Toll-like receptor 2-deficient mice are protected from insulin resistance and beta cell dysfunction induced by a high-fat diet.

AIMS/HYPOTHESIS: Inflammation contributes to both insulin resistance and pancreatic beta cell failure in human type 2 diabetes. Toll-like receptors (TLRs) are highly conserved pattern recognition receptors that coordinate the innate inflammatory response to numerous substances, including NEFAs. Here we investigated a potential contribution of TLR2 to the metabolic dysregulation induced by high-fat diet (HFD) feeding in mice. METHODS: Male and female littermate Tlr2(+/+) and Tlr2(-/-) mice were analysed with respect to glucose tolerance, insulin sensitivity, insulin secretion and energy metabolism on chow and HFD. Adipose, liver, muscle and islet pathology and inflammation were examined using molecular approaches. Macrophages and dendritic immune cells, in addition to pancreatic islets were investigated in vitro with respect to NEFA-induced cytokine production. RESULTS: While not showing any differences in glucose homeostasis on chow diet, both male and female Tlr2(-/-) mice were protected from the adverse effects of HFD compared with Tlr2(+/+) littermate controls. Female Tlr2(-/-) mice showed pronounced improvements in glucose tolerance, insulin sensitivity, and insulin secretion following 20 weeks of HFD feeding. These effects were associated with an increased capacity of Tlr2(-/-) mice to preferentially burn fat, combined with reduced tissue inflammation. Bone-marrow-derived dendritic cells and pancreatic islets from Tlr2(-/-) mice did not increase IL-1beta expression in response to a NEFA mixture, whereas Tlr2(+/+) control tissues did. CONCLUSION/INTERPRETATION: These data suggest that TLR2 is a molecular link between increased dietary lipid intake and the regulation of glucose homeostasis, via regulation of energy substrate utilisation and tissue inflammation.

IL-6 deficiency in mice neither impairs induction of metabolic genes in the liver nor affects blood glucose levels during fasting and moderately intense exercise.

AIMS/HYPOTHESIS: Fasting and exercise are strong physiological stimuli for hepatic glucose production. IL-6 has been implicated in the regulation of gluconeogenic genes, but the results are contradictory and the relevance of IL-6 for fasting- and exercise-induced hepatic glucose production is not clear. METHODS: Investigations were performed in rat hepatoma cells, and on C57Bl6 and Il6(-/-) mice under the following conditions: IL-6 stimulation/injection, non-exhaustive exercise (60 min run on a treadmill) and fasting for 16 h. Metabolite analysis, quantitative real-time PCR and immunoblotting were performed. RESULTS: IL-6 stimulation of rat hepatoma cells led to higher glucose production. Injection of IL-6 in mice slightly increased hepatic Pepck (also known as Pck1) expression. Fasting of Il6(-/-) mice for 16 h did not alter glucose production compared with wild-type mice, since plasma glucose concentrations were similar and upregulation of phosphoenolpyruvate carboxykinase (PEPCK) and Pgc-1alpha (also known as Ppargc1a) expression was comparable. In the non-fasting state, Il6(-/-) mice showed a mild metabolic alteration including higher plasma glucose and insulin levels, lower NEFA concentrations and slightly increased hepatic PEPCK content. Moderately intense exercise resulted in elevated IL-6 plasma levels in wild-type mice. Despite that, plasma glucose, insulin, NEFA levels and hepatic glycogen content were not different in Il6(-/-) mice immediately after running, while expression of hepatic G6pc, Pgc-1alpha, Irs2 and Igfbp1 mRNA was similarly increased. CONCLUSIONS/INTERPRETATION: These data suggest that in mice IL-6 is not essential for physiologically increased glucose production during fasting or non-exhaustive exercise.

Eccentric rehabilitation exercise increases peritendinous type I collagen synthesis in humans with Achilles tendinosis.

It has been shown that 12 weeks of eccentric heavy resistance training can reduce pain in runners suffering from chronic Achilles tendinosis, but the mechanism behind the effectiveness of this treatment is unknown. The present study investigates the local effect of an eccentric training regime on elite soccer players suffering from chronic Achilles tendinosis on the turnover of the peritendinous connective tissue. Twelve elite male soccer players, of whom six suffered from unilateral tendinosis and six were healthy controls, participated in this study. All participants performed 12 weeks of heavy-resistance eccentric training apart from their regular training and soccer activity. Before and after the training period the tissue concentration of indicators of collagen turnover was measured by the use of the microdialysis technique. After training, collagen synthesis was increased in the initially injured tendon (n=6; carboxyterminal propeptide of type I collagen (PICP): pre 3.9+/-2.5 microg/L to post 19.7+/-5.4 microg/L, P<0.05). The collagen synthesis was unchanged in healthy tendons in response to training (n=6; PICP: pre 8.3+/-5.2 microg/L to post 11.5+/-5.0 microg/L, P>0.05). Collagen degradation, measured as carboxyterminal telopeptide region of type I collagen (ICTP), was not affected by training neither in the injured nor in the healthy tendons. The clinical effect of the 12 weeks of eccentric training was determined by using a standardized loading procedure of the Achilles tendons showing a decrease in pain in all the chronic injured tendons (VAS before 44+/-9, after 13+/-9; P<0.05), and all subjects were back playing soccer following the eccentric training regime. The present study demonstrates that chronically injured Achilles tendons respond to 12 weeks of eccentric training by increasing collagen synthesis rate. In contrast, the collagen metabolism in healthy control tendons seems not to be affected by eccentric training. These findings could indicate a relation between collagen metabolism and recovery from injury in human tendons.