TNF and obesity due to melanocortin 4 receptor deficiency: To summarize, low-grade systemic inflammation is one possible mechanism linking obesity and asthma, but is unlikely to fully explain the obesity-asthma association, although TNF-α, IL-6, C-reactive protein (CRP), circulating neurotransmitter neuropeptide Y (NPY), and adiponectin levels have been independently associated with asthma prevalence [36].