Sort of funny that they're talking about leaky gut--> fatty liver like it's a new thing... or the fructose connection like it is. I've been seeing stuff about this on Pubmed probably at least for a decade.
Once you do have leaky gut--gluten and other food intolerances, possible autoimmune issues from partially digested proteins making it into the system. Fat is implicated under certain dietary contexts.
excessive fructose metabolism in intestinal cells reduces production of proteins that maintain the gut barrier
Here I wonder if there's something as simple as a draw on certain amino acids to process the fructose, leading to a decrease in protein synthesis. Animal models tend to eat more frequently with high sugar cafeteria-style diets. Meal timing or intermittent fasting protocols might help by ensuring long periods when fructose is not being processed. High fat diets--glycemic index, we've been told in the past that fat plus sugar slows absorption of sugars, this could effectively increase the window where fructose metabolism is occurring, meals blur together.
Okay, they give endoplasmic stress as the villain in the abstract...
ER stress occurs when the capacity of the ER to fold proteins becomes saturated. ER stress may be caused by factors that impair protein glycosylation or disulfide bond formation, or by overexpression of or mutations in proteins entering the secretory pathway.
In mice at least, fermentable fibers seem to be protective. The Eades suggested glutamine for leaky gut in Protein Power, I think Atkins probably did as well, somewhere, though I don't remember a specific time.
On fruit being okay--sort of. I've heard people say for years that people don't binge on fruit like they do other sugary foods. I'll go through a bunch of bananas in pretty short order, or would if I ever bought them. Even apples--for a while I was having one small one a day, that lasted a few days and then I ate the rest all at once.
I think we are talking about a high sugar diet and not an extremely
high sugar diet, here. I'd like to see something on fruitarian diets, juice fasts etc. Obviously these are worse in some other ways, whether they're as bad for this particular problem still might be an open question.
I've seen some studies where oatmeal and orange juice were protective against a diet that would otherwise cause leaky gut in mice.