SLEEP

 Sleep

PKGhatak, MD

Sleep is a state of the body during which most of the bodily functions are suspended, consciousness and voluntary actions are absent but readily reversible to external stimuli.

Sleep is a compulsory phase of daily occurrence for all animals - even whales sleep in water; and sharks who must move in order to force water through the gills to meet oxygen requirements, undertake a kind of restfulness, a phase equivalent to sleep. Young dolphins are seen sleeping while swimming but remaining in bodily contact with others within the pods. Plant physiologists have observed sleep like state in plants. Developing human fetuses also sleep in the mother's womb. Newborns sleep most of the time with short periods of wakefulness which gradually increases as the child advances in age. Adults sleep 6 to 8 hrs. a day, the elderly require less sleep and octogenarians experience short periods of awakening during nocturnal sleep.

People who work shift duty jobs have difficulties in falling asleep after switching over and most of them develop hypertension, diabetes, obesity, metabolic syndrome, ulcers, increased irritability and behavioral changes. Night duty workers have a 10 % reduction in longevity compared with the workers doing the same job during the daytime.

Sleep deprivation causes increased Cortisone release, increased Ghrelin secretion, decreased Leptin and increased hunger and appetite.

The circadian rhythm controls home release; at the start of darkness, Melatonin is released from the pineal gland which prepares the body to fall asleep. During sleep cortisol level falls, antidiuretic hormone release is stopped. Pituitary Growth hormone is released. Cytokines -tissue necrosis factor (TNF), interleukin 1(IL1) are released and help tissue repair at night; and also, TNF and IL 6 levels increase that activate the liver cell regeneration.

Long term memory development takes place during sleep, and growth in children accelerates during sleep. The BP, heart rate, respiration decrease, voluntary muscles cease to function temporarily but cardiac and smooth muscles continue to work. As we begin to wake up, all the above changes are revered. Increased cortisol and increased BP may trigger a heart attack in patients with coronary artery disease.

Dreams during sleep are a natural occurrence, many remember the dream on waking up, but most others fail to recall. Scientists believe rewiring neurons in the Neocortex and Hippocampus during sleep generates dreams. Many believe octopus dreams during sleep as evident by the color changes.

Young children develop nightmares during dreams which experts think is a benign phase of brain development. Sleepwalking at a young age is also a benign condition but in adults, it is not normal.

Sleep apnea in an obese person is a risk factor for hypertension, cardiac arrhythmia, and heart attacks. This condition is due to the decreased tone of muscles of the glottis and tongue falling backward obstructing the entry of air into the laryngopharynx. Snoring during sleep is a similar condition but airways still remain partially open and breathing does not stop.

In any discussion on sleep, REM (rapid eye movement) and Non-REM (NREM) are discussed. In adults, NREM sleep takes place about 70% of sleep time. Scientists have divided NREM into 3 phases based on the frequency of the brain waves. Phase 3 of NREM is deep sleep and most of the bodily functions are lowest during this period but at the same time tissue repairs, healing and rejuvenation of body and mind take place here. The changeover from one stage to the next does not necessarily follow any particular order. In babies REM happens 50% of sleep time, In younger adults NREM takes place at the beginning of sleep followed by REM about 90 minutes later. Initial REM sleep lasts only 10 minutes and increases progressively and at the end may last 60 minutes. Heart rate, BP and respiration increase during this phase and dreams happen during REM sleep. Reinforcement of memory happens in REM sleep. The brain switches REM and NREM in some order initially but in older individuals no particular pattern is recognizable. In old age REM and NREM switch back and forth in short order and even at the onset of sleep no order is observed.

Narcolepsy and Restless Leg Syndrome are neurological disorders and are not discussed here.

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Folic Acid

 Folic Acid

PKGhatak, MD

Folic acid is a water soluble yellow crystalline substance. It is a chemical made of Pteridine, p-aminobenate and Glutamic acid. Glutamic acid may be present as monoglutamate but usually exists in polyglutamine forms, containing anywhere from 2 to 7 glutamic acid residues. About 30 different derivatives of folic acid are present in nature. In the plasma, the Folic Acid (FA) is pteroylmonoglutamic acid, but within the cells, folic acid exists in polyglutamic form. In the blood, the majority of folic acid is present in RBC. The normal Plasma FA level in adults is 3 to 17 ng/ml. RBC folate level resembles body storage and deficiency appears 90 days before low plasma FA.

Other names.

Citrovorum factor. An essential growth factor for bacteria Leuconostoc citrovorum was detected and named citrovorum factor and later was identified to be folic acid but the name remains. At one time FA was called vitamin B9.

Folic acid however cannot enter the cells as such, until it is reduced to Tetrahydrofolate (THF) by the enzyme THF Reductase, B12 methyl coenzyme and NADH acting as H donors. Once inside the cells, lysosomal enzymes convert it into polyglutamate and then combine with substrates to form Folic acid coenzymes.

Folic acid coenzymes are single C-atom transfer and utilization agents. One [C-atom] maybe 1. Formyl group [-CHO], 2. Formate [- H COOH] , 3. Hydroxymethyl [– CH2.OH]. These three groups are metabolically interchangeable. THF coenzymes combine with one of the above one atom C and form and play a very important role in DNA, RNA and phospholipids synthesis.

Dietary source.

Source - fruits, leafy vegetables, field mushrooms, liver, and fortified food items.

Daily requirement is 400 micrograms for adults and for pregnant women 600 mcg/day. A FA dose of 5000 mcg/day to pregnant women is harmful to the developing child, and increased incidence in respiratory allergy, insulin resistance and delayed psychomotor development are seen in these children.

The Folic acid storage in the liver is good for 3 months of use and the total amount is 5 mg.

Absorption of FA.

Polyglutamic FA in food is converted to monoglutamate in the intestinal mucosa, then FA is absorbed in the upper small intestinal epithelial brushed border by a transported protein. Renal tubular cells reabsorb FA from glomerular filtrate.

Transport of FA in and out of cells requires conversion of FA to polyglutamate and monoglutamate and vice versa. And each phase requires a specific transporter protein.

Actions of FA coenzymes are necessary for methylation. Folic acid is required in the formation of choline, Serine, Glycine, Methionine. and histidine.

Purine and thymine are used in DNA synthesis.

FA coenzymes convert amino acid histidine to glutamic acid through an intermediate step where foraminmonoglutamic acid is formed. This is the basis of the Figlu test to detect folic acid deficiency. This test is just of historical importance, the blood FA test has replaced Figlu test.

The function of FA.

It is an essential vitamin for all cells of the body for cell growth, maturation, and repair. FA is utilized for DNA, RNA, mRNA and phospholipid synthesis. It is necessary for the methylation of fatty acids, metabolism of several amino acids. Growth and development of the fetus. 

FA deficiency.

Deficiency. Alcoholism, dietary habits, overcooked vegetables in a large volume of water.

Drug interference- anticonvulsants, oral contraceptives, Methotrexate. Trimethoprim-sulfamethoxazole and Sulfadiazine. Aminopterin (MTX) is a permanent folic acid antagonist and is used in the treatment of Leukemia and immunosuppressant, used as an adjunct in order to reduce steroid dose.

The medical condition leading to deficiency - pregnancy, hemolytic anemia, exfoliative dermatitis, GI mucosal atrophy, psoriasis.

Effects of FA deficiency.

The tissues which turn over rapidly exhibit the earliest changes in the development of the nucleus but the cytoplasm continues to develop normally. Blood cells- RBC, WBC and Platelets are not only decreased in number but also deformed. Since RBCs have no nucleus, the nuclear abnormality is clearly visible in peripheral WBC. CBC. Anemia. Most RBCs are large and come in various thicknesses and sizes giving an increase in RWD, PVC, and a low HCT. Leukopenia and polysegmented neutrophils and decreased Platelet count. Erythroblasts in peripheral blood. 

Neurological.

Changes are noted in a fetus and newborn, commonly spina bifida and anencephaly.

Folic acid deficiency is common in pregnancy due to increased demand by the fetus which cannot be met by diet alone. WHO recommends fortification of rice, cereals, flour, pasta and bread with folic acid. It plays a vital role in the synthesis of the nucleus of all cells.

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Vitamin B12

 

Vitamin B 12

PKGhatak, MD

Vitamin B12 is a water soluble vitamin, a chemical compound containing a cobalt atom. Vitamin B12 is essential for humans and must be supplied in food. Liver, meat, milk, egg, herring and mackerel fish are the chief source of B12; vegetables are nearly devoid of B12. Stomach acid and pepsin release B12 from the food, B12 then combines with a glycoprotein. B12 is absorbed in the terminal ileum. The liver is the principal store of B12. Breast milk contains enough B12 to meet a developing child's requirements. The daily requirement for adults is 3 micrograms, for infants 0.3 micrograms and for children the amount varies according to age. Adults have about 3 year reserve of B12 in the liver.

Chemistry:

B12 was originally obtained from the liver by Dr. Castleman in 1948. The isolated compound was light sensitive but when combined with a cyanide group, B12 becomes a stable crystalline form - cyanocobalamin. The central part of the molecule is four pyrrole rings surrounding a single six valent cobalt atom. This ring is called the Corrin ring system. The corrin ring is synthesized from delta aminolaevulinic acid by a process where the methyl group is supplied by methionine (amino acid). The central cobalt atom is attached to the N molecule of each of the four pyrrole rings. The 5th valent of Cobalt is attached to the N molecule

 of 5,6-dimethyl benzimidazole ribose phosphate and the 6th valent of the cobalt is attached to a variable group, R - cyano or 5-deoxyadenosyl or a methyl group. These forms are interchangeable with the cells. The R binding compound gives the type of B12 that will be formed eg- cyanocobalamin and adenosylcobalamin. In food, B12 presents as Adenosyl B12, Hydoxyadenosyl B12, Methyl B12, Cyano B12 and Sulphito B12, of which the first two forms are commonly found.

In nature, B12 is also present as hydroxocobalamin, a red color compound and nitrocobalamin. Methylcobalamin and  Hydroxycobalamin are therapeutically active and last longer in the body. B12 in plasma is bound to plasma proteins in variable amounts. The intracellular B12 level in the mitochondria is dependent on the amount of free B12 present in the serum. 

Physiology:

Acid and pepsin in the stomach release B12 from the food. The intrinsic factor (IF) of Castle, a glycoprotein, secreted by the parietal cells of the stomach, combines with B12 in the duodenum and prevents B12 from digestion by GI enzymes and keeps it safe from gut bacteria using it. As B12 reaches the terminal ilium, the receptors present on the surface epithelial cell of the ilium bind with it, then release B12 from the IF. Only free B12 is available for absorption. About 1 to 2 % B12 is absorbed by simple diffusion, the rest is ferried across the cells by an active process and carried by the Transporter I protein. The Transporter II protein carries B12 to the liver, bone marrow and other tissues. The proportion of B12 absorbed from food is limited by the amount of available IF. As a result, only about 20% is absorbed; that amount generally satisfies the daily 3 micrograms of B12 requirement. In macrocytic anemia or pernicious anemia, 1500 to 3000 micrograms of B12 are prescribed and 1 to 2% absorption by diffusion meets the therapeutic needs. The only source of B12 for the herbivorous animal is that produced by gut bacteria. 

B12 inside the cells.

B12 with the attached transport protein enters the cells. The lysozymes free the B12. The B12 then is taken up by mitochondria. Here B12 first converted to Cobalamin II alamin. Then cobalamin II alamin is converted to adenosylcobalamin and methylcobalamin. Hydroxycobalamin is also present in the cytoplasm. 

The action of coenzymes:

Methylcobalamin is the cofactor of methionine synthase. Methionine synthase converts Homocysteine to Methionine. In another reaction methionine synthase transfer the methyl group from 5 methyltetrahydrofolate (THF) to homocysteine. THF is the active form of vitamin Folic Acid. THF is essential in DNA synthesis.

The adenosylcobalamin is the cofactor of methylmalonyl CoA mutase (CoA means coenzyme A). Methylmalonyl CoA mutase converts methylmalonyl CoA to Succinyl CoA in the Krebs tricarboxylic acid cycle.  Energy supplying amino acid metabolism requires to pass through succinyl CoA step. Similarly, the fatty acid metabolism is also dependent on this methyl B12 coenzyme.

The function of B12:

B12 coenzymes are required for the synthesis of 1. Purine Nucleotides, 2. metabolism of several amino acids and fatty acids 3. the normal growth and development of cells.

Myelin sheath of nerve fibers.

In the initial steps of myelin sheath synthesis, the B12 coenzyme produces methylmalonyl-CoA from branched amino acids threonine, isoleucine and valine. In B12 deficiency malonyl CoA is reduced and methylmalonyl-CoA is substituted. This results in defective myelin and early breakdown of the myelin sheath.

Causes of B12 deficiency.

Dietary.

 B12 deficiency is expected in strict vegetarian Hindus in India. In the west, vegans are similarly affected.

Diseases of the stomach.

Acid suppression by pantoprazole over a prolonged period, atrophic gastritis, partial gastrectomy,

Intrinsic factor (IF) deficiency.

Congenital absence of IF.

Acquired autoimmune disease producing antibodies to the parietal cells or antibodies to IF.

Diseases of the terminal ileum.

Crohn's disease. Surgical removal of terminal ilium, Celiac disease. Tropical sprue. Malabsorption syndrome. HIV infection, Frequent bacterial enteritis. Change of gut bacterial population.

Intestinal parasite. Diphyllobothrium latum, a fish water fluke, infestation of the gut.

Diseases associated with Megaloblastic anemia.

Type 1 diabetes mellitus, Graves disease, Hypothyroidism, Addition's disease. Parkinson syndrome.

Risk factors. North European ancestry. Alcoholism.

Diagnosis of B12 deficiency:

1. Blood test.

B12 deficiency is easily detected by obtaining blood B12 levels.

2. Associated abnormalities of blood picture.

CBC. Any or all of these features may be present. Anemia, Macrocytic RBCs, 

Increased RWD (Red blood cell width distribution), Ovalocytes, Leukopenia, and hypersegmented neutrophils. Thrombocytopenia, pancytopenia. Increased blood LDH, Bilirubin. and AST. Decreased Haptoglobin, and increased serum Methylmalonic acid and Homocysteine.

Some neurological symptoms are suspected to be from the B12 deficiency but the serum B12 levels may be normal. The B12 deficiency is confirmed by finding a blood methylmalonic acid over 1000 mcg/ml and high homocysteine levels.

Diagnosis of Pernicious Anemia.  

1. Presence of megaloblastic anemia and 2. deficiency of Intrinsic factor.

Intrinsic factor deficiency may be due to congenital or hereditary.  Acquired causes are due to the presence of antibodies. Antibodies are of two types. 1. Complement fixing antibodies to parietal cells and, 2. antibodies against the Intrinsic factor.

Symptoms of B12 deficiency.

Weakness, glossitis, anemia.

Neurological.

Some or none of the following symptoms are usual findings.

Peripheral neuritis, Depression, dementia, Psychosis, Cerebellar ataxia, Subacute combined degeneration of the spinal cord. Optic atrophy. Cranial nerve nephropathy.

In general, Megaloblastic anemia is common in B12 deficiency, neurological manifestations are variable and occasionally appear before hematological changes.

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