Cytokines, Inflammation and Pain

Darned microbial litterbugs…8)

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ABSTRACT

Cytokines are small secreted proteins released by cells have a specific effect on the interactions and communications between cells. Cytokine is a general name; other names include lymphokine (cytokines made by lymphocytes), monokine (cytokines made by monocytes), chemokine (cytokines with chemotactic activities), and interleukin (cytokines made by one leukocyte and acting on other leukocytes). Cytokines may act on the cells that secrete them (autocrine action), on nearby cells (paracrine action), or in some instances on distant cells (endocrine action). There are both pro-inflammatory cytokines and anti-inflammatory cytokines. There is significant evidence showing that certain cytokines/chemokines are involved in not only the initiation but also the persistence of pathologic pain by directly activating nociceptive sensory neurons. Certain inflammatory cytokines are also involved in nerve-injury/inflammation-induced central sensitization, and are related to the development of contralateral hyperalgesia/allodynia. The discussion presented in this chapter describes several key pro-inflammatory cytokines/chemokines and anti-inflammatory cytokines, their relation with pathological pain in animals and human patients, and possible underlying mechanisms.

Keywords: cytokine, inflammation, pain, hyperalgesia

  1. INTRODUCTION

Inflammatory responses in the peripheral and central nervous systems play key roles in the development and persistence of many pathological pain states []. Certain inflammatory cytokines in spinal cord, dorsal root ganglion (DRG), injured nerve or skin are known to be associated with pain behaviors and with the generation of abnormal spontaneous activity from injured nerve fibers or compressed/inflamed DRG neurons.

Cytokines are small secreted proteins released by cells have a specific effect on the interactions and communications between cells. Cytokine is a general name; other names include lymphokine (cytokines made by lymphocytes), monokine (cytokines made by monocytes), chemokine (cytokines with chemotactic activities), and interleukin (cytokines made by one leukocyte and acting on other leukocytes). Cytokines may act on the cells that secrete them (autocrine action), on nearby cells (paracrine action), or in some instances on distant cells (endocrine action).

It is common for different cell types to secrete the same cytokine or for a single cytokine to act on several different cell types (pleiotropy). Cytokines are redundant in their activity, meaning similar functions can be stimulated by different cytokines. They are often produced in a cascade, as one cytokine stimulates its target cells to make additional cytokines. Cytokines can also act synergistically or antagonistically.

Cytokines are made by many cell populations, but the predominant producers are helper T cells (Th) and macrophages. Cytokines may be produced in and by peripheral nerve tissue during physiological and pathological processes by resident and recruited macrophages, mast cells, endothelial cells, and Schwann cells. Following a peripheral nerve injury, macrophages and Schwann cells that gather around the injured site of the nerve secrete cytokines and specific growth factors required for nerve regeneration. Localized inflammatory irritation of the dorsal root ganglion (DRG) not only increases pro-inflammatory cytokines but also decreases anti-inflammatory cytokines []. Cytokines can also be synthesized and released from the herniated nucleus pulposus, synthesized inside the spinal cord [], the DRG soma [], or the inflamed skin []. Furthermore, cytokines may be transported in a retrograde fashion from the periphery, via axonal or non-axonal mechanisms, to the DRG and dorsal horn, where they can have profound effects on neuronal activity [] and therefore contribute to the etiology of various pathological pain states.


2. Cytokines and Pain

PRO-INFLAMMITORY CYTOKINES

Proinflammatory cytokines are produced predominantly by activated macrophages and are involved in the up-regulation of inflammatory reactions. There is abundant evidence that certain pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α are involved in the process of pathological pain.

IL-1β is released primarily by monocytes and macrophages as well as by nonimmune cells, such as fibroblasts and endothelial cells, during cell injury, infection, invasion, and inflammation. Very recently, it was found that IL-1β is expressed in nociceptive DRG neurons []. IL-1β expression is enhanced following crush injury to peripheral nerve and after trauma in microglia and astrocytes in the central nervous system (CNS) []. IL-1β can produce hyperalgesia following either intraperitoneal, intracerebroventricular or intraplantar injection []. Moreover, IL-1β was found to increase the production of substance P and prostaglandin E2 (PGE2) in a number of neuronal and glial cells []. IL-1ra, a specific IL-1 receptor antagonist, competitively binds to the same receptor as IL-1β but does not transduce a cellular signal, thereby blocking IL-1β-mediated cellular changes. Administrations of IL-1ra and other anti-inflammatory cytokines have been demonstrated to prevent or attenuate cytokine-mediated inflammatory hyperalgesia [] and nerve-injury induced mechanical allodynia [].

IL-6 has been shown to play a central role in the neuronal reaction to nerve injury. Suppression of IL-6R by in vivo application of anti-IL-6R antibodies led to reduced regenerative effects []. IL-6 is also involved in microglial and astrocytic activation as well as in regulation of neuronal neuropeptides expression []. There is evidence that IL-6 contributes to the development of neuropathic pain behavior following a peripheral nerve injury []. For example, sciatic cryoneurolysis, a sympathetically-independent model of neuropathic pain involving repeatedly freezing and thawing a section of the sciatic nerve, results in increased IL-6 immunoreactivity in the spinal cord []. In addition, intrathecal infusion of IL-6 induces tactile allodynia and thermal hyperalgesia in intact and nerve-injured rats, respectively.

TNF-α, also known as cachectin, is another inflammatory cytokine that plays a well-established, key role in some pain models. TNF acts on several different signaling pathways through two cell surface receptors, TNFR1 and TNFR2 to regulate apoptotic pathways, NF-kB activation of inflammation, and activate stress-activated protein kinases (SAPKs). TNF-α receptors are present in both neurons and glia []. TNF-α has been shown to play important roles in both inflammatory and neuropathic hyperalgesia. Intraplantar injection of complete Freund’s adjuvant in adult rats resulted in significant elevation in the levels of TNF-α, IL-1β, and nerve growth factor (NGF) in the inflamed paw. A single injection of anti-TNF-α antiserum before the CFA significantly delayed the onset of the resultant inflammatory hyperalgesia and reduced IL-1β but not NGF levels []. Intraplantar injection of TNF-α also produces mechanical [] and thermal hyperalgesia []. It has been found that TNF-α injected into nerves induces Wallerian degeneration [] and generates the transient display of behaviors and endoneurial pathologies found in experimentally painful nerve injury []. TNF binding protein (TNF-BP), an inhibitor of TNF, is a soluble form of a transmembrane TNF-receptor. When TNF-BP is administered systemically, the hyperalgesia normally observed after lipopolysaccharide (LPS) administration is completely eliminated []. Intrathecal administration of a combination of TNF-BP and IL-1 antagonist attenuated mechanical allodynia in rats with L5 spinal nerve transection [].

CHEMOKINES

A variety of cytokines are known to induce chemotaxis. One particular subgroup of structurally related cytokines is known as chemokines. The term chemotactic cytokines (CHEMOtactic CytoKINES) usually refers to this. These factors represent a family of low molecular weight secreted proteins that primarily function in the activation and migration of leukocytes although some of them also possess a variety of other functions. Chemokines have conserved cysteine residues that allow them to be assigned to four groups: C-C chemokines (RANTES, monocyte chemoattractant protein or MCP-1, monocyte inflammatory protein or MIP-1α, and MIP-1β), C-X-C chemokines (IL-8 also called growth related oncogene or GRO/KC), C chemokines (lymphotactin), and CXXXC chemokines (fractalkine).

Various chemokines including MIP-1α, MCP-1 and GRO/KC are up-regulated not only in models of neuroinflammatory [] and demylinating diseases, but also in various forms of CNS trauma [] and in injured peripheral nerve []. Receptors for MCP-1, MIP-1α and GRO/KC are expressed on DRG neurons []. Interestingly, mice lacking the CCR2 receptor completely fail to develop mechanical allodynia in the partial sciatic injury model although pain sensitivity in uninjured animals is normal. In the same study, normal mice showed a sustained upregulation of the receptors in both DRG and peripheral nerve after the injury []. This suggests that the chemokines, including MCP-1 in particular, play very key roles in neuropathic pain as well as in neuroinflammatory conditions.

ANTI-INFLAMMATORY CYTOKINES

The anti-inflammatory cytokines are a series of immunoregulatory molecules that control the pro-inflammatory cytokine response. Cytokines act in concert with specific cytokine inhibitors and soluble cytokine receptors to regulate the human immune response. Their physiologic role in inflammation and pathologic role in systemic inflammatory states are increasingly recognized. Major anti-inflammatory cytokines include interleukin (IL)-1 receptor antagonist, IL-4, IL-10, IL-11, and IL-13. Leukemia inhibitory factor, interferon-alpha, IL-6, and transforming growth factor (TGF)-β are categorized as either anti-inflammatory or pro-inflammatory cytokines, under various circumstances. Specific cytokine receptors for IL-1, TNF-α, and IL-18 also function as inhibitors for pro-inflammatory cytokines.

Among all the anti-inflammatory cytokines, IL-10 is a cytokine with potent anti-inflammatory properties, repressing the expression of inflammatory cytokines such as TNF-α, IL-6 and IL-1 by activated macrophages. In addition, IL-10 can up-regulate endogenous anti-cytokines and down-regulate pro-inflammatory cytokine receptors. Thus, it can counter-regulate production and function of pro-inflammatory cytokines at multiple levels. Acute administration of IL-10 protein has been well-documented to suppress the development of spinally-mediated pain facilitation in diverse animal models such as peripheral neuritis, spinal cord excitotoxic injury, and peripheral nerve injury []. Blocking spinal IL-10, on the other hand, has been found to prevent and even reverse established neuropathic pain behaviors []. Recent clinical studies also indicate that low blood levels of IL-10 and another anti-inflammatory cytokine, IL-4, could be key to chronic pain since low concentrations of these two cytokines were found in patients with chronic widespread pain [].

The family of TGF-β comprises 5 different isoforms (TGF-β1 to -β5). TGF-β1 is found in meninges, choroid plexus, and peripheral ganglia and nerves []. It is known that TGF-β suppresses cytokine production by inhibiting macrophage and Th1 cell activity; counteracts IL-1, IL-2, IL-6, and TNF; and induces IL-1ra 6 []. Its mRNA is induced following axotomy and may be involved in a negative-feedback loop to limit the extent of glial activation []. TGF-β1 also antagonizes nitric oxide production in macrophages []. Nitric oxide has been strongly implicated in the final common pathway of neuropathic pain []. It is expected that by its anti-cytokine action, TGF-β1 or agents that induce its activity may be effective therapy for neuropathic pain.

GLIAL ACTIVATION IN CNS AND PNS


In the CNS, there are two types of glial cells, microglia and astrocytes, which can be activated by excitatory neurotransmitters released from nearby neurons. These neurotransmitters include EAA, SP, PGEs, adenosine triphosphate (ATP), and nitric oxide. A novel neuron to glia signal is fractalkine, a protein expressed on the extracellular surface of neurons []. Fractalkine is tethered to the neuronal membrane by a mucin stalk. When the neuron is sufficiently activated, the stalk breaks, releasing fractalkine into the extracellular fluid. As immunocompetent cells, activated glia release several key pro-inflammatory cytokines, including TNF-α, IL-1β, and IL-6 [].

It has been well demonstrated that spinal glial activation is necessary for induction of the neuropathic pain state []. Spinal administration of glial activator, fractalkine, induces cutaneous hyperalgesia, whereas spinal administration of a fractalkine receptor antagonist blocks neuropathic pain []. Furthermore, blocking the activation of spinal cord glia with the inhibitor fluorocitrate blocks the pathological pain state in rats with peripheral sciatic nerve neuritis []. Recently, it was found that administration of a new glia-specific inhibitor, minocycline, blocked the development of neuropathic pain. Minocycline, a lipid-soluble tetracycline derivative with anti-inflammatory effects, inhibits an IL-1β-converting enzyme and inducible nitric oxide synthesis up-regulation. Minocycline also prevents glial cell proliferation and inhibits the activation of p38 MAPK [].

Non-neuronal cells in the peripheral nervous system also react to nerve injury. In addition to hematogenous macrophage infiltration, the satellite glia that surround the somata of sensory neurons proliferate [], elaborate processes [], and become immunoreactive for glial fibrillary acidic protein (GFAP) [].


4. MECHANISMS UNDERLYING CYTOKINES- MEDIATED PATHALOGICAL PAIN

There is evidence that pro-inflammatory cytokines (e.g., IL-1β, TNF-α) [] and chemokines (e.g., MCP-1) [] may directly modulate neuronal activity in various classes of neurons in the peripheral and central nervous system. In the peripheral nervous system, abnormal spontaneous activity can be evoked from nociceptive neurons by topical application of TNF-α to the peripheral axons in vivo [], or to the somata of the DRG neurons in vitro []. Large, myelinated fast conducting Aβ neurons can also be excited by topical application of TNF-α to the DRG [] or by an autologous HNP extract []. TNF-α can enhance the sensitivity of sensory neurons to the excitation produced by capsaicin and this enhancement likely is mediated by the neuronal production of prostaglandins []. It was found that TNF-α-induced neuronal excitation is mediated by cAMP-dependent protein kinase (PKA) pathway []. The p38 mitogen-activated protein kinase (MAPK) is also involved in TNF-α-induced cutaneous hypersensitivity to mechanical or thermal stimulation []. Results obtained from IL-6 knockout mice indicates that IL-6 plays a facilitating role in sympathetic sprouting induced by nerve injury and that its effect on pain behavior is indirectly mediated through sympathetic sprouting in the DRG []. Most recently, it is reported that localized inflammation of the DRG up-regulates a number of pro-inflammatory cytokines including IL-6 and induces abnormal sympathetic sprouting in the absence of peripheral nerve injury []. It suggests a possible correlation between inflammatory responses and sympathetic sprouting, which are two well-known mechanisms implicated in various chronic pain states.

In summary, proinflammatory cytokines are involved in the development of inflammatory and neuropathic pain. Just as specific cytokines and their neutralizing antibodies have been introduced into clinical trials for the treatment of stroke, Alzheimer’s disease, autoimmune diseases, wound healing, and amyotrophic lateral sclerosis, one could utilize local or systemic delivery of anti-inflammatory cytokines or inflammatory cytokine antagonists for the treatment of chronic pain. These specific cytokines or antagonists would act to disrupt the hyperexcitability cycle taking place in the sensory neurons, providing a new, non-opioid therapeutic approach for the treatment of pathological pain due to inflammation or peripheral nerve injury.


 

A Case of Pellagra Associated with Long Term Alcoholism

Content Source: The Journal of Psychiatry and Neurological Sciences

To the Editor,

Pellagra is a systemic, nutritional disease associated with deficiency of vitamin B3 (niacin) and/or tryptophan and often other B vitamins (1). Pellagra is mostly seen in chronic alcoholics as a result of nutritionally poor diet and malabsorption (2). We present a pellagra case with long history of alcohol use, admitted with psychiatric complaints to our clinic.

Mr. A. was a 44 year old, married, primary school graduate male, who was running a coffeehouse. His socioeconomic status was low. His complaints were irritability, nausea, vomiting and loss of appetite. He had been drinking alcohol every day, for 33 years; its amount had increased to about 100cl for the last 15 years. The longest duration of remission was 3 months, when he was 13 years old. He was experiencing sweating, tremor of hands, insomnia, and irritability as withdrawal symptoms. In the last 2 years, periodically, he had problems in focusing and maintaining attention, delay in reaction time in answering any questions. He had depressive symptoms for 1 year and he had attempted suicide. In the last 2 months, he had diarrhea, vomiting, loss of appetite and erythema, followed by dark discoloration on the dorsal surfaces of his hands. On physical examination, hyper-keratotic plaques with well-defined borders on the dorsal surfaces of both hands, squamous lesions between fingers of both feet, loss of villi and hyperemia on the tongue was detected. He had tremor of both hands and wide-based gait. On psychiatric examination, he was confused, his time orientation was disturbed, self care was poor. Affect was restricted; associations and psychomotor activity were slow. The possibility of pellagra was considered as dermatitis, diarrhea and distortion of cognitive functions were observed. Electrocardiography (ECG), complete blood count, routine blood biochemical tests, routine urine tests, thyroid function tests, VDRL, microscopic stool examination, electroencephalography (EEG), vitamin B12 and folate measurements, cranial MRI, echocardiography, esophago-gastro-duodenoscopy were performed and no significant pathology was detected. As the patient’s symptoms did not respond to oral niacin treatment, niacin malabsorption was considered and a mixture of vitamin B1, B2, B6, B12, nicotinamide and dexpanthenol was given by intramuscular injection and a dramatical recovery was observed.

Pellagra is characterized by photosensitive symmetrical skin lesions, gastrointestinal disturbances, neurologic and psychiatric manifestations. The syndrome is known as “4 D’s”: dermatitis, diarrhea, dementia and death (1). Skin lesions seen in pellagra are photosensitive rash, primarily on the dorsal surfaces of the hands, arms, face and feet. In acute phase, skin lesions are erythema and bullae which resemble sunburn (wet pellagra), but after exposure to sun light, progress to chronic, symmetrical, scaled lesions occurs. Typically they are located on the neck (Casal necklace), hands and forearms (pellagra gauntlet) (3). Irritability, concentration problems, anxiety, fatigue, restlessness, apathy and depression are common psychiatric and neurological manifestations. Even uncommon, psychosis can be seen in pellagra, especially in pellagroid encephalopathy mostly encountered in chronic alcoholics. Confusion and eventually death occurs as the disease progresses (4). Gastrointestinal manifestations are fissures on the tongue and mouth, sourness, loss of appetite, dyspepsia and abdominal pain. Enteritis, which can be severe with nausea, vomitting and diarrhea can also be seen (5). Diagnosis is based on patient’s history and physical examination. There are no chemical tests to definitely diagnose pellagra (6).

In conclusion, low socioeconomic status, long duration of alcohol use, poor diet and characteristic findings should suggest pellagra, although it is a rare disease nowadays. It shouldn’t be considered as a disease that is seen only in undeveloped countries and considering pellagra in the differential diagnosis in chronic alcoholics with psychiatric, dermatologic and gastrointestinal symptoms has vital importance.

REFERENCES

1. World Health Organization. Pellagra and its prevention and control in major emergencies. Geneva, World Health Organization, 2000 (document WHO/NHD/00.10).

2. Stratigos JD, Katsambas A. Pellagra: a still existing disease. Br J Dermatol 1977; 96:99-106.

3. Pipili C, Cholongitas E, Ioannidou D. The diagnostic importance of photosensivity dermatoses in chronic alcoholism: Report of two cases. Dermatol Online J 2008; 14:15.

4. Cook CC, Hallwood PM, Thomson AD. B Vitamin deficiency and neuropsychiatric syndromes in alcohol misuse. Alcohol Alcohol 1998; 33:317-336.

5. Karthikeyan K, Thappa DM. Pellagra and skin. Int J Dermatol 2002; 41:476-481.

6. Hegyi J, Schwartz RA, Hegyi V. Pellagra: Dermatitis, dementia, and diarrhea. Int J Dermatol 2004; 43:1-5.

Nutrient Deficiency Diseases

~Content Source


Deficiency diseases – Scurvy, beriberi, pellagra, rickets, goiter, protein (amino acid) deficiencies, marasmus and kwashiorkor.


Nutrient deficiency diseases occur when there is an absence of nutrients which are essential for growth and health. Lack of food leading to either malnutrition or starvation gives rise to these diseases. Another cause for a deficiency disease may be due to a structural or biological imbalance in the individual’s metabolic system.

There are more than 50 known nutrients in food. Nutrients enable body tissues to grow and maintain themselves. They contribute to the energy requirements of the individual organism and they regulate the processes of the body. Carbohydrates, fats, and proteins provide the body with energy. The energy producing component of food is measured in calories. Aside from the water and fiber content of food, which are also important for their role in nutrition, the nutrients that serve functions other than energy production can be classified into four different groups: vitamins, fats, proteins, and minerals. All are necessary for proper body function and survival.

Early vitamin deficiency diseases

Polish-born Casimir Funk (1884-1967) originated the word vitamin in 1912, spelling it as vitamine, because he thought they were part of a group of organic compounds containing nitrogen, called amines. The final –e was later dropped in 1920 at the suggestion of the English nutritionist Jack Cecil Drummond who pointed out that these trace-like substances found only in food and essential for good health were not always amines. By 1914 Funk theorized that beriberi, scurvy, and pellagra were caused by a vitamin deficiency.

Scurvy

Scurvy is one of the oldest vitamin deficiency diseases recorded and the first one to be cured by adding a vitamin to the diet. Scurvy was a common malady of sailors of the age of exploration of the New World. It has been recorded that Vasco da Gama was supposed to have lost half of his crew to scurvy in his journey around the Cape of Good Hope at the end of the fifteenth century and Richard Hawkins reported that he lost 10,000 sailors from the disease a century later.

The main symptom of scurvy is hemorrhaging. Hemorrhage marks appear as spots under the skin or bruises, given the medical terms of petechiae and ecchymoses. The gums are swollen and usually become infected (gingivitis). Bleeding can take place in the membranes covering the large bones as well as in the membranes of the heart and brain. Wounds heal slowly and the bleeding in or around vital organs can be fatal. The disease is slow to develop and is manifested early by fatigue, irritability, and depression.

In 1747 a British naval physician, James Lind, in a response to a an outbreak of scurvy conducted a controlled experiment. He took 12 of the sailors who had developed scurvy and divided them up into six groups and gave each pair different medicines such as nutmeg, cider, seawater, and vinegar, while others were given lemons or oranges. The two men given the oranges and lemons both completely recovered in about a week after the experiment.

His Treatise of the Scurvy published in 1753 is the first example of a controlled clinical trial experiment. In his treatise, Lind gave a thorough review of other authors who had written on scurvy along with a careful clinical description of the condition. It was not until the end of the eighteenth century that the British navy finally had its sailors drink a daily portion of lime or lemon juice to prevent scurvy.

Vitamin C (ascorbic acid) is necessary for collagen formation, which is the protein component of connective tissue, strong blood vessels, healthy skin and gums, formation of red blood cells, wound healing, and the absorption of iron. In addition to scurvy, other scurvy-like conditions can develop from a deficiency of vitamin C, such as adult acne, easy bruising, sore gums, and hemorrhages around bones. Good sources for vitamin C are citrus fruit, broccoli, strawberries, cantaloupe, and other fruits and vegetables.

Beriberi

Discovering the causes for beriberi became part of the history of discovering vitamins. Christian Eijkman (1858-1930) was a Dutch physician who was a member of a government commission sent to the East Indies in the 1880s to study the disease beriberi, which was prevalent in southeast Asia, where the main diet is comprised of unenriched rice and wheat.

There are three forms of this disease: infantile beriberi, wet beriberi, and dry beriberi. Infantile beriberi occurs when a mother who breast feeds her child is lacking vitamin B1 thiamine. The mother who nurses the child may not manifest the disease, but the deficiency occurs through the breast feeding and the child usually dies after the fifth month. In the childhood and adult versions of the disease there is a preliminary condition of fatigue, loss of appetite, and a numb tingling feeling in the legs. This condition can then lead to either wet or dry beriberi.

In wet beriberi there is an accumulation of fluid throughout the body and a rapid heart rate that can lead to sudden death. In dry beriberi there is no fluid swelling, but there is a loss of sensation and a weakness in the legs. The patient first needs to walk with the aid of a stick and then becomes bedridden and easy prey to an infectious disease.

In Eijkman’s laboratory he noticed that some of the fowl he was experimenting with developed paralysis and polyneuritis, as in the dry form of beriberi. The director of the hospital forbade Eijkman from feeding these birds with table scraps which consisted mainly of polished rice. He therefore began to feed them with whole rice, after which he noticed that they regained their movement and there was no recurrence of paralysis.

The idea that the birds had some form of beriberi was rejected by Eijkman’s colleagues. His explanation for the cure was that the polished rice had some toxin in it which the unpolished rice did not have. This explanation was rejected by a fellow researcher, Gerrit Grijns (1865-1944), who also stayed on to study the disease after the commission had already left. He found that when the chickens were taken off the rice diet completely and feed with meat instead, they did not develop the characteristic paralysis, but if the meat were overcooked, then the condition would reappear. In 1901 Grijns showed that beriberi could be cured by putting the rice polishings back into the rice.

Vitamin B1 (thiamine) prevents the disease or symptoms of beriberi. Food sources for this vitamin are meats, wheat germ, whole grain and enriched bread, legumes, peanuts, peanut butter, and nuts.

Pellagra

Pellagra is a vitamin deficiency disease associated with poverty. The symptoms of pellagra are referred to as the “three D’s”: diarrhea, dermatitis, and dementia. If disease is not treated it may lead to death. Gaspar Casal (c. 1691-1759) was the first to publish a thorough explanation of pellagra in 1762 after his death. He studied and wrote about the disease which he observed in a region of Spain where it was called “mal de la rosa,” because of the reddened dermatitis which appeared around the back of the neck. Even though the belief of his time was the disease was caused by an infection, Casal believed origins were from inadequate nutrition.

The popular belief that pellagra was caused by infection lasted from the sixteenth century to the early twentieth century until Joseph Goldberger (1881-1929) a member of the United States Public Health Service studied the high numbers of cases in the southern United States. Goldberger established that pellagra was caused by an insufficient amount of niacin (vitamin B3) also known as nicotinic acid and the active form of niacin that the body uses called niacinamide.

Rickets

Rickets is a bone disease deficiency caused by a lack of vitamin D, called the “sunshine” vitamin because it is the only vitamin that can be produced by the effects of sunlight on the skin. It was a common disease of infants and children, but since all milk and infant formulas have vitamin D added to them, it is rarely seen today. In rickets, legs will become bowed by the weight of the body and the wrists and ankles are thickened. The teeth are badly affected and take a longer time to come in. All the bones are affected by not having sufficient calcium and phosphorous for their growth and development. Lack of exposure to sunlight, which helps to produce vitamin D, is a major cause for childhood rickets. Crowded slum conditions in areas where there was little or no sunlight were responsible for its appearance in the earlier stages of the industrial revolution.

An adult version of rickets caused by a deficiency of vitamin D, calcium, and phosphorous is called osteomalacia. The bones become soft and deformed and there is rheumatic pain. The disease is observed in the Middle East and Asia more so than in western countries. The way to prevent rickets and other bone diseases such as osteoporosis is a combination of calcium, phosphorous, and vitamin D.

Other vitamin deficiency diseases

Night blindness or the difficulty of seeing in dim light is caused by a deficiency in vitamin A which helps in the formation of visual purple needed by the eyes for night vision. The deficiency can also cause glare blindness when the eye is either exposed to too much light or a sudden change in the amount of light when entering a darkened room. Another eye disease caused by vitamin A deficiency is xerophthalmia which can lead to blindness. This condition affects the cells of the cornea, other eye tissues, and the tear ducts, which stop secreting.

Vitamin A deficiency can create a number of adverse skin conditions, problems with tasting and smelling, and it may also cause difficulties with the reproductive system.

Vitamin E and K deficiencies are rare. Vitamin E protects against substances that oxidize quickly and vitamin K promotes normal blood clotting. Vitamin B12 (cobalamin) provides protection against pernicious anemia and mental disturbances. Vitamin B 6can also protect against anemia as well as dermatitis, irritability, and convulsions.

Mineral deficiency diseases

There are about 25 mineral elements in the body usually appearing in the form of simple salts. Those which appear in large amounts are called macro minerals while those that are in small or trace amounts are micro minerals. Some that are essential are calcium, phosphorous, cobalt, copper, fluorine, iodine, iron, sodium, chromium, and tin. Aluminum, lead, and mercury are not as essential.

Goiter

Iodine is necessary for the proper functioning of the thyroid gland which controls the body’s basal metabolism rate through its production of two hormones, thyroxine, and triiodinethyronine. Without a sufficient amount of iodine in the diet the gland begins to enlarge its cells in its efforts to produce the hormone, thus producing a goiter, which is a swelling around the neck. Certain regions lack iodine in the soil which leads to cretinism, the physical and mental development of an infant passed on from the lack of iodine in the mother’s diet.

Protein (amino acid) deficiencies

Proteins are needed in the body for amino acids. Proteins are broken down in the digestive system to form amino acids which are then absorbed by the rest of the body to form new proteins in the form of vital body tissues such as muscle, connective tissue, and skin. There are two types of protein, fibrous and globular proteins. Fibrous protein is insoluble and goes into making the structural tissues of the body. Globular protein forms amino acids that become enzymes and hormones and other vital parts of cellular functioning within the body.

Adults rarely suffer from protein deficiency diseases unless there is an impairment in the intestinal tract, but in countries plagued by insufficient food children will develop protein deficiency diseases that lead to very high mortality rates.

Marasmus and kwashiorkor

A specific wasting away disease caused by protein deficiency in third world countries that lack adequate food supplies is called kwashiorkor. It is a word which describes the condition of an infant who has to be weaned away after a year to make room for the next baby. The weaning food, which is mainly sugar and water or a starchy gruel lacks protein or has a poor quality of protein. The weaning diet for these young children leads to other nutrient deficiency diseases as well.

Symptoms of kwashiorkor are apathy, muscular wasting, and edema. Both the hair and the skin lose their pigmentation. The skin becomes scaly and there is diarrhea and anemia, and permanent blindness can result from this condition. Marasmus is another condition of a wasting away of the body tissues from the lack of calories as well as protein in the diet. In marasmus the child is fretful rather than apathetic and is skinny rather than swollen with edema. Aside from contrasting symptoms between the two diseases, there may be converging symptoms which would be described as marasmic kwashiorkor.

There is a wide variation of deficiencies between energy and protein deficient diseases as in the cases described by marasmus and kwashiorkor. The term protein-energy malnutrition (PEM) is used to describe those differences. PEM is the result of poverty as well inadequate information on diet. In some countries there is the mistaken belief that the child should not be given high protein food, which is served to the father, while the child drinks the fluid the meat was cooked in.

In cases of severe PEM it is necessary to hospitalize the child and to administer antibiotics to prevent infections which accompany the condition. Diets rich in protein should be continued after hospitalization, using skimmed milk powder for an energy basis. Legumes (beans) and fish meal are also good sources for protein. Social and political problems have to be managed to allow relief workers to help and to provide an ongoing source of food preparations that can be consumed for adequate nourishment by those in need.

Treatment and prevention

The amounts of most nutrients, especially vitamins, needed to both prevent and treat deficiency diseases are small. The average intake of 1mg of vitamin B1 is sufficient to prevent a deficiency disease of that vitamin, while 10mg of B1 could cure an advanced case of someone about to die of beriberi. Although small doses of vitamins cure deficiencies, large doses of some vitamins such as A and D can be harmful since these two vitamins are already stored by the liver. Vitamins A and D are fat soluble vitamins and can accumulate to the point of becoming toxic. Most other vitamins are water soluble and are excreted in the urine throughout the day.

Diet and supplements

Most nutritionists insist on a well-balanced diet consisting of the major food substances as an effective and economical way of obtaining nutrients for health. On the other hand, advocates of health food stores maintain that the FDA’s required daily allowances (RDAs) for nutrients are much too low and that cultivation of much of our food supply and its preparation robs our diet of much of its nutrient value.

The American Dietetic Association (ADA) recommends that nutrient needs should come from a variety of foods taken from different dietary sources rather than self-prescribed vitamin supplementation. In order to avoid either the problem of nutrient deficiencies or excesses they recommend that physician’s or licensed dietician’s should be the source of prescribing supplementation.

The ADA, however, does make allowances for supplement usage under the following conditions: Iron supplements may be required by women when there is excessive menstrual bleeding. Pregnant and breast-feeding women need supplements, especially iron, folic acid, and calcium. People who are dieting and are therefore are on very low calorie diets may require supplementation if they are not getting the right amount of the nutrients they need. Vegetarians may need boosts of vitamin B-12, calcium, iron, and zinc. Newborns are sometimes given vitamin K to prevent abnormal bleeding. Those people who have diagonsised disorders or diseases or are being treated with medications which affects the absorption or metabolism of the nutrient may require supplementation.

KEY TERMS

Amino acid —An organic compound whose molecules contain both an amino group (-NH2) and a carboxyl group (-COOH). One of the building blocks of a protein.

Calcium —An essential macro mineral necessary for bone formation and other metabolic functions.

Controlled experiment —Also called a controlled trial. The dividing into groups of experimental subjects to see what the effects of a drug will be when tested along with a dummy drug or placebo (a drug other than the one being tested).

Dermatitis —An inflammation of the skin. A symptom of vitamin deficiency.

Edema —An abnormal collection of fluids in the body tissues. One of the forms of the disease beriberi called wet beriberi.

Essential nutrients —Those nutrients that must be obtained from food for good health and to prevent nutrient deficiency diseases.

Iodine —A mineral necessary for the proper functioning of the thyroid gland.

Niacin —An essential B vitamin needed to prevent pellagra.

Night blindness —Inability to see at night due to a vitamin A deficiency.

Recent research on vitamins A and C

Research using 22,000 physicians under the supervision of the Department of Medicine at Harvard is studying the long-term effects of beta carotene (vitamin A) in lowering the incidence of cancer and boosting resistance to infection. It is also being studied in the treatment of AIDS. Beta carotene is a safer version of vitamin A than the preformed oil form called retinol. It is found in carrots, sweet potatoes, broccoli, spinach, collards, turnip greens, kale, and many other vegetables that.

Vitamin C, also known as ascorbic acid, is used as a supplement by more people than any other supplement. Its popularity is due to the work of the two-time Nobel laureate, Linus Pauling who maintained that vitamin C was effective in preventing and lessening the effect of colds and in the treatment of cancer. Pauling’s vitamin C program called for megadoses that far exceeded the government’s RDA recommendations. Pauling recommended a daily dose of between 2,000 and 9,000 milligrams (mg). The National Research Council recommends 60 mg for adult daily and 100 mg for smokers.

The discovery of micro nutrition was made in the early twentieth century as a result of finding the cure for certain diseases, the nutrient deficiency diseases such as scurvy, beriberi, and pellagra. The new dimensions of fully understanding and using our knowledge of nutrients remain to be established from the ongoing research in this area of nutritional science.

Resources

BOOKS

Encyclopedia of Human Nutrition, edited by Benjamin Caballero, et al. London: Academic Press, 2005.

Hendler, Sheldon S. The Doctor’s Vitamin and Mineral Encyclopedia. New York: Simon and Schuster, 1990.

Kok, Frans J., et al. Introduction to Human Nutrition. Oxford: Blackwell Publishing, 2002.

Williams, Sue R. Nutrition and Diet Therapy. Boston: Mosby College Publishing, 1989.

Jordan P. Richman