Diabetics with severe insulin resistance exhibit poor physical fitness

01 Apr 2022
Diabetics with severe insulin resistance exhibit poor physical fitness

Individuals with severe insulin-resistant diabetes (SIRD) appear to have the lowest physical fitness compared with other diabetes subgroups despite similar endothelial function across all cohorts, a study has shown. Moreover, those with severe autoimmune diabetes (SAID) have the lowest cardiovascular risk within the first year following diagnosis relative to other clusters.

“Physical inactivity promotes insulin resistance and increases the risk of diabetes and cardiovascular disease,” the researchers said. “Recently introduced clustering based on simple clinical measures identified diabetes subgroups with different risks of diabetes-related comorbidities and complications.”

This study sought to determine the differences in physical fitness and cardiovascular risk between diabetes clusters and a glucose-tolerant control group (CON). The researchers assessed 746 participants with recent-onset diabetes (diabetes duration of <12 months, aged 18‒69 years) and 74 CONs of the German Diabetes Study (GDS), a prospective longitudinal cohort study.

Outcomes measured were as follows: physical fitness (VO2max from spiroerogometry), endothelial function (flow- and nitroglycerin-mediated dilation), and cardiovascular risk scores (Framingham Risk Scores for Coronary Heart Disease [FRS-CHD] and Atherosclerotic CardioVascular Disease [ASCVD] risk score). [J Clin Endocrinol Metab 2022;107:1127-1139]

After adjusting for age, sex, and body mass index, the SIRD subgroup had lower VO2max than CONs, SAID (p<0.001 for both), and mild-age-related diabetes (MARD) subgroups (p<0.01), but had comparable physical fitness compared to the severe insulin-deficient diabetes (SIDD; p=0.98) and moderate obesity-related diabetes (MOD) clusters (p=0.07).

In addition, endothelial function was similar across all subgroups, but SAID showed lower FRS-CHD and ASCVD than SIRD, MOD, and MARD (p<0.001 for all).

Peak power

Of note, the insulin-resistant SIRD subgroup demonstrated not only lowest VO2max but peak power at ventilatory threshold and peak power output as well.

“These findings confirm the close association between VO2max and insulin sensitivity as well as between cardiorespiratory fitness and muscular strength with the risk of type 2 diabetes,” the researchers said. [Diabetologia 2019;62:1129-1142; N Engl J Med 1996;335:1357-1362; Diabetologia 2016;59:2203-2207]

In previous studies, results showed an association between cardiovascular autonomic neuropathy and newly diagnosed diabetes, albeit more prominently with type 2 vs type 1 diabetes. Cardiovascular autonomic neuropathy also correlated with insulin resistance and hyperglycaemia. [Diabetes 2020;69:1011-1019]

“The present study supports this finding in that oxygen pulse was reduced in all nonautoimmune diabetes subgroups, classically summarized as type 2 diabetes, but not in SAID when compared to the CON group after adjustment for age, sex, and BMI,” the researchers said.

“Thus, these findings may help to explain the slight differences in maximal heart rate (HR) observed between subgroups before adjustment for age, sex, and body mass index suggesting impaired compensatory HR elevation during spiroergometry, specifically in SIRD,” they added.

The current study was limited by the small number of individuals with SIDD and SIRD. The researchers also did not assess other mediating factors, such as specific dietary patterns. Moreover, they recorded resting HR and systolic blood pressure before but did not continuously monitor during flow-mediated dilation measurements.