LOS ANGELES – Although menopausal hormone therapy is not approved for the prevention of type 2 diabetes because of its complex balance of risks and benefits, it should not be withheld from women with increased risk of type 2 diabetes who seek treatment for menopausal symptoms, according to .
“During the menopause transition, women accumulate metabolic disturbances, including visceral obesity, systemic inflammation, insulin resistance, dyslipidemia, and hypertension,” Dr. Mauvais-Jarvis, director of the Tulane Diabetes Research Program at Tulane University Health Sciences Center, New Orleans, said at the Annual World Congress on Insulin Resistance, Diabetes & Cardiovascular Disease. “They also lose muscle mass. Some of these abnormalities are partially explained by chronological aging, but they are also caused by estrogen deficiency. There’s a synergism between aging and estrogen deficiency.”
The best evidence of this synergy comes from older trials. Nearly 30 years ago, researchers examined the association between postmenopausal hormone use and the subsequent incidence of non–insulin dependent diabetes in a prospective cohort of 21,028 postmenopausal U.S. women aged 30-55 years, who were enrolled in the Nurse’s Health Study and followed for 12 years (). They found that study participants on hormone therapy experienced a 20% reduction in the incidence of type 2 diabetes. In a more recent trial, researchers examined the association between use of hormone therapy and new-onset diabetes in 63,624 postmenopausal women who were enrolled in the prospective French cohort of the Etude Epidemiologique de Femmes de la Mutuelle Générale de l’Education Nationale ( ) and followed for 15 years ( ). It found that study participants on hormone therapy experienced a 20% reduction in the incidence of type 2 diabetes.
In the Heart and Estrogen/Progestin Replacement Study, researchers evaluated the effect of hormone therapy on fasting glucose level and incident diabetes in 2,763 postmenopausal women with coronary heart disease (). At 20 U.S. centers, the study participants received 0.625 mg of conjugated estrogen plus 2.5 mg of medroxyprogesterone, or placebo, and were followed for 4 years. The researchers found that the use of hormone therapy reduced the incidence of diabetes by 35%.
According to Dr. Mauvais-Jarvis, the strongest data come from the Women’s Health Initiative (WHI), a randomized, double-blind trial that compared the effect of daily 0.625 mg conjugated estrogen plus 2.5 mg medroxyprogesterone acetate with that of placebo during 5.6 years of follow-up (). It showed a 20% decrease in the incidence of diabetes at 5 years. More recently, researchers found that, whether WHI participants took estrogen plus medroxyprogesterone or estrogen alone, the protection from diabetes was present ( ).
In 2006, researchers published results from a meta-analysis of 107 trials in an effort to quantify the effects of hormone therapy on components of metabolic syndrome in postmenopausal women (). In women without diabetes, hormone therapy reduced the HOMA-IR (Homeostatic Model Assessment for Insulin Resistance) score by 13% and incidence of type 2 diabetes by 30%. In women with diabetes, hormone therapy reduced fasting glucose by 11% and HOMA-IR by 36%.
The mechanisms by which estrogens improve glucose homeostasis are yet to be fully understood. “One of the most important [mechanisms] is a decrease in abdominal fat, which improves insulin resistance and systemic inflammation,” Dr. Mauvais-Jarvis said. “However, in the WHI, it was clear that the improvement in HOMA-IR was independent from the body weight and fat. Estrogen has also been found to increase insulin clearance and sensitivity, increase glucose disposal and effectiveness and decrease sarcopenia. There are fewer than 20 studies looking at beta-cell function. Half of them have shown that estrogen improves insulin secretion.”
Route of estrogen administration also comes into play. For example, oral estrogens increase liver exposure to estrogen, increase triglycerides, and increase clotting factors. “That is why oral estrogens are not indicated in women with risk of deep venous thrombosis,” Dr. Mauvais-Jarvis said. “They also increase inflammatory factors like C-reactive protein. Advantages are that they decrease LDL cholesterol levels and increase HDL cholesterol levels more than transdermal estrogen does.”
The main advantage with transdermal delivery of estrogen, he continued, is that it does not raise triglycerides, clotting factors, or inflammatory factors, and it confers less exposure to the liver. “That’s why it’s the preferred way of administration in women who are obese, who have a risk of DVT, or who have cardiovascular risk factors,” he said. “It has a lower suppression of hepatic glucose production, it increases circulating estradiol, and the delivery to nonhepatic tissue is increased. The oral form of estrogen is cheaper, compared with the transdermal form, though. This is a factor that is always taken into account.”
Dr. Mauvais-Jarvis and colleagues were first to evaluate the effect of conjugated estrogens plus bazedoxifene in mice (). “The idea was that by combining estrogen and bazedoxifene, you have the beneficial effect of estrogen in the tissues but you block estrogen in the breast and in the uterus, and therefore, you prevent the risk of cancer,” he said. “We found that tissue-selective estrogen complexes with bazedoxifene prevent metabolic dysfunction in female mice. It increased energy expenditure and decreased fatty liver.”
In a subsequent pilot study, he and his colleagues assessed the effect of 12 weeks’ treatment with bazedoxifene/conjugated estrogens, compared with placebo, on glucose homeostasis and body composition in 12 postmenopausal women (). “We did not find any significant alterations in the IVGTT [Intravenous Glucose Tolerance Test] but we observed improved fasting beta-cell function and serum glucose in menopausal women with obesity,” Dr. Mauvais-Jarvis said ( ).
In a separate, randomized, double-blind, placebo-controlled, crossover trial that he and his colleagues performed in eight postmenopausal women with obesity, the primary endpoint was insulin action as measured by a two-step hyperinsulinemic-euglycemic clamp. Secondary endpoints were body composition, basal metabolic rate, ectopic fat, and metabolome. “We did not find any difference in systemic insulin action, ectopic fat, or energy expenditure,” he said. “But we found something very interesting. We did a metabolic analysis and found that oral estrogens increase hepatic de novo lipogenesis and liver triacylglycerol production. In other words, the oral estrogens were increasing [triacylglycerol] synthesis from glucose, but it does not accumulate in the liver.”
Dr. Mauvais-Jarvis disclosed that he has received research support from the National Institutes of Health, the American Diabetes Association, the Department of Veterans Affairs, and Pfizer.