Networks representing the transcriptional coupling between lung and skeletal muscle in the guinea pig smoking model. Correlation network linking the expression of soluble factors in guinea pig lung with the transcriptional activity of enriched KEGG pathways in gastrocnemius (A) and soleus (B) muscles, respectively. Each network edge (grey line) represents the correlation with a given principal component, representative of several genes in each function/KEGG term. Some of the genes will be correlated positively and others will show a negative correlation. Only edges with a bootstrapped P value <0.01 are shown in this figure. Hexagons represent KEGG terms, and circles represent soluble factors that are secreted by lungs. Each circle has been divided into three sectors, representing the CS, CSCH and CH groups. A red sector indicates that the cytokine is significantly upregulated; a blue sector indicates significant downregulation; and a grey-coloured sector indicates that the transcriptional level is not significantly affected by the experimental condition.