Weight-sparing effect of insulin detemir: a consequence of central nervous system-mediated reduced energy intake?

Insulin therapy is often associated with adverse weight gain. This is attributable, at least in part, to changes in energy balance and insulin's anabolic effects. Adverse weight gain increases the risk of poor macrovascular outcomes in people with diabetes and should therefore be mitigated if possible. Clinical studies have shown that insulin detemir, a basal insulin analogue, exerts a unique weight-sparing effect compared with other basal insulins. To understand this property, several hypotheses have been proposed. These explore the interplay of efferent and afferent signals between the muscles, brain, liver, renal and adipose tissues in response to insulin detemir and comparator basal insulins. The following models have been proposed: insulin detemir may reduce food intake through direct or indirect effects on the central nervous system (CNS); it may have favourable actions on hepatic glucose metabolism through a selective effect on the liver, or it may influence fluid homeostasis through renal effects. Studies have consistently shown that insulin detemir reduces energy intake, and moreover, it is clear that this shift in energy balance is not a consequence of reduced hypoglycaemia. CNS effects may be mediated by direct action, by indirect stimulation by peripheral mediators and/or via a more physiological counter-regulatory response to insulin through restoration of the hepatic-peripheral insulin gradient. Although the precise mechanism remains unclear, it is likely that the weight-sparing effect of insulin detemir can be explained by a combination of mechanisms. The evidence for each hypothesis is considered in this review.

Weight change upon once-daily initiation of insulin detemir with or without dietary intervention in overweight or obese insulin-naïve individuals with type 2 diabetes: results from the DIET trial

AIMS

Weight gain upon insulin initiation is opposite to clinical goals in diabetes management. This trial aimed to determine the impact of modest dietary intervention on weight change and examine weight change in baseline body mass index strata when initiating once-daily insulin detemir (IDet) in overweight or obese insulin-naïve individuals with type 2 diabetes (T2D).

METHODS

DIET (Impact of Dietary Intervention on Weight Change in Subjects With Type 2 Diabetes) was a 26-week, randomized, treat-to-target, stratified, controlled, open-label, multinational trial. Subjects were randomized 1 : 1 to either the IDet group, which received basic dietary and physical exercise advice at baseline, or the Diet+IDet group, which had additional dietary consultations with a certified dietician (three face-to-face meetings, three phone contacts).

RESULTS

Mean estimated change in body weight from baseline ± standard error (SE) was -1.05 ± 0.23 kg for Diet+IDet and -0.56 ± 0.23 kg for IDet alone. Estimated mean difference was 0.49 kg (95% confidence interval: -0.15; 1.13, p = 0.132). Glycaemic control, measured by haemoglobin A1c (HbA1c) and fasting plasma glucose, improved similarly in both groups. Both groups reported variable reductions in caloric intake and overall physical activity levels. No difference in hypoglycaemia rates between groups was observed.

CONCLUSION

This study suggests that a modest dietary intervention plus basic lifestyle advice, compared with basic lifestyle advice alone, resulted in similar weight change, efficacy, safety and tolerability when initiating IDet once daily in overweight or obese insulin-naïve individuals with T2D.

Weight maintenance and additional weight loss with liraglutide after low-calorie-diet-induced weight loss: the SCALE Maintenance randomized study

OBJECTIVE

Liraglutide, a once-daily human glucagon-like peptide-1 analog, induced clinically meaningful weight loss in a phase 2 study in obese individuals without diabetes. The present randomized phase 3 trial assessed the efficacy of liraglutide in maintaining weight loss achieved with a low-calorie diet (LCD).

METHODS

Obese/overweight participants (≥18 years, body mass index ≥30 kg m(-2) or ≥27 kg m(-2) with comorbidities) who lost ≥5% of initial weight during a LCD run-in were randomly assigned to liraglutide 3.0 mg per day or placebo (subcutaneous administration) for 56 weeks. Diet and exercise counseling were provided throughout the trial. Co-primary end points were percentage weight change from randomization, the proportion of participants that maintained the initial ≥5% weight loss, and the proportion that lost ≥5% of randomization weight (intention-to-treat analysis). ClinicalTrials.gov identifier: NCT00781937.

RESULTS

Participants (n=422) lost a mean 6.0% (s.d. 0.9) of screening weight during run-in. From randomization to week 56, weight decreased an additional mean 6.2% (s.d. 7.3) with liraglutide and 0.2% (s.d. 7.0) with placebo (estimated difference -6.1% (95% class intervals -7.5 to -4.6), P<0.0001). More participants receiving liraglutide (81.4%) maintained the ≥5% run-in weight loss, compared with those receiving placebo (48.9%) (estimated odds ratio 4.8 (3.0; 7.7), P<0.0001), and 50.5% versus 21.8% of participants lost ≥5% of randomization weight (estimated odds ratio 3.9 (2.4; 6.1), P<0.0001). Liraglutide produced small but statistically significant improvements in several cardiometabolic risk factors compared with placebo. Gastrointestinal (GI) disorders were reported more frequently with liraglutide than placebo, but most events were transient, and mild or moderate in severity.

CONCLUSION

Liraglutide, with diet and exercise, maintained weight loss achieved by caloric restriction and induced further weight loss over 56 weeks. Improvements in some cardiovascular disease-risk factors were also observed. Liraglutide, prescribed as 3.0 mg per day, holds promise for improving the maintenance of lost weight.

Weight change with liraglutide and comparator therapies: an analysis of seven phase 3 trials from the liraglutide diabetes development programme

AIM

We investigated the relationship between weight change and related factors in subjects with type 2 diabetes mellitus (T2DM) treated with liraglutide versus comparator diabetes therapies.

METHODS

Twenty-six-week data from seven phase 3, randomized trials in the liraglutide T2DM development programme were analysed by trial and treatment group: liraglutide (1.2 and 1.8 mg), active comparator and placebo. Outcome measures included proportions of subjects in various weight change categories and their percentage weight change from baseline; impact of body mass index (BMI) and gastrointestinal (GI) adverse events (AEs) on weight change and correlation of weight change with change in glycosylated haemoglobin (HbA1c).

RESULTS

A number of subjects experienced >5% weight loss during the trials (24.4% liraglutide 1.8 mg and 17.7% liraglutide 1.2 mg; 17.7% exenatide, 10.0% sitagliptin, 3.6-7.0% sulphonylurea, 2.6% thiazolidinedione and 2.6% glargine; 9.9% placebo). More weight loss was seen with liraglutide 1.2 and 1.8 mg than with active comparators except exenatide. Across trials, higher initial BMI was associated with slightly greater weight loss with liraglutide. Mean weight loss increased slightly the longer GI AEs persisted. Although HbA1c reduction was slightly larger in higher weight loss categories across treatments (including placebo), sample sizes were small and no clear correlation could be determined. Liraglutide-treated subjects experienced additional HbA1c reduction beyond that which appeared weight induced; thus, not all HbA1c-lowering effect appears weight mediated.

CONCLUSIONS

The majority of liraglutide-treated T2DM subjects experienced weight loss in this analysis. Weight loss was greater and occurred more in glucagon-like peptide-1 receptor agonist-treated subjects than in active comparator-treated subjects.

Structural instability of mutant beta-cell glucokinase: implications for the molecular pathogenesis of maturity-onset diabetes of the young (type-2)

The catalytic function and thermal stability of wild-type and mutant recombinant human pancreatic beta-cell glucokinase was investigated. The mutants E70K and E300K, which are thought to be the cause of impaired insulin production by the pancreatic beta-cell and decreased glucose uptake by the liver of patients with maturity-onset diabetes of the young, were found to be functionally indistinguishable from the wild-type, i.e. their kcat.S0.5, inflection point and h were normal. However, these two mutants showed markedly reduced stability under a variety of test conditions. Glucokinase instability, not low enzyme catalytic activity, may be the cause of diabetes mellitus with E70K and E300K mutants.

Variable effects of maturity-onset-diabetes-of-youth (MODY)-associated glucokinase mutations on substrate interactions and stability of the enzyme

Mutations in the human glucokinase (GK) gene are thought to cause maturity-onset diabetes of youth (MODY) by leading to the production of enzymes with reduced catalytic activities and increased glucose Km values. However, in some cases the diabetic phenotype is more severe than might be predicted from these apparent kinetic effects alone. To determine whether these mutations might also effect other characteristics of the enzyme, nine MODY-associated mutants were expressed as fusion proteins with Schistosoma japonicum glutathione S-transferase (GST) and compared with three wild-type human GK isoforms that were also expressed in the same manner. Three GST-GK isoforms (liver 1, liver 2 and islet) were kinetically indistinguishable from each other and from purified rat liver GK. Noteworthy is a glucose-induced fit effect for the interaction of trinitrophenyl (TNP)-ATP with GST-GK, whereby glucose significantly increased the affinity of TNP-ATP binding to GST-GK without changing the stoichiometry of binding. The nine MODY-associated mutations studied either showed diminished catalytic activity, substrate affinities, allosteric regulation, or stability of the fusion enzyme. We conclude that: (1) Gly261 and Lys414 are important for ATP binding; (2) Val203 may be essential for a glucose-induced fit effect; and (3) the stability of fusion protein may be significantly reduced when Glu300 is replaced by Lys. These results suggest that, in addition to effects on the Km and Vmax. of GK, a decrease in the ATP-binding affinity or stability of the mutated enzyme may also contribute to a reduction of GK activity in individuals with GK-MODY. In the B-cell this would have the effect of blunting glucose-stimulated insulin release, thereby contributing to the diabetic phenotype.

Cyclosporine-induced autoimmunity in rats carrying thymus allografts

An autoimmune syndrome occurs in cyclosporine-treated, lethally irradiated, and marrow-reconstituted rats after cyclosporine is discontinued. This syndrome, referred to as cyclosporine-induced autoimmunity, requires the presence of a thymus. In this report, we demonstrate that the disease will occur in animals transplanted with thymus tissue from an allogeneic donor, incompatible with the recipient at the major histocompatibility complex. T cells generated from these allogeneic thymic chimeras respond in vitro to thymic donor antigens, suggesting that cyclosporine inhibits self-tolerance induction in the thymus. Because disease is more frequent when the tolerizing antigens expressed in the thymus differ from those expressed in the periphery, the possibility that cyclosporine may mediate its effect via the downregulation of self-antigen presented in the thymus is discussed.