Different role of advanced glycation end products in pathology of transplanted heart in patients with or without diabetes mellitus type 2

Pleiotropic consequences of metabolic stress for the major histocompatibility complex class II molecule antigen processing and presentation machinery

Hyperglycemia and hyperlipidemia are often observed in individuals with type II diabetes (T2D) and related mouse models. One dysmetabolic biochemical consequence is the non-enzymatic reaction between sugars, lipids, and proteins, favoring protein glycation, glycoxidation, and lipoxidation. Here, we identified oxidative alterations in key components of the major histocompatibility complex (MHC) class II molecule antigen processing and presentation machinery in vivo under conditions of hyperglycemia-induced metabolic stress. These modifications were linked to epitope-specific changes in endosomal processing efficiency, MHC class II-peptide binding, and DM editing activity. Moreover, we observed some quantitative and qualitative changes in the MHC class II immunopeptidome of Ob/Ob mice on a high-fat diet compared with controls, including changes in the presentation of an apolipoprotein B100 peptide associated previously with T2D and metabolic syndrome-related clinical complications. These findings highlight a link between glycation reactions and altered MHC class II antigen presentation that may contribute to T2D complications.

Risk factors of cardiac allograft vasculopathy

Despite advances in prevention and treatment of heart transplant rejection, development of cardiac allograft vasculopathy (CAV) remains the leading factor limiting long-term survival of the graft. Cardiac allograft vasculopathy etiopathogenesis is not fully understood, but a significant role is attributed to endothelial cell damage, caused by immunological and non-immunological mechanisms. Immunological factors include the differences between the recipient's and the donor's HLA systems, the presence of alloreactive antibodies and episodes of acute rejection. Among the non-immunological factors the most important are the age of the donor, ischemia-reperfusion injury and cytomegalovirus infection. The classical cardiovascular risk factors (diabetes, hypertension, obesity and hyperlipidemia) are also important. This study presents an up-to-date overview of current knowledge on the vasculopathy etiopathogenesis and the role played by endothelium and inflammatory processes in CAV, and it also investigates the factors which may serve as risk markers of cardiac allograft vasculopathy.

Acute heart transplant graft failure in association with hyperosmolar hyperglycemia state

We report a 38-year-old male with end-stage ischemic cardiomyopathy requiring left ventricular assist device placement, followed by orthotopic heart transplantation, who presented 18 months post-orthotopic heart transplant with acute graft failure with estimated left ventricular ejection fraction of 5% to 10%, in association with a glucose level of 550 mg/dL, and hemoglobin A1C of 13.8% and a negative pathology for a graft cellular and humoral rejection and no vasculaopthy. His left ventricular ejection fraction improved significantly to 40% to 45% within three days of optimal glucose control.

Paradox of advanced glycation end-products in late cardiac biopsies of heart transplant recipients

BACKGROUND

A pilot study of orthotopic heart transplant (OHT) recipients showed that advanced glycation end-product (AGE) deposits were related to acute rejection episodes among subjects with diabetes mellitus (DM); in contrast, among non-DM patients it was associated with prolonged freedom from coronary artery vasculopathy (CAV). However the number of observations in non-diabetic subjects was low. The aim of the current study was to establish the role of AGEs in late endomyocardial biopsies (EMBs) among a larger group of non-diabetic patients.

MATERIAL AND METHODS

Elective EMBs were performed at 3 years post OHT in 62 subjects with DM, namely, 57 males and 5 females of overall mean age of 50±8 years versus 92 free of DM, including 79 males and 13 females of mean age 51±13 years. We localized AGEs in myocardial paraffin sections using monoclonal mouse anti-AGE antibodies. The presence of AGEs in cardiomyocytes, stromal cells, capillaries, and arterioles was described with a semiquantitative scale.

RESULTS

All-cause deaths, CAV, and CAV-related events were observed in 28% versus 23%, 27% versus 29%, and 15% versus 19% of non-DM versus DM patients (P=NS). The occurrence of AGEs was significantly more frequent among non-DM than DM subjects: cardiocytes, 100% versus 69% (P<.0001); stroma, 54% versus 31% (P=.0037); capillaries, 67% versus 31% (P<.0001); and arterioles, 26% versus 3% (P=.0002; chi-square). Among the DM group, mean EMB score correlated with AGE presence in cardiomyocytes (n=0.29; P<.05, Spearman test) AGE presence had no impact on survival or CAV development.

CONCLUSION

AGE presence was more common in late EMB from non-diabetic than diabetic OHT recipients; they had no impact on survival or CAV in non-diabetic patients.

Advanced glycation end-products in myocardium-supported vessels: effects of heart failure and diabetes mellitus

BACKGROUND

Disturbed glucose metabolism, particularly in diabetes, is an important but not the sole factor leading to advanced glycation end-product (AGE) formation. The AGE amount and its distribution in cardiopathic myocardial tissues in the presence or absence of diabetes are not well documented. The aim of this study was to assess AGE deposition in unaffected myocardial vessels in heart failure patients with and without diabetes mellitus type 2 (DM2) undergoing transplantation.

METHODS

The following groups were established: 14 hearts harvested from subjects with ischemic cardiopathy and DM2; 8 hearts from subjects with dilated cardiopathy with DM2; 67 hearts from subjects with ischemic cardiopathy; 47 hearts from subjects with dilated cardiopathy; and 14 hearts from autopsy cases with diagnosed DM2. A control group consisted of 20 heart donors. AGE localization was determined immunohistochemically in tissue sections. A semi-quantitative scale was used to assess reaction intensity in arteries, arterioles, capillaries, venules and veins.

RESULTS

Both types of cardiomyopathy increased AGE accumulation in intramyocardial veins more than in arteries. The presence of DM2 significantly increased AGE in arterioles and capillaries, especially when coexisting with cardiomyopathy. The type of cardiopathy did not influence the pattern of AGE accumulation in myocardial vessels.

CONCLUSION

Both chronic heart failure and DM2 intensified AGE pathology and changed the susceptibility of myocardial vasculature to glycation. However, chronic heart failure increases AGE deposition mostly in veins, whereas DM2 predisposes arterioles to AGE accumulation.