Native Oxyntomodulin Has Significant Glucoregulatory Effects Independent of Weight Loss in Obese Humans With and Without Type 2 Diabetes

Oxyntomodulin (OXM), an enteroendocrine hormone, causes appetite suppression, increased energy expenditure, and weight loss in obese humans via activation of GLP-1 and glucagon receptors. However, the effects of OXM on glucose homeostasis remain ill defined. To address this gap, we evaluated the effects of an i.v. infusion of native OXM on insulin secretion rates (ISRs) and glycemic excursion in a graded glucose infusion (GGI) procedure in two separate randomized, placebo (PBO)-controlled, single-dose crossover trials in 12 overweight and obese subjects without diabetes and in 12 obese subjects with type 2 diabetes mellitus (T2DM), using the GLP-1 analog liraglutide (LIRA) as a comparator in T2DM. In both groups, in the GGI, 3.0 pmol/kg/min of OXM significantly increased ISR and blunted glycemic excursion relative to PBO. In T2DM, the effects of OXM were comparable to those of LIRA, including restoration of β-cell glucose responsiveness to that of nonobese subjects without diabetes. Our findings indicate that native OXM significantly augments glucose-dependent insulin secretion acutely in obese subjects with and without diabetes, with effects comparable to pharmacologic GLP-1 receptor activation and independent of weight loss. Native OXM has potential to improve hyperglycemia via complementary and independent induction of insulin secretion and weight loss.

Oxyntomodulin increases energy expenditure in addition to decreasing energy intake in overweight and obese humans: a randomised controlled trial

BACKGROUND

Oxyntomodulin has recently been found to decrease body-weight in obese humans and may be a potential anti-obesity therapy.

OBJECTIVE

To determine whether oxyntomodulin alters energy expenditure, in addition to reducing energy intake, in 'free-living' overweight and obese volunteers.

DESIGN

Randomized double-blind controlled cross-over trial.

SETTING

Community and hospital-based.

PARTICIPANTS

Fifteen healthy overweight and obese men and women (age: 23-49 years, BMI: 25.1-39.0 kg/m(2)). All volunteers completed the study protocol.

INTERVENTIONS

Four-day subcutaneous self-administration of pre-prandial oxyntomodulin, three times daily. Participants were advised to maintain their normal dietary and exercise regimen.

MEASUREMENTS

(1) Energy expenditure, measured by indirect calorimetry and combined heart rate and movement monitoring; (2) energy intake, measured during a study meal.

RESULTS

Oxyntomodulin administration reduced energy intake at the study meal by 128+/-29 kcal (P=0.0006) or 17.3+/-5.5% (P=0.0071), with no change in meal palatability. Oxyntomodulin did not alter resting energy expenditure; but increased activity-related energy expenditure by 143+/-109 kcal/day or 26.2+/-9.9% (P=0.0221); total energy expenditure by 9.4+/-4.8% (P=0.0454) and physical activity level by 9.5+/-4.6% (P=0.0495). A reduction in body weight of 0.5+/-0.2% was observed during the oxyntomodulin administration period (P=0.0232).

CONCLUSION

Oxyntomodulin increases energy expenditure while reducing energy intake resulting in negative energy balance. This data supports the role of oxyntomodulin as a potential anti-obesity therapy.