Risk factors for the development of diabetic retinopathy in Japanese type 2 diabetic patients

This study investigated the risk factors for development of diabetic retinopathy (DR) in 787 type 2 diabetic patients with no retinopathy at the first visit. The subjects were followed up for at least 3 years (mean, 6.7 years). Among the baseline factors, significant correlations were observed between the development of DR and HbA1c (P < 0.0001), the method of therapy (P < 0.005), the duration of diabetes at the first visit (P < 0.005) and the past maximal body mass index (BMI) (P < 0.01). No significant correlation was found with the blood pressure, age, gender, TC or BMI. Among the follow-up variables, the mean HbA1c (P < 0.0001) and duration of diabetes (P < 0.001) correlated significantly with DR development, whereas the blood pressure and age did not. We found that a 1% decrease in HbA1c led to a 35% reduction in the risk of development of DR during the follow-up. The patients whose HbA1c at the first visit was higher than the median value of 8.2% showed a higher probability of development of DR during the next 3 years even when the same blood glucose control was maintained during the follow-up. In conclusion, our study demonstrated that the most important risk factor influencing the development of DR was the blood glucose control. Moreover, we found that the glycemic level at the first visit also influenced the development of DR.

The role of PPARgamma as a thrifty gene both in mice and humans

The biological role of peroxisome proliferator-activated receptor gamma (PPARgamma) was investigated by gene targeting and case-control study of the Pro12Ala PPARgamma2 polymorphism. Homozygous PPARgamma-deficient embryos died at 10.5-11.5 days post conception (dpc) due to placental dysfunction. Heterozygous PPARgamma-deficient mice were protected from the development of insulin resistance due to adipocyte hypertrophy under a high-fat diet, whose phenotypes were abrogated by PPARgamma agonist treatment. Heterozygous PPARgamma-deficient mice showed overexpression and hypersecretion of leptin despite the smaller size of adipocytes and decreased fat mass, which may explain these phenotypes at least in part. This study reveals a hitherto unpredicted role for PPARgamma in high-fat diet-induced obesity due to adipocyte hypertrophy and insulin resistance, which requires both alleles of PPARgamma. A Pro12Ala polymorphism has been detected in the human PPARgamma2 gene. Since this amino acid substitution may cause a reduction in the transcriptional activity of PPARgamma, this polymorphism may be associated with decreased insulin resistance and decreased risk of type 2 diabetes. To investigate this hypothesis, we performed a case-control study of the Pro12Ala PPARgamma2 polymorphism. In an obese group, subjects with Ala12 were more insulin sensitive than those without. The frequency of Ala12 was significantly lower in the diabetic group, suggesting that this polymorphism protects against type 2 diabetes. These results revealed that in both mice and humans, PPARgamma is a thrifty gene mediating type 2 diabetes.

Diabetes mellitus and life-style--for the primary prevention of diabetes mellitus: the role of diet

Diet treatment for diabetes requires restriction of the food amount (energy intake). It is desirable that patients have a proper relative consumption of the three main nutrients (proteins, carbohydrates, fats) and also habitually take low-energy foods such as vegetables, mushrooms and seaweeds, etc. as often as possible in each meal. Therefore, we can replace the expression 'a diet for diabetes' with 'a diet for healthy living'. By showing a clinical case of an obese diabetic patient, who succeeded to reduce their body weight, HbA1c and oral agents through diet treatment, and finally could go on diet treatment only, the importance of diet therapy can be emphasized. Furthermore, the estimation index was examined to evaluate how accurately diabetic patients could estimate food energy. According to this study, a large amount of food on the plate leads most patients to underestimate the amount of real energy, and patients are apt to eat too much compared with having smaller amounts of food on the plate. By analyzing questionnaires on the diet therapy of approximately 3000 diabetics, it has been shown that the majority of patients at our hospital recognize that diet therapy is the most important factor in the treatment of diabetes. Interestingly, patients who ate all the food served showed a significantly higher body mass index compared with those who left served food.

The Pro12Ala polymorphism in PPAR gamma2 may confer resistance to type 2 diabetes

Peroxisome proliferator-activated receptor gamma (PPARgamma) has been implicated in adipocyte differentiation. Recently it was reported that heterozygous deficiency of PPARgamma led to the protection from high-fat diet-induced insulin resistance in an animal model. A Pro12Ala polymorphism has been detected in the human PPARgamma2 gene. Since this amino acid substitution may cause a reduction in the transcriptional activity of PPARgamma, this polymorphism may be associated with decreased insulin resistance and decreased risk of type 2 diabetes. To investigate this hypothesis, we performed a case-control study of the Pro12Ala PPARgamma2 polymorphism in Japanese diabetic and non-diabetic subjects. The frequency of Ala12 was significantly lower in the diabetic group. In an overweight or obese group, subjects with Ala12 were more insulin sensitive than those without. These results suggest that the PPARgamma is a thrifty gene and that the Pro12Ala PPARgamma2 polymorphism protects against type 2 diabetes in the Japanese.

Evidence for association between the class I subset of the insulin gene minisatellite (IDDM2 locus) and IDDM in the Japanese population

Although the shortest (class I) minisatellite (i.e., variable number of tandem repeats [VNTR]) alleles in the 5' region of the insulin gene are positively associated with IDDM in Caucasians, the majority of Japanese are homozygous for class I alleles. Here, we determined the exact length, in number of repeat units (RUs), of class I alleles in Japanese subjects. The distribution of class I alleles in Japanese was trimodal, with peaks located at 32/33, 41, and 44 RUs. The shortest component (i.e., 1S [25-38 RUs]) alleles were significantly increased in the IDDM group compared with the control group (54 vs. 46%; P = 0.040). The 1S/1S genotype was significantly increased in the IDDM patients (34 vs. 20%; P = 0.005; relative risk 2.1). Furthermore, the transmission disequilibrium test of Japanese families with 1S/1M or 1S/1L heterozygous parents confirmed the association of 1S alleles; 17 alleles of 1S and 6 alleles of 1M (39-41 RUs) or 1L (42-44 RUs) were transmitted to affected offspring (P = 0.022). In addition, we found tight linkage of 1S with allele 9 of the tyrosine hydroxylase gene microsatellite and allele (-) of the IGF-II gene Apa I polymorphism, but neither 9 nor (-) alleles were significantly associated with IDDM. The present study suggests that a class I subset may have a role in IDDM susceptibility in Japan. It was revealed that the difference between 1S alleles and 1M or 1L alleles is almost consistently characterized by a sequence variation generated by deletion of two copies of an ACAGGGGTCC CGGGG repeat element, implying that sequence variation of class I alleles may influence disease susceptibility.

A prospective study of health check examinees for the development of non-insulin-dependent diabetes mellitus: relationship of the incidence of diabetes with the initial insulinogenic index and degree of obesity

A total of 1788 non-diabetic subjects, screened by a general health check, had either glycosuria or marginal elevation of fasting blood glucose and/or HbA1c. They were followed by repeated 100 g oral glucose tolerance tests for up to 8 years. Their initial mean age was 52 years and the mean BMI was 23.2. Low insulin secretory response was defined when the insulinogenic index, a ratio of increment of plasma insulin to that of plasma glucose 30 min after oral glucose load, was lower than 0.5. Cumulative incidence of diabetes with fasting blood glucose (FBG) exceeding 120 mg dl-1 was significantly higher in impaired glucose tolerance (IGT) than in non-IGT, and in each of IGT and non-IGT groups, the incidence was significantly higher for low than normal insulin responders. The mean initial plasma insulin response in subjects who developed diabetes was significantly lower than in those who remained non-diabetic with the same category of glucose tolerance at baseline irrespective of the degree of glucose intolerance. The mean baseline BMI did not differ whether or not they developed diabetes, but a few cases who developed diabetes despite normal initial insulin response were much more obese. Fasting insulin levels did not correlate with FBG during the course of development of diabetes. We suggest that defective insulin secretion plays a predominant role in the non-obese subtype of NIDDM which includes the majority of Japanese patients, while both insulin resistance and insulin secretory defect are important in the obese subtype for the development of diabetes.

Insulin response to oral glucose load is consistently decreased in established non-insulin-dependent diabetes mellitus: the usefulness of decreased early insulin response as a predictor of non-insulin-dependent diabetes mellitus

We studied the plasma insulin response during a 100 g oral glucose tolerance test (OGTT) in subjects with NIDDM and various other conditions associated with glucose intolerance. The criteria for definite diabetes and previously definite diabetes is proposed for those whose fasting blood glucose (FBG) is, or has been, greater than 140 mg dl-1 in the past. A diabetic type glucose tolerance with FBG lower than 140 mg dl-1 was called 'equivocal diabetes'. Insulin response was almost invariably lower in definite diabetes and previously definite diabetes compared to control groups with similar degree of glucose intolerance even in the states of non-diabetic glucose tolerance. This was in contrast to other conditions which are often associated with glucose intolerance such as corticosteroid treatment, post-gastrectomy, liver diseases, in which insulin response is increased with the impairment of glucose tolerance as far as the FBG remains below 140 mg dl-1. The low insulin response in definite diabetes can be represented by a decreased insulinogenic index, the ratio of increment of plasma insulin (muU ml-1) to that of blood glucose (mg dl-1) 30 min after the glucose load. Insulin response was judged to be low when this index was less than 0.5. Low insulin response was a reproducible feature, better than the category of glucose tolerance. It was highly correlated with acute insulin response (AIR) elicited by intravenous glucose injection. The prevalence of low insulin responders was high among groups with a family history of NIDDM. Diabetes with elevated FBG occurred more frequently in low insulin responders than in normal insulin responders. Fasting and 2-h insulin levels are lower in definite diabetes than in control groups with similar blood glucose levels. The so-called inverted-U shape relationship of plasma insulin to blood glucose was not so apparent in definite diabetes. We conclude that a low insulin response to oral glucose, as represented by a low insulinogenic index, is an important inherent characteristic in definite diabetes and probably plays a predominant role in the pathogenesis of NIDDM in most Japanese patients.

[Computed tomographical evaluation of diabetic nephropathy]

Diabetic nephropathy can be regarded mainly as a type of microangiopathy, but is a disease that may also include aspects of macroangiopathy. This is especially true of renal disease in non-insulin dependent diabetes mellitus (NIDDM), which is characterized not only by diabetic glomerulosclerosis, but also by atherosclerosis. We performed morphological studies on the kidney, using computed tomography (CT), focusing on such points as: (1) abdominal aortic calcifications at the level of kidney, (2) calcifications in the renal artery, and (3) wedge-shaped defects on the renal surface. We noted that these findings became more prominent in NIDDM patients during end-stage renal failure than during normal renal function, and were significantly more common in those two NIDDM groups than in age-matched nondiabetic patients without hypertension, hyperlipidemia or gout. NIDDM patients exhibited these features more frequently than IDDM patients.

Standardization of HbA1c value and its comparison to immunoassay--two years of experience

In spite of the routine use of hemoglobin Alc (HbAlc) value to guide diabetes therapy, substantial differences have been noted between results obtained by different instruments and laboratories. It was suggested that confusion between the terms used for HbA1c, i.e. between "total HbA1c' which includes labile content, and "stable HbA1c', which does not, may account for some of these inter-instrument and inter-laboratory differences. However, an undesirable difference was found even in measurements of only the stable component of HbAlc using the two most commonly used HPLC analyzers in our country. We found that a two-point calibration using lyophilized hemoglobin at lower and higher ranges was effective in matching up results of HbA1c measurement. This finding was concordant with a report by the Committee of the Japan Diabetes Society and other reports. Two methods of HbA1c immunoassay, one performed with the DCA 2000 automated analyzer and another performed using the Liquitech kit or a general automated analyzer, were evaluated and found to perform as well as HPLC analyzers in all respects except precision. The results derived from immunoassay were in good agreement with the calibrated results by HPLC, with (Liquitech) and without (DCA 2000) conversions.

No evidence for mutations in a putative subunit of the beta-cell ATP-sensitive potassium channel (K-ATP channel) in Japanese NIDDM patients

The ATP-sensitive K channel (K-ATP channel) in pancreatic beta cells is believed to play a crucial role in glucose-stimulated insulin release. We investigated whether defects in the recently cloned gene for a putative subunit of this channel (KATP-2) could be a cause of diabetes in Japanese patients. The coding region of this beta-cell type channel gene was investigated in 192 diabetics with a family history of the disorder by single-stranded conformational polymorphism (SSCP) analysis. Two silent polymorphisms were found and confirmed by sequencing, but no missense or nonsense mutations were detected. The allele frequency of the polymorphisms was compared with 96 control subjects without a family history of the disease, and no clear difference was found. These results indicate that genetic defects of the KATP-2 channel may not be a major cause of diabetes in Japan.

A subtype of diabetes mellitus associated with a mutation in the mitochondrial gene

Recently, in patients with diabetes and deafness, researchers have identified an A to G transition at position 3243 in transfer ribonucleic acid(Leu)(UUR) [3243 base-pair (bp) mutation], originally found in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes. To determine the prevalence of diabetic patients with this mutation in Japan, we screened selected cohorts of diabetic patients based upon type of diabetes, family history of diabetes, and age of onset; also screened were 550 unselected cohorts of diabetic patients, without prior information. We identified 5 patients with the 3243-bp mutation, suggesting that approximately 0.9% of diabetic patients have it. However, there were none with this mutation in 250 controls with normal glucose tolerance. We also studied the clinical characteristics and insulin secretory characteristics of diabetic patients with 3243-bp mutation. We propose that diabetes mellitus with 3243-bp mutation is a novel subtype of diabetes mellitus, maternally inherited diabetes, and deafness (MIDD).

Association of polymorphism in the interferon gamma gene with IDDM

Cytokines may play important roles in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). We analysed a dinucleotide repeat polymorphism within the first intron of the interferon gamma (IFN-gamma) gene in Japanese diabetic patients (175 IDDM and 145 non-insulin-dependent diabetes mellitus) and 267 control subjects. A significant difference was observed in the global allele distribution of the polymorphism between the IDDM and control groups (p = 0.039). The difference from the control group was more evident in the patients whose insulin therapy started within 1 year from onset (p = 0.006) or in the young-onset (< 10 years) patients (p = 0.0006). The alleles "3" and "6" were increased in the IDDM patients, and a significant increase in the frequency of the "3/6" genotype was observed in the IDDM patient group (9.1%, RR 2.9, p = 0.010), in the patients with initial insulin therapy less than 1 year from onset (10.6%, RR 3.4, p = 0.004), or in the young-onset patients (16.7%, RR 5.7, p = 0.0003) in comparison to the control subjects (3.4%). There was a tendency towards frequent occurrence of clinical characteristics which reflect young or abrupt onset of diabetes or both, and depletion of insulin secretion capacity in the patients with "3/6" or "6/6" in comparison to the patients with other genotypes. These results suggest that the IFN-gamma gene region may contribute to the pathogenesis of IDDM and could be a genetic marker for IDDM.

Insulin secretory response in Japanese type 2 (non-insulin-dependent) diabetic patients

Insulin (immunoreactive insulin, IRI) response during a 100 g oral glucose tolerance test was studied in a large number of patients with definite diabetes, equivocal diabetes, and other pathological states causing glucose intolerance. Definite diabetes was diagnosed in patients with overt fasting hyperglycemia. Once the diagnosis of definite diabetes was made, IRI response remained low after improvement of glucose tolerance. Glucose intolerance caused by other pathological extra-pancreatic conditions was usually accompanied by increased IRI response. IRI response in equivocal diabetes was variable, but almost always decreased in those who developed definite diabetes later. In subjects with a strong family history of type 2 diabetes, the prevalence of a low IRI response was high. In non-diabetic subjects, weight gain caused a marked increase in IRI response and a small increase in blood glucose, while in those who developed diabetes, IRI increased little despite the marked increase in blood glucose. These data suggest that low IRI response is an important feature of type 2 diabetes, perhaps with a hereditary basis in part. It precedes the occurrence of overt hyperglycemia and persists after improvement of glucose tolerance.

Family history of diabetic patients in Japan

The frequency of a positive family history of diabetes in diabetic patients has increased in recent studies. In this study, it was 16-33% for type 1 diabetes and 43-49% for type 2 diabetes. It was significantly higher than in non-diabetic subjects, and in type 2 than in type 1 diabetic patients. The prevalence of diabetes in parents and siblings of type 2 diabetic patients was higher than in those of type 1 patients, and it was particularly high in parents of young onset type 2 patients. Among type 2 diabetic patients, positive family history was somewhat lower in those with marked obesity in the past. Comparison of groups with varying degrees of glucose intolerance revealed that a family history of diabetes increased in parallel with the impairment of glucose tolerance. The results suggest that genetic factors in the pathogenesis of diabetes are more important in type 2 than in type 1 diabetes, and in the younger onset and less obese subjects than in older onset and more obese patients for type 2 diabetes.

Analysis of the glucokinase gene promoter in Japanese subjects with noninsulin-dependent diabetes mellitus

Glucokinase plays an important role in glucose metabolism in pancreatic beta-cells and liver. Recently, several mutations responsible for noninsulin-dependent diabetes mellitus (NIDDM) have been identified within the coding regions of the glucokinase gene. We screened the promoter regions using polymerase chain reaction followed by single strand conformation polymorphisms in 240 Japanese NIDDM and 111 control subjects. In the beta-cell promoter, two kinds of sequence variations were detected. One variation, in which 2 nucleotides at position -282 (C-->T) plus -194 (A-->G) were changed simultaneously, was found in 23 NIDDM (9.6%) and 12 control (10.8%) subjects. The other variation [e.g. -30 (G-->A)] was identified in 87 NIDDM (36.3%) and 40 control (36.0%) subjects. In the liver promoter, in addition to the -603 (G-->T) substitution in 1 NIDDM (0.4%) and 2 control (1.8%) subjects, the -120 (G-->T) substitution in 1 control (0.9%) subject was found. However, there were no differences in these allele frequencies between NIDDM and control subjects. We conclude that the prevalence of mutations in the promoter of the glucokinase gene responsible for NIDDM is rare among Japanese patients.

The high prevalence of the diabetic patients with a mutation in the mitochondrial gene in Japan

Recently, an A to G transition at position 3243 in transfer ribonucleic acidLeu(UUR) [the 3243 base-pair (bp) mutation] originally found in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes has been identified in patients with diabetes and deafness. To determine the prevalence of the diabetic patients with this mutation in Japan, we screened 550 randomly selected cohorts of diabetic patients without prior information about clinical features such as type of diabetes, family history of diabetes, age of onset, and mode of therapy. We have identified 5 patients with this mutation, suggesting that approximately 0.9% of diabetic patients have the 3243 bp mutation. However, there were no subjects with this mutation in 250 controls with normal glucose tolerance. The percentage of mutant DNA in whole mitochondrial DNA did not correlate to the degree of symptoms. We conclude that the 3243 bp mutation in the mitochondrial gene plays an important part as a cause of diabetes in Japan.

Molecular scanning of the glycogen synthase and insulin receptor substrate-1 genes in Japanese subjects with non-insulin-dependent diabetes mellitus

We studied a simple tandem repeat DNA polymorphism in the glycogen synthase gene and polymorphisms at codon 513 (Ala-->Pro) and 972 (Gly-->Arg) in the insulin receptor substrate-1 (IRS-1) gene in 197 non-insulin-dependent diabetes mellitus (NIDDM) and 178 control subjects in Japan. Eight alleles (-3G, -2G, -1G, 0G, 1G, 2G, 3G, and 4G) were identified in the tandem repeat polymorphism in the glycogen synthase gene. No difference in the frequencies of these alleles was found between diabetics and controls. The codon 972 polymorphism of IRS-1 gene was observed in 7 diabetics (3.6%) and 8 controls (4.5%), whereas the codon 513 polymorphism was not found in either of the two groups. We conclude that the tandem repeat polymorphism in the glycogen synthase gene and the polymorphisms at codons 513 and 972 of the IRS-1 gene are not associated with a higher risk for the development of NIDDM in Japanese subjects.

Sequence variations of the glucokinase gene in Japanese subjects with NIDDM

Mutations in the glucokinase gene have been identified recently in patients with maturity-onset diabetes of the young, a subtype of NIDDM. The proposed role of glucokinase as a glucose sensor, combined with the low insulin response to glucose found in most Japanese with NIDDM, prompted us to speculate that mutations in the glucokinase gene might be one of the major causes of NIDDM in Japanese subjects. To determine the prevalence of mutations and sequence variations in the glucokinase gene, we screened all 12 exons of the glucokinase gene, including exon/intron junctions, by polymerase chain reaction followed by single-strand conformation polymorphism in 209 Japanese NIDDM subjects. In addition to the mutation in exon 7, which substituted Arg (AGG) for Gly (GGG) at codon 261 (10), a silent mutation of Pro (CCC-->CCG) in exon 4 at codon 145 and several new sequence variations in intervening sequences and the 5'-untranslated region of exon 1 beta (beta-cell-specific exon 1) were identified. Because we identified only one subject who had a structurally abnormal glucokinase molecule, we conclude that the prevalence of structural mutations in the glucokinase gene responsible for NIDDM appears to be rare among Japanese patients. To our knowledge, this is the first thorough study describing the ethnic prevalence of mutations and sequence variations in the glucokinase gene in NIDDM.

Risk factors for retardation of renal function in IDDM and NIDDM with nephropathy

Risk factors for retardation of renal function in 22 patients with non-insulin-dependent diabetes mellitus (NIDDM) were studied and compared with those in 16 patients with insulin-dependent diabetes mellitus (IDDM). The annual decline rate of reciprocal serum creatinine was calculated from the rise of creatinine to the commencement of dialysis. The annual decline rate was compared with levels of blood pressure, fasting blood glucose, HbA1, and lipids, and clinical findings in patients with or without nephrotic syndrome during the same period. There was no significant difference in the rate of decline in levels of fasting blood glucose and HbA1, in IDDM and NIDDM. In NIDDM, the major risk factor is hypertension, as in IDDM. Triglycerides and total cholesterol also play roles in the retardation of renal function. Nephrotic syndrome also influenced the retardation of renal function in both IDDM and NIDDM.

Characteristics of cranial nerve palsies in diabetic patients

The incidence of palsy in the third, sixth and seventh cranial nerves was studied with regard to central nervous system involvement in diabetic patients. Among 1961 diabetic patients, 19 (0.97%) demonstrated cranial nerve palsies. Nine out of these 19 patients showed facial palsy; 6 palsy of the oculomotor nerve; 2 palsy of the abducent nerve; and 3 both oculomotor and abducent nerve palsies. In contrast, only 5 out of 3841 non-diabetic patients (0.13%) had any cranial nerve palsies; all 5 were cases of facial palsy. The incidence of cranial palsies in diabetic patients was significantly higher than that in non-diabetic patients (P less than 0.01). Concerning age, sex, the state of glycemic control, diabetic complications and method of treatment, there were no differences disclosed in the diabetic patients with cranial nerve palsy. The incidences of diabetic complications were compared between the patients with facial palsy and those with ophthalmoplegia. Only one out of 9 patients with facial palsy (11%) had diabetic complications, whereas 7 out of 10 patients with ophthalmoplegia (70%) demonstrated diabetic complications and the difference was significant. Thus ophthalmoplegia appears to be more closely related to diabetic metabolism while facial palsy is less strongly correlated with diabetes.

Serum gliclazide concentration in diabetic patients. Relationship between gliclazide dose and serum concentration

Serum levels of gliclazide were determined by radioimmunoassay in seven healthy controls and in 18 diabetic in-patients receiving single oral dosing and consecutive dosing over 5 days. Following a single oral dose of 40 mg in the seven controls and eight diabetic patients, and 120 mg in ten diabetic patients, the serum levels of gliclazide peaked on average at 2 h, followed by a slow decline, the t1/2 being 16.5 h in the volunteers, 12.3 h in the diabetic patients receiving 40 mg, and 10.5 h in those receiving 120 mg. During consecutive administration, the serum levels both at fasting and at the peak reached a plateau in 2 days and no further accumulations were observed. The steady-state peak levels of gliclazide in the diabetic patients revealed a strongly positive correlation with the dose per m2 body surface area (r = 0.78, P less than 0.001), and their steady-state fasting levels correlated positively but weakly with the dose per m2 body surface area (r = 0.48, P less than 0.05). Thus, measuring either the fasting or the peak concentration of gliclazide will be useful for monitoring drug concentration in the serum. Pharmacokinetics of gliclazide will contribute to the elucidation of the relationship of serum level and clinical effectiveness in diabetic subjects.

Risk factors for worsening to diabetes in subjects with impaired glucose tolerance

In a 5-12 year follow-up study of 288 subjects with impaired glucose tolerance after a 100-g glucose load, 48 worsened to overt Type 2 (non-insulin-dependent) diabetes with the elevation of fasting blood glucose. The initial level of blood glucose was a major predictor of subsequent worsening to diabetes. In addition, subjects with a lower insulin response to glucose showed a higher incidence of worsening to the disease, irrespective of blood glucose levels. Multivariate analysis indicated that a diminished insulin response and a high maximal body weight index, as well as a high level of fasting and 2-h glucose values at the initial 100-g oral glucose tolerance test were significant independent risk factors for the development of diabetes in Japanese subjects.

On the pathogenesis of type II diabetes with special reference to diminished insulin response and obesity: a 5-12 year follow-up study of subjects with borderline glucose tolerance

In a 5-12 year follow-up study of 288 subjects with borderline glucose tolerance, 56 of them worsened to overt noninsulin dependent diabetes mellitus (NIDDM). Multivariate analysis indicated that a high level of fasting and 2-hour blood glucose values at the initial 100 g oral glucose tolerance test, a large maximal body weight index (Max. BWI) and a diminished insulin response to glucose load were significant independent risk factors for worsening to diabetes. Deterioration to diabetes was observed 4.5 times, 6.1 times and 2.1 times more frequently in subjects with fasting blood glucose greater than or equal to 100 mg/100 ml, 2-hour blood glucose greater than or equal to 180 mg/100 ml and Max. BWI greater than or equal to 130%, respectively, as compared with those having lower values of each variable. Diabetes developed almost exclusively from low insulin responders in 253 non- or mildly obese subjects, while in 35 severely obese subjects a certain number of 'normal or high' insulin responders did develop diabetes. In conclusion, the majority of cases of NIDDM develop on the basis of low insulin secretion, with an additional precipitating factor of obesity, and, in some with higher insulin responses diabetes develops when extreme obesity exists, though these cases form a minor group in Japan today.

Chlorpropamide-induced hyponatremia: incidence and risk factors

The incidence and risk factors of chlorpropamide-induced hyponatremia were assessed in diabetic outpatients. In 176 chlorpropamide-treated patients, 11 (6.3%) exhibited hyponatremia (serum sodium less than or equal to 129 meq/L) during the mean follow-up period of 7.4 yr. In contrast, only one (0.6%) developed hyponatremia in 162 tolbutamide- or glibenclamide-treated patients (P less than 0.005). Moreover, administration to elderly patients and combination with thiazide diuretics were regarded as significantly potent risk factors for the development of hyponatremia in patients receiving chlorpropamide.

Insulin secretory responses in patients with glucose intolerance due to extra-pancreatic causes. Comparison with idiopathic diabetes mellitus

Insulin responses during 100 g glucose tolerance tests (GTT) were compared between three groups of patients with varying degrees of glucose intolerance. Patients who had no disease known to be associated with secondary diabetes were classified as patients with idiopathic diabetes mellitus. Those whose present and past fasting blood glucose (FBG) exceeded 140 mg/100 ml were assigned to Group A, and the rest of the patients to Group B. Group C included patients with liver disease, thyrotoxicosis, or myocardial infarction, or those treated with corticosteroids or who had undergone gastrectomy. Patients in Group A were found to have consistently subnormal insulin responses whether glucose tolerance was normal (i.e. previous abnormality of glucose tolerance), borderline, or diabetic. In contrast, patients in Group C without fasting hyperglycemia had enhanced rather than decreased insulin responses when glucose tolerance was the more impaired. Patients in Group B had insulin responses similar to those either of Group A or of Group C. The relationship between the sum of six insulin and six blood glucose values during GTT (sigma IRI and sigma BG) was examined. The sigma BG-sigma IRI plot revealed distinctly different distribution zones for Group A and Group C (Zones A and C). In Group A, sigma IRI values were below 300 microU/ml irrespective of sigma BG values. In Group C, sigma IRI tended to increase, paralleling the increase in sigma BG values in the range of sigma BG values lower than 1400 mg/100 ml. In patients whose sigma BG rose above 1400/100 ml during corticosteroid treatment, the sigma IRI values decreased and entered into Zone A. After the cessation of corticosteroids in a few of these patients, the sigma IRI values recovered and reentered Zone C, concomitant with an improvement in glucose tolerance. Similar recovery of insulin response from Zone A to Zone C was also observed after the treatment of two obese diabetic patients. Thus, patients with glucose intolerance due to extra-pancreatic causes may secrete insulin at a higher rate than normal so long as the FBG level remains below 120 mg/100 ml, but a further deterioration in glucose metabolism may lead to a failure of insulin secretory mechanisms.

Increase in insulin response after treatment of overt maturity-onset diabetes is independent of the mode of treatment

The changes in insulin response to a 100 g glucose tolerance test after treatment by diet, sulphonylurea and insulin were compared in non-ketotic diabetic patients who had fasting blood glucose concentrations higher than 160 mg/100 ml. Patients were selected so that their pre-treatment and post-treatment blood glucose levels were comparable between different treatment groups. Their insulin responses were poor initially but increased significantly when the diabetic state was improved by each treatment. The degree of improvement of insulin response was similar between different treatment groups, when their fasting blood glucose decreased below 140 mg/100 ml and the glucose tolerance curves were improved to a similar extent. Pre- and post-treatment sigma IRI values (sum of insulin values during glucose tolerance test, mean +/- SD) were 102 +/- 50 and 200 +/- 37 microU/ml in diet-treated group (n = 28), 90 +/- 40 and 195 +/- 53 microU/ml in sulphonylurea-treated group (n = 48), and 83 +/- 28 and 193 +/- 38 microU/ml in insulin-treated group (n = 13), respectively. The data suggest that the poor insulin response in overt diabetes results not only from an inherent insensitivity of B-cells to glucose but also from the metabolic derangement of diabetes. Poor insulin response and overtly diabetic metabolism seems to form a vicious cycle.

Insulin responses in equivocal and definite diabetes, with special reference to subjects who had mild glucose intolerance but later developed definite diabetes

Insulin secretory responses during the 100-gm. glucose tolerance test (GTT) were studied in subjects who had or had had glucose intolerance. Patients who had metabolic diseases other than diabetes were excluded. The ratio (ΔIRI/ΔBS) of increments of blood insulin to blood sugar 30 minutes after glucose load was used as the most sensitive index to detect the abnormality of early Insulin release In diabetes. In patients with definite diabetes (I.e., those whose fasting blood sugar values (FBS) were or had been higher than 140 mg./lOO ml. or who had diabetic retinopathy), ΔIRI/ΔBS ratios were almost invariably subnormal regardless of FBS levels and the types of glucose tolerance at the time of GTT. In the rest of the patients (equivocal diabetics), ΔIRI/ΔBS ratios were either normal or subnormal. The decrease in ΔIRI/ΔBS was a fairly stable characteristic of each individual; in 330 equivocal diabetics, only 28 cases (8.4 per cent) moved between high-and low-insulin-responder groups during the follow-up. In 39 patients who had equivocal diabetes at the initial examination but subsequently developed definite diabetes (20 who began to have FBS above 140 mg./lOO ml. and 19 who developed retinopathy), the insulin response were already subnormal at the initial GTT and remained low throughout the follow-up periods, although their glucose tolerance varied between normal, borderline, and diabetic types. Thus, definite diabetes occurred exclusively in the low-insulin-responder group among equivocal diabetics. The decrease in insulin response to glucose seems to be a more Inherent, specific, and stable feature of true diabetes than glucose intolerance, because it precedes the occurrence and persists after the remission of derangement of carbohydrate metabolism in definite diabetes.

Abnormal secretion of insulin and glucagon by the in vitro perfused pancreas of the genetically diabetic Chinese hamster

Hereditary insulin-deficient diabetes mellitus occurs in certain sublines of nonobese Chinese hamsters. Several characteristics of this syndrome are similar to those seen in insulin-deficient human diabetics. Therefore, to characterize pancreatic islet function, dynamic insulin and glucagon release from normal and nonketotic diabetic hamster pancreases in response to glucose (300 mg/100 ml) and theophylline (10 mM), infused singly and together, was studied in vitro.20-min glucose infusions of normal hamster pancreases caused biphasic insulin release, consisting of a rapid first peak and a gradually rising second phase, similar to that reported for man in vivo. Both phases were significantly reduced in the diabetic pancreases. Theophylline alone stimulated similar nonphasic insulin release in both the normal and the diabetic pancreases. Glucose and theophylline together caused greater insulin release than either stimulant alone in both normals and diabetics; however, the diabetic response was still subnormal. Glucose suppressed glucagon release from normal pancreases; suppression was significantly impaired in diabetics. Theophylline stimulated nonphasic glucagon release in both the normals and diabetics. Glucose partially suppressed the theophylline-stimulated release in both groups.Insulin/glucagon molar ratios of the diabetics were consistently subnormal, although individual hormone levels often overlapped into the normal range. IN SUMMARY, THE PANCREASES OF GENETICALLY DIABETIC CHINESE HAMSTERS PERFUSED IN VITRO SHOWED: (a) decreased first and second phase insulin release in response to glucose-containing stimuli-only partially ameliorated by theophylline-, and (b) impaired suppression of glucagon in response to glucose, resulting in (c) a decreased insulin/glucagon molar ratio. These data support the suggestion that both alpha and beta cells of diabetic pancreases may be insensitive to glucose.

Comparison of the inhibitory effects of diphenylhydantoin and diazoxide upon insulin secretion from the isolated perfused pancreas

Both diazoxide and diphenylhydantoin have been shown to cause hyperglycemie in man and to inhibit insulin secretion in vitro. The effects of these two drugs upon the response to 300 mg./100 ml. glucose were contrasted in the isolated, perfused rat pancreas. Similarities: Both drugs inhibited within seconds. At high concentrations (75 μg./ml.) of either drug, 95 to 100 per cent inhibition occurred. Upon withdrawal, return of secretion was rapid. Differences: During constant (five- and twenty-minute) infusions of diazoxide (10 to 75 μg./ml.), there was an initial fall in secretion and then an “escape” toward pre-inhibition levels; after diazoxide there was a postinhibitory overshoot. In contrast, five-minute infusions of diphenylhydantoin (5 to 75 μg./ml.), and twenty-minute infusions of 25 to 75 μg./ml., though causing comparable levels of initial inhibition, did not cause escape or postinhibitory overshoot. However, an incompletely inhibitory concentration of diphenylhydantoin (10 μg./ml.), given for twenty minutes, was followed by this overshoot.

Computer simulation, based on the compartmental-quantal model, suggested that diphenylhydantoin inhibits both secretion from a labile insulin compartment and provision of insulin and/or precursor to this compartment. Lower, partially inhibitory concentrations (i.e. 10 μg./ml.) of diphenylhydantoin might allow for some provision to proceed, and thus a postinhibitory overshoot would occur. The escape and overshoot noted with all inhibitory levels of diazoxide, when compared with the simulations, suggested that this drug may act primarily to inhibit a late step in the provisionary phase.

Changes in plasma insulin and glucose tolerance in stable diabetes in a young woman

In a seventeen-year-old woman with a strong family history of diabetes mellitus, changes in glucose tolerance and plasma insulin response to oral glucose were followed from the early stage of diabetes through exacerbations and remissions of the disease. At the first glucose tolerance test which revealed normal fasting and elevated postprandial blood sugar values, the plasma insulin level at thirty minutes was subnormal but the peak level, which was delayed to ninety minutes, was above normal. During the exacerbation when fasting blood sugar values were elevated, insulin response was markedly diminished. In the stage of improvement following treatment with oral drugs and insulin, plasma insulin response to oral glucose improved remarkably. During the course of subsequent exacerbation and improvement, the degree of plasma insulin response changed in a similar inverse manner with the blood sugar level. The observations suggest that the diminished insulinsecretory capacity in severe diabetes does not always indicate irreversible damage of insulin releasing mechanisms.