Host-microbiota interaction induces bi-phasic inflammation and glucose intolerance in mice

Objective: Gut microbiota modulates adiposity and glucose metabolism in humans and mice. Here we investigated how colonization of germ-free (GF) mice affects kinetics of adiposity and glucose metabolism. Methods: Adiposity and glucose metabolism were evaluated at different time points in ex-GF and antibiotic treated mice after colonization with gut microbiota from a conventionally raised (CONV-R) mouse. Mouse physiology, microbiome configuration, serum cytokine levels, and gene expression for inflammatory markers were performed in different tissues. Results: Colonization resulted in a bi-phasic glucose impairment: the first phase occurring within 3 days of colonization (early phase) and the second 14–28 days after colonization (delayed phase). The early phase co-occurred with an inflammatory response and was independent of adiposity, while the delayed phase was mostly ascribed to adipose tissue expansion and inflammation. Importantly, re-colonization of antibiotic treated mice displays only the delayed phase of glucose impairment and adiposity, suggesting that the early phase may be unique to colonization of the immature GF mice gut. Conclusions: Our results provide new insights on host–microbiota interaction during colonization of GF mice and the resulting effects on adiposity and glucose metabolism in a time resolved fashion

Gut microbiota regulates maturation of the adult enteric nervous system via enteric serotonin networks.

The enteric nervous system (ENS) is crucial for essential gastrointestinal physiologic functions such as motility, fluid secretion, and blood flow. The gut is colonized by trillions of bacteria that regulate host production of several signaling molecules including serotonin (5-HT) and other hormones and neurotransmitters. Approximately 90% of 5-HT originates from the intestine, and activation of the 5-HT receptor in the ENS has been linked to adult neurogenesis and neuroprotection. Here, we tested the hypothesis that the gut microbiota could induce maturation of the adult ENS through release of 5-HT and activation of 5-HT receptors. Colonization of germ-free mice with a microbiota from conventionally raised mice modified the neuroanatomy of the ENS and increased intestinal transit rates, which was associated with neuronal and mucosal 5-HT production and the proliferation of enteric neuronal progenitors in the adult intestine. Pharmacological modulation of the 5-HT receptor, as well as depletion of endogenous 5-HT, identified a mechanistic link between the gut microbiota and maturation of the adult ENS through the release of 5-HT and activation of the 5-HT receptor. Taken together, these findings show that the microbiota modulates the anatomy of the adult ENS in a 5-HT-dependent fashion with concomitant changes in intestinal transit

Impairment of gut microbial biotin metabolism and host biotin status in severe obesity: effect of biotin and prebiotic supplementation on improved metabolism

Objectives Gut microbiota is a key component in obesity and type 2 diabetes, yet mechanisms and metabolites central to this interaction remain unclear. We examined the human gut microbiome\u27s functional composition in healthy metabolic state and the most severe states of obesity and type 2 diabetes within the MetaCardis cohort. We focused on the role of B vitamins and B7/B8 biotin for regulation of host metabolic state, as these vitamins influence both microbial function and host metabolism and inflammation. Design We performed metagenomic analyses in 1545 subjects from the MetaCardis cohorts and different murine experiments, including germ-free and antibiotic treated animals, faecal microbiota transfer, bariatric surgery and supplementation with biotin and prebiotics in mice. Results Severe obesity is associated with an absolute deficiency in bacterial biotin producers and transporters, whose abundances correlate with host metabolic and inflammatory phenotypes. We found suboptimal circulating biotin levels in severe obesity and altered expression of biotin-associated genes in human adipose tissue. In mice, the absence or depletion of gut microbiota by antibiotics confirmed the microbial contribution to host biotin levels. Bariatric surgery, which improves metabolism and inflammation, associates with increased bacterial biotin producers and improved host systemic biotin in humans and mice. Finally, supplementing high-fat diet-fed mice with fructo-oligosaccharides and biotin improves not only the microbiome diversity, but also the potential of bacterial production of biotin and B vitamins, while limiting weight gain and glycaemic deterioration. Conclusion Strategies combining biotin and prebiotic supplementation could help prevent the deterioration of metabolic states in severe obesity

Polycystic ovary syndrome - Studies of metabolic and ovarian disturbances and effects of physical exercise and electro-acupuncture

Polycystic ovary syndrome (PCOS) is the most common endocrine abnormality in premenopausal women. The syndrome is characterized by hyperandrogenism, ovulatory dysfunction and polycystic ovarian (PCO) morphology. Metabolic disturbances, such as insulin resistance and obesity, are also associated with PCOS. Despite extensive research, the etiology and pathophysiological mechanisms of PCOS and related metabolic disturbances are largely unknown. The clinical management of PCOS is multifaceted but often unsatisfactory. The main aims of this thesis were 1) to develop new rat PCOS models displaying ovarian and/or metabolic abnormalities, and to evaluate the effects of low-frequency (2 Hz) electro-acupuncture (EA) and physical exercise in the most complete of these models, and 2) to characterize the adipose tissue of women with PCOS (normal weight/overweight/obese) in terms of distribution, cellularity, lipid metabolism, release of certain adipokines and macrophage density, and to identify factors among these characteristics and serum sex steroids that are associated with insulin sensitivity in these women. Female rats were continuously exposed either to the aromatase inhibitor letrozole or the nonaromatizable androgen dihydrotestosterone (DHT), starting before puberty, to induce a hyperandrogenic state. All rats exposed to letrozole became anovulatory and developed PCO morphology with structural changes strikingly similar to those in human PCOS, but without the metabolic abnormalities. Rats exposed to DHT displayed alterations in ovarian morphology and function, as well as metabolic abnormalities that included adiposity, enlarged adipocytes and insulin resistance in adulthood. EA and exercise improved both insulin resistance and ovarian morphology in rats with DHT-induced PCOS. These results indicate that both interventions break, at least partly, the vicious circle of androgen excess, insulin resistance and ovarian dysfunction in PCOS. Both EA and exercise also partly restored altered adipose tissue gene expression related to insulin resistance, obesity, inflammation and high sympathetic activity, suggesting that exercise and EA may both influence regulation of adipose tissue metabolism/production and sympathetic activity. Interestingly, in contrast to exercise, EA exerted its beneficial effects without influencing adiposity or adipose tissue cellularity. Compared to controls pair-matched by age and body mass index (BMI), women with PCOS had larger abdominal subcutaneous adipocytes, lower plasma adiponectin, and lower LPL activity (borderline significant). There were no differences in anthropometrical variables or in abdominal volumes of total, subcutaneous and visceral adipose tissue, as determined by MRI, between the groups. Women with PCOS also had lower insulin sensitivity, higher serum levels of testosterone, free testosterone and free estradiol as well as lower serum levels of sex hormone binding globulin. Multiple linear regression analysis revealed that adipocyte size, circulating adiponectin and waist circumference, but not circulating sex steroids, were the factors strongest associated with insulin sensitivity in women with PCOS. In conclusion, androgens are likely play a central role in the pathogenesis of PCOS. Our rat models of PCOS highlight the close relationship between androgen excess and the development of ovarian and/or metabolic disturbances typical of this syndrome. Women with PCOS display hyperandrogenemia, insulin resistance and adipose tissue abnormalities, although their adipose tissue distribution and abdominal volumes are indistinguishable from age/BMI-matched controls. The adipose tissue abnormalities in PCOS ― enlarged adipocyte size and low circulating adiponectin ― together with a large waistline, rather than the hyperandrogenemia, seem to be central factors in the development/maintenance of insulin resistance in these women. EA and exercise may both represent valuable non-pharmacological treatment alternatives in PCOS, with the potential to improve both ovarian dysfunction and metabolic disturbances

Polycystic ovary syndrome - morphologic and dynamic evaluation by magnetic resonance imaging

Polycystic ovary syndrome (PCOS) is a complex endocrine disorder, affecting up to 15% of women of reproductive age. The syndrome is characterized by oligo-anovulation, hyperandrogenism and polycystic ovaries. What constitutes the best definition of PCOS is still a matter of debate. Women with PCOS have a higher risk of developing abdominal obesity, insulin resistance with progression to type 2 diabetes, hypertension, and endometrial hyperplasia/cancer. The etiology of PCOS remains incompletely understood, but insulin resistance may be central in the pathogenesis. The main aims of this thesis were to: 1) characterize the distribution of abdominal adipose tissue in PCOS, 2) assess whether women with PCOS have altered uterine morphology or peristalsis, 3) compare transvaginal ultrasonography (TVUS) and magnetic resonance imaging (MRI) for estimation of ovarian volume and antral follicle count (AFC), and assess reproducibility and interobserver agreement of MRI measurements, and 4) investigate how well ovarian morphology and perfusion discriminate women with PCOS from controls and to elucidate associations between ovarian morphology and serum anti-Müllerian hormone (AMH), a potential surrogate for AFC. Sixty women with PCOS and 31 age- and BMI-matched controls were recruited by advertising in the local community. There were no differences in abdominal volumes of total, subcutaneous and visceral adipose tissue, as determined by MRI, between the groups. The endometrium was thinner in PCOS with oligo-amenorrhea compared to controls. Based on cine MRI, uterine peristalsis was less commonly observed in women with PCOS than in controls. 2D MRI revealed more antral follicles, especially of small size, than 3D TVUS. Ovarian volume estimation by 3D MRI provided volumes closer to 2D TVUS values than did 2D MRI. AFC, ovarian volume, ovarian stroma volume, ovarian total cross-sectional area, AMH, and free testosterone differ in women with PCOS compared with controls. AFC and free testosterone are the best variables to distinguish women with PCOS from controls. AMH was not independently associated with PCOS. In conclusion, women with PCOS display hyperandrogenemia, insulin resistance and adipose tissue abnormalities, although their abdominal adipose tissue distributions were indistinguishable from age/BMI-matched controls. A thinner rather than thicker endometrium was found in women with PCOS and oligo-amenorrhea as compared to controls, contrary to the general belief. Uterine peristalsis was less commonly observed in women with PCOS, but whether disturbed peristalsis contributes to infertility in PCOS remains to be investigated. Our findings suggest, when either oligo-anovulation or clinical signs of hyperandrogenism is absent, that AFC or free testosterone rather than AMH should be added in the estimation if a woman has PCOS or not. MRI had a high ability to distinguish and count small antral follicles, with an adequate intra- and interobserver reliability. MRI is a method well suited for scientific studies on this heterogeneous syndrome

Electrical vs manual acupuncture stimulation in a rat model of polycystic ovary syndrome: different effects on muscle and fat tissue insulin signaling.

In rats with dihydrotestosterone (DHT)-induced polycystic ovary syndrome (PCOS), repeated low-frequency electrical stimulation of acupuncture needles restores whole-body insulin sensitivity measured by euglycemic hyperinsulinemic clamp. We hypothesized that electrical stimulation causing muscle contractions and manual stimulation causing needle sensation have different effects on insulin sensitivity and related signaling pathways in skeletal muscle and adipose tissue, with electrical stimulation being more effective in DHT-induced PCOS rats. From age 70 days, rats received manual or low-frequency electrical stimulation of needles in abdominal and hind limb muscle five times/wk for 4-5 wks; controls were handled but untreated rats. Low-frequency electrical stimulation modified gene expression (decreased Tbc1d1 in soleus, increased Nr4a3 in mesenteric fat) and protein expression (increased pAS160/AS160, Nr4a3 and decreased GLUT4) by western blot and increased GLUT4 expression by immunohistochemistry in soleus muscle; glucose clearance during oral glucose tolerance tests was unaffected. Manual stimulation led to faster glucose clearance and modified mainly gene expression in mesenteric adipose tissue (increased Nr4a3, Mapk3/Erk, Adcy3, Gsk3b), but not protein expression to the same extent; however, Nr4a3 was reduced in soleus muscle. The novel finding is that electrical and manual muscle stimulation affect glucose homeostasis in DHT-induced PCOS rats through different mechanisms. Repeated electrical stimulation regulated key functional molecular pathways important for insulin sensitivity in soleus muscle and mesenteric adipose tissue to a larger extent than manual stimulation. Manual stimulation improved whole-body glucose tolerance, an effect not observed after electrical stimulation, but did not affect molecular signaling pathways to the same extent as electrical stimulation. Although more functional signaling pathways related to insulin sensitivity were affected by electrical stimulation, our findings suggest that manual stimulation of acupuncture needles has a greater effect on glucose tolerance. The underlying mechanism of the differential effects of the intermittent manual and the continuous electrical stimulation remains to be elucidated

Labisia pumila

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor that regulates lipid and glucose metabolism. We investigated the effects of Labisia pumila (LP) standardized water extract on PPARgamma transcriptional activity in adipocytes in vitro and in vivo. We used a rat model of dihydrotestosterone- (DHT-) induced polycystic ovary syndrome (PCOS), a condition characterized by insulin resistance. At 9 weeks of age, the PCOS rats were randomly subdivided into two groups: PCOS-LP (50 mg/kg/day of LP) and PCOS-control (1 mL of deionised water) for 4-5 weeks on the same schedule. Real-time RT-PCR was performed to determine the PPARgamma mRNA levels. LP upregulated PPARgamma mRNA level by 40% in the PCOS rats. Western blot analysis further demonstrated the increased PPARgamma protein levels in parallel with upregulation in mRNA. These observations were further proven by adipocytes culture. Differentiated 3T3-L1 adipocytes were treated with final concentration of 100 μg/mL LP and compared to untreated control and 10 μM of rosiglitazone (in type of thiazolidinediones). LP increased PPARgamma expressions at both mRNA and protein levels and enhanced the effect of glucose uptake in the insulin-resistant cells. The data suggest that LP may ameliorate insulin resistance in adipocytes via the upregulation of PPARgamma pathway

Microbial Imidazole Propionate Affects Responses to Metformin through p38γ-Dependent Inhibitory AMPK Phosphorylation

Koh et al. show that imidazole propionate, a microbial metabolite, impairs the glucose-lowering effect of the anti-diabetic drug metformin and inhibits metformin-induced AMPK activation by activating p38γ/Akt/inhibitory AMPK serine phosphorylation. They further show that metformin action is restored by blocking imidazole propionate-activated p38γ