Denis Raccah

Monitoring Bacterial Community of Human Gut Microbiota Reveals an Increase in Lactobacillus in Obese Patients and Methanogens in Anorexic Patients

Background Studies of the bacterial communities of the gut microbiota have revealed a shift in the ratio of Firmicutes and Bacteroidetes in obese patients. Determining the variations of microbial communities in feces may be beneficial for the identification of specific profiles in patients with abnormal weights. The roles of the archaeon Methanobrevibacter smithii and Lactobacillus species have not been described in these studies. Methods and Findings We developed an efficient and robust real-time PCR tool that includes a plasmid-based internal control and allows for quantification of the bacterial divisions Bacteroidetes, Firmicutes, and Lactobacillus as well as the methanogen M. smithii. We applied this technique to the feces of 20 obese subjects, 9 patients with anorexia nervosa, and 20 normal-weight healthy controls. Our results confirmed a reduction in the Bacteroidetes community in obese patients (p<0.01). We found a significantly higher Lactobacillus species concentration in obese patients than in lean controls (p = 0.0197) or anorexic patients (p = 0.0332). The M. smithii concentration was much higher in anorexic patients than in the lean population (p = 0.0171). Conclusions Lactobacillus species are widely used as growth promoters in the farm industry and are now linked to obesity in humans. The study of the bacterial flora in anorexic patients revealed an increase in M. smithii. This increase might represent an adaptive use of nutrients in this population.

Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithii

Background:Obesity is associated with increased health risk and has been associated with alterations in bacterial gut microbiota, with mainly a reduction in Bacteroidetes, but few data exist at the genus and species level. It has been reported that the Lactobacillus and Bifidobacterium genus representatives may have a critical role in weight regulation as an anti-obesity effect in experimental models and humans, or as a growth-promoter effect in agriculture depending on the strains.Objectives and methods:To confirm reported gut alterations and test whether Lactobacillus or Bifidobacterium species found in the human gut are associated with obesity or lean status, we analyzed the stools of 68 obese and 47 controls targeting Firmicutes, Bacteroidetes, Methanobrevibacter smithii, Lactococcus lactis, Bifidobacterium animalis and seven species of Lactobacillus by quantitative PCR (qPCR) and culture on a Lactobacillus-selective medium.Findings:In qPCR, B. animalis (odds ratio (OR)=0.63; 95% confidence interval (CI) 0.39–1.01; P=0.056) and M. smithii (OR=0.76; 95% CI 0.59–0.97; P=0.03) were associated with normal weight whereas Lactobacillus reuteri (OR=1.79; 95% CI 1.03–3.10; P=0.04) was associated with obesity.Conclusion:The gut microbiota associated with human obesity is depleted in M. smithii. Some Bifidobacterium or Lactobacillus species were associated with normal weight (B. animalis) while others (L. reuteri) were associated with obesity. Therefore, gut microbiota composition at the species level is related to body weight and obesity, which might be of relevance for further studies and the management of obesity. These results must be considered cautiously because it is the first study to date that links specific species of Lactobacillus with obesity in humans.

Incremental value of continuous glucose monitoring when starting pump therapy in patients with poorly controlled type 1 diabetes: The RealTrend study

OBJECTIVE To compare the improvements in glycemic control associated with transitioning to insulin pump therapy in patients using continuous glucose monitoring versus standard blood glucose self-monitoring. RESEARCH DESIGN AND METHODS The RealTrend study was a 6-month, randomized, parallel-group, two-arm, open-label study of 132 adults and children with uncontrolled type 1 diabetes (A1C ≥8%) being treated with multiple daily injections. One group was fitted with the Medtronic MiniMed Paradigm REAL-Time system (PRT group), an insulin pump with integrated continuous subcutaneous glucose monitoring (CGM) capability, with instructions to wear CGM sensors at least 70% of the time. Conventional insulin pump therapy was initiated in the other group (continuous subcutaneous insulin infusion [CSII] group). Outcome measures included A1C and glycemic variability. RESULTS A total of 115 patients completed the study. Between baseline and trial end, A1C improved significantly in both groups (PRT group −0.81 ± 1.09%, P < 0.001; CSII group −0.57 ± 0.94%, P < 0.001), with no significant difference between groups. When the 91 patients who were fully protocol-compliant (including CGM sensor wear ≥70% of the time) were considered, A1C improvement was significantly greater in the PRT group (P = 0.004) (PRT group −0.96 ± 0.93%, P < 0.001; CSII group −0.55 ± 0.93%, P < 0.001). Hyperglycemia parameters decreased in line with improvements in A1C with no impact on hypoglycemia. CONCLUSIONS CGM-enabled insulin pump therapy improves glycemia more than conventional pump therapy during the first 6 months of pump use in patients who wear CGM sensors at least 70% of the time.

Efficacy and Safety of the Once-Daily GLP-1 Receptor Agonist Lixisenatide in Monotherapy A randomized, double-blind, placebo-controlled trial in patients with type 2 diabetes (GetGoal-Mono)

OBJECTIVE To assess efficacy and safety of lixisenatide monotherapy in type 2 diabetes. RESEARCH DESIGN AND METHODS Randomized, double-blind, 12-week study of 361 patients not on glucose-lowering therapy (HbA1c 7–10%) allocated to one of four once-daily subcutaneous dose increase regimens: lixisenatide 2-step (10 μg for 1 week, 15 μg for 1 week, and then 20 μg; n = 120), lixisenatide 1-step (10 μg for 2 weeks and then 20 μg; n = 119), placebo 2-step (n = 61), or placebo 1-step (n = 61) (placebo groups were combined for analyses). Primary end point was HbA1c change from baseline to week 12. RESULTS Once-daily lixisenatide significantly improved HbA1c (mean baseline 8.0%) in both groups (least squares mean change vs. placebo: −0.54% for 2-step, −0.66% for 1-step; P < 0.0001). Significantly more lixisenatide patients achieved HbA1c <7.0% (52.2% 2-step, 46.5% 1-step) and ≤6.5% (31.9% 2-step, 25.4% 1-step) versus placebo (26.8% and 12.5%, respectively; P < 0.01). Lixisenatide led to marked significant improvements of 2-h postprandial glucose levels and blood glucose excursions measured during a standardized breakfast test. A significant decrease in fasting plasma glucose was observed in both lixisenatide groups versus placebo. Mean decreases in body weight (∼2 kg) were observed in all groups. The most common adverse events were gastrointestinal—nausea was the most frequent (lixisenatide 23% overall, placebo 4.1%). Symptomatic hypoglycemia occurred in 1.7% of lixisenatide and 1.6% of placebo patients, with no severe episodes. Safety/tolerability was similar for the two dose regimens. CONCLUSIONS Once-daily lixisenatide monotherapy significantly improved glycemic control with a pronounced postprandial effect (75% reduction in glucose excursion) and was safe and well tolerated in type 2 diabetes.

Efficacy and Safety of Lixisenatide Once Daily Versus Exenatide Twice Daily in Type 2 Diabetes Inadequately Controlled on Metformin: A 24-week, randomized, open-label, active-controlled study (GetGoal-X)

OBJECTIVE To compare efficacy and safety of lixisenatide once daily versus exenatide twice daily in type 2 diabetes inadequately controlled with metformin. RESEARCH DESIGN AND METHODS Adults with diabetes inadequately controlled (HbA1c 7–10%) with metformin were randomized to lixisenatide 20 μg once daily (n = 318) or exenatide 10 μg twice daily (n = 316) in a 24-week (main period), open-label, parallel-group, multicenter study. The primary objective was a noninferiority assessment of lixisenatide versus exenatide in HbA1c change from baseline to week 24. RESULTS Lixisenatide once daily demonstrated noninferiority in HbA1c reduction versus exenatide twice daily. The least squares mean change was −0.79% (mean decrease 7.97 to 7.17%) for lixisenatide versus −0.96% (mean decrease 7.96 to 7.01%) for exenatide, and treatment difference was 0.17% (95% CI, 0.033–0.297), meeting a predefined noninferiority upper CI margin of 0.4%. Responder rate (HbA1c <7.0%) and improvements in fasting plasma glucose were comparable. Both agents induced weight loss (from 94.5 to 91.7 kg and from 96.7 to 92.9 kg with lixisenatide and exenatide, respectively). Incidence of adverse events (AEs) was similar for lixisenatide and exenatide, as was incidence of serious AEs (2.8 and 2.2%, respectively). Discontinuations attributable to AEs occurred in 33 lixisenatide (10.4%) and 41 exenatide (13.0%) patients. In the lixisenatide group, fewer participants experienced symptomatic hypoglycemia (2.5 vs. 7.9%; P < 0.05), with fewer gastrointestinal events (especially nausea; 24.5 vs. 35.1%; P < 0.05). CONCLUSIONS Add-on lixisenatide once daily in type 2 diabetes inadequately controlled with metformin demonstrated noninferior improvements in HbA1c, with slightly lower mean weight loss, lower incidence of hypoglycemia, and better gastrointestinal tolerability compared with exenatide twice daily.

Visceral fat as a main determinant of plasminogen activator inhibitor 1 level in women

OBJECTIVE: To substantiate in a premenopausal population of women, the link between visceral adipose tissue and circulating plasminogen activator inhibitor 1 (PAI-1) levels.DESIGN: Study of correlations between anthropometric parameters and PAI-1 and evaluation of the changes induced by weight loss.SUBJECTS: Forty-two healthy pre-menopausal women (aged 18–51 y, with a wide range of body mass index (BMI, 21–48.8 kg/m2). Thirteen women were evaluated after weight loss (6.6±3.3 kg).MEASUREMENTS: BMI, waist and hip circumferences. Total, subcutaneous and visceral adipose tissue areas at the L3–L4 level by computed tomography. Insulin, cholesterol, triglyceride, HDL cholesterol, PAI-1 activity, PAI-1 antigen and tissue plasminogen activator (tPA) antigen.RESULTS: PAI-1 activity, PAI antigen and tPA antigen were positively correlated with visceral adipose tissue, but not with subcutaneous adipose tissue. This correlation was independent of insulin or triglyceride levels. The amount of visceral adipose tissue explained 28% of the PAI-1 activity variance.Weight loss confirmed this link, PAI-1 diminution being correlated only with visceral adipose tissue loss and not with total fat, insulin or triglyceride decrease.CONCLUSION: This study suggests, like in vitro studies, that visceral fat may be an important contributor to the circulating PAI-1.

Erythrocyte Na+-K+-ATPase Activity, Metabolic Control, and Neuropathy in IDDM Patients

OBJECTIVE To study the relationship among red blood cell Na+-K+-ATPase activity, metabolic control, and diabetic neuropathy. RESEARCH DESIGN AND METHODS Na+-K+-ATPase activity has been measured in the red cell membrane of 43 long-standing IDDM patients (duration of diabetes 17.5 ± 2 years, mean ± SE), with 20 of the patients presenting with peripheral neuropathy. There were 23 healthy subjects serving as the control group. RESULTS Na+-K+-ATPase activity was significantly lower in diabetic patients than in healthy subjects (236.5 ± 7.5 vs. 294 ± 10 nmol P1 · mg protein−1 · h−1, P < 0.05). Among diabetic patients, Na+/K+-ATPase activity was not dependent on the degree of diabetic control, nor was it correlated with either fasting blood glucose (r = 0.16, NS) or HbA1c (r = 0.01, NS). Na+-K+-ATPase activity was lower in patients with neuropathy than in those without it (212 ± 8.5 vs. 261 ± 6.6, P < 0.05). Furthermore, in a subgroup of 20 patients, a positive correlation was observed between erythrocyte Na+-K+-ATPase activity and nerve conduction velocity in the peroneal (r = 0.558, P < 0.02) and tibial nerve (r = 0.528, P < 0.05). CONCLUSIONS These results suggest that diabetes-induced Na+-K+-ATPase activity dysfunction could be implicated in the pathogenesis of human diabetic neuropathy and the electrophysiological abnormalities observed in these patients.

Effect of the aldose reductase inhibitor tolrestat on nerve conduction velocity, Na/K ATPase activity, and polyols in red blood cells, sciatic nerve, kidney cortex, and kidney medulla of diabetic rats.

Long-term prospective studies comparing the effects of conventional and intensive insulin therapy have linked diabetic hyperglycemia to the development of diabetic retinopathy, nephropathy, and neuropathy. The mechanisms through which glucose metabolism leads to the development of these secondary complications, however, are incompletely understood. In animal models of diabetic neuropathy, the loss of nerve function in myelinated nerve fibers has been related to a series of biochemical changes. Nerve glucose, which is in equilibrium with plasma glucose levels, rapidly increases during diabetic hyperglycemia because glucose entry is independent of insulin. This excess glucose is metabolized in large part by the polyol pathway. Increased flux through this pathway is accompanied by the depletion of myo-inositol, a loss of Na/K ATPase activity and the accumulation of sodium. Supportive evidence linking these biochemical changes to the loss of nerve function has come from studies in which aldose reductase inhibitors block polyol pathway activity, prevent the depletion of myo-inositol and the accumulation of sodium and preserve Na/K ATPase activity, as well as nerve function. The kidney and red blood cells (RBCs) are two additional sites of diabetic lesions that have been reported to develop biochemical changes similar to those in the nerve. We observed that polyol levels in the kidney cortex, medulla, and RBCs increased two- to ninefold in rats following 10 weeks of untreated diabetes. Polyol accumulation was accompanied by a 30% decrease in myo-inositol levels in the kidney cortex, but no change in RBCs or the kidney medulla. Na/K ATPase activity was decreased by 59% in RBCs but was unaffected in the kidney cortex or medulla. Aldose reductase inhibitor treatment that preserved myo-inositol levels, Na/K ATPase, and conduction velocity in the sciatic nerve also preserved Na/K ATPase activity in RBCs. Our results suggest that the pathophysiologic mechanisms underlying diabetic neuropathy are different from those of diabetic nephropathy. Our results also suggest that RBCs maybe a surrogate tissue for the assessment of diabetes-induced changes in nerve Na/K ATPase activity.

Beneficial effects of gamma linolenic acid supplementation on nerve conduction velocity, Na+, K+ ATPase activity, and membrane fatty acid composition in sciatic nerve of diabetic rats.

Metabolic and vascular abnormalities are implicated in the pathogenesis of diabetic neuropathy. Two principal metabolic defects are altered lipid metabolism resulting from the impairment of delta-6-desaturase, which converts linoleic acid (LA) into gamma linolenic acid (GLA), and reduced nerve Na+, K+ ATPase activity. This reduction may be caused by a lack of incorporation of (n-6) fatty acids in membrane phospholipids. Because this ubiquitous enzyme maintains the membrane electrical potential and allows repolarization, disturbances in its activity can alter the process of nerve conduction velocity (NCV). We studied the effects of supplementation with GLA (260 mg per day) on NCV, fatty acid phospholipid composition, and Na+, K+ ATPase activity in streptozotocin-diabetic rats. Six groups of 10 rats were studied. Two groups served as controls supplemented with GLA or sunflower oil (GLA free). Two groups with different durations of diabetes were studied: 6 weeks with no supplementation and 12 weeks supplemented with sunflower oil. To test the ability of GLA to prevent or reverse the effects of diabetes, two groups of diabetic rats were supplemented with GLA, one group for 12 weeks and one group for 6 weeks, starting 6 weeks after diabetes induction. Diabetes resulted in a 25% decrease in NCV (P < 0.0001), a 45% decrease in Na+, K+ ATPase activity (P < 0.0001), and an abnormal phospholipid fatty acid composition. GLA restored NCV both in the prevention and reversal studies and partially restored Na+, K+ ATPase activity in the preventive treatment group (P < 0.0001). These effects were accompanied by a modification of phospholipid fatty acid composition in nerve membranes. Overall, the results suggest that membrane fatty acid composition plays a direct role in NCV and confirm the beneficial effect of GLA supplementation in diabetic neuropathy.

Extra-Pancreatic Manifestations in Diabetes Secondary to Mitochondrial DNA Point Mutation Within the tRNALeu(UUR) Gene

OBJECTIVE A point mutation in the mitochondrial genome has been identified as a cause of diabetes and deafness. We report two pedigrees with and A-to-G transition at nucleotide 3243 of mtDNA within the tRNALeu(UUR) gene and focus our investigations on other localizations of the anomaly, particularly muscle and retina. RESEARCH DESIGN AND METHODS Muscular localization has been studied in probands by invasive and noninvasive methods, including muscle biopsy (evaluation of the proportion of mutated mtDNA in comparison to blood cells, measurement of respiratory chain complex activities and histological and histochemical aspects) and 31P-nuclear magnetic resonance (NMR) spectroscopy. Ophthalmic and angiographic examination of retina, electroretinography, and visual evoked potentials were performed in five subjects. RESULTS This mutation, previously described in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), was expressed more abundantly in muscle than in nucleated blood cells. This low expression in blood cells could hamper the diagnosis for some patients. In addition, despite poor clinical expression, muscle was found to be highly affected. Ragged red fibers and dystrophic mitochondria were observed in muscle biopsy. Histochemical assays showed decreased activity of respiratory chain complexes, and 31P-NMR in vivo data further confirmed the defect of muscle oxidative processes. Exercise-induced lactate production was increased. Finally, in both families, an atypical “salt and pepper” pigmentary retinopathy was observed without consequences on visual acuity. CONCLUSIONS In diabetes secondary to 3243 mtDNA mutation, infraclinical muscular and ocular lesions are frequent. These two locations of the disease, which are easily investigated by simple methods, can help in the diagnosis of this new type of diabetes.