Cholesterol Helps Brain Metabolize Proteins
Alzheimer’s disease is a devastating disease on the rise around the world. Several factors can influence the onset of neurodegenerative disease, including head trauma, nutrition and genetics. Fortunately, a significant number of research dollars are currently being spent to try to understand what causes Alzheimer’s disease.
ApoE-4 is a known risk factor. Since apoE plays a critical role in the transport of cholesterol and fats to the brain, it’s hypothesized that insufficient fat and cholesterol in the brain play a critical role in the neurodegeneration process.
Alzheimer’s disease patients have only 1/6 of the concentration of free fatty acids in the cerebrospinal fluid compared to individuals without Alzheimer’s disease.
In parallel, it is becoming very clear that cholesterol is pervasive in the brain, and that it plays a critical role both in nerve transport in the synapse and in maintaining the health of the myelin sheath coating nerve fibers.
An extremely high-fat (ketogenic) diet has been found to improve cognitive ability in Alzheimer’s patients. These and other observations described below lead me to conclude that both a low-fat diet and statin drug treatment increase susceptibility to Alzheimer’s disease.
Alzheimer’s is a devastating disease that takes away the mind bit by bit over a period of decades. It begins as odd memory gaps but then steadily erodes your life to the point where around-the-clock care is the only option. With severe Alzheimer’s disease, you can easily wander off and get lost, and may not even recognize your own daughter. Alzheimer’s disease was a little known disease before 1960, but today it threatens to completely derail the health system in the United States.
Currently, over 5 million people in America have Alzheimer’s disease. On average, a person over 65 with Alzheimer’s costs three times as much for health care as one without Alzheimer’s. More alarmingly, the incidence of Alzheimer’s is on the rise. Dr. Murray Waldman has studied epidemiological data comparing Alzheimer’s with femur fractures, looking back over the last fifty years. Alarmingly, he has found that, while the incidence of femur fractures (another condition which typically increases with age) has gone up only at a linear rate, the increase in the incidence of Alzheimer’s has gone up exponentially, between 1960 and 2010 Alzheimer’s Epidemic.
Just between 2000 and 2006, US Alzheimer’s deaths rose by 47%, while, by comparison, deaths from heart disease, breast cancer, prostate cancer, and stroke combined decreased by 11%. This increase goes far beyond people living longer: for people 85 and older, the percentage who died from Alzheimer’s disease rose by 30% between 2000 and 2005. Finally, it’s likely these are under-estimates, as many people suffering with Alzheimer’s ultimately die of something else. You likely have a close friend or relative who is suffering from Alzheimer’s.
Something in our current lifestyle is increasing the likelihood that we will succumb to Alzheimer’s. My belief is that two major contributors are our current obsession with low-fat diet, combined with the ever expanding use of statin drugs. I have argued elsewhere that low-fat diet may be a major factor in the alarming increase in autism and adhd in children. I have also argued that the obesity epidemic and the associated metabolic syndrome can be traced to excessive low-fat diet. Statins are likely contributing to an increase in many serious health issues besides Alzheimer’s, such as sepsis, heart failure, fetal damage, and cancer, as I have argued here. I believe the trends will only get worse in the future, unless we substantially alter our current view of “healthy living.”
The ideas developed in this essay are the result of extensive on-line research I conducted to try to understand the process by which Alzheimer’s develops. Fortunately, a great deal of research money is currently being spent on Alzheimer’s, but a clearly articulated cause is still elusive. However, many exciting leads are fresh off the press, and the puzzle pieces are beginning to assemble themselves into a coherent story. Researchers are only recently discovering that both fat and cholesterol are severly deficient in the Alzheimer’s brain. It turns out that fat and cholesterol are both vital nutrients in the brain. The brain contains only 2% of the body’s mass, but 25% of the total cholesterol. Cholesterol is essential both in transmitting nerve signals and in fighting off infections.
A crucial piece of the puzzle is a genetic marker that predisposes people to Alzheimer’s, termed “apoE-4.” ApoE plays a central role in the transport of fats and cholesterol. There are currently five known distinct variants of apoE (properly termed “alleles”), with the ones labelled “2”, “3” and “4” being the most prevalent. ApoE-2 has been shown to afford some protection against Alzheimer’s; apoE-3 is the most common “default” allele, and apoE-4, present in 13-15% of the population, is the allele that is associated with increased risk to Alzheimer’s. A person with apoE-4 allele inherited from both their mother and their father has up to a twenty-fold increased likelihood of developing Alzheimer’s disease. However, only about 5% of the people with Alzheimer’s actually have the apoE-4 allele, so clearly there is something else going on for the rest of them. Nonetheless, understanding apoE’s many roles in the body was a key step leading to my proposed low fat/statin theory.
Although I have tried to write this essay in a way that is accessible to the non-expert, it will still be helpful to first familiarize you with basic knowledge of the structure of the brain and the roles played by different cell types within the brain.
At the simplest level, the brain can be characterized as consisting of two major components: the gray matter and the white matter. The gray matter comprises the bodies of the neurons, including the cell nucleus, and the white matter contains the myriad of “wires” that connect each neuron to every other neuron it communicates with. The wires are known as “axons” and they can be quite long, connecting, for example, neurons in the frontal cortex (above the eyes) with other neurons deep in the interior of the brain concerned with memory and movement. The axons will figure prominently in the discussions below, because they are coated with a fatty substance called the myelin sheath, and this insulating layer is known to be defective in Alzheimer’s.
Neurons pick up signals transmitted through the axons at junctures known as synapses. Here the message needs to be transmitted from one neuron to another one, and various neurotransmitters such as dopamine and GABA exert excitatory or inhibitory influences on signal strength. In addition to a single axon, neurons typically have several much shorter nerve fibers called dendrites, whose job is to receive incoming signals from diverse sources. At a given point in time, signals received from multiple sources are integrated in the cell body and a decision is made as to whether the accumulated signal strength is above threshold, in which case the neuron responds by firing a sequence of electrical pulses, which are then transmitted through the axon to a possibly distant destination.
In addition to the neurons, the brain also contains a large number of “helper” cells called glial cells, which are concerned with the care and feeding of neurons. Three principle types of glial cells will play a role in our later discussion: the microglia, the astrocytes, and the oligodendrocytes.
Microglia are the equivalent of white blood cells in the rest of the body. They are concerned with fighting off infective agents such as bacteria and viruses, and they also monitor neuron health, making life-and-death decisions: programming a particular neuron for apoptosis (intentional self-destruction) if it appears to be malfunctioning beyond hope of recovery, or is infected with an organism that is too dangerous to let flourish.
The astrocytes figure very prominently in our story below. They nestle up against the neurons and are responsible for assuring an adequate supply of nutrients. Studies on neuron cultures from rodent central nervous systems have shown that neurons depend upon astrocytes for their supply of cholesterol. Neurons critically need cholesterol, both in the synapse and in the myelin sheath, in order to successfully transmit their signals, and also as a first line of defense against invasive microbes. Cholesterol is so important to the brain.
