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Increasing insulin resistance linked to low lean body mass in aging men

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October 11, 2018

Compared with men who experienced stable or relatively low increase in insulin resistance between young adulthood and middle age, those whose insulin resistance increased during that period had lower lean body mass, according to findings published in the Journal of Diabetes and its Complications.

The association was not observed for women, according to researchers.

“Significant loss of lean mass and strength, termed sarcopenia, is associated with adverse consequences, such as falls, hospitalization and mortality in geriatric populations,” Victor W. Zhong, PhD, postdoctoral fellow, of the department of preventive medicine at Northwestern University Feinberg School of Medicine, told Endocrine Today. “There is no cure for age- and disease-related lean mass loss. Identifying factors associated with lean mass loss and preservation in early and middle adulthood may play a critical role in improving quality of life and reducing health and economic burden in later life.”

Zhong and colleagues assessed data from the CARDIA fitness study on 925 men and 1,193 women without diabetes who were aged 18 to 30 years in 1985-1986. Physical examinations and laboratory tests were conducted at baseline and at 2, 5, 7, 10, 15 and 20 years, with DXA assessment at year 20 to determine bone mineral content, fat mass, nonfat bone mass and appendicular lean mass. Fasting serum blood glucose and insulin levels were recorded at baseline and 7, 10, 15 and 20 years, with insulin resistance estimated by homeostasis model assessment. A diet questionnaire and an exercise test to determine cardiorespiratory fitness were conducted at baseline and 7 and 20 years.

At year 20, researchers divided participants into sex-specific quartiles based on appendicular lean mass divided by BMI — 0.89, 1.03, 1.11 and 1.26 for quartiles 1 to 4, respectively, for men, and 0.59, 0.69, 0.77 and 0.89 for women.

Researchers also categorized participants into three groups based on amount of insulin resistance increase from baseline: low-stable (31.1% of men; 46.8% of women), medium-increase (54.8% of men; 40% of women) and high-increase (14.1% of men; 13.2% of women).

Researchers identified a link between insulin resistance trajectory and appendicular lean mass in men, but not in women. For men, the difference in appendicular lean mass divided by BMI between the low-stable insulin resistance group and the medium-increase group was –0.041 (95% CI, –0.06 to –0.022) and –0.114 (95% CI, –0.141 to –0.086) between the low-stable and the high-increase group. Women had differences of –0.052 (95% CI, –0.065 to –0.039) and –0.043 (95% CI, –0.063 to –0.023) between the low-stable and the medium-increase and high increase groups, respectively.

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“The difference in body composition, fat distribution (on average, women have more peripheral fat and men have more visceral fat), sex hormones and adipokines may be relevant to this noted sex difference,” the researchers wrote.

Adjusting for cardiorespiratory fitness, for men the difference in appendicular lean mass divided by BMI between the low-stable insulin resistance group and the medium-increase group was –0.022 (95% CI, –0.04 to –0.004) and –0.061 (95% CI, –0.089 to –0.034) between the low-stable and the high-increase groups. Women had differences of –0.026 (95% CI, –0.038 to –0.014) and –0.007 (95% CI, –0.026 to 0.012) between the low-stable and the medium-increase and high increase groups, respectively. The researchers noted that their findings maintained an association between increasing insulin resistance and lower appendicular lean mass only in adults without obesity.

“Our study shows that adjusting for cardiorespiratory fitness considerably attenuated the association between insulin resistance appendicular lean mass in men and eliminated the association in women,” Zhong said. “It remains unclear why the association only persists in nonobese individuals. For obese people, losing fat mass may be more important than specifically improving insulin sensitivity, although these two are not totally independent.” – by Phil Neuffer

For more information:

Victor W. Zhong, PhD , can be reached at wenze.zhong@northwestern.edu.

Disclosures: Zhong reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.