The following is my speculation based on the above studies as well as additional information I will post along. The most likely channels
through which AAs cause kidney damage are:
1) Increased blood pressure
2) Oxidative stress
3) Exacerbated myoglobin toxicity
4) Angiotensin II
5) Endothelin-1
6) Increased lean body mass
7) Increased protein consumption
8) Insufficient hydration
Let's look at each in turn and discuss what preventative measures we can take as AAS abusers.
1) Increased blood pressure
This one is pretty self-explanatory. The evidence that high blood pressure leads to kidney damage (especially over long periods of time) is overwhelming. Similarly, there is now a pretty good understanding of how AAS lead to increases in blood pressure, see this thread:
http://www.professionalmuscle.com/f...42419-maintaining-heart-health-while-aas.html
The same thread also contains information on how to manage AAS induced increases in blood pressure. it is important that you regularly check your BP throughout your cycle. Just because your blood pressure is under control with certain medications while taking one anabolic steroid does not mean it will also be the case when taking other steroids. For example, extremely androgenic steroids like trenbolone may require higher dosages of BP meds in general, and higher doses of beta blockers in particular. Conversely, steroids that lead to extreme bloat may require use of a diuretic (and/or diet changes). Constantly monitor your blood pressure and adjust medication accordingly. the bodybuilder from the Gollasch et al. (2018) case studyis a good example. he was taking blood pressure meds but they failed to adequately control his BP given his cycle at the time.
2) Oxidative stress
We have seen in several animal studies above that AAS induce oxidative stress that may overwhelm the body's antioxidative capacity. Supplementation of compounds with antioxidative activity may ameliorate the damage caused by it. In particular, we have seen that Glutathione levels in both liver and kidney are depleted due to AAS administration. In order to combat this, one should take NAC. There isn't too much research on this, but one study found beneficial effects of NAC supplementation.
See
https://academic.oup.com/ndt/article/19/8/1951/1918231 for a review on the potential role for Glutathione in kidney disease.
In addition to this supplementation, a healthy diet with lots of veggies (and moderate fruit) is recommended. Supplements with antioxidants, such as propolis is another promising avenue.
3) Exacerbated myoglobin toxicity
When people hear myoglobin, they probably think of rhabdomyolysis. The latter occurs when damaged muscle tissue breaks down and releases myoglobin into the blood stream, which then damages the kidneys while being filtered and excreted by them.
However, myoglobin is not just released in the case of extreme muscle damage that would lead to the condition of rhabdomyolysis. Even moderate intensity exercise causes sufficient muscle damage to increase serum myoglobin levels!
https://link.springer.com/article/10.1007/BF02343808
https://www.ncbi.nlm.nih.gov/pubmed/6861785
OK, so we know that a bodybuilding-style workout will release quite some myoglobin into the bloodstream. Here is how it then damages the kidney:
https://en.wikipedia.org/wiki/Myoglobin
https://en.wikipedia.org/wiki/Exertional_rhabdomyolysis
Thus the amount of damage done by myoglobin to the kidneys depends on the amount released, as well as the acidity of urine/the surrounding renal tissue. Rhabdomyolysis only occurs if too much myoglobin is released such that there is acute kidney failure. But even smaller amounts of myoglobin will do damage to the kidneys, in particular in case of chronic exposure.
Now, AAS abuse has a twofold impact here.
1) Increased myoglobin release. AAS allow for higher training volume and frequency. Furthermore, androgens lead to sizable strength increases, so that the mechanical tension on each set is higher, leading to more release on myoglobin per set. In addition, more sets are performed due to the ability to recover faster post exercise. Lastly, someone on juice will have less rest days to make the most of their cycle. As a result, total myoglobin load for the kidneys is higher, potentially leading to accumulated damage over time that culminates in FSGS.
2) Increased urine acidity. As described in the Aparicio et al. (2017) paper, urine acidity is increased after AAS treatment. We have also learned above that the nephrotoxicity of myoglobin depends on the acidity of the environment. Thus, i would speculate that for a given serum level of myoglobin, AAS induced acidity increases the damage done to the kidneys.
Note that there is also a potential interaction between AAS-induced antioxidant depletion and kidney damage due to myoglobin. In fact, all the channels are likely to interact in various ways and potentially exacerbate each other's effects.
In any case, this proposed increased myoglobin toxicity due to AAS abuse would lead to an accumulation of damage over time that could culminate is FSGS. Note that FSGS has only been observed in the human studies, whereas the animal studies showed more global glomerulosclerosis. This difference could be explained by the absence of resistance exercise in the animal subjects. This is pretty wild speculation on my part though.
So what can we do about this as AAS abusing bodybuilders? Unfortunately not much. My main recommendation would be to have at least some rest days and to not go ape shit on the volume. Occlusion training should be avoided. Similarly, forced reps, drop sets etc. should be used sparingly (so not almost every set). A good gauge of whether your training is too intense would be creatine kinase levels ~12 hours post exercise, given that serum CK is likely correlated with exercise induced myoglobin release. i'd say that your CK should not be above 3000 12 hours post exercise.
As mentioned before, there is an interaction between channels 1-8. For example, you can probably ameliorate myoglobin induced kidney damage by maintaining proper hydration around workouts, ensuring sufficient antioxidant activity, etc.
I will continue with the remaining points later.