Grape pomace is the source of bioactive compounds (anthocyanins, flavonols, flavan‐3‐ols, and stilbenes) which exhibit antiproliferative actions on cell cultures. We have investigated the antitumoral ...effects of grape pomace and grape seed extracts on colon cancer cells (Caco‐2, HT‐29) and fibroblasts. Crude extracts prepared from white and red pomace, and grape seeds, reduced the viability and proliferation of Caco‐2. HT‐29 cells were resistant to these actions. Purified extracts were then prepared from the same sources and compared with the LDH test; again, all three extracts were active and purified extract from grape seed was the most potent and specific on Caco‐2 cells. HT‐29 cells were more sensitive to these purified extracts. The biological activity resided almost exclusively in the flavonol and flavan‐3‐ols subfractions, rather than the anthocyanin subfraction. Preliminary results on the mechanisms involved in these effects revealed downregulation of Myc gene expression in HT‐29 and upregulation of Ptg2 in Caco‐2 cells.
The biological activity seems to reside almost completely in the nonanthocyanin phenolic fraction, since the anthocyanin fraction hardly produced any effect. Our results suggest a likely antitumor effect of the extracts studied. Decreased expression of Myc is compatible with an antiproliferative effect of the extracts, which could also be specific on colorectal tumor cells as long as it is not seen in fibroblasts.
Genome-wide association studies have reported that DNA polymorphisms at the CDKN2A locus modulate fasting glucose in human and contribute to type 2 diabetes (T2D) risk. Yet the causal relationship ...between this gene and defective energy homeostasis remains elusive. Here we sought to understand the contribution of Cdkn2a to metabolic homeostasis.
We first analyzed glucose and energy homeostasis from Cdkn2a-deficient mice subjected to normal or high fat diets. Subsequently Cdkn2a-deficient primary adipose cells and human-induced pluripotent stem differentiated into adipocytes were further characterized for their capacity to promote browning of adipose tissue. Finally CDKN2A levels were studied in adipocytes from lean and obese patients.
We report that Cdkn2a deficiency protects mice against high fat diet-induced obesity, increases energy expenditure and modulates adaptive thermogenesis, in addition to improving insulin sensitivity. Disruption of Cdkn2a associates with increased expression of brown-like/beige fat markers in inguinal adipose tissue and enhances respiration in primary adipose cells. Kinase activity profiling and RNA-sequencing analysis of primary adipose cells further demonstrate that Cdkn2a modulates gene networks involved in energy production and lipid metabolism, through the activation of the Protein Kinase A (PKA), PKG, PPARGC1A and PRDM16 signaling pathways, key regulators of adipocyte beiging. Importantly, CDKN2A expression is increased in adipocytes from obese compared to lean subjects. Moreover silencing CDKN2A expression during human-induced pluripotent stem cells adipogenic differentiation promoted UCP1 expression.
Our results offer novel insight into brown/beige adipocyte functions, which has recently emerged as an attractive therapeutic strategy for obesity and T2D. Modulating Cdkn2a-regulated signaling cascades may be of interest for the treatment of metabolic disorders.
The endoplasmic reticulum (ER) unfolded protein response (UPRer) pathway plays an important role in helping pancreatic β cells to adapt their cellular responses to environmental cues and metabolic ...stress. Although altered UPRer gene expression appears in rodent and human type 2 diabetic (T2D) islets, the underlying molecular mechanisms remain unknown. We show here that germline and β cell-specific disruption of the lysine acetyltransferase 2B (Kat2b) gene in mice leads to impaired insulin secretion and glucose intolerance. Genome-wide analysis of Kat2b-regulated genes and functional assays reveal a critical role for Kat2b in maintaining UPRer gene expression and subsequent β cell function. Importantly, Kat2b expression is decreased in mouse and human diabetic β cells and correlates with UPRer gene expression in normal human islets. In conclusion, Kat2b is a crucial transcriptional regulator for adaptive β cell function during metabolic stress by controlling UPRer and represents a promising target for T2D prevention and treatment.
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•The expression of UPR markers is altered in diabetic islets•Loss of Kat2b contributes to defective insulin secretion and β cell compensation•KAT2B regulates an UPR gene program in pancreatic β cells•KAT2B expression is reduced in mouse and human diabetic β cells
Rabhi et al. reveal a role for Kat2b in the control of insulin secretion and pancreatic β cell adaptation to metabolic stress through cell-autonomous regulation of the unfolded protein response (UPR). These data collected demonstrate that Kat2b expression is decreased in diabetic islets and suggest molecular links among KAT2B, the UPR, and diabetes.
Pancreatic β cell failure leads to diabetes development. During disease progression, β cells adapt their secretory capacity to compensate the elevated glycaemia and the peripheral insulin resistance. ...This compensatory mechanism involves a fine-tuned regulation to modulate the endoplasmic reticulum (ER) capacity and quality control to prevent unfolded proinsulin accumulation, a major protein synthetized within the β cell. These signalling pathways are collectively termed unfolded protein response (UPR). The UPR machinery is required to preserve ER homeostasis and β cell integrity. Moreover, UPR actors play a key role by regulating ER folding capacity, increasing the degradation of misfolded proteins, and limiting the mRNA translation rate. Recent genetic and biochemical studies on mouse models and human UPR sensor mutations demonstrate a clear requirement of the UPR machinery to prevent β cell failure and increase β cell mass and adaptation throughout the progression of diabetes. In this review we will highlight the specific role of UPR actors in β cell compensation and failure during diabetes.
Current pharmacological treatments for eating disorders and obesity are of limited value and thus the identification of novel targets is highly needed to enhance the development of more effective ...drugs. Among the bottlenecks limiting the introduction of new medicines is the reported heterogeneity of these diseases, which makes it difficult to find drugs with broad activity and the lack of animal models with translational validity, especially in the case of anorexia nervosa. Some kinds of obesity and eating disorders can be classified within the pathologies affecting the brain reward system together with drug addiction and others, and therefore specific treatments in these cases can be directed to restore normal function in brain reward pathways. Target identification in this field can greatly benefit from the combined application of genomic/proteomic techniques and robust animal models of reward deficits.
The ARF/INK4A (Cdkn2a) locus includes the linked tumour suppressor genes p16INK4a and p14ARF (p19ARF in mice) that trigger the antiproliferative activities of both RB and p53. With beta cell ...self-replication being the primary source for new beta cell generation in adult animals, the network by which beta cell replication could be increased to enhance beta cell mass and function is one of the approaches in diabetes research. In this review, we show a general view of the regulation points at transcriptional and posttranslational levels of Cdkn2a locus. We describe the molecular pathways and functions of Cdkn2a in beta cell cycle regulation. Given that aging reveals increased p16Ink4a levels in the pancreas that inhibit the proliferation of beta cells and decrease their ability to respond to injury, we show the state of the art about the role of this locus in beta cell senescence and diabetes development. Additionally, we focus on two approaches in beta cell regeneration strategies that rely on Cdkn2a locus negative regulation: long noncoding RNAs and betatrophin.
The identification of biomarkers associated with obesity and response to treatment could represent an important advance to design more effective and personalized therapeutic strategies. The ...complexity of morbid obesity could be explained as the combination of genetic, biochemical, cultural, and behavioral factors, among others. The study of biomarkers should be considered a determinant factor taken into account in this equation.
The aim of this study was to define better biomarker profiles potentially associated to the short-term outcome of bariatric surgery by paying attention to cocaine and amphetamine regulated transcript and brain-derived neurotrophic factor, 2 neuropeptides related to eating behavior.
University General Hospital of Ciudad Real, Spain.
Twenty-seven morbidly obese patients and 30 healthy weight individuals matched by age and sex were selected for the study.
Patients underwent bariatric surgery by Roux-en-Y gastric bypass and responded adequately in terms of weight loss and normalization of many biochemical parameters 1 year postsurgery. A multivariate analysis showed that the hormonal/neuropeptidic profile explained 82% of the variability of the weight loss response. The evolution of cocaine and amphetamine regulated transcript paralleled that of insulin and leptin, serum levels of this peptide were initially elevated in patients (4.24 ± .47 ng/mL) with respect to controls (2.94 ± .2 ng/mL), but this difference disappeared 1 year after Roux-en-Y gastric bypass (3.14 ± .26 ng/mL). Brain-derived neurotrophic factor levels were also decreased by Roux-en-Y gastric bypass (11.93 ± .96 ng/mL postsurgery versus 15.3 ± 1.02 ng/mL presurgery), even when this peptide was not elevated in patients before surgery (14.23 ± .86 ng/mL in controls).
The results suggest that cocaine and amphetamine regulated transcript and brain-derived neurotrophic factor could be envisaged as new candidate biomarkers of short-term outcome after surgery.
Background
The current therapeutics of morbid obesity could be significantly improved after the identification of novel biomarkers associated with the food addiction endophenotype of obesity and with ...bariatric surgery outcomes.
Methods
We applied differential expression proteomics and enzyme-linked immunosorbent confirmatory assays to identify (a) proteins that varied according to loss of control over eating in morbidly obese patients and (b) proteins that varied between normoweight controls and patients before and 1 year after bariatric surgery.
Results
Clusterin was the only protein that consistently varied according to eating control in patients. Patients showed increased levels of serum amyloid P protein, apolipoprotein A4, serotransferrin, complement factors B and C3 and haptoglobin with respect to controls; the levels of all these proteins tended to return to control values 1 year after surgery. In contrast, apolipoprotein A1 and transthyretin were initially downregulated in patients and were scarcely changed by surgery. Leucine-rich alpha-2-glycoprotein was markedly increased in patients only after surgery.
Conclusions
Clusterin could be of interest as a putative biomarker for food addiction diagnosis in people with morbid obesity. In addition, postsurgical normalization of the proteins initially dysregulated in obese subjects might help monitor clinical improvements after surgery, while lasting or newly detected alterations (i.e., those affecting transthyretin and leucine-rich alpha-2-glycoprotein) could reflect partial refractoriness and/or contribute to the early prediction of clinical problems.
The outcomes of bariatric surgery are very irregular and mostly unpredictable. The search for variables of predictive value is encouraged to help preventing therapeutic failures.
We aimed to confirm ...the hypothesis that preexisting eating behaviors could predict neuroendocrine and metabolic outcomes of gastric bypass surgery in morbidly obese subjects.
Twenty-one morbidly obese patients from the Bariatric Surgery Program of our hospital were selected according to the specific inclusion and exclusion criteria for this study. The subjects filled out a validated questionnaire to quantify the "loss-of-control" (LC) dimension of food craving and provided serum samples at the onset of the study and 1 year after gastric bypass surgery. Hematological, metabolic, and hormonal variables were studied by conventional clinical tests and enzyme immunoassays and checked for correlations with LC both before and after surgery.
Those patients that had exhibited worse eating control at the beginning of the study experienced a better metabolic response 1 year after surgery in terms of reduction of serum insulin, HOMA1-IR, HOMA2-IR, and vitamin D1; all these variables were inversely correlated with presurgical LC. Serum brain-derived neurotrophic factor (BDNF) levels showed the same tendency; in fact, BDNF significantly decreased only in those patients with worse eating control.
Problematic eating behaviors may predict a better response of insulin resistance and a specific reduction of serum BDNF in morbidly obese patients after gastric bypass surgery.
A mouse model has been developed to study the effect of dietary fat combined with food deprivation periods on palatable food seeking and on the expression of three potential addiction biomarkers in ...the nucleus accumbens: fumarate hydratase (FH), ATP synthase subunit alpha (ATP5a1) and transketolase (TKT). Forty C57BL/6 J male mice, four‐week old, were fed either with a high‐fat (HF) diet or standard diet along the experiment. After 3 weeks of differential feeding, animals underwent a two‐week training period of two daily sessions where visual cues were paired either to palatable food (chocolate cereals) or no food at all. This training was prolonged one more week with similar, one daily sessions preceded by 12 hours of food deprivation. A behavioural test was finally conducted where mice were confined for 30 minutes either in food unpaired compartments or in compartments previously paired with cereals, but now with empty food trays. Total activity during this behavioural test and serum corticosterone levels right after it were similar in all experimental groups. Mice tested in food‐paired compartments showed a marked preference for the empty food tray that gradually disappeared in standard diet‐fed individuals but persisted in HF‐fed mice. HF‐fed mice also overexpressed FH, ATP5a1 and TKT, which positively correlated with the persistence of preference for the empty food tray. It is suggested that HF diets combined with food deprivation may enhance food seeking behaviours while upregulating FH/ATP5a1/TKT, which are further envisaged as biomarkers of addiction.
A diet that combined high fat with food deprivation periods delayed the acute extinction of preference for places associated to palatable food in C57BL/6J male mice. This persistence in food seeking, as quantified by the time spent in food areas at longer intervals, correlated with the expression of three putative biomarkers of addiction in the nucleus accumbens: fumarate hydratase, ATP synthase subunit alpha and transketolase.
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