Aminophenazone

Background & objectives: Foetal undernutrition may have important role in adult insulin resistance and diabetes but insulin kinetics in very early life has not been well studied. The present study was undertaken to determine insulin levels in low birth weight neonates and compare with the levels in normal weight and high birth weight neonates.

Methods: Ten 7 day old children each of low birth weight (3500g, Group 3) selected successively over a period of one month were studied. All children were normally delivered at full term and were not suffering from any major illness. Detailed anthropometry was performed, a 6 h fasting blood sample was obtained for blood glucose, lipids, insulin and C-peptide estimation; 60 min after an intravenous glucose load a second sample was obtained for glucose and insulin. Insulin resistance was calculated using the homeostasis model assessment (HOMA).

Results: Levels of total cholesterol, triglycerides, low density and high density lipoprotein cholesterol and glucose were not significantly different in the three groups. Mean fasting and post-glucose load insulin levels (µU/ml) were 2.78±2.23 and 3.28±2.04 in Group 1, 1.67±1.20 and 2.60±2.32 in Group 2 and 3.37±2.08 and 4.40±3.05 in Group 3 and fasting C-peptide levels µg/ml) were 0.296±0.22, 0.208±0.09 and 0.327±0.23 respectively. There was no inter-group difference in insulin-glucose ratio, insulin levels adjusted for ponderal index and HOMA indices. A significant inverse quadratic correlation (U-shaped curve) of body weight with insulin (fasting and post-glucose) and C-peptide levels was observed (P

Interpretation & conclusion: Both low and high birth weight term neonates have high fasting and post-glucose insulin levels. This U-shaped trend suggests influence of foetal undernutrition (environmental) as well as genetic factors in these children.

Key words Barker hypothesis - foetal malnutrition - insulin - low birth weight

The epidemic of atherosclerotic diseases and diabetes has been attributed to foetal undernutrition1. Studies in Britain initially reported that the death rates due to coronary heart disease were twice as high in the poor areas of the country as compared to rich areas and high mortality was associated with poor nutrition in early life2,3. Since then many studies have reported that undernutrition in utero results in maladapted liver metabolism, changes in structure of heart, blood vessels and kidney, resetting of hypothalamic-pituitary-adrenal and growth hormone-insulin axis and changes in pancreas and peripheral muscle in the foetus1,4. In adult life, these alterations cause increase in circulating low density lipoprotein cholesterol5 and fibrinogen6, and lead to hypertension7, coronary heart disease8, and non-insulin dependent diabetes mellitus9.

Foetal undernutrition10 as well as diabetes11 and coronary heart disease12 are epidemic in India. However, their interaction has not been well studied. Yajnike et al13 and Bavdekar et al14 studied children at four and eight year of age, respectively, and detected significant fasting hyperinsulinaemia in low birth weight as compared to normal and high birth weight babiesz. A group from south India15,16 showed higher prevalence of type 2 diabetes and coronary heart disease in adults who had low birth weight. Whether the insulin resistance arises in utero or is a later development is not well understood17. While the thrifty genotype hypothesis18 emphasized the genetic variation, thrifty phenotype hypothesis19 considered suboptimal foetal environment important in insulin resistance, and foetal insulin hypothesis20 placed equal importance to genes and environment. Insulin resistance as well as type 2 diabetes have a significant genetic component and current knowledge suggests that genetic factors that modulate type 2 diabetes in population are common polymorphisms at multiple genes influenced by environment21. Early life (neonatal) insulin levels can provide important information in this regard. Therefore, to study the insulin kinetics in neonates we measured blood glucose and insulin levels and determined insulin resistance in 7 day old low birth weight, normal weight and high birth weight children.

Material & Methods

The study was performed at the Department of Paediatrics, Sawai Man Singh Medical College Hospital, Jaipur (Rajasthan) and approved by the institutional ethics committee. In a month about 400-600 deliveries are carried out in the Department of Obstetrics and enrolled in the neonatology unit of the Zenana Hospital affiliated to this medical college.

In the month of April 2002 there were 403 deliveries (male 215, female 188) in the medical college hospital, of which 44 were preterm, 120 were delivered by caeserean section and 35 had concurrent major illness and were excluded (n=199, 49.4%). Of the remaining 204 (50.5%), we included the first ten children each of low birth weight (3500g, Group 3) whose parents gave a written consent to participate in the study (n=30). All these children were normally delivered at full term (38-42 wk gestation) and were not suffering from any major illness. At 7 days of age each child was evaluated in the neonatology clinic. All the children belonged to urban based parents of middle socioeconomic class. None of the mothers used tobacco, one had diabetes, and one had hypertension. Preparous weight and glucose tolerance test status of the mothers were not available.

Detailed anthropometry was performed according to the guidelines by the World Health Organisation22 by a trained neonatologist. A 6 h fasting blood sample (5ml) was obtained for glucose, lipids, insulin and C-peptide estimation; 60 min after an intravenous glucose load (2.5 g/kg) a second (3 ml) blood sample was obtained for glucose and insulin levels. Glucose was estimated by glucose oxidase pcroxidase-aminophenazone-phenol (GOD-PAP) method using a commercially available kit (Human mBH, Weisbaden, Germany). Blood lipids were measured biochemically following previously reported techniques23 using commercial kits (Accurex Biomedicals, Mumbai). Serum insulin and C-peptide were estimated by immunoradiometric assay using commercial kits (DPC inc, Los Angeles, USA). The intra- and interassay coefficients of variation for the insulin were 5.2 and 7.3 per cent respectively, sensitivity was 1.2 µU/ml and specificity 80 per cent. For C-peptide the intra- and interassay coefficients of variation were 3.8 and 3.9 per cent respectively and sensitivity was 0.0056 µg/ml with specificity 96-98 per cent. Insulin resistance was calculated using the homeostasis model assessment (HOMA) formula24. For calculation of HOMA all values were converted to mmol/l and final values were derived from the formula used in an earlier study25.

Statistical analysis: The power of the study was placed at 90 per cent and sample size was determined using a commercially available statistical program (GBStat Version 7.0, Dynamic Microsystems, Silver Spring, MD, USA) to detect difference of > 30 per cent in various biochemical variables with alpha of

Results

A significant difference (P

Mean and median (95% confidence intervals, CI) fasting insulin levels (µU/ml) were 2.78±2.23 in Group 1 (median 2.95, Cl 0.18 to 7.00), 1.67±1.20 in Group 2 (1.35, 0.50 to 4.60) and 3.37±2.08 in Group 3 (4.20, 0.10 to 6.20) Post glucose load insulin levels were 3.28±2.04 in Group 1 (4.10, 0.24 to 5.61), 2.60±2.32 in Group 2 (1.75, 0.80 to 8.50) and 4.40±3.05 in Group 3 (5.50, 0.10 to 8.50) (P=n.s.). C-peptide levels (µg/ml) were 0.296±0.22 (0.20, 0.10 to 0.62), 0.208±0.09 (0.18, 0.12 to 0.42) and 0.327±0.23 (0.24, 0.12 to 0.90) respectively. There was no significant inter-group difference in insulin-glucose ratio, insulin levels adjusted for ponderal index and HOMA indices (Table II).

Correlation coefficients were estimated for insulin levels with various anthropometric and biochemical variables. Fasting and post glucose insulin levels show nonsignificant and weak correlation with various indices (Table III). An inverse quadratic correlation of weight with insulin levels (fasting and post glucose), and C-peptide is observed (Fig.). Analysis of quadratic trends revealed significant U-shaped trends for fasting insulin, post glucose insulin and C-peptide with increasing weight. Quadratic equation trends (a), (b) and (c) were 13.11,-7.47 and 1.24 for fasting insulin, 7.69, -3.48 and 0.64 for post glucose insulin and 1.01, -0.52 and 0.09 For C-peptide levels respectively (P

Discussion

This study shows that there is a U-shaped relationship of fasting and post glucose load insulin, and C-peptide levels with weight among 7 day old neonates. Multiple epidemiological observations have shown that in subjects of European descent size at birth is inversely related to development of insulin resistance and diabetes in adulthood1,4. Studies from Hertfordshire and Preston in Britain3, US male health professional26 and Swedish adults27 showed that there was an inverse relationship of adult onset impaired glucose tolerance and type 2 diabetes with birth weight.

Neel18 proposed a thrifty genotype hypothesis to explain the higher prevalence of type 2 diabetes in the western populations. He hypothesised that genes that would favour survival at a time of famine would become detrimental when the food supply is abundant. This theory encompasses the two major components of the present association: undernutrition and the later development of metabolic consequences. Hales and Barker19 proposed an alternative thrifty phenotype hypothesis in which environmental factors play a crucial role. They proposed that alteration in foetal nutrition and endocrine status results in developmental adaptations that permanently change structure, physiology and metabolism, thereby predisposing individuals to cardiovascular, metabolic and endocrine diseases in later life. McCance et al28 studied Pima Indians and proposed a surviving small-baby genotype hypothesis. Children genetically predisposed to insulin resistance and type 2 diabetes selectively survive conditions associated with reduced foetal growth. Hattcrslcy and Tooke20 proposed the foetal insulin hypothesis in keeping with the strong contribution of genetic factors in diabetes and insulin resistance and hypothesised that a genetically determined insulin resistance could result in a low insulin mediated foetal growth as well as insulin resistance in childhood and adulthood. However, the same authors acknowledged the importance of both genetic and environmental factors in the control of foetal growth. Sobgnwi et al29 demonstrated the importance of intrauterine diabetic environment in adult insulin resistance.

Yajnik et al13 examined 379 children aged 4 yr for insulin levels and insulin resistance in Pune, western India. They reported that 30 min post glucose insulin and glucose levels were inversely correlated with birth weight in those who were admitted to routine postnatal wards independently of their current size. Those admitted to special baby care units also had an inverse correlation of birth weight with 30 min post glucose insulin levels. Birth weight did not correlate with fasting glucose levels. Bavdekar et al14 reported glucose and insulin levels in 8 yr old children at Pune. An inverse correlation of adjusted current weight and birth weight was noted with fasting and post glucose insulin levels, pro-insulin levels and HOMA index of insulin resistance. No correlation of fasting glucose with birth weight was noted and there was a positive trend of glucose intolerance with increasing weight. The greatest insulin resistance was observed in those with low birth weight and high current weight, i.e., children with abnormal weight gain. Our study shows higher insulin levels in low birth weight neonates (Group 1) as compared to normal weight neonates (Group 2) and is in agreement with these studies.

From birth records in a hospital in the south Indian city Mysore, 506 men and women aged 39-60 yr were traced and examined. In contrast to the inverse relationship between diabetes and size at birth seen in Caucasian populations1, the prevalence of diabetes was positively related to ponderal index at birth15. It was speculated that the effects of gestational diabetes on size at birth and abnormal beta cell function in adult life might account for this association, in Salisbury, England, 30 min glucose levels were inversely con-elated with ponderal index but not to birth weight in a sample of 250 seven yr old white children30. In another study 659 Jamaican children born in the University Hospital were examined at ages from 6 to 16 yr. Children who were shorter at birth had thicker triceps skin folds and higher glycated haemoglobin levels indicating glucose intolerance31. In Mexican-Americans, no association of birth weight with fasting or 2 h glucose was found at the mean age of 32 yr32. The present study donc on a small number of babies shows a U-shaped relationship of birth weight to fasting and post glucose insulin levels, different from the study on Caucasian population1 and similar to that on Pima Indians28.

McKeigue4 suggested that in populations with a high prevalence of diabetes such as Pima Indians, Pacific islanders and urban Indians there could be a U-shaped curve of insulin resistance. This could be as a result of surviving small baby genotype as suggested by McCance et al28 and genetic predisposition to diabetes in the mothers producing large babies as suggested by Hattersley and Tooke20. Both, low birth weight babies as well as large babies, would therefore have increased insulin levels suggesting insulin resistance in both the groups. Our study, though done with small number of children, shows increased fasting and post glucose insulin levels in low as well as high birth weight babies and is concordant with McKeigue's hypothesis4. Larger prospective studies among Indian neonates are needed to confirm these findings as recently there has been criticism on the validity of the foetal undernutrition hypothesis in relation to hypertension as well as cardiovascular disease and diabetes33.

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K.K. Yadav, Rajeev Gupta*, Arvind Gupta* & Mukesh Gupta

Department of Paediatrics, SMS Medical College & * Monilek Hospital & Research Centre Jaipur, India

Received February 19, 2003

Reprint requests : Dr Rajeev Gupta, Department of Medicine, Monilek Hospital & Research Centre Jaipur 302004, India

e-mail: rajeevg@satyam.net.in

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