Several diseases including microbial infection, rheumatoid arthritis, multiple sclerosis, and cancer have been linked to fatigue. They all have in common an upregulation of cytokines, including interleukin (IL)-1β and tumor necrosis factor-α (TNF-α), which may interfere with clock gene functions (1). Increasing evidence associates type 2 diabetes with inflammatory processes characterized by elevated production of proinflammatory cytokines and infiltration of immune cells. Reducing IL-1 activity in prediabetes and diabetes improves insulin secretion, glycemic control, and markers of systemic inflammation (2–4). Given this background, we hypothesized that fatigue levels may be increased in type 2 diabetes and may be improved by IL-1β antagonism.
Within a placebo-controlled, double-blind study of IL-1β antagonism with a monoclonal anti–IL-1β antibody, XOMA052, involving 30 patients with type 2 diabetes (4), we evaluated fatigue using the Fatigue Scale for Motor and Cognitive functions (5). Besides differentiating between cognitive and motor fatigue, this scale offers a subdivision into different grades of fatigue severity.
At baseline, according to predefined cutoff values, 47% of the patients had no, 20% had mild, 17% had moderate, and 16% had severe fatigue, meaning that more than half of the patients suffered from considerable fatigue symptoms compared with a healthy population (5). A significant correlation between fatigue and duration of diabetes was evident (R = 0.532, P = 0.002). This correlation was stronger for cognitive fatigue (R = 0.541, P = 0.002) compared with motor fatigue (R = 0.486, P = 0.007). No correlation between fatigue and age, HbA1c, body weight, body temperature, and C-reactive protein was found. One month after treatment with XOMA052, a univariate ANOVA with the pre- and 1 month post-medication difference on total fatigue as the dependent variable and dosage as the fixed factor revealed that in the placebo and the lowest dose group (0.01 mg/kg), fatigue was slightly increased; in the two medium dose groups (0.03 mg/kg and 0.1 mg/kg), fatigue was slightly decreased; and in the two highest dose groups (0.3 mg/kg and 1.0 mg/kg), fatigue was decreased remarkably. The effect size for this dose-dependent effect was d = 0.3. When assessing the motor and cognitive function separately, a nonparametric analysis of pre- and 1 month post-medication effects revealed a meaningful trend (P = 0.07) on decrease in motor fatigue for patients under the dosage of 1.0 mg/kg of XOMA052. To further evaluate these findings with respect to the small group sizes, effect sizes for pre- and 1 month post-medication comparisons were calculated. Here it could be confirmed with an effect size of d = 1.05 that a dosage of 1.0 mg/kg of monoclonal anti–IL-1β antibody had a favorable effect on motor fatigue.
To our knowledge, this is the first study assessing fatigue in diabetes by means of a validated fatigue instrument. It shows that type 2 diabetic patients are more prone to fatigue than normal healthy individuals with a prevalence of more than 50%. Fatigue seems to be correlated with duration of diabetic disease but not with the extent of glycemia or C-reactive protein levels. Moreover, fatigue seems to partly improve following IL-1β blockade.
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No potential conflicts of interest relevant to this article were reported.
C.C.-W., R.F., and C.K. contributed to analysis of data, writing of manuscript, and performing the study. A.B.-B., A.M.S., H.G., and A.F. contributed to analysis of data and writing of manuscript. M.Y.D. conceived the study and contributed to analysis of data and writing of manuscript. I.K.P. performed the study and contributed to analysis of data and writing of manuscript.
