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How Dietary Sugars Damage Joints
High sugar intake is another way to create aging, stiffening joints.
To understand why, we have to imagine a freshly baked loaf of bread. On the outside is a golden brown, hardened crust. On the inside is the soft, moist, white, tasty delicacy that gives bread its appeal. The brown crust of baked bread is a well-known chemical reaction (called the Maillard reaction) where the sugars in the dough crosslink with the proteins in the bread to give that rigid and stiff quality we know as “crust.” Baking is what accelerates this process.
Now, think of your thanksgiving turkey. You stick it in the oven with white, pliable skin and it comes out of the oven with the brown, crispy skin we all love. It is the same chemistry—the Maillard reaction. Sugars in the turkey skin crosslink with proteins in the skin, causing the brown delight we must have for the turkey to be just right.
This familiar food chemistry is not confined to our favorite staples. It happens in our bodies, especially in our joints. Sugars in the blood crosslink with proteins in the cartilage of our joints (and other proteins throughout the body) to form rigid and sometimes brittle structures. The process is called glycation. The stiffened proteins are called advanced glycation endproducts (or the appropriately named A.G.E.)
Just as the skin of a turkey becomes brown from basting in the oven, our human interiors also “brown” from years of “cooking” at our natural body temperature. Just as the turkey’s skin becomes more rigid and stiff, so too do our own tissues become rigid and stiff. The greater the intake of dietary sugars, the more chance there is for sugars to interact with joint proteins in damaging ways. The longer this process is left unchecked, the less mobility we have with age. It is fundamental chemistry. It is well understood. And it is a constant threat to healthy joints.
This may be one of the most extraordinary discoveries yet, as we try to understand the process of how our joint cartilage ages.
While there is a great deal of research on this subject, we can use just one to illustrate the effect of sugars on arthritis. One of the most studied of the sugar-damaged molecules is called pentosidine. Doctors recently studied pentosidine levels in the blood and in the joint fluid of 38 people with osteoarthritis, and they compared them with levels in people without arthritis. Those with x-ray evidence osteoarthritis were found to have much higher levels of pentosidine in their blood and in their joint fluid.
Pentosidine levels in the blood of people with and without arthritis (nmol/l)
- Osteoarthritis: 132.1
- People without Osteoarthritis: 97.7
[Senolt, L, Braun, M, Olejarova, M. Increased pentosidine, an advanced glycation end product, in serum and synovial fluid from patients with knee osteoarthritis and its relation with cartilage oligomeric matrix protein. Ann Rheum Dis. 2005; 64(6): 886–890.]
In a very important study, doctors looked at several different sugar-damaged molecules and examined how these molecules were related to aging and cartilage stiffness. They found that glycation damaged proteins (aka sugar-damaged proteins) accumulated with age and that important structural amino acids in cartilage decreased with age, suggesting that they were being damaged by sugar-protein interactions. Using imaging methods, they also found that these sugar-damaged proteins were shown to be “browned,” much like the browning of the bread and turkey described above.
Histochem Cell Biol. 2002 Jun;117(6):541-6. Epub 2002 May 22.
Immunohistochemical demonstration of -(carboxymethyl)lysine protein adducts in normal and osteoarthritic cartilage.
Institute of Anatomy, Technical University Dresden, Medical Faculty Carl Gustav Carus, Fiedlerstrasse 42, Germany. Wolfgang.Schwab@mailbox.tu-dresden.de
N(epsilon)-(carboxymethyl)lysine (CML) is an advanced glycation end product formed by non-enzymatic glycation and oxidation of proteins. The distribution pattern of CML-modified proteins in normal and osteoarthritic (OA) cartilage was investigated using specific antibodies. In healthy articular cartilage, immunoreactivity for CML was preferably found in the extracellular matrix (ECM) of the superficial layer. In OA samples, CML immunoreactivity was not restricted to the ECM of the superficial layer. Interestingly, OA chondrocytes showed a remarkable cytoplasmic immunoreactivity for CML. With the help of a western blot analysis CML-modified proteins between 68 and 39 kDa could be demonstrated in OA cartilage samples. These results suggest that the accumulation of CML adducts contributes to the matrix damage in osteoarthritis. Therefore, the inhibition of CML accumulation may represent an effective therapeutic strategy to prevent severe OA cartilage injury.
These and many studies like them suggest the following:
- Sugar damages cartilage in our joints
- Sugars make the cartilage more stiff and brittle
- Sugars cause browning of cartilage tissue (just like browning of a turkey)
- The longer we are exposed to these sugars, the more damaging the effects
With specific reference to osteoarthritis, we must do the following:
- We must reduce our intake of all dietary sugars
- We must control our blood sugar by ensuring that we do not develop metabolic syndrome, diabetes, or conditions related to insulin resistance
Remember
Sugars + Cartilage ---> Browning & Stiffening ---> Osteoarthritis
[Verzijl, N, DeGroot, J, Oldehinkel, E, et al. Age-related accumulation of Maillard reaction products in human articular cartilage collagen. Biochem J 2000;350:381-7.]
Sugar Damage to Immune Proteins
Horm Metab Res. 2002 May;34(5):260-4.
Non-enzymatic glycation of IgG: an in vivo study.
Dipartimento Scienze Mediche e Chirurgiche, Università di Padova, Via Giustiniani 2, 35100 Padua, Italy. annunziata.lapollo-@unipd.it
The IgG glycation level of 30 healthy subjects and 60 type 2 diabetic patients with different degrees of metabolic control was evaluated by matrix-assisted laser desorption ionization mass spectrometry, a technique allowing the determination of mass increase of the IgG molecule. When applied to the digested mixture obtained by the action of papain on the plasma protein fraction, the same method established the mass increase of Fab and Fc fragments of IgG; for the former, a higher mass increase was found, possibly explained by its high reactivity to glucose. Experimental results were confirmed by molecular modeling calculations. Results suggest that the immunodeficiency observed in diabetic patients may be due to the inhibition of molecular recognition between antibody and antigen as a result of a change in functionality of the modified Fab fragment of IgG.
Another study looked at sugar-damaged proteins and fibromyalgia, a painful condition of the musculoskeletal system.
Rheumatology (Oxford). 2002 Oct;41(10):1163-7.
Are advanced glycation end-product-modified proteins of pathogenetic importance in fibromyalgia?
Department of Internal Medicine IV, Rheumatology and Osteology, Friedrich-Schiller-University of Jena, 07740 Jena, Germany.
OBJECTIVE: To quantify the serum levels of the advanced glycation end-product (AGE) pentosidine in 41 patients with fibromyalgia (FM) and 46 healthy controls. The formation of pentosidine is closely related to oxidative stress. METHODS: Pentosidine was measured by reverse-phased high-performance liquid chromatography with gradient separation on a RP-18 column. RESULTS: Patients with FM have significantly higher pentosidine serum levels than healthy subjects. CONCLUSION: AGE modification of proteins leads to reduced solubility and high resistance to proteolytic digestion of such altered proteins (e.g. AGE-modified collagens). AGEs are also able to stimulate different kinds of cells via activation of the NFkappaB, mediated by specific receptors of AGEs (e.g. RAGE) on the cell surface. Both mechanisms may contribute to the development, perpetuation and spreading of pain phenomena in FM patients.
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