Visfatin is a newly discovered adipocyte
hormone with a direct relationship between plasma
visfatin level and
type 2 diabetes mellitus.
Visfatin binds to the
insulin receptor at a site distinct from that of
insulin and causes hypoglycaemia by reducing
glucose release from liver cells and stimulating
glucose utilization in adipocytes and myocytes.
Visfatin is upregulated by
hypoxia,
inflammation and hyperglycaemia and downregulated by
insulin,
somatostatin and
statins. This
hormone is found in the cytoplasm as well as the nucleus of cells and has been identified in many tissues and organs including the brain, kidney, lung, spleen and testis but preferentially expressed in visceral adipose tissue and upregulated in some animal models of
obesity. Visceral adipose tissue is regarded to be more pernicious than subcutaneous adipose tissue.
Visfatin is an endocrine, autocrine as well as paracrine
peptide with many functions including enhancement of cell proliferation, biosynthesis of
nicotinamide mono- and dinucleotide and hypoglycaemic effect.
Visfatin, also known as a
pre-B cell colony-enhancing factor, consists of 491
amino acids (aa) in human, chimpanzee, cattle, pig, rat and mouse, 490 aa in rhesus monkey, 285 aa in sheep, 587 in opossum and 588 aa in canines.
Visfatin gene is well preserved during evolution. For example, the canine
visfatin protein sequence is 96% and 94% identical to human and rodent
visfatin, respectively. Since evidence of a direct link between
visfatin genotype and human
type 2 diabetes mellitus is still weak, more molecular, physiological and clinical studies are needed to determine the role of
visfatin in the etiology and pathogenesis of
type 2 diabetes mellitus.