Effect of oral glucosamine sulfate on serum leptin levels in human subjects

The anti-arthritic and immune-modulatory effects of NHAG: a novel glucosamine analogue in adjuvant-induced arthritis

Rheumatoid arthritis (RA) is potentially devastating condition which lacks good treatment options. Pro-inflammatory cytokines interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and oxidative stress markers such as nitric oxide (NO) and peroxide (PO) are mediators of RA pathogenesis. In the present study N-[2,4,5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-3-yl]acrylamide (NHAG), analogue of glucosamine, was evaluated in adjuvant-induced arthritic model of rats. The disease progression was monitored by analysing arthritis scoring, loss of body weight, paw oedema, and histological changes in joints. RA associated hyperalgesia was evaluated by gait analysis. The serum or plasma levels of NO, PO, glutathione (GSH) superoxide dismutase (SOD) IL-1β and TNF-α were analyzed to monitor the state of disease severity. The arthritic control animals exhibited significant increase in arthritic score (P < 0.003) and paw oedema (P < 0.001) with parallel loss in body weight (P < 0.04). The NHAG-treated arthritic animals exhibited refinement in the gait changes associated with arthritis. NHAG also significantly decreased the NO (P < 0.02) and PO (P < 0.03) with concurrent increased in GSH (P < 0.04) and SOD (P < 0.007). Both IL-1β (P < 0.001) and TNF-α (P < 0.001), were significantly decreased in NHAG-treated group. Thus NHAG might have a therapeutic potential for arthritis by exerting antioxidative and immunomodulatory effects.

The effect of glucosamine on glucose metabolism in humans: a systematic review of the literature

OBJECTIVE

Glucosamine is commonly used for the treatment of osteoarthritis. It is available as an over the counter preparation and also as a prescription pharmaceutical. There is concern from animal experiments that glucosamine may alter glucose metabolism through the hexosamine biosynthetic pathway. The objective of this systematic review is to determine if exogenous glucosamine adversely affects glucose metabolism in humans. This review does not separate out the effects on glucose metabolism of the various glucosamine preparations.

METHOD

An English-language literature search of MEDLINE, EMBASE and EBM Reviews (1950-February 2009) was conducted. The bibliographies of selected papers were manually searched for additional references. Two reviewers independently analyzed studies for quality and content using a standardized data extraction form.

RESULTS

Eleven studies were included. Six studies were randomized controlled trials and the remaining five were prospective studies with or without controls. Four of the studies found decreased insulin sensitivity or increased fasting glucose in subjects taking glucosamine. Three of these were clinical studies using oral glucosamine. Studies that included subjects with baseline impaired glucose tolerance or insulin resistance were more likely to detect an effect on glucose metabolism than studies without such subjects.

CONCLUSION

Clinical studies, including three using oral glucosamine, have provided mixed evidence about the effect of exogenous glucosamine on glucose metabolism in humans. Therefore, more studies are needed, particularly including subjects at high risk for impairments in glucose homeostasis, before a definite conclusion can be made.

A comprehensive review of oral glucosamine use and effects on glucose metabolism in normal and diabetic individuals

Glucosamine (GlcN) is a widely utilized dietary supplement that is used to promote joint health. Reports that oral GlcN supplementation at usual doses adversely affects glucose metabolism in subjects with impaired glucose tolerance have raised concerns that GlcN should be contraindicated in individuals with diabetes and those at risk for developing it. This review addresses its potential, when used at typical doses, to affect glucose metabolism and insulin sensitivity in healthy individuals and those with diabetes or 'pre-diabetes'. Publicly available scientific information and data on GlcN were systematically compiled using the electronic search tool, Dialog , and reviewed with special emphasis on human studies. In long-term clinical trials, including those containing subjects with type 2 diabetes or 'pre-diabetes', GlcN produced a non-significant lowering of fasting blood glucose concentrations in all groups of subjects treated for periods of up to 3 years. Owing to limitations in study design, conclusions based on studies that report adverse affects of GlcN on insulin sensitivity and glucose tolerance in pre-diabetic subjects are suspect. However, no definitive long-term studies of GlcN use for individuals with pre-diabetes are available. Nevertheless, based on available evidence, we conclude that GlcN has no effect on fasting blood glucose levels, glucose metabolism, or insulin sensitivity at any oral dose level in healthy subjects, individuals with diabetes, or those with impaired glucose tolerance.

The dual face of endogenous alpha-aminoketones: pro-oxidizing metabolic weapons

Amino metabolites with potential prooxidant properties, particularly alpha-aminocarbonyls, are the focus of this review. Among them we emphasize 5-aminolevulinic acid (a heme precursor formed from succinyl-CoA and glycine), aminoacetone (a threonine and glycine metabolite), and hexosamines and hexosimines, formed by Schiff condensation of hexoses with basic amino acid residues of proteins. All these metabolites were shown, in vitro, to undergo enolization and subsequent aerobic oxidation, yielding oxyradicals and highly cyto- and genotoxic alpha-oxoaldehydes. Their metabolic roles in health and disease are examined here and compared in humans and experimental animals, including rats, quail, and octopus. In the past two decades, we have concentrated on two endogenous alpha-aminoketones: (i) 5-aminolevulinic acid (ALA), accumulated in acquired (e.g., lead poisoning) and inborn (e.g., intermittent acute porphyria) porphyric disorders, and (ii) aminoacetone (AA), putatively overproduced in diabetes mellitus and cri-du-chat syndrome. ALA and AA have been implicated as contributing sources of oxyradicals and oxidative stress in these diseases. The end product of ALA oxidation, 4,5-dioxovaleric acid (DOVA), is able to alkylate DNA guanine moieties, promote protein cross-linking, and damage GABAergic receptors of rat brain synaptosome preparations. In turn, methylglyoxal (MG), the end product of AA oxidation, is also highly cytotoxic and able to release iron from ferritin and copper from ceruloplasmin, and to aggregate proteins. This review covers chemical and biochemical aspects of these alpha-aminoketones and their putative roles in the oxidative stress associated with porphyrias, tyrosinosis, diabetes, and cri-du-chat. In addition, we comment briefly on a side prooxidant behaviour of hexosamines, that are known to constitute building blocks of several glycoproteins and to be involved in Schiff base-mediated enzymatic reactions.