Mild intermittent hypoxia exposure alters gut microbiota composition in men with overweight and obesity

Results from high altitude studies in humans and controlled animal experiments suggest that hypoxia exposure induces alterations in gut microbiota composition, which may in turn affect host metabolism. However, well-controlled studies investigating the effects of normobaric hypoxia exposure on gut microbiota composition in humans are lacking. The aim of this study was to explore the impact of mild intermittent hypoxia (MIH) exposure on gut microbiota composition in men with overweight and/or obesity. We performed a randomised, single-blind crossover study, in which participants were exposed to MIH (FiO2: 15%, 3×2 h per day) and normoxia (FiO2: 21%) for seven consecutive days. Following the MIH and normoxia exposure regimens, faecal samples were collected for determination of faecal microbiota composition using 16S rRNA gene-amplicon sequencing in the morning of day 8. Paired faecal samples were available for five individuals. Furthermore, tissue-specific insulin sensitivity was determined using the gold-standard two-step hyperinsulinemic-euglycemic clamp. MIH did not affect microbial alpha and beta-diversity but reduced the relative abundance of Christensenellaceae and Clostridiaceae bacterial families. MIH significantly increased the abundances of obligate anaerobic bacterial genera including Fusicatenibacter, Butyricicoccus and Holdemania, whilst reducing Christensenellaceae R-7 group and Clostridium sensu stricto 1, although these findings were not statistically significant after correction for multiple testing. Furthermore, MIH-induced alterations in abundances of several genera were associated with changes in metabolic parameters such as adipose and peripheral insulin sensitivity, plasma levels of insulin, fatty acids, triacylglycerol and lactate, and substrate oxidation. In conclusion, we demonstrate for the first time that MIH exposure induces modest effects on faecal microbiota composition in humans, shifting several bacterial families and genera towards higher abundances of anaerobic butyrate-producing bacteria. Moreover, MIH-induced effects on faecal microbial composition were associated with parameters related to glucose and lipid homeostasis, supporting a link between MIH-induced alterations in faecal microbiota composition and host metabolism. The study was registered at the Netherlands Trial Register: NL7120/NTR7325.

A comparison between the abdominal and femoral adipose tissue proteome of overweight and obese women

Body fat distribution is an important determinant of cardiometabolic health. Lower-body adipose tissue (AT) has protective characteristics as compared to upper-body fat, but the underlying depot-differences remain to be elucidated. Here, we compared the proteome and morphology of abdominal and femoral AT. Paired biopsies from abdominal and femoral subcutaneous AT were taken from eight overweight/obese (BMI ≥ 28 kg/m²) women with impaired glucose metabolism after an overnight fast. Proteins were isolated and quantified using liquid chromatography-mass spectrometry, and protein expression in abdominal and femoral subcutaneous AT was compared. Moreover, correlations between fat cell size and the proteome of both AT depots were determined. In total, 651 proteins were identified, of which 22 proteins tended to be differentially expressed between abdominal and femoral AT after removal of blood protein signals (p < 0.05). Proteins involved in cell structure organization and energy metabolism were differently expressed between AT depots. Fat cell size, which was higher in femoral AT, was significantly correlated with ADH1B, POSTN and LCP1. These findings suggest that there are only slight differences in protein expression between abdominal and femoral subcutaneous AT. It remains to be determined whether these differences, as well as differences in protein activity, contribute to functional and/or morphological differences between these fat depots.

Abdominal subcutaneous and visceral adipocyte size, lipolysis and inflammation relate to insulin resistance in male obese humans

Obesity is associated with a disturbed adipose tissue (AT) function characterized by adipocyte hypertrophy, an impaired lipolysis and pro-inflammatory phenotype, which contributes to insulin resistance (IR). We investigated whether AT phenotype in different AT depots of obese individuals with and without type 2 diabetes mellitus (T2DM) is associated with whole-body IR. Subcutaneous (SC) and visceral (V) AT biopsies from 18 lean, 17 obese and 8 obese T2DM men were collected. AT phenotype was characterized by ex vivo measurement of basal and stimulated lipolysis (mature adipocytes), adipocyte size distribution (AT tissue sections) and AT immune cells (flow cytometry). In VAT, mean adipocyte size, CD45⁺ leukocytes and M1 macrophages were significantly increased in both obese groups compared to lean individuals. In SCAT, despite adipocyte hypertrophy, no significant differences in immune cell populations between groups were found. In SCAT, multiple linear regression analysis showed that none of the AT phenotype markers independently contributed to HOMA-IR while in VAT, mean adipocyte size was significantly related to HOMA-IR. In conclusion, beside adipocyte hypertrophy in VAT, M1 macrophage- or B-cell-mediated inflammation, may contribute to IR, while inflammation in hypertrophic SCAT does not seem to play a major role in IR.

The effects of angiotensin receptor neprilysin inhibition by sacubitril/valsartan on adipose tissue transcriptome and protein expression in obese hypertensive patients

Increased activation of the renin-angiotensin system is involved in the onset and progression of cardiometabolic diseases, while natriuretic peptides (NP) may exert protective effects. We have recently demonstrated that sacubitril/valsartan (LCZ696), a first-in-class angiotensin receptor neprilysin inhibitor, which blocks the angiotensin II type-1 receptor and augments natriuretic peptide levels, improved peripheral insulin sensitivity in obese hypertensive patients. Here, we investigated the effects of sacubitril/valsartan (400 mg QD) treatment for 8 weeks on the abdominal subcutaneous adipose tissue (AT) phenotype compared to the metabolically neutral comparator amlodipine (10 mg QD) in 70 obese hypertensive patients. Abdominal subcutaneous AT biopsies were collected before and after intervention to determine the AT transcriptome and expression of proteins involved in lipolysis, NP signaling and mitochondrial oxidative metabolism. Both sacubitril/valsartan and amlodipine treatment did not significantly induce AT transcriptional changes in pathways related to lipolysis, NP signaling and oxidative metabolism. Furthermore, protein expression of adipose triglyceride lipase (ATGL) (P_time*group = 0.195), hormone-sensitive lipase (HSL) (P_time*group = 0.458), HSL-ser660 phosphorylation (P_time*group = 0.340), NP receptor-A (NPRA) (P_time*group = 0.829) and OXPHOS complexes (P_time*group = 0.964) remained unchanged. In conclusion, sacubitril/valsartan treatment for 8 weeks did not alter the abdominal subcutaneous AT transcriptome and expression of proteins involved in lipolysis, NP signaling and oxidative metabolism in obese hypertensive patients.

Gut microbiota composition strongly correlates to peripheral insulin sensitivity in obese men but not in women

Gut microbiota composition may play an important role in the development of obesity-related comorbidities. However, only few studies have investigated gender-differences in microbiota composition and gender-specific associations between microbiota or microbial products and insulin sensitivity. Insulin sensitivity (hyperinsulinemic-euglycemic clamp), body composition (dual energy X-ray absorptiometry), substrate oxidation (indirect calorimetry), systemic inflammatory markers and microbiota composition (PCR) were determined in male (n=15) and female (n=14) overweight and obese subjects. Bacteroidetes/Firmicutes-ratio was higher in men than in women (P=0.001). Bacteroidetes/Firmicutes-ratio was inversely related to peripheral insulin sensitivity only in men (men: P=0.003, women: P=0.882). This association between Bacteroidetes/Firmicutes-ratio and peripheral insulin sensitivity did not change after adjustment for dietary fibre and saturated fat intake, body composition, fat oxidation and markers of inflammation. Bacteroidetes/Firmicutes-ratio was not associated with hepatic insulin sensitivity. Men and women differ in microbiota composition and its impact on insulin sensitivity, implying that women might be less sensitive to gut microbiota-induced metabolic aberrations than men. This trial was registered at clinicaltrials.gov as NCT02381145.

Diet-induced weight loss decreases adipose tissue oxygen tension with parallel changes in adipose tissue phenotype and insulin sensitivity in overweight humans

BACKGROUND/OBJECTIVES

Although adipose tissue (AT) hypoxia is present in rodent models of obesity, evidence for this in humans is limited. Here, we investigated the effects of diet-induced weight loss (WL) on abdominal subcutaneous AT oxygen tension (pO₂), AT blood flow (ATBF), AT capillary density, AT morphology and transcriptome, systemic inflammatory markers and insulin sensitivity in humans.

SUBJECTS/METHODS

Fifteen overweight and obese individuals underwent a dietary intervention (DI), consisting of a 5-week very-low-calorie diet (VLCD, 500 kcal day^-1; WL), and a subsequent 4-week weight stable diet (WS). Body composition, AT pO₂ (optochemical monitoring), ATBF (¹³³Xe washout), and whole-body insulin sensitivity were determined, and AT biopsies were collected at baseline, end of WL (week 5) and end of WS (week 9).

RESULTS

Body weight, body fat percentage and adipocyte size decreased significantly during the DI period. The DI markedly decreased AT pO₂ and improved insulin sensitivity, but did not alter ATBF. Finally, the DI increased AT gene expression of pathways related to mitochondrial biogenesis and non-mitochondrial oxygen consumption.

CONCLUSIONS

VLCD-induced WL markedly decreases abdominal subcutaneous AT pO₂, which is paralleled by a reduction in adipocyte size, increased AT gene expression of mitochondrial biogenesis markers and non-mitochondrial oxygen consumption pathways, and improved whole-body insulin sensitivity in humans.

Contribution of lipase deficiency to mitochondrial dysfunction and insulin resistance in hMADS adipocytes

BACKGROUND/OBJECTIVES

Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) are key enzymes involved in intracellular lipid catabolism. We have previously shown decreased expression and activity of these lipases in adipose tissue of obese insulin resistant individuals. Here we hypothesized that lipase deficiency might impact on insulin sensitivity and metabolic homeostasis in adipocytes not just by enhancing lipid accumulation, but also by altering lipid and carbohydrate catabolism in a peroxisome proliferator-activated nuclear receptor (PPAR)-dependent manner.

METHODS

To address our hypothesis, we performed a series of in vitro experiments in a human white adipocyte model, the human multipotent adipose-derived stem (hMADS) cells, using genetic (siRNA) and pharmacological knockdown of ATGL and/or HSL.

RESULTS

We show that ATGL and HSL knockdown in hMADS adipocytes disrupted mitochondrial respiration, which was accompanied by a decreased oxidative phosphorylation (OxPhos) protein content. This lead to a reduced exogenous and endogenous palmitate oxidation following ATGL knockdown, but not in HSL deficient adipocytes. ATGL deficiency was followed by excessive triacylglycerol accumulation, and HSL deficiency further increased diacylglycerol accumulation. Both single and double lipase knockdown reduced insulin-stimulated glucose uptake, which was attributable to impaired insulin signaling. These effects were accompanied by impaired activation of the nuclear receptor PPARα, and restored on PPARα agonist treatment.

CONCLUSIONS

The present study indicates that lipase deficiency in human white adipocytes contributes to mitochondrial dysfunction and insulin resistance, in a PPARα-dependent manner. Therefore, modulation of adipose tissue lipases may provide a promising strategy to reverse insulin resistance in obese and type 2 diabetic patients.

Targeting fatty acid metabolism to improve glucose metabolism

Disturbances in fatty acid metabolism in adipose tissue, liver, skeletal muscle, gut and pancreas play an important role in the development of insulin resistance, impaired glucose metabolism and type 2 diabetes mellitus. Alterations in diet composition may contribute to prevent and/or reverse these disturbances through modulation of fatty acid metabolism. Besides an increased fat mass, adipose tissue dysfunction, characterized by an altered capacity to store lipids and an altered secretion of adipokines, may result in lipid overflow, systemic inflammation and excessive lipid accumulation in non-adipose tissues like liver, skeletal muscle and the pancreas. These impairments together promote the development of impaired glucose metabolism, insulin resistance and type 2 diabetes mellitus. Furthermore, intrinsic functional impairments in either of these organs may contribute to lipotoxicity and insulin resistance. The present review provides an overview of fatty acid metabolism-related pathways in adipose tissue, liver, skeletal muscle, pancreas and gut, which can be targeted by diet or food components, thereby improving glucose metabolism.

Does interference with the renin-angiotensin system protect against diabetes? Evidence and mechanisms

Agents interfering with the renin-angiotensin system (RAS) were consistently shown to lower the incidence of type 2 diabetes mellitus (T2DM), as compared to other antihypertensive drugs, in hypertensive high-risk populations. The mechanisms underlying this protective effect of RAS blockade using angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers on glucose metabolism are not fully understood. In this article, we will review the evidence from randomized controlled trials and discuss the proposed mechanisms as to how RAS interference may delay the onset of T2DM. In particular, as T2DM is characterized by β-cell dysfunction and obesity-related insulin resistance, we address the mechanisms that underlie RAS blockade-induced improvement in β-cell function and insulin sensitivity.

Ectopic fat storage in the pancreas, liver, and abdominal fat depots: impact on β-cell function in individuals with impaired glucose metabolism

CONTEXT

Pancreatic fat content (PFC) may have deleterious effects on β-cell function.

OBJECTIVE

We hypothesized that ectopic fat deposition, in particular pancreatic fat accumulation, is related to β-cell dysfunction in individuals with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT).

DESIGN, SETTING AND PARTICIPANTS

This was a cross-sectional study in 64 age- and body mass index-matched individuals, with normal glucose tolerance (NGT; n = 16, 60% males), IFG (n = 29, 52% males), or IFG/IGT (n = 19, 63% males) was conducted.

INTERVENTION AND MAIN OUTCOME MEASURES

Participants underwent the following: 1) a combined hyperinsulinemic-euglycemic and hyperglycemic clamp, with subsequent arginine stimulation to quantify insulin sensitivity and β-cell function; 2) proton-magnetic resonance spectroscopy to assess PFC and liver fat content (LFC); and 3) magnetic resonance imaging to quantify visceral (VAT) and sc (SAT) adipose tissue. The disposition index (DI; insulin sensitivity adjusted β-cell function) was assessed.

RESULTS

IFG and IFG/IGT were more insulin resistant (P < 0.001) compared with NGT. Individuals with IFG/IGT had the lowest values of glucose- and arginine-stimulated C-peptide secretion (both P < 0.03) and DI (P < 0.001), relative to IFG and NGT. PFC and LFC gradually increased between NGT, IFG, and IFG/IGT (P = 0.02 and P = 0.01, respectively), whereas VAT and SAT were similar between groups. No direct associations were found between PFC, LFC, VAT, and SAT and C-peptide secretion. The DI was inversely correlated with PFC, LFC, and VAT (all P < 0.05).

CONCLUSIONS

PFC was increased in individuals with IFG and/or IGT, without a direct relation with β-cell function.

Obesity and the lung: 5. Obesity and COPD

Chronic obstructive pulmonary disease (COPD) and obesity are common and disabling chronic health conditions with increasing prevalence worldwide. A relationship between COPD and obesity is increasingly recognised, although the nature of this association remains unknown. This review focuses on the epidemiology of obesity in COPD and the impact of excessive fat mass on lung function, exercise capacity and prognosis. The evidence for altered adipose tissue functions in obesity--including reduced lipid storage capacity, altered expression and secretion of inflammatory factors, adipose tissue hypoxia and macrophage infiltration in adipose tissue--is also reviewed. The interrelationship between these factors and their contribution to the development of insulin resistance in obesity is considered. It is proposed that, in patients with COPD, reduced oxidative capacity and systemic hypoxia may amplify these disturbances, not only in obese patients but also in subjects with hidden loss of fat-free mass. The potential interaction between abnormal adipose tissue function, systemic inflammation and COPD may provide more insight into the pathogenesis and reversibility of systemic pathology in this disease.

Short-term beta-adrenergic regulation of leptin, adiponectin and interleukin-6 secretion in vivo in lean and obese subjects

AIM

Adipose tissue and skeletal muscle are endocrine organs, secreting substances that have been implicated in obesity-related disorders. This study examined short-term beta-adrenergic regulation of circulating leptin, adiponectin and interleukin-6 (IL-6) concentrations and secretion from abdominal subcutaneous adipose tissue and muscle (IL-6) in vivo in lean and obese subjects.

METHODS

Systemic concentrations and net fluxes of leptin, adiponectin and IL-6 across abdominal subcutaneous adipose tissue and forearm skeletal muscle (IL-6) were assessed before and during beta-adrenergic stimulation (intravenous isoprenaline infusion) in 13 lean and 10 obese men.

RESULTS

Basal circulating leptin concentrations were higher in the obese (p < 0.001), while circulating adiponectin (p = 0.45) and IL-6 concentrations (p = 0.41) were not different between groups. beta-Adrenergic stimulation decreased leptin concentrations in both groups (p < 0.01), but did not reduce net abdominal subcutaneous adipose tissue leptin release. Increased leptin clearance and/or decreased leptin secretion from other fat depots may explain the reduction in leptin concentrations. Adiponectin concentrations remained unchanged during beta-adrenergic stimulation in both groups. beta-Adrenergic stimulation increased IL-6 concentration, which was more pronounced in the obese (p = 0.01 vs. lean). This cannot be explained by increased IL-6 release per unit abdominal subcutaneous adipose tissue and muscle but might be because of the increased fat mass and fat-free mass at whole-body level.

CONCLUSIONS

Short-term beta-adrenergic stimulation decreases leptin concentrations, which cannot be explained by reduced net leptin release from abdominal subcutaneous adipose tissue, while it elevates IL-6 concentration partly by increased release from this fat depot and muscle. Finally, beta-adrenergic stimulation has no short-term regulatory role in adiponectin secretion.

Effect of beta-adrenergic stimulation on whole-body and abdominal subcutaneous adipose tissue lipolysis in lean and obese men

AIMS/HYPOTHESIS

Obesity is characterised by increased triacylglycerol storage in adipose tissue. There is in vitro evidence for a blunted beta-adrenergically mediated lipolytic response in abdominal subcutaneous adipose tissue (SAT) of obese individuals and evidence for this at the whole-body level in vivo. We hypothesised that the beta-adrenergically mediated effect on lipolysis in abdominal SAT is also impaired in vivo in obese humans.

METHODS

We investigated whole-body and abdominal SAT glycerol metabolism in vivo during 3 h and 6 h [2H5]glycerol infusions. Arterio-venous concentration differences were measured in 13 lean and ten obese men after an overnight fast and during intravenous infusion of the non-selective beta-adrenergic agonist isoprenaline [20 ng (kg fat free mass)(-1) min(-1)].

RESULTS

Lean and obese participants showed comparable fasting glycerol uptake by SAT (9.7+/-3.4 vs 9.3+/-2.5% of total release, p=0.92). Furthermore, obese participants showed an increased whole-body beta-adrenergically mediated lipolytic response versus lean participants. However, their fasting lipolysis was blunted [glycerol rate of appearance: 7.3+/-0.6 vs 13.1+/-0.9 micromol (kg fat mass)(-1) min(-1), p<0.01], as was the beta-adrenergically mediated lipolytic response per unit SAT [Delta total glycerol release: 140+/-71 vs 394+/-112 nmol (100 g tissue)(-1) min(-1), p<0.05] compared with lean participants. Net triacylglycerol flux tended to increase in obese compared with lean participants during beta-adrenergic stimulation [Delta net triacylglycerol flux: 75+/-32 vs 16+/-11 nmol (100 g tissue)(-1) min(-1), p=0.06].

CONCLUSIONS/INTERPRETATION

We demonstrated in vivo that beta-adrenergically mediated lipolytic response is impaired systematically and in abdominal SAT of obese versus lean men. This may be important in the development or maintenance of increased triacylglycerol stores and obesity.

Effect of short-term ACE inhibitor treatment on peripheral insulin sensitivity in obese insulin-resistant subjects

AIMS/HYPOTHESIS

This study was designed to investigate the effect of short-term ACE inhibitor treatment on insulin sensitivity and to examine possible underlying metabolic and haemodynamic effects in obese insulin-resistant subjects.

METHODS

A randomised, double-blind placebo-controlled trial was performed in 18 obese insulin-resistant men (age, 53 +/- 2 years; BMI, 32.6 +/- 0.8 kg/m(2); homeostasis model assessment of insulin resistance, 5.6 +/- 0.5; systolic blood pressure [SBP], 140.8 +/- 3.2; diastolic blood pressure [DBP], 88.8 +/- 1.6 mmHg), who were free of any medication. The aim was to examine the effects of 2 weeks of ACE inhibitor treatment (ramipril, 5 mg/day) on insulin sensitivity, forearm blood flow, substrate fluxes across the forearm, whole-body substrate oxidation and intramuscular triacylglycerol (IMTG) content.

RESULTS

Ramipril treatment decreased ACE activity compared with placebo (-22.0 +/- 1.7 vs 0.2 +/- 1.1 U/l, respectively, p < 0.001), resulting in a significantly reduced blood pressure (SBP, -10.8 +/- 2.1 vs -2.7 +/- 2.0 mmHg, respectively, p = 0.01; DBP, -10.1 +/- 1.3 vs -4.2 +/- 2.1 mmHg, respectively, p = 0.03). Ramipril treatment had no effect on whole-body insulin-mediated glucose disposal (before: 17.9 +/- 2.0, after: 19.1 +/- 2.4 micromol kg body weight(-1) min(-1), p = 0.44), insulin-mediated glucose uptake across the forearm (before: 1.82 +/- 0.39, after: 1.92 +/- 0.29 micromol 100 ml forearm tissue(-1) min(-1), p = 0.81) and IMTG content (before: 45.4 +/- 18.8, after: 48.8 +/- 27.5 micromol/mg dry muscle, p = 0.92). Furthermore, the increase in carbohydrate oxidation (p < 0.001) and forearm blood flow (p < 0.01), and the decrease in fat oxidation (p < 0.001) during insulin stimulation were not significantly different between treatments.

CONCLUSIONS/INTERPRETATION

Short-term ramipril treatment adequately reduced ACE activity and blood pressure, but had no significant effects on insulin sensitivity, forearm blood flow, substrate fluxes across the forearm, whole-body substrate oxidation and IMTG content in obese insulin-resistant subjects.

Angiotensin II: a hormone that affects lipid metabolism in adipose tissue

BACKGROUND

Alterations in adipose tissue lipolysis may contribute to the pathophysiology of obesity and insulin resistance. We examined the effects of angiotensin II (Ang II) on abdominal subcutaneous adipose tissue lipolysis in humans.

METHODS AND RESULTS

First, adipocytes obtained from nine normal weight and seven obese subjects were stimulated with Ang II (10(-14)-10(-6) M). Glycerol concentration in the medium, used as an indicator of adipocyte lipolysis, was significantly reduced (approximately 20%) after Ang II stimulation in adipocytes from normal weight (P=0.04) and obese subjects (P<0.001). Based on these observations, adipocytes of seven additional obese subjects were stimulated with lower doses of Ang II (10(-17)-10(-6) M) in the presence and absence of Ang II type 1 (AT(1)) receptor blockade. Lipolysis was dose dependently inhibited by approximately 20 to 25% after Ang II stimulation (P=0.001). AT(1) receptor blockade completely abolished the Ang II-induced effects (P=0.35).

CONCLUSION

Ang II directly inhibits abdominal subcutaneous adipocyte lipolysis in normal weight and obese subjects via the AT(1) receptor.

Angiotensin II: a major regulator of subcutaneous adipose tissue blood flow in humans

We investigated the functional roles of circulating and locally produced angiotensin II (Ang II) in fasting and postprandial adipose tissue blood flow (ATBF) regulation and examined the interaction between Ang II and nitric oxide (NO) in ATBF regulation. Local effects of the pharmacological agents (or contralateral saline) on ATBF, measured with 133Xe wash-out, were assessed using the recently developed microinfusion technique. Fasting and postprandial (75 g glucose challenge) ATBF regulation was investigated in nine lean healthy subjects (age, 29 +/- 3 years; BMI, 23.4 +/- 0.7 kg m(-2)) using local Ang II stimulation, Ang II type 1 (AT1) receptor blockade, and angiotensin-converting enzyme (ACE) inhibition. Furthermore, NO synthase (NOS) blockade alone and in combination with AT1 receptor blockade was used to examine the interaction between Ang II and NO. Ang II induced a dose-dependent decrease in ATBF (10(-9)m: -16%, P = 0.04; 10(-7)m: -33%, P < 0.01; 10(-5)m: -53%P < 0.01). Fasting ATBF was not affected by ACE inhibition, but was increased by approximately 55% (P < 0.01) by AT(1) receptor blockade. NOS blockade induced a approximately 30% (P = 0.001) decrease in fasting ATBF. Combined AT1 receptor and NOS blockade increased ATBF by approximately 40% (P = 0.003). ACE inhibition and AT1 receptor blockade did not affect the postprandial increase in ATBF. We therefore conclude that circulating Ang II is a major regulator of fasting ATBF, and a major proportion of the Ang II-induced decrease in ATBF is NO independent. Locally produced Ang II does not appear to regulate ATBF. Ang II appears to have no major effect on the postprandial enhancement of ATBF.

Angiotensin II-induced effects on adipose and skeletal muscle tissue blood flow and lipolysis in normal-weight and obese subjects

The present study was designed to investigate the effects of angiotensin II (Ang II) on adipose and skeletal muscle tissue blood flow and lipolysis in normal-weight and obese subjects using the microdialysis technique. Microdialysis probes were placed in the abdominal sc adipose tissue left and right from the umbilicus and in the gastrocnemius muscle of both legs in eight normal-weight and eight obese men. Probes were consecutively perfused with 1.0 nM Ang II, 1.0 microM Ang II, and 1.0 microM Ang II + 48 microM hydralazine or with Ringer solution (control). Ethanol and glycerol concentrations in the dialysate were measured as an indicator of local blood flow and lipolysis, respectively. Ang II caused an increase in ethanol outflow/inflow ratio, compared with baseline values both in adipose tissue (average of both groups, Ang 1.0 nM: 0.03 +/- 0.01, P = 0.02; Ang 1.0 microM: 0.05 +/- 0.01, P < 0.01) and muscle (average of both groups, Ang 1.0 nM: 0.02 +/- 0.01, P = 0.09; Ang 1.0 microM: 0.04 +/- 0.01, P = 0.01), indicating a decrease in local blood flow. These effects were not significantly different in obese and normal-weight subjects. The decrease in local blood flow was accompanied by unchanged interstitial glycerol concentrations in adipose tissue (except during the supraphysiological dose) and skeletal muscle, suggesting that Ang II inhibits lipolysis in both tissues. Thus, the present data suggest that Ang II decreases local blood flow in a dose-dependent manner and inhibits lipolysis both in adipose and skeletal muscle tissue. These effects were not significantly different in obese and normal-weight subjects in both tissues.

Possible involvement of the adipose tissue renin-angiotensin system in the pathophysiology of obesity and obesity-related disorders

Angiotensin II (Ang II), acting on the AT1 and AT2 receptors in mammalian cells, is the vasoactive component of the renin-angiotensin system (RAS). Several components of the RAS have been demonstrated in different tissues, including adipose tissue. Although the effects of Ang II on metabolism have not been studied widely, it is intriguing to assume that components of the RAS produced by adipocytes may play an autocrine, a paracrine and/or an endocrine role in the pathophysiology of obesity and provide a potential pathway through which obesity leads to hypertension and type 2 diabetes mellitus. In the first part of this review, we will describe the production of Ang II, the different receptors through which Ang II exerts its effects and summarize the concomitant intracellular signalling cascades. Thereafter, potential Ang II-induced mechanisms, which may be associated with obesity and obesity-related disorders, will be considered. Finally, we will focus on the different pharmaceutical agents that interfere with the RAS and highlight the possible implications of these drugs in the treatment of obesity-related disorders.

Cytokeratin in lens epithelial cells and its effect on anterior lens capsule opacification

Postoperative lens capsule opacification is a complication of extracapsular cataract extraction. To avoid this problem, we aspirated the epithelial cells lining the internal surface of the capsular bag. Anterior capsule specimens collected three and six years after the first surgical intervention (extracapsular cataract extraction with intercapsular implantation of a poly[methyl methacrylate] intraocular lens) and in vitro studies of epithelial cell cultures revealed the presence of intracellular and extracellular cytokeratin. After several years, the cytokeratin layers were arranged in a pattern analogous to that of liquid crystalline phases and many nonhuman extraocular tissues.

Priming solutions for cardiopulmonary bypass: comparison of three colloids

The present study was designed to compare the differences in the clinical effects of three colloidal solutions, albumin, urea-linked gelatin, and succinyl-linked gelatin, when used as priming fluids for cardiopulmonary bypass (CPB) under alpha-stat conditions. A consecutive series of 105 patients scheduled for cardiac surgery were randomized into three identically managed groups, except for the CPB prime. Variables relating to acid-base status, oncotic activity, metabolism, coagulation, and postoperative evaluation were measured. Marked differences in acid-base status, colloid osmotic pressure, additional prime requirements, blood lactate, urine output, and the need for buffer solutions occurred among groups, with the succinyl-linked gelatin group having better results than the other groups. Changes in hemodynamics, oxygen consumption, and blood-glucose levels during CPB did not vary among groups. There were also no important intergroup differences in hematologic and clotting variables or postoperative parameters such as blood loss or use of blood products. Electrolyte changes were similar except for a significant increase in ionized calcium that occurred in the urea-linked gelatin group after bypass. The results indicate that succinyl-linked gelatin is an adequate and safe alternative to human albumin for use as a colloid during CPB under alpha-stat conditions.