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R Assan

Publications and source records attributed to R Assan.

At least 37 records · Page 2Linked to original sources
PubMed1993

Regulation of glucose transporter and hexokinase II expression in tissues of diabetic rats.

Glucose transport and phosphorylation are decreased in muscle and adipose tissue in diabetes mellitus. The glucose transporter GLUT-4 and hexokinase II (HK II) are the main isoforms of proteins involved in glucose transport and phosphorylation in insulin-sensitive tissues, adipose tissue, skeletal muscle, and heart. The molecular mechanisms responsible for the decrease of glucose transport and phosphorylation have been studied during the first 3 days after streptozotocin (STZ) administration in adult male Wistar rats. GLUT-4 mRNA and protein and HK II mRNA and enzyme activity were measured. After the injection of STZ (30 h), GLUT-4 and HK II mRNAs were decreased to 10 +/- 1 and 20 +/- 3% that found in nondiabetic rats, respectively; they remained at these low levels for 72 h. Normalization of the blood glucose level by phlorizin infusion did not restore GLUT-4 and HK II mRNA concentrations to normal. In contrast, normalization of the blood glucose level by physiological infusion of insulin resulted in a total normalization of GLUT-4 and HK II mRNA concentrations. When insulin therapy was stopped, GLUT-4 and HK II mRNA and protein concentrations fell in 6 h to 40 and 20% of control levels, respectively. Minimal changes of GLUT-4 and HK II mRNA, and of HK II activity, were observed in skeletal muscle and heart of diabetic rats. We conclude that GLUT-4 and HK II mRNA are coordinately expressed in white adipose tissue. They are rapidly affected by an acute decrease of the plasma insulin concentrations but are not modified by hyperglycemia. In contrast, skeletal muscle and heart GLUT-4 and HK II mRNA are not greatly affected by short-term diabetes.

Adipose Tissue↗
PubMed1992

Evidence that GLUT-2 mRNA and protein concentrations are decreased by hyperinsulinaemia and increased by hyperglycaemia in liver of diabetic rats.

GLUT-2, glucokinase (GK) and phosphoenolpyruvate carboxykinase (PEPCK) mRNA expression was studied in the liver of chronically catheterized diabetic rats during the 3 days after an intravenous injection of 65 mg of streptozotocin (STZ)/kg. At 6 h after the STZ injection, portal plasma insulin levels were 270 +/- 32 mu-units/ml and blood glucose was 1.4 +/- 0.4 mmol/l, owing to pancreatic beta-cell destruction. GLUT-2 and PEPCK mRNA concentrations were rapidly and dramatically decreased (> 90%), whereas GK mRNA was increased. After 30 h, plasma insulin concentrations were lower than 5 mu-units/ml and blood glucose was > 20 mmol/l. GLUT-2 and PEPCK mRNA concentrations increased 2-fold and GK mRNA disappeared progressively. In order to assess the relative roles of hyperglycaemia and insulinopenia, blood glucose was clamped at 6.4 +/- 0.5 mmol/l from 18 to 72 h after STZ injection by phlorizin infusion (0.5-2 g/day per kg) or at 6.6 +/- 0.3 mmol/l from 18 to 48 h after STZ injection by insulin infusion (0.25 unit/min per kg). GLUT-2 mRNA concentrations were 50% lower in phlorizin-infused than in untreated diabetic rats. The low levels of GK mRNA and the high levels of PEPCK mRNA were unaffected by normalization of hyperglycaemia in phlorizin-infused diabetic rats. In insulin-infused rats (portal plasma insulin levels of 40 mu-units/ml) GLUT-2 mRNA levels were 25% of those in untreated diabetic rats, and they increased rapidly 6 h after insulin infusion was stopped. Liver GLUT-2 protein concentration showed similar changes in response to STZ injection and to phlorizin or insulin treatment, but after a delay of several hours. From this work we conclude that GLUT-2 gene expression is dramatically and rapidly (< 6 h) decreased by portal hyperinsulinaemia and increased by hyperglycaemia.

Animals↗
PubMed1992

Age-dependent HLA genetic heterogeneity of type 1 insulin-dependent diabetes mellitus.

The association of insulin-dependent diabetes mellitus (IDDM) with certain HLA alleles is well documented in pediatric patients. Whether a similar association is found in adult-on-set IDDM is not clear, although the disease occurs after the age of 20 in 50% of cases. HLA class II DRB1, DQA1, and DQB1 alleles were studied in 402 type I diabetics and 405 healthy controls (all Caucasian) using oligonucleotide typing after gene amplification. Alleles DRB1*03, DRB1*04, DQB1*0201, DQB1*0302, DQA1*0301, and DQA1*0501 were indeed enriched in diabetics and the highest relative risk was observed in patients carrying both the DRB1*03-DQB1*0201 and the DRB1*0402 or DRB1*0405-DQB1*0302 haplotypes. However none of these alleles, or specific residues, could alone account for the susceptibility to IDDM. Furthermore, there were major differences in HLA class II gene profiles according to the age of onset. Patients with onset after 15 yr (n = 290) showed a significantly higher percentage of non-DR3/non-DR4 genotypes than those with childhood onset (n = 112) and a lower percentage of DR3/4 genotypes. These non-DR3/non-DR4 patients, although presenting clinically as IDDM type 1 patients, showed a lower frequency of islet cell antibodies at diagnosis and a significantly milder initial insulin deficiency. These subjects probably represent a particular subset of IDDM patients in whom frequency increases with age. The data confirm the genetic heterogeneity of IDDM and call for caution in extrapolating to adult patients the genetic concepts derived from childhood IDDM.

Adolescent↗
PubMed1992

TAP1 and TAP2 transporter genes and predisposition to insulin dependent diabetes mellitus.

Genetic control of insulin dependent diabetes mellitus (IDDM) is mainly dependent on HLA genes in the major histocompatibility complex (MHC). The participation of TAP1 and TAP2 genes, located in the MHC region and coding for antigenic peptide transporters, was investigated in 116 IDDM patients and 98 normal controls using oligotyping after DNA amplification. The TAP2-B allele had a dominant protective effect, additive to that of the DR2 haplotype but antagonist to the susceptibility associated with the DR3 and/or DR4 haplotypes. The TAP2-A allele, in the homozygous state, had a predisposing effect. TAP1 allelic distribution did not differ among IDDM patients and controls. These data argue in favour of the role of peptide transporter gene in diabetogenesis.

Adult↗
PubMed1991

HLA-DQA1 and DQB1 alleles in French and Algerian type 1 diabetic subjects.

Some alleles of the HLA-DQB1 and DQA1 loci are preferentially associated with susceptibility to type 1 (insulin-dependent) diabetes mellitus (IDDM). Analysis of the HLA-DQ genetic profile may therefore become important for the screening of subjects at risk of IDDM. However ethnic variations in the genetic profile can occur and require background knowledge of the HLA-DQ allelic distribution before screening campaigns. In the present work, HLA-DQA1 and DQB1 genes have been analyzed, after PCR amplification of the genomic DNA, in French and Algerian control subjects (a total of 148) and diabetic patients (a total of 107). Allelic distributions have been investigated in view of a) possible inter-ethnic differences; b) identification of risk and protective alleles and c) the prevalence of DQB1 aspartate 57 negative and DQA1 arginine 52 positive alleles in control and diabetic groups. The DQB1 allelic distribution was similar in both control groups; alleles negative for aspartate at position 57 were 48% in French and 50% in Algerian. In both diabetic groups, the prevalence of alleles negative for aspartate at position 57 was significantly higher: 91% (French) and 81% (Algerian) (p less than 0.001). A majority of patients were homozygote for DQB1 Asp 57 negativity: 83% (French) and 63% (Algerian). The highest relative risk was associated with HLA-DQB1 0201/0302 heterozygosity. The HLA-DQA1 allelic distribution was also similar in French and Algerian controls. Alleles positive for arginine (ARG+) at position 52 were 50% (French) and 57% (Algerian) of controls. In both diabetic groups the prevalence of alleles positive for arginine at position 52 was significantly higher: 78% (French) and 84% (Algerian).(ABSTRACT TRUNCATED AT 250 WORDS)

Algeria↗
PubMed1990

Glucagon secretion is essential for aminoacid-induced hyperfiltration in man.

The role of glucagon as a mediator of aminoacid-induced alteration of renal haemodynamics was evaluated in man in three different protocols. In the first it was shown that the increase in glomerular filtration rate (GFR) and renal plasma flow (RPF) observed during an aminoacid infusion was prevented by the additional infusion of somatostatin (SRIF), but reproduced by a glucagon infusion in the presence of SRIF. In the second protocol it was shown that, at variance with normal subjects, six totally pancreatectomised patients, thus deprived of pancreatic glucagon secretion, did not increase their GFR and RPF when infused with amino-acids, whereas they exhibited the expected hyperfiltration when infused with glucagon. In the third protocol it was shown that glucagon infusion in a renal artery did not alter the homolateral renal haemodynamics. It is concluded that glucagon secretion is a mandatory step in the cascade of events linking the infusion of aminoacids to the renal hyperfiltration. Other steps beyond glucagon secretion are necessarily involved because glucagon has no direct renal effect.

Adult↗
PubMed1990

Hypoglycaemia and diabetes mellitus following parenteral pentamidine mesylate treatment in AIDS patients.

Of 18 AIDS patients with Pneumocystis carinii pneumonia treated with pentamidine mesylate parenterally, four developed serious to severe hypoglycaemia, three hypoglycaemia followed by insulin-requiring diabetes, and two others diabetes alone. Hypoglycaemia (blood glucose 2.1 +/- 0.2 (+/- SE) mmol l-1) occurred 9 (2-22) days after starting treatment, and diabetes (initial blood glucose 30 +/- 6 mmol l-1) after 60 (20-90) days. The other patients remained euglycaemic. The dysglycaemic patients (hypo- and hyper-glycaemic) had a higher pentamidine dosage (p less than 0.01), and higher serum creatinine levels at end of treatment (p less than 0.001), consistent with drug accumulation and dose-dependent toxicity. Plasma C-peptide levels were low in the diabetic patients, in the basal state (0.25-0.28 nmol l-1) and following stimulation by IV glucagon (0.35-0.40 nmol l-1), vs 0.80 +/- 0.06 nmol l-1 (basal) and 1.83 +/- 0.16 nmol l-1 (stimulated) in 23 healthy control subjects (mean +/- SE). Islet cell or insulin antibodies were not detected. Serum amylase levels rose abnormally in the dysglycaemic group, and pancreatitis was proved in one, and suspected in another patient. None of 28 similar AIDS patients whose P. carinii pneumonia was treated with cotrimoxazole showed blood glucose disturbance.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Plasma C-peptide levels and clinical remissions in recent-onset type I diabetic patients treated with cyclosporin A and insulin.

Remission from insulin dependency in insulin-treated recent-onset type I (insulin-dependent) diabetic patients can result from a partial recovery of insulin secretion, an improvement in tissue sensitivity to insulin, or both. The same hypothesis must be analyzed when remission occurs in cyclosporin A (CsA)-treated patients. In this study, plasma C-peptide levels were serially measured in the basal state and after stimulation in 219 recent-onset type I diabetic patients; 129 received CsA, and all patients were similarly monitored and insulin treated. The results were analyzed in view of the occurrence of remission. Remission was defined as good metabolic control in the absence of hypoglycemic treatment for greater than or equal to 1 mo. Remission occurred in 44% of the CsA-treated group and lasted for mean +/- SE 10.0 +/- 0.9 mo vs. 21.6% in the non-CsA-treated group with a duration of 4.4 +/- 0.8 mo. Plasma C-peptide levels were initially dramatically lower than normal in both groups in the basal and stimulated states. C-peptide levels increased significantly later, at 3 and 6 mo, in both groups. C-peptide values were proportional to the rates of remission in both groups. In the non-CsA-treated group, C-peptide levels later decreased, and these patients inexorably relapsed to insulin dependency. In contrast, in the CsA-treated group, the initial recovery in insulin secretory capacity was maintained over the 18-24 mo of the study. Furthermore, higher remission rates and longer-lasting remission were obtained in patients who reached higher C-peptide levels at the 3rd mo of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Hypertension induced by cyclosporin A in insulin-dependent diabetic patients. A one-year follow-up].

UNLABELLED: Forty-five recent insulin-dependent diabetics (IDD) were treated with cyclosporine A (CsA) 7.5 mg/kg b.i.d. as single immunosuppressive therapy to achieve remission of diabetes. Measurements of mean arterial pressure (MAP), glomerular filtration rate (GFR:inulin clearance), renal vascular resistance (RVR: MAP x [1-haematocrit] divided by PAH clearance), absolute (UNa.V) and fractional (FENa) urinary sodium excretion, were performed initially (M0) and after 3 (M3) and 12 (M12) months of treatment. Results were (mean +/- SD): [table: see text] Prevalence of hypertension defined as MAP greater than or equal to 107 mmHg was 12% at M3 and 24% at M12. Whereas the maximal changes in GFR and RVR occurred at M3, MAP increased further and sodium excretion decreased at M12. IN CONCLUSION: 1) CyA-induced increase in blood pressure paralleled that in RVR at M3 and decreased sodium excretion at M12. 2) There was a dissociation between MAP and GFR changes after 12 months of treatment with CyA.

Adult↗
PubMed1989

Short tertatolol treatment does not impair the hormone and metabolic responses to exercise and hypoglycemia in diabetics.

Beta-blockers can precipitate hypoglycemia and mask its warning signs. Ten male insulin-dependent, otherwise healthy diabetic patients underwent two submaximal exercise tests and two insulin-induced hypoglycemic events (0.2 u/Kg short-acting insulin IV) after six days administration of placebo followed by tertatolol, a non selective beta-blocker (5 mg once daily). Tertatolol modified neither the exercise-induced changes in blood glucose, lactate and plasma unesterified fatty acid levels, nor those of counter regulatory hormones (glucagon, growth hormone, cortisol), while blood pressure, heart rate and plasma renin activity were significantly reduced, proving that tertatolol had actually been ingested, and was active. During the insulin-induced hypoglycemia, similarly tertatolol did not modify the course of the plasma fuels and hormones. Particularly, hypoglycemia was neither deeper nor more prolonged in the presence than in the absence of tertatolol. Warning symptoms were not affected except for palpitations which were not perceived. These results suggest that tertatolol did not precipitate hypoglycemia following exercise, and did not aggravate insulin-induced hypoglycemia in short term administration, and in otherwise healthy diabetic patients.

Adrenergic beta-Antagonists↗
PubMed1989

[Effects of bombesin on gastrin, somatostatin, glucagon and acid secretion from isolated rat stomach in vitro].

Effects of bombesin on the secretion of gastric acid and gastro-intestinal hormones were investigated in isolated perfused rat stomach. Bombesin (intra-arterial, 2 x 10(-10) mol/L, 0.3 ml/min) stimulated gastric acid secretion from basal 2.50 +/- 0.05 x 10(-1) to 8.40 +/- 1.50 x 10(-1) mEq/min (P less than 0.001). Exogenous addition of pentagastrin did not potentiate this effect of bombesin. Bombesin induced twice releasing of gastrin and somatostatin in portal effluent but inhibited glucagon secretion. The basal releasing rates of these three hormones were 62 +/- 8 pg, 5.9 +/- 1.1 ng, and 0.40 +/- 0.03 ng/min respectively. The peak values of gastrin and somatostatin during bombesin stimulation were 1000 +/- 20 pg and 12.2 +/- 2.0 ng/min respectively, while the nadir value of glucagon was 0.17 +/- 0.05 ng/min. All three responses were dose-dependent. These three hormones were all detectable, albeit at much lower concentrations in the pyloric effluent perfusate than they were in the portal effluent.

Animals↗