Altered Lipid Moieties and Carbonyls in a Wistar Rat Dietary Model of Subclinical Fatty Liver: Potential Sex-Specific Biomarkers of Early Fatty Liver Disease?

Non-alcoholic fatty liver disease (NAFLD) is a condition in which excess fat builds up in the liver. To date, there is a lack of knowledge about the subtype of lipid structures affected in the early stages of NAFLD. The aim of this study was to analyze serum and liver lipid moieties, specifically unsaturations and carbonyls, by nuclear magnetic resonance (NMR) in a subclinical Wistar rat model of NAFLD for detecting early alterations and potential sex dimorphisms. Twelve weeks of a high-fat diet (HFD) induced fat accumulation in the liver to a similar extent in male and female Wistar rats. In addition to total liver fat accumulation, Wistar rats showed a shift in lipid subtype composition. HFD rats displayed increased lipid carbonyls in both liver and serum, and decreased in unsaturated fatty acids (UFAs) and polyunsaturated fatty acids (PUFAs), with a much stronger effect in male than female animals. Our results revealed that the change in fat was not only quantitative but also qualitative, with dramatic shifts in relevant lipid structures. Finally, we compared the results found in Wistar rats with an analysis in a human patient cohort of extreme obesity. For the first time to our knowledge, lipid carbonyl levels and lipoproteins profiles were analyzed in the context of subclinical NAFLD. The association found between lipid carbonyls and alanine aminotransferase (ALT) in a human cohort of extremely obese individuals further supports the potential role of lipid moieties as biomarkers of early NAFLD.

Comparison of Protein- or Amino Acid-Based Supplements in the Rehabilitation of Men with Severe Obesity: A Randomized Controlled Pilot Study.

BACKGROUND: Weight loss is associated with a reduction in all body compartments, including muscle mass (MM), and this effect produces a decrease in function and muscle strength. Our objective was to assess the impact of protein or amino acid supplements on MM loss in middle-aged men (age < 65 years) with severe obesity (BMI > 35 kg/m2) during weight loss. MATERIALS AND METHODS: We conducted a single-site randomized controlled trial (Clinicaltrials.gov NCT05143398) with 40 in-patient male subjects with severe obesity. Participants underwent an intervention program consisting of a low-calorie balanced diet and structured physical activity. They were randomly assigned to 4-week treatment groups: (1) control (CTR, N = 10), (2) protein (P, N = 10), (3) branched-chain amino acid (BCAA, N = 10), and (4) essential amino acid mixture with tricarboxylic acid cycle intermediates (PD-E07, N = 10) supplementation. RESULTS: Following 4 weeks of intervention, all groups showed similar reductions in body weight compared to baseline. When examining the delta values, a notable increase in muscle mass (MM) was observed in the PD-E07 intervention group [MM (kg): 2.84 ± 3.57; MM (%): 3.63 ± 3.14], in contrast to the CTR group [MM (kg): -2.46 ± 3.04; MM (%): -0.47 ± 2.28], with a statistical significance of p = 0.045 and p = 0.023, respectively. However, the MM values for the P group [MM (kg): -2.75 ± 5.98, p = 0.734; MM (%): -0.44 ± 4.02, p = 0.990] and the BCAA group [MM (kg): -1 ± 3.3, p = 0.734; MM (%): 0.34 ± 2.85, p = 0.956] did not exhibit a statistically significant difference when compared to the CTR group. CONCLUSIONS: Amino acid-based supplements may effectively mitigate the loss of MM typically observed during weight reduction. Further validation through large-scale studies is necessary.

Sex Dimorphism in the Metabolome of Metabolic Syndrome in Morbidly Obese Individuals.

Adult morbid obesity is defined as abnormal or excessive fat accumulation, mostly resulting from a long-term unhealthy lifestyle. Between 10% and 30% of people with obesity exhibit low cardiometabolic risk. The metabolic syndrome has been suggested as an indicator of obesity-related metabolic dysregulation. Although the prevalence of obesity does not seem to be sex-related and metabolic syndrome occurs at all ages, in the last few years, sex-specific differences in the pathophysiology, diagnosis, and treatment of metabolic syndrome have received attention. The aim of this study was to determine the prevalence of metabolic syndrome and its components in different sex and age groups in people with metabolic unhealthy obesity and to compare them with people with metabolic healthy obesity. We analyzed the metabolome in 1350 well-phenotyped morbidly obese individuals and showed that there is a strong sex-dependent association of metabolic syndrome with circulating metabolites. Importantly, we demonstrated that metabolic dysregulation in women and men with severe obesity and metabolic syndrome is age-dependent. The metabolic profiles from our study showed age-dependent sex differences in the impact of MetS which are consistent with the cardiometabolic characterization. Although there is common ground for MetS in the metabolome of severe obesity, men older than 54 are affected in a more extensive and intensive manner. These findings strongly argue for more studies aimed at unraveling the mechanisms that underlie this sex-specific metabolic dysregulation in severe obesity. Moreover, these findings suggest that women and men might benefit from differential sex and age specific interventions to prevent the adverse cardiometabolic effects of severe obesity.

A High Protein Diet Is More Effective in Improving Insulin Resistance and Glycemic Variability Compared to a Mediterranean Diet-A Cross-Over Controlled Inpatient Dietary Study.

The optimal dietary pattern to improve metabolic function remains elusive. In a 21-day randomized controlled inpatient crossover feeding trial of 20 insulin-resistant obese women, we assessed the extent to which two isocaloric dietary interventions-Mediterranean (M) and high protein (HP)-improved metabolic parameters. Obese women were assigned to one of the following dietary sequences: M-HP or HP-M. Cardiometabolic parameters, body weight, glucose monitoring and gut microbiome composition were assessed. Sixteen women completed the study. Compared to the M diet, the HP diet was more effective in (i) reducing insulin resistance (insulin: Beta (95% CI) = -6.98 (-12.30, -1.65) µIU/mL, p = 0.01; HOMA-IR: -1.78 (95% CI: -3.03, -0.52), p = 9 × 10-3); and (ii) improving glycemic variability (-3.13 (-4.60, -1.67) mg/dL, p = 4 × 10-4), a risk factor for T2D development. We then identified a panel of 10 microbial genera predictive of the difference in glycemic variability between the two diets. These include the genera Coprococcus and Lachnoclostridium, previously associated with glucose homeostasis and insulin resistance. Our results suggest that morbidly obese women with insulin resistance can achieve better control of insulin resistance and glycemic variability on a high HP diet compared to an M diet.

Plasma Oxytocin Concentration in Pre- and Postmenopausal Women: Its Relationship with Obesity, Body Composition and Metabolic Variables.

OBJECTIVE: To investigate the relationship between oxytocin, menopause and obesity. METHODS: A cross-sectional analysis on 56 obese (OB; 28 premenopausal) and 53 normal-weight women (NW; 27 premenopausal) was performed by measurement of oxytocin, leptin, adiponectin, gonadotropins, sex steroids, glucose, and lipid homeostasis as well as DXA assessment of fat mass (%FM) and fat-free mass (FFM). RESULTS: Women from NW and OB groups were comparable for age but differed in anthropometric measures. In our cohorts, menopause was not associated with changes in gluco-lipid homeostasis and %FM, while FFM was lower in postmenopausal women from both study groups (p < 0.05). In each group, leptin was unaltered, and adiponectin only marginally changed across menopause, while oxytocin levels were lower in post- than in premenopausal women (NW: p < 0.05; OB: p < 0.005), and lower in OB than NW women, either when assessed as whole groups or if stratified by menopause (p < 0.001). In correlation analysis, inverse associations related oxytocin to menopause, obesity, and adiposity-related measures. BMI (p < 0.0001) and menopause independently predicted oxytocin levels (p < 0.001), but their interaction was null (p = 0.5). CONCLUSIONS: Obesity and menopause are independent negative predictors of plasma oxytocin. Longitudinal studies should clarify the role of oxytocin on weight modifications experienced around and after menopause.

Autoimmune pituitary involvement in Prader-Willi syndrome: new perspective for further research.

The role of antipituitary antibodies in the pathophysiology of pituitary hormone deficiency has been increasingly elucidated over the last decade. Prader-Willi syndrome is a genetic disorder which includes hypothalamic/pituitary dysfunction as one of its main features. We looked for autoimmune pituitary involvement in 55 adults with Prader-Willi syndrome, discovering that about 30% of them have a positive titer of antipituitary antibodies. Although the presence of these autoantibodies could only be an "epiphenomenon", our results suggest that autoimmune mechanisms might contribute, at least in part, to the pituitary impairment of Prader-Willi syndrome, and in addition to genetically determined dysfunction of the central nervous system. This paper provides a new perspective on pituitary impairment in these patients, suggesting that the search for hypophisitis could be a reasonable and interesting field for further research.

Vascular Dynamics and Peripheral Oxygen Uptake in Obese Individuals during Progressive Physical Exercise.

BACKGROUND: Obese men show higher O2 consumption than lean men during physical exercise, with a trend toward higher peripheral O2 extraction; this is probably due to their larger muscle mass. OBJECTIVES: The aim of this study was to examine this phenomenon by measuring 2 vasoactive substances, endothelin-1 (ET-1) and nitric oxide (NO), during a progressive submaximal exercise. METHODS: Seventeen obese (body mass index [BMI] 38.6) and 15 lean (BMI 22.5) men performed a maximal progressive cycle ergometer exercise to determine peak power output (PPO) and peak O2 consumption (V∙O2peak); thereafter, they performed a submaximal cycle ergometer incremental test (every 6 min) at the same percentage of V∙O2peak until they reached 57.5% PPO. Blood samples were collected at rest and at the end of every step to measure ET-1 and NO concentrations. RESULTS: At rest, the ET-1 and NO concentrations in obese men and lean controls were the same. However, during exercise, the ET-1 concentration at each step was significantly lower (p < 0.05) in the obese group. There was no significant difference in NO concentration between the 2 groups, although the increase at the beginning of the exercise session was faster in obese individuals. During submaximal exercise, end-tidal O2 pressure (PETO2) was lower in the obese group, with a significant difference in the PETO2/fat-free mass ratio at each step. CONCLUSIONS: ET-1 and NO levels during physical exercise are different in obese versus lean men. This may support the notion that increased O2 consumption in obesity is due to different behaviors of the cardiorespiratory and circulatory systems.

Short-term HIIT and Fat max training increase aerobic and metabolic fitness in men with class II and III obesity.

OBJECTIVE: To compare the effects of two different 2-week-long training modalities [continuous at the intensity eliciting the maximal fat oxidation (Fatmax) versus high-intensity interval training (HIIT)] in men with class II and III obesity. METHODS: Nineteen men with obesity (BMI ≥ 35 kg · m(-2)) were assigned to Fatmax group (GFatmax) or to HIIT group (GHIIT). Both groups performed eight cycling sessions matched for mechanical work. Aerobic fitness and fat oxidation rates (FORs) during exercise were assessed prior and following the training. Blood samples were drawn to determine hormones and plasma metabolites levels. Insulin resistance was assessed by the homeostasis model assessment of insulin resistance (HOMA2-IR). RESULTS: Aerobic fitness and FORs during exercise were significantly increased in both groups after training (P ≤ 0.001). HOMA2-IR was significantly reduced only for GFatmax (P ≤ 0.001). Resting non-esterified fatty acids (NEFA) and insulin decreased significantly only in GFatmax (P ≤ 0.002). CONCLUSIONS: Two weeks of HIIT and Fatmax training are effective for the improvement of aerobic fitness and FORs during exercise in these classes of obesity. The decreased levels of resting NEFA only in GFatmax may be involved in the decreased insulin resistance only in this group.

Long maximal incremental tests accurately assess aerobic fitness in class II and III obese men.

This study aimed to compare two different maximal incremental tests with different time durations [a maximal incremental ramp test with a short time duration (8-12 min) (STest) and a maximal incremental test with a longer time duration (20-25 min) (LTest)] to investigate whether an LTest accurately assesses aerobic fitness in class II and III obese men. Twenty obese men (BMI≥35 kg.m-2) without secondary pathologies (mean±SE; 36.7±1.9 yr; 41.8±0.7 kg*m-2) completed an STest (warm-up: 40 W; increment: 20 W*min-1) and an LTest [warm-up: 20% of the peak power output (PPO) reached during the STest; increment: 10% PPO every 5 min until 70% PPO was reached or until the respiratory exchange ratio reached 1.0, followed by 15 W.min-1 until exhaustion] on a cycle-ergometer to assess the peak oxygen uptake [Formula: see text] and peak heart rate (HRpeak) of each test. There were no significant differences in [Formula: see text] (STest: 3.1±0.1 L*min-1; LTest: 3.0±0.1 L*min-1) and HRpeak (STest: 174±4 bpm; LTest: 173±4 bpm) between the two tests. Bland-Altman plot analyses showed good agreement and Pearson product-moment and intra-class correlation coefficients showed a strong correlation between [Formula: see text] (r=0.81 for both; p≤0.001) and HRpeak (r=0.95 for both; p≤0.001) during both tests. [Formula: see text] and HRpeak assessments were not compromised by test duration in class II and III obese men. Therefore, we suggest that the LTest is a feasible test that accurately assesses aerobic fitness and may allow for the exercise intensity prescription and individualization that will lead to improved therapeutic approaches in treating obesity and severe obesity.

Fat oxidation, hormonal and plasma metabolite kinetics during a submaximal incremental test in lean and obese adults.

This study aimed to compare fat oxidation, hormonal and plasma metabolite kinetics during exercise in lean (L) and obese (O) men. Sixteen L and 16 O men [Body Mass Index (BMI): 22.9 ± 0.3 and 39.0 ± 1.4 kg · m(-2)] performed a submaximal incremental test (Incr) on a cycle-ergometer. Fat oxidation rates (FORs) were determined using indirect calorimetry. A sinusoidal model, including 3 independent variables (dilatation, symmetry, translation), was used to describe fat oxidation kinetics and determine the intensity (Fat(max)) eliciting maximal fat oxidation. Blood samples were drawn for the hormonal and plasma metabolite determination at each step of Incr. FORs (mg · FFM(-1) · min(-1)) were significantly higher from 20 to 30% of peak oxygen uptake (VO2peak) in O than in L and from 65 to 85% VO2peak in L than in O (p ≤ 0.05). FORs were similar in O and in L from 35 to 60% VO2peak. Fat max was 17% significantly lower in O than in L (p<0.01). Fat oxidation kinetics were characterized by similar translation, significantly lower dilatation and left-shift symmetry in O compared with L (p<0.05). During whole exercise, a blunted lipolysis was found in O [lower glycerol/fat mass (FM) in O than in L (p ≤ 0.001)], likely associated with higher insulin concentrations in O than in L (p<0.01). Non-esterified fatty acids (NEFA) were significantly higher in O compared with L (p<0.05). Despite the blunted lipolysis, O presented higher NEFA availability, likely due to larger amounts of FM. Therefore, a lower Fat(max), a left-shifted and less dilated curve and a lower reliance on fat oxidation at high exercise intensities suggest that the difference in the fat oxidation kinetics is likely linked to impaired muscular capacity to oxidize NEFA in O. These results may have important implications for the appropriate exercise intensity prescription in training programs designed to optimize fat oxidation in O.

Novel PTRF mutation in a child with mild myopathy and very mild congenital lipodystrophy.

BACKGROUND: Mutations in the PTRF gene, coding for cavin-1, cause congenital generalized lipodystrophy type 4 (CGL4) associated with myopathy. In CGL4, symptoms are variable comprising, in addition to myopathy, smooth and skeletal muscle hypertrophy, cardiac arrhythmias, and skeletal abnormalities. Secondary features are atlantoaxial instability, acanthosis nigricans, hepatomegaly, umbilical prominence and metabolic abnormalities related to insulin resistance, such as diabetes mellitus, hyperlipidemia and hepatic steatosis. CASE PRESENTATION: We describe a 3 year-old child of Moroccan origin with mild muscle phenotype, mainly characterized by mounding, muscle pain, hyperCKemia and mild caveolin 3 reduction on muscle biopsy. No CAV3 gene mutation was detected; instead we found a novel mutation, a homozygous single base pair deletion, in the PTRF gene. Only after detection of this mutation a mild generalized loss of subcutaneous fat, at first underestimated, was noticed and the diagnosis of lipodystrophy inferred. CONCLUSIONS: The PTRF gene should be investigated in patients with hyperCKemia, mild myopathy associated with spontaneous or percussion-induced muscle contractions like rippling or mounding, and no CAV3 mutation. The analysis should be performed even if cardiac or metabolic alterations are absent, particularly in young patients in whom lipodystrophy may be difficult to ascertain.

Molecular and morphologic characterization of superficial- and deep-subcutaneous adipose tissue subdivisions in human obesity.

OBJECTIVE: Human abdominal subcutaneous white adipose tissue (SAT) is composed of two different subcompartments: a "superficial" SAT (SSAT), located between the skin and a fibrous-fascia plane; and a deeper SAT, located under this fibrous fascia plane, indicated as "deep" SAT (DSAT). DESIGN AND METHODS: In order to investigate whether SSAT and DSAT have different molecular and morphological features, paired SSAT/DSAT biopsies were collected from 10 female obese patients and used for microarray and morphologic analysis. The stroma-vascular fraction cells were also isolated from both depots and cultured in vitro to assess the lipid accumulation rate. RESULTS: SSAT and DSAT displayed different patterns of gene expression, mainly for metabolic and inflammatory genes, respectively. Detailed gene expression analysis indicated that several metabolic genes, including adiponectin, are preferentially expressed in SSAT, whereas inflammatory genes are over-expressed in DSAT. Despite a similar lipid accumulation rate in vitro, in vivo SSAT showed a significant adipocyte hypertrophy together with a significantly lower inflammatory infiltration and vascular vessel lumen mean size, when compared to DSAT. CONCLUSIONS: These data show that, SSAT and DSAT are functionally and morphologically different and emphasize the importance of considering independent these two adipose depots when investigating SAT biology and obesity complications.

Serum adiponectin levels in advanced-stage Parkinson's disease patients.

Patients with advanced Parkinson's disease (PD) experience body weight loss and reductions in the most common cardiovascular risk factors. At present, the pathogenetic mechanisms involved have not been elucidated. Increased serum concentrations of adiponectin, which possesses antiatherogenic and anti-inflammatory properties, are associated with a reduction in cardiovascular risk. The objective of this study was to determine adiponectin serum concentrations in PD patients. Thirty PD patients underwent a full nutritional status assessment, including the determination of adiponectin serum concentrations. Mean ± SD adiponectin concentrations were 9.59 ± 5.9 µg/mL (interquartile range: 5.92-12.9 µg/mL). In PD patients, adiponectin serum levels were similar to those in normal-weight, healthy, young subjects and significantly higher than that in an aged-matched group of morbidly obese subjects. Further studies are warranted to establish the role of adiponectin in the management of PD patients.

Rare melanocortin-3 receptor mutations with in vitro functional consequences are associated with human obesity.

In contrast to the melanocortin 4 receptor, the possible role of the melanocortin 3 receptor (MC3R) in regulating body weight is still debated. We have previously reported three mutations in the MC3R gene showing association with human obesity, but these results were not confirmed in a study of severe obese North American adults. In this study, we evaluated the entire coding region of MC3R in 839 severely obese subjects and 967 lean controls of Italian and French origin. In vitro functional analysis of the mutations detected was also performed. The total prevalence of rare MC3R variants was not significantly different in obese subjects when compared with controls (P= 0.18). However, the prevalence of mutations with functional alterations was significantly higher in the obese group (P= 0.022). In conclusions, the results of this large study demonstrate that in the populations studied functionally significant MC3R variants are associated with obesity supporting the current hypothesis that rare variants might have a stronger impact on the individual susceptibility to gain weight. They also underline the importance of detailed in vitro functional studies in order to prove the pathogenic effect of such variants. Further investigations in larger cohorts will be needed in order to define the specific phenotypic characteristics potentially correlated with reduced MC3R signalling.

Sporadic mutations in melanocortin receptor 3 in morbid obese individuals.

Several mutations in the melanocortin receptor 4 gene have been identified in humans and account for 3-6% of morbid obesity. In contrast, strong evidence of a causative role for melanocortin receptor 3 (MC3R) mutations are still lacking. In MC3R knockout mice, high feed efficiency rather than hyperphagia seems to contribute to increased fat mass. On the basis of this evidence, the objective of the present study was to investigate the presence of MC3R mutations in a group of 290 obese subjects (mean BMI 44.2+/-5.9 kg/m2). As a control, a group of 215 normal-weight subjects (mean BMI 22.4+/-2.7 kg/m2) was also screened. Three novel mutations in the MC3R gene (A293T, I335S and X361S) were identified among the obese patients. The mutations segregated with obesity in the members of the families studied. In vitro expression studies of each mutation demonstrated a loss of function of the I335S-mutated receptor. These findings suggest that, in humans, MC3R mutations may be a cause of a dominantly inherited form of obesity. However, this association as well as the specific phenotypic characteristics resulting from these mutations need to be further evaluated in larger series of obese subjects.

Subcutaneous abdominal adipose tissue subcompartments: potential role in rosiglitazone effects.

Abdominal visceral tissue (VAT) and subcutaneous adipose tissue (SAT), comprised of superficial-SAT (sSAT) and deep-SAT (dSAT), are metabolically distinct. The antidiabetic agents thiazolidinediones (TZDs), in addition to their insulin-sensitizing effects, redistribute SAT suggesting that TZD action involves adipose tissue depot-specific regulation. We investigated the expression of proteins key to adipocyte metabolism on differentiated first passage (P1) preadipocytes treated with rosiglitazone, to establish a role for the diverse depots of abdominal adipose tissue in the insulin-sensitizing effects of TZDs. Adipocytes and preadipocytes were isolated from sSAT, dSAT, and VAT samples obtained from eight normal subjects. Preadipocytes (P1) left untreated (U) or treated with a classic differentiation cocktail (DI) including rosiglitazone (DIR) for 9 days were evaluated for strata-specific differences in differentiation including peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and lipoprotein lipase (LPL) expression, insulin sensitivity via adiponectin and glucose transport-4 (GLUT4), glucocorticoid metabolism with 11 beta-hydroxysteroid dehydrogenase type-1 (11 beta HSD1), and alterations in the adipokine leptin. While depot-specific differences were absent with the classic differentiation cocktail, with rosiglitazone sSAT had the most potent response followed by dSAT, whereas VAT was resistant to differentiation. With rosiglitazone, universal strata effects were observed for PPAR-gamma, LPL, and leptin, with VAT in all cases expressing significantly lower basal expression levels. Clear dSAT-specific changes were observed with decreased intracellular GLUT4. Specific sSAT alterations included decreased 11 beta HSD1 whereas secreted adiponectin was potently upregulated in sSAT with respect to dSAT and VAT. Overall, the subcompartments of SAT, sSAT, and dSAT, appear to participate in the metabolic changes that arise with rosiglitazone administration.

The relation between two polymorphisms in the glucocorticoid receptor gene and body mass index, blood pressure and cholesterol in obese patients.

OBJECTIVE: We have recently reported that, in healthy elderly Dutch individuals, a N363S polymorphism in the glucocorticoid receptor (GR) gene is associated with higher sensitivity to low-dose dexamethasone (0.25 mg), evaluated as both cortisol suppression and insulin response, and with an increased body mass index (BMI). In the present study we investigated the role of the N363S polymorphism, and a BclI restriction site polymorphism in a group of Italian patients with severe obesity. DESIGN: Two hundred and seventy-nine patients (mean BMI 45.9 +/- 0.9 kg/m2) were genotyped using both PCR-restriction fragment length polymorphism analysis and Taqman Sequence Detection System. Determination of several metabolic and antropometric parameters was also performed in order to correlate them to the genotype. RESULTS: In this group of obese patients, 13 subjects (eight female, five males) were heterozygous for the N363S variant (allelic frequency 2.3%) and had significantly higher BMI (P < 0.04), resting energy expenditure (P < 0.03) and food intake (P < 0.01) when compared to wild-type homozygotes. When the data were analysed according to sex, female heterozygotes for the N363S allele had significantly higher BMI (P = 0.04), resting energy expenditure (P = 0.03) and food intake (P = 0.008) than obese women with the wild-type 363 GR gene. Male carriers of this variant also had higher values for these variables although the differences did not reach statistical significance. A case-control study with homozygous wild-type obese subjects which were age-, sex- and BMI-matched, revealed no difference in resting energy expenditure and food intake. The allele frequency of the BclI variant was 27% (89 females and 41 males out of 269 subjects). No differences in anthropometric and metabolic parameters were found between subjects heterozygous or homozygous for this variant GR in this obese population. However, when we studied the effect of the presence of the BclI polymorphism and the N363S variant in the same individual, we found that the subjects who carried both polymorphisms had a tendency towards higher systolic and diastolic blood pressure and significantly higher total and LDL-cholesterol levels (P = 0.005 and P = 0.05, respectively). DISCUSSION: Taking the results of this study and those obtained in the Dutch population, we speculate that heterozygous carriers of the N363S variant who develop obesity, may become even more obese, possibly because they have a hypersensitive insulin response and thus, via activation of lipogenesis, store fat more efficiently. Furthermore, these data suggest that N363S carriers who carry the BclI polymorphism as well, tend to have a slightly unfavourable cardiovascular profile.

GLUT-1 overexpression: Link between hemodynamic and metabolic factors in glomerular injury?

Mesangial matrix deposition is the hallmark of hypertensive and diabetic glomerulopathy. At similar levels of systemic hypertension, Dahl salt-sensitive but not spontaneously hypertensive rats (SHR) develop glomerular hypertension, which is accompanied by upregulation of transforming growth factor beta1 (TGF-beta1), mesangial matrix expansion, and sclerosis. GLUT-1 is ubiquitously expressed and is the predominant glucose transporter in mesangial cells. In mesangial cells in vitro, GLUT-1 overexpression increases basal glucose transport, resulting in excess fibronectin and collagen production. TGF-beta1 has been shown to upregulate GLUT-1 expression. We demonstrated that in hypertensive Dahl salt-sensitive (S) rats fed 4% NaCl (systolic blood pressure [SBP]: 236+/-9 mm Hg), but not in similarly hypertensive SHR (SBP: 230+/-10 mm Hg) or their normotensive counterparts (Dahl S fed 0.5% NaCl, SBP: 145+/-5 mm Hg; and Wistar-Kyoto, SBP: 137+/-3 mm Hg), there was an 80% upregulation of glomerular GLUT-1 protein expression (P< or =0.03). This was accompanied by a 2.7-fold upregulation of TGF-beta1 protein expression in glomeruli of DSH compared with DSN rats (P=0.02). TGF-beta1 expression was not upregulated and did not differ in the glomeruli of Wistar-Kyoto and SHR rats. As an in vitro surrogate of the in vivo hemodynamic stress imposed by glomerular hypertension, we used mechanical stretching of human and rat mesangial cells. We found that after 33 hours of stretching, mesangial cells overexpressed GLUT-1 (40%) and showed an increase in basal glucose transport of similar magnitude (both P< or =0.01), which could be blocked with an anti TGF-beta1-neutralizing antibody. These studies suggest a novel link between hemodynamic and metabolic factors that may cooperate in inducing progressive glomerular injury in conditions characterized by glomerular hypertension.