Is fish oil good or bad for heart disease? Two trials with apparently conflicting results.

Two successive randomized trials examined the effect of an increased intake of fatty fish, or the use of fish oil supplements, in reducing mortality in men with heart disease. The Diet and Reinfarction Trial (DART) was conducted in 2033 men who were recovering from acute myocardial infarction (MI). Those who were advised to eat fatty fish (or who opted to take fish oil capsules instead) had a 29% reduction in all-cause mortality over the following two years compared with those not so advised. The effect appeared in the first few months of the trial. The Diet and Angina Randomized Trial (DART 2) involved 3114 men with stable angina. Advice to eat fatty fish did not reduce mortality, and taking fish oil capsules was associated with a higher risk of cardiac and sudden death. The adverse effects of fish or fish oil were restricted to men not taking beta-blockers or dihydropyridine calcium-channel blockers, and were greater in those taking digoxin. Evidence from other sources strongly suggests an anti-arrhythmic action of fish oil, particularly after MI or in the presence of acute ischemia. The apparently conflicting results of the two trials may reflect different actions of n-3 fatty acids in acute and chronic conditions, together with different effects of eating fish and taking fish oil capsules. A mechanism is proposed that could account for these findings.

Rapid determination of gap junction formation using HeLa cells microinjected with cDNAs encoding wild-type and chimeric connexins.

A procedure for rapidly determining the functionality of gap junctions constructed of recombinant connexins in communication-deficient HeLa cells is described. Nuclear microinjection of cDNA encoding wild-type connexins (Cx) 26, 32, 43, and a range of connexin-aequorin (Cx-Aeq) chimerase resulted in generation of gap junction intercellular communication channels. Expression of recombinant protein was detected in > 95% of cells 18-72 h following nuclear microinjection, and the functionality of the channels generated was determined according to their ability to transfer the fluorescent dye tracers Lucifer yellow and propidium iodide. The dye transfer results obtained correlated closely with other published studies using stably transfected cells and yet are obtained as rapidly as 18 h following microinjection of cDNA. Expression of a truncated form of Cx43 (Cx43 delta 244) by this new method indicated diminished intercellular transfer of both dyes and supports a channel-gating mechanism that postulates interaction between the carboxyl tail and the intracellular loop.