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Insulin resistance, metabolic dysfunction common in Bardet-Biedl syndrome

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February 9, 2018

Adults with Bardet-Biedl syndrome are more than twice as likely to have insulin resistance and metabolic syndrome vs. healthy adults; however, most patients with the condition also had normal thyroid and pituitary function, according to a case-control analysis conducted in England.

The prevalence of Bardet-Biedl syndrome, a rare autosomal recessive disorder, is estimated to be about 1 in 125,000 in Europe, although it is more prevalent in some other countries, Safa Mujahid, of Guy’s and St. Thomas’ NHS Foundation Trust in London, and colleagues wrote in the study background. The disorder is characterized by obesity, rod-cone dystrophy, polydactyly, hypogonadism, renal abnormalities and cognitive impairment.

In a case-control study, Mujahid and colleagues analyzed data from 152 patients with Bardet-Biedl syndrome who attended two specialist clinics in England (mean age, 33 years; 55.3% men; mean BMI, 35.7 kg/m²; 82.9% white), as well as 103 age-, sex- and BMI-matched controls (mean age, 33 years; 46.6% men; mean BMI, 34.2 kg/m²; 60.1% white). Data collected from patients with Bardet-Biedl syndrome were part of routine clinical care, including measurements of thyroid function, liver function, lipid profile, and glucose and insulin levels. Metabolic syndrome was defined by International Diabetes Federation criteria.

Among patients with Bardet-Biedl syndrome, 76.3% had obesity.

Researchers found that, compared with controls, patients with Bardet-Biedl syndrome had higher fasting glucose (mean, 5.2 mmol/L vs. 4.9 mmol/L) and serum insulin levels (mean, 24.2 pmol/L vs. 14.2 pmol/L) and homeostatic model assessment of insulin resistance (mean, 5.55 vs. 3.09). When excluding patients with diabetes, there were no between-group differences for HbA1c; however, patients with Bardet-Biedl syndrome had mean HbA1c that was within range for impaired glucose tolerance.

Researchers also found that patients with Bardet-Biedl syndrome had higher levels of serum triglycerides vs. controls (mean, 2 mmol/L vs. 1.3 mmol/L) and higher systolic blood pressure (mean, 135.2 mm Hg vs. 129 mm Hg), and patients with Bardet-Biedl syndrome were more than twice as likely to have metabolic syndrome vs. controls (54.3% vs. 26%; P < .001).

Among patients with Bardet-Biedl syndrome, 15.8% had type 2 diabetes, and 14.7% of the women had polycystic ovary syndrome; however, 78.4% of these patients had normal pituitary function, and 77% were euthyroid.

“Our data also provide the first robust confirmation that the metabolic syndrome is more prevalent in [Bardet-Biedl syndrome] compared with matched controls, and is in keeping with increased cardiovascular mortality,” the researchers wrote. “Specifically, fasting blood glucose, triglycerides and systolic blood pressure were raised in the [Bardet-Biedl syndrome] group, and overall insulin resistance was higher.”

The researchers also noted that, contrary to previous reports, global pituitary dysfunction is uncommon; however, men with Bardet-Biedl syndrome are more likely to have hypogonadism, and there were more cases of subclinical hypothyroidism in patients with Bardet-Biedl syndrome vs. controls.

“Overt diabetes had not yet developed in many [patients], and this may represent an opportunity to intervene with lifestyle measures,” the researchers wrote. “Subclinical hypothyroidism was a novel finding that will need further exploration.” – by Regina Schaffer

Disclosures: The authors report no relevant financial disclosures.