My understanding is that neurodegenerative diseases cause permanent damage to neurons making the diseases difficult to treat. This makes prevention a preferred choice than treatment for the diseases. Insulin may have some role in preventing neurodegeneration but may likely not be clinically useful in treating/reversing neurodegeneration. Plus insulin may have systemic effects that are not needed in certain cases, which could affect management.

PMID: 19777393 [PubMed - indexed for MEDLINE]

Insulin resistance and neurodegeneration: roles of obesity, type 2 diabetes mellitus and non-alcoholic steatohepatitis.

This review article will give you some ideas how insulin regulates neurodegeneration process.

Intranasal insulin application improves memory formation in AD patients (see Suzanne Crafts work at University of Washington). Additionally, it has been shown that e.g. insulin regulates the transmission of ionotropic channels in hippocampal neurons , which is required for controlling synaptic plasticity and memory formation. There is indirect data that insulin has beneficial effects on mitochondrial function and thus effects cellular homeostasis. The question is how to apply insulin into brain. Intranasal is an option in humans but in animal models I would rather recommend ICV injection of insulin

Insulin is absolutely important for the brain's functioning, and most studies suggest that insulin is protective against neurodegenerative disease.

Several reports link defective insulin signaling to neurodegenerative disease (Steen et al, Journal of Alzheimer's Disease, 2005; de Felice et al., PNAS 2009; Talbot et al, J Clin Invest. 2012).

Other groups have also demonstrated direct interactions between insulin and amyloid beta at insulin receptors (Xie et al, J Neurosci, 2002).

Furthermore, insulin signaling is also upstream of PI3K/Akt/mTOR signaling, which is important in cell survival and preventing cell death.

I will not give insulin to anyone who does not have diabetes because it does not make sense to me. One condition where we give insulin to non-diabetics is treatment of hyperkalemia, but then we infuse glucose continuously to prevent hypoglycemia. Is there evidence that some neurodegenerative diseases are due to insulin-resistence in the neurones?

This is really an area worth pursuing. Brain insulin resistance can be shown not only in obesity and diabetes, but in some neurodegenerative conditions as well. Inflammatory cytokines may be the common denominator of brain insulin resistance in several neurodegenerative disorders ( Biochem Pharmacol. 2013 ;86:862-71). There is a real need for good basic research in well defined models of neurodegenerative diseases to identify1) how/whether such specific conditions are affected by insulin resistance and insulin re-sensitization; 2) new means to increase the brain's sensitivity to insulin;, 3) the role of peripheral vs. central insulin resistance in neurodegenerative diseases.

http://www.bmbreports.org/jbmb/pdf.php?data=MTMxMDIzMDBAcGRmX3JhaW50cmFjZV9sZWV5c0AlNUI0Mi04JTVEMDkwODI4MDkxOV8lMjg0NzUtNDgxJTI5Qk1CMjU3JTI4OC1SZXYxJTI5LnBkZg==

Look this research

https://www.researchgate.net/profile/George_Perry/?ev=brs_highl

I do believe that insulin has other non-metabolic functions that might include neuronal integrity and neuronal communication.