associated with insulin resistance, researchers found.

Each doubling of insulin resistance scores was significantly associated with a 0.34 to 0.4 standard deviation decrease in composite scores of femoral neck strength relative to load (P<0.001), according toPreethi Srikanthan, MD, MS, of the University of California Los Angeles, and colleagues.

Insulin resistance scores showed no association with bone mineral density in the femoral neck, they wrote online in the Journal of Bone and Mineral Research.

The authors noted that bone fractures “represent a significant morbidity and cost burden,” which is likely to be exacerbated by an aging Baby Boomer population and the increased prevalence of diabetes, the latter of which has been associated with an increased fracture risk.

Research presented by Srikanthan and colleagues at the Endocrine Society meeting in June  showed an association between insulin resistance and weakened bones.

The researchers studied associations between insulin resistance and various markers for bone strength, including bone mineral density and composite scores for femoral neck strength in compression, bending, and impact through a population of 717 participants in the Biomarker Project for Midlife.

Participants provided blood and urine assays and bone scans, as well as a medical history, a physical examination, a medication review, a fasting blood draw, and dual X-ray absorptiometry of the lumbar spine and left hip. Insulin resistance was assessed through the homeostatic model of insulin resistance (HOMA-IR).

Diabetes was defined as having any of the following: HbA1c of greater than or equal to 6.5%, a fasting glucose of 126 mg/dL or greater, self-report of having diabetes, or use of diabetes medication. Prediabetes was defined as having HbA1c greater than 5.7% but lower than 6.5% or fasting glucose greater than 100 mg/dL but less than 126 mg/dL, no report of diabetes, and no use of diabetes medications.

Compression strength was a measure of bone mineral density by femoral neck width over weight, while bending strength was density by neck width squared over femoral neck axis length by weight, and impact strength index was a function of density by neck width by axis length over height by weight.

Age, sex, and ethnicity were self-reported. Age was categorized as younger than 50, 50 to 59, and 60 and older among men, while women were categorized as pre-menopausal, early peri-menopausal, late peri-menopausal, post-menopausal without hormone therapy, and post-menopausal with hormone therapy.

Mean patient age was 56.8 years. Some 38% of men were 60 or older, while 59% of women were peri-menopausal or post-menopausal and not receiving hormone therapy.

Most patients had pre-diabetes (54.4%), while nearly 20% had diabetes (19.7%).

Median insulin resistance score was 2.47, with an interquartile range of 1.47 to 4.40. Median fasting insulin was 10 uIU/mL, median fasting glucose was 96 mg/dL, and median HbA1c was 5.86%.

Bone mineral density was not associated with insulin resistance, but there was a significant association between insulin resistance and the three measures of bone strength.

Gender did not modify these associations, nor did pre- or diabetes status.

Higher insulin levels — but not glucose levels — were independently associated with lower bone strength. Each doubling of fasting insulin was associated with a 0.10 to 0.18 standard deviation decrease in each of the bone strength measures.

The authors cautioned that their study was limited by a cross-sectional design, macroscopic measure of bones via x-ray, and a first-time use of a Lunar machine to measure strength indices, versus Hologic machine scans in prior studies.

Full Story:  http://www.medpagetoday.com/Endocrinology/Diabetes/41234