Protein kinase Cß is required for lupus development in Sle mice.

OBJECTIVE: To evaluate the requirement for protein kinase Cß (PKCß) in the development of lupus in mice, and to explore the potential of targeting PKCß as a therapeutic strategy in lupus. METHODS: Congenic mice bearing the disease loci Sle1 or Sle1 and Sle3, which represent different stages of severity in the development of lupus, were crossed with PKCß-deficient mice. The effect of PKCß deficiency in lupus development was analyzed. In addition, the effects of the PKCß-specific inhibitor enzastaurin on the survival of B cells from mice with lupus and human 9G4-positive B cells as well as the in vivo effect of enzastaurin treatment on the development of lupus in Sle mice were investigated. RESULTS: In Sle mice, PKCß deficiency abrogated lupus-associated phenotypes, including high autoantibody levels, proteinuria, and histologic features of lupus nephritis. Significant decreases in spleen size and in the peritoneal B-1 cell population, reduced numbers of activated CD4 T cells, and normalized CD4:CD8 ratios were observed. PKCß deficiency induced an anergic B cell phenotype and preferentially inhibited autoreactive plasma cells and autoantibodies in mice with lupus. Inhibition of PKCß enhanced apoptosis of both B cells from Sle mice and human autoreactive B cells (9G4 positive). Treatment of Sle mice with the PKCß-specific inhibitor enzastaurin prevented the development of lupus. CONCLUSION: This study identifies PKCß as a central mediator of lupus pathogenesis, suggesting that PKCß represents a promising therapeutic target for the treatment of systemic lupus erythematosus. Moreover, the results indicate the feasibility of using a PKCß inhibitor for the treatment of lupus.

Protein kinase Cß deficiency attenuates obesity syndrome of ob/ob mice by promoting white adipose tissue remodeling.

To explore the role of leptin in PKCß action and to determine the protective potential of PKCß deficiency on profound obesity, double knockout (DBKO) mice lacking PKCß and ob genes were created, and key parameters of metabolism and body composition were studied. DBKO mice had similar caloric intake as ob/ob mice but showed significantly reduced body fat content, improved glucose metabolism, and elevated body temperature. DBKO mice were resistant to high-fat diet-induced obesity. Moreover, PKCß deficiency increased ß-adrenergic signaling by inducing expression of ß1- and ß3-adrenergic receptors (ß-ARs) in white adipose tissue (WAT) of ob/ob mice. Accordingly, p38(MAPK) activation and expression of PGC-1α and UCP-1 were increased in WAT of DBKO mice. Consistent with results of in vivo studies, inhibition of PKCß in WAT explants from ob/ob mice also increased expression of above ß-ARs. In contrast, induction of PGC-1α and UCP-1 expression in brown adipose tissue of DBKO mice was not accompanied by changes in the expression of these ß-ARs. Collectively, these findings suggest that PKCß deficiency may prevent genetic obesity, in part, by remodeling the catabolic function of adipose tissues through ß-ARs dependent and independent mechanisms.

Disruption of the murine protein kinase Cbeta gene promotes gallstone formation and alters biliary lipid and hepatic cholesterol metabolism.

The protein kinase C (PKC) family of Ca(2+) and/or lipid-activated serine-threonine protein kinases is implicated in the pathogenesis of obesity and insulin resistance. We recently reported that protein kinase Cß (PKCß), a calcium-, diacylglycerol-, and phospholipid-dependent kinase, is critical for maintaining whole body triglyceride homeostasis. We now report that PKCß deficiency has profound effects on murine hepatic cholesterol metabolism, including hypersensitivity to diet-induced gallstone formation. The incidence of gallstones increased from 9% in control mice to 95% in PKCß(-/-) mice. Gallstone formation in the mutant mice was accompanied by hyposecretion of bile acids with no alteration in fecal bile acid excretion, increased biliary cholesterol saturation and hydrophobicity indices, as well as hepatic p42/44(MAPK) activation, all of which enhance susceptibility to gallstone formation. Lithogenic diet-fed PKCß(-/-) mice also displayed decreased expression of hepatic cholesterol-7α-hydroxylase (CYP7A1) and sterol 12α-hydroxylase (CYP8b1). Finally, feeding a modified lithogenic diet supplemented with milk fat, instead of cocoa butter, both increased the severity of and shortened the interval for gallstone formation in PKCß(-/-) mice and was associated with dramatic increases in cholesterol saturation and hydrophobicity indices. Taken together, the findings reveal a hitherto unrecognized role of PKCß in fine tuning diet-induced cholesterol and bile acid homeostasis, thus identifying PKCß as a major physiological regulator of both triglyceride and cholesterol homeostasis.

Heterotopic ossification in the residual lower limb in an adult nontraumatic amputee patient.

Heterotopic ossification in the residual lower limb in an adult nontraumatic amputee patient.Heterotopic ossification usually occurs in association with various neurologic injuries, trauma, and burns. There have been few reports in the literature of heterotopic bone formation at the distal residual limb in the adult amputee population. All previous cases with a documented cause have involved traumatic amputations. An adult diabetic patient who underwent left below-the-knee amputation for progressive Charcot foot is presented. The patient began to experience residual limb pain and decline in functional mobility 4-5 mos after surgery. Radiographs demonstrated heterotopic bone around the distal tibial and fibular remnant with extension into adjacent soft tissue. Triple-phase bone scan testing and tissue biopsy verified active heterotopic ossification. The patient was treated with etidronate and eventually was able to ambulate with a prosthesis on a regular basis. This case demonstrates that heterotopic ossification may occur and be a source of residual limb pain in the adult nontraumatic amputee population.

Loss of protein kinase Cbeta function protects mice against diet-induced obesity and development of hepatic steatosis and insulin resistance.

Obesity is an energy balance disorder in which intake is greater than expenditure, with most excess calories stored as triglyceride (TG). We previously reported that mice lacking the beta-isoform of protein kinase C (PKCbeta), a diacylglycerol- and phospholipid-dependent kinase, exhibit marked reduction in the whole body TG content, including white adipose tissue (WAT) mass. To investigate the role of this signaling kinase in metabolic adaptations to severe dietary stress, we studied the impact of a high-fat diet (HFD) on PKCbeta expression and the effect of PKCbeta deficiency on profound weight gain. We report herein that HFD selectively increased PKCbeta expression in obesity-prone C57BL/6J mice, specifically in WAT; the expression levels were little or unchanged in the liver, muscle, kidney, and heart. Basal PKCbeta expression was also found to be elevated in WAT of obese ob/ob mice. Remarkably, mice lacking PKCbeta were resistant to HFD-induced obesity, showing significantly reduced WAT and slightly higher core body temperatures. Unlike lean lipodystrophic mouse models, these mice did not have fatty livers, nor did they exhibit insulin resistance. Moreover, PKCbeta(-/-) mice exhibited changes in lipid metabolism gene expression, and such alterations were accompanied by significant changes in serum adipokines. These observations suggest that PKCbeta deficiency induced a unique metabolic state congruous with obesity resistance, thus raising the possibility that dysregulation of PKCbeta expression could contribute to dietary fat-induced obesity and related disorders.

Protein kinase C deficiency increases fatty acid oxidation and reduces fat storage.

Metabolic syndrome is common in the general population, but there is little information available on the underlying signaling mechanisms regulating triglyceride (TG) content in the body. In the current study, we have uncovered a role for protein kinase Cbeta (PKCbeta) in TG homeostasis by studying the consequences of a targeted disruption of this kinase. PKCbeta(-/-) mutant mice were considerably leaner and the size of white fat depots was markedly decreased compared with wild-type littermates. TG content in the liver and skeletal muscle of PKCbeta(-/-) mice was also significantly low. Interestingly, mutant animals were hyperphagic and exhibited higher food intake and reduced feed efficiency versus wild type. The protection from obesity involves elevated oxygen consumption/energy expenditure and increased fatty acid oxidation in adipose tissue with concurrent increased mitochondria genesis, up-regulation of PGC-1alpha and UCP-2, and down-regulation of perilipin. The ability of PKCbeta deficiency to promote fat burning in adipocytes may suggest novel therapeutic strategies for obesity and obesity-related disorders.