Sex-specific programming of adult insulin resistance in guinea pigs by variable perinatal growth induced by spontaneous variation in litter size.

Intrauterine growth restriction (IUGR) and subsequent neonatal catch-up growth are implicated in programming of insulin resistance later in life. Spontaneous IUGR in the guinea pig, due to natural variation in litter size, produces offspring with asymmetric IUGR and neonatal catch-up growth. We hypothesized that spontaneous IUGR and/or accelerated neonatal growth would impair insulin sensitivity in adult guinea pigs. Insulin sensitivity of glucose metabolism was determined by hyperinsulinemic-euglycemic clamp (HEC) in 38 (21 male, 17 female) young adult guinea pigs from litters of two-to-four pups. A subset (10 male, 8 female) were infused with d-[3-3H]glucose before and during the HEC to determine rates of basal and insulin-stimulated glucose utilization, storage, glycolysis, and endogenous glucose production. n males, the insulin sensitivity of whole body glucose uptake ( r = 0.657, P = 0.002) and glucose utilization ( r = 0.884, P = 0.004) correlated positively and independently with birth weight, but not with neonatal fractional growth rate (FGR10-28). In females, the insulin sensitivity of whole body and partitioned glucose metabolism was not related to birth weight, but that of endogenous glucose production correlated negatively and independently with FGR10-28 ( r = -0.815, P = 0.025). Thus, perinatal growth programs insulin sensitivity of glucose metabolism in the young adult guinea pig and in a sex-specific manner; impaired insulin sensitivity, including glucose utilization, occurs after IUGR in males and impaired hepatic insulin sensitivity after rapid neonatal growth in females.

Use of the hyperinsulinemic euglycemic clamp to assess insulin sensitivity in guinea pigs: dose response, partitioned glucose metabolism, and species comparisons.

The guinea pig is an alternate small animal model for the study of metabolism, including insulin sensitivity. However, only one study to date has reported the use of the hyperinsulinemic euglycemic clamp in anesthetized animals in this species, and the dose response has not been reported. We therefore characterized the dose-response curve for whole body glucose uptake using recombinant human insulin in the adult guinea pig. Interspecies comparisons with published data showed species differences in maximal whole body responses (guinea pig ≈ human < rat < mouse) and the insulin concentrations at which half-maximal insulin responses occurred (guinea pig > human ≈ rat > mouse). In subsequent studies, we used concomitant d-[3-3H]glucose infusion to characterize insulin sensitivities of whole body glucose uptake, utilization, production, storage, and glycolysis in young adult guinea pigs at human insulin doses that produced approximately half-maximal (7.5 mU·min-1·kg-1) and near-maximal whole body responses (30 mU·min-1·kg-1). Although human insulin infusion increased rates of glucose utilization (up to 68%) and storage and, at high concentrations, increased rates of glycolysis in females, glucose production was only partially suppressed (~23%), even at high insulin doses. Fasting glucose, metabolic clearance of insulin, and rates of glucose utilization, storage, and production during insulin stimulation were higher in female than in male guinea pigs (P < 0.05), but insulin sensitivity of these and whole body glucose uptake did not differ between sexes. This study establishes a method for measuring partitioned glucose metabolism in chronically catheterized conscious guinea pigs, allowing studies of regulation of insulin sensitivity in this species.

Assessment outcome is weakly correlated with lecture attendance: influence of learning style and use of alternative materials.

The relation between lecture attendance and learning is surprisingly weak, and the role of learning styles in this is poorly understood. We hypothesized that 1) academic performance is related to lecture attendance and 2) learning style influences lecture attendance and, consequently, affects performance. We also speculated that the availability of alternative resources would affect this relationship. Second-year Bachelor of Science physiology students (n = 120) self-reported their lecture attendance in a block of 21 lectures (attendance not compulsory) and use of alternative resources. Overall self-reported lecture attendance was 73 ± 2%. Female students (n = 71) attended more lectures (16.4 ± 0.6) than male students (14.3 ± 0.08, n = 49) and achieved a higher composite mark in all assessments (73.6% vs. 69.3%, P < 0.02). Marks in the final exam were not statistically different between the sexes and correlated only weakly with lecture attendance (r = 0.29, n = 49, P < 0.04 for male students; r = 0.10, n = 71, P = not significant for female students; and r =0.21, n = 120, P < 0.02 for the whole class). Of the students who passed the exam, poor attenders (<11 lectures) reported significantly more use of lecture recordings (37 ± 8%, n = 15, vs. 10 ± 1%, n = 85, P < 0.001). In a VARK learning style assessment (where V is visual, A is auditory, R is reading/writing, and K is kinesthetic), students were multimodal, although female students had a slightly higher average percentage of the R learning style (preferred read/write) compared with male students (28.9 ± 0.9%, n = 63, vs. 25.3 ± 1.3%, n = 32, P < 0.03). Lecture attendance was not correlated with measured learning style. We concluded that lecture attendance is only weakly correlated with academic performance and is not related to learning style. The substitution of alternative materials for lecture attendance appears to have a greater role than learning style in determining academic outcomes.