Could you elaborate on the physiological mechanisms underlying the regulation of blood glucose levels in the human body, including the roles of insulin, glucagon, and other hormones? How do pancreatic β-cells secrete insulin in response to elevated blood glucose levels, promoting glucose uptake by target tissues and storage as glycogen in the liver and muscles? Conversely, how does the pancreas release glucagon in response to low blood glucose levels, stimulating glycogen breakdown and gluconeogenesis to raise blood glucose concentrations? Additionally, how do factors such as dietary composition, physical activity, and insulin resistance influence blood glucose homeostasis and the development of conditions like diabetes mellitus?