Nutritional modulation of canine insulin-like growth factors and their binding proteins

The IGF system plays a crucial role in ovarian folliculogenesis, and changes in IGF-binding protein (IGFBP) levels modulate IGF bioavailability. Data from various mammalian models suggest a link between body size, IGF1 in serum and female reproduction parameters. Among the vertebrate species, the dog exhibits the widest span in body height. Height is known to be positively correlated with the concentration of serum IGF1. In this work, the ovarian physiology of 40 bitches exhibiting a wide span of height, and breed type was investigated. IGF1, IGF2, IGFBP3, estradiol (E 2 ), and progesterone concentrations in plasma and preovulatory follicular fluid were quantified. A total of 455 follicles, 2-8 mm in diameter, were recovered at the preovulatory stage, measured, and punctured. Intrafollicular levels of IGF1 were positively correlated with plasma levels, and plasma IGF1 levels were positively correlated with both bitch height and weight. The concentrations were threefold higher in large dogs compared with small dogs. A positive correlation between intrafollicular and plasmatic IGFBP3 levels and a positive correlation between plasmatic IGFBP3 levels, and both height and weight of the bitches were observed. The number of preovulatory follicles and the diameter of the three largest follicles were positively correlated with bitch height. E 2 intrafollicular concentrations were higher in preovulatory follicles from small animals than in those from large animals. In conclusion, the strong variability in height between dogs appeared to be associated with dramatic differences in IGF1, and IGFBP3 levels, in both plasma and follicular fluid. These differences were associated with significant differences in some functional aspects of ovarian follicles.

Section: Discussionmentioning

confidence: 45%

IGF system and ovarian folliculogenesis in dog breeds of various sizes: is there a link?

Reynaud¹,

Chastant-Maillard²,

Batard³

et al. 2010

“…Further, it must be noted that the results in mammals are based on studies in humans and laboratory rodents. In other mammalian species, ligand blotting studies have found that lower-molecular weight IGFBPs (putative IGFBP-1s) sometimes did not increase as expected during catabolic states (Maxwell et al 1998, Schmidt & Kelley 2001.…”

Section: Discussionmentioning

confidence: 85%

Metabolic hormones regulate insulin-like growth factor binding protein-1 mRNA levels in primary cultured salmon hepatocytes; lack of inhibition by insulin

Pierce¹,

Shimizu²,

Felli³

et al. 2006

IGF-binding proteins (IGFBPs) modulate the effects of the IGFs, major stimulators of vertebrate growth and development. In mammals, IGFBP-1 inhibits the actions of IGF-I. Rapid increases in circulating IGFBP-1 occur during catabolic states. Insulin and glucocorticoids are the primary regulators of circulating IGFBP-1 in mammals. Insulin inhibits and glucocorticoids stimulate hepatocyte IGFBP-1 gene expression and production. A 22 kDa IGFBP in salmon blood also increases during catabolic states and has recently been identified as an IGFBP-1 homolog. We examined the hormonal regulation of salmon IGFBP-1 mRNA levels and protein secretion in primary cultured salmon hepatocytes. The glucocorticoid agonist dexamethasone progressively increased hepatocyte IGFBP-1 mRNA levels (eightfold) and medium IGFBP-1 immunoreactivity over concentrations comparable with stressed circulating cortisol levels (10 K9-10 K6 M). Triiodothyronine had no effect on hepatocyte IGFBP-1 mRNA, whereas glucagon increased IGFBP-1 mRNA (2 . 2-fold) at supraphysiological concentrations (10 K6 M). This study suggests that the major inhibitory role of insulin in the regulation of liver IGFBP-1 production in mammals is not found in salmon. However, regulation of salmon liver IGFBP-1 production by other metabolic hormones is similar to what is found in mammals.

“…In humans, caloric restriction of 50% for 6 days resulted in an increase in plasma IGFBP-1 in adults but not in children (Smith et al 1995). Dietary energy restriction of 42·5 and 56% for 2 weeks had no effect on IGFBP-1 in dogs (Maxwell et al 1998). Plasma IGFBP-1 levels decreased in guinea pigs fed rations of 70% of ad libitum feeding levels for 80 days (Sohlström et al 1998).…”

Section: Discussionmentioning

confidence: 98%

Measurement of circulating salmon IGF binding protein-1: assay development, response to feeding ration and temperature, and relation to growth parameters

Shimizu¹,

Beckman²,

Hara³

et al. 2006

Fish plasma/serum contains multiple IGF binding proteins (IGFBPs), although their identity and physiological regulation are poorly understood. In salmon plasma, at least three IGFBPs with molecular masses of 22, 28 and 41 kDa are detected by Western ligand blotting. The 22 kDa IGFBP has recently been identified as a homolog of mammalian IGFBP-1. In the present study, an RIA for salmon IGFBP-1 was established and regulation of IGFBP-1 by food intake and temperature, and changes in IGFBP-1 during smoltification, were examined. Purified IGFBP-1 from serum was used for as a standard, for tracer preparation and for antiserum production. Cross-linking 125 I-labelled IGFBP-1 with salmon IGF-I eliminated interference by IGFs. The RIA had little cross-reactivity with salmon 28 and 41 kDa IGFBPs (<0·5%) and measured IGFBP-1 levels as low as 0·1 ng/ ml. Fasted fish had significantly higher IGFBP-1 levels than fed fish (21·6 4·6 vs 3·0 2·2 ng/ml). Plasma IGFBP-1 was measured in individually tagged 1-year-old coho salmon reared for 10 weeks under four different feeding regimes as follows: high constant (2% body weight/day), medium constant (1% body weight/day), high variable (2% to 0·5% body weight/day) and medium variable (1% to 0·5% body weight/day). Fish fed with the high ration had lower IGFBP-1 levels than those fed with the medium ration. Circulating IGFBP-1 increased following a drop in feeding ration to 0·5% and returned to the basal levels when feeding ration was increased. Another group of coho salmon were reared for 9 weeks under different water temperatures (11 or 7 C) and feeding rations (1·75, 1 or 0·5% body weight/day). Circulating IGFBP-1 levels were separated by temperature during the first 4 weeks; a combined effect of temperature and feeding ration was seen in week 7; only feeding ration influenced IGFBP-1 level thereafter. These results indicate that IGFBP-1 is responsive to moderate nutritional and temperature changes. There was a clear trend that circulating IGFBP-1 levels were negatively correlated with body weight, condition factor (body weight/body length 3 100), growth rates and circulating 41 kDa IGFBP levels but not IGF-I levels. During parr-smolt transformation of coho salmon, IGFBP-1 levels showed a transient peak in late April, which was opposite to the changes in condition factor. Together, these findings suggest that salmon IGFBP-1 is inhibitory to IGF action. In addition, IGFBP-1 responds to moderate changes in dietary ration and temperature, and shows a significant negative relationship to condition factor.