G. M. Molinatti

Bone metabolism in type 2 diabetes mellitus

Abstract Several conditions have been described to cause osteoporosis, including diabetes mellitus. While the relationship between type 1 diabetes and osteopenia is well documented in the literature, data on the presence of this complication in type 2 diabetes have not been well established. We studied a population composed of 66 post-menopausal women with type 2 diabetes and a control population. We examined bone mineral density with the dual-energy X-ray absorptiometry (DXA) technique at the lumbar and femoral levels and, in a subgroup of patients, we also measured the levels of markers of bone remodelling. We found significantly higher levels of bone mineral density at the femoral (but not lumbar) level in the diabetic subjects compared with the control population in all the examined subregions, except Wards triangle. Moreover, we found higher levels of some markers of bone resorption (urinary calcium and hydroxyproline, telopeptide) in the patients with diabetes, while urinary crosslinks were higher in the controls. On the basis of these results, we suggest that osteoporosis cannot be considered a complication of type 2 diabetes and that, from a metabolic point of view, bone resorption is greater in diabetic patients than in normal subjects, as suggested by the high levels of most of the markers of osteoclastic activity.

Endothelial cell function in diabetic microangiopathy

ConclusionsEndothelial cells are directly exposed to altered concentrations of circulating metabolites in diabetes and are likely to be involved early, if not primarily, in the natural history of the chronic complications of the disease. Thus, better understanding of the mechanisms underlying endothelial dysfunction and of their possible pathogenetic relevance might help to establish a rationale on which to base prospective trials for the prevention or treatment of microangiopathy.A word of caution should be made in warning that most data available today are derived from experiments in vitro or carried out under highly perturbed conditions in vivo and that virtually none of the methods employed has so far been standardised among different laboratories. Hence, it should come as no surprise if some results are in conflict with each other or will be refuted in the near future. Work on endothelium has only just begun and much still has to be done in this fascinating field of investigation.

Osteoporosis in type II diabetes

SummaryDouble photon absorptiometry comparison was done of lumbar bone mineral content (BMC) values in 40 women with well-compensated non-insulin-dependent diabetes mellitus (type II) and on dietary and/or oral hypoglycemic treatment, and 35 age-matched non-diabetic women, to determine the presence and degree of osteoporosis in this type of diabetes by means of a highly precise and sensitive method. No difference between the two groups was noted as regards blood calcium, phosphorus, PTH and thyrocalcitonin, and urinary calcium and phosphorus. BMC, on the other hand, was significantly lower in the diabetics, both in L2,L3,L4 and in L4 alone. No significant difference could be discerned between patients on diet and those on drugs. It can thus be maintained that osteoporosis is a possible complication of type II diabetes and may appear even in the absence of its classical complications.

Thiamine corrects delayed replication and decreases production of lactate and advanced glycation end-products in bovine retinal and human umbilical vein endothelial cells cultured under high glucose conditions.

Summary This study aimed at verifying whether thiamine, a co-enzyme which decreases intracellular glycolysis metabolites by allowing pyruvate and glyceraldheyde 3-phosphate to enter the Krebs cycle and the pentose-phosphate shunt, respectively, corrects delayed replication caused by high glucose concentrations in cultured human umbilical vein (HUVEC) and bovine retinal endothelial cells (BREC). After incubation in physiological (5.6 mmol/l) or high (28.0 mmol/l) glucose with or without 150 μmol/l thiamine, cells were counted and proliferation assessed by mitochondrial dehydrogenase activity. Lactate was measured in both cell types as an index of glycolytic activity and fluorescent advanced glycosylation end-products (AGE) concentration was determined in the HUVEC lysate. Both cell counts and proliferation assays in either of the cell types confirmed the impairment to cell replication induced by high glucose. When thiamine was added to cells kept under high glucose conditions, the number of surviving cells was significantly increased and the reduced cell proliferation appeared to be corrected. Lactate assays confirmed the increased production of this metabolite by BREC and HUVEC in high glucose, which was reduced by thiamine. Fluorescent AGE determination showed that thiamine may prevent non-enzymatic glycation in HUVEC. Thiamine restores cell replication, decreases the glycolytic flux and prevents fluorescent AGE formation in endothelial cells cultured in high glucose, suggesting that abnormal levels of glycolytic metabolite(s) may damage cells. [Diabetologia (1996) 39: 1263–1268]

Benfotiamine is similar to thiamine in correcting endothelial cell defects induced by high glucose

Abstract We investigated the hypothesis that benfotiamine, a lipophilic derivative of thiamine, affects replication delay and generation of advanced glycosylation endproducts (AGE) in human umbilical vein endothelial cells cultured in the presence of high glucose. Cells were grown in physiological (5.6 mM) and high (28.0 mM) concentrations of D-glucose, with and without 150 μM thiamine or benfotiamine. Cell proliferation was measured by mitochondrial dehydrogenase activity. AGE generation after 20 days was assessed fluorimetrically. Cell replication was impaired by high glucose (72.3% ±5.1% of that in physiological glucose, p=0.001). This was corrected by the addition of either thiamine (80.6%±2.4%, p=0.005) or benfotiamine (87.5%±89%, p=0.006), although it was not completely normalized (p=0.001 and p=0.008, respectively) to that in physiological glucose. Increased AGE production in high glucose (159.7%±38.9% of fluorescence in physiological glucose, p0.003) was reduced by thiamine (113.2%±16.3%, p=0.008 vs. high glucose alone) or benfotiamine (135.6%±49.8%, p=0.03 vs. high glucose alone) to levels similar to those observed in physiological glucose. Benfotiamine, a derivative of thiamine with better bioavailability, corrects defective replication and increased AGE generation in endothelial cells cultured in high glucose, to a similar extent as thiamine. These effects may result from normalization of accelerated glycolysis and the consequent decrease in metabolites that are extremely active in generating nonenzymatic protein glycation. The potential role of thiamine administration in the prevention or treatment of vascular complications of diabetes deserves further investigation.

Effect of testosterone on bone in hypogonadal males

Bone mineral content (BMC) and testosterone levels were evaluated and compared in 10 hypogonadal males and 10 normal, age-matched controls. In 6 of the subjects an investigation was also carried out into the effects of testosterone administration on lumbar BMC, calcitonin (CT) response to hypercalcaemia, osteocalcin (BGP) and the fasting urinary calcium/creatinine and hydroxyproline/creatinine ratios. Our results confirm that male hypogonadism is characterized by a low BMC and that testosterone administration is able to improve this parameter and to increase both basal BGP and CT response to hypercalcaemia. Testosterone therefore probably acts on bone tissue through both a direct action on osteoblast cells and an improvement in CT secretion.

Diabetic retinopathy as a cause of blindness in the province of Turin, north-west Italy, in 1967-1991.

Diabetes is known to be a major contributor to blindness in industrialized countries but few data are available on the situation in Italy. As an introductory step to the implementation of permanent screening for diabetic retinopathy, a search was carried out on the causes of visual loss in the provincial territory surrounding Turin, the main city of North‐West Italy. The case notes of all 4549 residents in the province who were certified blind between 1967 and 1991 were examined with regard to cause, age at onset, and year of onset of visual acuity 1/20. Diabetic retinopathy was the second commonest cause of bilateral blindness (13.1 % of cases), preceded by cataract (26.7%) and followed by myopia (11.1%), optic atrophy (8.9%), glaucoma (8.9%), retinitis pigmentosa (7.2%), and senile macular degeneration (4.1%). Diabetic retinopathy was the commonest eye disease among those who became blind between the ages of 50 and 70 and remained the leading cause of visual loss when the age groups 20 to 70 were pooled together. The incidence of diabetic retinopathy‐related blindness did not show any trend to decrease over the 25 years investigated. It is concluded that, in spite of widespread availability of facilities for its assessment and treatment, diabetic retinopathy remains a leading cause of blindness in North‐West Italy. This fully justifies the implementation of screening programmes and efficient referral chains for the early detection and prompt treatment of this complication of diabetes.

Antiandrogenic properties of spironolactone. Clinical trial in the management of female hirsutism

The effect of spironolactone on female hirsutism was studied in 18 patients. The drug was administered at the dose of 400 mg for the first ten days and 300–200 mg later on in a first group of women (Group A); a second group (Group B) was given 200 mg spironolactone for the whole length of therapy. A significant decrease of the index of Ferriman and Gallwey (p = 0.01) was noted from the 100th day of treatment; acne and seborrhoea improved concomitantly. Plasma total testosterone values fell from 0.64 + 0.24 ng/ml to 0.32 ± 0.12 ng/ml (p = 0.002) during the first 5 days only in the patients of Group A; in the other patients no significant changes were observed. PRL did not significantly change from prefreatment values; FSH and LH values at the 5th, 10th, and 15th day of therapy did not show a uniform course in both groups. On the basis of these results spironolactone administration appears promising in the therapy of female hirsutism.

Evidence for a positive correlation between serum cortisol levels and IL-1β production by peripheral mononuclear cells in anorexia nervosa

A hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis has been reported in anorexia nervosa (AN), together with some immunological abnormalities, involving citokine — and particularly Tumor Necrosis-Factor-α (TNF-α) — production by polymorphonuclear cells. The ability of pro-inflammatory cytokines to activate the HPA axis is well known; however, there are no data demonstrating an interdependence between immunological and endocrine response in AN. To investigate the presence of a correlation between immune response and pituitary-adrenal function, plasma ACTH and serum cortisol concentrations were measured in 13 AN patients and in the same number of controls. TNF-α and interleukin (IL)-1β production by ex-vivo unstimulated and LPS-stimulated peripheral mononuclear cells was also assessed. Circulating cortisol concentrations were higher (p<0.01) in AN (156.7±45.1 μg/l, mean±SD) than in controls (105.9±25.7 μg/l). Unstimulated IL-1β release in supernatants of mononuclear cell cultures was slightly but not significantly higher in AN than in controls, while TNF-α release was similar in the two groups. A positive correlation was found between IL-1β concentrations in unstimulated culture supranatants and serum cortisol levels in AN (r=0.782, p=0.002), while in normal subjects there was a trend toward a negative correlation; a slight positive correlation, while not significant, between IL-1β and plasma ACTH, as well as between TNF-α and serum cortisol was also found in AN. These data suggest that the normal relationship between pro-inflammatory cytokines release, particularly IL-1β and cortisol secretion is deranged in AN.

INCREASED THYROTROPHIN SECRETION INDUCED BY SULPIRIDE IN MAN

100 mg i.m. sulpiride (a dopamine‐receptor‐blocking drug) led to a significant rise in plasma TSH in normal women, in female patients with galactorrhoea, and, to a much more marked degree, in male and female patients with primary hypothyroidism. In the hypothyroid patients, there was a significant positive correlation between basal TSH and its maximum increment after sulpiride. The drug proved to be an even more potent stimulator of PRL, at least in subjects with normal blood PRL. Normal males, on the other hand, displayed no significant changes in TSH after sulpiride. Continuous administration (150 mg/day per os for 15 days) also resulted in enhancement of TSH in normal women. These results suggest that TSH release is controlled by a dopaminergic mechanism in man. The more accentuated TSH response in hypothyroid patients may perhaps be attributable to the absence of negative‐feedback on the part of thyroid hormones.