Pancreatic beta cell response in insulin treated NIDDM patients limitations of a random C-peptide measurement

Pancreatic beta cell function was evaluated in 30 insulin treated non-insulin dependent diabetic patients, by estimating serum C-peptide after meal stimulation. C-peptide response was low (less than 0.6 pmol/ml) in 15 patients and it was significant (greater than 0.6 pmol/ml) in the other 15 patients. All the patients were then started on a high carbohydrate, high fibre diet and a combination of glibenclamide and metformin. In 18 patients, optimal regulation of hyperglycemia was achieved in one week and the others required insulin treatment. Among the 15 with low C-peptide values, 8 patients responded to oral hypoglycaemic agents and their C-peptide responses improved (from 0.17 +/- 0.16 to 0.78 +/- 0.2 pmol/ml). Among the 15 with significant C-peptide values, 10 responded well to oral drugs and their C-peptide values improved further (from 0.79 +/- 0.21 to 1.17 +/- 0.44 pmol/ml); but the others required insulin despite the good beta cell reserve. This study shows that the beta cell response in insulin treated NIDDM varies widely as it is influenced by the exogenous insulin and hyperglycaemia a random estimation of C-peptide will be of limited value in predicting the response to therapy.

Exercise- and cold-induced changes in plasma beta-endorphin and beta-lipotropin in men and women

The plasma beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) response of men, eumenorrheic women, and amenorrheic women (n = 6) to 1 h of rest or to a bicycle ergometer test [20 min at 30% maximum O2 uptake (VO2max), 20 min at 60% VO2max, and at 90% VO2max to exhaustion] was studied in both normal (22 degrees C) and cold (5 degrees C) environments. beta-EP and beta-LPH was measured by radioimmunoassay in venous samples collected every 20 min during rest or after each exercise bout. Exhaustive exercise at ambient temperature (Ta) 22 degrees C induced significant increases in plasma beta-EP and beta-LPH in all subjects as did work at 60% VO2max in amenorrheic and eumenorrheic women. During work at Ta 5 degrees C, the relative increase in beta-EP and beta-LPH was suppressed in eumenorrheic women and completely prevented in amenorrheic women. Although significant lowering of beta-EP and beta-LPH was observed in men and eumenorrheic women during rest at 5 degrees C, amenorrheic women maintained precold exposure levels. These findings suggest that plasma beta-EP and beta-LPH may reflect a thermoregulatory response to heat load. There appears to be a sexual dimorphism in exercise- and cold-induced release of beta-EP and beta-LPH and amenorrhea may be accompanied by alterations in these responses.

Effects of vagotomy on circulating levels of catecholamines and corticosterone in the pigeon

The effects of bilateral cervical vagotomy on the blood levels of corticosterone, and catecholamines, adrenaline (A) and noradrenaline (NA), in pigeons, were studied. Plasma levels of corticosterone and NA were found to be significantly higher and of A lower, in the vagotomized (VgX) pigeons as compared to their sham-operated (VgS) controls. These changes in VgX pigeons are explained as caused mainly by the lack of the vagal tone.

Beta cell function in insulin-treated non-insulin-dependent diabetic patients

Non--insulin-dependent diabetes mellitus (NIDDM) patients, 94 in number, who were treated with insulin for various reasons for periods ranging from 2 to 10 years, were investigated to study the effect of long-term insulin therapy and also the effect of anti-insulin antibodies on the beta cell function. Insulin antibody titer and the stimulated C-peptide (CP) did not correlate with the duration of insulin therapy, dose of insulin, or the severity of hyperglycemia. The antibody titers were low in 45%, moderate in 10%, and high in 45%; no correlation was found between the antibody titers and the CP values. Satisfactory control of hyperglycemia was obtained in 54 patients after change of treatment to oral hypoglycaemic agents (OHA). The other 40 patients required continued insulin therapy. The initial CP values were similar in both the groups before initiating the new therapeutic patterns. Those who responded to OHA showed improved CP values on follow-up. The beta cell response to exogenous insulin is heterogeneous in NIDDM patients. In many patients, adequate preservation of beta cell function is present even after long-term insulin therapy. Many of them respond to OHA. Insulin antibodies do not influence the secretory status of the beta cells in NIDDM patients.

Errors in clinical assessment of glycemic control in patients with non-insulin-dependent diabetes mellitus

Errors in the assessment of glycemic control by clinicians, using the conventional method, based on random blood glucose and clinical parameters other than HbA1, were assessed in 125 non-insulin-dependent diabetic (NIDDM) patients (Group B). The expected mean post-prandial plasma glucose concentrations (y) for these patients were obtained from their HbA1 values (x) using the regression equation y = 39.6 X x - 157.6. This equation was derived using the data from 35 NIDDM patients (Group A), in whom mean post-prandial plasma glucose concentrations (measured twice daily), correlated excellently (r = 0.82; n = 100; p less than 0.001) with mean HbA1 values (measured monthly) determined over a period of 3 months. A comparison of the observed and expected post-prandial plasma glucose concentrations in Group B indicated that only an overall 42% of the total (n = 455) observed values (as against 60% in Group A) fell within the 99% confidence limits of the expected mean value. Fifty-eight % of the observed plasma glucose values fell outside the expected range of which 36% were underestimates and 22% were overestimates. Thus, we concluded that even in patients with stable diabetes the physician's assessment of the overall degree of glycemic control should be based on both plasma glucose and HbA1 concentrations for optimizing therapeutic measures.

Significance of impaired glucose tolerance in an Asian Indian population: a follow-up study

A prospective study was undertaken in 107 Indians with impaired glucose tolerance (IGT) for a period ranging from 2 to 10 years. On follow-up, 32% still had an impaired glucose tolerance, 32% reverted to normal glucose tolerance and 36% developed diabetes. Careful dietary adherence and weight reduction were found to favour normalisation of glucose tolerance. Poor dietary adherence, persistent obesity and weight gain were found to precipitate diabetes. The study stresses the need for intensive diet therapy in individuals with IGT. Insulin responses were heterogeneous in IGT and non-predictive of the follow-up changes in glucose tolerance.

Beta cell function in long term NIDDM (type 2) patients and its relation to treatment

Pancreatic beta cell function was assessed by estimation of fasting and post prandial plasma C-peptide in 183 non-insulin dependent diabetic patients, who were treated with oral hypoglycaemic drugs, for more than 10 years. One-hundred-and-forty-one patients, continued to respond to oral hypoglycaemic agents (Group I) and in 42 the control was not satisfactory and had to be changed over to insulin (secondary failure, Group II). Significant beta cell reserve (PP CP greater than or equal to 0.6 pmol/ml) was present in 89 out of 183 patients (48%) and 83 (93%) of them responded to oral hypoglycaemic agents. Among the 94 patients with low beta cell reserve, 58 (62%) were on oral hypoglycaemic agents and the other 36 (38%) were on insulin. Of the 42 patients with secondary failure to the oral drugs, 36 (86%) had low C-peptide while 6 (14%) had significant C-peptide values. Secondary failure to oral hypoglycaemic agents can also occur in spite of good beta cell reserve. Beta cell reserve was not correlated either to the duration of diabetes or the age at diagnosis of the patients.

Peripheral neuropathy in tropical pancreatic diabetes

Electrophysiological evaluation of peripheral neuropathy was done in 16 patients with tropical pancreatic diabetes (TPD) and the data compared with those of a matched group of 16 NIDDM patients. Peripheral neuropathy was present in 6 TPD and 5 NIDDM patients. Abnormal motor conduction velocity in the lateral popliteal nerve was seen in 9 TPD patients and in 8 NIDDM patients and biothesiometry was abnormal in 7 patients in each group. One TPD patient had an abnormal F wave in the lower limb. An abnormal sensory potential was recorded in the sural nerve in 6 TPD and 8 NIDDM patients. The study showed that occurrence of peripheral neuropathy in TPD was similar to that in NIDDM. Subclinical neuropathy could be detected by electromyographic recording in both groups of patients.

Insulin response in obese and nonobese offspring of conjugal Indian diabetic parents with increasing glucose intolerance

Pancreatic beta cell function in response to glucose was assessed in three different groups of offspring of conjugal diabetic parents (OCDP): those with normal glucose tolerance, those with impaired glucose tolerance (IGT), and those with diabetes. Serum immunoreactive insulin (IRI), C-peptide (CP), insulin/glucose (I/G) ratio, and IRI/CP ratios were estimated at fasting and 90 min after glucose load. Insulin secretion, measured as CP, was found to be low even in normal nonobese OCDP, but the change was not reflected in IRI value as the IRI/CP ratio was found to be elevated. The values decreased with increasing glucose intolerance. In obese OCDP, all the parameters were abnormal even among those with normal glucose tolerance, and further deterioration occurred with increasing glucose intolerance. The study shows that insulin secretory defects are detectable even in normal OCDP, and these changes deteriorate with increasing glucose intolerance. Differences are noted in the peripheral concentrations of IRI and CP between obese and nonobese OCDP before development of diabetes. After development of diabetes mellitus, these differences disappear, and the CP and IRI values in both groups are similar and low.

Suppression of sympathetic nervous system by short photoperiod and melatonin in the Syrian hamster

Exposure to short photoperiod or melatonin treatment brings about gonadal regression in Syrian hamsters. The possible influence of these treatments on the sympathetic nervous system (SNS) in these animals was investigated. Male Syrian hamsters were exposed to either long or short photoperiod or subjected to administration of melatonin or its vehicle solution. Exposure of hamsters to 10 weeks of short photoperiod, significantly reduced the noradrenaline (NA) turnover in the heart. Daily administration of melatonin for 8 weeks also resulted in a similar suppression of NA turnover in the heart. Hamsters that were treated with melatonin maintained a lowered metabolic rate as well, at and below thermoneutral temperature. These findings suggest that in a deep hibernator, short photoperiod could suppress the peripheral sympathetic activity and that melatonin may act as the endogenous mediator.

Effects of short photoperiod and melatonin treatment on thermogenesis in the Syrian hamster

This study investigated whether short photoperiod or melatonin-treatment could alter the thermogenic capacity of Syrian hamsters. Exposure of hamsters to short photoperiod and to exogenous melatonin treatment induced gonadal regression and hypertrophy of brown adipose tissue (BAT). Short photoperiod and melatonin-induced BAT hypertrophy was not accompanied by any change in noradrenaline (NA) turnover in this tissue. The concentration of NA was significantly decreased in hypertrophied BAT, indicating that sympathetic innervation in BAT did not effect its hypertrophy. No improvement in nonshivering thermogenic capacity was noticed in hamsters with increased BAT mass. However, capability for shivering thermogenesis seemed to be enhanced in melatonin-treated hamsters. These observations suggest that melatonin, in addition to mediating short photoperiod-induced gonadal regression in the Syrian hamster, also brings about thermoregulatory adjustments necessary for hibernation.

Abnormalities in insulin secretion in healthy offspring of Indian patients with maturity-onset diabetes of the young

Serum C-peptide (CP) and immunoreactive insulin (IRI) responses were studied in 47 euglycemic offspring of patients with maturity-onset diabetes of the young (MODY). Mean IRI responses were not significantly different in nonobese offspring of MODY patients (O-MODY) but they were lower in obese O-MODY than in respective controls. Mean CP responses were low in both groups, the change being more pronounced in obese O-MODY. These findings indicate that alterations of secretion and metabolism of insulin can be detected even before glucose intolerance is seen in O-MODY.