A peptidomimetic targeting white fat causes weight loss and improved insulin resistance in obese monkeys

Abstract

Obesity, defined as body mass index greater than 30, is a leading cause of morbidity and mortality and a financial burden worldwide. Despite significant efforts in the past decade, very few drugs have been successfully developed for the treatment of obese patients. Biological differences between rodents and primates are a major hurdle for translation of anti-obesity strategies either discovered or developed in rodents into effective human therapeutics. Here, we evaluate the ligand-directed peptidomimetic CKGGRAKDC-GG-(D)(KLAKLAK)(2) (henceforth termed adipotide) in obese Old World monkeys. Treatment with adipotide induced targeted apoptosis within blood vessels of white adipose tissue and resulted in rapid weight loss and improved insulin resistance in obese monkeys. Magnetic resonance imaging and dual-energy x-ray absorptiometry confirmed a marked reduction in white adipose tissue. At experimentally determined optimal doses, monkeys from three different species displayed predictable and reversible changes in renal proximal tubule function. Together, these data in primates establish adipotide as a prototype in a new class of candidate drugs that may be useful for treating obesity in humans.

Fig. 1

Anthropometric assessment of four obese rhesus monkeys treated with increasing doses of adipotide (0.10, 0.25, 0.43, and 0.75 mg/kg). (A to C) Obese rhesus monkeys displayed improved anthropometric measurements in a time- and dose-dependent manner. The percentage change from baseline for body weight (A), BMI (B), and abdominal circumference (C) was calculated weekly throughout dosing and recovery. Dose-dependent decreases occurred for these parameters in obese monkeys receiving adipotide; in contrast, no changes were observed in monkeys receiving saline. After a 2-week recovery period, the decrease in body weight, abdominal circumference, and BMI began to reverse.

Fig. 2

Anthropometric assessment of obese rhesus monkeys in a fixed-dose (0.43 mg/kg, subcutaneous daily) study of adipotide. (A to C) The average percentage change from baseline for body weight, abdominal circumference, and BMI was calculated weekly throughout the treatment (28 days) and recovery (28 days) intervals for each animal that received adipotide or saline. In the treatment group, we observed marked decreases in (A) the average body weight (10.6%), (B) BMI (10.0%), and (C) abdominal circumference (8.4%) relative to the baseline measurements. Error bars indicate SEM (control, n = 5; treated, n = 10). (D to F) These findings were statistically significant (mixed-effects model, P < 0.0001 for each variable). During a 4-week recovery period, the decrease in body weight, abdominal circumference, and BMI began to slowly reverse.

Fig. 3

DEXA imaging confirms a loss in total body fat percentage. Whole-body DEXA scans were obtained weekly throughout dosing and recovery for a subset of animals in the control (n = 3) and treatment groups (n = 6). (A) From the start of the study to the end of the recovery period, the percentage of total body fat decreased by 38.7 and 14.8% in animals receiving adipotide and saline, respectively. Error bars indicate SEM. (B) This change over time was statistically significant (mixed-effects model, P < 0.0001).

Fig. 4

MRI confirms that weight loss results from a marked decrease in the volume of white adipose tissue. (A) The percentage change in fat volume was determined by quantifying the volume with axial T1-weighted MR images. The change is represented as percentage change from baseline (day 1) and is significantly decreased at the end of treatment and at the end of recovery (Mann-Whitney-Wilcoxon test, P = 0.02 and P = 0.04, respectively). Error bars indicate SEM (control, n = 3; treated, n = 6). (B) A mixed-effects model of the data over time indicates significance in the decreasing fat percentage for the treated versus control groups (P < 0.0001). (C) Representative sagittal and axial T1-weighted images from one of the treated animals. The window level range is indicated by the color bar on the right. Axial images are taken at the cross section indicated by the white dashed line in the sagittal image. A decrease in fat content is represented by a decrease in window level (that is, intensity of the image display).

Fig. 5

Metabolic assessment and food consumption during a fixed-dose study of adipotide. (A) The average AUC for insulin was calculated from an IVGTT performed within 7 days of the initial dose (0.43 mg/kg) and 24 hours after the final dose (0.43 mg/kg) of adipotide. Animals receiving adipotide showed a statistically significant decrease in AUC compared to monkeys in the control groups (Mann-Whitney-Wilcoxon, P = 0.019). Error bars indicate SEM (control, n = 5; treated, n = 10). (B) The insulinogenic index from an IVGTT was calculated as the change in the AUC for insulin divided by the change in AUC for glucose (paired t test, P = 0.006). Error bars indicate SEM (fixed-dose study: control, n = 5; treated, n = 10; n.s., not significant). (C) Relationship between biscuit consumption and dosing. Consumption decreased with continued dosing and appeared to increase after cessation of drug administration in the treated groups; consumption remained relatively constant throughout the studies in the control groups (control, n = 5; treated, n = 10).

Fig. 6

Renal dysfunction is mild, dose-dependent, and reversible. (A) Serum creatinine was measured in four rhesus macaques used for the initial dose-finding study. There was a dose-dependent increase in serum creatinine in monkeys receiving adipotide that reversed after discontinuation of adipotide. (B) In the fixed-dose study, serum creatinine remained slightly to moderately elevated throughout the dosing interval and gradually returned to baseline during the recovery period (control, n = 5; treated, n = 10). (C) In contrast, BUN remained unchanged or decreased throughout dosing for the four monkeys receiving adipotide in the initial dose-finding study. (D) In the fixed-dose study, an initial elevation in BUN on day 8 was followed by a steady decline to a level below baseline by day 22 and an eventual return to baseline by the end of the recovery period. Creatinine and BUN remained unchanged throughout both studies in the control groups. Error bars indicate SEM (fixed-dose study: control, n = 5; treated, n = 10). Using a mixed-effects model to compare the change in BUN and creatinine over time (from day 1 to day 57) between the control and treated group, we found that only BUN reached significance (P = 0.001).

Fig. 7

Representative kidney images from control and high-dose monkeys from the 28-day repeat-dose safety study of adipotide. (A) Histological evaluation of kidney sections indicated normal kidney tubules in the control animal. (B) Twenty-four hours after the final high dose (0.75 mg/kg) of adipotide, renal tubules frequently display mild tubular degeneration, moderate regeneration, and single-cell necrosis (arrows). (C) At the end of the high-dose recovery period, minimal to mild tubular degeneration and regeneration were infrequently noted (arrow). Scale bars, 200 μm.