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JCI Insight. 2017 Oct 19;2(20). pii: 96783. doi: 10.1172/jci.insight.96783. [Epub ahead of print]

Lipoprotein lipase reaches the capillary lumen in chickens despite an apparent absence of GPIHBP1.

Author information

1
Department of Medicine and.
2
Department of Poultry Science and Faculty of Nutrition, Texas A&M University, College Station, Texas, USA.
3
University of California, Santa Cruz Genomics Institute and.
4
Centre for Microscopy, Characterisation, and Analysis, The University of Western Australia, Western Australia, Perth, Australia.
5
Division of Nutritional Science, Cornell University, Ithaca, New York, USA.
6
The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom.
7
Department of Human Genetics, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.

Abstract

In mammals, GPIHBP1 is absolutely essential for transporting lipoprotein lipase (LPL) to the lumen of capillaries, where it hydrolyzes the triglycerides in triglyceride-rich lipoproteins. In all lower vertebrate species (e.g., birds, amphibians, reptiles, fish), a gene for LPL can be found easily, but a gene for GPIHBP1 has never been found. The obvious question is whether the LPL in lower vertebrates is able to reach the capillary lumen. Using purified antibodies against chicken LPL, we showed that LPL is present on capillary endothelial cells of chicken heart and adipose tissue, colocalizing with von Willebrand factor. When the antibodies against chicken LPL were injected intravenously into chickens, they bound to LPL on the luminal surface of capillaries in heart and adipose tissue. LPL was released rapidly from chicken hearts with an infusion of heparin, consistent with LPL being located inside blood vessels. Remarkably, chicken LPL bound in a specific fashion to mammalian GPIHBP1. However, we could not identify a gene for GPIHBP1 in the chicken genome, nor could we identify a transcript for GPIHBP1 in a large chicken RNA-seq data set. We conclude that LPL reaches the capillary lumen in chickens - as it does in mammals - despite an apparent absence of GPIHBP1.

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