As the title says, I am speculating here.
Maple syrup disease is a rare disorder (> 1:100 000) affecting branched-chain amino acid (BCAA) catabolism. The parent molecules and their keto-acids accumulate leading, among other issues, to leucinosis, neurologic symptoms and death unless treated with a low BCAA diet. Blood levels of these amino acids remain elevated despite treatment as far as I know and this could suppress autophagy via mTOR, I speculate.
The BCAAs, especially leucine, are recognized as potent metabolic regulators of protein synthesis. This effect is mediated through mammalian target of rapamycin (mTOR)-dependent and mTOR-independent pathways (Kimball and Jefferson 2006). In the context of high BCAA levels experienced in MSUD, the effect on protein turnover has not been extensively studied.
Feel free to steal my idea, but do credit me and let me co-author.
If your urine smells funny, you can help science. Well, almost.