So has anyone managed to separate the effects of semaglutide from the effects of weight loss? If this is caused by the weight loss, it is a little disappointing that public health didn't act quicker - lots of people have been overweight for a century now, so literally 10's of millions of people could have been saved from dementia had action been taken 100 years ago.
GLP-1 receptor agonists such as semaglutide act partly through the brain to reduce hunger, increase satiety, and lower spontaneous energy intake. Sustained caloric reduction produces weight loss, including loss of visceral fat around the abdominal organs and ectopic fat stored in tissues such as the liver. These fat depots are metabolically active and contribute to insulin resistance through excess fatty-acid delivery, inflammatory signalling, and disruption of normal insulin action.
As they shrink, muscle and liver tissues become more responsive to insulin, so the pancreas no longer needs to secrete as much insulin to maintain normal glucose levels.
This reduces the compensatory hyperinsulinaemic state that can exist for years before diabetes develops and decreases the probability that impaired glucose regulation will progress toward overt type 2 diabetes.
Those changes propagate into the cardiovascular system.
Better insulin sensitivity and lower visceral and liver fat are commonly accompanied by lower triglycerides, improved blood pressure, reduced systemic inflammation, and better endothelial and vascular function, thereby reducing several mechanisms that contribute to atherosclerosis and cerebrovascular injury.
GLP-1 receptor agonists also have a direct metabolic action independent of weight loss: when glucose is elevated, they enhance pancreatic insulin secretion and suppress inappropriate glucagon secretion, improving glucose control without forcing insulin secretion when glucose is low.
The overall effect is therefore a combination of an immediate GLP-1-mediated improvement in appetite and glucose regulation followed by progressively larger downstream effects from weight and fat loss, which together reduce the metabolic and vascular abnormalities associated with cardiovascular disease and, over much longer periods, potentially with dementia risk.