Suggesting that neurotransmitter imbalance (e.g. serotonin re: depression) is the cause of mood disorders is like saying the ash is responsible for the fire. Many such examples in modern medicine. Happy 4th of July!

Another mechanism by which cholesterol depletion (e.g. via Statins) leads to insulin resistance - AKA diabetes. As it turns out, the insulin receptor depends on the presence of lipid rafts (made of cholesterol) to initiate its downstream effect: glucose transport.