INTRODUCTION<\/strong><\/p>\n Type 2 diabetes mellitus (T2DM) includes monogenic and polygenic forms.1<\/sup> Maturity onset diabetes of the young (MODY), which in most cases is a monogenic form of the disease, has an autosomal dominant mode of inheritance.2<\/sup> The polygenic form of diabetes has a complex pathophysiology and the multiple genes involved are known to produce insulin resistance and a variable degree of \u03b2-cell dysfunction.3<\/sup> Studies in offspring of type 2 diabetic parents demonstrate that insulin resistance most likely has a primary role in the development of T2DM because of its presence 1-2 decades before the diagnosis of disease.4-6<\/sup><\/p>\n In a number of ethnic groups, obesity is associated with evidence of insulin resistance and impaired insulin secretion.7<\/sup> Plasma concentration of adipose tissue metabolites, leptin and non-esterified fatty acids are shown to be higher in insulin resistant Asian Indians as compared to more insulin sensitive Caucasians.8<\/sup> Leptin has been regarded as a key molecule in the insulin signaling pathways that may be associated with the development of obesity, insulin resistance and diabetes at a later stage in life.9<\/sup> Also, peripheral leptin levels have been shown to be elevated in insulin resistant type 2 diabetics, independent of body composition.10<\/sup> The higher plasma leptin found in offspring of diabetic mothers may play a significant role in the development of hyperinsulinemia and subsequent insulin resistance in children.11<\/sup> Available data therefore suggest that leptin levels may serve as a useful marker of T2DM risk in children and young adults.12<\/sup><\/p>\n Evidence is available indicating that siblings of diabetic parents are at increased risk of developing diabetes, and the risk increases if grandparents are also diabetic.13,14<\/sup> In a study among Pima Indians, the incidence of the disease was shown to be highest if both parents were diabetic.15<\/sup> Furthermore, several studies, mainly in adults, have shown that family history (FH) of T2DM is associated with hyperinsulinemia.16-18<\/sup><\/p>\n In spite of the abundance of adult data, relatively few studies have focused on the impact FH of T2DM on parameters of carbohydrate and lipid metabolism at an early age.19-21<\/sup> The present study was undertaken to evaluate differences, if any, in the risk factors for development of T2DM in offspring with one or both type 2 diabetic parents, using a number of metabolic and endocrine indicators in Pakistani (Southeast Asian) male subjects. It is expected that the present investigation may provide useful leads to an early diagnostic regimen and better management of diabetes-prone individuals at an early age.<\/p>\n SUBJECTS AND METHODS<\/strong><\/p>\n The present study, based on a total of 130 Southeast Asian male subjects aged 15-25 years (mean\u00b1SD 20.66\u00b10.57), was approved by the Ethical Committee and the Research Board of the University of Health Sciences, Lahore.<\/p>\n The study subjects, who underwent a detailed medical examination, had fasting blood glucose levels (FBG) <6.9 mmol\/L22<\/sup> and no signs of acute or chronic illness. All participants and their parents were asked to complete a questionnaire on their FH of diabetes and any other major disease such as cardiovascular and autoimmune diseases, as well as on their life-style characteristics (e.g. physical activity, dietary habits, smoking, economic status). Subjects with a history of T1DM in either of the parents, on medications known to affect body growth or lipid metabolism, with endocrinopathies or any major illness since birth, were excluded from the study. None of the subjects were the product of diabetic pregnancy.<\/p>\n Study Design<\/strong><\/p>\n This is a cross-sectional study and the subjects were divided into the following 3 age-matched groups:<\/p>\n Physical Measurements and Blood Collection<\/strong><\/p>\n Body weight (BW), height, blood pressure and body mass index (BMI) were recorded for all patients. Six ml of venous blood was drawn from the cubital vein after overnight fasting of 12h for analytical purposes. The-two hour oral glucose tolerance test (2h-OGTT) was carried out to evaluate the glucose tolerance status according to the procedure recommended by WHO.23<\/sup> All subjects were put on a diet containing at least 150 gm of carbohydrates for 3 days prior to OGTT. In all cases blood was withdrawn between 0800-0900 h. Blood glucose levels were measured the same day. The remaining serum sample was aliquoted and stored at -80o<\/sup> C until used.<\/p>\n Analytical Determinations<\/strong><\/p>\n All biochemical parameters were determined in duplicate using standard procedures. The diabetic condition or otherwise of parents was reconfirmed by determining FBG levels. Parents\u00a0 who had FBG\u22656.9 mmol\/L were labeled as diabetic.22<\/sup> Serum glucose levels were determined by the glucose oxidase method using a commercial reagent kit (RANDOX Laboratories, Crumlin, UK). Fasting lipid profile was obtained by measuring serum triglycerides (TG) by the GPO-PAP method (RANDOX), HDL- and LDL-cholesterol by a direct quantitative method (Roche Diagnostics GmbH, Mannheim, Germany) and cholesterol by an enzymatic method (RANDOX). The estimations were made with a HumaStar 180 chemistry analyzer (Human, Wiesbaden, Germany). HbA1-c was estimated by affinity liquid chromatography with a D-SI Glycomat (Provalis Diagnostics, Deeside, UK).<\/p>\n Hormone Assays<\/strong><\/p>\n Serum insulin and leptin concentrations were determined by ELISA using commercial kits (insulin: Monobind Inc, Lake Forest, CA, USA; leptin: Diagnostic System Laboratories, Inc, Webster, TX, USA) with an automated EIA analyzer (Bio-Rad Laboratories, Hercules, CA, USA). Peripheral C-peptide levels were measured with a specific immunoradiometric assay (IRMA; Immunotech a.s., Prague, Czech Republic) using an automatic gamma counter (Perkin Elmer, Turku, Finland).<\/p>\n Insulin resistance index<\/strong><\/p>\n Fasting glucose and fasting insulin levels were used to measure homeostasis model assessment of insulin resistance (HOMA-IR) index by the formula: Statistical Analysis<\/strong><\/p>\n The significance of differences among the three groups was analyzed by-one way ANOVA followed by Scheffe,s multiple comparisons. The Pearson test was used to calculate correlation between variables of interest. P value <0.05 was considered statistically significant. All calculations were carried out with the SPSS version 12 (SPSS, Inc, Chicago, IL, USA).<\/p>\n RESULTS<\/strong><\/p>\n Body Weight, BMI and Blood Pressure<\/p>\n The body weight (BW) of offspring of BDP was significantly higher (P=0.015) than those of NDP but there was no significant difference in the BW of offspring of ODP and the control (NDP) group. However, the mean BMI of both groups of offspring of diabetic parents was significantly greater than that of offspring of NDP (Tables 1<\/a> and 3<\/a> ). The proportion of overweight25<\/sup> offspring was 4%, 34% and 45% in NDP, ODP and BDP groups, respectively. Although no significant difference was observed in the systolic BP of offspring of ODP and NDP, the mean systolic BP was slightly but significantly higher in offspring of BDP as compared to that of the ODP (P=0.002) and NDP (P=0.034) (Tables 1<\/a> and 3<\/a>). In 21% of the offspring of BDP the systolic and diastolic BP were above the normal range of 130\/80 mm Hg.22<\/sup><\/p>\n Glucose, 2-h OGTT and Hb A1-c<\/strong><\/p>\n Although the mean fasting glucose levels and the following OGTT were in the normal range of subjects, the mean FBG levels were significantly higher in the ODP and BDP offspring than in the NDP group (Tables 2<\/a> and 3<\/a> ). Blood glucose concentrations following fasting were >5.6 and <6.9 mmol\/L22<\/sup> in 2% of offspring of NDP, 34% of ODP and 37% of BDP, respectively. Blood glucose levels at 2-h following oral glucose administration (2h-OGTT) were also significantly higher (P=0.001) in offspring of diabetic parents compared to those of NDP (Tables 2<\/a> and 3<\/a>). In the present study, 24% offspring of BDP and 20% offspring of ODP had impaired glucose tolerance (IGT)22<\/sup> vs only 2% offspring of NDP. No statistically significant difference in the HbA1-c values was observed between the three groups.<\/p>\n Insulin, C-Peptide and HOMA-IR<\/strong><\/p>\n Mean fasting insulin concentrations were significantly higher in offspring of BDP as compared to those of NDP but no statistically significant difference in mean insulin concentration was found between NDP and ODP groups. The insulin resistance as assessed by HOMA-IR was markedly higher in the ODP and BDP group as compared to the control group (Tables 2<\/a> and 3<\/a>). The mean serum C-peptide levels in offspring of diabetic parents (ODP and BDP groups) were also significantly greater (P=0.026 and P<0.001, respectively) than in the control group (Tables 2<\/a> and 3<\/a>). Fasting C-peptide concentrations were higher than 630 pmol\/ml26 in 18% of offspring of NDP, 47% of ODP and 55% of BDP.<\/p>\n Lipid Profile and Serum Leptin<\/strong><\/p>\n Mean serum TG concentrations were significantly higher in offspring of BDP as compared to those of NDP and ODP (Tables 2<\/a> and 3<\/a>) but not between offspring of NDP and ODP. Interestingly, mean serum total cholesterol (P=0.001), HDL-C (P=0.039) and LDL-C (P=0.045) concentrations were slightly but significantly lower in offspring of ODP than those observed in the control group (Tables 2<\/a> and 3<\/a>), whereas no statistically significant difference was observed in the total cholesterol, HDL-C and LDL-C between BDP and control group. On the other hand, serum leptin levels of the offspring of ODP and BDP were significantly higher than those of NDP (Tables 2<\/a> and 3<\/a>). Significant positive correlation between BMI-leptin was observed in all three groups (Table 4<\/a> ). Also, significant positive correlations were found between serum leptin-insulin (P=0.017) and leptin-C-peptide (P<0.001) in offspring of BDP in contrast to the other two groups (Table 4<\/a> ). Acanthosis nigricans, a dermatalogical finding, was observed in 31% of offspring of BDP while none of the subjects in the other two groups had this finding (Table 1<\/a> ).<\/p>\n DISCUSSION<\/strong><\/p>\n Relatively few studies have been carried out in children regarding the impact of FH of T2DM on carbohydrate and lipid metabolism.11,20,21<\/sup> The present study in male offspring of diabetic parents (ODP and BDP) suggests the presence of certain risk factors of the disease at an early age. Some of the previous reports showing that offspring (both sexes) of diabetic mothers are overweight27<\/sup> are consistent with our findings, demonstrating that 35% male offspring of ODP and 45% of BDP are overweight. In the present study, higher BMI in offspring of BDP and ODP compared to the control group may be due to relatively higher levels of insulin. Our clinical observations emphasize the genetic factors underlying a predisposition to metabolic dysfunction. Recently, a common variant in the FTO (fat, mass and obesity) gene has been identified that predisposes to diabetes through an effect on the BMI.28<\/sup> It was shown that the risk of high BMI and hence of a predisposition to diabetes was additive and that individuals homozygous for this particular SNP (allele A) had a higher BMI as compared to heterozygote individuals<\/p>\n Approximately 36% of the offspring of diabetic parents included in the present study had impaired fasting glucose.22 A moderately high glycemia may therefore serve as a preclinical sign of disturbed glucose metabolism and insulin resistance.<\/p>\n In the present study, mean serum insulin levels were higher in offspring of BDP as compared to those of ODP, and a significantly positive correlation (Table 4<\/a>) between age and serum concentrations of insulin was found only in offspring of BDP, presumably indicating a progressive increase in insulin levels with age. Also, mean serum C-peptide levels were discernibly but not significantly higher in the BDP group than those of the ODP group. In contrast to our findings, a previous study in prepubertal offspring with FH of T2DM failed to demonstrate a significant difference in the fasting glucose and insulin levels and in insulin resistance, when compared with controls.20<\/sup><\/p>\n Hyperinsulinemia in the offspring with BDP is consistent with previous findings, indicating that hyperinsulinemia in the offspring with a FH of T2DM may be associated with obesity.5,29<\/sup> However, hyperinsulinemia may also be independently associated with a family history of T2DM, irrespective of obesity.17,18<\/sup> Insulin resistance estimated by HOMA, which has been shown to correlate well with clamp methods,30<\/sup> was significantly higher in offspring of diabetic parents than in offspring of non-diabetic parents. It has been suggested that increased ferritin concentration in offspring of T2DM parents may further contribute to hepatic insulin resistance in these subjects.5<\/sup> In our study, a positive correlation between age and HOMA-IR (Table 4<\/a> ) was found in the offspring of BDP, but no such correlation was observed in NDP and ODP study groups, presumably due to progressive development of hepatic insulin resistance in these subjects.<\/p>\n A large number of subjects in our study with BDP had acanthosis nigricans (Table 1<\/a>), which has been shown to be associated with hyperinsulinemia and IR in previous studies.31,32<\/sup> In a study conducted in New Mexico, acanthosis nigricans was detected in 21% of children with a FH of T2DM and the prevalence of acanthosis nigricans was shown to be even higher in children with a higher BMI in the same study.33<\/sup> Diagnosis of acanthosis nigricans may help in the identification of individuals at relatively high risk for T2DM.<\/p>\n In the offspring of BDP, insulin and C-peptide levels were robustly correlated with circulating leptin concentrations (Table 4<\/a> ). High leptin levels observed in offspring with a positive FH of T2DM are most probably due to a dysregulation of the adipo-insular axis. These data together with previous reports34,35<\/sup> lend support to the notion that high leptin secretion may play a significant role in the development of hyperinsulinemia and insulin resistance leading to development of T2DM later in life. A positive correlation between insulin resistance and leptin (Table 4<\/a> ) was found in the offspring of BDP. It has been reported previously that leptin plays an important role in the development of insulin resistance.35<\/sup> These observations suggest that increased circulating leptin values may serve as a useful marker of predisposition to T2DM among offspring of diabetic parents; however this observation needs futher verification.<\/p>\n\n
\nHOMA-IR = Fasting insulin (\u00b5IU\/ml) x Fasting glucose (mmol\/l)\/22.5.24<\/sup><\/p>\n