Observations on lipolysis in ketosis-resistant, growth-onset diabetes

Current Knowledge on the Pathophysiology of Lean/Normal-Weight Type 2 Diabetes

Since early times, being overweight and obesity have been associated with impaired glucose metabolism and type 2 diabetes (T2D). Similarly, a less frequent adult-onset diabetes in low body mass index (BMI) people has been known for many decades. This form is mainly found in developing countries, whereby the largest increase in diabetes incidence is expected in coming years. The number of non-obese patients with T2D is also on the rise among non-white ethnic minorities living in high-income Western countries due to growing migratory flows. A great deal of energy has been spent on understanding the mechanisms that bind obesity to T2D. Conversely, the pathophysiologic features and factors driving the risk of T2D development in non-obese people are still much debated. To reduce the global burden of diabetes, we need to understand why not all obese people develop T2D and not all those with T2D are obese. Moreover, through both an effective prevention and the implementation of an individualized clinical management in all people with diabetes, it is hoped that this will help to reduce this global burden. The purpose of this review is to take stock of current knowledge about the pathophysiology of diabetes not associated to obesity and to highlight which aspects are worthy of future studies.

Ketosis resistance in fibrocalculous pancreatic diabetes: II. Hepatic ketogenesis after oral medium-chain triglycerides

A majority of patients with fibrocalculous pancreatic diabetes (FCPD) do not become ketotic even in adverse conditions. It is not clear whether this ketosis resistance is due to reduced fatty acid release from adipose tissue or to impaired hepatic ketogenesis. We tested hepatic ketogenesis in FCPD patients using a ketogenic challenge of oral medium-chain triglycerides (MCTs) and compared it with that in matched insulin-dependent diabetes mellitus (IDDM) patients and healthy controls. After oral MCTs, FCPD patients showed only a mild increase in blood 3-hydroxybutyrate (3-HB) concentrations (median: fasting, 0.13 mmol/L; peak, 0.52) compared with IDDM patients (fasting, 0.44; peak, 3.39) and controls (fasting, 0.04; peak, 0.75). Plasma nonesterified fatty acid (NEFA) concentrations were comparable in the two diabetic groups (FCPD: fasting, 0.50 mmol/L; peak, 0.79; IDDM: fasting, 0.91; peak, 1.04). Plasma C-peptide concentrations were low and comparable in the two diabetic groups. Plasma glucagon concentrations were higher in IDDM patients in the fasting state, but declined to levels comparable to those in FCPD patients after oral MCTs. Plasma carnitine concentrations were comparable in the two groups of patients. It is concluded that the failure to stimulate ketogenesis under these conditions could be partly due to inhibition of a step beyond fatty acid entry into the mitochondria.

Adaptations in glucose homeostasis during chronic nutritional deprivation in rats: hepatic resistance to both insulin and glucagon

The role of glucagon in glucose homeostasis during chronic malnutrition was studied in weanling-littermate rats either fed ad libitum or restricted to 60% of ad libitum intake for 8 weeks. Fasting glucose and insulin levels were lower in malnourished rats, and their response to glucagon (0.02 mg/kg intravenous [IV]) after a 16-hour fast was significantly less than in control littermates for both glucose (P = .039) and insulin (P = .008). During euglycemic glucose clamp studies at identical plasma glucose (PG) levels, insulin suppression of hepatic glucose production (HGP) was impaired in malnourished rats, indicating insulin resistance (mean +/- SE HGP: 48 +/- 5 v 32 +/- 10 mumol.kg-1.min-1 for controls, P = .028). Glucose disposal was not significantly different in the two groups. However, after IV glucagon, the increase in HGP was markedly impaired in malnourished rats (P = .0004), with the total amount of glucose produced by the liver over 15 minutes being 1,397 +/- 114 mumol/kg as compared with 2,031 +/- 118 in controls (P = .0047). The impaired response was not due to defective glycogenolysis, because the release of glucose from prelabeled glycogen in response to glucagon injection contributed only 6% to 8% of the overall increase in glucose output from the liver, and was not different in the two groups. Furthermore, liver glycogen stores were virtually exhausted after the 16-hour fast, without glucagon injection. Glucagon receptor affinity and number were not affected by malnutrition. It is concluded that (1) chronic malnutrition is associated with hepatic resistance to both insulin and glucagon, (2) the glucagon resistance is not due to impaired glycogenolysis, and (3) it is mediated by a postreceptor defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic calcific pancreatitis of the tropics (CCPT): spectrum and correlates of exocrine and endocrine pancreatic dysfunction

The exocrine and endocrine pathophysiology of chronic calcific pancreatitis of the tropics (CCPT) remains elusive. The objective of this study was to evaluate the spectrum and correlates of the exocrine and endocrine pancreatic dysfunction in CCPT. Thirty-seven consecutive patients with a clinico-radiological diagnosis of CCPT were stratified into three subgroups: CCPT-normal glucose tolerance (NGT), CCPT-abnormal glucose tolerance (IGT) and CCPT-diabetes mellitus (DM). Ten ketosis resistant young diabetic (KRDY) patients, 10 classical insulin dependent diabetes mellitus (IDDM) patients and 18 healthy matched controls were included for comparison. Fecal chymotrypsin (FCT) levels and blood C-peptide levels (basal and post i.v. glucagon stimulation) were estimated for assessing the exocrine and endocrine pancreatic functions, respectively. Sonography was performed to evaluate the pancreatic size and ductal diameter. Pancreatic exocrine-endocrine correlation was examined by studying the C-peptide/fecal chymotrypsin ratio (CP/FCT) (CP/FCT of normal controls = 1). Mean FCT levels in all 3 subgroups of CCPT (NGT: 3.4 micrograms/g; IGT: 0.82 microgram/g; DM: 2.4 micrograms/g) were very low (87-96% reduction in exocrine pancreatic dysfunction; mean FCT in healthy controls was 22.8 micrograms/g) (P < 0.0001). In contrast, KRDY and IDDM patients displayed 50-54% reduction in pancreatic acinar function (P < 0.001). Basal and stimulated C-peptide levels progressively fell in the 3 CCPT subsets (NGT: 0.23 and 0.46 > IGT: 0.14 and 0.29 > DM 0.10 and 0.14) (P < 0.01). CCPT patients exhibited pancreatic atrophy and ductal dilation (> 3 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

The ketosis-resistance in fibro-calculous-pancreatic-diabetes. 1. Clinical observations and endocrine-metabolic measurements during oral glucose tolerance test

We measured circulating levels of C-peptide, pancreatic glucagon, cortisol, growth hormone and metabolites (glucose, non-esterified fatty acids, glycerol and 3-hydroxybutyrate) in fibro-calculous-pancreatic diabetic (FCPD, n = 28), insulin-dependent diabetic (IDDM, n = 28) and non-diabetic control (n = 27) subjects during an oral glucose tolerance test. There was no difference in the two diabetic groups in age (FCPD 24 +/- 2, IDDM 21 +/- 2 years, mean +/- SEM), BMI (FCPD 16.0 +/- 0.6, IDDM 15.7 +/- 0.4 kg/m2), triceps skinfold thickness (FCPD 8 +/- 1, IDDM 7 +/- 1 mm), glycaemic status (fasting plasma glucose, FCPD 12.5 +/- 1.5, IDDM 14.5 +/- 1.2 mmol/l), fasting plasma C-peptide (FCPD 0.13 +/- 0.03, IDDM 0.08 +/- 0.01 nmol/l), peak plasma C-peptide during OGTT (FCPD 0.36 +/- 0.10, IDDM 0.08 +/- 0.03 nmol/l) and fasting plasma glucagon (FCPD 35 +/- 4, IDDM 37 +/- 4 ng/l). FCPD patients, however, showed lower circulating concentrations of non-esterified fatty acids (0.73 +/- 0.11 mmol/l), glycerol (0.11 +/- 0.02 mmol/l) and 3-hydroxybutyrate (0.15 +/- 0.03 mmol/l) compared to IDDM patients (1.13 +/- 0.14, 0.25 +/- 0.05 and 0.29 +/- 0.08 mmol/l, respectively). This could be due to enhanced sensitivity of adipose tissue lipolysis to the suppressive action of circulating insulin and possibly also to insensitivity of hepatic ketogenesis to glucagon. Our results also demonstrate preservation of alpha-cell function in FCPD patients when beta-cell function is severely diminished, suggesting a more selective beta-cell dysfunction or destruction than hitherto believed.

Insulin-dependent ketosis-resistant diabetes in Ethiopia

Anthropometric, clinical and biochemical findings were compared in 30 rural (group A), 18 urban insulin-requiring (group B) and 45 urban oral-agent-responsive (group C) newly diagnosed diabetics. Mean ages at onset were 28.3 +/- 12.0, 25.6 +/- 14.5 and 42.1 +/- 10.5 years respectively. The differences between A and C and between B and C were significant. Group A were poor and malnourished, with body mass index (BMI) 15.9 +/- 1.9 and 17.2 +/- 3.7 kg/m2 for males and females respectively, presented with a long history of classical diabetes without ketoacidosis and required insulin in modest doses. 3 of 10 cases had excess stool fat but none of 13 unselected cases had pancreatic calcification. Group C were better nourished, with BMI 22.6 +/- 2.8 and 22.4 +/- 4.5 kg/m2, and responded to oral agents. Group B, with BMI 17.2 +/- 2.6 and 18.6 +/- 3.1 kg/m2, required insulin for control but had C-peptide levels above 0.02 nmol/1 in 10 of 15 cases. Anthropometric indices for males, but not for females, were significantly lower in group A than in group B or C. There were significant differences in levels of glucose between A and B and A and C, free fatty acids between A and C and B and C, insulin between A and B and A and C and C-peptide between A and C and B and C. Of the 3 groups the rural type most closely resembled the tropical variants.

Tropical or malnutrition-related diabetes: a real syndrome?

The syndrome known as tropical diabetes seems to be distinct from the two main types common in developed countries. Major pancreatic exocrine disease may or may not be present, and within these two groups there are clinical and biochemical variants. For these conditions the term malnutrition-related diabetes has been proposed. Although malnutrition is a plausible unifying factor, there is a good case for retaining the term tropical diabetes until there is more information on clinical and biochemical features and on aetiology.

Biochemical characterization of ketosis-resistant young diabetics of northern India. In vivo effects of i.v. glucose, s.c. epinephrine and i.v. glucagon and in vitro effects of anti-insulin serum on adipose tissue lipolysis

Epinephrine (10 micrograms/kg body weight) s.c., glucagon (1 microgram/kg body weight) i.v. and glucose (0.5 g/kg body weight) i.v. were injected in groups of ketosis-prone young diabetics, ketosis-resistant young diabetics, maturity-onset diabetics, young and mature controls, each group comprising 8 subjects. Samples were drawn at timed intervals and analyzed for glucose, FFA, acetone, citrate and plasma free insulin. FFA and glycerol release by the adipose tissue in vitro was studied in 6 of each of the following groups: young diabetics and young controls in the presence of norepinephrine, anti-insulin serum or both. Failure of the adipose tissue of ketosis-resistant young diabetics to respond to lipolytic and ketogenic hormones has been suggested by others as the basis for the clinically observed resistance to ketoacidosis. The present data do not confirm any failure of the liver or adipose tissue to respond to glucagon, epinephrine or norepinephrine in these diabetics. The ketosis-resistant young diabetics have some endogenous insulin secretory capacity still preserved as evident from their basal and post-glucose free insulin levels and effects of anti-insulin serum on in vitro lipolysis by their adipose tissues. The available endogenous insulin though adequate in preventing excessive lipolysis and ketogenesis, appears insufficient to check hyperglycemia.