Clinical studies have already established 1,5-AG in blood as a reliable marker of short-term glycemic control. Our study suggests that 1,5-AG in saliva can be used in national screening programs for undiagnosed diabetes, which are of particular interest for Middle Eastern countries with young populations and exceptionally high diabetes rates.

Aims/hypothesisMetabolomics has opened new avenues for studying metabolic alterations in type 2 diabetes. While many urine and blood metabolites have been associated individually with diabetes, a complete systems view analysis of metabolic dysregulations across multiple biofluids and over varying timescales of glycaemic control is still lacking.MethodsHere we report a broad metabolomics study in a clinical setting, covering 2,178 metabolite measures in saliva, blood plasma and urine from 188 individuals with diabetes and 181 controls of Arab and Asian descent. Using multivariate linear regression we identified metabolites associated with diabetes and markers of acute, short-term and long-term glycaemic control.ResultsNinety-four metabolite associations with diabetes were identified at a Bonferroni level of significance (p < 2.3 × 10−5), 16 of which have never been reported. Sixty-five of these diabetes-associated metabolites were associated with at least one marker of glycaemic control in the diabetes group. Using Gaussian graphical modelling, we constructed a metabolic network that links diabetes-associated metabolites from three biofluids across three different timescales of glycaemic control.Conclusions/interpretationOur study reveals a complex network of biochemical dysregulation involving metabolites from different pathways of diabetes pathology, and provides a reference framework for future diabetes studies with metabolic endpoints.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-015-3636-2) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Background Advanced glycation end products (AGEs) have been shown to be a predictor of cardiovascular risk in Caucasian subjects. In this study we examine whether the existing reference values are useable for non-Caucasian ethnicities. Furthermore, we assessed whether gender and smoking affect AGEs.Methods AGEs were determined by a non-invasive method of skin auto-fluorescence (AF). AF was measured in 200 Arabs, 99 South Asians, 35 Filipinos and 14 subjects of other/mixed ethnicity in the Qatar Metabolomics Study on Diabetes (QMDiab). Using multivariate linear regression analysis and adjusting for age and type 2 diabetes, we assessed whether ethnicity, gender and smoking were associated with AF.Results The mean AF was 2.27 arbitrary units (AU) (SD: 0.63). Arabs and Filipinos had a significant higher AF than the South Asian population (0.25 arbitrary units (AU) (95% CI: 0.11‒0.39), p = 0.001 and 0.34 (95% CI: 0.13‒0.55), p = 0.001 respectively). Also, AF was significantly higher in females (0.41 AU (95% CI: 0.29‒0.53), p < 0.001). AF associated with smoking (0.21 AU (95% CI: 0.01‒0.41), p = 0.04) and increased with the number of pack-years smoked (p = 0.02).Conclusions This study suggests that the existing reference values should take ethnicity, gender and smoking into account. Larger studies in specific ethnicities are necessary to create ethnic- and gender-specific reference values.

Background: The AGE reader is a non-invasive device that measures tissue accumulation of advanced glycation endproducts (AGEs) through skin auto-fluorescence (AF) and gives prediction of cardiovascular risk. For the risk prediction, the AGE reader uses a single reference curve, for both females and males, obtained from Caucasian subjects. Based on these reference curves, clinical cut-offs for a low, medium and high AF have been made. This study examines whether these reference values can be used for ethnic populations seen in Qatar. Furthermore, we assess whether gender and smoking affect skin AF in this particular population. Methods: Skin AF was measured in 200 Arabs, 99 South Asians and 35 Filipinos. Using multivariate linear regression analysis and adjusting for the covariates age and the presence of type 2 diabetes, we assessed whether ethnicity, smoking and gender were associated with skin AF. Results: The Arabs and the Filipinos had a significant higher skin AF then the South Asian population (0.272 (95% CI: 0.138, 0.406), p <0.001 and 0.354 (95% CI: 0.147- 0.561), p=0.001 respectively). This is equivalent to a horizontal shift of 14.6% and 19.0%, respectively. Also, skin AF was significantly higher in women compared to men (0.432 (95% CI: 0.307, 0.558), p <0.001). Smoking was positively associated with skin AF (0.21 (95% CI: -0.01, 0.41), p=0.056), with an increasing effect of number of pack-years smoked on AF (p=0.024). Conclusions: The results of this study suggest that the existing reference values should be expanded for ethnicity, gender and smoking. These results also indicate that the use of the AGE reader in clinical settings should be used with caution, since the clinical cut-off points are dependent on various factors such as ethnicity that still need to be studied in greater detail.