Energy regulation in newly diagnosed TB with chronic energy deficiency: free fatty acids and RBP4

Energy metabolism may be dysfunctionally integral between host and infective agent in active tuberculosis, mediated by adipocytokines and free fatty acids (FFA) as the products of triglyceride lipolysis in fat, blood or other tissues. Retinol Binding Protein 4 (RBP4) and asymmetric dimethylarginine (ADMA) are candidate adipocytokines. The possibility of a deleterious metabolic nexus in chronic energy deficiency (CED) (BMI <18.5 kg/m2) is explored.

Newly diagnosed patients with tuberculosis (n=63) were selected using consecutive random sampling at a Centre for the Care and Treatment of Lung Diseases in Makassar, Indonesia. Diagnosis of pulmonary TB required microscopy with Ziehl-Neelsen stain. Anthropometric measurements were taken. Venesection allowed glomerular filtration rate, FFA, serum glutamic oxaloacetic transaminase and glutamate-pyruvate transaminase to be assessed.

CED was evident in 60.3%. For the well and lesser nourished, medians were, respectively, FFA 0.30 and 0.37 mmol/mL (p=0.960); RBP4 199730 ng/mL and 11721 ng/mL (p=0.009); GFR 106 ml/min and 113 ml/min (p=0.673); and ADMA 0.52 ng/mL and 0.51 ng/mL (p=0.172). BMI and serum RBP4 were correlated (ρ=0.52, p<0.001), with odds ratios (OR) 5.8 (CI 1.68-20.3). RBP4 in CED was lower than in better nourished patients. Serum FFA is not evidently associated with BMI in patients with active TB.

RBP4 is some 6-fold lower when active TB patients have CED than when BMI >25 kg/m2. However, FFA was not associated with CED in these active TB patients which may be a type 2 error or represent an energy impasse where infection and the host's metabolic needs are in competition.