A recently published hypothesis raises the possibility that an enzyme involved in type-1 diabetes may also be an underlying cause of fibromyalgia (FMS).
The enzyme is glutamic acid decarboxylase (GAD) -- specifically, a form called GAD65. It's primary job is to help turn a neurotransmitter (chemical messenger in the brain) called glutamate into another neurotransmitter called GABA. Glutamtate is an excitotoxin, meaning it gets areas of the brain over stimulated to potentially dangerous levels, while GABA calms the brain. Some research shows that FMS involves an imbalance of these two chemicals.
In the journal Medical Hypotheses, researchers lay out several reasons they believe problems with GAD levels or activity could play a critical role in this condition:
- Mice without GAD65 develop hyperalgesia, which is a key symptom of FMS;
- GAD plays a role in other disorders involving muscle stiffness and rigidity, similar to the morning stiffness common in FMS;
- GAD activity is decreased by stress, depression and anxiety, all of which are common in FMS;
- The poor deep sleep of FMS could hamper GAD activity in the brain;
- A component of GAD, called cofactor pyroxidine, is more likely to be low in women, and women are more likely to develop FMS;
- Obesity and sedentary lifestyle are risk factors for FMS, while low-calorie diets and exercise have been shown to increase both expression and activity of GAD.
The researchers are calling for studies looking at GAD expression and activity in FMS to see what role, if any, it might play.
Some interesting facts about GAD65 that weren't discussed in the paper also could lend support for the hypothesis.
GAD65 plays a role in type-1 (juvenile-onset) diabetes. Blood-sugar issues, including diabetes, are common in people with FMS (although the adult-onset form is most common.)
Additionally, the fibromyalgia drug Lyrica (pregabalin) is believed to increase GAD activity and therefore raise GABA levels. This is also true of the supplement valerian root, which is sometimes recommended for helping improve sleep in FMS.
GAD levels can be hampered by poor diet, tobacco use and alcohol, all of which have been shown to exacerbate FMS symptoms.
The researchers behind the hypothesis conclude that interventions -- both medicinal and behavioral -- aimed at altering or mimicking the effects of GAD could be effective for treating FMS.
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