Sphingolipid Profiling Reveals Different Extent of Ceramide Accumulation in Bovine Retroperitoneal and Subcutaneous Adipose Tissues

Sphingolipids are bioactive lipids that can modulate insulin sensitivity, cellular differentiation, and apoptosis in a tissue-specific manner. However, their comparative profiles in bovine retroperitoneal (RPAT) and subcutaneous adipose tissue (SCAT) are currently unknown. We aimed to characterize the sphingolipid profiles using a targeted lipidomics approach and to assess whether potentially related sphingolipid pathways are different between SCAT and RPAT. Holstein bulls (n = 6) were slaughtered, and SCAT and RPAT samples were collected for sphingolipid profiling. A total of 70 sphingolipid species were detected and quantified by UPLC-MS/MS in multiple reaction monitoring (MRM) mode, including ceramide (Cer), dihydroceramide (DHCer), sphingomyelin (SM), dihydrosphingomyelin (DHSM), ceramide-1-phosphate (C1P), sphingosine-1-phosphate (S1P), galactosylceramide (GalCer), glucosylceramide (GluCer), lactosylceramide (LacCer), sphinganine (DHSph), and sphingosine (Sph). Our results showed that sphingolipids of the de novo synthesis pathway, such as DHSph, DHCer, and Cer, were more concentrated in RPAT than in SCAT. Sphingolipids of the salvage pathway and the sphingomyelinase pathway, such as Sph, S1P, C1P, glycosphingolipid, and SM, were more concentrated in SCAT. Our results indicate that RPAT had a greater extent of ceramide accumulation, thereby increasing the concentration of further sphingolipid intermediates in the de novo synthesis pathway. This distinctive sphingolipid distribution pattern in RPAT and SCAT can potentially explain the tissue-specific activity in insulin sensitivity, proinflammation, and oxidative stress in RPAT and SCAT.

Ovariectomy modifies lipid metabolism of retroperitoneal white fat in rats: a proteomic approach

Menopause is often accompanied by visceral obesity. With the aim of exploring the consequences of ovarian failure on visceral fat, we evaluated the effects of ovariectomy and estrogen replacement on the proteome/phosphoproteome and on the fatty acid profile of the retroperitoneal adipose depot (RAT) of rats. Eighteen 3-mo-old female Wistar rats were either ovariectomized or sham operated and fed with standard chow for 3 mo. A subgroup of ovariectomized rats received estradiol replacement. RAT samples were analyzed with data-independent acquisitions LC-MS/MS, and pathway analysis was performed with the differentially expressed/phosphorylated proteins. RAT lipid profile was analyzed by gas chromatography. Ovariectomy induced high adiposity and insulin resistance and promoted alterations in protein expression and phosphorylation. Pathway analysis showed that five pathways were significantly affected by ovariectomy, namely, metabolism of lipids (including fatty acid metabolism and mitochondrial fatty acid β-oxidation), fatty acyl-CoA biosynthesis, innate immune system (including neutrophil degranulation), metabolism of vitamins and cofactors, and integration of energy metabolism (including ChREBP activates metabolic gene expression). Lipid profile analysis showed increased palmitic and palmitoleic acid content. The analysis of the data indicated that ovariectomy favored lipogenesis whereas it impaired fatty acid oxidation and induced a proinflammatory state in the visceral adipose tissue. These effects are consistent with the findings of high adiposity, hyperleptinemia, and impaired insulin sensitivity. The observed alterations were partially attenuated by estradiol replacement. The data point to a role of disrupted lipid metabolism in adipose tissue in the genesis of obesity after menopause.

Insulin signaling and insulin response in subcutaneous and retroperitoneal adipose tissue in Holstein cows during the periparturient period

Adipose tissue response to endocrine stimuli, such as insulin, is crucial for metabolic adaptation at the onset of lactation in dairy cows. However, the exact molecular mechanisms behind this response are not well understood. Thus, the aim of this study was to determine the dynamics in protein expression and phosphorylation of key components in insulin signaling in subcutaneous (SCAT) and retroperitoneal (RPAT) adipose tissues of Holstein dairy cows. Furthermore, by ex vivo examinations, response to insulin was assessed in SCAT and RPAT at different time points during the periparturient period. Biopsy samples were taken 42 d prepartum, and 1, 21, and 100 d postpartum. Insulin and glucose concentrations were measured in blood serum in consecutive serum samples from d -42 until d +100. After parturition, the majority of the key components were downregulated in both adipose tissues but recovered by d +100. The extent of hormone-sensitive lipase phosphorylation increased postpartum and remained high throughout the experimental period. Strong differences in molecular response were observed between the 2 depots. The RPAT expressed a remarkably greater extent of AMP-activated kinase phosphorylation compared with SCAT, indicating that AMP-activated kinase as an energy sensor is highly active particularly in RPAT in times of energy scarcity. Consequently, this depot expressed a greater extent of hormone-sensitive lipase phosphorylation over the whole experimental period. Insulin response after parturition appeared to be greater in RPAT too, due to the significantly greater expression of the insulin receptor at d +21 and +100. Although insulin concentrations in plasma were low postpartum, the depot-specific changes in molecular modulation of insulin signaling and insulin response suggested that both adipose tissue depots studied were contributing to the periparturient homeorhetic adaptation, although most likely to a different extent.

Ginkgo biloba Extract Modulates the Retroperitoneal Fat Depot Proteome and Reduces Oxidative Stress in Diet-Induced Obese Rats

The rapid increase in the number of individuals with obesity, over the past four decades, is triggered by a number of complex interactions among factors. Despite the plethora of treatments available, side effects are commonly observed and, in this context, herbal medicines have been employed as an alternative form of therapy. Ginkgo biloba extract (GbE) has been described as a promising new pharmacological approach to treat obesity. In order to better comprehend the mechanisms involved with this potential effect, the present study evaluated the effects of GbE treatment on diet-induced obese rats, focusing on the proteome and the oxidative stress defense system of visceral adipose tissue. After 14 days treatment, GbE significantly modulated 25 proteins. Retroperitoneal adipose tissue of treated animals exhibited higher amounts of proteins associated with adipogenesis (decorin), carbon metabolism and mitochondrial function (citrate synthase), and a concomitant reduction in adipocyte hypertrophy. In parallel, GbE down-regulated proteins involved in oxidative stress (peroxiredoxin) and the inflammatory response (complement C3, mast cell protease 1, and Ig gamma-2B chain C region). Moreover, also related to oxidative stress defense, GbE stimulated catalase activity, reduced malondialdehyde levels (lipid peroxidation indicator), and increased lactoylglutathione lyase levels. It was concluded that GbE acts as an antioxidant agent, and improved the proteome profile and oxidative stress response in the adipose tissue of diet-induced obese rats.

Metachronous metastasis to contralateral retroperitoneal adipose tissue after radical nephrectomy: a case report and review of the literature

Renal cell carcinoma (RCC) metastasis to the adrenal gland, perirenal adipose tissue, and ureter on the contralateral side is rare. We report a case of solitary metachronous clear cell renal cell carcinoma (ccRCC) metastasis to the contralateral retroperitoneal adipose tissue, which was identified after radical nephrectomy. A patient had undergone retroperitoneal laparoscopic radical nephrectomy for RCC in the right kidney in December 2012. Postoperative pathological analysis showed Fuhrman grade I ccRCC, T_1bN₀M₀. Three years after surgery, a solitary tumor of 1.0 × 1.0 cm was identified by an abdominal computed tomographic scan inside the retroperitoneal fat pad in front of the left posterior abdominal wall, without adhesion to the abdominal wall. The tumor was then completely resected by retroperitoneal laparoscopic resection. Pathological analysis showed that it was a metastasized lesion from a previous tumor. Nine months after surgery, there was no sign of recurrence confirmed by radiographic follow-up. Findings from this case indicate the unpredictability of dissemination of RCC. Our findings support a follow-up regimen that includes regular postoperative computed tomographic scans to identify early metastasis. To the best of our knowledge, this is the first reported case of contralateral retroperitoneal adipose metastasis after laparoscopic tumorectomy.

Relationship between the Balance of Hypertrophic/Hyperplastic Adipose Tissue Expansion and the Metabolic Profile in a High Glucocorticoids Model

Adipose tissue (AT) expansion is the result of two processes: hyperplasia and hypertrophy; and both, directly or indirectly, depend on the adipogenic potential of adipocyte precursor cells (APCs). Glucocorticoids (GCs) have a potent stimulatory effect on terminal adipogenesis; while their effects on early stages of adipogenesis are largely unknown. In the present work, we study, in a model of high GC levels, the adipogenic potential of APCs from retroperitoneal AT (RPAT) and its relationship with RPAT mass expansion. We employed a model of hyper-adiposity (30- and 60-day-old rats) due to high endogenous GC levels induced by neonatal treatment with l-monosodium glutamate (MSG). We found that the RPAT APCs from 30-day-old MSG rats showed an increased adipogenic capacity, depending on the APCs’ competency, but not in their number. Analyses of RPAT adipocyte diameter revealed an increase in cell size, regardless of the rat age, indicating the prevalence of a hypertrophic process. Moreover, functional RPAT alterations worsened in 60-day-old rats, suggesting that the hyperplastic AT expansion found in 30-day-old animals might have a protective role. We conclude that GCs chronic excess affects APCs’ adipogenic capacity, modifying their competency. This change would modulate the hyperplastic/hypertrophic balance determining healthy or unhealthy RPAT expansion and, therefore, its functionality.

Long-Term Fructose Intake Increases Adipogenic Potential: Evidence of Direct Effects of Fructose on Adipocyte Precursor Cells

We have previously addressed that fructose rich diet (FRD) intake for three weeks increases the adipogenic potential of stromal vascular fraction cells from the retroperitoneal adipose tissue (RPAT). We have now evaluated the effect of prolonged FRD intake (eight weeks) on metabolic parameters, number of adipocyte precursor cells (APCs) and in vitro adipogenic potential from control (CTR) and FRD adult male rats. Additionally, we have examined the direct fructose effects on the adipogenic capacity of normal APCs. FRD fed rats had increased plasma levels of insulin, triglyceride and leptin, and RPAT mass and adipocyte size. FACS studies showed higher APCs number and adipogenic potential in FRD RPAT pads; data is supported by high mRNA levels of competency markers: PPARγ2 and Zfp423. Complementary in vitro experiments indicate that fructose-exposed normal APCs displayed an overall increased adipogenic capacity. We conclude that the RPAT mass expansion observed in eight week-FRD fed rats depends on combined accelerated adipogenesis and adipocyte hypertrophy, partially due to a direct effect of fructose on APCs.

Examining the aetiopathogenesis of varicoceles: the relationship between retroperitoneal adipose tissue and testicular venous drainage

This study evaluated the effect of retroperitoneal adipose tissue on testicular venous drainage and tested the nutcracker phenomenon by clinical and imaging findings. A total of 95 patients were included. The patients were evaluated with a detailed medical history and physical examination for varicocele. Their weight, height and waist circumference were also recorded. Body mass index was calculated as weight (kg)/height squared (m(2) ). Pampiniform plexus diameters were measured by scrotal colour Doppler ultrasonography, and retroperitoneal adipose tissue was evaluated by noncontrast abdominal computed tomography. We determined an almost significant correlation between BMI and varicocele presence by physical examination (P = 0.06). However, there was a significant relationship between WC and varicocele identified by physical examination (P = 0.021). There was a positive and significant relationship between BMI and pampiniform plexus diameters. Furthermore, we detected a negative correlation between retroperitoneal adipose tissue measurements and CDU findings. Additionally, there was a significant correlation between WC, pampiniform plexus diameters and CT findings. It is concluded that increasing BMI and increasing WC may play a protective role in the development of varicocele. There is a need for further studies to verify the effect of obesity on varicocele formation.

Insulin resistance, hepatic lipid and adipose tissue distribution in HIV-infected men

BACKGROUND

A large proportion of HIV-infected patients on antiretroviral medication develop insulin resistance, especially in the context of fat redistribution. This study investigates the interrelationships among fat distribution, hepatic lipid content, and insulin resistance in HIV-infected men.

METHODS

We performed a cross-sectional analysis of baseline data from 23 HIV-infected participants in three prospective clinical studies. Magnetic resonance spectroscopy was used to quantify hepatic lipid concentrations. Magnetic resonance imaging was used to quantify whole-body adipose tissue compartments: that is, subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) volumes, as well as the intermuscular adipose tissue (IMAT) subcompartment and the omental-mesenteric adipose tissue (OMAT) and retroperitoneal adipose tissue (RPAT) subcompartments of VAT. The homeostasis model for assessment of insulin resistance (HOMA-IR) was calculated from fasting glucose and insulin concentrations.

RESULTS

Hepatic lipid content correlated significantly with total VAT (r = 0.62, P = 0.0014), but not with SAT (r = 0.053, P = 0.81). In univariate analysis, hepatic lipid content was associated with the OMAT (r = 0.67, P = 0.0004) and RPAT (r = 0.53, P = 0.009) subcompartments; HOMA-IR correlated with both VAT and hepatic lipid contents (r = 0.61, P = 0.057 and r = 0.68, P = 0.0012, respectively). In stepwise linear regression models, hepatic lipid had the strongest associations with OMAT and with HOMA-IR.

CONCLUSION

Hepatic lipid content is associated with VAT volume, especially the OMAT subcompartment, in HIV-infected men. Hepatic lipid content is associated with insulin resistance in HIV-infected men. Hepatic lipid content might mediate the relationship between VAT and insulin resistance among treated, HIV-infected men.