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Enhanced insulin sensitivity seen in patients missing growth hormone in Ecuador
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CHICAGO — People lacking growth hormone receptors also have an insulin sensitivity that protects against diabetes and decreases cancer risks, according to research presented at the joint meeting of the International Congress of Endocrinology and the Endocrine Society.
Jaime Guevara Aguirre, MD, professor of diabetology and endocrinology at Universidad San Francisco de Quito, Ecuador, looked at the protective nature of the genetic growth hormone receptor deficiency (GHRD) in a group of villagers from southern Ecuador.
“We have good suggestions that there’s an enhanced insulin sensitivity in these subjects,” Aguirre said during his presentation.
Aguirre and colleagues embarked on three consecutive studies to look at insulin sensitivity in people with obesity and without GH receptor signaling. Participants were matched for age and BMI. Those with GHRD had approximately 50% more body fat and lower lean/fat due to their condition based on DXA scan data.
The researchers examined carbohydrate, lipid and adipocytokine concentrations in 27 adults with GHRD and 35 comparably overweight adults through fasting and a 2-hour glucose challenge. A 5-hour meal challenge allowed researchers to evaluate metabolic responses to a standard breakfast in 7 patients with GHRD and 11 patients from the control group. A 2-hour oral glucose tolerance test (OGTT) was also conducted in 7 patients with GHRD and 7 patients from the control.
The GHRD group had decreased fasting insulin, 2-hour blood glucose, VLDL and triglyceride levels indicative of insulin sensitivity, elevated cholesterol and HDL, as well as high LDL levels marking dependence of the receptor on GH action.
The insulin sensitivity indicator HOMA2-%S was more than two times higher in people with GHRD (261±133 vs. 108±87, P<.0001) compared with controls, and the measure of insulin resistance HOMA2-IR was one-third that of controls (0.59±0.51 vs 1.74±1.84, P<.01). High molecular weight adiponectin was also greater in GHRD (7.59±4.07 mg/L vs. 4.29±2.89, P<.001) and leptin lower (7.3±4.7 ng/mL vs. 10.4±5.2, P<.05).
With body weight of about 65% that of controls, those with GHRD consumed the same quantity at breakfast (approximately 1,000 calories, 114-g carbohydrates, 47-g fat, 40-g protein) and had significantly lower mean glucose concentrations (P<0.01), with mean insulin levels one third that of controls (11.4±4.2 vs. 33.1±15.5, P<0.01). Similar results were seen for glucose and insulin following the group engaged in OGTT.
For triglyceride responses to the meal, the area under the curve did not differ during the initial 150 minutes but significantly decreased in GHRD between 180 to 300 minutes.
“When we have those clinical findings of less diabetes and less cancer, we have the low IGF-1 report,” Aguirre said. “For me, since the 1900s, when you can see these … subjects with the GHRD in Ecuador with their relatives, they’re telling us exactly the same thing.” — by Allegra Tiver
For More Information: Aguirre JG. Abstract LB-OR02-1. Presented at: The joint meeting of the International Congress of Endocrinology and the Endocrine Society; June 21-24, 2014; Chicago.
Disclosures: Aguirre reports no relevant disclosures.