α-Lipoic acid increases energy expenditure by enhancing adenosine monophosphate-activated protein kinase-peroxisome proliferator-activated receptor-γ coactivator-1α signaling in the skeletal muscle of aged mice

Skeletal muscle mitochondrial dysfunction is associated with aging and diabetes, which decreases respiratory capacity and increases reactive oxygen species. Lipoic acid (LA) possesses antioxidative and antidiabetic properties. Metabolic action of LA is mediated by activation of adenosine monophosphate-activated protein kinase (AMPK), a cellular energy sensor that can regulate peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis. We hypothesized that LA improves energy metabolism and mitochondrial biogenesis by enhancing AMPK-PGC-1α signaling in the skeletal muscle of aged mice. C57BL/6 mice (24 months old, male) were supplemented with or without α-LA (0.75% in drinking water) for 1 month. In addition, metabolic action and cellular signaling of LA were studied in cultured mouse myoblastoma C2C12 cells. Lipoic acid supplementation improved body composition, glucose tolerance, and energy expenditure in the aged mice. Lipoic acid increased skeletal muscle mitochondrial biogenesis with increased phosphorylation of AMPK and messenger RNA expression of PGC-1α and glucose transporter-4. Besides body fat mass, LA decreased lean mass and attenuated phosphorylation of mammalian target of rapamycin (mTOR) signaling in the skeletal muscle. In cultured C2C12 cells, LA increased glucose uptake and palmitate β-oxidation, but decreased protein synthesis, which was associated with increased phosphorylation of AMPK and expression of PGC-1α and glucose transporter-4, and attenuated phosphorylation of mTOR and p70S6 kinase. We conclude that LA improves skeletal muscle energy metabolism in the aged mouse possibly through enhancing AMPK-PGC-1α-mediated mitochondrial biogenesis and function. Moreover, LA increases lean mass loss possibly by suppressing protein synthesis in the skeletal muscle by down-regulating the mTOR signaling pathway. Thus, LA may be a promising supplement for treatment of obesity and/or insulin resistance in older patients.     

Novel CYP17A1 mutation in a Japanese patient with combined 17α-hydroxylase/17,20-lyase deficiency

Combined 17α-hydroxylase/17,20-lyase deficiency is caused by a defect of P450c17 that catalyzes both 17α-hydroxylase and 17,20-lyase reactions in adrenal glands and gonads. In the present study, we analyzed the CYP17A1 gene in a Japanese girl with 17α-hydroxylase/17,20-lyase deficiency. The patient was referred to us for clitoromegaly at the age of 3 years. The karyotype was 46,XY. The patient was diagnosed as having 17α-hydroxylase/17,20-lyase deficiency based on the clinical and laboratory findings. Analysis of the CYP17A1 gene revealed a compound heterozygous mutation. One mutation was a deletion of codon 53 or 54 encoding Phe (TTC) in exon 1 (ΔF54) on a maternal allele, which has been previously shown to partially abolish both 17α-hydroxylase and 17,20-lyase activities. The other was a novel missense mutation resulting in a substitution of Asn (AAC) for His (CAC) at codon 373 in exon 6 (H373N) on a paternal allele. Functional expression study demonstrated that the H373N mutation almost completely eliminates enzymatic activity. Previous studies have demonstrated that replacement of histidine by leucine at position 373 causes complete loss of both 17α-hydroxylase and 17,20-lyase activities with a defect in heme binding due to a global alteration of P450c17 structure, indicating the importance of H373 for P450c17 structure and function. Together, these results indicate that the patient is a compound heterozygote for the ΔF54 and H383N mutations and that these mutations inactivate both 17α-hydroxylase and 17,20-lyase activities and give rise to clinically manifest combined 17α-hydroxylase/17,20-lyase deficiency.     

Risk factors for 28-day mortality in elderly patients with extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae bacteremia

Gram-negative bacteremia is common in elderly patients and, compared with younger patients, mortality rates in bacteremic elderly patients are high. ESBL-producing organisms were one of the most important risk factors associated with mortality. In addition, older age is one of risk factors for colonization or infection with ESBL-producing organisms. We conducted a retrospective cohort study to evaluate risk factors of all-cause 28-day mortality in elderly patients with ESBL-producing Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) bacteremia. Patients aged 65 years or older, who had one or more blood cultures positive for E. coli and K. pneumoniae and who were hospitalized between January 2006 and December 2010 at a tertiary-care teaching hospital, were included. 191 bacteremic elderly patients were eligible for the study. The all-cause 28-day mortality rate was 24.6% (47/191). In multivariate analysis, prior antimicrobial therapy (p = 0.014) and an elevated SOFA score (p < 0.001) were independent risk factors for increased mortality, while urinary tract infection (UTI) was an independent determinant for non-mortality (p = 0.011). In the current study, prior antimicrobial therapy within 30 days, an elevated SOFA score and nonurinary source of infection were significantly associated with adverse outcomes in elderly patients with ESBL-producing gram-negative bacteremia.     

Effects of meal size and composition on incretin, α-cell, and β-cell responses

The incretins glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) regulate postprandial insulin release from the β-cells. We investigated the effects of 3 standardized meals with different caloric and nutritional content in terms of postprandial glucose, insulin, glucagon, and incretin responses. In a randomized crossover study, 18 subjects with type 2 diabetes mellitus and 6 healthy volunteers underwent three 4-hour meal tolerance tests (small carbohydrate [CH]-rich meal, large CH-rich meal, and fat-rich meal). Non-model-based and model-based estimates of β-cell function and incremental areas under the curve of glucose, insulin, C-peptide, glucagon, GLP-1, and GIP were calculated. Mixed models and Friedman tests were used to test for differences in meal responses. The large CH-rich meal and fat-rich meal resulted in a slightly larger insulin response as compared with the small CH-rich meal and led to a slightly shorter period of hyperglycemia, but only in healthy subjects. Model-based insulin secretion estimates did not show pronounced differences between meals. Both in healthy individuals and in those with diabetes, more CH resulted in higher GLP-1 release. In contrast with the other meals, GIP release was still rising 2 hours after the fat-rich meal. The initial glucagon response was stimulated by the large CH-rich meal, whereas the fat-rich meal induced a late glucagon response. Fat preferentially stimulates GIP secretion, whereas CH stimulates GLP-1 secretion. Differences in meal size and composition led to differences in insulin and incretin responses but not to differences in postprandial glucose levels of the well-controlled patients with diabetes.     

Body fat changes and activity of tumor necrosis factor α system—a 5-year follow-up study

Obesity is associated with subclinical, chronic, and systemic immune activation characterized by increased serum concentration of proinflammatory cytokines released by adipose tissue. The aim of the present study was to determine the relationship between stage of development of obesity and changes in activity of tumor necrosis factor (TNF) system during 5-year follow-up observation. One hundred fifty-four women—102 obese, 24 overweight, and 28 lean—without concomitant diseases were examined for the first time from 2000 to 2001. After 5 years, 57 obese, 12 overweight, and 14 lean subjects were reexamined. In addition to anthropometric measurements, body composition was determined by the bioimpedance method; and serum concentrations of glucose, lipids, insulin, TNF-α, and soluble TNF receptors (sTNFRs) were measured. Only reexamined subjects were included in the analysis. After 5 years, fat mass increased significantly in 46 (66.7%) overweight or obese women and in all lean subjects (39.0 ± 12.3 vs 47.3 ± 13.6 kg, P < .001; 14.8 ± 3.7 vs 20.6 ± 5.4 kg, P < .01, respectively), whereas it decreased in 23 (33.3%) overweight or obese subjects (41.3 ± 12.5 vs 37.2 ± 14.0 kg, P < .005). The TNF-α levels increased significantly only in lean women (3.1 ± 3.0 vs 5.6 ± 2.0 pg/mL, P < .005), but remained unchanged in overweight and obese subjects regardless of fat mass changes. Serum concentrations of sTNFR1 and sTNFR2 decreased by 71% and 25% in obese, by 104% and 21% in overweight, and by 31% and 32% in lean group, respectively. The increase of plasma TNF-α level is an early event in abdominal fat accumulation. It seems that further fat mass gain does not enhance circulating TNF-α levels.     

Changes in α-glucosidase activities along the jejunal-ileal axis of normal rats by the α-glucosidase inhibitor miglitol

Miglitol, an α-glucosidase inhibitor that inhibits postprandial hyperglycemia by delaying carbohydrate digestion and absorption along the jejunal-ileal axis, has recently been approved for use in patients with type 2 diabetes mellitus. Miglitol treatment may lead to increased α-glucosidase activities toward the ileum because carbohydrate flow toward the ileum increases. However, it is not yet known if miglitol treatment alters the α-glucosidase activities along the jejunal-ileal axis. In this study, we examined the effects of miglitol supplementation for 3 or 7 days on α-glucosidase activities along the jejunal-ileal axis of Wistar rats. Supplementation with miglitol for 3 or 7 days in rats increased tissue weights of the lower jejunum and ileum, but did not alter tissue weights of the upper jejunum and cecum or the contents of the cecum. Furthermore, supplementation with miglitol for 7 days reduced the activities of isomaltase and maltase in the upper jejunum and increased the activities of sucrase, isomaltase, and maltase in the lower jejunum and ileum. These results suggest that the delay in carbohydrate digestion and absorption along the jejunal-ileal axis by miglitol supplementation in rats is associated with increased α-glucosidase activities toward the ileum.     

Role of γ melanocyte-stimulating hormone-renal melanocortin 3 receptor system in blood pressure regulation in salt-resistant and salt-sensitive rats

Melanocortin 3 receptor (MC3-R) has high affinity and specificity to γ melanocyte-stimulating hormone (γMSH), a natriuretic peptide involved in regulation of blood pressure (BP) and sodium excretion. Recent studies showing increased MC3-R expression and elevated plasma γMSH in normal rats fed a high-salt diet support the role of this system in sodium homeostasis. We hypothesized that dysregulation of MC3-R response to dietary salt may contribute to salt retention and BP elevation in salt-sensitive hypertension. We examined renal MC3-R expression, plasma γMSH concentration, and response to MC3-R agonist and antagonist in Dahl salt-sensitive (DSS) and Dahl salt-resistant (DSR) rats fed high-salt (8%) or low-salt (0.07%) diets for 3 weeks. Consumption of high-salt diet significantly increased BP in the DSS but not the DSR group. High-salt diet led to a 5-fold increase in plasma γMSH and a 2-fold increase in renal MC3-R in DSR rats. Plasma γMSH and renal MC3-R abundance in DSS rats were maximally elevated on low-salt diet and remained unchanged on high-salt diet. Administration of MC3-R agonist melanotan II significantly lowered BP and raised fractional Na excretion in the DSR but not the DSS rats consuming high-salt diet. In contrast, MC3-R antagonist SHU9119 significantly raised BP and lowered fractional Na excretion in both groups. Thus, the data suggest that γMSH-renal MC3-R pathway is activated and appears to be biologically functional in the DSS rats.     

Changes of peripheral α-melanocyte-stimulating hormone in childhood obesity

Relationships of blood circulating melanocortins to childhood obesity are not well established. We evaluated serum α-melanocyte-stimulating hormone (α-MSH) in lean children and different study groups of childhood obesity. We examined serum α-MSH in 52 otherwise healthy children with childhood obesity (Ob; mean age, 11 years; 32 girls/20 boys), 27 normal-weight children of same age, 7 additional obese patients with reduced melanocortin-4 receptor function (MC4Rmut), and 22 patients with craniopharyngioma (CP). Fasting serum α-MSH and leptin were measured by radioimmunoassay. Serum α-MSH was also evaluated 1 hour after 500-kcal liquid meal (CP and Ob) and at the end of 1-year lifestyle intervention in 24 Ob patients. The α-MSH levels were similar in obese vs lean children but significantly lower in CP (P< .001) and significantly higher (P < .05) in MC4Rmut patients compared with Ob. One hour after liquid meal, α-MSH increased in patients with Ob but not with CP. After 1 year, α-MSH levels increased significantly in the successful weight reduction Ob subgroup despite unchanged cortisol levels. The α-MSH changes correlated to weight status changes (r = 0.67, P = .0003) but not to changes of cortisol, insulin, or homeostasis model assessment of insulin resistance index. Persistently low α-MSH levels in CP patients are suspected to be due to pituitary or hypothalamic damage. High peripheral levels in MC4Rmut carriers indicate up-regulation of α-MSH. Changes of weight status are associated with changes of peripheral α-MSH.     

Plasma α-melanocyte-stimulating hormone: sex differences and correlations with obesity

Rodent experiments raise the possibility of a regulatory role of peripheral α-melanocyte-stimulating hormone (α-MSH) in obesity and metabolism, but human data on peripheral α-MSH levels remain fragmentary. Because of the possible relationship between α-MSH and obesity, we endeavored to test the hypothesis that higher levels of α-MSH in obese patients would correlate with leptin levels and with other markers of obesity. Sixty normal-weight to obese healthy men and women participated. Weight, measures of body composition, and diet diaries were obtained; fasting blood was analyzed for α-MSH, lipids, glucose, insulin, leptin, and adiponectin. To begin to understand the source of peripherally measured hormones, α-MSH was also measured in serum samples from 5 individuals with untreated Addison disease. Levels of α-MSH were higher in men vs women (10.1 ± 4.3 vs 7.6 ± 3.4 pmol/L, P = .019), and α-MSH levels were higher in patients with Addison disease vs controls (17.7 ± 2.3 vs 8.7 ± 0.52 pmol/L, P < .001). Measures of adiposity correlated with insulin and leptin in men and women, and with adiponectin in women. α-Melanocyte-stimulating hormone levels did not correlate significantly with any parameter of adiposity or diet composition. The elevated α-MSH levels in patients with untreated Addison disease suggest possible pituitary secretion of α-MSH to the periphery. The lack of correlation between peripheral α-MSH and parameters of adiposity suggests that endogenous plasma α-MSH levels are not a metric for body composition per se.     

Plasma interleukin-1β concentrations are closely associated with fasting blood glucose levels in healthy and preclinical middle-aged nonoverweight and overweight Japanese men

Plasma interleukin (IL)-1β and IL-6 are markers that predict the risk of inflammation in diabetes. In the current study, we examined the relationship between fasting glucose and plasma inflammatory cytokines (IL-1β and IL-6) concentrations in healthy and preclinical middle-aged Japanese men (mean ± SD, 58.7 ± 7.8 years old) divided according to body mass index (<25 kg/m², nonoverweight group; ≥25 kg/m², overweight group). We conducted a cross-sectional study of 413 healthy and preclinical men aged 40 to 69 years who participated in health checkups in Japan. We measured their clinical parameters, lifestyle factors, and plasma IL-1β and IL-6 concentrations. Participants were classified according to their fasting blood glucose levels, and we compared their plasma cytokine levels. Plasma IL-1β and IL-6 levels in nonoverweight subjects were positively and strongly associated with fasting blood glucose and hemoglobin A_1c; in contrast, these cytokines were strongly associated with homeostasis model assessment of insulin resistance and fasting glucose in overweight subjects. Significant positive associations between plasma IL-1β and glucose concentrations were observed within the groups classified according to glucose concentrations, after adjustment for age and body mass index. The results of our current study show that plasma IL-1β levels are strongly associated with fasting blood glucose concentrations in healthy and preclinical nonoverweight and overweight Japanese men.     

Are human male patients with DAX1/NR0B1 mutations infertile?

DAX-1 stands for Dosage sensitive sex-reversal, Adrenal hypoplasia congenital (AHC), on the X chromosome. DAX-1 mutations usually cause primary adrenal insufficiency or congenital adrenal hypoplasia in early childhood and hypogonadotropic hypogonadism (MIM # 300200). DAX-1 protein is necessary to maintain normal spermatogenesis. In humans, male fertility has been studied in few patients carrying DAX-1 mutations. Cases of azoospermia have been reported, as well as unsuccessful gonadotropin treatments. The clinician should be informed that TESE–ICSI technique carries a potential hope to father non-affected children, as shown in this review.     

Cytokines (interferon-γ and tumor necrosis factor-α)-induced nuclear factor-κB activation and chemokine (C-X-C motif) ligand 10 release in Graves disease and ophthalmopathy are modulated by pioglitazone

Until now, the following are not known: (1) the mechanisms underlying the induction of chemokine (C-X-C motif) ligand 10 (CXCL10) secretion by cytokines in thyrocytes; (2) if pioglitazone is able, like rosiglitazone, to inhibit the interferon (IFN)-γ-induced chemokine expression in Graves disease (GD) or ophthalmopathy (GO); and (3) the mechanisms underlying the inhibition by thiazolidinediones of the cytokines-induced CXCL10 release in thyrocytes. The aims of this study were (1) to study the mechanisms underlying the induction of CXCL10 secretion by cytokines in GD thyrocytes; (2) to test the effect of pioglitazone on IFNγ-inducible CXCL10 secretion in primary thyrocytes, orbital fibroblasts, and preadipocytes from GD and GO patients; and (3) to evaluate the mechanism of action of thiazolidinediones on nuclear factor (NF)-κB activation. The results of the study (1) demonstrate that IFNγ + TNFα enhanced the DNA binding activity of NF-κB in GD thyrocytes, in association with the release of CXCL10; (2) show that pioglitazone exerts a dose-dependent inhibition on IFNγ + TNFα-induced CXCL10 secretion in thyrocytes, orbital fibroblasts, and preadipocytes, similar to the effect observed with rosiglitazone; and (3) demonstrate that thiazolidinediones (pioglitazone and rosiglitazone) act by reducing the IFNγ + TNFα activation of NF-κB in Graves thyrocytes. To the best of our knowledge, this is the first study showing that cytokines are able to activate NF-κB in Graves thyrocytes and a parallel inhibitory effect of pioglitazone both on CXCL10 chemokine secretion and NF-κB activation. Future studies will be needed to verify if new targeted peroxisome proliferator-activated receptor-γ activators may be able to exert the anti-inflammatory effects without the risk of expanding retrobulbar fat mass.