Like Kelly so beautifully explained, there’s probably a mixture of fuel being burned during sleep, but the portion of carbs to fats is probably determined by your pre-bed feeding.
In addition, glucose needs will be met primarily by the liver, both through: 1. glycogenolysis, and 2. gluconeogenesis. The latter will probably be insignificant at this level of energy expenditure and will be a result of metabolic by-products (as opposed to amino acids). Glycogenolysis of liver glycogen will probably dominate the glucose substrate being utilized. At rest, the liver will supply about 5g/hr (i.e. 20kcal/hr). Therefore, you will probably deplete liver glycogen by 40-50g depending on your sleep length, which corresponds exactly to what Kelly stated. Note, though, that the rate of liver glycogen depletion is affected by: 1. physical activity, 2. exercise, and 3. incoming food (i.e. carbs).
As far as the amount of kcals burned during sleep, this equation should give you a pretty decent estimate:
Energy Expenditure (kcal per min) = 0.0175 kcal/kg/min x 0.9 x body weight (kg)
*Note: the 0.9 is a MET (i.e. metabolic equivalent) for sleeping and is a constant.
Finally, as Kelly illustrated, muscle glycogen is only used during activity involving the particular muscles. In addition, during very prolonged, strenuous exercise, muscle glycogen can be mobilized from inactive muscles, but only by first being converted into lactate, which then goes to the liver to be converted to glucose (i.e. gluconeogenesis).