Surfactant protein d deficiency in mice is associated with hyperphagia, altered fat deposition, insulin resistance, and increased basal endotoxemia.

Pulmonary surfactant protein D (SP-D) is a host defence lectin of the innate immune system that enhances clearance of pathogens and modulates inflammatory responses. Recently it has been found that systemic SP-D is associated with metabolic disturbances and that SP-D deficient mice are mildly obese. However, the mechanism behind SP-D's role in energy metabolism is not known.Here we report that SP-D deficient mice had significantly higher ad libitum energy intake compared to wild-type mice and unchanged energy expenditure. This resulted in accumulation but also redistribution of fat tissue. Blood pressure was unchanged. The change in energy intake was unrelated to the basal levels of hypothalamic Pro-opiomelanocortin (POMC) and Agouti-related peptide (AgRP) gene expression. Neither short time systemic, nor intracereberoventricular SP-D treatment altered the hypothalamic signalling or body weight accumulation.In ad libitum fed animals, serum leptin, insulin, and glucose were significantly increased in mice deficient in SP-D, and indicative of insulin resistance. However, restricted diets eliminated all metabolic differences except the distribution of body fat. SP-D deficiency was further associated with elevated levels of systemic bacterial lipopolysaccharide.In conclusion, our findings suggest that lack of SP-D mediates modulation of food intake not directly involving hypothalamic regulatory pathways. The resulting accumulation of adipose tissue was associated with insulin resistance. The data suggest SP-D as a regulator of energy intake and body composition and an inhibitor of metabolic endotoxemia. SP-D may play a causal role at the crossroads of inflammation, obesity, and insulin resistance.

Surfactant protein D is proatherogenic in mice.

Surfactant protein D (SP-D) is an important innate immune defense molecule that mediates clearance of pathogens and modulates the inflammatory response. Moreover, SP-D is involved in lipid homeostasis, and pulmonary accumulation of phospholipids has previously been observed in SP-D-deficient (Spd-/-) mice. Atherogenesis involves both inflammation and lipid deposition, and we investigated the role of SP-D in the development of atherosclerosis. SP-D synthesis was localized to vascular endothelial cells. Atherosclerotic lesion areas were 5.6-fold smaller in the aortic roots in Spd-/- mice compared with wild-type C57BL/6N mice on an atherogenic diet. HDL cholesterol (HDL-C) was significantly elevated in Spd-/- mice. Treatment of Spd-/- mice with a recombinant fragment of human SP-D resulted in decreases of HDL-C (21%) as well as total cholesterol (26%), and LDL cholesterol (28%). Plasma TNF-alpha was reduced in Spd-/- mice (45% difference). SP-D was proatherogenic in the mouse model used. The effect is likely to be due to the observed disturbances of plasma lipid metabolism and alteration of the inflammatory process, which underlie the reduced susceptibility to atherosclerosis in Spd-/- mice.

Cancer-associated cleavage of cytokeratin 8/18 heterotypic complexes exposes a neoepitope in human adenocarcinomas.

The intermediate filament network in simple glandular epithelial cells predominantly consists of heterotypic complexes of cytokeratin 8 (K8) and cytokeratin 18 (K18). In contrast to other cytokeratins, K8 and K18 are persistently expressed during malignant transformation, but changes in cell morphology are accompanied by alterations in the intermediate filament network. To study molecular changes, K8 and K18 were purified from surgically removed colon cancer and normal epithelia tissues. Western blotting and amino acid sequencing revealed the presence of abundant K8 and K18 fragments, truncated at the N terminus, from cancerous, but not normal, epithelial cells. The fragmentation pattern indicates proteolysis mediated by several enzymes, including trypsin-like enzymes. The cancer-associated forms of K8 and K18 are specifically recognized by the human antibody, COU-1, cloned from the B cells of a cancer patient. We demonstrate that COU-1 recognizes a unique conformational epitope presented only by a complex between K8 and K18. The epitope is revealed after proteolytic removal of the head domain of either K8 or K18. A large panel of recombinant K8 and K18 fragments, deleted N- or C-terminally, allowed for the localization of the COU-1 epitope to the N-terminal part of the rod domains. Using surface plasmon resonance, the affinity of COU-1 for this epitope was determined to be 10(9) x m(-1), i.e. more than 2 orders of magnitude higher than for intact heterotypic K8/K18 complexes. The cellular distribution of truncated K8/K18 heterotypic complexes in viable adenocarcinomas cells was probed using COU-1 showing small fibrillar structures distinct from those of intact K8/K18 complexes. Previously we demonstrated the binding and subsequent internalization of recombinant Fab COU-1 to live cancer cells. We have thus characterized a cancer neoepitope recognized by the humoral immune system. The results have biological as well as clinical implications.