MMP1 and Genetic obesity: During a prolonged HFD, C56BL/6J mice have increased adipose tissue levels of collagen I (Col1a1 and Col1a2) and TIMP1, and lower levels of MMP1 [94], consistent with the role of MMP1 in regulating collagen I deposition, a marker of fibrosis associated with insulin resistance, during dietary and genetic obesity [95,96].