Lipid and protein metabolism in asthma. Effects of diet and corticosteroid therapy

BACKGROUND: Because little is known about the effects of asthma and asthma therapy on lipid and protein metabolism, we have investigated the characteristics of diet and plasma/serum levels of fat and protein in a group of asthma patients with various degrees of severity. METHODS: A case-control study was carried out on 118 asthma patients recruited from an outpatient clinic and 121 healthy subjects. Asthma severity was characterized in four groups according to clinical symptoms, lung-function tests, and therapy. Normal dietary intake was estimated from a food frequency questionnaire. Serum protein, albumin, and fatty acids were determined by standard methods. RESULTS: The dietary energy intake of the asthmatics was significantly lower than that of the controls. However, no differences in the body mass index were found between asthma patients and healthy subjects. There were no differences in serum/plasma levels in any of the measured biochemical parameters between healthy subjects and asthmatics. Plasma levels of protein and albumin were significantly lower in severely corticosteroid-dependent patients. There was a significant negative correlation between plasma protein (r=0.36, P<0.05) and plasma albumin levels (r=0.43, P<0.01) and the daily dose of oral corticosteroids. We did not find any differences in plasma levels of cholesterol, HDL-cholesterol, LDL-cholesterol, and fatty acids between cortico-dependent patients and those not receiving this therapy. No correlation was found between any biochemical parameters and the daily dose of inhaled corticosteroids. CONCLUSIONS: Our results suggest that asthma induces a decrease in energy intake that does not result in a decreased body weight. Inhaled corticosteroids do not exert any metabolic effect, whereas severe asthma with regular oral corticosteroid therapy is associated with reduced plasma protein and albumin levels.