The Sun is the central integrating factor of the entire horoscope and represents cellular vitality and the body’s ability to slough of disease.  Under the rulership of Leo, the Sun governs the physical heart but influences the solar plexus chakra, the seat of will power and creative actualisation.  It is also the seat of Agni, the digestive fire and metabolism and hence is implicated in situations of toxic overload and a generally sluggish system.