Objective　To examine the intraindividual reproducibility of the octanoic acid breath test in normal subjects and diabetics and to investigate whether cardiovascular autonomic neuropathy and delayed gastric emptying influence the intraindividual reproducibility.Methods　Nine normal subjects (six men, three women,mean age 38 years) and 15 diabetics with insulin treatment ［nine men, six women; mean age 47 years; six had cardiovascular autonomic diabetic neuropathy (CADN) and/or delayed gastric emptying time］ were, after a nocturnal fasting period, given a standard test meal (labeled with 13C-octanoic acid, 1 046 kJ). Breath samples were taken at ten minute intervals over first one hour and at fifteen minute intervals over the following three hours and examined for 13CO2 by isotope ratio infrared spectrometry. Using a regression method gastric emptying half times (t1/2) and lag phase (tlag) were determined.Results　There was not a significant difference of t1/2 and tlag between two measurements in normal subjects and diabetics. The coefficients of variation of day-to-day reproducibility were 11.7% for t1/2, 19.4% for tlag in normal subjects and 17.8% for t1/2, 28.2% for tlag in diabetics, but there was not significant difference between normal subjects and diabetics. There was not significant difference of intraindividual coefficient of variation of t1/2 and tlag between diabetics with/without CADN and between diabetics with normal gastric emptying time and diabetics with delayed gastric emptying time.Conclusions　 The 13C-octanoic acid breath test has a high intraindividual reproducibility which is not affected by the cardiovascular autonomic neuropathy and delayed gastric emptying. It can be recommended as a non-invasive test for assessing gastric emptying time after a solid test meal in diabetics.

Increased oxidative stress is implicated in the pathogenesis of experimental diabetic neuropathy, but translational evidence in recent-onset diabetes is scarce. We aimed to determine whether markers of systemic oxidative stress are associated with diabetic sensorimotor polyneuropathy (DSPN) in recent-onset diabetes. In this cross-sectional study, we measured serum concentrations of extracellular superoxide dismutase (SOD3), thiobarbituric acid reactive substances (TBARS), and reduced glutathione (GSH) in 107 type 1 and 215 type 2 diabetes patients from the German Diabetes Study baseline cohort and 37 glucose-tolerant individuals (controls). DSPN was defined by electrophysiological and clinical criteria (Toronto Consensus, 2011). SOD3 and GSH concentrations were lower in individuals with type 1 and type 2 diabetes compared with concentrations in controls (P<0.0001). In contrast, the TBARS concentration was higher in participants with type 1 diabetes and type 2 diabetes compared with levels in controls (P<0.0001). In addition, the SOD3 concentration was higher in participants with type 1 diabetes compared to concentrations in those with type 2 diabetes (P<0.0001). A low SOD3 concentration was associated with DSPN in individuals with type 1 diabetes (β=−0.306, P=0.002), type 2 diabetes (β=−0.164, P=0.017), and in both groups combined (β=−0.206, P=0.0003). Lower SOD3 concentrations were associated with decreased motor nerve conduction velocity (NCV) in men and, to a lesser degree, with reduced sensory NCV in women with diabetes. In conclusion, several biomarkers of oxidative stress are altered in recent-onset diabetes, with only a lower SOD3 concentration being linked to the presence of DSPN, suggesting a role for reduced extracellular antioxidative defense against superoxide in the early development of DSPN.
Biomarkers ; Cohort Studies ; Consensus ; Cross-Sectional Studies ; Diabetic Neuropathies ; Female ; Glutathione ; Humans ; Male ; Neural Conduction ; Oxidative Stress ; Polyneuropathies* ; Superoxide Dismutase* ; Superoxides* ; Thiobarbituric Acid Reactive Substances