A linear combination of binomial mean and variance

Let $X$ be a random variable with the moment generating function $$M(t)=\frac{(1+3e^t)^2}{16},\quad -\infty<t<\infty.$$ Let $\alpha=E(X)-\mathrm{Var}(X)$. Then the value of $8\alpha$ is equal to __________ (answer in integer)