Sprouty1 is a weight-loss target gene in human adipose stem/progenitor cells that is mandatory for the initiation of adipogenesis

The differentiation of adipose stem/progenitor cells (ASCs) into adipocytes contributes to adipose tissue expansion in obesity. This process is regulated by numerous signalling pathways including MAPK signalling. In the present study, we show that weight loss (WL) interventions induce upregulation of Sprouty1 (SPRY1), a negative regulator of MAPK signalling, in human ASCs and elucidate the role of the Sprouty1/MAPK interaction for adipogenic differentiation. We found that the Sprouty1 protein levels are low in proliferating ASCs, increasing in density arrested ASCs at the onset of adipogenic differentiation and decreasing in the course of adipogenesis. Knock-down (KD) of Sprouty1 by RNA interference led to elevated MAPK activity and reduced expression of the early adipogenic transcription factor CCAAT/enhancer-binding protein β (C/EBP β), concomitant with an abrogation of adipogenesis. Intriguingly, co-treatment of Sprouty1 KD ASCs with differentiation medium and the pharmacological MEK inhibitor U0126 blunted ERK phosphorylation; however, failed to rescue adipogenic differentiation. Thus, the effects of the Sprouty1 KD are not reversed by inhibiting MAPK signalling although the inhibition of MAPK signalling by U0126 did not prevent adipogenic differentiation in wild type ASCs. In conclusion, we show that Sprouty1 is induced after WL in ASCs of formerly obese people acting as a negative regulator of MAPK signalling, which is necessary to properly trigger adipogenesis at early stages by a C/EBP β dependent mechanism.

Postpartum IGF-I and IGFBP-2 levels are prospectively associated with the development of type 2 diabetes in women with previous gestational diabetes mellitus

AIMS

Women with previous gestational diabetes mellitus (GDM) are at greater risk of developing type 2 diabetes. In the general population, the insulin-like growth factor (IGF) system has been implicated in the development of type 2 diabetes. The aim of this study was to determine if circulating IGF-I, IGF-II, IGFBP-1 and IGFBP-2 levels 12weeks following a GDM pregnancy are associated with an increased risk of developing type 2 diabetes.

METHODS

IGF-I, IGF-II, IGFBP-1 and IGFBP-2 levels were measured in 98 normal glucose tolerant women, 12weeks following an index GDM pregnancy using enzyme immunoassay. Women were assessed for up to 10years for the development of overt type 2 diabetes.

RESULTS

Among the 98 women with previous GDM, 21 (21%) developed diabetes during the median follow-up period of 8.5years. After adjusting for age and BMI, IGF-I and IGFBP-2 were significantly associated with the development of type 2 diabetes. In a clinical model of prediction of type 2 diabetes that included age, BMI, pregnancy fasting glucose and postnatal fasting glucose, the addition of IGF-I and IGFBP-2 resulted in an improvement in the net reclassification index of 17.8%.

CONCLUSIONS

High postpartum IGF-I and low postpartum IGFBP-2 levels are a significant risk factor for the development of type 2 diabetes in women with a previous history of GDM. This is the first report that identifies IGF-I and IGFBP-2 as a potential biomarker for the prediction of type 2 diabetes in women with a history of GDM.

Weight Loss Upregulates the Small GTPase DIRAS3 in Human White Adipose Progenitor Cells, Which Negatively Regulates Adipogenesis and Activates Autophagy via Akt-mTOR Inhibition

Long-term weight-loss (WL) interventions reduce insulin serum levels, protect from obesity, and postpone age-associated diseases. The impact of long-term WL on adipose-derived stromal/progenitor cells (ASCs) is unknown. We identified DIRAS3 and IGF-1 as long-term WL target genes up-regulated in ASCs in subcutaneous white adipose tissue of formerly obese donors (WLDs). We show that DIRAS3 negatively regulates Akt, mTOR and ERK1/2 signaling in ASCs undergoing adipogenesis and acts as a negative regulator of this pathway and an activator of autophagy. Studying the IGF-1–DIRAS3 interaction in ASCs of WLDs, we demonstrate that IGF-1, although strongly up-regulated in these cells, hardly activates Akt, while ERK1/2 and S6K1 phosphorylation is activated by IGF-1. Overexpression of DIRAS3 in WLD ASCs completely inhibits Akt phosphorylation also in the presence of IGF-1. Phosphorylation of ERK1/2 and S6K1 is lesser reduced under these conditions. In conclusion, our key findings are that DIRAS3 down-regulates Akt–mTOR signaling in ASCs of WLDs. Moreover, DIRAS3 inhibits adipogenesis and activates autophagy in these cells.

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Long-term weight loss (WL) induces DIRAS3 and IGF-1 in ASCs of sWAT in formerly obese humans.

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DIRAS3 selectively down-regulates IGF-1R-Akt–mTOR signaling in ASCs and channels the IGF-1 stimulus to the ERK1/2 branch.

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DIRAS3 inhibits adipogenesis and activates autophagy in ASCs.

Long-term weight loss (WL) interventions reduce insulin serum levels, protect from obesity and postpone age-associated diseases. The impact of WL on adipose-derived stromal/progenitor cells (ASCs), stem cell-like cells in human subcutaneous white adipose tissue (sWAT), is not understood. We found that WL induced GTP-binding RAS-like 3 (DIRAS3) and insulin-like growth factor 1 (IGF-1), regulators of the IGF-1–mTOR signal transduction pathway, in ASCs in sWAT of formerly obese humans. We demonstrate that DIRAS3 selectively down-regulates IGF-1R–Akt–mTOR signaling in ASCs upon WL even in the presence of high IGF-1 level and that DIRAS3 inhibits adipogenesis and activates autophagy in these cells.

Hypothalamic leptin gene therapy reduces body weight without accelerating age-related bone loss

Excessive weight gain in adults is associated with a variety of negative health outcomes. Unfortunately, dieting, exercise, and pharmacological interventions have had limited long-term success in weight control and can result in detrimental side effects, including accelerating age-related cancellous bone loss. We investigated the efficacy of using hypothalamic leptin gene therapy as an alternative method for reducing weight in skeletally-mature (9 months old) female rats and determined the impact of leptin-induced weight loss on bone mass, density, and microarchitecture, and serum biomarkers of bone turnover (CTx and osteocalcin). Rats were implanted with cannulae in the 3rd ventricle of the hypothalamus and injected with either recombinant adeno-associated virus encoding the gene for rat leptin (rAAV-Leptin, n=7) or a control vector encoding green fluorescent protein (rAAV-GFP, n=10) and sacrificed 18 weeks later. A baseline control group (n=7) was sacrificed at vector administration. rAAV-Leptin-treated rats lost weight (-4±2%) while rAAV-GFP-treated rats gained weight (14±2%) during the study. At study termination, rAAV-Leptin-treated rats weighed 17% less than rAAV-GFP-treated rats and had lower abdominal white adipose tissue weight (-80%), serum leptin (-77%), and serum IGF1 (-34%). Cancellous bone volume fraction in distal femur metaphysis and epiphysis, and in lumbar vertebra tended to be lower (P<0.1) in rAAV-GFP-treated rats (13.5 months old) compared to baseline control rats (9 months old). Significant differences in cancellous bone or biomarkers of bone turnover were not detected between rAAV-Leptin and rAAV-GFP rats. In summary, rAAV-Leptin-treated rats maintained a lower body weight compared to baseline and rAAV-GFP-treated rats with minimal effects on bone mass, density, microarchitecture, or biochemical markers of bone turnover.

Insulin-like growth factor-I (IGF-I) and clinical nutrition

IGF-I (insulin-like growth factor-I) is a peptide hormone, produced predominantly by the liver in response to pituitary GH (growth hormone), which is involved in a wide variety of physiological processes. It acts in an endocrine, paracrine and autocrine manner to promote growth. The production of IGF-I signals the availability of nutrients needed for its anabolic actions. Recently, there has been growing interest in its role in health and disease. IGF-I has long been known to be regulated by nutrition and dysregulated in states of under- and over-nutrition, its serum concentrations falling in malnutrition and responding promptly to refeeding. This has led to interest in its utility as a nutritional biomarker. A considerable evidence base supports utility for measurement of IGF-I in nutritional contexts. Its concentration may be valuable in providing information on nutritional status, prognosis and in monitoring nutritional support. However, it is insufficiently specific for use as a screening test for under nutrition as its serum concentration is influenced by many factors other than nutritional status, notably the APR (acute-phase response) and endocrine conditions. Concentrations should be interpreted along with clinical findings and the results of other investigations such as CRP (C-reactive protein). More recently, there has been interest in free IGF-I which holds promise as a nutritional marker. The present review covers nutritional regulation of IGF-I and its dysregulation in disease, then goes on to review recent studies supporting its utility as a nutritional marker in clinical contexts. Although not currently recommended by clinical guidelines, it is likely that, in time, measurement of IGF-I will become a routine part of nutritional assessment in a number of these contexts.

Endocrine changes (beyond diabetes) after bariatric surgery in adult life

Bariatric surgery is nowadays an effective therapeutic option for morbid obesity. Endocrinologists may thus have a growing opportunity to diagnose and treat obese patients eligible for surgery in pre- and post-operative phase. This requires a better understanding of endocrine changes caused by either obesity or weight loss surgery. Despite the large number of studies available in literature, only limited well-designed clinical trials have been performed so far to investigate changes of endocrine axes following bariatric procedures. There are still areas of unclear results such as female and male fertility, however, weight loss after bariatric surgery is considered to be associated with favorable effects on most endocrine axes. The aim of this clinical review is to overview the available literature on the effects of weight loss after bariatric surgery on the endocrine systems to suggest the most appropriate pre- and post-operative management of obese patients undergoing bariatric surgery in terms of "endocrine" health.

Aging-induced dysregulation of dicer1-dependent microRNA expression impairs angiogenic capacity of rat cerebromicrovascular endothelial cells

Age-related impairment of angiogenesis is likely to play a central role in cerebromicrovascular rarefaction and development of vascular cognitive impairment, but the underlying mechanisms remain elusive. To test the hypothesis that dysregulation of Dicer1 (ribonuclease III, a key enzyme of the microRNA [miRNA] machinery) impairs endothelial angiogenic capacity in aging, primary cerebromicrovascular endothelial cells (CMVECs) were isolated from young (3 months old) and aged (24 months old) Fischer 344 × Brown Norway rats. We found an age-related downregulation of Dicer1 expression both in CMVECs and in small cerebral vessels isolated from aged rats. In aged CMVECs, Dicer1 expression was increased by treatment with polyethylene glycol-catalase. Compared with young cells, aged CMVECs exhibited altered miRNA expression profile, which was associated with impaired proliferation, adhesion to vitronectin, collagen and fibronectin, cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing technology), and impaired ability to form capillary-like structures. Overexpression of Dicer1 in aged CMVECs partially restored miRNA expression profile and significantly improved angiogenic processes. In young CMVECs, downregulation of Dicer1 (siRNA) resulted in altered miRNA expression profile associated with impaired proliferation, adhesion, migration, and tube formation, mimicking the aging phenotype. Collectively, we found that Dicer1 is essential for normal endothelial angiogenic processes, suggesting that age-related dysregulation of Dicer1-dependent miRNA expression may be a potential mechanism underlying impaired angiogenesis and cerebromicrovascular rarefaction in aging.

Circulating factors induced by caloric restriction in the nonhuman primate Macaca mulatta activate angiogenic processes in endothelial cells

Moderate caloric restriction (CR) without malnutrition increases healthspan in virtually every species studied, including nonhuman primates. In mice, CR exerts significant microvascular protective effects resulting in increased microvascular density in the heart and the brain, which likely contribute to enhanced tolerance to ischemia and improved cardiac performance and cognitive function. Yet, the underlying mechanisms by which CR confer microvascular protection remain elusive. To test the hypothesis that circulating factors triggered by CR regulate endothelial angiogenic capacity, we treated cultured human endothelial cells with sera derived from Macaca mulatta on long-term (over 10 years) CR. Cells treated with sera derived from ad-libitum-fed control monkeys served as controls. We found that factors present in CR sera upregulate vascular endothelial growth factor (VEGF) signaling and stimulate angiogenic processes, including endothelial cell proliferation and formation of capillary-like structures. Treatment with CR sera also tended to increase cellular migration (measured by a wound-healing assay using electric cell-substrate impedance sensing [ECIS] technology) and adhesion to collagen. Collectively, we find that circulating factors induced by CR promote endothelial angiogenic processes, suggesting that increased angiogenesis may be a potential mechanism by which CR improves cardiac function and prevents vascular cognitive impairment.

DLK1(PREF1) is a negative regulator of adipogenesis in CD105⁺/CD90⁺/CD34⁺/CD31⁻/FABP4⁻ adipose-derived stromal cells from subcutaneous abdominal fat pats of adult women

The main physiological function of adipose-derived stromal/progenitor cells (ASC) is to differentiate into adipocytes. ASC are most likely localized at perivascular sites in adipose tissues and retain the capacity to differentiate into multiple cell types. Although cell surface markers for ASC have been described, there is no complete consensus on the antigen expression pattern that will precisely define these cells. DLK1(PREF1) is an established marker for mouse adipocyte progenitors which inhibits adipogenesis. This suggests that DLK1(PREF1) could be a useful marker to characterize human ASC. The DLK1(PREF1) status of human ASC is however unknown. In the present study we isolated ASC from the heterogeneous stromal vascular fraction of subcutaneous abdominal fat pats of adult women. These cells were selected by their plastic adherence and expanded to passage 5. The ASC were characterized as relatively homogenous cell population with the capacity to differentiate in vitro into adipocytes, chondrocytes, and osteoblasts and the immunophenotype CD105⁺/CD90⁺/CD34⁺/CD31⁻/FABP4⁻. The ASC were positive for DLK1(PREF1) which was well expressed in proliferating and density arrested cells but downregulated in the course of adipogenic differentiation. To investigate whether DLK1(PREF1) plays a role in the regulation of adipogenesis in these cells RNAi-mediated knockdown experiments were conducted. Knockdown of DLK1(PREF1) in differentiating ASC resulted in a significant increase of the expression of the adipogenic key regulator PPARγ2 and of the terminal adipogenic differentiation marker FABP4. We conclude that DLK1(PREF1) is well expressed in human ASC and acts as a negative regulator of adipogenesis. Moreover, DLK1(PREF1) could be a functional marker contributing to the characterization of human ASC.