Safarina G Malik

Prevalence of the mitochondrial DNA A1555G mutation in sensorineural deafness patients in island Southeast Asia

AbstractA mtDNA A1555G base substitution in a highly conserved region of the 12S rRNA gene has been reported to be the main cause of aminoglycoside induced deafness. This mutation is found in approximately 3% of Japanese and 0.5–2.4% of European sensorineural deafness patients. We report a high prevalence (5.3%) of the A1555G mutation in sensorineural deafness patients in Sulawesi (Indonesia). Our result confirms the importance of determining the prevalence of the mtDNA A1555G mutation in different populations, and the need for mutation detection before the administration of aminoglycoside antibiotics.

Factors Affecting the Binding of Bilirubin to Serum Albumins: Validation and Application of the Peroxidase Method

The unbound “free” bilirubin concentration (Bf), not the total bilirubin concentration, is the critical determinant of cellular uptake and toxicity of bilirubin. We compared Bf measured by a modified peroxidase method with published data obtained with ultrafiltration and examined conditions that affect the affinity (KF) of human (HSA) and bovine (BSA) serum albumin for bilirubin. The peroxidase and ultrafiltration methods yielded similar KF values that decreased with increasing HSA concentration and the presence of 50 mM chloride. When related to ionic strength, inhibition of BSA-bilirubin binding by chloride, bromide, and sulfate were similar, whereas phosphate buffer had a smaller effect. KF was lower at 37°C than at 25°C for HSA but not for BSA. KF for BSA was similar at pH 7.4 and 8.0. BSA and FCS had similar binding properties. The close agreement of Bf and KF values determined by the peroxidase method with published results obtained by ultrafiltration validates both methods and supports the use of the peroxidase method as a practical technique for measuring Bf under steady state conditions in minimally diluted serum or culture medium.

Uncoupling protein 2 gene polymorphisms are associated with obesity

BackgroundUncoupling protein 2 (UCP2) gene polymorphisms have been reported as genetic risk factors for obesity and type 2 diabetes mellitus (T2DM). We examined the association of commonly observed UCP2 G(−866)A (rs659366) and Ala55Val (C > T) (rs660339) single nucleotide polymorphisms (SNPs) with obesity, high fasting plasma glucose, and serum lipids in a Balinese population.MethodsA total of 603 participants (278 urban and 325 rural subjects) were recruited from Bali Island, Indonesia. Fasting plasma glucose (FPG), triglyceride (TG), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) were measured. Obesity was determined based on WHO classifications for adult Asians. Participants were genotyped for G(−866)A and Ala55Val polymorphisms of the UCP2 gene.ResultsObesity prevalence was higher in urban subjects (51%) as compared to rural subjects (23%). The genotype, minor allele (MAF), and heterozygosity frequencies were similar between urban and rural subjects for both SNPs. All genotype frequencies were in Hardy-Weinberg equilibrium. A combined analysis of genotypes and environment revealed that the urban subjects carrying the A/A genotype of the G(−866)A SNP have higher BMI than the rural subjects with the same genotype. Since the two SNPs showed strong linkage disequilibrium (D’ = 0.946, r2 = 0.657), a haplotype analysis was performed. We found that the AT haplotype was associated with high BMI only when the urban environment was taken into account.ConclusionsWe have demonstrated the importance of environmental settings in studying the influence of the common UCP2 gene polymorphisms in the development of obesity in a Balinese population.

Evidence for the de novo regeneration of the pattern of the length heteroplasmy associated with the T16189C variant in the control (D-loop) region of mitochondrial DNA

AbstractWe have investigated the genetics of the length heteroplasmy associated with the T16189C variant of mitochondrial DNA (mtDNA), and report here definitive evidence that the pattern of the length heteroplasmy is not simply the outcome of drift related to the random segregation of the mtDNA population during cell division, but is actively maintained and regenerated de novo following each cell division. The pattern of the length heteroplasmy was maintained in a fibroblast cell line during an extensive mtDNA depletion experiment by ethidium bromide treatment, and following the subsequent repopulation of the cells with mtDNA. The investigation of the pattern of the length heteroplasmy by single cell pick up shows a similar pattern in sister cells despite the evidence of the randomness of mtDNA segregation, providing definitive evidence for the de novo regeneration of the pattern following cell division. Consistent with this conclusion is the observation that similar patterns of length heteroplasmy are found in tissues of single individuals.

Nuclear mitochondrial interplay in the modulation of the homopolymeric tract length heteroplasmy in the control (D-loop) region of the mitochondrial DNA.

Abstract. We have studied the genetic characteristics of a homopolymeric tract length heteroplasmy associated with the 16189C variant in the mtDNA D-loop control region to identify the factor(s) involved in the generation of the length heteroplasmy. The relative proportion of the various lengths of the polycytosines (i.e., the pattern of the length heteroplasmy) is maintained in an individual, and previous evidence shows that it is regenerated de novo following cell divisions. The pattern is maintained in maternally related individuals, suggestive of mtDNA determinants. Of the 38 individuals with the 16189C variant studied, 39% were found to exhibit the 16180AAACCCCCCCCCCC16193 variant associated with A16183C polymorphism [(11C)-group], while 53% showed the 16180AACCCCCCCCCCCC16193 variant associated with a further A16182C polymorphism [(12C)-group]. Haplotype analysis of the mtDNA revealed a specific association of the longer mean length of the poly[C] in the (12C)-group with haplogroup B. A similar association was also observed in the (11C)-group, but with a novel haplogroup. Cybrid constructions revealed that the involvement of nuclear factor(s) in the generation of the length heteroplasmy is prominent in homopolymeric tract of eight cytosines. The nuclearly coded factor(s) is/are presumably related to the fidelity of the nuclearly coded components of the mitochondrial DNA replication machinery.

Effect of bilirubin on cytochrome c oxidase activity of mitochondria from mouse brain and liver

BackgroundThe unbound, free concentration (Bf) of unconjugated bilirubin (UCB), and not the total UCB level, has been shown to correlate with bilirubin cytotoxicity, but the key molecular mechanisms accounting for the toxic effects of UCB are largely unknown.FindingsMouse liver mitochondria increase unbound UCB oxidation, consequently increasing the apparent rate constant for unbound UCB oxidation by HRP (Kp), higher than in control and mouse brain mitochondria, emphasizing the importance of determining Kp in complete systems containing the organelles being studied. The in vitro effects of UCB on cytochrome c oxidase activity in mitochondria isolated from mouse brain and liver were studied at Bf ranging from 22 to 150 nM. The results show that UCB at Bf up to 60 nM did not alter mitochondrial cytochrome c oxidase activity, while the higher concentrations significantly inhibited the enzyme activity by 20% in both liver and brain mitochondria.ConclusionsWe conclude that it is essential to include the organelles being studied in the medium used in measuring both Kp and Bf. A moderately elevated, pathophysiologically-relevant Bf impaired the cytochrome c oxidase activity modestly in mitochondria from mouse brain and liver.

Nonsyndromic sensorineural deafness associated with the A1555G mutation in the mitochondrial small subunit ribosomal RNA in a Balinese family

AbstractSensorineural deafness associated with increased sensitivity to aminoglycoside antibiotics as the consequence of an A1555G mutation in the mitochondrial DNA (mtDNA) in a highly conserved region of the small (12S) rRNA gene has been reported in Caucasian, Chinese, and Japanese individuals. We report here a large family of Balinese Indonesian origin with progressive/congenital sensorineural deafness who carry the A1555G mutation. The pedigree shows a generally maternal inheritance pattern with some exceptions, which is the result of an unusual multiple entry of the mutation into the pedigree. A complete mtDNA genome sequence from three Balinese individuals revealed a relatively large number of single- nucleotide polymorphisms (20) not previously reported, and confirmed the genetic distance of Southeast Asian populations from those of Caucasians and Japanese. The biochemical expression of the A1555G mutation under the influence of this mtDNA background was investigated. Examination of respiratory enzyme activities showed a significant decrease in respiratory complex I activity, particularly in symptomatic family members.

Association of beta3-adrenergic receptor (ADRB3) Trp64Arg gene polymorphism with obesity and metabolic syndrome in the Balinese: a pilot study

BackgroundPrevalence of obesity is increasing all over the world. ADRB3 Trp64Arg gene polymorphism was proposed to be associated with obesity, although inconsistent findings and differences of the Arg64 allele frequency among various ethnics were reported. Westernization was reported to increase the prevalence of obesity in developing world. In this study we determined the prevalence of obesity and metabolic syndrome among urban and rural Balinese, and studied the association of ADRB3 Trp64Arg polymorphism with obesity and MetS.FindingsA total of 528 Balinese (urban 282, rural 246) were recruited. Body mass index (BMI) and waist circumference (WC) were determined; high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), systolic and diastolic blood pressure (SBP and DBP), and fasting plasma glucose (FPG) were measured using standard procedures. BMI and WC classifications were based on WHO classifications for Asian. Metabolic syndrome (MetS) was defined as described in the Joint Interim Statement. Chi-square test was employed to test the association between the ADRB3 Trp64Arg genotype and disease traits.Urban have higher BMI (p = 2.8 × 10-13), WC ( p < 2.2 × 10-16), TG (p = 0.0028), DBP (p = 1.8 × 10-5), and lower HDL-C (p = 0.0376) when compared to rural. Abdominal obesity and MetS prevalence were significantly higher in urban as compared to rural (both p < 0.001). The Arg64 allele frequency was similar between urban (0.06) and rural (0.05). The Arg64 rural female carriers have higher BMI and WC as compared to their Trp64 counterparts (p = 0.041 for BMI and p = 0.012 for WC), and consequently higher abdominal obesity prevalence (p = 0.007). Comparison between male and female, as well as urban and rural, showed different prevalence of MetS co-morbidities. Abdominal obesity and hypertriglyceridaemia were consistently appeared in all groups, suggesting to play a role as determinant of MetS in both urban and rural.ConclusionsPrevalence of obesity and MetS in urban were two times higher when compared to rural. Abdominal obesity and hypertriglyceridaemia appears to be the key determinant of MetS in both urban and rural Balinese. Our results indicated an association of the ADRB3 Trp64Arg gene polymorphism with obesity in the rural female.

Microphotometric analysis of NADH-tetrazolium reductase deficiency in fibroblasts of patients with Leber hereditary optic neuropathy

We employed a microphotometric approach to examine whether a defect in the mitochondrial respiratory complex I expected in Leber hereditary optic neuropathy (LHON) as the consequence of a mtDNA (11778G>A) mutation in the ND4 gene coding for a subunit of the respiratory complex I can be detected at the single-cell level. Genetically stable fibroblast cell lines were established from skin biopsies of two members of a Chinese Indonesian family with LHON. The fibroblasts were homoplasmic for the 11778G>A mutation. The activity of the respiratory complex I was examined histochemically by staining for NADH-tetrazolium reductase. The histochemical staining showed a typical pattern with an apparent concentration of the activity around the nucleus, suggested as the reflection of the gradient in the thickness of the unsectioned fibroblast cells. Microphotometric quantification of the staining intensity showed that the activity is linear for at least 60min. The activity shows a discontinuity in its Arrhenius kinetics with a break point at 13.0–13.5°C (activation energy at 50–58 J/mol and 209–238 J/mol above and below the break temperature, respectively), indicating the membrane association of the NADH-tetrazolium reductase activity. Both patients showed lower fibroblast NADH-tetrazolium reductase activity, with a reduction of ∼30%. Our results demonstrate the utility of microphotometric analysis in the study of biochemical defects associated with mutations in the mtDNA.

Coronary Heart Disease in a Remote Area

A study on coronary heart disease (CHD) in a remote area, Ceningan Island,was conducted.The nutrition states based on BMI were underweight,19.3%; normoweight, 54.9%; and overweight at risk, 13.3%; obese I, 9.5%; and obese II, 3.0%. The prevalence of impaired fasting glycemia (IFG), 15.1%; diabetes mellitus (DM), 6.9%; metabolic syndrome (MetS), 6.8%; and CHD, 11.5%. Age, systolic and diastolic blood pressure, levels of total cholesterol; low-density lipoprotein (LDL) cholesterol, apolipoprotein (Apo)A, ApoB, Apo B/A ratio were found higher among subjects with old myocardial infarction (OMI) than subjects without CHD; while BMI and waist circumference were lower among subjects with OMI than subjects without CHD. Conclusion: traditional risk factors such as age, blood pressure, and cholesterol, and Apo were related to CHD in the remote area.