Effect of high advanced glycation end-product diet on pulmonary inflammatory response and pulmonary function following gastric aspiration

Breath of fresh air: Investigating the link between AGEs, sRAGE, and lung diseases

Advanced glycation end products (AGEs) are compounds formed via non-enzymatic reactions between reducing sugars and amino acids or proteins. AGEs can accumulate in various tissues and organs and have been implicated in the development and progression of various diseases, including lung diseases. The receptor of advanced glycation end products (RAGE) is a receptor that can bind to advanced AGEs and induce several cellular processes such as inflammation and oxidative stress. Several studies have shown that both AGEs and RAGE play a role in the pathogenesis of lung diseases, such as chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, cystic fibrosis, and acute lung injury. Moreover, the soluble form of the receptor for advanced glycation end products (sRAGE) has demonstrated its ability to function as a decoy receptor, possessing beneficial characteristics such as anti-inflammatory, antioxidant, and anti-fibrotic properties. These qualities make it an encouraging focus for therapeutic intervention in managing pulmonary disorders. This review highlights the current understanding of the roles of AGEs and (s)RAGE in pulmonary diseases and their potential as biomarkers and therapeutic targets for preventing and treating these pathologies.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

Postnatal weaning to different diets leads to different reproductive phenotypes in female offspring following perinatal exposure to high levels of dietary advanced glycation end products

OBJECTIVE

To examine, following perinatal exposure to a diet high in advanced glycation end products (AGEs), whether the use of standard AGE-free mouse chow during the postweaning period alters metabolism and reproduction differently than exposure to a diet low in AGEs.

DESIGN

Experimental animal study.

SETTING

University-based research laboratory.

ANIMAL(S)

Female CD1 mice.

INTERVENTION(S)

Seven-week-old mice were placed on a diet either low or high in AGEs perinatally, before mating and then during pregnancy and lactation. All offspring were weaned onto an AGE-free normal chow.

MAIN OUTCOME MEASURE(S)

Growth curve, liver and abdominal fat weight, insulin and glucose tolerance tests, vaginal opening, estrous cyclicity, and serum levels of antimüllerian hormone, leptin, and adiponectin were assessed. Ovarian histologic examination for follicular count and gene expression was also performed.

RESULT(S)

Compared with the mice exposed to a diet low in AGEs, the mice exposed to a diet high in AGEs showed lower body weight in pups, lower liver weight, delayed vaginal opening, higher serum antimüllerian hormone levels, lower primordial and secondary follicle pools, and higher ovarian Fshr messenger RNA levels.

CONCLUSION(S)

Following weaning, perinatal AGEs can target puberty onset and folliculogenesis differently to standard mouse chow.

Effect of Advanced Glycation End-Products and Excessive Calorie Intake on Diet-Induced Chronic Low-Grade Inflammation Biomarkers in Murine Models

Chronic Low-Grade Inflammation (CLGI) is a non-overt inflammatory state characterized by a continuous activation of inflammation mediators associated with metabolic diseases. It has been linked to the overconsumption of Advanced Glycation End-Products (AGEs), and/or macronutrients which lead to an increase in local and systemic pro-inflammatory biomarkers in humans and animal models. This review provides a summary of research into biomarkers of diet-induced CLGI in murine models, with a focus on AGEs and obesogenic diets, and presents the physiological effects described in the literature. Diet-induced CLGI is associated with metabolic endotoxemia, and/or gut microbiota remodeling in rodents. The mechanisms identified so far are centered on pro-inflammatory axes such as the interaction between AGEs and their main receptor AGEs (RAGE) or increased levels of lipopolysaccharide. The use of murine models has helped to elucidate the local and systemic expression of CLGI mediators. These models have enabled significant advances in identification of diet-induced CLGI biomarkers and resultant physiological effects. Some limitations on the translational (murine → humans) use of biomarkers may arise, but murine models have greatly facilitated the testing of specific dietary components. However, there remains a lack of information at the whole-organism level of organization, as well as a lack of consensus on the best biomarker for use in CLGI studies and recommendations as to future research conclude this review.

Perinatal exposure to high dietary advanced glycation end products affects the reproductive system in female offspring in mice

Maternal nutrition and the intrauterine environment are important in determining susceptibility to reproductive and metabolic disturbances. Advanced glycation end products (AGEs) are widely consumed in Western diet. The purpose of this study was to determine whether perinatal exposure to a high levels of dietary AGEs affect metabolic and reproductive parameters in female mice offspring. Female CD1 mice, 7 weeks old, were placed on either a diet low (L-AGE) or high (H-AGE) in AGEs before mating and then during pregnancy and lactation. All offspring were weaned onto the L-AGE diet and studied through to 16 weeks of age; they were counted and weighed at birth and then every week for a total of 11 weeks. Vaginal opening, litter size, growth curve, liver and abdominal fat weights, serum levels of anti-Mullerian hormone, leptin and adiponectin, as well as insulin and glucose tolerance tests were compared. Ovaries were harvested for follicular count and gene expression by real-time polymerase chain reaction. Compared to perinatal exposure to the L-AGE diet, perinatal exposure to the H-AGE diet caused lower body weight at birth, and adult offspring exhibited delayed growth, lower serum leptin and adiponectin levels, delayed vaginal opening, irregular oestrous cyclicity, arrested follicular development and significant alterations in the expression of genes involved in folliculogenesis (Amh and Amhr2) and steroidogenesis (Cyp19a1). These results indicate that perinatal exposure to a diet elevated in AGEs causes deficits in perinatal growth, pubertal onset, and reproductive organ development in female mice. Whether these findings translate to humans remains to be determined in future studies.

Dietary phenotype and advanced glycation end-products predict WTC-obstructive airways disease: a longitudinal observational study

BACKGROUND

Diet is a modifier of metabolic syndrome which in turn is associated with World Trade Center obstructive airways disease (WTC-OAD). We have designed this study to (1) assess the dietary phenotype (food types, physical activity, and dietary habits) of the Fire Department of New York (FDNY) WTC-Health Program (WTC-HP) cohort and (2) quantify the association of dietary quality and its advanced glycation end product (AGE) content with the development of WTC-OAD.

METHODS

WTC-OAD, defined as developing WTC-Lung Injury (WTC-LI; FEV1 < LLN) and/or airway hyperreactivity (AHR; positive methacholine and/or positive bronchodilator response). Rapid Eating and Activity Assessment for Participants-Short Version (REAP-S) deployed on 3/1/2018 in the WTC-HP annual monitoring assessment. Clinical and REAP-S data of consented subjects was extracted (7/17/2019). Diet quality [low-(15-19), moderate-(20-29), and high-(30-39)] and AGE content per REAP-S questionnaire were assessed for association with WTC-OAD. Regression models adjusted for smoking, hyperglycemia, hypertension, age on 9/11, WTC-exposure, BMI, and job description.

RESULTS

N = 9508 completed the annual questionnaire, while N = 4015 completed REAP-S and had spirometry. WTC-OAD developed in N = 921, while N = 3094 never developed WTC-OAD. Low- and moderate-dietary quality, eating more (processed meats, fried foods, sugary drinks), fewer (vegetables, whole-grains),and having a diet abundant in AGEs were significantly associated with WTC-OAD. Smoking was not a significant risk factor of WTC-OAD.

CONCLUSIONS

REAP-S was successfully implemented in the FDNY WTC-HP monitoring questionnaire and produced valuable dietary phenotyping. Our observational study has identified low dietary quality and AGE abundant dietary habits as risk factors for pulmonary disease in the context of WTC-exposure. Dietary phenotyping, not only focuses our metabolomic/biomarker profiling but also further informs future dietary interventions that may positively impact particulate matter associated lung disease.

Dietary Advanced Glycation End Products (AGEs) could alter ovarian function in mice

Nutrition is an important source of exogenous AGEs and thermally processed foods present in western-style diets contain a large amount of these pro-inflammatory AGEs. Additionally, the intake of dietary AGEs could upregulate ovarian gene expression of inflammatory macrophage markers. The objective of this study was to investigate the effect of diet rich in AGEs on estrous cyclicity and ovarian function in a mouse model. Six-week old C57BL/6 J female mice were randomly subjected to either a diet low in AGEs (L-AGE) or a diet high in AGEs (H-AGE) for a total of 13 weeks. Experiments performed included daily vaginal smears to assess estrous cyclicity, ovarian superovulation with gonadotropins to assess the number of oocytes released, whole ovarian tissue mRNA quantification by RT-PCR to quantify genes involved in folliculogenesis, steroidogenesis, and macrophage markers, and ovarian morphology for follicle count. Outcome measures included estrous cyclicity, number of oocytes following superovulation, expression of genes involved in folliculogenesis, steroidogenesis, and macrophage infiltration as well as the number of primordial, primary, secondary, antral follicles and corpora lutea. Compared to mice on L-AGE diet, mice on H-AGE spent significantly longer time in the diestrus phase, had similar number of oocytes released following ovarian superovulation, and showed significant alterations in genes involved in steroidogenesis (increase in Star mRNA expression levels) and folliculogenesis (increase in Gdf-9 and Fshr mRNA expression levels). Mouse macrophage marker F4/80 mRNA expression was upregulated in mice on H-AGE diet compared to mice on L-AGE diet. Finally, mice on H-AGE diet had significantly fewer corpora lutea in their ovaries. These results indicate that the ingestion of high amounts of dietary AGEs could disrupt folliculogenesis and steroidogenesis that might lead to abnormal estrous cyclicity. Intake of dietary AGEs could also upregulate ovarian gene expression of inflammatory macrophage markers.

Immediate Prone Positioning After Massive Gastric Aspiration Reduces Lung Injury Possibly by Attenuating Interleukin-6-Mediated Lung-Tissue Inflammation in Pigs

Gastric aspiration, which can cause acute, diffuse, inflammatory lung injury, is of particular concern in critically ill patients. This study aimed to determine the effects of immediate prone positioning on the degree of lung injury and inflammatory response induced by gastric aspiration. Following induction of gastric aspiration by injection of gastric fluid, 16 healthy pigs were randomized to one of two groups: supine position (SP) or prone position (PP). After ventilation and monitoring for 6 hr, all pigs were euthanized. The ratio of the partial pressure of arterial oxygen/fraction of inspired oxygen (P_aO2/F_IO2) and the partial pressure of arterial carbon dioxide (P_aCO2) were recorded during the 6-hr study period. Serum levels of interleukin (IL)-6 were measured every 2 hr, and the mean optical density (MOD) of IL-6 in lung tissues and lung-injury scores were measured at the end of the experiment. The PP group showed a significantly higher P_aO2/F_IO2 ratio, lower serum IL-6 concentration (p = .015), lower lung-injury scores (p = .012), and lower IL-6 concentration and MOD of IL-6 in lung tissue, especially in dorsal (p = .001, p = .021, respectively) and nondependent regions (p = .005, p = .035, respectively) than the SP group. There were no statistically significant differences in P_aCO2 between the groups. Lung-injury severity was positively correlated with the IL-6 concentration and MOD of IL-6 in lung tissues (p < .05). These results suggest that immediate prone positioning alleviated the degree of aspiration-induced lung injury, possibly through mitigating IL-6-mediated lung inflammation.

Metformin and risk of chronic obstructive pulmonary disease in diabetes patients

PURPOSE

This study aimed to investigate whether metformin can affect risk of chronic obstructive pulmonary disease (COPD) in type 2 diabetes (T2D) patients.

METHODS

T2D patients newly diagnosed during 1999-2005 were enrolled from the reimbursement database of Taiwan's National Health Insurance system and followed up to 31 December 2011. Analyses were conducted in an unmatched cohort (92,272 ever-users and 10,697 never-users of metformin) and a propensity score (PS) matched pair cohort (10,697 ever-users and 10,697 never-users). Cox regression incorporated into the inverse probability of treatment weighting using the PS was used to estimate hazard ratios (HRs).

RESULTS

In the unmatched cohort, 2573 never-users and 13,840 ever-users developed COPD with respective incidences of 5994.64 and 3393.19 per 100,000 person-years. The overall HR was 0.560 (95% confidence interval [CI]: 0.537-0.584). HRs for the first (<25.27months), second (25.27-55.97months) and third (>55.97months) tertiles of cumulative duration were 1.021 (0.975-1.070), 0.575 (0.548-0.603) and 0.265 (0.252-0.280), respectively. Analyses of the matched cohort showed an overall HR of 0.643 (0.605-0.682), with HRs of 1.212 (1.122-1.309), 0.631 (0.578-0.689) and 0.305 (0.273-0.340) for the respective tertiles.

CONCLUSION

A reduced risk of COPD is observed in metformin users with T2D.

Effect of diet-derived advanced glycation end products on inflammation

Advanced glycation end products (AGEs) formed via the Maillard reaction during the thermal processing of food contributes to the flavor, color, and aroma of food. A proportion of food-derived AGEs and their precursors is intestinally absorbed and accumulates within cells and tissues. AGEs have been implicated in the pathogenesis of diabetes-related complications and several chronic diseases via interaction with the receptor for AGEs, which promotes the transcription of genes that control inflammation. The dicarbonyls, highly reactive intermediates of AGE formation, are also generated during food processing and may incite inflammatory responses through 1) the suppression of protective pathways, 2) the incretin axis, 3) the modulation of immune-mediated signaling, and 4) changes in gut microbiota profile and metabolite sensors. In animal models, restriction of dietary AGEs attenuates chronic low-grade inflammation, but current evidence from human studies is less clear. Here, the emerging relationship between excess dietary AGE consumption and inflammation is explored, the utility of dietary AGE restriction as a therapeutic strategy for the attenuation of chronic diseases is discussed, and possible avenues for future investigation are suggested.

Dietary advanced glycation end-products, its pulmonary receptor, and high mobility group box 1 in aspiration lung injury

BACKGROUND

Gastric aspiration is a significant cause of acute lung injury and acute respiratory distress syndrome. Environmental risk factors, such as a diet high in proinflammatory advanced glycation end-products (AGEs), may render some patients more susceptible to lung injury after aspiration. We hypothesized that high dietary AGEs increase its pulmonary receptor, RAGE, producing an amplified pulmonary inflammatory response in the presence of high mobility group box 1 (HMGB1), a RAGE ligand and an endogenous signal of epithelial cell injury after aspiration.

MATERIALS AND METHODS

CD-1 mice were fed either a low AGE or high AGE diet for 4 wk. After aspiration injury with acidified small gastric particles, bronchoalveolar lavage and whole-lung tissue samples were collected at 5 min, 1 h, 5 h, and 24 h after injury. RAGE, soluble RAGE (sRAGE), HMGB1, cytokine and chemokine concentrations, albumin levels, neutrophil influx, and lung myeloperoxidase activity were measured.

RESULTS

We observed that high AGE-fed mice exhibited greater pulmonary RAGE levels before aspiration and increased bronchoalveolar lavage sRAGE levels after aspiration compared with low AGE-fed mice. Lavage HMGB1 levels rose immediately after aspiration, peaking at 1 h, and strongly correlated with sRAGE levels in both dietary groups. High AGE-fed mice demonstrated higher cytokine and chemokine levels with increased pulmonary myeloperoxidase activity over 24 h versus low AGE-fed mice.

CONCLUSIONS

This study indicates that high dietary AGEs can increase pulmonary RAGE, augmenting the inflammatory response to aspiration in the presence of endogenous damage signals such as HMGB1.