Posted on January eight, 2019
Reality-checked by Dr. Anthony Gustin, DC, MS.
Written by Brian Stanton
Glycogen storage illness (GSD) is a uncommon genetic dysfunction that impacts about one in 20,000 individuals within the U.S.[*]. Individuals with GSD have hassle synthesizing and breaking down glucose, which may trigger a laundry listing of well being points, together with continual low blood sugar, enlarged liver, weak muscle tissues, and extra.
And though glycogen storage illness is inherited, it’s not essentially a hopeless analysis. Gene therapies present early promise, and enzyme alternative medicine seem to assist a few of the GSD inhabitants with enzyme deficiency. Vitamin modifications may additionally supply some aid. Learn on to seek out out.
- 1 What Is Glycogen Storage Illness?
- 2 How Your Physique Shops Glucose
- 3 Kinds of Glycogen Storage Illness
- 4 How Widespread Is Glycogen Storage Illness?
- 5 Medicine And Gene Remedy For GSD
- 6 Sugar And GSD
- 7 The Keto Food regimen For GSD
- 8 Glycogen Storage Illness Subsequent Steps
What Is Glycogen Storage Illness?
Glycogen storage illness is a metabolic illness that impacts your means to synthesize or break down and use glycogen — the storage type of glucose (extra on this within the subsequent part).
With a number of exceptions, most types of GSD inhibit glycogen breakdown. This causes extra glycogen to build up in muscular tissues, liver, kidney, and different organ tissue — which is poisonous.
Usually, glycogen storage illness begins early in life. Relying on the kind of GSD, the signs vary from delicate to extreme — with muscle ache, enlarged organs, stunted progress, low blood sugar, and muscle weak spot being a couple of of the most typical unwanted effects[*].
How Your Physique Shops Glucose
If you eat a meal — particularly a carb-rich meal — a lot of that meal results in your bloodstream as glucose, a easy sugar that gives your cells with power[*].
This rise in blood glucose, or blood sugar, then alerts your pancreas to launch insulin — your blood sugar regulation hormone.
Insulin’s job is crucial — it ushers glucose out of your blood and into your cells for power or shops it away for later. This not solely offers you with the gasoline you must perform, it additionally maintains wholesome blood sugar ranges.
Since excessive blood sugar, or hyperglycemia, is linked to most continual illnesses and metabolic issues — you undoubtedly need balanced blood sugar and insulin-sensitive cells[*][*][*].
After insulin sends its message to get glucose out of your blood, your cells retailer glucose in considered one of two types: glycogen or fats. When insulin is working appropriately — if you’re insulin delicate — most of your extra blood glucose will get saved as the primary type (glycogen) in muscle and liver cells.
Glycogen storage requires sure enzymes, together with:
- Glycogen synthase
- Glycogen debranching enzyme
Wholesome glycogen storage enzymes promote wholesome quantities of glycogen in your cells.
How Glycogen Storage Works
Right here’s an oversimplification of glycogen storage from begin to end[*]:
- Your blood sugar rises after consuming
- Insulin instructions your cells to retailer any extra glucose as glycogen
- Glucose will get transformed to glucose-6-phosphate
- Glucose-6-phosphate will get transformed to glucose-1-phosphate
- Glucose-1-phosphate will get transformed to UDP-glucose
- UDP-glucose turns into glycogen because of the enzyme glycogen synthase
As soon as saved, glycogen sits in your muscle and liver cells till you’ve got low blood sugar — throughout a quick or intense train session, for example.
Then, to boost your low blood sugar, glycogen converts into glucose so your physique can use it for power — a course of referred to as glycogenolysis.
How Glycogenolysis Works
Right here’s what glycogenolysis seems to be like beneath regular circumstances[*]:
- Your blood sugar drops since you haven’t eaten for some time, are deliberately fasting, or an intense exercise
- Low blood sugar alerts glycogen shops to transform into glucose-1-phosphate
- Glucose-1-phosphate converts into glucose-6-phosphate
- Your physique makes use of glucose-6-phosphate for power (glycolysis) or turns it into glucose and releases it into the blood by way of an enzyme referred to as glucose-6-phosphatase
A minimum of that’s how glycogen storage and breakdown usually work. However when somebody has glycogen storage illness, a number of of those steps is disrupted — and this results in issues with muscle, liver, coronary heart, and different organ tissue.
Kinds of Glycogen Storage Illness
Consider it or not, there are at the least 16 varieties of GSD (sort zero by way of 15). This text, nevertheless, will solely cowl the primary eight, not counting the subtypes inside every sort.
Recall that glycogen storage illness outcomes from genetic mutations that disrupt the storage and breakdown of glycogen. Kinds of GSD, then, are differentiated by particular genetic mutations.
Sort zero (GSD zero)
Overview[*]: Sort zero is the oddball of the GSDs. That’s as a result of individuals with GSD zero don’t have points storing glycogen, however somewhat points synthesizing glycogen.
This can be a drawback as a result of glycogen is essential for powering muscle tissue, particularly throughout train. And so glycogen insufficiency typically results in impaired muscle perform in these affected with Sort zero GSD.
- Sort 0a — issues synthesizing muscle glycogen
- Sort 0b — issues synthesizing liver glycogen
Bodily Trigger: mutations within the GYS1 and GYS2 genes impair the perform of glycogen synthase — an enzyme that provides glucose to glycogen shops
Typical Signs: muscle cramping, coronary heart pumping points, hypoglycemia (low blood sugar)
Frequency: Unknown (underneath 40 instances reported, in all probability underdiagnosed)
Sort I (GSD1, Von Gierke Illness)
Overview[*]: Sort I GSD sufferers can’t break down glucose-6-phosphate, and find yourself with an excessive amount of glycogen of their liver, kidney, and small intestinal cells. Due to this, these with Von Gierke illness current with low blood sugar, enlarged organs, and a number of different signs.
- Sort Ia — extra widespread, commonplace presentation
- Sort Ib — 20% of instances, scarcity of white blood cells
Bodily Trigger: an lack of ability to interrupt down glucose-6-phosphate — an intermediate type of glucose — results in extra glycogen storage. G6PC and SLC37A4 gene mutations look like in charge.
Typical Signs: hypoglycemia, overproduction of lactic acid, too many lipids within the blood (hyperlipidemia), enlarged liver, stunted progress
Frequency: 1 in 100,000 (sort Ia accounts for 80% of instances)
Sort II (GSD2, Pompe Illness)
Overview[*]: Pompe illness is brought on by a dysfunction of acid alpha-glucosidase — an enzyme for dissolving glycogen inside cells. This leads to muscle weak spot, particularly within the coronary heart. Most
- Basic — impacts infants early in life, extra extreme signs
- Delayed onset — delayed to maturity, milder signs
Bodily Trigger: mutations within the GAA gene causes dysfunction of acid alpha-glucosidase — an enzyme wanted to interrupt down glycogen
Typical Signs: muscle weak spot, weak coronary heart (cardiomyopathy), respiratory points
Frequency: 1 in 40,000-60,000[*]
Sort III (GSD3, Cori Illness)
Overview[*]: Cori illness is brought on by a deficiency of the glycogen debranching enzyme, which leads to poisonous ranges of glycogen within the liver and muscle tissue. Cori illness begins early, and youngsters with this situation sometimes have an enlarged liver, stunted progress, and low blood sugar.
- IIIa — impacts liver and muscular tissues, extra widespread
- IIIb — impacts liver solely, extra widespread
- IIIc — impacts liver and muscle mass, much less widespread
- IIId — impacts liver solely, much less widespread
Bodily Trigger: AGL gene mutations impair the perform of glycogen debranching enzyme — which helps break down glycogen
Typical Signs: enlarged liver, hyperglycemia, stunted progress, hyperlipidemia
Frequency: 1 in 100,000
Sort IV (Andersen illness, GSD IV)
Overview[*]: Andersen illness stems from a deficiency in glycogen branching enzyme, which results in irregular glycogen storage. Relying on its severity and subtype, GSD IV ranges from muscle and coronary heart weak spot to a deadly childhood situation.
- Deadly perinatal neuromuscular — most extreme, low muscle tone, typically deadly to newborns
- Congenital muscular — issues respiration, weak coronary heart, typically deadly within the first few months
- Progressive hepatic — commonest, liver failure, typically deadly in early childhood
- Non-progressive hepatic — just like progressive hepatic, however much less extreme
- Childhood neuromuscular — late childhood onset, muscle weak spot, coronary heart weak spot
Bodily Trigger: GBE1 gene mutations trigger issues with glycogen branching enzyme manufacturing, which directs correct glycogen storage
Typical Signs: enlarged liver, muscle weak spot, liver illness, poor muscle tone
Frequency: 1 in 600,000 – 800,000
Sort V (GSDV, McArdle Illness)
Overview[*]: Individuals with McArdle illness can’t break up muscle glycogen, which results in muscle cramping, muscle ache, and fatigue throughout train. GSDV doesn’t often current till the teenagers or early 20s.
Bodily Trigger: PYGM gene mutations disable myophosphorylase — an enzyme that dissolves muscle glycogen into glucose-1-phosphate
Typical Signs: train intolerance, muscle weak spot, muscle cramps, muscle ache
Frequency: Unknown (discovered to have an effect on 1 in 100,000 round Dallas, TX)
Sort VI (GS DVI, Hers Illness)
Overview[*]: Hers illness impacts glycogen storage liver, versus muscle tissue. Hers illness typically begins in infancy, and youngsters with Hers current with an enlarged liver and hypoglycemia. Luckily, signs often enhance with time.
Bodily Trigger: PYGL gene mutations hamper the perform of liver glycogen phosphorylase — an enzyme that dissolves liver glycogen into glucose-1-phosphate
Typical Signs: enlarged liver, hypoglycemia, liver dysfunction
Frequency: Unknown (solely a few dozen instances reported)
Sort VII (GSDVII)
Overview[*]: GSDVII is one other muscle glycogen dysfunction. Besides in a single subtype, these with GSDVII expertise muscle ache and muscle weak spot. GSDVII often begins in childhood.
- Classical (commonest) — train results in muscle ache and breakdown of muscle tissue, which may injury the kidneys
- Extreme Childish — poor muscle tone, enlarged coronary heart, typically deadly within the first yr
- Late Onset — muscle weak spot sometimes begins in maturity
- Hemolytic — characterised by the breakdown of pink blood cells, which results in anemia (low pink blood cells)
Bodily Trigger: PFKM gene mutations impair the perform of phosphofructokinase — an enzyme that helps convert muscle glycogen into glucose
Typical Signs: muscle ache, muscle weak spot, muscle cramps, enlarged coronary heart, excessive uric acid, train intolerance
Frequency: Unknown, in all probability uncommon
How Widespread Is Glycogen Storage Illness?
There are no less than seven different varieties of GSD described within the literature. And these varieties have comparable roots to varieties I by way of VII.
The reality is: GSDs of every type are in all probability underdiagnosed. As genetic testing turns into extra widespread, and as analysis progresses, the variety of reported instances might improve.
And with extra diagnoses, it’s additionally possible that researchers will uncover extra (and higher) therapies.
However GSD isn’t essentially a hopeless prognosis. There are promising therapies — each pharmaceutical and dietary — for this group of genetic issues. And they deserve a point out right here.
Medicine And Gene Remedy For GSD
GSD remedy often revolves round symptom-management, however scientists have lately developed therapies that transcend managing symptomatology. Under are a number of of those therapies.
However first, a regular disclaimer. This text doesn’t take the place of medical recommendation. Please seek the advice of a healthcare skilled for that.
In 2014, the FDA authorised the drug Lumizyme to deal with Pompe illness (GSD2). Lumizyme is an is enzyme alternative remedy that replaces the glycogen breakdown enzyme that folks with Pompe illness lack[*].
Also referred to as alglucosidase alfa, Lumizyme exhibits promise for treating each Pompe illness and Cori illness in medical trials[*][*].
Rapamycin is a drug that regulates the mammalian goal of rapamycin (mTor) pathway. In short, the mTor pathway governs cell metabolism, progress, and far more. Related right here: the mTor pathway additionally impacts the enzyme glycogen synthase, answerable for correct glycogen storage
Skipping to the punchline: rapamycin given to canine with Cori illness (GSD IIIa) inhibited glycogen synthase, lowered muscle and liver glycogen, and prevented injury to each liver and muscle tissue[*].
# three Gene Remedy
Need to modify gene expression in your common mammal? It’s attainable. Simply inject that mammal with a virus.
You learn that proper. Injecting canine, cats, mice, and even sheep with adeno-associated virus (AAV) has delivered promising outcomes for a number of types of GSD, together with von Gierke illness, Pompe illness, and McArdle illness[*].
What about human trials? Nicely, 5 individuals with Pompe illness confirmed modest enchancment, with few unwanted effects, from AAV remedy[*].
But probably the most accessible remedy for GSD isn’t a drug or a virus. It’s vitamin.
Sugar And GSD
When you or a liked one suffers from glycogen storage illness, the very first thing you are able to do is handle sugar consumption.
Sugary, extremely processed, and high-carb meals will increase your blood sugar, aka blood glucose. Excessive blood glucose is a large drawback in case your physique has a tough time breaking down, storing, or releasing glycogen.
Sure, individuals with GSD will retailer extra glucose as glycogen; however, sadly, that glycogen can’t convert again to glucose for power afterward. Which suggests glycogen builds to poisonous ranges.
Much less glycogen is often a very good factor for individuals with GSD, so it’s logical that minimizing the blood sugar response (referred to as hypoglycemia remedy) might help[*]. With much less sugar within the blood, much less glycogen will get saved.
The apparent solution to scale back sugar within the blood? Eat fewer carbs.
And so for treating GSD, researchers are specializing in very low-carb, high-fat diets to maintain glycogen storage at a minimal.
The Keto Food regimen For GSD
Your physique tends to run on glucose. However in a low-sugar, hypoglycemic state, your physique doesn’t simply name it quits. As an alternative, it begins producing ketones from dietary and saved fats — your backup power supply.
Ketones, like glucose, are ultimately transformed to ATP (aka mobile power) via a course of referred to as the Krebs cycle. However in contrast to glucose, ketones don’t spike your blood sugar, and don’t have to be saved as glycogen.
Due to this, the ketogenic eating regimen — a high-fat, low-carb dietary plan that will get you burning fats over sugar — has proven promise for treating glycogen storage illness. Listed here are some examples:
- A high-fat food regimen lessened myopathy (muscle weak spot) in two boys with Cori illness (sort III GSD) over the course of about 2.5 years. This profit stopped when the high-fat food plan stopped and resumed once they resumed the high-fat eating regimen[*].
- A high-fat eating regimen alleviated cardiomyopathy (coronary heart muscle weak spot) in two siblings with Cori illness over the course of 1 yr. Cardiac enzymes, together with indicators of congestive coronary heart failure, each improved measurably[*].
- A ketogenic weight-reduction plan was used to deal with a affected person with GSD V, or McArdle illness — leading to much less muscle ache and weak spot[*]
Admittedly, these trials are small, and extra analysis is required — however a ketogenic or very low-carb weight loss plan might supply some hope to households coping with GSD.
Glycogen Storage Illness Subsequent Steps
Should you assume your youngster or a liked one suffers from glycogen storage illness, the very first thing to do is seek the advice of your physician. Relying on the kind of GSD, there are a number of potential drug therapies available on the market or within the pipeline.
You may also analysis dietary choices for GSD. Analysis on low carb keto diets continues to be early, however a number of small case research have proven promise.
To study extra about keto, you’ll be able to learn our free startup information right here.
READ NEXT: Ketosis For Youngsters
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