The Relation between β Cell The Relation between β Cell Secretary Capacity of the Pancreas and the Nervous System in Diabetic Subjects

Abstract

ABSTRACT

Background: Diabetes mellitus is a state of chronic hyperglycemia which may results from many environmental and genetic factors, often acting jointly. The connecting peptide level is a measure of β-cell secretary capacity in basal state and after stimulation.

Objectives: To detect the relation between the residual β cell secretary capacity of the pancreas with the nervous system function parameters centrally and peripherally in diabetic subjects.

Methods: Department of Physiology in the Medical College of Al–Mustansiriah University in cooperation with Neurophysiology section in Al-Yarmouk Teaching Hospital. The period of the study extends from June 2003 till Sept. 2004. Thirty healthy subjects with twenty seven type I diabetics and thirty eight type II diabetic subjects were enrolled in this study. Residual β cell secretary capacity was assessed by measuring the connecting peptide (C-peptide) in the fasting state using the radioimmunoassay technique. The central nervous system function parameters was assessed by using the visual evoked potential component the P100 latency, while the peripheral nervous system function parameters were assessed using the nerve conduction study of posterior tibial nerve  and sural nerve of the lower limb.

Results: The fasting blood sugar in the control group was (91.50 ± 4.49 mg/dl) while in type I diabetics was (189.9 ± 17.5) and in the type II DM subjects was (200.61 ± 14.02) with P value < 0.0001 significance value difference between the control and the diabetic groups. The basal serum C-peptide level was equal to 932.4 ± 18 pmol/L in the control group  while in type I diabetics it was  (341.38±59.6) which is  significantly lower than the control group (P value < 0.0001), indicating a severe reduction in the β cells secretary capacity, while in type II diabetics it was (1273.6 ± 72.6) with P value < 0.0001, indicating hyperinsulinemia mechanism. There was no significant difference in P100 latency between the control group and type I diabetics  as the P100 in type I DM subject was (100.7±4.1) while in the control group it was (92.43±1.7). Also, there was no significant difference in P100 latency between type II diabetic subjects and the control group as P100 was (100.29 ± 3.5) in type II diabetics. There was no significant correlation between the C-peptide value and P100 latency in all the studied groups nor with nerve function parameters studied in these groups. Also, some of studied parameters representing the peripheral nervous system (posterior tibial nerve latency, velocity and amplitude with sural nerve latency, velocity and amplitude) showed significant difference between the healthy control subjects and the other two groups with P-value < 0.0001, indicating the hazardous effect of hyperglycemia on the peripheral nervous system.

Conclusion: The results of this study ensures the hazardous effects of hyperglycemia and shows that the central nervous system is also affected by elevated levels of plasma glucose as the peripheral nerves although it was a symptomatic. Also, this study ensures the heterogeneity of neuropathy associated with diabetes as there was no significant correlation between the pathological process of β-cell dysfunction of the pancreas and neuropathy in diabetic subjects.

Keywords: C-peptide, visual evoked potential, P100, diabetes mellitus, Peripheral neuropathy.

Iraqi Medical Journal Vol. 56, No.1, June 2010; p.7-16