Green tea extract and epigallocatechin gallate decrease muscle pathology and NF-κB immunostaining in regenerating muscle fibers of mdx mice

Abstract

Duchenne muscular dystrophy is a debilitating genetic disorder characterized by severe muscle wasting and early death in affected boys. The primary cause of this disease is mutations in the dystrophin gene resulting in the loss of the dystrophin protein from the plasma membrane of muscle fibers. In the absence of dystrophin, muscles undergo massive muscle degeneration and inflammation. Inflammation is believed to contribute substantially to dystrophic muscle pathology. The transcription factor NF-κB regulates inflammatory gene expression and provides a logical target for therapeutic treatments. Green tea extract and its primary polyphenol, epigallocatechin gallate, have been shown to have anti-inflammatory properties and to improve dystrophic muscle pathology. The purpose of these studies was to determine if dietary treatment with green tea extract or epigallocatechin gallate administered prior to disease onset could reduce dystrophic muscle pathology during the early disease time course and identify potential mechanisms through which NF-κB may be involved. Green tea extract has been shown to decrease muscle pathology and increase muscle function in mdx mice, a dystrophic mouse model. These changes have been attributed to the antioxidant potential of epigallocatechin gallate; however, other mechanisms such as suppression of the inflammatory response have not been evaluated. In the studies reported herein, both green tea extract and epigallocatechin gallate significantly decreased muscle pathology in mdx mice when provided in their diets prior to disease onset. In green tea extract (0.25% and 0.5%) treated mdx mice, serum creatine kinase, a systemic marker of muscle damage, was decreased by 85% at age 42 days. Normal fiber morphology in the tibialis anterior muscle was increased by 32% at this age (P≤0.05). The primary histopathological change was a 21% decrease in regenerating fibers (P≤0.05). NF-κB staining in central nuclei of regenerating fibers was decreased by 34% (P≤0.05). In epigallocatechin gallate (0.1%) treated mdx mice, serum creatine kinase was unchanged; however, normal fiber morphology in the tibialis anterior was increased by 20% at ages 28 and 42 days (P≤0.05). At age 42 days, the primary histopathological change was a 21% decrease in regenerating fibers (P≤0.05). NF-κB staining in central nuclei of regenerating muscle fibers was decreased by 21% at this age (P≤0.05). Epigallocatechin gallate appears to be the primary polyphenol of green tea extract responsible for many of the beneficial changes in dystrophic muscle. These data suggest that both green tea extract and epigallocatechin gallate decrease NF-κB activity in regenerating fibers resulting in reduced muscle pathology. Complimentary and alternative medicine approaches, including the use of green tea, provide important therapeutic options for ameliorating Duchenne muscular dystrophy. Green tea extract and epigallocatechin gallate are effective at decreasing muscle pathology potentially by reducing NF-κB activity in regenerating fibers in mdx mice. Use of these botanicals appears to elicit a beneficial response in dystrophic muscle that may ultimately lead to effective therapies for patients with this incurable disease.