Selective Vulnerability of Peripheral Nerves in Avian Riboflavin Deficiency Demyelinating Polyneuropathy

Abstract

Abstract. Riboflavin (vitamin B2) deficiency in young chickens produces a demyelinating peripheral neuropathy. In this study, day-old broiler meat chickens were fed a riboflavin-deficient diet (1.8 mg/kg) and killed on posthatch days 6, 11, 16, 21, and 31, while control chickens were given a conventional diet containing 5.0 mg/kg riboflavin. Pathologic changes were found in sciatic, cervical, and lumbar spinal nerves of riboflavin-deficient chickens from day 11 onwards, characterized by endoneurial oedema, hypertrophic Schwann cells, tomacula (redundant myelin swellings), demyelination/remyelination, lipid deposition, and fibroblastic onion bulb formation. Similar changes were also found in large and medium intramuscular nerves, although they were less severe in the latter. However, by contrast, ventral and dorsal spinal nerve roots, distal intramuscular nerves, and subcutaneous nerves were normal at all time points examined. These findings demonstrate, for the first time, that riboflavin deficiency in young, rapidly growing chickens produces selective injury to peripheral nerve trunks, with relative sparing of spinal nerve roots and distal nerve branches to muscle and skin. These novel findings suggest that the response of Schwann cells in peripheral nerves with riboflavin deficiency differs because either there are subsets of these cells in, or there is variability in access of nutrients to, different sites within the nerves.Key words: Avian species; demyelination; neuropathy; peripheral nerves; riboflavin deficiency.The normal functioning of the nervous system depends on a constant supply of nutrients. A deficiency of vitamins, particularly groups B (thiamine, cobalamin, pyridoxine, and niacin) and E, generally produces an axonal type of polyneuropathy.22,41 However, riboflavin (vitamin B2) deficiency is characterized by demyelination with hypertrophy of Schwann cells, marked lipid accumulation, paranodal tomacula, and fibroblastic onion bulbs. [6][7][8]19,20 There is, at least initially, sparing of axons, and spinal cord and brain are apparently unaffected. 7 Riboflavin (7,8-dimethyl-10-ribityl-isoalloxazine) is a water-soluble vitamin and a dietary requirement in both chickens and humans. It is a precursor of flavin mononucleotide and flavin adenine dinucleotide, and decreased levels of these coenzymes impair oxidative phosphorylation. 36 Riboflavin deficiency leads to decreased beta-oxidation of fatty acids with relative preservation of the tricarboxylic acid cycle. 37 The lipid deposition in Schwann cells and the formation of paranodal redundant loops of normal myelin (paranodal tomacula) suggest a disturbance of lipid metabolism and control of myelin membrane formation in the myelinating Schwann cell.The novel findings in this study that Schwann cells in spinal nerve roots and subcutaneous and distal intramuscular nerves do not show these pathologic changes suggest that Schwann cells in different parts of the peripheral nerve system respond differently to riboflavin deficiency. Materials and MethodsOur a...

Galliformes and Columbiformes

“…Deficiency causes a generalized demyelinating polyneuropathy. The sciatic, brachial, cervical, and lumbar nerves and large and medium intramuscular nerves are commonly affected and may be swollen and soft (Cai et al, 2009). The sciatic nerves may be 4-5 times larger than normal (Swayne et al, 2013).…”

Poultry and Avian Diseases

“…Deficiency causes reduced egg production. Hatched chickens may be dwarfed, show depigmentation, and 'curled toe paralysis' due to the presence of degenerative changes in nerve trunks (Cai et al, 2009).…”

Scientific Opinion on the substantiation of health claims related to riboflavin (vitamin B2) and contribution to normal energy-yielding metabolism (ID 29, 35, 36, 42), contribution to normal metabolism of iron (ID 30, 37), maintenance of normal skin and m

“…The presence of lipid depositions in Schwann cells and the formation of paranodal redundant loops of normal myelin suggest a disturbance of lipid metabolism and control of myelin membrane formation in the myelinating Schwann cell. Spinal cord and brain are unaffected (Cai et al, 2009). Some case reports are available in humans showing the presence of peripheral polyneuropathy in riboflavin depleted subjects (Powers, 2003;Bates, 2005).…”