👤 M D López-Tejero

Lipoprotein lipase (LPL) is responsible for the intravascular catabolism of triglyceride-rich lipoproteins and plays a central role in whole-body energy balance and lipid homeostasis. As such, LPL is subject to tissue-specific regulation in different physiological conditions, but the mechanisms of this regulation remain incompletely characterized. Previous work revealed that LPL comprises a set of proteoforms with different isoelectric points, but their regulation and functional significance have not been studied thus far. Here we studied the distribution of LPL proteoforms in different rat tissues and their regulation under physiological conditions. First, analysis by two-dimensional electrophoresis and Western blot showed different patterns of LPL proteoforms (i.e., different pI or relative abundance of LPL proteoforms) in different rat tissues under basal conditions, which could be related to the tissue-specific regulation of the enzyme. Next, the comparison of LPL proteoforms from heart and brown adipose tissue between adults and 15-day-old rat pups, two conditions with minimal regulation of LPL in these tissues, yielded virtually the same tissue-specific patterns of LPL proteoforms. In contrast, the pronounced downregulation of LPL activity observed in white adipose tissue during fasting is accompanied by a prominent reconfiguration of the LPL proteoform pattern. Furthermore, refeeding reverts this downregulation of LPL activity and restores the pattern of LPL proteoforms in this tissue. Importantly, this reversible proteoform-specific regulation during fasting and refeeding indicates that LPL proteoforms are functionally diverse. Further investigation of potential differences in the functional properties of LPL proteoforms showed that all proteoforms exhibit lipolytic activity and have similar heparin-binding affinity, although other functional aspects remain to be investigated. Overall, this study demonstrates the ubiquity, differential distribution and specific regulation of LPL proteoforms in rat tissues and underscores the need to consider the existence of LPL proteoforms for a complete understanding of LPL regulation under physiological conditions. Show less

The need for a non-invasive diagnosis of the effects of ethanol in utero on the development of the intestine in humans led us to look for a serum marker of the structural integrity of the intestine. We propose apolipoprotein A-IV (apoA-IV) as a possible candidate. In humans this protein is synthesized only by intestinal mucosa, it is expressed in the enterocyte of the foetus from 20 weeks of gestation, and it is released to the blood stream after synthesis. We measured the levels of apoA-IV in the umbilical cord serum of neonates whose mothers had consumed alcohol during pregnancy and neonates born to women who had not (controls). The gestational age at delivery of the cases studied ranged from 36 to 42 weeks. ELISA and Western blot analysis were used. There was no difference in the mean body weight of neonates from either group. Nevertheless, exposure to ethanol in utero significantly reduced (by about 30%) the apoA-IV levels in serum at birth, regardless of body weight. Our findings suggest that circulating apoA-IV levels could be used as a clinical marker of the prenatal effects of ethanol on the structural integrity of the intestine. Neonatal diagnosis of these intestinal effects could improve post-natal outcome. Show less