Clive J. Petry

Diabetes in Old Male Offspring of Rat Dams Fed a Reduced Protein Diet

Restricted fetal growth is associated with increased risk for the future development of Type 2 diabetes in humans. The study aim was to assess the glucose tolerance of old (seventeen months) male rats, which were growth restricted in early life due to maternal protein restriction during gestation and lactation. Rat mothers were fed diets containing either 20% or 8% protein and all offspring weaned onto a standard rat diet. In old-age fasting plasma glucose concentrations were significantly higher in the low protein offspring: 8.4 (1.3)mmol/l v. 5.3 (1.3)mmol/l (p = 0.005), Areas under the curves were increased by 67% for glucose (p = 0.01) and 81% for insulin (p = 0.01) in these rats in intravenous glucose tolerance tests, suggesting (a degree of) insulin resistance. These results show that early growth retardation due to maternal protein restriction leads to the development of diabetes in old male rat offspring. The diabetes is predominantly associated with insulin resistance.

The Association between the FTO Gene and Fat Mass in Humans Develops by the Postnatal Age of Two Weeks

OBJECTIVE Little is known about the genetic determinants of fat mass around birth. We hypothesized that the common rs9939609 single-nucleotide polymorphism (SNP) in FTO is associated with fat mass and metabolic parameters in neonates. DESIGN We conducted a cross-sectional, hospital-based study. PATIENTS Patients included 234 full-term, healthy newborns [122 girls and 112 boys; gestational age (mean, range), 39.0 (37.0-42.0) wk; birth weight, 3.2 (1.9-4.2) kg]. METHODS Cord-blood insulin, IGF-I, IGF-binding protein-1, adiponectin, and visfatin were measured by specific immunoassays. Body composition was assessed by dual-energy x-ray absorptiometry at about 13 d (range, 9-20 d). Genotyping of rs9939609 was achieved by restriction fragment length polymorphism analysis. RESULTS The rs9939609 SNP in FTO was not associated with birth weight; however, it was associated with serum visfatin (P < 0.001), with weight and ponderal index at age 2 wk (P < 0.05), and with total, truncal, and abdominal fat (P < 0.05 to P = 0.01), so that AA homozygotes had 37% higher plasma visfatin concentration and 17, 20, and 17% higher total, truncal, and abdominal fat mass, respectively, than T-carrier neonates. CONCLUSION Our findings support a role of the common rs9939609 SNP in FTO gene in the early stages of fat accretion in humans and disclose novel associations between this SNP and both serum visfatin and abdominal fat mass in neonates.

Effect of maternal iron restriction during pregnancy on renal morphology in the adult rat offspring.

In rats, maternal anaemia during pregnancy causes hypertension in the adult offspring, although the mechanism is unknown. The present study investigated the renal morphology of adult rats born to mothers who were Fe-deficient during pregnancy. Rats were fed either a control (153 mg Fe/kg diet, n 7) or low-Fe (3 mg/kg diet, n 6) diet from 1 week before mating and throughout gestation. At delivery, the Fe-restricted (IR) mothers were anaemic; the IR pups were also anaemic and growth-retarded at 2 d of age. At 3 and 16 months, systolic blood pressure in the IR offspring (163 (sem 4) and 151 (sem 4) mmHg respectively, n 13) was greater than in control animals (145 (sem 3) and 119 (sem 4) mmHg respectively, n 15, P<0.05). At post mortem at 18 months, there was no difference in kidney weight between treatment groups, although relative kidney weight as a fraction of body weight in the IR offspring was greater than in control animals (P<0.05). Glomerular number was lower in the IR offspring (11.4 (sem 1.1) per 4 mm(2), n 13) compared with control rats (14.8 (sem 0.7), n 15, P<0.05). Maternal treatment had no effect on glomerular size, but overall, female rats had smaller and more numerous glomeruli per unit area than male rats. When all animals were considered, inverse relationships were observed between glomerular number and glomerular size (r-0.73, n 28, P<0.05), and glomerular number and systolic blood pressure at both 3 months (r-0.42, n 28, P<0.05) and 16 months of age (r-0.64, n 28, P<0.05). Therefore, in rats, maternal Fe restriction causes hypertension in the adult offspring that may be due, in part, to a deficit in nephron number.

Gestational diabetes: risk factors and recent advances in its genetics and treatment.

The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study of over 23000 diabetes-free pregnancies has shown that at a population level an unequivocal linear relationship exists between maternal glucose concentrations around the beginning of the third trimester of pregnancy and the risk of their baby being born above the ninetieth centile for weight. With the rising incidence of gestational diabetes (GDM) across the developed world, largely paralleling the increased prevalence of obesity, there has been a sharp increase in the risk of pregnancy complications developing related to the birth of macrosomic babies. The associated additional long-term complications of GDM pregnancies means that in the future there is likely to be a large increase in the incidence of type 2 diabetes and associated conditions in both the mothers and their affected offspring. The present review seeks to highlight recent advances and remaining gaps in knowledge about GDM in terms of its genetics (where some of the recently discovered polymorphic risk factors for type 2 diabetes have also proved to be risk factors for GDM) and its treatment by diet, exercise and drugs.

Long-term programming of blood pressure by maternal dietary iron restriction in the rat

We have reported that blood pressure was elevated in 3-month-old rats whose mothers were Fe-restricted during pregnancy. These animals also had improved glucose tolerance and decreased serum triacylglycerol. The aim of the present study was to determine whether these effects of maternal nutritional restriction, present in these animals at 3 months of age, can be observed in the same animals in later life. Pulmonary and serum angiotensin converting enzyme (ACE) concentrations were also measured to investigate whether the renin-angiotensin system was involved in the elevation of blood pressure observed in the offspring of Fe-restricted dams. Systolic blood pressure was higher in the offspring of Fe-restricted dams at 16 months of age. Heart and kidney weight were increased as a proportion of body weight in the offspring of Fe-restricted dams. The pulmonary ACE concentration was not significantly different between the groups. The serum ACE concentration was significantly elevated in the offspring of Fe-restricted dams at 3 but not 14 months of age. There was a strong correlation between serum ACE levels at 3 and 14 months of age. Glucose tolerance and serum insulin were not different between the maternal diet groups. Serum triacylglycerol tended to be lower in the offspring of Fe-restricted dams. There were no differences in serum non-esterified fatty acids or serum cholesterol between the maternal diet groups. This study provides further evidence that maternal nutrition has effects on the offspring that persist throughout life. At 16 months of age, the elevation of blood pressure in Fe-restricted offspring does not appear to be mediated via changes in ACE levels. Both cardiac hypertrophy and decreased serum triacylglycerol have also been observed in Fe-restricted fetuses, suggesting that these changes may be initiated in utero.

Maternal low protein diet in rats programmes fatty acid desaturase activities in the offspring.

Summary Numerous studies show an association between poor fetal growth and adult insulin resistance. Recent studies have shown relation between the long chain polyunsaturated fatty acid composition of skeletal muscle membranes and insulin sensitivity. More detailed analysis has indicated that the activity of Δ5 desaturase is inversely correlated to insulin resistance. The amount of docosahexaenoic acid (C22:6n3) is also thought to play a part in determining insulin sensitivity. The purpose of this study was to test the hypothesis that early growth retardation in the rat, as a result of maternal protein restriction, would lead to alterations in desaturase activities similar to those observed in human insulin resistance. There were no differences in phospholipid fatty acid composition in liver or muscle from control and low protein rats. In both muscle and liver the ratio of docosahexaenoic acid to docosapentaenoic acid was, however, reduced in low protein offspring. Direct measurement of Δ5 desaturase activity in hepatic microsomes showed a reduction (p < 0.03) in the low protein offspring which was negatively corrrelated (r = – 0.855) with fasting plasma insulin. No correlation was observed in controls. These results show that it is possible to programme the activity of key enzymes involved in the desaturation of long chain polyunsaturated fatty acids. This is possibly a mechanism linking fetal growth retardation to insulin resistance. [Diabetologia (1998) 41: 1337–1342]

Common polymorphism in H19 associated with birthweight and cord blood IGF-II levels in humans

BackgroundCommon genetic variation at genes that are imprinted and exclusively maternally expressed could explain the apparent maternal-specific inheritance of low birthweight reported in large family pedigrees. We identified ten single nucleotide polymorphisms (SNPs) in H19, and we genotyped three of these SNPs in families from the contemporary ALSPAC UK birth cohort (1,696 children, 822 mothers and 661 fathers) in order to explore associations with size at birth and cord blood IGF-II levels.ResultsBoth offsprings and mothers H19 2992C>T SNP genotypes showed associations with offspring birthweight (P = 0.03 to P = 0.003) and mothers genotype was also associated with cord blood IGF-II levels (P = 0.0003 to P = 0.0001). The offspring genotype association with birthweight was independent of mothers genotype (P = 0.01 to P = 0.007). However, mothers untransmitted H19 2992T allele was also associated with larger birthweight (P = 0.04) and higher cord blood IGF-II levels (P = 0.002), suggesting a direct effect of mothers genotype on placental IGF-II expression and fetal growth. The association between mothers untransmitted allele and cord blood IGF-II levels was more apparent in offspring of first pregnancies than subsequent pregnancies (P-interaction = 0.03). Study of the independent Cambridge birth cohort with available DNA in mothers (N = 646) provided additional support for mothers H19 2992 genotype associations with birthweight (P = 0.04) and with mothers glucose levels (P = 0.01) in first pregnancies.ConclusionThe common H19 2992T allele, in the mother or offspring or both, may confer reduced fetal growth restraint, as indicated by associations with larger offspring birth size, higher cord blood IGF-II levels, and lower compensatory early postnatal catch-up weight gain, that are more evident among mothers smaller first-born infants.

Catecholamine levels and receptor expression in low protein rat offspring

SUMMARY

Sex-Discordant Associations With Adiponectin Levels and Lipid Profiles in Children

In adults, lower circulating levels of the adipocyte-derived hormone adiponectin are associated with obesity, type 2 diabetes, and cardiovascular disease risks. Its use as a risk marker in children is less clear. In 839 children aged 8 years from a representative birth cohort, circulating adiponectin levels were associated with body weight, BMI, waist circumference, and fasting and 30-min insulin levels, but the associations were opposite in boys, with positive associations, and girls, with inverse associations (P = 0.008–0.00001 for interaction with sex). Girls had overall higher adiponectin, higher total cholesterol, lower HDL cholesterol, and higher triglyceride levels than boys, even after adjustment for BMI. With increasing BMI, girls showed steeper declines in HDL cholesterol (P = 0.01 for interaction) and adiponectin levels (P = 0.0005 for interaction) and a steeper increase in triglyceride levels (P = 0.009 for interaction) compared with boys. In conclusion, plasma adiponectin is not a simple marker of central fat and insulin sensitivity in children. With increasing BMI, decreasing adiponectin levels in girls could contribute to their faster deterioration in lipid profiles in comparison with boys. Our data suggest a complex age- and sex-related regulation of adiponectin secretion or clearance.

Genetic Variations and Normal Fetal Growth

Size at birth is said to be a highly heritable trait, with an estimated 30–70% of the variability a result of genetics. Data from family studies may be confounded, however, by potential interactions between fetal genes and the maternal uterine environment. Overall, the maternal environment tends to restrain fetal growth, and this is most evident in first pregnancies. Restraint of fetal growth appears to be inherited through the maternal line. Potential genetic candidates include the mitochondrial DNA 16189 variant, and common variants of exclusively maternally expressed genes, such as H19, which have been associated with size at birth. Maternal blood glucose levels and blood pressure are also correlated with size at birth, but the degree to which these changes relate to genetic variation in the mother is unclear. Elegant studies in mouse knockout models and rare genetic variants in humans have highlighted the importance of insulin-like growth factor I (IGF-I), IGF-II, insulin and their respective receptors in determining fetal growth. However, data linking common variation in the genes that regulate these proteins and receptors with size at birth are few and inconsistent. Interestingly, common variation in the insulin gene (INS) variable number tandem repeats, which regulates the transcription of insulin and IGF-II, has been associated with size at birth, largely in second and subsequent pregnancies, where maternal restraint is least evident. This suggests that fetal genes, and in particular paternally expressed genes, may have significant effects on fetal growth during pregnancies where maternal restraint of fetal growth is less evident.