Testing genetic susceptibility loci for alcoholic heart muscle disease.

BACKGROUND: Although many heavy alcohol users have subclinical alcoholic heart muscle disease, only a very few develop severe dilated cardiomyopathy. Therefore, and because cardiac abnormalities correlate only weakly with the duration or quantity of drinking, individual susceptibility differences may exist. In this work we examined whether common gene variants previously associated with cardiac hypertrophy or altered alcohol metabolism could modify the effects of alcohol on the heart. METHODS: We studied 700 middle-aged male victims of sudden death who underwent a medicolegal autopsy. In addition to routine postmortem examination, the weights and the cavity and wall dimensions of the left and right ventricle were measured. Coronary artery stenoses were determined from a silicone rubber cast of the arteries. Alcohol consumption and cardiovascular risk factors were assessed by a structured interview of the spouse. The following gene polymorphisms were determined by using polymerase chain reaction restriction fragment length polymorphism and solid-phase minisequencing techniques: angiotensin converting enzyme I/D, angiotensin II type 1 receptor 1166A/C, aldosterone synthase -344C/T, alcohol dehydrogenases 2 and 3, acetaldehyde dehydrogenase 2, and cytochrome P-450 2E1 DraI, PstI, RsaI, and MspI. RESULTS: The most consistent effects of alcohol (p < 0.05) were a higher total heart weight and a larger right ventricle size with increasing daily drinking. However, these and other effects of alcohol were statistically fully independent of the studied genotypes. CONCLUSIONS: The gene polymorphisms selected for and analyzed in our study are unlikely to modify the effects of alcohol on the heart. Other unknown factors determine the individual susceptibility to alcoholic heart muscle disease.

Association of neuropeptide y polymorphism with the occurrence of type 1 and type 2 alcoholism.

BACKGROUND: The susceptibility to alcoholism can be explained partially by genetic factors. Neuropeptide Y (NPY) has emerged as one potential factor contributing the development of alcoholism. A recent study indicated that the NPY gene variant producing a leucine-to-proline substitution (T to C at position 1128) was associated with 34% higher average alcohol consumption. METHODS: The subjects consisted of 122 alcoholics classified as type 1 and type 2 subtypes by psychiatric evaluation. A random sample of 59 social drinkers was used as a control group to compare the distribution of NPY genotypes with those of alcoholics. RESULTS: In a logistical regression model, there was a significantly lower frequency of the leucine(7)/proline(7) heterozygotes among well characterized type 2 alcoholics, compared with the controls (10.8 vs. 24.1%, p = 0.028). CONCLUSIONS: We speculate that the genetic polymorphism producing the proline(7) substitution of NPY might not predispose to alcoholism, but indeed retard the transition to alcoholism.

Prominent mitochondrial DNA recombination intermediates in human heart muscle.

Recombination intermediates containing four-way (Holliday) junctions are generated during DNA repair and replication in many systems, including yeast mitochondrial DNA (mtDNA). In contrast, convincing evidence for recombination in mammalian mtDNA is lacking. We have used two-dimensional agarose-gel electrophoresis to analyse non-linear forms of mtDNA in human heart muscle. Replication intermediates from both the coupled and strand-asynchronous mtDNA replication pathways were detected. An additional class of non-linear molecules, with the electrophoretic properties of four-way junctions, was also prominent. These molecules were insensitive to topoisomerase I or RNase H, but were diminished by branch migration or RuvC treatment. Junctional molecules were detected in all regions of the mitochondrial genome, were found in myocardial DNA from young and old adults, but were present at lower levels in skeletal muscle and placenta. We suggest that they could represent intermediates of mtDNA repair, given their prevalence in the oxyradical-rich environment of heart muscle mitochondria.

Dose dependent but non-linear effects of alcohol on the left and right ventricle.

OBJECTIVE: To assess how left (LV) and right ventricular (RV) size, wall thickness, and mass depend on daily alcohol consumption. Among alcoholics, most common findings have been LV hypertrophy and mild systolic or diastolic dysfunction, accompanied occasionally by ventricular dilatation resembling dilated cardiomyopathy. Although it is commonly agreed that chronic heavy alcohol use is injurious to the heart, the dose-injury relation remains a matter of dispute. DESIGN: Prospective series of 700 Finnish men aged 33-70 years who died out of hospital and underwent a medicolegal necropsy. METHODS AND RESULTS: Data on alcohol use and other risk factors were obtained from the spouse. At necropsy, a transversal slice of the heart was traced on a transparent sheet and analysed later for LV and RV cavity areas and wall thicknesses. Coronary artery stenoses were measured from silicone casts of the arteries. In analyses of all men, daily alcohol dose predicted heart weight (beta = 0.17, p < 0.001) and RV cavity area (beta = 0.14, p = 0.007) independent of body size, age, coronary artery disease, hypertension, diabetes, and smoking. In the subgroup of men free of significant coronary artery disease, LV area averaged (SEM) 11.0 (1.0) cm(2) in men drinking < 12 g/day, 7.7 (0.7) cm(2) in those drinking 72-180 g/day, and 10.0 (0.9) cm(2) in those drinking > 180 g/day (p = 0.054). Very heavy drinking (> 180 g/day) was associated with an increase in RV cavity area (p = 0.005). CONCLUSIONS: The effects of alcohol on the heart in middle aged men are dose dependent but partly non-linear. In the absence of coronary artery disease, LV size shows a U shaped reduction with increasing daily alcohol use accompanied by an increase in RV size with very heavy drinking. These findings question the idea of progressive LV dilatation with increasing alcohol consumption among male victims of sudden death.

Coronary artery disease modifies left ventricular remodelling due to heavy alcohol consumption.

BACKGROUND: Coronary artery disease (CAD) and excessive alcohol use can both damage the myocardium. Their combined effect on the heart muscle has not been characterized. We set out to assess whether the presence of CAD modifies the effects of chronic alcohol consumption on the left ventricular (LV) structure in middle-aged men. METHODS: A postmortem examination was performed on 700 Finnish men (age range, 33-70 years) who experienced a sudden, nonhospital death. A coronary arteriography and measurement of the LV wall thickness, cavity area, and ratio by planimetry of transversal ventricular slices were done at the autopsy. The men were grouped by the most severe coronary artery diameter stenosis (<30%, 30-60%, >60%) and by daily alcohol dose (<12 g, 12-72 g, 72-180 g, >180 g) estimated by a structured interview of their lifetime partner. RESULTS: Analysis by ANCOVA, adjusted for age, body size, smoking, hypertension, and diabetes, showed a statistically significant interaction between the effects of coronary artery stenosis and daily alcohol dose on the LV cavity area (p = 0.037) and on the LV wall thickness/cavity area ratio (p = 0.018). In the group with <30% stenosis, the LV wall thickness/cavity area ratio (mean +/- SEM) increased from 1.6 +/- 0.2 mm/cm2 in men drinking <12 g/day to 6.2 +/- 1.4 mm/cm2 in men drinking 72-180 g/day (p = 0.021). A similar trend was seen in men with 30-60% coronary stenosis (p = 0.32). By contrast, in men with >60% coronary stenosis, the LV wall thickness/cavity area ratio decreased with increasing daily alcohol use from 2.2 +/- 0.3 to 1.4 +/- 0.1 mm/cm2 (p = 0.27). CONCLUSIONS: CAD modulates the effects of alcohol on the heart muscle. Heavy drinking results in concentric LV remodelling in men with no or only mild coronary artery stenoses whereas an opposite trend is seen in men with severe coronary artery obstructions. The mechanism of the interaction remains unknown.

Human mtDNA sublimons resemble rearranged mitochondrial genoms found in pathological states.

Sublimons, originally identified in plant mitochondria, are defined as rearranged mtDNA molecules present at very low levels. We have analysed the primary structures of sublimons found in human cells and tissues and estimated their abundance. Each tissue of a given individual contains a wide range of different sublimons and the most abundant species differ between tissues in a substantially systematic manner. Sublimons are undetectable in rho(0) cells, indicating that they are bona fide derivatives of mtDNA. They are most prominent in post-mitotic tissue subject to oxidative stress. Rearrangement break-points, often defined by short direct repeats, are scattered, but hotspot regions are clearly identifiable, notably near the end of the D-loop. The region between the replication origins is therefore frequently eliminated. One other hotspot region is located adjacent to a known site of protein binding, suggesting that recombination may be facilitated by protein-protein interactions. For a given primary rearrangement, both deleted and partially duplicated species can be detected. Although each sublimon is typically present at a low level, at most a few copies per cell, sublimon abundance in a given tissue can vary over three orders of magnitude between healthy individuals. Collectively, therefore, they can represent a non-negligible fraction of total mtDNA. Their structures are very similar to those of the rearranged molecules found in pathological states, such as adPEO and MNGIE; therefore, we propose that, as in plants, human mtDNA sublimons represent a pool of variant molecules that can become amplified under pathological conditions, thus contributing to cellular dysfunction.

Mitochondrial DNA--all things bad?

Mutations in mitochondrial DNA (mtDNA) are undoubtedly associated with a diverse spectrum of human disorders. More controversially, it has been claimed that they accumulate during ageing, and that they are responsible for an age-related decline in bioenergetic function and tissue viability. Here, we review the evidence for this assertion, concluding that claims for the age-accumulation of mtDNA mutations are based largely on non-quantitative methods, and that no clear, functional deficit of mitochondrial respiration has been shown to result from such lesions in aged individuals. The mitochondrial theory of ageing, however attractive in principle, is supported by very little hard evidence.

Long-extension PCR to detect deleted mitochondrial DNA molecules is compromized by technical artefacts.

Long-extension PCR (LX-PCR), followed by Southern hybridization to probes for two different regions of the mitochondrial genome, was used to evaluate the presence of deleted mtDNA molecules in heart muscle samples from alcoholic cardiomyopathy patients compared with age-matched controls. Two different primer pairs capable of amplifying the entire genome, as well as a variety of other primer pairs predicted to amplify the genome in large, overlapping fragments, were tested. Products indicating the presence of a variety of subgenomic, deleted molecules were detected in variable amounts from patient and control myocardial samples alike. Most of these hybridized with a probe for the 16S/ND1 region, but not with a probe for the ND4/ND5 region that is commonly deleted. Dilution of a given template DNA in which deleted products were prominent resulted in the disappearance of the subgenomic bands in favour of the full-length, undeleted product. Therefore, the appearance and amount of such products is subject to template concentration or quality. The results indicate that the application of LX-PCR to the detection and quantitation of deleted mtDNAs is inherently unreliable, and findings using this technique should be treated with caution unless supported by an independent method.