Belly fat, irregular eating habits and poor diet are among the most common contributing factors to insulin resistance. Insulin resistance is a condition in which the metabolic hormone insulin cannot transfer its signal properly. Insulin resistance can impair cognitive and memory functions. It also promotes the synthesis of proteins that can lead to plaque formations in the brain's memory center. This causes Alzheimer's disease.
Insulin Function
The pancreas secretes insulin in response to nutrients entering the bloodstream. Insulin binds to cell receptors, which causes nutrient transporters to embed in the cell membrane and transport the nutrients into the cells. The cells use the nutrients as an energy source or store them as fat or glycogen. Insulin also has receptors in the brain. According to a report published in the April 2008 issue of "Journal of Alzheimer's Disease," insulin in the brain helps neurons absorb glucose, and it also facilitates communication between neurons.
Insulin Resistance
Insulin resistance is a precursor to type 2 diabetes. When cells are flooded with nutrients from overeating, they gradually shut down their insulin receptors. As blood sugar accumulates in the bloodstream, the pancreas responds by secreting more insulin. This initially helps remove blood sugar from the bloodstream. The high insulin levels promote further shut-downs of insulin receptors. Eventually the pancreas has reached its limits, and the insulin that it produces no longer suffices for removing blood sugar from the bloodstream. So sugar accumulates in the blood and must be excreted in the urine.
Alzheimer's Disease
Alzheimer's disease is a progressive disorder that affects the hippocampus, the brain's main memory center. Proteins called amyloid beta and tau form a layer of plaque around neurons in the hippocampus. This prevents neurons from communicating with each other. Over time the plaque formation leads to tangles and a progressive loss of memory. Researchers reporting in the January 2007 issue of "Experimental Gerontology" suggest that insulin resistance increases the formation of tau and amyloid beta proteins and thus increases the risk of Alzheimer's disease.
Insulin and Norepinephrine
According to a study published in the January 2006 issue of "Neurobiology of Aging," insulin modulates the brain's levels of the neurotransmitter norepinephrine. Norepinephrine is directly correlated with the synthesis of the reward-and-motivator chemical dopamine. Low levels of dopamine can lead to depression. Because insulin cannot transmit its signal properly in patients with insulin resistance, these patients are at risk of developing depression. A review published in "The Journal of Neuropsychiatry and Clinical Neurosciences" suggests that fluctuating norepinephrine levels, which could be due to insulin resistance, may explain some of the behavioral symptoms in Alzheimer's disease, including their tendency to develop depression and agitation.
References
- "Journal of Neurosciences"; Insulin Resistance, Inflammation, and Cognition in Alzheimer's Disease: Lessons for Multiple Sclerosis; G.S. Watson and S. Craft; April 2006
- "Journal of Alzheimer's Disease"; An Integrated and Unifying Hypothesis for the Metabolic Basis of Sporadic Alzheimer's Disease; A. Erol; April 2008
- "Experimental Gerontology"; The Role of Insulin and Neurotrophic Factor Signaling in Brain Aging and Alzheimer's Disease; G.M. Cole and S. A. Frautschy; January/February 2007
- "Neurobiology of Aging"; Insulin Effects on CSF Norepinephrine and Cognition in Alzheimer's Disease; G. S. Watson, et al.; January 2006
- "The Journal of Neuropsychiatry and Clinical Neurosciences"; The Role of Norepinephrine in the Behavioral and Psychological Symptoms of Dementia; Nathan Herrmann, et al.; August 2004
