With mine it's been 14-18 yrs and they are starting to improve now. Still quite self centred though. They can't help it; something to do with brain plasticity. It's not fully formed again until they are 24 apparently!
Step back, don't take it personally, be confident and do things to boost your own happiness as it is a very draining time when they are constantly pointing out all of your weaknesses and you get ignored or spoken to dismissively when you ask them something benign like "please pass the peas"! 
Don't follow them too closely up and down the emotional rollercoaster. Be available to talk and keep the lines of communication open, but aside from anything really life threatening or dangerous, leave them to make their own mistakes and be less "available". Focus on your own well-being and reach out to friends with teens. Model happiness to your adolescents! Don't expect them to show much interest in you or anything that concerns or interests you.
They need you there and will come and seek you out (usually at the most inconvenient time known to man) if there is anything really bothering them and it's then you drop everything and give them your full attention. You can also check in with them from time to time by inventing an errand and taking them on a drive with a lure of picking up food on the way home.
Other than that, provide bowls of healthy food that are available at all hours in the fridge , be cheerful, do your own thing and largely ignore the rudeness. Obviously decide on what you will and won't tolerate and set your boundaries but choose your battles.
Good luck op. Hang in there. Sending you strength as I know first hand how draining this stage can be. We love them to death but adolescence can be very hard emotionally for the entire family, especially mothers! 