CRP and obesity due to melanocortin 4 receptor deficiency: Ultimately, this review found that gut flora such as Akkermansia and Verrucomicrobia, serum albumin levels, inflammatory mediators such as IFN-γ and CRP, leukocyte telomere length, protein, diabetic retinopathy, thyroid dysfunction, obesity, coffee intake, and sleep were all causally associated with the development of DN (Figure 6).