Analysis of the Gly40Ser polymorphism in the glucagon receptor gene in a German non-insulin-dependent diabetes mellitus population

A heterozygous polymorphism changing GGT40 (Gly) to AGT40 (Ser) in the glucagon receptor gene (GCG-R) was reported to be associated with non-insulin-dependent diabetes mellitus (NIDDM). A possible involvement of this polymorphism in impaired glucose tolerance was also suggested in a French population. However, the prevalence of this polymorphism differs markedly among different ethnic groups, whereby the results in German populations were found to be contradictory. We thus investigated the association of this mutation with NIDDM and healthy subjects in 508 German subjects (196 NIDDM, and 312 controls). None of the control subjects, but one of the NIDDM patients demonstrated the Gly40Ser polymorphism. Since no first-degree relative of the index patient had this genetic variance, a de novo mutation is suggested. Although the frequency of the Gly40Ser polymorphism in NIDDM observed in France is not confirmed in our population, this genetic variance is also evident in Germany.

Differentiation of hypoglycaemia induced cognitive impairments. An electrophysiological approach

Effects of hypoglycaemia on distinct cognitive processes were assessed with event-related brain-potential (ERP) measures and reaction times in a hybrid selective-attention/response-choice task. One group of subjects received a euglycaemia-hypoglycaemia-euglycaemia treatment order and a second group a euglycaemia-placebo(euglycaemia)-euglycaemia sequence of treatments. During hypoglycaemia, ERP measures of selective attention (selection negativity), response choice (lateralized readiness potential) and reaction time were delayed compared with baseline performance. After restoration of euglycaemia, the onset of the selection negativity returned to baseline, whereas the lateralized readiness potential was still delayed, and error frequencies remained elevated. These results suggest that hypoglycaemia delays both the stimulus selection and the motor-response selection. They further suggest that the stimulus-selection process recovers quickly after restoration of euglycaemia, but that the response-selection process does not. Slow shifts in cortical potentials with a broad frontal distribution that occurred during hypoglycaemia, are discussed in relation to frontal lobe mechanisms involved in the control of subordinate, modality-specific selection mechanisms.

Peripheral osteopenia in adult patients with insulin-dependent diabetes mellitus

Alterations in bone metabolism in diabetes mellitus is a topic of special interest. Bone blood flow is increased in the distal limb of diabetic patients, which is believed to increase osteoclastic activity. We measure bone mineral density using dual-photon absorptiometry in the distal lower limb, the femoral neck, and the lumbar spine in 41 IDDM patients and in 30 control persons. In the diabetic group there was a 10% reduction of bone mineral density in the femoral neck (p < 0.01) and a 12% reduction in the distal limb (p < 0.001) compared with the control group. No significant difference was found in the lumbar spine (p = 0.22). Our data yield incidence for peripheral osteopenia in IDDM-patients, independent of any systemic bone disease such as osteoporosis. A link between decreased bone mineral density and diabetic neuropathy has been observed for the femoral neck (p < 0.001), but not for the distal limb or axial skeleton. Whether there is a common aetiological link or a casual connection between diabetic neuropathy and bone mineral density has still to be determined.

Association between "diabetic thick skin syndrome" and neurological disorders in diabetes mellitus

Skin thickness on the extremities of patients with diabetes mellitus has been described controversially. Using high resolution ultrasonography, we were able to show a significant increase in skin thickness at the forearm (P < 0.05), thigh (P < 0.001) and lower limb (P < 0.05) of diabetic patients, most prominent at the thigh. No difference in skin thickness was found at the dorsum of the foot. In addition, skin thickness was not related to the duration of diabetes, age or HbA1. A close association was found between diabetic neuropathy and increasing skin thickness. Diabetic patients with neurological disorders had a significant increase in skin thickness versus diabetic patients without neuropathy. The present findings suggest that diabetic neuropathy and abnormalities of connective tissue have a common etiological link in their development or that both are time-dependent processes. Whether changes in capillary blood flow, increase of nonenzymatic glycosylation, polyol accumulation or other metabolic disorders are responsible for these findings remains still to be established.