Comparison of Continuous Glucose Monitoring between Dexcom G4 Platinum and HD-XG Systems in Nonhuman Primates (Macaca Fascicularis)

Abstract

Timely knowing glucose level helps diabetic patients to manage the disease, including decisions about food, physical activity and medication. This study compared two continuous glucose monitoring systems in conscious and moving-free nonhuman primates (NHPs, Macaca fascicularis). Each normoglycemic or diabetic monkey was implanted with one Dexcom G4 Platinum subcutaneously or one HD-XG glucose sensor arterially for glucose monitoring. The glucose levels measured by both telemetry devices significantly correlated with the glucometer readings. The data of oral glucose tolerance test (oGTT) showed that the glucose levels measured by either Dexcom G4 Platinum or HD-XG transmitter were very similar to glucometer readings. However, compared to HD-XG transmitter or glucometer, Dexcom G4 Platinum detected a decreased glucose peak of ivGTT with approximately 10 min delay due to interstitial glucose far behind blood glucose change. Our data showed the advantages of the telemetry systems are: (1) consecutive data collection (day and night); (2) no bleeding; (3) no anesthesia (moving freely); (4) recording natural response without physical restriction and stress; (5) less labor intensity during ivGTT and other tests; (6) quick outcomes without lab tests. This article summarized and compared the differences of the general characteristics of two continuous glucose monitoring systems in diabetic research.

Figure 1

(A) FDA-approved Dexcom G4 Platinum sensor for continuous glucose monitoring. The free tip was an 0.12 mm diameter platinum electrode (Glucose sensor) for sensing glucose after subcutaneous implantation and the other end was connected to a transmitter placed on the skin surface. The inserts show a sensor delivery syringe loaded with one glucose sensor ready for subcutaneous implantation and a signal transmitter. (B) Implantable HD-XG telemetry device for continuous monitoring of glucose, temperature, and locomotor activity. (C) Significant correlation between the glucose levels measured by Dexcom G4 Platinum and glucometer. (D) Significant correlation between the blood glucose levels measured by HD-XG telemetry device and glucometer.

Figure 2

Representative traces collected continuously from one conscious monkey implanted with a Dexcom G4 Platinum and another monkey with a HD-XG device. Panel A The marker on the top showed the day time (open bar) and night time (filled bar). Calibrations (Spots in red) were conducted twice per day during the period of glucose continuous monitoring. More variabilities of glucose levels occurred during the 2^nd day resulted from experimental procedures and feeding. Panel B From top to bottom: body temperature (1^st trace) with the marker on top to indicate day time (open bar) and night time (filled bar), physical activity (2^nd trace), blood glucose electrical signal (3^rd trace), and blood glucose level (4^th trace) after calculation from the corresponding glucose electrical signal. One ivGTT was conducted in the monkey during the 1^st day monitoring (see the arrows).

Figure 3

Oral glucose tolerance test (oGTT) was performed in the conscious normoglycemic (Panel A, n = 5 and B, n = 3) and hyperglycemic (Panel C, n = 5 and D, n = 2) monkeys. The glucose levels during glucose gavage oGTT were continuously monitored by the subcutaneously implanted Dexcom G4 platinum devices (tissue glucose, Panel A and C) or by the arterially implanted HD-XG devices (blood glucose, Panels B and D) and also by the glucometer simultaneously (blood glucose, Panel A,B,C and D).

Figure 4

Intravenous glucose tolerance test (ivGTT) was performed in the conscious normoglycemic (Panel A, n = 5 and B, n = 3) and hyperglycemic (Panel C, n = 5 and D, n = 2) monkeys. The glucose levels were continuously monitored by the subcutaneously implanted Dexcom G4 platinum devices (interstatial glucose, Panel A and C) or by the arterially implanted HD-XG devices (blood glucose, Panel B and D) and also by the glucometer simultaneously (blood glucose, Panel A,B,C and D).

Figure 5

The tissue glucose changes during glucose-gavage oGTT and banana-glucose feed oGTT in the conscious normoglycemic (Panel A, n = 5) and hyperglycemic (Panel B, n = 5) monkeys. The interstitial glucose levels were continuously monitored by the implanted Dexcom G4 platinum devices. Panel C, The blood glucose changes measured by the glucometer during banana-glucose feed oGTT and glucose gavage oGTT in the conscious hyperglycemic monkeys (n = 24).