goals are to understand the mechanism of growth regulation and utilize
hormones/proteins involved in growth regulation as indices to evaluate growth
status. Our focus is on insulin-like growth factor (IGF)-I and its binding
of fish is influenced by various environmental factors such as photoperiod,
water temperature, feeding ration and stress. Such stimuli are integrated by
the brain and hormones regulate growth. Growth hormone (GH) and insulin-like
growth factor (IGF)-I are two major hormones regulating growth. GH stimulate
growth directly acting on target tissues such as muscle and bone or indirectly
through stimulating hepatic production of IGF-I. This system is called “the
GH-IGF-I system”. Circulating IGF-I mediates action of GH and has a negative
feedback effect on the secretion of GH from the pituitary gland.
Most circulating IGF-I is bound to one of
six IGF-binding proteins (IGFBPs). IGFBPs can inhibit or stimulate the activity
of IGF-I depending on the type, post-translational modification and
microenvironment. Thus, IGFBPs play a key role in modulating growth. Teleosts
have up to 12 IGFBP subtypes due to the third-round whole genome duplication in
this lineage. In addition, salmonids are tetraploid origin and thus have 22
Goal: We are interested in unraveling
functions of IGF-I and IGFBPs in salmonids and utilize them as indices of
growth. Availability of growth indices is useful to improve aquaculture and
IGFBPs in salmon blood and their functions
Three major IGFBPs are detected in
serum/plasma of salmonids. They are believed to inhibit or/and promote action
Relationships of circulating IGF-I, IGFBP-2b and IGFBP-1b with growth rate
IGF-I and IGFBP-2b positively correlated with individual growth rate whereas a
negative correlation was seen between IGFBP-1b and growth rate. These results
suggest that they are useful as growth indices.
Evaluation of growth status by IGF-I of juvenile chum salmon along the coast
Growth status of out-migrating
juvenile chum salmon was monitored by using serum IGF-I as a growth index. The
results suggest that fish under poor growth condition stayed in the estuary and
might suffer growth-dependent mortality thereafter.
more recombinant IGFBP subtypes for functional analyses and unravel their roles
in growth regulation.
Establish a diagnosis method by using
IGF-I and IGFBPs as growth/stress indices. Availability of such method is useful to evaluate rearing
conditions of farmed fish and growth status of free-swimming fish.