A pilot study to explore circulating tumour cells in pancreatic cancer as a novel biomarker

Background:

Obtaining tissue for pancreatic carcinoma diagnosis and biomarker assessment to aid drug development is challenging. Circulating tumour cells (CTCs) may represent a potential biomarker to address these unmet needs. We compared prospectively the utility of two platforms for CTC enumeration and characterisation in pancreatic cancer patients in a pilot exploratory study.

Patients and methods:

Blood samples were obtained prospectively from 54 consenting patients and analysed by CellSearch and isolation by size of epithelial tumour cells (ISET). CellSearch exploits immunomagnetic capture of CTCs-expressing epithelial markers, whereas ISET is a marker independent, blood filtration device. Circulating tumour cell expression of epithelial and mesenchymal markers was assessed to explore any discrepancy in CTC number between the two platforms.

Results:

ISET detected CTCs in more patients than CellSearch (93% vs 40%) and in higher numbers (median CTCs/7.5 ml, 9 (range 0–240) vs 0 (range 0–144)). Heterogeneity observed for epithelial cell adhesion molecule, pan-cytokeratin (CK), E-Cadherin, Vimentin and CK 7 expression in CTCs may account for discrepancy in CTC number between platforms.

Conclusion:

ISET detects more CTCs than CellSearch and offers flexible CTC characterisation with potential to investigate CTC biology and develop biomarkers for pancreatic cancer patient management.

Time-resolved detection of structural changes during the photocycle of spin-labeled bacteriorhodopsin

Bacteriorhodopsin was selectively spin labeled at residues 72, 101, or 105 after replacement of the native amino acids by cysteine. Only the electron paramagnetic resonance spectrum of the label at 101 was time-dependent during the photocycle. The spectral change rose with the decay of the M intermediate and fell with recovery of the ground state. The transient signal is interpreted as the result of movement in the C-D or E-F interhelical loop, or in both, coincident with protonation changes at the key aspartate 96 residue. These results link the optically characterized intermediates with localized conformational changes in bacteriorhodopsin during the photocycle.

Direct and indirect effects of amino acids on hepatic glucose metabolism in humans

AIM/HYPOTHESIS

The study was designed to examine the contribution of direct (substrate-mediated) and indirect (hormone-mediated) effects of amino acids on hepatic glucose metabolism in healthy men.

METHODS

The protocols were: (i) CON+S (n=7): control conditions with somatostatin to inhibit endogenous hormone release resulting in fasting plasma concentrations of amino acids, insulin (approximately 28 pmol/l) and glucagon (approximately 65 ng/l), (ii) AA+S ( n=7): amino acid infusion-fasting insulinaemia-fasting glucagonaemia, (iii) GLUC+S ( n=6): fasting amino acids-fasting insulinaemia-hyperglucagonaemia (approximately 99 ng/l) and (iv) AA-S (n=5): amino acid infusion without somatostatin resulting in amino acid-induced hyperinsulinaemia (approximately 61 pmol/l)-hyperglucagonaemia (approximately 147 ng/l). Net glycogenolysis was calculated from liver glycogen concentrations using (13)C nuclear magnetic resonance spectroscopy. Total gluconeogenesis (GNG) was calculated by subtracting net glycogenolysis from endogenous glucose production (EGP) which was measured with [6,6-(2)H(2)]glucose. Net GNG was assessed with the (2)H(2)O method.

RESULTS

During AA+S and GLUC+S, plasma glucose increased by about 50% (p<0.01) due to a comparable rise in EGP. This was associated with a 53-% (p<0.05) and a 65% increase (p<0.01) of total and net GNG during AA+S, whereas net glycogenolysis rose by 70% (p<0.001) during GLUC+S. During AA-S, plasma glucose remained unchanged despite nearly-doubled (p<0.01) total GNG.

CONCLUSION/INTERPRETATION

Conditions of postprandial amino acid elevation stimulate secretion of insulin and glucagon without affecting glycaemia despite markedly increased gluconeogenesis. Impaired insulin secretion unmasks the direct gluconeogenic effect of amino acids and increases plasma glucose.

Molecular mechanisms of lipid-induced insulin resistance in muscle, liver and vasculature

Increased body fat content correlates with insulin resistance and is a key feature of type 2 diabetes. Excessive intake of fat results in deposition of lipids not only in fat tissue but also in skeletal muscle and liver. Subsequently, both plasma and intracellular concentrations of free fatty acids and their metabolites rise and activate signal transduction pathways, which will induce inflammation and impair insulin signalling. Furthermore, elevated circulating lipids impair endothelial function and fibrinolysis, which contributes to the development of vascular disease. Thus, therapeutic strategies aiming at reduction of (intracellular) lipid availability in skeletal muscle and liver and pharmacological modulation of the signalling pathways activated by increased lipid stores represent promising targets for future treatment of insulin resistance and prevention of its complications. This review focuses on the effects of increased lipid availability on the regulation of glucose metabolism in skeletal muscle and liver as well as on vascular function.

Impact of adipose tissue on plasma plasminogen activator inhibitor-1 in dieting obese women

The increased incidence of cardiovascular diseases in obese subjects could be partially attributed to impaired fibrinolysis due to elevated plasma levels of tissue plasminogen activator inhibitor 1 (PAI-1). The associations between changes in plasma PAI-1, metabolic variables, and adipose tissue during weight loss and regain were studied in 52 healthy, premenopausal, obese women participating in a weight reduction program with a hypocaloric diet. PAI-1, insulin, triglyceride, leptin, and adipsin levels were determined at entry, after the first week, after completion of the program, and after 5 months of follow-up. In the 33 obese women who completed the program, decreases in PAI-1 antigen (-54%), PAI activity (-74%), and leptin (-51%), but not of adipsin, were observed. Changes in PAI-1 were associated with changes in body mass index (BMI), body fat, leptin, and insulin. The decreased level of PAI-1 remained low after follow-up in the 14 women who maintained their reduced weight but increased in the 16 women who regained weight. This increase in PAI-1 was correlated with an increase in body fat and leptin. On multivariate analysis, BMI was the major determinant of PAI-1 level. In conclusion, during weight reduction with a hypocaloric diet, the decrease in PAI-1 is more closely related to changes in adipose tissue than to changes in metabolic variables, suggesting a significant role for adipose tissue in regulating plasma levels of PAI-1.

Effects of short-term improvement of insulin treatment and glycemia on hepatic glycogen metabolism in type 1 diabetes

Insufficiently treated type 1 diabetic patients exhibit inappropriate postprandial hyperglycemia and reduction in liver glycogen stores. To examine the effect of acute improvement of metabolic control on hepatic glycogen metabolism, lean young type 1 diabetic (HbA1c 8.8 +/- 0.3%) and matched nondiabetic subjects (HbA1c 5.4 +/- 0.1%) were studied during the course of a day with three isocaloric mixed meals. Hepatic glycogen concentrations were determined noninvasively using in vivo 13C nuclear magnetic resonance spectroscopy. Rates of net glycogen synthesis and breakdown were calculated from linear regression of the glycogen concentration time curves from 7:30-10:30 P.M. and from 10:30 P.M. to 8:00 A.M., respectively. The mean plasma glucose concentration was approximately 2.4-fold higher in diabetic than in nondiabetic subjects (13.6 +/- 0.4 vs. 5.8 +/- 0.1 mmol/l, P < 0.001). Rates of net glycogen synthesis and net glycogen breakdown were reduced by approximately 74% (0.11 +/- 0.02 vs. 0.43 +/- 0.04 mmol/l liver/min, P < 0.001) and by approximately 47% (0.10 +/- 0.01 vs. 0.19 +/- 0.01 mmol/l liver/min, P < 0.001) in diabetic patients, respectively. During short-term (24-h) intensified insulin treatment, the mean plasma glucose level was not different between diabetic and nondiabetic subjects (6.4 +/- 0.1 mmol/l). Net glycogen synthesis and breakdown increased by approximately 92% (0.23 +/- 0.04 mmol/l liver/min, P = 0.017) and by approximately 40% (0.14 approximately 0.01 mmol/l liver/min, P = 0.011), respectively. In conclusion, poorly controlled type 1 diabetic patients present with marked reduction in both hepatic glycogen synthesis and breakdown. Both defects in glycogen metabolism are improved but not normalized by short-term restoration of insulinemia and glycemia.

Lipid-dependent control of hepatic glycogen stores in healthy humans

AIMS/HYPOTHESIS

Non-esterified fatty acids and glycerol could stimulate gluconeogenesis and also contribute to regulating hepatic glycogen stores. We examined their effect on liver glycogen breakdown in humans.

METHODS

After an overnight fast healthy subjects participated in three protocols with lipid/heparin (plasma non-esterified fatty acids: 2.2 +/- 0.1 mol/l; plasma glycerol: 0.5 +/- 0.03 mol/l; n = 7), glycerol (0.4 +/- 0.1 mol/l; 1.5 +/- 0.2 mol/l; n = 5) and saline infusion (control; 0.5 +/- 0.1 mol/l; 0.2 +/- 0.02 mol/l; n = 7). Net rates of glycogen breakdown were calculated from the decrease of liver glycogen within 9 h using 13C nuclear magnetic resonance spectroscopy. Endogenous glucose production was measured with infusion of D-[6,6-2H2]glucose.

RESULTS

Endogenous glucose production decreased by about 25 % during lipid and saline infusion (p < 0.005) but not during glycerol infusion (p < 0.001 vs lipid, saline). An increase of plasma non-esterified fatty acids or glycerol reduced the net glycogen breakdown by about 84 % to 0.6 +/- 0.3 micromol x kg(-1) x min(-1) (p < 0.001 vs saline: 3.7 +/- 0.5 micromol x kg(-1) x min(-1)) and by about 46 % to 2.0 +/- 0.4 micromol x kg(-1) x min(-1) (p < 0.01 vs saline and lipid), respectively. Rates of gluconeogenesis increased to 11.5 +/- 0.8 micromol x kg(-1) x min(-1) (p < 0.01) and 12.8 +/- 1.0 micromol x kg(-1) min(-1) (p < 0.01 vs saline: 8.2 +/- 0.7 micromol x l(-1) x min(-1)), respectively.

CONCLUSION/INTERPRETATION

An increase of non-esterifled fatty acid leads to a pronounced inhibition of net hepatic glycogen breakdown and increases gluconeogenesis whereas glucose production does not differ from the control condition. We suggest that this effect is not due to increased availability of glycerol alone but rather to lipid-dependent control of hepatic glycogen stores.

Nutrient-Induced Insulin Resistance in Human Skeletal Muscle

Nutrient excess is associated with reduced insulin sensitivity (insulin resistance) and plays a central role in the pathogenesis of type 2 diabetes. Recently, free fatty acids as well as amino acids were shown to induce insulin resistance by decreasing glucose transport/phosphorylation with subsequent impairment of glycogen synthesis in human skeletal muscle. These results do not support the traditional concept of direct substrate competition with glucose for mitochondrial oxidation but indicate that the cellular mechanisms of such lipotoxicity and "proteotoxicity" might primarily affect the insulin signaling cascade. The signaling pathways involved in nutrient dependent modulation of insulin action include protein kinase C isoforms and IkappaB kinase. Therefore, pharmacological modulation of these enzymes might represent a promising target for future treatment of insulin resistance. Finally, hyperglycemia which occurs late in the insulin resistance syndrome further augments insulin resistance by mechanisms summarized as glucose toxicity. Chronic hyperglycemia might lead to inhibition of lipid oxidation and thereby to accumulation of intracellular lipid metabolites. Therefore, glucotoxicity might be in part indirectly caused by lipotoxicity (glucolipotoxicity). In conclusion, different nutrients affect common metabolic pathways and thereby induce insulin resistance in humans.

Therapeutic potential of valproic acid for retinitis pigmentosa

BACKGROUND/AIM

To examine the efficacy and safety of valproic acid (VPA) in patients with retinitis pigmentosa (RP).

METHODS

Thirteen eyes were examined before and after brief treatment (average 4 months) with VPA. Visual fields (VF) for each eye were defined using digitised Goldmann Kinetic Perimetry tracings. VF areas were log-transformed and VF loss/gain relative to baseline was calculated. Visual acuity was measured using a Snellen chart at a distance of 20&emsp14;feet (6.1 m). Values were converted to the logarithm of the minimum angle of resolution (logMAR) score.

RESULTS

Nine eyes had improved VF with treatment, two eyes had decreased VF and two eyes experienced no change, with an overall average increase of 11%. Assuming typical loss in VF area without treatment, this increase in VF was statistically significant (p<0.02). An average decrease (0.172) in the logMAR scores was seen in these 13 eyes, which translates to a positive change in Snellen score of approximately 20/47 to 20/32, which was significant (p<0.02) assuming no loss in acuity without treatment. Side effects were mild and well tolerated.

CONCLUSION

Treatment with VPA is suggestive of a therapeutic benefit to patients with RP. A placebo-controlled clinical trial will be necessary to assess the efficacy and safety of VPA for RP rigorously.

MiR-205-driven downregulation of cholesterol biosynthesis through SQLE-inhibition identifies therapeutic vulnerability in aggressive prostate cancer

Prostate cancer (PCa) shows strong dependence on the androgen receptor (AR) pathway. Here, we show that squalene epoxidase (SQLE), an enzyme of the cholesterol biosynthesis pathway, is overexpressed in advanced PCa and its expression correlates with poor survival. SQLE expression is controlled by micro-RNA 205 (miR-205), which is significantly downregulated in advanced PCa. Restoration of miR-205 expression or competitive inhibition of SQLE led to inhibition of de novo cholesterol biosynthesis. Furthermore, SQLE was essential for proliferation of AR-positive PCa cell lines, including abiraterone or enzalutamide resistant derivatives, and blocked transactivation of the AR pathway. Inhibition of SQLE with the FDA approved antifungal drug terbinafine also efficiently blocked orthotopic tumour growth in mice. Finally, terbinafine reduced levels of prostate specific antigen (PSA) in three out of four late-stage PCa patients. These results highlight SQLE as a therapeutic target for the treatment of advanced PCa.

Influence of age, performance status, cancer activity, and IL-6 on anxiety and depression in patients with metastatic breast cancer

Depression and anxiety are the core disorders causing emotional distress in patients (pts) with metastatic breast cancer. The aim of our study was to screen metastatic breast cancer outpatients for anxiety and depression, and to investigate the influence of age, Karnofsky Performance Status (KPS), cancer activity, and inflammation as represented by IL-6 levels on these two mood disorders. Pts treated with chemotherapy for metastatic breast cancer (n = 70) were assessed using the Hospital Anxiety and Depression Scale (HADS) for symptoms (scores 0-21) and caseness (score ≥11) of clinical depression and anxiety. Blood samples for IL-6 concentrations were collected at 10:00 a.m. A total of 22 (31.4 %) pts were diagnosed with caseness of clinical depression and 23 (32.9 %) pts with clinical anxiety, while 12 pts were diagnosed positive for both mood disorders. Depression and anxiety were positively but moderately correlated (Spearman's r (2) = 0.24, p < 0.001). IL-6 was significantly correlated with symptoms of depression (r (2) = 0.42, p < 0.001) and to a lesser extent to symptoms of anxiety (r (2) = 0.16, p = 0.001). In addition, IL-6 was positively associated with tumor progression (p < 0.001). Multiple linear regression analysis showed that tumor progression (standardized b = 0.226, p = 0.047), symptoms of anxiety (b = 0.292, p = 0.016), and IL-6 (b = 0.314, p = 0.007) were independently associated with clinical depression, whereas anxiety was linked to tumor progression (b = 0.238, p = 0.030), symptoms of depression (b = 0.407, p < 0.001) and age (b = -0.381, p < 0.001), but not to IL-6 (b = 0.168, p = 0.134). Even though a positive correlation between depression and anxiety exists, clinical parameters like age, cancer activity, KPS, and IL-6 do influence depression and anxiety differently. Unlike clinical depression, anxiety is not associated with increased IL-6 levels, however, shows a reciprocal correlation with age.

Prevention of urinary tract infection during intermittent catheterization

We studied prospectively 40 patients with recent spinal cord injuries to determine the effectiveness of the combination of oral methenamine and an intravesicular acidifying agent for prevention of urinary tract infection during intermittent catheterization. The incidences of bacteriuria and symptomatic urinary tract infections were significantly less in the treated group. This combination appears to be a safe, effective means to reduce pyelonephritis in spinal cord injury patients on intermittent catheterization.

Severe acute renal failure in adults: place of care, incidence and outcomes

BACKGROUND

Department of Health guidelines recommend specialist critical care facilities for patients with severe single-organ failure such as acute renal failure (ARF). Prospective studies examining incidence, causes and outcomes of ARF outside of intensive care settings are lacking.

AIM

To determine the incidence, causes, place of care and outcomes of severe single-organ ARF.

DESIGN

Prospective observational study.

METHODS

For 6 weeks in June-July 2003, renal physicians were contacted daily, and ICUs on alternate days, to identify cases of severe single-organ ARF in the Greater Manchester area. All patients with serum creatinine >or=500 micromol/l and not requiring other organ support were included. Patients with end-stage renal disease were excluded. Survivors were followed up at 90 days and 1 year from admission. Two independent consultant nephrologists assessed each case using anonymized summaries.

RESULTS

Eighty-five patients had multi-organ ARF and 28 had severe single-organ ARF (380 and 125 pmp/year, respectively). Of those with single-organ ARF, 10 (36%) had known pre-existing chronic kidney disease. Renal replacement therapy (RRT) was required in 15 (54%). Total bed occupancy on ICUs relating to single-organ ARF was 59 days (range per patient 1-21). At 90 days, 18 (64%) were alive, and 17 (94%) had independent renal function. At 1 year, 4/18 had died, none receiving RRT at the time of death. Survivors all had independent renal function. In 13 (46%) cases there was an unacceptable delay in patient transfer and in 7 (25%), delays in assessment or commencement of RRT may have adversely affected patient outcome.

DISCUSSION

The incidence of ARF treated with RRT is rising. Delays in transfer to renal services may result in inappropriate ICU bed use, and may adversely affect patient outcomes. There are serious problems regarding the appropriate use of expensive and limited medical resources in the critical care area, and in providing safe and effective treatment of patients with ARF.

Amino acid-dependent modulation of glucose metabolism in humans

Despite its high prevalence and severe complications, the aetiology of the primary defects leading to Type 2 diabetes mellitus remain unknown. In addition to polygenic predisposition, environmental factors including dietary behaviour are increasingly recognized as being of crucial importance for the development of this disease. This strongly supports the concept that nutrient excess leading to increased availability of substrates adversely influences whole-body metabolic regulation and plays a major role in the development of type 2 diabetes. We have shown previously that a short-term increase in free fatty acid availability impairs glucose metabolism in liver and skeletal muscle. Despite the widespread interest in protein-rich diets, the effects of plasma amino acid elevation on human glucose metabolism have not yet been studied in detail. This editorial summarizes recent advances in the identification of mechanisms responsible for amino acid-dependent modulation of glucose metabolism in liver and skeletal muscle in vivo.

GDF15 reflects beta cell function in obese patients independently of the grade of impairment of glucose metabolism

BACKGROUND AND AIMS

Growth differentiation factor 15 (GDF15) is a strong predictor of cardiovascular morbidity and mortality found to be both marker and target of impaired glucose metabolism. GDF15 increases following glucose administration and is up-regulated in obesity and diabetes. We investigate here the relationship between GDF15 and beta cell function.

METHODS AND RESULTS

In this cross-sectional study we evaluated GDF15 concentrations in 160 obese subjects (BMI 35-63 kg/m², age 39.4 ± 18.6 years, m/f 38/122) who underwent a 75 g oral glucose tolerance test (OGTT). Based on the OGTT results, the cohort was divided into two groups: 1) normal fasting glucose and normal glucose tolerance (n = 80), 2) impaired fasting glucose, impaired glucose tolerance or type 2 diabetes (n = 80). The relationship of GDF15 to fasting and OGTT-based dynamic insulin sensitivity and insulin secretion parameters was evaluated. GDF15 was higher in the prediabetes and diabetes groups and correlated with HbA1c, glucose, insulin as well as baseline and dynamic indices of insulin sensitivity and estimated beta cell function. Multiple regression analysis revealed that age, waist-to-height ratio, glomerular filtration rate and prehepatic beta cell function, but not the grade of impairment of glucose metabolism, were independent predictors of GDF15. Subgroup analysis showed that of all parameters of glucose metabolism only C-peptide, fasting prehepatic beta cell function and insulinogenic index remained significantly related to GDF15 in both groups.

CONCLUSION

We conclude that in patients with severe obesity, GDF15 strongly relates to beta cell function and should be further investigated as a potential therapeutic target and biomarker guiding treatment options.

Effectiveness of mattress overlays in reducing interface pressures during recumbency

This study evaluates the pressure-reduction characteristics of seven mattress overlays. Thirty subjects were evaluated on each support surface to determine the interface pressures that are generated under the most common pressure sore sites. The results of this study indicate that there is great variability in the effectiveness of traditional mattress overlays. The most effective overlays are the Roho and Akros DFD mattresses; whereas 2-inch thick convoluted foam provides no significant protection for the trochanter when the subjects were lying on their sides (lateral position).

Insulin resistance is not associated with myocardial steatosis in women

AIMS/HYPOTHESIS

Insulin resistance, an independent risk-factor for cardiovascular disease, precedes type 2 diabetes and is associated with ectopic lipid accumulation in skeletal muscle and liver. Recent evidence indicates that cardiac steatosis plays a central role in the development of diabetic cardiomyopathy. However, it is not known whether insulin resistance as such in the absence of type 2 diabetes is associated with heart steatosis and/or impaired function. We therefore assessed myocardial steatosis and myocardial function in a sample of women with normal insulin sensitivity, insulin resistance, impaired glucose tolerance (IGT) and type 2 diabetes.

METHODS

Magnetic resonance imaging and localised spectroscopy were used to measure left ventricular dynamic variables and myocardial lipid accumulation in interventricular septum of non-diabetic, age- and BMI-matched insulin-sensitive (n = 11, 47 ± 6 years, BMI 25 ± 2 kg/m(2); clamp-like index [CLIX] = 9.7 ± 0.7) and insulin-resistant (n = 10, 48 ± 5 years, 27 ± 4 kg/m(2); CLIX = 4.5 ± 0.4) women with normal glucose tolerance as well as of women with IGT (n = 6, 45 ± 5 years, 28 ± 6 kg/m(2); CLIX = 3.6 ± 1.1) and type 2 diabetes (n = 7, 52 ± 10 years, 27 ± 3 kg/m(2)).

RESULTS

Myocardial lipid content was increased in type 2 diabetic women only (insulin-sensitive 0.4 ± 0.2% [means ± SD]; insulin-resistant 0.4 ± 0.1%; IGT 0.5 ± 0.2%; type 2 diabetes 0.7 ± 0.3%; p < 0.05). In insulin-resistant and type 2 diabetic women, stroke volume was lower (-15% and -27%, respectively, vs insulin-sensitive) and heart rate was higher (11% and 14%, respectively, vs insulin-sensitive, p < 0.05). No other differences in systolic and diastolic function were observed between study groups.

CONCLUSIONS/INTERPRETATION

In contrast to liver and skeletal muscle, insulin resistance as such is not associated with increased myocardial lipid accumulation.

[Verification of normative values for the Swiss version of the Freiburg speech intelligibility test]

BACKGROUND AND OBJECTIVE

In the Swiss version of the Freiburg speech intelligibility test five test words from the original German recording which are rarely used in Switzerland have been exchanged. Furthermore, differences in the transfer functions between headphone and loudspeaker presentation are not taken into account during calibration. New settings for the levels of the individual test words in the recommended recording and small changes in calibration procedures led us to make a verification of the currently used normative values.

PATIENTS AND METHODS

Speech intelligibility was measured in 20 subjects with normal hearing using monosyllabic words and numbers via headphones and loudspeakers.

RESULTS

On average, 50% speech intelligibility was reached at levels which were 7.5 dB lower under free-field conditions than for headphone presentation. The average difference between numbers and monosyllabic words was found to be 9.6 dB, which is considerably lower than the 14 dB of the current normative curves.

CONCLUSIONS

There is a good agreement between our measurements and the normative values for tests using monosyllabic words and headphones, but not for numbers or free-field measurements.

The use of transrectal longitudinal real-time ultrasonography in urodynamics

A total of 63 combined transrectal ultrasonographic and urodynamic studies was performed to evaluate the voiding dysfunction in 49 spinal cord injury patients and 7 other patients. Ultrasonography provided excellent real-time imaging of the bladder neck, prostatic urethra, prostate and external sphincter, and allowed for accurate diagnosis of detrusor-sphincter dyssynergia, detrusor-bladder neck dyssynergia, prostatic hypertrophy and bladder neck strictures. In addition to offering these capabilities, ultrasonography is less expensive than x-ray and it does not involve exposure of either the patient or examiner to radiation. However, it does not provide a means to detect vesicoureteral reflux.

Free fatty acids inhibit the glucose-stimulated increase of intramuscular glucose-6-phosphate concentration in humans

To test Randle's hypothesis we examined whether free fatty acids (FFAs) affect glucose-stimulated glucose transport/phosphorylation and allosteric mediators of muscle glucose metabolism under conditions of fasting peripheral insulinemia. Seven healthy men were studied during somatostatin-glucose-insulin clamp tests [plasma insulin, 50 pmol/L; plasma glucose, 5 mmol/L (0-180 min), 10 mmol/L (180-300 min)] in the presence of low (0.05 mmol/L) and increased (2.6 mmol/L) plasma FFA concentrations. (31)P and (1)H nuclear magnetic resonance spectroscopy was used to determine intracellular concentrations of glucose-6-phosphate (G6P), inorganic phosphate, phosphocreatine, ADP, pH, and intramyocellular lipids. Rates of glucose turnover were measured using D-[6,6-(2)H(2)]glucose. Plasma FFA elevation reduced rates of glucose uptake at the end of the euglycemic period (R(d 150-180 min): 8.6 +/- 0.5 vs. 12.6 +/- 1.6 micromol/kg.min, P < 0.05) and during hyperglycemia (R(d 270-300 min): 9.9 +/- 0.6 vs. 22.3 +/- 1.7 micromol/kg.min, P < 0.01). Similarly, intramuscular G6P was lower at the end of both euglycemic (G6P(167-180 min): -22 +/- 7 vs. +24 +/- 7 micromol/L, P < 0.05) and hyperglycemic periods (G6P(287-300 min): -7 +/- 9 vs. +28 +/- 7 micromol/L, P < 0.05). Changes in intracellular inorganic phosphate exhibited a similar pattern, whereas FFA did not affect phosphocreatine, ADP, pH, and intramyocellular lipid contents. In conclusion, the lack of an increase in muscular G6P along with reduction of whole body glucose clearance indicates that FFA might directly inhibit glucose transport/phosphorylation in skeletal muscle.

Effects of free fatty acids on carbohydrate metabolism and insulin signalling in perfused rat liver

BACKGROUND

Elevated circulating free fatty acids (FFAs) induce insulin resistance and play a crucial role in the development of type 2 diabetes, in which fasting hepatic glucose production (HGP) is increased. However, direct effects of FFAs on fasting HGP are still unclear because indirect endocrine and metabolic effects contribute to FFA action. Thus, we aimed to investigate acute direct effects of specific FFAs on fasting HGP, lactate uptake, and insulin signalling.

MATERIALS AND METHODS

Isolated livers obtained from 20 h fasted rats were perfused with albumin-bound palmitate or oleate (200 micromol L(-1) each) or vehicle (control) for 180 min (n = 5-7/group).

RESULTS

Compared to control, hepatic lactate uptake was increased by palmitate and oleate (~+40%; P < 0.05), while HGP from lactate (~3 mmol L(-1)) and liver glycogen content were similar. Tyrosine phosphorylation (pY) of insulin-receptor-substrate-(IRS)-2 and p70S6-kinase phosphorylation were not affected by FFAs. Palmitate decreased insulin-receptor-beta pY, IRS-1 pY and phosphoinositol-3-kinase expression by 46 +/- 16%, 46 +/- 11% and 20 +/- 9%, respectively (P < 0.03), while oleate reduced Akt phosphorylation by 85 +/- 7% (P < 0.006).

CONCLUSIONS

Isolated liver perfusion with saturated or unsaturated FFAs reduced insulin signalling protein phosphorylation at different sites and increased lactate uptake without affecting HGP or glycogen content. These results suggest that at fasting, both saturated and unsaturated FFAs increase hepatic glucose precursor uptake and may, independently of insulin's presence, accelerate protein dephosphorylation of the insulin signalling cascade at different sites.