ReviewImpact of glycemic variability on cardiovascular outcomes beyond glycated hemoglobin. Evidence and clinical perspectives
Introduction
In recent years, several papers and reviews have focused on the possible effects of glucose variability (GV) on cardiovascular diseases, and, in fact, when searching the term “glucose variability” on pubmed, 2891 results are found. However, going through the titles of these papers, it becomes immediately clear that the term “glucose variability” implies many different concepts.
The first concept relates to the day-to-day variability of fasting glucose, the second meaning refers to post-prandial spikes, the third to glycated hemoglobin (HbA1c) variability and, finally, the last concerns the intra-day GV. Further, in this last meaning, two different kinds of measurements are included: self-monitoring blood glucose (SMBG) or continuous glucose monitoring (CGM).
The labyrinth becomes even more intricate, when trying to address the impact of GV on cardiovascular mortality, as recently extensively discussed in the paper by Standl et al. [1], the only evidence being available for day-to-day variability of fasting blood glucose (FBG) [2] and for post-prandial glucose (PPG) [3], [4]. Only two papers investigated the relationship between HbA1c variability and cardiovascular mortality [5], [6]. Lastly, the role of intra-day GV on cardiovascular outcomes is still controversial [7], [8].
It should also be noticed that most of the available data have been collected in type 1 and type 2 diabetic patients, whilst in non-diabetic population, no data on the predictive role of GV on cardiovascular outcomes are available, possibly due to the paucity of data collected by CGM or SMBG in subjects without overt glycemic abnormalities [9].
The aim of this review is to focus on intra-day GV, specifically reviewing its correlation with HbA1c, the methods currently available to measure it, and finally the relationship between GV and cardiovascular outcomes, in type 1 and type 2 diabetic patients, and in non-diabetic population.
Section snippets
Relationship between glucose variability and HbA1c
Since evidence from the Diabetes Control and Complications Trial (DCCT) [10] has linked the reduction of HbA1c to lower incidence and progression of micro-vascular complications, current glycemic management mainly relies on HbA1c measurement. The DCCT investigators observed that ‘total glycemic exposure’ (HbA1c and duration of diabetes) only explained about 11% of the variation in retinopathy risk in the complete DCCT cohort, meaning that factors independent of HbA1c must presumably explain the
Methods to measure glucose variability
Many different indexes have been proposed to assess GV, however, at the moment no “gold standard” procedure is available. The introduction of CGM into clinical practice has resulted in a more accurate assessment of glycemic profile. Recently, Hill et al. [19] have proposed the normal reference ranges for mean blood glucose and GV derived from CGM for subjects without diabetes in different ethnic groups. The most commonly used indices of intra-day GV are hereinafter described.
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Standard deviation
Evidence in vitro
Glycemic fluctuations are more deleterious for endothelial cells than constantly high glucose concentrations [30]. Apoptosis is significantly higher in human umbilical vein endothelial cells incubated for 14 days in media containing a daily alternating 5 or 20 mmol/l glucose versus stable high glucose. Moreover, Quagliaro et al. [31] showed that intermittent high glucose levels enhance, in endothelial cells, the formation of nitrotyrosine and 8-hydroxydeoxyguanosine (8-OHdG), markers of
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Cited by (36)
Glycemic variability in diagnosis of gestational diabetes as predictor of pharmacological treatment
2024, Endocrinologia, Diabetes y NutricionEffect of the GSTM1 gene deletion on glycemic variability, sympatho-vagal balance and arterial stiffness in patients with metabolic syndrome, but without diabetes
2018, Diabetes Research and Clinical PracticeCitation Excerpt :To calibrate CGM, GlucoCard G+ meter blood glucose monitoring system (Menarini, Neuss, Germany) was used. The following Glycemic Variability indexes (GV) were calculated: mean (MEAN), mean amplitude of glucose excursion (MAGE); J-index (JINDEX); mean absolute glucose (MAG); continuous overall net glycemic action (CONGA1, 2, 3, and 4); Coefficient of Variation (COEFF_VAR), low blood glucose (LBGI), high blood glucose index (HBGI), lability index (LI) and M value (M_VALUE) [9]. A 24-h Ambulatory Blood Pressure Measurement (ABPM) set to measure every 15 min during the day and every 30 min during nighttime was used.
Diabetes remission after bariatric surgery is characterized by high glycemic variability and high oxidative stress
2017, Nutrition, Metabolism and Cardiovascular DiseasesCitation Excerpt :The dynamics of glucose fluctuations are well depicted by the measure of GV and the assessment of its two most important components, i.e., the amplitude of glucose excursions and the time a person spent within a certain range of blood glucose. At present, there are consistent data from pathophysiological and clinical studies that high GV may be involved in the pathogenesis of diabetic vascular complications via activation of inflammatory pathways, increased oxidative stress and endothelial dysfunction [15,18,20–22]. In addition, GV is reported to impact depression, quality of life and other mental health outcomes in diabetic individuals [12].
The potential effect of ultra-long insulin degludec on glycemic variability
2017, Diabetes Research and Clinical PracticeCitation Excerpt :MAGE has been proposed as the “gold-standard” system for evaluating GV by some authors, but it presents limitations, such as a bias towards hyperglycemic peaks over hypoglycemic nadirs. CONGA has the benefits of being reproducible and it is unaffected by asymmetry of the glycemic profile [15]. Although MODD is not ideal to evaluate the glucose variability within a day, it reflects the day-to-day glucose variability and therefore is a very important index to evaluate the variability of the action of basal insulins.
Diurnal glycemic fluctuation is associated with severity of coronary artery disease in prediabetic patients: Possible role of nitrotyrosine and glyceraldehyde-derived advanced glycation end products
2017, Journal of CardiologyCitation Excerpt :The mean amplitude of glycemic excursions (MAGE) was calculated using these data. The MAGE represents fluctuations in blood glucose levels over a 24-h period and was calculated by measuring the arithmetic mean of the differences between consecutive peaks and nadirs, provided that the differences were >1 standard deviation (SD) of the mean glucose value [16]. Blood samples were collected from an antecubital vein at admission and in the morning following an overnight fast.
Glycemic control and variability in association with body mass index and body composition over 18 months in youth with type 1 diabetes
2016, Diabetes Research and Clinical PracticeCitation Excerpt :While BMI is strongly correlated with body fat, it is an indirect measure, and does not reflect body fat distribution [17], which may be differentially associated with glycemic control. Similarly, while HbA1c is the clinical benchmark for assessing chronic glycemic control, the measure does not reflect short-term glucose excursions shown to predict diabetes complications [18]. Complementary measures of overall glycemic control include 1,5-anhydroglucitol (1,5-AG), which is sensitive to recent glucose excursions in moderately well-controlled type 1 diabetes [19–22], and continuous glucose monitoring, which can be used to assess glycemic variability.