The effect of insulin-induced hypoglycemia on inflammatory markers: A systematic review

Hypoglycaemic stimulation of macrophage cytokine release is suppressed by AMP-activated protein kinase activation

AIMS

Acute hypoglycaemia promotes pro-inflammatory cytokine production, increasing the risk for cardiovascular events in diabetes. AMP-activated protein kinase (AMPK) is regulated by and influences the production of pro-inflammatory cytokines. We sought to examine the mechanistic role of AMPK in low glucose-induced changes in the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF), which is elevated in people with diabetes.

METHODS

Macrophage cell line Raw264.7 cells, primary macrophage bone marrow-derived macrophages obtained from wild-type mice or AMPK γ1 gain-of-function mice, were used, as were AMPKα1/α2 knockout mouse embryonic fibroblasts (MEFs). Allosteric AMPK activators PF-06409577 and BI-9774 were used in conjunction with inhibitor SBI-0206965. We examined changes in protein phosphorylation/expression using western blotting and protein localisation using immunofluorescence. Metabolic function was assessed using extracellular flux analyses and luciferase-based ATP assay. Cytokine release was quantified by enzyme-linked immunosorbent assay (ELISA). Oxidative stress was detected using a fluorescence-based reactive oxygen species (ROS) assay, and cell viability was examined using flow cytometry.

RESULTS

Macrophages exposed to low glucose showed a transient and modest activation of AMPK and a metabolic shift towards increased oxidative phosphorylation. Moreover, low glucose increased oxidative stress and augmented the release of macrophage MIF. However, pharmacological activation of AMPK by PF-06409577 and BI-9774 attenuated low glucose-induced MIF release, with a similar trend noted with genetic activation using AMPKγ1 gain-of-function (D316A) mice, which produced a mild effect on low glucose-induced MIF release. Inhibition of NFĸB signalling diminished MIF release and AMPK activation modestly but significantly reduced low glucose-induced nuclear translocation of NFĸB.

CONCLUSIONS

Taken together, these data indicate that pharmacological AMPK activation suppresses the release of MIF from macrophages caused by energy stress, suggesting that AMPK activation could be a useful strategy for mitigating hypoglycaemia-induced inflammation.

Severe hypoglycaemia-induced microglial inflammation damages microvascular endothelial cells, leading to retinal destruction

Human microglia (HMC) are stress-induced inflammatory cells of the retina. It is unknown whether severe hypoglycaemia causes inflammation in microglia, affects the permeability of human retinal microvascular endothelial cells (HRMECs), and causes retinal damage. This study aimed to explore the effects of severe hypoglycaemia on retinal microglial inflammation and endothelial cell permeability and evaluate the damage caused by hypoglycaemia to the retina. The CCK-8 assay was used to measure cell viability. Western blotting was used to detect IL-1β, IL-6, TNF- α, claudin-1, and occludin expression. ELISA was used to detect IL-1β, IL-6, and TNF- α. Transmission electron microscopy (TEM) and haematoxylin and eosin staining were used to observe the retinal structure. Immunohistochemistry and immunofluorescence staining assays were also used to detect IL-1β, IL-6, TNF- α, claudin-1, and occludin expression. Severe hypoglycaemia promoted inflammation in HMC3 cells. Inflammation caused by hypoglycaemia leads to the decreased expression of tight junction proteins. In vivo, severe hypoglycaemia induced structural damage to the retina, increased the expression of inflammatory factors, and decreased the expression of tight junction proteins. Our results suggest that severe hypoglycaemia leads to acute retinal inflammation, affecting the permeability of HRMECs and causing retinal damage.

Stress, hypoglycemia, and the autonomic nervous system

Stress can be classified as either psychosocial or physiologic. Physiologic stress refers to stresses due to acute illness, trauma, pain, hypoglycemia, and sleep deprivation-much less is known regarding its health consequences. This review focuses on hypoglycemia as a model to further investigate physiological stress. Experimental mild to moderate hypoglycemia is a paradigmatic physiological stress that evokes autonomic, neuroendocrine, and immune responses. Hypoglycemic stress is an ideal model to examine the interactions and consequences of physiological stress on the autonomic nervous system. Acute hypoglycemia has been demonstrated to increase inflammatory markers, prolong QTc, and impair cardiac-vagal baroreflex sensitivity. Some of these consequences may not reverse completely when euglycemia is restored. For example, there is attenuation of the cardiac-vagal baroreflex, attenuation of the vascular sympathetic baroreflex (muscle sympathetic nerve activity response to transient hypotension), and attenuation of the catecholamine response to lower body negative pressure that is present the next day after hypoglycemia has resolved.

Metabolism and Health Effects of Rare Sugars in a CACO-2/HepG2 Coculture Model

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent liver disease worldwide and is impacted by an unhealthy diet with excessive calories, although the role of sugars in NAFLD etiology remains largely unexplored. Rare sugars are natural sugars with alternative monomers and glycosidic bonds, which have attracted attention as sugar replacers due to developments in enzyme engineering and hence an increased availability. We studied the impact of (rare) sugars on energy production, liver cell physiology and gene expression in human intestinal colorectal adenocarcinoma (Caco-2) cells, hepatoma G2 (HepG2) liver cells and a coculture model with these cells. Fat accumulation was investigated in the presence of an oleic/palmitic acid mixture. Glucose, fructose and galactose, but not mannose, l-arabinose, xylose and ribose enhanced hepatic fat accumulation in a HepG2 monoculture. In the coculture model, there was a non-significant trend (p = 0.08) towards higher (20–55% increased) median fat accumulation with maltose, kojibiose and nigerose. In this coculture model, cellular energy production was increased by glucose, maltose, kojibiose and nigerose, but not by trehalose. Furthermore, glucose, fructose and l-arabinose affected gene expression in a sugar-specific way in coculture HepG2 cells. These findings indicate that sugars provide structure-specific effects on cellular energy production, hepatic fat accumulation and gene expression, suggesting a health potential for trehalose and l-arabinose, as well as a differential impact of sugars beyond the distinction of conventional and rare sugars.

Characterization of Post-Hypoglycemic Hyperglycemia in Children and Adolescents With Type 1 Diabetes: The EPHICA Study

BACKGROUND

In patients with diabetes, the dynamics in which hypoglycemia recovers impacts cardiovascular disease risk. Our study investigated the extents of "post-hypoglycemic hyperglycemia (PHH)" (i.e. hypoglycemia that recover to hyperglycemia in any circumstance) and factors likely to influence PHH characteristics in a pediatric cohort of patients with type 1 diabetes (T1D).

METHODS

We collected retrospective continuous glucose monitoring (CGM) data from 142 pediatric patients with T1D to characterize episodes of PHH during a two-month follow-up period. Factors influencing PHH were determined using univariate and multivariate analyses.

RESULTS

In our EPHICA cohort, PHH rate was 0.6 ± 0.3 episode/day and correlated (r=0.33; p<0.0001) with hyperglycemia rate (2.6 ± 0.5 episodes/day). The global proportion of hyperglycemia corresponding to PHH was 0.22 ± 0.1, yet 14.8% of patients had more than 1/3 of hyperglycemia related to PHH. Episodes of PHH lasted 239.6 ± 124.8 minutes with a hyperglycemic peak of 258.8 ± 47.1 mg/dL. Only 12.2% of PHH occurred at night. While a younger age (<12 years) and lower body mass index (BMI) (SDS: -2 to 1.6) were associated with higher daily PHH rates, teenagers (≥12 years) and obese patients experienced longer PHH and higher hyperglycemic peaks. Parameters of glycemic variability (i.e. HbA_1C, IDAA_1C and GTAA_1C) moderately correlated with PHH duration and related hyperglycemic peak. Multivariate analysis confirmed these results, as factors likely to influence PHH rate were phenotype (age and BMI) and glycemic variability parameters (time in range, mean glycemia, HbA_1C and GTAA_1C).

CONCLUSION

Our EPHICA study highlights the importance of PHH as a prominent component of hyperglycemia in some children and adolescents with T1D. Factors associated with PHH features are age, BMI and parameters of glycemic control. Young and lean children are more prone to experience hypoglycemia that recover with hyperglycemia, but adolescents and obese children tend to experience hyperglycemia of longer duration.

Effect of ketamine on the physiological responses to combined hypoglycemic and psychophysical stress

There is evidence that hypoglycemic stress can interact with other stressors, and that ketamine can mitigate the impact of these stressors on behavior and physiology. The current study in male Sprague-Dawley rats investigated whether pre-treatment with 0, 10, or 20 mg/kg ketamine could modulate the interaction between hypoglycemia induced by 0 or 300 mg/kg 2-deoxy-D-glucose (2-DG) and the psychophysical stress of forced swimming (FSS; 6 sessions, 10 min/session) on serum concentrations of corticosterone (CORT) and the pro-inflammatory cytokine, tumor necrosis factor (TNF)-α. It was found that 2-DG enhanced the CORT response to an initial session of FSS, and this effect dissipated after multiple sessions. More importantly, animals displayed significantly higher levels of CORT and lower levels of TNF-α in response to a drug-free test swim conducted 1 week after exposure to the combined stressors, and these responses were not observed in rats that were pre-treated with ketamine. Overall, these findings indicate that ketamine has the potential to reduce the negative impact of interacting stressors on the biological reactivity of the hypothalamic-pituitary-adrenal axis and the immune system.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

Copeptin response to hypoglycemic stress is linked to prolactin activation in children

PURPOSE

The physiological role of arginine vasopressin (AVP) in the acute stress response in humans and especially in children is unclear. The aim of this study was to explore the interaction between copeptin, a well-established surrogate marker of AVP release, and anterior pituitary hormone activation in response to acute hypoglycemic stress in children and adolescents.

METHODS

We conducted an exploratory single center study involving 77 children and adolescents undergoing insulin-induced hypoglycemia. Blood levels of copeptin, ACTH, cortisol, GH, prolactin, interleukin-6 (IL-6), adrenaline and noradrenaline were determined at baseline and after insulin-induced hypoglycemia.

RESULTS

Basal plasma levels of copeptin (median: 5.2 pmol/L) increased significantly after hypoglycemia (median 9.7 pmol/L; P < 0.0001). Subjects with insufficient HPA axis response or severe GH deficiency had lower hypoglycemia-induced copeptin increase (median: 2.3 pmol/L) compared with individuals with intact pituitary response (median: 5.2 pmol/L, P = 0.02). Copeptin increase correlated significantly with the maximal increase of ACTH (r_s = 0.30; P = 0.010), cortisol (r_s = 0.33; P = 0.003), prolactin (r_s = 0.25; P = 0.03), IL-6 (r_s = 0.35; P = 0.008) and with BMI-SDS (r_s = - 0.28, P = 0.01). In multivariate regression analysis, prolactin increase was the only independent variable associated with copeptin increase (P = 0.0004).

CONCLUSION

Our data indicate that: (1) hypoglycemic stress elicits a marked copeptin response in children and adolescents, pointing out its role as an acute stress marker in this population; (2) stress-induced AVP/copeptin release is associated with anterior pituitary activation, mainly a prolactin response.

Interleukin-6 response to insulin-induced hypoglycemia is associated with hypothalamic-pituitary-adrenal axis activation

Increased plasma levels of interleukin-6 (IL-6) in response to acute hypoglycemia have been well documented. Aiming to study the interaction between IL-6 and counter-regulatory hormones during hypoglycemic stress we conducted an exploratory single center study involving 26 adult patients undergoing insulin tolerance test. Insulin-induced hypoglycemia elicited a significant dynamic response of IL-6, adrenaline, noradrenaline, GH, prolactin, ACTH and serum and salivary cortisol (P < 0.001 for all variables). Patients with insufficient HPA axis response had lower hypoglycemia-induced IL-6 increase (median: 0.88 pg/mL) compared with individuals with intact HPA axis response (2.03 pg/mL, P = 0.007). IL-6 maximal increase correlated with the maximal increase of serum cortisol (rs = 0.48; P = 0.013), salivary cortisol (rs = 0.66; P = 0.012), plasma ACTH (rs = 0.48; P = 0.013) and with the increase in procedure-related symptoms of anxiety and hypoglycemia (rs = 0.57; P = 0.003). In conclusion, hypoglycemic stress-induced IL-6 increase is associated with activation of the HPA axis, suggesting that IL-6 response to hypoglycemic stress may be regarded as part of the counter-regulatory response, possibly contributing to the maintenance of glucose homeostasis.

The risk trajectory between preoperative fasting glucose and common digestive tract cancer-specific mortality in the FIESTA cohort involving 6865 Chinese patients

Backgrounds: High blood glucose or hyperglycemia is an established risk factor for the development and progression of cancer at many sites, whereas data on the relevance between low blood glucose or hypoglycemia and cancer survival are lacking.

Aims: We aimed to assess the shape of risk trajectory between preoperative fasting glucose and postoperative digestive cancer-specific mortality in Chinese.

Methods: In total, 6865 patients who underwent radical surgery for esophageal cancer (n=2535), gastric cancer (n=3012) and colorectal cancer (n=1318) during 2000-2010 were followed up as of December 2015. All patients received neither chemotherapy nor radiotherapy before and after the surgery. Optimal cutoff points were determined using survival tree analysis.

Results: The median follow-up time was 44.9 months (range: 0.5-188.9 months), with 1065 deaths from esophageal cancer, 1331 from gastric cancer and 412 from colorectal cancer. Using fasting glucose (4.36, 6.09] mmol/L as the reference group, hazard ratios for fasting glucose ≤4.36, (6.09, 8.95], (8.95, 11.5] and >11.5 mmol/L were 1.35 (95% confidence interval: 1.19, 1.54), 2.82 (2.57, 3.11), 3.56 (3.10, 4.08) and 4.27 (3.67, 4.97), respectively (p<0.001).

Conclusions: Our findings indicate a U-shaped risk trajectory between preoperative fasting glucose and digestive tract cancer-specific mortality in Chinese. Further external validation is warranted.

Lichen planus and diabetes mellitus: Systematic review and meta-analysis

OBJECTIVE

The aim of this study was to perform a systematic review and meta-analysis answering the following questions: (a) "What is the prevalence and risk of oral lichen planus among patients with diabetes mellitus?" and (b) "What is the prevalence and risk of diabetes mellitus among patients with oral lichen planus?".

MATERIAL AND METHODS

A bibliographic search was conducted in PubMed/Medline and Scopus database from 1966 to March 2018, using the following terms: "Lichen planus" AND "Diabetes mellitus" AND "Prevalence" AND "Oral mucosal lesions".

RESULTS

Twenty-two studies were included in this review. Twelve studies assessed the prevalence of diabetes mellitus among patients with lichen planus. The prevalence reported ranges from 1.6% to 37.7% with a relative risk of 2.432. Ten studies assessed the prevalence of lichen planus among patients with diabetes mellitus which showed a prevalence of lichen planus ranging from 0.5% to 6.1% with a relative risk of 1.4.

CONCLUSIONS

Contradictory results were found when analyzing the relationship between lichen planus and diabetes mellitus. Diverse factors should be considered when studying this association for a correct interpretation of results. Diabetes mellitus has high prevalence and morbidity, which is why new case-control studies are needed to further investigate this association.