Glucose intolerance and diabetes mellitus are both prevalent in cirrhosis, yet the pathogenesis of impaired glucose metabolism remains unknown. Therefore insulin secretion (hyperglycemic clamp, +125 mg/dl), insulin sensitivity (euglycemic hyperinsulinemic insulin clamp, +10 microU/ml and +50 microU/ml), whole-body glucose oxidation (indirect calorimetry) and glucose turnover ([6,6-2H2]glucose isotope dilution) were evaluated in a homogenous group of cirrhotic patients with glucose intolerance (n = 7) or frank diabetes mellitus (n = 6). The results were compared with those obtained in control subjects (n = 8). In glucose-intolerant patients, whole-body glucose uptake (mainly reflecting glucose utilization by muscle) was significantly impaired in patients during both insulin infusions as a result of decreased stimulation of the two major intracellular pathways of glucose disposal--nonoxidative glucose disposal (i.e., glycogen synthesis) and glucose oxidation. Hepatic glucose production was normal in the basal state and was normally suppressed during stepwise insulin infusion (by 65% and 85%, respectively, p = NS vs. controls). Hyperglycemia-induced increases of plasma C-peptide concentrations were comparable to those in controls (p = NS). In diabetic patients, insulin-mediated glucose uptake was significantly reduced, mainly because of impaired non-oxidative glucose disposal. Glucose oxidation appeared to be reduced, too. Hepatic glucose production was significantly increased in the basal state (3.03 +/- 0.24 vs. 2.34 +/- 0.10 mg/kg min, p < 0.02) and during insulin infusion (+50 microU/ml: 0.67 +/- 0.17 vs. 0.13 +/- 0.08 mg/kg min, p < 0.05) compared with that in controls. Both the first and second phases of beta-cell secretion were significantly reduced in response to steady-state hyperglycemia (both p < 0.01 vs. control values). In conclusion, glucose intolerance in cirrhosis results from two abnormalities that occur simultaneously: (a) insulin resistance of muscle and (b) an inadequate response (even when comparable to that of controls) of the beta-cells to appropriately secrete insulin to overcome the defect in insulin action. Diabetes mellitus in insulin-resistant cirrhotic patients develops as the result of progressive impairment in insulin secretion together with the development of hepatic insulin resistance leading to fasting hyperglycemia and a diabetic glucose tolerance profile.

Insulin resistance is a characteristic feature of glucose-intolerant and diabetic cirrhotic patients. The pathogenic factors, however, that are responsible for the development of impaired glucose tolerance in cirrhosis, remain unclear. To examine whether the ability of hyperglycemia per se to enhance glucose uptake (by means of mass-action effect) is impaired in cirrhosis, we measured (insulin-independent) whole-body glucose disposal during hyperglycemia (hyperglycemic clamp studies, +125 mg/dl, in combination with an infusion of somatostatin (500 micrograms/hr), insulin (0.1 mU/kg min) and glucagon (0.5 ng/kg min) to "clamp" hormone levels at baseline), whole-body glucose oxidation (indirect calorimetry) and glucose turnover (prime-continuous infusion of [6,6-2H2-]glucose in a clinically homogeneous group of cirrhotic patients with glucose intolerance (n = 7) or frank diabetes mellitus (n = 7) and in control individuals (n = 7). Fasting plasma glucose concentrations were normal in glucose-intolerant patients but were significantly increased in diabetic patients (158 +/- 19 vs. 87 +/- 2 mg/dl in controls; p < 0.01). Plasma glucose concentrations were clamped at 214 +/- 4 mg/dl in controls, at 212 +/- 4 mg/dl in glucose-intolerant patients and at 287 +/- 19 mg/dl in diabetic patients; plasma insulin and glucagon concentrations were maintained at baseline levels. In the basal state, total-body glucose disposal (which equals basal hepatic glucose output) was normal in glucose-intolerant patients (2.25 +/- 0.11 mg/kg min) but was increased in diabetic patients compared with controls (3.32 +/- 0.26 mg/dl vs. 2.45 +/- 0.10 mg/dl; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

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