The modified amino sugar N-Butyryl Glucosamine fed to ovariectomized rats preserves bone mineral through increased early mineralization, but does not affect body composition

Authors

  • Tassos Anastassiades Queen's University
  • Karen Rees-Milton
  • Wilma M. Hopman

DOI:

https://doi.org/10.31989/ffhd.v7i10.377

Abstract

Background:  The toxicities of pharmaceuticals for chronic arthritis and osteoporosis should be of concern to consumers. This partially accounts for the popularity of consumption of the amino sugar glucosamine, in-spite of controversy about its efficacy. We chemically synthesized N-butyryl glucosamine (GlcNBu), which we discovered protected bone and cartilage in an inflammatory arthritis rat model when used as a feed supplement. GlcNBu can also be potentially synthesized biochemically, since we recently demonstrated that human acetyl-CoA: glucosamine-6-phosphate N-acetyltransferase 1 has a relaxed donor specificity and transfers acyl groups of up to four carbons in length, i.e. the butyryl moiety. Oral GlcNBu had no detectable toxicity and also protected against bone loss in ovariectomized (OVX) rats as a model for osteoporosis. However, we demonstrated this only for bones excised at 6 months. Thus, the current study aims to determine when bone mineralization is maximized during daily GlcNBu supplementation, in both OVΧ and Sham-OVX rats, in addition to the relationship of bone mineralization to body composition.

Methods: Female Sprague-Dawley rats were randomized into 4 groups, containing 8 rats each. The groups consisted of OVX or Sham-OVX rats whose diets were supplemented with either 200 mg/kg/day of GlcNBu or an equimolar amount of glucose. We performed sequential bone density and body composition measurements, by dual-energy X-ray absorptiometry in the live, anesthetised rats, over a 6-month experimental period, starting at the age of 8 weeks. Results were analyzed by descriptive statistics and 2-way ANOVA. 

Results: The major increases in the mineral content and density of the spine and the femur in GlcNBu-supplemented rats occurred early, from the baseline to week 8.  Ovariectomy resulted in a number of significant differences in body composition, while feeding GlcNBu had no significant effects on body composition. The significant effects of ovariectomy on body composition initially appeared at 8 weeks, while the GlcNBu effects on increased bone mineral initially appeared at 2 weeks. An interaction between OVX and GlcNBu was seen only at 16 weeks for the bone mineral density of the femoral head.

Conclusions: Supplementation of the diet by GlcNBu in both OVX and Sham-OVX rats increases bone mineral as early as 2 weeks. Ovariectomy but not GlcNBu supplementation had a significant effect on body composition. The effect of GlcNBu occurs independently of changes in body composition, probably as a direct effect of stimulation of bone matrix synthesis which continues to be mineralized.  This work represents an important step in the development and commercialization of GlcNBu for the prevention and treatment osteoporosis, where there is now an increasing demand for safe, long term agents.

Key words: osteoporosis, ovariectomy, N-butyryl glucosamine, bone, mineralization, body composition, dual-energy X-ray absorptiometry

Author Biography

  • Tassos Anastassiades, Queen's University

    I am a career clinician scientist and Professor Emeritus, in the Division of Rheumatology, Department of Medicine, Queen's University, in Canada. I obtained my MD and PhD (Connective Tissue Biochemistry) at McGill University, Montreal, having done most of my PhD research at Rockefeller University, New York. My career has involved clinical practice in Rheumatology and Osteoporosis at the University. As well I have maintained a Laboratory Research program in Biochemistry, on connective tissue molecules, and in observational epidemiological research in osteoporosis.

    I have taken on multiple leadership roles in administration, teaching and research. I was head of the Division of Rheumatology for many years and established the osteoporosis program at my University. I have served on many research panels in Canada, including the Arthritis Society, where I led the development of the Research Scientist Program, and in the Canadian Institutes of Health Research (equivalent to the NIH). I have received National recognition by the Canadian Government for my work in the Arthritis field.

    In my research, I have been particularly interested in naturally occurring carbohydrates whose functional properties I can change. I do this by chemically modifying a part of the molecule, in a fashion that I obtain modifications that are similar to those that occur naturally through metabolic processes. In this way, we hope to discover new or improved bio-medical functions, while retaining safety.

     My current interest is focused in chemical modifications of, glucosamine (GlcN), which is commercially derived from the highly abundant polymer, chitin. GlcN in mammals is contained in glycosaminoglycans, such as hyaluronic acid (HA), and in glycoproteins and it is almost invariably in an N-acetylated form. However, the reason for this N-acetylation of GlcN, and other aminosugars, is not known. We have synthesized a number of N-acylated derivatives of GlcN. For one of these, the butyrylated compound (GlcNBu), we have shown striking properties in preserving bone and cartilage in experimental animal systems. GlcNBu has proven to be essentially without detectable toxify in culture and when administered to animals. The main applications of GlcNBu in human and animal health would be in osteoporosis and in arthritis.

    We have also synthesized a number of N-acylated hyaluronic acid (HA) compounds among which the N-butyrylated (BHA) turned out to be the most interesting. Intact HA is structurally important and has no pro-inflammatory activity, however, lower molecular weight HA shows prominent pro-inflammatory activity in a number of systms. We showed that the N-acetyl moiety of the GlcN of the lower molecular weight HA was central in the stimulation of pro inflammatory cytokine production by human macrophages. This finding then allowed us to investigate possible mechanisms of action. Remarkably, out of the different N-acylations of lower molecular weight HA that we tested, BHA has shwon prominent anti-inflammatory effects in the macrophage system. This effect is apparently through the Toll-like receptor TLR-4. Thus, we now have tools with which to investigate the changes in the bio-medical properties of N-acylated GlN, both in the form of a sugar monomer as well as part of a polymer.

    We have protected the medical applications of these modified naturally occurring compounds through our University office of Technology and Innovations.

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Published

2017-10-31

Issue

Vol. 7 No. 10 (2017): October 2017

Section

Research Articles

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