Acute elevation of plasma lipids does not affect ATP synthesis in human skeletal muscle.

Prolonged elevation of plasma triglycerides and free fatty acids (FFA) reduces insulin-stimulated glucose disposal and myocellular flux through ATP synthase (fATPase). However, the early effects of lipids per se on fATPase are as yet unclear. Thus, this study examined glucose disposal and fATPase during 3 h of FFA elevation in the presence of low plasma insulinemia. Euglycemic pancreatic clamps with low-dose insulin supplementation (6 mU.m body surface area(-2).min(-1)) were performed in eight healthy men with (LIP) or without (CON) lipid infusion to measure whole body glucose disposal. (31)P/(1)H magnetic resonance spectroscopy of calf muscle was applied to quantify fATPase and concentrations of glucose 6-phosphate (G6P), inorganic phosphate (P(i)), phosphocreatine (PCr), ADP, pH, and IMCL before and during the clamps. Lipid infusion increased plasma FFA approximately twofold and decreased glucose disposal by approximately 50% (110-180 min: LIP 0.87 +/- 0.45 vs. CON 1.75 +/- 0.42 mg.kg(-1).min(-1), P = 0.002; means +/- SD). Intramyocellular G6P tended to rise only under control conditions, whereas PCr, ADP, pH, and IMCL remained unchanged from fasting in LIP and CON. Although P(i) concentrations increased by approximately 18%, fATPase remained unchanged from fasting during the clamps (LIP 10.2 +/- 2.2 vs. CON 10.5 +/- 2.6 micromol.g muscle(-1).min(-1), P = not significant). We conclude that 3 h of lipid elevation fail to affect ATP synthesis despite marked reduction of whole body glucose uptake. This suggests that lipid-induced insulin resistance results primarily from mechanisms decreasing glucose uptake rather than from direct interference of fatty acid metabolites with mitochondrial function.

Glucose turnover and intima media thickness of internal carotid artery in type 2 diabetes offspring.

BACKGROUND: First-degree offspring (OFF) of type 2 diabetic (T2DM) patients bear a approximately 40% lifetime risk of developing T2DM. They are insulin resistant and carry a risk of premature atherosclerosis, the extent of which can be estimated by intima media thickness (IMT) of the carotid artery (CA). Thus, this study examines parameters of glucose and lipid metabolism, insulin sensitivity, beta cell function (BCF) and IMT with their interrelationships in middle-aged OFF. MATERIALS AND METHODS: T2DM-OFF (n = 18, 14f/4m, 45.6 +/- 2.1 years, BMI: 26 +/- 1 kg m(-2)) were compared with 18 matching humans without a family history of diabetes (CON; 14f/4m, 44.5 +/- 2.1 years, BMI: 24 +/- 1 kg m(-2); each P > 0.30), all with normal glucose tolerance as tested by three-hour (75 g) oral glucose tolerance tests (OGTT). Two-hour hyperinsulinaemic (40 mU min(-1).m(-2))isoglycaemic clamp tests were performed with simultaneous measurement of endogenous glucose (D-[6,6-(2)H(2)]glucose) production (EGP). IMT [internal (ICA), common CA, and bulb] were measured sonographically. BCF was assessed by Adaptation Index (AI). RESULTS: Before and during OGTT, both groups were similar in plasma glucose, insulin, C-peptide and free fatty acids (FFA), whereas OFF showed ~30% lower (P < 0.03) fasting plasma triglycerides before OGTT. During hyperinsulinaemic clamps, insulin sensitivity was approximately 38% lower (P < 0.03) in OFF who showed higher plasma FFA (44 +/- 9 micromol L(-1)) than CON (26 +/- 3 micromol L(-1), P < 0.05) after 90 min. EGP was similar in both groups. OFF had 38% (P < 0.007) reduced AI. ICA-IMT was approximately 18% higher in OFF (P < 0.002), but did not correlate with insulin sensitivity. CONCLUSION: The data obtained show middle-aged T2DM-OFF with normal glucose tolerance displaying reduced total insulin sensitivity and impaired beta cell function, which relates to impaired insulin-dependent suppression of plasma FFA and increased ICA-IMT.

Progesterone impairs cell respiration and suppresses a compensatory increase in glucose transport in isolated rat skeletal muscle: a non-genomic mechanism contributing to metabolic adaptation to late pregnancy?

AIMS/HYPOTHESIS: The aim of the study was to gain better insight into the mechanisms responsible for impaired glucose metabolism during late pregnancy. We explored the direct effects of progesterone on glucose metabolism of skeletal muscle. METHODS: Specimens of skeletal muscle from untreated rats were incubated with progesterone and rates of substrate fluxes through the various pathways of glucose metabolism were analysed. RESULTS: Progesterone dose-dependently reduced the rates of glucose and pyruvate oxidation (insulin-stimulated rates after 5 h of exposure to 1 and 10 mumol/l progesterone: glucose oxidation, -6 +/- 4%, NS, and -39 +/- 4%, p < 0.001; pyruvate oxidation, -28 +/- 2% and -55 +/- 4%, p < 0.001 each) and increased lactate release (+28 +/- 4% and +58 +/- 9%, p < 0.005 each), which indicated inhibition of mitochondrial respiratory function. Impairment of cell respiration, e.g. by the specific inhibitor rotenone, is known to trigger a compensatory increase in glucose transport, but this response was blunted in the case of progesterone (change of glucose transport in response to 10 mumol/l progesterone vs 60 nmol/l rotenone, both causing a reduction in glucose oxidation by -39%: progesterone, +14 +/- 8% vs rotenone, +84 +/- 23%, p < 0.03). Further experiments dealt with the underlying mechanisms and revealed a rapid mode of action (50 mumol/l progesterone, reduction in insulin-stimulated glucose oxidation after 30 min: -29 +/- 7%, p < 0.01) not affected by blockers of gene expression or the nuclear progesterone receptor. CONCLUSIONS/INTERPRETATION: Progesterone inhibits cell respiration and at the same time suppresses a compensatory increase in glucose transport, causing cellular carbohydrate deficiency in isolated rat skeletal muscle. This effect is mediated by a direct, rapid and non-genomic mechanism and could contribute to pregnancy-associated changes in glucose homeostasis.

Prevention of high-fat diet-induced adipose tissue remodeling in obese diabetic mice by n-3 polyunsaturated fatty acids.

OBJECTIVE: Obesity is associated with reduced insulin sensitivity and extensive reorganization of adipose tissue. As polyunsaturated fatty acids (PUFA) appear to inhibit diabetes development, we investigated PUFA effects on markers of matrix remodeling in white adipose tissue. METHODS AND PROCEDURE: Male obese diabetic (db/db) mice were treated with either a low-fat standard diet (LF), or high-fat diets rich in saturated and monounsaturated fatty acids (HF/S), n-6 PUFA (HF/6) or the latter including marine n-3 PUFA (HF/3). White adipose tissue was analyzed for gene expression, fatty acid composition and by immunofluorescence. RESULTS: HF/S treatment increased adipose tissue expression of a number of genes involved in matrix degradation including matrix metalloproteinase (MMP)-12, -14 and cathepsin K, L and S compared with LF. MMP-12 gene was expressed in macrophages and adipocytes, and MMP-12 protein colocalized with both cell types. In addition, mean adipocyte area increased by 1.6-fold in HF/S-treated mice. Genes essential for collagen production, such as procollagen I, III, VI, tenascin C and biglycan were upregulated in HF/S-treated animals as well. N-3 PUFA supplementation resulted in enrichment of these fatty acids in adipose tissue. Moreover, n-3 PUFA inhibited the HF/S-induced upregulation of genes involved in matrix degradation and production I restored mean adipocyte area and prevented MMP-12 expression in macrophages and adipocytes. CONCLUSION: N-3 PUFA prevent high-fat diet-induced matrix remodeling and adipocyte enlargement in adipose tissue of obese diabetic mice. Such changes could contribute to diabetes prevention by n-3 PUFA in obese patients.

Activation of PPAR-delta in isolated rat skeletal muscle switches fuel preference from glucose to fatty acids.

AIMS/HYPOTHESIS: GW501516, an agonist of peroxisome proliferator-activated receptor-delta (PPAR-delta), increases lipid combustion and exerts antidiabetic action in animals, effects which are attributed mainly to direct effects on skeletal muscle. We explored such actions further in isolated rat skeletal muscle. MATERIALS AND METHODS: Specimens of rat skeletal muscle were pretreated with GW501516 (0.01-30 mumol/l) for 0.5, 4 or 24 h and rates of fuel metabolism were then measured. In addition, effects on mitochondrial function were determined in isolated rat liver mitochondria. RESULTS: At concentrations between 0.01 and 1 mumol/l, GW501516 dose-dependently increased fatty acid oxidation but reduced glucose utilisation in isolated muscle. Thus after 24 h of preincubation with 1 mumol/l GW501516, palmitate oxidation increased by +46+/-10%, and the following decreased as specified: glucose oxidation -46+/-8%, glycogen synthesis -42+/-6%, lactate release -20+/-2%, glucose transport -15+/-6% (all p<0.05). Reduction of glucose utilisation persisted independently of insulin stimulation or muscle fibre type, but depended on fatty acid availability (the effect on glucose transport in the absence of fatty acids was an increase of 30+/-9%, p<0.01), suggesting a role for the glucose-fatty acid cycle. At higher concentrations, GW501516 uncoupled oxidative phosphorylation by direct action on isolated mitochondria. CONCLUSIONS/INTERPRETATION: GW501516-induced activation of PPAR-delta reduces glucose utilisation by skeletal muscle through a switch in mitochondrial substrate preference from carbohydrate to lipid. High concentrations of GW501516 induce mitochondrial uncoupling independently of PPAR-delta.

Adipose tissue inflammation induced by high-fat diet in obese diabetic mice is prevented by n-3 polyunsaturated fatty acids.

AIMS/HYPOTHESIS: Inflammatory alterations in white adipose tissue appear to underlie complications of obesity including diabetes mellitus. Polyunsaturated fatty acids (PUFA), particularly those of the n-3 series, modulate immune responses and may ameliorate insulin sensitivity. In this study, we investigated how PUFA affect white adipose tissue inflammation and gene expression in obese diabetic animals. MATERIALS AND METHODS: We treated db/db mice as well as lean non-diabetic mice (db/+) with either low-fat standard diet (LF) or high-fat diets rich in (1) saturated/monounsaturated fatty acids (HF/S), (2) n-6 PUFA (HF/6) and (3) the latter including purified marine n-3 PUFA (HF/3). RESULTS: Many genes involved in inflammatory alterations were upregulated in db/db mice on HF/S compared with LF in parallel with phosphorylation of c-Jun N-terminal kinase (JNK). In parallel, adipose tissue infiltration with macrophages was markedly enhanced by HF/S. When compared with HF/S, HF/6 showed only marginal effects on adipose tissue inflammation. However, inclusion of n-3 PUFA in the diet (HF/3) completely prevented macrophage infiltration induced by high-fat diet and changes in inflammatory gene expression, also tending to reduce JNK phosphorylation (p<0.1) in diabetic mice despite unreduced body weight. Moreover, high-fat diets (HF/S, HF/6) downregulated expression and reduced serum concentrations of adiponectin, but this was not the case with n-3 PUFA. CONCLUSIONS/INTERPRETATION: n-3 PUFA prevent adipose tissue inflammation induced by high-fat diet in obese diabetic mice, thereby dissecting obesity from adipose tissue inflammation. These data suggest that beneficial effects of n-3 PUFA on diabetes development could be mediated by their effect on adipose tissue inflammation.

Fibrinolytic dysfunction in insulin-resistant women with previous gestational diabetes.

BACKGROUND: Women with a history of gestational diabetes (p-GDM) are at increased risk of developing type 2 diabetes mellitus (DM2) later in life, and therefore at increased risk for future cardiovascular disease. MATERIALS AND METHODS: Three months after delivery we investigated the plasma levels of plasminogen activator inhibitor type 1 (PAI-1), tissue plasminogen activator (t-PA), fibrinogen and von Willebrand factor (vWF) in 74 women with p-GDM and 20 healthy females with normal glucose tolerance during and after pregnancy, as well as the relation of fibrinolytic parameters to insulin resistance and glycaemic control. All women underwent an oral (OGTT) as well as an intravenous glucose tolerance test (FSIGT). Mathematical model analysis disclosed that 50% (n=37 each) of the p-GDM subjects had normal (NIS) or impaired (IIS) insulin sensitivity. Parameters of interest were determined using commercially available test systems. RESULTS: Women with p-GDM and IIS had significantly increased body fat mass (BFM) (P

Changes in hepatic glycogen cycling during a glucose load in healthy humans.

AIMS/HYPOTHESIS: Glycogen cycling, i.e. simultaneous glycogen synthesis and glycogenolysis, affects estimates of glucose fluxes using tracer techniques and may contribute to hyperglycaemia in diabetic conditions. This study presents a new method for quantifying hepatic glycogen cycling in the fed state. Glycogen is synthesised from glucose by the direct and indirect (gluconeogenic) pathways. Since glycogen is also synthesised from glycogen, i.e. glycogen-->glucose 1-phosphate-->glycogen, that synthesised through the direct and indirect pathways does not account for 100% of glycogen synthesis. The percentage contribution of glycogen cycling to glycogen synthesis then equals the difference between the sum of the percentage contributions of the direct and indirect pathways and 100. MATERIALS AND METHODS: The indirect and direct pathways were measured independently in nine healthy volunteers who had fasted overnight. They ingested (2)H(2)O (5 ml/kg body water) and were infused with [5-(3)H]glucose and acetaminophen (paracetamol; 1 g) during hyperglycaemic clamps (7.8 mmol/l) lasting 8 h. The percentage contribution of the indirect pathway was calculated from the ratio of (2)H enrichments at carbon 5 to that at carbon 2, and the contribution of the direct pathway was determined from the (3)H-specific activity, relative to plasma glucose, of the urinary glucuronide excreted between 2 and 4, 4 and 6, and 6 and 8 h. RESULTS: Glucose infusion rates increased (p<0.01) to approximately 50 mumol kg(-1) min(-1). Plasma insulin and the insulin : glucagon ratio rose approximately 3.6- and approximately 8.3-fold (p<0.001), respectively. From the difference between 100% and the sum of the direct (2-4 h, 54+/-6%; 4-6 h, 59+/-5%; 6-8 h, 63+/-4%) and indirect (32+/-3, 38+/-4, 36+/-3%) pathways, glycogen cycling was seen to be decreased (p<0.05) from 14+/-4% (2-4 h) to 4+/-3% (4-6 h) and 1+/-3% (6-8 h). CONCLUSIONS/INTERPRETATION: This method allows measurement of hepatic glycogen cycling in the fed state and demonstrates that glycogen cycling occurs most in the early hours after glucose loading subsequent to a fast.

Polymorphisms in exon 13 and intron 14 of the RET protooncogene: genetic modifiers of medullary thyroid carcinoma?

CONTEXT: Single-nucleotide polymorphisms (SNPs) of the RET protooncogene (RET) could modify disease susceptibility and clinical phenotype in patients with sporadic or familial medullary thyroid carcinoma (FMTC). OBJECTIVE/DESIGN OF THE STUDY: Because frequencies of RET SNPs have not yet been evaluated in patients with elevated serum concentrations of calcitonin (hCt), a biochemical marker for medullary thyroid carcinoma (MTC), we studied RET SNPs in patients with FMTC (n = 22), patients with sporadic MTC (n = 45), and 71 subjects presenting with moderately elevated hCt concentrations (basal, >10 pg/ml; pentagastrin stimulated, > 50 < 100 pg/ml) in comparison with an age- and gender-matched control group (n = 79) with basal hCt concentrations in the normal range (<5 pg/ml). METHODS: After DNA extraction from citrated whole blood, RET exons 10, 11, 13, 14, 15, and 16 and exon/intron boundaries were analyzed by PCR-based cycle sequencing for RET germ line mutations, exonic (G691S, L769L, S836S, S904S) and intronic (IVS13+158; NCBI rs2472737 = IVS14-24) SNPs. RESULTS: In FMTC patients, the F791Y mutation was found to be associated (P = 0.001) with the L769L SNP. The exonic SNPs (G691S, L769L, S836S, and S904S) were not different among the four groups. The intron 14 SNP (IVS14-24), however, was more frequent in individuals with elevated hCt serum concentrations (P = 0.016) and patients with sporadic MTC (P < 0.001) when compared with the control group. CONCLUSIONS: These data suggest that the exon 13 (L769L) and the intron 14 (IVS14-24) SNPs could act as genetic modifiers in the development of some forms of hereditary and sporadic MTC, respectively.

Urinary steroid excretion rates in acromegaly.

Using gas chromatography/mass spectrometry, urinary excretion rates of cortisol, cortisone and of various steroid metabolites were determined in 35 acromegalic patients (18 men, 17 women) and in 45 age- and weight-matched controls. The ratio of excreted cortisol/cortisone was similar in acromegalics (0.75 +/- 0.20) and in controls (0.75 +/- 0.24). Hence, the preponderance of the main cortisone-derived metabolite, tetrahydrocortisone, over the main metabolites of cortisol (tetrahydrocortisol and allotetrahydrocortisol; p < 0.01), which was seen both in female and in male acromegalics and which was directly correlated with the postglucose concentrations of growth hormone (r = 0.508, p < 0.01), suggests a decreased activity of 11beta-hydroxysteroid dehydrogenase type 1 in acromegaly. Furthermore, the preponderance of etiocholanolone over androsterone (p < 0.01) in men (though not in women) with acromegaly--the ratio androsterone/etiocholanolone being negatively correlated with the serum concentrations of insulin-like growth factor type 1 (r = -0.406, p < 0.05)--suggests a relatively reduced activity of hepatic 5alpha-reductase in male acromegalics.

Thiazolidinediones inhibit proliferation of microvascular and macrovascular cells by a PPARgamma-independent mechanism.

AIMS/HYPOTHESIS: This study evaluated the hypothesis that peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists, including thiazolidinediones (TZDs) and the rexinoid LG100268 (LG), directly affect human vascular cell function (proliferation, cell cycle, protein expression, lactate release) independently of (1) their PPARgamma-activating potential and (2) the cells' vascular origin. METHODS: Human umbilical vein endothelial cells (HUVECs), human adult vein endothelial cells (HAVECs), human retinal endothelial cells (HRECs) and human retinal pericytes (HRPYCs) were incubated (48 h) with 2-50 micromol/l rosiglitazone (RSG), RWJ241947 (RWJ), pioglitazone (PIO), troglitazone (TRO), 15-deoxy-Delta(12,14)-prostaglandin J2 (PGJ2) and LG. Proliferation, cell cycle distribution, protein expression, peroxisome proliferator-activated receptor responsive element (PPRE) transcriptional activity and mitochondrial effects were determined by [3H]thymidine incorporation, FACS analyses, western blots, reporter assays and lactate release respectively. RESULTS: In HUVECs, RSG, RWJ, PIO, TRO, PGJ2 and LG reduced (p<0.01) proliferation (due to a G0/G1 cell cycle arrest) by up to 23%, 36%, 38%, 86%, 99% and 93% respectively. The antiproliferative response was similar in HRPYCs and HAVECs, but was attenuated in HRECs. Whereas p21WAF-1/Cip1 and p27Kip were differently affected in HUVECs, all agents reduced (p<0.05) expression of cyclins (D3, A, E, B), cyclin-dependent kinase-2 and hyperphosphorylated retinoblastoma protein. The rank order of the antiproliferative effects of TZDs in HUVECs (RSG approximately PIO approximately RWJ

Lower within-subject variability of fasting blood glucose and reduced weight gain with insulin detemir compared to NPH insulin in patients with type 2 diabetes.

AIM: The aim of this study was to compare the efficacy and safety of a basal-bolus insulin regimen comprising either insulin detemir or neural protamine hagedorn (NPH) insulin in combination with mealtime insulin aspart in patients with type 2 diabetes. METHODS: This was a 26-week, multinational, open-label, parallel group trial with 505 patients with type 2 diabetes (mean age, 60.4 +/- 8.6 years; mean BMI, 30.4 +/- 5.3 kg/m(2); mean HbA(1c), 7.9 +/- 1.3%). Patients, randomized 2:1 to insulin detemir or NPH insulin, received basal insulin either once or twice daily according to their pretrial insulin treatment and insulin aspart at mealtimes. RESULTS: After 26 weeks of treatment, significant reductions in HbA(1c) were observed for insulin detemir (0.2%-points, p = 0.004) and NPH insulin (0.4%-points; p = 0.0001); HbA(1c) levels were comparable at study end (insulin detemir, 7.6%; NPH insulin, 7.5%). The number of basal insulin injections administered per day had no effect on HbA(1c) levels (p = 0.50). Nine-point self-measured blood glucose (SMBG) profiles were similar for the two treatment groups (p = 0.58), as were reductions in fasting plasma glucose (FPG) (insulin detemir, 0.5 mmol/l; NPH insulin, 0.6 mmol/l). At study end, FPG concentrations were similar for the two treatment groups (p = 0.66). By contrast, within-subject day-to-day variation in fasting SMBG was significantly lower with insulin detemir (p = 0.021). Moreover, patients receiving insulin detemir gained significantly less body weight than those who were administered NPH insulin (1.0 and 1.8 kg, respectively, p = 0.017). The frequency of adverse events and the risk of hypoglycaemia were comparable for the two treatment groups. CONCLUSIONS: Patients with type 2 diabetes, treated for 26 weeks with insulin detemir plus insulin aspart at mealtimes, experienced comparable glycaemic control but significantly lower within-subject variability and less weight gain compared to patients treated with NPH insulin and insulin aspart. Insulin detemir was well tolerated and had a similar safety profile to NPH insulin.

Carrier frequency of congenital adrenal hyperplasia (21-hydroxylase deficiency) in a middle European population.

Based on newborn screening data, the carrier frequency of congenital adrenal hyperplasia (CAH) in the general population has been estimated to be 1:55. The higher CAH frequency (particularly of milder forms of the disease) reported for certain populations including Yugoslavs (1.6%) relates to population genetic and hormonal data. However, so far, true carrier frequency for CAH due to 21-OH deficiency has not been determined by comprehensive mutation analysis of the 21-OH gene (CYP21A2) in an unselected European population. This study used CYP21A2 genotyping (sequence/Southern blot analysis) to determine CAH carrier frequency in a middle European (Austrian) population. The study included 100 migrants from the former Yugoslavia and 100 individuals of non-Yugoslavian origin. None of these individuals showed clinical hyperandrogenism or had a family history of CAH. Genotyping 400 unrelated alleles from 200 clinically unaffected individuals, this study revealed a carrier frequency of 9.5%, including so-called "classic" (5.5%) and "nonclassic" (4%) CYP21A2-gene aberrations. The observed heterozygosity for CAH in Yugoslavs was not different (P = 0.8095) from that in non-Yugoslavs. In conclusion, the observed CAH carrier frequency of 9.5% suggests a higher prevalence of CAH heterozygosity in a middle European population than hitherto estimated independently of the individuals' Yugoslav or non-Yugoslav origin.

Expression of uncoupling protein-3 mRNA in rat skeletal muscle is acutely stimulated by thiazolidinediones: an exercise-like effect?

AIMS/HYPOTHESIS: We examined whether thiazolidinediones (TZDs) acutely affect uncoupling protein-3 ( UCP-3) expression in skeletal muscle and plasma NEFA in Sprague-Dawley rats. METHODS: Expression of UCP-3 mRNA in hindlimb muscles and plasma NEFA were measured after a single intraperitoneal injection of TZDs in healthy male rats. RESULTS: Independent of which TZD was injected (50 micromol/kg), UCP-3 expression in gastrocnemius muscle was distinctly increased after 6 h (increase vs vehicle-injected control: pioglitazone, 10.3+/-3.2-fold, p=0.03; rosiglitazone, 8.7+/-1.2-fold, p=0.001; RWJ241947, 9.5+/-2.7-fold, p=0.03). This was accompanied by elevated plasma NEFA (control 158+/-13 micromol/l; pioglitazone, 281+/-40 micromol/l, p=0.03; rosiglitazone, 276+/-27 micromol/l, p=0.005; RWJ241947, 398+/-51 micromol/l, p=0.004). The increase in plasma NEFA could in part have mediated TZD-induced UCP-3 expression, but increased UCP-3 mRNA was also found in isolated muscle after 2 h of TZD exposure in vitro (25 micromol/l pioglitazone, 1.7+/-0.3-fold, p=0.046), suggesting that TZDs act directly and independently of NEFA on skeletal muscle. CONCLUSIONS/INTERPRETATION: In healthy rats, a single dose of TZDs rapidly increases UCP-3 mRNA in skeletal muscle and plasma NEFA. This effect resembles the acute response to a bout of exercise.

Production rates of cortisol in men with hypogonadism.

Healthy men have a larger endogenous cortisol production rate (PR) than healthy women. To investigate whether this sex-specific difference is maintained in men with low serum testosterone concentrations the endogenous PRs (2 pm to 6 pm) of testosterone, dihydrotestosterone (DHT), and cortisol were simultaneously determined in 10 hypogonadal men. As expected, hypogonadal men were characterized by subnormal PRs of testosterone (19.6 +/- 5.7 microg/h; normal, 180 to 346 microg/h) and of DHT (1.6 +/- 1.1 microg/h; normal, 11 to 20 microg/h). In hypogonadal patients with an intact pituitary-adrenal axis (n = 8), plasma concentrations (7.3 +/- 1.8 microg/dL), metabolic clearance rates (MCRs) (10.0 +/- 4.6 L/h), and endogenous PRs (0.6 +/- 0.2 mg/h) of cortisol were comparable to those seen in eugonadal men. Hence, the sex-specific difference in endogenous cortisol PRs does not depend on the prevailing serum concentrations and on the endogenous PRs of testosterone.

Brain energy metabolism during hypoglycaemia in healthy and type 1 diabetic subjects.

AIMS/HYPOTHESIS: This study aimed to examine brain energy metabolism during moderate insulin-induced hypoglycaemia in Type 1 diabetic patients and healthy volunteers. METHODS: Type 1 diabetic patients (mean diabetes duration 13 +/- 2.5 years; HbA1c 6.8 +/- 0.3%) and matched controls were studied before, during (0-120 min) and after (120-240 min) hypoglycaemic (approximately 3.0 mmol/l) hyperinsulinaemic (1.5 mU x kg(-1) min(-1)) clamp tests. Brain energy metabolism was assessed by in vivo 31P nuclear magnetic resonance spectroscopy of the occipital lobe (3 Tesla, 10-cm surface coil). RESULTS: During hypoglycaemia, the diabetic patients showed blunted endocrine counter-regulation. Throughout the study, the phosphocreatine:gamma-ATP ratios were lower in the diabetic patients (baseline: controls 3.08 +/- 0.29 vs diabetic patients 2.65 +/- 0.43, p<0.01; hypoglycaemia: 2.97 +/- 0.38 vs 2.60 +/- 0.35, p<0.05; recovery: 3.01 +/- 0.28 vs 2.60 +/- 0.35, p<0.01). Intracellular pH increased in both groups, being higher in diabetic patients (7.096 +/- 0.010 vs. 7.107 +/- 0.015, p<0.04), whereas intracellular magnesium concentrations decreased in both groups (controls: 377 +/- 33 vs 321 +/- 39; diabetic patients: 388 +/- 47 vs 336 +/- 68 micromol/l; p<0.05). CONCLUSIONS/INTERPRETATION: Despite a lower cerebral phosphocreatine:gamma-ATP ratio in Type 1 diabetic patients at baseline, this ratio does not change in control or diabetic patients during modest hypoglycaemia. However, both groups exhibit subtle changes in intracellular pH and intracellular magnesium concentrations.

Free fatty acids exert a greater effect on ocular and skin blood flow than triglycerides in healthy subjects.

BACKGROUND: Free fatty acids (FFAs) and triglycerides (TGs) can cause vascular dysfunction and arteriosclerosis. Acute elevation of plasma FFA and TG concentration strongly increase ocular and skin blood flow. This study was designed to discriminate whether FFA or TG independently induce hyperperfusion by measuring regional and systemic haemodynamics. METHODS: In a balanced, randomized, placebo-controlled, double-blind, three-way, crossover study nine healthy subjects received either Intralipid (Pharmacia and Upjohn, Vienna, Austria) with heparin, Intralipid alone or placebo control. Pulsatile choroidal blood flow was measured with laser interferometry, retinal blood flow and retinal red blood cell velocity with laser Doppler velocimetry, and skin blood flow with laser Doppler flowmetry during an euglycaemic insulin clamp. RESULTS: A sevenfold increase of FFA during Intralipid/heparin infusion was paralleled by enhanced choriodal, retinal, and skin blood flow by 17 +/- 4%, 26 +/- 5% (P < 0.001), and 47 +/- 19% (P = 0.03) from baseline, respectively. In contrast, a mere threefold increase of FFA by infusion of Intralipid alone did not affect outcome parameters, despite the presence of plasma TG levels of 250-700 mg dL(-1); similar to those obtained during combined Intralipid/heparin infusion. Systemic haemodynamics were not affected by drug infusion. CONCLUSIONS: Present findings demonstrate a concentration-dependent increase in ocular and skin blood flow by FFA independently of elevated TG plasma concentrations. As vasodilation of resistance vessels occur rapidly, FFA may play a role in the development of continued regional hyperperfusion and deteriorate microvascular function.

11beta-Hydroxysteroid dehydrogenase Type 1 in obesity and Type 2 diabetes.

Obesity and Type 2 diabetes mellitus are associated with abnormal regulation of glucocorticoid metabolism that are highlighted by clinical similarities between the sequelae of insulin resistance and Cushing's syndrome, as well as glucocorticoids' functional antagonism to insulin. 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) activates functionally inert glucocorticoid precursors (cortisone) to active glucocorticoids (cortisol) within insulin target tissues, such as adipose tissue, thereby regulating local glucocorticoid action. Recent data, mainly from rodents, provide considerable evidence for a causal role of 11beta-HSD1 for the development of visceral obesity and Type 2 diabetes though data in humans are not unequivocal. This review summarizes current evidence on a possible role of 11beta-HSD1 for development of the metabolic syndrome, raising the possibility of novel therapeutic options for the treatment of Type 2 diabetes by inhibition or down-regulation of 11beta-HSD1 activity.

Effect of systemic vitamin C on free fatty acid-induced lipid peroxidation.

OBJECTIVES: Plasma malondialdehyde (MDA), a reactive product of lipid peroxidation, may be influenced by anti-oxidant therapy. The aim of the present study was to investigate if elevated MDA as induced by increased free fatty acids (FFA) correlates with endothelial function and is affected by high doses of vitamin C. METHODS: The study design was randomised, placebo-controlled, double blind, 2-way cross over. Plasma MDA concentrations and forearm blood flow (FBF) responses to intra-arterial acetylcholine (ACh) and glyceryl trinitrate were assessed during co-administration of vitamin C or placebo in the presence of increased plasma FFA by Intralipid/heparin infusion in 10 healthy male subjects. RESULTS: The seven-fold rise in plasma FFA was associated with an increase in plasma MDA concentrations (r=0.7, p<0.001) and decreased FBF responses to ACh (r=-0.4, p<0.01). Co-administration of vitamin C restored the impaired reactivity of FBF to ACh but had no effect on elevated MDA concentrations. CONCLUSIONS: Anti-oxidant vitamin C improves lipid-induced impairment of endothelium-dependent vasodilation, but does not alter MDA formation or breakdown.

Measurement of fractional whole-body gluconeogenesis in humans from blood samples using 2H nuclear magnetic resonance spectroscopy.

Several problems limit quantification of gluconeogenesis. We applied in vitro 2H-nuclear magnetic resonance (NMR) spectroscopy to simultaneously measure 2H in all glucose carbons for direct assessment of gluconeogenesis. This method was compared with 2H measurement in carbons 5 and 2 using gas chromatography-mass spectrometry (hexamethylenetetramine [HMT]) and with in vivo 13C magnetic resonance spectroscopy (MRS). After 14 h of fasting, and following 2H2O ingestion, blood was obtained from nine healthy and seven type 2 diabetic subjects. Glucose was purified, acetylated, and analyzed for 2H in carbons 1-6 with 2H-NMR. Using 5:2 ratios, gluconeogenesis increased (P < 0.05) over time and mean gluconeogenesis was lower in control subjects than in type 2 diabetic patients (63 +/- 3 vs. 75 +/- 2%, P < 0.01). 13C-MRS revealed higher hepatic glycogenolysis in control subjects (3.9 +/- 0.4 vs. 2.3 +/- 0.2 micromol.kg(-1).min(-1)) yielding mean contribution of gluconeogenesis of 65 +/- 3 and 77 +/- 2% (P < 0.005). Measurement of gluconeogenesis by 2H-NMR correlated linearly with 13C-MRS (r = 0.758, P = 0.0007) and HMT (r = 0.759, P = 0.0007). In an additional protocol, 2H enrichments demonstrated a fast decline of gluconeogenesis from approximately 100 to approximately 68% (P < 0.02) within 4 h of galactose infusion after 40-44 h of fasting. Thus, in vitro 2H-NMR offers an alternative approach to determine fractional gluconeogenesis in good agreement with standard methods and allows monitoring of rapid metabolic alterations.