Why Some Researchers Are Calling Alzheimer’s Disease a ‘Type 3 Diabetes’

How is diabetes related to cognitive decline? It’s complicated and not entirely understood, but more and more evidence connects the two conditions. While the term “type 3 diabetes” has been used in health media and literature to refer to Alzheimer’s disease , the most common cause of dementia, it may not be a direct result of diabetes. “[Type 3 diabetes] is really more of a research term, rather than a medical term,” says Guojun Bu, PhD , a chair professor in the division of life science at the Hong Kong University of Science and Technology and a leading researcher in the field of genetics and Alzheimer’s. People with diabetes have at least one vascular risk factor, and this may place them at increased risk of Alzheimer’s . Socioeconomic factors likely contribute to both diabetes and Alzheimer’s disease. For example, a sedentary lifestyle is probably a risk factor for both, but diabetes forms first, so it tricks us into thinking diabetes is causing Alzheimer’s. While doctors won’t be using type 3 diabetes as a diagnosis anytime soon, it’s a placeholder for a growing body of research into the relationships between insulin resistance and neurodegenerative conditions that can result in cognitive decline, Alzheimer’s disease, or other types of dementia .
Insulin Resistance and Diabetes Diabetes Normally, the body uses insulin to admit glucose from the bloodstream into cells. But when a person has insulin resistance , the cells do not respond normally to insulin, and some of the glucose remains in the bloodstream, leading to high blood glucose ( high blood sugar ). Initially, the body responds by releasing more insulin from the pancreas to compensate, but if the pancreas cannot keep up with the demand for more insulin, a person will develop prediabetes or type 2 diabetes. Virtually everyone with type 2 diabetes has some degree of insulin resistance, and many people with type 1 diabetes — an autoimmune disease in which the pancreas produces little to no insulin — have insulin resistance, as well.e60dc2a1-f33c-4a05-9b50-8e3e8e597629a9f44aeb-6fad-4275-b2ec-c377681c2edf Increasingly, it’s thought that insulin resistance and poorly controlled blood sugar are involved in the development of Alzheimer’s.e60dc2a1-f33c-4a05-9b50-8e3e8e5976292c39d3f1-8683-4628-98c6-1acbe100bef8 e60dc2a1-f33c-4a05-9b50-8e3e8e597629686d8d31-c100-44e5-b019-51f158970ce5
Insulin Resistance and Alzheimer’s Disease Alzheimer’s Disease Researchers are still trying to figure out exactly what causes Alzheimer’s disease. According to Heather M. Snyder, PhD , the vice president of medical and scientific relations at the Alzheimer’s Association in Chicago, the immune system and hormonal pathways may be among the factors involved in the development of the condition. Yet increasingly, researchers are also looking at a connection between insulin resistance and Alzheimer’s disease. “Individuals who have diabetes have an increased risk of Alzheimer’s disease and related dementias in later life,” says Dr. Snyder. But the exact mechanisms are not fully understood. “While diabetes increases a person’s risk of Alzheimer’s, not everyone with diabetes develops Alzheimer’s and not everyone with Alzheimer’s has diabetes,” says Snyder. “Individuals with diabetes may have an impacted supply of glucose to the brain, and this could influence the metabolism process, but it is likely not that simple. The interactions are complex and engage our processing of energy, immune mechanisms, vascular processes, and clearance and transport systems, for example.”
How Insulin Resistance May Work in the Brain Insulin and the Brain Our understanding of how insulin resistance may affect the brain is evolving. “For many years, we thought that the brain was not [made of] insulin-sensitive tissue. But over the past 15 years, this notion has really changed dramatically,” says C. Ronald Kahn, MD , the head of integrative physiology and metabolism at the Joslin Diabetes Center at Harvard University in Boston. “We know that insulin gets across the blood-brain barrier in different areas of the brain and also gets into the spinal fluid, which is the fluid that bathes the brain. The brain tissue is exposed to insulin at somewhat reduced levels compared with other tissues in the body but is still very much regulated in response to things that cause insulin levels in blood to increase, such as a lot of carbohydrates in a meal or a lot of sugar. We also now know that this response in the brain has effects on both the metabolism of the brain cells and the way the brain cells signal the body for different functions,” Dr. Kahn says.e60dc2a1-f33c-4a05-9b50-8e3e8e597629db7d37bd-e47d-4dd4-9ac7-ed02531ffa87 Kahn participated in a study published in Neuron that looked at mice with the APOE4 gene that were fed a high-fat diet and developed insulin resistance.e60dc2a1-f33c-4a05-9b50-8e3e8e597629b404eb82-a5e5-4e89-8923-fca79948874b The older the mice were, the more dramatic the impairment was to the functioning of insulin in the brain. This gene is important because of its link to Alzheimer’s disease. “Twenty percent of the general human population carries at least one allele for the APOE4,” Dr. Bu points out. (An allele is a variant of a gene, and they come in pairs, with one inherited from each parent.) “Somewhere between 50 percent and 70 percent of people with Alzheimer’s disease carry at least one copy of the allele, making it a strong risk factor.” Genetic testing is available for the APOE4 gene and other variants, but it’s worth noting that the gene is only a risk factor, and not everyone who has it will develop the disease. Bu points out that ongoing research is exploring potential treatments for preventing Alzheimer’s disease in people with insulin resistance. Knowing how a person’s genetic profile affects the progression of the disease could help healthcare providers customize treatments in the future.
Using Diabetes Drugs to Treat Alzheimer’s Diabetes Drugs Snyder notes that one of the key translations of the relationship between insulin resistance and the brain has been investigating medications developed for insulin resistance or diabetes as possible therapies in Alzheimer’s disease. Both Bu and Kahn cite ongoing research led by the neuropsychologist Suzanne Craft, PhD, on a treatment that administers insulin to the brain through a special device that allows patients to inhale the insulin, where it hopefully can reach the brain at higher levels. Kahn notes that while the results have not been dramatic, some studies have shown modest effects.e60dc2a1-f33c-4a05-9b50-8e3e8e597629642397cc-f9f1-4e12-ab60-8c28fb0ccf0e Snyder points to several studies funded by the Alzheimer’s Association, including a phase 2 clinical trial led by Dr. Craft, looking into the safety, feasibility, and dosing of a combination of insulin and empagliflozin (a metabolism-targeting drug) in individuals with mild cognitive impairment or Alzheimer’s disease.e60dc2a1-f33c-4a05-9b50-8e3e8e5976295a70b793-8423-420f-90ab-1dd3196555a4 Another clinical trial is investigating the intranasal administration of insulin and another medication ( semaglutide ) in individuals at risk for dementia.e60dc2a1-f33c-4a05-9b50-8e3e8e597629f111ccbb-3ad1-49ea-b9a9-fa9aa3940471 Research into the use of metformin , a commonly prescribed type 2 diabetes oral drug that helps improve the body’s response to insulin and control the amount of glucose in the blood, hasn’t shown it to be especially effective with respect to Alzheimer’s. But Kahn notes that there’s “a lot of interest in the potential of new-generation anti-diabetic drugs, such as GLP-1 analogs , SGLT-2 inhibitors , and DPP-4 inhibitors , as therapeutic approaches for Alzheimer’s disease. Studies in animals suggest they may have value, but thus far there are no human studies.”
Lifestyle Measures to Lower Your Risk Lifestyle Meanwhile, it’s important for people who have type 2 diabetes, prediabetes, or a family history of diabetes to understand that they are not automatically destined to develop Alzheimer’s disease. Nor will consuming sugar in moderation necessarily lead one down that path, assuming that your blood glucose levels are under control. But lifestyle changes to reverse or manage type 2 diabetes are important. One of the best preventive measures you can take is to exercise . “People with diabetes, especially if it is poorly controlled, are at risk of increased vascular problems, including vascular dementia, which can complicate other forms of dementia, including Alzheimer’s disease,” says Kahn. “It is worth emphasizing that in all individuals, including nondiabetics, exercise has been shown to lower the risk of Alzheimer’s disease significantly, so exercise is one of the best ways to reduce your risk of both Alzheimer’s and diabetes.” Additional reporting by Moira Lawler and Deborah Shapiro .
Resources
Resources We Trust Mayo Clinic: Type 2 DiabetesAlzheimer Society: Diabetes and DementiaBrightFocus Foundation: Diabetes: A Modifiable Risk Factor for Alzheimer’s DiseaseDiabetes Daily: Alzheimer’s Disease and Diabetes: What’s the Connection?Harvard Health Publishing: What’s the Relationship Between Diabetes and Dementia?

Are you and your partner neglecting sex play? Learn how to add it back into your routine to boost your bond in and out of the bedroom. While "quickies" can be fun and spontaneous, skipping foreplay means missing out on a great way to connect emotionally and physically. According to Pepper Schwartz, PhD, a sexual health expert and researcher at the University of Minnesota in Minneapolis, foreplay is critical, elemental, and necessary. Foreplay, also known as "outercourse," is any sexual activity that occurs before intercourse. There is no single way to engage in foreplay, as it can mean different things to different people. It can involve kissing, caressing, cuddling, flirty texting or talking, massage, and oral sex. If you like it a little rough, biting, pinching, scratching, and spanking can be a turn-on. The goal is to increase sexual excitement, which can help prepare the body for intercourse. Foreplay is sometimes thought of as a warm-up for sex, but it doesn't necessarily have to lead to intercourse. Some couples find foreplay itself to be sexually fulfilling as a main event. The benefits of foreplay include lubrication of the vagina, an extended erection, and the prevention of premature ejaculation for people with penises. The female body pulls the uterus up when aroused, lengthening the vagina. This process, called uterine tenting, creates a pool area for semen, which is part of the reproductive sophistication of our machinery, according to Dr. Schwartz. As those muscles relax, the nerve endings start to get stimulated, paving the way for a more pleasurable experience. Research involving married couples has found that 1 to 10 minutes of foreplay was associated with 40% of women achieving orgasm during sex. That percentage rose to 50 with 12 to 20 minutes of foreplay and 60 with more than 20 minutes of foreplay. If you want more action in bed, you have to let your partner know what you want. But talking about sex can be easier said than done for some. Dr. Lyndsey Harper, a clinical assistant professor of obstetrics and gynecology at Texas A&M School of Medicine in Bryan, Texas, recommends two sentence starters to try when expressing sexual desire to your partner: "I want you to..." and "It feels so good when you...". If it makes you more comfortable, you can bring up your sexual needs outside of the bedroom. If you don't know how to bring it up, she suggests starting the conversation with something like, "Our sex life is really important, and I'd love for us to feel open talking about things. Would it be okay for me to share with you some things I like?" Communication comfort is closely linked to trust. To experience true intimacy and fun foreplay, trusting each other is essential, especially since our needs constantly change. Couples who find it difficult to communicate about their desires should consider seeing a couple's counselor or sex therapist who can help them navigate these discussions.
  • Foreplay is just play. Couples can engage in it however they want. According to Dr. Harper, it generally takes about 20 minutes of arousal for women to become fully lubricated and ready for penetrative sex. However, it is best to abolish the idea of "foreplay" and the "main event" of penetrative sex and work together with your partner to create a fun and intimate sexual life where everyone's needs are met.

https://www.everydayhealth.com/sexual-health/sexual-foreplay.aspx