Jorge Joven

Abnormalities of Lipoprotein Metabolism in Patients with the Nephrotic Syndrome

BACKGROUND AND METHODS Patients with the nephrotic syndrome characteristically have multiple abnormalities of lipoprotein metabolism, but the cause and exact nature of these abnormalities are uncertain. In this study, we measured serum lipids and apoproteins in 57 patients with the nephrotic syndrome. We also determined the kinetic indexes of low-density lipoprotein (LDL) metabolism in six patients, and again in three of the six after recovery. RESULTS The patients with the nephrotic syndrome had elevated serum concentrations of cholesterol, triglycerides, and phospholipids, which were confined to the lipoproteins containing apoprotein B. The serum concentrations of high-density lipoproteins and the associated A-I and A-II apoproteins were similar in the patients with the nephrotic syndrome and normal subjects. The relative proportions of lipids and their positive association with the increased serum concentrations of apoproteins B, C-II, C-III, and E suggest quantitative rather than qualitative differences in the lipoproteins. All the patients had lipiduria, which probably reflected the excretion of high-density lipoproteins, although no intact immunoreactive apoprotein A-I was found in urine. Serum albumin concentrations were inversely related to serum lipid concentrations in the patients, the severity of the hypoalbuminemia corresponding to the degree of change in serum lipoprotein concentrations. The kinetic studies of lipoprotein metabolism revealed an overproduction of LDL apoprotein B that returned to normal after recovery. CONCLUSIONS The elevated serum concentrations of LDL cholesterol, other lipids, and apoprotein B in patients with uncomplicated nephrotic syndrome are due to reversible increases in lipoprotein production.

The paraoxonases: role in human diseases and methodological difficulties in measurement

Research into the paraoxonase (PON) gene family has flourished over the past few years. In the 1970s and 1980s, only PON1 was known, and the investigations were conducted, essentially, by toxicologists focusing on protection against organophosphate poisoning. Since then, two new members of the family, PON2 and PON3, have been identified, both being shown to play antioxidant and anti-inflammatory roles. Evidence exists indicating that the PON family is central to a wide variety of human illnesses such as cardiovascular disease, diabetes mellitus, metabolic syndrome, obesity, non-alcoholic steatohepatitis, and several mental disorders. However, research is hampered considerably by the methods currently available to measure the activity of these enzymes. In this review, we summarize the state of knowledge on PON biochemistry and function, the influence of genetic variations, and the involvement of PON in several diseases. The problems associated with PON measurement, such as sample acquisition, lack of reference methods, and variety of substrates, will be presented. Also, we cover some of the present lines of research and propose some others for future progress in this field.

Metformin against TGFβ-induced epithelial-to-mesenchymal transition (EMT): from cancer stem cells to aging-associated fibrosis.

Transforming Growth Factor-b (TGFb) is a major driving force of the Epithelial-to-Mesenchymal (EMT) genetic program, which becomes overactive in the pathophysiology of many age-related human diseases. TGFb-driven EMT is sufficient to generate migrating cancer stem cells by directly linking the acquisition of cellular motility with the maintenance of tumor-initiating (stemness) capacity. Chronic diseases exhibiting excessive fibrosis can be caused by repeated and sustained infliction of TGFb-driven EMT, which increases collagen and extracellular matrix synthesis. Pharmacological prevention and/or reversal of TGFb-induced EMT may therefore have important clinical applications in the management of cancer metastasis as well as in the prevention and/or treatment of end-state organ failures. Earlier studies from our group have revealed that clinically-relevant concentrations of the biguanide derivative metformin, the most widely used oral agent to lower blood glucose concentration in patients with type 2 diabetes and metabolic syndrome, notably decreased both the self-renewal and the proliferation of trastuzumab-refractory breast cancer stem cell populations. Given that: a.) tumor-initiating cancer stem cells display a significant enrichment in the expression of basal/mesenchymal or myoepithelial markers, including an increased secretion of TGFb; b.) metformin treatment impedes the ontogeny of generating the stem cell phenotype by transcriptionally repressing key drivers of the EMT genetic program (e.g. ZEB1, TWIST1, SNAIL2 [Slug], TGFbs), we recently hypothesized that prevention of TGFb-induced EMT might represent a common molecular mechanism underlying the anti-cancer stem cells and anti-fibrotic actions of metformin. Remarkably, metformin exposure not only impedes TGFb-promoted loss of the epithelial marker E-cadherin in MCF-7 breast cancer cells but it prevents further TGF-induced cell scattering and accumulation of the mesenchymal marker vimentin in Madin-Darby canine kidney (MDCK) cells. We now propose that metformin, by weakening the ability of TGFb signaling to fully induce mesenchymal cell states in a variety of pathological processes including fibrosis (e.g. chronic renal disease, non-alcoholic steatohepatitis, heart failure or sclerosis) and malignant progression (and likely by reducing TGFb-regulated inflammation and immune responses -inflamm-aging-), molecularly behaves as a bona fide anti-aging modality.

Regulation of Serum Paraoxonase Activity by Genetic, Nutritional, and Lifestyle Factors in the General Population

BACKGROUND Paraoxonase may protect lipoproteins and cell membranes from peroxidation, and alterations in the activity of this enzyme have been associated with some chronic diseases. Serum paraoxonase appears to be mainly under genetic control, but some studies suggest that environmental factors may also modulate its activity. The aim of the present study was to investigate whether diet and lifestyle affect serum paraoxonase activity. METHODS We studied a population-based sample of 388 individuals (194 women and 194 men; age range, 18-75 years) and assessed their daily dietary intake using a 3-day estimated food record. The variables studied included serum paraoxonase activity, paraoxonase polymorphisms at positions 55 and 192, age, gender, smoking status, physical exercise, body mass index, energy consumption, nutrient intake (total lipids, saturated fatty acids, beta-carotenes, vitamins C and E), and serum lipid concentrations. RESULTS Multiple linear regression analysis showed that only genetic polymorphisms, serum cholesterol, HDL-cholesterol concentrations, and cigarette smoking were significant predictors of serum paraoxonase activity. HDL-cholesterol concentrations were also related to body mass index, daily energy consumption, and saturated fatty acid intake. CONCLUSIONS The between-individual variability of serum paraoxonase activity is regulated mainly by genetic determinants. Although HDL-cholesterol and tobacco smoking may contribute to the modulation of this enzyme, the other nutritional and lifestyle factors do not seem to play a significant role.

Immunohistochemical analysis of paraoxonases-1, 2, and 3 expression in normal mouse tissues.

The paraoxonase (PON) enzyme family, comprising PON1, PON2, and PON3, are antioxidant enzymes that degrade oxidised phospholipids. We describe the immunohistochemical localisation of the PON proteins in the normal mouse. Antibodies were obtained by inoculating rabbits with peptides derived from specific sequences of mature PONs. PON1 and PON3 were detected in the skin external epithelium, acini of the sebaceous glands, tongue epithelium, acini of the submandibular gland, surface epithelia of the stomach and the intestine, hepatocytes, exocrine pancreas acini, fibre tracts of the encephalon and the spinal cord, skeletal and cardiac muscle, eye lens epithelium and retinal layers, adipocytes, chondrocytes, epithelial cells of the trachea and bronchiole, ovary follicular fluid, seminiferous tubules, spermatozoa, and kidney proximal tubules. PON2 expression was weaker than that of PON1 and PON3, and was absent in some of the tissues studied, such as submandibular gland, nerve cells, and adipocytes. In muscle cells, PON2 expression was restricted to the endomysium. Apolipoprotein A-I did not colocalise with PONs, suggesting local synthesis. This study provides an experimental model to investigate the role played by these enzymes as antioxidants and their relationship with the development of a variety of diseases.

Association study of schizophrenia with polymorphisms at six candidate genes

Clinical studies have shown that there is a genetic contribution to the pathogenesis of schizophrenia. The molecular mechanisms of effective antipsychotic drugs and recent advances in neural development suggest that several dopamine receptor, serotonin receptor and neurotrophic factor genes might be involved in the disorder. In this study, we assessed the associations between schizophrenia and polymorphisms in the D2 and D3 dopamine receptor (DRD2, DRD3), the serotonin 2A receptor (5HTR2A), the brain-derived neurotrophic factor (BDNF), the ciliary neurotrophic factor (CNTF) and the neurotrophin-3 (NT-3) genes. Our results suggest that the polymorphisms at the DRD3, 5HTR2A, CNTF and BDNF gene loci are unlikely to make our sample more genetically susceptible to schizophrenia. However, we found significant differences in microsatellite allele frequencies between schizophrenic and control groups for DRD2 in the whole sample and for DRD2 and NT-3 only in women. Therefore, clinical differences in the presentation of schizophrenia between gender might be related to genetic factors.

Atherosclerosis in Patients Infected With HIV Is Influenced by a Mutant Monocyte Chemoattractant Protein-1 Allele

Background—Patients infected with HIV present with premature atherosclerosis, and the 2 diseases share common pathogenic pathways. We investigated mutations in the monocyte chemoattractant protein-1 (MCP-1) and CCR-2 genes, which are known to control aspects of these pathways, to ascertain whether they are involved in atherogenesis in these patients. Methods and Results—We performed carotid and femoral artery ultrasonography to detect subclinical atherosclerosis in patients infected with HIV (n=183). MCP-1–2518G and CCR-2 64I polymorphisms were determined in the HIV group and in a population-based control group (n=348). We also determined MCP-1 circulating levels in the HIV group. The presence of MCP-1–2518G in the group of patients with subclinical atherosclerosis was significantly higher than in patients without atherosclerotic lesions (47.5% versus 18.2%, respectively; P<0.001). Furthermore, the patients with atherosclerotic lesions had higher MCP-1 plasma concentrations than did patients without lesions (74.15 [4.03] versus 57.81 [3.67] pg/mL, respectively; P=0.03). When adjusted for known cardiovascular risk factors, the MCP-1–2518G allele was associated with subclinical atherosclerosis (OR 5.72, 95% CI 1.74 to 18.80, P=0.004). Compared with measurements conducted ≈2.5 years earlier in a subset of 40 patients, intima-media thickness (IMT) in the carotid artery progressed at a mean rate of 0.06 mm/y more rapidly in patients bearing the MCP-1–mutated allele (P=0.08). Conclusions—HIV-infected patients with the MCP-1–2518G allele have a 5-fold increased risk for atherosclerosis, as assessed by ultrasonography.

CCL2 Shapes Macrophage Polarization by GM-CSF and M-CSF: Identification of CCL2/CCR2-Dependent Gene Expression Profile

The CCL2 chemokine mediates monocyte egress from bone marrow and recruitment into inflamed tissues through interaction with the CCR2 chemokine receptor, and its expression is upregulated by proinflammatory cytokines. Analysis of the gene expression profile in GM-CSF– and M-CSF–polarized macrophages revealed that a high CCL2 expression characterizes macrophages generated under the influence of M-CSF, whereas CCR2 is expressed only by GM-CSF–polarized macrophages. Analysis of the factors responsible for this differential expression identified activin A as a critical factor controlling the expression of the CCL2/CCR2 pair in macrophages, as activin A increased CCR2 expression but inhibited the acquisition of CCL2 expression by M-CSF–polarized macrophages. CCL2 and CCR2 were found to determine the extent of macrophage polarization because CCL2 enhances the LPS-induced production of IL-10, whereas CCL2 blockade leads to enhanced expression of M1 polarization-associated genes and cytokines, and diminished expression of M2-associated markers in human macrophages. Along the same line, Ccr2-deficient bone marrow–derived murine macrophages displayed an M1-skewed polarization profile at the transcriptomic level and exhibited a significantly higher expression of proinflammatory cytokines (TNF-α, IL-6) in response to LPS. Therefore, the CCL2-CCR2 axis regulates macrophage polarization by influencing the expression of functionally relevant and polarization-associated genes and downmodulating proinflammatory cytokine production.

Metabolomic assessment of the effect of dietary cholesterol in the progressive development of fatty liver disease.

Nonalcoholic fatty liver disease is considered to be the hepatic manifestation of metabolic syndrome and is usually related to high-fat, high-cholesterol diets. With the rationale that the identification and quantification of metabolites in different metabolic pathways may facilitate the discovery of clinically accessible biomarkers, we report the use of (1)H NMR metabolomics for quantitative profiling of liver extracts from LDLr(-/-) mice, a well-documented mouse model of fatty liver disease. A total of 55 metabolites were identified, and multivariate analyses in a diet- and time-comparative strategy were performed. Dietary cholesterol increased the hepatic concentrations of cholesterol, triglycerides, and oleic acid but also decreased the [PUFA/MUFA] ratio as well as the relative amount of long-chain polyunsaturated fatty acids in the liver. This was also accompanied by variations of the hepatic concentration of taurine, glutathione, methionine, and carnitine. Heat-map correlation analyses demonstrated that hepatic inflammation and development of steatosis correlated with cholesterol and triglyceride NMR derived signals, respectively. We conclude that dietary cholesterol is a causal factor in the development of both liver steatosis and hepatic inflammation.

The Warburg effect version 2.0: Metabolic reprogramming of cancer stem cells

When fighting cancer, knowledge on metabolism has always been important. Today, it matters more than ever. The restricted cataloging of cancer genomes is quite unlikely to achieve the task of curing cancer, unless it is integrated into metabolic networks that respond to and influence the constantly evolving cancer stem cell (CSC) cellular states. Once the genomic era of carcinogenesis had pushed the 1920s Otto Warburg’s metabolic cancer hypothesis into obscurity for decades, the most recent studies begin to support a new developing paradigm, in which the molecular logic behind the conversion of non-CSCs into CSCs can be better understood in terms of the “metabolic facilitators” and “metabolic impediments” that operate as proximate openings and roadblocks, respectively, for the transcriptional events and signal transduction programs that ultimately orchestrate the intrinsic and/or microenvironmental paths to CSC cellular states. Here we propose that a profound understanding of how human carcinomas install a proper “Warburg effect version 2.0” allowing them to “run” the CSCs’ “software” programs should guide a new era of metabolo-genomic-personalized cancer medicine. By viewing metabolic reprogramming of CSCs as an essential characteristic that allows dynamic, multidimensional and evolving cancer populations to compete successfully for their expansion on the organism, we now argue that CSCs bioenergetics might be another cancer hallmark. A definitive understanding of metabolic reprogramming in CSCs may complement or to some extent replace, the 30-y-old paradigm of targeting oncogenes to treat human carcinomas, because it can be possible to metabolically create non-permissive or “hostile” metabotypes to prevent the occurrence of CSC cellular states with tumor- and metastasis-initiating capacity.