부산대학교 도서관

Cushing's syndrome (CS), a rare disease due to excessive cortisol secretion, is associated with increased morbidity and mortality, even after therapy compared to background population and is associated with premature aging processes. On the other hand, telomeres are repetitive DNA sequences, essential to maintain genomic stability. Without telomeres, genetic material could be lost after every cell division; thus, when telomeres are critically short, cell division stops and senescence and apoptosis are induced. To avoid telomere length (TL) attrition an enzymatic complex called telomerase is produced. Telomerase can be regulated by genetic, epigenetic and hormonal factors such as cortisol. Hypercortisolism also occurs in chronic depressive disorders and psychosocial stress, where TL is shorter than in controls. Moreover, TL shortening has also been associated with cardiovascular disease, cardiovascular risk factors (CVRF) and chronic inflammation processes. TL shortening is considered a novel cardiovascular risk marker, and is associated with inflammation biomarkers. Based on these previous evidences, we hypothesized that hypercortisolemia could contribute to premature ageing by inducing accelerated telomere shortening, which in turn could be implied in the persistent morbidity and clinical consequences associated with CS, even years after biochemical remission. Additionally, TL shortening, might be involved in the “low grade” inflammatory state and higher prevalence of CVRF observed in CS. Therefore, this research was designed to answer our hypothesis, being the main aims of this project to investigate TL in CS patients compared to controls, and to evaluate relationships between TL, CVRF and inflammation markers in CS. This is the first research to evaluate TL in this rare disease with a relatively large series of CS patients, which could provide a unique opportunity to examine the effects of hypercortisolism on telomere maintenance. Seventy-seven CS patients were compared with 77 gender-, age-, and smoking-matched controls. Fifteen CS were also evaluated longitudinally, during active disease and after remission of hypercortisolism. Clinical data and blood samples were collected (lipids, adrenal function...). Adiponectin, interleukin-6 (IL6) and C-reactive protein (CRP) were available in a subgroup of patients (n=32). Leukocyte TL was measured by telomere restriction fragment-Southern technique. Mean TL in CS and controls was similar, however in the longitudinal evaluation after adjustment for age, TL was shorter in active disease than after remission. No correlation was found between other circulating cortisol parameters, duration of exposure to hypercortisolism or biochemical cure and TL. We observed that dyslipidemic CS had shorter TL than non-dyslipidemic subjects. After adjustment for age and body mass index, cured and active CS dyslipidemic patients had shorter TL than non-dyslipidemic subjects. Additionally, higher TL shortening was observed in dyslipidemic obese patients who were also hypertensive, compared to those with two or less CVRF. Total-cholesterol and triglycerides negatively correlated with TL, as well as CRP and IL6. No differences in TL according the presence of other CVRF were observed in CS or the control group. The main conclusions are that individual CS patients in whom hypercortisolism is controlled after successful treatment, TL increases despite being on average 3 years older. It would appear therefore that telomerase activity would be induced once hypercortisolism disappears, and this could be one of the mechanisms by which increased morbidity, mortality and biological aging improve when disease is controlled. These preliminary results suggest that hypercortisolism might negatively impact telomere maintenance. Moreover, TL is shortened in dyslipidemic CS patients, further worsened if hypertension and/or obesity coexist and is negatively correlated with increased inflammation markers. Therefore, increased lipids and a “low-grade” inflammation may contribute to TL shortening and consequently to premature ageing and increased morbidity in CS.