Control of IGFBP-2 Expression by Steroids and Peptide Hormones in Vertebrates

Serum Insulin-like Growth Factor-Binding Protein-2 as a Prognostic Factor for COVID-19 Severity

Insulin-like growth factor-binding protein (IGFBP)-2 is a regulator of anabolic pathways, which become inactivated in severe illness. Here, we measured the serum IGFBP-2 levels of COVID-19 patients with moderate and severe disease as well as healthy controls to identify the associations of serum IGFBP-2 levels with disease severity. Patients with severe COVID-19 had higher serum IGFBP-2 levels than those with moderate disease and healthy controls, who had similar levels. Non-survivors of COVID-19 tended to have elevated serum IGFBP-2 levels compared to survivors. Increased serum IGFBP-2 levels were observed in patients requiring dialysis and vasopressor therapy. Serum IGFBP-2 was positively correlated with procalcitonin in both patient groups. Bacterial co-infection in severe COVID-19 patients did not influence serum IGFBP-2 levels. Patients with liver cirrhosis and obesity, showing increased and decreased serum IGFBP-2 levels, respectively, were excluded from the study. The present analysis showed that higher serum IGFBP-2 levels are associated with increased disease severity in COVID-19 patients. The similarity in serum IGFBP-2 levels between patients with moderate COVID-19 and healthy controls suggests that elevated IGFBP-2 is associated with critical illness rather than SARS-CoV-2 infection itself.

Similar dietary regulation of IGF-1- and IGF-binding proteins by animal and plant protein in subjects with type 2 diabetes

Increased animal but not plant protein intake has been associated with increased mortality in epidemiological studies in humans and with reduced lifespan in animal species. Protein intake increases the activity of the IGF-1 system which may provide a link to reduced lifespan. We, therefore, compared the effects of animal versus plant protein intake on circulating levels of IGF-1 and the IGF-binding proteins (IGFBP)-1 and IGFBP-2 over a 6-week period. Thirty seven participants with type 2 diabetes consumed isocaloric diets composed of either 30% energy (EN) animal or plant protein, 30% EN fat and 40% EN carbohydrates for 6 weeks. The participants were clinically phenotyped before and at the end of the study. Both diets induced similar and significant increases of IGF-1 which was unaffected by the different amino acid compositions of plant and animal protein. Despite improvements of insulin sensitivity and major reductions of liver fat, IGFBP2 decreased with both diets while IGFBP-1 was not altered. We conclude that animal and plant protein similarly increase IGF-1 bioavailability while improving metabolic parameters and may be regarded as equivalent in this regard.

Circulating IGFBP-2 levels reveal atherogenic metabolic risk in schizophrenic patients using atypical antipsychotics

OBJECTIVES

Second generation antipsychotics (SGAs) induce weight gain and dyslipidemia, albeit with important intervariability. Insulin-like growth factor binding protein (IGFBP)-2 is proposed as a circulating biomarker negatively associated with waist circumference and hypertriglyceridemia. Thus, we tested whether metabolic alterations developed upon the use of SGAs are associated with plasma IGFBP-2 levels.

METHODS

A cross-sectional study was performed in 87 men newly diagnosed with schizophrenia and administered for approximately 20 months with olanzapine or risperidone as their first antipsychotic treatment. Plasma IGFBP-2 concentration, anthropometric data, as well as glucose and lipid profiles were determined at the end of the treatments.

RESULTS

IGFBP-2 levels were similar between patients using olanzapine or risperidone and were negatively correlated with waist circumference, insulin sensitivity, and plasma triglycerides (TG). A higher proportion of men with a hypertriglyceridemic (hyperTG) waist phenotype was found in patients with IGFBP-2 levels lower than 220 ng/mL (43% for olanzapine and 13% for risperidone) compared to those with IGFBP-2 above this threshold (10% and 0%, respectively).

CONCLUSIONS

IGFBP-2 may have a role in altering metabolic risk in schizophrenic patients using SGAs. Longitudinal studies are required to evaluate whether IGFBP-2 can predict the development of a hyperTG waist phenotype in this population.

Sex-Specific Control of Muscle Mass: Elevated IGFBP Proteolysis and Reductions of IGF-1 Levels Are Associated with Substantial Loss of Carcass Weight in Male DU6PxIGFBP-2 Transgenic Mice

In farmed animals, carcass weight represents an important economic trait. Since we had demonstrated that IGFBP-2 represents a potent inhibitor of muscle accretion in inbred mice, we wanted to quantify the inhibitory effects of IGFBP-2 under conditions of elevated protein mass in growth selected non-inbred mice (DU6P). Therefore, we crossed male DU6P mice with female IGFBP-2 transgenic mice. Male IGFBP-2 transgenic offspring (DU6P/IGFBP-2) were characterized by more than 20% reductions of carcass mass compared to male non-transgenic littermates. The carcass mass in males was also significantly lower (p < 0.001) than in transgenic female DU6P/IGFBP-2 mice, which showed a reduction of less than 10% (p < 0.05) compared to non-transgenic female DU6P/IGFBP-2 mice. Although transgene expression was elevated in the muscle of both sexes (p < 0.001), serum levels were normal in female, but significantly reduced in male transgenic DU6P/IGFBP-2 mice (p < 0.001). In this group, also IGFBP-3 and IGFBP-4 were significantly reduced in the circulation (p < 0.01). Particularly in male transgenic mice, we were able to identify proteolytic activity against recombinant IGFBP-2 included in diluted serum. IGFBP-proteolysis in males correlated with massive reductions of IGF-1 in serum samples and the presence of elevated levels of IGFBP-2 fragments. From our data, we conclude that elevated tissue expression of IGFBP-2 is an essential effector of muscle accretion and may block more than 20% of carcass mass. However, in the circulation, intact IGFBP-2 contained no reliable biomarker content. Notably, for the estimation of breeding values in meat-producing animal species, monitoring of IGFBP-2 expression in muscle appears to be supported by the present study in a model system.

Early-life exposure to 17β-estradiol and 4-nonylphenol impacts the growth hormone/insulin-like growth-factor system and estrogen receptors in Mozambique tilapia, Oreochromis mossambicus

It is widely recognized that endocrine disrupting chemicals (EDCs) released into the environment through anthropogenic activities can have short-term impacts on physiological and behavioral processes and/or sustained or delayed long-term developmental effects on aquatic organisms. While numerous studies have characterized the effects of EDCs on temperate fishes, less is known on the effects of EDCs on the growth and reproductive physiology of tropical species. To determine the long-term effects of early-life exposure to common estrogenic chemicals, we exposed Mozambique tilapia (Oreochromis mossambicus) yolk-sac fry to 17β-estradiol (E2) and nonylphenol (NP) and subsequently characterized the expression of genes involved in growth and reproduction in adults. Fry were exposed to waterborne E2 (0.1 and 1 μg/L) and NP (10 and 100 μg/L) for 21 days. After the exposure period, juveniles were reared for an additional 112 days until males were sampled. Gonadosomatic index was elevated in fish exposed to E2 (0.1 μg/L) while hepatosomatic index was decreased by exposure to NP (100 μg/L). Exposure to E2 (0.1 μg/L) induced hepatic growth hormone receptor (ghr) mRNA expression. The high concentration of E2 (1 μg/L), and both concentrations of NP, increased hepatic insulin-like growth-factor 1 (igf1) expression; E2 and NP did not affect hepatic igf2 and pituitary growth hormone (gh) levels. Both E2 (1 μg/L) and NP (10 μg/L) induced hepatic igf binding protein 1b (igfbp1b) levels while only NP (100 μg/L) induced hepatic igfbp2b levels. By contrast, hepatic igfbp6b was reduced in fish exposed to E2 (1 μg/L). There were no effects of E2 or NP on hepatic igfbp4 and igfbp5a expression. Although the expression of three vitellogenin transcripts was not affected, E2 and NP stimulated hepatic estrogen receptor (erα and erβ) mRNA expression. We conclude that tilapia exposed to E2 and NP as yolk-sac fry exhibit subsequent changes in the endocrine systems that control growth and reproduction during later life stages.

Potential Functions of IGFBP-2 for Ovarian Folliculogenesis and Steroidogenesis

Ovarian follicles, as transient structural and functional complexes with the oocyte and the associated cells, determine the female reproductive cycle and thus fertility. Ovarian function is subject to the strict control of hormones and growth factors and thus regulated by auto-, para-, and endocrine mechanisms but influenced also by endogenous factors. During the waves of follicular growth and development, one follicle (monoovulatory) or a limited number of them (polyovulatory) are selected under hypothalamic-gonadal control for maturation until ovulation, resulting in the fertile oocyte. Subordinate follicles inevitably enter different stages of atresia. A number of studies have observed species-specific alterations of IGFBP-2 levels during the phases of growth and development or selection and atresia of follicles. IGFBP-2 is thus probably involved in the process of follicle growth, differentiation, and degeneration. This may occur on the levels of IGF-dependent and -independent growth control but also due to the control of steroidogenesis, e.g., via induction of aromatase expression. In mice, IGFBP-2 delayed reproductive development most probably by IGF-independent mechanisms. Because reproductive development is closely linked to the control of life- or health-span and energy metabolism, we feel that the time is right now to resume research on the effects of IGFBP-2 in the ovarian follicular compartment.

A comparative proteomic study of secretomes in kaempferitrin-treated CTX TNA2 astrocytic cells

ETHNOPHARMACOLOGICAL RELEVANCE

Kaempferitrin is extracted in significantly high quantities from the leaves of Cinnamomum osmophloeum (C.O) and Bauhinia forficata, and are used as an antidiabetic herbal remedy in China and Brazil. Commercial product using dry Cinnamomum osmophloeum leaves has been sold locally in Taiwan. Oral administration of kaempferitrin reduced blood sugar in diabetic rats.

AIM OF THE STUDY

Though previously demonstrated to activate the classical insulin signaling pathways, a mechanism for kaempferitrin is still not fully understood. Also, studies on kaempferitrin on immune related cells have been inconclusive, and people consuming extract containing kaempferitrin often happen to be at high risk of diabetes and neurodegenerative diseases. Therefore, for kaempferitrin to be used every day, a comprehensive study is needed.

MATERIALS AND METHODS

Astrocytic cell line was used as a model to test the differentially regulated secretomes, to test kaempferitrin effect on CNS glia, on pro-inflammatory cytokines, and to test how different the mechanism of kaempferitrin is from that of insulin. CTX TNA2 astrocytic cells were differentially treated with and without 10 µM kaempferitrin for 24 h, and the conditioned medium was collected. For the proteomic study, protein in conditioned medium was trypsin digested, and resulting peptides in kaempferitrin/non-treated sample pair were differentially dimethyl labeled. The labeled peptides were further fractionated by StageTip-based strong-exchange method before LC-MS/MS analyses. Levels of interesting proteins were verified using Western or Eliza. C.O. leaf crude extract treated samples were included for a comparison of effects of purified kaempferitrin vs. kaempferitrin containing crude extract.

RESULTS AND CONCLUSIONS

Data were obtained via ProteomeXchange with identifier PXD002814. It was found that no pro-inflammatory cytokines or inhibitory ECM were elevated upon treatment of kaempferitrin or a crude extract of C.O. leaves. This suggests that prolonged use of kaempferitrin containing herbs may not increase pro-inflammatory reaction. LDL-R trafficking between the cell membrane and the extracellular niche was regulated by kaempferitrin toward reduced secretion. Our proteomic study also demonstrated that molecules related to plasma membrane recycling were regulated by kaempferitrin. Our discoveries provide evidence that link kaempferitrin regulation for LDL-R and membrane recycling to the blood lipid regulation by the C.O. leaves extract. However, these proteins were differently regulated when cells were treated with crude extract. This demonstrates that the molecular interactions within crude extract of herbs are complex and may not act similar to the compound purified from the crude extract.

Quantitative Western ligand blotting reveals common patterns and differential features of IGFBP-fingerprints in domestic ruminant breeds and species

The insulin-like growth factor binding proteins (IGFBPs) are determinants of local IGF-effects and thus have an impact on growth and metabolism in vertebrate species. In farm animals, IGFBPs are associated with traits such as growth rate, body composition, milk production, or fertility. It may be assumed, that selective breeding and characteristic phenotypes of breeds are related to differential expression of IGFBPs. Therefore, the aim of the present study was to investigate the effects of selective breeding on blood IGFBP concentrations of farm animals. Breeds of the sheep, goat, and cattle species were investigated. IGFBP-3, -2, and -4 were analyzed with quantitative Western ligand blotting (qWLB), enabling comprehensive monitoring of intact IGFBPs with IGF-binding capacity. We show that in sera of all species and breeds investigated, IGFBP-3, -2, and -4 were simultaneously detectable by qWLB analysis. IGFBP-3 and the total amount of IGFBPs were significantly increased (P<0.05) in Cameroon sheep, if compared to 3 of 4 other sheep breeds, as well as in Dwarf goats versus Toggenburg and Boer goats (P<0.01). IGFBP-2 was elevated in Cameroon sheep and Boer goats, if compared to other breeds of these species (P<0.01), respectively. Holstein Friesian dairy cows had higher levels of IGFBP-4 (P<0.05), if compared to conventional crossbreeds of beef cattle. In Dwarf goats the ratio of IGFBP-3/IGFBP-2 was about 3-fold higher than in other goat breeds (P<0.001). The total IGFBP amount of Toggenburg goats was reduced (P<0.05), compared to the other goat breeds. In conclusion, our data indicate that common and specific features of IGFBP fingerprints are found in different ruminant species and breeds. Our findings may introduce quantitative Western ligand blotting as an attractive tool for biomarker development and molecular phenotyping in farm animal breeds.

Gender-specific effects on food intake but no inhibition of age-related fat accretion in transgenic mice overexpressing human IGFBP-2 lacking the Cardin-Weintraub sequence motif

IGFBP-2 affects growth and metabolism and is thought to impact on energy homeostasis and the accretion of body fat via its heparin binding domains (HBD). In order to assess the function of the HBD present in the linker domain (HBD1) we have generated transgenic mice overexpressing mutant human IGFBP-2 lacking the PKKLRP sequence and carrying a PNNLAP sequence instead. Transgenic mice expressed high amounts of human IGFBP-2, while endogenous IGFBP-2 or IGF-I serum concentrations were not affected. In both genders we performed a longitudinal analysis of growth and metabolism including at least 4 separate time points between the age of 10 and 52 weeks. Body composition was assessed by nuclear magnetic resonance (NMR) analysis. Food intake was recorded by an automated online-monitoring. We describe negative effects of mutant human IGFBP-2 on body weight, longitudinal growth and lean body mass (p < 0.05). Very clearly, negative effects of mutant IGFBP-2 were not observed for fat mass accretion throughout life. Instead, relative fat mass was increased in transgenic mice of both genders (p < 0.05). In male mice transgene expression significantly increased absolute mass of total body fat over all age groups (p < 0.05). Food intake was increased in female but decreased in male transgenic mice at an age of 11 weeks. Thus our study clearly provides gender- and time-specific effects of HBD1-deficient hIGFBP-2 (H1d-BP-2) on fat mass accretion and food intake. While our data are in principal agreement with current knowledge on the role of HB-domains for fat accretion we now may also speculate on a role of HBD1 for the control of eating behavior.

IGF-Binding Protein 2 - Oncogene or Tumor Suppressor?

The role of insulin-like growth factor binding protein 2 (IGFBP2) in cancer is unclear. In general, IGFBP2 is considered to be oncogenic and its expression is often observed to be elevated in cancer. However, there are a number of conflicting reports in vitro and in vivo where IGFBP2 acts in a tumor suppressor manner. In this mini-review, we discuss the factors influencing the variation in IGFBP2 expression in cancer and our interpretation of these findings.