Disruption of the murine intestinal alkaline phosphatase gene Akp3 impairs lipid transcytosis and induces visceral fat accumulation and hepatic steatosis.

Abstract

Intestinal alkaline phosphatase (IAP) is involved in the process of fat absorption, a conclusion confirmed by an altered lipid transport and a faster body weight gain from 10 to 30 wk in both male and female mice with a homozygous null mutation of the IAP coding gene (Akp3(-/-) mice). This study was aimed to delineate morphologically and quantitatively the accelerated lipid absorption in male Akp3(-/-) mice. Feeding a corn oil bolus produced an earlier peak of triacylglycerol in serum (2 vs. 4 h for Akp3(-/-) and wild-type mice, respectively) and an approximately twofold increase in serum triacylglycerol concentration in Akp3(-/-) mice injected with a lipolysis inhibitor, Triton WR-1339. A corn oil load induced the threefold enlargement of the Golgi vacuoles in male wild-type mice but not in Akp3(-/-) mice, indicating that absorbed lipids rarely reached the Golgi complex and that the transcytosis of lipid droplets does not follow the normal pathway in male Akp3(-/-) mice. Force feeding an exaggerated fat intake by a 30% fat chow for 10 wk induced obesity in both male Akp3(-/-) and wild-type mice, and therefore no phenotypic difference was observed between the two. On the other hand, the forced high-fat chow induced an 18% greater body weight gain, hepatic steatosis, and visceral fat accumulation in female Akp3(-/-) mice but not in female wild-type controls. These results provide further evidence that IAP is involved in the regulation of the lipid absorption process and that its absence leads to progressive metabolic abnormalities in certain fat-forced conditions.

• Authors: Takanari Nakano, Ikuo Inoue, Iwao Koyama, Kenta Kanazawa, Koh-Ichi Nakamura, Sonoko Narisawa, Kayoko Tanaka, Masumi Akita, Taku Masuyama, Makoto Seo, Shigeru Hokari, Shigehiro Katayama, David H Alpers, José Luis Millán, Tsugikazu Komoda
• Journal: American journal of physiology. Gastrointestinal and liver physiology (Am J Physiol Gastrointest Liver Physiol) Vol. 292 Issue 5 Pg. G1439-49 (May 2007) ISSN: 0193-1857 [Print] United States
• PMID: 17332477 (Publication Type: Journal Article)

Chemical References

• Dietary Fats
• Triglycerides
• Polyethylene Glycols
• Lipoprotein Lipase
• Akp3 protein, mouse
• Alkaline Phosphatase
• tyloxapol

Topics

• Alkaline Phosphatase (antagonists & inhibitors, genetics, metabolism)
• Animals
• Dietary Fats (administration & dosage)
• Fatty Liver (etiology)
• Female
• Intestinal Absorption (drug effects)
• Intestine, Small (enzymology)
• Intra-Abdominal Fat (drug effects, growth & development)
• Lipid Metabolism (drug effects)
• Lipoprotein Lipase (antagonists & inhibitors)
• Male
• Mice
• Polyethylene Glycols (pharmacology)
• Triglycerides (blood)