Insulin-like growth factors I and II: aging and bone density in women

Isolation and characterization of insulin-like growth factor-II from human bone

Human bone was sequentially extracted with 4 M guanidine hydrochloride to remove nonmineralized tissue components, 0.5 M EDTA to dissolve the mineral phase, 4 M guanidine hydrochloride to remove matrix associated proteins and finally a combination of 4 M guanidine hydrochloride and 0.5 M EDTA to remove residual proteins. The extracts were examined for the presence of factors that were able to stimulate the incorporation of [3H] thymidine into DNA and [14C] leucine into protein in a cloned rat bone cell culture system. The majority of the bioactivity was found in the first guanidine hydrochloride extract (59 +/- 12%) while the second guandine hydrochloride extract contained 27 +/- 8%. In addition to several known growth factors already reported to be present in bone (transforming growth factor-beta and insulin-like growth factor-I) insulin-like growth factor-II was identified by its chromatographic, electrophoretic and immunological properties as well as by N-terminal sequence data. The insulin-like growth factor-II levels (802 +/- 112 micrograms/kg wet weight bone) were 10 fold higher than that found for insulin-like growth factor-I (84 +/- 23 micrograms/kg wet weight).

Exogenous growth hormone treatment alters body composition and increases natural killer cell activity in women with impaired endogenous growth hormone secretion

In order to assess the potential relationship between human growth hormone (GH) and body composition (BC) and natural immunity (NI), we measured the effects of exogenous GH on fat weight (FW), fat-free weight (FFW), and the cytotoxic activity of natural killer (NK) cells in women with impaired GH secretion. Mean peak serum concentrations of GH in response to L-dopa/arginine stimulation were 6.2 +/- 1.1 (SEM) ng/mL in 6 untreated subjects (US) and 5.4 +/- 1.5 ng/mL in 6 GH-treated subjects (TS). Moreover, the pretreatment circulating levels of IGF-I were low in both groups (US 684 +/- 121 mU/mL and TS 583 +/- 83 mU/mL), and they correlated with pretest levels of NK cell activity (r = .59, P less than .05) when both groups were combined. The TS were given 700 micrograms of human GH IM for an average of 14 days while the US were studied in parallel without GH treatment. As measured by hydrodensitometry or skinfold anthropometry, FW decreased (26.1 +/- 6.8 kg to 23.8 +/- 6.3 kg, P less than .05) and FFW increased (44.9 +/- 3.3 kg to 46.2 +/- 3.8 kg, P less than .05) in the TS. In the US, there were no significant (P less than .05) changes in either FW or FFW. Using a standard 51Cr release assay to measure the specific lytic (SL) activity of NK cells, mean SL activity increased from 24.4 +/- 7.0% to 44.1 +/- 8.9% (P less than .05) in the TS, whereas levels in the US were not altered significantly (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous release of interleukin 1 from human blood monocytes reflects bone formation in idiopathic osteoporosis

Osteoporosis is a state of reduced skeletal mass characterized by various rates of bone remodeling. Multiple locally elaborated factors have been identified that appear to influence the cellular events in bone remodeling. The possible role(s) of these factors in the pathogenesis of osteoporosis is unknown. One such factor, interleukin 1 (IL-1), is of particular interest, as this protein is known to stimulate bone resorption and perhaps formation. Consequently, we have measured the spontaneous secretion of IL-1 activity by cultured peripheral blood monocytes obtained from 22 osteoporotic patients and 14 age-matched control subjects. Monocytes from osteoporotic patients produced more IL-1 than did monocytes from control subjects. When patients were grouped according to monocyte-produced IL-1 activity, dynamic parameters of bone formation, as judged by quantitative histomorphometric analysis of iliac crest bone biopsies and by circulating levels of bone 4-carboxyglutamic acid protein (BGP)--a marker of bone formation--were higher in subjects with elevated IL-1 activity; whereas, indices of bone resorption and static indices of bone formation were similar in subjects with either high or normal IL-1 activity. IL-1 activity released by peripheral blood monocytes appears to reflect bone formation rate in osteoporotic patients and may be of pathogenetic significance in a subset of individuals with osteoporosis.

Oestrogens and bone metabolism: a hypothesis

The explanations so far proposed for the effects of oestrogens on bone metabolism in post-menopausal women have been based on the changes seen in calciotrophic hormones. However, we demonstrated in a previous study [6] that there is a decrease in the concentration of somatomedin (an insulin-like growth factor) and an increase in that of growth hormone (GH) in oestrogen-treated post-menopausal women. On the basis of those findings and the relevant data published in the literature, we advance a hypothesis to the effect that the bone-metabolism changes that occur in post-menopausal women following oestrogen replacement therapy come about via changes in serum somatomedin and growth hormone concentrations.