Step 1 to cancer free: Limit stress that leads to high blood glucose and lipids

Adrenals and liver come to the rescue as blood sugar levels drop.  The endocrine pancreas, liver and adrenal glands work to normalize blood sugar and triglycerides.

Take care of your stress so it will be easier for you to prevent obesity, depression, sugar cravings and nerve pain which may start to happen at around 55 years of age. When we take care of our stress level, we take care of our metabolism , brain , whole body and we then prevent chronic diseases that lead to cancer.

Activities to make you happy

Beach stroll, dancing, watching comedians , laughing , sleeping at nigh, massage , happy and loving friends and relationships , spending time with family and friends , playing with your pets, gardening , singing , praying , deep breathing exercise, meditation

Side effects of chronically elevated cortisol can include:

Anxiety , Autoimmune diseases , Cancer,  Chronic fatigue syndrome , Common Colds , Hormone imbalance , Irritable bowel disease , Thyroid conditions , Weight loss resistance

Needed nutrients

Digestive enzymes, vitamin C (citrus, kiwi, berries, tamarind), vitamin B, L-carnitine, chromium, anti-oxidants, fiber-rich foods (squash, yams, sulfur family of garlic and onions, greens, okra, radish), spearmint, ginger, beets, carrots, all root crops, sprouts, pineapple, papaya , taurine rich foods (breastmilk, sea algae, fish)

Adaptogenic herbs

  1. Eleuthero ginseng
  2. Holy basil
  3. Rodiola rosea
  4. ashwagandha
  5. Astralagus
  6. Sour date
  7. Mimosa pudica
    Extracts of Mimosa pudica are successful in wiping out harmful bacteria and can be useful in antibacterial products
  8. Medicinal mushrooms
    Mushrooms are rich in B vitamins such as riboflavin (B2), folate (B9), thiamine (B1), pantothenic acid (B5), and niacin (B3).
  9. Licorice root
  10. Valerian


Cancer Hijacks the Microbiome to Glut Itself on Sugar

Cancer Hijacks the Microbiome to Glut Itself on Glucose

Source: University of Colorado Anschutz Medical Campus.

Cancer needs energy to drive its out-of-control growth. It gets energy in the form of glucose, in fact consuming so much glucose that one method for imaging cancer simply looks for areas of extreme glucose consumption — where there is consumption, there is cancer. But how does cancer get this glucose? A University of Colorado Cancer Center study published today in the journal Cancer Cell shows that leukemia undercuts the ability of normal cells to consume glucose, thus leaving more glucose available to feed its own growth.

“Leukemia cells create a diabetic-like condition that reduces glucose going to normal cells, and as a consequence, there is more glucose available for the leukemia cells. Literally, they are stealing glucose from normal cells to drive growth of the tumor,” says Craig Jordan, PhD, investigator at University of Colorado Cancer Center, division chief of the Division of Hematology and the Nancy Carroll Allen Professor of Hematology at the University of Colorado School of Medicine.

Like diabetes, cancer’s strategies depend on insulin. Healthy cells need insulin to use glucose. In diabetes, either the pancreas under-produces insulin or tissues cannot not respond to insulin and so cells are left starved for energy while glucose builds up in the blood. The current study shows that leukemia goes about creating similar conditions of glucose buildup in two ways.

First, tumor cells trick fat cells into over-producing a protein called IGFBP1. This protein makes healthy cells less sensitive to insulin, meaning that when IGFBP1 is high, it takes more insulin to use glucose than it does when IGFBP1 is low. Unless the supply of insulin goes up, high IGFBP1 means that the glucose consumption of healthy cells goes down. (This protein may also be a link in the chain connecting cancer and obesity: The more fat cells, the more IGFBP1, and the more glucose is available to the cancer.)

Of course, cancer has a second strategy that ensures insulin production does not go up to meet the need created by increased IGFBP1. In fact, cancers turn insulin production down. In large part, they do this in the gut.

“In the course of doing this systemic analysis, we realized that some of the factors that help regulate glucose are made by the gut or bacteria in the gut. We looked there and found that the composition of the microbiome in leukemic animals was different than in control mice,” Jordan says.

One major difference in the guts of leukemic mice was the lack of a specific kind of bacteria known as bacteroids. These bacteroids produce short-chain fatty acids that in turn feed the health of cells lining your gut. Without bacteroids, gut health suffers. And the current study shows that without bacteroids, gut health suffers in ways that specifically aid cancer.

One way is the loss of hormones called incretins. When blood glucose gets high, for example after you eat, your gut releases incretins, which tamp down blood glucose, reducing it back into the normal range. Working through the gut, leukemia inactivates these incretins, allowing blood glucose to remain higher than it should. Leukemia also nixes the activity of serotonin. Serotonin is well-known as a “feel good” chemical that helps to regulate mood and is found in many antidepressants. But serotonin is also essential for the manufacture of insulin in the pancreas, and by attacking serotonin, leukemia reduces insulin production (and thus, down the line, glucose use).

The result of less insulin secretion and less insulin sensitivity is that cancer undercuts healthy cells’ use of insulin from both sides: Healthy cells need more insulin, just as there is less insulin available. Less insulin use by healthy cells leaves more glucose for the cancer.

“It’s a classic parasite trick: Take advantage of something the host does and subvert it for your own purposes,” Jordan says.

Interestingly, just as a parasite might eat a host’s food leading to malnourishment, cancer’s energy theft may play a role in the fatigue and weight loss common in cancer patients.

“The fairly prevalent observation is that cancer patients have a condition called cachexia, basically wasting away — you lose weight. If cancers are inducing systemic changes that result in depletion of normal energy stores, this could be part of that story,” Jordan says.

However, Jordan and colleagues including first author Haobin Ye, PhD, not only showed how leukemia dysregulates healthy cells’ glucose consumption, but also showed how to “re-regulate” this consumption.

“When we administered agents to recalibrate the glucose system, we found that we could restore glucose regulation and slow the growth of leukemia cells,” Ye says.

These “agents” were surprisingly low-tech. One was serotonin. Another was tributyrin, a fatty acid found in butter and other foods. Serotonin supplementation replaced the serotonin nixed by leukemia and tributyrin helped to replace the short-chain fatty acids that were absent due to loss of bacteroids.


The group calls the combination Ser-Tri therapy. And they show that it is more than a theory. Ser-Tri therapy led to the recovery of insulin levels and reduction of IGFPB1. And leukemic mice treated with Ser-Tri therapy lived longer than those without. Twenty-two days after leukemia was introduced in mice, all of the untreated mice had died, while more than half of the mice treated with Ser-Tri were still alive.

The continuing line of work shows that cancer may depend on the ability to out-compete healthy cells for limited energy. Healthy tissues have strategies to regulate insulin, glucose and other factors controlling energy consumption; cancer cells have strategies to subvert this regulation with the goal of making more energy available for their own use.

“We now have evidence that what we observed in our mouse models is also true for leukemia patients.” Ye says.

Understanding these mechanisms that cancer uses to unbalance the body’s system of energy in their favor is helping doctors and researchers learn to thumb the scale in favor of healthy cells.

“This furthers the notion that you can do things systemically to disfavor leukemia cells and favor normal tissue,” Jordan says. “This could be part of limiting growth of tumors.”


Source: Garth Sundem – University of Colorado Anschutz Medical Campus
Publisher: Organized by
Image Source: image is in the public domain.
Original Research: Abstract for “Subversion of Systemic Glucose Metabolism as a Mechanism to Support the Growth of Leukemia Cells” by Haobin Ye, Biniam Adane, Nabilah Khan, Erica Alexeev, Nichole Nusbacher, Mohammad Minhajuddin, Brett M. Stevens, Amanda C. Winters, Xi Lin, John M. Ashton, Enkhtsetseg Purev, Lianping Xing, Daniel A. Pollyea, Catherine A. Lozupone, Natalie J. Serkova, Sean P. Colgan, and Craig T. Jordan in Cancer Cell. Published September 27 2018.

What body systems are responsible for energy production?

Skeletal muscle is powered by one important compound; adenosine triphosphate (ATP). The body only stores small amounts of ATP in the muscles so it has to replace and resynthesize this energy compound on an ongoing basis. Understanding how it does this is the key to understanding energy systems.

There are 3 separate energy systems through which the body produces ATP. Describing each of these systems in detail goes beyond the aim of this article. Instead it is intended that the brief outlines provided will assist in describing the role of blood lactate during energy production for exercise, and how this knowledge can be used to help with training for improved endurance performance.


The ATP-PCr system

This system produces energy during the first 5-8 seconds of exercise using ATP stored in the muscles and through the breakdown of phosphocreatine (PCr). This system can operate with or without the presence of oxygen but since it doesn’t rely on oxygen to work it is said to be anaerobic. When activity continues beyond this period the body relies on other ways to produce ATP.

The Glycolytic System

This system produces ATP through the breakdown of glucose in a series on enzymatic reactions. The end product of glycolysis is pyruvic acid. This either gets funneled through a process called the Kreb’s cycle (slow glycolysis) or gets converted into lactic acid (fast glycolysis). The fast glycolytic system produces energy more quickly than slow glycolysis but the end product of lactic acid can accumulate and is thought to lead to muscular fatigue. The contribution of the fast glycolytic energy system rapidly increases after the first 10 seconds and activity lasting up to 45 seconds is supplied by energy mainly from this system. Anything longer than this and there is a growing reliance on the Oxidative system.

The Oxidative system

This is where pyruvic acid from slow glycolysis is converted into a substance called acetyl coenzyme A rather than lactic acid. This substance is then used to produce ATP by funneling it through the Krebs cycle. As it is broken down it produces ATP but also leads to the production of hydrogen and carbon dioxide. This can lead to the blood becoming more acidic. However, when oxygen is present it combines with the hydrogen molecules in series of reactions known as the electron transport chain to form water thus preventing acidification. This chain, which requires the presence oxygen, also leads to the production of ATP. The Krebs cycle and the electron transport chain also metabolise fat for ATP production but this again requires the presence of oxygen so that the fats can be broken down. More ATP can be liberated from the breakdown of fats but because of the increased oxygen demand exercise intensities must be reduced. This is also the most sustainable way of producing ATP.

It is important to remember that these systems are all constantly working to produce energy for all bodily functions and one system is never working exclusively over the others. When it comes to energy production for exercise one system will play a more dominant role (this will be dictated by the type of activity being performed) but all 3 systems will still be working to provide adequate amounts of ATP.

What is Blood Lactate?

It is through the Glycolytic System that the role and production of blood lactate becomes apparent. Recall the end product of glycolysis is pyruvic acid. When this is converted into lactic acid it quickly dissociates and releases hydrogen ions. The remaining compound then combines with sodium or potassium ions to form a salt called lactate. Far from being a waste product, the formation of lactate allows for the continued metabolism of glucose through glycolysis. As long as the clearance of lactate is matched by its production it becomes an important source of fuel.

Clearance of lactate from the blood can occur either through oxidation within the muscle fibre in which it was produced or it can be transported to other muscle fibres for oxidation. Lactate that is not oxidized in this way diffuses from the exercising muscle into the capillaries and it is transported via the blood to the liver. Lactate can then be converted to pyruvate in the presence of oxygen, which can then be converted into glucose. This glucose can either be metabolized by working muscles (as an additional substrate) or stored in the muscles as glycogen for later use. So lactate should be viewed as a useful form of potential energy. Lactic acid and lactate do not cause fatigue per se.

In fact, it is a common misinterpretation that blood lactate or even lactic acid has a direct negative effect on muscle performance. It is now generally accepted that any decrease in muscle performance associated with blood lactate accumulation is due to an increase in hydrogen ions, leading to an increased acidity of the inter-cellular environment. This acidosis is thought to have an unfavourable effect on muscle contraction, and contributes to a feeling of heavy or ‘jelly’ legs.

The term ‘accumulation’ is therefore the key, as an increased production of hydrogen ions (due to an increase production of lactic acid) will have no detrimental effect if clearance is just as fast. During low intensity exercise blood lactate levels will remain at near resting levels as clearance matches production. As exercise intensity increases there comes a break point where blood lactate levels will start to rise (production starts to exceed clearance). This is often referred to as the lactate threshold (LT). If exercise intensity continues to increase a second and often more obvious increase in lactate accumulation is seen. This is referred to as the lactate turn point (LTP).

Physical inactivity, dopamine, lactate , glucose and aging

aging exerAfter 96 years of age, he has crying spells in the afternoon or early evening hours when our brain hormones are slowing down to ready for sleep.  With less exercise and more time sitting down watching TV and eating every 2 hours, he forgets to remember things as his brain and muscles are not working as it should when he was young.  Whenever I see him, I give him a hug and trains other caregivers to hug him more. He perks up and can do more walking.

Hugging can increase the production of dopamine in your brain, and this can be seen in PET scans of the brain. Dopamine levels are low in people with conditions like Parkinsonism and mood disorders like Depression.

So if you see someone depressed, give him a hug, and bring a little joy to their life.
Dopamine levels are low to those with Alzheimer and Parkinson’s diseases.
Dopamine containing neurons control  voluntary movements. The association with a physiologically reduced glutamate release from frontal and prefrontal cortices, hippocampi and amygdala would induce further decrease of Dopamine release, inducing hypo-activity, gait disturbances and decline of executive functions.

The earlier the impairment of Dopamine system occurs, the fastest the cognitive decline goes.

Hormones and nuerotransmitters dopamine, norepinephrine and epinephrine are responsible for our emotions and affects our memory and muscles causing Alzheimer and Parkinson’s disease.
In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons (nerve cells) to send signals to other nerve cells. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior.
Epinephrine, also called adrenaline, hormone that is secreted mainly by the medulla of the adrenal glands and that functions primarily to increase cardiac output and to raise glucose levels in the blood.
Norepinephrine, also called noradrenaline, substance that is released predominantly from the ends of sympathetic nerve fibers and that acts to increase the force of skeletal muscle contraction and the rate and force of contraction of the heart.

Supplements and Nutrition

Eat happy foods: eggs, colorful whole foods and yams and whole foods/dietary supplements rich in the following nutrients:
Folate, Vitamin B complex, SAM-E,omega 3, digestive enzymes, probiotic, Vitamin C, copper, iron from greens, NAC
Suggested exercises should include walking, dancing , stretching, yoga, meditation, and other body movement.
Remember all the above information assumes that you have a healthy liver. Take care of the laboratory organ of your body, the liver which processes all chemicals, drugs, alcohol and nutrition in your body.
During sleep, your brain is helping the liver detox your body. The lymphatic system which travels opposite your circulatory system is responsible for cleaning your blood.

Lactate and brain

Lactate is considered an important metabolite in the human body, but there has been considerable debate about its roles in brain function. Research in recent years has suggested that lactate from astrocytes may be crucial for supporting axonal function, especially during times of high metabolic demands or hypoglycemia. The astrocyte-neuron lactate transfer shuttle system serves a protective function to ensure a supply of substrates for brain metabolism, and oligodendrocytes appear to also influence availability of lactate. There is increasing evidence for lactate acting as a signaling molecule in the brain to link metabolism, substrate availability, blood flow and neuronal activity.
The brain produces its own lactate from the metabolism of glycogen and tends to export lactate at rest []. Lactate is brought into the brain across the BBB to be used as fuel when plasma lactate is high or plasma glucose is low [].

Healthy Glucose Levels Key to a Healthy Aging Brain

Healthy Glucose Levels Key to a Healthy Aging Brain

Summary: Even during early stages of the disease, gut bacteria in those with Parkinson’s differs significantly from those without the disease, a new study reports.

Source: Australian National University.

New research has found blood glucose levels even at the normal range can have a significant impact on brain atrophy in ageing.

Dr Erin Walsh, lead author and post-doctoral research fellow at ANU, said the impacts of blood glucose on the brain is not limited to people with type 2 diabetes.

“People without diabetes can still have high enough blood glucose levels to have a negative health impact,” said Dr Walsh from the Centre for Research on Ageing, Health and Wellbeing (CRAHW) at ANU.

“People with diabetes can have lower blood glucose levels than you might expect due to successful glycaemic management with medication, diet and exercise.

“The research suggests that maintaining healthy blood glucose levels can help promote healthy brain ageing. If you don’t have diabetes it’s not too early and if you do have diabetes it’s not too late.”

Dr Walsh said people should consider adopting healthy lifestyle habits, such as regular exercise and healthy diets.

“Having a healthy lifestyle contributes to good glycaemic control without needing a diabetes diagnosis to spur them into adopting these good habits,” she said.

Image shows a brain and bag of sugar.

“It helps to keep unhealthy highly processed and sugary foods to a minimum. Also, regular physical activity every day can help, even if it is just a going for walk.”

The research is part of the “Too sweet for our own good: An investigation of the effects of higher plasma glucose on cerebral health” project led by Associate Professor Nicolas Cherbuin, which is part of the longitudinal PATH through life study led by Professor Kaarin Anstey at ANU.

“The work would not be possible without being able to longitudinally explore blood glucose in members of the general public,” said Dr Walsh.

Binding or cross linking of glucose to protein damages tissues

The role of collagen crosslinks in ageing and diabetes – the good, the bad, and the ugly

Jess G. Snedeker1 and Alfonso Gautieri2

The non-enzymatic reaction of proteins with glucose (glycation) is a topic of rapidly growing importance in human health and medicine. There is increasing evidence that this reaction plays a central role in ageing and disease of connective tissues. Of particular interest are changes in type-I collagens, long-lived proteins that form the mechanical backbone of connective tissues in nearly every human organ. Despite considerable correlative evidence relating extracellular matrix (ECM) glycation to disease, little is known of how ECM modification by glucose impacts matrix mechanics and damage, cell-matrix interactions, and matrix turnover during aging.

More daunting is to understand how these factors interact to cumulatively affect local repair of matrix damage, progression of tissue disease, or systemic health and longevity. This focused review will summarize what is currently known regarding collagen glycation as a potential driver of connective tissue disease. We concentrate attention on tendon as an affected connective tissue with large clinical relevance, and as a tissue that can serve as a useful model tissue for investigation into glycation as a potentially critical player in tissue fibrosis related to ageing and diabetes.

Keywords: collagen, advanced glycation end-products, crosslinks, tendon mechanics, diabetes, ageing

Setting the stage: central functional roles of collagen

The term collagen comes from the Greek word κολλα (kolla, meaning “glue”), due to the use of animal skin and collagen-rich tissues a glue source1. In a broader sense, collagen is in fact the “glue” of our body, holding it together by providing elasticity and strength to most tissues where mechanical function is essential, such as skin, cartilage, tendons and bones 2,3.

The collagen family of proteins is the most abundant in the human body – representing a basic building block within nearly every tissue and organ. Collagen structures form largely by cell-mediated self-assembly of small collagen molecules (300 nm in length; circumscribable with an approximate 1.5 nm diameter)4. During the process of collagen self-assembly, various types of inter-molecular crosslinks stabilize the helical supramolecular structures that form. Collagen crosslinks can be conceptually classed as either enzymatic or non-enzymatic, with enzymatic crosslinking representing an essential step in the development and repair of collagen connective tissues. Whether in the early stages of embryonic tendon development or the late stages of connective tissue disease, collagen crosslinks play a key role in tissue mechanics, cell signaling, matrix damage accumulation, and tissue repair.

Cell-matrix interactions involving collagen include a wide range of classical receptor-ligand mediated signaling pathways5. Nonetheless the main functional feature of most collagens (this review will focus on type-I collagen) is mechanical load bearing of tensile force.The mechanical function of any connective tissue results from often highly sophisticated architectural arrangement of collagen substructures, along with other elastic extracellular matrix proteins such as elastin, and water binding proteoglycans. Although soft connective tissues of the body are composed of nearly identical basic molecular building blocks, their varied arrangement makes possible an exquisite range of potential tissue mechanical properties. The cells that mediate the functional assembly of these building blocks do so according to their epigenetic pre-program as guided by the mechanical demands on the tissue.

Within any collagenous connective tissue, the functional building blocks that provide tensile strength and elasticity are called collagen “fibrils”. The collagen fibril is a helically arranged supramolecular structure that can range in diameter from a few to several hundred nanometers, with lengths that can run on the order of centimeters6. How collagen molecules are accrued into these structures (a process known as fibrillogenesis) relies on sequences of elegant intracellular and extracellular events that, while fascinating, are outside the scope of the present review. Current evidence suggests that the mature collagen fibrils resulting from fibrillogenesis are highly elastic structures – meaning that they mechanically load and unload in a mostly reversible fashion. To be able to reversibly load and unload, without damage, is the defining functional requirement of these protein superstructures. Collagen cross linking is a central enabler (and potential disabler) of this function.

The good: enzyme mediated collagen cros-slinking

The mechanical competence of individual type-I collagen fibrils heavily depends on the enzyme lysyl oxidase, which regulates the robust formation of stable inter-molecular collagen crosslinks during maturation7. The absence of these head to tail chemical bonds drastically diminishes collagen fibril strength and whole tissue function8,9. Lysyl oxidase specifically acts on lysine or hydroxylysine in the telopeptide region of the collagen molecule, and results in a divalent, immature crosslink with an opposing amino-acid in the triple-helical region10. These immature crosslinks later spontaneously convert into more stable trivalent crosslinks that increase collagen interconnectivity, fibril stability and whole tendon mechanical integrity (for excellent reviews)7,11.

Simple biochemical correlations of native crosslink content with tendon mechanical properties are rather weak12–15, reflecting the likely confounding influence of other dominant structural or compositional factors16. The essential functional role of crosslinking in collagen fibril stability and whole tissue integrity, however, is clearly demonstrated in the severely compromised connective tissues of animals subjected to dietary inhibition of lysyl oxidase, which results in collagen fibrils and tendons with reduced strength8,9. The importance of crosslinks to fibril integrity has been indicated theoretically17 and demonstrated experimentally9,18 by balancing molecular slip and stretch under load.

The importance of crosslinking in preventing molecular slippage and resultant fibrillar damage can also be inferred from the decreased thermal stability of ten-dons that is known to take place after sub-maximal tissue overload19. Given that lysyl oxidase mediated crosslinks are so essential to the proper development of fibril structure and mechanical integrity, these are perhaps the best-characterized collagen crosslinkers.

The bad: advanced glycation endproduct crosslinking

While enzyme driven crosslinking plateaus at maturation, connective tissue stiffness has been shown to further increase with age and diabetes20–26. This tissue stiffening has been associated with non-enzymatic, oxidative reactions between glucose and collagen which lead to the formation of so-called advanced glycation end-products (AGEs)27,28. AGE accumulation is particularly high in long-lived proteins, such as collagen. Indeed, collagen half-life varies between tissues but remains generally large, from 1–2 years for bone collagen to about 10 years for type I in skin29. The low biological turnover of collagen makes it therefore susceptible to interaction with metabolites, primarily glucose. Aside from protein longevity, another factor that influences the formation of AGEs is the glucose level in the blood stream. Hyperglycemia related to diabetes is suspected to strongly predispose tissues of these patients to accumulation of AGEs30,31.

The glycation reaction initiates with the formation of a reversible Schiff base between a carbohydrate – typically glucose – and a protein amino group (e.g., a collagen lysine side-chain) (Fig. 1). The unstable Schiff base becomes a stable intermediate keto amine, often designated asa so-called Amadori product. Afterwards, a complex series of reactions (over the course of months or years) lead to various metabolic by-products of glycolysis including the products glyoxal, methyl glyoxal (MGO) and 3-deoxyglucosone, all of which can interact with extracellular proteins to form AGEs32. Some AGEs can bridge between the free amino groups of neigh boring proteins to form inter-molecular crosslinks, while others known as ‘adducts’ affect only a single protein33. Among the different AGEs, the most abundant in collagen tissues has been recently found to be glucosepane, a lysinearginine crosslink34,35.

Figure 1.
Figure 1.
(Left) Schematic of the sequence of metabolic chemical reactions behind AGE formation (e.g. pentosidine)72 and (Right) how such products may form adducts and/or crosslinks on collagen structures39.
So far, there is no direct experimental evidence linking AGEs with increases in collagen fibril stiffness, which in turn would cause increased stiffness at higher levels of tissue architecture. Although the mechanical effects of AGEs at the molecular and supramolecular levels are poorly understood, this link seems plausible and has been widely presumed to exist on the basis of the well documented correlation between AGE markers (pentosidine; auto-fluorescence) and increasing tissue stiffness36.

The ugly: functional consequences of AGEs in connective tissue

Despite the recognized importance of AGEs in the development of age – and diabetes – related conditions, there are still several important open questions regarding their role in the onset and progression of connective tissue disease. These can be broadly divided into two functional classes, biological and bio-mechanical.

The biological aspect relates primarily to collagen-protein and collagen-cell interactions. Here, the formation of AGEs (adducts or crosslinks) on specific amino acids involved in intermolecular recognition could lead to the dramatic modification of the interaction of collagen with other molecules such as proteoglycans (PGs), enzymes (e.g., collagenase) and cell integrins. AGEs modify the collagen surface and are known to affect cell-matrix interactions in a manner leading to inhibited wound repair and exacerbated inflammation37,38. A recent modeling study39 based on atomistic model of collagen40 has shown that collagen amino acids that are most likely prone to form glucosepane crosslinks (due to their position and configuration) are found close to collagenase and cell integrin binding sites, as well as near interaction domain for heparin and keratansulphate. These findings resonate with experimental investigations showing that collagen glycation induces a reduced affinity for heparin and keratansulphate proteoglycans (but not for dermatansulphate and decorin) as well as reduced endothelial cell migration41. Protein glycation ultimately stimulate cellular production of reactive oxygen species, and the activation of inflammatory signaling cascades via AGE signaling receptors (RAGEs)42.

On the other hand, nonenzymatic intermolecular crosslinking are believed to alter the biomechanics of collagenous tissue. Glucose reaction with the amino acid side-chains, and subsequent further reaction to form a crosslink with an adjacent collagen molecule, results in a modification of the physical properties of the collagen, but the detailed effects of AGEs on collagen mechanics at the different hierarchical scales are still poorly understood.

While these intermolecular crosslinks have been tied to higher failure loads, stiffness, and denaturation temperatures, they are also associated with increased mechanical fragility of the tissue. AGE crosslinks have also been implicated in reduced remodeling capacity, a concept that has been demonstrated in vitro as reduced sensitivity to collagenase.

How collagen crosslinks affect whole tendon function is complex, as indicated by an increased failure load of individual collagen fibers that paradoxically yields diminished tissue failure properties. The picture is further muddied by contradictory reports in the literature that have inconsistently correlated crosslink density to tissue stiffness13,44,47–52. In an attempt to eliminate potentially confounding effects of genotype, systemic alterations due to age or disease state, and lifestyle, some studies have investigated the effects of crosslinking by direct incubation of tendon with a range of sugars and/or aldehydes solutions, serving as valuable models for ageing and diabetes (Fig. 2).

These studies have generally well-mimicked the structural changes of collagen fibrils that have been found in vivo, but these studies clearly associate AGE crosslinks to tissue stiffening and brittleness.

Such changes are potentially critical, since altered extracellular matrix mechanics will subsequently affect the mechanical stimuli that drive resident cell behavior and regulate cellular repair of matrix damage. It is more than feasible that age-related mechanical changes in the collagen matrix could thus play a role in loss of tissue homeostasis and ability to cope with the micro-damage that accumulates in everyday life27,28.
Crosslinking by AGEs induces various physical changes in type-I collagen dominated tissues. In the left-most panels, it can be seen that incubation of rat tail tendon fascicles in high concentrations of metabolite methylglyoxal (MGO) clearly affects tissue …
Clinical experience suggests that aged and diabetic connective tissues appear stiffer to the touch than healthy tissues, although changes in stiffness cannot be explained by increased collagen content alone.

Aged and diabetic tissues are also accompanied by characteristic yellowing of the collagen matrix that accords with experimental evidence indicating age-related decreases in collagen solubility and heightened collagen resistance to protease breakdown. These phenomena have been causally linked to non-enzymatic glycation of proteins.