The Penguins (44 points) lead the Eastern Conference division from the Islanders (42), with the pair well clear of the third-placed Washington Capitals (33).
Pittsburgh beat the Tampa Bay Lightning 4-2, denying the latter the chance to go clear top of the East's Atlantic division - the Lightning sit second, level on points with the Detroit Red Wings (both 41).
Brandon Sutter put Pittsburgh ahead in the final minute of the first period, but they would not lead at the break as Jonathan Drouin equalised on a power-play for Tampa Bay just 24 seconds later.
The Penguins pulled clear, however, as Bryan Rust's first NHL goal early in the second period was followed by Steve Downie's power-play goal late in the middle stanza.
Downie then assisted Brian Dumoulin to score in the final period, before Nikita Kucherov - who assisted in Tampa Bay's opening goal - scored late to join Downie in producing a two-point game.
The Islanders stayed within one win of their rivals, after edging the New Jersey Devils 3-2 after a shoot-out.
New Jersey opened up a two-goal lead in the space of 3:05 in the first period, with Marek Zidlicky, Scott Gomez and Jaromir Jagr all combining for both goals.
Zidlicky opened the scoring on a power-play - Gomez and Jagr with the assists - before Gomez struck moments later, as Jagr and Zidlicky were credited with points in the build-up.
But Josh Bailey and Matt Martin goals brought the Islanders level, before Bailey scored the decisive goal in the shoot-out - after New York's Kyle Okposo and Devils man Gomez had been on target earlier in the tie-breaker.
The Buffalo Sabres made it four straight wins over fellow Atlantic strugglers the Ottawa Senators - albeit after coughing up a two-goal lead before prevailing 5-4 after a shoot-out.
The Sabres led 3-1 after three quick-fire goals in the second period, only for the Senators to respond with three goals of their own to lead heading into the final 15 minutes.
But Brian Flynn equalised for Buffalo in the 17th minute of the final period, and Matt Moulson - who earlier put Buffalo in front for the first time in the middle stanza - struck the only goal in the shoot-out.