The '728 is not about Apo-B. The "Patent Office found that a decrease in Apo B was an unexpected benefit" in case of the '727 patent.
Can we assume USPTO Examiner had at least considered Kurabayshi?
Well … I could not imagine that somebody (an examiner) says
The prior art is either silent or teaches that there is no statistically significant change in Apo-B levels when patients with TG levels less than 150 mg/dl or between 150-499 mg/dl are treated with either 96% pure ethyl-EPA or a mixture of ethyl-EPA and DHA