Think of NAD+ like a supercharged shuttle bus inside our cells—it zips around, transferring electrons and making sure all sorts of important reactions happen. Team up NAD+ with its sidekick, NADH, and you've got the dynamic duo powering up our cells. They're the energy generators, making sure our cells can do their thing and keep us going.

But here's the deal: if our NAD+ levels are low, our cells hit a roadblock—they can't whip up the energy they need to function. NAD+ isn't just an energy powerhouse; it's also the boss in charge of our body's sleep/wake cycle, keeping our circadian rhythm in check.

So, without enough NAD+, our cells would be on a bit of an energy slump, and our sleep schedule might get a little wonky. It's safe to say; NAD+ is like the VIP of cellular energy and keeping our internal clock ticking!

let's break it down. When our genetic code takes a hit, it signals some proteins into action—like the superhero enzymes called PARPs. These PARPs use up NAD+ like fuel to swoop in and fix the damaged DNA. Now, here's the kicker: as we age, this NAD+ superhero supply seems to run low, adding to the risk of different health issues. Many experts think PARPs are the main culprits in this NAD+ drama.

But that's not all! Our immune system, another superhero in the body, also loves a good NAD+ snack. The busier our immune system gets (especially as we get older), the more NAD+ it chomps through, leaving less in the tank for other crucial functions.

Enter sirtuins, the cool kids linked to healthy aging and a longer life. These guys use NAD+ to control metabolism, keep our chromosomes in check, and fix up DNA boo-boos. But as we rack up more birthdays, and the DNA damage piles up, sirtuins start hogging even more NAD+.

Now, if you check out the charts, you'll see a bit of a sad story: as both guys and gals age, NAD+ levels take a bit of a dip. The red line shows how NAD+ changes over a whole lifetime, while the blue line focuses on the changes post-puberty. It's like our NAD+ levels are on a rollercoaster ride of aging!

they've got a few tricks up their sleeves through a process called "biosynthesis." Let's break it down in plain language:

First up, we've got the kynurenine (de novo) pathway. This one kicks off with the superstar amino acid, tryptophan, the same one blamed for post-Thanksgiving snoozefests. You can find tryptophan in goodies like meat, cheese, eggs, and fish. The conversion magic happens in the watery part of cells (cytosol), away from the cell's inner workings.

Then, there's the Preiss-Handler pathway, starring nicotinic acid. You can snag this from your diet or pop it as a supplement. It's also a gift from the bacteria in your guts. Nicotinic acid goes through a three-step dance, transforming into NAD+ with the help of enzymes like NAPRT, NMNAT, and NADS.

Last but not least, there's the salvage pathway, where the cell recycles compounds related to vitamin B3. Think nicotinamide, nicotinic acid, NMN, and NR. Enzymes like phosphoribosyltransferase and NMNAT do a makeover on nicotinamide, turning it into NMN, and then finally into the coveted NAD+.

So, in a nutshell, our cells have these cool pathways to whip up NAD+ from the goodies we eat or recycle within. Talk about some cellular kitchen magic!