Leptin responses to long-term cardiorespiratory exercise training without concomitant weight loss: a prospective study

AIM

The aims of the present study were to examine 1) whether changes in circulating leptin levels occur in response to six months of aerobic exercise training (ET) without concomitant weight loss; 2) whether there is a different response with respect to gender; and 3) the relationship between age and leptin and whether this relationship has any impact on the response to ET without weight-loss.

METHODS

Thirty-eight healthy, sedentary men and women (age 38.43+/-2.24, range 18-59 years) participated in 6 months of supervised, moderate intensity (ET) performed 4 days per week. Maintenance of usual dietary practices were encouraged to minimize weight-loss. Participants were evaluated for circulating fasting leptin, body mass, body fat percentage and maximal aerobic power (VO2max) prior to and after ET.

RESULTS

There was no decrease in body weight or leptin concentration (17.69+/-2.67 vs 16.85+/-3.12 ng dL(-1)). Gender did not affect the response to exercise training. The bivariate correlation between leptin and age was not significant, but the relationship reached significance after controlling for body fat percentage and VO2max (r = -0.358, P < 0.05). Age did not affect the response of leptin concentration to ET.

CONCLUSION

It is probable that changes in leptin concentration reported previously with ET may be attributable to concomitant weight loss, but age does not play a role in how leptin responds to ET.

Sulphur-containing amino acids are agonists for group 1 metabotropic receptors expressed in clonal RGT cell lines

Comparison of the pharmacological effects of a range of sulphur-containing amino acids on human mGluR1alpha and mGluR5a has been undertaken. cDNAs of each mGluR were transfected into a Syrian hamster tumour cell line AV12-664 that was previously transfected with the rat glutamate-aspartate transporter protein (GLAST). The L-isomers of cysteine sulphinic acid (CSA), homocysteine sulphinic acid (HCSA), cysteic acid (CA) and serine-O-sulphate (SOS) stimulated PI hydrolysis in human mGluR1alpha and mGluR5a cells with full agonist effects. D-CSA, the only active D-isomer, was a partial agonist for mGluR5a whereas L-sulphocysteine (S-CYS) showed weak agonist-like effects at high concentrations on both mGluR1alpha and mGluR5a. L-Homocysteic acid was inactive on both mGluR1alpha and mGluR5a cells. Treatment of mGluR cultures with glutamate pyruvate transaminase did not alter the potencies of the S-amino acids on PI hydrolysis responses. Inhibitor constants (Ki) obtained for L-HCSA, L-CSA, L-CA and L-SOS in [3H]glutamate receptor binding studies with mGluR1alpha cells indicated that L-HCSA, L-CSA, L-CA and L-SOS can bind specifically to mGluR1 with L-HCSA showing the highest affinity. These results confirm that certain endogenously produced S-amino acids may interact directly with group 1 mGluRs.

Is bran efficacious in irritable bowel syndrome? A double blind placebo controlled crossover study

Twenty eight patients with classical irritable bowel syndrome completed a double blind placebo controlled crossover trial in which they added to their normal diet a daily supplement of either 12 bran biscuits (1 = 1.3 g fibre) or 12 placebo biscuits (1 = 0.23 g fibre). Each biscuit was given for three months in random order with crossover to the alternative biscuit at three months. After the initial three months therapy, there was a significant symptomatic improvement compared with pretreatment in both the bran treated (p less than 0.01) and placebo treated groups (p less than 0.01), but there was no significant difference in symptom scores between these two groups. There was no further improvement in either group after the second three months treatment with the alternative therapy. When crossover data for all 28 subjects were combined, symptoms scores after three months bran therapy and after three months placebo therapy did not differ significantly. Twenty four patients completed three day stool collections in both treatment periods. When the symptomatic response to bran among 15 subjects in whom stool weights rose on bran was compared with that among nine subjects whose stool weights were static or fell on the bran, it was shown that symptomatic improvement was independent of an increase in stool weight. These data suggest that in irritable bowel syndrome, especially that associated with abdominal pain, the beneficial effects of bran are due to a placebo response which is independent of an increase in stool weight.