Oral monosaccharide therapies to reverse renal and muscle hyposialylation in a mouse model of GNE myopathy

Abstract

GNE myopathy, previously termed hereditary inclusion body myopathy (HIBM), is an adult-onset neuromuscular disorder characterized by progressive muscle weakness. The disorder results from biallelic mutations in GNE, encoding UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase, the key enzyme of sialic acid synthesis. GNE myopathy, associated with impaired glycan sialylation, has no approved therapy. Here we test potential sialylation-increasing monosaccharides for their effectiveness in prophylaxis (at the embryonic and neonatal stages) and therapy (after the onset of symptoms) by evaluating renal and muscle hyposialylation in a knock-in mouse model (Gne p.M712T) of GNE myopathy. We demonstrate that oral mannosamine (ManN), but not sialic acid (Neu5Ac), mannose (Man), galactose (Gal), or glucosamine (GlcN), administered to pregnant female mice has a similar prophylactic effect on renal hyposialylation, pathology and neonatal survival of mutant offspring, as previously shown for N-acetylmannosamine (ManNAc) therapy. ManN may be converted to ManNAc by a direct, yet unknown, pathway, or may act through another mode of action. The other sugars (Man, Gal, GlcN) may either not cross the placental barrier (Neu5Ac) and/or may be able to directly increase sialylation. Because GNE myopathy patients will likely require treatment in adulthood after onset of symptoms, we also administered ManNAc (1 or 2 g/kg/day for 12 weeks), Neu5Ac (2g/kg/day for 12 weeks), or ManN (2g/kg/day for 6 weeks) in drinking water to 6 month old mutant Gne p.M712T mice. All three therapies markedly improved the muscle and renal hyposialylation, as evidenced by lectin histochemistry for overall sialylation status and immunoblotting of specific sialoproteins. These preclinical data strongly support further evaluation of oral ManNAc, Neu5Ac and ManN as therapy for GNE myopathy and conceivably for certain glomerular diseases with hyposialylation.

Sialic acid supplementation ameliorates puromycin aminonucleoside nephrosis in rats

“…Again this would imply that in those parameters, the effects of sialic acid were largely mediated via its properties as an antioxidant. Despite the efficacy of ManNAc in GNE myopathy, 17,18 its benefits as a therapeutic supplement in this study were not comparable to those of sialic acid. In experimental murine GNE myopathy, desialylation occurs as a consequence of a specific mutation in one enzyme of the sialic acid biosynthetic pathway, which although lethal, is adequately bypassed using ManNAc as a substrate (and also notably sialic acid 42 ).…”

“…17,18 We hypothesize that dietary supplementation of PAN nephrotic rats with free sialic acid, given its antioxidant properties, may be a more effective treatment modality in a proteinuric model of kidney disease exhibiting both desialylation and oxidative stress.…”

Podocyte directed therapy of nephrotic syndrome—can we bring the inside out?

“…The study has been completed, but the results are not yet available. Oral ManNAc is currently being tested in two phase I clinical trial for the treatment of the rare disorder distal myopathy with rimmed vacuoles-hereditary inclusion body myopathy (http://clinicaltrials.gov/NCT01236898 and NCT01359319) [117]. To our knowledge, there is no ongoing study involving ManNAc in patients with glomerular disease.…”

Fibromodulin and Biglycan Modulate Periodontium through TGFβ/BMP Signaling

“…Mouse PDL tissues were harvested and fixed in 2% glutaraldehyde in 0.1M cacodylate buffer (pH 7.4) at 4°C and prepared for TEM as previously described (Niethamer et al, 2012). Quantification data were obtained by Image J (NIH, Bethesda, MD, USA) analysis.…”