Study design and sample collection

Diabetic and normal rats were randomly divided into 9 groups: control (healthy animals that received no treatments), type 1 diabetic rats induced by STZ that received no treatments, insulin-treated type 1 diabetic rats, superovulated rats induced by HMG/HCG, superovulated type 1 diabetic rats, superovulated and insulin-treated type 1 diabetic rats, type 2 diabetic rats induced by NA-STZ that received no treatments, 20 mg/kg/day pioglitazone (Sobhan, Iran)-treated diabetic rats (20), and 100 mg/kg/day metformin (Sobhan, Iran) -treated diabetic rats (21). There were 7 rats in each group and animals were kept in diabetic conditions for 4 weeks (for more than one sex cycle), and administered with drugs for 4 weeks. During all diabetic conditions and treatments, FBS levels were monitored by a glucometer (HemoCue Glucose 201+, Sweden) and glucose reagent strips (ACCU-CHEK Active, Germany), every 4 days.

Four days earlier than the end of the treatment period, two female rats of each group were mated with a male rat and vaginal plug was checked in the following morning. The day when the vaginal plugs were observed or vaginal smears showed spermatozoa, was considered the first day of pregnancy. Rats were fasted overnight during the 3rd night and anesthetized through intraperitoneal injection of ketamine hydrochloride (50 mg/kg; ROTEXMEDICA, Germany) and xylazine hydrochloride (7 mg/kg; Daroupakhsh, Iran) on the following day; then, they were sacrificed under sterile conditions on the 4^th day of gravidity (the day of implantation). Uterine horns were surgically separated and snap-frozen in liquid nitrogen and stored at -80°C for further investigations.