The ketotic ratio (KB/NEFA) in man

Diabetic and dyslipidaemic morbidly obese exhibit more liver alterations compared with healthy morbidly obese

Background & aims

To study the origin of fat excess in the livers of morbidly obese (MO) individuals, we analysed lipids and lipases in both plasma and liver and genes involved in lipid transport, or related with, in that organ.

Methods

Thirty-two MO patients were grouped according to the absence (healthy: DM − DL −) or presence of comorbidities (dyslipidemic: DM − DL +; or dyslipidemic with type 2 diabetes: DM + DL +) before and one year after gastric bypass.

Results

The livers of healthy, DL and DM patients contained more lipids (9.8, 9.5 and 13.7 times, respectively) than those of control subjects. The genes implicated in liver lipid uptake, including HL, LPL, VLDLr, and FAT/CD36, showed increased expression compared with the controls. The expression of genes involved in lipid-related processes outside of the liver, such as apoB, PPARα and PGC1α, CYP7a1 and HMGCR, was reduced in these patients compared with the controls. PAI1 and TNFα gene expression in the diabetic livers was increased compared with the other obese groups and control group. Increased steatosis and fibrosis were also noted in the MO individuals.

Conclusions

Hepatic lipid parameters in MO patients change based on their comorbidities. The gene expression and lipid levels after bariatric surgery were less prominent in the diabetic patients. Lipid receptor overexpression could enable the liver to capture circulating lipids, thus favouring the steatosis typically observed in diabetic and dyslipidaemic MO individuals.

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The criteria used to define the “metabolically healthy” obese is not applicable to morbidly obese patients.

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Virtually no studies of how bariatric surgery affects depending on comorbidities and less how affect to the liver.

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Anthropometrics, fat, lipid profile and inflammation parameters are different depending of comorbidities, not only in plasma but also in liver.

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The extent of lipases and lipids in the liver biopsies could help not only the diagnosis but also to follow the course of recovery after surgery.

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The morbidly obese individuals with diabetes and dyslipidemia have more altered metabolic profiles than the other two groups.

Differential effects of physiological versus pathophysiological plasma concentrations of epinephrine and norepinephrine on ketone body metabolism and hepatic portal blood flow in man

Few studies that have examined the effects of catecholamines on ketogenesis have considered the effects of catecholamines on hepatic portal blood flow. Since hepatic blood flow is a major determinant of hepatic ketogenesis (via modification of free fatty acid availability), interpretation of these studies is difficult. To better define the relative contributions of these variables, we studied the effects of physiological and pathophysiological plasma concentrations of epinephrine and norepinephrine on plasma ketone body concentrations and hepatic portal blood flow in controlled paired studies in young healthy male volunteers. To assess the effects of physiological catecholamine concentrations, each of eight subjects received 60-minute sequential infusions of epinephrine (10 ng/kg/min) and norepinephrine (32.5 ng/kg/min) together with a control infusion of heparin (0.4 U/kg/min) separated by 60-minute washout periods. Similar increments in plasma nonesterified fatty acid ([NEFA] to approximately 1 mmol/L) were observed during each infusion. The ketotic ratios, calculated as the ratio of plasma ketone bodies to fatty acids integrated above baseline for 90 and 120 minutes, respectively, for epinephrine and norepinephrine infusions were both significantly greater (P < .005 for each) than for the heparin control infusion. To assess the effects of pathophysiological plasma catecholamine concentrations, each of eight subjects also received sequential 60-minute infusions of epinephrine 60 ng/kg/min, norepinephrine 80 ng/kg/min (plus heparin 0.1 U/kg/min), and a separate control infusion of heparin with or without Intralipid (KabiVitrum, Alameda, CA). Whereas integrated plasma fatty acid levels were approximately twofold greater than those observed in the physiological protocol, the absolute integrated ketone body response to the pathophysiological concentration of epinephrine was significantly lower than that observed for the physiological dose of the hormone (P < .05). In contrast, the ketotic ratio for norepinephrine was significantly greater (P < .005) than for both epinephrine and the control infusion of heparin with or without Intralipid. Significant (P < .01) increases above baseline fasting levels were observed in plasma glucose and immunoreactive insulin concentrations during infusion of pathophysiological concentrations of epinephrine. Because of the technical difficulties of simultaneously measuring portal blood and sampling blood frequently, studies were repeated in six additional subjects using noninvasive image-guided flowmetry to measure percentage changes in hepatic portal blood flow during catecholamine infusion. Norepinephrine reduced hepatic portal blood flow significantly at the low-physiological concentration by 12% (P < .05) and at the pathophysiological concentration by 18% (P < .05). In summary, (1) both epinephrine and norepinephrine were associated with significant ketotic effects at physiological plasma concentrations; and (2) when infused at pathophysiological concentrations, only norepinephrine exerted a significant additional ketotic effect. Since norepinephrine has a significant simultaneous effect of reducing hepatic portal blood flow, we conclude that previous studies may have underestimated the effect of norepinephrine on hepatic ketogenesis.

Effects of autonomic neuropathy on glucose, fatty acid, and ketone body metabolism following insulin withdrawal in patients with insulin-dependent diabetes

It has been postulated that sympathetic denervation due to autonomic neuropathy may protect against the development of diabetic ketoacidosis in patients with insulin-dependent diabetes. We tested this hypothesis by withdrawing exogenous insulin from five men with established insulin-dependent diabetes and severe symptomatic autonomic neuropathy. Six men also with insulin-dependent diabetes of more than 5-years duration but no clinical evidence of neuropathy served as controls. Normoglycemia was maintained during the night before the study using a variable intravenous insulin infusion that was terminated at 0800 h the following morning (time 0 min). During a 600-min observation period following termination of the insulin infusion the rise (mean +/- SEM) in blood glucose concentration between 0 min and 600 min was comparable between the autonomic neuropathy and control groups (8.2 +/- 1.3 versus 8.3 +/- 1.1 mmol/L; p > 0.1). The rise in plasma nonesterified fatty acids was significantly less for the autonomic neuropathy patients (0.96 +/- 0.06 versus 1.65 +/- 0.14 mmol/L; p < 0.01) with a similar trend for the rise in total ketone body concentration (2.74 +/- 0.85 versus 3.72 +/- 0.38 mmol/L). Capillary pH at 600 min, however, was not significantly different between the groups (23 +/- 2 versus 20 +/- 1 mmol/L). In conclusion, plasma fatty acids and ketone body concentrations rise less rapidly following withdrawal of insulin in patients with insulin-dependent diabetes and autonomic neuropathy suggesting that such patients may have a degree of protection against the development of diabetic ketoacidosis.

Hypophagia following dietary obesity

Two experiments examined the hypophagia that occurs when rats are switched from a high-fat to a low-fat diet. In the first experiment, rats fed a high-fat diet for eight weeks weighed 79 g more than rats fed a low-fat diet. Removal of the high-fat diet led to reduced food intake for at least four weeks. Reducing the body weight of the rats by a 24 hour fast did not alter the time course of the hypophagia. Plasma levels of free glycerol, free fatty acids and ketones were elevated during and after feeding the high-fat diet; suggesting that feeding a high-fat diet increases fat oxidation even after the high-fat diet is withdrawn. In the second experiment, feeding rats the high-fat diet for four weeks increased body weight and body fat. Starving the rats for two days after feeding the high-fat diet did not alter subsequent hypophagia and did not alter the percentage of body fat. This pattern of results is similar to that previously seen following termination of obesity-inducing insulin treatment. The results are consistent with the idea that a persistent increase in fat oxidation is responsible for the hypophagia.

Metabolic concomitants of hypophagia during recovery from insulin-induced obesity in rats

Rats were given daily injections of protamine-zinc insulin (PZI) that increased food intake and body weight. Termination of insulin treatment resulted in transient hypophagia and weight loss. Simultaneously with the weight loss, plasma levels of glycerol, free fatty acids, glucose, and ketones increased, whereas adipose tissue lipoprotein lipase activity and liver glycogen decreased. These changes in food intake and metabolism after termination of PZI treatment were accentuated in streptozotocin-diabetic rats. Two antilipolytic drugs (nicotinic acid and 3,5-dimethylpyrazole) blocked the elevation in plasma glycerol while having no effect on food intake. A 1-day fast after termination of insulin treatment equalized insulin-treated and control groups for plasma glycerol and ketones and reversed group differences in free fatty acids; the elevation in plasma glucose persisted despite starvation. Following starvation, previously PZI-treated rats ate less than controls on refeeding. The results show that enhanced lipolysis does not invariably accompany hypophagia during excess weight loss and suggest that a disturbance in carbohydrate metabolism or an increase in hepatic fatty acid oxidation may underlie this decrease in food intake.