Mitochondrial targeted antioxidants, mitoquinone and SKQ1, not vitamin C, mitigate doxorubicin-induced damage in H9c2 myoblast: pretreatment vs. co-treatment

BACKGROUND

Preconditioning of the heart ameliorates doxorubicin (Dox)-induced cardiotoxicity. We tested whether pretreating cardiomyocytes by mitochondrial-targeted antioxidants, mitoquinone (MitoQ) or SKQ1, would provide better protection against Dox than co-treatment.

METHODS

We investigated the dose-response relationship of MitoQ, SKQ1, and vitamin C on Dox-induced damage on H9c2 cardiomyoblasts when drugs were given concurrently with Dox (e.g., co-treatment) or 24 h prior to Dox (e.g., pretreatment). Moreover, their effects on intracellular and mitochondrial oxidative stress were evaluated by 2,7-dichlorofluorescin diacetate and MitoSOX, respectively.

RESULTS

Dox (0.5-50 μM, n = 6) dose-dependently reduced cell viability. By contrast, co-treatment of MitoQ (0.05-10 μM, n = 6) and SKQ1 (0.05-10 μM, n = 6), but not vitamin C (1-2000 μM, n = 3), significantly improved cell viability only at intermediate doses (0.5-1 μM). MitoQ (1 μM) and SKQ1 (1 μM) significantly increased cell viability to 1.79 ± 0.12 and 1.59 ± 0.08 relative to Dox alone, respectively (both p < 0.05). Interestingly, when given as pretreatment, only higher doses of MitoQ (2.5 μM, n = 9) and SKQ1 (5 μM, n = 7) showed maximal protection and improved cell viability to 2.19 ± 0.13 and 1.65 ± 0.07 relative to Dox alone, respectively (both p < 0.01), which was better than that of co-treatment. Moreover, the protective effects were attributed to the significant reduction in Dox-induced intracellular and mitochondrial oxidative stress.

CONCLUSION

The data suggest that MitoQ and SKQ1, but not vitamin C, mitigated DOX-induced damage. Moreover, MitoQ pretreatment showed significantly higher cardioprotection than its co-treatment and SKQ1, which may be due to its better antioxidant effects.

Characteristics of Turkish children with Type 2 diabetes at onset: a multicentre, cross-sectional study

AIMS

To describe the baseline clinical and laboratory findings and treatment modalities of 367 children and adolescents diagnosed with Type 2 diabetes in various paediatric endocrinology centres in Turkey.

METHODS

A standard questionnaire regarding clinical and laboratory characteristics at onset was uploaded to an online national database system. Data for 367 children (aged 6-18 years) newly diagnosed with Type 2 diabetes at 37 different paediatric endocrinology centres were analysed.

RESULTS

After exclusion of the children with a BMI Z-score < 1 SD, those with genetic syndromes associated with Type 2 diabetes, and those whose C-peptide and/or insulin levels were not available, 227 cases were included in the study. Mean age was 13.8 ± 2.2 (range 6.5-17.8) years, with female preponderance (68%). Family history of Type 2 diabetes was positive in 86% of the children. The mean BMI was 31.3 ± 6.5 kg/m² (range 18.7-61) and BMI Z-score was 2.4 ± 0.8 (range 1-5). More than half (57%) of the children were identified by an opportunistic diabetes screening due to existing risk markers without typical symptoms of diabetes. Only 13% (n = 29) were treated solely by lifestyle modification, while 40.5% (n = 92) were treated with metformin, 13% (n = 30) were treated with insulin, and 33.5% (n = 76) were treated with a combination of insulin and metformin initially. Mean HbA_1C levels of the insulin and combination of insulin and metformin groups were 98 (11.1%) and 102 mmol/mol (11.5%), respectively, and also were significantly higher than the lifestyle modification only and metformin groups mean HbA_1C levels (70(8.6%) and 67 mmol/mol (8.3%), respectively).

CONCLUSIONS

An opportunistic screening of children who are at high risk of Type 2 diabetes is essential, as our data showed that > 50% of the children were asymptomatic at diagnosis. The other important result of our study was the high rate of exclusion from the initial registration (38%), suggesting that accurate diagnosis of Type 2 diabetes in youth is still problematic, even for paediatric endocrinologists.

Late effects of childhood ALL treatment on body mass index and serum leptin levels

BACKGROUND

It is well known that survivors of acute lymphoblastic leukemia (ALL) show a tendency to become overweight. Cranial irradiation (CRT), is considered to be the primary risk factor for development of obesity.

AIMS

The aim of our study was to evaluate body mass index (BMI) and serum leptin levels in survivors of childhood ALL.

METHODS

Subjects (Group I) consisted of 93 survivors of childhood ALL (53 males > or = 9 years old, 40 females > or = 8 years old) diagnosed between January 1975 and December 2002 in the Hematology-Oncology Division in Cerrahpasa Medical Faculty, Istanbul University after a follow up 10.21 +/- 4.90 (mean +/- SD) years. Fifty healthy individuals of similar chronological age were taken as controls (29 males, 21 females). Seventy-four subjects had received radiotherapy (Group IA) and 19 had not (Group I B).

RESULTS

In Group I, BMI was significantly higher than in Group II (21.65 +/- 4.02 vs 20.31 +/- 3.49, p = 0.04). However, BMI was significantly higher only in Group I A (21.83 +/- 4.27) than in Group II (p = 0.032). Leptin levels were significantly higher in Group I A females than in Group II females. There was a significant correlation between BMI-SDS and serum leptin levels in group IA females.

CONCLUSIONS

Leukemia treatment leads to obesity. Higher leptin levels in girls may suggest that sex may be a differentiating factor for this late effect.