Circulating metabolomic markers in association with overall burden of microvascular complications in type 1 diabetes.

INTRODUCTION: Diabetic retinopathy (DR), diabetic kidney disease (DKD) and distal symmetric polyneuropathy (DSPN) share common pathophysiology and pose an additive risk of early mortality. RESEARCH DESIGN AND METHODS: In adults with type 1 diabetes, 49 metabolites previously associated with either DR or DKD were assessed in relation to presence of DSPN. Metabolites overlapping in significance with presence of all three complications were assessed in relation to microvascular burden severity (additive number of complications-ie, presence of DKD±DR±DSPN) using linear regression models. Subsequently, the same metabolites were assessed with progression to endpoints: soft microvascular events (progression in albuminuria grade, ≥30% estimated glomerular filtration rate (eGFR) decline, or any progression in DR grade), hard microvascular events (progression to proliferative DR, chronic kidney failure, or ≥40% eGFR decline), and hard microvascular or macrovascular events (hard microvascular events, cardiovascular events (myocardial infarction, stroke, or arterial interventions), or cardiovascular mortality), using Cox models. All models were adjusted for sex, baseline age, diabetes duration, systolic blood pressure, HbA1c, body mass index, total cholesterol, smoking, and statin treatment. RESULTS: The full cohort investigated consisted of 487 participants. Mean (SD) follow-up was 4.8 (2.9, 5.7) years. Baseline biothesiometry was available in 202 participants, comprising the cross-sectional cohort. Eight metabolites were significantly associated with presence of DR, DKD, and DSPN, and six with additive microvascular burden severity. In the full cohort longitudinal analysis, higher levels of 3,4-dihydroxybutanoic acid (DHBA), 2,4-DHBA, ribonic acid, glycine, and ribitol were associated with development of events in both crude and adjusted models. Adding 3,4-DHBA, ribonic acid, and glycine to a traditional risk factor model improved the discrimination of hard microvascular events. CONCLUSIONS: While prospective studies directly assessing the predictive ability of these markers are needed, our results strengthen the role of clinical metabolomics in relation to risk assessment of diabetic complications in chronic type 1 diabetes.

Visit-to-visit variability of clinical risk markers in relation to long-term complications in type 1 diabetes.

BACKGROUND: Clinical characteristics such as HbA1c , systolic blood pressure (SBP), albuminuria and estimated glomerular filtration rate (eGFR) are important when treating type 1 diabetes. We investigated the variability in these measures as risk markers for micro- and macrovascular complications. METHODS: This prospective study included 1062 individuals with type 1 diabetes. Visit-to-visit variability of HbA1c , SBP, albuminuria and eGFR was calculated as the SD of the residuals in individual linear regression models using all available measures in a specified period of 3 years (VV). Endpoints included were as follows: cardiovascular events (CVE) defined as myocardial infarction, non-fatal stroke, or coronary or peripheral arterial intervention; end-stage kidney disease (ESKD) defined as eGFR <15 ml/min/1.73 m2 , chronic dialysis or kidney transplantation; eGFR decline ≥30%; and mortality. Adjustment included age, sex, cholesterol, HbA1c , SBP, body mass index, smoking, albuminuria, eGFR, and mean, intercept, slope of respective exposure variables and regression models. RESULTS: SBP VV was significantly associated with CVE (adjusted hazard ratio per 50% increase, (CI 95%); p: 1.21 [1.05-1.39]; p = 0.008), ESKD (1.51 [1.16-1.96]; p = 0.002) and mortality (1.25 [1.09-1.44]; p = 0.002). HbA1c VV was significantly associated with mortality (1.51 [1.30-1.75]; p < 0.001); albuminuria VV with eGFR decline (1.14 [1.08-1.20]; p = 0.024) and ESKD (1.14 [1.02-1.27]; p < 0.001), but neither CVE nor mortality. Adjusted eGFR VV was not associated with endpoints. CONCLUSION: In type 1 diabetes, higher variability of basic clinical risk markers adds important risk stratification information for the development of micro- and macrovascular complications.

Assessment of the sublingual microcirculation with the GlycoCheck system: Reproducibility and examination conditions.

BACKGROUND: The glycocalyx is an extracellular layer lining the lumen of the vascular endothelium, protecting the endothelium from shear stress and atherosclerosis and contributes to coagulation, immune response and microvascular perfusion. The GlycoCheck system estimates glycocalyx' thickness in vessels under the tongue from perfused boundary region (PBR) and microvascular perfusion (red blood cell (RBC) filling) via a camera and dedicated software. OBJECTIVES: Evaluating reproducibility and influence of examination conditions on measurements with the GlycoCheck system. METHODS: Open, randomised, controlled study including 42 healthy smokers investigating day-to-day, side-of-tongue, inter-investigator variance, intraclass-correlation (ICC) and influence of examination conditions at intervals from 0-180 minutes on PBR and RBC filling. RESULTS: Mean (SD) age was 24.9 (6.1) years, 52% were male. There was no significant intra- or inter-investigator variation for PBR or RBC filling nor for PBR for side-of-tongue. A small day-to-day variance was found for PBR (0.012µm, p = 0.007) and RBC filling (0.003%, p = 0.005) and side-of-tongue, RBC filling (0.025%, p = 0.009). ICC was modest but highly improved by increasing measurements. Small significant influence of cigarette smoking (from 40-180 minutes), high calorie meal intake and coffee consumption was found. The latter two peaking immediately and tapering off but remained significant up to 180 minutes, highest PBR changes for the three being 0.042µm (p<0.05), 0.183µm (p<0.001) and 0.160µm (p<0.05) respectively. CONCLUSIONS: Measurements with the GlycoCheck system have a moderate reproducibility, but highly increases with multiple measurements and a small day-to-day variability. Smoking, meal and coffee intake had effects up to 180 minutes, abstinence is recommended at least 180 minutes before GlycoCheck measurements. Future studies should standardise conditions during measurements.

Carotid-Femoral Pulse Wave Velocity as a Risk Marker for Development of Complications in Type 1 Diabetes Mellitus.

Background The value of carotid-femoral pulse wave velocity (cfPWV) as risk factor for development of complications in type 1 diabetes mellitus remains to be determined. We investigated associations between cfPWV and renal outcomes, cardiovascular events, and all-cause mortality in people with type 1 diabetes mellitus. Methods and Results cfPWV was measured with SphygmoCor in 633 people with type 1 diabetes mellitus. Median (interquartile range) follow-up was 6.2 (5.8-6.7) years. End points included progression in albuminuria group, decline in estimated glomerular filtration rate (eGFR) ≥30%, end-stage kidney disease, cardiovascular event, mortality, and a composite renal end point. Hazard ratios (HRs) were calculated per 1-SD increase in cfPWV. Adjustments included age, sex, hemoglobin A1c, mean arterial pressure, body mass index, low-density lipoprotein cholesterol, smoking, urine albumin excretion rate, and eGFR. The cohort included 45% women, mean (SD) age was 54 (13) years, mean (SD) eGFR was 83.2 (27.9) mL/min per 1.73 m2, and mean (SD) cfPWV was 10.4 (3.3) m/s. Median (interquartile range) albumin excretion rate was 17 (17-63) mg/24 h. After adjustment, higher cfPWV was associated with increased hazard of progression in albuminuria (HR, 1.59; 95% CI, 1.10-2.32); decline in eGFR ≥30% (HR, 1.38; 95% CI, 1.06-1.79); cardiovascular event (HR, 1.31; 95% CI, 1.01-1.70); mortality (HR, 1.36; 95% CI, 1.00-1.85); and the composite renal end point (HR, 1.30; 95% CI, 1.04-1.63), but not with end-stage kidney disease (HR, 1.18; 95% CI, 0.62-2.26). Higher cfPWV was associated with steeper yearly increase in albumin excretion and steeper yearly decline in eGFR after adjustment (P=0.002 and P=0.01, respectively). Conclusions cfPWV was associated with increased hazard of renal outcomes, cardiovascular event, and mortality. cfPWV may be suited for risk stratification in type 1 diabetes mellitus.

Trimethylamine N-oxide (TMAO) as a New Potential Therapeutic Target for Insulin Resistance and Cancer.

BACKGROUND: The intake of animal products in food has been associated with both the development of insulin resistance and gastrointestinal cancers (GIC). Through the digestion of animal protein and other constituents of animal products, the commensal bacteria in the gut (the gut microbiota) forms metabolites that can contribute to the development of both insulin resistance and cancer. Trimethylamine-N-Oxide (TMAO) is such a molecule and has recently drawn a lot of attention as it may be a risk factor for - and a link between - the gut microbiota and cardiovascular and renal disease. Further, TMAO is anticipated to have significance as a biomarker of - or even an independent risk factor for - other undesirable conditions, including insulin resistance and GIC. TMAO originates from a precursor, trimethylamine (TMA) that is a metabolite of various precursors; mainly choline and carnitine from ingested foods. METHODS: We review the literature on TMAO as a shared risk factor and/or pathway between insulin resistance and GIC risk and take the reader through the literature of interventions that could reduce formation of TMAO and thereby the risk of insulin resistance and GIC. The purpose of the work is to generate a hypothesis to be tested in preclinical and clinical studies. RESULTS: TMAO seems to be associated with both insulin resistance and GIC risk and also with atherosclerotic cardiovascular disease. One shared pathway is the formation of N-Nitroso compounds, a group of metabolites that can cause DNA-damage and epigenetic changes. Levels of TMAO can be reduced by limiting the dietary intake of certain foods, most importantly animal products. Further, certain drugs, namely Meldonium and 3,3-dimethyl- 1-butanol, may inhibit the formation of TMAO by inhibiting bacterial enzymes. CONCLUSIONS: The TMAO pathway and its metabolites are possibly involved in the development of two major health problems: insulin resistance and cancer. Within these pathways novel therapeutic targets may be identified. Further research is needed in order to verify existing or develop new pharmacological agents that modify these pathways and reduce the risk of insulin resistance and GIC.