A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Ectopic pancreas and the islet cell dysmaturational syndrome

Two cases of ectopic pancreas are described in the setting of the islet cell dysmaturational syndrome. Microscopic and immunostaining studies revealed both lesions to be composed of primarily (80 percent to 90 percent) islet tissue with nuclear hyperchromasia and probable depletion of immunoreactive insulin in one case. Persistent hyperinsulinemic hypoglycemia required a second laparotomy with resection of ectopic pancreas in one case. Awareness of the phenomenon led to successful identification and resection of ectopic islet tissue on first surgery in a subsequent case. Ectopic pancreas is a relatively common developmental pancreatic anomaly, and knowledge of its potential contribution to life-threatening hypoglycemia may obviate the need for multiple surgeries in some cases of islet cell dysmaturational syndrome.

Vasopressin-induced antinociception: an investigation into its physiological and hormonal basis

Systemically administered lysine-8-vasopressin (LVP; 16-128 micrograms/kg) was found to induce a potent and dose-dependent antinociceptive effect, as measured by the tail-flick test in the rat. This effect could be seen in the absence of any significant change in general activity, indicating that it was not due to sedation or general motor debilitation. The antinociceptive effect of LVP does not appear to be mediated by endogenous opiates or other pituitary hormones, as evidenced by: 1) the lack of antagonism by the opiate receptor blocker naloxone, 2) the lack of cross-tolerance with morphine, and 3) its persistence after hypophysectomy. Des-glycinamide-LVP, a vasopressin analog with no appreciable pressor or antidiuretic action, showed no antinociceptive activity (128 micrograms/kg), and des-amino-arginine-vasopressin, a vasopressin analog with minimal pressor activity but greatly enhanced antidiuretic activity, was also relatively ineffective (128 micrograms/kg). These results suggest that the antinociceptive activity of vasopressin may be related to receptor types similar to those mediating its pressor effects. Nevertheless, the antinociceptive action of vasopressin does not appear to be secondary to its pressor activity, since phenylephrine failed to induce an antinociceptive effect at a dosage that mimicked the pressor response to vasopressin. These results are in concert with a growing body of evidence suggesting that vasopressin may be one of several nonopiate peptides that play a role in the modulation of pain sensitivity.